MULTI-STRING DIMMABLE LED DRIVER

• US 20140333216A1
• Filed: 05/07/2014
• Published: 11/13/2014
• Est. Priority Date: 05/10/2013
• Status: Active Grant

• Current Assignee: Marvell Asia Pte Limited (Marvell Technology Group Limited)
• Original Assignee: Marvell World Trade Limited (Marvell Technology Group Limited)
• Inventors: ZHANG, Wanfeng, SUTARDJA, Pantas
• Granted Patent: US 9,320,097 B2
• Time in Patent Office: Days
• US Class Current: 315/185.R
• CPC Class Codes: H05B 45/46 having LEDs disposed in parallel lines

Abstract

An apparatus includes a first LED driver configured to control a first string of LEDs, a second LED driver configured to control a second string of LEDs, a third LED driver configured to control a third string of LEDs, and a control circuit configured to receive a control signal and to control the first, second, and third LED drivers so that the first, second, and third strings of LEDs cooperate in producing light according to the control signal and a color curve.

Claims

1. An apparatus, comprising:

a first LED driver configured to control a first string of LEDs;

a second LED driver configured to control a second string of LEDs;

a third LED driver configured to control a third string of LEDs; and

a control circuit configured to receive a control signal and to control the first, second, and third LED drivers so that the first, second, and third strings of LEDs cooperate in producing light according to the control signal and a color curve.

2. The apparatus of claim 1, wherein the color curve indicates light having a predetermined Correlated Color Temperature (CCT) when one or more of the strings of LEDs are dimmed.

3. The apparatus of claim 1, wherein the color curve indicates light having a Correlated Color Temperature (CCT) according to the luminance of the strings of LEDs.

4. The apparatus of claim 3, wherein the first, second, and third LED drivers are controlled so that the CCT of the luminance of the strings of LEDs substantially follows a black body curve.

5. The apparatus of claim 1, wherein one or more of the first, second, and third LED drivers are configured to control duty cycles of currents of the respective strings of LEDs.

6. The apparatus of claim 5, wherein the one or more of the first, second, and third LED drivers are configured to control magnitudes of the currents of the respective strings of LEDs.

7. The apparatus of claim 6, wherein the one or more of the first, second, and third LED drivers are configured to control the magnitudes of the currents using a linear mode.

8. The apparatus of claim 6, wherein the one or more LED drivers are configured to control the duty cycles of the currents of the respective strings of LEDs when in a first mode, and configured to control the magnitudes of the currents of the respective strings of LEDs when in a second mode.

9. The apparatus of claim 7, wherein the second mode is a linear mode.

10. The apparatus of claim 5, wherein the first LED driver is configured to operate a buck converter for controlling the first string of LEDs.

11. The apparatus of claim 1, further comprising:

a sensor circuit configured to sense a current of one or more of the first, second, and third strings of LEDs.

12. The apparatus of claim 1, wherein the color curve indicates ratios of currents of the first, second, and third strings of LEDs.

13. The apparatus of claim 1, wherein the control circuit is configured to receive a color sense signal and to control the first, second, and third LED drivers according to the control signal, the color curve, and the color sense signal.

14. The apparatus of claim 1, wherein a single integrated circuit includes the apparatus.

16. The method of claim 1, wherein the color curve indicates light having a Correlated Color Temperature (CCT) according to the luminance of the strings of LEDs.

17. The method of claim 16, wherein the first, second, and third LED drivers are controlled so that the CCT of the luminance of the strings of LEDs substantially follows a black body curve.

18. The method of claim 1, further comprising controlling a duty cycle of a current of a string of LEDs of the plurality of strings of LEDs.

19. The method of claim 18, further comprising controlling a magnitude of the current of the string of LEDs.

20. The method of claim 19, further comprising controlling the duty cycle of the current when the LED driver is in a first mode, and controlling the magnitude of the current when the LED driver is in a second mode.

21. The method of claim 1, further comprising sensing a current of one or more of the first, second, and third strings of LEDs and controlling the LED driver according to the sensed current.

22. The method of claim 1, further comprising receiving a color sense signal and determining the target value according to the color sense signal, the control signal, and the color curve.

15. A method of controlling a plurality strings of LEDs in a multi-string LED driver, the method comprising:

receiving a control signal;

determining a target value according to the control signal and a color curve; and

controlling an LED driver according to the target value so that the plurality of LED strings cooperate in producing light according to the control signal and the color curve, wherein the LED driver is one of first through third LED drivers of the multi-string LED driver.