光照入射角对太阳能电池输出功率的影响

为了研究在自然条件下,光照入射角对太阳能电池实际输出功率的影响,对单晶硅、多晶硅和非晶硅太阳能电池进行了不同倾角和方位角的测试实验,得到了太阳能电池转换效率关于倾角和方位角的对应关系,并用转换效率的变化曲线分析和说明光照入射角对太阳能电池输出功率的影响.     

D类音频功放研究

与传统音频功放相比,D类音频功放具有不同的拓扑结构,它工作在开关状态,主要由调制器、开关放大器和LC低通滤波器三个部分组成,具有高效率、低功耗、失真小的特点,克服了传统功放的缺陷,成为音频功放发展的方向。     

胆机功放的测量与常见故障

1胆机功放的测量1)测量功放管的屏极电压如图1中①所示,测量输出变压器初级绕组中心抽头与地之间的直流电压,一般不直接测量功放管屏极与地之间的电压,这是为了防止直接测量时产生高频振荡损坏万用电表。2)测量功放管的帘栅压如图1中①所示,直接测量帘栅极与地之间的直流电压。如用6P3P功放管作甲乙1类推挽放大,帘栅压在280～330 V之间,栅负压一般在25 V左右,如果屏压高于400 V     

光伏发电系统输出功率预测分析

本文主要提出了建立在马尔科夫链基础之上的光伏发电系统输出功率预测的方式,通过数据建模的方式,将光伏电站的出力进行直接预测。通过理论推测,从而证实该方式在预测光伏发电系统输出具有可行性。以某光伏中心电站作为案例进行建模预测,从而证实该方式的有效性,并对模型参数进行调整,从而提高结果的精确性。     

KT88并联单端甲类功放的制作

1制作目的采用低电压、大电流并联单端甲类推动方式,即能增强对音箱的驱动力,在不减少偶次谐波的情况下,确保电子管甲类放大状态下的温柔、甜美的味道,以解决单端甲类胆机功率小,成本高的问题。2使用器材KT884只,6N8P、6N9P各2只,5Z3P1只,400W     

功放技术参数的分析

艺术团体经常进行巡回演出,音响器材尤其是功率放大器要经过火车、汽车运输,各种地形复杂的道路会带来振动,所以要求功率放大器结构非常结实、抗振特性良好、设计科学、加工工艺精细。在不同城市、乡镇进行的文艺演出还会遇到各种意想不到的复杂情     

基于D类功放的声呐发射机驱动信号分析

针对声呐发射机对功放电路提出的大输出功率、输出功率可调以及谐波能量小的需求,提出了一种改良的脉冲宽度调制方法.该方法选用中心宽脉冲,两边对称分布两个窄脉冲的半周期三脉冲信号形式,得到了宽窄脉冲间的比例关系,最后通过计算找到了最优的脉冲间距.MATLAB仿真以及水池声呐实验表明,该方法在基波能量的整个变化过程中,3次与5次谐波能量最大不超过基波能量最大处的2%.     

D类功放中数字调制器的研究与实现

数字脉冲宽度调制(Digital Pulse Width Modulation,DPWM)结构简单、稳定性好,是主动声呐D类功放中常用的调制技术,但是它会产生信号失真和电磁干扰问题。针对主动声呐中D类功放的要求,设计了一种新的1.5bitΣ-Δ调制器。该调制器不仅能够改善DPWM存在的信号失真和电磁干扰问题,而且能够解决常规Σ-Δ调制器存在的高开关频率导致的高开关损耗问题。采用现场可编程逻辑门阵列(FPGA)对该调制器进行实现,在全桥D类功放上进行了实验验证。通过1.5bitΣ-Δ调制器和DPWM性能对比,表明该1.5bitΣ-Δ调制器适合主动声呐D类功放的应用。     

D类功放在便携式设备中的应用

采用D类放大器可延长电池供电终端产品的工作时间,并产生更少的热量,因此高效率D类音频功率放大器正越来越多地被用在移动电话、智能电话,PDA及其他类似便携式应用中,以取代AB类放大器.简单陈述D类功放的构成及原理,并以TI公司的芯片TPA2012D2为例,着重介绍该芯片在便携式媒体播放器(PMP)中的应用实例.该例在实际应用中得到较好的音频播放表现.     

