Current tuneback in light emitting diode luminaires
View Patent ↗Safety improvements to Light Emitting Diodes (LED) are discussed herein. As the LEDs that are part of a luminaire heat up and cool down, the current supplied will be tuned to improve the safety of the luminaire to manage the levels of light and heat produced. At least one thermally active electrical component is incorporated into the LED load of the luminaire, which is communicated to an LED current control to signal when to adjust current levels providing by a driving circuit. Current is reduced when the temperature of the LED load exceeds a threshold, and or returned to an optimal current when the temperature no longer exceeds the threshold.
1. A light emitting diode (LED) luminaire, comprising:
an LED load, including at least one light emitting diode and at least one temperature sensor;
a driving circuit providing power to the LED load, including a current controller in communication with the at least one temperature sensor, the current controller configured to regulate an amount of power provided to the LED load in response to a temperature of the LED load measured by the at least one temperature sensor, wherein the current controller is configured to receive an indication of the temperature of the LED from the at least one temperature sensor and output signals to the driving circuit to regulate the amount of power by
providing a predetermined nominal amount of power to the LED load;
decreasing the amount of power provided to the LED load below the nominal amount of power in response to the temperature of the LED load as measured by the at least one temperature sensor exceeding a predetermined high threshold temperature;
after decreasing the amount of power provided to the LED load, increasing the amount of power provided to the LED load up to the nominal amount of power in response to the temperature of the LED load measured by the at least one temperature sensor reaching a predetermined cooldown temperature and in response to the amount of power provided to the LED load being below the nominal amount of power;
wherein increasing the amount of power up to the nominal amount of power in response to the temperature reaching the predetermined cooldown temperature further comprises waiting to increase the power until a predetermined time threshold has passed after decreasing the amount of power; and
wherein the predetermined time threshold is set according to at least one of a number of clock cycles in a microprocessor between determining that the temperature of the LED load as measured by the at least one temperature sensor does not exceed the predetermined high threshold temperature and determining the temperature of the LED load measured by the at least one temperature sensor has reached the predetermined cooldown temperature and the amount of power provided to the LED load is below the nominal amount of power, an averaging of a plurality of the temperatures in a register of the LED load measured by the at least one temperature sensor, or an operating speed of the current controller.
2. The LED luminaire of claim 1 , further comprising a second LED load, including at least one second light emitting diode and at least one second temperature sensor, the at least one second temperature sensor in communication with the current controller for regulating a second amount of direct current power provided to the second LED load in response to changes in a second temperature associated with the second LED load.
3. The LED luminaire of claim 2 , wherein the amount of power to the LED load is regulated in response to the second temperature; and wherein the second amount of direct current power provided to the second LED load is regulated in response to the temperature of the LED load.
4. The LED luminaire of claim 2 , wherein the current controller regulates the power provided to the LED load and the second amount of direct current power provided to the second LED load to be equal.
5. The LED luminaire of claim 1 , wherein the LED luminaire is adapted for use in a hazardous environment.
6. The LED luminaire of claim 1 , wherein the at least one temperature sensor includes a thermistor.
7. The LED luminaire of claim 1 , wherein the at least one temperature sensor includes a thermocouple.
8. The LED luminaire of claim 1 , wherein the at least one temperature sensor includes a photodiode operable to receive infrared light.
9. The LED luminaire of claim 1 , wherein the at least one temperature sensor includes a resistance temperature detector.
10. A light emitting diode (LED) luminaire, comprising:
a temperature sensor proximate to an LED load, operable to measure a temperature of the LED load;
a current controller disposed remotely from the LED load and in communication with the temperature sensor, the current controller operable to
provide a predetermined nominal level of current to the LED load;
receive an indication of the temperature of the LED from the temperature sensor;
decrease the level of current provided to the LED load in response the temperature measured by the temperature sensor exceeding a predetermined high threshold temperature; and thereafter
increase the level of current provided to the LED load up to the nominal current level in response the level of current provided to the LED being below the nominal current level and in response to the temperature measured by the temperature sensor reaching a predetermined cooldown temperature;
wherein increasing the amount of power up to the nominal amount of power in response to the temperature reaching the predetermined cooldown temperature further comprises waiting to increase the power until a predetermined time threshold has passed after decreasing the amount of power; and
wherein the predetermined time threshold is set according to at least one of a number of clock cycles in a microprocessor between determining that the temperature of the LED load as measured by the temperature sensor does not exceed the predetermined high threshold temperature and determining the temperature of the LED load measured by the temperature sensor has reached the predetermined cooldown temperature and the amount of power provided to the LED load is below the nominal amount of power, an averaging of a plurality of the temperatures in a register of the LED load measured by the temperature sensor, or an operating speed of the current controller.
