Voltage-Programming Scheme for Current-Driven Arnoled Displays

• US 20080191976A1
• Filed: 06/28/2005
• Published: 08/14/2008
• Est. Priority Date: 06/29/2004
• Status: Active Grant

• Current Assignee: IGNIS Innovation Incorporated
• Original Assignee: IGNIS Innovation Incorporated
• Inventors: Alexander, Stefan, Nathan, Arokia, Huang, Rick
• Granted Patent: US 8,115,707 B2
• Time in Patent Office: Days
• US Class Current: 345/76
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0861 with additional control of the display period without amending the charge stored in a pixel memory, e.g. by means of additional select electrodes
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• CPC Class Codes: G09G 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• CPC Class Codes: G09G 2320/0285 using tables for spatial correction of display data
• CPC Class Codes: G09G 2320/0295 by monitoring each display pixel
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2320/0693 Calibration of display systems
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3241 the current through the light-emitting element being set using a data current provided by the data driver, e.g. by using a two-transistor current mirror
• 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
• CPC Class Codes: G09G 3/3291 in which the data driver supplies a variable data voltage for setting the current through, or the voltage across, the light-emitting elements

Abstract

A system and method for driving an AMOLED display is provided. The AMOLED display includes a plurality of pixel circuits. A voltage-programming scheme, a current-programming scheme or a combination thereof is applied to drive the display. Threshold shift information, and/or voltage necessary to obtain hybrid driving circuit may be acquired. A data sampling may be implemented to acquire a current/voltage relationship. A feedback operation may be implemented to correct the brightness of the pixel.

Claims

1. A system for driving a display which includes a plurality of pixel circuits, each having a plurality of thin film transistors (TFTs) and an organic light emitting diode (OLED), comprising:

a voltage driver for generating a voltage to program the pixel circuit through a data node;

a programmable current source for generating a current to program the pixel circuit through the data node; and

a switching network for selectively connecting the data driver or the current source to one or more pixel circuits through the data node.

2. A system according to claim 1, wherein the switching network includes:

a first switch for connecting the voltage driver to one or more pixel circuits, and

a second switch for connecting the current source to one or more pixel circuits.

3. A system according to claim 2, wherein the switching network includes:

a shift register for controlling the operation of the first and second switches.

4. A system according to claim 1, further comprising:

a analog/digital converter for sampling a voltage on the data node of the pixel circuit.

5. A system according to claim 1, further comprising:

a lookup table for storing a current/voltage information representing a relationship between the program current on the data node and a program voltage on the data node associated with the program current on the data node.

6. A system according to claim 5, further comprising:

a sensing network for sensing a current consumed in the data node of the pixel circuit, or the voltage at the data node of the pixel circuit, to correct the lookup table.

7. A system according to claim 5, further comprising:

a module for correcting the voltage information during the voltage-based programming.

8. A system according to claim 1, further comprising:

a programming circuit for acquiring the threshold voltage of the TFT from the pixel circuit, having an analog to digital converter for converting an analog threshold voltage information to a digital threshold voltage information, and for programming the pixel circuit based on the digital threshold voltage information and the voltage associated with incoming video information.

23. A system according to claim 1, wherein the system is applicable to a current-programmed pixel circuit and a voltage-programmed pixel circuit.

24. A system according to claim 1, wherein the TFT includes amorphous silicon, polysilicon (n-type or p-type), crystalline silicon, or organic based TFT.

25. A system according to claim 1, wherein the OLED includes NIP or PIN OLED, and is locatable in the source or the drain of one or more driving TFTs.

34. A hybrid driving circuit for implementing the switching network according to claim 1, wherein the hybrid driving circuit is applicable to driving schemes, including drive schemes that use timing of the data, select or power inputs to the pixel circuits to achieve increased brightness uniformity, drive schemes that use current or voltage feedback, and drive schemes that use optical feedback.

36. A system according to claim 1, wherein the OLED material includes fluorescent, phosphorescent, polymer, or dendrimer.

9. A system for driving a pixel circuit having a plurality of thin film transistors (TFTs) and an organic light emitting diode (OLED), comprising:

a pre-charge controller for pre-charging and discharging a data node of the pixel circuit to acquire threshold voltage information of the TFT from the data node using an external driving circuit outside the pixel circuit; and

a hybrid driving circuit for programming the pixel circuit based on the acquired threshold voltage information and video data information displayed on the pixel circuit.

10. A system according to claim 9, wherein the hybrid driving circuit includes a capacitor coupled to the data node, and the capacitor is located outside the pixel circuit.

11. A system according to claim 9, wherein the hybrid driving circuit includes:

a sampling circuit for sampling the threshold voltage information on the data node,

a summer for summing the video data voltage and the sampled voltage threshold information, and

a switch for selectively connecting the output of the summer to the data node.

12. A system according to claim 9, wherein the hybrid driving circuit includes:

an analog to digital converter for converting the threshold voltage information to a digital threshold voltage information,

a microcomputer for storing the digital threshold voltage information and summing the digital threshold voltage information and the voltage, and

a digital to analog converter for converting the summing result output from the microcomputer to an analog data and providing the analog data to the data node.

13. A system according to claim 9, further comprising:

a programming circuit for providing a current on the data node to program the pixel circuit.

