Rev 1.0November 2005 1/15

15

IntroductionThis application note describes a power supply that can be used as a wall transformer replacement or asa power module for a small consumer appliance. The design objectives are:

■ The outside case dimensions (in inches) are 2L x 2W x 1H, with smaller inside dimensions,

■ the Line and Neutral pins (of equal size and 8mm from the end of the assembly) are attached to the case,

■ the input voltage ranges are 95VAC to 135VAC; and 190VAC to 270VAC,

■ the output voltage is 15V (max) at 1mA (min) and is 12V (min) at 500mA (max), with a 50% duty cycle,

■ the ambient temperature range is –5°C to 55°C, and

■ the Electromagnetic Interference (EMI) is measured for all loads.

The power supply for the wall transformer replacement application consists primarily of a re-packagedVIPer12 Demonstration Board (12V, single output voltage, see Application Note AN1734 for details).

Figure 1. VIPer12-based Power Supply Assembly, Top View

AN2173APPLICATION NOTE

Using a VIPer12-based Power Supplyto Replace a Wall Transformer

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AN2173 - APPLICATION NOTE

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Table of Contents

1 VIPer12-based Power Supply Features and Assembly . . . . . . . . . . . . . . . 4

1.1 Layout and Component Placement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

1.2 Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

1.3 Heat Sink Enhancement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2 Operation Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

3 Transformer Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

4 Transformer Mechanical Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Appendix A. Schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Appendix B. KIDDE VIPer12 Demo Board BOM . . . . . . . . . . . . . . . . . . . . 13

5 Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

AN2173 - APPLICATION NOTE

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List of Figures

Figure 1. VIPer12-based Power Supply Assembly, Top View . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1Figure 2. PCB Layout. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Figure 3. PCB Component Placement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Figure 4. EMI Measurements (EMI EN5502, Class B). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Figure 5. Heat Sink Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Figure 6. Drain to Source Voltage (Vds) and Drain Current (Id) Waveforms . . . . . . . . . . . . . . . . . . . . 8Figure 7. Power Supply Efficiency with Line Variation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Figure 8. Line Regulation: Power Supply Output Voltage vs. Varied Input Line Voltage. . . . . . . . . . . 9Figure 9. Load Regulation: Power Supply Output Voltage vs. Varied Load . . . . . . . . . . . . . . . . . . . . 9Figure 10. Transformer Winding Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Figure 11. Transformer Mechanical Drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11Figure 12. VIPer12-based Power Supply Schematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

1 VIPer12-based Power Supply Features and Assembly AN2173 - APPLICATION NOTE

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1 VIPer12-based Power Supply Features and Assembly

● Fixed 60kHz Switching Frequency

● Switch mode General Purpose Power Supply

● Burst Mode Operation in Standby for Blue Angel operation

● Current Mode Control

● Typical 75% Efficiency at Full Load

● Auxiliary Undervoltage Lockout with Hysteresis

● Output Short Circuit Protection

● Thermal Shutdown Protection

● Meets EN55022 Class B EMI specification

1.1 Layout and Component Placement

To meet Printed Circuit Board (PCB) space requirements, both sides of the PCB are used for either low or high voltage power supply mains by selecting the appropriate voltage rating for the bulk capacitors and the Metal Oxide Varistor (MOV). Surface-mount components should be used wherever possible to reduce the size of the assembly. The remaining axial lead devices (e.g., resistors, diode, and “pigtail” fuse) are mounted vertically to save PCB space.

The line and neutral pins are molded into the bottom of the case and pass through two holes in the top of the case, and a line cord attachment is on the side opposite the line and neutral pins (see Figure 2 on page 5 and Figure 3 on page 5). The PCB size is determined by the overall dimensions and the side wall thicknesses of the case (1.78in x 1.78in, with rectangular mounting slots in each side). A 0.118in mounting hole is provided. Additional support using 0.75in PCB standoffs is recommended, with the component leads trimmed to 0.65in (max).

See Appendix A. Schematics on page 12 and Appendix B. KIDDE VIPer12 Demo Board BOM on page 13 for details.

