基于SiC MOSFET的同步Buck变换器电磁干扰噪声分析及预测

Analysis and Prediction of Electromagnetic Interference Noise in Synchronous Buck Converter with SiC MOSFET

碳化硅(SiC)MOSFET相比于传统的硅型MOSFET,具有更高的工作结温和更大的功率密度。但由于其更快的开关速度以及电路中存在的寄生参数,SiC MOSFET的输出波形会产生很大的开关振荡。该文基于开关过程的等效模型,建立分析模型以计算同步Buck变换器开关波形的频谱以及相应的频谱边界。通过将实验结果与数值计算结果进行比较,准确地预测出开关波形频谱的边界,并且发现,SiC MOSFET的寄生参数对高频成分含量及其边界具有明显的影响。

Compared to silicon MOSFETs,silicon carbide(SiC)MOSFETs have higher operating junction temperature and higher power density.However,due to its faster switching speed and parasitic parameters,a large switching oscillation will occur on the output waveform of SiC MOSFET.This paper derives the mathematical formulas of the time-domain switching waveforms based on equivalent circuit models for the switching transition.Then,analytical models are developed to calculate the spectra and the corresponding spectral bounds of the switching waveforms of SiC MOSFETs in a synchronous Buck converter.By comparing the experimental results with the numerical calculation results,the boundary of the switching waveform spectrum is accurately predicted,and it is found that the parasitic parameters of SiC MOSFET have significant effect on the high-frequency spectrum and its bounds.