脉冲偏压下电弧离子镀等离子体负载的等效电路模型及其定量表征

为了解决电弧离子镀（AIP）工艺中脉冲偏压电源与AIP等离子体负载间的匹配问题，结合脉冲偏压下AIP工艺实验，运用等离子体鞘层理论、电路理论和仿真模拟技术，得到AIP等离子体负载本质上是由鞘层引起的容性负载，在电路中可以等效为电容和电阻相并联的单元；根据AIP等离子体鞘层演化的特性，将AIP等离子体负载的等效电容表征为与时间无关而只与脉冲偏压幅度和等离子体相关参数有关的量，AIP等离子体负载的等效电阻，可以在直流偏压下通过测量与脉冲偏压幅值对应的AIP等离子体负载电流来确定。经验证，本文建立的AIP等离子体负载的等效电路模型及其定量表征是有效的。     

高频宽气隙介质阻挡放电负载特性研究

为了研究高频宽气隙条件下介质阻挡放电特性,实现电源和放电管之间的负载匹配。使用频率20~40 k Hz连续可调的全桥方波逆变电源作为主电路,采用脉冲宽度调制作为控制策略,利用高频变压器漏感和放电管等效电容进行阻抗匹配。重点研究了高频宽气隙放电特性,采用Lissajous图形法研究放电过程中等效电容,等效电阻等电学参数。研究结果表明,稳态工作时的放电负载可等效为电容电阻相串联的模型,随着放电负载两端电压的升高,放电管的等效电容增加;随着放电功率的增加,放电负载的等效电阻线性增加。     

磁控溅射等离子体阻抗影响因素研究

了解等离子体阻抗在磁控溅射放电过程中的变化规律,有利于调控电源和负载之间的阻抗匹配,达到最大化利用溅射功率,提高镀膜质量的目的。为了研究磁控溅射镀膜工艺过程中等离子体的阻抗特性的变化趋势,本文采用V-I probe测量等离子体阻抗大小、极板负偏压等参数,研究了气体流量和溅射功率对等离子体阻抗特性的影响。结果表明,在本文的实验条件下,等离子体始终呈现为容抗特性。当气体流量增大时,受氩气的电离率影响,等离子体阻抗实部R呈现先增大后减小的趋势,阻抗虚部X受到鞘层的影响呈现先减小后增大的趋势。当溅射功率增大时,等离子体阻抗实部R受欧姆加热的影响一直增大,阻抗虚部X受到负偏压和鞘层的影响逐渐减小。     

脉冲偏压作用下MgO薄膜表面的荷电效应

采用脉冲偏压电弧离子沉积技术在玻璃基片上制备了透明的、具有择优取向的MgO薄膜。针对绝缘性薄膜表面的荷电效应,比较了脉冲偏压作用下鞘层对离子的加速时间(即鞘层的寿命)与脉冲宽度的大小以及偏压鞘层的初始厚度与离子穿越的距离的大小,讨论了不同占空比下偏压鞘层对离子的加速效应。利用X射线衍射及扫描电子显微镜对样品的观察结果表明,由于荷电效应,脉冲偏压幅值为-150 V,占空比在10%~40%的范围内,占空比的变化并不能改变MgO薄膜的微观结构和表面形貌。     

2.4GHz负电容电路设计及仿真

设计了一个应用于2.4 GHz频段的负电容电路,并对其进行了理论分析和仿真分析.与以往的负电容电路相比该电路使用一个基准电阻替代基准电流源,从而简化了电路;同时,电路中还引入了分压电阻,分压电阻的引入起到了稳定电路、降低功耗的作用.采用TSMC 0.25μm工艺,在ADS下进行仿真.通过对电路的优化,最后可以得到一个中心频率为2.45 GHz、带宽为1.2 GHz、最大容抗为2.8 kΩ的负电容电路;整个电路的功耗只有4.2 mW,预示着该电路具有很好的应用前景.     

射频激励铜离子激光器的功率消耗

通过对射频激励激光器放电电压、电流以及相位的精确测量,基于射频放电等离子体等效电路,得出等离子体总电阻(包括等离子体总电阻和鞘层电阻分量),经非线性最小平方拟合分别得到等离子体电阻和鞘层电阻,进而定量地得到等离子体和鞘层功率消耗,鞘层电压以及鞘层厚度随放电电流变化的关系,借此可以诊断出射频放电处于α或γ放电。研究表明在中等气压氦气中随着气体压强的增加和电流的增加,气体的放电模式将从α放电为主转向γ放电为主。     

射频激励铜离子激光器的功率消耗

通过对射频激励激光器放电电压、电流以及相位的精确测量，基于射频放电等离子体等效电路，得出等离子体总电阻(包括等离子体总电阻和鞘层电阻分量)，经非线性最小平方拟合分别得到等离子体电阻和鞘层电阻，进而定量地得到等离子体和鞘层功率消耗，鞘层电压以及鞘层厚度随放电电流变化的关系，借此可以诊断出射频放电处于α或γ放电。研究表明在中等气压氦气中随着气体压强的增加和电流的增加，气体的放电模式将从α放电为主转向γ放电为主。     

