Prediction and Mitigation of DM Noise From Magnetic Couplings in PFC Converters

Electromagnetic compatibility (EMC) remains a serious challenge in the design of high-density power supplies. Advancements in power semiconductors have enabled higher switching frequencies and greater system integration. However, the combination of fast switching and compact layout exacerbates the effects of parasitic near-field couplings within the power supply. These couplings create unintended paths for EMI propagation, which are layout-dependent and difficult to measure or quantify analytically. As a result, designers often rely on iterative trial and-error methods to comply with EMC standards. This paper introduces a framework to accurately predict the differential mode (DM) noise of front-end converters, including the effects of magnetic couplings between components in the power factor correction (PFC) and EMI filter stages. A lumped element DM noise model is presented, and each magnetic coupling value is quantified with 3D finite-element analysis (FEA). The model is then simplified, and a novel experimental approach is introduced to validate the impact of individual magnetic couplings. Finally, this framework is used to evaluate various EMI mitigation techniques, demonstrating up to 30 dB reduction in DM noise.