| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching power supply device which can prevent the stoppage of a control unit caused by reduction in power supply to a switching element control unit under a light load, without increasing the number of components. SOLUTION: The switching power supply device includes a switching element connected to the primary winding of a transformer, wherein a control unit 50a performs ON/OFF control of the switching element in a case where a voltage is input to the primary winding of the transformer, thereby rectifying/smoothing the voltage induced in the secondary winding of a transformer and outputting the voltage to a load. The device further includes: an auxiliary power supply circuit that rectifies and smoothes the voltage induced in the auxiliary winding of the transformer, and charges a capacitor owned by the auxiliary power supply circuit with the voltage to thereby supply power to the control unit 50a; and a starting circuit 57 that supplies a current to the capacitor of the auxiliary power supply circuit in a case of starting the control unit 50a and in a case where the load is light and the switching element is turned off. COPYRIGHT: (C)2010,JPO&INPIT
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