14. A system according to claim 9, wherein the hybrid driving circuit includes a switching matrix for selecting one of a voltage programming mode and a current programming mode to program the pixel by the selected programming mode.

35. A hybrid driving circuit for implementing the system according to claim 9, wherein the hybrid driving circuit is applicable to any driving schemes, including drive schemes that use timing of the data, select or power inputs to the pixel circuits to achieve increased brightness uniformity, drive schemes that use current or voltage feedback, and drive schemes that use optical feedback.

37. A system according to claim 9, wherein the system is applicable to a current-programmed pixel circuit and a voltage-programmed pixel circuit.

39. A system according to claim 9, wherein the TFT includes amorphous silicon, polysilicon (n-type or p-type), crystalline silicon, or organic based TFT.

41. A system according to claim 9, wherein the OLED includes NIP or PIN OLED, and is locatable in the source or the drain of one or more driving TFTs.

44. A system according to claim 9, wherein the OLED material includes fluorescent, phosphorescent, polymer, or dendrimer.

15. A system for driving a pixel circuit having a plurality of thin film transistors (TFTs) and an organic light emitting diode (OLED), comprising:

a sampler for sampling, from a data node of the pixel circuit, a voltage required to program the pixel circuit;

a programming circuit for programming the pixel circuit based on the sampled voltage and video data information displayed on the pixel circuit.

16. A system according to claim 15, further comprising:

a current source for providing current to the pixel circuit during a calibration mode; and

a lookup table for storing a current/voltage information representing a relationship between the programming current applied to the data node and the sampled voltage associated with the current.

17. A system according to claim 16, wherein the lookup table is created to each pixel circuit.

18. A system according to claim 16, further comprising:

a correction calculation module for correcting data from a data source based on the current/voltage information, obtained by programming the data node with a current,

during a writing mode, a voltage associated with the corrected data being applied to the pixel circuit through the data node.

19. A system according to claim 16, further comprising:

a module for extracting a threshold voltage shift of the TFT based on the sampled voltage obtained by current-programming through the data node.

20. A system according to claim 15, further comprising:

a lookup table for storing a current/voltage curve representing a relationship between a current and a voltage necessary to program the current into the pixel circuit through the data node;

a module for correcting the current/voltage curve based on the sampled voltage associated with information currently displayed on the pixel circuit,

during a writing mode, a voltage to be programmed being determined based on the current/voltage curve.

21. A system according to claim 20, wherein the lookup table is created to each pixel circuit.

22. A system according to claim 20, further comprising:

a module for extracting a threshold voltage shift of the TFT based on the corrected current/voltage curve.

38. A system according to claim 15, wherein the system is applicable to a current-programmed pixel circuit and a voltage-programmed pixel circuit.

40. A system according to claim 15, wherein the TFT includes amorphous silicon, polysilicon (n-type or p-type), crystalline silicon, or organic based TFT.

42. A system according to claim 15, wherein the OLED includes NIP or PIN OLED, and is locatable in the source or the drain of one or more driving TFTs.

43. A hybrid driving circuit for implementing the system according to claim 15, wherein the hybrid driving circuit is applicable to any driving schemes, including drive schemes that use timing of the data, select or power inputs to the pixel circuits to achieve increased brightness uniformity, drive schemes that use current or voltage feedback, and drive schemes that use optical feedback.

45. A system according to claim 15, wherein the OLED material includes fluorescent, phosphorescent, polymer, or dendrimer.

26. A method of driving a pixel circuit having a plurality of thin film transistors (TFTs) and an organic light emitting diode (OLED), comprising:

selecting a pixel circuit and pre-charging a data node of the pixel circuit using an external circuit connected through the data node;

allowing the pre-charged data node to be discharged;

extracting a threshold voltage of the TFT through the discharging step; and

programming the pixel circuit, including compensating a programming data based on the extracted threshold voltage using an external compensation circuit.

27. A method according to claim 26, wherein the extracting step includes:

sampling the threshold voltage, and

recording the sampled threshold voltage, the compensating step utilizing the recorded sampled threshold voltage.

28. A method according to claim 27, wherein the programming step includes:

subsequently programming the pixel circuit through the data node based on the threshold voltage recorded using an external circuit.

29. A method according to claim 26, wherein the programming step includes:

programming information on the pixel circuit with a current-programming scheme and a voltage-programming scheme.

30. A method of driving a pixel circuit having a plurality of thin film transistors (TFTs) and an organic light emitting diode (OLED), comprising:

sampling, from a data node of the pixel circuit, a voltage required to program the pixel circuit;

programming the pixel circuit based on the sampled voltage and information displayed on the pixel circuit.

31. A method according to claim 30, further comprising:

enabling a calibration mode, and implementing a current-programming scheme to the pixel circuit,

the sampling step implementing sampling operation during the calibration mode.

32. A method according to claim 31, further comprising:

creating, based on the sampling, a lookup table storing a current/voltage correction information representing the current used to program the pixel via the data node and the sampled voltage associated with the current,

the programming step including the step of correcting data from a data source based on the current/voltage correction information.

33. A method according to claim 30, further comprising:

storing a current/voltage correction information representing a current and a voltage necessary to program the current into the pixel circuit, and

correcting the current/voltage correction information based on the sampled voltage associated with information currently displayed on the pixel circuit.