Research On Junction Temperature Evaluation Method Of SiC MOSFET Based On Device Transconductance

Power semiconductor devices play a central role in power electronics.At the performance development of traditional silicon(Si)-based semiconductor power devices has approached the theoretical limit of materials,power devices made of new-generation of wide-bandgap semiconductor materials represented by silicon carbide(SiC)and gallium nitride(Ga N)have received extensive attention.From the perspective of band gap,SiC material is three times that of Si material.As one of the typical representatives of wide bandgap semiconductor power devices,SiC MOSFET has more prominent advantages in high voltage,high frequency,high temperature and high power density and other occasions,its application prospects are really broad.However,the long-term operational reliability of SiC MOSFET is not yet clear.Junction temperature as a momentous parameter for status monitoring,reliability evaluation and health management and other work of power devices.Therefore,it is really crucial to accurately extract the junction temperature of the device.At present,the junction temperature measurement of SiC MOSFET has attracted more and more attention.The temperature sensitive electrical parameter method is considered to be one of the most promising junction temperature measurement methods.Firstly,the SiC MOSFET’s temperature characteristics and temperature-sensitive parameters are investigated,the law of its transconductance affected by temperature is analyzed.The assumption that the arithmetic square root of transconductance is linear with junction temperature is proposed.The function obtained by fitting the data obtained from the pre-experiment proves the correctness of the hypothesis.Furthermore,the square root of the transconductance arithmetic is proposed as a thermosensitive electrical parameter to evaluate the junction temperature of SiC MOSFET.Secondly,by using the arithmetic square root of transconductance as the temperaturesensitive electrical parameter,the junction temperature evaluation of SiC MOSFET is then investigated.The SiC MOSFET model SCT3060 AL of ROHM company is selected as the research object.A double pulse test platform is built,and the junction temperature calibration curve of the device is established.The junction temperature of the device in double pulse mode and continuous pulse mode of the converter is evaluated and measured by using the calibration curve.The junction temperature evaluation experiments are carried out at different temperatures according to the method proposed in this paper.The maximum error of the experimentally obtained junction temperature evaluation measurement results is 4.0%,the minimum error is only 1.9 %,and the error temperature is within ±3℃.In the two working modes,the junction temperature of the device can be measured more accurately,which proves the accuracy of the proposed method.In order to explore the junction temperature evaluation method of SiC MOSFET in the long-term operation aging process,the thermal resistance between the device and the radiator is changed to simulate the fatigue aging process of the device,and the junction temperature evaluation experiments are carried out on the devices with different aging degrees.The experimental results show that the more serious the aging degree,the greater the error of junction temperature evaluation,so the necessary compensation measures need to be taken.Finally,the research work and conclusions of the full text are summarized,and the further research is prospected.