Power loss and efficiency analysis of quasi-resonant converters

Abstract

Because of the circulating energy in the ON/OFF state of zero voltage (ZVS) and zero current (ZCS) quasi-resonant converters, the topologies do have a power factor or dc/rms ratio although they are subjected to an dc input source. The reactive power varies with normalized frequencies, affecting the efficiency of the converter, accordingly. This paper introduces an intrinsic power loss factor which are closely related to the currents flowing through the switching and resonant elements. High efficiency can only be achieved by employing low loss components, reducing the output current rating for ZVS and increasing current for ZCS, elevating the characteristic impedance of resonant components, and operating in a bounded frequency range with high dc conversion ratio. Comparisons between ZCS and ZVS topologies in terms of efficiencies and stress are verified by computer simulation and experimental data.