6.8 A Real-Time Pixel-Compensated Source-Driver IC with Dual-Slope Error Detection and Multi-Channel Time-Multiplexing Compensator for Compact OLED Displays

Active-matrix organic light-emitting diode (AMOLED) displays, especially those using low-temperature polycrystalline silicon (LTPS) thin-film transistors (TFTs), have been widely used in mobile devices thanks to their high mobility and low power consumption. The OLED pixels are illuminated by supplying current based on the data voltage $(V_{DATA})$ of the source driver (SD) IC through the driving TFT (DTFT). However, the polycrystalline structure of LTPSTFT leads to non-uniform TFT parameter $(K_{P})$ and threshold voltage $(V_{TH})$ across different pixels [1]. Also, there are deviations in $V_{DATA}$ across different channels $(V_{OS})$. This inconsistency causes variations in the DTFT drain current $(I_{TFT})$, resulting in different luminance levels even with identical input data and degrading the overall display quality, as shown in Fig. 6.8.1 (top left). To address this issue, internal compensation methods using additional TFTs and capacitors have been studied, but the increased complexity of the pixel structure reduces the aperture ratio, leading to lower luminance efficiency and higher costs, as depicted in Fig. 6.8.1 (top right) [2]. Another effective method is to utilize external compensation by sensing the characteristic of each DTFT and adjusting $V_{DATA}$ accordingly. This method offers a simpler pixel structure, enabling high aperture ratio and luminance efficiency.