Freescale Semiconductor M68HC08 User Manual

Download

Dimmable Light Ballast with Power Factor Correction

Designer Reference Manual

M68HC08 Microcontrollers

DRM067 Rev. 1 12/2005

freescale.com

Dimmable Light Ballast with Power Factor Correction

Designer Reference Manual

by: Petr Frgal

Freescale Czech Systems Center Roznov pod Radhostem, Czech Republic

To provide the most up-to-date information, the revision of our documents on the World Wide Web will be the most current. Your printed copy may be an earlier revision. To verify that you have the latest information available, refer to

http://www.freescale.com

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Freescale Semiconductor 3

Dimmable Light Ballast with Power Factor Correction, Rev. 1

4 Freescale Semiconductor

Draft 2 for Review

Chapter 1

Introduction

1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

1.2 Benefits of this Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

1.3 The MC68HC908LB8 Microcontroller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Chapter 2

Control Theory

2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2.1.1 Fluorescent Lamp Control Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2.1.2 Fluorescent Lamp Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2.1.3 Controlling the Fluorescent Lamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

2.2 PFC Control Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.2.2 Digital Power Factor Concept — Hysteresis Current Control Mode . . . . . . . . . . . . . . . . . . 16

2.2.3 Digital Power Factor Concept — Discontinuous Conduction Mode. . . . . . . . . . . . . . . . . . . 17

2.2.4 Concept Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Chapter 3

Reference Design

3.1 Application Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

3.2 Dimmable Light Ballast Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

3.3 Application Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

3.3.1 Light Ballast Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

3.3.2 Power Factor Correction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

3.3.3 Protection Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

3.4 Software Specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

3.5 Hardware Specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Chapter 4

Hardware Design

4.1 Hardware Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

4.2 System Modules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

4.2.1 Input and PFC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

4.2.2 Inverter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

4.2.3 Microcontroller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

4.2.4 Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Freescale Semiconductor 5

Chapter 5

Software Design

5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

5.2 Control Algorithm Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

5.2.1 Power Factor Correction Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

5.2.1.1 DC-bus Voltage Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

5.2.1.2 Phase Shift Synchronization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

5.2.1.3 Reference Sine Wave Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

5.2.1.4 Generation of Output PFC Control SIgnal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

5.2.2 Light Ballast Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

5.2.2.1 Tube Start Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

5.2.2.2 Luminance Level Control (Tube Run Mode). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

5.3 Software Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

5.3.1 Initialization Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

5.3.1.1 PWM Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

5.3.1.2 HRP Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

5.3.2 Main Program Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

5.3.3 Synchronization Interrupt Routine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

5.3.4 Sine Wave Generation Interrupt Routine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

5.3.4.1 Fault Detection and Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

5.4 Detailed Software Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

5.5 Microcontroller Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

5.5.1 Microcontroller Peripheral Usage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

5.5.1.1 High Resolution PWM (HRP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

5.5.1.2 Pulse-Width Modulator (PWM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

5.5.1.3 Comparator Module (CM). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

5.5.1.4 Timer Interface Module (TIM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

5.5.1.5 External Interrupt (IRQ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

5.5.2 Program and Data Memory Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

5.5.3 I/O Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

5.6 Definitions of Constants and Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

5.6.1 System Setup Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

5.6.2 System Constants and Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

Chapter 6

Demo Setup

6.1 Hardware Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

6.2 Software Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

6.2.1 Required Software Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

6.2.2 Building and Uploading the Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

6.2.3 Executing the Application. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

6.2.4 Project Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

Appendix A. Schematics and Part List

A.1 Schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

A.2 Parts List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

Appendix B. References

Dimmable Light Ballast with Power Factor Correction

6 Freescale Semiconductor

Chapter 1 Introduction

1.1 Introduction

This reference design describes the design of a fully digital dimmable light ballast with power factor correction (PFC) control for two parallel connected fluorescent lamps.

This reference design focuses on the lamp ballast hardware and software implementation using the Freescale MC68HC908LB8 microcontroller (MCU), which is designed specifically for light ballast applications. This MCU includes a set of peripherals that are appropriate for light dimming and power factor correction.

The reference design incorporates both hardware and software parts of the system including detailed hardware descriptions and full software listings. The application uses half-bridge topology, typical for this kind of applications. The MC68HC908LB8 MCU is well suited to this topology.

Figure 1-1. Dimmable Light Ballast with PFC Demo

1.2 Benefits of this Solution

Microcontrollers offer the advantages of low cost and attractive digital light ballast design. Using a dedicated on-chip high resolution PWM (HRP) allows easy implementation of dimming features. PFC improves the efficiency of the light ballast. Harmonic content of the input current for the mains supplied equipment meets the European regulation

The advantages of the presented digital solution over standard analog solutions can be summarized as follows:

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Freescale Semiconductor 7

EN 61000-3-2 and the international standard IEC 1000-3-2.

Introduction

• Energy saving

• Ease of adapting software for different lamps

• Ease of re-programming the system behavior

• Software can simplify the hardware

• Diagnostic functions — fault state, tube end-of-life, ignition fault, tube removed

• Open to innovation

The MC68HC908LB8 is designed for light ballast applications. It contains a HRP that is assigned to control a lamp ballast circuit using half-bridge topology. The HRP provides two complementary outputs for controlling a half-bridge drive. Pulse Width Modulation (PWM) with constant duty cycle is used for light ballast control. The HRP frequency can be adjusted easily by software in range 40

kHz to 120 kHz in 256

steps. Dimming levels down to 5% are possible.

The PFC circuit uses an on-chip comparator on the MC68HC908LB8. This peripheral simplifies the dimming light ballast solution with PFC, since it eliminates the need of external components and thus decreases the system cost.

The reference design is intended for all geographic regions, so 110V/60Hz and 230V/50Hz input voltage supplies are supported.

The application can be debugged using the MON08 CYCLONE debug tool in monitor mode.

WARNING Since the application runs at high voltage, it is dangerous to connect development tools directly to the board. Therefore, it is recommended to use an opto-isolation monitor mode board. This separate board provides an opto-isolated interface for the MON08 debug tool, using the MON08 standard connector. This allows the user to safely debug or examine code in-circuit.

1.3 The MC68HC908LB8 Microcontroller

The MC68HC908LB8 is a member of the low-cost, high performance MC68HC08 Family of 8-bit MCUs. All MCUs in the family use the enhanced MC68HC08 central processor unit (CPU08) and are available with a variety of modules, memory sizes and types, and package types.

Standard features of microcontroller MC68HC908LB8 are:

•8 MHz internal bus frequency

• Trimmable internal oscillator: –4.0 MHz internal bus operation – 8-bit trim capability – 25% untrimmed –2% trimmed

• 8K bytes of 10K write/erase cycle typical on-chip in application programmable FLASH with security option

• 128 bytes of on-chip random access memory (RAM)

(1)

memory

1. Non volatile memory that retains its data when the power is removed.

Dimmable Light Ballast with Power Factor Correction, Rev. 1

8 Freescale Semiconductor

The MC68HC908LB8 Microcontroller

• Dual channel high resolution PWM (HRP) with deadtime insertion and shutdown input to perform light control and dimming functions for ballasts. The outputs use frequency dithering to achieve a

3.9 ns output resolution.

• Dual channel pulse width modulator module to provide power factor correction capability

• 7-channel, 8-bit successive approximation analog-to-digital converter (ADC)

• Comparator for power factor correction capability or for general-purpose use

• 7-bit keyboard interrupt

• One 16-bit, 2-channel timer interface module with one output available on port pin (PTA6) for input capture and PWM

• 17 general-purpose input/output (I/O) pins and one input-only pin – Three shared with HRP module – Three shared with PWM module – Three shared with comparator – Seven shared with ADC module (AD[0:6]) – One shared with timer channel 0 – Two shared with OSC1 and OSC2 – One shared with reset – Seven shared with keyboard interrupt – One input-only pin shared with external interrupt (IRQ)

• Available packages: – 20-pin small outline integrated chip (SOIC) package – 20-pin plastic dual in-line package (PDIP)

• On-chip programming firmware for use with host personal computer which does not require high voltage for entry

• System protection features: – Optional computer operating properly (COP) reset – Low-voltage reset – Illegal opcode detection with reset – Illegal address detection with reset

• Low-power design; fully static with stop and wait modes

• Standard low-power modes of operation: – Wait mode – Stop mode

• Master reset pin and power-on reset (POR)

• 674 bytes of FLASH programming routines in read-only memory (ROM)

• Break module (BRK) to allow single breakpoint setting during in-circuit debugging

• Internal pullup on RST pin to reduce customer system cost

• Selectable pullups on ports A and C – Selection on an individual port bit basis – During output mode, pullups are disengaged

• High current 10 mA sink / 10 mA source capability on all port pins

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Freescale Semiconductor 9

Introduction

Dimmable Light Ballast with Power Factor Correction, Rev. 1

10 Freescale Semiconductor

Chapter 2 Control Theory

2.1 Introduction

This chapter covers fluorescent lamp theory and two PFC concepts - discontinuous conduction mode and hysteresis current control mode.

2.1.1 Fluorescent Lamp Control Theory

To light a low-pressure fluorescent lamp, the electronic circuit must perform the following four main functions:

• Provide a startup voltage across the electrodes of the lamp

• Maintain a constant current when the lamp is operating in the steady state

• Ensure that the circuit will remain stable, even under fault conditions

• Comply with the applicable domestic and international regulations (PFC, THD and safety)

Most generally, light ballast topology fairly closely matches target lamps in terms of tube wattage, length, and diameter. The digital electronic lamp ballast includes also additional features like dimming capability, tube end-of-life, startup fault, tube removed indication, and so on. Different tubes require different software settings; also, some hardware components may have to be adapted accordingly.

2.1.2 Fluorescent Lamp Operation

When the lamp is off, no current flows through the tubes, and the apparent impedance is nearly infinite. When the voltage across the electrodes reaches the V an arc is generated across the two terminals of the lamp. This behavior is depicted by the typical operating curve shown in

Figure 2-1.

value, the gas mixture is highly ionized and

strike

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Freescale Semiconductor 11

Control Theory

Figure 2-1. Typical Low Pressure Fluorescent Tube I/V Characteristic

The value of V

is a function of several parameters:

strike

• Gas filling mixture

• Gas pressure and temperature

• Tube length

• Tube diameter

• Temperature of electrodes: cold or hot

Typically, values of V to the on-state voltage (V the tube. Typically, V

are in range 500 V to 1200 V. Once the tube is on, the voltage across it drops

strike

, the magnitude of this voltage being dependent upon the characteristics of

on)

is in range 40 V to 110 V.

The value of Von will vary during the operation of the lamp but, in order to simplify the analysis, we will assume, as a first approximation, that the on-state voltage is constant when the tube is running in steady state.

Consequently, the equivalent steady state circuit can be described by two back-to-back Zener diodes as shown in

Figure 2-2. The startup network is far more complex, particularly during ionization of the gas.

This is a consequence of the negative impedance exhibited by the lamp when the voltage across its electrodes collapses from V

strike

to Von.

Dimmable Light Ballast with Power Factor Correction, Rev. 1

12 Freescale Semiconductor

Introduction

Figure 2-2. Typical Fluorescent Tube Equivalent Circuit in Steady State

Up to now, there is no model available to describe the start up sequence of these lamps. However, since most of the phenomena are dependent upon the steady state characteristics of the lamp, one can simplify the analysis by assuming that the passive networks control the electrical behavior of the circuit. This assumption is wrong during the time elapsed from V

to Von, but since this time interval is very short,

strike

the results given by the proposed simple model are accurate enough to design the converter. When a fluorescent tube is aging, its electrical characteristics degrade from the original values, yielding less light for the same input power, and different V

and Von voltages. A simple, low-cost electronic lamp ballast

strike

cannot optimize the overall efficiency throughout the lifetime of the tube, but the circuit must be designed to guarantee the operation of the lamp even under worst case “end of life” conditions. As a consequence, the converter will be slightly oversized to make sure that, after 8000 hours of operation, the system will still drive the fluorescent tube.

2.1.3 Controlling the Fluorescent Lamp

As already stated, both the voltage and the current must be accurately controlled to make sure that a given fluorescent lamp operates within its specifications.

The most commonly used network is built around a large inductor, connected in series with the lamp, and associated with a bimetallic switch generally named “the starter”. schematic diagram for the standard, line operated, fluorescent tube control.

Figure 2-3. Standard Ballast Circuit for Fluorescent Tube

Figure 2-3 gives the typical electrical

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Freescale Semiconductor 13

Control Theory

The operation of a fluorescent tube requires several components around the tube, as shown in Figure 2-3. The gas mixture enclosed in the tube is ionized by means of a high voltage pulse applied between the two electrodes.

To make this startup easy, the electrodes are actually made of filaments that are heated during the tube ionization startup (i.e. increasing the electron emission), their disconnection being automatic when the tube goes into the steady state mode. At this time, the tube impedance decreases toward its minimum value (depending upon the tube internal characteristics), the current in the circuit being limited by the inductance L in series with the power line. The starting element, commonly named “starter”, is an essential part to ignite the fluorescent tube. It is made of a bimetallic contact, enclosed in a glass envelope filled with a neon based gas mixture, and is normally in the OPEN state. When the line voltage is applied to the circuit, the fluorescent tube exhibits a high impedance, allowing the voltage across the “starter” to be high enough to ionize the neon mixture. The bimetallic contact gets hot, turning ON the contacts which, in turn, will immediately de-ionize the “starter”. Therefore, the current can flow in the circuit, heating up the two filaments. When the bimetallic contact cools down, the electrical circuit is rapidly opened, giving a current variation in the inductance L which, in turn, generates an over-voltage according to Lenz’s law.

