Compensation pixel circuit to improve image quality for mobile AMOLED displays

Chih Lung Lin; Po Chun Lai; Li Wei Shih; Chia Che Hung; Po Cheng Lai; Tsu Yuan Lin; Kuang Hsiang Liu; Tsang Hong Wang

doi:10.1109/JSSC.2018.2881922

Compensation pixel circuit to improve image quality for mobile AMOLED displays

Chih Lung Lin, Po Chun Lai, Li Wei Shih, Chia Che Hung, Po Cheng Lai, Tsu Yuan Lin, Kuang Hsiang Liu, Tsang Hong Wang

Department of Electrical Engineering

Research output: Contribution to journal › Article › peer-review

55 Citations (Scopus)

Abstract

This paper proposes a new pixel circuit using lowerature polycrystalline silicon thin-film transistors (LTPS TFTs) for use in mobile active matrix organic light-emitting diode (AMOLED) displays. The purpose of a pixel circuit is to supply stable and uniform currents to current-driving devices of OLEDs. The proposed pixel circuit uses overlapping compensation times to extend the period of precise sensing of V_TH variations of LTPS TFTs. Moreover, the proposed circuit prevents a current from flowing into an OLED when the OLED is not operated in the emission stage to avoid image flicker. An 1.3-in panel that uses the proposed pixel circuit is fabricated. Measurement results verify that the increased T_COMP of 33.3 μs results in higher contrast ratio and lower required data voltages than those at T_COMP values of 4.3 and 2.2 μs. Red, green, and blue images displayed by the fabricated panel with a T_COMP of 33.3 μs with a 255 gray level are all much more uniform than with T_COMPS of 4.3 and 2.2 μs. White images with a T_COMP of 33.3 μs for 16 and 8 gray levels on the fabricated panel confirm that the serious line and spot defects in the images with T_COMP values of 4.3 and 2.2 μs are effectively eliminated. Therefore, the proposed pixel circuit is suitable for use in mobile AMOLED displays.

Original language	English
Article number	8551265
Pages (from-to)	489-500
Number of pages	12
Journal	IEEE Journal of Solid-State Circuits
Volume	54
Issue number	2
DOIs	https://doi.org/10.1109/JSSC.2018.2881922
Publication status	Published - 2019 Feb

All Science Journal Classification (ASJC) codes

Electrical and Electronic Engineering

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10.1109/JSSC.2018.2881922

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@article{9981e062b1e64e27995e918321a394ac,

title = "Compensation pixel circuit to improve image quality for mobile AMOLED displays",

abstract = "This paper proposes a new pixel circuit using lowerature polycrystalline silicon thin-film transistors (LTPS TFTs) for use in mobile active matrix organic light-emitting diode (AMOLED) displays. The purpose of a pixel circuit is to supply stable and uniform currents to current-driving devices of OLEDs. The proposed pixel circuit uses overlapping compensation times to extend the period of precise sensing of VTH variations of LTPS TFTs. Moreover, the proposed circuit prevents a current from flowing into an OLED when the OLED is not operated in the emission stage to avoid image flicker. An 1.3-in panel that uses the proposed pixel circuit is fabricated. Measurement results verify that the increased TCOMP of 33.3 μs results in higher contrast ratio and lower required data voltages than those at TCOMP values of 4.3 and 2.2 μs. Red, green, and blue images displayed by the fabricated panel with a TCOMP of 33.3 μs with a 255 gray level are all much more uniform than with TCOMPS of 4.3 and 2.2 μs. White images with a TCOMP of 33.3 μs for 16 and 8 gray levels on the fabricated panel confirm that the serious line and spot defects in the images with TCOMP values of 4.3 and 2.2 μs are effectively eliminated. Therefore, the proposed pixel circuit is suitable for use in mobile AMOLED displays.",

author = "Lin, {Chih Lung} and Lai, {Po Chun} and Shih, {Li Wei} and Hung, {Chia Che} and Lai, {Po Cheng} and Lin, {Tsu Yuan} and Liu, {Kuang Hsiang} and Wang, {Tsang Hong}",

