Oxide TFT‐Based Micro‐LED Pixel Circuit With Piecewise Linear Sweep Slope Signal for Improved Low Gray‐Level Expression

In this paper, we present an amorphous indium‐gallium‐zinc‐oxide (a‐IGZO) based pulse width modulation (PWM) pixel circuit for micro light‐emitting diode (micro‐LED) displays, designed to enhance low gray‐level expression. Conventional PWM circuits suffer from a long falling time, causing inaccurate gray‐level representation. To address this, the proposed circuit employs a continuous piecewise linear sweep signal with two distinct slopes: a steeper slope for low gray levels and a shallower slope for mid‐to‐high gray levels. This approach reduces the falling time from 209 to 62 μs, enabling accurate gray‐level expression down to 41 G without distortion. To prevent falling time distortion from sweep signal slope transitions, a newly proposed separation part divides the emission period into low and high gray phases. By maintaining a constant sweep signal slope within each phase, the circuit ensures stable emission and eliminates distortion. HSPICE simulation verifies the circuit operation and confirms that it maintains stable performance under threshold voltage variations.