A controller IC has, for example, a current detection terminal for detecting a coil current passing in a switching power supply and an on-timing setter configured to check for a ground short circuit at the current detection terminal when an output transistor turns off to generate an on-timing setting signal so as to turn on the output transistor, during normal operation, at the time point that the coil current has decreased to a zero value or a value close thereto and, during a ground short circuit, after the lapse of a predetermined minimum off-period.