Rotating Phase-Shedding Control Method for Three-Phase LLC Resonant Converter

This paper presents a new strategy for a three-phase LLC resonant converter operating over an extended output-voltage range. The converter employs three-phase, two-phase full-bridge, and single-phase half-bridge modes to regulate the output voltage from approximately 400 V to 100 V within the specified switching-frequency range. In conventional fixed half-bridge operation, one phase continuously transfers power, resulting in unequal component utilization and localized thermal loading. The proposed rotating phase-shedding method periodically rotates the active, supporting, and inactive states among the three converter phases. Consequently, the accumulated current stress and power losses are distributed uniformly without requiring additional power components. The operating principles and phase-rotation sequence are analyzed, and the proposed strategy is experimentally validated on an 11 kW three-phase LLC resonant converter prototype. Measured current waveforms confirm the correct transfer of the active state among the phases. Thermal-camera measurements demonstrate a more uniform temperature distribution across the secondary-side rectifier diodes compared with fixed phase-shedding operation, confirming improved component utilization and thermal performance.