Acer H15AAX, Руководство по обслуживанию

Страница: 11 / 71

Circuit Description
H15AAX (AL502)
Page 8
10. Inverter
This unit operates on an output voltage of 15V from power source.
10.1 Regulator: Q101 get a +5VDC for I102 power supply.
10.2 UVP: Q106 turns off when the Vin is under 14V. Then pin 3 of I102 is pulled low and inverter off immediately.
That is the under voltage protection.
10.3 Control IC: I102 (OZ960S)
10.3.1 Enable : Whe n pin 3 of I102 is ove r 1.5V, I102 works. If it is under 1.5V, I10 2 turns off.
10.3.2 OSC: When I102 enabled, R108/C115 (pin 17/pin18 of I102) determine the operating frequency.
10.3.3 SST: C104 (pin 4 of I102) provides soft start function.
10.3.4 Ignition: R109 (pin 8 of I102) provides higher operating frequency for more striking voltage until regulation
of feedback of lamp current. C103 (pin 1 of I102) determine the striking time.
10.3.5 Dimming control: The divided voltage of R106/R105/R104 control the duty pulse of burst-mode to drive Q105
and perform a wide dimming co ntrol for the CCFL. The burst-mode frequency is determined by C116.
10.3.6 Regulation: Pin 9/pin 10 of I102 provide regulation of the CCFL current from feedback. The non-inverting
reference (pin 10 of I102) is at 1.25 V nominal.
10.3.7 Protection: Open-lamp protection in the ignition period is provided through both pin1 and pin 2 of I102.
Removal of the CCFL during normal operation wil l trigger Q104 to turns on and shuts off the inverter. This
is latch function.
10.3.8 Output drivers: The configuration prevents any shoot-through issue associated with bridge-type power
conversion applications. Adjusting the overl ap conduction between I101 P-MOSFET and I103 N-MOSFET,
I101 N-MOSFET and I103 P-MOSFET, the CCFL curren t regulation is achieved.
10.4 Full-bridge swit ching/Transformer: I101/I103 /C123/C125/T101/T102 compose full-bridge swit ching to
convert DC int o AC for driver the CCFL.
10.5 Detection: C124/C119/CR102 detect the output voltage and ensure a rated voltage by pin2 of I102. Q102/Q103
ensure not a o pen-lamp.
10.6 Feedback: CR101/R120/R121/D108 sense the lamp current for negative feedback and regulation. The divided
voltage on R121 will be at 1.25V.
Inverter Board Block Diagram
VCC
Regulator
U.V.P. Enable
OSC
SST
Dimming
control
Output driver
Protection
Ignition
Regulation
Control IC : OZ960
ON / OFF
Full-bridge switching
Transformer
Lamp
Feed back
Detection
Brightness
control
VDD