Patent ID: 7166993

Claim:
A step-down switching regulator of a synchronous rectification type converting a voltage input to an input terminal into a set voltage and outputting the converted voltage from an output terminal, the step-down switching regulator comprising: a first switching element configured to switch in accordance with a first control signal input to a control electrode thereof so as to perform output control of the input voltage; a smoothing circuit part configured to smooth an output voltage of the first switching element and output the smoothed voltage to the output terminal, the smoothing circuit including an inductor connected between an output end of the first switching element and the output terminal, and a second switching element for synchronous rectification configured to release energy stored in the inductor in accordance with a second control signal input to a control electrode thereof; a switching controller circuit part configured to control switching of the first switching element so that the set voltage is output from the output terminal, and to cause the second switching element to perform switching opposite to the switching of the first switching element; and a reverse current detector circuit part configured to detect a reverse current flowing from the inductor to the second switching element, and to interrupt the reverse current by causing the switching controller circuit part to turn off the second switching element upon detection of the reverse current, wherein upon detection of a change in the set voltage, the reverse current detector circuit part stops, for a predetermined period of time, the operation of causing the switching controller circuit part to turn off the second switching element due to detection of the reverse current, and after the predetermined period of time is over, the reverse current detector circuit part causes the switching controller circuit part to turn off the second switching element upon detection of the reverse current.