High current and current rise rate thyristor based switches

Operation of the thyristor-based switches triggered in impact-ionization wave mode has been investigated. The thyristor switch contained two series connected tablet thyristors having a silicon wafer of 56 mm in diameter. At applying across the switch a triggering pulse with a voltage rise rate dU/dt of over 1 kV/ns the thyristors transition time to conductive state was less than 1 ns. It is shown that the maximum amplitude of no-failure current is increased with increasing dU/dt at the triggering stage. A possible mechanism of the dU/dt value effect on the thyristors breakdown current is discussed. In safety operation regime at dU/dt = 6 kV/ns (3 kV/ns per a single thyristor) the switch discharged 1-mF capacitor, which was charged to a voltage of 5 kV, to a resistive load of 18 mΩ. The following results were obtained: a peak current was 200 kA, an initial dI/dt was 58 kA/ps, a FWHM was 25 ps, and switching efficiency was 0.97. It is shown that a temperature of the silicon wafer is one of the main factors that affects on the thyristor switching process. Results of the thyristors testing in pulse repetition mode are given also.