A New Pixel Circuit for Active Matrix Mini&Micro Light Emitting Diodes

Abstract

A novel pixel circuit with indium gallium zinc oxide thin-film transistors (IGZO-TFTs) for driving active-matrix Mini& Micro light-emitting diode (AM-MLED) display is proposed. The pixel circuit is built with seven n-type IGZO-TFTs and two capacitors. It can be conducted both under Pulse Amplitude Modulation (PAM) mode and Pulse Width Modulation (PWM) mode, bringing about more gray levels and a better picture quality. The pixel circuit can compensate for the threshold voltage (VTH) deviation of the driving TFT(T2) in the PAM mode through external compensation method. It also can compensate for the threshold voltage (Vth) deviation of the driving TFT (T4) in the PWM mode through the internal compensation circuit. The simulation results show that the pixel circuit under the T2 detecting timing can accurately detect the Vth of T2. On this basis, correct compensation can function well through adjusting data input value by external IC. The simulation results also demonstrate that when the deviation of the T4 threshold voltage occurs ± 1V, the average bit error rate of the light-emitting time is 2%. Therefore, the circuit can effectively compensate the VTH of T4. As a result, the proposed pixel circuit with hybrid driving mode exhibits high immunity to the threshold voltage deviation of T2 and T4, and good brightness uniformity of AM-MLED display can be obtained.