LOW INTENSITY DIMMING CIRCUIT FOR AN LED LAMP AND METHOD OF CONTROLLING AN LED

• US 20140184076A1
• Filed: 12/27/2012
• Published: 07/03/2014
• Est. Priority Date: 12/27/2012
• Status: Active Grant

• Current Assignee: IDEAL Industries Lighting, LLC (Ideal Industries Incorporated)
• Original Assignee: Rudd Lighting, Inc.
• Inventors: Murphy, Matthew K.
• Granted Patent: US 9,661,706 B2
• Time in Patent Office: Days
• US Class Current: 315/121
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/14 using electrical feedback from LEDs or from LED modules
• CPC Class Codes: H05B 45/44 with an active control inside an LED matrix

Abstract

A driver is connectable to an external power supply and configured to output a variable driving current for one or more loads, such as LEDs. A low intensity dimming module is operable to divert some or all of the driving current away from the LEDs when a user selects a very low level of light intensity so that the driver has a constant minimum load. The low intensity dimming module prevents performance issues that commonly affect drivers under light load conditions.

Claims

1. A dimmable lighting device, comprising:

at least one light emitting diode (LED);

an LED driver configured to develop a driving current to power the at least one LED; and

a dimming control circuit comprising a shunt load, said dimming control circuit being configured to divert current from said at least one LED through said shunt load in response to the driving current being below a low intensity level.

2. The device of claim 1, wherein the level of the driving current is determined in accordance with a dimming control signal.

3. The device of claim 1, wherein the dimming control circuit is configured not to divert current from said at least one LED when said driving current is at or above the low intensity level.

4. The device of claim 3, wherein the LED driver is operable above a minimum current magnitude and wherein the low intensity level is greater than the minimum current magnitude.

5. The device of claim 1, wherein the at least one LED is powered by a portion of the driving current that is not diverted through said shunt load.

6. The device of claim 1, further including a junction box, wherein the dimming module is disposed within said junction box.

7. The device of claim 1, wherein the shunt load includes a resistor, and wherein power generated by the diverted current is dissipated as heat by the resistor.

8. The device of claim 7, wherein the shunt load further includes a transistor coupled to the resistor.

9. The device of claim 1, wherein the dimming control circuit is responsive to an input command signal.

10. The device of claim 9, wherein the input command signal is static.

11. The device of claim 10, wherein the dimming control circuit directly controls a magnitude of current through the at least one LED.

12. The module of claim 10, wherein the shunt load receives a current having a magnitude regulated by the dimming control circuit.

13. The device of claim 10, wherein the input command signal is dynamic.

14. The device of claim 1, wherein the at least one LED receives a current magnitude represented by a response curve having a step.

15. A dimming circuit for a lighting device, comprising:

first current path configured to be connected to a light emitting diode (LED) driver, wherein the LED driver is configured to develop a driving current to power at least one LED;

a second current path connected to the first current path, wherein the second current path includes a shunt load; and

a dimming control circuit that causes current to flow in the shunt load and controls current flow through one of the first current path and the second current path when a commanded driving current is less than or equal to a low intensity level.

16. The circuit of claim 15, wherein the shunt load includes a resistor and a junction transistor, and wherein current flowing through the shunt load is dissipated as heat by the resistor.

17. The circuit of claim 16, wherein LED driver is operable above a minimum current magnitude and wherein the low intensity level is greater than the minimum current magnitude.

18. The circuit of claim 16, wherein the at least one LED is powered by a current having a magnitude regulated by the dimming control circuit.

19. The circuit of claim 16, wherein the shunt load receives a current having a magnitude regulated by the dimming control circuit.

20. The circuit of claim 15, wherein the dimming control circuit is responsive to an input command signal.

21. The circuit of claim 20, wherein the input command signal is static.

22. The circuit of claim 21, wherein the dimming control circuit directly controls a magnitude of current through the at least one LED.

23. The circuit of claim 21, wherein the shunt load receives a current having a magnitude regulated by the dimming control circuit.

24. The circuit of claim 21, wherein the input command signal is dynamic.

25. The circuit of claim 15, wherein the at least one LED receives a current magnitude represented by a response curve having a step.

26. A method of controlling a light emitting diode (LED), comprising the steps of:

providing a driving current to power the LED; and

shunting a portion of the driving current away from the LED when the driving current is less than a low intensity level.

27. The method of claim 26, further including the step of powering the LED with a portion of the driving current that is not shunted away from the LED.

28. The method of claim 26, wherein the shunted portion of the driving current is shunted through a resistor and a transistor.

29. The method of claim 27, wherein power generated by the diverted portion of the driving current is dissipated as heat by the resistor

30. The method of claim 26, wherein the driving current is developed by an LED driver operable above a minimum current magnitude and wherein the low intensity level is greater than the minimum current magnitude

31. The method of claim 26, wherein the current through the shunt load is controlled by a control circuit to control a magnitude of current provided to the LED.

32. The method of claim 26, wherein the current provided to the LED is directly controlled by a control circuit.

33. The method of claim 26, wherein the step of shunting is undertaken by a dimming control circuit responsive to an input command signal.

34. The method of claim 33, wherein the input command signal is static.

35. The method of claim 34, wherein the dimming control circuit directly controls a magnitude of current through the LED.

36. The method of claim 35, wherein the shunt load receives a current having a magnitude regulated by the dimming control circuit.

37. The method of claim 34, wherein the LED receives a current magnitude represented by a response curve having a step.

38. The method of claim 33, wherein the input command signal is dynamic.