Method and apparatus for controlling driving current of illumination source in a display system

• US 20050093488A1
• Filed: 10/28/2003
• Published: 05/05/2005
• Est. Priority Date: 10/28/2003
• Status: Active Grant

• Current Assignee: AU Optronics Corporation
• Original Assignee: AU Optronics Corporation
• Inventors: Lo, I-Hsin, Hung, Mao-Chi
• Granted Patent: US 7,057,359 B2
• Time in Patent Office: Days
• US Class Current: 315/307
• CPC Class Codes: H05B 31/50 specially adapted for ac
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/345 Current stabilisation; Maintaining constant current
• CPC Class Codes: H05B 47/18 via data-bus transmission

Abstract

The present application describes a programmable current controller for regulating an operating driving current flowing through an illumination source. The driving current is regulated according to a digital reference corresponding to a predetermined operating current for the illumination source. The digital reference can be converted into a reference electrical parameter (current or voltage). The reference electrical parameter is compared with an operating electrical parameter (current or voltage) corresponding to the operating driving current of the illumination source. Based on the comparison, a driving bias current is generated, which is used to regulate the operating driving current of the illumination source.

Claims

1. A programmable current controller comprising:

a programmable interface configured to program a digital reference in a memory,

wherein the digital reference corresponds to a predetermined driving current for at least one illumination source;

a digital-to-analog converter coupled to the programmable interface and configured to convert the digital reference into a first electrical parameter;

a comparator coupled to the programmable interface and configured to

compare the first electrical parameter with a second electrical parameter corresponding to an operating driving current of the at least one illumination source, and

generate a driving bias current; and

a current regulator coupled to the comparator and configured to

regulate the operating driving current of the at least one illumination source according to the driving bias current, wherein the driving bias current corresponds to a difference between the first and second electrical parameters.

2. A programmable current controller according to claim 1, wherein

the comparator is a voltage comparator;

the first electrical parameter is a voltage corresponding to the predetermined driving current for the at least one illumination source; and

the second electrical parameter is a feedback voltage corresponding to the operating driving current of the at least one illumination source.

3. A programmable current controller according to claim 1, wherein

the comparator is a current detector;

the first electrical parameter is a current corresponding to the predetermined driving current for the at least one illumination source; and

the second electrical parameter is a feedback current corresponding to the operating driving current of the at least one illumination source.

4. A programmable current controller according to claim 1, further comprising:

a sensor coupled to the at least one illumination source and configured to measure the second electrical parameter.

6. A programmable current controller according to claim 1, wherein the programmable interface is an inter-integrated circuit serial interface.

7. A programmable current controller according to claim 1, wherein the programmable interface is a three-wire serial interface.

8. A programmable current controller according to claim 1, wherein the current regulator further comprises

a metal-oxide semiconductor transistor, wherein

a gate terminal of the metal-oxide-semiconductor transistor receives the driving bias current,

a drain terminal of the metal-oxide-semiconductor transistor is coupled to a power supply, and

a source terminal of the metal-oxide-semiconductor transistor is grounded.

9. A programmable current controller according to claim 1, wherein the at least one illumination source comprises at least one light-emitting diode.

5. A programmable current controller according to claim 5, wherein the sensor is a resistor.

10. A display system comprising:

a display panel having at least one illumination source; and

a programmable current controller coupled to the at least one illumination source,

wherein the programmable current controller is configured to regulate an operating driving current of the at least one illumination source according to a digital reference corresponding to a predetermined reference driving current.

11. A display system according to claim 10, wherein the display panel is a liquid crystal display panel.

12. A display system according to claim 10, wherein the programmable current controller comprises:

a programmable interface configured to program the digital reference in a memory;

a digital-to-analog converter coupled to the programmable interface and configured to convert the digital reference into a first electrical parameter;

a comparator coupled to the programmable interface and configured to

compare the first electrical parameter with a second electrical parameter corresponding to the operating driving current of the at least one illumination source, and

generate a driving bias current; and

a current regulator coupled to the comparator and configured to

regulate the operating driving current of the at least one illumination source according to the driving bias current, wherein the driving bias current corresponds to a difference between the first and second electrical parameters.

13. A display system according to claim 12, wherein the programmable current controller further comprising:

a sensor coupled to the at least one illumination source and configured to measure the second electrical parameter.

14. A programmable current controller according to claim 12, wherein the sensor is a resistor.

15. A method of regulating an operating driving current for at least one illumination source of a display system comprising:

measuring a first electrical parameter corresponding to the operating driving current of the at least one illumination source;

converting a digital reference into a second electrical parameter, wherein the digital reference corresponds to a predetermined driving current for the at least one illumination source;

comparing the first electrical parameter with the second electrical parameter;

based on the comparison, generating a driving bias current; and

regulating the operating driving current of the at least one illumination source according to the driving bias current.

16. A method according to claim 15, wherein

the first electrical parameter is a feedback voltage corresponding to the operating driving current of the at least one illumination source;

and

the second electrical parameter is a voltage corresponding to the predetermined driving current for the at least one illumination source.

17. A method according to claim 15, wherein

the first electrical parameter is a feedback current corresponding to the operating driving current of the at least one illumination source;

and

the second electrical parameter is a current corresponding to the predetermined driving current for the at least one illumination source.

18. A method according to claim 15, wherein the digital reference is stored in a memory.

19. A method according to claim 15, wherein the driving bias current corresponds to a difference between the first and second electrical parameters.

20. A method according to claim 15, wherein the display system is a liquid crystal display system.

21. A method according o claim 15, wherein the at least one illumination source includes at least one light-emitting diode.