Abstract
Using low-temperature poly-silicon thin-film transistors (LTPS TFTs) as a basis, a pixel circuit for an active matrix organic light-emitting diode (AMOLED) with narrow bezel displays was developed. The pixel circuit features mono-type scanning signals, elimination of static power lines, and pixel-integrated emitting control functions. Therefore, gate driver circuits of the display bezel can be simplified efficiently. In addition, the pixel circuit has a high-resolution design due to an increase of the pulse width of the scan signal to extend the threshold voltage and internal–resistance drop (IR drop) detection period. Further, regarding the influences of process–voltage–temperature (PVT) variation in the pixel circuit, comparison investigations were carried out with the proposed circuit and other pixel circuits with mono-type scanning signals using Monte Carlo analysis. The feasibility of the proposed pixel circuit is well demonstrated, as the current variations can be reduced to 2.1% for the supplied power reduced from 5 V to 3 V due to IR drop, and the current variation is as low as 10.6% with operating temperatures from –40 degrees to 85 degrees.
Highlights
Active-matrix organic light-emitting diode (AMOLED) displays have an important presence in mainstream next-generation displays due their extremely high contrast ratio, fast electrical-optical response, and excellent compatibility with flexible electronics [1,2]
The drawbacks of LTPS TFTs lie in the obvious variations in the threshold voltage (VTH ) and mobility [7,8], which hinder the implementation of high-quality
This paper proposed a pixel circuit suitable for a narrow border display, which can compensate
Summary
Active-matrix organic light-emitting diode (AMOLED) displays have an important presence in mainstream next-generation displays due their extremely high contrast ratio, fast electrical-optical response, and excellent compatibility with flexible electronics [1,2]. To avoid image flicker, Lin et al employed overlapping compensation waveforms to extend the VTH detection time and to suppress the OLED current during the compensation time [19] These previous investigations illustrate that, through a proper circuit topology and timing diagram to offset VTH variations and IR drop, a good display uniformity can be obtained. For conventional schematics, the pixel circuit array requires multiple scan signals with different types, which complicates both the pixel circuit and the external gate driver circuit. A compensation AMOLED pixel circuit with mono-type scanning lines is proposed. For conventional pixel circuits, complicated gate drivers are required, as multiple types of scan signals are used, while the proposed circuit has fewer control signals for simpler external drivers.
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