Power Board Diagram - BenQ G700 Service Manual

BenQ G700
dimming frequency is determined by the external resistor R507 and capacitor C516 connected to pin11 of
IC501. C511 is used for soft start and compensation, C507, C518 are used for dump noise.
The output drives, include DRV1, DRV2 (pins1,15 respectively) output square pulses to drive
MOSFET U501, U502, and each of U501, U502 , is consist of a N channel MOSFET. U501,OR U502
work as Push-Pull- topology, it is high efficient, PWM switching.
During start up, VSEN (pin6) senses the voltage at the transformer secondary. When VSEN reaches 3.0V,
the output voltage is regulated. If no current is sensed approximately 2seconds IC501 shut off.
The current flowing through CCFL is sensed and regulated through sense resistor R509, R534. The feedback
voltage connected to Pin5 (ISEN), then compared with a reference voltage (1.5V) via a current amplifier,
resulting in PWM drive outputs to PUSH-PULL switches

5.2.2 Power board diagram:

EMI EMI
COMPONENTS COMPONENTS
LINE LINE
100~240V 100~240V
HVDC HVDC
INPUT REXTIFIER INPUT REXTIFIER
AND FILTER AND FILTER
PWM PWM
PHOTO-COUPLER PHOTO-COUPLER
COMTROL COMTROL
CIRCUIT CIRCUIT
PRIMARY PRIMARY
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Service Manual
66KHz 66KHz
ENERGY ENERGY
TRANSFER TRANSFER
ISOLATION ISOLATION
SECONDARY SECONDARY
12V 12V
5V 5V
OUTPUT RECTIFIER OUTPUT RECTIFIER
AND FILTER AND FILTER
GND GND
SIGNAL SIGNAL
COLLENTION COLLENTION