Power Integrations RDR-142 Technical data

Title

Reference Design Report for a 35 W Power
Supply Using TOP258PN

90 VAC to 265 VAC Input

Specification

5 V, 2.2 A and 12 V, 2 A Output

Application
Author

LCD Monitor

Power Integrations Applications Department

Document

RDR-142

Number
Date
Revision

Summary and Features

• Low cost, low component count, high efficiency

• Delivers 35 W at 50°C ambient without requiring an external heat sink

• Meets output cross regulation requirements without linear regulators

• EcoSmart® – meets requirements for low no-load and standby power

consumption

• 0.42 W output power for <1 W input

• No-load power consumption < 300 mW at 230 VAC

• >82% full load efficiency

• Integrated safety/reliability features:

• Accurate, auto-recovering, hysteretic thermal shutdown function maintains

safe PCB temperatures under all conditions

• Auto-restart protects against output short circuits and open feedback loops

• Output OVP protection configurable for latching or self recovering

• Input UV prevents power up / power down output glitches

• Meets EN55022 and CISPR-22 Class B conducted EMI with > 10 dBµV margin

The products and applications illustrated herein (including circuits external to the products and transformer
construction) may be covered by one or more U.S. and foreign patents or potentially by pending U.S. and foreign
patent applications assigned to Power Integrations. A complete list of Power Integrations’ patents may be found at

www.powerint.com.

September 24, 2007

1.0

Power Integrations

5245 Hellyer Avenue, San Jose, CA 95138 USA.

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RDR-142 35 W, TOP258PN Dual Output Supply 24-Sep-07

Table of Contents

1 Introduction................................................................................................................. 4

2 Power Supply Specification ........................................................................................ 5

3 Schematic...................................................................................................................6

4 Circuit Description ......................................................................................................7

4.1 Input EMI Filtering ...............................................................................................7

4.2 TOPSwitch-HX Primary.......................................................................................7

4.3 Output Rectification .............................................................................................8

4.4 Output Feedback.................................................................................................9

4.5 PCB Layout ....................................................................................................... 10

5 Bill of Materials ......................................................................................................... 11

6 Transformer Specification......................................................................................... 13

6.1 Electrical Diagram .............................................................................................13

6.2 Electrical Specifications..................................................................................... 13

6.3 Materials............................................................................................................13

6.4 Transformer Build Diagram ...............................................................................14

6.5 Transformer Construction.................................................................................. 15

7 Design Spreadsheet .................................................................................................16

8 Performance Data ....................................................................................................20

8.1 Efficiency ...........................................................................................................20

8.1.1 Active Mode CEC Measurement Data........................................................20

8.2 No-load Input Power.......................................................................................... 22

8.3 Available Standby Output Power.......................................................................23

9 Regulation ................................................................................................................24

9.1.1 Load ...........................................................................................................24

9.1.2 Line ............................................................................................................25

9.1.3 Cross Regulation Matrix .............................................................................26

10 Thermal Performance ...........................................................................................27

11 Waveforms............................................................................................................ 28

11.1 Drain Voltage and Current, Normal Operation...................................................28

11.2 Output Voltage Start-up Profile..........................................................................28

11.3 Drain Voltage and Current Start-up Profile ........................................................ 30

11.4 Load Transient Response (75% to 100% Load Step) .......................................31

11.5 Output Over-voltage Protection ......................................................................... 32

11.6 Output Ripple Measurements ............................................................................33

11.6.1 Ripple Measurement Technique ................................................................33

11.6.2 Measurement Results ................................................................................34

12 Line Surge.............................................................................................................35

13 Control Loop Measurements.................................................................................36

13.1 90 VAC Maximum Load..................................................................................... 36

13.2 265 VAC Maximum Load................................................................................... 36

14 Conducted EMI .....................................................................................................37

15 Revision History ....................................................................................................38

Important Note:

Page 2 of 40

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24-Sep-07 RDR-142 35 W, TOP258PN Dual Output Supply

Although this board is designed to satisfy safety isolation requirements, the engineering
prototype has not been agency approved. Therefore, all testing should be performed
using an isolation transformer to provide the AC input to the prototype board.

