Two-phase Three-Dimension Common Inductor LLC Resonant Converter with Automatic Current Sharing

Two-phase Three-dimension (3D) common inductor LLC resonant converter is proposed to achieve automatic current sharing. The series inductor of each phase are connected by a Coupled impedance which is inductor, capacitor or short-circuit. A Coupled index is indicated to analyze the current sharing performance under three types converter based on the Fundamental Harmonic Analysis (FHA). The previous method only work at Coupled index equals to 1 and 0, However, the Coupled index can be design any value in (-infinity, +infinity) for two-phase 3D common inductor LLC converter, and the current sharing performance is better if the Coupled index is designed in negative value. Four steady-state operations under Coupled index is 1, 0.5, 0,-1 are discussed to verify the current sharing improving. A 600W, 12V two-phase LLC converter with short-circuit Coupled impedance prototype is built. The prototype verified the feasibility and demonstrated advantages of the proposed converter.