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

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