LG Electronics LCD 782LS Primary, Seconda Ry, Block Diagram Power Board, EMI components

BLOCK DIAGRAM

POWER BOARD

50 ~ 60Hz

LINE 100 ~ 240V

EMI

COMPONENTS

INPUT RECTIFIER

AND FILTER

HVDC

ENERGY TRANSFER

100KHz

OUTPUT RECTIFIER

AND FILTER

12V

5V

GND

PWM CONTROL

CIRCUIT

PHOTO-COUPLER

ISOLATION

SIGNAL

COLLENTION

PRIMARY

SECONDA RY

DESCRIPTION OF BLOCK DIAGRAM

1. EMI components.

This part contains of EMI components to comply with global marketing EMI standards like FCC the circuit included a line-filter, across line capacitor and of course the primary protection fuse.

2. Input rectifier and filter.

This part function is for transfer the input AC voltage to a DC voltage through a bridge rectifier and a bulk capacitor.

3. Energy Transfer.

This part function is transfer the primary energy to secondary through a power transformer.

4. Output rectifier and filter.

This part function is to make a pulse width modulation control and to provide the driver signal to power switch, to adjust the duty cycle during different AC input and output loading condition to achive the dc output stablize, and also the over power protection is also monitor by this part.

5. Photo-Coupler isolation.

This part function is to feed back the dc output changing status through a photo transistor to primary controller to achive the stablized dc output voltage.

6. Signal collection.

This part function is to collect the any change from the dc output and feed back to the primary through photo transistor

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