Electroluminescent display device and driving method of the same

Patent metadata

Field	Value
Publication number	US-10467960-B2
Application number	US-201715858917-A
Country	US
Kind code	B2
Filing date	Dec 29, 2017
Priority date	Jul 27, 2017
Publication date	Nov 5, 2019
Grant date	Nov 5, 2019

Abstract

The present disclosure relates to an electroluminescent display device and a driving method of the same. The electroluminescent display device comprises a display panel, including a plurality of data lines, a plurality of sensing lines, a plurality of gate lines, and pixels which are arranged in matrix at each intersection between those lines to form a plurality of display lines; a sensing circuit, for sensing a pixel current in the pixels, integrating the pixel current to obtain a sensing voltage, and generating a sensing data based on the sensing voltage during a sensing operation period; and a compensation unit for calculating a compensation value for electrical characteristics of the pixels based on the sensing data.

First claim

What is claimed is:

1. An electroluminescent display device, comprising:
a display panel, including a plurality of data lines, a plurality of sensing lines, a plurality of gate lines, and pixels of multiple colors which are arranged in matrix at each intersection between those lines to form a plurality of display lines,
a sensing circuit, for sensing a pixel current in the pixels, integrating the pixel current to obtain a sensing voltage, and generating a sensing data based on the sensing voltage during a sensing operation period, wherein the sensing circuit senses pixels of one specific color among the pixels of multiple colors to obtain electrical characteristics of the pixels of the multiple colors, and continuously senses a threshold voltage and an electron mobility of a driving TFT in the pixels of the one specific color as the sensing data; and
a compensation unit for calculating a compensation value for electrical characteristics of a threshold voltage and an electron mobility of a driving TFT of the pixels of the multiple colors based on the sensing data of the threshold voltage and the electron mobility of the driving TFT in the pixels of the one specific color,
wherein the sensing circuit continuously senses the threshold voltage and the electron mobility of the driving TFT in the pixels of the one specific color within one line sensing ON time that is allocated to sense the pixels of the one specific color arranged in one display line among the plurality of display lines, and
wherein the one display line includes a group of pixels arranged to be adjacent to each other along a horizontal direction where the plurality of gate lines extends.

2. The electroluminescent display device according to claim 1 , wherein
the sensing circuit includes a sensing unit, which includes:
an amplifier, including an inverting input terminal which is connected to the sensing line and receives the pixel current from the sensing line, a non-inverting input terminal which receives a reference voltage, and an output terminal that outputs the sensing voltage;
an integrating capacitor connected between the inverting input terminal and the output terminal; and
a first switch connected to both ends of the integrating capacitor.

3. The electroluminescent display device according to claim 2 , wherein
each pixel includes:
an OLED for emitting light according to the pixel current;
a driving TFT for generating the pixel current depending on a gate-source voltage, including a gate electrode connected to a first node, a drain electrode connected to a high-potential driving voltage, and a source electrode connected to a second node;
a first switch TFT including a gate electrode connected to the gate line, a drain electrode connected to the data line, and a source electrode connected to the first node; and
a second switch TFT including a gate electrode connected to the gate line, a drain electrode connected to the sensing line, and a source electrode connected to the second node.

4. The electroluminescent display device according to claim 3 , wherein the sensing operation period includes an initialization period and a sensing period, and
wherein
in the initialization period, the first switch, the first switch TFT, and the second switch TFT are turned on so as to initialize the second node to the reference voltage and to apply a sensing data voltage to the first node N 1 through the data line, thereby causing the pixel current corresponding to a potential difference between the first node and the second node to flow in the driving TFT, and
in the sensing period, the first switch TFT and the second switch TFT remain turned-on and the first switch is turned off, thereby causing the amplifier to integrate the pixel current flowing in the driving TFT and to output the sensing voltage.

5. The electroluminescent display device according to claim 1 , wherein the sensing circuit continuously senses the threshold voltage and the electron mobility of the driving TFT in the pixels of the one specific color within one line sensing ON time is performed by employing a two-point current sensing scheme,
wherein the two-point current sensing scheme is a sensing method, over a voltage-current curve, using a first point in a low gray level area where a threshold voltage variation has more influence than an electron mobility variation and a second point in a high gray level area where the electron mobility variation has more influence than the threshold voltage variation.

6. The electroluminescent display device according to claim 1 , wherein the compensation unit retrieves a threshold voltage-related compensation parameter and an electron mobility-related compensation parameter from a memory,
wherein, the sensing circuit performs a two-point sensing on the pixels of the one specific color repeatedly with respect to each of the display lines, to obtain a first sensing data for sensing the threshold voltage and a second sensing data for sensing the electron mobility, and
the compensation unit calculates a threshold voltage compensation value for a driving TFT between pixels of the one specific color and pixels of other colors based on the first sensing data which is acquired with respect to the pixels of the one specific color, calculates an electron mobility compensation value for a driving TFT between the pixels of the one specific color and pixels of other colors based on the second sensing data which is acquired with respect to the pixels of the one specific color, updates the threshold voltage-related compensation parameter in the memory with the threshold voltage compensation value, and updates the electron mobility-related compensation parameter in the memory with the electron mobility compensation value.

7. The electroluminescent display device according to claim 6 , wherein the sensing circuit is configured to:
use the first point in the low gray level area and the second point in the high gray level area over the voltage-current curve, to generate a first sensing data voltage corresponding to the first point and a second sensing data voltage corresponding to the second point;
sense a first pixel current according to the first sensing data voltage in a first section for sensing the threshold voltage included in the one line sensing ON time, the first section including a first initialization period and a first sensing period, and the first pixel current flowing in pixels of the one specific color in a corresponding display line during the first initialization period;
integrate the first pixel current which flows in the pixels of the one specific color during the first sensing period, so as to output a first sensing voltage and to generate a first sensing data based on the first sensing voltage;
sense a second pixel current according to the second sensing data voltage in a second section for sensing the electron mobility included in the one line sensing ON time, the second section including a second initialization period and a second sensing period, and the second pixel current flowing in pixels of the one specific color in a corresponding display line during the second initialization period; and
integrate the second pixel current which flows in the pixels of the one specific color during the second sensing period so as to output a second sensing voltage and to generate a second sensing data based on the second sensing voltage.

8. The electroluminescent display device according to claim 7 , wherein the first section takes longer in time than the second section to increase sensing accuracy.

9. The electroluminescent display device according to claim 6 ,
wherein the compensation unit derives a threshold voltage variation dependent upon the first sensing da

Assignees

• Lg Display Co Ltd

Inventors

• Do Osung
• Woo Kyoungdon
• Kim Hyuckjun
• Bae Jaeyoon

Classifications

• G09G2300/0819

  used for counteracting undesired variations, e.g. feedback or autozeroing · CPC title

• G09G3/3258

  with pixel circuitry controlling the voltage across the light-emitting element · CPC title

• G09G2310/08

  Details of timing specific for flat panels, other than clock recovery · CPC title

• 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

• G09G2300/0842

  forming a memory circuit, e.g. a dynamic memory with one capacitor · CPC title