Wide ZVS operation of a semi-dual-bridge resonant converter under variable-frequency phase-shift control

Abstract

A secondary phase-shifted dual-bridge converter with semi-active rectifier is able to perform buck boost dc dcconversion with soft-switching. However, it can not maintain zero-voltage switching (ZVS) operation for all switches in a wideload range. Besides, the root mean square/peak tank current increases inversely with the decreasing of load in the light loadregion. To alleviate these problems and extend its load range, a hybrid varying-frequency phase-shift (VFPS) control isproposed to manipulate the power for a semi-dual-bridge converter with the primary half-bridge and secondary semi-activerectifier topology. Steady-state analysis of the converter under VFPS control is performed using the fundamental harmonicapproximation approach. A detailed design procedure is given then to find a full ZVS trajectory with a fixed ZVS margin at lightload. Experimental results proved that the VFPS control can effectively extend the operation range with full ZVS and maintainhigh efficiency at light load for the semi-dual-bridge resonant converter.