Simple Approach to Predict Near Field Electromagnetic Interference in SMPS using the Induced EMF Method

The electromagnetic interference generated by a switched-mode power supply on a victim circuit is analysed representing their electromagnetic field coupling by two-port networks. The essential electromagnetic interference sources of the switched-mode power supplies are individuated and their mutual impedances with the victim circuit are calculated by the induced EMF method. The two-port representation of the field coupling allows the noise voltage on a victim circuit to be predicted. As a victim circuit a circular loop representing a magnetic field probe used in near field measurements is considered. The approach is applied to a flyback converter and validated through experimental measurements.