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RDR-142 35 W, TOP258PN Dual Output Supply 24-Sep-07

1 Introduction

This document is an engineering report describing a LCD Monitor power supply utilizing a
TOP258PN. This power supply is intended as a general purpose evaluation platform for

TOPSwitch-HX.

The document contains the power supply specification, schematic, bill of materials,
transformer documentation, printed circuit layout, and performance data.

Figure 1 – Populated Circuit Board Photograph (5”L x 2.84”W x 1.16”H)

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24-Sep-07 RDR-142 35 W, TOP258PN Dual Output Supply

2 Power Supply Specification

Description Symbol Min Typ Max Units Comment

Input

Voltage
Frequency
No-load Input Power (230 VAC) 0.3 W

Output

Output Voltage 1
Output Ripple Voltage 1
Output Current 1

Output Voltage 2

Output Ripple Voltage 2
Output Current 2

Total Output Power

Continuous Output Power

Efficiency

Full Load

Standby Input Power 1 W

Required average efficiency at
25, 50, 75 and 100 % of P

OUT

Environmental

Conducted EMI

Safety

Surge

Differential
Common Mode

Surge

Ring Wave

Ambient Temperature

*Shown for information only as CEC requirement does not apply to internal power supplies

V

f

LINE

IN

90 265 VAC
47 50/60 64 Hz

3 wire input

V

OUT1

V

RIPPLE1

I

OUT1

V

OUT2

V

RIPPLE2

I

OUT2

4.75 5 5.25 V
100 mV

0 2.2 A

9.6 12 14.4 V

500 mV

0 2 A

± 5%

20 MHz bandwidth

± 20%

20 MHz bandwidth

P

OUT

35 W

Measured at P

5 V @ 82 mA, 12 V @ 0 mA;

Vin at 264 VAC

Per California Energy Commission

(CEC) / Energy Star requirements

η

η

CEC

82 %

*

81

%

Meets CISPR22B / EN55022B

Designed to meet IEC950, UL1950

1
2

1 kV

0 50

T

AMB

Class II

1.2/50 µs surge, IEC 1000-4-5,

kV
kV

o

C

Series Impedance:
Differential Mode: 2 Ω
Common Mode: 12 Ω

100 kHz ring wave, 500 A short

circuit current, differential and

common mode

Free convection, sea level

OUT

25

o

C

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RDR-142 35 W, TOP258PN Dual Output Supply 24-Sep-07

3 Schematic

*

Figure 2 – Schematic.

Optional for 2 wire input, floating output

*

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24-Sep-07 RDR-142 35 W, TOP258PN Dual Output Supply

4 Circuit Description

A Flyback converter configuration built around TOP258PN is used in this power supply to
obtain two output voltages. The 5 V output can supply a load current of 2.2 A, and the 12
V output can supply a load current of 2.0 A. This power supply can operate between 90
– 264 VAC. The 5 V output is the main regulated output. This output is regulated using a
TL431 voltage reference. Some feedback is also derived from the 12 V output for
improved cross regulation.

4.1 Input EMI Filtering

The three wire AC supply is connected to the circuit using connector J1. Fuse F1
provides protection against circuit faults and effectively isolates the circuit from the AC
supply source. Thermistor RT1 limits the inrush current drawn by the circuit at start up.
Optional capacitors C1 and C2 are Y capacitors connected from the Line/Neutral to Earth
to reduce common mode EMI.

Capacitor C3 is the X capacitor and helps to reduce the differential mode EMI. Resistors
R1 and R2 discharge C3 on AC removal, preventing potential user shock. Inductor L1 is
a common-mode inductor and helps in filtering common-mode EMI from coupling back to
the AC source.

Diodes D1, D2, D3 and D4 form a bridge rectifier. The bridge rectifier rectifies the
incoming AC supply to DC, which is filtered by capacitor C4.

Diodes D1 and D3 are fast recovery type diodes. These diodes recover very quickly
when the voltage across them reverses. This reduces excitation of stray line inductance
in the AC input by reducing the subsequent high frequency turnoff snap and hence EMI.
Only 2 of the 4 diodes in the bridge need to be fast recovery type, since 2 diodes conduct
in each half cycle.

