An integrated planar EMI filter for ultra-high frequency power converters

In this paper, we propose an integrated planar electromagnetic interference (EMI) filter for ultra-high frequency power converters switching at or above 10MHz. The integrated planar EMI filter structure consists of coreless planar spiral windings (CPSW) and parallel copper plates. The entire structure includes both the differential-mode (DM) and common-mode (CM) filters and can be fabricated in a single multilayer printed circuit board. The CPSW is firstly characterized by a lumped high-frequency circuit model which is then extended to form the equivalent circuit of the EMI filter. The performance of the differential-mode (DM) and common-mode (CM) filters is investigated individually and then they are combined to form a planar EMI filter which can handle the DM and CM noise simultaneously. Simulated and measured results are included and they confirm the filtering effectiveness of the integrated planar EMI filter.