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

International audienceThis 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

Experimental evaluation and FDTD method for predicting electromagnetic fields in the near zone radiated by power converter systems

International audienceThis paper presents the study of conducted electromagnetic interference (EMI) currents flowing through thepower cables of a DC-DC converter system and its correlation with the near field radiated from these cables. The radiatedemission measurement contains a common mode (CM) and a differential mode (DM), and accurate separation of theradiated emissions of these two modes is necessary. The finite-difference time-domain (FDTD) method is used to predictthe electromagnetic radiation caused by CM currents and DM currents. An experimental bench has been designed toallow access to the measurement of EMI disturbances at various sensitive places. The CM and DM voltages resultingfrom the experimental measurement are implemented in the FDTD algorithm as voltage sources of disturbances, thesedisturbance voltages causing the generation of CM and DM currents flowing through the cable. Finally, single and bifilarwire models for modeling the near field using the FDTD method are presented and the simulation results of the nearfield caused by both of the modes are evaluated and compared with the experimental ones. The main objective is toinvestigate the significance of the contribution of each of the current modes on the radiated emissions from the cableusing the FDTD method, thus characterizing the level of cable radiation versus a specific standard. This allows showingthat the radiation is often caused by the CM current along the cable and the largest level is located in the switchingnoise zone located within the frequency range from 1 MHz to 10 MHz