A Separate Floating Heatsink Based Suppression Method for Conducted Common-Mode EMI

Abstract

In order to effectively suppress the intractable high-frequency conducted common-mode (CM) electromagnetic interference (EMI) and reduce the dependence on the high-frequency performance of the EMI filter, this article proposes a separate floating heatsink based suppression method (SFHBSM). SFHBSM suppresses high-frequency CM EMI by improving both the CM EMI source and the propagation path. On the one hand, SFHBSM achieves the nonringing CM EMI source without introducing additional resistive loss, by properly designing the parameters of the SFHBSM, the ringing effect in the CM EMI source can be pushed into a narrow bandwidth in the very high-frequency domain, where the ringing effect can be naturally killed by the skin effect. On the other hand, the CM EMI propagation path of the SFHBSM-based power converter is mathematically deduced, verifying that the SFHBSM can provide effective blocking for the CM EMI propagation in the high-frequency domain. Experiments show that under the combined effect of the ringing suppression and propagation blocking, SFHBSM achieves EMI reduction in almost the whole high-frequency domain, and provides up to 35 dB attenuation in a two-level three-phase power converter. Besides, ablation experiments have been conducted to evaluate the individual and combined effectiveness of each part of the SFHBSM.