Inverter Circuit - HP f1723 Service Manual

9. Inverter Circuit

This unit operates on an output voltage of 15V from power source.
9.1 Regulator: Q101 get a +5VDC for I101 power supply.
9.2 UVP: Q106 turns off when the Vin is under 10V. Then pin 3 of I101 is pulled low and inverter off immediately.
That is the under voltage protection.
9.3 Control IC: I101 (OZ960S)
9.3.1 Enable : When pin 3 of I101 is over 1.5V, I101 works. If it is under 1.5V, I101 turns off.
9.3.2 OSC: When I101 enabled, R108/C115 (pin 17/pin18 of I101) determine the operating frequency.
9.3.3 SST: C104 (pin 4 of I101) provides soft start function.
9.3.4 Ignition: R109 (pin 8 of I101) provides higher operating frequency for more striking voltage until regulation of
feedback of lamp current. C103 (pin 1 of I101) determine the striking time.
9.3.5 Dimming control: The divided voltage of R106/R105/R104 control the duty pulse of burst-mode to drive Q105
and perform a wide dimming control for the CCFL. The burst-mode frequency is determined by C116.
9.3.6 Regulation: Pin 9/pin 10 of I101 provide regulation of the CCFL current from feedback. The non-inverting reference
(pin 10 of I101) is at 1.25V nominal.
9.3.7 Protection: Open-lamp protection in the ignition period is provided through both pin1 and pin 2 of I101.
Removal of the CCFL during normal operation will trigger Q107 to turns on and shuts off the inverter. This is latch
function.
9.3.8 Output drivers: The configuration prevents any shoot-through issue associated with bridge-type power
conversion applications. Adjusting the overlap conduction between I102 P-MOSFET and I103 N-MOSFET, I102 N-
MOSFET and I103 P-MOSFET, the CCFL current regulation is achieved, same as I104 and I105.
9.4 Full-bridge swit ching/Transformer: I102/I103/C123/I104/I105/C137/T101/T102 compose full-bridge swit ching to
convert DC into AC for driver the CCFL.
9.5 Detection: C128/C129/C130/C131/C132/C133 detect the output voltage and ensure a rated voltage by pin2 of I101/
Q108/Q109 ensure not a open-lamp.
9.6 Feedback: D116/D117/D122/D123/D109/R120/R121/D108 sense the lamp current for negative feedback and
regulation.
VCC
Regulator
ON / OFF
U.V.P.
Brightness
control
Page 12
Inverter Board Block Diagram
VDD
Control IC : OZ960
Enable Output driver
OSC Protection
SST Ignition
Dimming
Regulation
control
f1723 / FP7317 / L1702 / vf17 / FP17
Full-bridge switching
Transformer
Detection
Feed back
Lamp