Parasitic Capacitance Cancellation for Emi Filters with an Embedded Ground Layer

Planar structures are often used in the construction of different equipment due to their many advantages like reducing the magnetic profiles, lower leakage inductance, lower HF losses in the windings and improving thermal management. One of the greatest disadvantages is the presence of the equivalent parasitic capacitance (EPC) which is also present in our area of interest, EMI filters. In previous researches, the parasitic capacitance was reduced using various methods like increasing the width of the kapton layer, placing an air layer between the windings and shifting the windings. This paper presents the method of EPC cancellation with an embedded ground layer placed so that the electric field energy will be shifted from the unwanted space to ground. The aim of this study, besides eliminating parasitic capacitance, is to maintain the selfcapacitances of the windings as close as possible to their original values. Considering the other studies and their results, two different methods of parasitic capacitance reduction are combined to determine if it is possible to have an even lower EPC. The influence of the embedded ground layer on the whole structure is analyzed, considering the shape, position and thickness of the copper layer and modeling a multitude of structures with varying parameters. The obtained results are compared to ones determined with an energetic parameter method in order to evaluate their accuracy.