Mitigation of CM conducted EMI IN SMPS

Abstract

The offline SMPS are efficient, lightweight widely used converters in consumer electronics connected to utility mains. Because of high-frequency switching, they produce conducted and radiated EMI also offering low power factor to the utility mains. The two issues involved in the SMPS are to increase the Power Factor and to mitigate the EMI, to comply with EMC standards. Techniques for reducing the conducted EMI for offline SMPS and NUPF have been developed. A design procedure has been adopted for line filter and it has been tested on commercially available offline SMPS and on NUPF which was designed and fabricated. Experimentation and simulation are carried out with and without EMI line filter for a 30W flyback NUPF and a significant reduction in CM conducted EMI is presented. Advances in computer-aided design software and device models have enabled the simulation of NUPF converter and to obtain accurate waveforms. Simulation result obtained are in close agreement with experimental results.