Output Rectifying And Smoothing Circuit; Error Detection Amplifier Circuit And Control Circuit - NEC MultiSync LCD2080UX -BKA Service Manual

2.9.5 Output Rectifying and Smoothing Circuit

The fly-back voltage which are generated at the secondary windings of T901 are rectified by D951.
Then, these voltage are smoothed by C951,C952 and C953 so that DC voltages are obtained.
The DC voltage is maintained constantly by controlling the ON period duty cycle of Q901 in the converter
circuit.

2.9.6 Error Detection Amplifier Circuit and Control Circuit

The output voltage +18VA is divided by the network resistors.
This divided voltage is compared with the reference voltage at the error amplifier IC951.
An error signal is applied to the control circuit via the photo coupler PC901.
The control circuits are contained in IC901.
The output of the error detection amplifier circuit is feed back to IC901 pin3 via PC901 to control the duty
cycle of Q901. In result, the output voltage is kept constant.
GND
D951
T901
(Fig. 2.9.5) Output Rectifying and Smoothing Circuit
DFB IC901
3
C915
PC901
R918
(Fig. 2.9.6) Error Detection Amplifier Circuit and Control Circuit
C951 C952 C953
R951
R952
R953
IC951
R954
7-14
+18V
+18VC
GND