Multi-LED control

• US 8,587,217 B2
• Filed: 08/23/2008
• Issued: 11/19/2013
• Est. Priority Date: 08/24/2007
• Status: Active Grant

• Current Assignee: Signify Holding B.V. (Signify N.V.)
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Melanson, John L.
• Primary Examiner(s): Owens, Douglas W
• Assistant Examiner(s): HAMMOND, DEDEI KHALIEAH
• Application Number:
  US12/675,035
• Publication Number:
  US 20110210674A1
• Time in Patent Office: 1,914 Days
• Field of Search: None
• US Class Current: 315/294
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/375 using buck topology
• CPC Class Codes: H05B 45/48 having LEDs organised in strings and incorporating parallel shunting devices
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

A LED driver and controller system utilizes switches to parallel connect to respective sets of one or more LEDs and a current source to provide efficient control of the LEDs. In at least one embodiment, the LEDs are connected in series. An LED controller of the LED driver and controller system 200 controls conductivity of the switches. In at least one embodiment, the LED controller provides control signals to one or more LED drivers. The LED drivers receive the control signals and, in response to the control signals, control the conductivity of each switch. In at least one embodiment, the conductivity of the each switch is controlled using a duty cycle modulated control signal. In at least one embodiment, the duty cycle modulated control signal is a pulse width modulated control signal. In another embodiment, the duty cycle modulated control signal is a pulse density modulated control signal.

Claims

1. An apparatus for controlling multiple, series coupled light emitting diodes (LEDs), the apparatus comprising:

a first LED driver to generate;

a first switch control signal to control a duty cycle of a first switch coupled in parallel across at least a first LED; and

a second switch control signal to control a duty cycle of a second switch coupled to at least a second LED to vary a relative intensity of the first and second LEDs, wherein the first LED is coupled in series with the second LED;

a buck-type constant current source coupled to the first switch to provide a bias current for the first and second LEDs, wherein the buck-type constant current source includes an inductor and further includes a voltage source coupling switch to receive a control signal from a current controller to control coupling of an input voltage source to the inductor; and

a second LED driver to generate;

a third switch control signal to control a duty cycle of a third switch coupled in parallel across at least a third LED; and

a fourth switch control signal to control a duty cycle of a fourth switch coupled to at least a fourth LED to vary a relative intensity of the third and fourth LEDs, wherein the third LED is coupled in series with the fourth LED.

2. The apparatus of claim 1 further comprising:

an LED controller coupled to the LED driver to generate and provide data to the first LED driver to control generation of the first and second switch control signals.

3. The apparatus of claim 1 wherein the second switch is coupled in parallel with the second LED.

4. The apparatus of claim 1 wherein the first LED driver is further configured to generate N additional control signals to control duty cycles of N additional switches, wherein each of the N additional switches is coupled in parallel with at least one LED, each LED, including the first and second LEDs, are coupled in series, and N is an integer greater than or equal to one.

5. The apparatus of claim 1 wherein the first switch control signal controls shunting of the first LED further comprising:

a current controller to generate a control signal to control an LED current flowing through the first and second LEDs, wherein an intensity of the first and second LEDs is controlled by varying a level of the LED current and color mixing of the first and second LEDs is controlled by varying duty cycles of the respective first and second switches.

6. The apparatus of claim 1 further comprising an LED sensor coupled to at least the first LED to detect malfunctions of the first LED.

7. The apparatus of claim 6 wherein the LED sensor is further configured to shunt the first LED with the first switch upon any detection of a malfunction of the first LED.

8. The apparatus of claim 1 further comprising:

an LED controller coupled to the first LED driver to generate and provide first control data to the first LED driver to control generation of the first and second switch control signals;

wherein the first LED driver is coupled to the LED controller and the second LED driver, and the second LED driver receives second control data from the LED controller via the first LED driver.

9. The apparatus of claim 8 wherein the first LED driver is configured to provide the second control data serially to the second LED driver.

10. The apparatus of claim 1 wherein the first LED driver is further configured to generate a third switch control signal to control a duty cycle of a third switch coupled to at least a third LED to vary a relative intensity of the first, second, and third, wherein the first, second, and third LEDs are coupled in series, the second switch is coupled in parallel with the second LED, the third switch is coupled in parallel with the third LED, the first LED is a red LED, the second LED is a green LED, the third LED is a blue LED, and the LED driver is further configured to vary a duty cycle of the first, second, and third switches to vary colors generated by color mixing of the first, second, and third LEDs.

11. The apparatus of claim 1 wherein to control the duty cycle of the first switch comprises generating a pulse width modulated first switch control signal and to control the duty cycle of the second switch comprises generating a pulse width modulated second switch control signal.

12. The apparatus of claim 1 wherein to control the duty cycle of the first switch comprises generating a pulse width density modulated first switch control signal and to control the duty cycle of the second switch comprises generating a pulse width density modulated second switch control signal.

