Estimation of switching losses in resonant converters based on datasheet information

Abstract

The class of resonant converters is very attractive due to its ability to achieve nearly lossless switching by using zero current or zero voltage switching (ZCS/ZVS) for the switching devices in the input bridge. Since most switched-mode power supplies (SMPS) today use MOSFETs as semiconductor devices, a ZVS operation is typically preferred. However, the ongoing trend towards higher switching frequencies makes reaching of ZVS more and more difficult. Thus, a (partial) loss of ZVS might be the consequence, making the need for a reasonable estimation of the occurring losses of vital importance. Due to the half-or full-bridge configuration, this estimation becomes much more complex compared to a traditional hard-switched boost or buck converter. This paper gives a detailed insight into the switching transients of resonant converters and proposes a proper test circuit. A powerful method is presented to estimate the generated switching and driving losses during the turn-on event of the switches in case of incomplete ZVS. This approach is purely based on the semiconductors' datasheet information. No additional knowledge about the internal device structure is necessary.