Pixel sensing device, organic light emitting display device, and pixel compensation method thereof

Patent metadata

Field	Value
Publication number	US-10964273-B2
Application number	US-201916593182-A
Country	US
Kind code	B2
Filing date	Oct 4, 2019
Priority date	Oct 4, 2018
Publication date	Mar 30, 2021
Grant date	Mar 30, 2021

Abstract

A pixel sensing device, an organic light emitting display device and a pixel compensation method thereof are disclosed. The pixel sensing device comprises a plurality of current integrators for sensing driving characteristics of pixels. Each current integrator comprises: an operational amplifier equipped with an inverting input terminal to which a first input voltage is applied according to a pixel current of the pixels, a non-inverting input terminal to which a second input voltage is applied according to the pixel current, and an output terminal through which an integral voltage corresponding to the pixel current is output; and a feedback capacitor connected between the inverting input terminal and the output terminal. The operational amplifier comprises: a pre-amplifying unit for lowering an amplifier input gain and being equipped with the inverting and non-inverting input terminals; and two gain amplifying units for receiving an output of the pre-amplifying unit and for making an amplifier output gain higher than the amplifier input gain.

First claim

What is claimed is:

1. A pixel sensing device, comprising:
a plurality of current integrators for sensing driving characteristics of pixels, each of the current integrators including:
an operational amplifier having an inverting input terminal configured to receive a first input voltage according to a pixel current of the pixels, a non-inverting input terminal configured to receive a second input voltage according to the pixel current, and an output terminal configured to output an integral voltage corresponding to the pixel current; and
a feedback capacitor connected between the inverting input terminal and the output terminal,

wherein the operational amplifier includes:
a pre-amplifying circuit configured to lower an amplifier input gain, the pre-amplifying circuit including the inverting and non-inverting input terminals; and
two gain amplifying circuits configured to receive an output of the pre-amplifying circuit and increase an amplifier output gain to a level that is higher than the amplifier input gain,

wherein the two gain amplifying circuits includes:
a first gain amplifying circuit configured to receive the output of the pre-amplifying circuit and increase the amplifier output gain by a first value through MOS transistors connected in a differential diode manner; and
a second gain amplifying circuit connected to the first gain amplifying circuit, the second gain amplifying circuit including the output terminal, and configured to increase the amplifier output gain by a second value which is less than the first value, and

wherein the pre-amplifying circuit includes:
a first MOS transistor having a gate electrode connected to the inverting input terminal, a drain electrode connected to a first node, and a source electrode connected to a second node;
a second MOS transistor having a gate electrode connected to the non-inverting input terminal, a drain electrode connected to a third node, and a source electrode connected to the second node;
a third MOS transistor having gate and drain electrodes connected to the first node, and a source electrode connected to a high potential driving voltage source;
a fourth MOS transistor having gate and drain electrodes connected to the third node, and a source electrode connected to the high potential driving voltage source; and
a fifth MOS transistor equipped having a gate electrode connected to a bias voltage source, a drain electrode connected to the second node, and a source electrode connected to a low potential driving voltage source.

2. The pixel sensing device of claim 1 , wherein an inverting output voltage of the pre-amplifying circuit is output through the first node, and a non-inverting output voltage of the pre-amplifying circuit is output through the third node, and
wherein the first, second and fifth MOS transistors are implemented as N-type transistors, and the third and fourth MOS transistors are implemented as P-type transistors.

3. The pixel sensing device of claim 1 , wherein the first gain amplifying circuit comprises:
a sixth MOS transistor having a gate electrode connected to the third node, a drain electrode connected to a fourth node, and a source electrode connected to a fifth node;
a seventh MOS transistor having a gate electrode connected to the first node, a drain electrode connected to a sixth node, and a source electrode connected to the fifth node;
an eighth MOS transistor having a gate electrode connected to the sixth node, a drain electrode connected to the fourth node, and a source electrode connected to the high potential driving voltage source;
a ninth MOS transistor having gate and drain electrodes connected to the fourth node, and a source electrode connected to the high potential driving voltage source;
a tenth MOS transistor having a gate electrode connected to the fourth node, a drain electrode connected to the sixth node, and a source electrode connected to the high potential driving voltage source;
an eleventh MOS transistor having gate and drain electrodes connected to the sixth node, and a source electrode connected to the high potential driving voltage source; and
a twelfth MOS transistor having a gate electrode connected to the bias voltage source, a drain electrode connected to the fifth node, and a source electrode connected to the low potential driving voltage source.

4. The pixel sensing device of claim 3 , wherein the sixth, seventh and twelfth MOS transistors are implemented as N-type transistors, and the eighth, ninth, tenth and eleventh MOS transistors are implemented as P-type transistors.

5. The pixel sensing device of claim 3 , wherein the second gain amplifying circuit comprises:
a thirteenth MOS transistor having a gate electrode connected to the sixth node, a drain electrode connected to the output terminal, and a source electrode connected to the high potential driving voltage source; and
a fourteenth MOS transistor having a gate electrode connected to the bias voltage source, a drain electrode connected to the output terminal, and a source electrode connected to the low potential driving voltage source.

6. The pixel sensing device of claim 1 , wherein an input impedance of the operational amplifier is proportional to the amplifier output gain and inversely proportional to the amplifier input gain.

7. The pixel sensing device of claim 1 , wherein each current integrator senses the pixel current which flows through a driving TFT of each pixel in response to a data voltage for sensing, and senses a total amount of charges accumulated in capacitors of each pixel in response to the data voltage for sensing.

8. The pixel sensing device of claim 5 , wherein the thirteenth MOS transistor is implemented as a P-type transistor, and the fourteenth MOS transistor is implemented as an N-type transistor.

9. The pixel sensing device of claim 1 , wherein when the pixel current is applied, the integral voltage of the operational amplifier decreases, a gate voltage of the first MOS transistor decreases based on negative feedback through the feedback capacitor, and the integral voltage is smaller than a gate voltage of the second MOS transistor by the pixel current accumulated in the feedback capacitor.

10. An organic light emitting display device, comprising:
a display panel including pixels and sensing lines and data lines connected to the pixels;
a data driving circuit configured to supply a data voltage for sensing to the data lines;
a pixel sensing device including a plurality of current integrators for sensing driving characteristics of pixels,
a timing controller configured to compensate for digital image data to be written on the display panel based on a sensing result of the pixel sensing device,
a first switch connected between each data line and an output terminal of the data driving circuit through which the data voltage for sensing is output;
a second switch connected to each sensing line and an output terminal of the data driving circuit through which a reference voltage is output;
a third switch connected between each sensing line and the inverting input terminal of the operational amplifier included in the pixel sensing device; and
a fourth switch connected between each data line and the inverting input terminal of the operational amplifier included in the pixel sensing device,
wherein each of the current integrators includes:
an operational amplifier having an inverting input terminal configured to receive a first input voltage according to a pixel current of the pixels, a non-inverting input terminal configured to receive a second input voltage according to the pixel current, and an output terminal configured to output an integral voltage corresponding to the pixel curren

Assignees

• Lg Display Co Ltd

Inventors

• Oh Hyemi
• Song Minkyu
• Choi Jisu
• Lee Byungjae
• Lim Myunggi
• Woo Kyoungdon
• Kim Seungtae
• Kim Bumsik

Classifications

• G09G2320/0233

  Improving the luminance or brightness uniformity across the screen · CPC title

• G09G2320/043

  Preventing or counteracting the effects of ageing · CPC title

• G09G2320/0295

  by monitoring each display pixel · 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

• G09G3/3233 Primary

  with pixel circuitry controlling the current through the light-emitting element · CPC title