Low-Temperature Polycrystalline Silicon Thin-Film Transistor-Based Micro Light-Emitting Diode Pixel Circuit Using Quaternary Digital Pulse Width Modulation for Simple Structure and Short Delay Time

We propose a low-temperature polycrystalline silicon thin-film transistor (TFT)-based micro light-emitting diode (μLED) pixel circuit using quaternary digital pulse width modulation (PWM). The proposed circuit uses a stepwise control signal to modulate the emission time of each subframe in four levels, thereby reducing the number of subframes by half compared with conventional binary digital driving. Because the stepwise control signal can directly change the PWM driving TFT from off-state to on-state, the proposed circuit exhibits a short delay time of 1.83 μs and low luminance variations of 3.45% without requiring a compensation structure for the threshold voltage of the PWM driving TFT. The proposed pixel circuit can be efficiently used in high-quality μLED displays, ensuring a stable operation.