Since there is no synchronization with the line frequency (the switch operates on a random basis), the circuit opens at a current level anywhere between maximum and zero.

If the voltage pulse is too low, the tube does not turn on, and the startup sequence is automatically repeated until the fluorescent tube ionizes. At that time, the tube impedance falls to its minimum value, yielding a low voltage drop across its end electrodes and, hence, across the switch. Since the starter can no longer be ionized, the electrical network of the filaments remains open until the next turning on of the circuit.

We must point out that the fluorescent tube turns off when the current is zero; this is the source of the

Hz flickering in a standard circuit. This is an important problem, which can lead to visual problems due

50 to the stroboscopic effect on any rotating machines or computer terminals.

To take care of this phenomena, the fluorescent tubes, at least those used in industrial plants, are always set on a dual basis in a single light spreader, and are fed from two different phases (real or virtual via a capacitor) in order to eliminate the flickering.

On the other hand, the magnetic ballast provides a very low cost solution for driving a low pressure fluorescent tube. To overcome the flickering phenomenon and the poor startup behavior, the engineers have endeavored to design electronic circuits to control the lamp operation at a much higher frequency. The efficiency (Pin/Lux) of the fluorescent lamp increases significantly, as soon as the current through the lamp runs above a few kilo Hertz.

The electronic circuits that can be used to build a fluorescent lamp controller can be divided into two main groups:

• Single switch topology, with unipolar AC current, (unless the circuit operates in the parallel resonant mode)

• Dual switch circuit, with a bipolar AC output current

Manufacturers of fluorescent lamps usually recommend operating the tubes with a bipolar AC current. This avoids constantly biasing the electrodes as an anode-cathode pair, which, in turn, decreases the expected lifetime of the lamp. In fact, when a unipolar AC current flows into the tube, the electrodes behave like a diode and the material of the cathode side is absorbed by the electron flow, yielding a rapid wear out of the filaments. As a consequence, all of the line operated electronic lamp ballasts are designed with either a dual switch circuit (the only one used in Europe), or a single switch, parallel resonant configuration (mainly used in countries with 110

V lines), providing an AC current to the tubes. A few low

Dimmable Light Ballast with Power Factor Correction, Rev. 1

14 Freescale Semiconductor

PFC Control Theory

power, battery operated fluorescent tubes are driven with a single switch fly-back topology, but, the output transformer is coupled to the tube by a capacitive network and the current through the lamp is alternating current. However, the filaments (if any) cannot be automatically turned off by this simple configuration and the global efficiency is downgraded accordingly.

Dual switch circuits are divided into two main topologies:

• Half-bridge, series resonant

• Current fed push-pull converter

The half-bridge is, by far, the most widely used in Europe (100% of the so-called “energy saving” lamps and industrial applications are based on this topology), while the push-pull is the preferred solution in the USA with around 80% of the electronic lamp ballasts using this scheme today.

Both of these topologies have their advantages and drawbacks, the consequence for the associated power transistors being not at all negligible, as shown by

Table 2-1. The half-bridge topology controlled

by the dedicated MC68HC908LB8 MCU is implemented in Chapter 3. For more details about electronic lamp ballast theory see Reference [1.].

Table 2-1. Main Characteristics of the Dual Switch Topologies

Parameters Half-bridge Push-pull

V(BR)CER 700 V

Inrush Current 3 to 4 times I nom

tsi window 2.6 – 3.6 µs 1.9 – 2.3 µs

Drive High and Low side Low side only

Intrinsic Galvanic Isolation no yes

NOTES:

1. These numbers are typical for operation on a 230 V supply.

2. I nom is the current into the transistors in steady state.

(1)

(2)

2 to 3 times I nom

1100 - 1600 V

(1)

(2)

2.2 PFC Control Theory

2.2.1 Introduction

The most practical electronic systems contain a conventional single-phase full-bridge rectifier and an input filter capacitor. It is well known that this type of circuit draws high current peaks from the power line and produces a high level of harmonics. High total harmonic distortion (THD) and low power factor therefore reduce the maximum power available from the mains and the efficiency of the electricity supply networks. The European Normative EN 61000-3-2 defines the limits of the harmonic content of the input current for mains supplied equipment.To meet the norms, new designs require an active PFC at the input.

Many specific integrated circuit devices (ICs) are available on the market to perform power factor correction. This approach requires additional electronic components, which increases the system cost and complexity. On the other hand, there is a way to implement PFC control using the MCU, in addition to the MCU’s main control tasks, such as motor control. Digital PFC allows missing out these specific ICs, thereby reducing the system cost. Another benefit of the software implementation is the potential for easy modifications without changing the hardware.

Two power factor correction approaches were implemented in this design, discontinuous conduction mode and hysteresis current control mode. Each of these topologies has advantages and drawbacks. Both topologies are described in the following.

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Freescale Semiconductor 15

Control Theory

2.2.2 Digital Power Factor Concept — Hysteresis Current Control Mode

The control technique is based on hysteretic current control. The system operates in continuous conduction mode with variable switching frequency (30–100 kHz) (see

This PFC concept is designed to have the minimum of MCU performance requirements. The basic principles of the scheme are depicted in

Figure 2-4. The PFC control algorithm includes two control loops,

a fast one for input current control and a slow one for output voltage control. The output voltage controller is implemented digitally using the MCU. A value proportional to the required input current is modulated by the PWM and is taken as an input to the current control loop, which is realized by the analogue comparator. The comparator switches the MOSFET in order to maintain the required current value.

The desired shape of the input current is a sine wave. The generated current waveform is shown in

Figure 2-8.

A hysteresis current control mode PFC concept has several drawbacks, including variable MOSFET switching frequency, non sinusoidal input current waveform and switching under current, which causes higher losses than other PFC topologies.

The input current harmonics content, however, complies with EN 61000-3-2 standard.

The advantages are simple control circuit, low MCU resources consumption, continuous conduction mode operation, and low total harmonic distortion (THD).

Figure 2-5).

AC Line Voltage

AC Line Current

DC Bus

MCU

ADC

Voltage

PWM

Reference

Voltage

Comparator

Actual

Current

Current Sensing

LINE

Zero

Crossing

Figure 2-4. Hysteresis Current Control Mode Principle

+ DC BUS

MOSFET

GND

Dimmable Light Ballast with Power Factor Correction, Rev. 1

16 Freescale Semiconductor

Figure 2-5. Hysteresis Current Control Mode Current Waveform

2.2.3 Digital Power Factor Concept — Discontinuous Conduction Mode

PFC Control Theory

The control technique is based on discontinuous conduction mode with a current loop with a constant switching frequency (40 kHz) (see

Figure 2-7).

The basic principles of the scheme are depicted in Figure 2-6. The PFC control algorithm includes two control loops, the same as the previous approach. The output voltage controller is implemented digitally using the MCU. A value proportional to the required input current is modulated by the PWM0 and is taken as an input to the current control loop, which is realized by the analog comparator. The comparator output is connected to the PWM fault pin that disables the PWM output. PWM1 is used directly for switching the MOSFET in order to maintain the required current value. PWM1 is switched off in every period where the reference sine wave signal generated by PWM0 is higher than the actual current sensed signal on the shunt resistor.

The desired shape of the input current is a sine wave. The generated current waveform is shown in

Figure 2-8.

The discontinuous conduction mode PFC concept has several drawbacks — higher THD than hysteresis current control mode, non sinusoidal input current waveform, and the discontinuous conduction mode itself. The input current harmonics content, however, complies with EN 61000-3-2 standard.

The advantages are a simple control circuit, with low MCU resource consumption, and low losses.

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Freescale Semiconductor 17

Control Theory

DC Bus Voltage

LINE

Reference

Zero

Crossing

ADC

MCU

PWM

FAULT

Voltage

PWM0

PWM1

Actual

Current

Comparator

MOSFET

Current Sensing

Figure 2-6. Discontinuous Conduction Mode Principle

+ DC BUS

GND

Figure 2-7. Discontinuous Conduction Mode Current Waveform

Dimmable Light Ballast with Power Factor Correction, Rev. 1

18 Freescale Semiconductor

Figure 2-8. Generated Input Current Waveform

2.2.4 Concept Summary

PFC Control Theory

Both the PFC solutions can be used for applications that do not require a large portion of the MCU’s resources, because they consume only a fraction of the MCU performance. Compared to a dedicated IC solution, digital PFC offers high flexibility and cost reduction in the overall design, as the PFC function can be provided within the MCU capability of the main application. Digital PFC also provides additional benefits such as a wide range of input voltages (85

V to 265 V AC) at a constant output DC voltage.

However, hysteresis current control mode is more suitable for power above 100W, and discontinuous conduction mode for low power consumption.

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Freescale Semiconductor 19

Control Theory

Dimmable Light Ballast with Power Factor Correction, Rev. 1

20 Freescale Semiconductor

Chapter 3 Reference Design

3.1 Application Outline

The presented system is designed to control two parallel connected fluorescent lamps. The reference design meets the following performance specification:

• Single board solution with MC68HC908LB8 microcontroller

• Supported power supply: 110V/60Hz and 230V/50Hz

•Low THD

• High power factor achieved using the PFC circuit

• Control techniques incorporating: – Preheating –Strike – Run mode

• User interface (dimming level potentiometer, monitor mode interface)

• Flickering effect removal

• Lamp aging recognition

• Fault detection – DC-bus under-voltage detection (software) – DC-bus over-voltage detection (software) – Ignition fault (software) – Zero current fault (software)

3.2 Dimmable Light Ballast Characteristics

Table 3-1 provides the basic characteristics of the Dimmable Light Ballast Demo with PFC at 25°C and

400 V DC-bus voltage.

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Freescale Semiconductor 21

Reference Design

Table 3-1. Light Ballast Characteristics

Parameter Unit Value

Lamp Type F18W/33

Input Power W 8...31

Input Current

(230VAC)

Preheat Output

Frequency

Preheat Output

Volt age

Preheat Time ms 900

Running Output

Frequency Range

Running Output

Voltage Range

Input AC Voltage VAC 110V/60Hz, 230/50Hz

Ambient

Temperature Range

Power Factor 0.94...0.99

Total Harmonic

Distortion

Output Ignition

Volt age

mA 40...290

kHz 86

Vpp 345

kHz 50...100

V 200...235

°C 0.50

% 5.2...24.6

Vpp 510

3.3 Application Description

The system concept is shown in Figure 3-1. The system consists of:

• Control board with MC68HC908LB8 microcontroller

• Two fluorescent lamps

The MC68HC908LB8 MCU runs the main control algorithm. According to the dimming level potentiometer It generates output signals for the half-bridge inverter which controls the ballast circuit. It also controls PFC. The desired dimming value is set by the potentiometer, because the human eye is more sensitive at lower light levels. The input values from the potentiometer are converted using brightness linearization. The HRP uses a frequency control method for dimming. It incorporates hardware that allows dithering between two adjacent frequencies for smooth light level dimming.

Dimmable Light Ballast with Power Factor Correction, Rev. 1

22 Freescale Semiconductor

MAINS

FILTER RECTIFIER

CROSSING

ZERO

CONTROL BOARD

USER INTERFACE

MONITOR

MONITOR MODE

MODE

LUMINANCE

LUMINANCE LEVEL

LEVEL

REQ

BUS VOLTAGE

BUS VOLTAGE DC-

DC-

BRIGHTNESS

LINEARIZATION

DRIVER

ACTUAL CURRENT

PWM

GENERATION

sineGain

REGULATOR

DC-BUS

PFC

PWM

FILTER

req

MC68HC908LB8

POWER

SUPPLY

DRIVER

PWM

HIGH

RESOLUTION

PWM

REGULATOR

act

Application Description

RESONANT

CIRCUIT

HALF BRIDGE

DIFFERENTIAL

VOLTAGE

CURRENT

CURRENT 1

HRP

CURRENT

PROCESSING

PROCESSING e

TUBE 2 CURRENT

TUBE

FLUORESCENT LAMPS

Figure 3-1. Dimmable Light Ballast — System Concept

3.3.1 Light Ballast Control

The HRP provides two complementary PWM outputs for controlling a half-bridge in a light ballast application. It uses a dithering control method to provide a high step resolution (3.9 ns) from an 8

MHz

input clock when driving inductive loads.

The High Resolution PWM Module (HRP) uses a dithering technique to increase the resolution of the output signal.The output switches between two frequencies or duty cycles at a programmable rate. By varying the percentage of time spent on each frequency/duty cycle, the output will appear to be at a value between the two dithering frequencies/duty cycles when driving an inductive load.

The advantage is easy implementation of a control method for half-bridge inverter using few external devices. The main advantage is simple performance using few instructions to perform the dithering control algorithm.

