Optically toggled bidirectional switch
First Claim
1. A normally-on switch comprising a pair of terminals,semiconductive circuit means connected between said terminals including a pair of serially connected normally-on field-effect transistors forming a current path between said terminals, the point between said two transistors forming a control node for providing controllable conduction between said terminals and including photovoltaic means for switching the state of conduction, andprotective circuit means connected between said terminals for protecting the semiconductive circuit means against current or voltage surges including at least one thyristor connected essentially in parallel between said terminals, the gate of each being effectively connected to said control node.
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Accused Products
Abstract
An optically toggled bidirectional normally-on switch is provided with protection against bilateral voltage and bidirectional current surges by the inclusion of a pair of oppositely poled thyristors. One version uses a large junction-type field-effect transistor in its main path and a pair of smaller junction-type transistors in the subsidiary path. A photodiode array controls the gate voltage on each of the transistors and turns them off when illuminated. A control node in the subsidiary path is connected to the gates of the SCRs so that excess current in this path turns on the appropriately-poled thyristor to provide an additional shunt path for the current.
32 Citations
21 Claims
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1. A normally-on switch comprising a pair of terminals,
semiconductive circuit means connected between said terminals including a pair of serially connected normally-on field-effect transistors forming a current path between said terminals, the point between said two transistors forming a control node for providing controllable conduction between said terminals and including photovoltaic means for switching the state of conduction, and protective circuit means connected between said terminals for protecting the semiconductive circuit means against current or voltage surges including at least one thyristor connected essentially in parallel between said terminals, the gate of each being effectively connected to said control node.
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19. A normally-on switch comprising
a pair of terminals, semiconductive circuit means including a pair of field-effect transistors connected serially between said terminals for providing controllable conduction between said terminals and including photovoltaic means for switching the state of conduction, the voltage at the node between said transistors providing a measure of the conduction, branch circuit means between said node and each terminal including blocking diode means, and protection circuit means across said terminals including at least one thyristor having its gate effectively connected to said node.
Specification