Abstract

The switch mode power supply (SMPS) have been widely used in the electrical and electronics systems for AC-DC and DC-DC power conversion, which can generate a lot of electromagnetic interference (EMI), especially conducted emission (CE) from 9kHz to 30MHz. The traditional CE models and mechanisms have been present for three line systems, including live, neutral and ground lines, while a novel CE models and mechanisms have been proposed in the paper for two line SMPS. And the voltage division factor, isolation factor and impedance under SMPS side of artificial mains network have been studied based on high frequency parasitic parameters to analyze the CE measurement uncertainty. Moreover, three methods have been designed to reduce the CE of SMPS, such as the capacitor shunt between the source and drain electrodes of MOSFET, CM choke and crosstalk choke, and the capacitors matrix. The experiment results show that the CE of the power concentrator and colonoscopy can be suppressed well and pass EN 55022 class B, thus realize the proposed approaches good validation.