Methods and Systems for Controlling LEDs

• US 20140084811A1
• Filed: 09/27/2013
• Published: 03/27/2014
• Est. Priority Date: 09/27/2012
• Status: Active Grant

• Current Assignee: Melexis Technologies NV (Sensinnovat BVBA)
• Original Assignee: Melexis Technologies NV (Sensinnovat BVBA)
• Inventors: BENDER, Michael, FREY, Michael
• Granted Patent: US 9,414,460 B2
• Time in Patent Office: Days
• US Class Current: 315/297
• CPC Class Codes: H05B 45/50 responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
• CPC Class Codes: H05B 45/56 involving measures to prevent abnormal temperature of the LEDs

Abstract

The present invention relates to an electronic device, the electronic device comprising at least one LED, a driving unit for applying a driving algorithm for driving the LED during normal operation, and a measurement unit for determining a forward voltage of the LED by imposing a test current to the LED, the measurement unit being programmed for determining test current characteristics taking into account said driving algorithm.

Claims

1. An electronic device, the electronic device comprising

at least one LED,

a driving unit for applying a driving algorithm for driving the LED during normal operation,

and a measurement unit for determining a forward voltage of the LED by imposing a test current to the LED, the measurement unit being programmed for determining test current characteristics taking into account said driving algorithm.

2. An electronic device according to claim 1, the measurement unit being programmed for dynamically adjusting the test current as function of the driving algorithm.

3. An electronic device according to claim 1, wherein the measurement unit comprises a differential amplifier for measuring the forward voltage differentially.

4. An electronic device according to claim 1, wherein the measurement unit comprises a differential amplifier, a variable current source and an ADC converter, for determining a forward voltage of the LED.

5. An electronic device according to claim 1, the electronic device comprising a plurality of different LEDs, wherein a single differential amplifier is configured for measuring the forward voltage differentially for different LEDs.

6. An electronic device according to claim 1, wherein the differential amplifier is configured for selecting an input for each LED of a set of LEDs of an RGB LED configuration in the electronic device.

7. An electronic device according to claim 1, wherein the electronic device comprises a controller for determining the forward voltage over different LEDs of a set of LEDs in a sequential manner.

8. An electronic device according to claim 3, wherein the electronic device furthermore comprises an offset compensation means for compensating for an offset of the differential amplifier.

9. An electronic device according to claim 8, wherein the offset compensation means is a hardware (HW) offset compensation means or software (SW) offset compensation means.

10. An electronic device according to claim 1, the electronic device furthermore comprising an adjustment means for adjusting the driving of the LED for compensating for the determined effects due to aging and/or environmental effects.

11. An electronic device according to claim 3, wherein the differential amplifier comprises continuous time switched capacitors with integrated offset compensation.

12. An electronic device according to claim 1, wherein the measurement unit comprises a differential amplifier circuit comprising a first and second input, the first and the second input of the differential amplifier circuit being connected such that the forward voltage over the LED can be determined from the output of the differential amplifier.

13. A method for measuring and/or compensating environmental effects or aging effects on a LED, the method comprising

determining a forward voltage of the LED and using the forward voltage of the LED device for determining environmental effects and/or aging effects.

14. A method according to claim 13, wherein determining the forward voltage comprises differentially measuring the voltage in relation to the voltage where the LED is connected to.

15. A method according to claim 13, wherein the method comprises compensating for a change in properties of the LED device related to environmental effects and/or aging effects.

16. A method according to claim 13, wherein determining environmental effects comprises determining an ambient temperature.

17. A method according to claim 13, wherein the method comprises distinguishing between different effects based on the rate of change of the performance of the LED device.

18. A method according to claim 13, wherein the method comprises distinguishing between different effects by taking into account different performance characteristics.

19. A method according to claim 13, wherein the method comprises compensating for each LED of one or more RGB-LED devices.

20. A controller being programmed for performing a method for measuring and/or compensating environmental effects or aging effects on a LED according to claim 13.