Patent ID: 8295062

Claim:
A switching power supply apparatus, comprising: a transformer including a primary winding, a secondary winding, and an auxiliary winding; a switching device connected in series with said primary winding; an output voltage generation circuit which is connected between said secondary winding and a load and generates a direct-current output voltage by rectifying and smoothing a first alternating-current voltage induced in said secondary winding; an auxiliary power voltage generation circuit which is connected to said auxiliary winding and generates an auxiliary power voltage by rectifying and smoothing a second alternating-current voltage induced in said auxiliary winding; and a control circuit which operates using the auxiliary power voltage and controls an operation of said switching device; wherein said control circuit includes: a driver circuit which generates first pulse signals for driving said switching device; an intermittent operation control circuit which controls said driver circuit so that an intermittent oscillation is performed in which the first pulse signals are generated less frequently when the output voltage is higher than or equal to a first output voltage than when the output voltage is lower than the first output voltage; an auxiliary power voltage detection circuit which detects a magnitude of the auxiliary power voltage; and a peak current control circuit which: (i) sets, to a first peak current value, a peak of a current flowing through said switching device when the output voltage is lower than the first output voltage, (ii) sets, to a second peak current value that is smaller than the first peak current value, the peak of the current flowing through said switching device when the output voltage is higher than or equal to the first output voltage and the auxiliary power voltage is higher than a first auxiliary power voltage, (iii) sets, to a third peak current value that is smaller than the second peak current value, the peak of the current flowing through said switching device when the output voltage is higher than or equal to the first output voltage and the auxiliary power voltage is lower than or equal to the fist auxiliary power voltage, and (iv) outputs a signal to said driver circuit.