IntroductionThis 24 V/100 W output converter with reinforced isolation represents an ideal auxiliary power supply for many industrialapplications. It features a very wide input range from the standard European 230 VAC up to 690 VAC or 1 kVDC, and cancontinue operation for a limited time with input voltages as low as 150 VDC.

The default fixed-frequency operation can be changed to quasi-resonant mode through a simple resistor setting.

Figure 1. STEVAL-ISA211V1 photo top view

Ultra-wide range 100 W flyback converter with STEVAL-ISA211V1

AN5548

Application note

AN5548 - Rev 1 - December 2020For further information contact your local STMicroelectronics sales office.

www.st.com

1 Overview

Table 1. STEVAL-ISA211V1 board parameters

Symbol Parameter Test Conditions min typ. max Unit

VIN

Input voltage AC 100W load 230 - 690

VInput voltage DC 100W load 250 - 1000

Input voltage AC 50W load 180 - 690

Input voltage DC 50W load 150 - 1000

VOUTt Output voltage - - 24 - V

POUT Output power Vin 230VAC – 1kVDC 100 - - W

η Efficiency

Vin 230VAC, 100W load - 86.0 -

%Vin 400VAC, 100W load - 88.0 -

Vin 1kVDC, 100W load - 85.9 -

Vin 150VDC, 50W load - 86.2 -

AN5548Overview

AN5548 - Rev 1 page 2/15

2 Design description

The converter is based on the L6566BH multi-mode controller in standard single-switch Flyback topology withisolated output, implementing discontinuous-conduction mode operation for every input voltage.

2.1 Input stageThe board comes equipped with an industrial 1 kV 10.3x38 mm fuse, but a footprint for a standard 5x20 mmfuse is available for testing on lower voltages. The input voltage is rectified and stabilized by six 68 μF / 400 Vcapacitors arranged in a series of three paralleled pairs, which are balanced with two 1206 SMD resistors.

Figure 2. HV startup circuit

68μF / 400V

R8

470k

C14

68μF / 400V

470k

R9

470k

C1668μF / 400V

R7

R10

470k

68μF / 400V

D1215V

C17

1K

R11

C12

68μF / 400V

C11

V+

GND

R5

470k

Q1STD1NK60

C1368μF / 400V

R6

470k

D1115V

L6 L6566BH HV pin

The above circuit provides safe HV startup. Transistor Q1 acts as a simple voltage follower of the voltage dividedby the input capacitors, approx. ⅔ of V+. During off-state, the HV pin voltage is only biased by leakage currents.Both Q1 and HV pin are protected by Zener diodes D11 and D12.

2.2 Soft startThe capacitor connected to the SS pin of the L6566BH controller is used for both soft-start and overloadprotection. During the soft-start phase, the capacitor is charged by current iSS = 20 μA (typ.) from zero voltageuntil VSS reaches 2 V. During this period, the setpoint for the primary winding current rises from zero to maximum,and the COMP pin used for feedback is ignored. After soft-start, the voltage remains at 2 V until an overloadappears, in which case the capacitor is again charged with a current exactly one quarter of the soft-start current. Ifthe overload lasts long enough for VSS to reach 5 V, the device stops switching, thus allowing some tolerance forshort overload events.

AN5548Design description

AN5548 - Rev 1 page 3/15

The time to charge the output capacitors to the nominal output voltage depends on the load and input voltage.As the COMP pin is ignored during soft-start, an inappropriate SS capacitor may provoke output overvoltage. Toprevent this, the soft-start time must be set for a maximum input voltage and no load, thus triggering an overloadstate for any other condition.It is not possible in this application to ensure a safe soft-start and no stops due to overload for every conditionwith one capacitor, so the board implements a modified soft-start circuit shown below.

