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 poly-crystalline 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 $48\times48$ 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.

Keywords

• Liquid crystal display (LCD)
• low-temperature poly-crystalline silicon (LTPS)
• minilight-emitting diode (mini-LED)
• power consumption
• pulse width modulation (PWM)
• threshold voltage (VTH)