ST STCC05-B User Manual

®

STCC05-B

HOME APPLIANCE CONTROL CIRCUIT

APPLICATIONS

■ Home Appliance digital control

■ AC Power drive and functional safety management

■ Air Conditioner, Refrigerator and Oven applications

■ Compressor, fan, heater and valve drive circuit

FEATURES

■ Wide range input supply voltage operation:

7 to 18V

■ 5 V +/- 5% full tolerance voltage regulator and

50mA output current

■ MCU reset circuit with activation delay time and

hysteresis (3.75V Hi, 3.4V Lo)

■ 30µs digitally filtered inverting Zero Voltage

Synchronization

■ Three 50mA relay coil drivers with demagnetiz-

ing diode

■ One 150mA relay coil driver with demagnetizing diode for a 20A relay

■ One 30mA peak enhanced buzzer driver with enable pin and soft turn off

■ 12 to 5V robust non inverting level shifter for speed sensor or door switch interface

■ Ambient temperature: - 20 to 85°C

Table 1. Order Code

Part Number Marking

STCC05-BD4 STCC05-B

DIP-20

BENEFITS

■ Higher module compactness with reduced component count

■ Drastic reduction of soldered pins on the board for lower use of lead metal

■ Faster module assembly time

■ High transient burst immunity and ESD robustness compliant with IEC61000-4 standards

■ Enhanced functional reliability

■ Enhanced circuit parametric quality

■ Easy to design for short time to market

Figure 1: STCC05 based Air Conditioner application diagram

SMPS

AC Line

V

PS

COMPRESSOR RELAY

POWER RELAYS

R

S

V

PS

V

PS

BUZZER

COM

V

VPSV

RL

4

V

VPSV

RL

3

V

VPSV

RL

2

V

VPSV

RL

1

BZ

2

BZ

1

V

PS

SYN

IN

S

R

INS

V

PS

STCC05

PS

V

VPSV

PS

5V REGULATOR

ZEROVOLTS SYNC.

LEVEL SHIFTER

JP

V

PS

30µs FILTER

EMI FILTER

RELAYDRIVER

RESET

20A RELAY

DRIVER

BUZZER DRIVER

IN

EN

IN

V

RST\

ZVS

OUT

4

3

2

1

BZ

DD

P

PWM

V

/RS T

04

03

02

01

06

DD

V

DD

V

C

SS

DD

NMI

S

C

P

07

UP

MCU

October 2004 REV. 1

SPEED

SENSOR

1/13

STCC05-B

Figure 2. Block diagram Figure 3. Pin-out connections

V

PS

RL

BZ

VP

COM

SYN

IN

4

3

2

1

2

1

S

V

PS

V

PS

V

PS

V

PS

5V REGULATOR

ZERO VOLTS SYNC.

LEVEL SHIFTER

V

PS

RESET

30µs FILTER

EMI FILTER

20A RELAY

RELAY DRIVER

DRIVER

BUZZER

DRIVER

IN

EN

IN

V

DD

RST\

ZVS

OUT

4

3

2

1

BZ

S

V

PS

SYN /RST

IN

RL

BZ

EN

BZ

1

2

3

S

4

1

5

2

6

3

7

4

8

1

9

2

10

20

19

18

17

16

15

14

13

12

11

V

DD

ZVS

OUT

IN

1

IN

2

IN

3

IN

4

IN

BZ

COM

S

FUNCTIONAL DESCRIPTION

The STCC05 is a control circuit embedding most of the analog & power circuitry of an air conditioner or refrigirator control module. It interfaces the micro-controller MCU with the AC power and cooling process sections.

■ The voltage supply

The 5V voltage regulator supplies the micro-controller MCU. Its input voltage ranges from 7V to 18V; and its average DC output current up to 50mA. With an output filtering capacitor of 100µF, its output voltage accuracy is better than +/- 5% in the whole operating range of the ambient temperature T current I

and the input voltage VPS , contributing directly to the ADC accuracy.

DD

AMB

, the load

The regulator includes also an over current limiter and a thermal shutdown. The over current limiter protects the regulator against output short circuits and inrush currents during the power up. The current limiter is made of a serial shunt resistance as current sensor and a circuit that regulates the input current. Moreover, the thermal shutdown protects the whole circuit against overload operations. It is made of a thermal sensing junction and a hysteresis comparator that is able to switch off the passing element.

