293 research outputs found

    Thin-Film Transistor Integration for Biomedical Imaging and AMOLED Displays

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    Thin film transistor (TFT) backplanes are being continuously researched for new applications such as active-matrix organic light emitting diode (AMOLED) displays, sensors, and x-ray imagers. However, the circuits implemented in presently available fabrication technologies including poly silicon (poly-Si), hydrogenated amorphous silicon (a-Si:H), and organic semiconductor, are prone to spatial and/or temporal non-uniformities. While current-programmed active matrix (AM) can tolerate mismatches and non-uniformity caused by aging, the long settling time is a significant limitation. Consequently, acceleration schemes are needed and are proposed to reduce the settling time to 20 ยตs. This technique is used in the development of a pixel circuit and system for biomedical imager and sensor. Here, a metal-insulator-semiconductor (MIS) capacitor is adopted for adjustment and boost of the circuit gain. Thus, the new pixel architecture supports multi-modality imaging for a wide range of applications with various input signal intensities. Also, for applications with lower current levels, a fast current-mode line driver is developed based on positive feedback which controls the effect of the parasitic capacitance. The measured settling time of a conventional current source is around 2 ms for a 100-nA input current and 200-pF parasitic capacitance whereas it is less than 4 ฮผs for the driver presented here. For displays needed in mobile devices such as cell phones and DVD players, another new driving scheme is devised that provides for a high temporal stability, low-power consumption, high tolerance of temperature variations, and high resolution. The performance of the new driving scheme is demonstrated in a 9-inch fabricated display intended for DVD players. Also, a multi-modal imager pixel circuit is developed using this technique to provide for gain-adjustment capability. Here, the readout operation is not destructive, enabling the use of low-cost readout circuitry and noise reduction techniques. In addition, a highly stable and reliable driving scheme, based on step calibration is introduced for high precision displays and imagers. This scheme takes advantage of the slow aging of the electronics in the backplane to simplify the drive electronics. The other attractive features of this newly developed driving scheme are its simplicity, low-power consumption, and fast programming critical for implementation of large-area and high-resolution active matrix arrays for high precision

    Eurodisplay 2019

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    The collection includes abstracts of reports selected by the program by the conference committee

    A Survey on Recent Advances in Organic Visible Light Communications

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    Visible light communication (VLC) employs light emitting diodes (LEDs) to provide illumination and data communications simultaneously. Organic LEDs (OLEDs) employing small molecules and long-chain polymers PLEDs, have been gaining attention within the VLC research community due to their inherent advantages such as flexible substrates and low-cost manufacturing. However, the carrier mobility of organic semiconductors is much slower than the devices composed of metal alloys, such as gallium nitride, thus leading to a restriction in the OLED modulation bandwidth. The manufacturing processes, materials and the photoactive size of the devices can affect the raw bandwidth of OLEDs. To increase the transmission speeds, novel approaches have been proposed including equalization techniques, signalling schemes and the optimum driver circuits. The paper provides a survey on the evolution of OLED-based VLC systems, and the respective challenges and recent progresses