4.2 TOPSwitch-HX Primary

Resistor R3 and R4 provide line voltage sensing and provide a current to U1, which is
proportional to the DC voltage across capacitor C4. At approximately 95 V DC, the
current through these resistors exceeds the line under-voltage threshold of 25 µA, which
results in enabling of U1.

The TOPSwitch-HX regulates the output using PWM-based voltage mode control. At
high loads the controller operates at full switching frequency (66 kHz for P package
devices). The duty cycle is controlled based on the control pin current to regulate the
output voltage.

The internal current limit provides cycle-by-cycle peak current limit protection. The
TOPSwitch-HX controller has a second current limit comparator allowing monitoring the
actual peak drain current (IP) relative to the programmed current limit I

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LIMITEXT

. As soon

RDR-142 35 W, TOP258PN Dual Output Supply 24-Sep-07

as the ratio IP/I

LIMITEXT

falls below 55%, the peak drain current is held constant. The
output is then regulated by modulating the switching frequency (variable frequency PWM
control). As the load decreases further, the switching frequency decreases linearly from
full frequency down to 30 kHz.

Once the switching frequency has reached 30 kHz the controller keeps this switching
frequency constant and the peak current is reduced to regulate the output (fixed
frequency, direct duty cycle PWM control).

As the load is further reduced and the ratio IP/I

LIMITEXT

falls below 25%, the controller will
enter a multi-cycle-modulation mode for excellent efficiency at light load or standby
operation and low no-load input power consumption.

Diode D5, together with R6, R7, C6 and Zener VR1, forms a clamp network that limits the
drain voltage of U1 at the instant of turn-off. Zener VR1 provides a defined maximum
clamp voltage and typically only conducts during fault conditions such as overload. This
allows the RCD clamp (R6, C6 and D5) to be sized for normal operation, thereby
maximizing efficiency at light load. Resistor R7 is required due to the choice of a fast
recovery diode for D5. A fast versus ultra fast recovery diode allows some recovery of
the clamp energy but requires R7 to limit reverse diode current and dampen high
frequency ringing.

The output of the bias winding is rectified by diode D6 and filtered by resistor R10 and
capacitor C10. This rectified and filtered output is used by the optocoupler U2 to provide
the control current to the control terminal of U1.

Should the feedback circuit fail (open loop condition), the output of the power supply will
exceed the regulation limits. This increased voltage at output will also result in an
increased voltage at the output of the bias winding. Zener VR2 will break down and
current will flow into the “M” pin of IC U1, thus initiating a hysteretic OVP shutdown with
automatic restart attempts. Resistor R5 limits the current into the M pin; if latching OVP
is desired, the value of R5 can be reduced to 20 Ω.

The output voltage of the power supply is maintained in regulation by the feedback circuit
on the secondary side of the circuit. The feedback circuit controls the output voltage by
changing the optocoupler current. Change in the optocoupler diode current results in a
change of current into the control pin of IC U1. Variation of this current results in
variation of duty cycle and hence the output voltage of the power supply.

4.3 Output Rectification

Output rectification for the 5 V output is provided by diode D8. Low ESR capacitor C17
provides filtering. Inductor L3 and capacitor C18 form a second stage filter that
significantly attenuates the switching ripple across C17 and ensures a low ripple output.

Page 8 of 40

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24-Sep-07 RDR-142 35 W, TOP258PN Dual Output Supply

Output rectification for the 12 V output is provided by diode D7. Low ESR capacitors C13
and C14 provide filtering. Inductor L2 and capacitor C15 form a second stage filter that
significantly attenuates the switching ripple and ensures low ripple at the output.

Snubber networks comprising R11, C12 and R12, and C16 damp high frequency ringing
across diodes D7 and D8, which results from leakage inductance of the transformer
windings and the secondary trace inductances.

