A semiconductor integrated circuit for controlling power supply which has a function of preventing a reverse current flowing in a coil under a light load condition and ensures good response of output voltage to load variation. In a synchronous rectification switching regulator having a reverse current detection circuit which can detect a reverse current flowing in an inductor (coil) and a reverse current prevention function, when a prescribed time has elapsed after detection of a reverse current based on a detection signal from the reverse current detection circuit or after the number of times of reverse current detection has reached a prescribed value, the reverse current prevention function is activated to turn Off a synchronous rectification switching device.