Hidden Buck Chopper Circuits Topology in a Switch Controlled Singe Phase Rectifier, Size and Cost Analysis

Abstract

This paper shows hidden buck chopper circuits topology in a single phase switch controlled full wave rectifier. Justification of this realization yields the opportunity to use the single circuit structure for both AC to DC and DC to DC conversion processes. Generally, two diodes out of four diodes are replaced by two switches to offer voltage gain and input power factor regulation in a single phase full wave rectifier. Such modification proves the existence of two buck chopper circuits. Buck circuit is a dc to dc step down converter. This research also includes filter sizing and comparisons of Fast Fourier Transform (FFT) analysis of output voltage for two modes of operations excluding filter stage. To get proper DC output LC filter is used. LC filter size is inversely proportional to switching frequency for a particular output load. The research shows that, size of LC filter for DC-DC conversion process can be chosen flexibly and minimized because the fundamental frequency component of the chopped voltage before filter stage is similar to the switching frequency which can be easily selected to a higher value to reduce the size of filter. In case of controlled AC-DC conversion process the rectified discontinuous voltage before the filter stage naturally includes low frequency components which cannot be eliminated using small filter. So, the size of filter for both of the cases becomes issue of comparisons. It also shows cost analysis.

Keywords: Rectifier, buck converter, switching frequency, LC filter, filter sizing