Analysis and Reduction Methods of EMI Radiational Noise from Converter System

Abstract

It is well known that high dv/dt rates on the switching devices are the source of EMI noise. This paper describes a mechanism and reduction methods of EMI radiation noise on IGBTs. The radiational noise is generated by oscillating current flowing through the IGBT's output capacity and the snubber circuit, which we call equivalent circuit of radiational noise. The oscillating current of the equivalent circuit is forced to flow by the high dv/dt rates of IGBT switching operation. Radiational noise can be analyzed by frequency evolution of oscillating current. These results of this analysis show the relationship of high frequency impedance of the equivalent circuit to radiational noise, as well as the relationship of IGBT's switching voltage waveform. In addition, it is indicated that using a di/dt control gate drive circuit is effective as a means for reducing radiational noise. It is clarified that the standard for industrial equipment of CISPR can be satisfied by using proposed gate drive circuit. The effect of the method has been verified by expeimental and simulational results.