The Estimation Of MOSFET Core Temperature

Temperature is one of the most critical factors affecting the service life of power devices.Studies show that 55% of the failure of power devices is due to overheating of power devices.Therefore,this paper uses Foster model to estimate the core temperature of MOSFET.The main contents of this paper are as follows: 1.The research background and significance of core temperature estimation of power devices are introduced,as well as the current status of core temperature estimation methods at home and abroad.2.Analyzing the source of power device loss,dividing power device loss into switching loss,conduction loss and continuation loss,and calculating them theoretically.It is pointed out that conduction resistance and other parameters change with the change of current and temperature,so it is not easy to estimate the temperature of tube core with conduction resistance and other parameters.3.Put forward the concept of thermal resistance and heat capacity,and some methods of temperature estimation,which are mainly divided into TSEP temperature estimation method and core temperature estimation method based on equivalent model of thermal resistance and heat capacity,namely Foster and Cauer model,analyze the advantages and disadvantages of the two models,and determine that Foster model is used in this paper.4.The Foster model is modeled and simulated with MATLAB.Based on the 5 kW controller with MOSFET,the inductance is used as the load,and the parameters of the model are determined by engineering calibration.The calibration process can be roughly divided into the same angular velocity,different phase currents and different angular velocities.5.Aiming at the problem that the integral in the core temperature estimation model is cleared when the controller is powered off,which leads to the inaccuracy of the initial temperature estimation after power-up,a solution is proposed,which can accurately estimate the initial temperature of the MOSFET core.6.In order to improve the reliability of the controller,the logic of temperature protection is added to the control algorithm,such as the control logic of power reduction and over-temperature shutdown.At the same time,in order to enhance the heat transfer ability of MOSFET and the heat dissipation ability of aluminium platforms,increase the contact area between aluminium platforms and environment,and enhance the heat dissipation ability and reliability of the controller,it is pointed out that the thickness and uniformity of silicone grease coating should be paid attention to in the heat dissipation scheme of adding silicone grease to ceramic platforms.