Patent ID: 8558529

Claim:
A control circuit of a synchronous rectification type of step-down switching regulator, the control circuit comprising: an output monitoring comparator which compares output voltage of the switching regulator and a reference voltage that is a target value thereof, and when the output voltage goes lower than the reference voltage, outputs an ON signal; a pulse modulator which generates a pulse signal which goes to a predetermined level in a predetermined ON time from when the ON signal was outputted from the output monitoring comparator; a driver circuit which generates a first and a second control signal based on the pulse signal outputted from the pulse modulator, and alternately turns ON a switching transistor by the first control signal and a synchronous rectification transistor by the second control signal; and a light load mode detector which receives a switching voltage occurring at a connection point of the switching transistor and the synchronous rectification transistor and a predetermined threshold voltage, compares the switching voltage with the predetermined threshold voltage, and at timing at which the ON signal is outputted from the output monitoring comparator, when the switching voltage is higher than the threshold voltage, nullifies the ON signal, wherein the light load mode detector, at timing at which the second control signal is inputted and the ON signal is outputted from the output monitoring comparator, when the switching voltage is higher than the threshold voltage, delays and outputs the second control signal to the pulse modulator; and the pulse modulator generates the pulse signal based on a result of a logical operation on the second control signal that is delayed and the ON signal.