镁合金微弧氧化的负载模型及仿真分析

为了确定镁舍金微弧氧化负载对电源形式及参数的要求,基于电化学和电弧物理理论,对单极性和双极性脉冲输出方式下的负载波形进行分析,建立了负载等效电路模型。微弧氧化负载呈现极强的电容性,其负载模型可简化为1个电容和2个电阻等效的一阶RC系统。通过构造电阻可调的强制放电回路,用matlab软件对负载波形曲线进行参数拟合,对等效电路简化模型参数进行了定量分析。所得模型中电容和电阻的数值与计算机仿真结果相符。     

本安电路电容放电模型与仿真分析

通过对电容实际放电电路的分析,建立了电容电路放电仿真模型和数学模型,利用MATLAB仿真出了在固定电容值下,串联电阻-放电能量及端电压-放电能量的关系曲线,从曲线中可查询到在特定条件下电阻与放电能量、端电压与放电能量的数值对应关系,并且通过了IEC火花试验装置火花点燃试验的验证.结果表明,曲线中高于放电能量阈值525μJ的电路发生了点燃,相反则未点燃,仿真模型评价结果与火花点燃试验结果一致,当设计电容电路中的等效电容值不在标准范围内或者没有专用的本安电路火花试验装置进行验证时,可以利用该方法进行模拟仿真,通过查询曲线与放电能量阈值进行比较来评定所设计电路的本安防爆性能.     

脉冲偏压对等离子体沉积DLC膜化学结构的影响

以乙炔为气源，用等离子体基脉冲偏压沉积（plasma based pulsd bias deposition缩写PBPBD）技术进行了不同负脉冲偏压条件下制备DLC膜的试验，通过X射线光电子谱（XPS）、激光喇曼光谱[Raman]以及电阻分析方法考察了负脉冲偏压幅值对DLC膜化学结构的影响，结果表明由-50kV到-10kV随负脉冲偏压降低，DLC膜中SP^3键分数单调增加，但当脉冲偏压为0时形成高电阻的类聚合物膜，说明荷能离子的轰击作用形成DLC化学结构的必要条件，键角混乱度和SP^2簇团尺寸与脉冲偏压之间不具有单调关系，在中等幅值负脉冲偏压条件下，键用混乱度较大且SP^2簇团尺寸细小。     

AC-PDP放电特性参量及其测量

根据气体放电特性和交流等离子体显示器的放电单元结构,提出了AC-PDP等效电路模型和表征该模型的3个特性参量:击穿电压、气体维持放电的最小电压和放电单元电容比.通过分析放电过程,推导出最大维持电压、最小维持电压和维持电压余裕度的表达式.利用外接串联电容,提出一种放电特性参量的测量方法,并对12英寸PDP实验屏进行实际测量,获得了放电特性参量的测量结果.本文所提放电特性参量及其测量方法对AC-PDP显示屏的放电单元设计具有参考作用.     

静态电荷量测试仪校准源研制

静态电荷量标准采用精密程控电压源和精密电容器输出高准确度静态电荷量,利用电压负反馈进行自动调整,克服负载电容和输出电压对输出电荷量的影响,实现静态电荷量的稳恒输出,可方便地检定静电计和电荷放大器。该静态标准电荷源的稳恒特性比传统的电荷源提高了5个数量级。该标准源静态电荷量Qx范围为200pC～2μC;允许误差为0.1%Qx+0.1pC;等效源内电容为10^-15F。     

Modeling of charge switching in ferroelectric capacitors

To simulate charge switching in ferroelectric capacitors, a pair of exponential growth and decay currents is mapped to the process of polarization reversal. This is based on the fact that these exponential currents [i.e., i = I(m) e(t/tau) (t < or = 0) and i = I(m) e(-t/tau) (t > or = 0)], are completely specified by two constants I(m) and tau and each accommodates an integral charge Q = I(m) x tau. Equating this charge to the remanent spontaneous polarization allows for the modeling of switching current. For practical circuit simulations for charge switching, this modeling of switching current is simplified to an exponential decay current whose integral charge is set equal to the total reversed spontaneous polarization. This is because an exponential decay current can be conveniently implemented by charging a series resistor and capacitor (RC) circuit with a pulse-voltage source. The voltage transitions of the pulse source are associated with the polarization reversal and can be controlled with a noninverting Schmitt trigger that toggles at the positive and negative coercive voltages of a ferroelectric capacitor. The final circuit model incorporates such electrical and geometrical parameters as capacitance, remanent spontaneous polarization, coercive field, electrode area, and film thickness of a ferroelectric, thin-film capacitor.     

