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Digital thermostat with protection against power interruption

  • US 4,431,134 A
  • Filed: 11/08/1982
  • Issued: 02/14/1984
  • Est. Priority Date: 11/08/1982
  • Status: Expired due to Fees
First Claim
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1. A temperature control apparatus comprising:

  • terminal means for connection to a source of AC power;

    rectifier means connected to the terminal means for rectifying the AC power to produce a DC charging current;

    a voltage supply terminal;

    voltage supply capacitor means for providing a DC supply voltage at the voltage supply terminal, the voltage supply capacitor means being charged by the DC charging current;

    read/write storage means connected to the voltage supply terminal and powered solely by the DC supply voltage for storing time and temperature data, the read/write storage means being capable of retaining the time and temperature data so long as the DC supply voltage at the voltage supply terminal exceeds a first predetermined value;

    temperature sensing means for sensing temperature;

    control circuit means powered solely by the DC supply voltage for providiing temperature control signals as a function of the sensed temperature and the stored time and temperature data;

    switching means connected between the voltage supply terminal and the control circuit means for supplying the DC supply voltage to the control circuit means to power the control circuit means when in a first state and for preventing the control circuit means from receiving the DC supply voltage when in a second state, the switching means having the first and second states as a function of a power control signal; and

    voltage sensing means for sensing the DC supply voltage of the voltage supply terminal and providing the power control signal as a function of the sensed DC supply voltage, the power control signal causing the switching means to have the second state when the DC supply voltage is less than a second, higher predetermined value.

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