| The research on junction temperature measurement of SiC MOSFET plays an important supporting role in its reliability analysis.The temperature sensitive electrical parameter method is one of the most widely studied junction temperature measurement methods at present.However,almost all temperature sensitive electrical parameters will shift to a certain extent with the aging of SiC MOSFET devices,which will reduce the measurement accuracy of junction temperature.Therefore,based on the aging mechanism of SiC MOSFET,this paper studies the influence of device aging on temperature sensitive electric parameters,proposes a junction temperature measurement method with multi-parameter aging compensation,and designs a corresponding junction temperature measurement system.Firstly,based on the detailed analysis of the basic principle and aging mechanism of SiC MOSFET,the temperature-sensitive characteristics of various electrical parameters of SiC MOSFET are studied experimentally.Accelerated aging of SiC MOSFET was carried out on the power cycle experiment platform.The deviation of temperature sensitive characteristics of threshold voltage,on-resistance and on-delay time with aging of SiC MOSFET was studied.A multi-parameter junction temperature measurement method for aging compensation based on threshold voltage,on-resistance and on-delay time was proposed.Compared with the traditional method of re-calibration of junction temperature,the advantage of this method is that it can greatly reduce the workload of aging compensation on the premise of ensuring the measurement accuracy of junction temperature.Secondly,based on the measurement method of junction temperature with multi-parameter aging compensation proposed in this paper,a junction temperature measurement system is designed,which includes drive and parameter acquisition module,data processing module and host computer.The drive and acquisition system uses FPGA as the core to protect SiC MOSFET and collect electric parameters such as on-resistance.The data processing module uses STM32 to calculate the junction temperature and upload it to the upper computer.The upper computer uses QT for development,which can display and save the junction temperature.Finally,an experimental platform is set up to verify the function and performance of the system.The results show that the designed system can drive SiC MOSFET normally,and can accurately collect three electrical parameters: on-resistance,threshold voltage and on-delay time.The junction temperature measurement error of the unaged device is within ±2℃.The junction temperature measurement error of the aging device can be reduced from 90℃ before compensation to less than 7℃.The final experimental results show that the designed system can effectively reduce the junction temperature measurement error caused by device aging. |