3.3.2 Power Factor Correction

The power factor correction circuitry provides the “sinusoidal” input current by controlling the PFC switch. In the control loop, the actual DC-bus voltage is compared with the desired one. The control error is processed by the PI (proportional-integral) controller, which generates the amplitude of the input “sinusoidal” current. The PWM generator generates the desired sinusoidal current profile using a PWM technique. The digital output signal is filtered by a passive filter and the resulting analog waveform is compared with the actual input current by an on-chip comparator. The comparator output controls directly

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Freescale Semiconductor 23

Reference Design

the PFC switch in hysteresis current control mode or output is used for switch off PWM1 in DCM. Than PWM1 signal is used directly for switching the PFC switch transistor.

3.3.3 Protection Features

During the startup phase and run phase, some erroneous states can occur. When the DC-bus voltage does not reach the required value or is out of limits then a fault signal is generated. The DC-bus voltage is also checked against limits in run mode. If any of the previously mentioned faults occurs, all modules are disabled, lamps go out, and the fault diode blinks.

3.4 Software Specification

The software is written in C. The software specifications are listed in Table 3-2. A useful feature of this application is the ability to debug software via the MON08 CYCLONE debug tool connected to JP1 header connector. The Real-Time Debugger from Metrowerks can be used as a debug tool.

Tabl e 3-2. Software Specification

Dithering control

Control Algorithm

Target Processor MC68HC908LB8

Language C with some arithmetical functions in assembler

Compiler Metrowerks ANSI-C/C++ Compiler for HC08

MCU Oscillator Frequency 16 MHz (with default software setting)

MCU Bus Frequency 4 MHz (with default software setting)

Targeted Hardware Dimmable Light Ballast With PFC Demo Board

Current loop control

Voltage loop control

A detailed description of how to set Debugger for commutation with MON08 CYCLONE is given in Reference [

2]. For safe debugging it is recommended use an opto-isolation board connected between the

MON08 CYCLONE and the Light Ballast Demo Board. The Opto-isolation Board user manual can be found in Reference [

3].

3.5 Hardware Specification

The other system specifications are determined by the target hardware and lamp characteristics. The board and its connections are shown in

This hardware set is designed for fluorescent lamp and mains voltage. The specifications for a high voltage hardware and fluorescent lamp set are listed in and 110 VAC mains.

Chapter 4 Hardware Design.

Table 3-1. The hardware operates on 230 VAC

Dimmable Light Ballast with Power Factor Correction, Rev. 1

24 Freescale Semiconductor

Chapter 4 Hardware Design

4.1 Hardware Implementation

This chapter covers the system hardware implementation. The dimmable light ballast board is shown in

Figure 4-1.

Figure 4-1. Dimmable Light Ballast - Demo Board

4.2 System Modules

The light ballast system hardware is shown in the block diagram in Figure 4-2. It incorporates the controller board, powered from AC line and fluorescent tubes. As can be seen, the controller board contains four major parts:

• Input and PFC (Input EMI Filter, Bridge Rectifier, Boost topology PFC circuit, DC-bus Voltage, DC-bus Sensing, Mains Zero Crossing Sensing, Comparator Circuit, Buffer Circuit)

• Inverter (Half-bridge Drive, Resonant Circuit, Output Inductance Circuity, Different Voltage Sensing, Tube Currents Sensing)

• Microcontroller (MC68HC908LB8)

• Power Supply (Switch Mode Power Supply)

Detailed descriptions of the individual parts of the controller boards follows. Note that the reference design includes the PCB design files and bill of materials (BOM).

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Freescale Semiconductor 25

Hardware Design

Figure 4-2. Dimmable Light Ballast with Hysteresis PFC HW variation — Hardware Block Diagram

4.2.1 Input and PFC

The input and the PFC part provide the DC-bus voltage to supply the inverter. The schematic for hysteresis current control mode is shown in against hysteresis mode is that the gate of Q4 is connected to pin PWM1 of the MCU (see Figure A-2), not to the output of the comparator. The input stage consists of an EMI filter and a single-phase full-bridge rectifier. Although the PFC regulator is called an active filter, it does not suppress all harmonics. For this reason, the EMI filter is placed at the input.

The PFC is based on the most popular non transformer isolated DC-DC boost (step-up) converter topology. The PFC stage is built with input inductor L1, power MOSFET switch Q1, output rectifier diode D1, and output capacitor C4. Capacitor C3 performs a filtering function. The input stage converts the mains AC voltage, rectified by the diode bridge U1, to an output DC voltage on the output capacitor C4. The current flowing through inductor L1 is sensed by the current sense resistor R4. There are two different values of resistor R4, 1.5

Ω for rectified input voltage lower than half of DC-Bus voltage and 2.7Ω for higher

voltage. The voltage drop over the current sense resistor corresponds to the measured current. The circuit, with resistors R3, R5, R7, R9, diodes D2 and D15, and capacitor C27 works as a mains zero-crossing detector. It senses rectified mains voltage and generates zero-crossing pulses with an amplitude of 5

volts. With the help of this detector, the microcontroller synchronizes its operation with the

mains frequency.

The DC-bus voltage sensor consists of resistors R1, R2, R6, and R8. It senses the output voltage of the PFC, and its output is connected to the MCU AD converter. In hysteresis current control mode the output

Figure 4-3. The difference in discontinuous conduction mode

Dimmable Light Ballast with Power Factor Correction, Rev. 1

26 Freescale Semiconductor

System Modules

signal of the comparator (Comp Out) controls the power switch Q1 through the output buffer, which consists of transistors Q2, Q3, and Q4, resistors R10, R13, R34, R35, R36, and R37, and capacitor C7.

For discontinuous conduction mode the comparator output is disconnected from the Q4 transistor gate. The PWM1 pin is connected to the Q4 transistor gate.

Digital PFC is driven by the MCU. The MC68HC908LB8 peripherals used for PFC are listed below:

• AD converter — channels ADC1 and ADC2

• PWM0 for generating sine wave

• comparator

• IRQ pin for zero-crossing detection

The PFC control algorithm

• converts the sensed output voltage to a digital value

• provides software PI regulator for a voltage feedback loop

• programs its PWM channel to create the pattern of the input current

• synchronizes operation with the mains frequency using mains zero-crossing detection

The control algorithm is described in 5.2 Control Algorithm Description.

DC-BUS VOLTAGE OUTPUT AND SENSING

PM100-INP_CONN-6

PFC Current Sense

INPUT EMI FILTER AND BRIDGE RECTIFIER

1 4

C1 10nF 275V X2

10nF 275V X2

R14

2K0

1 4

2 3

GND

1 2

4n7 250/1000V Y2

CMFIL2

R11

R11 3K0

3K0

C8 82pF

82pF

RV1

RV1 275V

275V

Comp -

COMPARATOR CIRCUIT

GND

2.7mH

L1B

L1B PFCIND3

DF1510S

AC2

AC1

R3 220K

220K

R5 220K

220K

2 1

R7 220K

220K

C10

C10 220nF

220nF

Comp Out

150nF 275V X2

DC+

DC-

MAINS ZERO CROSSING SENSING

D15

BAT48

47K

GND

D2 BZV55C5V6

BZV55C5V6

GND

R12

R12 10K

10K

DF1510S

PFCIND3

PFC Gate

1 2

R4 2R7

PFC Current Sense

Zero Detect

C27 1n5

GND

100nF

R10

R10 6K8

6K8

GND

BEQ2

R13

620R

BCQ3

MMBF0201

GND

BOOST CONVER TER

MURS160T3

15V

R35

R35 0R

R34

R34 0R

BC846B

BC856B

GND

IRF820A

R36

PFC Gate

BUFFER CIRCUIT

10nF 630V TC356

R37

15V/1

GND

C4 22uF 450V

22uF 450V

C6 100nF

R1 560K

R2 560K

R6 510K

DCB Divider

R8 18K

GNDGND

DCB

1 2

CONN/HDR/2X1

GND

JP6

Figure 4-3. Dimmable Light Ballast — Input and PFC

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Freescale Semiconductor 27

Hardware Design

4.2.2 Inverter

The power inverter generates the proper voltage for the fluorescent tubes. The power inverter consists of two MOSFET transistors driven by a half-bridge driver. It incorporates the half-bridge, a resonant circuit, different voltage and tube current sensing, and output inductance circuity.

The half-bridge driver IR2106 from International Rectifier is electrically connected according to the manufacturer’s recommendations. The half-bridge is supplied from the DC-bus voltage. It is controlled by the TOP and BOT signals from the MCU.

The half-bridge lamp resonant circuit consists of capacitor C15 and inductance L7. It provides preheating, ignition, and running operating conditions by changing the operating frequency.

The tube voltage difference circuit consist of coils L3A, L3B, and L3D, resistors R21, R24, R22, and R151, diode D8, and capacitor C17, and is used to sensing voltage differences between lamps. It helps to recognize aging of the lamps.

Coils L4 and L5 and diodes D4 and D5 are for filament preheating. Diodes maintain a small offset to remove the flickering effect. Coils L3A and L3D balance possible differences in current flow into tubes, mainly at ignition stage. Devices R19, D7, R152, D6, C16, and R20 sense the current flow in tube 1 (and similarly for tube 2).

For different tubes parameters, the tube currents are different. The ignition circuit formed by L3D, L3A, and R17 balance the current. The compensation current flows through R17 until the tube currents are equal, at which time the ignition of both tubes can be done reliably.

Tubes preheating heats the tubes to the desired temperature before startup. It decreases the wear-out and increases the life-time and reliability in startup. Also, the voltage required for ignition is smaller.

Each tube has its own preheating circuity. Tube 1 uses L4. Tube 2 uses L5. The preheating voltage and time is set-up in software and is controlled by the TOP and BOT signals from the HRP.

The flickering effect is caused by reducing the voltage to zero during the light ballast operation. To avoid this, the Zener diodes D4 and D5 maintain a small voltage on both tubes at all times.

The output inductance circuity performs several important functions in the light ballast application. It helps to ignite lamps, when tube parameters differ (due, for example, to different aging of the lamps). It removes the flickering effect and provides filament preheating.

Dimmable Light Ballast with Power Factor Correction, Rev. 1

28 Freescale Semiconductor

DCB

TOP BOT

15V/1

1 2

MURA160

C13 1uF

25V

R15

IC1

Vcc

HIN

LIN COM4LO

IR2106

Tube V o l t ag e d i f fe r e nc e

HALF BRIDGE

10R

8 7 6

System Modules

L4C HEAT7

R23 20R

0.5W

TU BE C onn ector

O11O22O33O44O55O66O77O8

6 5

L4D

L5C

HEAT7

HEAT6

R19 20R

0.5W

1 2

GND

3 4

R152

D7 MBRS140

1 2

GND

R150

D10 MBRS140

TUBE CURRENTS SENSING

L5D HEAT6

D9 BAT48

D6 BAT48

C18 22nF

C16 22nF

R25

10K

Tube Current 1

R20

10K

Tube Current 2

OUTPUT INDUCTANCE CIRCUITY

C26

IRF830A

33R

C11 100nF

33R

IRF830A

GND

C17 6n8

GND

R16

R18

10nF 630V TC356

GND

RESONANT CIRCUIT

C28 470pF 1KV

1 3

C14 470pF 1KV

D8 BAT48

R22

30K

GND

L7 RES5

1mH

R151

C12

100nF 630V

1 2

8n2 1KV

C15

GND

BZG05C22

L3D DIFF8

1 8

L3A DIFF8

BZG05C22

R21

3K3

R24

N/P

L3BDIFF8

2 7

L4B HEAT7

1 2

R17 10K

L5B HEA T6

GND

DIFFERENT VOLTAGE SENSING

Figure 4-4. Dimmable Light Ballast — Inverter

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Freescale Semiconductor 29

Hardware Design

4.2.3 Microcontroller

The MC68HC908LB8 microcontroller is the core of the application. It processes the input and feedback signals and generates appropriate control signals. The description of the pins follows.

The inverter is controlled by signals on the TOP and BOT pins of the MCU.

Signal PWM0 is used to generate a sine wave. This signal (on comparator pin V+) is compared with the real current (on comparator pin V-) in the on-board comparator. The real current is sensed using the shunt resistor R4. The signal from PWM0 is filtered in the RC filter comprised of R30, R31 and capacitor C9. The output of the comparator appears on pin VOUT.

The IRQ pin is used for the zero-crossing detection circuit and for entry to the monitor mode.

The microcontroller stage incorporates two header connectors, the Luminance Level connector and the Monitor Mode connector. The Luminance Level connector is used for the Luminance Level potentiometer (see

Table 4-1). The Monitor Mode connector enables the MCU to enter the Monitor Mode. For Monitor

Mode, the IRQ, OSC1, PTA0, and PTA1 pins are used (see Table 4-2).

The Fault LED is connected to pin PTA5; it indicates the actual state of the application.

DC-bus shift-down voltage is sensed on pin ADC2.

Real currents through tube1 and tube2 are sensed on pins ADC3 and ADC4. The tube voltage difference is sensed on pin ADC5.

In the discontinuous conduction mode HW variation, PWM1 pin is used directly for switching the PFC switch transistor (see

Figure A-5). Comparator output is internally connected to the PWM fault pin. In the

hysteresis current control mode HW variation, it is not used.

