Two-wire dimmer with improved zero-cross detention

• US 9,674,933 B2
• Filed: 08/28/2015
• Issued: 06/06/2017
• Est. Priority Date: 09/14/2012
• Status: Active Grant

• Current Assignee: Lutron Technology Company LLC
• Original Assignee: Lutron Electronics Company Incorporated (Lutron Electronics)
• Inventors: Zotter, William, Yang, Bingrui, Kite, Henry
• Primary Examiner(s): Owens, Douglas W
• Assistant Examiner(s): Kaiser, Syed M
• Application Number:
  US14/839,443
• Publication Number:
  US 20150373817A1
• Time in Patent Office: 648 Days
• Field of Search: 315291, 315294, 315307, 315224, 315194, 315246, 315247
• CPC Class Codes: H05B 39/048 with reverse phase control
• CPC Class Codes: H05B 39/08 by shifting phase of trigger voltage applied to gas-filled controlling tubes also in controlled semiconductor devices in converters H02M5/00; with regulation G05F1/44
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/305 Frequency-control circuits
• CPC Class Codes: H05B 45/31 Phase-control circuits
• CPC Class Codes: H05B 47/10 Controlling the light source
• CPC Class Codes: H05B 47/16 by timing means
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
• CPC Class Codes: Y02B 20/40 Control techniques providing energy savings, e.g. smart controller or presence detection

Abstract

A two-wire lighting control device, may include a controllably conductive device, a signal generation circuit, and a filter circuit. The controllably conductive device may apply an AC line voltage to a load, being conductive for a first duration of time and non-conductive for a second duration of time within a half-cycle of the AC line voltage. The signal generation circuit may generate a non-zero-magnitude signal. And, the filter circuit may receive a signal from the controllably conductive device during the first duration of time and the non-zero-magnitude signal from the signal generation circuit during the second duration of time. The non-zero-magnitude signal may, in effect, fill-in or complement the signal from the controllably conductive device, and any delay variation as a function of the firing angle of the controllably conductive device through the filter circuit may be mitigated by the presence of the non-zero-magnitude signal.

Claims

1. A lighting control device comprising:

a controllably conductive device configured to supply an AC line voltage to a load in response to a drive signal, wherein the controllably conductive device is non-conductive for a first duration of time and is conductive for a second duration of time, wherein the first duration of time and the second duration of time are within the same half-cycle of the AC line voltage;

a control circuit configured to;

receive a signal from the controllably conductive device during the first duration of time;

generate a fill signal during the second duration of time; and

filter the signal from the controllably conductive device during the first duration of time and the fill signal during the second duration of time;

wherein a delay associated with filtering the signal from the controllably conductive device during the first duration of time and filtering the fill signal during the second duration of time is consistent with a delay associated with filtering the AC line voltage.

2. The lighting control device of claim 1, wherein the control circuit is configured to:

generate a filtered signal by filtering the signal from the controllably conductive device during the first duration of time and filtering the fill signal during the second duration of time; and

determine a zero-crossing of the AC line voltage from the filtered signal.

3. The lighting control device of claim 2, wherein the control circuit is configured to generate the drive signal to control the controllably conductive device based on the determined zero-crossing of the AC line voltage.

4. The lighting control device of claim 3, wherein the control circuit is configured to control the controllably conductive device using forward phase control, such that the first duration of time occurs before the second duration of time during each half cycle.

5. The lighting control device of claim 4, wherein the control circuit is configured to generate the drive signal to render the controllably conductive device conductive at a time measured from the determined zero-crossing of the AC line voltage.

6. The lighting control device of claim 3, wherein the control circuit is configured to control the controllably conductive device using reverse phase control, such that the second duration of time occurs before the first duration of time during each half cycle.

7. The lighting control device of claim 6, wherein the control circuit is configured to generate the drive signal to render the controllably conductive device non-conductive at a time measured from the determined zero-crossing of the AC line voltage.

8. The lighting control device of claim 1, wherein the control circuit comprises:

a signal generation circuit configured to generate the fill signal;

a combiner circuit for combining a signal from the controllably conductive device during the first duration of time and the fill signal during the second duration of time; and

a filter circuit configured to filter the combined signal from the combiner circuit.

9. The lighting control device of claim 8, wherein the combiner circuit comprises a switch configured to switch between the signal from the controllably conductive device and the fill signal based on the drive signal, the switch configured to select the signal from the controllably conductive device during the first duration of time and the fill signal during the second duration of time.

10. The lighting control device of claim 9, wherein the switch comprises a multiplexer that switches in concert with the drive signal.

