Feedback Circuit; Inverter Circuit Operation Theory; An Intelligent Ccfl Inverter Controller – Oz9933 - BenQ G2220HD Product Service Manual

#6 Feedback circuit

PC123 is a photo-coupler and TL431 is a shunt regulation. They are used to detect the
output voltage change and be the primary and secondary isolation. When output voltage
changes, the feedback voltage will be compared and duty cycle will be decided to control the
correct output voltage. (See Fig.7)
A-3.) Inverter Circuit Operation Theory
An Intelligent CCFL Inverter Controller – OZ9933
OZ9933 is a high performance, cost-effective CCFL controller designed for driving large-size
LCD applications requiring 2 to 6 CCFLs.
The controller converts unregulated DC voltages into a nearly sinusoidal lamp voltage and
current waveforms.
The OZ9933 supports full-bridge power conversion topologies while maintaining high-
efficiency operation, current and voltage regulation, over-voltage and over-current protection,
high drive capability.
The control logic provides s regulated ignition voltage and appropriate protection features for
over-voltage or over-current conditions.
R619 27K
IC602
PC123FY 1J00F
- 60 -
R709
680 J
R708
1K F
R710 10K F
R
IC702
KA431AZT A_NL
Fig. 7
R711
10K F
C711
1U 50V K
R712
10K F