Dimmable Light Ballast with Power Factor Correction, Rev. 1

30 Freescale Semiconductor

System Modules

TOP

BOT

Comp Comp Out

Zero Detect

R30

13K

D11

R26

R27

R38

N/P

R29

11K

R31

3K9

GND

C9 100nF

1 2

GNDGND

IC2

PTB0/TOP

PTB1/BOT

PTB2/FAULT

PTB3/PWM0

PTB4/PWM1

PTB5/V+

PTB6/V-

PTB7/VOUT/ADC6/FAULT

PTC0/OS C1

PTC1/OS C2

PTC2/SHTDWN/IRQ

MC68HC908LB8-CASE_751D

Serial Da ta

LED

PTA0/ADC0/KBI0 PTA1/ADC1/KBI1 PTA2/ADC2/KBI2 PTA3/ADC3/KBI3 PTA4/ADC4/KBI4

PTA5/RST/KBI5

PTA6/ADC5/TCH0/KBI6

VDD

VSS

1 2 3 4 5 6

GND

CONN/HDR/6X1

JP5

R28

1K8

R33

10K

R260

14 15 16 17 18 19 20

1 2

GND

Serial Data DC B Di v i d er

Tube Cur r en t 1 Tube Cur r en t 2

Tube Vol t age differe nce

C19 100nF

1 2

25V

R39

1 2 3

Luminance Leve l

GND

JP2

Figure 4-5. Dimmable Light Ballast — Microcontroller

NOTE

The Luminance Level potentiometer should be connected to the PCB in the required manner. This means that if the potentiometer is in a zero position, a 0% Luminance is required and 0V must be available on pin 2 of connector JP2.

Table 4-1. J1 Luminance Header

Pin number Signal

1 +5V

2 PTA1

3 GND

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Freescale Semiconductor 31

Hardware Design

Table 4-2. J2 Interface Header

Pin number Signal

1 +5V

2 PTC2

3 PTC0

4 PTA0

5 GND

6 PTA1

Dimmable Light Ballast with Power Factor Correction, Rev. 1

32 Freescale Semiconductor

System Modules

4.2.4 Power Supply

The function of the switch mode power supply (SMPS) is to feed the inverter and output buffer circuit with

V and to supply the microcontroller stage by 5 V (see Table 4-3). The SMPS is supplied from the

15 DC-bus voltage. It uses the monolithic high-voltage regulator NCP1010 from ON Semiconductor connected as recommended by the manufacturer. It can provide 15 power supply from a 15

V source, a step-down resistor R32, 5V1 Zener diode D13, and filtering capacitor

C25 are used.

22uF

35V

C20

1 2

DCB

GND

IC3

VCC

DRAIN

C23

1uF

450V

NCP1010-SOT223

1 2

1nF 25V

C24

GND

D12 MURA160

SFH6106

TL-RAD EZK

4.7mH

D14 BZV55C13

VDC @ 100 mA. To achieve a 5 V

15V 5V

C21

100uF

35V

GND GND

C22 1uF

1 2

25V

15V/1

R32

390R

GND

D13

BZV55C5V1

GND GND

Figure 4-6. Dimmable Light Ballast — Power Supply

Table 4-3. Supplied Voltages

Volt age Supply

+15V Driving stage, Output buffer circuit

+5V Microcontroller stage

C25 220nF

1 2

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Freescale Semiconductor 33

Hardware Design

Dimmable Light Ballast with Power Factor Correction, Rev. 1

34 Freescale Semiconductor

Chapter 5 Software Design

5.1 Introduction

This section describes software features and behavior of the software in all function modes. The software is described in terms of:

• Control Algorithm Description

• Software Implementation

• Detailed Software Description

• Microcontroller Usage

• Constant and Variable Definitions

5.2 Control Algorithm Description

The application performs dimmable light ballast for fluorescent lamp control and PFC control. It uses microcontroller built-in peripherals. current control mode HW variation. Software block diagram for DCM HW variation is not placed because diagram is very similar. As can be seen, the PFC Control and Light Ballast Control are separate routines.

Figure 5-1 shows the high level software block diagram for hysteresis

Figure 5-1. Dimmable Light Ballast with Hysteresis PFC HW Variation — Software Block Diagram

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Freescale Semiconductor 35

Software Design

5.2.1 Power Factor Correction Control

PFC control consists of DC-bus voltage control using the PI controller, phase shift synchronization, reference sine wave generation and generation of output PFC control signals. It also includes the trimming of the internal oscillator frequency according to the frequency of the mains provided.

5.2.1.1 DC-bus Voltage Control

The actual value of the DC-bus voltage is sensed by the AD converter. This value is compared with the required DC-bus value. The regulation error is then the input value for the PI regulator. The output value from the PI regulator is the reference sine wave gain. The PWM module generates a reference sine wave with calculated amplitude. The filtered reference sine wave is compared with the actual current using the on-chip comparator. For the hysteresis current control mode HW variation, the output from the comparator is the switching signal for the PFC MOSFET transistor. For the discontinuous conduction mode HW variation, the output comparator is connected to the PWM fault pin. The PWM1 signal is directly used for switching the PFC MOSFET transistor.

5.2.1.2 Phase Shift Synchronization

Phase shift synchronization synchronizes the generated PFC reference sine wave to the frequency of the mains. It is realized by means of:

• Zero voltage crossing detection (zero voltage sensor) The zero voltage crossing sensor generates a falling edge every time when the input voltage crosses zero from positive to negative polarity.

• External interrupt An external interrupt is triggered by the zero voltage crossing sensor. The interrupt subroutine is used to get the content of timer TIM registers TCNTH:TCNTL for automatic microcontroller trimming and for PFC reference sine wave amplitude gain calculation in lamp run mode.

• MCU oscillator frequency trimming For microcontroller automatic trimming, the timer TIM is used as an interval counter. The timer is incremented by the internal clock (divided by prescaler). Its content is cleared every produced by the voltage zero crossing sensor. A user defined value determines what number should be found in TIM registers TCNTH:TCNTL. On the basis of the comparison between required and actual counter values, the content of the oscillator trim register OSCTRIM is adjusted with ramp.

IRQ interrupt

5.2.1.3 Reference Sine Wave Generation

Reference is performed by the PWM peripheral. The software contains a sine wave table with values for interval and maximum amplitude. The amplitude of the sine wave depends on the value of the DC-bus voltage and it is adjusted by the PI controller every 20ms. Two different sets of PI controller parameters are used, one for MCU startup, when the DC-bus voltage must reach the required value quickly and HRP is not activated, and the second during standard running operation.

5.2.1.4 Generation of Output PFC Control SIgnal

The generated output PFC signal controls the PFC power MOSFET. An on-chip operational amplifier is used in comparator mode. It compares the reference sine wave, filtered by the RC filter, with the actual current and generates a switching signal for the PFC MOSFET transistor in the hysteresis current control mode HW variation. In discontinuous conduction mode comparator output is used for switching off the PWM1 signal. It works as a fault detection in fact. When the actual current sensed on the shunt resistor

Dimmable Light Ballast with Power Factor Correction, Rev. 1

36 Freescale Semiconductor

Control Algorithm Description

is higher than the generated sine waveform, then the comparator output is in log.1 and PWM1 is switched off. This happens every PWM period and this process is called cycle by cycle limiting. PWM1 operates at a 40 kHz frequency with variable duty cycle. For safety reasons, the comparator is enabled when the microcontroller is initialized and mains voltage synchronization is provided.

5.2.2 Light Ballast Control

Light Ballast Control controls the fluorescent tubes. The control process consists of two parts (modes), tube start mode and tube run mode. and run mode.

Figure 5-2 shows the software control time diagram during start mode

Figure 5-2. Dimmable Light Ballast — Control Time Diagram

5.2.2.1 Tube Start Mode

When the DC-bus voltage reaches the required value, the HRP is enabled at maximum ballast frequency and kept for a set time. Then the ballast frequency is ramped down to the preheat frequency and kept for a set time. This procedure preheats the filaments. In the next stage, the ballast frequency is ramped down until the lamps are ignited. During the lamp ignition procedure, the frequency and tube currents are controlled (see Reference [

4]).

5.2.2.2 Luminance Level Control (Tube Run Mode)

Luminance Level Control is active after tube ignition. The actual values of the tube currents are sensed by the AD converter. Average value of currents is compared with required current value after luminance

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Freescale Semiconductor 37

Software Design

level adjustment (brightness linearization). The regulation error is then the input value for the PI regulator. The output value from the PI regulator is the HRP period for half bridge power stage.

Input required luminance level adjustment adapts the required luminance level to its exponential value. This is done because of the nonlinear function dependence of luminance on the lamp current. The transformation table is used. The table contains the required current values.

The values in the table can be calculated using the following expression.

⋅

req

where:

•i

• A is the exponential curve gain

• q is the exponential curve offset

To calculate the coefficients A and q correctly, the following values must be known.

• Minimum HRP frequency f

• Maximum HRP frequency f

• Tube current measurement range i

• Minimum required tube current i

• Maximum required tube current i

• ADC maximum value AD

• ADC minimum value AD

• Minimum required tube current value converted to ADC range i

• Maximum required tube current value converted to ADC range i

• k determines function precision

is the required current in the exponential expression used for the control algorithm calculation

reg

is the required current measured by the AD converter

regAD

reqAD

q+⋅= (EQ 5-1)

min

max

min

tmax

max

min

tADmin

Then:

tADmin

tADmax

This is a time-consuming calculation, but it can be simplified by using the sheet “HRP_Setup” provided in the Excel file “DLB_Setup.xls”. This file can be downloaded along with this designer reference manual.

Dimmable Light Ballast with Power Factor Correction, Rev. 1

round i round i

----------------------------------------------------=

kAD

tADmin

tmin

tmax

tADmaxitADmin

⋅

max

–

kAD

–

kAD

⋅–=

maximax

⋅

min

⋅

⁄ 0;⋅()=

min

(EQ 5-2)

⁄ 0;⋅()=

(EQ 5-3)

(EQ 5-4)

(EQ 5-5)

38 Freescale Semiconductor

Software Implementation

5.3 Software Implementation

The general software implementation is illustrated in Figure 5-3. It incorporates the main routine entered from Reset and three interrupt states. The main routine includes the initialization of the microcontroller including PWM, HRP, ADC, and pins used in the application, and sets initial values for the PI regulator. The infinite loop is performed as long as board remains connected to the mains and no fault conditions are detected.

The interrupt states provide for trimming the internal oscillator, mains synchronization, reference sine wave generation, and fault detection and processing.

OverFlow Interrupt

of Timer, Fault

Interrupt

Fault

Interrupt

Routine

done

RESET

PWM Reload Inte rrupt

done

IRQ Interrupt

done

Sinewave

Generation

Interrupt

Routine

Synchronization

Interrupt

Routine

MCU & Application

Initialization

done

Main

Infinite

Loop

Figure 5-3. Software Implementation

5.3.1 Initialization Setup

Prior to running the main program loop, the initialization setup sets the microcontroller operation mode and peripherals. The quickest way to set and PWM is to use the auxiliary Excel sheet Reference [ achieve the required system behavior and communication with peripherals, the following registers and initial values are set.

• Set configuration registers CONFIG1 and CONFIG2 at the beginning of the initialization; they can be written once only after each reset.

The register CONFIG1 sets: – long COP time-out period – enable LVI module – disable STOP instruction

4]. To

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Freescale Semiconductor 39

Software Design

The register CONFIG2 sets: – internal oscillator – IRQ interrupt enabled – IRQPUD must be 0 to connect the internal pullup resistor between IRQ pin and Vdd.

• IRQ status and control register INTSCR sets: – IMASK enable IRQ interrupt requests – IRQ interrupt on falling edge only

• Analog to digital converter clock register (ADCLK) – sets the ADC clock. ADC clock = bus clock / prescaler. The recommended value for the ADC

clock is 1

MHz.

• PWM setup — void Set_PWM(void) The subroutine initializes PWM values, and sets 0% duty cycle on PWM. For a better understanding of PWM setup and logic, see 5.3.1.1 PWM Setup.

• HRP setup — void Set_HRP(void) The subroutine initializes and sets HRP registers. For a better understanding of HRP setup and logic, see

5.3.1.2 HRP Setup.

5.3.1.1 PWM Setup

The PWM module can generate two independent PWM signals used for PFC control. These signals are edge-aligned. PWM resolution is one clock period which is dependent on the internal bus frequency (BUSCLK) and a programmable prescaler (PRSC0, PRSC1). Also, programmable fault protection and PWM signal polarity controls are provided.

For the application, the PWM is set to 40 kHz, resulting in 101 levels of PWM0 at a 4 MHz bus frequency. Because of the hardware configuration, negative polarity control of the PWM output is required.

For proper operation of the PWM module, the following registers must be set:

• PWM counter modulus registers PMODH and PMODL hold a 12-bit unsigned number that determines the maximum count for the up-only counter. It is set to 100.

• PVAL0H and PVAL0L registers determine duty cycle value (duty cycle = PVAL0/PMOD*100). In initialization phase this is set to 0.

• PCTL1 register controls PWM enabling/disabling, the location of the PWM Fault bit, the loading of

new modulus, prescaler, and PWM values, and the PWM correction method.

In the application, PCTL1 is set as follows: – Fault pin is PTB7 – interrupt is enabled – load new values active – module enabled

• PCTL2 register controls the PWM reload frequency, PWM channel enabling/disabling, the PWM polarity, the PWM correction method, and the PWM counter prescaler. For safety reasons, some of these register bits are buffered. The PWM generator will not use the prescaler value until the

LDOK bit has been set and a new PWM cycle is starting. The load frequency bits are not used until

the current load cycle is complete.

