A Novel Real-Time TFT Threshold Voltage Compensation Method for AM-OLED Using Double Sampling of Source Node Voltage

• Published in: IEEE journal of the Electron Devices Society Vol. 9; pp. 311 - 317
• Main Authors: Kang, Kyeong-Soo, Lee, Jin-Kyu, Kang, Ji-Min, Lee, Soo-Yeon
• Format: Journal Article
• Language: English
• Published: IEEE 2021
• Subjects: compensation; Degradation; JND; Logic gates; OLED; Organic light emitting diodes; real-time; Real-time systems; Sensors; SPICE; Thin film transistors; threshold voltage
• ISSN: 2168-6734; 2168-6734
• DOI: 10.1109/JEDS.2021.3058348

In this article, we propose a novel real-time threshold voltage (<inline-formula> <tex-math notation="LaTeX">V_{th} </tex-math></inline-formula>) compensation method for AM-OLED display. The proposed method predicts <inline-formula> <tex-math notation="LaTeX">V_{th} </tex-math></inline-formula> shift of driving thin-film transistors (TFTs) based on the equation derived from the sensing line charging with TFT's drain current. The prediction equation requires two consecutive source node voltages to consider the mobility variation, and only takes hundreds of microseconds to predict <inline-formula> <tex-math notation="LaTeX">V_{th} </tex-math></inline-formula> shift. It is short enough to monitor the real-time <inline-formula> <tex-math notation="LaTeX">V_{th} </tex-math></inline-formula> degradation, since the prediction can be carried out during the vertical blank time. Also, very high prediction accuracy was confirmed through Smart SPICE simulation. We simulated severe mobility variation and <inline-formula> <tex-math notation="LaTeX">V_{th} </tex-math></inline-formula> shift circumstances, and the simulation results showed that the prediction error was less than one just noticeable difference (JND) margin though out all gray levels. We expect that the proposed method can achieve more accurate and faster real-time <inline-formula> <tex-math notation="LaTeX">V_{th} </tex-math></inline-formula> degradation compensation for high resolution and large-sized OLED displays than conventional one.