System and methods for thermal compensation in AMOLED displays

• US 10,460,669 B2
• Filed: 05/15/2018
• Issued: 10/29/2019
• Est. Priority Date: 12/02/2010
• Status: Active Grant

• Current Assignee: IGNIS Innovation Incorporated
• Original Assignee: IGNIS Innovation Incorporated
• Inventors: Jaffari, Javid, Chaji, Gholamreza, Liu, Tong
• Primary Examiner(s): Lin, Chun-Nan
• Application Number:
  US15/979,658
• Publication Number:
  US 20180261162A1
• Time in Patent Office: 532 Days
• CPC Class Codes: G06F 2119/08 Thermal analysis or thermal optimisation
• CPC Class Codes: G06F 30/23 using finite element methods [FEM] or finite difference methods [FDM]
• CPC Class Codes: G09G 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• CPC Class Codes: G09G 2310/0289 Details of voltage level shifters arranged for use in a driving circuit
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/0271 Adjustment of the gradation levels within the range of the gradation scale, e.g. by redistribution or clipping
• 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 2320/041 Temperature compensation
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• 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 3/3258 with pixel circuitry controlling the voltage across the light-emitting element
• 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

Disclosed is a circuit and technique to determine the temperature of an AMOLED display in order to calibrate programming data signals. The temperature of selected pixels of a plurality of pixels in an AMOLED display is measured via one of several disclosed methods. A thermal sensor for the selected pixels may be used. A measurement of output voltage data may be used to estimate temperature. A finite element analysis model may be used based on consumed power of the selected pixel. The temperature data for the selected pixel is then interpolated to the neighboring non-selected pixels to estimate the temperature of those pixels.

Claims

1. A semiconductor device, comprising:

a plurality of pixels arranged in an array, the plurality of pixels including one or more first pixels, one or more second pixels different from the one or more first pixels, and a pixel different from the one or more first pixels and the one or more second pixels; and

a controller for programming the pixel to control the brightness of the pixel, and for estimating a temperature of the pixel at a first time with use of one or more pixel temperatures determined only for the one or more first pixels, and for estimating a temperature of the pixel at a second time different from the first time with use of one or more pixel temperatures determined only for the one or more second pixels.

2. The semiconductor device of claim 1 wherein the controller is further for determining the one or more pixel temperatures of the one or more first pixels and determining the one or more pixel temperatures of the one or more second pixels, and wherein the one or more first pixels are in the form of a first spaced array, and the one or more second pixels are in the form of a second spaced array, spaced away from and substantially similar to the first spaced array.

3. The semiconductor device of claim 2 wherein the one or more first pixels and a spacing of the first spaced array away from the second spaced array are randomly determined.

4. The semiconductor device of claim 1 wherein the one or more first pixels and the one or more second pixels are randomly determined.

5. The semiconductor device of claim 1, wherein the estimating is performed by interpolating the determined one or more pixel temperatures of the one or more first pixels or the one or more second pixels to the pixel, the interpolation including one of nearest neighbor, bilinear, bicubic or Kriging.

6. The semiconductor device of claim 1, wherein the controller compensates the programming of the pixel to offset the effect of the estimated temperatures on the pixel.

7. The semiconductor device of claim 1, further comprising one or more thermal sensors each respectively in proximity to one pixel of the one or more first pixels or one pixel of the one or more second pixels and for use by the controller for determining the one or more pixel temperatures of the one or more first pixels and determining the one or more pixel temperatures of the one or more second pixels.

8. The semiconductor device of claim 1, wherein the controller is further for determining the one or more pixel temperatures of the one or more first pixels and determining the one or more pixel temperatures of the one or more second pixels, and wherein during at least one blank frame a gate terminal of a drive transistor of each of the one or more first pixels and each of the one or more second pixels is charged to a calibration voltage via a data line input to produce an output voltage having a change in value used by the controller to determine the pixel temperatures of each of the one or more first pixels and each of the one or more second pixels.

9. The semiconductor device of claim 1, wherein each pixel includes a drive transistor and an organic light emitting device coupled to the drive transistor, each drive transistor having a gate, and wherein the controller causing a programming voltage to be applied to the gate of the respective drive transistors to control the brightness of each pixel.

10. The semiconductor device of claim 9, wherein the one or more pixel temperatures of the one or more first pixels and the one or more second pixels is determined by the controller using a finite difference model to reduce a differential equation of pixel power to an equivalent circuit, the equivalent circuit being based on measured power of each pixel and the dimensions of the OLED to solve for a voltage equivalent model of pixel temperature.

