Improvement of input power factor in AC choppers using asymmetrical PWM technique

An asymmetrical pulse width modulated (APWM) control technique for AC choppers is proposed to improve the input power factor. The switching function for the proposed technique is derived and hence converted into the asymmetrical PWM waveform for practical implementation of an AC chopper. Through digital simulation several characteristics are investigated theoretically and then compared with those of the conventional PWM control technique. The proposed strategy is simplified to an approximate APWM which can be realized by the analog circuit. Practical verification of the theoretical predictions is presented to confirm the capabilities of the proposed technique