Size and weight dependence of the single stage input EMI filter on switching frequency for low voltage bus aircraft applications

Hope is present that Gallium-nitride (GaN) power electronics technology can lead to the significant increase in switching frequency of power converters. The ability to switch more frequently gives potential to increase the power density of converters. EMI filters engage a large portion of system weight and volume, and it is not so straight forward to conclude that increasing switching frequency will benefit size and weight reduction of EMI filters. In this work, the impact of increasing switching frequency on the single stage EMI filter size and weight is investigated in a DC/DC converter for low voltage bus aircraft applications. In the initial paper design, it was assumed that the corner frequency of the EMI filter is determined by the low frequency noise spike. Obtained in that way, differential mode (DM) filter size and weight would reduce with increasing switching frequency, while Common Mode (CM) filter will increase little due to smaller CM propagation path impedance at higher frequencies. For verification purposes, two different resonant LLC converters are implemented at switching frequencies of 1 MHz and 2 MHz. Experiment results shows that EMI filter was larger and heavier for 2 MHz case due to high frequency noise spikes at tens of mega-hertz.