A novel planar transformer with integrated EMI suppression Y-caps applicable to high frequency high power DC-DC converters for automotive applications

DC/DC converters in electric vehicles (EVs) use planar magnetics to minimize their size and weight an to increase their ability to withstand mechanical vibrations. Typical planar transformers (PT) in DC/DC converters used in EVs have high inter-turn and inter-layer capacitances that cause them to draw high peak currents, increase voltage overshoot across secondary rectifying devices, and increase leakage current, which causes EMI problems. The paper proposes a novel winding layout strategy to mitigate the stray capacitance of planar transformers and also reduce overall EMI of a full-bridge DC-DC converter. The effectiveness of the proposed winding strategy is validated by analytical and experimental results that are presented in the paper.