Devices for the separation of the common and differential mode noise: design and realization

EMI measurements and the design of proper filter to mitigate the EMI noise is very important, since the EU Directive 336/89 has been published. For conduction emission noise, the separation of the common and the differential mode noise is important for determining whether the differential or common mode component is dominant. Therefore, it will be possible determine whether an anticipated change in a value of an element in the power supply filter will be effective on the considered component. Two devices for the separation of the conducted EMI noise into the common and the differential mode components have been realized and tested. In this paper the authors show the design considerations that have to be taken into account for the realization of the two devices