February 2014 DocID025645 Rev 1 1/18

AN4419Application note

VIPER37HE: 15 W wide range single output evaluation board

By Fabio Cacciotto

Introduction

This application note describes a 15 W wide range evaluation board, based on Viper37HE, which is designed as an example of an isolated auxiliary power supply.

The board and the transformer were designed and optimized in order to have a very compact size evaluation board.

www.st.com

Contents AN4419

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Contents

1 Test board: design and evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.1 Output voltage characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

1.2 Efficiency and light load measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

1.3 No-load and light load consumptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

1.4 Typical board waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2 Conducted noise measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

3 Thermal measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

5 Evaluation tools and documentation . . . . . . . . . . . . . . . . . . . . . . . . . . 16

6 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

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AN4419 Test board: design and evaluation

18

1 Test board: design and evaluation

Table 1 summarizes the electrical specification of the power supply, Table 2 provides the BOM and Table 4 lists transformer's spec. The electrical schematic is shown in Figure 2 and the PCB layout in Figure 3 and Figure 4.

Figure 1. Electrical schematic

Table 1. VIPer37H evaluation board electrical specification

Parameter Min. Typ. Max. Unit

AC Main Input voltage 100 265 VAC

Mains frequency (fL) 50 60 Hz

Output Voltage 11.7 12 V 12.3 V

Output Current 1.25 A

Output ripple voltage 50 mV

Rated output power 15 W

Input power in standby @ 230VAC 50 mW

Active mode efficiency 78 %

Ambient operating temperature 60 °C

C633uF

D4

BAT41ZFILM

L2

3.3uH

R430k

16NTC

C41nF

GND

12V-1.25A

OPTOSFH610A-2

OPTOSFH610A-2

C1210nF

C10100uF

IC2TS432

BR

CONT

DRAIN

GND

CONTROL

VDD

FB

IC1VIPER37HE

-+ BR

RMB6S

R71k

T1

F1

2A

D2BAT41ZFILM

AC IN AC IN

D6

STPS5H100UF

D3

BAT41ZFILM

R647k

R24.7

21

34

CM2X20mH

C833nF

R812k

C72.2nF

R3133K

C9470uF

D518V

R1115k

R982k

C315uF

R10130k

R5220

D1STTH1L06A

C13

2.2nF

R1220k

RV

320V

R122.2M

1mH

L1

C5220pF

C215uF

C111uF

C1

220nF - X2

AM18323v1

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Figure 2. Evaluation board (30 x 72 mm) max

AM18336v1

Table 2. VIPer37H evaluation board: bill of material

Reference Part Description Note

R1 220 kΩ 0.33 W – 200 V

R2 4.7 Ω 1% tolerance

R3 133 kΩ 1% tolerance

R4 30 kΩ 1% tolerance

R5 220 Ω 0.25 W

R6 47 kΩ 1% tolerance

R7 1 kΩ

R8 12 kΩ

R9 82 kΩ 1% tolerance

R10 130 kΩ 1% tolerance

R11 15 kΩ 1% tolerance

R12 2.2 MΩ 1% tolerance

C1 BFC233920224 220 nF - 275 V x 2 Vishay

C2, C3 450BXF15M10X20 15 μF - 450 V electrolytic Rubycon

C4 C3216C0G2J102JT 1 nF - 630 V MLCC TDK

C5 GRM188R71H221KA01D 220 pF - 16 V MLCC Murata

C6 35YXM33MEFC5X11 33 μF - 35 V electrolytic Rubycon

C7 GRM1885C1H222FA01D 2.2 nF - 50 V MLCC Murata

C8 GRM188R71H333KA61D 33 nF -16 V MLCC Murata

C9 25ZLJ470M10X12.5 470 μF - 25 V electrolytic Rubycon

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AN4419 Test board: design and evaluation

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Note: If not otherwise specified, all resistors are ± 5%, 0.1 .

