Patent ID: 8270187

Claim:
An electric power supply circuit comprising: a rectifier circuit, coupled to an alternating current power supply, for rectifying an alternating current; a switching element for causing, when being turned ON, a short-circuit for output power of the rectifier circuit; a zero-cross detector section for detecting a zero-cross point of an input voltage or a point at which the input voltage reaches a level equal to or higher than a predetermined voltage level; a PAM waveform output section for outputting, with a predetermined output timing such that the outputting of the pulse signals is started at a time of detection by the zero-cross detector section, a plurality of pulse signals to cause the switching element to perform switching so that a waveform of the input current of the rectifier circuit approximates to a sine wave; and a correction section for invalidating, based on a determination that chattering has occurred on a zero-cross detection signal when a detection interval from previous detection to current detection by the zero-cross detector section is equal to or shorter than a predetermined value, the previous detection, and correcting the predetermined output timing for the PAM waveform output section so that the output timing for the PAM waveform output section is delayed by a time difference between a detection interval from detection before previous detection to current detection, and an average value for detection intervals from initial detection to the detection before the previous detection.