Patent ID: 7187564

Claim:
A switching power source apparatus comprising: a first series circuit being connected to both ends of a DC power source and having a first reactor, a primary winding of a transformer, and a main switch that are connected in series; a second series circuit being connected to both ends of the main switch or both ends of the primary winding and having an auxiliary switch and a clamp capacitor that are connected in series; a saturable reactor being connected in parallel with the primary winding of the transformer; a rectifying-smoothing circuit configured to rectify and smooth a voltage generated on a secondary winding of the transformer; and a control circuit configured to alternately turn on/off the main and auxiliary switches and to turn off the auxiliary switch as a current of the auxiliary switch increases due to saturation of the saturable reactor, wherein the first reactor has a leakage inductance being formed between the primary and secondary windings of the transformer, and the primary winding is divided into two sections that are connected in series, the secondary winding is arranged between the two sections of the primary winding, and the numbers of turns of the two sections of the primary winding is adjusted to adjust the leakage inductance between the primary and secondary windings of the transformer.