Research Of SiC MOSFET Model And Equivalent High-temperature Switching Power Supply Design

At room temperature, the power devices of switching power supply are mainly based on Silicon(Si) material, but the upper limit of its operating junction temperature is only 125℃. Since switching power supply at work will generate a lot of heat, and it requires a cooling system of large volume and weight to keep normal working, which can lead to complexity and instability. A new generation of Silicon Carbide(SiC) power devices well overcome the heat problem of the bulk silicon power devices, and its operating junction temperature can reach 250℃, so it reduce dependence on cooling equipment. Therefore, research on high-temperature switching power supply based on SiC power devices can promote the development of high-temperature power systems.The main purpose of this thesis is to pave the way for the design of a high-temperature switching power supply, research mainly focus on two aspects: high-temperature device model and equivalent high-temperature switching power supply design. This major work completes as follows:In the aspect of high-temperature device model, firstly, the thesis gives a brief introduction to power Metal-Oxide-Semiconductor Field-Effect-Transistor (MOSFET) and SiC material; Secondly, it completes theoretical analysis on the temperature characteristics for threshold voltage, the channel effective mobility, on-resistance and body leakage current of SiC power MOSFET; Thirdly, it builds a device model of SiC power MOSFET, which is divided into three parts:the kernel MOSFET, the temperature-dependent device and the switch mode capacitance. Finally, the thesis compares the simulation results of static and dynamic performance with the standard experimental values, which verify the correctness of the established model.In the aspect of equivalent high-temperature switching power supply design, firstly, the thesis analyzes the basic operation theory of phase-shift full bridge zero-voltage-switching(ZVS) as well as the theory of control system; Secondly, the system is introducted overall, including technical indicators; Thirdly, this thesis calculates the main parameters including the selection of power devices, the design of transformer, the output filter inductor and capacitor as well as the blocking capacitor; Finally, this thesis introduces the control system of the converter including protection circuit, sampling circuit, slope compensation circuit and feebback compensation circuit.Finally, the SiC MOSFET model is applied to the equivalent high-temperature switching power supply. Though simulating, firstly, the equivalent high-temperature switching power supply can work properly; Secondly, the SiC power MOSFET model can work at 25℃ and 175℃ with high accuracy and reliability.