Automatic Mitigation of Current Imbalance for m-Phase Interleaved LLC Resonant Converter

Abstract

The <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> resonant converter offers a promising solution for dc power conversion. The input-parallel output-parallel system offers low specification switches to use in high power applications. Moreover, the interleaving of the converters reduces the requirement of input and output passive filters, providing better dynamic performance and higher power density. However, the tolerances in the designed resonant components and the unavoidable mismatch in the circuit parameters lead to unbalanced estimated tank gain characteristics. Consequently, the zero-voltage-switching is lost, a serious imbalance in currents appears, and a thermal runaway is likely to occur. The proposed method utilizes the existing magnetics of resonant inductors and self-alleviates the imbalance in the output, input, and tank currents without increasing active or passive components, dedicated balancing controls, and expensive sensors. A 4 kW four-phase prototype is tested during steady state, transients, and phase-shedding modes to validate the performance of the proposed method.