C10 25YXJ100M5X11 100 μF - 25 V electrolytic Rubycon

C11 GRM188C81E105KAADD 1 μF - 25 V MLCC Murata

C12 GRM188R71H103KA01D 10 nF - 50 V MLCC Murata

C13 DE2E3KY222MA2BM01 2.2 nF - 250 V X1/Y1 CAP Murata

D1 STTH1L06A Ultra-fast diode 600 V - 1 A STMicroelectronics

D2, D3, D4 BAT41ZFILM Signal Schottky diode STMicroelectronics

D5 MMSZ5248B-V-GS08 18 V Zener diode Vishay

D6 STPS5H100B Power Schottky 100 V - 5 A STMicroelectronics

L1 B82144A2105J 1 mH Axial inductor Epcos

L2 SD43-332ML 3.3 μH Power inductor Coilcraft

CM 744821120 20 mH CM choke Wurth Elektronik

IC1 VIPer37LE Offline HV converter STMicroelectronics

IC2 TS432ILT 1.24 V Shunt voltage reference STMicroelectronics

OPTO SFH610A-2 Optocoupler Vishay

TF YJ-310V600210 Flyback transformer Yujing Technology

BR RMB6S Bridge 600 V - 1 A Taiwan Semiconductor

NTC B57236S160M NTC Inrush current limiter Epcos

Fs 0461002.ER 2 A fuse Littlefuse

Table 2. VIPer37H evaluation board: bill of material (continued)

Reference Part Description Note

Table 3. Transformer characteristic

Reference Description

Manifacturer Yujing Technology CO. LTD.

Part number YJ-310V600210

Core EEE - 13 V

Ferrite 3C94 Ferroxcube

Primary Inductance 0.85 mH ±10%.

Leakage inductance 40 µH max

Primary turns (N1+N3) 75

Secondary turns (N2) 12

Auxiliary turns (N4) 14

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Figure 3. Electrical scheme

Figure 4. Drawing transformer (mm.)

AM18338v1

AM18337v1

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1.1 Output voltage characteristics

The output voltage of the board is measured in different line and load conditions. Figure 5 shows the results: the output voltage variation range is a few tens mV for all the tested conditions.

All output voltages have been measured on the output connector of the board.

Figure 5. Line and load regulation

1.2 Efficiency and light load measurements

Any external power supply (EPS) must be capable to meet the international regulation agency limits. The European code of conduct (EC CoC) and US department of energy (DoEUS EISA 2007) limits are taken as reference. EPS limits are fixed up to 77.76%, when the average efficiency is measured. The average efficiency measures the average value at 25%, 50%, 75% and 100% of the rated output power, at both 115 VAC and 230 VAC. Figure 6 shows the results.

0.00 0.25 0.50 0.75 1.00 1.25 1.5011.8

11.9

12.0

12.1

12.2

12.3

115 Vac 230 VacO

utpu

t vol

tage

[V]

Output current [mA]

AM18324v1

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Figure 6. Efficiency vs. output power

1.3 No-load and light load consumptions

No-load consumptions and light load consumption are two important parameters that must be considered when selecting the IC controller and very often they are the key parameters of choice.

The presented board was optimized in order to provide an extremely low consumption at zero load but also in order to meet EµP Lot 6 energy saving regulation, which requires that the efficiency of the converter must be higher than 50% when the output is loaded with 250 mW.

In Figure 7 and Figure 8 the consumption in the said condition are shown.

Figure 7. No load consumption vs. input voltage

AM18325v1

0 2 4 6 8 10 12 14 1670

72

74

76

78

80

82

84

86

88

EC Code of Conduct

115 Vac 230 Vac average @ 115 Vac average @ 230 Vac

Effic

ienc

y [%

]

Output power [W]

AM18326v1

50 100 150 200 250 30010

15

20

25

30

35

40

45

50

55

60

65

Inpu

t pow

er [m

W]

Input voltage [Vac]

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AN4419 Test board: design and evaluation

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Figure 8. Light load consumptions at 250 mW O/P

1.4 Typical board waveforms

In this section, typical waveforms are reported.

