Inverter - HP VF15 Service Manual

2. Inverter

This unit operates on an output voltage of 15V from power source.
2.1 Regulator: Q101 get a +5VDC for I101 power supply.
2.2 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.
2.3 Control IC: I101 (OZ960S)
2.3.1 Enable : When pin 3 of I101 is over 1.5V, I101 works. If it is under 1.5V, I101 turns off.
2.3.2 OSC: When I101 enabled, R108/C115 (pin 17/pin18 of I101) determine the operating frequency.
2.3.3 SST: C104 (pin 4 of I102) provides soft start function.
2.3.4 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.
2.3.5 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.
2.3.6 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.
2.3.7 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.
2.3.8 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.
2.4 Full-bridge swit ching/Transformer: I102/I103 /C123/I104/I105/C137/C125/T101/T102 compose full-bridge swit ching
to convert DC into AC for driver the CCFL.
2.5 Detection: C124/C125/C126 detect the output voltage and ensure a rated voltage by pin2 of I101. Q108/Q109
ensure not a open-lamp.
2.6 Feedback: D119/R123/D120 sense the lamp current for negative feedback and regulation.
VCC
Regulator
ON / OFF
U.V.P.
Brightness
control
Page 4
Inverter Circuit
VDD
Control IC : OZ960
Enable Output driver
OSC Protection
SST Ignition
Dimming
Regulation
control
vf15 / FP15 / f1523 / FP5315
Full-bridge switching
Transformer
Detection
Feed back
Lamp