Electronic ballast with interface circuitry for multiple dimming inputs

• US 5,691,605 A
• Filed: 08/09/1995
• Issued: 11/25/1997
• 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, Xia, Yongping, Jayaraman, Raj, Zhu, Joshua
• Primary Examiner(s): Pascal, Robert
• Assistant Examiner(s): SHINGLETON, MICHAEL B
• Application Number:
  US08/512,868
• Time in Patent Office: 839 Days
• Field of Search: 315/307, 315/DIG. 4, 315/224, 315/308, 315/DIG. 7, 315/324, 315/292, 315/293, 315/314, 315/316
• US Class Current: 315/307
• CPC Class Codes: H05B 41/2855 against abnormal lamp operating conditions
• CPC Class Codes: H05B 41/2985 against abnormal lamp operating conditions
• CPC Class Codes: H05B 41/36 Controlling
• CPC Class Codes: H05B 41/3921 with possibility of light intensity variations
• CPC Class Codes: H05B 41/3924 by phase control, e.g. using a triac H05B41/3922 takes precedence
• CPC Class Codes: H05B 47/185 via power line carrier transmission
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
• CPC Class Codes: Y10S 315/04 Dimming circuit for fluorescent lamps

Abstract

A lamp controller includes an interface circuit, or receiver, which receives an input signal and decodes control signals supplied from a transmitting device, such as a power line wall controller, according to at least two of the following communication techniques: phase angle control, step control, and coded control. The receiver tests the input signal and identifies which type of control technique is employed by the wall controller connected to the lamp controller. The receiver then decodes the control command from the input signal. In a disclosed embodiment, the lamp controller is gas discharge lamp dimming ballast having a two wire input for connection to the hot dimmed and neutral leads of the power line controller. The ballast has an improved topology in which a pre-conditioner supplies a substantially constant DC voltage to a ballast stage including an inverter, a resonant tank output and a control circuit. The dim signal output by the receiver is independent of the DC rail voltage and, in combination with the maintenance of a substantially constant DC rail voltage, permits of improved dimming control while providing the ease of installation of a two wire ballast.

Claims

1. A controller for an electric lamp, comprising:

a) a receiver for receiving an "input signal carrying control commands", said input signal having a fundamental period with a nominal voltage waveform, said receiver including decoding means for decoding control commands present in the input signal according to at least two of;

(i) a first control technique wherein commands are indicated by the phase angle of a phase angle cut in the nominal waveform;

(ii) a second control technique wherein commands are indicated by the number of fundamental periods between start and stop points of the command, the stop and start points being fundamental periods having a nominal voltage less than the nominal waveform; and

(iii) a third control technique wherein commands are indicated by an occurrence signature of a pre-selected perturbation in the nominal waveform occurring within a control period of a pre-selected number of fundamental periods; and

b) means for controlling the operation of the electric lamp in response to the decoded command.

2. A lamp controller according to claim 1, wherein said decoding means includes means for decoding commands from each of said three control techniques.

3. A lamp controller according to claim 2, wherein:

said decoding means includes first means for decoding control commands according to said first control technique, second means for decoding control commands according to said second control technique, third means for decoding control commands according to said third control technique, and identifying means for identifying the control technique of commands encoded according to any of said first, second and third techniques and for activating the respective one of said first, second and third means corresponding to the control technique identified by said identifying means.

4. A lamp controller according to claim 3, wherein said decoding means includes means for generating a first detection signal for each occurrence of (i) a said phase cut in said first control technique and (ii) a said perturbation in said third control technique.

5. A lamp controller according to claim 4, wherein said means for generating said first detection signal includes means for differentiating the input signal.

6. A lamp controller according to claim 4, wherein said means for generating said first detection signal generates a said first detection signal when said perturbation for said third control technique is a phase cut.

7. A lamp controller according to 4, wherein said identifying means first tests for the presence of control commands according to said first control technique by counting the number of first detection signals generated in a first pre-determined time period.

