GTO thyristor and bipolar transistor cascode switches

The switching performance of both the bipolar transistor and gate turn-off thyristor is improved when used in a cascode switch configuration. `Snubberless´ turn-off occurs without second breakdown and the technique results in shorter saturation delay times, faster current fall and higher operational sustaining voltages than obtained with conventional switching techniques. Improved switching performance is traded for increased drive circuit complexity and an increased on-state power loss associated with two series connected power semiconductor switches. The circuit techniques features and performance of two 720 V DC, 320 A cascode switches are presented. The bipolar transistor cascode switch is tested up to 100 kHz, whereas tail current power loss limits the GTO thyristor cascode switch to 16 kHz