基于馈通电压自动补偿的OLED电性能测试波形设计研究

常规馈通电压计算原理涉及到OLED体的电容值,不同型号OLED产品电容值是个变量,为了得到最佳的电容值,OLED制造企业测试部门需做大量的验证实验。本文直接通过栅极电压上拉使OLED体的储存电容产生馈通电压来补偿栅极电压关闭时栅极和漏极之间寄生电容产生的馈通电压,无需测量OLED体的电容值和修正Vcom值即可补偿栅极电压关闭时栅极和漏极之间的寄生电容产生的馈通电压。实验结果表明,基于馈通电压自动补偿原理设计的Shorting Bar Test Waveform与Vcom人工修正原理设计的电性能测试波形的检测效果一致,而对不同缺陷的检测率有微小差异。     

具有软件可编程能力的精密电流源

只要增加几个廉价小型元件，以前的硬连线压控电流源就可变成软件可编程的压控电流源(图1）。数字电位器IC1与精密运算放大器IC2一起设定流过传输晶体管的电流ISET而并联稳压器IC3则在数字电位计两端提供一个恒定参考电压。传输晶体管只要工作在其线性区域内。就可根据所加的栅极电压来控制负载电流。数字电位器的每一个增量大小均可提高或降低运算放大器非倒相输入端的动触点电压VIN+。因此，VIN+相对于参考电压而变化，而参考电压又相对于电源电压保持稳定：     

功率MOSFET零温度系数点的研究

为研究功率MOSFET零温度系数点（Zero Temperature Coefficient,ZTC）,不同栅极电压对温度系数的影响,本文基于阈值电压和迁移率的温度关系并结合功率MOSFET输出特性模型,得到了随栅极电压变化而出现的三种不同温度系数。利用实际测试验证了温度系数的变化规律,结果表明：在小栅极电压条件下,线性区和饱和区均为正温度系数;随栅极电压增大,线性区先进入负温度系数,饱和区仍然为正温度系数,并因此产生了零温度系数点;随栅极电压进一步增大,线性区和饱和区都进入负温度系数。同时根据测试数据,分析了ZTC在不同栅极电压条件下随温度的变化原因,并基于测试数据讨论了迁移率随栅极电压和温度的变化关系。     

高压LDMOS准饱和效应研究

借助于SILVACO TCAD仿真工具,研究了高压LDMOS电流准饱和效应(Quasi-saturation effect)的形成原因。通过分析不同栅极电压下漂移区的耗尽情况以及沟道与漂移区电势、电场和载流子漂移速度的分布变化,认为当栅压较低时,LDMOS的本征MOSFET工作在饱和区,栅压对源漏电流的钳制明显,此时沟道载流子速度饱和;而在大栅压下,随着沟道导电能力的增加以及漂移区两端承载的电压的增大,本征MOSFET两端压降迅速降低,器件不能稳定地工作在饱和区而进入线性工作区,此时沟道中的载流子速度不饱和。LDMOS器件的源漏电流的增大主要受漂移区影响,栅压逐渐失去对器件电流的控制,此时增大栅压LDMOS器件的源漏电流变化很少,形成源漏电流的准饱和效应。最后,从器件工作过程对电流与栅压的关系进行了理论分析,并从理论结果对电流准饱和效应进行了深入分析。     

功率电子管帘栅极的稳定供电

在电子管功率放大器中．当工作信号为峰值时．输出功率管的屏极电流和帘栅极电流都将增大，这会引起相应电路的供电电压下降，其中帘栅极电流的变化又远大于屏极电流的变化。帘栅极电压的降低对五极或集射功率电子管的工作影响很大，     

IGBT关断瞬态电压尖峰影响及抑制

绝缘栅双极晶体管(IGBT)是一种性能优良的全控型电力电子器件,由于线路和器件内部分布电感的存在,关断时集电极电流的快速变化会感应产生一个较大的电压尖峰从而引起过电压击穿。分析了栅极结电容放电时间常数和拖尾电流对电压尖峰的影响,通过改变栅极驱动电阻和温度可以抑制电压尖峰。分析了电压尖峰引起过压击穿的失效机理以及失效模式,表明IGBT过压击穿引起失效的本质仍然是结温过高引起的热击穿失效。     

三阶驱动原理在TFT LCD电测波形设计中的应用

将三阶驱动原理应用于TFT-LCD 电测波形的设计,并通过实验验证了其有效性.设计过程中,直接通过栅极电压上拉,将Cs产生的Feed Through电压用来补偿栅极电压关闭时使Cgd产生的Feed Through电压.这样无需通过修正Vcom电压来补偿(栅极电压关闭时产生的Feed Through电压),避免了获取Clc参数难的问题.     