    Mathematical Analysis of Charge and Heat Flow in Organic Semiconductor Devices

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    Organische Halbleiterbauelemente sind eine vielversprechende Technologie, die das Spektrum der optoelektronischen Halbleiterbauelemente erweitert und etablierte Technologien basierend auf anorganischen Halbleitermaterialien ersetzen kann. Fรผr Display- und Beleuchtungsanwendungen werden sie z. B. als organische Leuchtdioden oder Transistoren verwendet. Eine entscheidende Eigenschaft organischer Halbleitermaterialien ist, dass die Ladungstransporteigenschaften stark von der Temperatur im Bauelement beeinflusst werden. Insbesondere nimmt die elektrische Leitfรคhigkeit mit der Temperatur zu, so dass Selbsterhitzungseffekte, einen groรŸen Einfluss auf die Leistung der Bauelemente haben. Mit steigender Temperatur nimmt die elektrische Leitfรคhigkeit zu, was wiederum zu grรถรŸeren Strรถmen fรผhrt. Dies fรผhrt jedoch zu noch hรถheren Temperaturen aufgrund von Joulescher Wรคrme oder Rekombinationswรคrme. Eine positive Rรผckkopplung liegt vor. Im schlimmsten Fall fรผhrt dieses Verhalten zum thermischen Durchgehen und zur Zerstรถrung des Bauteils. Aber auch ohne thermisches Durchgehen fรผhren Selbsterhitzungseffekte zu interessanten nichtlinearen Phรคnomenen in organischen Bauelementen, wie z. B. die S-fรถrmige Beziehung zwischen Strom und Spannung. In Regionen mit negativem differentiellen Widerstand fรผhrt eine Verringerung der Spannung รผber dem Bauelement zu einem Anstieg des Stroms durch das Bauelement. Diese Arbeit soll einen Beitrag zur mathematischen Modellierung, Analysis und numerischen Simulation von organischen Bauteilen leisten. Insbesondere wird das komplizierte Zusammenspiel zwischen dem Fluss von Ladungstrรคgern (Elektronen und Lรถchern) und Wรคrme diskutiert. Die zugrundeliegenden Modellgleichungen sind Thermistor- und Energie-Drift-Diffusion-Systeme. Die numerische Diskretisierung mit robusten hybriden Finite-Elemente-/Finite-Volumen-Methoden und Pfadverfolgungstechniken zur Erfassung der in Experimenten beobachteten S-fรถrmigen Strom-Spannungs-Charakteristiken wird vorgestellt.Organic semiconductor devices are a promising technology to extend the range of optoelectronic semiconductor devices and to some extent replace established technologies based on inorganic semiconductor materials. For display and lighting applications, they are used as organic light-emitting diodes (OLEDs) or transistors. One crucial property of organic semiconductor materials is that charge-transport properties are heavily influenced by the temperature in the device. In particular, the electrical conductivity increases with temperature, such that self-heating effects caused by the high electric fields and strong recombination have a potent impact on the performance of devices. With increasing temperature, the electrical conductivity rises, which in turn leads to larger currents. This, however, results in even higher temperatures due to Joule or recombination heat, leading to a feedback loop. In the worst case, this loop leads to thermal runaway and the complete destruction of the device. However, even without thermal runaway, self-heating effects give rise to interesting nonlinear phenomena in organic devices, like the S-shaped relation between current and voltage resulting in regions where a decrease in voltage across the device results in an increase in current through it, commonly denoted as regions of negative differential resistance. This thesis aims to contribute to the mathematical modeling, analysis, and numerical simulation of organic semiconductor devices. In particular, the complicated interplay between the flow of charge carriers (electrons and holes) and heat is discussed. The underlying model equations are of thermistor and energy-drift-diffusion type. Moreover, the numerical approximation using robust hybrid finite-element/finite-volume methods and path-following techniques for capturing the S-shaped current-voltage characteristics observed in experiments are discussed

    Visible Light Optical Camera Communication for Electroencephalography Applications

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    Due to the cable-free deployment and flexibility of wireless communications, the data transmission in the applications of home and healthcare has shown a trend of moving wired communications to wireless communications. One typical example is electroencephalography (EEG). Evolution in the radio frequency (RF) technology has made it is possible to transmit the EEG data without data cable bundles. However, presently, the RF-based wireless technology used in EEG suffers from electromagnetic interference and might also have adverse effects on the health of patient and other medical equipment used in hospitals or homes. This puts some limits in RF-based EEG solutions, which is particularly true in RF restricted zones like Intensive Care Units (ICUs). As a recently developed optical wireless communication (OWC) technology, visible light communication (VLC) using light-emitting diodes (LEDs) for both simultaneous illumination and data communication has shown its advantages of free from electromagnetic interference, potential huge unlicensed bandwidth and enhanced data privacy due to the line transmission of light. The most recent development of VLC is the optical camera communication (OCC), which is an extension of VLC IEEE standard 802.15.7, also referred to as visible light optical camera communication (VL-OCC). Different from the conventional VLC where traditional photodiodes are used to detect and receive the data, VL-OCC uses the imaging camera as the photodetector to receive the data in the form of visible light signals. The data rate requirement of EEG is dependent on the application; hence this thesis investigates a low cost, organic LED (OLED)-driven VL-OCC wireless data transmission system for EEG applications

