Modelling Asymmetry and Mode Conversion in Common-Mode Chokes

This work analyzes the impact of asymmetries in common-mode chokes, critical components for suppressing electromagnetic interference in electronic circuits. The study introduces a novel characterization method specifically designed to account for the effects of geometric imperfections or variations in core material properties. The proposed method builds upon a well-established symmetrical model for CMCs, incorporating modifications that facilitate the estimation of mode conversion. This phenomenon arises when asymmetries cause common-mode noise to convert into differential-mode noise, ultimately hindering EMI suppression efforts. The key advantage of the proposed approach lies in its ability to enhance the capabilities of the symmetrical model without compromising accuracy or significantly increasing its complexity. To validate the method’s effectiveness, it has been applied to a commercially available choke. The model successfully reproduces the characterization measurements outlined in the CISPR-17 standard, thus demonstrating its reliability and applicability in practice.