不同激光二极管能量触发下GaAs 光导开关研究

GaAs 光导开关在较高的场强下可工作于雪崩模式,为此设计了异面体结构的GaAs 光导开关以提高开关场强。 设计的开关芯片厚度为2mm,电极间隙为3mm,利用半导体激光二极管对开关进行了触发实验。当开关充电电压超过 8kV 后,开关输出脉冲幅度显著增强,输出脉冲前沿快于光脉冲,开关开始了雪崩工作模式,且随着开关电场不断增加, 开关输出电压幅值也线性增加。在不同触发能量下,开关输出电压幅值和波形基本没有改变,但在较高的触发能量和高 的偏置电场下,开关抖动较小,实验中开关获得的最小抖动约500ps。     

半导体激光二极管触发GaAs光导开关

半导体激光二极管触发下砷化镓（GaAs）光导开关工作于雪崩模式,为此设计了异面体结构的GaAs 光导开关以提高开关场强.设计的开关芯片厚度为2 mm,电极间隙为3 mm,利用半导体激光二极管对开关进行触发实验.当开关充电电压超过8 kV 后,开关输出脉冲幅度显著增强,输出脉冲前沿快于光脉冲,开关开始雪崩工作模式.随着开关电场不断增加,开关输出电压幅值也线性增加,但开关输出波形没有改变.对开关抖动进行测试,其测试结果显示开关偏压对抖动影响很大,随着开关偏压增加,开关抖动减小,当开关偏压升至15 kV 时,开关获得最小抖动约500 ps.     

触发光脉冲对光电导开关响应速度的影响

实验测试了触发光脉冲对光电导开关响应速度的影响;建立了满足光导开关触发光脉冲参量的光生载流子速率方程,并模拟出光生载流子浓度随触发光脉冲、脉冲宽度的变化规律,分析了光脉冲对光电导开关响应速度的影响及引起输出电脉冲上升沿变化的原因.     

用1064nm激光脉冲触发半绝缘GaAs光电导开关的奇特光电导现象

报道了用1064nm激光脉冲触发半绝缘GaAs光电导开关的一种奇特光电导现象.GaAs光电导开关的电极间隙为4mm,当偏置电场分别为2.0和6.0kV/cm时,用脉冲能量为0.8mJ,宽度为5ns的激光触发开关,观察到开关输出的线性和非线性工作模式.当偏置电场增至9.5kV/cm,触发光脉冲能量在0.5～1.0mJ范围时,观察到奇特的光电导现象,开关先输出一个线性电脉冲,经过大约20～250ns时间延迟后,触发光脉冲消失,开关又输出一个非线性电脉冲.这一奇特光电导现象的物理机制与半绝缘GaAs中的反位缺陷和吸收机制有关.分析计算了线性与非线性电脉冲之间的延迟时间,结果与实验观察基本吻合.     

激光触发光导开关产生超短电磁脉冲的实验研究

本文介绍了用光导开关和微带线结构产生电脉冲的实验装置,研究了激光能量和偏置电压对光导开关输出超短电脉冲的影响和三种尺寸光导开关的特性,测得了一种低掺杂Cr:GaAs材料的载流子寿命约为1.8ns,显示了这种装置用作高速光探测器的可能性。     

激光触发光导开关产生超短电磁脉冲的实验研究

本文介绍了用光导开关和微带线结构产生电脉冲的实验装置，研究了激光能量和偏置电压对光导开关输出超短电脉冲的影响和三种尺寸光导开关的特性，测得了一种低掺杂Ｃｒ：ＧａＡｓ材料的载流子寿命约为１．８ｎｓ，显示了这种装置用作高速光探测器的可能性。     

基于光导开关和平板线的固态脉冲功率技术

紧凑型固态化是脉冲功率技术发展的趋势,研究了基于 GaAs光导开关和陶瓷平板传输线的固态脉冲功率技术。紧凑型固态脉冲功率系统的关键部件主要包括固态陶瓷平板传输线,高功率 GaAs光导开关以及激光二极管触发系统。研究了单路 Blumlein脉冲形成线输出特性,分析了 GaAs光导开关非线性导通带来的损伤,并开展了单路 Blumlein脉冲形成线实验。结果表明：研制基于固态平板传输线、光导开关以及激光二极管触发系统的紧凑型脉冲功率具有可行性,负载上获得了超过20 kV的高压脉冲输出。     

介质壁加速器用GaAs光导开关的通态电阻测量

GaAs光导开关可作为紧凑型脉冲功率系统的主要器件,如光导开关在介质壁加速器中的应用。为了研究通态电阻对开关性能的影响,采用平板传输线和同轴电缆作为脉冲形成线,测量了3mm电极间隙的GaAs光导开关的通态电阻。测量结果表明：电极间隙为3mm的GaAs光导开关的通态电阻为14．9Ω,光导开关通态电阻的存在将导致开关热损伤,降低脉冲功率系统的电压输出能力,缩短GaAs光导开关的使用寿命。     

