A Novel Grounding Impedance Based Active Common-Mode EMI Filter With Enhanced Safety

Active electromagnetic interference (EMI) filters (AEFs) are effective alternatives to passive EMI filters for increasing the power density of switched-mode power converters. This article presents a grounding impedance-based active common-mode (CM) EMI filter (GI-AEF). Unlike conventional filters placed in the primary circuit, the GI-AEF is installed in the grounding loop to suppress CM EMI without bulky transformers. It only handles low-CM currents and avoids needing high gain-bandwidth operational amplifiers, resulting in a compact and cost-effective design. Additionally, the GI-AEF ensures low-grounding voltage even during power failures, enhancing safety. Experimental results show that it reduces filter volume and weight by over 50% while cutting costs by 34%—marking the first instance of cost reduction in the academic literature through AEF technology.