Analysis of Passive and Active EMI Filters for On-Board Chargers in Electric Vehicles

The usage of Wide-bandgap semiconductors with high switching frequencies to shrink the size of passive components, leads to the need for large Passive EMI Filters (PEFs) to comply with Electromagnetic Interference (EMI) standards. This paper analyzes the generation of conducted EMI on the example of an 11 kW On-Board Charger (OBC). The distinction between Common Mode (CM) and Differential Mode (DM) EMI is highlighted. An Active EMI Filter (AEF) for CM EMI attenuation is developed with the target to decrease the size of bulky Common Mode Chokes (CMCs) of a typically used PEF. From the structure of the PEF, the corresponding equivalent circuit diagrams for CM and DM EMI are used to implement the AEF with the least possible effort, into an already existing EMI Filter. Within this paper, it is outlined why a Voltage Sense Current Inject (VSCI) Feedback (FB)-type AEF fits best for this use case. The PEF and AEF are compared on the basis of the achievable CM and DM Insertion Loss (IL). Simulation results show that the AEF is able to increase the CM IL by 28 dB at 150 kHz and 21 dB at 1 MHz.