Over-temperature handling for lighting device

Patent metadata

Field	Value
Publication number	US-10021756-B2
Application number	US-201213565113-A
Country	US
Kind code	B2
Filing date	Aug 2, 2012
Priority date	Oct 2, 2011
Publication date	Jul 10, 2018
Grant date	Jul 10, 2018

Abstract

A lighting device employs at least one string of LEDs as a lighting source. The string of LEDs is coupled in series with a first switch, wherein the string of LEDs and the first switch are coupled between a power supply node and ground. During a normal operation mode, a system controller is configured to close the first switch to deliver a drive current to the string of LEDs from the power supply node. The system controller is further associated with a temperature sensor and is configured to detect an over-temperature condition based on information provided by the temperature sensor. Upon detecting the over-temperature condition, the system controller will open the first switch to stop the drive current from flowing through the string of LEDs.

First claim

What is claimed is:

1. A lighting device comprising:
a first string of LEDs and a first switch coupled in series between a power supply node and ground;
a temperature sensor;
a system controller comprising an input/output port that is initially configured as an input port for receiving communications from an external device, and configured to:
close the first switch during a normal operation mode to deliver a drive current to the first string of LEDs;
detect an over-temperature condition based on information provided by the temperature sensor;
upon detecting the over-temperature condition, open the first switch to stop the drive current from flowing through the first string of LEDs; and
upon detecting the over-temperature condition, reconfigure the input/output port as an output port and set the output port to a logic level indicative of the lighting device having experienced the over-temperature condition.

2. The lighting device of claim 1 wherein to set the output port to the logic level indicative of the lighting device having experienced the over-temperature condition, the output port is tied to ground.

3. The lighting device of claim 1 wherein the input/output port is coupled to a wireless communication sensor.

4. The lighting device of claim 3 wherein the wireless communication sensor is an infrared sensor.

5. A lighting device comprising:
a first string of LEDs and a first switch coupled in series between a power supply node and ground;
a temperature sensor; and
a system controller associated with memory and configured to:
close the first switch during a normal operation mode to deliver a drive current to the first string of LEDs;
detect an over-temperature condition based on information provided by the temperature sensor;
upon detecting the over-temperature condition, open the first switch to stop the drive current from flowing through the first string of LEDs; and
store information in the memory that indicates an over-temperature condition has occurred upon detecting the over-temperature condition.

6. The lighting device of claim 5 wherein the system controller is configured to store information for each over-temperature condition that occurs.

7. The lighting device of claim 5 wherein the system controller is configured to keep track of a number of over-temperature conditions that have occurred.

8. The lighting device of claim 5 , wherein the system controller is further configured to
keep the first switch open upon detecting the over-temperature condition until the system controller is reset, wherein the system controller is reset when power at the power supply node is turned off and then turned back on.

9. The lighting device of claim 8 wherein the system controller is further configured to close the first switch after being reset.

10. The lighting device of claim 8 wherein the over-temperature condition occurs when the information from the temperature sensor indicates a temperature associated with the first string of LEDs has exceeded a defined threshold.

11. The lighting device of claim 8 wherein light emitted from the lighting device is white light at a desired color temperature.

12. The lighting device of claim 11 wherein the first string of LEDs comprises a plurality of series connected LEDs.

13. The lighting device of claim 12 wherein the plurality of series connected LEDs comprises a plurality of LEDs of a first type that emit light of a first color and a plurality of LEDs of a second type that emit light of a second color.

14. The lighting device of claim 13 wherein the light of the first color is reddish light and the light of the second color is one of greenish light and yellowish light.

15. The lighting device of claim 13 further comprising a second switch coupled across at least one of the plurality of LEDs of the first type and a third switch coupled across at least one of the plurality of LEDs of the second type wherein during the normal operation mode, the system controller is further configured to operate the second switch with a first pulse width modulated signal to control a relative intensity of the at least one of the plurality of LEDs of the first type and operate the third switch with a second pulse width modulated signal to control a relative intensity of the at least one of the plurality of LEDs of the second type.

16. The lighting device of claim 15 wherein the first pulse width modulated signal has a first duty cycle that is variable, the second pulse width modulated signal has a second duty cycle that is variable, and the system controller is configured to vary the first duty cycle and the second duty cycle based on an operating temperature derived from the temperature sensor.

17. The lighting device of claim 8 wherein the lighting device has a power supply port, which is configured to receive DC power from a power supply that is separate from the lighting device.

18. The lighting device of claim 8 wherein the first switch is a transistor.

19. The lighting device of claim 8 further comprising a second string of LEDs and wherein the second string of LEDs and the first switch are coupled in series between the power supply node and ground.

20. The lighting device of claim 8 further comprising a second string of LEDs and a second switch coupled in series between the power supply node and ground wherein the system controller is configured to:
close the second switch during the normal operation mode to deliver a drive current to the second string of LEDs; and
upon detecting the over-temperature condition, open the second switch to stop the drive current from flowing through the second string of LEDs.

21. A lighting device comprising:
a first string of LEDs and a first switch coupled in series between a power supply node and ground;
a temperature sensor; and
a system controller configured to:
close the first switch during a normal operation mode to deliver a drive current to the first string of LEDs;
detect an over-temperature condition based on information provided by the temperature sensor;
upon detecting the over-temperature condition, open the first switch to stop the drive current from flowing through the first string of LEDs; and
keep the first switch open upon detecting the over-temperature condition until the system controller is reset, wherein the over-temperature condition occurs when the information from the temperature sensor indicates a temperature associated with the first string of LEDs has exceeded a defined threshold for a given period of time.

22. A lighting device comprising:
a first string of LEDs and a first switch coupled in series between a power supply node and ground;
a temperature sensor; and
a system controller comprising an input/output port that is initially configured as an input port for receiving communications from an external device, wherein the system controller is configured to:
close the first switch during a normal operation mode to deliver a drive current to the first string of LEDs;
detect an over-temperature condition based on information provided by the temperature sensor;
upon detecting the over-temperature condition, open the first switch to stop the drive current from flowing through the first string of LEDs;
keep the first switch open upon detecting the over-temperature condition until the system controller is reset; and
upon detecting the over-temperature condition, reconfigure the input/output port as an output port and set the output port to

Assignees

• Bradford Everett
• Perry John
• Cree Inc

Inventors

• Bradford Everett
• Perry John

Classifications

• H10W90/756

  between a chip and a stacked lead frame, conducting package substrate or heat sink · CPC title

• H05B45/58 Primary

  involving end of life detection of LEDs · CPC title

• H01L2924/1305

  Electricity · mapped topic

• H01L2924/13033

  Electricity · mapped topic

• H01L2924/00014

  Electricity · mapped topic