Patent ID: 8385095

Claim:
An electric power supply circuit comprising: a rectifier circuit which is connected to an alternating current power source and which rectifies alternating current power; a smoothing circuit which has two capacitors serially connected to each other and which is connected to an output side of the rectifier circuit; a switching element which, when turned into an ON state, connects the alternating current power source and a midpoint between the two capacitors and which causes a short circuit of an output power of the rectifier circuit; and a PAM control section which outputs a pulse signal for switching the switching element, at a predetermined timing based on a zero-cross point of an input voltage of the rectifier circuit, wherein the PAM control section includes: a phase difference detection section which detects, based on an amount of charge in the two capacitors, a shift between an output phase of the pulse signal and a phase of a pulse signal that makes an input current of the rectifier circuit have a sine waveform; and a phase correction section which shifts the output phase of the pulse signal in a lead direction or a lag direction so that the phase shift detected by the phase difference detection section is removed.