Measurement of wall charge and capacitance variation for a single cell in the AC plasma display panel

Real-time dynamic measurements are performed on a single cell in a standard commercially available large plasma panel. The measurements determine cell response to variations in address pulses, sustain waveforms, or priming from neighboring cells. The wall-charge measurement indicates the internal dielectric surface charge and the capacitance measurement indicates the existence of a plasma in the gas volume. These measurements have shown that neighboring on cells can cause a large wall-charge transfer in off cells that results in reduced write and sustain voltage margins. Direct wall-charge measurements allows use of a simple technique for determination of the voltage transfer curve of the plasma cell which greatly aids device characterization. The capacitance measurement has shown that a plasma exists in commercial MgO panels for 10-15 µs after the discharge-current peak. The capacitance and wall-charge measurements can be combined to give simultaneous real-time results.     

Quantitative wall voltage characteristics of AC plasma displays

This paper presents the results of a quantitative characterization effort for the ac plasma display panel. A new characteristic curve is developed that we have named the wall voltage input-output (WVIO) curve. It is a simple quantitative transfer curve that relates the values of the wall voltage before and after the gas discharge to be characterized. Because of the tedious nature of measuring WVIO curves, we have developed a computer-controlled hardware system and the necessary algorithms for automatically measuring and plotting these curves in real time. This has resulted in orders of magnitude increase in the detailed characterization data taken on ac plasma panels. The most interesting characteristics of these data are presented in this paper. Detailed data showing the influence of sustain waveshape, priming, electrode structure, and gas mixture is presented.     

Charge transport in an AC plasma panel

A transverse voltage applied between a display cellDand a transfer cellTon a standard 60 lines/inch ac plasma panel can simultaneously cause a previously ON cellDto fire and transport a large amount of electrons from cellDtoward cellT. The same transverse voltage combines with the voltage due to transported electrons to produce subsequent discharges which, initiated near cellT, grow rapidly as they propagate along the row toward cellD. A voltage pulse (≃sustain pulse), applied to cellT, will combine with the local row wall voltage to produce another sequence of discharges along the row. These discharges, initiated near cellD, gain intensity as they spread toward cellT. This dynamic process results in a large and controllable charge transfer between the display cellDand the transfer cellT, a key mechanism for shift address display. By reversing the polarity of the transverse voltage, ions also can be transported, but ion transport produces smaller charge transfer.     

Charge spreading and its effect on AC plasma panel operating margins

Like normal wall charges in an ac plasma panel, the spread charges from neighbor "on" cells to an "off" cell site can cause an increase or decrease in the required write voltage depending on the relative location of the write pulse with respect to sustain pulses. The net changes in write voltage can be accurately measured. The results obtained show that spread charges increase sharply with panel resolution and have a dominant influence over other priming effects on operating margin, e.g., to compensate for the wall voltage due to spread charges, an additional 15.5 V, or 10 percent of the voltage used to write an isolated cell, is required to write a cell which is located in the middle of a cluster of"on" cells on a high resolution 512-60 panel.     

State inversion of plasma panel cell

Two pulses applied in sequence to a cell of a plasma panel cause inversion of the state of the cell. The first, an inverting write pulse Vwi, narrower than a normal write pulse and positioned within the discharge recovery time ahead of a sustain pulse, can cause a cell to switch "on" in such a way that the cell wall voltage builds up to its steady-state value gradually over several sustain cycles. The second is a conventional erase pulse Ve. If the cell is initially "on," Vwihas no effect while Veinverts the cell to the "off" state. On the other hand, if the cell is initially "off," Vwicauses a low-level discharge such that the wall voltage is too low at the time Veis applied to the cell to cause a discharge, but the wall voltage keeps building up to a steady "on" state through a number of sustain cycles. Thus Vehas no effect and the cell remains "on." Using the state inversion, a blinking cursor has been successfully demonstrated on an 80 × 256 plasma panel. Negative image and bandwidth reduction in bilevel picture transmission could also be achieved with state inversion.     

