Analysis of drain ac stress‐induced hot‐carrier degradation in low‐temperature poly‐Si TFTs

We investigated hot‐carrier degradation in low‐temperature (≤425° C) polycrystalline‐silicon thin‐film transistors (poly‐Si TFTs). When the appropriate stress is applied to the TFTs, a decrease in on‐current and an increase in off‐current are induced by the drain avalanche hot carriers (DAHC). The extent of the degradation is quite large, however, when the ac stress is applied to the drain (drain ac stress). Moreover, the degradation is accelerated by an increase in the frequency of the drain ac stress. We found that the pulse number of the drain ac stress dominated this degradation. It is well known that hot carriers are generated by impact ionization, and the impact ionization rate increases with an increase in the carrier density and the electric field in the channel. When the dc stress is supplied to the drain (drain dc stress), the electric field near the drain is high, while the electron density near the drain is low because of the formation of a pinch‐off region. On the other hand, for the case of drain AC stress, both the electric field and electron density near the drain become high during the transition when the voltage of the stress pulse changes from low to high. The impact ionization rate increases at this point. As this cycle is repeated, it is thought that the degradation of TFTs is accelerated.     

Development and application of less‐mercury flat fluorescent lamps for backlights and general lighting

Abstract— A novel flat discharge fluorescent lamp used as the light source of backlight modules for LCDs and general lighting systems has been researched and developed. This new type of lamp is a less‐mercury flat fluorescent lamp with two‐dimensional emission and superior to conventional one‐dimensional cold‐cathode fluorescent lamps in terms of optics, energy‐savings, production efficiency, reliability, and chromatic performances. Physical characterization of the optics, temperature, mechanical design, thermal shocking, reliability, and corresponding environments have verified that flat fluorescent lamps will be the next‐generation light sources for backlight modules and general lighting systems.     

Higher‐output more‐compact UHP lamp systems

Abstract— Projection systems have reached convincing performance with several thousand screen lumens created by systems of only a few liters in volume. With more than 10 lm/W they are the most efficient display systems realized today. The tremendous progress achieved up to now relies on the outstanding properties of the UHP lamp. The combination of high brightness with lifetimes extending up to more than 10,000 hours is ideal for projection applications. This paper will summarize some recent technological achievements: the volume of the lamp and driver system has been reduced by a factor of 10, exploiting a reduced ignition voltage as well as new optical concepts for the reflector. The optical performance of short‐arc projection lamps can be improved dramatically: a dichroic coating on one half of the UHP burner is applied to focus all light into one hemisphere. This allows for extremely compact reflector systems and an improvement by 20–30% in light collection.     

Nonlinear output feedback control of V2G single‐phase on‐board BEV charger

In this work, we consider the problem of controlling a single‐phase on‐board battery electric vehicle (BEV) charger with vehicle‐to‐grid (V2G) technology. The BEV charger consists of a bidirectional ac‐dc power converter connected to the single‐phase power grid, followed by a bidirectional dc‐dc power converter interfacing an EV battery pack. The main control objectives are fourfold: (i) Unitary Power Factor (UPF) in grid‐side; (ii) tight dc‐bus voltage regulation; (iii) safety battery charge and battery discharge during the grid‐to‐vehicle (G2V) mode and V2G mode, respectively; and (iv) asymptotic stability of the closed loop system. After an accurate system modelling, a nonlinear controller is designed using a backstepping design technique. The point is that the battery inner voltage is not accessible to measurement. Therefore, a nonlinear observer is invoked in order to estimate all non‐measured variables making the solution cheaper and noiseless. It is shown using a formal analysis and numerical simulations, that the proposed output feedback controller (combining a nonlinear controller and a nonlinear observer) meets all control objectives.     

多相空间矢量脉宽调制技术研究

近年来，三臂三相空间矢量脉宽调制(SVPWM)逆变器在三相交流电机变频调速中得到了广泛的应用。但三臂三相SVPWM难于胜任大转速-力矩调节范围、大功率、高可靠性的要求。本文对三相SVPWM技术进行推广，提出并分析一种多臂多相的空间矢量脉宽调制和极相调制技术。特别地．将9相SVPWM技术应用到九绕组感应电机中，并将9相SVPWM技术与9相SPWM进行比较。     

A 15‐in. XGA thresholdless antiferroelectric LCD addressed by TFTs and using the quasi‐dc driving method

Abstract— A 15‐in. TFT‐LCD with XGA resolution using thresholdless antiferroelectric liquid crystal (TLAF) has been developed. TLAF materials show V‐shaped switching and enable display of analog gray scale, wide viewing angle, and fast response. However, in the case that high‐resolution TFT‐LCDs using materials with large spontaneous polarization such as TLAF were driven by the conventional method, alternating current (ac) driving, the obtained contrast ratio was limited because of a sharp decline of holding voltage due to the growth of a depolarization field. In order to enhance the contrast ratio, a novel driving method referred to as quasi‐dc driving was proposed. In the quasi‐dc driving, the polarity of the applied voltage to liquid crystals inverts at certain intervals of several seconds. Moreover, the applied voltage and the charging time at the time of polarity inversion are increased more than the intended signals. By this method, the 15‐in. TFT‐LCD using TLAF with high contrast ratio (more than 100:1) and wide viewing angle was realized.     

