Avalanche Thyristor

Avalanche Thyristor Using a special technology it is possible to create in thyristors, as well as in diodes, a structure in which avalanche breakdown happens when reverse voltage is applied. Such thyristors remain serviceable when great reverse voltage values are applied. Unlike regular thyristors they have avalanche areas on a forward-bias (AB) region and a reverse-bias (CD) region of a volt-ampere characteristic. Avalanche areas allow us to switch on the thyristor not only with the help of a control current but also by supplying forward voltage, which is greater than breakover voltage, on the anode. Besides, avalanche thyristors confine narrow voltage pulses in the same way as rectifier avalanche diodes do. In this case dissipated energy at a p-n junction should not exceed 1 joule. Highly purified and homogenous silicon along with advanced technology of making p-n junctions is used in these devices. This allows to increase permissible temperature of a silicon element up to 140 °С. Thus it is possible to increase the thyristor's rated current without increasing p-n junction area. By using avalanche thyristors in converter installations we avoid using additional safety devices.