一种双极性输出大功率压控恒流源的设计

本文介绍了一种双极性输出的大功率压控恒流源的设计方法.该恒流源采用简单的运放系统,经过电压扩展和电流扩展,可提供25V、0～2A的可调恒定电流,既达到了提供大输出电流的目的,而且电路结构简单,成本较低,精度较高.经测试该恒流源有较高哌的负载稳定度和较低的纹波.     

Polarization-stable oxide-confined VCSELs with enhanced single-mode output power via monolithically integrated inverted grating reliefs

It has been proven experimentally that the single-mode output power of vertical-cavity surface-emitting lasers (VCSELs) can be increased significantly with an inverted surface relief and that a reliable polarization control can be achieved by a monolithically integrated surface grating for even highly multimode VCSELs. In this paper, for the first time we report on a combination of these two techniques, namely, an inverted grating relief to realize VCSELs with a stable polarization and an increased single-mode output power. A statistically relevant number of monolithic, oxide-confined 850-nm VCSELs is investigated. All devices with a grating relief have a stable polarization with its orientation defined by the grating grooves. On the other hand, 64% of the reference devices exhibit polarization switches. Concurrently, the maximum single-mode output power is enhanced by more than a factor of three. Within the entire range of implemented grating parameters, the worst grating relief device still delivers higher single-mode output power than the best reference device.     

应用于高功率领域的改进型谐振直流环节逆变器

为减小位于逆变器直流环节的辅助谐振电路的损耗,提出一种新型的辅助电路与直流母线并联的谐振直流环节软开关逆变器,其直流母线上没串联辅助开关器件和谐振元件,而且辅助谐振电路中只有1个储能电容,无中性点电位的变化问题。依据不同工作模式下的等效电路图,分析电路的换流过程和设计规则,并建立起辅助谐振电路损耗的数学模型,讨论谐振参数对辅助电路损耗的影响。制作1台5 k W的实验样机,实验结果表明逆变器的工作过程符合原理分析,能实现软开关功能,而且相比于同类型软开关逆变器,效率得到了进一步提高。因为该软开关逆变器的辅助电路与直流母线并联,辅助电路损耗相对较低,所以有利于在高功率领域提高逆变器效率。     

一种高精度宽范围的大功率开关电源设计

为满足精密测量测试设备对电源高精度、高效率和高稳定的要求,设计了输出电压0～80 V、输出电流0～100 A、输出功率6 kW的开关电源。电源前级采用单相桥式半控整流滤波电路调节直流母线电压以改善电源在轻载时的输出表现,后级采用移相全桥电路实现大功率的电能变换。介绍了电源的组成结构和工作原理,详细描述了电源主电路中关键元器件的计算与选型。研制了一台样机,并进行了实验验证,实验结果表明：电源实际输出电压能够跟随设定电压,且在负载变化时仍能满足0.5%的精度要求,最高效率可达87.4%。     

Improved voltage source inverter with 18-step output waveforms

In this article, an improved voltage source inverter is proposed. This circuit is based on the NPC (neutral point clamped) inverter. By dividing the input DC source into four sections and adding four auxiliary switching elements, the proposed circuit can be performed as if an 18-step inverter as far as the harmonic components in the AC output voltages are concerned. The performances of the proposed circuit and the output AC voltage waveforms are discussed. Then the optimum conditions are determined by minimizing the distortion of the output waveform, and the effects for the harmonic reductions can be clarified by theoretical results. The ratings of circuit components, such as the separated DC sources and the switching devices, should be investigated. Moreover, we suggest the adjusting methods of the output voltages     

Laser Doppler velocimetry with polarization-bistable VCSELs

We present a rate equation model of a single mode vertical-cavity surface-emitting laser (VCSEL) with two states of linear polarization, subject to Doppler-shifted optical feedback. Recent experimental work has shown that the polarization bistability often observed in VCSELs can be exploited to enhance the responsivity of these semiconductor lasers in speed-sensing applications. We review these experimental results briefly and use the rate equation model to explain the increased signal-to-noise ratio.     

