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A CONTROL CIRCUIT UTILIZING TEMPERATURE ACTUATED SWITCHES AND SILICON CONTROLLED RECTIFIERS FOR REVERSING THE POLARITY OF DIRECT CURRENT APPLIED TO A LOAD

  • US 3,858,106 A
  • Filed: 10/25/1973
  • Issued: 12/31/1974
  • Est. Priority Date: 10/25/1973
  • Status: Expired due to Term
First Claim
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1. A control circuit for maintaining the temperature of a substance, such as medicine, between specific limits by reversing the polarity of direct electrical current applied to a thermoelectric element, said circuit including:

  • positive and negative input terminals, a bridge connecting said input terminals, a thermoelectric element connected across the bridge output terminals, a temperature actuated switch located in each leg of the bridge connected to the positive input terminal, said temperature actuated switches being normally open and one of said switches operating at a higher temperature range than the other of said switches with said temperature actuated switch operating in the higher range closing at an upper temperature limit and opening at a slightly lower temperature limit and said temperature actuated switch operating in the lower temperature range closing at a lower temperature limit and opening at a slightly higher temperature limit, a semiconductor device located in each leg of the bridge connected to the negative input terminal, and means to gate the semiconductor device in the opposite leg of the bridge when either temperature actuated switch is closed.

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