Improvement of Asymmetrical Pulse Width Modulation Switching Function for AC Chopper

AC chopper power circuit driven by asymmetrical Pulse Width Modulation (PWM) is a method which used for improving input power factor. The PWM is created by two signals: a saw-tooth signal and a slop reference signal. Originally, the modulation signal has two selective operation modes: 1) varying the level of the referent signal up or down, 2) varying the slope of the referent signal up or down. This paper proposes an alternative operation mode of the modulation signal which use for driving the ac chopper circuit. On this mode, the slope and the average level of the referent signal can be increased or decreased at ωt=0, while the two characteristics of the signal are fixed at ωt=π. The modulation signals obtained from this method can apply for driving the AC chopper power circuit like the two precedent modes. The circuit results are performed by Pspice simulation.