Common Mode EMI Noise Characteristics of Low-Power AC–DC Converters

Low-power (below several hundred watts) ac-dc converters have unique common mode (CM) noise characteristics compared to higher power converters. A detailed CM noise model is derived in this paper to predict the original CM noise of such converters and to provide insight into CM noise generation and propagation. Further analysis on the model yields some general converter design rules for engineers to follow at the design stage in order to minimize the converter CM noise emission. The proposed model and design rules have been verified and demonstrated on a critical mode boost power factor corrector and a single-stage PFC converter.