Zero-Phase-Filtering based Digital Active EMI Filter

Zero-phase filtering is a methodology of achieving filtering without any phase distortion. This methodology is applied to digital active EMI filters to enhance the attenuation at frequencies from 100 kHz to 1 MHz. The methodology for implementing zero-phase filtering in an FPGA are presented. The novel filter is then demonstrated in a feed-forward voltage- sense voltage-cancellation active EMI filter for differential mode noise attenuation. The proposed filter is tested with small signal source and as well in a power converter. The test results show that the proposed filter can have up to 46 dB attenuation around 150 kHz and have a bandwidth of a few MHz.