Efficient Integrated Magnetics With Winding Cancellation Technique to Reduce Common-Mode EMI Noise for a Single-Phase CLLC Converter

This article proposed a printed-circuit-board (PCB) based integrated magnetics with a winding cancellation technique to reduce common-mode (CM) noise for an 11-kW single-phase CLLC (1PCLLC) resonant converter. Shielding design is effective in reducing CM noise; however, its benefits come along with increased cost with more layers of PCB and increased winding loss due to increased eddy effect in the shielding layers. More shielding layers are required for multiple-turn applications, which makes the idle shielding design unattractive. Implementing windings as active shielding for noise cancellation is a good solution. A symmetrical 1PCLLC converter with symmetrical resonant tanks and symmetrical integrated magnetics is required to achieve the winding cancellation technique. The proposed integrated magnetics consists of three elemental transformers (ETs) with two identical ETs with built-in leakage inductance and one pure transformer. The physical middle points in the primary and secondary windings of the pure transformer become the static-electrical-potential points that can adopted as the starting point to achieve winding cancellation with proper winding arrangements. The effectiveness of the proposed concept was demonstrated through a high-efficiency, high-power density 1PCLLC dc/dc converter for an 800-V 11-kW onboard charger. The designed converter can achieve a power density of 420 W/in³ and a peak efficiency of 98.5%. Compared with the existing solution, the proposed integrated transformer with winding cancellation techniques shows 17-dB CM noise reduction at switching frequency.