Electronic thermostat with switched power converter

• US 4,632,303 A
• Filed: 10/25/1985
• Issued: 12/30/1986
• Est. Priority Date: 10/25/1985
• Status: Expired due to Fees

• Current Assignee: John N. Rodittis
• Original Assignee: John N. Rodittis
• Inventors: Rodittis, John N.
• Primary Examiner(s): Wayner, William E.
• Application Number:
  US06/791,299
• Time in Patent Office: 431 Days
• Field of Search: 165/12, 165/26, 236/46 R, 236/47, 236/10, 236/78 R
• US Class Current: 236/10
• CPC Class Codes: G05D 23/1909 whose output amplitude can only take two discrete values
• CPC Class Codes: G05D 23/24 the sensing element having a resistance varying with temperature, e.g. a thermistor

Abstract

An electronic thermostat utilizing a switched power supply which operates either from a voltage appearing across an open circuit at a heater or air conditioner activation circuit (de-energized state) or from a current flowing in the activation circuit upon short circuiting (energized state) of the activation circuit. The power supply provides an uninterrupted source of power to the electronic thermostat which controls the source of input power to the power supply in addition to the state of the activation circuit. The electronic circuit implements a piecewise linear, with hysteresis loop discontinuity, control function.

Claims

1. An electronic thermostat for controlling the energization of a heater activation circuit comprising:

bistate sensor means responsive to the environmental temperature for generating a corresponding environmental temperature signal, and for generating a predetermined reference signal in response to an operator'"'"'s input and for, while in a first state changing to a second state when said environmental temperature signal has a predetermined relationship with said reference signal, and for, while in said second state changing to said first state when said environmental temperature signal has said predetermined relationship with said reference signal, said sensor means providing a control signal when in said second state;

power supply means for receiving and controlling the flow of alternating current in a heater activation circuit and for providing uninterrupted power at a predetermined voltage level to said sensor means, said power supply means including;

a. first control means for receiving said alternating current, for controlling said alternating current at a first predetermined level as a first control current and for converting said first control current into a first unidirectional current provided at a first output to said sensor means, said first control means comprising a full wave rectifier having a pair of rectifier inputs and a pair of rectifier outputs, said rectifier inputs connecting said rectifier in series with a heater activation circuit and said rectifier outputs connected to said sensor means, and a current limiting resistor connected in series between one of said rectifier inputs and a heater activation circuit;

b. second control means for controlling said alternating current at a second predetermined level as a second control current and for converting a portion of said second control current into a second unidirectional current provided at a second output coupled to said sensor means, said second control current being greater than said first control current;

c. switch means coupled to said first and second control means and responsive to said control signal for respectively coupling said first and second control currents to said first and second control means respectively during said first and second states; and

wherein a heater activation circuit is de-energized during said first state and energized during said second state.

2. The thermostat of claim 1 wherein said second control means comprises:

a transformer having primary and secondary windings, said primary winding being coupled in series with a heater activation circuit by said switch means so as to receive said alternating current;

voltage limiter means coupled across said primary winding for limiting the voltage appearing across said primary winding and the corresponding voltage developed across said secondary winding; and

rectifier means coupled across said secondary winding for providing said second unidirectional current.

3. The thermostat of claim 2 wherein said bistate sensor means generates first and second linear environmental temperature signals when respectively in said first and second states, said first and second temperatures signals having substantially identical linear responses to variations in temperature while offset by a predetermined constant.

4. An electronic thermostat for controlling the energization of a heater activation circuit comprising:

bistate sensor means responsive to the environmental temperature for generating a corresponding environmental temperature signal, and for generating a predetermined reference signal in response to an operator'"'"'s input and for, while in a first state changing to a second state when said environmental temperature signal has a predetermined relationship with said reference signal, and for, while in said second state changing to said first state when said environmental temperature signal has said predetermined relationship with said reference signal, said sensor means providing a control signal when in said second state;

power supply means for receiving and controlling the flow of alternating current in a heater activation circuit and for providing uninterrupted power at a predetermined voltage level to said sensor means, said power supply means including;

a. first control means for receiving said alternating current, for controlling said alternating current at a first predetermined level as a first control current and for converting said first control current into a first unidirectional current provided at a first output to said sensor means, said first control means comprising a full wave rectifier having a pair of rectifier inputs and a pair of rectifier outputs, said rectifier inputs connecting said rectifier in series with a heater activation circuit and said rectifier outputs connected to said sensor means, and a current limiting resistor connected in series between one of said rectifier inputs and a heater activation circuit;

b. second control means for controlling said alternating current at a second predetermined level as a second control current and for converting a portion of said second control current into a second unidirectional current provided at a second output coupled to said sensor means, said second control current being greater than said first control current;

c. switch means coupled to said first and second control means and responsive to said control signal for respectively coupling said first and second control currents to said first and second control means respectively during said first and second states;

filter means coupled to said first and second outputs for filtering the voltage and current waveforms of said first and second unidirectional currents wherein said filter means stores sufficient energy so as to support uninterrupted operation of said sensor means during the transition between said first and second control means; and

regulating means coupled to said filter means and said bistate sensor means for regulating the voltage associated with said first and second unidirectional currents to a predetermined level, and

wherein a heater activation circuit is de-energized during said first state and energized during said second state.

