PFS757HG POWERINT [Power Integrations, Inc.], PFS757HG Datasheet - Page 21

• Manufacturer Part Number: PFS757HG
• Description: Combined Two-Switch Forward and Flyback Power Supply Controllers with Integrated High Voltage MOSFETs
• Manufacturer: POWERINT [Power Integrations, Inc.]

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
Figure 27. Schematic of High-Efficiency +12 V, 25 A Main Output and +5 V, 2.5 A Standby Power Supply.
www.powerint.com
J3-1
J4-1
J3-3
1N5404
D13*
4 A
F2
*Optional component for accidental reverse connection
4.7 kΩ
PC817X1J00F
R20
U3B
4.7 kΩ
MMSZ5243BT1G
R22
380 VDC
MMBT4401
VR4
13 V
7.5 kΩ
Q1
C18
1 nF
R16
BAS16HT1G
1 kΩ
R23
D10
820 Ω
R17
PC817X1J00F
PC817XI1J00F
PC817XI1J00F
FB
232 kΩ
470 Ω
R29
R25
U4B
U1B
U2B
1.33 MΩ
1.33 MΩ
1.33 MΩ
R12
R13
R35
EN
280 kΩ
R27
P6KE150A
VR3
1.33 MΩ
100 Ω
1.33 M
1 nF
C19
R19
R6
R18
1.33 MΩ
R36
3.3 nF
4.7 Ω
C2
C12
1 µF
R7
TFS762HG
FB
BP
EN
10
11
R
L
7
9
8
4.7 Ω
4.7 Ω
U6
R5
R8
CONTROL
13
5
G
VDDH
1N4007
1N4007
D3
D4
6
S
16
HD
14
HS
1
D
3
DSB
UF4005
D8
2.2 Ω
R1
330 µF
14 - 25 V
C20
100 nF
C6
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.
R14
2 kΩ
270 µF
C1
UF4005
D9
100 nF
BAV20
C3
D5
2.2 nF
RGP100
C21
D12
T
1
1
2
6
2
3
5
STANDBY
T
MAIN
13,14
9,10
6,7
9,10
100 nF
C13
M6060C-E3/45
STPS1045B
M6060C-E3/45
D7
D11
D6
2200 µF
C17
47 Ω
R26
PC817XI1J00F
3.3 µH
LM431
L1
U5
U2A
LM431
100
TFS757-764HG
R28
U7
Ω
750
R15
PC817XI1J00F
2
R21
Ω
kΩ
1 nF
1
C9
R33
U1A
kΩ
2.2 µH
15
100 nF
L2
470 nF
1
R30
330 nF
R9
C14
C16
C8
kΩ
kΩ
12 V
ZMM5242B-7
100 nF
3.92
221
C4
R10
R24
12 V
VR1
4.75
4.75
kΩ
Ω
R31
R34
kΩ
kΩ
100
43.2
47 nF
ZMM5230B-7
PI-5969-102810
R3
R11
C5
3300 µF
2200 µF
Ω
C10
kΩ
4.7 V
VR2
C15
PC817XI1J00F
4.7
Remote ON/OFF
R32
150
D2
R4
Rev. C 02/11
kΩ
U3A
Ω
3300 µF
+12 V
SW1
+5 V
RTN
RTN
RTN
C11
5 V
21