Ji‐Hwan Park

Seoul National University

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Soo‐Yeon Lee

Seoul National University

Kyeong‐Soo Kang

Seoul National University

Jimin Kang

Stanford University

Chanjin Park

Yonsei University

Chanjin Park

Seoul National University

J. H. Lee

Seoul National University

Yong‐Duck Kim

Electronics and Telecommunications Research Institute

Changwon Jeong

Seoul National University

Yumin Yun

Seoul National University

Minji Kim

Seoul National University

Cooperative Institutions

Seoul National University

Pohang University of Science and Technology

Samsung (South Korea)

Daegu Gyeongbuk Institute of Science and Technology

Institute for Basic Science

Electronics and Telecommunications Research Institute

Pusan National University

Chungnam National University

Korea Advanced Institute of Science and Technology

Catholic University of Korea

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P‐7: Student Poster: AMOLED Pixel Circuit for Strain Compensation in Stretchable Display

SID Symposium Digest of Technical Papers (2022)

Jimin Kang Kyeong‐Soo Kang Ji‐Hwan Park Soo‐Yeon Lee

This paper proposes a compensation pixel circuit for stretchable active‐matrix organic light‐emitting diode (AMOLED) display that compensates for the threshold voltage variation and luminance reduction caused by display stretching. The simulated results of the current error rate are suppressed under 10 % at 20 % strain with ±0.5 V threshold voltage shift. Also, the luminance variation was significantly reduced from 19.3 % to 0.12 %.

AMOLED

10.1002/sdtp.15682

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A New PWM Operational Scheme for MicroLED Displays Using Inverter and Dynamic SWEEP Signal Slope for Low Gray Level Expression

IEEE Access (2023)

Kyeong‐Soo Kang Ji‐Hwan Park Chan‐Jin Park J. H. Lee Soo‐Yeon Lee

In this paper, we present a novel pulse width modulation (PWM) operational scheme for micro-light-emitting-diode (μLED) displays using inverter and dynamic SWEEP signal slope.In the proposed PWM operational scheme, the slope of the SWEEP signal steepens as the gray level decreases.This adjustable SWEEP signal slope further shortens the falling time compared to the inverter-only strategy, leading to an exceptional capability to express extremely low gray levels.We implement the proposed scheme with low-temperature poly-Si oxide (LTPO) thin-film transistor (TFT) pixel circuit, and verify the operation through HSPICE based on measured TFT data.The simulation results show that the proposed scheme can significantly shorten the falling time to under 1 μs level.The gray level of 14 G is accurately expressed without wavelength shift or pulse distortion, achieving a falling time of 0.21 μs.In addition, we also verify the compensation accuracy of the pixel circuit, and the results indicate that the proposed pixel circuit can reliably compensate for TFT variations.

Signal edge

SIGNAL (programming language)

10.1109/access.2023.3337889

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Citations (3)

7‐3: A New Line‐by‐Line SWEEP Signal Generation Method for PWM Driving MicroLED TFT Pixel Circuit

SID Symposium Digest of Technical Papers (2023)

Kyeong‐Soo Kang Ji‐Hwan Park Chanjin Park Soo‐Yeon Lee

This paper proposes a novel method to generate a SWEEP signal line‐by‐line for PWM driving microLED pixel circuit. The proposed method generates a SWEEP signal based on the linearly increasing voltage of the capacitor by flowing a constant current to the horizontal line parasitic capacitive load. The constant current is supplied by the sweep generation (SG) circuit in each line. Since the SG circuit utilizes the existing SCAN signals for the pixel circuit, additional SCAN or clock signals are not required. By using the proposed method, an individual SWEEP signal for each line can be generated without a significant increase in operational complexity in the display panel.

Line (geometry)

SIGNAL (programming language)

10.1002/sdtp.16490

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Citations (5)

7‐4: A Novel a‐IGZO TFT Micro‐LED Circuit with Improved Stability and Area Efficiency

SID Symposium Digest of Technical Papers (2023)

Chanjin Park Kyeong‐Soo Kang Ji‐Hwan Park Soo‐Yeon Lee

In this paper, a novel amorphous Indium‐Gallium‐Zinc‐Oxide (a‐IGZO) thin‐film transistor (TFT) pixel circuit for pulse width modulation (PWM) driving micro light emitting diode (μLED) display is proposed. During the circuit operation, single signal is used for two different purposes and data line for constant current generation (CCG) unit is eliminated. Furthermore, the impact of connection structure between PWM unit and CCG unit on compensation error is investigated, and showed that the structure used in the proposed circuit is effective in reducing current error rate of CCG unit, especially in low gray level area.

