ViewSonic VA502mb-1 Service Manual page 12

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
OSC and
Output
Circuit
Lamp
Feedback
Circuit
4.4 INTRODUCTION OF IC
MST8011B (U401): integrate ADC, OSD, SCALER, LVDS, convert analog RGB into digital and
room and shrink scaling output to LCD panel.
PIN Function:
ViewSonic Corporation
Bridge
Rectifier
and Filter
Start Circuit
R906, R907
PWM
Control
DC Convert
Circuit
Over
Voltage
Rectifier
Transformer
CMOS
Over
Voltage
Protect
MOSFET
Q203
PWM
Control
9
Confidential - Do Not Copy
CN102
5V
12V
ON/OFF
ON/OFF
Control
DIM
VA502mb-1