In the application, PCTL2 is set as follows: – PWM0 enabled – PWM1 enabled – PWM0 negative polarity control – reload frequency bits LDFQ0 and LDFQ1 to 0 — reload every PWM cycle

Dimmable Light Ballast with Power Factor Correction, Rev. 1

40 Freescale Semiconductor

Software Implementation

– PWM clock frequency set to BUSCLK by prescaler bits PRSC0 and PRSC1

• DISMAP is a write-once register which controls the PWM pins to be disabled if an external fault

occurs. When this register is written for the first time, it cannot be rewritten unless a reset o ccurs.

PWM0 is not disabled when an external fault appears. PWM1 is disabled if an external fault appears.

• The FCR register controls the fault protection circuitry. A fault does not cause a CPU interrupt in hysteresis current control mode. The fault protection circuitry operates in automatic mode for DCM HW variation. In hysteresis current control mode operates in manual mode.

The PWM frequency is affected by the setup of the internal bus frequency, PWM modulus registers PMODH, PMODL, and the prescaler value in the PRSC0 and PRSC1 registers. Consequently, the PWM frequency is given by the equation:

BusFrequency

PWM Frequency

------------------------------------------------- -

Hz; Hz, -, -[]=

(EQ 5-6)

PMOD PRSC[0:1]×

According to the setting, the PWM frequency is 40 kHz.

5.3.1.2 HRP Setup

The HRP provides two complementary outputs for controlling a half-bridge in a light ballast application. It uses a dithering control method to provide a high step resolution (< 4 ns) from an 8 MHz input clock when driving inductive loads.

For the to operate properly, the HRP registers must be set correctly. The HRP works in variable frequency mode with 50% duty cycle. The output frequency varies from 40 kHz up to 120 kHz, depending on the level of dimming required. The MCU BUSCLKX2 is 8 MHz. The transistors controlling the lamp require a deadtime of 1 µs. The deadtime must be set by software.

Four steps are required to configure the HRP:

1. Set the dithering timebase to the appropriate value

2. Set the deadtime to the appropriate value

3. Set HRPPERH:HRPPERL to select the desired frequency

4. Select variable frequency mode and enable the module

Detailed description follows:

1. Set the dithering timebase to appropriate value:

The dithering timebase is determined by HRPTBH:HRPTBL registers. It should be calculated according to the condition:

Dithering timebase (seconds) >= (1/max ballast frequency) HRPTBH:HRPTBL = (1/max ballast frequency) * BUSCLKX2

In this case, dithering timebase = 1/120 kHz = 8.33 µs For BUSCLKX2 = 8 Mhz, the HRPTBH:HRPTBL = $0054

2. Set deadtime to appropriate value:

The deadtime is defined by HRPDT register. The transistors used in the ballast require 1 µs of deadtime to prevent both being on at the same

time. HRPDT register = required deadtime / (1 /BUSCLKX2)

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Freescale Semiconductor 41

Software Design

For BUSCLKX2 = 8 MHz, the HRPDT= $08

3. Set HRPPERH:HRPPERL to select the desired frequency (e.g. 88 kHz)

The period of 88 kHz = 1/88 kHz Output period (seconds) = HRPPERH:HRPPERL / (BUSCLKX2 * 32) then,

HRPPERH:HRPPERL = 1/88 kHz * (internal bus frequency * 32) = 2909 = $B5D

4. Select variable frequency mode and start the HRP

Writing $01 to the HRPCTRL register configures the module for variable frequency mode (HRPODE = 0) and enables the module (HRPEN = 1).

5.3.2 Main Program Loop

The functions of the main program can be broken down into several chronological phases, as follows:

1. Check required DC-bus voltage

2. Go to maximum ballast frequency

3. Apply maximum ballast frequency for start time

4. Go to preheat frequency

5. Apply preheat frequency for preheat time

6. Go to ignition frequency

7. Run mode

After the initialization stage, the software checks the DC-bus voltage value. When the DC-bus voltage does not reach the required value within the start time or the value is out of limits then the faultISR routine is launched.

In phase 2, the HRP frequency is set to the maximum ballast frequency, and this is maintained for the start time in phase 3.

In phase 4, the HRP frequency is ramped down to the preheat frequency, and this is maintained for the preheat time in phase 5.

In phase 6, the HRP frequency is ramped down to the ignition frequency. If the minimum ballast frequency is reached, then the controller tries again to ignite the lamps. If, in a defined number of attempts, the lamps did not ignite, the ignition is interrupted and the faultISR routine is launched.

Phase 7 is Run mode - a never ending loop. During this phase, the required dimming value is sensed from the dimming level potentiometer. The dimming value is sensed every ADDMININTERVAL. The tube currents are measured every cycle in never ending loop. The ballast frequency is control by PI regulator every 500us according required dimming level sensed from dimming potentiometer.

Dimmable Light Ballast with Power Factor Correction, Rev. 1

42 Freescale Semiconductor

Software Implementation

5.3.3 Synchronization Interrupt Routine

The interrupt procedure is used for trimming the internal oscillator and for synchronization of the phase shift of the reference sine wave with the mains voltage. A detailed illustration of this is shown in

interrupt void IRQisr(void)

Get actual timer value

Stop and reset timer

Run timer

Enable PI PFC stage regulator computing

Enable trimming value calculation

Figure 5-4.

Reset sine wave table pointer

Clear IRQ flag

End of subroutine

Figure 5-4. Flow Chart — Synchronization Interrupt Routine

5.3.4 Sine Wave Generation Interrupt Routine

The PWM modulator is used to generate the reference sine wave for PFC control. The amplitude of generated sine wave depends on output DC-bus voltage and it is calculated by means of PI regulator. The phase shift of the sine wave is synchronized by means of voltage zero crossing detector. The table bSinTab[PWM_RELOADS] contains duty cycle values for PWM. These values can be calculated by means of worksheet PWM_Setup of the file DLB_Setup.xls (see Reference [4]). For service PWM reload interrupt the pwmISR() routine is used (see Figure 5-5). Moreover, inside the PWM, a counter generates a reload interrupt signal every 1 ms. This interval is used for software timing.

IRQ interrupt that is launched by input AC

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Freescale Semiconductor 43

Software Design

interrupt void pwmISR(void)

Read new (PWM value from table * sineGain)

Increment of table index

Was end of sine tab. reached ?

yes

Table index = 0

Increment 500us counter

yesHas 500us gone ?

Enable PI ballast stage regulator comp uting

Increment 1ms counter

Reset LDOK to enable new PWM reload

and clear reload flag

End of subroutine

and reset 500us counter

yesHas 1ms gone ?

Set 1ms flag and reset 1ms counter

Figure 5-5. Flow Chart — Sine Wave Generation Interrupt Routine

Dimmable Light Ballast with Power Factor Correction, Rev. 1

44 Freescale Semiconductor

Software Implementation

5.3.4.1 Fault Detection and Processing

The following application faults are detected by the software:

• DC-bus under voltage

• DC-bus over voltage

• Failure of the DC-bus voltage to reach the required value within the start time

• Zero current fault

• Ignition fault

• COP overflow

A zero current fault launches the faultISR routine when one of the tube currents is zero during the zero current checking interval in run mode for the specified time.

An ignition fault launches the faultISR routine when the lamps do not ignite within a specified number of attempts.

All these fault states are serviced by the following fault service routines:

• timovISR() — services interrupts from TIM

• faultISR() — services HRP fault interrupts and all other faults

The timovISR routine is launched when the COP counter overflows (this occurs when the correct input voltage is missing). The timovISR routine calls the faultISR routine (see

Figure 5-6).

The faultISR routine serves all fault states. It disables all interrupts, stops PWM, HRP, TIM, CM (see the flow chart in

Figure 5-6). The fault state is indicated by the fault diode blinking in a never ending loop.

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Freescale Semiconductor 45

Software Design

interrupt void timovISR(void)

interrupt void faultISR(void)

Disable all interrupts

Stop timer and enable timer overflow interrupts

Stop HRP

Disconnect internal comparator from pins

Set Vout(PTB7) pin as an output and set it to log. 1

and powered off

Stop PWM

Blink fault diode

Figure 5-6. Flow Chart — timovISR and faultISR

5.4 Detailed Software Description

This section provides a detailed graphical description of the software. It explains each particular part of the application software in detail.

Dimmable Light Ballast with Power Factor Correction, Rev. 1

46 Freescale Semiconductor

RESET

Detailed Software Description

Set PWM0 (PTB3), set PWM1 (PTB4), Vout (PTB7)

and fault diode (PTA5) pins as outputs and set

Set configuration registers CONFIG1, CONFIG2

Set IRQ register (INTSCR): falling edge,

Wait for a moment to stabilize internal oscillator

- reset sine tab. pointer

- PMOD = PWM_MODULUS

- PVAL0 = 0, PVAL1 = 0;

- PCTL2 - reload cycles PWM prescaler, negati ve polarity, disable PWM1, enable PWM0

- DISMAP - disable PWM1 if ext.fault occurs // result 0000 0010=0x02

- FCR - disable fault interrupt, set manual or automatic fault mode according HW variation

- PCTL1 - set fault pin bit, enable PWM int.,clear

PWM reload flag, clear LDOK,

enable PWM module

them to log. 1

enable IRQ interrupt request

Disable all interrupts

Set PWM :

Disable PI PFC stage regulator calculation

Enable all interrupts

Set values of PI PFC stage regulator for sta rt PFC :

- integralPortionK_1 = 0;

- sineGain = 0;

Set values of PI ballast stage regulator :

- proportionalGainI = PI_KP_RUNI;

- integralGainI = PI_KI_RUNI;

- integralPortionK_1I = 0;

Microcontroller and application setup

Reset DC-BUS voltage variable

Enable comparator module and powered on

Reset current values

Set value of PI PFC stage regulator for start PFC :

- integralPortionK_1 = 0;

- HRPCTRL - disable HRP

- HRPDCR - set dual freq. generator as a clock

for HRP and set divide ratio

- HRPTBH,HRPTBL- set time base

- HRPPER - set maximum ballast frequency

- HRPDT- set deadtime

- HRPCTRL - disable SHTDWN pin

disable SHTDWN interrupt enable TOP,BOT pins set HRP frequency mode

Set nr. of attemps (currFltCNT) when

zero current fault appears during run mode

Set nr. of attemps (ignitFltCNT) when

Set HRP :

Set ADC clock prescaler

ignition is unsuccesful

Figure 5-7. Flow Chart — Main Flow, Part 1

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Set values of PI PFC stage regulator for sta rt PFC :

- proportionalGain = PI_KP_START;

- integralGain = PI_KI_START;

Measure DC-BUS voltage

Enable PI PFC stage regulator calculation

Microcontroller and

application setup

Freescale Semiconductor 47

Software Design

Measure DC-BUS voltage

Is DCM HW variation selected ?

yes

PVAL1 = DUTY_CYCLE_MAX;

Actual DC-BUS voltage < DC-BUS

Increment required DC-BUS voltage by ramp step

start voltage ?

yes

Is enabled PI PFC stage

regulator calculation ?

yes

voltage

Actual DC-BUS vo ltage >

maximum allowed DC-BUS

voltage ?

phase 1 - Reach DC-bus

voltage

Required DC-BUS voltage = DC-BUS run voltage

Set maximum ballast frequency and time interval

Has time interval for keep maximu m

Enable HRP

frequency gone ?

yes

faultISR()

Required DC-BUS voltage > DC-BUS

Required DC-BUS voltage = DC-BUS start voltage

Calculate PI PFC stage regulator for

phase 1 - Reach DC-bus

voltage

start voltage ?

yes

reference sine gain

Has start time gone ?

Figure 5-8. Flow Chart — Main Flow, Part 2

Dimmable Light Ballast with Power Factor Correction, Rev. 1

yes

faultISR()

yes

Is enabled PI PFC stage

regulator calculation ?

yes

Calculate PI PFC stage regulator for

reference sine gain

Test DC-BUS voltage on limits

phase 2 - Keep maximum

frequency

48 Freescale Semiconductor

Detailed Software Description

yes

Is preheat frequency reached?

Has 1ms gone?

yes

Decrement ballast frequency by ramp step

Calculate PI PFC stage regulator

Test DC-BUS voltage on limits

frequency

for reference sine gain

Has preheat time gone?

phase 3 - Go to preheat

frequency

yes

Has 1ms gone?

yes

Decrement ballast frequency by ramp step

Is min. ignition frequency reached?

Calculate PI PFC stage regulator

Test DC-BUS voltage on limits

frequency

Set ballast frequency

for reference sine gain

Measure lamp currents

frequency

faultISR()

Calculate PI PFC stage regulator

for reference sine gain

Test DC-BUS voltage on limits

phase 4 - Keep for

Is attemp to ignite > 0 ?

yes

Set maximum ballast frequency

Figure 5-9. Flow Chart — Main Flow, Part 3

Dimmable Light Ballast with Power Factor Correction, Rev. 1

preheat time

yes

Are currents through lamps >

minimum tube current ?

