Pixel circuits for amoled displays

• US 10,242,619 B2
• Filed: 02/23/2018
• Issued: 03/26/2019
• Est. Priority Date: 03/08/2013
• Status: Active Grant

• Current Assignee: IGNIS Innovation Incorporated
• Original Assignee: IGNIS Innovation Incorporated
• Inventors: Chaji, Gholamreza, Azizi, Yaser
• Primary Examiner(s): Lee, Jr., Kenneth B
• Application Number:
  US15/903,698
• Publication Number:
  US 20180182293A1
• Time in Patent Office: 396 Days
• Field of Search: None
• CPC Class Codes: G06F 1/3218 of display devices
• CPC Class Codes: G06F 1/3265 Power saving in display device
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2300/0465 Improved aperture ratio, e.g. by size reduction of the pixel circuit, e.g. for improving the pixel density or the maximum displayable luminance or brightness
• CPC Class Codes: G09G 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• 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 2300/0866 by means of changes in the pixel supply voltage
• CPC Class Codes: G09G 2310/08 Details of timing specific for flat panels, other than clock recovery
• 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 2320/045 Compensation of drifts in the characteristics of light emitting or modulating elements
• CPC Class Codes: G09G 2320/048 using evaluation of the usage time
• CPC Class Codes: G09G 2320/0613 The adjustment depending on the type of the information to be displayed
• 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 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2330/022 in absence of operation, e.g. no data being entered during a predetermined time
• CPC Class Codes: G09G 2330/023 using energy recovery or conservation
• CPC Class Codes: G09G 2340/0435 Change or adaptation of the frame rate of the video stream
• CPC Class Codes: G09G 2360/12 : Frame memory handling
• CPC Class Codes: G09G 2360/18 : Use of a frame buffer in a display terminal, inclusive of the display panel
• CPC Class Codes: G09G 3/3233 : with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: Y02D 10/00 : Energy efficient computing, e.g. low power processors, power management or thermal management

Abstract

A system for driving a display that includes a plurality of pixel circuits arranged in an array, each of the pixel circuits including a light emitting device and a driving transistor for conveying a driving current through the light emitting device. Methods of measuring characteristics of circuit elements of pixels sharing a monitor line include the control of biasing to selectively turn off circuit elements or render their response known while measuring other circuit elements of interest.

Claims

1. A method of determining a characteristic of a circuit element of a first pixel of a display device, the first pixel sharing a monitor line with a second pixel of the display device, the method comprising:

biasing the first pixel;

biasing the second pixel to fix a current passing through the second pixel over the monitor line to a known current; and

measuring the characteristic of the circuit element of the first pixel with use of said monitor line.

2. The method of claim 1, wherein measuring the characteristic of the circuit element of the first pixel with use of said monitor line comprises measuring a current over the monitor line.

3. The method of claim 2, wherein measuring the characteristic of the circuit element of the first pixel with use of said monitor line further comprises subtracting from a current value of the measured current a current value of the known current.

4. The method of claim 1, wherein the known current is zero.

5. The method of claim 1, wherein biasing the second pixel comprises biasing an optoelectronic device of the second pixel to turn off the optoelectronic device.

6. The method of claim 5, wherein the second pixel includes a drive transistor for supplying current to the optoelectronic device and coupled between a supply voltage and the optoelectronic device, and wherein biasing the optoelectronic device comprises biasing the drive transistor to set a voltage at a node between the drive transistor and the optoelectronic device, to bias the optoelectronic device and turn the optoelectronic device off.

7. The method of claim 1, wherein the second pixel includes a source switch coupled between the monitor line and remaining elements of the second pixel, and wherein biasing the second pixel comprises biasing the source switch.

8. The method of claim 7, wherein biasing the source switch comprises biasing with a known voltage difference across a source and a drain of the source switch resulting in the known current passing through the source switch.

9. The method of claim 8, wherein the known voltage difference is zero.

10. The method of claim 8, further comprising prior to biasing with the known voltage difference across the source and the drain of the source switch, determining the known voltage difference across the source and the drain of the source switch which results in the known current passing through the source switch including:

biasing the first pixel to turn off an optoelectronic device of the first pixel and then biasing the first pixel to turn off a drive transistor of the first pixel;

biasing the monitor line to a first voltage and biasing the second pixel so that the known current passes through the source switch as a result of a particular voltage difference across the source and the drain of the source switch; and

determining the known voltage difference from the particular voltage difference.

11. The method of claim 8, wherein the first pixel includes a drive transistor for supplying current to an optoelectronic device of the first pixel and coupled between a supply voltage and the optoelectronic device, and wherein biasing the first pixel comprises biasing the drive transistor to turn the drive transistor off and biasing over the monitor line the optoelectronic device to turn the optoelectronic device on.

12. The method of claim 11, further comprising prior to the biasing with the known voltage difference across the source and the drain of the source switch, determining the known voltage difference across the source and the drain of the source switch which results in the known current passing through the source switch including:

biasing the first pixel to turn off the optoelectronic device and then biasing the first pixel to turn off the drive transistor;

biasing the monitor line to a first voltage and biasing the second pixel so that the known current passes through the source switch as a result of a particular voltage difference across the source and the drain of the source switch; and

determining the known voltage difference from the particular voltage difference.

13. The method of claim 1, further comprising prior to biasing the second pixel to fix the current passing through the second pixel over the monitor line to the known current, determining the known current which results from said biasing of the second pixel by:

varying a biasing of the second pixel so that the known current passes through the source switch as a result of a particular biasing of the second pixel; and

determining the biasing of the second pixel from the particular biasing of the second pixel.

14. The method of claim 1, wherein the first pixel includes a drive transistor for supplying current to an optoelectronic device of the first pixel and coupled between a supply voltage and the optoelectronic device, and wherein the first pixel includes a source switch coupled between the monitor line and remaining elements of the first pixel, and wherein biasing the first pixel comprises:

at a first time, biasing the drive transistor to cause a first current to pass through the source switch; and

at a second time after the first time, adjusting a biasing of the drive transistor to maintain the same first current passing through the source switch;

determining a change in a current characteristic of the optoelectronic device from the change in the biasing of the drive transistor which maintains the same first current passing through the source switch.