    ์œ ๊ธฐ๋ฐœ๊ด‘ ๋‹ค์ด์˜ค๋“œ ํ‘œ์‹œ์žฅ์น˜๋ฅผ ์žฅ์ฐฉํ•œ ์ด๋™ํ˜• ์‹œ์Šคํ…œ์˜ ์ „๋ ฅ ๊ณต๊ธ‰ ์ตœ์ ํ™”

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    ํ•™์œ„๋…ผ๋ฌธ (๋ฐ•์‚ฌ)-- ์„œ์šธ๋Œ€ํ•™๊ต ๋Œ€ํ•™์› : ์ „๊ธฐยท์ปดํ“จํ„ฐ๊ณตํ•™๋ถ€, 2012. 8. ์žฅ๋ž˜ํ˜.์˜ค๋Š˜๋‚  ์Šค๋งˆํŠธํฐ, ํƒœ๋ธ”๋ฆฟ PC ์™€ ๊ฐ™์€ ํœด๋Œ€์šฉ ์ „์ž๊ธฐ๊ธฐ๋Š” ๊ณ ์„ฑ๋Šฅ์˜ ์ค‘์•™์ฒ˜๋ฆฌ์žฅ์น˜ (CPU), ๋Œ€์šฉ๋Ÿ‰ ๋ฉ”๋ชจ๋ฆฌ, ๋Œ€ํ˜• ํ™”๋ฉด, ๊ณ ์†์˜ ๋ฌด์„  ์ธํ„ฐํŽ˜์ด์Šค ๋“ฑ์„ ํƒ‘์žฌํ•จ์—๋”ฐ๋ผ ์ „ ๋ ฅ ์†Œ๋ชจ๋Ÿ‰์ด ๊ธ‰์†ํžˆ ์ฆ๊ฐ€ํ•˜์—ฌ ๊ทธ ์ „๋ ฅ ์†Œ๋ชจ๋Š” ์ด๋ฏธ ์†Œํ˜•์˜ ๋žฉํƒ‘ ์ปดํ“จํ„ฐ ์ˆ˜์ค€์— ์ด๋ฅด๊ณ  ์žˆ๋‹ค. ์„ฑ๋Šฅ๊ณผ ์ „๋ ฅ ์†Œ๋ชจ๋Ÿ‰์˜ ์ธก๋ฉด์—์„œ ํœด๋Œ€์šฉ ์ „์ž๊ธฐ๊ธฐ์™€ ๋žฉํƒ‘ ์ปดํ“จํ„ฐ ์‚ฌ ์ด์˜ ๊ตฌ๋ถ„์ด ์ ์ฐจ ์‚ฌ๋ผ์ง€๊ณ  ์žˆ์Œ์—๋„ ๋ฐฐํ„ฐ๋ฆฌ ๋ฐ ์ „๋ ฅ ๋ณ€ํ™˜ ํšŒ๋กœ๋Š” ๊ธฐ์กด์˜ ์„ค๊ณ„ ์›์น™๋“ค๋งŒ์„ ๋”ฐ๋ผ ์„ค๊ณ„๋˜๊ณ  ์žˆ๋Š” ์‹ค์ •์ด๋‹ค. ์‚ผ์„ฑ์ „์ž์˜ ๊ฐค๋Ÿญ์‹œ ํƒญ ๋ฐ Apple ์‚ฌ์˜ iPad ๋“ฑ ์Šค๋งˆํŠธํฐ ๋ฐ ํƒœ๋ธ”๋ฆฟ PC์˜ ๊ฒฝ์šฐ 1-cell ์ง๋ ฌ ๋ฆฌํŠฌ ์ด์˜จ ์ „์ง€๋ฅผ ์‚ฌ์šฉํ•˜๋Š” ๋ฐ˜ ๋ฉด, ๋žฉํƒ‘ ์ปดํ“จํ„ฐ์˜ ๊ฒฝ์šฐ๋Š” ์ œ์กฐ์‚ฌ์— ๋”ฐ๋ผ 3-cell ์—์„œ 5-cell ์ง๋ ฌ ๋“ฑ์œผ๋กœ ์„ค๊ณ„๋˜๊ณ  ์žˆ๋‹ค. ์ด๋Š” ๋ฐฐํ„ฐ๋ฆฌ ์ถœ๋ ฅ ์ „์••์„ ๋‹ค๋ฅด๊ฒŒ ํ•จ์œผ๋กœ์จ ์ „๋ ฅ ๋ณ€ํ™˜ ํšจ์œจ์— ์˜ํ–ฅ์„ ์ค€๋‹ค. ์ „๋ ฅ ๋ณ€ํ™˜ ํšŒ๋กœ์˜ ํšจ์œจ ๋ฐ ๋ฐฐํ„ฐ๋ฆฌ์˜ ์ˆ˜๋ช…์€ ์ž…์ถœ๋ ฅ ์ „์••/์ „๋ฅ˜๋ฅผ ๋น„๋กฏํ•œ ๋™์ž‘ ํ™˜๊ฒฝ์˜ ์˜ํ–ฅ์„ ๋ฐ›๋Š”๋‹ค. ํœด๋Œ€์šฉ ์ „์ž๊ธฐ๊ธฐ์— ์‚ฌ์šฉ๋˜๋Š” ๊ฐ์ข… ์ „์ž๋ถ€ํ’ˆ์€ ์ „๋ ฅ ์†Œ๋ชจ๋ฅผ ์ค„์ด๊ธฐ ์œ„ํ•œ ๋‹ค์–‘ํ•œ ๊ธฐ๋Šฅ๋“ค์„ ๊ตฌํ˜„ํ•˜๊ณ  ์žˆ์œผ๋ฉฐ, ์ค‘์•™์ฒ˜๋ฆฌ์žฅ์น˜์˜ ๋™์  ์ „์••/์ฃผํŒŒ ์ˆ˜ ์กฐ์ ˆ ๊ธฐ๋ฒ• ๋“ฑ ๊ณต๊ธ‰์ „์••์˜ ๋ณ€ํ™”๋ฅผ ์ˆ˜๋ฐ˜ํ•˜๋Š” ๊ธฐ๋ฒ• ์—ญ์‹œ ๋‹ค์–‘ํ•˜๊ฒŒ ์ ์šฉ๋˜๊ณ  ์žˆ๋‹ค. ์ด๋Š” ๊ฐ ์žฅ์น˜์˜ ๊ณต๊ธ‰ ์ „์•• ๋ฐ ์ „๋ฅ˜์˜ ๋ณ€ํ™”๋กœ ์ธํ•œ ์ „๋ ฅ ๋ณ€ํ™˜ ํšŒ๋กœ์˜ ํšจ์œจ์˜ ๋ณ€ํ™” ๋ฅผ ์ดˆ๋ž˜ํ•œ๋‹ค. ๋”ฐ๋ผ์„œ ์ค‘์•™์ฒ˜๋ฆฌ์žฅ์น˜, ๋””์Šคํ”Œ๋ ˆ์ด ๋“ฑ ์ฃผ์š” ์ „๋ ฅ ์†Œ๋น„ ์žฅ์น˜์˜ ์ „๋ ฅ ์ ˆ๊ฐ ๊ธฐ๋ฒ•์„ ๊ฐœ๋ฐœํ•  ๋•Œ์—๋Š” ๊ฐœ๋ณ„ ์žฅ์น˜์˜ ์ „๋ ฅ ์†Œ๋น„๋ฅผ ์ค„์ด๋Š” ๊ฒƒ๊ณผ ๋™์‹œ์— ๊ฐœ๋ณ„ ์žฅ ์น˜์˜ ๋™์ž‘ ํ–‰ํƒœ์— ๋Œ€ํ•œ ์ •ํ™•ํ•œ ๋ถ„์„์— ๊ธฐ๋ฐ˜ํ•˜์—ฌ ๋ฐฐํ„ฐ๋ฆฌ, ์ „๋ ฅ ๋ณ€ํ™˜ํšŒ๋กœ์˜ ์„ค๊ณ„๊ฐ€ ํ•จ๊ป˜์ด๋ฃจ์–ด์ ธ์•ผ ํ•œ๋‹ค. ์„ ํ–‰ ์—ฐ๊ตฌ๋ฅผ ํ†ตํ•ด ๋ฐฐํ„ฐ๋ฆฌ์˜ ํŠน์„ฑ์„ ๊ณ ๋ คํ•œ ๋ฐฐํ„ฐ๋ฆฌ ๊ตฌ์„ฑ์˜ ์ตœ์ ํ™” ๊ธฐ๋ฒ•์ด ์ œ์•ˆ๋˜์—ˆ๋‹ค [1]. ์ค‘์•™์ฒ˜๋ฆฌ์žฅ์น˜์˜ ๋™์  ์ „์••/์ฃผํŒŒ์ˆ˜ ์ œ์–ด ๊ธฐ๋ฒ•์— ์ด์–ด ์œ ๊ธฐ๋ฐœ๊ด‘๋‹ค์ด์˜ค๋“œ(OLED) ๊ธฐ๋ฐ˜ ๋””์Šคํ”Œ๋ ˆ์ด์˜ ๋™์  ๊ตฌ๋™ํšŒ๋กœ ๊ณต๊ธ‰ ์ „์•• ๊ธฐ๋ฒ•์ด ์ œ์•ˆ๋˜์—ˆ๋‹ค [2]. ์œ ๊ธฐ๋ฐœ๊ด‘๋‹ค ์ด์˜ค๋“œ ๋””์Šคํ”Œ๋ ˆ์ด๋Š” ์ „๋ ฅ ์†Œ๋ชจ ๋ฐ ์‹œ์•ผ๊ฐ ๋“ฑ ๊ธฐ์กด ์•ก์ • ํ‘œ์‹œ์žฅ์น˜์— ๋น„ํ•ด ์—ฌ๋Ÿฌ ์šฐ์ˆ˜ํ•œ ํŠน์„ฑ์œผ๋กœ ์ธํ•ด ์ฃผ๋ชฉ๋ฐ›๊ณ  ์žˆ๋Š” ์ฐจ์„ธ๋Œ€ ๋””์Šคํ”Œ๋ ˆ์ด ์žฅ์น˜์ด๋‹ค. ์œ ๊ธฐ๋ฐœ๊ด‘๋‹ค ์ด์˜ค๋“œ ๋””์Šคํ”Œ๋ ˆ์ด์˜ ์ ์€ ์ „๋ ฅ ์†Œ๋ชจ๋Ÿ‰์—๋„ ๋ถˆ๊ตฌํ•˜๊ณ  ํ™”๋ฉด์˜ ๋Œ€ํ˜•ํ™” ๋ฐ ํ•ด์ƒ๋„์˜ ๊ณ ๋ฐ€๋„ํ™”์— ๋”ฐ๋ผ ์‹œ์Šคํ…œ ์ „๋ ฅ ์†Œ๋ชจ์—์„œ ์—ฌ์ „ํžˆ ํฐ ๋น„์ค‘์„ ์ฐจ์ง€ํ•˜๊ณ  ์žˆ๋‹ค. ์œ ๊ธฐ๋ฐœ ๊ด‘๋‹ค์ด์˜ค๋“œ ๋””์Šคํ”Œ๋ ˆ์ด์˜ ๋™์  ๊ตฌ๋™ํšŒ๋กœ ๊ณต๊ธ‰ ์ „์•• ๊ธฐ๋ฒ•(OLED DVS)๋Š” ์ƒ‰์ƒ์˜ ๋ณ€ํ™”์˜ ๊ธฐ์ดˆํ•œ ๊ธฐ์กด์˜ ์œ ๊ธฐ๋ฐœ๊ด‘๋‹ค์ด์˜ค๋“œ ๋””์Šคํ”Œ๋ ˆ์ด ์ „๋ ฅ ์ ˆ๊ฐ ๊ธฐ๋ฒ•๊ณผ๋Š” ๋‹ฌ๋ฆฌ ์ตœ ์†Œํ•œ์˜ ์ด๋ฏธ์ง€ ์™œ๊ณก๋งŒ์„ ์ˆ˜๋ฐ˜ํ•˜์—ฌ ๋Œ€๋ถ€๋ถ„์˜ ์‚ฌ์ง„, ๋™์˜์ƒ ๋“ฑ์— ์ ์šฉ๊ฐ€๋Šฅํ•œ ์ „๋ ฅ ์ ˆ๊ฐ ๊ธฐ๋ฒ•์ด๋‹ค. ํ•ด๋‹น ๊ธฐ๋ฒ•์€ ๊ณต๊ธ‰ ์ „์••์˜ ๋ณ€ํ™”์‹œํ‚ฌ ํ•„์š”๊ฐ€ ์žˆ์œผ๋ฉฐ, ์ด๋ฅผ ์‹œ์Šคํ…œ์— ์˜ฌ๋ฐ”๋ฅด๊ฒŒ ํ†ตํ•ฉ์‹œํ‚ค๊ธฐ ์œ„ํ•ด์„œ๋Š” ์ „๋ ฅ ๋ณ€ํ™˜ ํšŒ๋กœ ๋ฐ ๋ฐฐํ„ฐ๋ฆฌ ๊ตฌ์„ฑ์— ๋ฏธ์น˜๋Š” ์˜ํ–ฅ์„ ๊ณ ๋ คํ•ด์•ผ ํ•œ๋‹ค. ๋ณธ ๋…ผ๋ฌธ์—์„œ๋Š” ์œ ๊ธฐ๋ฐœ๊ด‘๋‹ค์ด์˜ค๋“œ ๋””์Šคํ”Œ๋ ˆ์ด์˜ ์ „๋ ฅ ์†Œ๋ชจ์™€ ํ•จ๊ป˜ ์ „์ฒด ์‹œ์Šค ํ…œ ํšจ์œจ์— ๋ฏธ์น˜๋Š” ์˜ํ–ฅ์„ ํ•จ๊ป˜ ๊ณ ๋ คํ•˜์—ฌ ์‹œ์Šคํ…œ์„ ์ตœ์ ํ™”ํ•œ๋‹ค. ๋ฐฐํ„ฐ๋ฆฌ ๊ตฌ์„ฑ ์—ญ ์‹œ ๊ธฐ์กด์˜ ์„ค๊ณ„ ํ‘œ์ค€ ๋Œ€์‹  ์ฒด๊ณ„์ ์ธ ์‹œ์Šคํ…œ ๋ถ„์„์— ๊ธฐ๋ฐ˜ํ•œ ์ตœ์ ํ™”๊ฐ€ ์‹œ๋„๋˜์—ˆ๋‹ค. ๊ณต๊ธ‰์ „์••์ด ์กฐ์ ˆ ๊ฐ€๋Šฅํ•œ ์œ ๊ธฐ๋ฐœ๊ด‘๋‹ค์ด์˜ค๋“œ ๋””์Šคํ”Œ๋ ˆ์ด ํ•˜๋“œ์›จ์–ด ๋ฐ ์ œ์–ด๊ธฐ ์‹œ์Šค ํ…œ-์˜จ-์นฉ (System-on-a-chip, SoC) ๊ฐ€ ์ œ์ž‘๋˜์—ˆ๊ณ , ๊ทธ ๋™์ž‘ ํŠน์„ฑ์ด ๋ถ„์„๋˜์—ˆ๋‹ค. ๊ธฐ์กด ์Šค๋งˆํŠธํฐ ๋ฐ ํƒœ๋ธ”๋ฆฟ PC ๊ฐœ๋ฐœ์šฉ ํ”Œ๋žซํผ์˜ ์ „๋ ฅ ๋ณ€ํ™˜ ํšจ์œจ ๋ฐ ๋™์ž‘ ํŠน์„ฑ ์—ญ์‹œ ๋ถ„์„ ๋˜์—ˆ๋‹ค. ์œ ๊ธฐ๋ฐœ๊ด‘๋‹ค์ด์˜ค๋“œ ๋””์Šคํ”Œ๋ ˆ์ด์˜ ๋™์  ๊ตฌ๋™ํšŒ๋กœ ๊ณต๊ธ‰ ์ „์•• ๊ธฐ๋ฒ•์˜ ๋™์ž‘ ํŠน์„ฑ ๋ฐ ์Šค๋งˆํŠธํฐ ํ”Œ๋žซํผ์˜ ๋™์ž‘ ํŠน์„ฑ, ๋ฐฐํ„ฐ๋ฆฌ ํŠน์„ฑ์— ๋Œ€ํ•œ ๋ถ„์„์„ ๊ธฐ๋ฐ˜์œผ๋กœ ์‹œ์Šค ํ…œ ์ˆ˜์ค€์—์„œ์˜ ์ „๋ ฅ ๋ณ€ํ™˜ ํšจ์œจ์ด ์ตœ์ ํ™”๋˜์—ˆ๋‹ค.Modern mobile devices such as smartphone or tablet PC are typically equipped a high-performance CPU, memory, wireless interface, and display. As a result, their power consumption is as high as a small-size laptop computer. The boundary between the mobile devices and laptop computer is becoming unclear from the perspective of the performance and power. However, their battery and related power conversion architecture are only designed according to the legacy design so far. Smartphone and tablet PCs from major vendors such as iPad from Apple or Galaxy-tab from Samsung uses 1-cell Li-ion battery. The laptop PC typically has 3-cell Li-ion battery. The output voltage of the battery affect system-level power conversion efficiency. Furthermore, traditional power conversion architecture in the mobile computing system is designed only considering the fixed condition where the system-level low-power techniques such as DVFS are becoming mandatory. Such a low-power techniques applied to the major components result in not only load demand fluctuation but also supply voltage changing. It