A heat sink model for EMI resonance frequency determination

The capacitive couplings between electronic power devices and heatsink are responsible of impulsive current circulation in the latter. These phenomena make this system similar to an antenna. The electromagnetic noise produced can give rise to the incorrect behavior of electronic circuits and of control system. The analysis and the prediction of these effects are of fundamental importance to avoid system malfunction and to guarantee the satisfaction of EMC standards. A EMI modellisation of heatsink used in electronic power system is presented in this paper. The proposed algorithm allows to determine the resonance frequency of the heatsink in closed analytical form. A comparative analysis between the results of the proposed algorithm and that deduced by finite element investigations highlights a good matching. The first experimental results conducted on a EMC laboratory have also confirmed the validity of the proposed method.