A New Approach To Series Semiconductor Switch Applications

Previous reports showed that series semiconductor stacks could outperform thyratrons in ccrtain laser applications'. The arduous requirements of ensuring voltage sharing in series-connected high-voltage semiconductor configurations, does however limit the implementation of this technique. A new approach to solving this problem is the series stacking of multiple LC inversion stages, operating at voltages that can be withheld by single scmiconductor elcmcnts. Each stage consists of a series pair of capacitors, a thyristor with optically isolated gate drive circuitry and isolated charging transformer windings with associated diode networks. The current and voltage ratings requircd of the thyristors and diodes in each of the stages can be adapted to fall well within the capabilities of commercial devices. The peak current requirements of the thyristors, laid down by the pulse width and pulse energy, can be accommodated, as the switching of large peak currents at short pulse widths by mcans of thyristors has bccti demonstrated in lhe litcraturc2. A single stage syslcm, charging 1 J at 2 kV, with a pulse width of 1.5 pS and a peak current of 2.5 kA has been constructed and tcstcd. An overall energy eficiency of 80% has been achicvcd. Experimental results are presented.