Method and system for programming, calibrating and driving a light emitting device display

• US 7,619,597 B2
• Filed: 12/15/2005
• Issued: 11/17/2009
• Est. Priority Date: 12/15/2004
• Status: Active Grant

• Current Assignee: IGNIS Innovation Incorporated
• Original Assignee: IGNIS Innovation Incorporated
• Inventors: Chaji, Gholamreza Reza, Servati, Peyman, Nathan, Arokia
• Primary Examiner(s): Abdulselam; Abbas I
• Application Number:
  US11/304,162
• Publication Number:
  US 20060158402A1
• Time in Patent Office: 1,433 Days
• Field of Search: 345/204, 345/82, 345/92, 345/55, 345/77, 345/76, 345/600, 345/602, 345/690, 315/169.3, 702/107, 348/245, 348/246, 348/247, 348/251, 358/504
• US Class Current: 345/82
• CPC Class Codes: G01R 19/0092 measuring current only all subgroups of G01R19/00 take precedence
• 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 2310/0262 The addressing of the pixel, in a display other than an active matrix LCD, involving the control of two or more scan electrodes or two or more data electrodes, e.g. pixel voltage dependent on signals of two data electrodes
• 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 2320/029 by monitoring one or more pixels in the display panel, e.g. by monitoring a fixed reference pixel
• 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 2320/045 Compensation of drifts in the characteristics of light emitting or modulating elements
• CPC Class Codes: G09G 2320/0693 Calibration of display systems
• CPC Class Codes: G09G 3/006 Electronic inspection or testing of displays and display drivers, e.g. of LED or LCD displays testing individual LED's G01R31/2635; testing lamps G01R31/44; testing of optical features of LCD displays G02F1/1309
• CPC Class Codes: G09G 3/3208 organic, e.g. using organic light-emitting diodes [OLED]
• 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 3/3258 with pixel circuitry controlling the voltage across the light-emitting element
• 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 method and system for programming, calibrating and driving a light emitting device display is provided. The system may include extracting a time dependent parameter of a pixel for calibration.

Claims

1. A method of real-time calibration for a display array having a plurality of pixel circuits arranged in rows and columns, the method comprising:

generating a priority list of pixels, associating calibration priorities with a plurality of pixel circuits from the pixel circuits of the display array;

selecting one or more pixels (n) from the priority list, the n selected pixels having the highest calibration priorities of a set of pixels in the priority list that are from a column of the display array being programmed;

programming each of the n selected pixels in the column, with a respective driving voltage;

monitoring a pixel current of each of the n selected pixels;

determining calibration information for each of the n selected pixels based on their respective driving voltages and their monitored pixel currents;

updating a compensation voltage of the n selected pixels stored in a memory based on the calibration information; and

updating the priority list to associate a lowest calibration priority with each of the n selected pixels.

2. The method according to claim 1, further comprising the steps of:

enabling a calibration mode for each of the n selected pixels; and

enabling normal operation mode for the rest of the pixels in the column of the display array being programmed.

3. The method according to claim 2, wherein the step of implementing programming includes the step of:

programming the pixels on the normal operation mode based on a combination of the calibration data stored in the compensation memory and a programming data.

4. The method as claimed in claim 3, wherein the driving voltage of each pixel is based on a programming voltage of each pixel and a compensation voltage of each pixel stored in memory.

5. The method according to claim 1, wherein the priority list is an ordered list with the highest calibration priority pixel at the top, and wherein the step of updating the priority list comprises moving the n selected pixels to the bottom of the priority list.

6. The method as claimed in claim 1, wherein α

is 3.

7. A method according to claim 1, wherein the step of determining the calibration information comprises comparing the pixel current of each of the n selected pixels with an expected current for each of the n selected pixels.

8. The method as claimed in claim 7, further comprising the step of programming the rest of the pixels in the selected column with a respective driving voltage.

9. The system according to claim 1, wherein the display array is an AMOLED array.

10. The system according to claim 1, wherein the pixel circuit includes an organic light emitting diode.

11. The system according to claim 1, wherein the pixel circuit includes at least one n-type or p-type thin film transistor (TFT).

12. The method as claimed in claim 1, wherein the n selected pixels from the priority list have a programming current above a threshold current (I_th).

13. The method as claimed in claim 1, wherein generating the priority list comprises associating the calibration priorities with the plurality of pixel circuits from the pixel circuits of the display array, the plurality of pixel circuits having a programming current above a threshold current (I_th).

14. The method as claimed in claim 1, wherein:

15. A system for real-time calibration for a display array having a plurality of pixel circuits arranged in rows and columns, the system comprising:

a voltage driver for providing a plurality of driving voltages for programming a plurality of pixels in a column of the display array being programmed;

a calibration scheduler for selecting one or more pixels (n) from a priority list of pixels, the priority list, associating calibration priorities with a plurality of pixel circuits from the pixel circuits of the display array, the n selected pixels having the highest calibration priorities of a set of pixels in the priority list that are from the column of the display array being programmed;

a monitor for selectively coupling the voltage driver to the n selected pixels in the display array and measuring a pixel current of each of the n selected pixels;

a compensation voltage generator for generating a compensation voltage for each of the n selected pixels based on the measured n pixel currents; and

a compensation memory for storing the compensation voltages of the n selected pixels.

16. The system according to claim 15, wherein the monitor comprises:

a sensor for sensing voltages across n resistors based on the pixel currents flowing through the resistors;

a translator for translating a programming current to a corresponding programming voltage; and

a comparator for comparing the sensed voltage with the programming voltage.

17. The system according to claim 16, wherein each of the pixel circuits are current programmed pixel circuits.

18. The system according to claim 16, wherein the driving voltages for programming the plurality of pixels provided by the voltage driver are based on programming voltages for the plurality of pixels and the compensation voltages of the plurality of pixels stored in the compensation memory.

19. The system according to claim 16, wherein the monitor includes n switches for selectively connecting the voltage driver to the n selected pixels through the sensor.

20. The system as claimed in claim 15, wherein the calibration scheduler includes the priority list, the priority list with the highest calibration priority pixel at the top, and wherein the calibration scheduler updates the priority list by moving the n selected pixels to the bottom of the priority list.

21. The system as claimed in claim 15, wherein the calibration scheduler places each of the n selected pixels into a calibration mode, and places the rest of the plurality of pixels in the column being programmed into a normal operation mode.

22. The system as claimed in claim 21, wherein the voltage driver is coupled directly to the pixels in the normal operation mode, and is coupled to the pixels in the calibration mode through the monitor.

23. The system as claimed in claim 15, wherein the n selected pixels from the priority list have a programming current above a threshold current (I_th).

24. The system as claimed in claim 15, wherein the priority list is generated by associating the calibration priorities with the plurality of pixel circuits from the pixel circuits of the display array, the plurality of pixel circuits having a programming current above a threshold current (I_th).

25. The system as claimed in claim 15, wherein:

26. The system as claimed in claim 25, wherein α

is 3.