Reset auxiliary variable aux

Are lamps ignited?

yes4

Are lamps ignited?

phase 5 - Go to ignition

yes

1no

Freescale Semiconductor 49

Software Design

Run mode

Set Dimming value and Dimming value array

Set zero current checking interval counter

Set values of PI PFC stage regulator for run mode:

- proportionalGain = PI_KP_RUN;

- integralGain = PI_KI_RUN;

to minimal value

(currFltMS)

yes

Measure lamp currents

Test DC-BUS voltage on limits

Is enabled PI PFC stage

regulator calculation ?

Has 1ms gone?

yes

Is time to measure Dimming value ?

yes

Get dimming value and compute moving avg. filter

Is current through Tube1

or Tube2 zero ?

Reset current checking interval counter

yes

Calculate PI PFC stage regulator

for reference sine gain

Is enabled PI ballast stage

regulator calculation ?

yes

Control lamp currents

Figure 5-10. Flow Chart — Main Flow, Part 4

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Has zero current checking

interval gone?

Trimming internal oscillator

Is attemp to start > 0 ?

faultISR()

yes

50 Freescale Semiconductor

Microcontroller Usage

5.5 Microcontroller Usage

5.5.1 Microcontroller Peripheral Usage

5.5.1.1 High Resolution PWM (HRP)

The HRP controls the ballast half-bridge power stage. The module is configured for frequency mode (constant 50% duty cycle, variable frequency, deadtime). For setting up the module, the worksheet HRP_Setup in file DLB_Setup.xls can be used (see Reference [

5.5.1.2 Pulse-Width Modulator (PWM)

The PWM modulator is used to generate the reference sine wave for PFC control by PWM signal. The PWM1 signal is used only in the discontinuous conduction mode HW variation to directly switch the PFC switch transistor. For service PWM reload interrupt the pwmISR() routine is used (see

5.5.1.3 Comparator Module (CM)

The comparator module is used to compare the reference sine wave signal for PFC control with the actual current value. The result is the control signal for the PFC power MOSFET transistor in the hysteresis current control mode HW version. In the DCM HW version the comparator output is used for switching off the PWM1 signal.

4]).

Figure 5-5).

5.5.1.4 Timer Interface Module (TIM)

Since an internal oscillator is used and its features do not guarantee constant frequency, this module is used to automatically trim the internal oscillator to the base of frequency of the mains voltage supply (PLL). The timer counts the time between two zero input voltage detections (

IRQ); the resulting timer content is compared to the expected value, and the trimming register is adjusted accordingly (see

Figure 5-4).

5.5.1.5 External Interrupt (IRQ)

The external interrupt is active on pin IRQ. The interrupt procedure is used for trimming the internal oscillator and synchronizing the phase shift of the reference sine wave with the mains voltage. The IRQisr() routine is used to service the

IRQ interrupt.

5.5.2 Program and Data Memory Usage

Table 5-1 shows the memory that is used by the software. A significant part of the memory remains

available.

Table 5-1. Memory Usage

Memory Available on LB8 Used

ROM 8192 Bytes 3010 Bytes

RAM 128 Bytes 40 Bytes

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Freescale Semiconductor 51

Software Design

5.5.3 I/O Usage

Table 5-2 summarizes the use of the I/O pins.

Table 5-2. I/O Usage

I/O pin Direction Purpose

PTC0/OSC1 INPUT OSC1(EXTERNAL OSCILLATOR IN MONITOR MODE)

PTC1/OSC2 - UNUSED

PTC2/SHTDWN/IRQ INPUT

PTB0/TOP OUTPUT TOP (HRP OUTPUT)

PTB1/BOT OUTPUT BOT (HRP OUTPUT)

PTB2/FAULT - UNUSED

PTB3/PWM0 OUTPUT PWM0 (REFERENCE SINUS WAVE GENERATING)

PTB4/PWM1 OUTPUT SWITCHING PFC TRANSISTOR ONLY IN DCM HW VARIATION

PTB5/V+ INPUT V+ (COMPARATOR INPUT)

PTB6/V- INPUT V- (COMPARATOR INPUT)

PTB7/VOUT/ADC6/FAULT OUTPUT

PTA0/ADC0/KBI0 INPUT/OUTPUT

PTA1/ADC1/KBI1 INPUT ADC1 (LUMINANCE LEVEL /PTA1 IN MONITOR MODE)

PTA2/ADC2/KBI2 INPUT ADC2 (DC-BUS VOLTAGE)

PTA3/ADC3/KBI3 INPUT ADC3 (TUBE CURRENT 1)

PTA4/ADC4/KBI4 INPUT ADC4 (TUBE CURRENT 1

IRQ (MAINS ZERO CROSSING DETECTION/ IRQ IN MONITOR

MODE)

VOUT (COMPARATOR OUTPUT) AND MOREOVER AS PWM

FAULT PIN IN DCM HW VARIATION

PTA0 (COMMUNICATION PIN IN MONITOR MODE AND FOR

SERIAL BOOTLOADER PROGRAMMING)

PTA5/RST/KBI5 OUTPUT PTA5 (USER LED)

PTA6/ADC5/TCH0/KBI6 INPUT ADC5 (TUBE VOLTAGE DIFFERENCE

The installation CodeWarrior Version 3 Service Pack for LB8 is part of the Emulation Board software. This includes examples of how to tune and work with the HRP.

5.6 Definitions of Constants and Variables

This section provides definitions of the constants and variables used in the program. The definitions can be divided into two parts:

• System setup definitions

• System constants and variables

Dimmable Light Ballast with Power Factor Correction, Rev. 1

52 Freescale Semiconductor

Definitions of Constants and Variables

5.6.1 System Setup Definitions

The following constants can be used to set up the system behavior, according to required conditions.

1. #define HW_VAR HYST

...defines HW variation - hysteresis current control mode (HYST) or discontinuous conduction mode (DCM).

2. #define INP_VOLT U110V

...defines input voltage lower (U110V) or higher (U230V) than half of DC-bus voltage.

3. #define INPVOLTFREQ 50

...defines the mains voltage frequency as 50 Hz or 60 Hz.

4. #define BUSCLK 4000000

...sets the internal bus frequency to 4 MHz.

5. #define BUSCLKX2 8000000

...set according to the internal bus frequency (BUSCLKX2=2*BUSCLK).

6. #define TIMPRSC 2

...sets BUSCLK/4 as a TIM clock source.

7. #define PWM_MODULUS 100 /*see DLB_setup.xls */

...represents the number of possible PWM duty cycles from 0% to 100% duty cycle.

8. #define PWM_RELOADCYCLES 4 /*see DLB_setup.xls */

...defines that PWM values are reloaded every 4th PWM cycle.

9. #define PWM_RELOADS 100 /*see DLB_setup.xls */

...represents the PWM reload period.

10. #define PWM_PRESCALER 1 /*see DLB_setup.xls */

...sets BUSCLK as a PWM clock frequency.

11. #define PWM_START_POINTER 97

...represents a start pointer to a value in table bSinTab[].

12. #define DUTY_CYCLE_MAX 99

...represents a maximum allowed duty cycle value according input voltage and frequency.

13. #define HRP_SCALINGFACTOR 32 /*see DLB_setup.xls */

...sets the scaling factor for the HRP.

14. #define HRPTB_H 0X00 /*see DLB_setup.xls */

...represents the HRP time base high byte.

15. #define HRPTB_L 0X43 /*see DLB_setup.xls */

...represents the HRP time base low byte.

16. #define HRP_DEADTIME 0X08 /*see DLB_setup.xls */

...defines the HRP deadtime.

17. #define MAX_HRP_FREQ 120 /*see DLB_setup.xls */

...defines the maximum HRP frequency in kHz.

18. #define MAX_HRP_FREQ_TIME 20

...defines the time spent at maximum HRP frequency in ms.

19. #define MIN_HRP_FREQ 40 /*see DLB_setup.xls */

...defines the minimum HRP frequency in kHz.

20. #define PREHEAT_FREQ 86

...defines the preheat HRP frequency in kHz.

21. #define PREHEAT_TIME 900

...defines the time spent at preheat HRP frequency in ms.

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Freescale Semiconductor 53

Software Design

22. #define MIN_IGNITION_FREQ 45

...defines the minimum HRP frequency in kHz.

23. #define MAX2PREHEAT_RAMP 100

...represents the number of frequency steps between the maximum HRP frequency and the preheat HRP frequency.

24. #define IGNITION_RAMP 2000

...represents the number of frequency steps between preheat HRP frequency and ignition HRP frequency.

25. #define MIN_RUN_HRP_FREQ 50 /*see DLB_setup.xls */

...defines the minimum HRP frequency in kHz during run mode.

26. #define MAX_RUN_HRP_FREQ 100 /*see DLB_setup.xls */

...defines the maximum HRP frequency in kHz during run mode.

27. #define TUBE_CURR_MIN 10 /*see DLB_setup.xls */

...represents the minimum tube current.

28. #define TUBE_CURR_MAX 245 /*see DLB_setup.xls */

...represents the maximum tube current.

29. #define CURRFLT_MS 100

...sets the zero current checking interval in ms.

30. #define CURRFLT_CNT 3

...represents the number of fault states during run mode.

31. #define INGITION_CNT 3

...represents the number of fault states during tube ignition.

32. #define ADDMINITERVAL 100

...represents the interval of dimming value measurement in ms.

33. #define UC_REQUIRED_AN 390L

...represents the required DC-bus voltage in V.

34. #define UC_ALLOWED_MIN_AN 290L

...represents the minimum allowed DC-bus voltage in V.

35. #define UC_ALLOWED_MAX_AN 450L

...defines the maximum allowed DC-bus voltage in V.

36. #define UC_MAX_VAL_AN 458L

...represents the maximum value of the DC-bus voltage in V.

37. #define UC_START_PREHEAT_AN 370L

...represents the preheat DC-bus voltage in V.

38. #define UC_START_CYCLES_MAX 50

...represents the interval in ms in which the DC-bus voltage must reach the required value.

39. #define UC_START_RAMP_STEPS 30

...represents the number of steps needed to reach the DC-bus required value from the zero value.

40. #define PI_KP_START 10

...represents the proportional gain of the PI PFC stage regulator in the start phase.

41. #define PI_KI_START 3

...represents the integral gain of the PI PFC stage regulator in the start phase.

42. #define PI_KP_RUN 2

...represents the proportional gain of the PI PFC stage regulator in run mode.

43. #define PI_KI_RUN 1

Dimmable Light Ballast with Power Factor Correction, Rev. 1

54 Freescale Semiconductor

Definitions of Constants and Variables

...represents the integral gain of the PI PFC stage regulator in run mode.

44. #define PI_SCALE 0

...represents the scaling factor of the PI PFC stage regulator (2^scale).

45. #define PI_MIN_VAL 0

...represents the minimum value of the PI PFC stage regulator output.

46. #define PI_MAX_VAL 255

...represents the maximum value of the PI PFC stage regulator output.

47. #define PI_KP_RUNI 2

...represents the proportional gain of the PI ballast stage regulator in run mode.

48. #define PI_KI_RUNI 1

...represents the integral gain of the PI ballast stage regulator in run mode.

49. #define PI_SCALEI 0

...represents the scaling factor of the PI ballast stage regulator (2^scale).

5.6.2 System Constants and Variables

This section describes the external global variables and constants used in the program.

1. extern tSW_FLAGS SW_FLAGS;

This variable represents auxiliary program control flags and is defined as:

typedef union uSW_FLAGS

{tU08byte; struct { tU08 pi_en 1;// - bit enables or disables PI PFC stage regulator calculation tU08 trim_comp_en :1;// - bit enables or disables trimmable value of internal

oscillator calculation

tU08 f_1_ms: 1;// - bit represents if 1 ms time interval has gone tU08 pi_eni :1;// - bit enables or disables PI ballast stage regulator calculation tU08: 4;// - the others five bits are not used }bit; }tSW_FLAGS;

2. extern tU08 pwm_sin_tab_pointer;

This variable acts as a pointer to a value in table bSinTab[].

3. extern tU08 m_avg_Dim[8];

This buffer saves the last eight AD conversion values of the required dimming value, for moving average calculations.

4. extern tU08 p_m_avg_Dim;

This variable acts as a pointer to a value in the m_avg_Dim[8] array.

5. extern tU16 m_avg_sum_Dim;

This variable represents the sum of all values in the m_avg_Dim[8] array.

6. extern tU08 act_Uc;

This variable represents the actual value of the DC-bus voltage.

7. extern tU08 time1ms;

This variable counts PWM interrupts. The variable is incremented at every PWM interrupt. It is used

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Freescale Semiconductor 55

Software Design

for timing 1 ms intervals.

8. extern tU08 curr_T1;

This variable represents the current in tube 1.

9. extern tU08 curr_T2;

This variable represents the current in tube 2.

10. extern tU08 avg_CurrentT1T2;

This variable represents the average value of the tube currents.

11. extern tU16 mscounter;

This variable counts 1 ms intervals. It is incremented every 1 ms. It is used for application timing.

12. extern tU08 sineGain;

This variable represents the gain of the reference sine waveform.

13. extern tU16 timCntVal;

This variable represents an auxiliary variable used to get the timer value required to trim the internal oscillator to the reference frequency (frequecy of mains * 2)

14. extern tU08 aux;

This variable represents an auxiliary variable.

15. extern tU16 ramp;

This variable represents an auxiliary variable (HRP frequency) for dimming by ramping.

16. extern tU08 currFltCNT;

This variable represents the number of fault states occurring during run mode.

