Patent ID: 8878506

Claim:
A switching power supply device, comprising: a chopper circuit that turns on/off the passage of a current to an inductor by means of a switching element; and a switching control circuit that switches the switching element so that an input voltage waveform and an input current waveform with respect to a phase of an input voltage become substantially similar in shape, wherein the switching control circuit is configured to switch the switching element at a switching frequency that is proportional to an input voltage dependent term of a formula that expresses a third harmonic component of ripples of the current flowing to the inductor, and wherein the formula is stated as V fs =V fs max *sin(3*π*(1 −V i /V o )), V fs min ) where V fs is a switching frequency control voltage, V fs max is a voltage at a maximum oscillation frequency, V fs min is a voltage at a minimum oscillation frequency, V i is the input voltage, and V o is an output voltage of the control circuit.