NEC MultiSync LCD2080UX -BKA Service Manual page 143

2.9.9 Power Factor Collector (PFC) Circuit
Oscillation starts when the voltage of IC901 pin1 reaches 17.5V by this charging operation.
After the start of oscillation, the pulse voltage of auxiliary winding of L9X1 is rectified and smoothed by
D9X2, C925, R928 and R926. The resulting DC voltage is supplied to IC901 pin8.
The PFC converter circuit consists of the main winding of L9X1 and a switching device in IC901. The
switching device in IC901 begin to turn ON and OFF.
In result, the pulse voltage is applied to the main winding of L9X1.
The pulse voltage generated at the main winding of L9X1 rectified by D9X1. Then, this voltage are
smoothed by C906 so that DC voltage are obtained. The DC voltage are maintained constantly by
controlling the ON period duty cycle of IC901 in the PFC converter circuit.
The DC voltage is divided by the resistors R9X5, R9X6, R9X7 and R9X8.
This divided voltage is compared with the reference voltage at the error amplifier in IC901.
D901
D901
L9X1
R9X9
11
ZCD
(Fig.2.9.9) Power Factor Collector (PFC) Circuit
D9X1
IC901
15
D
PFB
9
S
13
R9Y3
7-16
CONVERTER
CIRCUIT
R9X5
R9X6
C906
R9X7
R9X8