Drain voltage and current waveforms were reported at nominal input voltages and full load in Figure 9 and Figure 10.

The startup phase is shown in Figure 11 and Figure 12: the IC starts with very clean waveforms and no overshoot/undershoot appear on the output.

Finally also the output voltage when the converter is submitted to dynamic load variations is measured, in order to be sure that good stability is ensured and no overvoltage on undervoltage occurs

The board was submitted to dynamic load variations from 0% to 100% load (Figure 13 and Figure 14): no abnormal oscillations were noticed on the output and the over/under shoot were well within acceptable values.

AM18327v1

50 100 150 200 250 300200

250

300

350

400

450

500

250 mWIn

put p

ower

[mW

]

Input voltage [Vac]

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Figure 9. Drain current and voltage at full load 115 VAC

Figure 10. Drain current and voltage at full load 230 VAC

AM18328v1

Ch1 (Max): 340 VCh2 (Max): 596.mA

IDS

VDS

M: 4.0 µs/div

AM18329v1

Ch1 (Max): 517 VCh2 (Max): 612 mA

M: 4.0 µs/div

IDS

VDS

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AN4419 Test board: design and evaluation

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Figure 11. Startup at full load and 115 VAC

Figure 12. Startup at full load and 230 VAC

AM18330v1

Ch3 (Max): 12.04 V M: 40 ms/div

VDD

VD S

VOUT

AM18331v1

Ch3 (Max): 12.06 V M: 40 ms/div

VDD

VD S

VOUT

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Figure 13. Step load at 115 VAC

Figure 14. Step load at 230 VAC

AM18332v1

Ch1 (Max): 0 ACh1 (Min): 1.26 A

Ch2 (Max): 12.07 VCh2 (Min): 11.73 V M: 20 .0 ms/div

VOUT

IOUT

AM18333v1

Ch1 (Max): 0 ACh1 (Min): 1.26 A

Ch2 (Max): 12. 06 VCh2 (Min): 11.7 4 V M: 20 .0 ms/div

VOUT

IOUT

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AN4419 Conducted noise measurements

18

2 Conducted noise measurements

A pre-compliance test for EN55022 (Class B) European normative was performed using peak measurements detector of the conducted noise emissions at full load and nominal mains voltages. Figure 15 and Figure 16 show the results. As seen in the diagrams, in all test conditions there is a good margin for the measurements with respect to the AV and QP limits, also using the peak detector with max-hold function.

Figure 15. CE average measurement at 115 VAC and full load

Figure 16. CE average measurement at 230 VAC and full load: Peak measurement

AM18334v1

AM18335v1

Thermal measurements AN4419

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3 Thermal measurements

A thermal analysis of the board was performed using an IR camera.

The board was submitted to full load at nominal input voltage and the thermal map was taken 30 min. after the power on at ambient temperature (25 °C).

Figure 17, Figure 18, Figure 19 and Figure 20 show the results.

Figure 17. Thermal map at 115 VAC and full load top side

Figure 18. Thermal map at 115 VAC and full load bottom side

Figure 19. Thermal map at 230 VAC and full load top side

Figure 20. Thermal map at 230 VAC and full load bottom side

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AN4419 Conclusions

18

4 Conclusions

A 15 W wide range single output flyback converter using the new VIPer37HE has been introduced and the results are presented.

The transformer arrangement and the very compact sizes make the PSU suitable as external adapter or as an auxiliary power supply in all the applications where performances and dimensions are the main constrains.

The efficiency performances were compared with requirements of the most important international regulation agencies for external AC-DC adapters, resulting in a wide margin respect the minimum required.

Evaluation tools and documentation AN4419

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5 Evaluation tools and documentation

The VIPer37LE evaluation board order code is: STEVAL-ISA140V1.

Further information about this product are available in the VIPer37 datasheet at www.st.com.

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AN4419 Revision history

18

6 Revision history

Table 4. Document revision history

Date Revision Changes

24-Feb-2014 1 Initial release.

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