Patent ID: 7558091

Claim:
A switching power supply apparatus comprising: a transformer including a primary coil and a secondary coil; an input smoothing capacitor that is connected in parallel to the primary coil and smoothes a DC voltage to be inputted into the primary coil; main switching means causing, by switching the DC voltage, the DC voltage to be outputted to the secondary coil as a pulse; output means that smoothes and outputs the pulse; control means for controlling a switching operation of the main switching means so that an output voltage from the output means becomes constant; detection means for detecting that leak current of the input smoothing capacitor becomes equal to or more than a predetermined value; and first auxiliary switching means connected in series with respect to the input smoothing capacitor, the first auxiliary switching means being in an on state during a normal operation, whereas the first auxiliary switching means goes into an off state when the detection means detects that the leak current of the input smoothing capacitor becomes equal to or more than the predetermined value.