雪崩模式下的体结构GaAs光导开关

利用能量较低的脉冲激光二极管,在较高场强下触发GaAs光导开关,使其工作于雪崩模式,从而产生纳秒上升前沿的快脉冲电压。GaAs光导开关采用垂直体结构设计,芯片厚度为2 mm,电极形状分别为圆环和圆面,触发光脉冲从圆环穿过。快脉冲产生由同轴Blumlein脉冲形成线完成。对基于GaAs光导开关的同轴Blumlein脉冲线进行了模拟仿真和实验,当充电电压超过8 kV(40 kV/cm)后,开关开始了雪崩工作模式。当充电电压约为15 kV(75 kV/cm)时,在50 Ω负载上获得了约11 kV的脉冲电压,实验波形与仿真波形一致。对开关抖动进行了测试,其测试结果显示开关充电电压对抖动影响很大,随着开关偏压增加,开关抖动减小,开关获得了最小抖动约700 ps。     

基于GaAs光导开关的纳秒脉冲源设计

以高密度聚乙烯介质平板型B线为储能器件,设计了一台层叠Blumlein传输线型脉冲功率源。以GaAs PCSS为开关,通过4级B线层叠结构实现电压倍增。单级B线阻抗25Ω,时间常数2.5 ns,功率源总阻抗100Ω。Pspice模拟表明:随着开关导通电阻上升,输出电压脉冲幅度下降,脉宽增大;随着开关转换时间增长,输出脉冲延迟时间上升,前、后沿时间增长。采用波长为1 064 nm,能量为30 mJ,脉宽为5 ns的Nd:YAG激光器触发光导开关,当充电25 kV时,负载上得到电压38 kV,上升沿1.4 ns,脉冲约5 ns的近似方波输出。     

Digital Control of Single-Phase Power Factor Preregulators Based on Current and Voltage Sensing at Switch Terminals

This paper proposes a fully digital control of boost power factor preregulators (PFPs) with input voltage estimation that is suitable for smart-power integration. The proposed solution features a minimum pin count by avoiding input voltage sensing for the generation of the internal current reference and by sensing the output voltage through the direct sampling of the voltage across the power switch during its off interval at the line voltage peak. The control algorithm requires the estimation of the rectified input voltage, that is simply done by exploiting the integral part of the current loop proportional–integral regulator, and a phase-looked-loop (PLL) synchronization with the estimated line frequency for sampling the output voltage and rejecting the low-frequency output voltage ripple. The provisions needed to ensure correct output voltage sensing, even during transient and light-load conditions, are also discussed. Experimental results on a single-phase boost PFP show the properties of the proposed approach.     

AOT控制的降压型转换器的稳定性分析

为了保证自适应导通时间控制的降压型转换器能在输入电压全范围内正常工作,通过理论分析和时域推导,研究了输出电容的ESR对系统稳定性的影响。结果表明,只有ESR足够大,才能保证其电压变化率大于输出电容电压变化率,从而保证系统的稳定。此外,建立了ESR的最小临界值与输入电压之间的数学模型,并揭示了二者存在反比例关系。不同ESR条件下的输入电压扰动时域仿真结果说明了ESR对系统稳定的重要性。通过比较理论数学模型的拟合曲线与实际仿真结果,验证了理论分析和数学模型的正确性。     

An accurate approach of nonlinearity compensation for VSI inverter output voltage

An accurate nonlinearity compensation technique for voltage source inverter (VSI) inverters is presented in this paper. Because of the nonlinearity introduced by the dead time, turn-on/off delay, snubber circuit and voltage drop across power devices, the output voltage of VSI inverters is distorted seriously in the low output voltage region. This distortion influences the output torque of IM motors for constant V/f drives. The nonlinearity of the inverter also causes 5th and 7th harmonic distortion in the line current when the distributed energy system operates in the grid-connected mode, i.e., when the distributed energy system is parallel to a large power system through the VSI inverter. Therefore, the exact compensation of this nonlinearity in the VSI inverter over the entire range of output voltage is desirable. In this paper, the nonlinearity of VSI inverter output voltage and the harmonic distortion in the line current are analyzed based on an open-loop system and a L-R load. By minimizing the harmonic component of the current in a d-axis and q-axis synchronous rotating reference frame, the exact compensation factor was obtained. Simulations and experimental results in the low frequency and low output voltage region are presented.     

