Patent ID: 7521911

Claim:
A switching power supply comprising: a switching power portion including a switching element and a control circuit for controlling turning-on/off of said switching element, wherein said switching power portion comprises a current resonance type DC/DC converting portion, and said current resonance type DC/DC converting portion comprises: (i) a resonance circuit that includes a resonance inductor and a resonance capacitor, (ii) an energizing switch, as said switching element, for energizing said resonance inductor, and (iii) a current detection arrangement for detecting a current flowing through said energizing switch to produce a current detected signal, wherein said control circuit comprises a zero-current detection circuit for detecting a zero-current based on the current detected signal to produce a zero-current detected signal indicative of the zero-current, and said control circuit comprises a delay correction circuit for correcting a delay involved in driving said energizing switch, wherein said delay correction circuit produces a delay correction signal based on the zero-current detected signal and a driving control signal for turning said energizing switch on/off, and said delay correction circuit produces the delay correction signal so that a timing for turning off said energizing switch by the driving control signal substantially coincides with an output timing of the zero-current detected signal.