| 摘要 |
PURPOSE:To restrain an input current from being increased and prevent harmonic distortion from being generated by detecting that an input voltage of a chopper circuit is decreased lower than a predetermined value so as to shut off power supply to a control circuit. CONSTITUTION:When a voltage detection circuit 14 detects that an input voltage Vin of a chopper circuit 1 is decreased lower than a predetermined value, a switch circuit 13 is opened on the basis of the obtained detection output and supply of a controlling power source Vcc to a control circuit 7 is stopped. Accordingly, operation of the circuit 7 is stopped so that a switching control signal cannot be supplied to an FET 6. As a result, the operation of the circuit 1 is stopped, thus restraining an increase in an input current Iin according to the decrease in an input voltage Vin. Consequently, it is possible to prevent a harmonic distortion from being generated and fracture of a circuit element caused by an excessive increase in the input current Iin. |
