V/sub BO/-protection of power thyristors using an external trigger thyristor

Design options for the V/sub BO/ protection of power thyristors are reviewed. A technique that uses a separate trigger device which provides gate current to the main or power thyristor, both when triggered by light and by avalanche current due to a V/sub BO/-voltage, is described. The development of the gating strategy, evaluation-results, which include characteristics and maximum ratings of the device, and processing of the V/sub BO/ devices are discussed. Conclusions are presented as guides for the next level of design and evaluation of the V/sub BO/-trigger devices.< >