Design method for the minimization of common-mode inductor volume taking into account saturation issues in EMI filters for variable duty cycle applications

The subject of this paper is to propose a design method of the EMI filters that allows to minimize the volume of the common-mode inductor with consideration of core saturation issues. Inductor volume depends not only on its inductance value, but also on the relationship between the filter and its environment which can saturate the magnetic material due to many parameters, especially when the filter resonance frequency F_r is higher than the converter switching frequency Fg. One of these parameters is the converter duty cycle D. This study explains why it is more desirable to set F_r below Fg in order to reduce the coupled inductor volume while increasing the filter performances.