Comparison study of fixed-frequency control strategies for ZVS DC/DC series resonant converters

Nowadays, resonant power converters are not commonly used, mainly due to their comparatively high conduction losses and component stresses. However, they are useful for some specific applications requiring low noise, high power density or high-frequency operation. In these applications, MOSFETs are the usual devices for which ZVS operation is recommended. This normally requires a switching frequency above the resonant frequency, so higher conduction and turn-off losses may be expected. In this paper, three different fixed-frequency control strategies for the ZVS full-bridge series resonant converter are analyzed and compared, in order to determine which one achieves the least conduction and turn-off losses, without losing ZVS and considering input-voltage and load variations