LED thermal management

• US 9,668,306 B2
• Filed: 11/17/2010
• Issued: 05/30/2017
• Est. Priority Date: 11/17/2009
• Status: Active Grant

• Current Assignee: LEDVANCE LLC (MLS Co. Ltd.)
• Original Assignee: TerraLUX Incorporated
• Inventors: Harrison, Daniel J., Davis, Steven S.
• Primary Examiner(s): Rankins, William
• Assistant Examiner(s): Johnson, Christine
• Application Number:
  US12/948,591
• Publication Number:
  US 20110121760A1
• Time in Patent Office: 2,386 Days
• Field of Search: 315309
• CPC Class Codes: H05B 45/3575 by means of dummy loads or bleeder circuits, e.g. for dimmers
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/375 using buck topology
• CPC Class Codes: H05B 45/38 using boost topology
• CPC Class Codes: H05B 45/50 responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
• CPC Class Codes: H05B 45/59 for reducing or suppressing flicker or glow effects

Abstract

A thermal-management circuit detects a temperature of the LED, obtains a thermal operating range of the LED, and generates a control signal in response.

Claims

1. A thermal-management circuit for an LED, the circuit comprising:

circuitry for determining a current thermal operating point of the LED;

circuitry for obtaining a thermal operating range of the LED and for calculating a new operating point of the LED based on the current thermal operating point and the thermal operating range, wherein the new operating point is within the thermal operating range; and

a generator for generating a control signal that adjusts power delivered to the LED to cause the LED to operate at the new operating point, thereby extending the life of the LED.

2. The circuit of claim 1, further comprising a thermal sensor for measuring the current thermal operating point of the LED.

3. The circuit of claim 1, further comprising a storage device for storing the thermal operating range of the LED.

4. The circuit of claim 3, wherein the storage device comprises a look-up table.

5. The circuit of claim 1, further comprising a dimmer control circuit for dimming the LED in accordance with a dimmer setting.

6. The circuit of claim 5, wherein the control signal is generated based at least in part on the dimmer setting or the current thermal operating point.

7. The circuit of claim 5, further comprising circuitry for selecting the lesser of a first brightness level based on the dimmer setting and a second brightness level based on the current thermal operating point, wherein the control signal that adjusts power delivered to the LED is generated based at least in part on an output of the comparison circuit.

16. The circuit of claim 7, wherein the power delivered to the LED is based on the dimmer setting and not the current thermal operating point.

17. The circuit of claim 7, wherein a brightest setting of the LED is defined based on the current thermal operating point and wherein the dimmer control circuit dims the LED down from the brightest setting.

8. A method of thermal management for an LED, the method comprising:

detecting a temperature of the LED;

obtaining a thermal operating range of the LED at the detected temperature;

calculating a new operating point of the LED based on the current thermal operating point and the thermal operating range, wherein the new operating point is within the thermal operating range; and

adjusting power delivered to the LED based at least in part on the thermal operating range to cause the LED to operate at the new operating point, thereby extending the life of the LED.

9. The method of claim 8, wherein obtaining the thermal operating range of the LED comprises referencing a look-up table.

10. The method of claim 9, wherein the look-up table comprises LED thermal-power data.

11. The method of claim 8, wherein detecting the temperature of the LED comprises receiving input from a thermal sensor.

12. The method of claim 8, wherein adjusting power delivered to the LED comprises setting the LED to its maximum brightness level within the thermal operating range.

13. The method of claim 8, wherein adjusting power delivered to the LED is further based in part on a dimmer setting.

14. The method of claim 13, further comprising comparing a first brightness level based on the dimmer setting and a second brightness level based on the temperature and adjusting power delivered to the LED based at least in part on the lesser of the first and second brightness levels.

15. The method of claim 14, wherein the comparison is performed digitally.