LG L1900J, Service Manual

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Adapter Board Block Diagram
EMI
COMPONENTS
LINE
100 ~ 240V
INPUT RECTIFIER
AND FILTER
SWITCHING
TRANSFORMER
OUTPUT RECTIFIER
AND FILTER
12V
GND
SIGNAL
COLLENT-
ION
PHOTO-
COUPLER
ISOLATION
PWM
CONTROL
CIRCUIT
HVDC
100KHz
PRIMARY SECONDARY
50 ~ 60Hz
INVERTER CIRCUIT High Voltage 12V
Operation description
1. EMI components.
This part contains of EMI components to comply with global marketing EMI standards like FCC,VCCI CISPR, 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 for 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 achieve the dc output stabilized, 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
achieve the stabilized 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.