4.4 Output Feedback

Output voltage is controlled using the shunt regulator TL431 (U3). Diode D9, capacitor
C20 and resistor R16 form the soft finish circuit. At start-up, capacitor C20 is discharged.
As the output voltage starts rising, current flows into the optocoupler diode (U2A) via
resistor R13 and diode D9. This provides feedback to the circuit on the primary side.
The current in the optocoupler diode U2A gradually decreases as capacitor C20 charges
and U3 becomes operational. This ensures that the output voltage increases gradually
and settles to the final value without any overshoot. Resistor R16 provides a discharge
path for C20 into the load at power down. Diode D9 isolates C20 from the feedback
circuit after startup.

Resistor R18, R20 and R21 form a voltage divider network that senses the output voltage
from both the outputs for better cross-regulation. Resistor R19 and Zener VR3 improve
cross regulation when only the 5 V output is loaded, which results in the 12 V output
operating at the higher end of the specification.

Resistors R13, R17 and capacitor C21 set the frequency response of the feedback
circuit. Capacitor C19 and resistor R14 form the phase boost network that provides
adequate phase margin to ensure stable operation over the entire operating voltage
range.

Resistor R15 provides the bias current required by the IC U3 and is placed in parallel with
U2A to ensure that the bias current to the IC does not become a part of the feedback
current. Resistor R13 sets the overall DC loop gain and limits the current through U2A
during transient conditions.

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RDR-142 35 W, TOP258PN Dual Output Supply 24-Sep-07

4.5 PCB Layout

Figure 3 – Printed Circuit Layout.

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24-Sep-07 RDR-142 35 W, TOP258PN Dual Output Supply

5 Bill of Materials

Item Qty

1 2
2 1 C3 220 nF, 275 VAC, Film, X2 Panasonic ECQ-U2A224ML

3 1 C4
4 1 C6 3.9 nF, 1 kV, Disc Ceramic, Y5P Panasonic ECK-A3A392KBP

5 2
6 1 C8 100 nF, 50 V, Ceramic, Z5U Kemet C317C104M5U5TA

7 1 C9

8 2

9 2

10 2

11 1 C15

12 1 C17

13 1 C18
14 1 C19 1.0 uF, 50 V, Ceramic, X7R Epcos B37984M5105K000
15 1 C21 220 nF, 50 V, Ceramic, X7R Epcos B37987F5224K000

16 2

17 2

18 2
19 1 D7 60 V, 5 A, Schottky, DO-201AD Vishay SB560
20 1 D8 30 V, 5 A, Schottky, DO-201AD Fairchild SB530
21 1 D9 75 V, 300 mA, Fast Switching, DO-35 Vishay 1N4148
22 1 F1 3.15 A, 250V,Fast, TR5 Wickman 37013150410
23 1 J1 5 Position (1 x 5) header, 0.156 pitch Molex 26-48-1055
24 2 J2 J3 2 Position (1 x 2) header, 0.156 pitch Molex 26-48-1025

25 1 JP1

26 1 JP2

27 1 JP3
28 1 L1 6.8 mH, 0.8 A, Common Mode Choke Panasonic ELF15N008
29 2 L2 L3 3.3 uH, 5.0 A Coilcraft RFB0807-3R3L

30 2

31 2

Ref
Des

C11 2.2 nF, Ceramic, Y1 Vishay 440LD22-R

C10
C20
C12
C16 470 pF, 100 V, Ceramic, COG AVX Corp 5NK471KOBAM
C13
C14

Description Mfg Mfg Part Number

C1
C2

1 nF, Ceramic, Y1 Panasonic ECK-ANA102MB

100 uF, 400 V, Electrolytic, Low ESR,
630 mOhm, (16 x 40)

C7

47 uF, 16 V, Electrolytic, Gen Purpose,
(5 x 11.5) Panasonic ECA-1CHG470
10 uF, 50 V, Electrolytic, Gen Purpose,
(5 x 11)

680 uF, 25 V, Electrolytic, Very Low
ESR, 23 mOhm, (10 x 20)
220 uF, 25 V, Electrolytic, Low ESR,
120 mOhm, (8 x 12)
2200 uF, 10 V, Electrolytic, Very Low
ESR,21 mOhm, (12.5 x 20)
220 uF, 10 V, Electrolytic, Low ESR,
250 mOhm, (6.3 x 11.5)

