Abstract: This paper presents a filter analysis of conducted Electro-Magnetic Interference (EMI) for switching power converters (SPC) based on noise impedances. The EMI characteristics of the SPC can be analytically deduced from a circuit theoretical viewpoint. The analytical noise model is first investigated to get a full understanding of the EMI mechanism. It is shown that with the suitable and justified model, filters pertinent to EMI noise are investigated. The EMI noise is identified by time domain measurements associated with an isolated half-bridge ac–dc converter. The practical filters like LC filter, Ï€ filter and Complete EMI filters are investigated. The analysis and results proposed can provide a guideline for future effectiveness of filtering schemes in SPC. Experimental results are also included to verify the validity of the proposed method. The results obtained satisfy the Federal Communications Commission (FCC) class A and class B regulations.