Switching power supply capable of always switching a switching element at an optimal timing

Abstract

A control circuit has a delay correction circuit for correcting a delay involved for driving a switching element. The delay correction circuit has a reference voltage generating circuit for generating a reference voltage, a first comparator for comparing the reference voltage with a driving control signal to produce a first comparison result signal, an error signal generating circuit for generating a lag direction signal or a lead direction signal on the basis of the first comparison result signal and a zero-current detected signal, a voltage level error signal generating circuit for generating a voltage level error signal in response to the lag direction signal or the lead direction signal, a timer for producing a timer signal having a predetermined sawtooth waveform, and a second comparator for comparing the voltage level error signal with the timer signal to produce a second comparison result signal as a delay correction signal.