has an effect on the battery lifetime as well as the system-level power delivery efficiency. The efficiency is affected by the operating condition including input voltage, output voltage, and output current. We should consider the operating condition of the major power consumer such as a display to enhance the system-level power delivery efficiency. Therefore, we need to design the system not only from the perspective of the power consumption but also energy storage design. The optimization of battery setup considering battery characteristics was presented in [1]. Beside the DVFS of microprocessor, a power saving technique based on the supply voltage scaling of the OLED driver circuit was recently introduced [2]. An organic light emitting diode (OLED) is a promising display device which has a lot of advantages compared with conventional LCD, but it still consumes significant amount of power consumption due to the size and resolution increasing. The OLED dynamic voltage scaling (OLED DVS) technique is the first OLED display power saving technique that induces only minimal color change to accommodate display of natural images where the existing OLED low-power techniques are based on the color change. The OLED DVS incurs supply voltage change. Therefore we need to consider the system-level power delivery efficiency and battery setup to properly integrate the DVS-enabled OLED display to the system. In this dissertation, we not only optimize the power consumption of the OLED display but also consider its effect on the whole system power efficiency. We perform the optimization of the battery setup by a systematic method instead of the legacy design rule. At first, we develop an algorithm for the OLED DVS for the still images and a histogram-based online method for the image sequence with a hardware board and a SoC. We characterize the behavior of the OLED DVS. Next, we analyze the characteristics of the smartphone and tablet-PC platforms by using the development platforms. We profile the power consumption of each components in the smartphone and power conversion efficiency of the boost converter which is used in the tablet-PC for the display devices. We optimize not only the power consuming components or the conversion system but also the energy storage system based on the battery model and system-level power delivery efficiency analysis.1 Introduction 1.1 Supply Voltage Scaling for OLED Display 1.2 Power Conversion Efficiency in MobileSystems 1.3 Research Motivation 2 Related Work 2.1 Low-Power Techniques for Display Devices 2.1.1 Light Source Control-Based Approaches 2.1.2 User Behavior-Based Approaches 2.1.3 Low-Power Techniques for Controller and Framebuffer 2.1.4 Pre-ChargingforOLED 2.1.5 ColorRemapping 2.2 Battery discharging efficiency aware low-power techniques 2.2.1 Parallel Connection 2.2.2 Constant-Current Regulator-Based Architecture 2.3 System-level power analysis techniques 3 Preliminary 38 3.1 Organic Light Emitting Diode (OLED) Display 3.1.1 OLED Cell Architecture 3.1.2 OLED Panel Architecture 3.1.3 OLED Driver Circuits 3.2 Effect of VDD scaling on driver circuits 3.2.1 VDD scaling for AM drivers 3.2.2 VDD scaling for PWM drivers 4 Supply Voltage Scaling and Image Compensation of OLED displays 4.1 Image quality and power models of OLED panels 4.2 OLED display characterization 4.3 VDD scaling and image compensation 5 OLED DVS implementation 5.1 Hardware prototype