High-Frequency Equivalent Circuit Model for Common-Mode Noise of Buck Converter

In a PWM power converter system, serious issues of electromagnetic interference (EMI) can result from dv/dt and di/dt due to the high-speed switching of the power semiconductors. This paper presents a simplified approach to the analytical estimation of the common-mode conducted EMI generated by a DC-DC buck converter in high frequency noise spectra at 150 kHz - 30 MHz. The equivalent circuit of DC-DC buck converter at high frequency was proposed in this paper for the purpose to reduce the complexity of the circuit and minimize the time simulation. The simulated CM EMI waveform of the equivalent circuit is compared with the detailed circuit to determine the accuracy of the proposed model. In the results of simulated CM noise spectra, the resonance point of frequency and magnitude are matched at 7.7 MHz, at 88 dBuV.