Adaptive power stealing thermostat

• US 9,261,287 B2
• Filed: 10/06/2011
• Issued: 02/16/2016
• Est. Priority Date: 09/14/2010
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Google Inc. (Alphabet Inc.)
• Inventors: Warren, Daniel Adam, Smith, Ian C., Satterthwaite, Edwin H. Jr., Palmer, Joseph E.
• Primary Examiner(s): Barnie, Rexford
• Assistant Examiner(s): Ortiz, Elim
• Application Number:
  US13/267,871
• Publication Number:
  US 20120199660A1
• Time in Patent Office: 1,594 Days
• Field of Search: 700/278, 700/277, 700/275, 700/9, 700/1, 165/201, 165/200, 236/1.C, 236/1.R, 263/17
• US Class Current: 1/1
• CPC Class Codes: B01D 46/0086 Filter condition indicators
• CPC Class Codes: F24F 11/30 for purposes related to the operation of the system, e.g. for safety or monitoring
• CPC Class Codes: F24F 11/32 Responding to malfunctions or emergencies
• CPC Class Codes: F24F 11/39 Monitoring filter performance
• CPC Class Codes: F24F 11/46 Improving electric energy efficiency or saving
• CPC Class Codes: F24F 11/47 Responding to energy costs
• CPC Class Codes: F24F 11/52 Indication arrangements, e.g. displays
• CPC Class Codes: F24F 11/56 Remote control
• CPC Class Codes: F24F 11/58 using Internet communication
• CPC Class Codes: F24F 11/61 using timers
• CPC Class Codes: F24F 11/62 characterised by the type of control or by internal processing, e.g. using fuzzy logic, adaptive control or estimation of values
• CPC Class Codes: F24F 11/63 Electronic processing
• CPC Class Codes: F24F 11/64 using pre-stored data
• CPC Class Codes: F24F 11/89 Arrangement or mounting of control or safety devices
• CPC Class Codes: F24F 2110/00 Control inputs relating to air properties
• CPC Class Codes: F24F 2110/10 Temperature
• CPC Class Codes: F24F 2120/10 Occupancy
• CPC Class Codes: F24F 2120/20 Feedback from users
• CPC Class Codes: F24F 2130/40 Noise
• CPC Class Codes: F24F 2140/00 Control inputs relating to system states
• CPC Class Codes: F24F 2140/60 : Energy consumption
• CPC Class Codes: G05B 13/0265 : the criterion being a learning criterion
• CPC Class Codes: G05B 15/02 : electric
• CPC Class Codes: G05D 23/19 : characterised by the use of electric means G05D23/1393 takes precedence
• CPC Class Codes: G05D 23/1902 : characterised by the use of a variable reference value
• CPC Class Codes: G05D 23/1917 : using digital means
• CPC Class Codes: H01R 9/2416 : Means for guiding or retaining wires or cables connected to terminal blocks
• CPC Class Codes: H04W 4/70 : Services for machine-to-machine communication [M2M] or machine type communication [MTC]
• CPC Class Codes: Y02B 10/20 : Solar thermal
• CPC Class Codes: Y02B 10/70 : Hybrid systems, e.g. uninterruptible or back-up power supplies integrating renewable energies
• CPC Class Codes: Y02D 30/70 : in wireless communication networks
• CPC Class Codes: Y10T 29/49826 : Assembling or joining

Abstract

An electronic thermostat and associated methods are disclosed for power stealing from an HVAC triggering circuit. The methods include making voltage measurements while controlling the amount of current drawn by the power stealing circuitry so as to determine a relationship that can be used to select how much current to draw during power stealing. Through the use of the described methods, the likelihood of inadvertent switching of the HVAC function (on or off) can be significantly reduced.

Claims

1. A method for harvesting power from an HVAC triggering circuit that includes a call switch to turn on and turn off an HVAC function, the harvested power being used by a thermostat connected to the HVAC triggering circuit, the harvested power being harvested by a power harvesting circuit including an energy-storage element and a current controller, the method comprising:

operating the current controller of the power harvesting circuit at a predetermined first setting associated with a first power level of the power harvesting circuit and at a predetermined second setting associated with a second, higher power level of the power harvesting circuit;

making at least one first measurement corresponding to an amount of energy stored by the energy-storage element while said current controller is operated at said first setting;

making at least one second measurement corresponding to an amount of energy stored by the energy-storage element while said current controller is operated at said second setting;

determining that a difference between said at least one first measurement and said at least one second measurement is less than a first predetermined threshold; and

responsive to said determining that said difference between said at least one first measurement and said at least one second measurement is less than said first predetermined threshold, operating the current controller of the power harvesting circuit at a predetermined third setting associated with a third power level of the power harvesting circuit that is higher than said second level;

whereby an amount of power harvested from the HVAC triggering circuit by said thermostat is increased while at the same time a reduced likelihood of an inadvertent on or off switching of said HVAC function is maintained.

