Pixel circuits for AMOLED displays

• US 9,697,771 B2
• Filed: 02/17/2016
• Issued: 07/04/2017
• Est. Priority Date: 03/08/2013
• Status: Active Grant

• Current Assignee: IGNIS Innovation Incorporated
• Original Assignee: IGNIS Innovation Incorporated
• Inventors: Azizi, Yaser, Chaji, Gholamreza
• Primary Examiner(s): XAVIER, ANTONIO J
• Application Number:
  US15/045,382
• Publication Number:
  US 20160163262A1
• Time in Patent Office: 503 Days
• Field of Search: None
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2300/043 Compensation electrodes or other additional electrodes in matrix displays related to distortions or compensation signals, e.g. for modifying TFT threshold voltage in column driver
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2310/0218 with collection of electrodes in groups for n-dimensional addressing
• 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 2320/0693 Calibration of display systems
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3696 Generation of voltages supplied to electrode drivers

Abstract

A method and system determine the characteristics of drive devices and load devices in selected pixels in an array of pixels in a display in which each pixel includes a drive device for supplying current to a load device. The method and system supply current to the load device via the drive device in a selected pixel, the current being a function of a current effective characteristic of at least one of the drive device and the load device; measure the current via a measurement line that is shared by adjacent pixels, and extract the value of a selected effective characteristic of one of the drive and load devices from the effect of the current on another of the drive and load devices. Current may be measured via a read transistor in each pixel.

Claims

1. A method of determining at least one characteristic of an organic light emitting device (OLED) in a selected pixel in an array of pixels in a display in which each pixel includes a supply voltage source, a drive transistor coupling said supply voltage source to an OLED for controlling the supply of current to the OLED from said supply voltage source, said display system including a plurality of monitor lines each of which is controllably coupled to two pixels at a node between said drive transistor and said OLED in each of said two pixels, said method comprising

measuring a first current in a monitor line for a selected pair of said pixels while turning on both the drive transistors in the selected pair of pixels coupled to said monitor line and while the supply voltage of one of said two pixels is set to the voltage level at the node between said drive transistor and said OLED of said one pixel,

measuring a second current in said monitor line for said selected pair of pixels while the drive transistor of said one of said two pixels is turned off so that the OLED in said one pixel is controlled by said monitor line, and

determining a characteristic of the OLED in said one pixel, from the first and second measured currents.

2. The method of claim 1 in which said current is measured via a read transistor in each pixel.

3. The method of claim 1 in which the current is measured in different stages, and the selected effective characteristic is extracted from the measurements.

4. A system for determining the characteristics of drive devices and load devices in selected pixels in an array of pixels in a display in which each pixel includes a drive device for supplying current to a load device, and a plurality of said pixels share a common measurement line, the system comprising a controller adapted to

force the load device in at least one of the pixels sharing said common measurement line to a known status,

control via said measurement line the status of the load device of a second pixel sharing said common measurement line,

measure a first current in said common measurement line for a selected pair of said pixels while turning on both the drive transistors in the selected pair of pixels coupled to said monitor line and while the supply voltage of one of said two pixels is set to the voltage level at the node between said drive transistor and said OLED of said one pixel,

measure a second current in said common measurement line for said selected pair of pixels while the drive transistor of said one of said two pixels is turned off so that the OLED in said one pixel is controlled by said monitor line,

determine a characteristic of the OLED in said one pixel, from the first and second measured currents, and

use the measured characteristic in compensating for a change in the characteristic of the first load device.

5. The system of claim 4 in which said current is measured via a read transistor in each pixel.

6. The system of claim 4 in which the current is measured in different stages, and the selected effective characteristic is extracted from the measurements.