Coupled Resonant Tank Current-Sharing Topology for Multiphase LLC-DCX Converter with Phase-Shedding Ability

Phase-shedding ability is an important feature of the multiphase LLC converter, which can improve the system’s efficiency under light load. Existing passive current-sharing methods cannot achieve phase-shedding, while the active current sharing methods can achieve phase-shedding but have complex system control and high cost. This paper reveals a coupled resonant tank (CRT) topology with phase-shedding ability. Compared with existing methods, it can not only achieve natural current sharing, but also achieve phase-shedding with only a single current sensor, which has the advantages of low cost and high reliability. Firstly, the operation mode of CRT topology is analyzed, then, based on the first harmonic approximation (FHA) equivalent circuit, the voltage gain of each mode is derived to illustrate the feasibility of phase-shedding. Secondly, based on the extended description function (EDF) method, we established a small signal model of CRT topology and analyzed the stability of the system during mode switching. Furthermore, the current sharing mechanism of CRT topology is analyzed and the current sharing error model is deduced. Finally, simulation and experiments verified the correctness of the theoretical analysis. test results shows that the efficiency of light load increases by 3.05%, and the current sharing error is less than 2%.