a-IGZO TFT µLED Pixel Circuit for PWM Driving and Its Color Shift with Different Duty Ratios and Current Amplitudes

In this paper, a µLED pixel circuit with a-IGZO TFT for pulse-width-modulation (PWM) driving is proposed. Using HSPICE, the PWM operation of the proposed circuit and the uniformity under threshold voltage variations are verified. Furthermore, the color shift according to the various combinations of current duty ratio and amplitude is analyzed. When the LED current is high enough to be in the color shift saturation region, utilizing higher current level and smaller duty ratio can decrease the color shift. However, when the current is in the non-color shift saturation region, longer emission period with smaller current level is beneficial. Therefore, to enhance the image quality of micro-LED display, adequate current level and the duty ratio need to be determined accordingly.