Patent ID: 7298631

Claim:
A switching power source apparatus comprising: a first series circuit connected to each end of a DC power source and having a primary winding of a transformer and a main switch that 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 connected to each end of the main switch or to each end of the primary winding of the transformer and having an auxiliary switch and a clamp capacitor those are connected in series; a third series circuit connected to each end of the primary winding of the transformer and having an auxiliary reactor, a first diode, and a snubber capacitor those are connected in series; a fourth series circuit connected to each end of the auxiliary switch and having a second diode and the snubber capacitor those are connected in series; and a control circuit to alternately turn on/off the main switch and auxiliary switch, the snubber capacitor being charged when the main switch is turned on, and the snubber capacitor being discharged to the clamp capacitor when the main switch is turned off, to relax the inclination of a voltage increase of the main switch.