Digital Driver Apparatus, Method and System for Solid State Lighting

• US 20090079355A1
• Filed: 09/21/2007
• Published: 03/26/2009
• Est. Priority Date: 09/21/2007
• Status: Active Grant

• Current Assignee: Chemtron Research LLC (Intellectual Ventures LLC)
• Original Assignee: Exclara, Inc. (Million Star Technology Ltd.)
• Inventors: Rodriguez, Harry, Shteynberg, Anatoly, Eason, Mark, Zhou, Dongsheng, Nguyen, Lanh
• Granted Patent: US 7,880,400 B2
• Time in Patent Office: Days
• US Class Current: 315/246
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/375 using buck topology

Abstract

An apparatus, method and system are provided for controlling the solid state lighting, such as LEDs. An exemplary apparatus comprises: a switch for switching electrical current through the LEDs, a current sensor; a first comparator adapted to determine when a switch electrical current has reached a first predetermined threshold; a second comparator adapted to determine when the switch electrical current has reached a predetermined average current level; and a controller. The controller is adapted to turn the switch into an on state and an off state, to determine a first on time period as a duration between either a detection of a second predetermined current threshold or the turning the switch into the on state, and the detection of the predetermined average current level; to determine a second on time period as a duration between the detection of the predetermined average current level and the detection of the first predetermined current threshold; and to determine an on time period of the switch as substantially proportional to a sum of the first on time period and the second on time period. Additional exemplary embodiments utilize a difference between the first and second on time periods to generate an error signal to adjust the on time period of the switch.

Claims

1. A method of controlling solid state lighting, the solid state lighting coupled to a switch providing an electrical current path, and the solid state lighting having an electrical current, the method comprising:

turning the switch into an on state;

detecting when the electrical current has reached a predetermined average current level;

detecting when the electrical current has reached a first predetermined current threshold;

determining a first on time period as a duration between detection of a second predetermined current level or turning the switch into the on state and the detection of the predetermined average current level;

determining a second on time period as a duration between the detection of the predetermined average current level and the detection of the first predetermined current threshold; and

determining an on time period of the switch as substantially proportional to a sum of the first on time period and the second on time period.

2. The method of claim 1, further comprising:

when the on time period has elapsed, turning the switch into an off state.

3. The method of claim 2, further comprising:

subsequent to turning the switch into the off state, when a fixed time period has elapsed from having turned the switch into the on state, again turning the switch into the on state and repeating the detection and determination steps.

4. The method of claim 3, further comprising:

generating an error signal as a difference between the second on time period and the first on time period.

6. The method of claim 2, further comprising:

when a current off time period has elapsed, turning the switch into the on state and repeating the detection and determination steps.

7. The method of claim 6, further comprising:

determining the current off time period of the switch as a function of the first on time period and the second on time period.

8. The method of claim 6, further comprising:

determining the current off time period of the switch as a function of the first on time period, the second on time period, and a previous off time period.

9. The method of claim 6, further comprising:

determining the current off time period of the switch as;

$T_{\mathrm{OFF}}<br><br>\left(K+1\right)\approx <br><br>\frac{2·<br><br>T_{\mathrm{ON}<br><br><br><br>2}<br><br>\left(K\right)·<br><br>T_{\mathrm{OFF}}<br><br>\left(K\right)}{T_{\mathrm{ON}<br><br><br><br>1}<br><br>\left(K+1\right)+T_{\mathrm{ON}<br><br><br><br>2}<br><br>\left(K\right)},$

in which T_OFF(K+1) is the current off time period, T_ON2(K) is a previous second on time period, T_OFF(K) is a previous off time period, and T_ON1(K+1) is a current first on time period.

10. The method of claim 6, further comprising:

determining the current off time period of the switch as;

$T_{\mathrm{OFF}}<br><br>\left(K+1\right)\approx <br><br>\frac{\left({T_{\mathrm{ON}<br><br><br><br>1}<br><br>\left(K\right)}_A+T_{\mathrm{ON}<br><br><br><br>2}<br><br>\left(K\right)\right)·<br><br>T_{\mathrm{OFF}}<br><br>\left(K\right)}{T_{\mathrm{ON}<br><br><br><br>1}<br><br>\left(K+1\right)+T_{\mathrm{ON}<br><br><br><br>2}<br><br>\left(K\right)},$

in which T_OFF(K+1) is the current off time period, T_ON1(K)_A is a previous first on time period determined using the detection of the second predetermined current level, T_ON2(K) is a previous second on time period, T_OFF(K) is a previous off time period, and T_ON1(K+1) is a current first on time period.

