Coded communication system and method for controlling an electric lamp

• US 5,872,429 A
• Filed: 03/25/1997
• Issued: 02/16/1999
• Est. Priority Date: 03/31/1995
• Status: Expired due to Fees

• Current Assignee: Philips Electronics North America Corporation (Koninklijke Philips N.V.)
• Original Assignee: Philips Electronics North America Corporation (Koninklijke Philips N.V.)
• Inventors: Farkas, Thomas, Venkitasubrahmanian, Sreeraman, Jayaraman, Raj, Xia, Yongping
• Primary Examiner(s): Pascal, Robert J.
• Assistant Examiner(s): VU, DAVID HUNG
• Application Number:
  US08/824,024
• Time in Patent Office: 693 Days
• Field of Search: 315/291, 315/194, 315/199, 315/DIG. 4, 315/294, 315/299, 315/225, 315/226
• US Class Current: 315/194
• CPC Class Codes: H05B 41/2828 using control circuits for the switching elements H05B41/2827 takes precedence
• CPC Class Codes: H05B 41/2981 for protecting the circuit against abnormal operating conditions
• CPC Class Codes: H05B 41/3921 with possibility of light intensity variations
• CPC Class Codes: H05B 47/185 via power line carrier transmission
• CPC Class Codes: Y10S 315/04 Dimming circuit for fluorescent lamps

Abstract

A communication method particularly suited for lighting control employs encoding of perturbations in a voltage signal having a fundamental period with a nominal waveform. A control period includes a pre-selected number of fundamental periods of the voltage signal. Different control commands are indicated by imposing a selected perturbation, such as a phase cut, on the nominal waveform with a respective occurrence signature within the control period. The control commands are decoded from the voltage signal by detecting the occurrence signature of the perturbations within each control period. Decoding is accomplished by differentiating the nominal waveform to detect encoded perturbations. The technique is particularly suited for two-wire dimming applications for gas discharge lamps, in which the voltage signal carrying the encoded commands is the sinusoidal mains voltage powering the ballast, since the encoded perturbations may be small enough so that lamp flicker is avoided even with encoded signals on the line voltage. In a favorable embodiment for dimming, no perturbations are introduced on the line voltage unless a change in the operating characteristic, for example the light level, of the electric lamp is desired. This has the advantage that when lamp operation is to be kept constant, no distortions are imposed on the mains voltage, so that flicker of the lamp(s) is completely avoided and there are no adverse effects to the power factor, THD or component stress.

Claims

1. A method of communicating a control signal for an electric lamp, comprising:

a) supplying a voltage signal having a fundamental period and a nominal waveform;

b) within a control period comprised of a predetermined, fixed number of said fundamental periods, encoding one of two control commands to control an operating characteristic of the electric lamp, the control commands including a first command for lowering of the light level by imposing a preselected perturbation in the nominal waveform a first number of times and a second command for raising of the light level by imposing the perturbation a second, different number of times that does not significantly disturb the nominal waveform; and

c) decoding one of said first and second commands by counting the number of occurrences of the perturbation within each control period.

2. A method according to claim 1, wherein the imposed preselected perturbation is a phase cut of the nominal waveform.

3. A method according to claim 2, wherein said voltage signal is an AC signal in which the fundamental period includes a negative half-cycle and a positive half-cycle.

4. A method according to claim 3, wherein said phase cuts all have substantially a same phase angle.

5. A method according to claim 3, wherein said phase cuts always occur at the end of the respective half-cycle.

6. A method according to claim 3, wherein said phase cuts always occur at the beginning of the respective half-cycle.

7. A method according to claim 6, wherein said decoding step detects a location pattern of the imposed preselected perturbation within the control period.

8. A method according to claim 7, wherein said location pattern is binary.

9. A method according to claim 3, wherein said operating characteristic is the light level of a gas discharge lamp.

10. A method according to claim 1, wherein a command for no change in the operation of the lamp is encoded by not imposing the preselected perturbation on any fundamental period within said control period.

