United States Patent 4,119,845
October 10, 1978

Thermally-Sensitive Photo-Controlled Semiconductor Switching Systems
Stanley V. Jaskolski
Robert W. Lade
Herman P. Schutten

Filed March 21, 1977
Image of US PATENT 4,119,845

Abstract of the Disclosure

A switching system having a photo-sensitive power switching or control element such as a photo SCR, photo triac, photo transistor or the like that is normally turned on or off by coupled light from a controlled light source such as an LED (light emitting diode), neon lamp, incandescent lamp or the like. A thermally-sensitive light-gating element such as an LC (liquid crustal) element controls the light impinging on the phono-sensitive element. The gating element may sense the temperature of the photo-sensitive power switching or control element directly if the two are integral in which case the combined device would be self-protecting. On the other hand, the gating element may be separate and may be arranged to sense the temperature of an external source that may or may not be controlled by the photo-sensitive power switching or control element in which case the latter would be controlled by the temperature. Different types of temperature-sensitive gating elements or combinations thereof may be used in the systems.
Figure descriptions: cover graphic

  • a system where a thermally-controlled photo-thyristor is connected in series with the gate of an electrically-gated power switching thyristor.

 Citations [54]:
2,666,583 01/1954 Whitney 2,792,484 05/1957 Gurewitsch et al. 3,654,474 04/1972 Jacobs 3,719,789 03/1973 Harnden
National Museum of American History
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