5. The thermostat of claim 4 wherein said second control means comprises:

a transformer having primary and secondary windings, said primary winding being coupled in series with a heater activation circuit by said switch means so as to receive said alternating current;

voltage limiter means coupled across said primary winding for limiting the voltage appearing across said primary winding and the corresponding voltage developed across said secondary winding; and

rectifier means coupled across said secondary winding for providing said second unidirectional current.

6. The thermostat of claim 5 wherein said filter means comprises a capacitor coupled to said first and second outputs and said regulating means comprises a zener diode coupled to said capacitor and said sensor means.

7. The thermostat of claim 6 further comprising a resistor coupled between said capacitor and said zener diode.

8. The thermostat of claim 5 wherein said bistate sensor means generates first and second linear environmental temperature signals when respectively in said first and second states, said first and second temperatures signals having substantially identical linear responses to variations in temperature while offset by a predetermined constant.

9. An electronic thermostat for controlling the energization of a heater activation circuit comprising:

bistate sensor means responsive to the environmental temperature for generating a corresponding environmental temperature signal, and for generating a predetermined reference signal in response to an operator'"'"'s input and for, while in a first state changing to a second state when said environmental temperature signal has a predetermined relationship with said reference signal, and for, while in said second state changing to said first state when said environmental temperature signal has said predetermined relationship with said reference signal, said sensor means providing a control signal when in said second state;

power supply means for receiving and controlling the flow of alternating current in a heater activation circuit and for providing uninterrupted power at a predetermined voltage level to said sensor means, said power supply means including;

a. first control means for controlling said alternating current at a first predetermined level as a first control current and for converting said first control current into a first unidirectional current provided at a first output to said sensor means;

b. second control means for controlling said alternating current at a second predetermined level as a second control current and for converting a portion of said second control current into a second unidirectional current provided at a second output coupled to said sensor means, said second control current being greater than said first control current;

c. switch means coupled to said first and second control means and responsive to said control signal for respectively coupling said first and second control currents to said first and second control means respectively during said first and second states;

filter means coupled to said first and second outputs for filtering the voltage and current waveforms of said first and second unidirectional currents wherein said filter means stores sufficient energy so as to support uninterrupted operation of said sensor means during the transition between said first and second control means, said filter means comprising a capacitor coupled to said first and second outputs;

regulating means coupled to said filter means and said bistate sensor means for regulating the voltage associated with said first and second unidirectional currents to a predetermined level, said regulating means comprising a zener diode coupled to said filter means capacitor and said sensor means; and

wherein a heater activation circuit is de-energized during said first state and energized during said second state.

10. The thermostat of claim 9 further comprising a resistor coupled between said capacitor and said zener diode.

11. An electronic thermostat for controlling the energization of a heater activation circuit comprising:

bistate sensor means responsive to the environmental temperature for generating a corresponding environmental temperature signal, and for generating a predetermined reference signal in response to an operator'"'"'s input and for, while in a first state changing to a second state when said environmental temperature signal has a predetermined relationship with said reference signal, and for, while in said second state changing to said first state when said environmental temperature signal has said predetermined relationship with said reference signal, said sensor means providing a control signal when in said second state;

power supply means for receiving and controlling the flow of alternating current in a heater activation circuit and for providing uninterrupted power at a predetermined voltage level to said sensor means, said power supply means including;

a. first control means for receiving said alternating current, for controlling said alternating current at a first predetermined level as a first control current and for converting said first control current into a first unidirectional current provided at a first output to said sensor means;

b. second control means for receiving said alternating current, for controlling said alternating current at a second predetermined level as a second control current and for converting a portion of said second control current into a second unidirectional current provided at a second output coupled to said sensor means, said second control current being greater than said first control current, said second control means comprising a transformer having primary and secondary windings, voltage limiter means coupled across said primary winding for limiting the voltage appearing across said primary winding and the corresponding voltage developed across said secondary winding and rectifier means coupled across said secondary winding for providing said second unidirectional current;

c. switch means coupled to said first and second control means and responsive to said control signal for respectively coupling said first and second control currents to said first and second control means respectively during said first and second states, said second control means transformer primary winding coupled in series with a heater activation circuit by said switch means during said second state; and

wherein a heater activation circuit is de-energized during said first state and energized during said second state.