11. A method according to claim 1, wherein said imposed preselected perturbations are substantially constant.

12. A method according to claim 1, wherein said operating characteristic is the light level of a gas discharge lamp.

13. A method according to claim 1, wherein the encoded control command is decoded by counting the number of imposed preselected perturbations within each control period.

14. A method according to claim 1, wherein said decoding step includes differentiating the input signal.

15. A method according to claim 1, wherein each encoded control command is indicated by a pattern of occurrence of imposed preselected perturbations in the control period.

16. A method according to claim 15, wherein said pattern is binary.

17. A method according to claim 16, wherein the imposed preselected perturbation is a phase cut of the nominal waveform.

18. A method according to claim 15, wherein the imposed preselected perturbation is a phase cut of the nominal waveform.

19. A method of controlling the light level of a gas discharge lamp, comprising:

a) receiving a sinusoidal AC voltage having a fundamental period;

b) within a control period comprised of a predetermined, fixed number of said fundamental periods, encoding one of two commands which include

(i) a first command for lowering of the light level by imposing a pre-selected perturbation on said AC voltage a first number of times within the control period and (ii) a second command for raising of the light level by imposing the perturbation a second, different number of times within the control period, wherein the perturbation does not significantly change the shape of the sinusoidal waveform;

c) decoding one of said first and second commands by counting the number of occurrences of the perturbation within each control period; and

d) adjusting the light level of the lamp in the direction corresponding to a decoded one of said first and second commands.

20. A method according to claim 19, wherein said fundamental period includes a negative half-cycle and a positive half-cycle, and said perturbation is imposed during either of said positive half-cycle and said negative half-cycle.

21. A method according to claim 20, wherein said perturbation is a phase cut having a substantially constant phase angle.

22. A method according to claim 21, wherein said phase angle is less than about 45 degrees.

23. A method according to claim 21, wherein said phase angle is about 30 degrees.

24. A method according to claim 21, wherein said phase cut always occur at the beginning of the respective half-cycle.

25. A method according to claim 21, wherein within a subsequent control period a command indicative of no light level change is encoded by not imposing the phase cut in any fundamental period within the control period.

26. A method according to claim 19, wherein within a subsequent control period a command indicative of no light level change is encoded by not imposing the perturbation in any fundamental period within the control period.

27. A method according to claim 19, wherein said perturbations are all substantially identical.

28. A system for controlling the light level of a gas discharge lamp, said system comprising:

A) a transmitter for controlling changes in the light level of the gas discharge lamp, said transmitter comprising

(i) an input for receiving an AC voltage having a sinusoidal waveform within a fundamental period,

(ii) encoding means for imposing a pre-selected perturbation on the AC voltage a first number of times within a control period comprised of a fixed number of fundamental periods to indicate a first command to increase the light level of the lamp and for imposing the perturbation a second, different number of times within the control period to indicate a second command to decrease the light level of the lamp wherein the perturbation does not significantly change the shape of the sinusoidal waveform; and

(iii) a transmitter output for outputting the encoded AC voltage from said encoding means; and

B) a ballast for operating the gas discharge lamp, said ballast comprising;

(i) a ballast input for receiving the encoded AC voltage from said transmitter output,

(ii) decoding means for decoding the first and second commands from the encoded AC voltage received at said ballast input, and

(iii) control means, responsive to said decoding means, for adjusting the light level of the lamp in the direction corresponding to the command decoded by said decoding means.

29. A system according to claim 28, wherein said control means, in response to the decoding of one of said first and second commands, changes the light level of the lamp by a fixed incremental amount.

30. A system according to claim 29, wherein for an AC voltage in which the fundamental period includes a negative half cycle and a positive half cycle, said transmitter encoding means imposes said perturbation during one of (i) said positive half cycle and (ii) said negative half-cycle.