2. The method of claim 1, further comprising:

making at least one third measurement corresponding to an amount of energy stored by the energy-storage element while said current controller is operated at said third setting;

determining that a difference between said at least one second measurement and said at least one third measurement is greater than a second predetermined threshold; and

responsive to said determining that said difference between said at least one second measurement and said at least one third measurement is greater than said second predetermined threshold, operating the current controller of the power harvesting circuit at said second setting associated with said second power level of the power harvesting circuit.

3. The method of claim 1, further comprising:

making at least one third measurement corresponding to the amount of energy stored by the energy-storage element while said current controller is operated at said third setting;

determining that a difference between said at least one second measurement and said at least one third measurement is less than a second predetermined threshold; and

responsive to said determining that said difference between said at least one second measurement and said at least one third measurement is less than said second predetermined threshold, operating the current controller of the power harvesting circuit at a predetermined fourth setting associated with a fourth power level of the power harvesting circuit that is higher than said third level.

4. The method of claim 1, wherein said energy storage element comprises a capacitor in series between said current controller and a voltage rectifier circuit.

5. The method of claim 1, wherein said current controller is digitally controlled by a processor.

6. The method of claim 1, wherein said first predetermined threshold is programmed into said current controller.

7. The method of claim 1, wherein said first predetermined threshold is determined in advance by empirical testing of various HVAC systems.

8. The method of claim 1, wherein said at least one first measurement comprises a digital voltage measurement of said energy-storage element.

9. A thermostat comprising:

an HVAC triggering circuit comprising a call switch to turn on and turn off an HVAC function;

a power harvesting circuit comprising;

a current controller configured to operate at;

a predetermined first setting associated with a first power level of the power harvesting circuit; and

a predetermined second setting associated with a second, higher power level of the power harvesting circuit; and

an energy-storage element;

a measurement circuit configured to;

make at least one first measurement corresponding to an amount of energy stored by the energy-storage element while said current controller is operated at said first setting; and

make at least one second measurement corresponding to an amount of energy stored by the energy-storage element while said current controller is operated at said second setting; and

a processor programmed to;

determine that a difference between said at least one first measurement and said at least one second measurement is less than a first predetermined threshold; and

responsive to said determining that said difference between said at least one first measurement and said at least one second measurement is less than said first predetermined threshold, cause the current controller of the power harvesting circuit to operate at a predetermined third setting associated with a third power level of the power harvesting circuit that is higher than said second level;

whereby an amount of power harvested from the HVAC triggering circuit by said thermostat is increased while at the same time a reduced likelihood of an inadvertent on or off switching of said HVAC function is maintained.

10. The thermostat of claim 9, wherein:

the measurement circuit is further configured to make at least one third measurement corresponding to an amount of energy stored by the energy-storage element while said current controller is operated at said third setting; and

the processor is further programmed to;

determine that a difference between said at least one second measurement and said at least one third measurement is greater than a second predetermined threshold; and

responsive to said determining that said difference between said at least one second measurement and said at least one third measurement is greater than said second predetermined threshold, cause the current controller of the power harvesting circuit to operate at said second setting associated with said second power level of the power harvesting circuit.

11. The thermostat of claim 9, wherein:

the measurement circuit is further configured to make at least one third measurement corresponding to the amount of energy stored by the energy-storage element while said current controller is operated at said third setting; and

the processor is further programmed to;

determine that a difference between said at least one second measurement and said at least one third measurement is less than a second predetermined threshold; and

responsive to said determining that said difference between said at least one second measurement and said at least one third measurement is less than said second predetermined threshold, cause the current controller of the power harvesting circuit to operate at a predetermined fourth setting associated with a fourth power level of the power harvesting circuit that is higher than said third level.

12. The thermostat of claim 9, further comprising a voltage rectifier circuit, wherein:

said energy storage element comprises a capacitor in series between said current controller and a voltage rectifier circuit.

13. The thermostat of claim 9, wherein said first predetermined threshold is programmed into said current controller.

14. The thermostat of claim 9, wherein said first predetermined threshold is determined in advance by empirical testing of various HVAC systems.

15. The thermostat of claim 9, wherein said at least one first measurement comprises a digital voltage measurement of said energy-storage element.