EL34 AB类推挽放大器与UL接法推挽放大器的比较

一、EL34 AB类推挽放大器EL34 AB类放大器电路原理如图1所示。它与B类工作时的电路结构完全相同。输出级的栅极偏置电压-24.6V时,屏极电流64mA,帘栅极电流8.3mA。屏极电压374V时,其功耗为24W;帘栅极电压360V时,其功耗为3W。EL34的屏极额定功耗为25W;帘栅极为8W,说明该放大器实际功耗低于极限功耗。     

VDMOS准饱和特性数学模型研究

借助电脑软件仿真深入研究了VDMOS电场分布特性,并且从数学角度研究了VDMOS漂移区垂直方向上电压降落的情况。建立了VDMOS准饱和特性的数学模型,给出了VDMOS工作在临界准饱和区域的栅极电压的计算方法,为器件工作的安全区域设定了边界条件。在研究过程中发现,VDMOS漂移区垂直方向上的电场最大值出现的位置基本固定不变,它不随着栅极电压、漂移区掺杂浓度和栅氧厚度的变化而变化,而是随着漏电压的变化而变化,这主要是由于漂移区内B区域横截面积和电子速度都在随着栅极电压的增大而增大造成的。此结论不仅为文中准饱和模型的创建提供了一种简便的方法,而且对以往模型的简化和改进提供了理论依据。     

一种通道复用的高可靠性隔离IGBT栅极驱动器

采用SIMC 0.18 um BCD工艺,设计一种输出电流2 A,隔离电压5 kV,CMTI为100 kV/us的单通道隔离IGBT栅极驱动器,该IGBT栅极驱动器集成双侧欠压保护、退饱和保护,具有高可靠性.为节省芯片面积和成本,提出一种通道复用技术,将高压侧退饱和状态监测信号(FLTH)和欠压闭锁状态监测信号(RDH)编码后使用一个数字隔离通道同时传输至低压侧,简化电路结构,节省芯片面积约10%.当发生欠压闭锁时,隔离式IGBT栅极驱动器不工作;当未发生欠压闭锁时,可以通过编码信号的脉冲宽度来区分是否发生退饱和状态.仿真与测试结果表明：采用通道复用技术可以准确的将高压侧的退饱和状态监测信号和欠压闭锁状态监测信号传输至低压侧.     

An Approximate Time-Domain Formula for the Calculation of the Horizontal Electric Field from Lightning

This paper presents an approximate formula to calculate the horizontal electric field from lightning, considering finitely conducting earth. The formula is represented by an analytical expression in the time domain, which is useful for the calculation of lightning-induced voltages on power and telecommunication lines, without the need of domain transformations. The paper also compares the results of the formula with the results obtained from frequency-domain techniques, namely the numerical calculation of Sommerfeld's integrals and the Cooray-Rubinstein's formula. The comparison is favorable for a wide range of distances from the lightning channel and values of earth's conductivity. The horizontal electric field calculated by the formula is composed of two components of opposed polarities, one due to the return stroke charge and the other due to the return stroke current, resulting in an electric field with a bipolar wave shape. The charge component prevails in the region close to the lightning channel, while the current component prevails in the region far from it.     

三种PCMA返回信号捕获方案分析与比较

成对载波多址(Paired Carrier Multiple Access,PCMA)是一种共频谱卫星通信方式,为了解调对端信号,必须先捕获并消除本站发射的返回信号,该站返回信号捕获是其关键技术之一。针对直接捕获、基于时间窗的捕获以及基于前导码辅助的捕获3种捕获方式进行了详细的分析,分析结果表明,基于前导码辅助的捕获方式具有最短的捕获时间。     

Hot-electron capture by negatively charged centers in an approximation of quasi-elastic scattering

The capture coefficient at the repulsive Coulomb centers is calculated in an explicit form within the approximation of quasi-elastic scattering in crossed strong electric and magnetic fields. It is shown that, along with the Sommerfeld factor, the capture probability must depend exponentially on the energy of an electron that has tunneled through a barrier. The dependence of the critical electric field, above which the exponential dependence should be considered, on the magnetic field and the scattering mechanism is determined. In fields lower than the critical one, the Bonch-Bruevich approximation is valid.     

