Simulation and Modeling of Common Mode EMI Noise in Planar Transformers

The transformer is the key circuit component of the common-mode noise current when an isolated converter is working. The high-frequency characteristics of the transformer have an important influence on the common-mode noise of the converter. Traditionally, the measurement method is used for transformer modeling, and a single lumped device is used to establish the transformer model, which cannot be predicted in the transformer design stage. Based on the transformer common-mode noise transmission mechanism, this paper derives the transformer common-mode equivalent capacitance under ideal conditions. According to the principle of experimental measurement of the network analyzer, the electromagnetic field finite element simulation software three-dimensional(3D) modeling and simulation method is used to obtain the two-port parameters of the transformer, extract the high-frequency parameters of the transformer, and establish its electromagnetic compatibility equivalent circuit model. Finally, an experimental prototype is used to verify the correctness of the model by comparing the experimental measurement results with the simulation prediction results.