1 200 V SiC MOSFET 参数分散性对并联均流的影响分析

Based on the 1 200V 20A SiC MOSFET developed by our team, this paper studies the influence of device parameter dispersion on current sharing of parallel components. Firstly, the deviation degree and coefficient of variation of the device are introduced, and the influence of the three wire method and the two wire method test platform on the test results of the device threshold voltage and the on resistance are analyzed. The conclusion shows that the three wire method is more reliable and has more parameters to be measured. Based on the test platform of the three wire method, the basic characteristic parameters of the device are tested, including threshold voltage, on resistance, transconductance, etc, and the dispersion of 30 devices are analyzed. Finally, the threshold voltage and on resistance are taken as the research objects of parallel current sharing. SiC MOSFETs with similar device characteristic parameters and large dispersion are selected to carry out parallel double pulse experiment. On the basis of eliminating the parasitic parameters of the test circuit through the experiment, the influence of the on resistance and threshold voltage on the device parallel current sharing are verified. The results show that the threshold voltage has a great influence on the current sharing of the transient process before and after switching, and the devices with smaller threshold voltage will bear greater overshoot current, which will affect the reliability of the parallel system; Compared with the switching transient process, the on resistance has a greater impact on the current sharing after steady-state. The devices with smaller on resistance will bear greater current and affect the reliability of branch devices.