IMPROVEMENT OF INPUT POWER-FACTOR IN AC CHOPPERS USING ASYMMETRICAL PWM TECHNIQUE

Asymmetrical pulse width modulated (APWM) control technique for the ac choppers is proposed to improve the input power factor. The switching function for the proposed technique is derived and hence converted in to the symmetrical PWM waveform for practical implementation of an ac chopper. Through digital simulation several characteristics are invest igated theoretically and then compared with those of the conventional PWM control technique. The proposed strategy is simplified to an appro ximate APWM which can be realized by the analog circuit. Practical ver ification of the theoretical predictions is presented to conform the c apabilities of the proposed technique.