Metal oxide TFTs gate driver and analog PWM pixel circuit employing progressive slope-compensated ramp signal for micro-LED displays

A new metal oxide thin film transistors (MO TFT) gate driver has been presented for micro light-emitting diode (Micro-LED) displays with line-by-line driving method, where progressive and adjustable slope-compensated ramp signals are employed into each row of pixel array. A compensated analog pulse width modulation (PWM) pixel circuit is presented to construct the Micro-LED driving framework. This proposed gate driver with one input module and three output modules provides all the control signals for pixel array without any external integrated circuits (ICs), which simplifying the driving system. The experimented results show that the gate driver outputs integrated signals, including SCAN, EM and PWM. And the pixel circuit with single Micro-LED chip could achieve different grayscale levels from (100 to 3000 cd/m²), successfully. The slope and current of Micro-LED (I_LED) can be adjusted by applying an external bias, where the slope ranges from −0.35 to −0.57 within a bias range of −6 to −7 V, while I_LED varies from 17.3 to 61.7 μA under a bias range of 3 to 9 V. Then, the error rate of slope and brightness can achieve within 2 % and 5 % with V_th shift of about ±0.7 V after undergoing 1.5 h positive and negative bias stress test of TFT, respectively. Moreover, the proposed gate driver and pixel circuit have been verified to operate normally at high speeds with SCAN output width of 8.68 us, 6.51 us and 4.32 us, which is suitable for high-resolution Micro-LED displays.