Electric power supply circuit

An electric power supply circuit comprising:

• a rectifier circuit (12), coupled to an alternating current power supply, for rectifying an alternating current;
• a switching element (S) for causing, when being turned ON, a short-circuit for output power of the rectifier circuit (12);
• a zero-cross detector section (5a) 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 (5c) 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 (5a), a plurality of pulse signals to cause the switching element (S) to perform switching so that a waveform of the input current of the rectifier circuit (12) approximates to a sine wave;
• and
• a correction section (5e) for invalidating, when a detection interval from previous detection to current detection by the zero-cross detector section (5a) is equal to or shorter than a predetermined value, the previous detection, and correcting the predetermined output timing for the PAM waveform output section (5c) according to 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.