42
#14,#22,#10,#21 through R141,R138,R135,R140,via CN901 #5, #6, #8, #7.
- LED Indicator on Front Bezel
1 When press button “power”, U102 (MCU) #1 sends out a low potential, via R130, flow to CN901 #2
on keypad, LED Blue ON.
2 When in “Suspend” mode, U102 (MCU) #48 sends out a low potential, via R129, flows to CN901 #4
on keypad, LED Amber ON.
1.3.2.3 Realtk CHIP U104 (scaler)&U102 (MCU)
- U104 (RTD2025L) #21~#28 output 8 bit even LVDS digital data to panel control circuit through
CN104.
- U104 (RTD2025L) #29~#36 output 8 bit odd LVDS digital data to panel control circuit through
CN104.
- U102 (RTD2120) #44 outputs Brightness “PWM” signals to control CCFL brightness.
- U102 (RTD2120) #39 output PPWR ”H” potential to make Q104 conducted, and then make Q101
conducted, +5V flow to CN104#1~#3 as Panel VDD .
- U102 (RTD2120) #46 output CCFL_ON/OFF ”H” potential to control Inverter on/off.
- TCLK by Crystal 24.000MHz input to U102 (RTD2120) #15, #16.
Please refer to RTD2120&RTD2025L Pin Assignments table in page.
1.3.2.4 Regulator Circuit
- +5V is from switching mode power supply for Panel used.
- +3.3V generates from +5V through C101 and C102 filtering and U101 which is output +3.3V LDO
to generate MCU_VCC for U102, U103 and TMDS_VDD for U104.
- +1.8V generates from +3.3V through Q110 and C134, C133, C135, C136, C137 for U104 used.
Inverter circuit
14VDC provides the power for IC501; the control signals Brightness and ON/OFF come from I/F
board. ON/OFF signal connect to pin8 of IC501 and makes IC501 enable. Brightness signal
connect to pin7 of IC501 and regulates the panel brightness, R510 , R511, C507 make up a
network of delaying time circuit . The striking frequency is determined by the external Resistor
R505 pin5 of IC505and r516. The operation frequency is determined by the external Resistor
R505 pin5 of IC505. the capacitor and resistrer connected to pin4 to set striking time and shunt
down delay time. BURST MODE dimming pulse frequency and duty is regulated by I/F board.
The output drives, include square pulses output of pin14,12,11 to drive MOSFET U501, U502, and
U501, U502 are N channel MOSFETs. U501 and U502 work as harf-bridge topology.Two
transformers are connected in parallel with each transformer driving two lamps in series. Turning
each N-Channel MOSFET “on/off” complementarily, produces an alternating current through the
transformer primary and secondary. The “on” duration of the switches determines the amount of
energy delivered to the CCFLs.
The current flowing through CCFL is sensed and regulated through sense resistor R502, R543.
The feedback voltage connected to Pin2 (ISEN), then compared with a interal reference
voltage ,resulting in PWM signal outputs to adjust output voltage.
Over Voltage Protection and over-current protection are monitored by the voltage on OV(Pin 1)
and LI (Pin2) During normal operation , if a CCFL is damaged or removed ,the voltage at OV
(Pin6) increases .Once the voltage at OV Pin exceeds 1.2V (OVPT Setting) the driver output
duty cycle is regulated and the shutdown delay timer is activated. Once over the delay time the
IC will shut down
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