17. extern tU08 currFltMS;

This variable counts the zero current checking interval. It is incremented every 1 ms.

18. extern tU08 ignitFltCNT;

This variable represents the number of fault states occurring during tube ignition.

19. extern tU16 integralPortionK_1;

This variable represents integral n-1 value of the PI PFC stage regulator.

20. extern tU08 proportionalGain;

This variable represents proportional gain of the PI PFC stage regulator.

21. extern tU08 integralGain;

This variable represents integral gain of the PI PFC stage regulator.

22. extern tU08 uCreq;

This variable represents the required value of the DC-bus voltage.

23. extern tU16 integralPortionK_1I;

This variable represents integral n-1 value of the PI ballast stage regulator.

24. extern tU08 proportionalGainI;

This variable represents proportional gain of the PI ballast stage regulator.

25. extern tU08 integralGainI;

This variable represents integral gain of the PI ballast stage regulator.

26. extern tU08 req_Cur;

This variable represents the actual value of the required dimming value.

27. extern tU08 time500us;

This variable counts PWM interrupts. The variable is incremented at every PWM interrupt. It is used for timing 500

us intervals.

Dimmable Light Ballast with Power Factor Correction, Rev. 1

56 Freescale Semiconductor

Chapter 6 Demo Setup

WARNING This circuit is powered directly from the mains voltage supply. It is dangerous to touch any part of the circuit. When working with such circuits, do not connect any scope or development system without using an isolation transformer.

6.1 Hardware Setup

This section describes the setup and operation of the light ballast demo. Since the tubes are an integral part of the application, the whole demo system is considered. A photograph of the demo is shown in

Figure 1-1. No hardware setup is required to run the application. If you wish to debug the application using

Monitor Mode, you must take apart the plexi glass, disconnect the light ballast from the mains supply, and connect the Monitor Mode connector to header JP5. In this case the light ballast must be supplied with a DC-bus voltage.

NOTE

The dimming level potentiometer must be set to the correct position for entry to Monitor Mode (pin PTA1 must be at logic level 1).

The dimming level potentiometer is connected to the JP2 header.

6.2 Software Setup

6.2.1 Required Software Tools

Metrowerks CodeWarrior for MC68HC08 microcontrollers version 3.0, or later, is required for developing the application.

6.2.2 Building and Uploading the Application

The application software is delivered as DLB-LB8-001.mcp project file (see Reference [5]) with C-sources and header files.To build the application software, open the DLB-LB8-001.mcp project file. Set definition lines at the beginning of “dlb_program_config.h” file as described in execute the Make command in the Project menu. This will build and link the application and all required Metrowerks libraries. Using Metrowerks CodeWarrior, the executable s19 file will be created. There are six possible versions of s19 file, which are also delivered as part of the software package.

The following SW versions are available:

• Hysteresis current control mode for 50 Hz— Hyst50Hz.s19

• Hysteresis current control mode for 60 Hz — Hyst60Hz.s19

• Discontinuous conduction mode for 50 Hz and for input voltage lower than half of DC-Bus voltage — DCM50HzL.s19

5.6.1 System Setup Definitions. Then

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Freescale Semiconductor 57

Demo Setup

• Discontinuous conduction mode for 50 Hz and for input voltage higher than half of DC-Bus voltage — DCM50HzH.s19

• Discontinuous conduction mode for 60 Hz and for input voltage lower than half of DC-Bus voltage — DCM60HzL.s19

• Discontinuous conduction mode for 60 Hz and for input voltage higher than half of DC-Bus voltage — DCM60HzH.s19

For reprogramming the microcontroller you have the choice of serial bootloader or MON08 Cyclone. In the case of the serial bootloader, the bootloader must be programmed into the MCU before uploading the software application to the MCU by the MON08 Cyclone. After that, reprogramming the application is quicker than reprogramming by the MON08 Cyclone. For a detailed description of the bootloader functionality, refer to the application note in Reference [

6]. For a detailed description of the MON08

Cyclone functionality, refer to the application note in Reference [2].

6.2.3 Executing the Application

The application is ready for operation when connected to a power supply.

6.2.4 Project Files

The dimmable light ballast application comprises the following files:

• ...\DLB-LB8-001.mcp, application project file

• ...\prm\P&E_FCS_linker.prm, linker program file

• ...\Sources\Start08.c, startup code for 68HC08 core

• ...\Sources\MC68HC908LB8.h, MC68HC908LB8 registers and bits definitions header file

• ...\Sources\MC68HC908LB8.c, MC68HC908LB8 register and bits definition file

• ...\Sources\ram.h, RAM global variables declaration header file

• ...\Sources\ram.c, RAM global variables definition file

• ...\Sources\dlb_macros.h, application macros definition header file

• ...\Sources\dlb_program_config.h, program and LB8 setup definitions header file

