Systems and methods for external off-time pixel sensing

Patent metadata

Field	Value
Publication number	US-12136394-B2
Application number	US-202016802354-A
Country	US
Kind code	B2
Filing date	Feb 26, 2020
Priority date	Apr 19, 2019
Publication date	Nov 5, 2024
Grant date	Nov 5, 2024

Abstract

An electronic device includes a display having multiple regions of pixels. Each pixel includes a diode that emits light based on an amount of current through the diode and a transistor that controls the amount of current flowing through the diode. The electronic device includes driver-integrated circuitry that reduces hysteresis in a first transistor of a first pixel of a region of pixels, settles a threshold voltage of the first transistor, applies a test voltage to the first transistor, and senses a current across the first transistor. The electronic device includes processing circuitry that determines a predetermined voltage based on the current and a predetermined current-voltage relationship determined at an initial temperature, determines a voltage difference between the test voltage and the predetermined voltage, and applies the predetermined voltage and the voltage difference to a second transistor of a second pixel of the region of pixels.

First claim

What is claimed is:

1. An electronic display comprising:
a pixel, wherein the pixel comprises:
a diode configured to emit light based at least in part on an amount of current through the diode; and
a driver transistor configured to control the amount of current flowing through the diode based at least in part on a voltage applied to the driver transistor;
driver-integrated circuitry configured to, during a current sensing process associated with not displaying image content via the diode:
send a hysteresis-reducing signal to the driver transistor;
send a threshold-settling signal to the driver transistor;
send a test voltage to the driver transistor without illuminating the diode, wherein the driver-integrated circuitry is configured to send the test voltage to the driver transistor without illuminating the diode by reducing a source voltage of the driver transistor, wherein the diode is directly electrically coupled to a drain of the driver transistor; and
sense a current across the driver transistor in response to the test voltage;

a plurality of display regions, wherein a first display region of the plurality of display regions comprises the pixel; and
a plurality of power planes configured to selectively supply independent supply voltages to the plurality of display regions, wherein a first power plane of the plurality of power planes is configured to supply a first supply voltage of the independent supply voltages to the first display region during the current sensing process, and wherein a second power plane of the plurality of power planes is configured to supply a second supply voltage of the independent supply voltages to a second display region, of the plurality of display regions, configured to display the image content while the first display region undergoes the current sensing process.

2. The electronic display of claim 1 , communicatively coupled to processing circuitry separate from the electronic display, wherein the processing circuitry is configured to adjust image data configured to be sent to the pixel to compensate for operational variations of the electronic display based at least in part on the current sensed across the driver transistor.

3. The electronic display of claim 2 , wherein the processing circuitry is configured to adjust the image data at least in part by:
determining a certain voltage based at least in part on the current and a predetermined current-voltage relationship determined at an initial temperature;
determining a voltage difference between the test voltage and the certain voltage; and
applying a sum of the certain voltage and the voltage difference to the driver transistor.

4. The electronic display of claim 2 , wherein the electronic display comprises a plurality of regions of pixels, wherein a region of pixels of the plurality of regions of pixels comprises the pixel, wherein the processing circuitry is configured to adjust the image data at least in part by:
determining a certain voltage based at least in part on the current and a predetermined current-voltage relationship determined at an initial temperature;
determining a voltage difference between the test voltage and the certain voltage; and
applying a sum of the certain voltage and the voltage difference to a second driver transistor of a second pixel of the region of pixels.

5. The electronic display of claim 1 , wherein the driver-integrated circuitry is configured to send the hysteresis-reducing signal, send the threshold-settling signal, and sense the current during an off-time of the electronic display.

6. The electronic display of claim 1 , wherein the hysteresis-reducing signal is configured to alternate between a higher voltage value and a lower voltage value.

7. The electronic display of claim 1 , wherein the threshold-settling signal comprises a settling voltage, wherein the threshold-settling signal is configured to settle a threshold voltage of the driver transistor to the settling voltage.

8. A method comprising:
determining whether a usage time since a previous current sensing process of a display of an electronic device has exceeded a compensation time threshold;
determining whether a current time is indicative of a lack of use of the electronic device in response to determining that the usage time has exceeded the compensation time threshold;
determining whether the electronic device is charging or a battery of the electronic device has sufficient charge; and
in response to determining that the current time is indicative of the lack of use of the electronic device and that the electronic device is charging or the battery of the electronic device has sufficient charge, performing a current sensing process, wherein the current sensing process comprises:
sending a hysteresis-reducing signal to a transistor of pixel driving circuitry configured to provide power to a diode of the display;
sending a test voltage to the transistor; and
sensing current in response to the test voltage.

9. The method of claim 8 , comprising determining whether the usage time has exceeded a second compensation time threshold, less than the compensation time threshold, wherein the compensation time threshold is associated with a higher urgency to initiate the current sensing process than the second compensation time threshold.

10. The method of claim 8 , comprising determining whether the current time is nighttime in response to determining that the usage time has exceeded the compensation time threshold, wherein determining whether the current time is indicative of the lack of use of the electronic device occurs in response to determining that the current time is nighttime in response to determining that the usage time has exceeded the compensation time threshold.

11. The method of claim 8 , comprising determining whether a temperature at the display is sufficiently stable in response to determining that the electronic device is charging or the battery of the electronic device has sufficient charge, wherein sending the hysteresis-reducing signal to the transistor, sending the test voltage to the transistor, and sensing the current, occur in response to determining that the temperature at the electronic device is sufficiently stable.

12. The method of claim 8 , comprising:
determining a predetermined current-voltage relationship of a pixel of the display at initial conditions, the pixel comprising the diode;
determining a certain voltage corresponding to the current based at least in part on the predetermined current-voltage relationship;
determining a voltage difference between the certain voltage and the test voltage; and
storing the voltage difference in a lookup table.

13. The method of claim 12 , comprising:
determining a gamma voltage value configured to cause the diode of the pixel to emit light at a target luminance; and
determining a gain voltage value or an offset voltage value configured to adjust the gamma voltage value and cause the diode to emit the light of the target luminance.

14. The method of claim 13 , comprising applying a sum of the voltage difference, the gamma voltage value, and the gain voltage value or the offset voltage value at the pixel to cause the diode of the pixel to emit the light of the target luminance.

15. The method of claim 8 , comprising:
determining whether the electronic device is about to be used or in use while sending the hysteresis-reducing signal to the transistor, sending the test voltage to the transistor, or sensing the current; and
interrupting sending the hysteresis-reducing signal to the transistor, sending the test voltage to the transi

Assignees

• Apple Inc

Inventors

• Nho Hyunwoo
• Choi Myungjoon
• Kim Hyunsoo
• Jangda Mohammad Ali
• Ryu Jie Won
• Shen Shiping
• Brahma Kingsuk
• Wang Chaohao
• Yao Wei H
• Pai Alex H

Classifications

• G09G2310/0262

  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 title

• G09G2310/04

  Partial updating of the display screen · CPC title

• G09G2310/0251

  Precharge or discharge of pixel before applying new pixel voltage · CPC title

• G09G2300/0842

  forming a memory circuit, e.g. a dynamic memory with one capacitor · CPC title

• G09G3/3233 Primary

  with pixel circuitry controlling the current through the light-emitting element · CPC title