Modeling and Analysis of Thyristor and Diode Reverse Recovery in Railgun Pulsed Power Circuits

As pulsed-power systems used to drive EM launchers evolve from laboratory to operational environments, high- power solid-state devices are emerging as the leading switch technology for these systems. These devices, specifically high-power thyristors and diodes, offer the advantages of improved energy efficiency, reduced volume, and reduced auxiliaries over spark-gaps and ignitrons. Proper application of these devices requires understanding of their behavior both during forward conduction and during reverse recovery. The semiconductor device models available in most circuit simulation software packages do not accurately characterize large power thyristors and diodes for thermal management and snubber design. A semiconductor- device model is presented that captures device reverse- recovery and on-state conduction behavior utilizing a time-varying resistance that depends on the solid-state device properties and operating circuit parameters. The information needed to construct this model can be extracted from the device datasheet or obtained from the manufacturer. This circuit model is used to analyze pulsed-power circuits typically used to drive railguns. Of key interest in these simulations are the voltage transients and energy losses in the solid-state devices during the reverse- recovery process. This behavior is analyzed for different circuit element values and device parameters such as peak reverse current, and reverse recovery charge.