Patent ID: 7130204

Claim:
A switching power source apparatus comprising: a first series circuit being connected to each end of a DC power source and including a primary winding of a transformer and a main switch those are connected in series; a rectifying-smoothing circuit to rectify and smooth a voltage that is outputted from a secondary winding of the transformer when the main switch is turned on; a second series circuit being connected to each end of the main switch or to each end of the primary winding of the transformer and including an auxiliary switch and a clamp capacitor those are connected in series; a third series circuit being connected to each end of the main switch and including a first diode and a snubber capacitor those are connected in series; a fourth series circuit being connected to a node between the first diode and the snubber capacitor and a node between the auxiliary switch and the clamp capacitor and including an auxiliary winding of the transformer and a second diode those are connected in series; and a control circuit to alternately turn on/off the main switch and auxiliary switch, wherein the snubber capacitor is discharged through the auxiliary winding to the clamp capacitor when the main switch is turned on; and the snubber capacitor is charged when the main switch is turned off, to relax the inclination of a voltage increase of the main switch.