8. A lamp controller according to claim 7, wherein in the absence of control commands according to said first control technique, said identifying means then tests for the presence of control commands according to said second technique;

if the control commands according to said second technique are identified, said identifying means activates said second means of said decoding means and if control commands according to said second technique are not identified, said identifying means activates said third means of said decoding means.

9. A lamp controller according to claim 8, wherein said identifying means includes means for generating a second detection signal in response to the presence of a said start and stop point according to said second control technique.

10. A lamp controller according to claim 9, wherein said identifying means tests for the presence of commands according to said second control technique by counting the number of said second detection signals generated in a second pre-determined time period.

11. A lamp controller according to claim 10, wherein said means for controlling controls a gas discharge lamp.

12. A lamp controller according to claim 10, wherein said means for controlling controls a low pressure mercury vapor fluorescent lamp.

13. A lamp controller according to claim 12, wherein said controller includes power inputs for receiving an AC power signal for powering said controller, and said receiver is coupled to said power inputs for receiving control commands carried by said AC power signal.

14. A lamp controller according to claim 13, wherein said nominal waveform is sinusoidal and said fundamental period is a half-cycle of a full-wave rectified sinusoidal signal.

15. A lamp controller according to claim 2, wherein said decoding means includes means for differentiating the input signal.

16. A lamp controller according to claim 1, wherein said means for controlling controls a gas discharge lamp.

17. A lamp controller according to claim 1, wherein said means for controlling controls a low pressure mercury vapor fluorescent lamp.

18. A lamp controller according to claim 1, wherein said decoding means decodes perturbations according to said third technique in the form of a phase cut in the nominal waveform of the input signal.

19. A lamp controller according to claim 1, wherein said nominal waveform is sinusoidal and said fundamental period is a half-cycle of a full-wave rectified sinusoidal signal.

20. A lamp controller according to claim 1, wherein said decoding means includes identifying means for identifying the control technique of control commands on said input signal as either one of any two control techniques of said first, second and third control techniques.

21. A lamp controller according to claim 1, wherein said controller includes power inputs for receiving an AC power signal for powering said controller, and said receiver is coupled to said power inputs for receiving control commands carried by said AC power signal.

22. A lamp controller according to claim 1, further comprising:

a pair of mains input terminals for receiving an AC mains voltage carrying said input signal, said receiver being coupled to said mains input terminals for receiving said input signal;

said means for controlling the operation of the electric lamp comprising;

(a) ballasting means for providing electrical power to a gas discharge lamp, said ballasting means including (i) a DC input at which a substantially constant DC voltage is received, (ii) a dim input separate from said DC input for receiving a dimming signal from said receiver and (iii) first control means for controlling the electrical power supplied to the gas discharge lamp at a level corresponding to a characteristic of the dimming signal; and

(b) power supply means connected to said mains input terminals for supplying the substantially constant DC voltage to said DC input of said ballasting means; and

said dimming signal supplied by said receiver being independent of the DC voltage provided by said power supply means at said DC input of said ballasting means.

23. A ballast according to claim 22, further comprising rectifier means connected to said mains input terminals for providing a full-wave rectified DC output voltage to said power supply means and said receiver, and wherein the fundamental period of the input signal decoded by said receiver is the sinusoidal half-cycle of the rectified DC output voltage from said rectifier means.

24. A lamp ballast according to claim 23, wherein said ballasting means includes (i) inverting means, connected to said DC inputs, said inverting means being adjustable by said first control means to control the power supplied to the discharge lamp, and (ii) said first control means comprises means for deriving a voltage signal representing the lamp power, and first feedback means for adjusting said inverter so that the voltage of the lamp power signal and said dimming signal are equal.

54. A lamp controller according to claim 1 further comprising a power supply for deriving a substantially constant DC voltage, wherein said controlling means comprises a ballast circuit which receives said DC voltage as its operating voltage, wherein said receiver derives a dimming signal which is independent of said constant DC voltage, and

means for supplying said dimming signal to a dim control input of the ballast circuit.

