Controlling a controllably conductive device based on zero-crossing detection

• US 9,991,075 B2
• Filed: 10/03/2014
• Issued: 06/05/2018
• Est. Priority Date: 10/04/2013
• Status: Active Grant

• Current Assignee: Lutron Technology Company LLC
• Original Assignee: Lutron Electronics Company Incorporated (Lutron Electronics)
• Inventors: Lenig, Robert William, Sizemore, Michael, Thaler, Joshua Wilson, MacAdam, Russell L.
• Primary Examiner(s): Tran, Thienvu
• Assistant Examiner(s): CLARK, CHRISTOPHER JAY
• Application Number:
  US14/506,204
• Publication Number:
  US 20150098164A1
• Time in Patent Office: 1,341 Days
• CPC Class Codes: H01H 47/18 for introducing delay in the operation of the relay short-circuited conducting sleeves, bands or discs H01H50/46
• CPC Class Codes: H01H 9/56 for ensuring operation of the switch at a predetermined point in the ac cycle

Abstract

A load control device may control power delivered to an electrical load from an AC power source. The load control device may include a controllably conductive device adapted to be coupled in series electrical connection between the AC power source and the electrical load, a zero-cross detect circuit configured to generate a zero-cross signal representative of the zero-crossings of an AC voltage. The zero-cross signal may be characterized by pulses occurring in time with the zero-crossings of the AC voltage. The load control device may include a control circuit operatively coupled to the controllably conductive device and the zero cross detect circuit. The control circuit may be configured to identify a rising-edge time and a falling-edge time of one of the pulses of the zero-cross signal, and may control a conductive state of the controllably conductive device based on the rising-edge time and the falling-edge time of the pulse.

Claims

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

a controllably conductive device adapted to be coupled in series electrical connection between the AC power source and the electrical load;

a zero-cross detect circuit configured to generate a zero-cross signal representative of zero-crossings of an AC voltage, the zero-cross signal characterized by a plurality of pulses occurring in time with the zero-crossings of the AC voltage, and the AC voltage comprising a switched-hot voltage generated by the controllably conductive device to be provided to the electrical load when the controllably conductive device is conductive; and

a control circuit operatively coupled to the controllably conductive device and the zero-cross detect circuit and configured to;

identify a rising-edge time and a falling-edge time of one of the pulses of the zero-cross signal;

control a conductive state of the controllably conductive device based on the rising edge time and the falling-edge time of the pulse;

set an error window based on the rising-edge time and the falling-edge time of the pulse;

determine whether a conductive state change time falls within the error window; and

adjust a relay actuation adjustment time period associated with the controllably conductive device upon a determination that the conductive state change time falls within the error window.

2. The load control device of claim 1, wherein the control circuit is configured to set the error window as a period of time between the falling-edge time of a first subsequent pulse and the rising-edge time of a second consecutive subsequent pulse.

3. The load control device of claim 1, wherein the control circuit is configured to:

set a start time of the error window to be at a time equal to the falling-edge time of a first subsequent pulse plus a first buffer period, and

set an end time of the error window at a time equal to the rising-edge time of a second consecutive subsequent pulse minus a second buffer period.

4. The load control device of claim 1, wherein the control circuit is configured to generate a drive voltage that is operatively coupled to the controllably conductive device for rendering the controllably conductive device conductive and non-conductive, the controllably conductive device rendered conductive a first period of time after the drive voltage is adjusted and rendered non-conductive a second period of time after the drive voltage is adjusted, and the relay actuation adjustment time period is indicative of a time at which the drive voltage is adjusted relative to a subsequent zero-crossing for rendering the controllably conductive device conductive.

5. The load control device of claim 1, wherein the control circuit is configured to generate a drive voltage that is operatively coupled to the controllably conductive device for rendering the controllably conductive device conductive and non-conductive, the controllably conductive device rendered conductive a first period of time after the drive voltage is adjusted and rendered non-conductive a second period of time after the drive voltage is adjusted, and the relay actuation adjustment time period is indicative of a time at which the drive voltage is adjusted relative to a subsequent zero-crossing for rendering the controllably conductive device nonconductive.