• ...\Sources\dlb_constants.h, tables of constant values header file

• ...\Sources\dlb_ISR_bodies.h, program interrupt service routines header file

• ...\Sources\pi_types.h, definitions header file for PI regulators

• ...\Sources\pi_sdkmath.asm, basic mathematical functions asm file

• ...\Sources\pi_sdkmath.h, basic mathematical functions definition header file

• ...\Sources\pi_sdkmath.c, basic mathematical functions file

• ...\Sources\pi_controller.h, PI regulators header file

• ...\Sources\pi_controller.c, PI regulators file

• ...\Sources\code_fun.h, functions declaration header file

• ...\Sources\code_fun.c, functions definition file

• ...\Sources\main.c, main program

Dimmable Light Ballast with Power Factor Correction, Rev. 1

58 Freescale Semiconductor

Appendix A. Schematics and Part List

A.1 Schematics

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Freescale Semiconductor 59

PM100-INP_CONN-6

PFC Current Sense

C1 10nF 275V X2

1 2

4n7 250/1000V Y2

R14

1 4

2 3

GND

2K0

GND

CMFIL2

R11 3K0

C8 82pF

Comp -

2.7mH

L1 PFCIND3

1 4

R9 47K

PFC Gate

1 2

R4 2R7

PFC Current Sense

Zero Detect

C27 1n5

GND

R10 6K8

R13

620R

GND

MMBF0201

DC+

DC-

D15 BAT48

D2 BZV55C5V6

150nF 275V X2

GND

R12 10K

DF1510S

GND

R3 220K

R5 220K

R7 220K

AC2

AC1

GND

C10 220nF

Comp Out

RV1 275V

GND

7 53

15V

C7 100nF

BEQ2

BCQ3

GND

MURS160T3

SPP04N60S5

R35 0R

R36

R34 0R

BC846B

BC856B

10nF 630V TC356

R37

PFC Gate

15V/1

GND

C4 22uF 450V

C6 100nF

JP6

1 2

DCB

R1 560K

R2 560K

R6 510K

DCB Divider

R8 18K

GNDGND

CONN/HDR/2X1

GND

Figure A-1. Input and PFC for hysteresis current control mode HW variation

PM100-INP_CONN-6

PFC Current Sense

C1 10nF 275V X2

1 2

4n7 250/1000V Y2

R14

1 4

2 3

GND

2K0

GND

CMFIL2

R11 3K0

C8 82pF

Comp -

2.7mH

L1 PFCIND3

1 4

R9 47K

PFC Gate

1 2

R4 2R7

PFC Current Sense

Zero Detect

C27 1n5

GND

R10 6K8

R13

620R

GND

MMBF0201

DC+

DC-

D15 BAT48

D2 BZV55C5V6

150nF 275V X2

GND

DF1510S

GND

R3 220K

R5 220K

R7 220K

AC2

AC1

GND

C10 220nF

PWM1

RV1 275V

GND

C7 100nF

7 53

15V

GND

MURS160T3

SPP04N60S5

R35 0R

R34 0R

Q2 BC846B

Q3 BC856B

R36

10nF 630V TC356

R37

PFC Gate

15V/1

GND

C4 22uF 450V

C6 100nF

JP6

1 2

DCB

R1 560K

R2 560K

R6 510K

DCB Divider

R8 18K

GNDGND

CONN/HDR/2X1

GND

Figure A-2. Input and PFC for discontinuous conduction mode HW variation

DCB

TOP BOT

15V/1

1 2

MURA160

1 2 3

C13 1uF

25V

R15

10R

IC1

Vcc HIN LIN COM4LO

IR2106

Tube Voltage difference

R16

R18

IRF830A

33R

C11 100nF

33R

IRF830A

J2 TUBE Connector

O11O22O33O44O55O66O77O8

C26

GND

C17 6n8

GND

10nF 630V TC356

GND

C28 470pF 1KV

1 3

C14 470pF 1KV

D8 BAT48

R22

30K

L7 RES5

1mH

R151

C12

100nF 630V

1 2

8n2 1KV

C15

GND

BZG05C22

L3D DIFF8

1 8

L3A DIFF8

BZG05C22

R21

3K3

R24

N/P

L3BDIFF8

GND

2 7

L4B HEAT7

1 2

R17 10K

L5B HEAT6

L4C HEAT7

GND

6 5

3 4

L4D

L5C

HEAT7

HEAT6

GND

R23 20R

0.5W

R19 20R

0.5W

GND

R150

D10 MBRS140

1 2

L5D HEAT6

D9 BAT48

D6 BAT48

C18 22nF

R152

D7 MBRS140

1 2

Tube Current 1

C16 22nF

Tube Current 2

R25

10K

R20

10K

Figure A-3. Inverter

GND

D11

R28

TOP

BOT

Comp Comp Out

Zero Detect

R30

13K

R26

R27

R38

R29

11K

R31

3K9

N/P

1 2

GND

C9 100nF

IC2

PTB0/TOP

PTB1/BOT

PTB2/FAULT

PTB3/PWM0

PTB4/PWM1

PTB5/V+

PTB6/V-

PTB7/VOUT/ADC6/FAULT

PTC0/OSC1

PTC1/OSC2

PTC2/SHTDWN/IRQ

MC68HC908LB8-CASE_751D

Serial Data

LED

PTA0/ADC0/KBI0 PTA1/ADC1/KBI1 PTA2/ADC2/KBI2 PTA3/ADC3/KBI3 PTA4/ADC4/KBI4

PTA5/RST/KBI5

PTA6/ADC5/TCH0/KBI6

VDD

VSS

2 3 4 5 6

1K8

14 15 16 17 18 19 20

1 2

GND

JP5

CONN/HDR/6X1

R33

10K

R260

Serial Data DCB Divider

Tube Current 1 Tube Current 2

Tube Voltage difference

C19 100nF

1 2

25V

C29 150nF

1 2

GND1

R39

JP2

1 2 3

Luminance Level

GND

GNDGND

GND

Figure A-4. Microcontroller for hysteresis current control mode HW variation

TOP

BOT

PWM1 Comp -

Zero Detect

R30

R12

10K

13K

R26

R27

R38

R29

11K

R31

3K9

N/P

1 2

GND

C9 100nF

IC2

PTB0/TOP

PTB1/BOT

PTB2/FAULT

PTB3/PWM0

PTB4/PWM1

PTB5/V+

PTB6/V-

PTB7/VOUT/ADC6/FAULT

PTC0/OSC1

PTC1/OSC2

PTC2/SHTDWN/IRQ

MC68HC908LB8-CASE_751D

Serial Data

D11

LED

PTA0/ADC0/KBI0 PTA1/ADC1/KBI1 PTA2/ADC2/KBI2 PTA3/ADC3/KBI3 PTA4/ADC4/KBI4

PTA5/RST/KBI5

PTA6/ADC5/TCH0/KBI6

R28

1K8

14 15 16 17 18 19 20

VDD

VSS

GND

JP5

1 2 3 4 5 6

CONN/HDR/6X1

R33

10K

R260

Serial Data DCB Divider

Tube Current 1 Tube Current 2

Tube Voltage difference

C19 100nF

1 2

25V

C29 150nF

1 2

GND

R39

1 2 3

Luminance Level

GND

JP2

GNDGND

GND

Figure A-5. Microcontroller for discontinuous conduction mode HW variation

DCB

GND

22uF

35V

C20

1 2

D12 MURA160

SFH6106

TL-RAD EZK

4.7mH

GND GND

D14 BZV55C13

15V 5V

C21

100uF

35V

C22 1uF

1 2

25V

15V/1

R32

390R

IC3

VCC

DRAIN

NCP1010-SOT223

C23

1uF

450V

C24

1 2

1nF 25V

GND

Figure A-6. Power supply

D13

BZV55C5V1

1 2

GND GND

C25 220nF

A.2 Parts List

Table A-1. Printed Circuit Board Parts List

DESIGNATORS QUANTITY DESCRIPTION MANUFACTURER PART NUMBER

C1 1 10nF/275V X2 ANY ACCEPTABLE C2 1 150nF/275V X2 ANY ACCEPTABLE -

C3,C26 2 10nF/630V TC356 ANY ACCEPTABLE -

C4 1 22 µF/450V ANY ACCEPTABLE C5 1 4.7nF 250/1000V ANY ACCEPTABLE -

C6,C7,C9,C11,C19 5 100nF ceramic 0805 ANY ACCEPTABLE -

C8 1 82pF ceramic 0805 ANY ACCEPTABLE -

C10,C25 2 220nF ceramic 0805 ANY ACCEPTABLE -

C12 1 100nF/630V ANY ACCEPTABLE C13,C22 2 1µF ANY ACCEPTABLE C14,C28 2 470pF/1000V ANY ACCEPTABLE -

C15 1 8.2nF/1000V ANY ACCEPTABLE C16,C18 2 22nF ceramic 0805 ANY ACCEPTABLE -

C17 1 6.8nF ceramic 0805 ANY ACCEPTABLE -

C20 1 22µF/35V ANY ACCEPTABLE -

C21 1 100µF/35V ANY ACCEPTABLE -

C23 1 1µF/450V ANY ACCEPTABLE -

C24 1 1nF ceramic 0805 ANY ACCEPTABLE -

C27 1 1.5nF ceramic 0805 ANY ACCEPTABLE -

D1 1 1A/600V Ultrafast Rectifier/SMA

D2 1 Zener ANY ACCEPTABLE BZV55C5V6

D3,D12 2 SMB

D4,D5 2 VISHAY BZG05C22

D6,D8,D9,D15 4 VISHAY BAT48

D7,D10 2 SMB

D11 1 Red Display LED ANY ACCEPTABLE -

D13 1 Zener ANY ACCEPTABLE BZV55C5V1

D14 1 Zener ANY ACCEPTABLE BZV55C13

IC1 1 Power MOSFET Driver/SOIC8

IC2 1 Microcontroller/SOIC20 FREESCALE MC68HC908LB8

IC3 1 SMPS Controller/SOT-223

JP2 1 HEADER 3X1 ANY ACCEPTABLE -

JP5 1 HEADER 6X1 ANY ACCEPTABLE -

J1 1 CONN-6 ANY ACCEPTABLE J2 1 CONN-8 ANY ACCEPTABLE L1 1 2.7mH CUSTOMS -

L3 1

L4 1

L5 1

L6 1 L6A - 90mH, L6B - 90mH CUSTOMS -

L3A - 16.6mH, L3B - 9.5µH,L3C -

9.5µH,L3D - 16.6mH

L4A - 80µH, L4B - 130µH,L4C -

150µH,L4D - 150µH

L5A - 80µH, L5B - 130µH,L5C -

150µH,L5D - 150µH

SEMICONDUCTOR

INTERNATIONAL

RECTIFIER

CUSTOMS -

MURS160T3

MURA160

MBRS140

IR2106

NCP1010

Dimmable Light Ballast with Power Factor Correction, Rev. 1

66 Freescale Semiconductor

Table A-1. Printed Circuit Board Parts List (Continued)

DESIGNATORS QUANTITY DESCRIPTION MANUFACTURER PART NUMBER

L7 1 1mH CUSTOMS L8 1 4.7mH ANY ACCEPTABLE 4.7mH - TL-RAD

Q1 1

Q2 1 transistor SOT-23 FAIRCHILD BC846B Q3 1 transistor SOT-23 FAIRCHILD BC856B

Q4 1 Power MOSFET transistor SOT-323

Q5,Q6 2

RV1 1 275V varistor ANY ACCEPTABLE -

R1,R2 2 560kΩ resistor 1/10W 1% 0805 ANY ACCEPTABLE -

R3,R5,R7 3 220kΩ resistor 1/10W 1% 0805 ANY ACCEPTABLE -

R4 1

R6 1 510kΩ resistor 1/10W 1% 0805 ANY ACCEPTABLE R8 1 18kΩ resistor 1/10W 1% 0805 ANY ACCEPTABLE -

R9 1 47kΩ resistor 1/10W 1% 0805 ANY ACCEPTABLE R10 1 6.8kΩ resistor 1/10W 1% 0805 ANY ACCEPTABLE R11 1 3kΩ resistor 1/10W 1% 0805 ANY ACCEPTABLE -

R12, R20,R25,R33 4 10kΩ resistor 1/10W 1% 0805 ANY ACCEPTABLE

R13 1 620 Ω resistor 1/10W 1% 0805 ANY ACCEPTABLE R14 1 2kΩ resistor 6/10W 1% size 0207 ANY ACCEPTABLE R15 1 10Ω resistor 1/10W 1% 0805 ANY ACCEPTABLE R16 1 33Ω resistor 6/10W 1% size 0207 ANY ACCEPTABLE R17 10kΩ resistor 6/10W 1% size 0207 ANY ACCEPTABLE R18 1 33Ω resistor 1/10W 1% 0805 ANY ACCEPTABLE -

R19,R23 2 20Ω resistor 6/10W 1% size 0207 ANY ACCEPTABLE -

R21 1 3.3kΩ resistor 1/10W 1% 0805 ANY ACCEPTABLE R22 1 30kΩ resistor 1/10W 1% 0805 ANY ACCEPTABLE R24 1 N/P ANY ACCEPTABLE -

R26,R27 2 1kΩ resistor 1/10W 1% 0805 ANY ACCEPTABLE -

R28 1 1.8kΩ resistor 1/10W 1% 0805 ANY ACCEPTABLE R29 1 11kΩ resistor 1/10W 1% 0805 ANY ACCEPTABLE R30 1 13kΩ resistor 1/10W 1% 0805 ANY ACCEPTABLE R31 1 3.9kΩ resistor 1/10W 1% 0805 ANY ACCEPTABLE R32 1 390Ω resistor 1/10W 1% 0805 ANY ACCEPTABLE -

R34,R150,R151,

R152,R260

R35,R36,R37,R39 4 0Ω resistor 1/10W 1% 0805 ANY ACCEPTABLE -

R38 1 N/P ANY ACCEPTABLE -

U1 1 Bridge Rectifier VISHAY DF1510S

U3 1 5.3kV Optocoupler VISHAY SFH6106

5 0Ω resistor 1/4W 1% 1206 ANY ACCEPTABLE -

Power MOSFET

transistor TO-220

Power MOSFET

transistor TO-220

1.5Ω/2.7Ω resistor 2,5W 1% wirewound

INTERNATIONAL

RECTIFIER

SEMICONDUCTOR

INTERNATIONAL

RECTIFIER

ANY ACCEPTABLE -

SPP04N60S5

MMBF0201

IRF830A

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Freescale Semiconductor 67

Dimmable Light Ballast with Power Factor Correction, Rev. 1

68 Freescale Semiconductor

Appendix B. References

1. Electronic Lamp Ballast Design (AN1543/D), Motorola 1995

2. MON08 Cyclone User Manual, P&E Microcomputer Systems Inc. 2002

3. Opto-isolation Board User Manual, Freescale 2005

4. DLB_Setup.xls — HRP_Setup Excel sheet

5. DLB-LB8-001.mcp — project, debugger under CodeWarrior CW V3.0

6. Developer’s Serial Bootloader for MC68HC08 (AN2295/D), Motorola 2002

7. MC68HC908LB8 data sheet, Freescale 2004

8. Freescale web page: http://www.freescale.com

9. CodeWarrior for Motorola HC08 manual version 3.0, Metrowerks 2002

10. Modular Evaluation Board System, MC68HC908LB8 Evaluation Board MMEVS

11. Modular Development System, MC68HC908LB8 MMDS Emulation Board

Dimmable Light Ballast with Power Factor Correction, Rev. 1

Freescale Semiconductor 69

Dimmable Light Ballast with Power Factor Correction, Rev. 1

70 Freescale Semiconductor

How to Reach Us:

Home Page:

www.freescale.com

E-mail:

support@freescale.com

USA/Europe or Locations Not Listed:

Freescale Semiconductor Technical Information Center, CH370 1300 N. Alma School Road Chandler, Arizona 85224 +1-800-521-6274 or +1-480-768-2130 support@freescale.com

Europe, Middle East, and Africa:

Freescale Halbleiter Deutschland GmbH Technical Information Center Schatzbogen 7 81829 Muenchen, Germany +44 1296 380 456 (English) +46 8 52200080 (English) +49 89 92103 559 (German) +33 1 69 35 48 48 (French) support@freescale.com

Japan:

Freescale Semiconductor Japan Ltd. Headquarters ARCO Tower 15F 1-8-1, Shimo-Meguro, Meguro-ku, Tokyo 153-0064, Japan 0120 191014 or +81 3 5437 9125 support.japan@freescale.com

Asia/Pacific:

Freescale Semiconductor Hong Kong Ltd. Technical Information Center 2 Dai King Street Tai Po Industrial Estate Tai Po, N.T., Hong Kong +800 2666 8080 support.asia@freescale.com

For Literature Requests Only:

Freescale Semiconductor Literature Distribution Center P.O. Box 5405 Denver, Colorado 80217 1-800-441-2447 or 303-675-2140 Fax: 303-675-2150 LDCForFreescaleSemiconductor@hibbertgroup.com

Information in this document is provided solely to enable system and software implementers to use Freescale Semi conductor prod ucts. There are no express or implied copyright licenses granted hereunder to design or fabricate any integrated circuits or integrated circuits based on the information in this document.

Freescale Semiconductor reserves the right to m ake changes without furt her notice to any products herein. Freescal e Semiconductor ma kes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does Freescale Semiconductor assume any liability arising out of the application or use of any prod uct or circuit, and specifica lly disclaims any and all liability, including without limitation consequential or incidental damages. “T ypic al” param eters that may be provid ed in Freescal e Semiconductor data sheets and/ or specification s can and do vary in dif ferent applications and actual perf ormance may vary over time. All operating parameters, including “Typicals”, must be validated for each customer application by customer’s technical experts. Freescale Semicondu ctor does not convey any license under its patent rights nor the rights of others. Freescale Semiconductor products are not design ed, intended, or authorized for use as components in systems intended for surgical implant in to the body , or other applications intended to support or sustain life, or for any other application in which the failure of the Freescal e Semiconductor product could create a situation where personal injury or death may occur. Should Buyer purchase or use Freescale Semiconductor product s for any such unintended or unauthorized application, Buyer shall indemnify and hold Freescale Semiconductor and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, co sts, damages , and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that Freescale Semiconductor was neg ligent regarding the design or manufacture of the part.

Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. P&E is a trademark of P&E Microcomputer Systems, Inc. CodeWarrior a wholly owned subsiduary of Freescale Semiconductor, Inc. MetroWerks and the MetroWerks logo are registered trademarks of MetroWerks, Inc., a wholly owned subsiduary of Freescale Semiconductor, Inc. IR registered trademark of International Rectifier Corporation.

DRM067 Rev. 1 12/2005

is a registered trademark of MetroWerks, Inc.,

is a

Freescale Semiconductor M68HC08 User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

Contents

Appendix A. Schematics and Part List

Appendix B. References

Chapter 1 Introduction

1.1 Introduction

1.2 Benefits of this Solution

1.3 The MC68HC908LB8 Microcontroller

Chapter 2 Control Theory

2.1 Introduction

2.1.1 Fluorescent Lamp Control Theory

2.1.2 Fluorescent Lamp Operation

2.1.3 Controlling the Fluorescent Lamp

2.2 PFC Control Theory

2.2.1 Introduction

2.2.4 Concept Summary

Chapter 3 Reference Design

3.1 Application Outline

3.2 Dimmable Light Ballast Characteristics

3.3 Application Description

3.3.1 Light Ballast Control

3.3.2 Power Factor Correction

3.3.3 Protection Features

3.4 Software Specification

3.5 Hardware Specification

Chapter 4 Hardware Design

4.1 Hardware Implementation

4.2 System Modules

4.2.1 Input and PFC

4.2.2 Inverter

4.2.3 Microcontroller

4.2.4 Power Supply

Chapter 5 Software Design

5.1 Introduction

5.2 Control Algorithm Description

5.2.1 Power Factor Correction Control

5.2.1.1 DC-bus Voltage Control

5.2.1.2 Phase Shift Synchronization

5.2.1.3 Reference Sine Wave Generation

5.2.1.4 Generation of Output PFC Control SIgnal

5.2.2 Light Ballast Control

5.2.2.1 Tube Start Mode

5.2.2.2 Luminance Level Control (Tube Run Mode)

5.3 Software Implementation

5.3.1 Initialization Setup

5.3.1.1 PWM Setup

5.3.1.2 HRP Setup

5.3.2 Main Program Loop

5.3.3 Synchronization Interrupt Routine

5.3.4 Sine Wave Generation Interrupt Routine

5.3.4.1 Fault Detection and Processing

5.4 Detailed Software Description

5.5 Microcontroller Usage

5.5.1 Microcontroller Peripheral Usage

5.5.1.1 High Resolution PWM (HRP)

5.5.1.2 Pulse-Width Modulator (PWM)

5.5.1.3 Comparator Module (CM)

5.5.1.4 Timer Interface Module (TIM)

5.5.1.5 External Interrupt (IRQ)

5.5.2 Program and Data Memory Usage

5.5.3 I/O Usage

5.6 Definitions of Constants and Variables

5.6.1 System Setup Definitions

5.6.2 System Constants and Variables

Chapter 6 Demo Setup

6.1 Hardware Setup

6.2 Software Setup

6.2.1 Required Software Tools

6.2.2 Building and Uploading the Application

6.2.3 Executing the Application

6.2.4 Project Files

Appendix A. Schematics and Part List

A.1 Schematics

Figure A-1. Input and PFC for hysteresis current control mode HW variation

Figure A-2. Input and PFC for discontinuous conduction mode HW variation

Figure A-3. Inverter

Figure A-4. Microcontroller for hysteresis current control mode HW variation