Service Manual
7
Electronic Circuit Theory
2.1 Inverter PWM circuit
2.1.1)Inverter Control circuit:(fig.2)
Fig.2
27VDC provides the power for U1; the control signals Brightness and ON/OFF come from I/F
board. ON/OFF signal connect to pin
16
of U1 and makes U1 enable. Brightness signal connect to
pin
12
of U1 and regulates the panel brightness, make up a network of delaying time circuit and R23
make up a divided voltage network, C
3
is used to
control start-up timing
. The operation
frequency is determined by the external Resistor R16 and capacitor C8 connected to pin3 of U1.
C7 is used for soft start and compensation.
The output drives, include DRV1, DRV2 (pins8,9 respectively) output square pulses to drive
MOSFET Q6, Q7 and each of Q6, Q7 is consist of a N+P channel MOSFET. Q6 and Q7 work as All
Bridge structure, it is high efficient, PWM switching.
During start up, VSEN (pin1) senses the voltage at the transformer secondary. When VSEN
reaches 3.0V, the output voltage is regulated. If no current is sensed approximately 2seconds U1 shut
off.
The current flowing through CCFL is sensed and regulated through sense resistor R6, R19. The
feedback voltage connected to Pin1 (ISEN), then compared with a reference voltage (1.5V) via a
current amplifier, resulting in PWM drive outputs to All Bridge switches.
2.1.2
)
Protection Circuit
Summary of Contents for E2209Wf
Page 1: ...Service Manual 0 Service Manual LCD Monitor E2209Wf ...
Page 7: ...Service Manual 6 Fig 12 ...
Page 16: ...Service Manual 15 8 Key Parts Pin Assignments U105 TSUMU58EHJ LF 2 ...
Page 17: ...Service Manual 16 ...
Page 18: ...Service Manual 17 ...
Page 21: ...Service Manual 20 Chapter 4 Disassembly Assembly 1 Exploded Diagram ...
Page 23: ...Service Manual 22 3 Assembly Block Note 1 The arrows point out the direction of assembly ...
Page 44: ...Service Manual 43 ...
Page 45: ...Service Manual 44 ...
Page 46: ...Service Manual 45 2 power board schematic ...
Page 47: ...Service Manual 46 ...
Page 48: ...Service Manual 47 ...
Page 49: ...Service Manual 48 ...
Page 50: ...Service Manual 49 Attachment 3 PCB Layout power inverter bd power inverter board Top Layer ...