Method and system for precharging OLED/PLED displays with a precharge latency

• US 20030142088A1
• Filed: 10/17/2002
• Published: 07/31/2003
• Est. Priority Date: 10/19/2001
• Status: Active Grant

• Current Assignee: Clare Micronix Integrated Systems, Inc.
• Original Assignee: Clare Micronix Integrated Systems, Inc.
• Inventors: LeChevalier, Robert
• Granted Patent: US 7,126,568 B2
• Time in Patent Office: Days
• US Class Current: 345/211
• CPC Class Codes: G09G 2310/0248 Precharge or discharge of column electrodes before or after applying exact column voltages
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• CPC Class Codes: G09G 2310/0259 with use of an analog or digital ramp generator in the column driver or in the pixel circuit
• CPC Class Codes: G09G 2320/0223 Compensation for problems related to R-C delay and attenuation in electrodes of matrix panels, e.g. in gate electrodes or on-substrate video signal electrodes
• CPC Class Codes: G09G 2320/029 by monitoring one or more pixels in the display panel, e.g. by monitoring a fixed reference pixel
• CPC Class Codes: G09G 3/3216 using a passive matrix
• CPC Class Codes: G09G 3/3283 in which the data driver supplies a variable data current for setting the current through, or the voltage across, the light-emitting elements

Abstract

An organic light emitting diode (OLED)/polymer OLED (PLED) displays and operation with a precharge latency. Particularly, precharging operation of such a display device with a precharge switch latency. According to the operation, a capacitive aspect of a display element is precharged, and the display element is activated so as to conducting a current therethrough. The precharging is terminated after the activation of the display element. Then a current is supplied and conducted through the display element for exposure of the display element. In this operation, a precharge droop that may occur during the transition between precharge and exposure can be avoided or minimized.

Claims

1. A display device comprising:

a voltage source; and

a display element configured to emit light, said display element being electrically connected to said voltage source, wherein said voltage source is configured to supply a voltage to said display element for a duration that is longer than the duration necessary to raise a voltage level across said display element to a precharge voltage level.

2. The display device of claim 1, wherein said display element is an OLED.

3. The display device of claim 1, wherein said display element is an PLED.

4. The display device of claim 1, wherein said precharge voltage level is substantially equal to the voltage level which causes the display element to begin luminescing substantially immediately upon receiving current from a current source.

5. The display device of claim 4, further comprising:

a first switch configured to electrically connect a first terminal of said display element to said voltage source; and

a second switch configured to electrically connect a second terminal of said display element to ground.

6. The display device of claim 5, wherein said first switch and said second switch each comprise a metal oxide semiconductor (MOS) transistor.

7. The display device of claim 6, wherein said first switch electrically connects said voltage source to said first terminal of said display element before said second switch electrically connects said second terminal of said display element to ground, and thereafter said first switch maintains said electrical connection between said voltage source and said first terminal for a predetermined period of time.

8. The display device of claim 7, wherein a current source is applied to said display element after said predetermined time period.

9. The display device of claim 1, further comprising:

a plurality of display elements having N rows and M columns, such that a first terminal of each of the display elements in each column is electrically connected to a column line and a second terminal of each of the display elements in each row is electrically connected to a row line.

10. The display device of claim 9, further comprising:

a plurality of M column driver circuits, each being electrically connected to a respective column line; and

a plurality of N row driver circuits, each being electrically connected to a respective row line.

11. The display device of claim 10, wherein each of said plurality of M column driver circuits comprises a first switch configured to electrically connect each of said respective column lines to said voltage source, and each of said plurality of N row driver circuits comprises a second switch configured to electrically connect each of said respective row lines to said ground.

12. A display device comprising:

a voltage source;

a plurality of display elements having N rows and M columns, such that a first terminal of each of the display elements in each column is electrically connected to a column line and a second terminal of each of the display elements in each row is electrically connected to a row line;

a representative display element electrically connected to row line J and column line K; and

a controller configured to apply said voltage source to said column line K before applying a ground signal to said row line J, and thereafter continue to apply said voltage source to said column line K for a predetermined period of time.

13. The display device of claim 12, wherein each of said plurality of display elements comprises an OLED.

14. The display device of claim 12, further comprising:

a plurality of M column driver circuits, each being electrically connected to a respective column line;

a plurality of N row driver circuits, each being electrically connected to a respective row line;

wherein each of said plurality of M column driver circuits comprises a first switch configured to electrically connect each of said respective column lines to said voltage source, and each of said plurality of N row driver circuits comprises a second switch configured to electrically connect each of said respective row lines to said ground;

a controller configured to control the operation of said plurality of M column driver circuits and said plurality of N row driver circuits such that, with respect to said representative display element, said voltage source is electrically connected to said column line K before applying said ground signal to said row line J, and thereafter the electrical connection between said voltage source and said column line K is maintained for a predetermined period of time.

15. The display device of claim 12, wherein after said predetermined period of time a current source is electrically connected to each of said first terminals of said display elements in said column K.

16. A display device comprising:

means for supplying a voltage; and

means for emitting light in response to an electrical current, wherein said supplying means provides a first terminal of said emitting means with said voltage for a duration that is longer than necessary to raise a voltage level across said emitting means to a precharge voltage level.

