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

• US 20060158402A1
• Filed: 12/15/2005
• Published: 07/20/2006
• 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
• Granted Patent: US 7,619,597 B2
• Time in Patent Office: Days
• 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 row and column, comprising the steps of:

generating a priority list of pixels, which is used to prioritize pixels for calibration based on display and previous calibration data, the priority list being used to select one or more (n) pixels which are programmed with currents higher than a threshold current for calibration;

selecting n pixels in a selected column of the display array from the linked list;

implementing programming to the pixels in the selected column, including;

monitoring a pixel current for the n pixels and obtaining calibration data;

updating a compensation memory based on the calibration data for calibration;

sorting the priority list for the next programming.

2. A method according to claim 1, wherein the step of implementing programming includes the step of:

enabling calibration mode for the n pixels in the selected column, and enabling normal operation mode for the rest of the pixels in the selected column.

3. A method according to claim 1, wherein the step of sorting the list includes the step of:

moving the n pixels that are just calibrated to the end of the priority list.

4. A method according to claim 1, wherein the step of monitoring includes the step of:

sensing the current, and

comparing the current with an expected current.

5. A 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.

12. A system according to claim 1, wherein the display array is an AMOLED array.

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

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

6. A system for real-time calibration for a display array having a plurality of pixel circuits arranged in row and column, each pixel circuit having a light emitting device and a driving transistor, the system comprising:

a calibration scheduler for controlling programming and calibration of the display array, including;

a priority list for listing one or more pixels for calibration based on display data;

module for enabling, during a programming cycle, calibration mode for one or more pixels in the selected column, which are selected from the priority list, and during a programming cycle, enabling normal operation mode for the rest of the pixels in the selected column;

a monitor for monitoring a pixel current for the pixels in the calibration mode through the selected column;

a generator for generating a calibration data based on the monitoring result;

a memory for storing calibration data; and

an adjuster for adjusting a programming data applied to the display array based on the calibration data when the pixel on the normal operation mode is programmed.

7. A system according to claim 6, wherein the monitor includes a sensor for sensing the current in a form of voltage, a translator for changing a programming data in a form of current to an expected voltage data, and a comparator for comparing the sensed voltage with the expected voltage data.

8. A system according to claim 7, wherein the pixel circuit is a current programmed pixel circuit.

9. A system according to claim 7, wherein the display array is connected to a voltage data driver, and an input to the voltage data driver is changed based on the calibration data stored in the memory.

10. A system according to claim 7, wherein the monitor includes a switch for selectively connecting the selected column to the sensor.

11. A system according to claim 9, wherein the monitor includes a switch for selectively connecting the pixels in the calibration mode or the pixels in the normal operation mode to the voltage data driver.

15. 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 for providing a programming data into the pixel circuit;

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

16. A system for a display array including a plurality of pixel circuits, 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 on the pixel circuit;

a data process unit for controlling the operation of the display array, the data process unit extracting information on an aging of the pixel circuit, based on the monitored current or voltage and determining a state of the pixel circuit;

a driver controlled by the data process unit and for providing programming and calibration data to the pixel circuit, based on the state of the pixel circuit.

17. A system for driving a display array, the display array including a plurality of pixel circuits, 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 on the pixel circuit;

a data process unit for predicting a shift in the voltage of the light emitting device, based on the monitored current or voltage and determining the state of the pixel circuit; and

a circuit for providing, to the light emitting device, a bias associated with the shift in the voltage of the light emitting device.

18. A system for a display array including a plurality of pixel circuits, each pixel circuit having a driving transistor, at least one switch transistor, a storage capacitor and a light emitting device, the light emitting device being located at a programming path for programming the pixel circuit, the system comprising:

a controller for controlling the operation of the display array;

a driver for providing operation voltage to the pixel circuit based on the control of the controller; and

the driver providing the operation voltage to the pixel circuit during a programming cycle such that the light emitting device being removed from the programming path.