implementation 5.2 OLED DVS System-on-Chip implementation 5.3 Optimization of OLED DVS SoC 5.4 VDD transition overhead 6 Power conversion efficiency and delivery architecture in mobile Systems 6.1 Power conversion efficiency model of switching-Mode DCโ€“DC converters 6.2 Power conversion efficiency model of linear regulator power loss model 6.3 Rate Capacity Effect of Li-ion Batteries 7 Power conversion efficiency-aware battery setup optimization with DVS- enabled OLED display 7.1 System-level power efficiency model 7.2 Power conversion efficiency analysis of smartphone platform 7.3 Power conversion efficiency for OLED power supply 7.4 Li-ion battery model 7.4.1 Battery model parameter extraction 7.5 Battery setup optimization 8 Experiments 8.1 Simulation result for OLED display with AM driver 8.2 Measurement result for OLED display with PWM driver 8.3 Design space exploration of battery setup with OLED displays 9 Conclusion 10 Future WorkDocto

    Hybrid Nanomaterials

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    Two of the hottest research topics today are hybrid nanomaterials and flexible electronics. As such, this book covers both topics with chapters written by experts from across the globe. Chapters address hybrid nanomaterials, electronic transport in black phosphorus, three-dimensional nanocarbon hybrids, hybrid ion exchangers, pressure-sensitive adhesives for flexible electronics, simulation and modeling of transistors, smart manufacturing technologies, and inorganic semiconductors

    Basic Research Needs for Solid-State Lighting. Report of the Basic Energy Sciences Workshop on Solid-State Lighting, May 22-24, 2006

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