一种优化动态特性SiC-MOSFET模型及其在高压固态开关的应用

An optimized model for SiC-MOSFET dynamic characteristics and its application to high-voltage solid-state switch

为设计一款保护J-TEXT托卡马克电子回旋管的高压固态开关,新型宽禁带半导体SiC-MOSFET凭借低开关损耗、高耐压和MHz级别的开关频率等优良电气特性,在其中承担核心作用。但是极快的开关速度加剧了开关振荡,导致器件直串时的关断波形质量下降,对均压和抑制过压方法提出更高要求,因此亟需建立精准的模型为SiC-MOSFET在高压保护开关中的应用提供指导。在分析制造商CREE商用模型基础上,提出了一种优化动态特性SiC-MOSFET模型。该优化模型综合考虑栅源电压和漏源电压的影响,对非线性结电容采用多种函数拟合建模,并对杂散阻抗等关键寄生参数进行修正。通过仿真和300 V/3 A双脉冲测试,证明该模型在漏源电压变化率、漏源电流变化率、振荡频率和关断尖峰电压等方面具有更高的准确性。应用该优化模型设计高压固态开关的均压与过压抑制拓扑,在1400 V/700 A条件下对开关模块进行双脉冲测试。在关断时长和尖峰电压等关键指标上,仿真波形与实验波形高度吻合,实测开通关断时间均小于120 ns,指标满足开关模块设计要求,优化模型的实用性得到体现。

To design a high-voltage solid-state switch to protect the protect the electron cyclotron tube of J-TEXT Tokamak,the new wide-band-gap semiconductor SiC-MOSFET plays a central role with outstanding electrical characteristics such as low switching loss,high voltage withstand and switch frequency at MHz level.However,the extremely fast switching speed aggravates the switching oscillation,which causes the decreasing quality of the switching waveform when the devices are in straight series.Therefore,it is necessary to develop a precise model to provide guidance for the application of SiC-MOSFET in high-voltage switch.Based on the commercial model developed by CREE,an optimized dynamic characteristic SiC-MOSFET model that can better simulate the influence of nonlinear junction capacitance is proposed.The optimized model comprehensively considers the factors of gate-source voltage and drain-source voltage.A variety of functions are used to reproduce the nonlinear junction capacitance,and the key parasitic parameters such as stray impedance are validated.Through the simulation and 300 V/3 A double pulse test,it is proved that the optimized model has higher accuracy in the change rate of drain-source voltage,change rate of drain-source current,oscillation frequency and turn-off peak voltage.The optimization model is also applied to design the topology of voltage sharing and overvoltage suppression for high-voltage solid-state switch,and the switching module is tested under the condition of 1400 V/700 A.On the key indicators such as turn-off time and peak voltage,the simulation waveform is highly consistent with the experimental waveform.The measured turn-on and turn-off time is less than 120 ns,which meets the design requirements of switching module,and the practicability of the optimization model is reflected.