Characteristics of a New Series Resonant Converter

This paper describes a new series resonant converter for a 150-volt dc power supply system. This converter has been studied in order to overcome the disadvantage of conventional series resonant converters which must widely vary the conversion frequency to keep the output voltage constant, thus causing audible noise under light-load conditions. A series resonsnt circuit is added parallel to the output circuit of the conventional converter. By utilizing the impedance characteristics of the additional circuit, the output voltage can be regulated with less conversion frequency variation than in conventional circuits. From experimental results, the conversion frequency variation necessary to keep the output voltage constant in a 0-to-100 ampere output current range was found to be only about 30% of that of conventional circuits. The conversion efficiency of this converter is about 85% at 100 ampere output current.