D1

600 V, 1 A, Fast Recovery Diode,

D3

200 ns, DO-41
D2
D4 1000 V, 1 A, Rectifier, DO-41 Vishay 1N4007
D5

800 V, 1 A, Fast Recovery Diode,
D6

500 ns, DO-41 Diodes Inc. FR106

Wire Jumper, Non insulated,

22 AWG, 0.4 in

Wire Jumper, Non insulated,

22 AWG, 0.8 in Alpha 298

Wire Jumper, Non insulated,

22 AWG, 0.3 in Alpha 298

R1
R2 1 M, 5%, 1/4 W, Carbon Film Yageo CFR-25JB-1M0
R3
R4 2.0 M, 5%, 1/4 W, Carbon Film Yageo CFR-25JB-2M0

Nippon Chemi­Con

Panasonic ECA-1HHG100

Nippon Chemi­Con EKZE250ELL681MJ20S
Nippon Chemi­Con
Nippon Chemi­Con EKZE100ELL222MK20S
Nippon Chemi­Con ELXZ100ELL221MFB5D

On
Semiconductor 1N4937RLG

Alpha 298

EKMX401ELL101ML40
S

ELXZ250ELL221MH12D

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RDR-142 35 W, TOP258PN Dual Output Supply 24-Sep-07

32 1 R5 5.1 k, 5%, 1/4 W, Carbon Film Yageo CFR-25JB-5K1
33 1 R6 22 k, 5%, 2 W, Metal Oxide Yageo RSF200JB-22K
34 1 R7 20 R, 5%, 1/2 W, Carbon Film Yageo CFR-50JB-20R
35 1 R8 6.8 R, 5%, 1/8 W, Carbon Film Yageo CFR-12JB-6R8
36 1 R9 100 R, 5%, 1/4 W, Carbon Film Yageo CFR-25JB-100R
37 1 R10 4.7 R, 5%, 1/4 W, Carbon Film Yageo CFR-25JB-4R7

R11
38 2
39 1 R13 330 R, 5%, 1/4 W, Carbon Film Yageo CFR-25JB-330R
40 1 R14 22 R, 5%, 1/4 W, Carbon Film Yageo CFR-25JB-22R
41 1 R15 1 k, 5%, 1/4 W, Carbon Film Yageo CFR-25JB-1K0

42 2
43 1 R18 196 k, 1%, 1/4 W, Metal Film Yageo MFR-25FBF-196K
44 1 R19 10 R, 5%, 1/4 W, Carbon Film Yageo CFR-25JB-10R
45 1 R20 12.4 k, 1%, 1/4 W, Metal Film Yageo MFR-25FBF-12K4
46 1 R21 10 k, 1%, 1/4 W, Metal Film Panasonic ERO-S2PHF1002
47 1 RT1 NTC Thermistor, 10 Ohms, 1.7 A Thermometrics CL-120

48 1 T1

49 1 U1 TOPSwitch-HX, TOP258PN, DIP-8B

50 1 U2

51 1 U3

52 1 VR1
53 1 VR2 20 V, 5%, 500 mW, DO-35 Microsemi 1N5250B
54 1 VR3 8.2 V, 500 mW, 2%, DO-35 Vishay BZX55B8V2

R12 33 R, 5%, 1/4 W, Carbon Film Yageo CFR-25JB-33R

R16

R17 10 k, 5%, 1/4 W, Carbon Film Yageo CFR-25JB-10K

Core
Bobbin: EER28, Horiz., 12 pins (6/6),

Complete Assembly (custom)

Opto coupler, 80 V, CTR 80-160%, 4­DIP NEC PS2501-1-H-A

2.495 V Shunt Regulator IC, 2%, 0 to
70C, TO-92
200 V, 600 W, 5%, TVS, DO204AC
(DO-15)

TDK
Ying-Chin

Ice Components
Magtel
Precision Inc.
Power
Integrations

On
Semiconductor TL431CLPG

OnSemi P6KE200ARLG

PC40EER28-Z
YC-2806-5

TOP07074
32/07 TR.RDK-142
019-4967-00R

TOP258PN

Note – Parts listed above are RoHS compliant

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