11. The LED luminaire of claim 10 , wherein the temperature sensor is mounted on a printed circuit board on which LEDs comprising the LED load are mounted.
12. The LED luminaire of claim 10 further comprising, a second temperature sensor disposed of on the LED load, operable to measure a second temperature of the LED load.
13. The LED luminaire of claim 12 , wherein the current controller uses a higher temperature of the temperature measured by the temperature sensor and the second temperature measured by the second temperature sensor to adjust the level of current provided to the LED load.
14. The LED luminaire of claim 12 , wherein the current controller uses an algorithm based on the cumulative temperature data of the temperature measured by the temperature sensor and the second temperature measured by the second temperature sensor to adjust the level of current provided to the LED load.
15. The LED luminaire of claim 10 , wherein the LED luminaire is adapted for use in a hazardous environment.
16. The LED luminaire of claim 10 , wherein the temperature sensor is a thermistor.
17. A light emitting diode (LED) luminaire, comprising:
at least one LED that is provided an operating current from a power source;
a temperature sensor configured such that a resistance of the temperature sensor changes in relationship with a change in a temperature of the at least one LED, the temperature sensor provided a reference current of a predetermined value from the power source such that a voltage across the temperature sensor varies in accordance with the change in temperature of the at least one LED, while the at least one LED is provided the operating current; and
a current controller in communication with the power source and the temperature sensor, the current controller operable to measure the voltage across the temperature sensor and to reduce the operating current provided from the power source to the at least one LED when the voltage reaches a predetermined high threshold temperature, and after reducing the operating current, the current controller further operable to increase the operating current provided from the power source to the at least one LED up to a predetermined nominal current level in response to the voltage reaching a predetermined cooldown temperature and the operating current being below the predetermined nominal current level; and
wherein increasing the amount of power up to the nominal amount of power in response to the temperature reaching the predetermined cooldown temperature further comprises waiting to increase the power until a predetermined time threshold has passed after decreasing the amount of power; and
wherein the predetermined time threshold is set according to at least one of a number of clock cycles in a microprocessor between determining that the temperature of the LED load as measured by the temperature sensor does not exceed the predetermined high threshold temperature and determining the temperature of the LED load measured by the temperature sensor has reached the predetermined cooldown temperature and the amount of power provided to the LED load is below the nominal amount of power, an averaging of a plurality of the temperatures in a register of the LED load measured by the temperature sensor, or an operating speed of the current controller.
18. The LED luminaire of claim 17 , wherein the predetermined high threshold temperature is set according to an industrial standard for use of luminaires in a hazardous environment.
19. The LED luminaire of claim 17 , wherein the temperature sensor is located between the power source and the at least one LED, wherein the reference current is the operating current.
20. The LED luminaire of claim 19 , wherein the temperature sensor is a thermistor.
21. The LED luminaire of claim 17 , wherein the reference current is a constant value current.
22. A light emitting diode (LED) luminaire, comprising:
a power source;
at least one LED that is provided an operating current from the power source;
a temperature sensor, having variable resistance at different temperatures and is part of a voltage divider circuit operated from a constant voltage; and
a current controller in communication with the power source and the temperature sensor, the current controller operable to measure a voltage across the temperature sensor and to reduce the operating current provided from the power source to the at least one LED when the voltage reaches a predetermined high threshold temperature and the current controller further operable to increase the operating current provided from the power source to the at least one LED up to a nominal current level in response to the voltage reaching a predetermined cooldown threshold temperature and the operating current being below the nominal current level;
wherein increasing the amount of power up to the nominal amount of power in response to the temperature reaching the predetermined cooldown temperature further comprises waiting to increase the power until a predetermined time threshold has passed after decreasing the amount of power; and
wherein the predetermined time threshold is set according to at least one of a number of clock cycles in a microprocessor between determining that the temperature of the LED load as measured by the temperature sensor does not exceed the predetermined high threshold temperature and determining the temperature of the LED load measured by the temperature sensor has reached the predetermined cooldown temperature and the amount of power provided to the LED load is below the nominal amount of power, an averaging of a plurality of the temperatures in a register of the LED load measured by the temperature sensor, or an operating speed of the current controller.