AM Mini-LED Backlight Driving Circuit Using PWM Method With Power-Saving Mechanism

Abstract

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.

7‐4: A Novel a‐IGZO TFT Micro‐LED Circuit with Improved Stability and Area Efficiency

“…Figure 3 shows two different methods PWM unit and gate node of TCCG is connected. Many other previously proposed analog PWM pixel circuits with a-IGZO TFTs [9], [10], [11], adopted a structure that directly connects PWM unit and gate node of TCCG, or Case 2(figure 3(b)) connection scheme. In the proposed pixel circuit, PWM unit is connected to the gate node of driving TFT of CCG through CCCG, where VTH_CCG is stored instead of gate node of TCCG, like in Case 1(figure 3.(a)).…”

Integrated 2T1C pixel circuit with a-Si TFT and NMOS for active matrix mini-LED displays

“…Deng et al proposed an AM driving circuit using a low-temperature poly-silicon TFT to reduce the power consumption of mini-LED backlight LCD by lowering the drain-source voltage (V DS ) of the switching TFT on the driving current path and reducing the range of required voltage across the proposed circuit [12]. Lin et al reported a mini-LED driving circuit to produce a stable driving current by compensating for the current-resistance rise of the negative voltage of the source (V SS ) and the threshold voltage (V TH ) variation of the driving TFT to reduce the power consumption of the circuit and improve luminous efficiency of mini-LEDs [13,14].…”

A New PWM Operational Scheme for MicroLED Displays Using Inverter and Dynamic SWEEP Signal Slope for Low Gray Level Expression

“…However, the wavelength of μLED's light can shift depending on its current density, resulting in color distortion [8]- [10]. Therefore, pulse width modulation (PWM) driving, which adjusts the emission period with a constant current to express gray levels, must be applied to μLED displays [5], [11]- [14].…”