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

• US 8,816,946 B2
• Filed: 02/07/2014
• Issued: 08/26/2014
• Est. Priority Date: 12/15/2004
• Status: Active Grant

• Current Assignee: IGNIS Innovation Incorporated
• Original Assignee: IGNIS Innovation Incorporated
• Inventors: Nathan, Arokia, Chaji, Gholamreza, Servati, Peyman
• Primary Examiner(s): ABDULSELAM, ABBAS I
• Application Number:
  US14/175,493
• Publication Number:
  US 20140168203A1
• Time in Patent Office: 200 Days
• Field of Search: 345/76, 345/82, 345/83, 345/204, 345/211, 345/214, 315/169.3
• 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;

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

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

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

responsive to updating the compensation voltage, updating the priority list.

2. The method of claim 1, further comprising:

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

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

3. The method of claim 2, further comprising programming the pixels in the normal operation mode based on the calibration information stored in the memory and programming data representing the driving voltage.

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

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

6. The method of claim 1, wherein the determining the calibration information includes comparing the pixel current of each of the n selected pixels with an expected current for each of the n selected pixels.

7. The method of claim 1, wherein the display array is an AMOLED array and wherein the pixel circuit includes an organic light emitting diode and at least one n-type or p-type thin film transistor.

8. The method of claim 1, wherein the n selected pixels from the priority list have a programming current above a threshold current (I_th).

9. The method of claim 1, wherein the generating the priority list includes 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).

10. A system for a display array having a pixel circuit, the pixel circuit being programmed through a data line, the system comprising:

a data source providing a programming data into the pixel circuit;

a current-controlled voltage source converting a current on a data line to a voltage associated with the current to extract a time-dependent parameter of the pixel circuit;

a data process and calibration unit controlling a driver to drive the pixel circuit according to at least the programming data, the data process and calibration unit receiving the time-dependent parameter extracted from the pixel circuit; and

a calibration memory storing a calibration value for the pixel circuit to compensate for the time-dependent parameter and calibrate the programming data based on the time-dependent parameter.

11. The system of claim 10, wherein the pixel circuit includes a driving transistor connected in series with a light emitting device, and wherein the extracted time-dependent parameter includes a threshold voltage of the driving transistor.

12. The system of claim 11, wherein the extracted time dependent parameter of the pixel circuit also includes a turn on voltage of the light emitting device.

13. The system of claim 11, wherein the programming data provided to the pixel circuit via the data source is modified according to the extracted time dependent parameter.

14. The system of claim 10, wherein the pixel circuit is programmed via a voltage modified according to the extracted time dependent parameter.

15. The system of claim 10, wherein the pixel circuit includes a driving transistor connected in series with a light emitting device, a storage capacitor connected to a gate terminal of the driving transistor, and wherein the pixel circuit is programmed by applying the programming voltage on the data line, via the current conveyor, the programming voltage corresponding to the programming data, and wherein the pixel circuit is configured such that the current on the data line, conveyed to the current-controlled voltage source via the current conveyor, is the current through the driving transistor while the programming voltage is applied.

16. The system of claim 15, wherein the extracted time dependent parameter is a threshold voltage of the driving transistor and is determined according to a function including the voltage associated with the current provided by the current-controlled voltage source and the programming voltage.

17. The system of claim 10, wherein the data source is operated to calibrate a subsequent programming voltage according to the extracted time dependent parameter.

18. The system of claim 10, wherein the system implements, to pixel circuits in each row of the display array, an extraction operation for extracting the time-dependent parameter of the pixel circuits during a frame time.

19. The system of claim 10, wherein the pixel circuit includes:

a first switch transistor connected to the data line conveying the programming and calibration data from the data source; and

a second switch transistor connected to a monitor line conveying the current or voltage to the data process and calibration unit.

20. The system of claim 10, wherein the data source is incorporated in the data process and calibration unit.

21. The system of claim 10, wherein the display array is an AMOLED display.

22. A system for a display array including a plurality of pixel circuits arranged in a plurality of rows, each pixel circuit including a driving transistor, at least one switch transistor, a storage capacitor and a light emitting device, the system comprising:

a monitor for monitoring a current or voltage associated with each of the plurality of pixel circuits;

a driver for providing respective programming data and calibration data to each of the plurality of pixel circuits; and

a data process unit for controlling the driver to operate the display array, the data process unit extracting a time dependent parameter of each of at least some of the plurality of pixel circuits, based on the monitored current or voltage, and

wherein the system implements, to pixel circuits in each row of the display array;

an extraction operation for extracting the time dependent parameter of each of the pixel circuits in the row, the calibration data being based on the extracted time dependent parameter,

a programming operation for programming each of the pixel circuits in the row according to at least the programming data, and

a driving operation for driving each of the pixel circuits in the row based on at least the programming data and the calibration data.

23. The system of claim 22, wherein the time dependent parameter is (a) a shift in a characteristic of the driving transistor or the light emitting device or (b) a degradation of the light emitting device.

24. The system of claim 23, wherein the characteristic is a threshold voltage of the driving transistor or a current or voltage of the light emitting device.

25. The system of claim 23, wherein the degradation of the light emitting device is determined by measuring a voltage or current of the light emitting device.

26. The system of claim 22, wherein the time dependent parameter is an aging of the driving transistor or the light emitting device.

27. The system of claim 22, wherein the extraction operation is carried out by determining a voltage or current of the light emitting device to extract aging information of the pixel circuit.

28. The system of claim 22, wherein the extraction operation is carried out during the programming operation or during the driving operation.

29. The system of claim 28, wherein the extraction operation is carried out using the same line that the programming operation uses to program each of the pixel circuits in the row or using a separate line from that used by the programming cycle to program each of the pixel circuits in the row.

30. The system of claim 22, wherein the system implements the extraction operation, the programming operation, and the driving operation sequentially.