Power stealing for a wireless-enabled thermostat
View Patent ↗Disclosed are exemplary embodiments of apparatus, systems and methods for power stealing for a wireless-enabled thermostat. In an exemplary embodiment, a wireless-enabled thermostat generally includes a control having a wireless network interface that intermittently connects the thermostat in a wireless network in accordance with a duty cycle, the duty cycle having a connect time in which the thermostat is connected in the wireless network and a sleep time in which the thermostat is not connected in the wireless network. A power stealing circuit of the thermostat steals power through an “on-mode” load of a climate control system to charge a capacitor or other energy storage device to provide the power for the wireless network interface. The control adjusts at least the sleep time in accordance with a time for charging the capacitor or other energy storage device to a threshold voltage.
1. A wireless-enabled thermostat for use in a climate control system, the thermostat comprising:
a control having a wireless network interface configured to intermittently connect the thermostat in a wireless network in accordance with a duty cycle, the duty cycle having a connect time in which the thermostat is connected in the wireless network and a sleep time in which the thermostat is not connected in the wireless network; and
a power stealing circuit configured to steal power through an “on-mode” load of the climate control system and to charge a capacitor to provide the power for the wireless network interface, the power stealing circuit having a current transformer in series with a relay operable to switch the load between “on” and “off” modes, the current transformer configured to obtain current from the “on-mode” load for charging the capacitor;
the control configured to adjust at least the sleep time in accordance with a time for charging the capacitor to a threshold voltage.
2. The thermostat of claim 1 , wherein the time for charging the capacitor varies with current through the “on-mode” load.
3. The thermostat of claim 1 , wherein the control is configured to monitor the charge of the capacitor and control the wireless network interface based on the monitoring.
4. The thermostat of claim 1 , wherein the power stealing circuit comprises:
a clipper circuit connected across the current transformer;
a rectifier connected between the current transformer and the capacitor and configured to charge the capacitor from the current transformer; and
a regulator circuit for powering the wireless network interface, the regulator circuit powered by the capacitor.
5. The thermostat of claim 4 , wherein the regulator circuit comprises a buck circuit, and/or the control is configured to monitor the charge of the capacitor and control the regulator circuit based on the monitoring.
6. The thermostat of claim 1 , wherein the power stealing circuit is configured to steal power without using a climate control system common “C” wire.
7. The thermostat of claim 1 , wherein the control is configured to provide intermittent connection of the thermostat with the wireless network substantially only when power from the power stealing circuit is available.
8. The thermostat of claim 1 , wherein the control is configured to disconnect the thermostat from the wireless network when power from the power stealing circuit has become unavailable, and reconnect the thermostat in the wireless network when power from the power stealing circuit has been restored.
9. The thermostat of claim 1 , wherein the current transformer comprises a step-up current transformer.
10. A wireless-enabled thermostat for use in a climate control system, the thermostat comprising:
a control having a wireless network interface configured to intermittently connect the thermostat in a wireless network in accordance with a duty cycle, the duty cycle having a connect time in which the thermostat is connected in the wireless network and a sleep time in which the thermostat is not connected in the wireless network; and
a power stealing circuit configured to steal power through at least an “on-mode” load of the climate control system and to charge an energy storage device over a time period varying with current through the “on-mode” load, to provide the power for the wireless network interface, the power stealing circuit having a current transformer in series with a relay operable to switch the load between “on” and “off” modes, the current transformer configured to obtain current from the “on-mode” load for charging the energy storage device;
the control configured to adjust at least the sleep time in accordance with the varying time period.
11. The thermostat of claim 10 , wherein the control is configured to monitor the charge of the energy storage device and enable or disable the wireless network interface based on the monitoring.
12. The thermostat of claim 10 , wherein the power stealing circuit comprises:
a clipper circuit connected across the current transformer;
a rectifier connected between the current transformer and the energy storage device and configured to charge the energy storage device from the current transformer; and
a regulator circuit for powering the wireless network interface, the regulator circuit powered by the energy storage device.
13. The thermostat of claim 12 , wherein the regulator circuit comprises a buck circuit and/or the current transformer comprises a step-up current transformer.
14. The thermostat of claim 12 , wherein the regulator circuit is configured to operate in one or more of the following modes: open loop, and under control of the control.
15. The thermostat of claim 10 , wherein the control is configured to provide intermittent connection of the thermostat with the wireless network substantially only when power from the power stealing circuit is available.
16. The thermostat of claim 10 , wherein the control is configured to disconnect the thermostat from the wireless network when power from the power stealing circuit has become unavailable, and reconnect the thermostat in the wireless network when power from the power stealing circuit has been restored.
17. The thermostat of claim 10 , wherein the sleep time decreases with increasing current through the “on-mode” load.
18. A method of communicating in a wireless network, the method performed by a wireless thermostat of a climate control system, the method comprising:
controlling a wireless network interface of the thermostat to intermittently connect the thermostat in a wireless network in accordance with a duty cycle, the duty cycle having a connect time in which the thermostat is connected in the wireless network and a sleep time in which the thermostat is not connected in the wireless network;
stealing power through at least an “on-mode” load of the climate control system, the stealing performed at least in part by receiving current from the “on-mode” load from a current transformer in series with a relay operable to switch the load between “on” and “off” modes and using the received current for charging an energy storage device to provide the power for the wireless network interface, where the current being received from the current transformer for the charging increases as current increases through the “on-mode” load; and
adjusting at least the sleep time in accordance with a time for charging the energy storage device to a threshold voltage.
19. The method of claim 18 , wherein the sleep time period decreases with increasing current through the “on-mode” load.
20. The method of claim 18 , wherein:
the energy storage device comprises a capacitor; and
the method further comprises:
determining whether a duty cycle timer has expired and/or whether the capacitor is charged to the threshold voltage; and
based on the determining, initiating a connect time and resetting the timer.