11. The method of claim 6, further comprising:

determining the current off time period of the switch as a function of a current first on time period, a previous second on time period, and a previous off time period.

12. The method of claim 6, further comprising:

determining the current off time period of the switch as a function of a current first on time period, a previous first on time period, a previous second on time period, and a previous off time period.

13. The method of claim 6, further comprising:

adjusting the current off time period to provide that the first on time period is substantially equal to the second on time period.

14. The method of claim 6, further comprising:

decreasing the current off time period proportionally to a driving gate rising edge time period.

15. The method of claim 1, further comprising:

decreasing the on time period proportionally to a driving gate falling edge time period and a comparator falling edge time period.

16. The method of claim 1, further comprising:

determining a blanking time interval following turning the switch into the on state.

17. The method of claim 16, further comprising:

ignoring the detection of the second predetermined current threshold, the detection of the predetermined average current level, or the detection of the first predetermined current threshold during the blanking time interval.

18. The method of claim 16, further comprising:

determining the blanking time interval as proportional to a gate rising edge time period and a transient current time period.

19. The method of claim 16, further comprising:

determining the blanking time interval as proportional to a gate rising edge time period and detection of the predetermined average current level.

20. The method of claim 1, further comprising:

adjusting a brightness level of the solid state lighting by using at least two different and opposing electrical biasing techniques.

21. The method of claim 1, further comprising:

adjusting a brightness level of the solid state lighting by using a hysteresis of at least two electrical current amplitude levels and at least two electrical current duty cycle ratios.

22. The method of claim 1, further comprising:

adjusting the second on time period proportionally to a driving gate falling edge time period.

23. The method of claim 1, further comprising:

decreasing the second on time period proportionally to a driving gate falling edge time period and a comparator falling edge time period.

24. The method of claim 1, further comprising:

detecting when the electrical current has reached the second predetermined current threshold.

25. The method of claim 1, wherein the solid state lighting comprises at least one light emitting diode.

26. The method of claim 25, wherein the at least one light emitting diode is coupled to a power converter, and wherein the electrical current detections occur at a comparatively low side of the power converter.

27. The method of claim 1, wherein the solid state lighting comprises a plurality of arrays of a plurality of series-connected light emitting diodes, and each array of the plurality of arrays further coupled to a corresponding switch providing an electrical current path.

28. The method of claim 27, further comprising:

separately determining a corresponding first on time period, a corresponding second on time period, and a corresponding on time period as substantially proportional to the sum of the corresponding first on time period and the corresponding second on time period for each array of the plurality of arrays.

29. The method of claim 28, further comprising:

when the corresponding on time period has elapsed, separately turning the corresponding switch into the off state.

30. The method of claim 29, further comprising:

separately determining a corresponding off time period for each array of the plurality of arrays.

31. The method of claim 29, further comprising:

interleaving the corresponding on time periods of the corresponding switches of the plurality of arrays.

32. The method of claim 27, further comprising:

successively switching electrical current to each array of the plurality of arrays for the corresponding on time period.

5. The method of claim 5, further comprising:

adjusting the on time period proportionally to the error signal.

33. An apparatus for controlling solid state lighting, the apparatus comprising:

a switch couplable to the solid state lighting;

a first comparator adapted to determine when a switch electrical current has reached a first predetermined current threshold;

a second comparator adapted to determine when the switch electrical current has reached a predetermined average current level; and

a controller coupled to the first comparator and to the second comparator, the controller adapted to turn the switch into an on state and an off state, to determine a first on time period as a duration between either a detection of a second predetermined current threshold or the turning the switch into the on state, and the detection of the predetermined average current level;

to determine a second on time period as a duration between the detection of the predetermined average current level and the detection of the first predetermined current threshold; and

to determine an on time period of the switch as substantially proportional to a sum of the first on time period and the second on time period.