11. The lighting control device of claim 8, wherein the filter circuit is a low-pass filter.

12. The lighting control device of claim 11, wherein the low-pass filter provides a substantially linear phase delay of less than one-half of a period of the fundamental frequency and attenuates frequency components of a filter-input signal that are substantially equal to third order harmonics and greater of the fundamental frequency.

13. The lighting control device of claim 1, wherein the control circuit comprises a controller configured to sample the signal from the controllably conductive device during the first duration of time.

14. The lighting control device of claim 13, wherein the controller is configured to filter the signal from the controllably conductive device and the fill signal using a digital Bessel filter.

15. The lighting control device of claim 13, wherein the signal from the controllably conductive device is a scaled version of the voltage developed across the controllably conductive device that is referenced about a reference voltage to prevent the magnitude of the signal from dropping below zero volts.

16. The lighting control device of claim 1, wherein the signal from the controllably conductive device represents a voltage developed across the controllably conductive device.

17. The lighting control device of claim 16, wherein the fill signal during the second duration of time is sine-wave-shaped to complement the voltage developed across the controllably conductive device.

18. The lighting control device of claim 1, wherein the control circuit is configured to:

combine the signal from the controllably conductive device and the fill signal to produce a combined signal; and

filter the combined signal by filtering the signal from the controllably conductive device during the first duration of time and filtering the fill signal during the second duration of time.

19. The lighting control device of claim 1, further comprising:

a power supply coupled in parallel with the controllably conductive device for conducting a charging current through the load to generate a DC supply voltage for powering the control circuit.

20. lighting control device of claim 1, wherein the fill signal is shaped to maintain stability of the lighting control device, the lighting control device being a two-wire lighting control device.

21. A lighting control device comprising:

a controllably conductive device for supplying an AC line voltage to a load in response to a drive signal, wherein the controllably conductive device is non-conductive for a first duration of time and is conductive for a second duration of time, wherein the first duration of time and the second duration of time are within the same half-cycle of the AC line voltage;

a control circuit configured to;

receive a signal from the controllably conductive device that represents a voltage developed across the controllably conductive device during the first duration of time;

generate a sine-wave-shaped signal that complements the voltage developed across the controllably conductive device during the second duration of time;

combine the signal from the controllably conductive device and the sine-wave-shaped signal to produce a combined signal; and

filter the combined signal by filtering the signal from the controllably conductive device during the first duration of time and the sine-wave-shaped signal during the second duration of time.

22. The lighting control device of claim 21, wherein the sine-wave-shaped signal is a step-sine wave.

23. The lighting control device of claim 22, wherein the step-sine wave comprises steps based on at least one pulse-width modulated signal.

24. The lighting control device of claim 22, wherein the step-sine wave comprises steps based on at least one phase correction corresponding to a zero-crossing detected by a zero crossing detector.

25. The lighting control device of claim 21, wherein the control circuit comprises a switch configured to switch between the signal from the controllably conductive device and the sine-wave-shaped signal based on the drive signal, the switch configured to select the signal from the controllably conductive device during the first duration of time and the sine-wave-shaped signal during the second duration of time.

26. The lighting control device of claim 25, wherein the switch comprises a multiplexer that switches in concert with the drive signal.

27. The lighting control device of claim 21, wherein the control circuit comprises a low-pass filter.

28. The lighting control device of claim 27, wherein the low-pass filter provides a substantially linear phase delay of less than one-half of a period of the fundamental frequency and attenuates frequency components of a filter-input signal that are substantially equal to third order harmonics and greater of the fundamental frequency.

29. The lighting control device of claim 21, wherein the control circuit comprises a controller configured to sample the signal from the controllably conductive device during the first duration of time.

30. The lighting control device of claim 29, wherein the controller is configured to filter the signal from the controllably conductive device and the sine-wave-shaped signal using a digital Bessel filter.

31. The lighting control device of claim 21, wherein the control circuit is configured to:

generate a filtered signal by filtering the signal from the controllably conductive device during the first duration of time and filtering the sine-wave-shaped signal during the second duration of time; and

determine a zero-crossing of the AC line voltage from the filtered signal.

32. The lighting control device of claim 31, wherein the control circuit is configured to generate the drive signal to control the controllably conductive device based on the determined zero-crossing of the AC line voltage.

33. The lighting control device of claim 21, wherein the sine-wave-shaped signal is shaped such that delay associated with filtering the signal from the controllably conductive device during the first duration of time and the sine-wave-shaped signal during the second duration of time is consistent with delay associated with filtering the AC line voltage.

34. The lighting control device of claim 21, wherein the sine-wave-shaped signal is shaped to maintain stability of the two-wire lighting control device.