note = "Funding Information: Manuscript received February 24, 2018; revised June 5, 2018 and August 24, 2018; accepted November 4, 2018. Date of publication November 28, 2018; date of current version January 25, 2019. This work was supported in part by the Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan, Taiwan, in part by the Ministry of Science and Technology of Taiwan under Project MOST 107-2221-E-006-188-MY3 and Project MOST 106-2622-E-006-011-CC2, and in part by AU Optronics Corporation. This paper was approved by Associate Editor David Stoppa. (Corresponding author: Chih-Lung Lin.) C.-L. Lin is with the Department of Electrical Engineering, National Cheng Kung University, Tainan 701-01, Taiwan, and also with the and the Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 701-01, Taiwan (e-mail: cllin@ee.ncku.edu.tw). Publisher Copyright: {\textcopyright} 2018 IEEE.",

year = "2019",

month = feb,

doi = "10.1109/JSSC.2018.2881922",

language = "English",

volume = "54",

pages = "489--500",

journal = "IEEE Journal of Solid-State Circuits",

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T1 - Compensation pixel circuit to improve image quality for mobile AMOLED displays

AU - Lin, Chih Lung

AU - Lai, Po Chun

AU - Shih, Li Wei

AU - Hung, Chia Che

AU - Lai, Po Cheng

AU - Lin, Tsu Yuan

AU - Liu, Kuang Hsiang

AU - Wang, Tsang Hong

N1 - Funding Information: Manuscript received February 24, 2018; revised June 5, 2018 and August 24, 2018; accepted November 4, 2018. Date of publication November 28, 2018; date of current version January 25, 2019. This work was supported in part by the Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan, Taiwan, in part by the Ministry of Science and Technology of Taiwan under Project MOST 107-2221-E-006-188-MY3 and Project MOST 106-2622-E-006-011-CC2, and in part by AU Optronics Corporation. This paper was approved by Associate Editor David Stoppa. (Corresponding author: Chih-Lung Lin.) C.-L. Lin is with the Department of Electrical Engineering, National Cheng Kung University, Tainan 701-01, Taiwan, and also with the and the Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 701-01, Taiwan (e-mail: cllin@ee.ncku.edu.tw). Publisher Copyright: © 2018 IEEE.

PY - 2019/2

Y1 - 2019/2

N2 - This paper proposes a new pixel circuit using lowerature polycrystalline silicon thin-film transistors (LTPS TFTs) for use in mobile active matrix organic light-emitting diode (AMOLED) displays. The purpose of a pixel circuit is to supply stable and uniform currents to current-driving devices of OLEDs. The proposed pixel circuit uses overlapping compensation times to extend the period of precise sensing of VTH variations of LTPS TFTs. Moreover, the proposed circuit prevents a current from flowing into an OLED when the OLED is not operated in the emission stage to avoid image flicker. An 1.3-in panel that uses the proposed pixel circuit is fabricated. Measurement results verify that the increased TCOMP of 33.3 μs results in higher contrast ratio and lower required data voltages than those at TCOMP values of 4.3 and 2.2 μs. Red, green, and blue images displayed by the fabricated panel with a TCOMP of 33.3 μs with a 255 gray level are all much more uniform than with TCOMPS of 4.3 and 2.2 μs. White images with a TCOMP of 33.3 μs for 16 and 8 gray levels on the fabricated panel confirm that the serious line and spot defects in the images with TCOMP values of 4.3 and 2.2 μs are effectively eliminated. Therefore, the proposed pixel circuit is suitable for use in mobile AMOLED displays.

AB - This paper proposes a new pixel circuit using lowerature polycrystalline silicon thin-film transistors (LTPS TFTs) for use in mobile active matrix organic light-emitting diode (AMOLED) displays. The purpose of a pixel circuit is to supply stable and uniform currents to current-driving devices of OLEDs. The proposed pixel circuit uses overlapping compensation times to extend the period of precise sensing of VTH variations of LTPS TFTs. Moreover, the proposed circuit prevents a current from flowing into an OLED when the OLED is not operated in the emission stage to avoid image flicker. An 1.3-in panel that uses the proposed pixel circuit is fabricated. Measurement results verify that the increased TCOMP of 33.3 μs results in higher contrast ratio and lower required data voltages than those at TCOMP values of 4.3 and 2.2 μs. Red, green, and blue images displayed by the fabricated panel with a TCOMP of 33.3 μs with a 255 gray level are all much more uniform than with TCOMPS of 4.3 and 2.2 μs. White images with a TCOMP of 33.3 μs for 16 and 8 gray levels on the fabricated panel confirm that the serious line and spot defects in the images with TCOMP values of 4.3 and 2.2 μs are effectively eliminated. Therefore, the proposed pixel circuit is suitable for use in mobile AMOLED displays.

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Compensation pixel circuit to improve image quality for mobile AMOLED displays

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