34. The apparatus of claim 33, wherein the controller is further adapted, when the on time period has elapsed, to turn the switch into an off state.

35. The apparatus of claim 34, wherein the controller is further adapted, subsequent to turning the switch into the off state and when a fixed time period has elapsed from having turned the switch into the on state, to turn the switch into the on state.

36. The apparatus of claim 35, wherein the controller is further adapted to generate an error signal as a difference between the second on time period and the first on time period.

37. The apparatus of claim 36, wherein the controller is further adapted to adjust the on time period proportionally to the error signal.

38. The apparatus of claim 34, wherein the controller is further adapted to determine a current off time period of the switch as a function of the first on time period and the second on time period.

39. The apparatus of claim 34, wherein the controller is further adapted to determine a current off time period of the switch as a function of the first on time period, the second on time period, and a previous off time period.

40. The apparatus of claim 34, wherein the controller is further adapted to determine a current off time period of the switch as:

$T_{\mathrm{OFF}}<br><br>\left(K+1\right)\approx <br><br>\frac{2·<br><br>T_{\mathrm{ON}<br><br><br><br>2}<br><br>\left(K\right)·<br><br>T_{\mathrm{OFF}}<br><br>\left(K\right)}{T_{\mathrm{ON}<br><br><br><br>1}<br><br>\left(K+1\right)+T_{\mathrm{ON}<br><br><br><br>2}<br><br>\left(K\right)},$

in which T_OFF(K+1) is the current off time period, T_ON2(K) is a previous second on time period, T_OFF(K) is a previous off time period, and T_ON1(K+1) is a current first on time period.

41. The apparatus of claim 34, wherein the controller is further adapted to determine a current off time period of the switch as a function of a current first on time period, a previous second on time period, and a previous off time period.

42. The apparatus of claim 34, wherein the controller is further adapted to determine a current off time period of the switch as a function of a current first on time period, a previous first on time period, a previous second on time period, and a previous off time period.

43. The apparatus of claim 34, wherein the controller is further adapted to adjust a current off time period to provide that the first on time period is substantially equal to the second on time period.

44. The apparatus of claim 33, further comprising:

a gate driver circuit coupled between the controller and the switch, and wherein the controller is adapted to turn the switch on and to turn the switch off by generating a corresponding signal to the gate driver circuit.

45. The apparatus of claim 44, wherein the controller is further adapted to decrease a current off time period proportionally to a rising edge time period of the gate driver circuit.

46. The apparatus of claim 44, wherein the controller is further adapted to decrease the on time period proportionally to a falling edge time period of the gate driver circuit and a falling edge time period of the first comparator.

47. The apparatus of claim 44, wherein the controller is further adapted to adjust the second on time period proportionally to a falling edge time period of the gate driver circuit.

48. The apparatus of claim 44, wherein the controller is further adapted to decrease the second on time period proportionally to a falling edge time period of the gate driver circuit and a falling edge time period of the first comparator.

49. The apparatus of claim 44, wherein the controller is further adapted to determine a blanking time interval following turning the switch into the on state.

50. The apparatus of claim 49, further comprising:

a third comparator adapted to determine when the electrical current has reached the second predetermined current threshold.

51. The apparatus of claim 50, further comprising:

a current sensor coupled to the first, second and third comparators and to the switch.

52. The apparatus of claim 51, wherein the current sensor is embodied as a resistive circuit element.

53. The apparatus of claim 50, wherein the controller is further adapted to determine a current off time period of the switch as:

$T_{\mathrm{OFF}}<br><br>\left(K+1\right)\approx <br><br>\frac{\left({T_{\mathrm{ON}<br><br><br><br>1}<br><br>\left(K\right)}_A+T_{\mathrm{ON}<br><br><br><br>2}<br><br>\left(K\right)\right)·<br><br>T_{\mathrm{OFF}}<br><br>\left(K\right)}{T_{\mathrm{ON}<br><br><br><br>1}<br><br>\left(K+1\right)+T_{\mathrm{ON}<br><br><br><br>2}<br><br>\left(K\right)},$

in which T_OFF(K+1) is the current off time period, T_ON1(K)_A is a previous first on time period determined using the detection of the second predetermined current level, T_ON2(K) is a previous second on time period, T_OFF(K) is a previous off time period, and T_ON1(K+1) is a current first on time period.

