P‐73: Student Poster: MicroLED Pixel Circuit Based on Metal Oxide Thin‐Film Transistor with Progressive Emission Method Using Pulse Width Modulation

Abstract

The novel pixel circuit was proposed for the microLED display.We applied the progressive emission and PWM to use tens of μA current and hundreds of us emission time in considering of EQE characteristic. The proposed circuit was verified to operate stably in depletion mode of a‐IGZO TFT.

A Compact Amorphous In-Ga-Zn-Oxide Thin Film Transistor Pixel Circuit With Two Capacitors for Active Matrix Micro Light-Emitting Diode Displays

“…Meanwhile, the layout design in fig. 1(c) has smaller size than latest works using metal oxide TFTs [19]- [21] due to the small number of capacitors as shown in table 1. Hence, the proposed circuit can achieve very high pixel density.…”

“…Meanwhile, the constant LED current of the proposed circuit is above 20 A, as it is generally known that the current range of tens of μA can ensures the high EQE of the μLED [21]. The gray level is adjusted by modulating the width of the emission period.…”

7‐3: A New Line‐by‐Line SWEEP Signal Generation Method for PWM Driving MicroLED TFT Pixel Circuit

“…Meanwhile, in order to control the LED emission time through the PWM part, an additional signal from the gate driver IC should be applied to the PWM part. This additional signal is generally referred to as a SWEEP signal in previously published papers, and has a waveform of linearly increasing from a reference voltage [15], [16]. The gate-to-source voltage (VGS) of the driving TFT (DRT) in PWM part is also set to increase based on the SWEEP signal, and the on/off state of the PWM DRT is switched when the SWEEP signal voltage (VSWEEP) reaches the threshold.…”

“…This will bring the growth of the operational complexity in the display panel. Therefore, a proposal of a novel method to generate a SWEEP[N] signal in a simpler and more efficient way is essential at this point when the microLED driving is changing from the simultaneous emission to the progressive emission [15]. In this paper, we propose a new method to generate a SWEEP[N] signal without increasing the burden of the gate driver operation.…”