25. A gas discharge lamp ballast for use with a power line controller, said ballast comprising:

only two mains input terminals for connection to a common line and a hot dimmed line from a power line controller, the hot dimmed line carrying an AC mains voltage including dimming control commands encoded by the power line controller;

a full bridge rectifier connected to the two mains input terminals for providing a full wave rectified DC output voltage, the rectified DC output voltage including the control commands encoded by the power line controller and having a peak voltage;

a preconditioner circuit connected to the full-bridge rectifier, said pre-conditioner circuit including an up converter for providing a DC supply voltage at a level higher than the peak voltage of the rectified DC output voltage from said full-bridge rectifier;

an inverter circuit receptive of the DC supply voltage from said pre-conditioner circuit, said inverter converting the DC supply voltage from said preconditioner to a high frequency AC voltage having a frequency substantially greater than the frequency of the AC mains supply;

a resonant tank output circuit receptive of the high frequency AC inverter output voltage, said output circuit having lamp connection terminals for connection to a gas discharge lamp, said output circuit providing a substantially sinusoidal lamp current to a gas discharge lamp connected at said lamp terminals;

a control circuit connected to the inverter for controlling the AC inverter output voltage, said control circuit having (i) means for receiving a dimming signal separate from the DC output of the pre-conditioner circuit, (ii) means for sensing the power supplied to the gas discharge lamp, and (iii) means for adjusting the AC inverter output frequency fed to said resonant tank output circuit to thereby control the electrical power supplied to the gas discharge lamp at a level corresponding to the voltage of the dimming signal; and

a dimming interface circuit receptive of the encoded rectified DC output voltage from said full-bridge rectifier, said dimming interface circuit including decoding means for decoding control commands present in the input signal according to any one of at least two of the following;

(i) a first control technique wherein commands are indicated by the phase angle of a phase angle cut in the nominal waveform;

(ii) a second control technique wherein commands are indicated by the number of fundamental periods between start and stop points of the command, the stop and start points being fundamental periods having a nominal voltage less than the nominal waveform; and

(iii) a third control technique wherein commands are indicated by an occurrence signature of a pre-selected perturbation in the nominal waveform occurring within a control period of a pre-selected number of fundamental periods; and

said dimming interface circuit further including means coupled to said decoding means for generating a said dimming signal corresponding to the dimming command decoded by said decoding means.

26. A ballast according to claim 25, wherein said preconditioner circuit maintains said DC voltage at a substantially constant level.

27. A receiver for use with a controller for an electric lamp, said receiver comprising:

1) input means for receiving an input signal carrying control commands, said input signal having a fundamental period with a nominal voltage waveform; and

2) decoding means for decoding control commands present in the input signal according to at least two of;

(i) a first control technique wherein commands are indicated by the phase angle of a phase angle cut in the nominal waveform;

(ii) a second control technique wherein commands are indicated by the number of fundamental periods between start and stop points of the command, the stop and start points being comprising fundamental periods having a nominal voltage less than the nominal waveform; and

(iii) a third control technique wherein commands are indicated by an occurrence signature of a pre-selected perturbation in the nominal waveform within a control period of a pre-selected number of fundamental periods.

28. A receiver according to claim 27, wherein said decoding means decodes control commands from any of said three control techniques.

29. A receiver according to claim 28, wherein:

said decoding means includes first means for decoding control commands according to said first control technique, second means for decoding control commands according to said second control technique, third means for decoding control commands according to said third control technique, and identifying means for identifying the control technique of commands according to any of said first, second and third techniques and for activating the respective one of said first, second and third means for decoding corresponding to the control technique identified by said identifying means.

30. A receiver according to claim 29, wherein said decoding means includes means for generating a first detection signal for each occurrence of (i) a said phase cut in said first control technique and (ii) a said perturbation in said third control technique.