Development of 100‐in. TFT‐LCDs for HDTV and public‐information‐display applications

Abstract— LCDs have achieved a full‐high‐definition resolution of 1920 × 1080 (16:9), 600‐nit brightness, 3000:1 dynamic contrast ratio, 92% color gamut, 178° viewing angle, and 5‐msec response time at all gray levels and are targeted for HDTV and public‐information‐display applications. Some unique technologies, such as Cu bus line, advanced wide view polarizer, and wide‐color‐gamut lamp, were applied. A new stitching‐free technology was developed to overcome the size limitation of the photomask in both the TFT and color‐filter processes. The size of the panel (100 in.), based on the wide format (16:9), is determined by the maximum efficiency of the world's first seventh‐generation line (glass size, 1950 × 2250 mm) in LG.Philips LCD's (LPL) Paju display cluster. The issues facing 100‐in. TFT‐LCDs will be discussed.     

Étendue‐density homogenization lamps with light concentration function

Abstract— In order to increase the screen brightness of Digital Micromirror Device? projectors (DMD? projectors), we designed a new compact lamp. In our previous work, we discussed a lamp that has an aspherical lamp reflector and an aspherical front glass, which we called EHLa. Although EHLas improve the light convergence at the entrance of rod integrators, they require external lenses for light condensation. We, therefore, discuss a new EHLa that can converge light without the need for external lenses. The new lamp corresponds to conventional elliptic reflector‐type lamps, which are widely used for mobile‐type DMD? projectors. Our simulations demonstrated that the ratio of increased brightness is 17.1% for the new lamp design versus conventional lamps in a 0.7‐in.‐diagonal DDR DMD? panel.     

A 100,000‐cd/m2 capacity‐coupled electrodeless discharge backlight with high efficacy for LC TVs

A capacity‐coupled electrodeless Hg discharge lamp has been developed for LC TV backlightings. By applying sinusoidal voltages which are 180° out of phase with a pair of external electrodes, a luminous uniformity of over 84% is attained in two types of lamps whose lengths are 190 and 390 mm. Luminance, efficacy, and input power to the lamp are 114,000 cd/m², 35 lm/W, and 21.5 W when the 390‐mm lamp is driven at 5 MHz. With a frequency below 1.1 MHz, eight 390‐mm lamps, connected in parallel to one another without external ballast impedance, can be driven by using a single inverter.     

Potential‐based path planning for robot manipulators

In this paper, a potential‐based path‐planning algorithm for a high DOF robot manipulator is proposed. Unlike some c‐space‐based approaches, which often require expensive preprocessing for the construction of the c‐space, the proposed approach uses the workspace information directly. The approach computes, similar to that done in electrostatics, repulsive force and torque between objects in the workspace. A collision‐free path of a manipulator will then be obtained by locally adjusting the manipulator configuration to search for minimum potential configurations using that force and torque. The proposed approach is efficient because these potential gradients are analytically tractable. Simulation results show that the proposed algorithm works well, in terms of computation time and collision avoidance, for manipulators up to 9 degrees of freedom (DOF). © 2005 Wiley Periodicals, Inc.     

Light‐emitting polymers for full‐color display applications

The latest developments in light‐emitting‐polymer (LEP) technology at CDT continue to show steady progress. Device performance for blue, green, and red systems as well as a high‐performance yellow system in terms of device efficiency and stability will be described. Some of the issues associated with the commercialization of LEP technology including the development of direct‐patterning techniques enabling full‐color passive‐ and active‐matrix display will be discussed.     

变频调速系统的设计与应用 第5讲 变频调速系统的制动设计

在本节中,主要阐述的是变频器的制动设计,阐述了能耗制动、回馈到共用直流母线方式的制动,回馈到交流电网的制动共3种典型制动方式的工作原理,以及应用范围和优缺点。     

Three‐Time‐Scale Singular Perturbation Stability Analysis of Three‐Phase Power Converters

