Quantitative Design and Evaluation of EMI Filters in a Digitally Controlled Boost PFC Converter

This paper presents a quantitative design procedure for electromagnetic interference (EMI) filters and investigates the effectiveness of the designed EMI filters in a digitally controlled boost power factor correction (PFC) converter. In most modern electrical equipment, the problem of low power factor due to their intrinsic impedance characteristics has greatly reduced the efficiency of using electric energy. In order to improve the quality of electric power supply while achieving the goal of energy conservation, high-power converters tend to use an active PFC circuit as their front stage connecting to the mains. However, active PFC circuits which utilize high-frequency switching techniques in tracking input line currents often bring EMI and harmonic distortion problems to distribution systems. To ensure that the equipment can meet the relevant EMI standards, some properly designed EMI filters must be used to reduce the common mode and differential mode noises. Due to inevitable nonlinear interactions of the EMI filter and the PFC bridge rectifier, the EMI filter is normally designed by repeated trial-and-errors in practice. To improve the design efficiency, this paper firstly introduces a single-switch boost PFC circuit widely used in various ac-dc converters along with the proposed systematic design procedure for EMI filters and followed by simulation analysis in PSIM software environment. Finally, a 1 kW digitally controlled boost PFC converter prototype with the designed EMI filter is practically constructed and tested to verify the effectiveness of the proposed design method.