Development Of IGBT Power Cycle System

With the development of the times,Insulated Gate Bipolar Transistor?IGBT?as a new generation of high-power switching devices occupies an important position in many fields.However,the failure rate of IGBT is still high in wind power converter,high-speed rail and new energy vehicles.Therefore,it is necessary to study the reliability and life of IGBT.In this paper,power cycle experiments are mainly used to study the reliability of IGBT,and the changes of IGBT related electrical parameters under overstress are obtained.The fault prediction quantity that can reflect the operating state of IGBT is found,and the mechanism of fault occurrence is further analyzed to set a good foundation for establishing a life prediction model.There are many reasons for IGBT failure:overvoltage,overcurrent,high temperature and other factors will shorten the service life of the device.In the actual environment,IGBT mainly works under the periodic switching condition.Based on the existing research conclusions and the actual operating conditions of the device,this topic designs an experimental system that can carry out multi-channel IGBT power cycle at the same time.The device can operate at different power and realize period operation through temperature control strategy.This paper mainly completes the following work:Firstly,temperature control includes case temperature control and junction temperature control of IGBT.The internationally recognized high precision resistor PT100 is used as the temperature sensor for case temperature measurement to realize real-time high precision measurement.The junction temperature is measured by electrical parameter method.Through multi-party comparison,IGBT pre-threshold voltage V_pre-th is selected as the temperature-sensitive parameter.The negative linear correlation between pre-threshold voltage and temperature is used to collected junction temperature.It also has the advantages of high sensitivity and easy acquisition.Secondly,aiming at the difficulties in junction temperature acquisition,the experimental control strategy is optimized.The measurement time is in the IGBT turn-off process,and the change of the pre-threshold voltage,i.e.the cold response curve,needs to be collected in a short time.Since this process involves the turn-off characteristics of IGBT,the influence of trailing current on acquisition should be considered.Therefore,when designing the system,it is considered from two aspects of hardware and software:hardware aspect,perfect the window voltage acquisition circuit,realize the fast cut-off of heating current and reduce the influence of noise in the circuit;software aspect,by measuring the turn-off delay of IGBT under different conditions,the corresponding relation between trailing current duration and power is determined,according to the analysis of the data,discard the data with interference.Finally,the platform was built and IGBT power cycle experiment was carried out.Under different setting conditions,six devices of two types are divided into three groups for experiments.IGBT threshold voltage V_th and collector leakage current I_ceses are selected as characteristics for monitoring IGBT aging state,and finally,several groups of experimental data are obtained,and the causes of experimental phenomena are analyzed according to semiconductor physics and microelectronic theory.The experimental process and data results have reference value for IGBT reliability evaluation and life model establishment.