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Automatic temperature control device for an electric appliance such as an electric blanket

  • US 4,485,296 A
  • Filed: 05/20/1981
  • Issued: 11/27/1984
  • Est. Priority Date: 05/30/1980
  • Status: Expired due to Term
First Claim
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1. An automatic temperature control device for an electric appliance comprising:

  • a heater element connected to an alternating current source to be fed therefrom;

    a sensor made of a thermosensitive material having an impedance, which changes as the temperature varies, for detecting the temperature of said heater element;

    a temperature responsive circuit including a grounded-base transistor with its base-emitter circuit connected in series with said sensor, the series connection being connected across said alternating current source, and a diode connected across the base-emitter junction of said transistor so that the P-N junction of said diode and the base-emitter junction of said transistor are coupled in the direction opposite to each other, whereby a collector current of said grounded-base transistor is used as a sensed signal;

    an electric potential setting circuit for producing an electric potential for setting a desired temperature;

    a comparison circuit for comparing an output signal of said temperature responsive circuit with an output signal of said electric potential setting circuit; and

    switching means driven by an output of said comparison circuit and connected in series with said heater element for regulating the supply of electric power to said heater element.

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