An integrated EMI suppression Y-caps applicable to high frequency planar transformers in high power DC-DC converters used for electric vehicle

Planar magnetics are very suitable for automotive applications due to the low profile structure. DC/DC converters in electric vehicles (EVs) use planar magnetics to minimize their size and weight and to increase their ability to withstand mechanical vibrations. Typical planar transformers (PT) in DC/DC converters used in EVs have high inter-turn and interlayer capacitances, which have detrimental effects such as high peak currents, increase voltage overshoot across secondary rectifying devices, and increase leakage current. The paper proposes two winding structures to mitigate the effects of inevitable stray capacitances of planar transformers. In addition, the second strategy integrates the Y-capacitors into the transformer in order to suppress Common-mode (CM) EMI noise generated in the DC-DC converter. The effectiveness of the proposed winding strategy is validated by analytical and experimental results that are presented in the paper.