Incomplete transfer in charge-transfer devices

The authors present a general analysis of incomplete charge transfer in charge transfer devices. By using a lumped-charge model to characterize the dynamics of the charge transfer, they calculate /spl alpha/, the small-signal coefficient of incomplete transfer, in terms of single-device small-signal parameters. They show that three contributions to incomplete transfer are common to all charge-transfer shift registers: an intrinsic transfer rate contribution, an output conductance or feedback contribution, and a storage-capacitance modulation contribution. The analysis suggests that most relevant measurements necessary to characterize incomplete transfer can be made on a single cell of a shift register that has input and output diffusions. This allows transconductance etc., to be measured on a small-signal basis as a function of transfer current, from which one can calculate transfer efficiencies. An analysis of the influence of interface states which may be important for some charge transfer devices, is also included.     

Study on discharge stability of cost-effective driving method based on V/sub t/ close-curve analysis in AC plasma-display panel

A new cost-effective driving method that can drive plasma-display panel cells without applying any driving waveform to the common electrode is proposed based on a V/sub t/ close-curve analysis. In this driving method, it is very important to prevent a misfiring discharge due to the inversion of the polarity of the wall charges accumulated between the scan and address electrodes. The measured V/sub t/ close-curve showed that a misfiring discharge caused by the polarity inversion phenomenon of the wall charges on the scan and address electrode could be prevented by minimizing the potential difference between the scan and address electrodes by applying a positive auxiliary pulse to the address electrode, especially while applying the positive sustain pulse during a sustain period. As a result, the proposed cost-effective driving method can reduce the driving cost by about 20% through eliminating the common driving board and successfully display various image patterns, such as the white, red, green, and blue patterns, on a 42-in plasma television without any misfiring discharge.     

Multiple states and variable intensity in the plasma display panel

The plasma display panel, in its usual mode, retains information in the form of wall charges that determine whether or not a sequence of discharges will be maintained at a given cell. These discharges are stable in the sense that a perturbation in wall voltage at a particular discharge will damp out over the succeeding discharges. Recent work has shown that a cell in a plasma display panel can exist in one of several states, each with a unique set of wall voltages and each with a unique average intensity. As with the bistable case, each state is stable in the sense that perturbations damp out. Three states have been achieved simultaneously, with brightnesses that can be characterized as bright, medium, and dim. Within the constraints of a simple theoretical model, the conditions for stability can be stated in terms of the products of the slopes of charge transfer curves. This technique for achieving variable intensity retains the advantage, inherent in the plasma display technique, that the information, once imparted to the display, is retained as long as the sustaining signal is applied to the entire panel.     

发射和接收光束同时开关的激光测距法

采用同一电光器件对发射和接收光束同时开关的原理,提出了一种新颖的激光测距方法。光源发出的连续激光被待测目标反射后,往返两次通过光源端的电光晶体,在晶体上施加边沿急速变化的电压,利用其高速响应的开关特性,同时对往返光线产生影响,截取出一段包含激光往返待测距离所需时间信息的光强变化曲线。实验中利用雪崩管电路实现了纳秒级的高压上升沿,并利用单轴晶体的双折射和全内双反射性质,用特殊结构的单块LiNbO3晶体实现了该方法的测距装置。示波器分析的实验结果验证了该方法的可行性,从而为激光测距开拓了一种新的思路。     

A high efficiency charge pump circuit for low power applications

A high efficiency charge pump circuit is designed and realized. The charge transfer switch is biased by the additional capacitor and transistor to eliminate the influence of the threshold voltage. Moreover, the bulk of the switch transistor is dynamically biased so that the threshold voltage gets lower when it is turned on during charge transfer and gets higher when it is turned off. As a result, the efficiency of the charge pump circuit can be improved. A test chip has been implemented in a 0.18 μm 3.3 V standard CMOS process. The measured output voltage of the eight-pumping-stage charge pump is 9.8 V with each pumping capacitor of 0.5 pF at an output current of 0.18 μA, when the clock frequency is 780 kHz and the supply voltage is 2 V. The charge pump and the clock driver consume a total current of 2.9 μA from the power supply. This circuit is suitable for low power applications.     

