Load control device having stuck relay detection

• US 10,325,740 B2
• Filed: 02/15/2017
• Issued: 06/18/2019
• Est. Priority Date: 03/31/2015
• Status: Active Grant

• Current Assignee: Lutron Technology Company LLC
• Original Assignee: Lutron Technology Company LLC
• Inventors: Zotter, William
• Primary Examiner(s): Amaya, Carlos
• Application Number:
  US15/433,542
• Publication Number:
  US 20170162351A1
• Time in Patent Office: 853 Days
• Field of Search: 307130
• CPC Class Codes: H01H 2047/003 Detecting welded contacts and applying weld break pulses to coil
• CPC Class Codes: H01H 47/002 Monitoring or fail-safe circuits
• CPC Class Codes: H05B 45/00 Circuit arrangements for operating light-emitting diodes [LED]
• CPC Class Codes: H05B 45/30 Driver circuits
• CPC Class Codes: H05B 45/37 Converter circuits

Abstract

A load control device (e.g., a switching device) for controlling power delivered from an AC power source to an electrical device (e.g., a lighting load) may be configured to detect that a relay is stuck closed and attempt to fix the relay. The relay of the load control device may be adapted to be coupled between the source and the electrical device to control the power delivered to the electrical device so as to generate a switched-hot voltage. The load control device may comprise a detect circuit configured to generate a detect signal indicating a magnitude of the switched-hot voltage, and a control circuit configured to monitor the detect signal. The control circuit may be configured to determine that the relay is stuck closed in response to the detect signal, and to control the relay in order to attempt to fix the relay by repeatedly closing and opening the relay.

Claims

1. A load control device for controlling power delivered from an AC power source to an electrical device, the load control device comprising:

a relay adapted to be electrically coupled between the AC power source and the electrical device, the relay being configured to receive a hot voltage from the AC power source and generate a switched-hot voltage for controlling the power delivered to the electrical device;

a detect circuit electrically coupled to the relay to receive the switched-hot voltage and configured to generate a detect signal indicating a magnitude of the switched-hot voltage;

a control circuit configured to generate a drive signal for attempting to open and close the relay, configured to monitor the detect signal, and configured to determine whether the relay is open or closed based on the detect signal;

wherein, in response to determining that the relay is stuck closed, the control circuit is configured to;

attempt to close the relay;

attempt to open the relay;

monitor the detect signal; and

determine whether the relay is stuck closed.

2. The load control device of claim 1, wherein the control circuit is configured to repeatedly attempt to close and open the relay until the control circuit determines that the relay is open based on the detect signal or until the control circuit attempts to close and open the relay a maximum number of times.

3. The load control device of claim 2, further comprising:

a memory coupled to the control circuit;

wherein, if the control circuit attempts to close and open the relay the maximum number of times, the control circuit is configured to wait a predetermined amount of time or mark the relay as stuck closed in the memory.

4. The load control device of claim 3, wherein, if the control circuit waits the predetermined amount of time, the control circuit is configured to repeatedly attempt to close and open the relay until the control circuit determines that the relay is open based on the detect signal or until the control circuit attempts to close and open the relay the maximum number of times.

5. The load control device of claim 4, wherein, if the control circuit attempts to close and open the relay the maximum number of times for a maximum number of cycles, the control circuit is configured to mark the relay as stuck closed in the memory.

6. The load control device of claim 3, wherein, after marking the relay as stuck closed in the memory, the control circuit is configured to attempt to close and open the relay at least one additional time.

7. The load control device of claim 1, wherein the control circuit is configured to receive a command to open the relay.

8. The load control device of claim 7, wherein, in response to receiving the command to open the relay, the control circuit is configured to control the drive signal to open the relay and to subsequently wait for a predetermined amount of time before monitoring the detect signal to determine if the relay is stuck closed.

9. The load control device of claim 7, further comprising:

an actuator configured to receive a user input;

wherein the control circuit is configured to receive the command to open the relay via the actuator.

10. The load control device of claim 7, further comprising:

a communication circuit configured to receive a digital message;

wherein the control circuit is configured to receive the command to open the relay via the digital message.

11. The load control device of claim 1, further comprising:

a visual indicator configured to be illuminated to provide feedback to a user;

wherein the control circuit is configured to illuminate the visual indicator in response to determining that the relay is stuck closed.

12. The load control device of claim 11, wherein the control circuit is configured to blink the visual indicator in response to determining that the relay is stuck closed.

13. The load control device of claim 1, wherein the relay comprises a latching relay.

14. The load control device of claim 13, wherein the control circuit is configured to pulse a SET coil of the latching relay in response to determining that the relay is stuck closed.

15. The load control device of claim 1, wherein the relay comprises a non-latching relay.

16. The load control device of claim 1, further comprising:

a communication circuit configured to transmit a digital message in response to determining that the relay is stuck closed.

17. The load control device of claim 1, wherein, in response to determining that the relay is stuck closed, the control circuit is configured to start with attempting to close the relay.

18. The load control device of claim 1, further comprising:

a memory coupled to the control circuit;

wherein the control circuit is configured to mark the relay as stuck closed in the memory in response to determining that the relay is stuck closed.

19. A method for controlling a relay, the method comprising:

generating a drive signal for attempting to open and close the relay;

generating a detect signal indicating a magnitude of a switched-hot voltage;

monitoring the detect signal;

determining whether the relay is open or closed based on the detect signal; and

in response to determining that the relay is stuck closed,

attempting to close the relay;

attempting to open the relay;

monitoring the detect signal; and

determining whether the relay is stuck closed.

20. The method of claim 19, further comprising:

repeatedly attempting to close and open the relay until it is determined that the relay is open based on the detect signal or until attempting to close and open the relay a maximum number of times.

21. The method of claim 19, further comprising:

repeatedly attempting to close and open the relay the maximum number of times; and

waiting a predetermined amount of time or marking the relay as stuck closed in a memory.

22. The method of claim 19, further comprising:

receiving a command to open the relay; and

in response to receiving the command to open the relay, controlling the drive signal to open the relay and subsequently waiting for a predetermined amount of time before monitoring the detect signal to determine if the relay is stuck closed.

23. The method of claim 19, further comprising:

waiting a predetermined amount of time after attempting to open the relay and before monitoring the detect signal.