54. The apparatus of claim 50, wherein the controller is further adapted to ignore the detection of the second predetermined current threshold, the detection of the predetermined average current level, or the detection of the first predetermined current threshold during the blanking time interval.

55. The apparatus of claim 50, wherein the controller is further adapted to determine the blanking time interval as proportional to a rising edge time period of the gate driver circuit and a transient current time period.

56. The apparatus of claim 50, wherein the controller is further adapted to determine the blanking time interval as proportional to a rising edge time period of the gate driver circuit and detection of the predetermined average current level.

57. The apparatus of claim 33, wherein the controller is further adapted to adjust a brightness level of the solid state lighting by generating control signals to a driver circuit for using at least two different and opposing electrical biasing techniques.

58. The apparatus of claim 33, wherein the controller is further adapted to adjust a brightness level of the solid state lighting by generating control signals to a driver circuit to use a hysteresis of at least two electrical current amplitude levels and at least two electrical current duty cycle ratios.

59. The apparatus of claim 33, wherein the solid state lighting comprises at least one light emitting diode.

60. The apparatus of claim 59, wherein the at least one light emitting diode is coupled to a power converter, and wherein the first and second comparators are coupled to a current sensor at a comparatively low side of the power converter.

61. The apparatus of claim 33, wherein the solid state lighting comprises a plurality of arrays of a plurality of series-connected light emitting diodes, each array of the plurality of arrays is further coupled to a corresponding switch, and wherein the controller is further adapted to turn each corresponding switch into an on state and an off state.

62. The apparatus of claim 61, wherein the controller is further adapted to separately determine a corresponding first on time period, a corresponding second on time period, and a corresponding on time period as substantially proportional to the sum of the corresponding first on time period and the corresponding second on time period for each array of the plurality of arrays.

63. The apparatus of claim 62, wherein the controller is further adapted, when the corresponding on time period has elapsed, to separately turn the corresponding switch into an off state.

64. The apparatus of claim 62, wherein the controller is further adapted to separately determine a corresponding off time period for each array of the plurality of arrays.

65. The apparatus of claim 62, wherein the controller is further adapted to interleave the corresponding on time periods of the corresponding switches of the plurality of arrays.

66. The apparatus of claim 62, wherein the controller is further adapted to successively turn into an on state each corresponding switch for each array of the plurality of arrays for the corresponding on time period.

67. The apparatus of claim 33, further comprising:

a reference voltage generator coupled to the first and second comparators and adapted to provide reference voltages respectively corresponding to the first predetermined current threshold and to the predetermined average current level.

68. The apparatus of claim 33, further comprising:

an input-output interface coupled to the controller and adapted to receive an input control signal.

69. The apparatus of claim 33, wherein the apparatus is coupled to a DC-DC power converter receiving a DC input voltage or coupled to AC-DC power converter receiving a rectified AC input voltage.

70. A solid state lighting system, the system couplable to a power source, the system comprising:

a plurality of arrays of series-connected light emitting diodes;

a plurality of switches, a corresponding switch of the plurality of switches coupled to each the array of the plurality of arrays of light emitting diodes;

at least one corresponding first comparator adapted to determine when a corresponding switch electrical current has reached a corresponding first predetermined current threshold;

at least one corresponding second comparator adapted to determine when the corresponding switch electrical current has reached a corresponding predetermined average current level; and

at least one controller coupled to the corresponding first comparator and to the corresponding second comparator, the controller adapted to turn the corresponding switch into an on state and an off state, to determine a corresponding first on time period as a duration between either a detection of a corresponding second predetermined current threshold or the turning the corresponding switch into the on state, and the detection of the corresponding predetermined average current level;

to determine a corresponding second on time period as a duration between the detection of the corresponding predetermined average current level and the detection of the corresponding first predetermined current threshold; and

to determine a corresponding on time period of the corresponding switch as substantially proportional to a sum of the corresponding first on time period and the corresponding second on time period.

71. The system of claim 70, wherein the at least one controller is further adapted, when the corresponding on time period has elapsed, to turn the corresponding switch into an off state.