热电堆型激光功率计设计与仿真

针对紫外、可见、红外等激光器输出功率测试需求,提出一种由传热体、吸收层、绝缘层和热电偶构成的热电堆型激光功率计.结合热效应和塞贝克效应理论,采用Solidworks三维设计软件构建不同关键结构尺寸的模型,通过ANSYS Workbench仿真软件建立了热电耦合仿真分析模型,分析关键结构尺寸参数对输出电压以及温度分布的影...     

The effect of parasitic charge on the output stability of MEMS gyroscopes

Output voltage drifting was observed in MEMS gyroscopes.Other than the quadrature error,frequency mismatch and quality factor,the dielectric parasitic charge was thought to be a major determinant.We studied the mechanism and variation of the parasitic charge in the MEMS gyroscopes,and analyzed the effect of the parasitic charge on the output stability.This phenomenon was extremely obvious in the Pyrex encapsulated MEMS gyroscopes.Due to the DC voltage required for the electrostatic actuation,the parasitic charge in the dielectric layer would accumulate and induce a residual voltage.This voltage had an impact on the resonant frequency of the gyroscopes,so as to affect the output stability.The theoretical studies were also confirmed by our experimental results.It was shown that the parasitic charge was harmful to the output stability of MEMS gyroscopes.     

MOPA结构准分子激光电源的高精度电压控制研究

为了减小激光器双腔放电时间的相对抖动、稳定激光器输出能量,采用闭环控制回路电压泄放方法,设计了一套主振荡功率放大结构准分子激光谐振充电高精度电压控制方案。通过对电容电压取样处理,动态监测储能电容电压,当电容电压大于目标电压时,由泄放电路泄放电压至目标值,得到高精度的充电电压,使用此电压控制方案后,充电电压的波动由1.67减小到0.83。结果表明,该方案很好地提高了谐振电源储能电容上的电压精度,减小了激光器双腔放电时间的相对抖动,并为后期的激光器能量输出稳定控制打下良好基础。     

Improved three-phase high-quality rectifier with line-commutated switches

The paper presents a three-phase diode rectifier with an add-on simple cell with line-frequency commutated ac switches that is able to greatly improve both power factor and output voltage regulation of rectifiers with passive L-C filters. The boost action introduced by the commutation cell allows for a complete compensation of the voltage drop across the input inductors, so as output voltage regulation can be maintained from no-load to full-load. Moreover, as compared to other line-frequency commutated rectifiers, the proposed circuit allows compliance with the low-frequency harmonic limits defined in the technical report IEC 61000-3-4 for any power range. High-efficiency and minimum EMI are obtained due to the low-frequency commutations. A converter prototype was built and tested. The results confirm the theoretical analysis.     

Performance of field-induced directional coupler switches

Switching in a GaAs field-induced, three-waveguide straight directional coupler is studied theoretically. This device can be tuned externally by changing the voltage across the waveguides. Because of this tunability, the device has some very attractive features as a switching element. The performance change due to variations in the device parameters such as length, waveguide separation, waveguide width, and wavelength of operation is numerically computed. The effect of material absorption, input and output coupling, and asymmetric excitation are included in the performance evaluation. For a device length of 1400 μm, a crosstalk of -34 dB and a power transfer efficiency of -2 dB is predicted, while for the same device size a two-guide directional coupler is predicted a crosstalk of -13.4 dB. The device has a 400 nm voltage tunable bandwidth with a maximum crosstalk penalty of 3 dB     

Flexible and low cost design for a flyback AC/DC converter with harmonic current correction

This study presents a new simple flyback ac/dc converter with harmonic current correction and fast output voltage regulation. In the proposed ac/dc converter, an extra winding wound in the transformer provides two key advantages. The size of the bulk inductor used in the conventional boost-based power factor correction cell can be significantly reduced in the proposed converter. The voltage across bulk capacitor can be held under 450V by tuning the transformer winding ratio even though the converter operates in a wide range of input voltages (90 V/spl sim/265V/ac). This new converter complies with IEC 61000-3-2 under the load range of 200 W, and can achieve fast output voltage regulation.     

Modeling and Small-Signal Analysis of a Switch-Mode Rectifier With Single-Loop Current Sensorless Control

The conventional multiloop control with one inner current loop and one outer voltage loop is often applied to a single-phase boost-type switch-mode rectifier where the output of the voltage loop is a current amplitude signal. In the duty phase control (DPC) proposed recently, the output of the voltage loop is a phase signal used to generate the switching signals without current loop and sensing current. To improve the clamped current waveform of DPC, a single-loop current sensorless control (SLCSC) with some nominal parameters had also been proposed to compensate for the voltage drops across the switch, diodes, and inductor resistance. In this paper, the effect of the differences between nominal and real circuit parameters on the input current waveforms of SLCSC are addressed in detail. The results are helpful in the design of SLCSC. From the simulated and experimental results, we can find that the output voltage is well regulated by the only voltage loop and the input current harmonics are significantly improved.