A performance comparison of full- and half-bridge series resonantinverters in high-frequency high-power applications

Load-commutated full- and half-bridge series resonant inverters are dual at lower operating frequencies where the di/dt inductance L_s has negligible effect on their performance. At higher frequencies, however, the effect of inductor L_s dominates the ratings of components, and their performance is significantly different. The difference in their performance is a function of the operating frequency and is more pronounced at higher frequencies. To study the behavior of inverters at higher frequencies, a detailed analysis is presented which includes the effect of the di/dt inductance. Finally, the performance of two inverters is compared in terms of inverter kVA rating, and the kVA rating of the compensating capacitor     

Input and intrinsic device modeling of VCSELs

An efficient model scheme that combines the non-linear behavior of the input parasitics with the intrinsic fundamental device rate equations of the Vertical Cavity Surface Emitting Lasers (VCSELs) is proposed. A systematic methodology for the model parameter extraction from dc and ac, electrical and optical measurements, is also presented and simulation results are compared with the experimental measurements. Extraction and simulation procedures are implemented in commercial integrated circuit design tools and they are proved to be very fast while they preserve adequate accuracy.     

积灰对光伏电池板输出特性影响研究

积灰对光伏电池板输出特性具有显著影响,且因地域、实验环境等因素不同存在较大差 异。为此,本文分析了不同自然积灰的粒径分布特征,分别利用黄土、红土和高岭土,构造了我国不同地域自然积灰的模拟样本;搭建了由光伏电池阵列、MPPT控制器、上位机以及光强测量仪、温度测量模块等构成的实验平台,开展了积灰对光伏电池板的伏安特性、温度、相对透光率以及输出功率影响的测量实验;基于实验数据建立了相对透光率、相对发电效率与积灰密度关系的拟合模型。结果表明:随着积灰密度的增加,光伏电池板的温度、相对透光率和相对发电效率均逐渐降低,且降低幅度与积灰类型有关;应用算例表明,所建模型可用于光伏发电功率预测以及光伏电池板积灰的清洗周期选取。     

Sensitivity of proton implanted VCSELs to electrostatic dischargepulses

The sensitivity of vertical cavity surface-emitting lasers to electrostatic discharge (ESD) pulses has been investigated under human body model test conditions. Very similar degradation behavior has been found for vertical-cavity surface-emitting lasers (VCSELs) from two different manufacturers, both with proton-implantation for lateral current confinement. For all investigated devices we observed during forward bias stress that the optical degradation precedes the electrical degradation and the forward bias damage threshold pulse amplitudes were only slightly higher than the reverse bias values. At the initial stage of the VCSEL degradation, damage of the upper p-DBR mirror region has been observed without modification of the active layer. During the ESD tests we monitored the electrical and the optical parameters of the VCSELs and measured during forward bias stress additionally the optical emission transients. The optical transients during ESD pulsing enable a fast evaluation of the damage threshold and give also an indication of the time scale of the junction heating during ESD pulses     

Improved performance MRAC of linear and non-linear systems

The problem of improved performance adaptive control (IPAC) of a class of linear and non-linear systems is considered. A method for its solution is presented, the main feature of which lies in augmenting the ‘standard’ model reference adaptive controller by a signal properly designed to compensate for the effect of plant parameter uncertainty on the output error. One of the main performance improvement characteristics of the proposed IPAC is that the zero-state output error can be made arbitrarily small under standard model reference adaptive control (MRAC) assumptions in the case of linear systems, while a similar result holds true for a class of linearizable systems as well. the structure of the proposed controller is such that several existing MRAC results, such as exponential convergence of output and parameter errors in the presence of sufficiently rich reference inputs, remain valid. the proposed controller also achieves improved performance in the presence of a class of bounded disturbances and/or unmodelled dynamics as well as in the case of an adaptation switch-off.     

抗磁悬浮能量采集器结构参数对输出特性影响

对微型振动抗磁悬浮能量采集器各个结构的参数进行分析,研究其变化对能量采集器的输出特性的影响。提升永磁体的尺寸的变化对悬浮永磁体的平衡位置影响很大,但对系统固有频率和输出电压影响很小。悬浮永磁体尺寸变化对平衡位置没有影响,但对系统的固有频率和输出电压影响很大。热解石墨材料的尺寸变化对于抗磁力的影响有一个边界值,超出边界值时抗磁力不随尺寸变化而变化。并通过COMSOL软件进行电压仿真,得到的最大输出电压为6.15 m V,系统工作的频率范围为2.2~10.3 Hz。     

