High power semiconductors for pulsed switching

The design of large high power thyristors will be described with respect to their application in closing switches e.g. for electromagnetic launchers. The basic limitation today is the plasma spreading of the ignited area within the thyristor chip. As closing switch, the turn-off characteristics are unimportant and a large charge carrier lifetime is advantageous to improve plasma spreading. Available devices with VDRM= 4400 - 6500 V and silicon diameters 80 - 100 mm are analyzed and the circuit requirements for their application are described. These devices can be used for switching load currents of more than 100 kA in less than 100 /spl mu/s. The possible requirement of series and/or parallel connection for higher powers is in many cases offset by the inherent ruggedness of thyristors compared to ignitrons or other gas tubes. Main advantages of thyristors for suchs applications can be summarized with longer lifetime, no degradation, high rep. frequencies and no warming up time. The performance of high power diodes to turn-on at high di/dt > 100 A//spl mu/s in free-wheeling applications is also considered.