Lighting devices including current shunting responsive to LED nodes and related methods

• US 8,847,516 B2
• Filed: 12/12/2011
• Issued: 09/30/2014
• Est. Priority Date: 12/12/2011
• Status: Active Grant

• Current Assignee: IDEAL Industries Lighting, LLC (Ideal Industries Incorporated)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Chobot, Joseph P.
• Primary Examiner(s): Tran, Thienvu
• Assistant Examiner(s): LO, CHRISTOPHER KWOK YEUNG
• Application Number:
  US13/323,074
• Publication Number:
  US 20130147359A1
• Time in Patent Office: 1,023 Days
• Field of Search: 315/169.3, 315/185.R, 315/246, 315/291, 315/307, 315/308, 315/312, 345/102, 345/213, 345/504, 345/519, 345/520, 345/522
• US Class Current: 315/307
• CPC Class Codes: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: H05B 45/48 having LEDs organised in strings and incorporating parallel shunting devices

Abstract

A solid state lighting device may include a power supply and a light emitting device electrically coupled between the power supply and a reference node, with the light emitting device defining a node. A control element may be provided in a current shunting path electrically coupled in parallel with the light emitting device between the power supply and the reference node, with the control element being configured to control a voltage drop across the current shunting path responsive to an electrical signal from the node of the light emitting device. Related methods are also discussed.

Claims

1. A device comprising:

a power supply;

a light emitting device electrically coupled between the power supply and a reference node, wherein the light emitting device defines a node;

a control element in a current shunting path electrically coupled in parallel with the light emitting device between the power supply and the reference node, wherein the control element is configured to control a voltage drop across the current shunting path responsive to an electrical signal from the node of the light emitting device, wherein the control element comprises a regulating transistor and wherein a control electrode of the regulating transistor is electrically coupled to the node of the light emitting device;

a switching transistor electrically coupled in series with the regulating transistor in the current shunting path between the power supply and the reference node; and

a controller coupled to a control electrode of the switching transistor, wherein the controller is configured to generate a pulse width modulated control signal that is applied to the control electrode of the switching transistor to vary a current though the current shunting path.

2. The device according to claim 1 further comprising:

a mirroring transistor electrically coupled in series between the light emitting device and the reference node, wherein a control electrode of the mirroring transistor is electrically coupled to the control electrode of the regulating transistor, wherein the node of the light emitting device is between the light emitting device and the mirroring transistor so that the control electrodes of the regulating transistor and the mirroring transistor are electrically coupled to the node between the light emitting device and the mirroring transistor.

6. The device according to claim 2 further comprising:

a reverse biased Zener diode electrically coupled in series in the current shunting path between the regulating transistor and the power supply.

8. The device according to claim 1 wherein the power supply comprises a current controlled power supply, and wherein the light emitting device comprises a first light emitting device, the solid state lighting device further comprising:

a second light emitting device electrically coupled between the power supply and the reference node, wherein the first and second light emitting devices are electrically coupled in series between the power supply and the reference node, and wherein a sum of electrical currents through the first light emitting device and the current shunting path is equal to an electrical current through the second light emitting device.

9. The device according to claim 1 wherein the light emitting device comprises a plurality of light emitting devices electrically coupled in series between the power supply and the reference node.

27. The device according to claim 1 wherein the control element comprises a bipolar junction transistor including a base, and wherein the base is electrically coupled to the node of the light emitting device.

28. The device according to claim 1 wherein the control element comprises a field effect transistor including a gate, and wherein the gate of the field effect transistor is electrically coupled to the node of the light emitting device.

3. A device comprising:

a power supply;

a light emitting device electrically coupled between the power supply and a reference node, wherein the light emitting device defines a node;

a control element in a current shunting path electrically coupled in parallel with the light emitting device between the power supply and the reference node, wherein the control element is configured to control a voltage drop across the current shunting path responsive to an electrical signal from the node of the light emitting device, wherein the control element comprises a regulating transistor, and wherein a control electrode of the regulating transistor is electrically coupled to the node of the light emitting device;

a switching transistor electrically coupled in series with the regulating transistor in the current shunting path between the power supply and the reference node;

a mirroring transistor electrically coupled in series between the light emitting device and the reference node, wherein a control electrode of the mirroring transistor is electrically coupled to the control electrode of the regulating transistor, wherein the node of the light emitting device is between the light emitting device and the mirroring transistor so that the control electrodes of the regulating transistor and the mirroring transistor are electrically coupled to the node between the light emitting device and the mirroring transistor, wherein the light emitting device comprises a plurality of light emitting devices electrically coupled in series between the power supply and the mirroring transistor, wherein the node between the light emitting device and the mirroring transistor comprises a first node between the plurality of light emitting devices and the mirroring transistor, wherein the regulating transistor comprises a first regulating transistor; and

a second regulating transistor electrically coupled in series in the current shunting path between the first regulating transistor and the power supply, wherein a control electrode of the second regulating transistor is electrically coupled to a second node between two of the plurality of light emitting devices.

