Analysis and Design of an Active Common-Mode EMI Filter without Auxiliary Power Supply

Active electromagnetic interference (EMI) filters (AEFs) employ active components to actively suppress conducted EMI in power electronics systems, with their electric power typically provided by an isolated auxiliary power supply (APS). However, the addition of an APS can increase the volume and weight of the AEF, while its maximum output power may limit the EMI suppression effectiveness of the AEF. This article proposes an AEF design scheme without an APS. This is achieved by utilizing the DC power source of the device under test for power supply. The working principle is analyzed in detail, and experimental tests are conducted. The experimental results demonstrate that the proposed AEF design without an APS achieves the same EMI suppression effectiveness as when an APS is used.