| 摘要 |
PURPOSE:To obtain the titled device with built-in over voltage protecting ufnction which can trigger the voltage at a high di/dt dielectric strength against over voltage impression by a method wherein the minimum gate trigger current of a pilot trigger apart is set at 1/2 or less of the allowable breakdown current of a voltage breakdown region. CONSTITUTION:A P type base layer 20 having a curved part 19 is arranged in the inner periphery of the pilot thyristor PT. When an over current is impressed between the anode and cathode electrodes, an electric field concentrates on the curved part 19. At the time, the pilot thyristor PT and a main thyristor MT successively turn on by means of the breakdown current generated in the neighborhood of the curved part 19. In this case, the munimum trigger current IGT of said device PT is set at 1/2 or less of the maximum non destruction value IR (max) of a forward directional breakdown current by sufficiently increasing the gate sensitivity of said device PT first turning on. Thereby, the di/dt dielecric strength in voltage trigger can be largely improved. |