Figure 3. Soft start circuit

10nFC23

33nFC26

GND

D9

BAT48

SoftStart pin

GND

D10

IN4148

33nFC27

Vref pin

In this circuit, the soft-start capacitor C23 ensures a smooth soft-start for every input voltage and output load,while the Vref voltage divider (capacitors C26 and C27) with D10 delays overload protection. D9 clamps the SSpin to Vref to trigger an auto-restart in case of an overload.

Note: For a latch function, D9 diode can be soldered out.

2.3 QR mode, switching frequency, ZCD and OVPTo change from the default Fixed-frequency (FF) mode to Quasi-resonant (QR) mode, R26 = 0Ω must bemounted. Both ZCD resistors R23 and R28 must also be mounted for QR operation. These resistors also provideovervoltage protection (OVP) in both QR and FF modes. If OVP is not required, it is necessary to clamp ZCD pinto GND with resistor R23 (e.g., 330 kΩ) to ensure stability.If QR operation is selected, the switching frequency increases with lower load. When it reaches its limit (set withR25), the converter starts implementing valley skipping mode for lower loads and burst mode for no load or verylight loads. As switching losses are proportional to switching frequency and input voltage, for a full input voltagerange it is advisable to choose the limit near the 51.3 kHz FF operation switching frequency; i.e., R25 = 39 kΩ.If input voltage range for QR operation only involves lower voltages (e.g., only 230 VAC), R25 may be reduced to16 kΩ; i.e., approx. 125 kHz frequency limit.

2.4 Other featuresThe PCB is designed to accommodate modifications and additional features, including footprints for VoltageFeed-Forward and AC_OK components. While the values depend on the required purpose, they should be similarto or the same as the ratios indicated in schematic to ensure necessary clearance.

AN5548QR mode, switching frequency, ZCD and OVP

AN5548 - Rev 1 page 4/15

3 Realized application

The following figures show the layout of the two-layer, 35µm Cu thickness, 226mm x 57.5mm application board.

Figure 4. STEVAL-ISA211V1 photo top view

Figure 5. STEVAL-ISA211V1 silk top layer

Figure 6. STEVAL-ISA211V1 silk top layer

AN5548Realized application

AN5548 - Rev 1 page 5/15

The Mains are connected to input terminal J1, and the output terminal is J4. For voltage sensing or for anotherlight load, two test points marked + and – near J4 are also connected to output.

Figure 7. Mains and load connection

3.1 Measurement resultThe following figure shows the efficiency measurement results for various input voltages.

Figure 8. STEVAL-ISA211V1 efficiency measurements

Effic

ienc

y [%

]

Pout [W]

Vin = 150VDC Vin = 230VAC Vin = 400VAC

Vin = 600VAC Vin = 690VAC Vin = 1kVDC

65

70

75

80

85

90

0 10 20 30 40 50 60 70 80 90 100

AN5548Measurement result

AN5548 - Rev 1 page 6/15

4 Schematic diagrams

Figure 9. STEVAL-ISA211V1 circuit schematic

120kR39

C21

1

1 HV

Q2

GND

C3

GND

GND

C17

100nF

100nC25

C9

470kR5

N/A

1k5

GD1

VREF

ZCD 11

D8

ca100kR18

3

D10

U3TL431_SMD

10R

N/A

1

C15

D2

C32

15V

R4

Vout

1

R27

GND

C36

R2316k / 330k

C23

C35

R38S1

C19

1.5KE350A

D7

GND2

GND

68uF / 400V

15

16AC_OK

U1

68uF / 400VC12

3

D14BAT48

N/A

C5 N/A

_J3

ca1MR16

ca1M

R13

N/A / 0R

47k

1

3

2n2

C1

GND

1

22k

GND

C8

V+

4 GND9

GND2

F1 N/A

DIS

2

14VFF

N/A

R22

GNDC26

4

Q3

1K

C29

H1

33n

Rf

Rg

Rh

470kR8

2n2

1200uF

C11

R30 N/A Vout

D12

D5

470kR10

R25

1200uF

1.5KE350A

2T1

1K

R37

715V

Cc3

1k

R33

S4

10R

D17 STPS20LCD200

R22x3.6mH

COMP

10

GND

1

Optoisolator1

470kR6

15k

D1

SGBJ2516

SS

C22

68uF / 400VC14

NTC

L6566B(H)