72. The system of claim 70, wherein the at least one controller is further adapted, subsequent to turning the corresponding switch into the off state and when a fixed time period has elapsed from having turned the corresponding switch into the on state, to turn the corresponding switch into the on state.

73. The system of claim 72, wherein the at least one controller is further adapted to generate a corresponding error signal as a difference between the corresponding second on time period and the corresponding first on time period.

74. The system of claim 73, wherein the at least one controller is further adapted to adjust the corresponding on time period proportionally to the corresponding error signal.

75. The system of claim 70, wherein the at least one controller is further adapted to determine a corresponding current off time period of the corresponding switch as a function of the corresponding first on time period and the corresponding second on time period.

76. The system of claim 70, wherein the at least one controller is further adapted to determine a corresponding current off time period of the corresponding switch as a function of the corresponding first on time period, the corresponding second on time period, and a corresponding previous off time period.

77. The system of claim 70, wherein the at least one controller is further adapted to determine a corresponding current off time period of the corresponding switch as:

$T_{\mathrm{OFF}}<br><br>\left(K+1\right)\approx <br><br>\frac{2·<br><br>T_{\mathrm{ON}<br><br><br><br>2}<br><br>\left(K\right)·<br><br>T_{\mathrm{OFF}}<br><br>\left(K\right)}{T_{\mathrm{ON}<br><br><br><br>1}<br><br>\left(K+1\right)+T_{\mathrm{ON}<br><br><br><br>2}<br><br>\left(K\right)},$

in which T_OFF(K+1) is the corresponding current off time period, T_ON2(K) is a corresponding previous second on time period, T_OFF(K) is a corresponding previous off time period, and T_ON1(K+1) is a corresponding current first on time period.

78. The system of claim 70, wherein the at least one controller is further adapted to determine a corresponding current off time period of the corresponding switch as a function of a corresponding current first on time period, a corresponding previous second on time period, and a corresponding previous off time period.

79. The system of claim 70, wherein the at least one controller is further adapted to determine a corresponding current off time period of the corresponding switch as a function of a corresponding current first on time period, a corresponding previous first on time period, a corresponding previous second on time period, and a corresponding previous off time period.

80. The system of claim 70, wherein the at least one controller is further adapted to adjust a corresponding current off time period to provide that the corresponding first on time period is substantially equal to the corresponding second on time period.

81. The system of claim 70, further comprising:

at least one corresponding gate driver circuit coupled between the at least one controller and the corresponding switch, and wherein the at least one controller is adapted to turn the corresponding switch on and to turn the corresponding switch off by generating a corresponding signal to the corresponding gate driver circuit.

82. The system of claim 81, wherein the at least one controller is further adapted to decrease a corresponding current off time period proportionally to a rising edge time period of the at least one corresponding gate driver circuit.

83. The system of claim 81, wherein the at least one controller is further adapted to decrease the corresponding on time period proportionally to a falling edge time period of the at least one corresponding gate driver circuit and a falling edge time period of the at least one first comparator.

84. The system of claim 81, wherein the at least one controller is further adapted to adjust the corresponding second on time period proportionally to a falling edge time period of the at least one corresponding gate driver circuit.

85. The system of claim 81, wherein the at least one controller is further adapted to decrease the corresponding second on time period proportionally to a falling edge time period of the at least one corresponding gate driver circuit and a falling edge time period of the at least one first comparator.

86. The system of claim 81, wherein the at least one controller is further adapted to determine a corresponding blanking time interval following turning the corresponding switch into the on state.

87. The system of claim 86, further comprising:

at least one corresponding third comparator adapted to determine when the corresponding electrical current has reached the corresponding second predetermined current threshold.

88. The system of claim 87, wherein the at least one controller is further adapted to determine a corresponding current off time period of the corresponding switch as:

$T_{\mathrm{OFF}}<br><br>\left(K+1\right)\approx <br><br>\frac{\left({T_{\mathrm{ON}<br><br><br><br>1}<br><br>\left(K\right)}_A+T_{\mathrm{ON}<br><br><br><br>2}<br><br>\left(K\right)\right)·<br><br>T_{\mathrm{OFF}}<br><br>\left(K\right)}{T_{\mathrm{ON}<br><br><br><br>1}<br><br>\left(K+1\right)+T_{\mathrm{ON}<br><br><br><br>2}<br><br>\left(K\right)},$

in which T_OFF(K+1) is the corresponding current off time period, T_ON1(K)_A is a corresponding previous first on time period determined using the detection of the second predetermined current level, T_ON2(K) is a corresponding previous second on time period, T_OFF(K) is a corresponding previous off time period, and T_ON1(K+1) is a corresponding current first on time period.

