SYSTEMS AND METHODS FOR INDIRECT THRESHOLD VOLTAGE SENSING IN AN ELECTRONIC DISPLAY

• US 20170103702A1
• Filed: 09/22/2016
• Published: 04/13/2017
• Est. Priority Date: 10/09/2015
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Bi, Yafei, Wang, Xiaofeng, Li, Haifeng, Vahid Far, Mohammad B., Bae, Hopil, Lin, Hung Shen, Nho, Hyunwoo, Yao, Wei H.
• Granted Patent: US 10,573,209 B2
• Time in Patent Office: Days
• CPC Class Codes: G09G 2300/0809 Several active elements per pixel in active matrix panels
• CPC Class Codes: G09G 2300/0814 used for selection purposes, e.g. logical AND for partial update
• CPC Class Codes: G09G 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• CPC Class Codes: G09G 2310/0202 Addressing of scan or signal lines
• CPC Class Codes: G09G 2310/0291 Details of output amplifiers or buffers arranged for use in a driving circuit
• CPC Class Codes: G09G 2310/061 for resetting or blanking
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/0295 by monitoring each display pixel
• CPC Class Codes: G09G 2320/045 Compensation of drifts in the characteristics of light emitting or modulating elements
• 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 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 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3266 Details of drivers for scan electrodes
• 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

An electronic device includes a display panel with pixels arranged in at least one row and at least one column. The electronic device also includes a sensing channel coupled to the at least one column. The sensing channel indirectly calculates a threshold voltage of the plurality of pixels based on an application of a first current level and a second current level to a data line of a first column of the at least one column of the pixels.

Claims

1. An electronic device comprising:

a display panel comprising a plurality of pixels arranged in at least one row and at least one column; and

a sensing channel coupled to the at least one column configured to indirectly calculate a threshold voltage of the plurality of pixels based on an application of a first current level and a second current level to a data line of a first column of the at least one column of the plurality of pixels.

2. The electronic device of claim 1, wherein the sensing channel is included within a source driver of the electronic device.

3. The electronic device of claim 1, comprising a plurality of sensing channels, wherein each of the plurality of sensing channels corresponds to a particular column of the at least one column of the plurality of pixels and is separate from others of the plurality of sensing channels.

4. The electronic device of claim 1, comprising:

a data voltage source amplified by a first amplifier within a gate driver of the electronic device; and

an initialization voltage source amplified by a second amplifier within a source driver IC of the electronic device.

5. The electronic device of claim 1, wherein the sensing channel comprises a sensing amplifier and an integrating capacitor;

and

wherein the sensing amplifier and the integrating capacitor function together as an amplifier integrator capable of producing a signal representative of a current coming from at least one of the plurality of pixels.

6. The electronic device of claim 5, wherein the sensing channel comprises a plurality of switches that, upon being set a first configuration, cause resetting of the integrating capacitor.

7. The electronic device of claim 6, wherein an initialization voltage source, a pixel current, a panel current leakage, or any combination thereof is provided to a negative terminal of the sensing amplifier when one of the plurality of switches is closed.

8. The electronic device of claim 7, wherein a comparison voltage (Vcm) is provided to a positive terminal of the sensing amplifier.

9. The electronic device of claim 8, wherein an output of the sensing amplifier (Vsa) is provided to compensation circuitry of the electronic device, such that the compensation circuitry may compensate for the current leakage that is provided to the negative terminal of the sensing amplifier.

10. A computer-implemented method for calculating a threshold voltage (V_th) of a unit pixel of a system, comprising:

applying a current on a data line at a first level;

reading a first voltage output from a sensing amplifier for the current at the first level;

applying a second current on the data line at a second level;

reading a second voltage output from the sensing amplifier for the second current at the second level; and

calculating V_th based upon the reading of the first voltage output and the reading of the second voltage output.

11. The computer-implemented method of claim 10, wherein the current on the data line at the first level is provided from a compensating current source of a sensing channel of an electronic device.

12. The computer-implemented method of claim 10, wherein the first voltage output is related to the threshold voltage according to:

13. The computer-implemented method of claim 12, wherein the second voltage output is related to the threshold voltage according to:

14. The computer-implemented method of claim 13, comprising calculating Vain accordance with an equation:

15. The computer-implemented method of claim 10, wherein the second level is within 5%-15% higher or lower than the first level.

16. The computer-implemented method of claim 10, comprising calibrating an entire column of unit pixels based upon the calculated V_th.

17. A computer-implemented method to calculate a threshold voltage (V_th) of a unit pixel, comprising:

program an integrating capacitor and a line capacitor, by discharging the integrating capacitor and charging the line capacitor to a voltage equal to a voltage of an initialization voltage source;

sense a display panel leakage current;

provide the display panel leakage current to compensation circuitry via a sensing amplifier;

re-program the integrating capacitor and the line capacitor;

sense a pixel current and the display panel leakage current;

determining the V_th based upon the sensed pixel current and the display panel leakage current; and

calibrating a channel of associated unit pixels, based upon the V_th.

18. The computer-implemented method of claim 17, comprising, providing sensing values to an analog to digital controller, resulting in a digital output.

19. The computer-implemented method of claim 18, comprising calibrating the channel using the digital output.

20. The computer-implemented method of claim 17, comprising:

re-program the integrating capacitor and the line capacitor a second time; and

sense a second pixel current and the display panel leakage current; and

determining the V_th based upon the sensed pixel current, the second pixel current, and the display panel leakage current.