13. The apparatus of claim 4 wherein N is selected from group consisting of:

greater than or equal to 6, 12, and 13.

14. A method for controlling multiple, series coupled light emitting diodes (LEDs), the method comprising:

generating a first switch control signal to control a duty cycle of a first switch coupled in parallel across at least a first LED;

generating a second switch control signal to control a duty cycle of a second switch coupled to at least a second LED to vary a relative intensity of the first and second LEDs, wherein the first LED is coupled in series with the second LED;

generating a constant current from a constant current source to provide a bias current for the first and second LEDs, wherein the constant current source comprises a buck-type constant current source and the buck-type constant current source includes an inductor and a voltage source coupling switch;

receiving a control signal to control the voltage source coupling switch to couple an input voltage source to the inductor;

generating a third switch control signal to control a duty cycle of a third switch coupled in parallel across at least a third LED;

generating a fourth switch control signal to control a duty cycle of a fourth switch coupled to at least a fourth LED to vary a relative intensity of the third and fourth LEDs, wherein the third LED is coupled in series with the fourth LED;

generating and providing first control data to a first LED driver to control generation of the first and second switch control signals; and

receives second control data with a second LED driver via the first LED driver, wherein the first LED driver is coupled to the first and second switches and the second LED driver is coupled to the third and fourth switches.

15. The method of claim 14 further comprising:

generating and providing data to an LED driver to control generation of the first and second switch control signals.

16. The method of claim 14 wherein the second switch is coupled in parallel with the second LED.

17. The method of claim 14 further comprising:

generating N additional control signals to control duty cycles of N additional switches, wherein each of the N additional switches is coupled in parallel with at least one LED, each LED, including the first and second LEDs, are coupled in series, and N is an integer greater than or equal to one.

18. The method of claim 14 wherein the first switch control signal controls shunting of the first LED, the method further comprising:

generating a control signal to control an LED current flowing through the first and second LEDs;

varying an intensity of the first and second LEDs by varying a level of the LED current;

varying duty cycles of the respective first and second switches to control color mixing of the first and second LEDs.

19. The method of claim 18 further comprising:

generating a constant current to provide a bias current for the first and second LEDs.

20. The method of claim 14 further comprising:

detecting a malfunction of the first LED.

21. The method of claim 20 further comprising:

upon detection of the malfunction of the first LED, shunting the first LED with the first switch.

22. The method of claim 14 further comprising:

providing the second control data serially from the first LED driver to the second LED driver.

23. The method of claim 14 further comprising:

generating a third switch control signal to control a duty cycle of a third switch coupled to at least a third LED to vary a relative intensity of the first, second, and third, wherein the first, second, and third LEDs are coupled in series, the second switch is coupled in parallel with the second LED, the third switch is coupled in parallel with the third LED, the first LED is a red LED, the second LED is a green LED, the third LED is a blue LED; and

varying a duty cycle of the first, second, and third switches to vary colors generated by color mixing of the first, second, and third LEDs.

24. The method of claim 14 wherein to control the duty cycle of the first switch comprises generating a pulse width modulated first switch control signal and to control the duty cycle of the second switch comprises generating a pulse width modulated second switch control signal.

25. The method of claim 14 wherein to control the duty cycle of the first switch comprises generating a pulse width density modulated first switch control signal and to control the duty cycle of the second switch comprises generating a pulse width density modulated second switch control signal.

26. The method of claim 17 wherein N is selected from group consisting of:

greater than or equal to 6, 12, and 13.

27. An apparatus for controlling multiple, series coupled light emitting diodes (LEDs), the apparatus comprising:

means for generating a first switch control signal to control a duty cycle of a first switch coupled in parallel across at least a first LED;

means for generating a second switch control signal to control a duty cycle of a second switch coupled to at least a second LED to vary a relative intensity of the first and second LEDs, wherein the first LED is coupled in series with the second LED;

means for generating a constant current from a constant current source to provide a bias current for the first and second LEDs, wherein the constant current source comprises a buck-type constant current source and the buck-type constant current source includes an inductor and a voltage source coupling switch;

means for receiving a control signal to control the voltage source coupling switch to couple an input voltage source to the inductor;

means for generating a third switch control signal to control a duty cycle of a third switch coupled in parallel across at least a third LED;

means for generating a fourth switch control signal to control a duty cycle of a fourth switch coupled to at least a fourth LED to vary a relative intensity of the third and fourth LEDs, wherein the third LED is coupled in series with the fourth LED;

means for generating and providing first control data to a first LED driver to control generation of the first and second switch control signals; and

means for receives second control data with a second LED driver via the first LED driver, wherein the first LED driver is coupled to the first and second switches and the second LED driver is coupled to the third and fourth switches.