AN2173 - APPLICATION NOTE 1 VIPer12-based Power Supply Features and Assembly

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1.2 Assembly

The initial PCBs and power supply assemblies were routed, built, and tested in the lab. An assembly fits into the case with the attached output wire cable that is connected from the flange to the end. If a Pollution Degree 1 rating is desired, the assembly should be in a sealed case, since the cable runs from the secondary (across the transformer) to the primary. Additionally, the transformer can be smaller if the case is sealed. If a sealed case is not used, then thicker insulation or triple-insulated wire may be required.

Assembly EMI (EN5502, Class B) measurements are shown in Figure 4 on page 6.

Figure 2. PCB Layout

Figure 3. PCB Component Placement

1 VIPer12-based Power Supply Features and Assembly AN2173 - APPLICATION NOTE

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Figure 4. EMI Measurements (EMI EN5502, Class B)

AN2173 - APPLICATION NOTE 1 VIPer12-based Power Supply Features and Assembly

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1.3 Heat Sink Enhancement

The smaller layout, though useful for PCB space savings, is also prone to heat sink area reduction. To enhance the cooling capacity for the VIPer12, mounting a small heat sink directly in the holes with the 4 DRAIN pins in the VIPer12’s DIP package is recommended (see Figure 5).

Figure 5. Heat Sink Configuration

2 Operation Characteristics AN2173 - APPLICATION NOTE

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2 Operation Characteristics

Figure 6. Drain to Source Voltage (Vds) and Drain Current (Id) Waveforms

Note: Measured during normal operation with an input line of 115VAC and the output at full load.

Figure 7. Power Supply Efficiency with Line Variation

Note: Measured at full load, when the line is varied from 85VAC to 137VAC.

72

73

74

75

76

77

78

80 90 100 110 120 130 140

Input Line Voltage (VAC)

Eff

icie

ncy

(%

)

AI11834

AN2173 - APPLICATION NOTE 2 Operation Characteristics

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Figure 8. Line Regulation: Power Supply Output Voltage vs. Varied Input Line Voltage

Note: Power supply output voltage is monitored while running at full load, and the line is varied from 85VAC to 134VAC.

Figure 9. Load Regulation: Power Supply Output Voltage vs. Varied Load

Note: Power supply output voltage is monitored while running at 115VAC, and the load is varied from 0.01A to 0.51A.

12.1

12.12

12.14

12.16

12.18

12.2

80 90 100 110 120 130 140

Input Line Voltage (VAC)

Ou

tpu

t V

olt

age

(VO

)

AI11835

12.1

12.12

12.14

12.16

12.18

12.2

0.00 0.10 0.20 0.30 0.40 0.50 0.60

Load (A)

Ou

tpu

t V

olt

age

(VO

)

AI11836

3 Transformer Electrical Specifications AN2173 - APPLICATION NOTE

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3 Transformer Electrical Specifications

When the VIPer12A (U4) is ON, energy is stored in the primary winding of transformer (10-8), TR1. This energy is transferred to the auxiliary winding (5-6), and to the output (1-2) when the VIPer12A is OFF. The auxiliary winding provides the bias voltage for the VIPer12A at pin 4 (VDD).

Figure 10. Transformer Winding Schematic

Table 1. Winding Inductance RatingsParameter Value Units

Primary Inductance (Lp) 3.25 ± 10% mH

Primary Leakage Inductance (Llp) 34 (typ) µH

N1 N212V @ 0.50A

N4

N315V @ 0.02A

1

2

8

9

6

105

120 - 400V@ 60kHz,50% DC

1/2 Primary

1/2 PrimarySecondaryAuxiliary

AI11837

TR1

AN2173 - APPLICATION NOTE 4 Transformer Mechanical Information

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4 Transformer Mechanical Information

Figure 11. Transformer Mechanical Drawing

0.71 (max)

0.71 (max)

0.48 ± 0.02

1 4

10 5

0.65 (max)

0.19 REF

0.055 REF

0.022 (typ)

0.13 ± 0.02 (3x)

