Abstract: This paper proposes a multi-phase interleaved LLC resonant converter based on phase-to-phase active impedance balance unit. By designing the active impedance balance unit to match the impedance of resonant network between the adjacent phases, the current imbalance caused by parameter tolerances of resonant components can be solved. Since the phase-to-phase active impedance balance unit only transfers the part of energy between the adjacent phases, the increased loss is very small. Several possible structures of phase-to-phase active impedance balance unit are compared, and the switch-controlled inductor as an active impedance balance unit is applied in the proposed topology. Then, the current sharing mechanism and design process of the proposed scheme are analyzed, and the corresponding control strategy and multiphase expansion are also discussed. Finally, a 12 V/40 A two-phase interleaved experimental prototype is built to verify the feasibility of the proposed scheme.