| 摘要 |
PROBLEM TO BE SOLVED: To provide a control circuit for a switching power unit, capable of reducing power consumption by detecting AC cut-off with a low voltage.SOLUTION: A control circuit 1 for a switching power unit is provided in which a voltage obtained by rectifying and smoothing an AC voltage of an AC power source AC connected between both terminals of a power source is turned on/turned off by a capacitor C0, high frequency voltages are generated in a primary winding P and a secondary winding S of a transformer T, and a DC output voltage is obtained by rectifying and smoothing the high frequency voltage in the secondary winding. The control circuit 1 comprises: a detection circuit 11 for detecting whether AC power supply is cut off, on the basis of a half-wave rectified voltage obtained by half-wave rectifying the AC voltage; and discharge circuits 13, R11, Q2 for discharging the capacitor in the case where the cut-off of the AC power supply is detected by the detection circuit 11. |
