Current balance method for the two-phase interleaved LLC-RDCX with parallel PWM output regulation

The interleaving technique is necessary for multiphase LLC resonant converters in high output current high power level applications. But the conventional frequency-controlled LLC converters will lose current sharing if all the phases are operating at the same switching frequency. In this paper, a two-phase interleaved LLC-Regulated DCX (LLC-RDCX) with parallel PWM output regulation is presented to solve the load-sharing problem. Two LLC-RDCXs operate at the same constant switching frequency. The current sharing of two phases is achieved by the PWM regulations of the assistant DC-DC stages. What's more, only partial energy is transferred through the assistant transformer, the high efficiency is also guaranteed. A 1kW, two-phase interleaved LLC-RDCX prototype is built to verify the feasibility and demonstrate the advantages.