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9.1.3
Format Power board
Block diagram
Format Power Board
DC 380V from PFC
IC7
D
5
F
4
S
3
X
2
L(M)
C
Image 9-4
Block diagram Format power board
Description
The format power board repeats operation which turns on an off at pin 7 of IC7, and the pulse appears in secondary sides through
the converter transformer T2. At the time, the voltage of 3.3V at the secondary side is detected by IC8, the negative feedback to IC7
is carried out at photo coupler ISO3 and then the voltage is stabilized. Other outputs are determined by the turn ratio of secondary
side of T2, and the voltage rectified, smoothed through the series regulator (5V is stabilized at IC6, 2.5V is stabilized at IC4). The
voltage rectified ans smoothed by D14 and C53 at primary winding of T2 is supplied as a power supply voltage of IC7 on primary
side.
The format power board is a flyback voltage mode controlled and switched by a hybrid IC7, which has 6 pins that includes pi 5 (F) for
frequency setting (short to C is 66kHz, to S is 132kHz); pin 7 (D) for drain of MOSFET; pin 4 (S) fo source of MOSFET; pin 2 (L) for
line sense; pin 3 (X) for external current limit (on-off controls, current limiting) and pin 1 (C) 5.7Vdc for control feedback. Main control
loop comes from 3.3Vdc output that was connected to error amplifier IC3, isolated photo-coupler ISO3 and feedback to control pin
1 in the primary side. In addition, the others output also regulated by dropper and dc-to-dc converter for +5V and +2.5V separately.
IC500 is a protection IC for sensing OV and UV in the output voltage. Once abnormal voltage was detected , it will be shut down
the IC7 by ISO4 immediately.
R5976766 RLM G5 22/04/2004
7
COL
1
D14
C53
ISO3
4
1
3
2
ISO4
4
1
3
2
T2
D11
1
DC/DC Converter
+B
3
GND
Linear regulator
GND
AUX
5
4
GND
GND
IC8
TL431CLP
9. Technical Board Information
IC4
2.5V
D81
D82
IC6
5V
9
>>Input
12
D83
16
OV/UV
D84
Protec
3.3V
Output
5V from Standby
IC500
V
3
49
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