Display device and method for controlling the same

• US 10,460,670 B2
• Filed: 01/17/2017
• Issued: 10/29/2019
• Est. Priority Date: 01/19/2016
• Status: Active Grant

• Current Assignee: JDI Design and Development GK
• Original Assignee: JOLED Inc.
• Inventors: Maeda, Tomoyuki
• Primary Examiner(s): Nguyen, Jimmy H
• Application Number:
  US15/407,605
• Publication Number:
  US 20170206841A1
• Time in Patent Office: 1,015 Days
• Field of Search: 345 76- 83
• 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 2300/0819 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 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• CPC Class Codes: G09G 2310/08 Details of timing specific for flat panels, other than clock recovery
• CPC Class Codes: G09G 3/2018 by time modulation using two or more time intervals
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3266 Details of drivers for scan electrodes
• CPC Class Codes: G09G 3/3291 in which the data driver supplies a variable data voltage for setting the current through, or the voltage across, the light-emitting elements

Abstract

A display device is provided that includes a plurality of pixels, each of which includes an electroluminescent (EL) element and a drive transistor that controls a current flowing through the EL element. The display device also includes a gate driver circuit that applies, to each of the plurality of pixels, a compensation voltage for compensating a threshold voltage of the drive transistor, in each of compensation voltage application periods included in a period other than a period in which a video signal voltage is applied. The display device further includes a control circuit that controls the gate driver circuit, wherein the control circuit adjusts a length of, among the compensation voltage application periods, a preceding compensation voltage application period immediately before the video signal voltage is applied.

Claims

1. A display device, comprising:

a plurality of pixels, each of which includes an electroluminescent (EL) element and a drive transistor that controls a current flowing through the EL element;

a gate driver circuit that applies, to each of the plurality of pixels, a compensation voltage enable pulse for compensating a threshold voltage of the drive transistor, in each of compensation voltage application periods included in a period other than a period in which a video signal voltage is applied; and

a control circuit that controls the gate driver circuit,

wherein the control circuit adjusts a length of, among the compensation voltage application periods, a preceding compensation voltage application period immediately before the video signal voltage is applied,

wherein the control circuit adjusts the length of the preceding compensation voltage application period based on a timing of a vertical synchronization signal,

wherein a compensation voltage is applied to a gate terminal of the drive transistor of each of the plurality of pixels a predetermined number of compensation voltage application periods in a predetermined compensation operation period that causes a gradual reduction of a pixel voltage to approach the threshold voltage of the drive transistor, and

wherein the predetermined number of compensation application voltage periods is in the range of 20-30.

2. The display device according to claim 1,

wherein the control circuit adjusts the preceding compensation voltage application period to be longer as an interval between two vertical synchronization signals immediately before the video signal voltage is applied is shorter.

3. The display device according to claim 1,

wherein the compensation voltage is applied to the plurality of pixels via data lines for applying the video signal voltage to the plurality of pixels.

4. A method for controlling a display device, including a plurality of pixels each of which includes an EL element and a drive transistor that controls a current flowing through the EL element, the method comprising:

applying, to each of the plurality of pixels, a compensation voltage for compensating a threshold voltage of the drive transistor, in each of compensation voltage application periods included in a period other than a period in which a video signal voltage is applied;

adjusting a length of, among the compensation voltage application periods, a preceding compensation voltage application period immediately before the video signal voltage is applied;

adjusting the length of the preceding compensation voltage application period based on a timing of a vertical synchronization signal,

applying a compensation voltage to a gate terminal of the drive transistor of each of the plurality of pixels a predetermined number of compensation voltage application periods in a predetermined compensation operation period to cause a gradual reduction of a pixel voltage to approach the threshold voltage of the drive transistor, and

wherein the predetermined number of compensation application voltage periods is in the range of 20-30.