Improved EMC filter performance of ferrite cores based on hysteresis and saturation

In conventional EMC-filter design for power converters, common mode chokes are designed with sufficient margin to saturation. However, for chokes based on toroidal ferrite cores, nonlinear effects like saturation and hysteresis can improve the filter performance, since hysteretic losses and the strongly varying inductance smear out resonances in the noise spectrum. The effect is demonstrated for a common mode choke placed at the output of a power converter in order to damp the cable resonance.