C34

ca1M

D13

N/A

R11

10RR1

L2 680uH

U

R12

39k

V+

3

STPS1150

R21

0R

GND

N/A

J4

68uF / 400V

14

8

R32

330m

C27

100nF

Ld

330R

R35

C33

2

Cc1

Ri

2

2n2

C20

D4

4n7

BC817

FMODCS 7

N/A

La V+a

PEa

PEb

Na

Ga

GS

S

Ra

Rb

Rc

Rd

Re

2

C24

N/A

Snubber

NTC

3

470k

J2+

100n

Cc2

Q1

2n2

N/A

68uF / 400VC13 D11

C37

R3

FF: R28 & R26 N/A; R25 39k; R23 330kQR: R26 0R; R25 16k

R7

C18

1

2n2

N/A

100n

GND2

Source

S3

33u

8

1

1k1

N/A

H2

R20330k / N/A

1K

3 IN

ca1MR14

NTCW

PE

J1LN

Input 1.5KE350A

D6

R34

R24

R31 10R

68uF / 400VC16

-

C31

R28

10n

12 Mode/SC

OSC13

330p

33n

C2

4n7

GND

C7L1

GND

5

R17

C10

GND

VCC

6

F2 SPF 8A

STD1NK60

2

R36

R40

D15

0R

N/A

V

GND

3

S2

3G

ND

N/A

BAT48

9k1

470kR9

R26

+

10n

V+

2n2

C30

OCP Latch: D9 N/AOCP AutoRestart: D9 BAT41AC_OK & VFF not used -> R20 330k, R19 0RAC_OK & VFF not used - > R12-18 N/A, C15 & C24 N/A

C28

100n

Le

STTH112

Output

R19

6

C6

18V

U2

4GD

VCC

D16

D3

Gate5

D9BAT48

47u

VAR

C4

Snubber

ca1MR15

2

Lb Lc

G

AN

5548 - Rev 1

page 7/15

AN

5548Schem

atic diagrams

5 Bill of materials

Table 2. STEVAL-ISA211V1 bill of materials

Item Q.ty Ref. Part/Value Description Manufacturer Order code

1 4 C1, C2, C3,C4

2n2 Y1 cap RM 10 12mm dia Y1 cap RM10 12mm dia 760 V Capacitors Vishay VY1222M37Y5VQ63V0

2 2 C5, C6 100n CAP RM22.5 26x13.5 CAP RM22.526x13.5 2000 VDC Capacitors Kemet PHE450SD6100JR06L2

3 0 C7, C8, C9,C10 1206 Capacitors (not

mounted) Any

4 6C11, C12,C13, C14,C16, C17

68 µF RM7.5 18 mm 400 V Electrolytic capacitor Würth Elektronik 860241381006

5 0C15, C21,C24, C28,C29, C30

0805 Capacitors (notmounted) Any

6 1 C18 33µ RM2.5 6.3 mm 50 V Electrolytic capacitor Würth Elektronik 860080673003

7 1 C19 47µ RM2.5 6.3 mm 25 V Electrolytic capacitor Würth Elektronik 860240473003

8 4 C20, C25,C36, C37 100 n 0805 50 V ±10% Multilayer capacitors Any

9 1 C22 330 p 0805 50 V ±10% Multilayer capacitor Any

10 2 C23, C33 10 n 0805 50 V ±10% Multilayer capacitors Any

11 2 C26, C27 33 n 0805 50 V ±10% Multilayer capacitors Any

12 2 C31, C32 1200 µF RM5 13 mm 35 V Electrolytic capacitors Würth Elektronik 860040578015

