Patent ID: 7324355

Claim:
A DC-DC converter comprising: a switching element to perform a switching operation thereby converting a DC electric power supplied from a DC power source into an AC electric power; an inductance element to store up and discharge the AC electric power; a rectifying smoothing circuit to rectify and smooth the AC electric power discharged and reconvert the AC electric power back into a DC electric power, the rectifying smoothing circuit comprising a rectifying smoothing circuit diode and an output capacitor; a diode; and an auxiliary transformer having a primary winding and a secondary winding, wherein: the primary winding and one member of the switching element and the rectifying smoothing circuit diode constitute a first series circuit such that the primary winding is connected in series to the one member; the secondary winding and the diode constitute a second series circuit such that the secondary winding is connected in series to the diode, where one terminal of the second series circuit is connected to one terminal of one of the DC power source and the output capacitor, and the other terminal of the second series circuit, together with the other terminal of the output capacitor, is connected to the other terminal of the DC power source; and an electromagnetic energy stored up in the auxiliary transformer is either returned to the DC power source via the second series circuit or discharged to an output side when the switching element turns on and off.