Block Diagrams
LW32A23W/LW40A23W
PFC Circuit
Operating Principles
As the stand-by power circuit starts oscillating,the control IC of the PFC circuit (L4981) is applied with Vcc
and starts oscillating. The oscillation frequency is determined by the resistance (RP824) connected to 17Pin
and the condenser (CP816) connected to 18Pin. For regulation,the output voltage is divided by resistors and
monitored by 14Pin. The 4Pin voltage, which is entered after dividing this voltage and the AC voltage by
resistors, is calculated in the IC and the command value of the main FET is prepared. Therefore, the output
voltage is controlled by the voltage determined by the dividing resistors, and the input current has the
same waveform (sine wave) as the AC voltage, producing a power factor of almost 100%.
Protections
1. Overvoltage
The circuit has an overvoltage protection function of the voltage limit type. In the event of a sudden
interruption of the input, of overshooting [overload?] during a sudden change of load,or non-control
status, this function protects the circuit by narrowing the ON width of the FET and preventing the
voltage from rising above the overvoltage setting. The overvoltage can be set with RP834, RP835, RP836
and RP840. (The power source is set to approximately 385V)
2. Overcurrent
The current is converted into the voltage value through RP831 and RP832,and monitored by 2 Pin and 8
Pin of the control IC. If the voltage of the detecting resistor rises above the set value due to an increase in
current, the pulse width is narrowed to limit the output.
3. Thermal Shutdown
Although the IC has a thermal shutdown function, a thermistor (TH) is installed on the heat-radiating fin
of the main FET and the circuit is stopped if overheated by overload, etc.
FET VDS Waveform (Input of 100V)
FET VDS Waveform (Input of 230V)
Summary of Contents for LW32A23W
Page 3: ...Block Diagrams LW32A23W LW40A23W Sound Block diagram ...
Page 4: ...Block Diagrams LW32A23W LW40A23W Video Block diagram ...
Page 5: ...Block Diagrams LW32A23W LW40A23W Power Block diagram ...
Page 6: ...LCD TV 32 40 Power Block diagram Block Diagrams LW32A23W LW40A23W Inverter Power Source ...
Page 29: ...LW32A23W LW40A23W Schematic Diagrams 1 DC 6V ...
Page 31: ...LW32A23W LW40A23W Schematic Diagrams 1 DC 6V ...
Page 33: ...LW32A23W LW40A23W Schematic Diagrams D009 D010 D012 D014 ...
Page 35: ...LW32A23W LW40A23W Schematic Diagrams D013 D014 D015 D016 D021 ...
Page 37: ...LW32A23W LW40A23W Schematic Diagrams D017 D018 ...
Page 39: ...LW32A23W LW40A23W Schematic Diagrams D019 D020 ...