4. The device according to claim 3 wherein the second regulating transistor comprises a bipolar junction transistor, and wherein the control electrode of the second regulating transistor comprises a base of the bipolar junction transistor, the solid state lighting device further comprising:

at least one diode electrically coupled between the base of the bipolar junction transistor and the second node.

5. The device according to claim 3 wherein the second regulating transistor comprises a field effect transistor, wherein the control electrode of the second regulating transistor comprises a gate field effect transistor, and wherein the gate of the field effect transistor is electrically coupled to the second node.

7. A device comprising:

a power supply;

a light emitting device electrically coupled between the power supply and a reference node, wherein the light emitting device defines a node wherein the light emitting device comprises a plurality of light emitting devices electrically coupled in series between the power supply and the reference node, and wherein the node is between two of the plurality of light emitting devices;

a control element in a current shunting path electrically coupled in parallel with the light emitting device between the power supply and the reference node, wherein the control element is configured to control a voltage drop across the current shunting path responsive to an electrical signal from the node of the light emitting device, wherein the control element comprises a regulating transistor and wherein a control electrode of the regulating transistor is electrically coupled to the node of the light emitting device, and wherein the control electrode of the regulating transistor is electrically coupled to the node between the two of the plurality of light emitting devices; and

a switching transistor electrically coupled in series with the regulating transistor in the current shunting path between the power supply and the reference node.

10. A device comprising:

a power supply;

a light emitting device electrically coupled between the power supply and a reference node;

a first mirroring transistor electrically coupled between the light emitting device and the reference node wherein a control electrode of the first mirroring transistor is electrically coupled to a node between the light emitting device and the first mirroring transistor wherein the light emitting device comprises a plurality of light emitting devices electrically coupled in series between the power supply and the first mirroring transistor, and wherein the node between the light emitting device and the first mirroring transistor comprises a first node between the plurality of light emitting devices and the first mirroring transistor;

a second mirroring transistor in a current shunting path between the power supply and the reference node wherein the current shunting path is electrically coupled in parallel with the light emitting device, and wherein a control electrode of the second mirroring transistor is electrically coupled to the node between the light emitting device and the first mirroring transistor; and

a regulating transistor electrically coupled in series with the second mirroring transistor in the current shunting path between the second mirroring transistor and the power supply, and wherein a control electrode of the regulating transistor is electrically coupled to a second node between two of the plurality of light emitting devices.

11. The device according to claim 10 wherein the regulating transistor comprises a bipolar junction transistor, and wherein the control electrode of the regulating transistor comprises a base of the bipolar junction transistor, the solid state lighting device further comprising:

at least one diode electrically coupled between the base of the bipolar junction transistor and the second node.

12. The device according to claim 10 wherein the regulating transistor comprises a field effect transistor, wherein the control electrode of the regulating transistor comprises a gate of the field effect transistor, and wherein the gate of the field effect transistor is electrically coupled to the second node.

16. The device according to claim 10 wherein the light emitting device comprises a plurality of light emitting devices electrically coupled in series between the power supply and the first mirroring transistor.

25. The device according to claim 10 further comprising:

a switching transistor electrically coupled in series with the second mirroring transistor in the current shunting path.

26. The device according to claim 10 further comprising:

a Zener diode electrically coupled in series with the second mirroring transistor in the current shunting path, wherein the Zener diode is electrically coupled between the second mirroring transistor and the power supply.

29. The device according to claim 10 wherein the regulating transistor comprises a bipolar junction transistor, wherein the control electrode comprises a base of the bipolar junction transistor, and wherein the base is electrically coupled to the second node.

13. A device comprising:

a power supply;

a light emitting diode electrically coupled between the power supply and a reference node;

a first mirroring transistor electrically coupled between the light emitting diode and the reference node wherein a control electrode of the first mirroring transistor is electrically coupled to a node between the light emitting diode and the first mirroring transistor, wherein a cathode of the light emitting diode is electrically coupled between an anode of the light emitting diode and the first mirroring transistor, and wherein the cathode of the light emitting diode is electrically coupled between the anode of the light emitting diode and the node between the light emitting diode and the first mirroring transistor;

a second mirroring transistor in a current shunting path between the power supply and the reference node wherein the current shunting path is electrically coupled in parallel with the light emitting diode, and wherein a control electrode of the second mirroring transistor is electrically coupled to the node between the light emitting diode and the first mirroring transistor; and

a Zener diode electrically coupled in series with the second mirroring transistor in the current shunting path, wherein the Zener diode is electrically coupled between the second mirroring transistor and the power supply.