31. A system according to claim 30, wherein the perturbation encoded by said encoding means is a phase cut.

32. A system according to claim 31, wherein said phase cut has a phase angle of less than about 45 degrees.

33. A system according to claim 31, wherein said phase cut has a phase angle of about 30 degrees.

34. A system according to claim 31, wherein within a subsequent control period a command indicative of no light level change is encoded by said encoding means by not imposing any said perturbations within the control period.

35. A system according to claim 29, wherein within a subsequent control period a command indicative of no light level change is encoded by said encoding means by not imposing any said perturbations within the control period.

36. A system according to claim 28, wherein said ballast input is receptive of an AC power supply voltage for powering said ballast, and said voltage signal encoded by said transmitter is said power AC power supply voltage.

37. A system for communicating control signals for controlling the operation of an electric lamp, said system comprising:

A) a transmitter for generating control signals, said transmitter comprising;

(i) means for receiving a voltage signal having a waveform with a fundamental period,

(ii) encoding means for encoding each control signal by imposing a pre-selected perturbation on said voltage signal a first number of times to indicate a first command to increase the light level or a second, different number of times to indicate a second command to decrease the light level of the lamp within a control period comprised of a fixed number of fundamental periods, wherein the perturbation does not significantly change the shape of the waveform; and

B) a receiver comprising;

(i) an input for receiving the control signals from said transmitter,

(ii) decoding means for decoding said control signals encoded by said transmitter, and

(iii) signal generating means for generating a signal corresponding to a decoded command.

38. A system according to claim 37, further including (i) means for operating the electric lamp and (ii) means, responsive to said signal generating means, for adjusting the light level of the lamp corresponding to the decoded command.

39. A system according to claim 38, wherein said perturbation is a phase cut.

40. A system according to claim 38, wherein said encoding means imposes a phase cut of substantially the same phase angle on every fundamental period having said phase cut.

41. A system according to claim 38, wherein said encoding means imposes substantially the same perturbation in every fundamental period having said perturbation.

42. A system according to claim 38, wherein within a subsequent control period a control signal indicative of no change in lamp operation is encoded by said encoding means by not imposing any perturbations within the control period.

43. A controller for generating signals to control an electric lamp, said controller comprising:

(i) means for providing a voltage signal having a waveform with a fundamental period, and

(ii) encoding means for encoding control signals in a control period comprised of a fixed number of fundamental periods, each control signal being encoded by said encoding means imposing a pre-selected perturbation on the voltage signal a first number of times to indicate a first command to increase the light level or a second, different number of times to indicate a second command to decrease the light level of the lamp within said control period, wherein the perturbation does not significantly change the shape of the waveform.

44. A controller according to claim 43, wherein said perturbation is a phase cut with a pre-selected phase angle.

45. A controller according to claim 43, wherein within a subsequent control period a control signal indicating no change in the operation of the lamp is encoded by said encoding means not imposing said perturbation within said control period.

46. A controller according to claim 43, wherein said voltage signal is a sinusoidal AC mains voltage.

47. A lamp controller for use with a coded-type remote controller, said ballast comprising:

(i) an input for receiving a voltage signal from the coded remote controller, the voltage signal having a waveform with a fundamental period and commands encoded therein, each command being encoded by a respective occurrence signature of pre-selected perturbation in a control period of a predetermined fixed number of fundamental periods, wherein the perturbation does not significantly change the shape of the waveform;

(ii) decoding means for detecting, within each control period, a respective occurrence signature of the pre-selected perturbation for the control commands; and

(iii) means, responsive to said decoding means, for controlling operation of the electric lamp in a manner corresponding to a decoded command.

48. A lamp controller according to claim 47, wherein said decoding means includes means for differentiating said voltage signal to detect said perturbations.

49. A lamp controller according to claim 47, wherein said input includes a pair of terminals for receiving an AC power line voltage including said control commands, a full bridge rectifier connected to said terminals for providing a full wave rectified DC signal, said decoding means decoding said control commands from said full-wave rectified DC signal.