Automatic current balancing for two-phase interleaved LLC resonant converter

This study proposes a novel balanced two-phase interleaved LLC resonant converter. The LLC resonant converter offers a promising solution for dc power conversion. This converter can achieve high efficiency and high-power density by implementing zero-voltage-switching (ZVS) for primary switches and zero-current-switching for secondary rectifier diodes. The input-parallel output-parallel systems that increase their power ratings by connecting two converters in parallel allow the use of low-current rated switches in high-current applications. Moreover, the input and output passive filter size requirements in the two-phase interleaved converters are reduced, and they provide higher power density and improved dynamic performance. However, the estimated tank gain characteristics become imbalanced due to the tolerances and the inevitable mismatch of the resonant parameters. Accordingly, this system operates outside the ZVS region, and a severe current imbalance with thermal runaway will occur. The proposed method achieves the perfect balance of input, output, and tank currents utilizing the existing resonant inductor magnetics without additional active or passive components, expensive sensors, and dedicated control schemes. The proposed method retains the advantages of the conventional LLC resonant converter over the operating frequency range. Mathematical analysis and experimental results are presented to validate the performance of the proposed method.