A Novel Current Sharing Method of Interleaved LLC Resonant Converter by a Common CL Filter

Abstract

A circuit topology for an interleaved LLC resonant converter is analyzed to achieve automatic current sharing. The LLC series resonant converter has emerged as a solution to applications requiring power conversion with isolation, reduced volume and high efficiency, such as PV systems and EV chargers. However, the LLC resonant converter is limited in power, so it requires a multi-phase configuration in order to provide higher currents. It is a challenge to achieve an equalized current sharing between the paralleled modules in multi-phase power conversion circuits. A small difference in the parameters difference between modules may cause the larger current imbalance of the module. The method is achieved by connecting a common CL filter to the output of interleaved LLC modules and matching the equivalent output impedance of each phase automatically. In this paper, the current-sharing principle of the common CL filter interleaved LLC resonant converter is explained by the passive-impedance-matching (PIM) technology. The basic accuracy of the common CL filter current balancing is investigated. And the optimal value of CL filter parameters is identified. As a result, simulation results show that the proposed common CL filter can well prevent the current imbalance due to the resonant component parameter mismatch.