Analysis of EMI Radiation Noise from a Novel Passive Energy Recovery type Soft Switching Circuit

Abstract

High dv/dt rate at switching of IGBTs become source of EMI noise. For this problem, various methods that makes low dv/dt rate by using soft switching circuit are proposing. In this paper, a novel snubber circuit with passive energy recovery for soft switching inverter is proposed. This novel circuit uses a capacitor which makes zero voltage switching to both upper and lower IGBTs, and a transformer which regenerates the snubber energy. And this paper describes the EMI noise from the novel soft switching circuit. From results of experiment and analysis, we clarified that radiational noise is not reduced by making low dv/dt rate of only IGBT. Radiational noise generates from resonant current flowing through the soft switching circuit and IGBT. This resonant current don't flow trough the conventional hard switching circuit. So, we indicate the reducing methods of radiational noise that the reducing the resonant current by using saturation type reactor and RC snubber with snubber diodes. The effect of the methods has been verified by experimental and simulational results.