An efficiency optimization method for a high frequency quasi-ZVS controlled resonant flyback converter

Abstract

A MHz single-switched resonant flyback converter with quasi-ZVS is applied to improve the power density. In the quasi-ZVS control, as the control parameters are adjusted and varying continuously, the conventional efficiency calculation is no longer applicable. A dynamic analytical loss model is thus proposed for the quasi-ZVS control, and an optimized on-off control algorithm is further used for efficiency improvement. Based on the loss model with variable parameters, the efficiency of the quasi-ZVS control under different load can be calculated by iteration of multiple switching cycles, and the highest efficiency working condition can be obtained and used for on-off control to improve the overall efficiency. The efficiency is greatly improved with the optimized on-off control. A FPGA controlled 12V/3A resonant converter with eGaN HEMTs is established to verify the proposed control method. The peak efficiency under the proposed optimized on-off control without synchronous rectification is 90%, and the light load efficiency is more than 80%. Compared with the quasi-ZVS control, there is an improvement of 1.2% under full-load condition, and increases by 6.2% under 10% load condition.