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

a controllably conductive device adapted to be coupled in series electrical connection between the AC power source and the electrical load;

a zero-cross detect circuit configured to generate a zero-cross signal representative of zero-crossings of an AC voltage, the zero-cross signal characterized by a plurality of pulses occurring in time with the zero-crossings of the AC voltage, wherein the AC voltage comprises a switched-hot voltage generated by the controllably conductive device to be provided to the electrical load when the controllably conductive device is conductive;

a control circuit operatively coupled to the controllably conductive device and the zero-cross detect circuit and configured to;

identify a rising-edge time and a falling-edge time of one of the pulses of the zero-cross signal;

control a conductive state of the controllably conductive device based on the rising edge time and the falling-edge time of the pulse;

set a close error detection window as a period of time after the falling-edge time of a subsequent pulse of the zero-cross signal; and

determine that an error in a conductive state change time has occurred when the controllably conductive device becomes conductive within the close error detection window.

7. The load control device of claim 6, wherein the control circuit is configured to:

set a start time of the close error detection window at a time equal to the falling-edge time of the subsequent pulse of the zero-cross signal plus a buffer period; and

set an end time of the close error detection window at a time equal to the start time plus a close error detection window length.

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

a controllably conductive device adapted to be coupled in series electrical connection between the AC power source and the electrical load;

a zero-cross detect circuit configured to generate a zero-cross signal representative of zero-crossings of an AC voltage, the zero-cross signal characterized by a plurality of pulses occurring in time with the zero-crossings of the AC voltage, wherein the AC voltage comprises a switched-hot voltage generated by the controllably conductive device to be provided to the electrical load when the controllably conductive device is conductive;

a control circuit operatively coupled to the controllably conductive device and the zero-cross detect circuit and configured to;

identify a rising-edge time and a falling-edge time of one of the pulses of the zero-cross signal;

control a conductive state of the controllably conductive device based on the rising edge time and the falling-edge time of the pulse;

set an open error detection window as a period of time before the rising-edge time of a subsequent pulse of the zero-cross signal; and

determine that an error in a conductive state change time has occurred when the controllably conductive device becomes non-conductive within the open error detection window.

9. The load control device of claim 8, wherein the control circuit is configured to:

set a start time of the open error detection window at a time equal to the falling-edge time of the subsequent pulse of the zero-cross signal plus a buffer period; and

set an end time of the open error detection window at a time equal to the start time plus an open error detection window length.

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

a controllably conductive device adapted to be coupled in series electrical connection between the AC power source and the electrical load;

a zero-cross detect circuit configured to generate a zero-cross signal representative of zero-crossings of an AC voltage, the zero-cross signal characterized by a plurality of pulses occurring in time with the zero-crossings of the AC voltage;

a control circuit operatively coupled to the controllably conductive device and the zero-cross detect circuit and configured to;

identify a rising-edge time and a falling-edge time of one of the pulses of the zero-cross signal;

control a conductive state of the controllably conductive device based on the rising edge time and the falling-edge time of the pulse;

set an error detection threshold based on the rising-edge and falling-edge times;

determine whether an error in a conductive state change time has occurred based on the error detection threshold; and

adjust a relay actuation adjustment time period associated with the controllably conductive device upon a determination that the error has occurred.

11. The load control device of claim 10, wherein the control circuit is configured to:

compare a falling-edge time of a subsequent pulse of the zero-cross signal to the error detection threshold; and

determine that the error in the conductive state change time has occurred on a condition that the falling-edge time exceeds the error detection threshold.

12. The load control device of claim 10, wherein the control circuit is configured to:

compare a rising-edge time of a subsequent pulse of the zero-cross signal to the error detection threshold; and

determine that the error in the conductive state change time has occurred on a condition that the rising-edge time does not exceed the error detection threshold.

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

a controllably conductive device adapted to be coupled in series electrical connection between the AC power source and the electrical load;

a zero-cross detect circuit configured to generate a zero-cross signal representative of the zero-crossings of an AC voltage generated by the controllably conductive device to be provided to the electrical load when the controllably conductive device is conductive, the zero-cross signal characterized by a plurality of pulses occurring in time with the zero-crossings of the AC voltage; and

a control circuit operatively coupled to the controllably conductive device and the zero-cross detect circuit and configured to;

identify a rising-edge time and a falling-edge time of one of the pulses of the zero-cross signal;

set an error detection window based on the rising-edge time and the falling-edge time of the pulse; and

determine whether an error in a conductive state change time of the controllably conductive device has occurred based on the error detection window.

14. The load control device of claim 13, wherein the control circuit is configured to:

determine whether the conductive state change time falls within the error detection window; and

adjust a relay actuation adjustment time period associated with the controllably conductive device upon a determination that the conductive state change time falls within the error detection window.

15. The load control device of claim 13, wherein the control circuit is configured to set the error detection window as a period of time between the falling-edge time of a first subsequent pulse and the rising-edge time of a second consecutive subsequent pulse.