A planar single-substrate AC plasma display

A novel method is described for constructing an acsustained gas-discharge display (plasma panel). Electrodes and insulating layers are applied alternatively on a single base substrate to produce a matrix of insulated crossovers. A second clear substrate is used to contain gas on the electrode side of the base substrate where glow discharge occurs. As in conventional two-substrate panels, internal memory is obtained by charge storage on the dielectric. The pulsed write and the sustain mechanisms of single- and twin-substrate display elements are discussed with regard to the effects of cell and field geometries. In the sustain mode, glow-propagation effects are observed, especially in the nonhomogeneous fields of the single-substrate design. Here cathode-type glows which form a narrow band are observed with a high-speed photomultiplier and shown to sweep across the dielectric surfaces. Luminance, intensity distributions, and luminous efficiency data are compared on small 10 × 10-line panels using single-substrate and conventional designs. A three- to four-fold improvement in luminance is achieved with the single-substrate geometry.     

基于激光散斑数字图像相关法的热应变测量

为了解决常规数字图像相关法应用于高温工况下热应变测量时,人工制作的散斑受高热载荷冲击容易出现变色、熔化、脱落的问题,采用激光散斑作为数字图像相关法特征纹理的方法,计算温度变化前后散斑图像相关性来测量金属热应变,进行了非真空环境下加热试件的实验,以及在管式加热炉中分别对铝试件和钨试件进行人工散斑和激光散斑的真空加热实验对比,取得了相应的散斑图像,并计算出平均应变曲线数据。结果表明,在非真空环境下,由于热流扰动导致激光散斑图像抖动较大,测量出的热应变曲线存在较大的干扰噪声;铝从室温升至450℃和钨从室温升至800℃的热应变与人工散斑结果相对一致;激光散斑数字图像相关法在类似聚变堆偏滤器高真空、高热流条件下,可以有效地测出金属壁面的动态热应变。该研究为聚变堆偏滤器第一壁材料的损伤诊断提供了新思路。     

A capacitorless double-gate DRAM cell

A capacitorless double-gate DRAM (DG-DRAM) cell is proposed in this study. Its dual gates and thin body reduce off state leakage and. disturb problems. Dopant fluctuations, which can be particularly important in high-density arrays, are avoided by using a thin, lightly doped body. The cell's large body coefficient ((dV_T)/(dV_BD) transforms small gains of body potential into increased drain current. MEDICI simulations for 85°C show that a DG-DRAM cell may sustain a measurable change in drain current several hundred milliseconds after programming. These characteristics suggest that a thin body, double-gate cell is an interesting candidate for high density DRAM technologies     

Temporal distribution of space charge in AC plasma cell discharge

By measuring the transported electrons produced by transverse sampling pulses, the temporal space-charge distribution of an operating ac plasma display cell is established for the first time. Results show that the space charge buildup continues beyond discharge breakdown (∼ 0.85 µs from the sustain pulse leading edge) and reaches a peak at ∼2.25 µs. These space charges, usually lost in the recombination process due to weak internal field, can be transported out and effectively used in new devices such as shift displays and plasma logic gates.     

Electron transport self-shift display using an AC plasma panel

Using an electron transport mechanism, a self-shift display has been successfully implemented on an ac plasma panel providing higher resolution, higher shifting speed, and wider operating margins than previously obtained. The mechanism consists of a unidirectional and efficient transport of a large portion of electrons (generated during the display site discharge) to a neighboring OFF transfer site by a low transverse voltage. The process results in a large wall voltage build-up at the transfer site to switch its state from OFF to ON. The implemented electron transport self-shift display consists of a 7 × 128 site array of an Owens-Illinois 60 lines per inch panel where the 128 columns are driven by a four-phase driver. A resolution of one display site for every two electrodes and a shifting speed better than 600 characters per second have been successfully demonstrated. The ranges of the shifting voltages VDand VTare better than 15 V over a 10-V sustain range. The shifting operation also was successfully demonstrated on an 83 lines per inch panel with good operating margins.     

