Filter Design for AC to DC Converter

Abstract

AC power is available commercially at low cost. DC power is relatively expensive to produce. Therefore a method for changing ac to dc is needed in relatively less expensive way as a source of dc power. The method presented in this paper to convert ac power to dc power is a full-wave bridge rectifier. But the output from the rectifier contains undesirable ripple. In many applications, the ripple has to be under specified limit. To control the ripple, the method suggested in this paper is utilizing a filter circuit. Filter circuits use either capacitor or inductor or both to limit the ripple. Mathematical formula to calculate the value of filter capacitor or filter inductor is available when they are used alone but when both capacitor and inductor are used together, there is no mathematical formula available to calculate their values for controlling the amount of ripple. In this paper, the Alternative Transients Program, ATP model for the case when a filter consists of either only capacitor or only inductor is verified with mathematical formula. After verification of the computer model with mathematical formula, a methodology is presented to design a combined capacitor-inductor filter to control the ripple at specified level.