This work proposes a mini-LED driving circuit that adopts the pulse-width modulation (PWM) driving method for use in a liquid-crystal display (LCD) backlight. The proposed circuit can compensate for the threshold voltage (VTH) variation in a lowtemperature poly-crystalline silicon thin-film transistor (LTPS TFT) and a VSS current-resistance (I-R) rise, to generate a stable driving current to power the mini-LED. Since the proposed circuit uses the PWM method, the mini-LED can be operated at the best luminance-efficacy point, minimizing the power consumption of the circuit. The electrical characteristic of fabricated LTPS TFTs are measured to establish a simulation model to demonstrate the feasibility of the proposed circuit. Simulation results demonstrate that the relative mini-LED current error rates are below 9% when the VTH varies ± 0.3 V and VSS rises by 1 V. With respect to precise control of the gray level, the time shifts of current pulses are within 11.48 us over the whole grayscale. The improvement in the power consumption of the proposed circuit is more than 21% than that of a circuit that is driven by pulse amplitude modulation.

This work proposes a hydrogenated amorphous silicon (a-Si:H) thin-film transistor (TFT) gate driver with a low-leakage capacitive coupling structure to reduce the delay of the clock signal. The proposed circuit suppresses the fluctuation in the gate node of the driving TFT induced by clock-feedthrough effect, reducing the leakage current that flows from the clock signal line to the power source line with a low voltage level. This reduction in the leakage current can improve the degradation in the voltage of the clock signal and thus avoid the increase in the rising time of the scan pulse. Measurements for extracting the drain current versus gate-to-source voltage (I D-V GS) curves of a fabricated a-Si:H TFT are made to establish a simulation TFT model by fitting the obtained curves. For the same parameters of the TFTs and capacitances, the leakage current and the rising time of the output waveform of the proposed circuit are 45.45% and 21.36% lower, respectively, than those of previously developed gate driver. INDEX TERMS a-Si:H TFTs, capacitive-coupling effect, clock-feed-through effect, gate driver, leakage current.

This paper proposes a mini-light-emitting diode (mini-LED) driving circuit that is driven by pulse width modulation (PWM) for the backlights of active-matrix (AM) liquid crystal displays (LCDs). The proposed circuit compensates for threshold voltage (VTH) variations of low-temperature polycrystalline silicon thin-film transistors (LTPS TFTs) and the current-resistance (I-R) rise in VSS lines to supply a stable driving current. Operating the mini-LED at the high luminous efficacy by the PWM driving method and setting only the driving TFT on the path of the driving current reduce the power consumption of the backlight. Based on a 2.89-inch LCD panel with an AMLED 48 × 48 backlit module, the TFTs are fabricated, measured, and fitted. Simulation results show that the relative current error rates are all below 4.67% when the VTH of the driving TFT varies by ±0.3 V and the VSS rises by 0.5 V. The voltage across VDD and VSS of the proposed circuit is 4.5 V lower than that of the 6T1C compensating driving circuit, so the power consumption of the circuit is at least 27.05% lower. Therefore, the proposed driving circuit is well suitable to use in mini-LED backlit LCDs.

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