Steady-state analysis of the bidirectional CLLLC resonant converter in time domain

In this paper, the operating modes of the bidirectional CLLLC resonant converter are analyzed in time domain to determine the steady-state operating point. The operating mode boundaries, mode transitions and mode distribution are discussed and the dependencies of modes on voltage transfer ratio, inductor ratio and switching frequency are illustrated. Based on the mode analysis results, normalized equations and characteristics for the resonant tank currents and voltages are presented, which support the designer selecting the optimal operating point. A prototype system is built and it is shown that the calculations predict the resonant current, voltage behavior, and output power characteristic very well.