Certain investigations on ZVS ZCS high frequency DC DC converters

Abstract

As the demand for high efficiency, high power density and costeffective newlineDC-DC converters continues to increase, power system design has newlinebecome more challenging and complex than ever before. newlinefrequency DC-DC converters use smaller size, passive components like newlinecapacitor, inductor and transformer due to large circulating current, newlineconduction losses are high. As most of the losses are frequency dependent, newlinesoft switching techniques are developed to reduce switching losses. In high frequency converters, soft switching techniques are used to newlinereduce the switching loss that results from high switching frequency. Hence newlinethe current research is focused on soft switching techniques applied to newlineregulated DC-DC converters to enhance their performance. The detailed newlineinvestigation on methodologies, design of the various soft switched DC-DC newlineconverters are presented in this thesis. The performance of these converters is newlinejustified with the help of simulation and experimental results which are newlinepresented in this thesis. The configuration of the converter adopted here is soft-switched newlinequasi-resonant converters (QRC) the rising and falling edges of the newlinewaveforms which are smoothed without transient spikes. The switch current and voltage waveforms are forced to oscillate in a quasi-sinusoidal manner, so newlinethat Zero Current Switching and Zero Voltage Switching can be achieved. newlineOutput voltage regulation is achieved by controlling the switching frequency. newlineOperation and characteristics of the converter depend mainly on the design of newlinethe resonant circuit inductance and capacitance. It has overcome the newlineshortcomings of the early configurations such as switching losses and newlinestresses, electromagnetic interference during the hard switching conditions. newlineThe aim of this research work is to overcome the shortcomings of newlinethe earlier configurations such as extending the ZVS range for change in load, newlinehigh reverse recovery losses caused by the diode, voltage overshoot and newlineringing and to improvise the efficiency from light load to high load.