10.1002/sdtp.16491

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Citations (3)

Stretchable AMOLED Display Pixel Circuit Compensating for $\mathbf{V}_{\mathbf{th}}$ Variation and Strain Effect

Jimin Kang Kyeong‐Soo Kang Ji‐Hwan Park Minsik Kong Soo‐Yeon Lee

This paper suggests a novel pixel circuit which can cope with the image quality issues in the stretchable active-matrix organic light-emitting diode (AMOLED) display. The proposed pixel circuit can compensate for the threshold voltage variation and the luminance reduction due to the deformation of the display panel. The simulated results demonstrate that the proposed pixel circuit can reduce the luminance reduction from 83 cd/m2 to 16 cd/m ² .

AMOLED

10.23919/am-fpd54920.2022.9851286

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Depletion-Mode Oxide TFT-Based MicroLED Pixel Circuit for High-Current Pulsewidth Modulation With Low Driving Voltage

IEEE Transactions on Electron Devices (2024)

Kyeong‐Soo Kang Hee-Ok Kim Jong‐Heon Yang Jae‐Eun Pi Yong‐Duck Kim

Modulation (music)

10.1109/ted.2024.3456767

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P‐16: Student Poster: New a‐IGZO TFT Pixel Circuit Compensating Threshold Voltage and Mobility for Active‐Matrix OLED with Source Follower Method

SID Symposium Digest of Technical Papers (2022)

Ji‐Hwan Park Kyeong‐Soo Kang Jimin Kang Soo‐Yeon Lee

This paper proposes a new amorphous indium gallium zinc oxide (a‐IGZO) pixel circuit for the simultaneous emission active‐matrix organic light‐emitting diode (AMOLED) displays, which can compensate for the non‐uniform threshold voltage (V TH ) and mobility (μ) of the thin‐film transistor (TFT). The Negative V TH are successfully compensated by adopting the source follower method, and then mobility compensation is carried out by additional voltage adjustment. The OLED current error rate is within 9 % against the V TH and mobility variations in the simulation.

AMOLED

Oxide thin-film transistor

10.1002/sdtp.15691

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Citations (2)

Oxide-Based Pixel Circuit for PWM Driving Micro-LED Displays Employing Double-Gate Structure TFT

Proceedings of the International Display Workshops (2022)

Changwon Jeong Jimin Kang Kyeong‐Soo Kang Ji‐Hwan Park Soobin An

LED display

Oxide thin-film transistor

10.36463/idw.2022.0234

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Highly Uniform Low Gray AMOLED Pixel using Stable Circuit and Duty Ratio Modulation Driving

IEEE Journal of the Electron Devices Society (2024)

Chanjin Park Hee-Ok Kim Jong‐Heon Yang Jae‐Eun Pi Yong‐Duck Kim

AMOLED

Duty cycle

Gray (unit)

Modulation (music)

10.1109/jeds.2024.3452753

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Citations (1)

A Mura model‐based optical compensation for organic light‐emitting diode display luminance nonuniformity utilizing two image capturing

Journal of the Society for Information Display (2024)

H.I. Kwon Chanjin Park Kyeong‐Soo Kang Ji‐Hwan Park Soo‐Yeon Lee

Abstract In this paper, we proposed a new optical Mura compensation method that requires only a few Mura detections for all gray levels. We analyzed the characteristics of Mura resulting from process variations in the thin film transistor (TFT) of each pixel and developed a new model using a logarithmic function. The proposed compensation algorithm has been verified with simulation and experimental results. We found that the uniformity of the proposed compensation algorithm at 7G, 24G, 75G, 100G, 150G, and 255G, which required only two image captures, was comparable to those that required five captures. The model improved uniformity from 41.32% to 68.60% at 0.18 nit brightness, demonstrating its effectiveness. Additionally, the method significantly reduces the number of image captures needed from five to two and decreases the image capturing process time from 2183 to 150 ms, saving over 14 times in process efficiency. The proposed methodology demonstrates significant advancements in achieving luminance uniformity in OLED displays, addressing mass production constraints.

Mura

Stereo display

Viewing angle

10.1002/jsid.2017

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