LTPS TFT-Based Backlight Unit Using PWM Driving With Compensation for V TH Variation and Voltage Rise in Power Line
IEEE Transactions on Electron Devices(2024)
摘要
A novel mini-light-emitting diode (mini-LED) driving circuit based on the low-temperature polysilicon thin-film transistors (LTPS TFTs) for used in the active matrix (AM) backlight unit (BLU) of a liquid-crystal display (LCD) is proposed. By the pulsewidth modulation driving method, the mini-LED is operated at a high luminance efficacy point than that is achieved using the pulse-amplitude modulation (PAM) method to reduce the power consumption at a low gray level. To generate the uniform driving current of the mini-LED, the threshold voltage (
${V}_{\text {TH}}$
) variation of the driving thin-film transistor (TFT) is compensated for by the diode-connection structure. Since the large driving current could exacerbate the current–resistance effect in the power source line, the negative supply voltage (VSS)
${I}$
–
${R}$
rise is also compensated for. The
${V}_{\text {TH}}$
variation of the control TFT is compensated for by the matched TFT method to ensure the precise emission time of the mini-LED. The results of a simulation based on the fitting model of the LTPS TFTs indicate that the relative time shifts are below
$0.581~\mu \text{s}$
. The samples of the proposed circuit are fabricated to verify the feasibility of compensation in the proposed mini-LED BLU. Measurements demonstrate that the maximum error rate among samples is 1.46%. When the VSS rises from −6 to −5 V, the measured current error rates are all less than 6.03%. Hence, the proposed circuit is verified to generate uniform driving currents for the mini-LED BLU of LCDs.
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关键词
Active matrix (AM),current–resistance rise/drop,liquid-crystal display (LCD),low-temperature poly-silicon (LTPS),mini-light-emitting diode (mini-LED),pulsewidth modulation (PWM),thin-film transistors (TFTs),threshold voltage (VTH)
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