Compound electrical circuit unit comprising a main power type thyristor and auxiliary control semiconductor elements structurally and electrically united to form a compact assembly

Claim 1

An encapsulated power thyrIstor assembly which comprises a main high power thyristor constituted from a silicon disc carried by an underlying support plate which is both electrically and heat conductive, a housing enclosing said power thyristor, said housing including end plates which are both electrically and heat conductive, said plates being spaced from each other by a wall of electrically insulating material which surrounds said power thyristor, one of said end plates being in electrical and heat transfer contact with said underlying support plate for the silicon disc and the other end plate being in contact with said silicon disc through an intermediate electrical and heat conductive member having a smaller diameter than said silicon disc, at least one auxiliary low power thyristor connected in circuit with and controlling the ignition of said power thyristor and which is secured in place on the upper surface of said silicon disc outwardly from said intermediate conductive member and thus outwardly from the main path of the heat flow through said power thyristor, a light sensitive device mounted within said housing and which is connected to said auxiliary thyristor for controlling the ignition thereof which in turn controls the ignition of said power thyristor, and means providing a window into said housing for admitting light to said light sensitive device.