Phase control with adaptive parameters

• US 8,618,751 B2
• Filed: 12/30/2009
• Issued: 12/31/2013
• Est. Priority Date: 12/30/2009
• Status: Active Grant

• Current Assignee: Leviton Manufacturing Company Incorporated
• Original Assignee: Leviton Manufacturing Company Incorporated
• Inventors: Ostrovsky, Michael, LiBretto, John
• Primary Examiner(s): Owens, Douglas W
• Assistant Examiner(s): Chen, Jianzi
• Application Number:
  US12/650,420
• Publication Number:
  US 20110156610A1
• Time in Patent Office: 1,462 Days
• Field of Search: 315/194, 315/177, 315/209.R, 315/224, 315/226, 315/291, 315/299, 315/307, 315/326, 315/362, 315/DIG.4
• US Class Current: 315/362
• CPC Class Codes: H02M 5/2573 with control circuit
• CPC Class Codes: H02M 5/293 using semiconductor devices only
• CPC Class Codes: H02M 5/34 using mechanical contact-making and -breaking parts
• CPC Class Codes: H05B 39/083 by the variation-rate of light intensity
• CPC Class Codes: H05B 47/17 Operational modes, e.g. switching from manual to automatic mode or prohibiting specific operations

Abstract

A method for determining a limit of a phase control power range includes applying a first gate pulse to a switch at a first firing angle near the limit of the power range, sensing the conductive state of the switch after the first gate pulse, and determining the limit of the power range in response to the conductive state of the switch. If the switch remains conductive after the first gate pulse, the first firing angle may be used as the limit of the power range. If the switch does not remain conductive after the first gate pulse, the limit may be determined by repeatedly incrementing the firing angle, applying a gate pulse to the switch at the incremented firing angle, and sensing the conductive state of the switch after each gate pulse until the switch is conductive after a gate pulse.

Claims

1. A method for determining a limit point on a waveform of an AC power supply coupled to a load through a switch in a field installable control apparatus, the method comprising:

selecting a first point on the waveform as a test point; and

a process which may be repeated one or more times, the process comprising;

applying a control pulse to the switch at the test point on the waveform;

sensing the conductive state of the switch by monitoring voltage across the switch; and

if the switch does not remain conductive in response to the control pulse, selecting a new point as the test point on the waveform.

2. The method of claim 1 where the limit point is a point which provides maximum power flow from the AC power supply to the load.

3. The method of claim 2 where selecting the first point comprises selecting a point near the beginning of a half-cycle of the waveform.

4. The method of claim 1 where the limit point is a point which provides minimum power flow from the AC power supply to the load.

5. The method of claim 4 where selecting the first point comprises selecting a point near the end of a half-cycle of the waveform.

6. The method of claim 1 further comprising using the last selected point as the limit point.

7. The method of claim 1 where selecting a new point as the test point comprises selecting a new point in a first direction along the waveform at a distance away from the previous test point on the waveform.

8. The method of claim 1 further comprising repeating the process using a point between the last selected test point and the next-to-last selected test point as the test point.

9. The method of claim 1 where the switch comprises a latching switch.

10. The method of claim 9 where sensing the conductive state of the switch comprises determining whether the switch has latched.

11. The method of claim 10 where determining whether the switch has latched comprises sampling the state of the switch one or more times during a predetermined interval after applying the control pulse.

12. The method of claim 1 where the new point is a predetermined incremental distance from the previous test point on the waveform.

13. The method of claim 1 further comprising coupling the power switch to a compact fluorescent lamp.

14. The method of claim 13 where the limit point prevents the compact fluorescent lamp from flickering.

15. The method of claim 1 where the field installable control apparatus comprises a wiring device.

16. A field installable system comprising:

a switch configured to control the flow of AC power from a line terminal to a load terminal; and

a controller coupled to the switch and adapted to apply a control pulse to the switch and determine a limit point on a waveform of the AC power by sensing the conductive state of the switch after the control pulse, the controller adapted to determine the limit point by;

selecting a first point on the waveform as a test point; and

performing a process which may be repeated one or more times, the process comprising;

applying the control pulse to the switch at the test point on the waveform;

sensing the conductive state of the switch by monitoring a voltage across the switch; and

if the switch does not remain conductive after terminating the control pulse, selecting a new point as the test point on the waveform.

17. The system of claim 16 where the controller is adapted to determine the limit point continuously while the system is operating.

18. The system of claim 16 where the controller is adapted to determine the limit point when the system begins operation.

19. The system of claim 16 where the controller is adapted to periodically determine the limit point.

20. The system of claim 16 where the controller is adapted to determine the limit point in response to a mode input.

21. The system of claim 20 further comprising a mode switch configured to provide the mode input to the controller.

22. The system of claim 16 where the switch comprises a latching switch.

23. The system of claim 16 further comprising a sensor coupled to the switch and adapted to sense the conductive state of the switch.

