Display compensation using current sensing across a diode without user detection

Patent metadata

Field	Value
Publication number	US-11488529-B2
Application number	US-202016849712-A
Country	US
Kind code	B2
Filing date	Apr 15, 2020
Priority date	May 16, 2019
Publication date	Nov 1, 2022
Grant date	Nov 1, 2022

Abstract

A current-voltage (IV) relationship of a pixel having a diode is initially determined. A first voltage is determined that does not cause the diode to emit light, and a first current across the diode is sensed by applying the first voltage. A predetermined current is determined based on the first voltage and the IV relationship. A ratio is determined based on the first current, a target current, and the predetermined current. A ratio voltage is determined by applying the ratio to a predetermined target voltage. If the first current is less than the predetermined current, then the ratio voltage is applied to supply a target current to the diode. If the first current is greater than the predetermined current, then a second voltage is determined by averaging the first test voltage and the ratio voltage, and the second voltage is applied to supply the target current to the diode.

First claim

What is claimed is:

1. A mobile electronic device comprising:
a display comprising a pixel, wherein the pixel comprises:
a diode configured to emit light based on an amount of current through the diode;
a transistor configured to control the amount of current flowing through the diode based on a voltage received; and
a driver-integrated circuit configured to:
sense the amount of current through the diode in response to applying a test voltage, wherein the amount of current comprises a nonzero amount;
determine a predetermined current based on the test voltage and a predetermined current-voltage relationship, wherein the pre-determined current-voltage relationship is determined at an initial condition of the diode; and
apply a predetermined voltage determined based on a target current and the predetermined current-voltage relationship in response to determining that the amount of current is approximately equal to the predetermined current.

2. The mobile electronic device of claim 1 , wherein the diode emits substantially no light while the driver-integrated circuit senses the amount of current through the diode.

3. The mobile electronic device of claim 1 , wherein the driver-integrated circuit is configured to:
sense a second amount of current through the diode in response to applying a second test voltage;
determine a second predetermined current based on the second test voltage and the predetermined current-voltage relationship;
determine a ratio based on the second amount of current, a second target current, and the second predetermined current;
sense a test current by applying a second test voltage determined based on the ratio; and
apply the second test voltage to the diode in response to determining that the test current is approximately equal to the second target current.

4. The mobile electronic device of claim 3 , wherein the second test voltage is determined by applying the ratio to the second test voltage in response to determining that the second amount of current is less than the second predetermined current.

5. The mobile electronic device of claim 3 , wherein the second test voltage is determined by applying the ratio to the test voltage to determine a ratio voltage, and averaging the second test voltage and the ratio voltage, in response to determining that the second amount of current is greater than the second predetermined current.

6. The mobile electronic device of claim 3 , wherein the driver-integrated circuit is configured to determine that the test current is approximately equal to the second target current if the test current is within a threshold range of the second target current.

7. The mobile electronic device of claim 1 , wherein the driver-integrated circuit is configured to prepare image data to send to the pixel and adjust the image data to compensate for operational variations of the display by applying the predetermined voltage.

8. The mobile electronic device of claim 7 , wherein the operational variations comprise temperature variation at the pixel, aging of the pixel, or both.

9. The mobile electronic device of claim 8 , wherein one or more additional electronic components of the display causes the temperature variation at the pixel.

10. The mobile electronic device of claim 7 , wherein applying the predetermined voltage comprises adjusting the image data.

11. A method for determining a target voltage to apply to a transistor of a pixel at a present temperature to cause a current across a diode of the pixel that causes the diode to emit light at a target luminance, wherein the method comprises:
determining a predetermined current-voltage relationship of the pixel at an initial temperature;
determining a first test voltage that does not cause the diode of the pixel to emit light;
sensing a first test current across the diode by applying the first test voltage;
determining a first predetermined current based on the first test voltage and the predetermined current-voltage relationship;
performing a lower temperature process loop in response to determining that the present temperature is less than the initial temperature; and
performing a higher temperature process loop in response to determining that the present temperature is greater than the initial temperature.

12. The method of claim 11 , wherein performing the lower temperature process loop comprises:
determining a ratio of a difference between the first test current and the first predetermined current and a difference between a target current and the first predetermined current;
sensing a test current by applying a second test voltage determined by applying the ratio to the first test voltage; and
applying the second test voltage to the diode in response to determining that the test current is approximately equal to the target current.

13. The method of claim 11 , wherein performing the higher temperature process loop comprises:
determining a ratio of a difference between the first test current and the first predetermined current and a difference between a target current and the first predetermined current;
sensing a test current by applying a second test voltage determined by:
determining a ratio voltage by applying the ratio to the first test voltage; and
averaging the first test voltage and the ratio voltage; and

applying the second test voltage to the diode in response to determining that the test current is approximately equal to the target current.

14. The method of claim 11 , comprising applying a predetermined voltage determined based on a target current and the predetermined current-voltage relationship in response to determining that the present temperature is approximately equal to the initial temperature.

15. The method of claim 11 , wherein determining that the present temperature is less than the initial temperature comprises determining that the first test current is less than the first predetermined current, and determining that the present temperature is greater than the initial temperature comprises determining that the first test current is greater than the first predetermined current.

16. A display comprising:
a pixel comprising:
a diode configured to emit light based on an amount of current through the diode; and
a transistor configured to control the amount of current flowing through the diode based on a voltage received; and

a driver-integrated circuit configured to:
sense a first test current across the diode by applying a first test voltage that does not cause the diode of the pixel to emit light;
determine a first predetermined current based on the first test voltage and a predetermined current-voltage relationship determined at an initial temperature;
perform a lower temperature process loop in response to determining that the first test current is less than the first predetermined current; and
perform a higher temperature process loop in response to determining that the first test current is greater than the first predetermined current.

17. The display of claim 16 , wherein the display comprises a plurality of pixels including the pixel, wherein the driver-integrated circuit is configured to sense the first test current by applying the first test voltage to each transistor of the plurality of pixels, sense a plurality of test currents across each diode of the plurality of pixels, average the plurality of test currents to determine a present average test current, compare the present average test current to a previous average test current, and return the first test current in response to determining that the presen

Assignees

• Apple Inc

Inventors

• Hwang Injae
• Kim Jesun
• Nho Hyunwoo
• Ryu Jie Won
• Kim Hyunsoo
• Tan Junhua
• Choi Myungjoon
• Park Rebecca
• Shen Shiping
• Chang Sun-Il
• Gao Shengkui
• Brahma Kingsuk
• Richmond Jesse Aaron
• Min Changki
• Zhang Yifan
• Lee Jiye
• Wang Chaohao

Classifications

• G09G3/006

  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 title

• G09G2320/043

  Preventing or counteracting the effects of ageing · CPC title

• G09G3/3233 Primary

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

• G09G2320/041

  Temperature compensation · CPC title

• G09G2320/0626

  for control of overall brightness · CPC title