Thermostat switching circuitry with overcurrent shutdown

Patent metadata

Field	Value
Publication number	US-10241526-B2
Application number	US-201615349809-A
Country	US
Kind code	B2
Filing date	Nov 11, 2016
Priority date	Nov 11, 2016
Publication date	Mar 26, 2019
Grant date	Mar 26, 2019

Abstract

A thermostat may include HVAC wire connectors that receive a call relay wire and a power return wire, switching elements having a first operating state in which they create a connection between the call relay wire and the power return wire and a second operating state in which the connection between the call relay wire and the power return wire is interrupted. The thermostat may also include control circuitry configured to cause the switching elements to operate in the first operating state to actuate an HVAC function; detect an anomaly associated with measurements from power monitoring circuitry; cause the switching elements to continue to operate in the first operating state until a zero-crossing is detected; and then cause the one or more switching elements to operate in the second operating state.

First claim

What is claimed is:

1. A thermostat comprising:
a plurality of wire connectors configured to receive a plurality of wires from an environmental control system, the plurality of wire connectors comprising a call relay wire connector and a power return wire connector;
one or more solid-state switching elements coupled to the call relay wire connector and the power return wire connector, the one or more solid-state switching elements having a first operating state in which the one or more solid-state switching elements create a connection between the call relay wire connector and the power return wire connector, the one or more solid-state switching elements also having a second operating state in which the connection between the call relay wire connector and the power return wire connector is interrupted;
a zero-crossing detection circuit that detects when an electrical signal of the one or more solid-state switching elements is zero; and
power monitoring and control circuitry coupled to the one or more solid-state switching elements and configured to:
cause the one or more solid-state switching elements to operate in the first operating state to actuate at least one environmental control function;
measure the electrical signal of the one or more solid-state switching elements when the one or more solid-state switching elements are operating in the first operating state;
detect an anomaly associated with the electrical signal;
in response to detecting the anomaly, store an indication that the anomaly occurred while continuing to cause the one or more solid-state switching elements to operate in the first operating state;
receive an indication from the zero-crossing detection circuit that the electrical signal of the one or more solid-state switching elements is zero; and
in response to receiving the indication from the zero-crossing detection circuit, cause the one or more solid-state switching elements to operate in the second operating state.

2. The thermostat of claim 1 , wherein the power monitoring and control circuitry is further configured to:
after detecting the anomaly, and before receiving the indication from the zero-crossing detection circuit, dynamically adjusting an on-resistance of the one or more solid-state switching elements to maintain the electrical signal of the one or more solid-state switching elements below a predetermined threshold.

3. The thermostat of claim 2 , wherein the power monitoring and control circuitry comprises an amplifier that receives electrical signal measurements through the one or more solid-state switching elements, measures a difference between the electrical signal and the predetermined threshold, and dynamically adjusts a control voltage applied to the one or more solid-state switching elements.

4. The thermostat of claim 1 , wherein the call relay wire connector and the power return wire connector are connected to an inductive load of the environmental control system.

5. The thermostat of claim 4 , wherein an on-resistance of the one or more solid-state switching elements is at least 10 times a resistance of the inductive load of the environmental control system.

6. The thermostat of claim 1 , wherein the power monitoring and control circuitry comprises:
a first integrated circuit (IC) comprising a microprocessor; and
a second IC comprising power monitoring circuitry, the one or more solid-state switching elements, and a drive circuit for the one or more solid-state switching elements.

7. The thermostat of claim 6 , wherein the second IC is isolated from other circuitry in the thermostat through one or more isolation capacitors, wherein the second IC and the first IC communicate with each other using clocked pulses.

8. The thermostat of claim 7 , wherein the second IC is powered by the clocked pulses provided by the first IC.

9. The thermostat of claim 1 , wherein the anomaly associated with the electrical signal comprises a current running through the one or more solid-state switching elements exceeding a threshold of approximately 4.0 A.

10. The thermostat of claim 1 , wherein the one or more solid-state switching elements comprises a pair of complementary metal-oxide semiconductor field-effect transistors.

11. A method of responding to electrical anomalies by a thermostat, the method comprising:
causing one or more solid-state switching elements of the thermostat to operate in a first operating state to actuate at least one environmental control function, wherein:
the one or more solid-state switching elements are coupled to a call relay wire connector and a power return wire connector of the thermostat;
the one or more solid-state switching elements are configured to operate in the first operating state in which the one or more solid-state switching elements create a connection between the call relay wire connector and the power return wire connector; and
the one or more solid-state switching elements are configured to operate in a second operating state in which the connection between the call relay wire connector and the power return wire connector is interrupted;

measuring an electrical signal of the one or more solid-state switching elements when the one or more solid-state switching elements are operating in the first operating state;
detecting an anomaly associated with the electrical signal;
in response to detecting the anomaly, storing an indication that the anomaly occurred while continuing to cause the one or more solid-state switching elements to operate in the first operating state;
receiving an indication from a zero-crossing detection circuit that the electrical signal of the one or more solid-state switching elements is zero; and
in response to receiving the indication from the zero-crossing detection circuit, causing the one or more solid-state switching elements to operate in the second operating state.

12. The method of claim 11 , wherein power monitoring and control circuitry of the thermostat comprises a first terminal and a second terminal associated with the one or more solid-state switching elements, wherein the anomaly is detected by monitoring a voltage difference between the first terminal and the second terminal.

13. The method of claim 11 , wherein power monitoring and control circuitry of the thermostat is further configured to send an indication of the anomaly to a remotely-located thermostat monitoring server.

14. The method of claim 11 , further comprising, after detecting the anomaly, and before receiving the indication from the zero-crossing detection circuit, dynamically adjusting an on-resistance of the one or more solid-state switching elements to maintain the electrical signal between the call relay wire connector in the power return wire connector below a predetermined threshold.

15. The method of claim 14 , wherein power monitoring and control circuitry of the thermostat comprises an amplifier that receives electrical signal measurements through the one or more solid-state switching elements, measures a difference between the electrical signal and the predetermined threshold, and dynamically adjusts a control voltage applied to the one or more solid-state switching elements.

16. The method of claim 11 , wherein the call relay wire connector and the power return wire connector are connected to an inductive load of the environmental control system.

17. The method of claim 16 , wherein an on-resistance of the one or more solid-state switching elements is at least 10 times a resistance of the inductive load of the environmental control system.

18. The m

Assignees

• Google Llc

Inventors

• Marschalkowski Eric
• Buenaventura Orville
• Warren Daniel Adam

Classifications

• G01R31/52

  Testing for short-circuits, leakage current or ground faults · CPC title

• G01R19/15

  Indicating the presence of current · CPC title

• H02H3/08

  responsive to excess current (responsive to abnormal temperature caused by excess current H02H5/04) · CPC title

• H02H3/20

  responsive to excess voltage · CPC title

• H02M1/083

  for the ignition at the zero crossing of the voltage or the current · CPC title