Multiphase LLC Resonant Converter with Natural Current Sharing and Phase-Shedding

The multiphase LLC converter is commonly used for high-power and high step-down applications. However, the tolerances in the tank circuit parameters cause uneven current sharing (CS), reducing system reliability. Additionally, phase-shedding (PS) can improve converter efficiency at partial load by turning-OFF phases. This paper proposes a multiphase input-parallel output-parallel LLC resonant converter with a common inductor-capacitor branch, with the objective to achieve excellent CS and phase-shedding at the same time. Thanks to the shared branch, current-sharing is natural, and phase-shedding is realized without affecting the operating point. With fewer passive comp- onents and a simple phase connection, the design offers low-cost, high-power density, and improved light-load efficiency compared to existing solutions. Detailed analysis shows improved CS on both the primary and secondary sides, when compared to previous approaches. Simulation and experimental results for the proposed two-phase LLC resonant converter validate the analysis and illustrate the effectiveness of the CS and PS capabilities. At the rated load of 800 W, CS error is 2.48% on the primary side and 2.0% on the secondary side. Phase-shedding improves efficiency by 3.60% at 50% load and 6.82% at 25% load.