Control Method Selection Strategy with Peak Current and Efficiency of CLLC Resonant Converter in Step-Down Operation

This paper newly proposes a control method selection strategy of CLLC resonant converter to improve its peak current or efficiency in step-down operation. The conventional pulse-frequency modulation (PFM) controlled CLLC resonant converter suffers from low efficiency in step-down operation due to its high switching loss. To address this issue, various phase-shift control methods have been introduced. However, they cause a large conduction loss with high peak current, which aggravates the lifespan and heat generation of system. Nevertheless, there are no papers that fairly analyze the relationship between them. For this purpose, the calculations of peak current and efficiency for the existing control methods are performed through the time-domain analysis. Then, based on the results, the selection strategy is proposed to achieve the high performance of CLLC resonant converter. Its reliability is verified by the simulation test.