驱动时序设计中影响SMPDP显示亮度的相关因素研究

等离子体显示屏的显示亮度除了受其本身的发光单元结构设计、制造工艺和荧光粉材料等因素的影响,其驱动方案及电路系统设计中的若干参数调整也会对其实际性能产生影响。本文通过对驱动时序方案中可能影响SMPDP亮度指标的因素进行分析和实验,指出了寻址速度和维持脉冲频率两大因素对显示屏亮度指标的核心影响,并讨论了如何利用该结果改进驱动时序参数设计从而提高SMPDP显示亮度。     

LCD面板TFT特性相关残像研究

残像是影响TFT-LCD画面品质的重要因素,也是发生原因最为复杂的一种不良。本论文提出了一种定量测量残像水平的方法,同时对TFT特性引起的残像不良进行了实验研究,得到了由TFT特性引起的交流(AC)残像发生规律及发生机理。本文通过对比研究残像画面黑白格亮度与TFT漏电流变化曲线,同时结合像素充放电计算公式进行电压差模拟,发现黑白格像素放电差异导致的像素保持电位差异(ΔV12.5mV)是发生残像的根本原因。根据以上机理,本论文提出了两种方法改善此类残像。第一种是通过改善TFT a-Si成膜工艺减小漏电流(50pA),同时提升TFT特性的稳定性,可以减小棋盘格画面残像评价导致的TFT转移特性曲线偏移;第二种是通过改变栅压低电平,避开关态时不同显示区域的TFT漏电流差异峰值;以上两种方法均可以有效改善残像(ΔL0.5cd/m~2)。     

基于SOC估算的锂电池组复合型均衡拓扑设计

锂电池的均衡管理可以提高锂电池的使用寿命和续航里程。针对磷酸铁锂电池串联电池组中,电池组中各个单体电池之间存在电量不一致的问题,提出一种复合式均衡拓扑结构,通过对单体电池之间的电感或电池组间的变压器选择性放电均衡,实现电池组内的各个单体电池的电量均衡,并测量实际的锂电池放电曲线,拟合锂电池开路电压与SOC的曲线。此外,建立了对应的磷酸铁锂电池Simulink模型,使用SOC估算值作为判断均衡的条件,以提高启动或停止均衡子电路的准确性。在Matlab/Simulink的软件仿真下证明,所提出的复合式均衡方案均衡效果良好,易于实现,控制简易。     

New reset waveform for the contrast ratio improvement of AC-PDP

We propose a new reset waveform for the improvement of contrast ratio. A square pulse is applied to the address electrode while the reset pulse ramps and before the discharge between the sustain electrodes occurs. The square pulse induces a discharge between the address electrode and the X electrode, and the induced wall charge between the sustain electrodes is opposite to the applied ramping voltage between the sustain electrodes. Thus, the next discharge between the sustain electrodes becomes weaker. The weaker discharge during the reset period lowers background luminance and improves contrast ratio. The experimental results show that the contrast ratio can be improved by 35/spl sim/58% using this method compared with the conventional ramp reset method.     

Optical write-in for the plasma display panel

Techniques of changing the state of plasma display cells with externally applied light are presented. Optical write-in offers the advantage of high-speed parallel data transfer from a photographic transparency to a plasma display panel. It is established that light incident on a plasma cell causes a photoemission from the inner glass surface. The emitted electrons perturb the wall voltage and cause a change in state. The intensity of light needed to change the state of cells can be reduced, without changing the solid panel materials, by two techniques, Electron avalanches initiated by the photoelectrons can be used to decrease the light needed by a factor of 100. By flashing light during the plasma display cell gas discharge, the intensity of the light can be further reduced.