Data voltage current drive amoled pixel circuit

• US 20030095087A1
• Filed: 11/05/2002
• Published: 05/22/2003
• Est. Priority Date: 11/20/2001
• Status: Active Grant

• Current Assignee: InnoLux Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Libsch, Frank R., Sanford, James L.
• Granted Patent: US 7,071,932 B2
• Time in Patent Office: Days
• US Class Current: 345/82
• CPC Class Codes: G09G 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0866 by means of changes in the pixel supply voltage
• CPC Class Codes: G09G 2310/0254 Control of polarity reversal in general, other than for liquid crystal displays
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element

Abstract

There is provided a circuit for driving an organic light emitting diode (OLED). The circuit includes a current source for providing current to a first terminal of the OLED, and a generator for providing a variable voltage signal to a second terminal of the OLED to facilitate control of the current.

Claims

1. A circuit for driving an organic light emitting diode (OLED), comprising:

a current source for providing current to a first terminal of said OLED; and

a generator for providing a variable voltage signal to a second terminal of said OLED to facilitate control of said current.

2. The circuit of claim 1, wherein said variable voltage signal comprises:

a voltage level to turn off said OLED;

a voltage level to set said drive current for said OLED; and

a voltage level to allow luminance of said OLED.

3. The circuit of claim 1, wherein said current source comprises:

a current drive transistor for providing said current to said first terminal;

a capacitor for storing a preset voltage and a data voltage, to control said current drive transistor, wherein said capacitor is connected to said first terminal; and

a data transistor for adding said data voltage onto said capacitor.

4. A circuit for driving an organic light emitting diode (OLED), comprising:

a current drive transistor for providing current to a first terminal of said OLED;

a capacitor for storing a preset voltage and a data voltage to control said current drive transistor, wherein said capacitor is connected to said first terminal;

a data transistor for adding said data voltage onto said capacitor; and

a generator for providing a variable voltage signal to a second terminal of said OLED to facilitate said control of said current drive transistor.

5. The circuit of claim 4, wherein said current is substantially independent of a threshold voltage of said current drive transistor.

6. The circuit of claim 4, wherein said preset voltage and said data voltage are referenced to a data reference voltage.

7. The circuit of claim 6, further comprising a data reference voltage transistor for establishing said data reference voltage.

8. The circuit of claim 7, wherein a preset signal controls operation of said data reference voltage transistor.

9. The circuit of claim 7,

wherein said circuit is a member of a plurality of circuits in an array of rows and columns, and

wherein said preset signal is provided to said plurality of circuits.

10. The circuit of claim 7,

wherein said circuit is in a row of an array that contains a plurality of such circuits, and

wherein said preset signal is provided from a gate line signal that is used by another row in said array.

11. The circuit of claim 4, wherein said generator facilitates said storing of said preset voltage and said data voltage.

12. The circuit of claim 4, wherein said OLED has a capacitance that facilitates said storing of said preset voltage and said data voltage.

13. The circuit of claim 4, wherein said variable voltage signal comprises a voltage level for turning off said OLED.

14. The circuit of claim 4, wherein said variable voltage signal comprises a voltage level for facilitating said storing of said preset voltage.

15. The circuit of claim 4, wherein said variable voltage signal comprises a voltage level for facilitating said storing of said data voltage.

16. The circuit of claim 4, wherein said variable voltage signal comprises a voltage level for allowing luminance of said OLED.

17. The circuit of claim 4, wherein said variable voltage signal comprises a voltage level for reversing a voltage polarity across said OLED.

18. The circuit of claim 4, wherein said variable voltage signal comprises a voltage level for reversing a source to drain voltage polarity of said current drive transistor.

19. The circuit of claim 4, wherein said variable voltage signal comprises a voltage level for reversing a gate to drain voltage polarity of said current drive transistor.

20. The circuit of claim 4, wherein said current drive transistor and said data transistor are amorphous silicon transistors.

21. A method for driving an organic light emitting diode (OLED), comprising:

providing a current to a first terminal of said OLED; and

applying a variable voltage signal to a second terminal of said OLED to facilitate control of said current.

22. The method of claim 21, wherein said providing a current comprises storing a preset voltage and a data voltage to control a transistor that provides said current.

23. A method for driving an organic light emitting diode (OLED), comprising:

applying a voltage level to a terminal of said OLED to turn off said OLED;

applying a voltage level to said terminal to set a drive current for said OLED; and

applying a voltage level to said terminal to allow luminance of said OLED.

24. The method of claim 23, further comprising converting a voltage into said drive current.

25. The method of claim 24, wherein said voltage comprises a data voltage added to a preset voltage.

26. The method of claim 24,

wherein said converting is performed by a transistor, and

wherein said drive current is independent of a threshold voltage of said transistor.

27. The method of claim 26, further comprising applying a voltage level to said terminal to reverse a gate to drain terminal voltage polarity of said transistor.

28. The method of claim 26, further comprising applying a voltage level to said terminal to reverse s a source to drain terminal voltage polarity of said transistor.

29. The method of claim 23, further comprising applying a voltage level to said terminal to reverse a voltage polarity across said OLED.