13 2 C34, C35 4 n7 Y1 cap RM 10 12mm dia Y1 cap RM10 12 mm 760 V

Y1 cap RM 10 12mmdia Vishay VY1472M51Y5VQ63V0

14 1 D1 SGBJ bridge rectifier3-phase MULTICOMP PRO SGBJ2516

15 0 D2, D3, D4 SMC not mounted Any

16 3 D5, D6, D7 1.5KE350A DO-201 RM 15mm Transil Transil ST 1.5KE350A

17 1 D8 STTH112 SMA Diode Diode ST STTH112A

18 3 D9, D10, D13 BAT48 SOD123 Schottky diode Schottky diode ST BAT48ZFILM

19 3 D11, D12,D14 BZV55C18 SOD80_minimel Zener diode MULTICOMP PRO BZV55C18

20 1 D15 STPS1150 SMA Schottky diode Schottky diode ST STPS1150A

21 0 D16 SOD123 not mounted Any

22 1 D17 STPS20LCD200CT TO-220AB Schottkydiode Schottky diode ST STPS20LCD200CT

23 1 D17 Thermal paste Any

24 F1 Fuse holder LITTELFUSE 05200101Z

25 2 F2 10x38mm Fuse holder SCHURTER 0751.0505

26 1 F2 SPF 8A Fuse 10x38mm 1000 V 8 A Fuse LITTELFUSE 0SPF008.T

27 3 FM1, FM2,FM3 Fiducial Mark v1 Any

28 GD1 GDModule (notmounted) Any

29 1 H1 WA-T247-101E Heatsink TO247 OHMITE WA-T247-101E

AN5548Bill of materials

AN5548 - Rev 1 page 8/15

Item Q.ty Ref. Part/Value Description Manufacturer Order code

30 1 H2 WA-T220-101E Heatsink TO220 OHMITE WA-T220-101E

31 1 J1 3x MC000054 6x Screw 1kV RM 9.52 -3Pin 6x Screw 1kV RM 9.52 - 3Pin

6x Screw 1kV RM9.52 - 3Pin MULTICOMP PRO MC000054

32 2 J2, J3 1.32 mm Test point VERO 20-313145

33 1 J4 RM 9.52 2x Screw 1kV RM 9.52 Jumper MULTICOMP PRO MC000054

34 1 L1 2x3.6mH Coilcraft E35xx CMM Coilcraft E3502-AL

35 1 L2 680µH Ind Coilcraft PCV-2 1.3 A Ind Coilcraft PCV-2 Coilcraft PCV-2-684-01L

36 1 L2 8G206M3X30 Polyamide screw DREMEC 8G206M3X30

37 1 L2 M3/BN81 M3 Polyamide nut BOSSARD M3/BN81

38 2 L2 1404830 M3 Polyamide pad BOSSARD 1404830

39 1 Q1 STD1NK60T4 D pak MOSFET MOSFET ST STD1NK60T4

40 1 Q2 BC817-40 SOT23 Signal BJT Any

41 1 Q3 SMICA-SOT93-2 Isolation pad NINIGI SMICA SOT93-2

42 1 Q3 STW12N170K5 TO-247 Power MOSFET ST STW12N170K5

43 3 R1, R2, R3 10R NTC RM5 dia 8.5 NTC RM5 dia 8.5 Resistors EPCOS B57153S0100M000

44 1 R4 V1000LA160BP Var RM8.5 dia 20V1000LA Varistor Varistor LITTELFUSE V1000LA160BP

