Determining Power Stealing Capability of a Climate Control System Controller

• US 20150115045A1
• Filed: 10/30/2013
• Published: 04/30/2015
• Est. Priority Date: 10/25/2013
• Status: Active Grant

• Current Assignee: Copeland Comfort Control LP (Emerson Electric Company)
• Original Assignee: Emerson Electric Company
• Inventors: Tu, Lihui, Chu, Cuikun
• Granted Patent: US 9,404,667 B2
• Time in Patent Office: Days
• US Class Current: 236/1.C
• CPC Class Codes: F24F 11/30 for purposes related to the operation of the system, e.g. for safety or monitoring

Abstract

Disclosed are exemplary embodiments of systems and methods for determining a power stealing capability of a climate control system controller. In an exemplary embodiment, a controller for use in a climate control system generally includes a capacitor chargeable by current flowing through an off-mode load of the climate control system. A voltage detect circuit detects a voltage across the capacitor. The controller includes a timer for determining a charge time of the capacitor from a first specific voltage to a second specific voltage based on input from the voltage detect circuit. The controller determines a resistance of the off-mode load based on the charge time and, based on the determined resistance, determines a level of current for power stealing through the off-mode load.

Claims

1. A controller for use in a climate control system, the controller comprising:

a capacitor chargeable by current flowing through an off-mode load of the climate control system;

a voltage detect circuit for detecting a voltage across the capacitor; and

a timer for determining a charge time of the capacitor from a first specific voltage to a second specific voltage based on input from the voltage detect circuit;

the controller being configured to determine a resistance of the off-mode load based on the charge time and based on the determined resistance, to determine a level of current for power stealing through the off-mode load.

2. The controller of claim 1, wherein the controller is further configured to control the life of a battery providing power to the controller, the controlling performed by adjusting a duty cycle of the controller based on the determined level of current for power stealing.

3. The controller of claim 1, further comprising a power stealing circuit.

4. The controller of claim 1, further comprising a current limiting circuit between the capacitor and the HVAC equipment.

5. The controller of claim 1, wherein the controller is a thermostat.

6. The controller of claim 1, wherein the controller uses the determined resistance and a lookup table to determine the level of current for power stealing.

7. The controller of claim 1, wherein the resistance of the off-mode load is determined in accordance with:

V_t=V₀+(V₁−

V₀)×

(1−

e<sup>−

t/RC</sup>)

where V_t represents a voltage across the capacitor at a time t, R represents a circuit resistance that includes the resistance of the off-mode load, C represents capacitance of the capacitor, and V₀ and V₁ represent the first and second specific voltages.

8. A controller for use in a climate control system, the controller comprising:

a power stealing circuit for stealing power from an off-mode load of the climate control system;

a capacitor chargeable by current flowing through the off-mode load;

a voltage detect circuit for detecting voltages across the capacitor, including first and second specific voltages; and

a timer configured to determine a charge time of the capacitor from the first specific voltage to the second specific voltage as detected by the voltage detect circuit;

the controller being configured to;

determine a resistance of the off-mode load based on the charge time;

determine a power stealing capability of the power stealing circuit based on the determined resistance; and

adjust a duty cycle of the controller based on the determined power stealing capability.

9. The controller of claim 8, further comprising a current limiting circuit between the capacitor and the HVAC equipment.

10. The controller of claim 8, wherein the controller is a thermostat.

11. The controller of claim 8, wherein the controller uses the determined resistance and a lookup table to determine the level of current for power stealing.

12. The controller of claim 8, wherein the resistance of the off-mode load is determined in accordance with:

V_t=V₀+(V₁−

V₀)×

(1−

e<sup>−

t/RC</sup>)

where V_t represents a voltage across the capacitor at a time t, R represents a circuit resistance that includes the resistance of the off-mode load, C represents capacitance of the capacitor, and V₀ and V₁ represent the first and second specific voltages.

13. A method of determining a power stealing capability of a controller of a climate control system, the method comprising:

determining a time duration for charging a capacitor of the controller from a first specific voltage to a second specific voltage, where the capacitor receives charge current through an off-mode load of the climate control system;

determining a resistance of the off-mode load based on the time duration; and

using the determined resistance to determine a level of current stealing by the controller through the off-mode load.

14. The method of claim 13, further comprising adjusting a duty cycle of the controller based on the determined current stealing level, the adjusting performed to control the life of a battery of the controller.

15. The method of claim 13, wherein the controller is a thermostat.

16. The method of claim 13, wherein the controller uses the determined resistance and a lookup table to determine the level of current for power stealing.

17. The method of claim 13, wherein the resistance of the off-mode load is determined in accordance with:

V_t=V₀+(V₁−

V₀)×

(1−

e<sup>−

t/RC</sup>)

where V_t represents a voltage across the capacitor at a time t, R represents a circuit resistance that includes the resistance of the off-mode load, C represents capacitance of the capacitor, and V₀ and V₁ represent the first and second specific voltages.