Hybrid Control Strategy of Series Resonant DC/DC Converter for Realizing Active Soft Switch

This paper presents a novel active soft switch control strategy for full bridge series resonant DC/DC converter with phase-frequency hybrid modulation. The proposed control strategy has the capability of wider load range and higher efficiency (especially under light loads) compared with frequency modulation. Three possible work modes and their loss profiles are analyzed by means of the state trajectory method. The principle of the active soft switch is revealed, and its mechanism of enhancing efficiency and extending load range as opposed to frequency modulation is interpreted. The general state space averaging method is used to model power stage, modulation stage and output stage, and the control strategy for realizing active soft switch is designed. Comparisons between proposed strategy and frequency modulation in terms of load range and efficiency are implemented. Simulation and experiment validate the effectiveness of the control strategy.