The Study Of PWM-PFM Hybrid Contorlled LCC Resonant Converter

In the distributed power generation system,the output voltage variation range of new energy is wide.It's important to regulate output voltage for post-circuits through DC-DC converter.Traditional PWM converter operates in hard-switched state.Its efficiency is hard to increase because of the switching loss and the lower switching frequency.Resonant converter operates in ZVS state,which solves these problems.LCC resonant converter reaches more and more attention for realizing ZVS operation of the primary side switches under wide input voltage and load variation.Variable frequency controlled LCC resonant converter suffers from wide switching frequency variation,while phase-shift controlled LCC resonant converter loses ZVS operation when input voltage or load variation range is wide.A PWM-PFM hybrid controlled of LCC resonant converter is proposed to achieve ZVS operation with narrow switching frequency variation under wide input voltage and load variation.By modulating conduction angle and switching frequency simultaneously,the proposed converter can achieve voltage regulation without losing ZVS operation under wide input voltage and load variation.Furthermore,the proposed converter simplifies the design of magnetic components due to the narrow switching frequency variation.Fundamental harmonic approach(FHA)model of converter is derived.Operation principle and circuit characteristics were analyzed under continuous capacitor voltage mode(CCVM).The parameter design was given.Finally,experiment results of a 100V~200V input and 48V/500 W output prototype were provided to verify the theoretical analysis result.