Modeling and Analysis of Conducted and Radiated Emissions Due to Common Mode Current of a Buck Converter

This paper presents the study of conducted and radiated emissions due to common-mode (CM) currents flowing through the power cables of a DC-DC converter system. In order to predict the conducted electromagnetic interferences (EMI) emissions, a model of power converter system is presented. The finite-difference time-domain method (FDTD) is used for predicting the magnetic near field radiated by the power supply cable of a buck converter and that due to CM current flowing through the cable. The CM current resulting from the model is compared with the experimental ones and implemented in the FDTD algorithm as current source of disturbance. The comparison with experimental results shows the validity of the FDTD model over a wide frequency range. The goal of this study is to predict the level of conducted and radiated EMI emissions. Therefore, proposing and investigating a simple and effective filtering solution that allows to reduce the emissions located in the switching noise zone, the results show that the conducted and radiated emission levels can be reduced by as much as 30 dB when using this technique.