TFS757 datasheet(21/36 Pages) POWERINT

21 / 36 page

Rev. E 04/15

TFS757-764HG

www.power.com

Figure 27. Schematic of High-Efficiency +12 V, 25 A Main Output and +5 V, 2.5 A Standby Power Supply.

the Main converter. The Main converter will first turn on the

bottom switch to allow the high-side drive to receive the boot-

strap bias. After 14 ms the Main converter will start switching

both switches at 66 kHz and the main output voltage will rise.

Once the regulator U5 becomes active, current will flow through

the optocoupler U1. The collector of U1 will sink current out of

the FEEDBACK pin to adjust for appropriate duty cycle to

maintain regulation. The normal operating sink current is

between 1 mA and 2 mA. There is a forward phased bias

winding off the main transformer that provides sustained bias

for the high-side driver. During normal and brownout operation

the RESET pin senses the turn off clamp voltage via the resistor

chain R6, R18, R19 and the internal controller determines the

maximum safe duty factor by comparing the RESET pin current

with the LINE-SENSE pin current. This features guarantees that

saturation of the transformer is completely avoided in all conditions

including brownout and load transients. The LINE- SENSE pin

also has a UV low threshold which turns off the Main converter

when the input voltage is below 215 V.

This design in particular is intended to operate with a minimum

of 30 CFM airflow at full load.

Both the main and standby output have overvoltage protection

from sense circuit around U4 which will source >15 mA during

fault into bypass pin to cause latching shut-off of both converters.

The standby uses auto-restart to protect the standby output

from overpower and over-current. The main output is current

limited by the selected internal primary current limit of the main

switch path.

14 - 25 V

BAV20

VR4

MMSZ5243BT1G

13 V

M6060C-E3/45

UF4005

C21

2.2 nF

3.3

µH

100 nF

47 nF

C10

3300

µF

C11

3300

µF

R21

2 kΩ

R28

100 Ω

R30

1 kΩ

R34

4.75 kΩ

R31

4.75 kΩ

LM431

R33

1 kΩ

R32

4.7 kΩ

SW1

Remote ON/OFF

U3A

PC817XI1J00F

R24

3.92 kΩ

100 Ω

150 Ω

RTN

5 V

12 V

VR1

ZMM5242B-7

12 V

VR2

ZMM5230B-7

4.7 V

R15

750 Ω

U1A

PC817XI1J00F

15 kΩ

R10

221 Ω

1 nF

UF4005

C19

1 nF

C20

330 µF

*Optional component for accidental reverse connection

R26

47 Ω

C17

2200 µF

U2A

PC817XI1J00F

C14

470 nF

C16

330 nF

C15

2200 µF

C13

100 nF

U2B

PC817XI1J00F

U1B

PC817XI1J00F

R25

232 kΩ

R27

280 kΩ

D10

BAS16HT1G

J3-1

J4-1

J3-3

R14

2 kΩ

100 nF

1N4007

4.7 Ω

2.2 Ω

270 µF

4 A

D13*

1N5404

R20

4.7 kΩ

R16

7.5 kΩ

R17

820 Ω

R35

1.33 MΩ

R13

1.33 MΩ

R12

1.33 MΩ

R23

1 kΩ

R22

4.7 kΩ

U3B

PC817X1J00F

U4B

PC817X1J00F

100 Ω

VR3

P6KE150A

R18

1.33 MΩ

R19

1.33 M

R36

1.33 MΩ

4.7 Ω

TFS762HG

1N4007

D12

RGP100

D11

STPS1045B

9,10

13,14

380 VDC

RTN

TSTANDBY

TMAIN

VDDH

DSB

PI-5969-102810

C12

1 µF

6,7

CONTROL

+12 V

+5 V

R29

470 Ω

2.2

µH

4.7 Ω

C18

1 nF

3.3 nF

100 nF

R11

43.2 kΩ

MMBT4401

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