METHOD AND APPARATUS FOR CONTROLLING LIGHT EMITTING DIODE

• US 20080180414A1
• Filed: 01/30/2007
• Published: 07/31/2008
• Est. Priority Date: 01/30/2007
• Status: Abandoned Application

• Current Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: Lui, Chong Yiu Dennis, Fung, Kai Ming, Li, Che Chung Roy, Lau, Chin Tung Derek
• Application Number:
  US11/668,472
• Publication Number:
  US 20080180414A1
• Time in Patent Office: Days
• US Class Current: 345/204
• CPC Class Codes: G09G 2320/041 Temperature compensation
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/0686 with two or more screen areas displaying information with different brightness or colours
• CPC Class Codes: G09G 2360/145 the light originating from the display screen
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: G09G 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix

Abstract

A method of driving an LED includes determining an operational parameter of the LED, determining a driving signal parameter for the LED, and generating a periodic driving signal for driving the LED. The generated periodic driving signal has a duty cycle that depends on the determined driving signal parameter and the determined operational parameter of the LED.

Claims

1. A method of driving an LED, the method comprising:

determining an operational parameter of the LED;

determining a driving signal parameter for the LED;

generating a periodic driving signal for driving the LED, wherein the generated periodic driving signal has a duty cycle dependent on the determined driving signal parameter and the determined operational parameter of the LED.

2. The method of driving an LED according to claim 1, wherein the operational parameter corresponds to a range of characteristic values of a characteristic of the LED, the characteristic of the LED being one or a combination of wavelength of light output, brightness of light output, and LED forward voltage.

3. The method of driving an LED according to claim 2, wherein the range of characteristic values of the characteristic of the LED corresponds to a bin value.

4. The method of driving an LED according to claim 1, wherein the duty cycle of the generated periodic driving signal is also dependent on a second determined operational parameter that corresponds to a measured temperature value associated with the LED.

5. The method of driving an LED according to claim 1, wherein the determined driving signal parameter for the LED is dependent on a master driving signal that is not dependent on the determined operational parameter of the LED, the determined driving signal parameter being adjusted dependent on the determined operational parameter in order to generate the periodic driving signal.

6. The method of driving an LED according to claim 5, wherein determining the driving signal parameter comprises receiving a count or duration value for one of two states of the master driving signal.

7. The method of driving an LED according to claim 6, wherein receiving the count or duration value comprises counting a number of clock cycles during the one of two states of the master periodic driving signal, the master periodic driving signal being a pulse width modulation signal having a cycle of a predetermined number of clock cycles.

8. The method of driving an LED according to claim 1, wherein determining the driving signal parameter comprises receiving a control signal message containing the driving signal parameter.

9. The method of driving an LED according to claim 1, further comprising:

determining an operational parameter for a second LED;

generating a second periodic driving signal for driving the second LED, the generated second periodic driving signal having a duty cycle dependent on the determined driving signal parameter and the determined second operational parameter of the LED.

10. The method of driving an LED according to claim 9, wherein the driving signal parameter corresponds to the duty cycle of a master pulse width modulation signal, and generating the first and second periodic driving signals comprises adjusting the duty cycles of the master PWM driving signal according to the operational parameter of the first and second LEDs in order to generate the respective first and second periodic driving signals.

11. A driver for driving an LED, the driver comprising:

a memory that stores an operational parameter of the LED;

a controller coupled to the memory and arranged to determine a driving signal parameter for the LED; and

a periodic signal generator coupled to the controller and arranged to control a switch for switching the LED with a generated periodic driving signal, the periodic signal generator arranged to adjust a duty cycle of the generated periodic driving signal dependent on the determined driving signal parameter and the stored operational parameter of the LED.

12. A driver architecture for driving an array of LEDs, the array of LEDs being arranged into a plurality of regional arrays of LEDs each having a common LED operational parameter, the driver architecture comprising:

one or more controllers arranged to determine a driving signal parameter for each regional array of LEDs;

a memory coupled to the one or more controllers that stores each common LED operational parameter for each respective regional array of LEDs; and

a periodic signal generator coupled to the controller for each regional array of LEDs, each periodic signal generator arranged to generate a periodic driving signal for the respective regional array of LEDs, wherein a duty cycle of each periodic driving signal is controlled to be dependent on the respective LED operational parameter for the respective regional array of LEDs and the respective driving signal parameter.

13. The driver architecture according to claim 12, further comprising:

a plurality of drivers for driving a respective regional array of LEDs, each driver comprising a said controller and a said periodic signal generator;

a master LED driver coupled to the plurality of said drivers, wherein the master LED driver generates the or each respective driving signal parameter for each regional array of LEDs.

14. The driver architecture according to claim 13, wherein the master LED driver generates one or more master periodic driving signals according to the or each respective driving signal parameter and each said driver determines the respective driving signal parameter from the or the respective master periodic driving signal.

15. The driver architecture according to claim 14, wherein each periodic driving signal is synchronized with the master periodic driving signal.

16. The driver architecture according to claim 12, wherein the duty cycle of a said periodic driving signal is further controlled to be dependent on a non-linear parameter of the respective driver.

17. The driver architecture according to claim 12, wherein a said driver further comprises a second periodic signal generator, the second periodic signal generator generating a second periodic driving signal for a respective area of the respective regional array of LEDs, the duty cycle of each second periodic driving signal being controlled to be dependent on the respective LED operational parameter for the respective regional array of LEDs, the respective driving signal parameter and a dimming parameter for the respective area of the regional array of LEDs.

18. The driver architecture according to claim 12, wherein the array of LEDs form a backlighting unit for a liquid crystal display.

19. The driver architecture according to claim 12, wherein the driver further generates different driving signal parameters for each regional array of LEDs in order to implement regional dimming of the regional arrays of LEDs.

20. The driver architecture according to claim 13, wherein the drivers and the master LED driver are integrated into a single integrated circuit.