This paper analyzes the stability of the well‐known three‐phase two‐level power converter. Focusing on the rectifier operating mode, the dynamics of the system, when the instantaneous power and dc‐link voltage controllers are included, are described by a set of complex equations that results in a nonlinear autonomous singularly perturbed system. Hence, the closed‐loop system can be studied under the assumption of separate time scales. The analysis proposed in this work follows a novel three‐time‐scale approach, where the fast time scale corresponds with the instantaneous power dynamics, the mid‐range time scale is related to the dc‐link voltage dynamics, and the slow time scale is associated with the dc‐link voltage regulator dynamics. In this way, the analysis leads to the decomposition of the closed‐loop system into three simpler subsystems: fast, medium, and slow subsystems. These subsystems approximate the closed‐loop system behavior over the three different time scales. Finally, since the equilibrium point of each subsystem is exponentially stable and some other conditions are satisfied, it is shown that the equilibrium point of the closed‐loop system also presents exponential stability. Experimental results for a synchronous three‐phase power rectifier prototype are included to corroborate the analysis carried out.     

Electroluminescent large - area image display

This paper views the state of the art of a large area electroluminescent image display, which includes powder and film screens excited to luminescence by ac or dc voltage. Such screens appear to have potential only if they are completely integrated with a controlling tft circuitry. A brief look into the future attempts to predict new developments for the next ten years.     

Design of perfect electrical conductor wall‐loaded 2.45 GHz high‐efficiency rectenna

A 2.45 GHz industrial, scientific and medical band rectenna with a two‐layered structure for various applications involving microwave wireless power transmission (WPT) has been designed and measured in this article. A microstrip antenna with two perfect electrical conductor walls loaded for gain enhancement is designed. In addition, a typical single‐diode compact radio frequency (RF) rectifier with a series bandpass structure is presented. The simulated RF to dc conversion efficiency of the rectifier is above 50% when the input power ranges from 0 to 28 dBm. The fabricated rectenna is compact with a dimension of 0.5λ × 0.5λ. A RF to dc conversion efficiency of about 73% is achieved under received power density of 38.5 W/m² with a 500 Ω dc load. Due to the integration design of antenna and rectifier, the proposed rectenna is suitable to be well applied in miniaturization of rectenna array.     

Nematic liquid‐crystal technology for Si wafer‐based reflective spatial light modulators

Various nematic LC modes are reviewed and compared in terms optical throughput, driving voltage, response time, contrast ratio, and spectral responses for LCoS applications. The effects of fringe‐field‐induced disclination on display performance and the mechanism of slow response of the disclination line between two topologically non‐equivalent LC states will be discussed. Issues involving flicker and photo‐instability of LCoS displays will be addressed as well.     

Requirements for large‐sized high‐resolution TFT‐LCDs

Abstract— A 22‐in. prototype TFT‐LCD with a resolution of 200 pixels per inch and wide‐viewing‐angle capability has been developed and its requirements in terms of screen quality and technology will be discussed. An in‐plane‐switching mode with dual‐domain structure, post‐spacers, and high‐resolution process were implemented to achieve superior front‐of‐screen quality. And, also, in order to improve reliability and productivity, we developed a new injection method for liquid crystals which enabled us to eliminate injection holes.     

Mercury‐free 18‐in. flat fluorescent lamp with good uniformity

We have developed an 18‐in. 287 × 359‐mm flat fluorescent lamp (FFL) that uses a xenon dielectric barrier discharge and analyzed its electro‐optical characteristics. The surface luminance of the lamp having a diffuser sheet thickness of 3 mm was 5600 cd/m² and the luminance uniformity was 92% at an applied voltage of 950 Vrms. The luminous efficacy of the FFL was 24.5 lm/W for a luminance of 4200 cd/m² when driven by a sine‐wave voltage.     

Room‐temperature deposition of thin‐film indium tin oxide on micro‐fabricated color filters and its application to flat‐panel displays

Abstract— Direct deposition of indium tin oxide (ITO) thin film on color filters is of practical use in the fabrication of state‐of‐the‐art flat‐panel displays. Room‐temperature dc magnetron sputtering of thin‐film ITO and issues related to the integration of ITO‐on‐glass panels containing micro‐fabricated color filters and other functional materials have been investigated. The resulting polycrystalline ITO exhibited good adhesion to the underlying color filters, as well as good optical transparency and high electrical conductivity. Application of this ITO deposition technology to color liquid‐crystal and organic light‐emitting diode displays will also presented.     

Electrical feedback control for driving mercury‐free flat fluorescent lamp

Abstract— Recently, a mercury‐free flat fluorescent lamp has been developed for LCD backlight application, utilizing a glow‐discharge mode instead of a discharge contraction. This paper proposes a lamp‐driving system with a feedback loop which prevents discharge contraction and stabilizes the operation of the lamp ignition and radiation. By measuring the current that flows through the lamp, the loop can adjust the current level to a normal operational level and suppress the long‐term excitation that causes discharge contraction. The proposed method has been verified by hardware experiments which are compared to that of a conventional open‐loop circuit by discharge contraction time and a change in luminance.