Analysis of two resonant converters with the same converter leg

Abstract

A new series resonant converter composed of two resonant circuits with the same converter leg is presented to achieve the zero-voltage switching (ZVS) turn-on of power switches at a wide range of input voltage and load conditions and zero-current switching (ZCS) turn-off of rectifier diodes in a low input voltage case. Thus, the switching losses of power switches and reverse recovery current on rectifier diodes are improved. If the minimum dc voltage gain of the proposed converter is properly selected, the output voltage can be regulated at no-load condition. Two resonant converters using the same power switches are operated by the phase shift half-switching cycle. Thus, the current ripple at the input terminal capacitor can be reduced. In order to reduce the current stresses of output diodes, the output sides of two resonant converters are connected in parallel. The root mean square currents on transformer secondary windings, transformer copper losses and thermal losses can be further reduced. The output voltage doubler topology is adopted in the output side such that the voltage stress of rectifier diodes is equal to the output voltage instead of two times the output voltage in the conventional centre-tapped rectifier topology. Based on the resonant behaviour, all switches are turned on at ZVS and rectifier diodes are turned off at ZCS if the switching frequency is less than the series resonant frequency. The laboratory experiments with a 1000 W prototype are provided to verify the effectiveness of the proposed converter.