Electrical properties of ITO/benzylated cyclodextrins (β-CDs (Bz))/Al diode structures

Abstract

Investigations of the electrical characteristics of benzylated cyclodextrins (β-CDs (Bz)) diodes are reported. We present current–voltage characteristics and impedance spectroscopy measurements performed on partially benzylated cyclodextrins β-CDs (Bz) thin films in sandwich structures ITO/b-CDs (Bz)/Al. The static electrical characterizations show a space charge limited conduction (SCLC) and a conductivity with power low frequency behavior characteristic of a hopping transport in disordered materials. The impedance spectra can be discussed in terms of an equivalent circuit model designed as a parallel resistor R_p and capacitor C_p network in series with resistor R_s. We extract numerical values of these parameters by fitting experimental data. Their evolution with bias voltages has shown that the SCLC mechanism is characterized by an exponential trap distribution. We estimated from the capacitance voltage characteristic an acceptor concentration of about 10¹¹ cm^?3 due to trap states.     

Electrical properties of electrodeposited polyaniline nanotubes

The electrical properties of polyaniline nanotubes-aluminum like Schottky diode are described. Polyaniline nanotubes (PANI) were deposited on aluminum thin films using the polarographic technique. The nanotubes were characterized by scanning electron microscopy (SEM) and UV-Vis absorption spectra. The electrical properties of the heterojunction PANI-Al were examined. The current density–voltage (J × V) profile has shown a behavior typical of Schottky diode, with ideality factor (n) of 6.76 and ϕ _b of 0.70 eV. Impedance spectroscopy data apparently shows that the resistance dominated the AC behavior of the PANI-Al system. The equivalent circuit is composed from a resistor in series with a parallel resistor–capacitor circuit. The results indicate that polyaniline nanotubes may be interesting to the development of electro-optical devices with 2D structure.     

AM radio circuit using printed electronic components

In this paper, printing technologies have been employed to print the resonant circuit and detection circuit for an amplitude modulation system (AM radio), which consists of a printed inductor, capacitor, resistor and diode on plastic foils for using as an AM radio circuit. To test the printed inductor, capacitor, resistor and diode as components of AM radio, we selected 640 KHz, the strongest AM frequency in Sunchon City, Korea and monitored the audio signal by replacing each component by a corresponding printed one. As a result the 640 KHz AM radio signals were detected.     

Drive to generate digital current for control vertical field in asmall Tokamak

The horizontal position of a small Tokamak plasma has been controlled by a circuit to generate the control vertical field. The circuit must respond quickly to the position signal from a feedback circuit and feed a large current in a short time. We have assembled the circuit to generate a digital current called a drive. The drive includes several units, and each unit is made up of a capacitor, a transistor, a protective resistor and a comparator. We have installed the drive on a small Tokamak, the Hamana-T and obtained satisfactory results. The performance of the drive is described     

Pre-charging of module capacitors of MMC when the module switches are driven by a source derived from the module capacitor

A modular multilevel converter (MMC) is one of the latest multilevel converters used for high and medium-voltage power conversion. It is based on cascade connection of multiple identical modules using IGBTs as switching devices. Module switches of MMC are preferably driven by a source derived from the module capacitor. In each MMC module, the control circuit, consisting of gate drivers, is powered from a dc supply derived from the local capacitor. The module capacitors need to be pre-charged, to power the control circuit. The problem faced while doing so experimentally for MMC with two modules per arm and a solution have been reported earlier. If a fly-back converter is used to generate the power supply for driving the control circuit, the module capacitor voltages become unstable during uncontrolled pre-charging. It has been reported earlier that the reason for this is approximately constant power load on the module capacitor. This work provides theoretical understanding of the problem and shows by analysis that the power supply can be made stable if the load on the module capacitor is made a positive resistance load. As the complexity of MMC with more than two modules per arm is higher, the phenomenon is studied by simulation for MMC with four modules per arm. It shows that when a fly-back converter is used for generating the power supply, similar instability occurs in MMC with four modules per arm. It shows that when the module capacitor is made to have a load with positive resistance characteristics, the module capacitor voltages and consequently the power supplies stabilize even for MMC with four modules per arm. It further shows that even if the load on the module capacitor is negative resistance type, when fly-back converter is used to generate the module power supply, by switching devices in those modules where power supply becomes available first, followed by sorting algorithm, stable power supplies can be developed on all the modules and the capacitors can be fully charged to the desired voltage.     

Effects of a parallel resistor on electrical characteristics of a piezoelectric transformer in open-circuit transient state

This paper investigates electrical transient characteristics of a Rosen-type piezoelectric transformer (PT), including maximum voltages, time constants, energy losses and average powers, and their improvements immediately after turning OFF. A parallel resistor connected to both input terminals of the PT is needed to improve the transient characteristics. An equivalent circuit for the PT is first given. Then, an open-circuit voltage, involving a direct current (DC) component and an alternating current (AC) component, and its related energy losses are derived from the equivalent circuit with initial conditions. Moreover, an AC power control system, including a DC-to-AC resonant inverter, a control switch and electronic instruments, is constructed to determine the electrical characteristics of the OFF transient state. Furthermore, the effects of the parallel resistor on the transient characteristics at different parallel resistances are measured. The advantages of adding the parallel resistor also are discussed. From the measured results, the DC time constant is greatly decreased from 9 to 0.04 ms by a 10 k(omega) parallel resistance under open output.