High power thyristors triggering providing a subnanosecond closing time

A possibility of fast subnanosecond triggering of commercial low-frequency thyristors has been investigated. In experiments low dI/dt (100-400 A/μs) tablet thyristors having a silicon wafer of 32 to 40 mm in diameter and 2 kV DC operating voltage were used. For the thyristor triggering a fast subnanosecond pulse was applied across its main electrodes. During the switching process the voltage across 2-kV DC thyristor increased from 2 to 5-8 kV in about 0.8-1 ns, and then dropped in about 200 ps. Under such conditions the thyristor closing process occurred due to initiation and propagation of fast ionization front across the semiconductor structure. A stack of 6 thyristors connected in series operated at 13-kV charging voltage and switched 2-μF capacitor bank into resistive load of 0.25 Ω. At total circuit inductance of ~100 nH the following discharge parameters were obtained: a peak current was 27.6 kA, dI/dt was 113 kA/μs, FWHM was ~1 μs, and a peak power in the load was 190 MW.