A constant-current charging technique for the measurement of generation rates in MOS-capacitors

If a constant current is used to charge an MOS capacitor from accumulation into deep-depletion, then the space-charge region widens until the generation rate within that region exactly balances the charging current. At the same time the MOS capacitance is measured. From the known current and calculated space-charge width, the generation lifetime is immediately determined. Control of the charging current determines the depth of the sample studied.If the charging current is significantly larger than the generation current, then the time variation of the capacitive susceptance gives a direct plot of the cumulative impurity profile.The experimental circuit may be used without modification to perform a rapid “quasi-static” Q?V_G measurement, from which the surface potential, surface state density, flat-band voltage etc., may be found using Koomen's method.The generation rate may be studied as a function of temperature to identify the activation energy of the centres responsible.A study of the forced return to accumulation identifies the location of the minority fermi-level.     

Prebunched beam traveling-wave tube studies

A traveling-wave tube with a prebunched beam is found to have a considerably higher efficiency than the same tube without prebunching. For the particular tube tested the efficiency is increased from 20 to over 35 per cent at a gain of 8. Computer calculations using a discrete disk model give similar results. The beam is bunched tightly in energy at the position of highest efficiency, indicating that very high efficiency could be obtained with a depressed collector. Both current and velocity modulation are required for prebunching, and are obtained by means of a current grid followed by an inductively tuned velocity modulation cavity. The requirements of the current grid are not great so that operation should be possible at frequencies well above the normal operating region of a microwave triode. The operation of the tube is sensitive to the output match, and it appears to be difficult to obtain a good match with the beam on.     

Dependence of the electron capture velocity on the quantum-well depth in semiconductor lasers

Three laser structures with a single strained InGaAs quantum well of different depths and a GaAs or Al_0.1Ga_0.9As waveguide region are grown by metal-organic chemical vapor deposition. Using the experimentally determined values of the threshold current density and internal differential quantum efficiency, the velocity of electron capture into the quantum well is calculated for each of these structures. It is found that the capture velocity into deep quantum wells is significantly lower than into shallow ones.     

电容器高频损耗与材料的关系

鉴于电子镇流器对低损耗、耐大纹波铝电解电容器的需要,将电容器实验测量数据用理论公式进行推算,得到等效串联电阻Res与电容器选用的电解纸、阳极铝箔有极大关系。欲降低电容器在高频下的tgd,除降低电解液的电阻率外,还要注重电解纸和阳极铝箔的选用。     

Comparison of shielding by infinite and finite planar grids over alossy half space

The shielding properties of finitely extended and infinitely extended parallel thin-wire grids over a lossy half space are considered when illuminated by a downcoming plane wave whose electric field vector is parallel to the wires. Numerical comparisons of the electric field in the illuminated, transition, and shadow regions for the finitely extended case are made with the electric field in the shadow region for the infinitely extended case. The field responses of both grids in the shadow region are shown to be similar. Edge effects, however, may be significant if the field is observed near the truncation of the grid of finite extent. It is demonstrated that a reasonable approximation for the current distribution in the current region of the finite grid is the computed value determined for the infinite grid     

Fowler－Nordheim公式用于实际场发射体的修正

Ｆｏｗｌｅｒ－Ｎｏｒｄｈｅｉｍ公式是一个在理想条件下推导的计算场致发射电流的公式。对场发射体的实验测量表明：实测结果往往比根据Ｆｏｗｌｅｒ－Ｎｏｒｄｈｅｉｍ公式计算的结果大很多，说明这一理想化了的公式应用于实际场发射体时，必须给予修正。本文讨论了产生这一问题的原因，并提出了合理的定量修正方法。     

A Recursive Park Transformation to Improve the Performance of Synchronous Reference Frame Controllers in Shunt Active Power Filters

Load harmonic currents and load unbalances reduce power quality (PQ) supplied by electrical networks. Shunt active power filters (SAPFs) are a well-known solution that can be employed to enhance electrical PQ by injecting a compensation current at the point of common coupling (PCC) of the SAPF, the load, and the electrical grid. Hence, SAPF controllers must determine the instantaneous values of the compensation reference current, including nondesirable components of the load current. A family of SAPF controllers, which evaluates the compensation reference current using synchronous rotating frames (SRFs), employs a structure based on Park transformations: direct transform, low-pass filtering (LPF), and inverse transform. The cutoff frequency and the filter order of the LPF stage must be designed properly in order to obtain an accurate reference current and a fast dynamic response of these SAPF controllers. This paper proposes a recursive implementation of the direct Park transformation that avoids the filtering stage and allows accurate SRF controllers to be designed. Moreover, the proposed implementation is not dependent on PCC conditions. The proposed implementation is evaluated using a three-phase, three-wire SAPF and compared with LPF-based controllers by simulation and experiment.