A New Approach for Improving Stability of Active CM EMI Filters for AC/DC Power Converters

In this paper, a new approach for improving stability of active common-mode (CM) electromagnetic interference (EMI) filters is presented. The system model was developed based on the models of critical components including a current transformer (CT), a current feedback amplifier (CFA) circuit and injection RC network. The system model is more accurate and efficient, taking full account of the model of high frequency zero-pole and gain error of the CFA, the high frequency parasitic parameters of the current transformer and the injection network. Based on the system model, the loop gain and key parameters study are derived and presented. Both simulations and experiments are conducted to verified the developed model and the approach.