A 1280 x 720 Micro-LED Display Driver with 10-Bit Current-Mode Pulse Width Modulation

Abstract

Micro-light-emitting diode (micro-LED) displays are the most promising next-generation displays that use tiny LEDs acting as pixels [1–2]. Micro-LED displays are considerably brighter than are organic LED displays, which makes micro-LED displays suitable for head-up display (HUD), virtual-reality (VR), and augmented-reality (AR) applications [3]. A mass transfer technology is used to transfer a micro-LED array from epitaxy to a Si substrate. Pulse width modulation (PWM) is generally employed to generate gray levels in these arrays [4]. Micro-LED display drivers with voltage-mode PWM have strong driving ability but poor display uniformity. By contrast, current-mode PWM is a suitable driving method for achieving display uniformity. However, for high-resolution micro-LED displays, a large number of pixels must be connected to the data line, which creates a large capacitive load on the data line. A micro-LED consumes only tens of microamperes of current; thus, designing a display driver that uses a small current to drive a high-resolution and high-frame-rate display with current-mode PWM is challenging. In this paper, a precharge scheme and a pixel circuit with two transistors and one LED (2T1D) are proposed to solve the aforementioned issue. A $1280 \times 720$ micro-LED display driver with 10-bit current-mode PWM was designed and fabricated in this study. Furthermore, a micro-LED array was successfully integrated into the designed display driver chip, which verified the feasibility of the designed display driver.