Pixel circuits for AMOLED displays

• US 10,593,263 B2
• Filed: 02/05/2018
• Issued: 03/17/2020
• 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
• Application Number:
  US15/888,451
• Publication Number:
  US 20180158411A1
• Time in Patent Office: 771 Days
• 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 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 2320/048 using evaluation of the usage time
• CPC Class Codes: G09G 2320/0693 Calibration of display systems
• CPC Class Codes: G09G 2320/10 Special adaptations of display systems for operation with variable images
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3258 with pixel circuitry controlling the voltage across the light-emitting element
• CPC Class Codes: H05B 45/14 using electrical feedback from LEDs or from LED modules

Abstract

The OLED voltage of a selected pixel is extracted from the pixel produced when the pixel is programmed so that the pixel current is a function of the OLED voltage. One method for extracting the OLED voltage is to first program the pixel in a way that the current is not a function of OLED voltage, and then in a way that the current is a function of OLED voltage. During the latter stage, the programming voltage is changed so that the pixel current is the same as the pixel current when the pixel was programmed in a way that the current was not a function of OLED voltage. The difference in the two programming voltages is then used to extract the OLED voltage.

Claims

1. A method of determining the current effective voltage V_OLED of a light-emitting device in a selected pixel in an array of pixels in a display in which each pixel includes a light-emitting device and a drive transistor for supplying current to said light-emitting device, said method comprising

storing a programming voltage in the selected pixel using the light-emitting device of the selected pixel, the stored programming voltage being a function of the current effective voltage V_OLED of said light-emitting device,

supplying current to said light-emitting device via said drive transistor in said selected pixel according to said stored programming voltage, said current being a function of the current effective voltage V_OLED of said light-emitting device,

measuring said current, and

extracting the value of the current effective voltage V_OLED of said light-emitting device from said current measurement.

2. The method of claim 1 in which said light-emitting devices are OLEDs.

3. The method of claim 1 in which said current is supplied to said light-emitting device via a drive transistor in each pixel.

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

5. A method of determining the current effective voltage V_OLED of a light-emitting device in a selected pixel in an array of pixels in a display in which each pixel includes a light-emitting device and a drive transistor for supplying current to said light-emitting device, said method comprising

supplying a first predetermined programming voltage to said selected pixel to store a first programming voltage in the selected pixel, the stored first programming voltage being independent of the current effective voltage V_OLED of said light-emitting device,

supplying a first current to said light-emitting device in said selected pixel according to said stored first programming voltage, said first current being independent of the effective voltage V_OLED of said light-emitting device,

measuring said first current,

supplying a second predetermined programming voltage to said selected pixel to store a second programming voltage in the selected pixel using the light-emitting device of the selected pixel, the stored second programming voltage being a function of the current effective voltage V_OLED of said light-emitting device,

supplying a second current to said light-emitting device in said selected pixel according to said stored second programming voltage, said second current being a function of the current effective voltage V_OLED of said light-emitting device,

measuring said second current, and

extracting the value of the current effective voltage V_OLED of said light-emitting device from the difference between said first and second currents and current-voltage characteristics of said selected pixel.

6. A system for determining the current effective voltage V_OLED of a light-emitting device of a selected pixel in an array of pixels in a display in which each pixel includes a light-emitting device and a drive transistor for supplying current to the light-emitting device, the system comprising a controller adapted to

store a programming voltage in the selected pixel using the light-emitting device of the selected pixel, the stored programming voltage being a function of the current effective voltage V_OLED of said light-emitting device,

supply current to said light-emitting device via said drive transistor in said selected pixel according to said stored programming voltage, said current being a function of the current effective voltage V_OLED of said light-emitting device,

measure said current, and

extract the value of the current effective voltage V_OLED of said light-emitting device from said current measurement.