31. A receiver according to claim 30, wherein said means for generating said first detection signal includes means for differentiating the input signal.

32. A receiver according to claim 30, wherein said means for generating said first detection signal generates a said first detection signal when said perturbation for said third control technique is a phase cut.

33. A receiver according to claim 30, wherein said identifying means first tests for the presence of control commands according to said first control technique by counting the number of first detection signals generated in a first pre-determined time period.

34. A receiver according to claim 33, wherein in the absence of control commands according to said first control technique, said identifying means then tests for the presence of control commands according to said second technique;

if the control commands according to said second technique are identified, said identifying means activates said second means for decoding and if control commands according to said second technique are not identified, said identifying means activates said third means of said decoding means.

35. A receiver according to claim 34, wherein said identifying means includes means for generating a second detection signal in response to the presence of a said start and stop point according to said second control technique.

36. A receiver according to claim 35, wherein said identifying means tests for the presence of commands according to said second control technique by counting the number of said second detection signals generated in a second pre-determined time period.

37. A receiver according to claim 36, further including means for generating a control signal corresponding to a command decoded by said decoding means.

38. A receiver according to claim 36, wherein said nominal waveform is sinusoidal and said fundamental period is a half-cycle of a full-wave rectified sinusoidal signal.

39. A receiver according to claim 27, wherein said decoding means includes means for differentiating the input signal.

40. A receiver according to claim 27, wherein said decoding means decodes perturbations according to said third technique in the form of a phase cut in the nominal waveform of the control signal.

41. A receiver according to claim 27, wherein said decoding means includes identifying means for identifying the control technique of control commands on said input signal as either of said any two control techniques of said first, second and third control techniques.

42. A method of controlling an electric lamp, said method comprising the steps of:

a) receiving an input signal carrying control commands, said signal having a fundamental period with a nominal voltage waveform;

b) identifying the presence in said input signal of control commands according to any two of;

(i) a first control technique wherein commands are indicated by the magnitude of a phase angle cut in the nominal waveform;

(ii) a second control technique wherein commands are indicated by the number of fundamental of the between start and stop points of the command, the stop and start points being fundamental periods having a nominal voltage less than the nominal waveform; and

(iii) a third control technique wherein commands are indicated by an occurrence signature of a pre-selected perturbation in the nominal waveform within a control period of a pre-selected number of fundamental periods;

c) decoding a control command present according to the identified one of said techniques; and

d) controlling the operation of the electric lamp in response to the decoded command.

43. A method according to claim 42, wherein said identifying and decoding steps include identifying and decoding commands from any of said three control techniques.

44. A method according to claim 43, wherein said decoding step includes generating a first detection signal for each occurrence of (i) a said phase cut in said first control technique and (ii) a said perturbation in said third control technique.

45. A method according to claim 44, wherein said step of generating said first detection signal includes the step of differentiating the input signal.

46. A method according to 45, wherein said identifying step first tests for the presence of control commands according to said first control technique by counting the number of first detection signals generated in a pre-determined time period.

47. A method according to claim 46, wherein said identifying step, in the absence of control commands according to said first control technique, includes the step of testing for the presence of control commands according to said second technique.

48. A method according to claim 47, wherein said identifying step includes the step of generating a second detection signal in response to the presence of a said start and stop point according to said second technique.

49. A method according to claim 48, wherein said identifying step includes the step of testing for the presence of commands according to said second control technique by counting the number of said second detection signals generated in a second pre-determined time period.

50. A method according to claim 43, wherein said nominal waveform is sinusoidal and said fundamental period is a half-cycle of a full-wave rectified sinusoidal signal.

51. A method according to claim 42, wherein said step of controlling an electric lamp includes controlling a gas discharge lamp.

52. A method according to claim 42, wherein said step of controlling an electric lamp includes controlling a low pressure mercury vapor fluorescent lamp.

53. A method according to claim 42, wherein said input signal received is a sinusoidal AC mains signal for powering a lamp controller.