Radiated EMI Frequency Domain Analysis of a Power Converter Incorporating a Gate Driver Circuit Model

As the switching speed of power semiconductor devices gets faster, radiated electromagnetic interference (EMI), which causes malfunctions in other equipment, is increasing and the development of analysis methods for radiated EMI is urgently needed. This paper proposes an analysis method for common-mode (CM) currents, which are highly related to radiated EMI, above 30 MHz for a half-bridge circuit with a long output cable connected. First, the principle of converting the circuit into a CM equivalent circuit by dividing it into a noise source and a noise radiation source as an antenna is presented. Second, we obtain the CM equivalent circuit parameters by modeling the main circuit without using the experimental results and validate the analytical results. Third, we clarify the existence of CM currents generated by the gate drive circuit without a non-isolated DC-DC converter in the power supply. Finally, this paper suggests a method to incorporate the effect of the gate drive circuit on the CM current into the CM current analysis model. The proposed method allows highly accurate estimation of the CM current due to the main circuit without using experimental results. It was also shown that the CM current due to the gate drive circuit occurs regardless of the existence of the converter and that the CM current due to the gate drive circuit can be included in the analysis. The proposed analysis method, which does not require measurements in the design phase, will contribute to more efficient system design.