Prediction and Measurement Techniques for Radiated EMI of Power Converters with Cables

Recently, radiated electromagnetic interference (EMI) has become a research hotspot in power electronics systems, as the switching frequencies of power electronics systems have increased significantly with the adoption of wide-bandgap devices. In this article, a generalized radiated EMI model for power electronics converters with power cables is first reviewed. The radiated EMI model is then developed for a flyback power converter with critical ground impedance included. Based on the developed model, accurate high-frequency parameter extraction techniques and a radiated EMI prediction technique are developed and experimentally validated. Finally, essential measurement techniques are identified and developed to accurately extract parameters for accurate EMI prediction. The effects of the resolution bandwidth of the spectrum analyzer and critical PCB ground impedance on the radiated EMI are experimentally validated. PCB's impact on the common-mode (CM) choke's impedance and the radiated EMI is further validated. Techniques for minimizing the undesired near-field couplings in parameter extraction are discussed. The predicted EMI properly agreed with the measured EMI in the range of 30-230 MHz based on the EN55032 3 m class B standard. © 2017 CMP.