Pacific Scientific Company

Michael John Robinson

Photo-responsive lamp switching apparatus

A surge protection circuit provides multiple stages of protection for an electronic circuit having semiconductor components from damage due to passage of excessive amount of current during a line borne voltage surge. In particular, this circuit can protect any relay load switching device that requires an electronic control circuit. The circuit of the invention achieves performance superior to that of conventional surge protectors, such as those employing metal oxide varistors, by employing an expulsion arrester as the last stage of a multi-stage protection technique against voltage surges on power lines. Low impedance electrical paths parallel to the expulsion arrester and to the electronic circuitry provide protection before the arrester switches. One embodiment employs a zener diode and a silicon controlled rectifier to provide two such parallel electrical paths.

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Scituate, MA, United States of America

Michael John Robinson