Common-Mode Noise Mitigation Method for Planar Transformer Based on FB LLC converter

Planar transformers (PTs) have attracted tremendous attentions in many applications requiring low-profile power converters, such as server center and telecom. Today, traditional PTs still face large common-mode (CM) noise due to inter-winding capacitances and lager winding losses due to large eddy current in solid windings. Previous works show that there may exist a compromise between AC winding losses reduction and CM noise reduction. The paper proposes a novel high-performance PT based on CM currents cancellation in full-bridge (FB) LLC resonant converter and a novel winding arrangement to achieve low CM noise and low AC losses in PT. A 1.5kW 400V/50V FB LLC resonant converter prototype has been built as a platform to verify CM noise cancellation in PT of the proposed method. Experiment results show over 20dB CM noise reduction can be achieved while keeping low AC losses.