Investigation and Mitigation of Radiated EMI due to Near-field Coupling in a High-density Active-clamp Flyback Power Adapter

The article first measured the near electric field distribution of an active-clamp Flyback (ACF) power adapter under investigation with a near-field electromagnetic (EM) scanner, the critical near-field capacitive coupling issue between CM choke and transformer/ DM choke was then identified. Second, a radiated EMI model was developed and preliminarily quantified for the ACF power converter under investigation considering the near-field capacitive coupling effect. Third, two effective techniques were proposed to mitigate the radiated EMI due to the identified near-field capacitive coupling issue based on the developed EMI model. Both the analysis and proposed techniques were finally verified by experiments.