Optimizing capacitor placement in EMI-filter using back annotation of 3D field coupling parameters in circuit models

Abstract

To reduce common mode(CM) and differential mode(DM) interference, a DM/CM integrated filter is often required to reduce the level of interference. This paper will show coupling from a Common Mode Choke(CMC) into C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> capacitors can decrease the DM-filtering performance significantly at high frequencies. By retrieving equivalent circuit parameters from a 3D EM field simulation of the components, and include these parameters in the circuit simulator, an optimal capacitor orientation is determined. The optimized placement results in a 15 dB improvement between 5 MHz and 200 MHz.