Auxiliary Power Supply Circuit - NEC MultiSync LCD2080UX -BKA Service Manual

2.9.3 Auxiliary Power Supply Circuit

The auxiliary power supply circuit is needed to activate IC901.
When SW.REG PWB receives "PMS" signal, Q933 and Q908 is turned off with the above-mentioned
ON/OFF circuits. The charging current flows into the capacitor C911 through IC901 pin12, IC901 pin1.
Oscillation starts when the voltage of IC901 pin1 reaches 17.5V by this charging operation.
After the start of oscillation, the fly-back voltage of auxiliary winding of T901 is rectified and smoothed by
D911 and C910.
The resulting DC voltage is supplied to IC901 1pin.
C906
Startup
Circuit
C906
R904 R905 R906
IC901
Startup
12
VCC
1
GND
6
(Fig.2.9.3) Auxiliary Power Supply Circuit
R908
Q908
ZD908
Q933
D915
C911
7-12
T901
D911 R911
C910