Design and Implementation of An Active Common Mode EMI Filter for LV Automotive Applications

Abstract:
In low-voltage distribution system for electric vehicles, the size of passive electro-magnetic interference (EMI) filter is mainly determined by the size of common-mode (CM) choke. Active CM EMI filters emerged to be a good way to reduce the size of the CM filter. In this work, the design and implementation of a current sensing current compensation CM active EMI filter is discussed in detail. An analytical model of active EMI filter is derived and validated by simulation and measurement results. Based on the analytical model, an optimization algorithm is proposed to maximize the noise attenuation, while maintaining sufficient stability margin in the frequency range of interest. Measurements obtained from the constructed laboratory prototype of the active EMI filter demonstrate the accuracy of analytical model and effectiveness of this design approach. Measurement results demonstrate that the CM noise can be reduced by more than 30 dB over a wide range between 150 kHz to 10 MHz.