Research On Modeling And Junction Temperature Predicting Of IGBT Under High Temperature

With the development of power electronic technology and process technology,insulated gate bipolar translators(IGBTs)are widely used in electronic circuits.Many of these applications are under high temperature,such as oil and natural gas exploration,new energy projection and automobile industry,which put forward austere challenge for the safe and reliable operation of IGBTs.Under high temperature,the performance and system characteristics of power electronics systems containing IGBTs and other passive devices will change with the development of temperature and limitation of heat emission condition.The device electrical and thermal parameters and performance characteristics of the IGBT will change at high temperature,which leads to the rise of junction temperature,reduction of system efficiency,overheating of the device and even leads to the breakdown of system.Therefore,it is significant to study the IGBT device model and thermal characteristics,build IGBT thermal model,predict device junction temperature,discuss affecting factors of junction temperature in the converter at high temperature.Firstly,this paper studies the IGBT thermal characteristics and establishes the equivalent circuit model of IGBT based on the present models in Pspice to simulate the device static and dynamic characteristics.The thermal model parameters of the threshold voltage,on-resistance,saturation voltage and some other electrical characteristics of IGBT are extracted according to physical parameters inside the device and the relationship between parameters and electrical properties.Then the thermal equivalent circuit model of the IGBT is built to simulate the device thermal characteristics accurately.Secondly,this paper establishes the IGBT loss model considering the effect of parasitic elements by switching curve fitting method.The loss model parameters are extracted according to the IGBT data sheet and real switching waveforms.As a result,the switching loss and conduction loss model are built at room temperature.Then the IGBT thermal model of switching losses and conduction losses is established based on the thermal characteristics and device temperature model.Thirdly,a 3-D IGBT thermal model of the packaging is built using finite element method to simulate the distribution of temperature inside the device and extract the thermal impedance curve.Then a Foster network of IGBT is proposed according to the thermal impedance.Lastly,an electric-heat coupling model of IGBT is proposed combining IGBT loss model and the Foster network to predict device junction temperature based on its working condition in Buck converter.The electric-heat coupling model realizes realtime monitor of IGBT losses and junction temperature,and it can simulates the dynamic process from device power losses to junction temperature and predict device junction temperature precisely.Experimental platform is built to test the IGBT junction temperature,which is a power supply based on Buck converter.Experiments are carried out choosing saturation voltage as the heat-sensitive parameter,which can improve the accuracy of the electric-heat coupling model.Meanwhile,the experiments discuss the affecting factors of junction temperature in Buck converter such as frequency,duty cycle and ambient temperature.