15‐1: PWM Pixel Circuit with LTPS TFTs for Micro‐LED Displays

Abstract

Micro-LEDs have a characteristic for wavelength shifts depending on a current density. Therefore, a PAM pixel circuit generates wavelength shifts according to the current of gray scale control for micro-LED display. To solve this problem, this paper proposes a new PWM pixel circuit for gray scale controls using LTPS TFTs.Author Keywords P-type low temperature poly-silicon thin-film transistors (LTPS TFTs), Pulse width modulation (PWM) pixel circuit, Micro-LED, Wavelength shift.

AM PWM Driving Circuit for Mini-LED Backlight in Liquid Crystal Displays

“…Nevertheless, to meet the demand for mini-LED backlights, the current in the circuit must be at the milliampere level, which is difficult to achieve. Kim et al proposed another PWM driving circuit without a current source [20]. Although their circuit is more easily realizable, the rising and falling times must be reduced to less than the emission time of one gray level to achieve precise control of the gray levels.…”

9‐5: Late‐News Paper: A 3.9‐inch LTPS TFT Full Color MicroLED Display with Novel Driving and Reflector Cavity Process

“…However, the conventional current driving has intrinsic problems such as wavelength shift of the LED emission light as the current decreases [6]. In order to avoid these, a PWM pixel circuit for grayscale control using LTPS TFTs has been proposed in the previous work [4]. But quite a short time is allowed to emit the light of lower grayscales for the PWM driving, which limits achieving a higher frame rate.…”

“…Active matrix (AM) driving with LTPS backplanes has been considered to be suitable for microLED displays for various aspects, and so far several papers including our works have been reported [2][3][4][5]. However, the conventional current driving has intrinsic problems such as wavelength shift of the LED emission light as the current decreases [6].…”

7‐3: High ESD Robustness and Low Visible Light Reflectance Design for LTPS‐TFTs on Glass Substrates in Modular Micro‐LED Displays

“…Micro-LED displays with ultra-small LEDs smaller than 100 micrometers have excellent performance in luminance, contrast ratio, response speed, luminous efficiency, light source life, and power consumption compared to conventional AMLCDs [1]. For the micro-LED displays, backplanes with low-temperature polysilicon thin-film transistors (LTPS-TFTs) are prevalently adopted to supply high current and achieve high brightness [2]. On the other hand, a number of micro-LED display modules can be assembled to form an ultra-large display, and we call it a modular display.…”