BenQ G2010WP Service Manual page 33

The current flowing through CCFL is sensed and regulated through sense resistor R528, R523. The feedback voltage
connected to Pin4 (ISEN), then compared with a reference voltage (3.3V) via a current amplifier, resulting in PWM
drive outputs to PUSH-PULL switches.
5.5.2 Power board diagram:
AC Current Input Circuit
P801 is a connector for connecting AC Power. F801 is a fuse to protect all the circuit. AC input voltage is from 90V to
264V. R801 and R802 joined between two inputting main circuit to prevent man from shock. L801 is used to clear up
low frequency wave. C801 and C802 are used to discharge the waves that L801 produced. High frequency waves are
damped by C801 and C802. D801 is a rectifier which composed of 4 build-in diodes, it inverts AC to DC.
High Voltage to Low Voltage Control Circuit
C804 is used to smooth the waveform from rectifier. IC802 is a highly integrated PWM controller, which control the
power MOSFET Q804. When rectified DC high voltage is applied to the DRAIN pin during start-up, the MOSFET is
off initially, when the voltage VCC reaches the threshold level 11V,IC 802 start up and create a PWM signal to control
the power MOSFET, then energy is transferred to secondary terminal through the transformer T801,the auxiliary
voltage 15V and the output voltage 5V/16V be created ,the auxiliary voltage supply a continue current to IC802,the
level of output voltage is feedback to FB pin of IC802 through IC801 and IC801 witch control the duty of the PWM
signal, then all the convert circuit go to a stable operating station. R809,R810,R811,R812 is the brownout circuit to
pin1 of IC802.
Only the input AC voltage over the threshold level approximately 70V AC, the switch can supply a continue current
to IC802;R815,R816 Is a over line current protection circuit witch limited the input power under approximately 55W.
the current will create a high voltage for CS of IC802 and made IC802 off the PWM waveform; the high voltage spike
created by transformer's primary winding during the transistor turn off will be consumed through D802 R804 R834
R835and C806, This will prevent MOSFET Q804 being damaged under large current impulse and voltage spike.
5.5.3 I/F Circuit
5.5.3.1 RGB CAPTURE
- Signal RED,GREEN,BLUE input through CN102 #1,#2,#3, Stop DC via R114&C113, R115&C114 and
R116&C115 and then enter into U105 (scaler) analog input terminal #12,#14,#16, and then scaler deals with
signal internally.
- Signal DDC_SCL (series clock) inputs via CN102#15, and then passes through R131, goes into U108#5.
- Signal DDC_SDA (series data) inputs via CN102#12, and then passes through R132, goes into U108 #8.
- Signal TTL vertical sync. (Vsync) inputs via CN102 #14, and then clamped by ZD105 Zener, passes through
R134, and then goes into IC U105 (scaler) #8.
- Signal TTL horizontal sync. (Hsync) inputs via CN102 #13, and then clamped by ZD104 Zener, passes
through FB101,R133, and then goes into IC U105 (scaler) #9.
- CN102#5 is defined as cable detect pin, this detector realize passes through R125 Pull high, go into U108#24.
- U103 power is supplied by PC via CN102#9, or supplied by Monitor self via D106.
- U103 is an EEPROM IC which is memory and EDID data saved in it.
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