Physical Model Research For RSD Under Power Conversion Process

The fundamental concept of pulse power technology is introduced, and the category and characteristic of switch devices in pulse power technology field are summed up. The advantages of high-power and ultra-high-speed semiconductor switch RSD(Reversely Switched Dynistor )are illustrated. In comparison with traditional semiconductor switches, RSD has conspicuous advantages in the application field of pulse power technology: simultaneous turn-on in all area, high di/dt, high speed, very small delay in the turning-on process, low power loss, infinite series, easily used in series and parallel connection, convenient maintenance, low cost and long lifetime. Besides, RSDs have been produced domestically. To conclude, it has a very good prospect in the pulse power technology field.Considering the factors of manufacture cost, safty and so on, semiconductor devices, especially for high-voltage and high power semiconductor switches, it is necessary to have computation and simulation, which are based on the reasonable modeling for semiconductor devices. There are several guidelines to evaluate a good device model such as follows: well-posedness, simulation capability, qualitative similarity, predictive ability, structural stability, and so on.The working mechanism is analyzed from the fundamental theory of semiconductor. Grekhov's model is induced and anylized in details. From the basic theory of semiconductor device physics, the motion and distribution of non-equilibrium carries in RSD are given. The triggering process, conducting process and the physical behaviour around the turning point of current are analyzed quantitatively. As a result, the two conditions for normal turning-on are gotten: (1) in the process of triggering when the polar of voltage on RSD is reverse, the choke should shoulder on the majority of the voltage of the working circuit; (2) To avoid partial turn-on, sufficient charge must be injected in the triggering period. The injected plasma must be distributed along the whole J2 junction to avoid conducting locally. The conditions mentioned above provide foundation for circuit design. In terms of the induction of Grekhov's model, its advantages and disadvantages are analyzed, which give lessons for making more accurate numerical model of the author.The fundamental equations for the RSD are derived through the semiconductor theory. By considering the high level injection and high electric field effects, the physical model of RSD is constructed, in which the reversal injection process is under pnn+ diode operation mode and forward conduction process is under pin diode operation mode. The boundary conditions relevant to the level of current injection are gotten too. Through the limited difference method the partial differential equation of the semiconductor device is transformed into difference equation, and the corresponding boundary conditions are discretized with high accuracy. Combined with the typical circuit of RSD, the circuit equations are written, the voltage-time and the current-time waveform are gotten by means of Runge-Kutta algorithm and the non-equilibrium carrier distribution. By comparing of RSD discharge experiment and model computation, the difference between the theoretical results and the experimental results are analyzed .The practical value of the model and algorithm is shown through application circuits. As a result the physical model and the numerical algorithm are proved valid, which lead a predictive role for RSD device design and circuit simulation.