Display with peak luminance control sensitive to brightness setting

• US 9,747,840 B2
• Filed: 05/27/2016
• Issued: 08/29/2017
• Est. Priority Date: 11/06/2013
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Bi, Yafei, Yao, Wei H.
• Primary Examiner(s): Nguyen, Kevin M
• Application Number:
  US15/167,549
• Publication Number:
  US 20160275865A1
• Time in Patent Office: 459 Days
• CPC Class Codes: G09G 2300/0828 forming a digital to analog [D/A] conversion circuit
• 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 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• CPC Class Codes: G09G 2320/029 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 2320/0606 Manual adjustment
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2320/0673 for control of gamma adjustment, e.g. selecting another gamma curve
• CPC Class Codes: G09G 2320/0693 Calibration of display systems
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2330/12 Test circuits or failure detection circuits included in a display system, as permanent part thereof
• CPC Class Codes: G09G 2354/00 Aspects of interface with display user
• CPC Class Codes: G09G 2360/144 the light being ambient light
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• 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 3/3275 Details of drivers for data electrodes

Abstract

A display may have an array of display pixels to display images. Digital display data may be received by a digital-to-analog converter. The digital-to-analog converter can convert the digital display data to analog display data for the display pixels. The magnitudes of the analog display data signals that the digital-to-analog converter provides to the display pixels can be controlled by a control signal such as a reference voltage received by the digital-to-analog converter. A brightness controller may have multiple peak luminance control profiles. A brightness setting may be processed by a look-up table to produce information identifying a selected one of the peak luminance control profiles. The brightness controller may use the selected peak luminance control profile and average frame luminance for the digital display data to produce the reference voltage that controls the digital-to-analog controller.

Claims

1. Display circuitry, comprising:

an array of display pixels; and

display control circuitry that displays images on the array of display pixels, wherein the display control circuitry includes;

transistor performance measurement circuitry configured to apply signals to transistors in the array of display pixels and measure corresponding results to obtain threshold voltage information, wherein the display control circuitry is configured to calculate threshold voltage calibration data based on the threshold voltage information, wherein the transistor performance measurement circuitry comprises a digital-to-analog converter and a current supply, wherein the digital-to-analog converter and the current supply are configured to apply the signals to the transistors in the array of display pixels, wherein the transistor performance measurement circuitry comprises an additional digital-to-analog converter and a comparator, and wherein the additional digital-to-analog converter and the comparator are configured to measure the corresponding results to obtain the threshold voltage information; and

storage that is configured to store the threshold voltage calibration data, wherein the display control circuitry is configured to operate the array of display pixels using the threshold voltage calibration data from the storage.

2. The display circuitry defined in claim 1, wherein the storage comprises static random-access memory.

3. The display circuitry defined in claim 2, wherein each pixel in the array of display pixels comprises a drive transistor that is coupled in series with a corresponding light emitting diode.

4. The display circuitry defined in claim 3, wherein the digital-to-analog converter and the current supply are configured to apply the signals to the drive transistors.

5. The display circuitry defined in claim 4, wherein each pixel in the array of display pixels further comprises a first transistor that is coupled between the current supply and each drive transistor.

6. The display circuitry defined in claim 5, wherein the digital-to-analog converter and the current supply are configured to apply the signals to the drive transistor through the first transistor.

7. The display circuitry defined in claim 6, further comprising a second transistor that is coupled between a gate and a source of each drive transistor.

8. A method of operating a display, wherein the display comprises an array of display pixels and transistor performance measurement circuitry, the method comprising:

with the transistor performance measurement circuitry, measuring parameters of transistors in the array of display pixels, wherein each pixel in the array of display pixels comprises a drive transistor that is coupled in series with a light emitting diode, a first transistor that is coupled between the drive transistor and a current supply, a second transistor that is coupled between a gate and a source of the drive transistor, and a third transistor that is coupled between the gate of the drive transistor and a data line;

updating stored calibration data based on the measured parameters; and

after updating the stored calibration data, operating the display using the stored calibration data.

9. The method defined in claim 8, wherein measuring the parameters of the transistors comprises measuring the parameters of the transistors during a vertical blanking interval.

10. The method defined in claim 8, wherein measuring the parameters of the transistors in the array of display pixels comprises:

turning off the third transistor;

turning on the second transistor; and

turning on the first transistor.

11. The method defined in claim 10 wherein measuring the parameters of the transistors in the array of display pixels comprises:

applying a known current to the drive transistor through the first transistor using the current supply; and

using the comparator to determine a voltage for the drive transistor.

12. The method defined in claim 11, wherein operating the display using the stored calibration data comprises operating the display to display images on the array of display pixels, and wherein operating the display to display images on the array of display pixels comprises operating the display to display images on the array of display pixels while the first and second transistors are turned off.

13. A method of operating a display, wherein the display comprises an array of display pixels and display control circuitry that displays images on the array of display pixels, wherein the display control circuitry includes transistor performance measurement circuitry, wherein each pixel in the array of display pixels comprises a drive transistor that is coupled in series with a light emitting diode, a first transistor that is coupled between the drive transistor and a current supply, a second transistor that is coupled between a gate and a source of the drive transistor, and a third transistor that is coupled between the gate of the drive transistor and a data line, the method comprising:

turning off the third transistor;

turning on the second transistor to saturate the drive transistor;

turning on the third transistor;

with the transistor performance measurement circuitry, sending first signals to the array of display pixels, wherein sending first signals to the array of display pixels comprises applying a current to the drive transistor through the third transistor;

with the transistor performance measurement circuitry, receiving second signals from the array of display pixels;

comparing the first signals to the second signals to determine parameters for the array of display pixels;

updating stored calibration data based on the determined parameters; and

operating the display using the updated stored calibration data.

14. The method defined in claim 13, wherein receiving the second signals from the array of display pixels comprises receiving the second signals at a comparator.