89. The system of claim 87, wherein the at least one controller is further adapted to ignore the detection of the corresponding second predetermined current threshold, the detection of the corresponding predetermined average current level, or the detection of the corresponding first predetermined current threshold during the corresponding blanking time interval.

90. The system of claim 87, wherein the at least one controller is further adapted to determine the corresponding blanking time interval as proportional to a rising edge time period of the at least one corresponding gate driver circuit and a corresponding transient current time period.

91. The system of claim 87, wherein the at least one controller is further adapted to determine the corresponding blanking time interval as proportional to a rising edge time period of the at least one corresponding gate driver circuit and detection of the corresponding predetermined average current level.

92. The system of claim 70, wherein the at least one controller is further adapted to adjust a brightness level of at least one array of the plurality of arrays of light emitting diodes by generating control signals to a driver circuit for the at least one array for using at least two different and opposing electrical biasing techniques.

93. The system of claim 70, wherein the at least one controller is further adapted to adjust a brightness level of at least one array of the plurality of arrays of light emitting diodes by generating control signals to a driver circuit for the at least one array to use a hysteresis of at least two electrical current amplitude levels and at least two electrical current duty cycle ratios.

94. The system of claim 70, wherein each corresponding array of the plurality of arrays of light emitting diodes has a comparatively high voltage node and a comparatively low voltage node, and wherein the at least one first and second comparators are coupled via the corresponding switch to the comparatively low voltage node.

95. The system of claim 70, wherein the at least one controller is further adapted to interleave the corresponding on time periods of the corresponding switches of the plurality of arrays.

96. The system of claim 70, wherein the at least one controller is further adapted to successively turn into an on state each corresponding switch for each array of the plurality of arrays for the corresponding on time period.

97. The system of claim 70, further comprising:

at least one reference voltage generator coupled to the at least one corresponding first and second comparators and adapted to provide corresponding reference voltages respectively for the corresponding first predetermined current threshold and the corresponding predetermined average current level.

98. The system of claim 70, further comprising:

an input-output interface coupled to the at least one controller and adapted to receive an input control signal.

99. The system of claim 70, further comprising:

at least one rectifier couplable to the power source.

100. The system of claim 70, wherein the power source provides a DC input voltage or a rectified AC input voltage.

101. The system of claim 70, wherein when the power source provides a rectified AC input voltage, an electrical current through a corresponding switch is substantially zero when the rectified AC input voltage is below a selected or predetermined threshold.

102. The system of claim 70, wherein when the power source provides a rectified AC input voltage, the at least one controller is in an off state when the rectified AC input voltage is below a selected or predetermined threshold.

103. An apparatus for controlling solid state lighting, the apparatus comprising:

a switch couplable to the solid state lighting;

a current sensor coupled to the switch;

a first comparator adapted to determine when a switch electrical current has reached a first predetermined current threshold;

a second comparator adapted to determine when the switch electrical current has reached a predetermined average current level;

a third comparator adapted to determine when the switch electrical current has reached a second predetermined current threshold;

a reference voltage generator coupled to the first, second and third comparators and adapted to provide reference voltages respectively corresponding to the first predetermined current threshold, the second predetermined current threshold; and

to the predetermined average current level;

an input-output interface adapted to receive an input control signal; and

a controller coupled to the first, second and third comparators and to the input-output interface, the controller adapted to turn the switch into an on state and an off state, to determine a first on time period as a duration between either the detection of a second predetermined current threshold or the turning the switch into the on state, and the detection of the predetermined average current level;

to determine a second on time period as a duration between the detection of the predetermined average current level and the detection of the first predetermined current threshold;

to determine an on time period of the switch as substantially proportional to a sum of the first on time period and the second on time period;

to turn the switch into an off state when the on time period has elapsed; and

to determine a current off time period of the switch as a function of the first on time period, the second on time period, and a previous off time period.