ViewSonic VG920-1, Service Manual

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4.3 PWPC BOARD BLOCK FUNCTION DESCRIPTION
PWPC board combines to adapter and inverter, Adapter which commonly consists
of bridge rectifier and filter, start circuit, PWM control circuit, protection circuits and
convert to 12V, 5V DC voltage by input 90V-240V AC voltage that provide power supply
for each chips in the main board and inverter. Inverter is DC TO AC circuit. It changes
the 12v DC of power supply to about 600-800v AC that drives the backlight. It mostly
consists of starting circuit, PWM controller, DC changing circuit, LC surging circuit,
output circuit and protection circuit etc.
AC input
EMI filter
Bridge
Rectifier
and Filter
Start Circuit
R903, R904,R905
PWM
Control IC
Over
Voltage
Protect
Rectifier
CMOS
ON/OFF
Control
PWM
Control IC
Feedback
Circuit
OSC and
Output
Circuit
DC Convert
Circuit
MOSFET
Q203
Over
Voltage
CN902
Transformer
Lamp
5V
12V
ON/OF
DIM
14
ViewSonic Corporation
Co
nfidential - Do Not Copy VG920-1