45 6 R5, R6, R8,R9, R10, R11 470k 1206 Resistor 0.25 W 1% Resistors Any

46 1 R7 1K 1206 Resistor 0.25 W 1% Resistor Any

47 R12, R24,R27, R30 0805 Resistors (not

mounted) Any

48

R13, R14,R15, R16,R17, R18,R28

1206 Resistors (notmounted) Any

49 1 R19 0 R 0805 0.125 W ±1% Resistor Any

50 2 R20, R23 330 k 0805 0.125 W ±1% Resistor Any

51 2 R21, R32 0R 1206 0.25 W ±1% Resistor Any

52 1 R22 1k5 0805 0.125 W ±1% Resistor Any

53 1 R25 39k 0805 0.125 W ±1% Resistor Any

54 R26 0805 Resistor (notmounted) Any

55 1 R31 10 R 0805 Resistor 0.125 W ±1% Resistor Any

56 1 R33 330 m 2512 1 W ±1% Current SenseResistor Any

57 1 R34 1 k 0805 0.125 W ±1% Resistor Any

58 1 R35 330 R 0805 0.125 W ±1% Resistor Any

59 1 R36 9k1 0805 Resistor 0.125 W ±1% Resistor Any

60 1 R37 1k1 0805 Resistor 0.125 W ±1% Resistor Any

61 1 R38 22k 0805 Resistor 0.125 W ±1% Resistor Any

62 1 R39 120k 0805 Resistor 0.125 W ±1% Resistor Any

63 1 R40 15k 0805 Resistor 0.125 W ±1% Resistor Any

64 4 S1, S2, S3,S4 M3 10 mm Spacer stud Würth Elektronik 970100351

AN5548Bill of materials

AN5548 - Rev 1 page 9/15

Item Q.ty Ref. Part/Value Description Manufacturer Order code

65 4 S1, S2, S3,S4 Screw M3 Bossard 1006614

66 1 T1 Custom transformer Würth Elektronik 750318247

67 1 U1 L6566BH SOIC16 PWM controller PWM controller ST L6566BH

68 1 U2 HCPL-817-00DE PDIP4 Optoisolator Optoisolator Broadcom / Avago HCPL-817-00DE

69 1 U3 TL431AIL3T SOT23 LP Voltage reference Voltage reference ST TL431AIL3T

AN5548Bill of materials

AN5548 - Rev 1 page 10/15

Revision history

Table 3. Document revision history

Date Version Changes

11-Dec-2020 1 Initial release.

AN5548

AN5548 - Rev 1 page 11/15

Contents

1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

2 Design description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

2.1 Input stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.2 Soft start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.3 QR mode, switching frequency, ZCD and OVP. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2.4 Other features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

3 Realized application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

3.1 Measurement result . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

4 Schematic diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7

5 Bill of materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

AN5548Contents

AN5548 - Rev 1 page 12/15

List of figuresFigure 1. STEVAL-ISA211V1 photo top view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1Figure 2. HV startup circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Figure 3. Soft start circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4Figure 4. STEVAL-ISA211V1 photo top view . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Figure 5. STEVAL-ISA211V1 silk top layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Figure 6. STEVAL-ISA211V1 silk top layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Figure 7. Mains and load connection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Figure 8. STEVAL-ISA211V1 efficiency measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Figure 9. STEVAL-ISA211V1 circuit schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

AN5548List of figures

AN5548 - Rev 1 page 13/15

List of tablesTable 1. STEVAL-ISA211V1 board parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2Table 2. STEVAL-ISA211V1 bill of materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Table 3. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

AN5548List of tables

AN5548 - Rev 1 page 14/15

IMPORTANT NOTICE – PLEASE READ CAREFULLY

STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, enhancements, modifications, and improvements to STproducts and/or to this document at any time without notice. Purchasers should obtain the latest relevant information on ST products before placing orders. STproducts are sold pursuant to ST’s terms and conditions of sale in place at the time of order acknowledgement.

Purchasers are solely responsible for the choice, selection, and use of ST products and ST assumes no liability for application assistance or the design ofPurchasers’ products.

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Resale of ST products with provisions different from the information set forth herein shall void any warranty granted by ST for such product.

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Information in this document supersedes and replaces information previously supplied in any prior versions of this document.

© 2020 STMicroelectronics – All rights reserved

AN5548

AN5548 - Rev 1 page 15/15