Snubberless high-power rectifiers

Usually, a snubber circuit is put in parallel with a power diode to avoid the occurrence of destructive overvoltages during turn-off. Power rectifiers that do not need a snubber are described. Using numerical simulations from the computer program COMPASS (computer program for the analysis of semiconductors), it is shown that such snubberless rectifiers can be made by controlling the axial carrier lifetime profile in the rectifier. It is possible to choose this profile in such a way that the forward characteristic of the rectifier is not impaired. The absence of a snubber circuit also leads to major electrical improvements. In the snubberless case, the total current switches more than three times faster than in the case of a normal diode with a snubber circuit, and the reverse current peak of the total current is reduced by 33%. The total dissipated power per switching process in the snubberless case is less than half the power dissipated in the normal case     

基于实时数据的风力发电机组性能在线评价

在分析常规风电机组出力特性评价方法的基础上,探讨了评价过程中存在的诸多问题。介绍了一种通过实时/历史数据库获取风电场相关生产数据,并将所得数据换算成标准条件下的环境工况值,进行实时在线计算。通过自动绘制风电机组风速-电功率的特性曲线,结合标定的额定设计值,对实际运行结果数据进行离散度偏差比较,从而实时监测和评价风电机组在某段时间内和当前时期内的运行性能。     

涡旋膨胀机润滑系统设计及输出性能实验研究

为了研究涡旋膨胀机输出性能规律,将某商用涡旋压缩机改造成涡旋膨胀机,并对其润滑系统进行了设计和精确控制;基于此,搭建了以压缩空气作为工质的测试实验台,对比了膨胀机在有无润滑条件下的性能,并对膨胀机的性能进行了全面的测试.结果 表明:润滑系统在机械润滑和膨胀机性能方面都起到良好的效果;在实验工况范围内,膨胀机等熵效率均保...     

Design and analysis of single-mode oxidized VCSELs for high-speedoptical interconnects

Oxide-confined vertical-cavity surface-emitting laser diodes (VCSELs) are fabricated for applications in high-performance optical interconnects. Both 980-nm as well as 850-nm wavelength devices in one- and two-dimensional arrays are investigated. Noise properties of single- and multimode devices under different operation conditions are relative intensity noise of single-mode devices can be as low as -150 dB/Hz at output powers of about 1 mW and feedback levels up to -30 dB. Data rates up to 12.5 Gb/s with bit error rates below 10^-11 are achieved with VCSELs showing stable single-mode emission at large-signal modulation, combined with modulation bandwidths exceeding 10 GHz. Arrays with 4×8 elements flip-chip mounted on Si CMOS driver chips ready for use in parallel data transmission systems are presented     

1.55-μm InP-lattice-matched VCSELs with AlGaAsSb-AlAsSb DBRs

We review the design, fabrication, and characterization of 1.55-μm lattice-matched vertical-cavity surface-emitting lasers, operating continuous wave up to 88°C. For one embodiment, the threshold current is 800 μA, the differential quantum efficiency is 23%, and the maximum output power is more than 1 mW at 20°C and 110 μW at 80°C. The basic structure consists of AlAsSb-AlGaAsSb mirrors, which provide both high reflectivity and an InP-lattice-matched structure. The quaternary mirrors have poor electrical and thermal conductivities, which can raise the device temperature. However, a double-intracavity-contacted structure along with thick n-type InP cladding layers circumvents these drawbacks and finally leads to an excellent performance. The measured voltage and thermal impedances are much lower for the intracavity-contacted device than an air-post structure in which current is injected through the Sb-based quaternary mirror. The structure utilizes an undercut aperture for current and optical confinement. The aperture reduces scattering loss at the etched mirror and contributes to high differential efficiency and low threshold current density     

Temperature-Dependent Small-Signal Analysis of High-Speed High-Temperature Stable 980-nm VCSELs

980-nm VCSELs based on submonolayer growth show for 20-Gbit/s large-signal modulation clearly open eyes without adjustment of the driving conditions between 25 $^{circ}$ C and 120 $^{circ}$C. To access the limiting mechanism for the modulation bandwidth, a temperature-dependent small-signal analysis is carried out on these devices. Single-mode devices are limited by damping, whereas multimode devices are limited by thermal effects, preventing higher photon densities in the cavity.