17. The display device of claim 16, wherein said precharge voltage is substantially equal to the voltage level which causes the emitting means to begin luminescing immediately upon being supplied with said electrical current.

18. The display device of claim 17, wherein after said voltage level across said emitting means reaches a precharge voltage level, a second terminal of said emitting means is connected to a ground terminal so that said first terminal of said emitting means is electrically connected to said voltage source and said second terminal of said emitting means is concurrently electrically connected to said ground terminal.

19. The display device of claim 18 further comprising:

means for electrically connecting said supplying means and said first terminal of said emitting means; and

means for electrically connecting said ground terminal and said second terminal of said emitting means.

20. A display device comprising:

means for supplying a voltage;

a plurality of means for emitting light in response to an electrical current, wherein said plurality of emitting means are disposed in a matrix pattern having N rows and M columns, such that a first terminal of each of said emitting means in each column is electrically connected to a column line and a second terminal of each of said emitting means in each row is electrically connected to a row line; and

a representative emitting means electrically connected to a row line J and a column line K, wherein said supplying means supplies said voltage source to said column line K for a duration that is longer than necessary to raise a voltage level across said representative emitting means to a precharge voltage level.

21. The display device of claim 20 further comprising:

means for electrically connecting said supplying means and said column line K; and

means for electrically connecting a ground terminal and said row line J.

22. A program storage device storing instructions that, when executed by a processor, perform a method of operating a display device, the method comprising:

applying a voltage source to a display element until a voltage level across the display element reaches a precharge voltage level;

waiting a predetermined period of time beyond the time at which the precharge voltage level is reached across the display element; and

removing said applied voltage source from said display element.

23. The program storage device of claim 22, wherein said method of operating a display device further comprises conducting a current through the display element before said removing said applied voltage source from said display element.

24. A method of operating a display device comprising a display element, the method comprising:

applying a voltage source to said display element until a voltage level across said display element reaches a precharge voltage level;

waiting a predetermined period of time beyond the time at which the precharge voltage level is reached across the display element; and

removing said applied voltage source from said display element.

25. The method of claim 24, wherein said display element comprises an OLED.

26. The method of claim 24, wherein said display element comprises an PLED.

27. The method of claim 24, wherein said method of operating a display device further comprises conducting a current through the display element before said removing said applied voltage source from said display element.

28. A method of operating a display device comprising a display element having a first terminal and a second terminal, comprising:

precharging a capacitive aspect of said display;

conducting a current through said display element; and

terminating said precharging after said conducting of said current through said display element.

29. The method of claim 28, wherein the precharging comprises connecting said first terminal to a voltage source.

30. The method of claim 29, wherein said precharging is terminated after a time interval sufficient to settle the voltage level across said display element after said conducting said current through said display element.

31. The method of claim 29, wherein the termination of the precharge comprises operating a switch so as to disconnect said voltage source.

32. The method of claim 31, wherein said switch comprises a metal oxide semiconductor (MOS) transistor.

33. The method of claim 32, wherein said MOS transistor is opened to disconnect said voltage source from said first terminal of said display element after said conducting said current through said display element.

34. A method of manufacturing a display device, comprising:

forming a matrix of electrically connected display elements having N rows and M columns;

programming a controller with instructions to supply a voltage to a column of display elements for a duration longer than is necessary to raise a voltage level on said column of display elements to a level that is sufficient to illuminate a particular display element electrically connected to said column.

35. The method of claim 34, wherein said display elements are OLEDs.

36. The method of claim 34, wherein said display elements are PLEDs.

37. A method of illuminating an OLED having a first terminal and a second terminal comprising:

supplying said first terminal with a voltage source;

connecting said second terminal to ground when a voltage across said OLED is about equal to a precharge voltage level;

removing said voltage source from said first terminal.

38. The method of claim 37, wherein said precharge voltage level is substantially equal to the voltage level which causes the display element to begin luminescing substantially immediately upon receiving current from a current source.

39. The method of claim 37, wherein said supplying comprises electrically connecting said first terminal of said display element to said voltage source via a first switch.

40. The method of claim 39, wherein said connecting comprises electrically connecting said second terminal of said display element to ground via a second switch.

41. The method of claim 40, wherein said first switch and said second switch each comprise a metal oxide semiconductor (MOS) transistor

42. A method of operating a display device comprising a plurality of display elements having N rows and M columns, such that a first terminal of each of the display elements in each column is electrically connected to a column line and a second terminal of each of the display elements in each row is electrically connected to a row line, and a representative display element is electrically connected to a row line J and a column line K, the method comprising:

preparing said representative display element for illumination by applying a voltage source to said column line K before applying a ground signal to said row line J, and thereafter continue applying said voltage source to said column line K for a predetermined period of time.

43. The method of claim 42, wherein said display element is an OLED.

44. The method of claim 42, wherein said preparing is concurrently performed on at least some of said plurality of display elements in a particular row.

45. The method of claim 43, wherein after said predetermined period of time a current source is electrically connected to said column line K.