Improvement of the low gray-level expression using hybrid pulse width modulation and pulse amplitude modulation driving method for a micro light-emitting diode pixel circuit

Hong, Yong-Hoo; Jung, Eun Kyo; Im, Hwarim; Kim, Yong−Sang

doi:10.1080/15980316.2022.2084464

Cited by 15 publications

(11 citation statements)

References 14 publications

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“…Therefore, low rising and falling times are attributed to the rapid change of the current-driving capability of T7 due to the STEP signal. We expected that the proposed μLED pixel circuit could express low gray levels without a color shift because the rising and falling time is closely related to the expression capability of low gray levels [6].…”

Section: P-23 / H Immentioning

confidence: 99%

P‐23: Micro Light‐Emitting Diode Pixel Circuit Based on IGZO TFTs using a Stepwise Control Signal

Im,

Jung,

Kim

2023

Symp Digest of Tech Papers

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We proposed an IGZO TFT‐based micro light‐emitting diode (μLED) pixel circuit using a stepwise control signal. The proposed pixel circuit expressed the gray levels by modulating the emission time with the constant driving current to suppress a wavelength shift of μLEDs. The proposed pixel circuit successfully expressed 8‐bit grayscale using a quaternary digital driving. The simulated μLED current waveforms showed a delay time of approximately 2 μs. Furthermore, the proposed circuit exhibited a luminance error rate below 5% under a threshold voltage variation of ±1 V.

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Section: P-23 / H Immentioning

confidence: 99%

P‐23: Micro Light‐Emitting Diode Pixel Circuit Based on IGZO TFTs using a Stepwise Control Signal

Im,

Jung,

Kim

2023

Symp Digest of Tech Papers

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“…Meanwhile, it is also expected that PWM driving could help with retarding threshold voltage (VTH) shift of thin film transistor (TFT) by avoiding long time continuous bias stress. However, PWM driving usually needs to divide one frame into multiple subframes to obtain adequate grayscales, which requires high switching ability of TFT [9]. Moreover, PWM driving brings about the risk of flicker which might worsen the image quality and result in health concerns [10][11].…”

mentioning

confidence: 99%

“…In fact, both TFTs in PAM and PWM modules would suffer from long time bias. However, the VTH shift of TFT for PWM control is usually ignored [9]. In addition, the various conditions during manufacture in factory would lead to uneven initial VTH distribution for TFTs.…”

mentioning

confidence: 99%

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A New Pixel Circuit for Micro-Light Emitting Diode Displays With Pulse Hybrid Modulation Driving and Compensation

Xiao,

Huo,

Yuan

et al. 2024

IEEE J. Electron Devices Soc.

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A new pixel circuit consisting of eleven n-type IGZO transistors (TFTs) and four capacitors is proposed and applied for micro light emitting diode (MLED) displays. The circuit is driven by pulse hybrid modulation (PHM), combining pulse amplitude modulation (PAM) and pulse width modulation (PWM). In purpose, high grayscales are achieved by PAM mode and low grayscales are achieved by PWM mode, which keep the driving current of LED out of the small value range so as to avoid unstable luminance performance. It is conducted that the MLED display driven by PHM demonstrate a stable luminance at low grayscale with well suppressed luminance errors of over 30% decrease, in comparison with the display driven by PAM. Moreover, both threshold voltage (VTH) shifts of driving TFTs for PAM mode and PWM mode could be well compensated in this circuit. As revealed by simulations, the driving current variations of LED could be retained within 10% when VTH shifts in the ranges from −1 to 2 V for PAM driving TFT and from −1 to 1.5 V for PWM driving TFT, respectively. In practice, a good brightness uniformity over 90% after 240-hours aging of the MLED display could be realized.

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“…Oxide TFT is selected for low leakage current and cost-effectiveness. Meanwhile, LTPS TFT exhibits improved mobility, enabling the production of high pixel density and resolution displays [2]. The integration of LTPO technology, known for its dynamic refresh rate adjustment capabilities, plays a crucial role in mitigating power consumption [3].…”

mentioning

confidence: 99%

31‐1: Invited Paper: Exploring Future Display: Innovative Applications of Metal‐Oxide, LTPS, and LTPO Backplane for Micro‐LED Displays

Kim,

Moon,

et al. 2024

Symp Digest of Tech Papers

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Improvement of the low gray-level expression using hybrid pulse width modulation and pulse amplitude modulation driving method for a micro light-emitting diode pixel circuit

Cited by 15 publications

References 14 publications

P‐23: Micro Light‐Emitting Diode Pixel Circuit Based on IGZO TFTs using a Stepwise Control Signal

P‐23: Micro Light‐Emitting Diode Pixel Circuit Based on IGZO TFTs using a Stepwise Control Signal

A New Pixel Circuit for Micro-Light Emitting Diode Displays With Pulse Hybrid Modulation Driving and Compensation

31‐1: Invited Paper: Exploring Future Display: Innovative Applications of Metal‐Oxide, LTPS, and LTPO Backplane for Micro‐LED Displays

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