The first dynamic phase at turn-on of a thyristor

The first dynamic phase is characterized by a rapid voltage decay during which electron transport by field effects inside the space-charge layer (SCL) in the base region of an n-base thyristor are supposed to dominate. If the external circuit does not impose a voltage-current dependence, a simple one-dimensional model can be formulated which is based on mobile charges affecting the SCL. Comparison with electrical data about turn-on yields approximate information concerning the effective area of the initially conducting channel which is in good agreement with infrared observation. In conjunction with this model, the electrical measurements lead to a simple method to detect failure of a thyristor to turn on homogeneously.