0.10 ± 0.02 (5x)AI11838

Appendix A. Schematics AN2173 - APPLICATION NOTE

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Appendix A. Schematics

Figure 12. VIPer12-based Power Supply Schematics

R4

220

C4

22µF

/25V

C2

10µF

/250

V

C7

330µ

F/2

5VC8

330µ

F/2

5V

C11

0.04

7µF

DR

AIN

DR

AIN

DR

AIN

DR

AIN

SO

UR

CE

SO

UR

CE

Fb

3

VD

D4

U4

VIP

er12

A

1 2

4 3

U2

H11

A81

7A

R7

3.40

k

R5

1k C9

0.01

µF

21

D3

ST

TH

102

32

41

L1H

JC03

08Q

R2

2k 1

/2W

C3

47pF

88

1010

55

66

11

22

CV

P11

-021

4 3

21

BR

1S

M

C6

47nF

R8

4.7

D2

BA

V20

WS

*For

190

to 2

70V

AC

:

C1

= 1

.0µF

/400

VC

2 =

10µ

F/4

00V

R1

= 4

.7Ω

1/4

W C

CM

OV

= 4

40V

Line

Neu

tral

C5

3.3n

F25

0V Y1

R1

1%

1%

C1

4.7µ

F/2

50V

HS

F1

5.1Ω

Fus

able

Res

isto

r

Jum

per

1kV

TR

1

21

MO

V22

0V

R3

9.1k

21

3U3

TL4

31

95 to

135

VA

C

VIN

*

R6

13.3

k

R9

12.1

V

RT

N

3.3k

8 67 5 1 2

AI11184

AN2173 - APPLICATION NOTE Appendix B. KIDDE VIPer12 Demo Board BOM

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Appendix B. KIDDE VIPer12 Demo Board BOM

Table 2. Domestic Bill of MaterialsQty Reference Part Description Manufacturer Manufacturer Part Number

1 BR1 SM Bridge 600V 1.5A Diodes, Inc. DF1506S-T

1 C1 4.7uF/250V Electro Panasonic ECA-2EHG4R7

1 C2 10uF/250V Electro Panasonic ECA-2EHG100

1 C3 47pF 1kV Ceramic Panasonic ECC-D3A470JGE

1 C4 22uF/25V Electro Panasonic ECA-1EM220

1 C5 3.3nF 250V Y1 Panasonic ECK-ATS332ME

1 C6 47nF SMD 1206

2 C7, C8 330uF/25V Electro Panasonic EEU-FC1E331L

1 C9 0.01uF 0805 Panasonic ECJ-2VB1H103K

1 C11 0.047uF 250V Box Panasonic ECQ-U2A473ML

1 D2 200V .2A Micro Commercial BAV20WS-TP

1 D3 200V 1A STMicroelectronics STTH102

1 F1 5.1 Ohm Fusable Resistor

1 L1 Common Mode Hua Jung Comp. HJC0308Q

1 R1 JUMPER

1 R2 2K 5% 1/2W

1 R3 9.1K 5% 1206

1 R4 220 5% 805

1 R5 1K 5% 0805

1 R6 13.3K 1% SMD 0805 Panasonic ERJ-6ENF1332V

1 R7 3.40K 1% SMD 0805 Panasonic ERJ-6ENF3401V

1 R8 4.7 5% 1206

1 R9 3.3K 5% 1206

1 TR1 Output transformer Cramer Coil CVP11-021

1 U2 H11A817A Fairchild H11A817A

1 U3 TL431 STMicroelectronics TL431AIZ

1 U4 VIPer12A Dip STMicroelectronic VIPer12ADIP

1 MOV 220V Varistor

1 HS U4 Heat Sink

2 AC Wires

1 Output cable assembly

5 Revision History AN2173 - APPLICATION NOTE

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5 Revision History

Date Revision Changes

11-November-2005 1.0 First edition

AN2173 - APPLICATION NOTE 5 Revision History

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Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequencesof use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is grantedby implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are subjectto change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are notauthorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics.

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