11. A method of determining temperature of a pixel of a display including a controller and a plurality of pixels arranged in an array, the plurality of pixels including the pixel, one or more first pixels different from the pixel, and one or more second pixels different from the pixel and the one or more first pixels, the pixel programmed by the controller to control the brightness of the pixel, the method comprising:

estimating by the controller a temperature of the pixel at a first time with use of one or more pixel temperatures determined only for the one or more first pixels and

estimating by the controller a temperature of the pixel at a second time different from the first time with use of one or more pixel temperatures determined only for the one or more second pixels.

12. The method of claim 11 further comprising determining the one or more pixel temperatures of the one or more first pixels and determining the one or more pixel temperatures of the one or more second pixels, and wherein the one or more first pixels are in the form of a first spaced array, and the one or more second pixels are in the form of a second spaced array, spaced away from and substantially similar to the first spaced array.

13. The method of claim 12 wherein the one or more first pixels and a spacing of the second spaced array away from the first spaced array are randomly determined.

14. The method of claim 11 wherein the one or more first pixels and the one or more second pixels are randomly determined.

15. The method of claim 11, wherein the estimating is performed by interpolating the determined one or more pixel temperatures of the one or more first pixels or the one or more second pixels to the pixel, the interpolation including one of nearest neighbor, bilinear, bicubic or Kriging.

16. The method of claim 11, further comprising compensating the programming of the pixel to offset the effect of the estimated temperatures on the pixel.

17. The method of claim 11, wherein the one or more pixel temperatures of the one or more first pixels and the one or more pixel temperatures of the one or more second pixels are determined by one or more thermal sensors each respectively in proximity to one pixel of the one or more first pixels or one pixel of the one or more second pixels.

18. The method of claim 11, further comprising determining the one or more pixel temperatures of the one or more first pixels and determining the one or more pixel temperatures of the one or more second pixels, and wherein during at least one blank frame a gate terminal of a drive transistor of each of the one or more first pixels and each of the one or more second pixels is charged to a calibration voltage via a data line input to produce an output voltage having a change in value used to determine the pixel temperatures of each of the one or more first pixels and each of the one or more second pixels.

19. The method of claim 11, wherein each pixel includes a drive transistor and an organic light emitting device (OLED) coupled to the drive transistor, each drive transistor having a gate.

20. The method of claim 19, wherein the one or more pixel temperatures of the one or more first pixels and the one or more pixel temperatures of the one or more second pixels are determined by a finite difference model to reduce a differential equation of pixel power to an equivalent circuit, the equivalent circuit being based on measured power of each pixel and the dimensions of the OLED to solve for a voltage equivalent model of pixel temperature.

21. A non-transitory machine readable medium having stored thereon instructions for determining temperature of a pixel of a display including a plurality of pixels arranged in an array, the plurality of pixels including the pixel, one or more first pixels different from the pixel, and one or more second pixels different from the pixel and the one or more first pixels, the pixel programmed to control the brightness of the pixel, the non-transitory machine readable medium comprising machine executable code which when executed by at least one machine, causes the at least one machine to:

estimate a temperature of the pixel at a first time with use of one or more pixel temperatures determined only for the one or more first pixels; and

estimate a temperature of the pixel at a second time different from the first time with use of one or more pixel temperatures determined only for the one or more second pixels.

22. The non-transitory machine readable medium of claim 21, wherein the estimation includes interpolating the determined one or more pixel temperatures of the one or more first pixels or the one or more second pixels to the pixel, the interpolation including one of nearest neighbor, bilinear, bicubic or Kriging.

23. The non-transitory machine readable medium of claim 21, wherein the one or more pixel temperatures of the one or more first pixels and the one or more pixel temperatures of the one or more second pixels are determined by the at least one machine using a finite difference model to reduce a differential equation of pixel power to an equivalent circuit, the equivalent circuit being based on measured power of each pixel and the dimensions of the OLED to solve for a voltage equivalent model of pixel temperature.

24. The non-transitory machine readable medium of claim 21, wherein the machine executable code, when executed by the at least one machine, causes the machine to determine the one or more pixel temperatures of the one or more first pixels and determine the one or more pixel temperatures of the one or more second pixels, and wherein the one or more first pixels are in the form of a first spaced array, and the one or more second pixels are in the form of a second spaced array, spaced away from and substantially similar to the first spaced array.