Investigation of a diode-capacitor assisted single-phase power factor corrected boost-buck AC-DC converter

Abstract

Single phase active input power factor corrected and input current improved rectifiers use switching either between the rectifier and the load or between the supply and the rectifier. Voltage and current feedback control produces the gate pulse necessary for the improvement of input current total harmonic distortion, high input power factor and regulated output voltage at acceptably high power conversion efficiency. Usually the boost switching stage is popular due to its advantage of availability of input inductor current tracking with input voltage. The ĈUK and SEPIC switching stage having input boost switching topology may be used where boost-buck voltage/current gain is necessary. In all the topologies, the ideal voltage gain and conversion efficiency deviates significantly at very high or at very low duty cycle of the switching signal of the switch. In DC-DC converter this problem is addressed by pre/post gain or attenuation by flyback or feed forward high frequency transformer topologies. The same pre/post gain operation can be achieved by transformerless diode-capacitor-inductor voltage/current divider/multiplier circuit. In this research similar considerably high efficiency operation of a boost-buck AC-DC converter is investigated. The input to AC-DC rectifier has boost topology in the front followed by a capacitor diode voltage divider. AC-DC converters have additional requirements of input current total harmonic reduction and high input power factor. The proposed converter is therefore designed and studied for proper voltage/current feedbacks. The feedbacks also maintain regulated dc output voltage of the proposed converter. The open loop operation results of the proposed converter are substantiated by prototype small scale experimental circuit.