高压脉冲晶闸管热特性研究

发布时间：2018-05-27 23:17

  本文选题：脉冲晶闸管 + 热特性　； 参考：《华中科技大学》2015年硕士论文

【摘要】：高压脉冲晶闸管作为一种耐压高、通流大的半导体开关被广泛应用于脉冲功率领域。本文主要研究脉冲晶闸管的热特性,包括基于瞬态热阻抗网络晶闸管结温计算,有限元仿真分析晶闸管结温不均匀分布和晶闸管结温的实验测量。论文推导了晶闸管热阻抗网络模型与电路模型之间的等效过程,求解了晶闸管的热阻抗参数,在此基础上求解了不同脉冲电流下晶闸管结温响应曲线,同时计算了考虑结温对晶闸通态压降的反馈影响下的结温响应曲线。计算结果表明,流过晶闸管的脉冲电流其峰值对结温的影响比脉宽对结温的影响显著,考虑结温对晶闸管通态压降反馈影响后计算的结温要比不考虑反馈影响下的结温要大。论文分析了脉冲晶闸管开通过程中导通区域的扩展过程,建立了晶闸管耗散功率密度的不均匀分布数学模型,结合晶闸管传热有限元模型,求解晶闸管不均匀温度分布。仿真结果表明,晶闸管在流过脉冲大电流时,热量开始时主要集中在门极附近,随后开始逐渐往周围阴极区域扩散。热量扩散速度的快慢主要取决于导通区域的扩展速度。同时由于硅片和钼片的导热系数都比较小,所以晶闸管阀片上的热量主要集中在硅片上,从硅片往两侧钼片上扩散的热量很小,而扩散到钼片外侧铜基座上的热量就更少。晶闸管的温度不均匀分布导致局部温度高达数百至一千摄氏度,达到晶闸管阀片缺陷点的熔点,造成阀片熔化,导致晶闸管热击穿和损坏。论文基于热敏参数法的基本原理,针对热敏参数法测量脉冲晶闸管结温所存在的技术难点,设计了合理的实验方案,通过在待测晶闸管两端并联一个恒流源支路,提前触发待测晶闸管导通,这样待测晶闸管在整个实验测量过程中两端电压都维持在几伏至十几伏之间,因而可以采用普通示波器探头精确测量晶闸管通态压降,进而根据热敏曲线计算结温。通过实验验证了该方案的可行性。测量了晶闸管在200A直流电流下的热敏曲线,同时测量了脉宽为400μs,峰值分别为12.48kA,26kA,39.2kA的脉冲电流流过晶闸管后晶闸管的结温升,其结温升分别为56.9℃,74.3℃和100.6℃。
[Abstract]:High voltage pulse thyristor is widely used in pulse power field as a kind of semiconductor switch with high voltage and high current. In this paper, the thermal characteristics of pulse thyristors are studied, including the calculation of thyristor junction temperature based on transient thermal impedance network, the finite element simulation analysis of the non-uniform distribution of thyristor junction temperature and the experimental measurement of thyristor junction temperature. In this paper, the equivalent process between the Thyristor thermal impedance network model and the circuit model is derived, and the thermal impedance parameters of the thyristor are solved. On this basis, the temperature response curve of the thyristor junction under different pulse currents is solved. At the same time, the junction temperature response curve considering the effect of junction temperature on the on-state pressure drop of the gate is calculated. The calculated results show that the peak value of the pulse current flowing through the thyristor has more influence on the junction temperature than the pulse width on the junction temperature, and the junction temperature calculated after considering the influence of junction temperature on the on-state pressure drop of thyristor is greater than that without considering the feedback effect. In this paper, the expanding process of the conduction region in the process of pulse thyristor opening is analyzed, and the mathematical model of non-uniform distribution of the dissipation power density of thyristor is established, and the non-uniform temperature distribution of thyristor is solved by combining with the finite element model of thyristor heat transfer. The simulation results show that when the thyristor flows through the pulse high current, the heat is mainly concentrated near the gate pole at the beginning, and then diffuses gradually to the cathode region around it. The speed of heat diffusion mainly depends on the speed of expansion in the conduction region. At the same time, because the thermal conductivity of silicon wafer and molybdenum wafer are small, the heat on thyristor valve is mainly concentrated on silicon wafer, and the heat diffused from silicon wafer to both sides of molybdenum wafer is very small, and the heat diffused to copper base outside molybdenum wafer is even less. The uneven distribution of the temperature of the thyristor leads to the local temperature of hundreds to 1000 degrees Celsius, which reaches the melting point of the defect point of the thyristor valve, causes the melting of the valve sheet, and leads to the thermal breakdown and damage of the thyristor. Based on the basic principle of thermistor parameter method, a reasonable experimental scheme is designed for measuring the junction temperature of pulse thyristor by means of thermo-sensitive parameter method, and a constant current source branch is connected at the two ends of the thyristor to be measured. The thyristor conduction is triggered in advance, so that the voltage at both ends of the thyristor is kept between several volts and ten volts in the whole process of experimental measurement, so the on-state voltage drop of thyristor can be accurately measured by ordinary oscilloscope probe. Then the junction temperature is calculated according to the thermal sensitivity curve. The feasibility of the scheme is verified by experiments. The thermal sensitivity curves of the thyristor at 200A DC current were measured, and the junction temperature rise of the thyristor with pulse width of 400 渭 s and peak value of 12.48 Ka / 26kA / 39.2 Ka was measured respectively. The temperature rise of the thyristor was 56.9 鈩，

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