14. A device comprising:

a power supply;

a light emitting device electrically coupled between the power supply and a reference node;

a first mirroring transistor electrically coupled between the light emitting device and the reference node wherein a control electrode of the first mirroring transistor is electrically coupled to a node between the light emitting device and the first mirroring transistor;

a second mirroring transistor in a current shunting path between the power supply and the reference node wherein the current shunting path is electrically coupled in parallel with the light emitting device, and wherein a control electrode of the second mirroring transistor is electrically coupled to the node between the light emitting device and the first mirroring transistor;

a switching transistor electrically coupled in series with the second mirroring transistor in the current shunting path; and

a controller coupled to a control electrode of the switching transistor, wherein the controller is configured to generate a pulse width modulated control signal that is applied to the control electrode of the switching transistor to vary a current though the current shunting path.

15. The device according to claim 14 wherein the power supply comprises a current controlled power supply, and wherein the light emitting device comprises a first light emitting device, the solid state lighting device further comprising:

a second light emitting device electrically coupled in series between the power supply and the reference node, wherein the first and second light emitting devices are electrically coupled in series between the power supply and the reference node, and wherein a sum of electrical currents through the first light emitting device and the current shunting path is equal to an electrical current through the second light emitting device.

17. A device comprising:

a power supply;

a light emitting device electrically coupled between the power supply and a reference node, wherein the light emitting device comprises a plurality of light emitting devices electrically coupled in series between the power supply and the reference node; and

a regulating transistor in a current shunting path between the power supply and the reference node wherein the current shunting path is electrically coupled in parallel with the light emitting device, and wherein a control electrode of the regulating transistor is electrically coupled to a node of the light emitting device, wherein the node is between two of the plurality of light emitting devices so that the control electrode of the regulating transistor is electrically coupled to the node between the two of the plurality of light emitting devices.

18. The device according to claim 17 wherein the node between the two of the plurality of light emitting devices comprises a first node, the solid state lighting device further comprising:

a first mirroring transistor electrically coupled in series between the plurality of light emitting devices and the reference node wherein a control electrode of the first mirroring transistor is electrically coupled to a second node between the plurality of light emitting devices and the first mirroring transistor; and

a second mirroring transistor wherein a control electrode of the second mirroring transistor is electrically coupled to the second node between the plurality of light emitting devices and the first mirroring transistor, wherein the second mirroring transistor is electrically coupled in series with the regulating transistor in the current shunting path.

19. The device according to claim 18 wherein the regulating transistor comprises a bipolar junction transistor, and wherein the control electrode of the regulating transistor comprises a base of the bipolar junction transistor, the solid state lighting device further comprising:

at least one diode electrically coupled between the base of the bipolar junction transistor and the first node.

20. The device according to claim 18 wherein the regulating transistor comprises a field effect transistor, wherein the control electrode of the regulating transistor comprises a gate of the field effect transistor, and wherein the gate of the field effect transistor is electrically coupled to the first node.

30. The device according to claim 17 wherein the regulating transistor comprises a bipolar junction transistor including a base, and wherein the base is electrically coupled to the node of the light emitting device.

31. The device according to claim 17 wherein the regulating transistor comprises a field effect transistor including a gate, and wherein the gate of the field effect transistor is electrically coupled to the node of the light emitting device.

21. A device comprising:

a power supply;

a light emitting device electrically coupled between the power supply and a reference node;

a regulating transistor in a current shunting path between the power supply and the reference node wherein the current shunting path is electrically coupled in parallel with the light emitting device, and wherein a control electrode of the regulating transistor is electrically coupled to a node of the light emitting device;

a switching transistor electrically coupled in series with the regulating transistor in the current shunting path between the power supply and the reference node; and

a controller coupled to a control electrode of the switching transistor, wherein the controller is configured to generate a pulse width modulated control signal that is applied to the control electrode of the switching transistor to vary a current though the current shunting path.

22. The device according to claim 21 wherein the power supply comprises a current controlled power supply, and wherein the light emitting device comprises a first light emitting device, the solid state lighting device further comprising:

a second light emitting device electrically coupled in series between the power supply and the reference node, wherein the first and second light emitting devices are electrically coupled in series between the power supply and the reference node, and wherein a sum of electrical currents through the first light emitting device and the current shunting path is equal to an electrical current through the second light emitting device.

23. A method of operating a solid state lighting device including a power supply, a first light emitting device electrically coupled between the power supply and a reference node, and a second light emitting device electrically coupled in series with the first light emitting device, the method comprising:

controlling a voltage drop across a current shunting path by allowing a current through the current shunting path responsive to an electrical signal from a node of the light emitting device, wherein the current shunting path is electrically coupled in parallel with the light emitting device between the power supply and the reference node; and

providing a power supply current through the second light emitting device wherein the power supply current is equal to a sum of a current through the first light emitting device and the current through the current shunting path.

24. A method according to claim 23 wherein the current shunting path includes a regulating transistor and a switch electrically coupled in series, the method further comprising:

providing a pulse width modulated control signal to a control electrode of the switch to control a pulse width modulated shunt current through the current shunting path,

wherein controlling the voltage drop comprises controlling the regulating transistor responsive to the electrical signal from the node of the light emitting device while providing the pulse width modulated control signal.

32. The method according to claim 23 wherein the current through the first light emitting device is different than the current through the second light emitting device.