24. The system of claim 23 where the sensor comprises a zero-cross detector.

25. The system of claim 23 where the power switch, sensor and controller are arranged in a wiring device.

26. The system of claim 25 where the wiring device comprises a two wire device without a neutral pole of an AC power source.

27. The system of claim 16 where the system is adapted to control a compact fluorescent lamp over a maximum dimming range by determining a first limit point on the waveform of the AC power for use as a maximum brightness level and determining a second limit point on the waveform of the AC power for use as a minimum brightness level.

28. The system of claim 16 further comprising an active power supply to provide operating power to the controller using power derived from the line and load terminals.

29. The system of claim 28 where the active power supply comprises a linear regulator.

30. The wiring device of claim 28 where the active power supply comprises a switching power supply.

31. A method comprising:

applying control pulses to a latching switch in a field installable control apparatus, where the latching switch is coupled between an AC power source and a load, and the AC power source has a waveform with cycles; and

varying the amount of power delivered to the load by varying the points in the cycles at which the control pulses are applied to the latching switch;

where the durations of the control pulses depend on the points in the cycles at which the control pulses are applied to the latching switch.

32. The method of claim 31 where each control pulse begins substantially before a midpoint of a half cycle and ends at about the midpoint of the same half cycle.

33. The method of claim 31 where control pulses that begin at points substantially after a midpoint of a half cycle have substantially the same pulse duration.

34. A method for operating a phase control device having a latching switch in a field installable control apparatus configured to control the flow of power from an AC power source to a load, where the latching switch has a variable operating point corresponding to a point on a waveform of the AC power source at which the latching switch is switched on, and where the operating point may vary over an operating range between first and second limits, the method comprising:

placing the phase control device in an adjustment mode;

adjusting the operating point of the phase control device to select at least one of the first and second limits; and

adaptively constraining the operating point to prevent the latching switch from failing to latch during a line cycle of the waveform while in the adjustment mode.

35. The method of claim 34 where adjusting the operating point comprises manually adjusting the operating point.

36. The method of claim 34 where adaptively constraining the operating point comprises:

applying a first control pulse to the switch at a first point in a line cycle of the waveform near one of the first or second limits of the operating range;

sensing the conductive state of the switch in response to the first control pulse by sensing the voltage across the switch; and

determining the limit of the operating range in response to the conductive state of the switch.

37. The method of claim 34 where the limit is a lower limit.

38. The method of claim 34 where the limit is an upper limit.

39. The method of claim 34 where the phase control device is placed in the adjustment mode by actuating a dedicated mode switch.

40. The method of claim 34 where the phase control device is placed in the adjustment mode by actuating a control in a manner that would not be used during normal operation.

41. A method for operating a latching switch in a field installable control apparatus configured to control the flow of power from an AC power source to a load, where the latching switch has a variable operating point corresponding to a point in a cycle of a waveform of the AC power source at which the latching switch is switched on, and where the operating point may vary over an operating range having a lower limit corresponding to a point in the cycle that provides minimum power flow, the method comprising:

determining the lower limit by sensing a point in the cycle at which the latching switch becomes nonconductive by monitoring the voltage across the switch when the switch is switched on at a point substantially earlier in the cycle than the lower limit.

42. The method of claim 41 further comprising using the point in the cycle at which the latching switch became nonconductive as the lower limit.

43. The method of claim 41 further comprising using the point in the cycle at which the latching switch becomes nonconductive as a starting point for an adaptive limit determination.

44. A method for controlling a switch in a field installable control apparatus coupled between an AC power source and a load, the AC power source having a waveform with a first portion having a first polarity and a second portion having a second polarity, the method comprising:

applying a control pulse to the switch during the first portion of the waveform at a first point after the beginning of the first portion of the waveform;

applying a control pulse to the switch during the second portion of the waveform at a second point after the beginning of the second portion of the waveform;

where the time between the first point and the beginning of the first portion of the waveform is substantially different than the time between the second point and the beginning of the second portion of the waveform.

45. The method of claim 44 where the first portion of the waveform is a positive portion and the second portion of the waveform is a negative portion.

46. The method of claim 44 where the difference between the time between the first point and the beginning of the positive portion of the waveform and the time between the second point and the beginning of the negative portion of the waveform comprises a delay time.

47. The method of claim 46 where:

the field installable control apparatus includes a power supply configured to control the switch; and

the method further comprises charging the power supply with the AC power source during the delay time.

48. The method of claim 44 where the first point corresponds to a point of maximum power transfer.

49. The method of claim 44 where the switch comprises a Triac.

50. The method of claim 44 where the switch comprises two or more switching devices.

51. The method of claim 50 where the two or more switching devices comprise back-to-back silicon controlled rectifiers.