A New Analog PWM Pixel Circuit With Metal Oxide TFTs for Micro-LED Displays

• Published in: IEEE transactions on electron devices 2022-08, Vol.69 (8), p.4306-4311
• Main Authors: Zou, Pei-An, Xu, Yan-Gang, Liu, Chun, Zhang, Li-Rong, Zhang, Jin-Hui, Yuan, Yi-Kai, Cai, Wei, Han, Shao-Hu, Zhou, Lei, Xu, Miao, Wang, Lei, Wu, Wei-Jing, Peng, Jun-Biao
• Format: Article
• Language: English
• Subjects: Analog circuits; Analog data; Analog pulsewidth modulation (PWM) driving method; Arrays; Backplanes; Circuits; compensation; Glass substrates; High-voltage techniques; Light emitting diodes; metal oxide (MO) thin-film transistors (TFTs); Metal oxides; Metals; micro-light-emitting diode (LED) displays; pixel circuit; Pixels; Pulse duration modulation; Pulse width modulation; Semiconductor devices; Thin film transistors; Threshold voltage
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2022.3178363

This article presents a new uncompensated analog pulsewidth modulation (PWM) pixel circuit employing pull-up control for micro-light-emitting diode (LED) display. The time of emitting light for the micro-LED working at the constant current is modulated by the analog data voltage. A compensated pixel circuit is also further developed to improve the display uniformity by compensating the threshold voltage shift of PWM thin-film transistor (TFT) and driving TFT. Based on the back-channel etch (BCE) metal oxide TFTs process, 16\times GGG \times29 LED array with the uncompensated pixel circuit and 16 \times {G}\,\,\times15 LED array with the compensated pixel circuit are simultaneously fabricated on the same glass substrate. Compared with the uncompensated pixel circuit array, the display uniformity of the compensated pixel circuit array is improved from 74% to 88%.