R

1.25 V

SENSE

Over current

Limiter

R

1

V

DD

V

DD

6kΩ

3kΩ

/RST

CUP=

100nF

V

DD

R

2

V

H

V

L

VH= 3.75 V

= 3.40 V

V

L

MCU

V

DD

RUP> 100kΩ

RESET

V

PS

Thermal

Shutdown

Reference

2/13

V

DD

STCC05-B

■ The reset circuit

This circuit ensures a Low Voltage Detection (LVD) of the output of the regulator. Most micro-controllers have an active RESET pin in the low state: so, the /RST pin will be active at low state. The reset comparator senses the regulator voltage V the high threshold V low threshold V These delays are set by an external capacitor C thresholds of /RST: For C

■ The Zero Voltage Synchronization ZVS circuit

= 3.75V and after a delay time TUP; and is low when the VDD decreases below the

H

= 3.4V after the delay time TDW.

L

UP

= 100nF, TUP= 400µs with VTH= VH/2; TDW= 200µs with VTH= VL/2.

UP

The Zero Voltage Synchronization ZVS circuit generates the signal ZVS that synchronizes the whole operation with the AC line cycle (20 ms on 50 Hz or 16.7 ms on 60 Hz). This signal allows the MCU to control the AC loads and achieve the timing functions. The input pin SYN is an image of the mains voltage. It is connected to either the power supply transformer through a resistor R

or an opto-coupler that is controlled directly by the AC line voltage. The circuit is

ZV

protected against fast line transient voltages: a robust ESD protection and a 30µs digital filter are implemented to provide a higher immunity to the MCU operation. Its output signal ZVS is inverted respect to the input signal V

SYN

.

V

. The /RST pin goes high when VDD is higher than

DD

connected to the /RST pin and depend on the trigger

DD

30 µs FILTER

S

25 kΩ

SYN

70 kΩ

30 kΩ

COM

■ The relay coil drivers

1

Q

S

2

ZVS

These robust circuits allow a DC relay coil to be driven by an MCU output. The relay coil has a minimum resistance of 580Ω and has a power up to 0.25W for V

= 12 V. These characteristics are representative

PS

of 3A relays such as FTR-F3AA-12V or JQ1A-12V series. The output stage is made of a transistor and a demagnetization diode. The transistor is referred to the ground COM, has a DC current rating of 50mA; and its collector is connected to the output RL The diode is connected between the output pin RL

and the supply pin VPS.

I

(I=1, 2, 3).

I

Moreover, a fourth coil driver has an extended 150mA current capability to be able to drive the coil of a relay having a 130Ω minimum resistance and a 1.1W maximum power. These characteristics are representative of 20A relays such as G4A-E-DC12, OMIF-S-112 or UKH12S series.

3/13

STCC05-B

V

PS

V

PS

Demagnetizing Diode

V

IN

■ The buzzer driver with enable control

4kΩ

I

10 kΩ

IN

Relay

Transistor

RL

I

EN

IN

10 kΩ

BZ

V

IN

BZ

R

RBZ=

=1kΩ

OH

BZ

2

1

1kΩ

The MCU can excite a warning buzzer with a 50% PWM signal. The buzzer driver amplifies this signal in current and translates it from the 5V MCU output to the V

supply to produce the right sound level from

PS

the buzzer. The output stage is made of a NPN transistor, a PNP transistor and two 1kΩ resistors. The NPN transistor, referred to the power ground COM, is controlled by the input IN nected to the output BZ The PNP transistor, referred to the V nected to the output BZ

. The input INBZ is driven by a simple push-pull MCU buffer.

1

polarity, is controlled by the input ENBZ; and its collector is con-

PS

through a 1kΩ resistor. The input ENBZ is driven by a simple push-pull MCU

2

; its collector is con-

BZ

buffer. The pin BZ

is the supply terminal of the buzzer; and the circuit has a DC current rating of 9mA and the

2

PWM section runs from 10Hz up to 5kHz. A 1kΩ resistor R over, the addition of an external capacitor-resistor network on BZ off smoothly when the pin EN

■ The speed sensor level shifter

The OUT

signal is generated by an electronic signal such as the indoor fan speed clock issued of a Hall

S

Effect sensor or a door switch signal and is transmitted to the MCU. As the IN

is connected between the BZ1 and BZ2 pins to discharge the buzzer periodically. More-

BZ

pin will allow the buzzer to turn on and

2

is toggling.

BZ

input may be disturbed; a

S

spike suppressor and a simple EMI filter are added to increase the input robustness. The output signal OUT

is not inverted with respect to the input signal INS.

S

4/13

IN

V

DD

V

DD

EMI

50 kΩ

S

Filter

500Ω

OUT

S

50 kΩ