Abstract :
Automotive displays play a vital role in modern vehicles, enhancing user experience and delivering crucial information. The automotive industry is rapidly evolving in its adoption of advanced display technologies to enhance user experience, safety, and vehicle aesthetics. Displays such as Active Matrix Liquid Crystal Displays (AMLCD) and Active Matrix Organic Light Emitting Diode (AMOLED) are increasingly being integrated into vehicle cockpits, infotainment systems, digital clusters, and head-up displays. These technologies offer high brightness, wide viewing angles, and improved color performance suitable for varying lighting conditions within automotive environments. To support these advanced displays, there has been significant progress in backplane technologies such as amorphous silicon (a-Si), Low-Temperature Polycrystalline Silicon (LTPS) Among these, low-temperature polysilicon (LTPS) has emerged as a preferred choice due to its high carrier mobility, enabling high-resolution and high-refresh-rate displays. However, LTPS TFTs suffer from threshold voltage (VTH) variations, spatial nonuniformity, IR drop, and flickering, which impact display performance and longevity.
In active-matrix liquid crystal displays (AMLCDs) and active-matrix organic light-emitting diode (AMOLED) displays, pixel driving circuits play a crucial role in addressing these challenges. The conventional 2T1C pixel circuit, comprising two TFTs and one capacitor, is highly susceptible to VTH shifts, leading to nonuniform brightness and color inconsistencies. To overcome these limitations, more advanced pixel circuits, including 4T1C, 5T2C, 7T2C, and 9T2C, have been developed to improve VTH compensation, current stability, and power efficiency. These circuits introduce additional TFTs and capacitors to regulate voltage and current more effectively, reducing flickering and extending display lifespan. This paper presents a detailed analysis of pixel driving circuit architectures for LTPS TFT-based AMLCDs and AMOLEDs, evaluating their effectiveness in mitigating VTH variations and enhancing display performance. A comparative tabular analysis is provided, outlining the strengths and weaknesses of each circuit. Understanding these driving schemes is essential for the continued advancement of LTPS-based automotive displays, ensuring better visual performance, energy efficiency, and long-term durability.