D类音频功率放大器的关键技术

随着移动音频设备的迅速发展,传统的模拟线性放大器已不能满足大功率输出同时发热量少的要求,而D类放大器能克服以上缺点,但其引入的失真通常大于线性放大器,研究适合的控制方法以改善D类放大器的保真度,是近年来声学技术和音频功率放大领域研究的热点。本文除了介绍D类放大器的基本原理之外,还着重分析了几种新型的关键控制技术以及元器件选择、电磁兼容、电路板布局方面需要重视的一些问题。     

30MHz-512MHz宽带功率放大器的研制

功率放大器是射频前端中的关键部件，宽带是目前功率放大器的主要发展趋势。根据宽带功率放大器的设计原理，采用推挽结构晶体管，前馈线性化技术，传输线变压器和微带混和匹配电路，利用ADS进行仿真设计，成功的设计出一款宽带功率放大器。实现了多倍频程带宽、确保带内增益平坦、驻波小、线性范围和动态范围大。通过仿真和测试，得到较为理想的结果。     

Analysis of a class E power amplifier with series-parallel resonator

The authors propose new class E power amplifier configuration with an equivalent series-parallel resonator network. The boundary conditions for the 100% efficiency operations are analysed under the conditions that the duty ratio is 0.5 and the loaded quality factor is infinite. If the DC supply voltage and the output power are assumed the same, the load resistance R is 53.65% higher, the excess series inductance L/sub x/is 3.99% lower and the maximum frequency f/sub max/is improved by 6.47% compared with the conventional class E amplifier. The theoretical analysis is verified by numerical results and harmonic balance simulations. And a lumped element test board is built and measured at 200 MHz utilising a Lateral Double Diffused Metal Oxide Semiconductor (LDMOS) transistor MRF21010 as the switching device. An output power of 33.03 dBm, a drain efficiency of 85.6% and a gain of 16 dB are measured. The approximate transmission-line topology with harmonics suppression is also proposed.     

Design and development of high voltage high power operational amplifier using thick film technology

Applications of power operational amplifiers (opamps) are increasing day by day in the industry as they are used in audio amplifiers, Piezo transducer systems and the electron deflection systems. Power operational amplifiers have all the features of a general purpose opamp except the additional power handling capability. The power handling feature can be achieved using an external circuitry around a regular opamp. Normally power opamps can deliver current more than 50 mA and can operate on the supply voltage more than ±25 V. This paper gives the details of one of the power opamps developed to drive the Piezo Actuators for Active Vibration Control (AVC) of aircraft/aerospace structures. The designed power opamp will work on ±200 V supply voltage and can deliver 200 mA current.     

反射式光纤传感器光纤对输出特性的数学模型

从反我纤传感器中最基本的光纤对入手，以光度学原理为基础，建立了该传感器在镜反射时的输出特性数学模型。在此模型的基础上，利用计算机给出了光纤传感器输出特性的仿真结果并进一步讨论了输出特性与各参数之间的关系。     

Nonlinear Systems Identification via an Input-Output Model Based on a Feedforward Neural Network

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A re-parameterisation of the Power Model of the relationship between the speed of traffic and the number of accidents and accident victims

This paper presents a re-analysis of the Power Model of the relationship between the mean speed of traffic and road safety. Past evaluations of the model, most recently in 2009, have broadly speaking supported it. However, the most recent evaluation of the model indicated that the relationship between speed and road safety depends not only on the relative change in speed, as suggested by the Power Model, but also on initial speed. This implies that the exponent describing, for example, a 25% reduction in speed will not be the same when speed changes from 100 km/h to 75 km/h as it will when speed changes from 20 km/h to 15 km/h. This paper reports an analysis leading to a re-parameterisation of the Power Model in terms of continuously varying exponents which depend on initial speed. The re-parameterisation was accomplished by fitting exponential functions to data points in which changes in speed and accidents were sorted in groups of 10 km/h according to initial speed, starting with data points referring to the highest initial speeds. The exponential functions fitted the data extremely well and imply that the effect on accidents of a given relative change in speed is largest when initial speed is highest.     

微通道板的输出信噪比特性研究

阐述了微通道板(MCP)输出信噪比的概念内涵,提出了MCP输出信噪比测试的具体实现方法。设计了MCP噪声特性分析系统,该系统由真空系统、电子枪组件、高压电源系统、信号处理模块、数据采集和控制模块、计算机和测试软件等部件组成。利用热阴极组成面电子源,产生的面电子流作为输入信号,采用硬件滤波和软件数字滤波相结合的方法对MCP的输出电子流信号进行了处理,实现了MCP输出信噪比测试。利用该系统在不同测试条件下对MCP的输出信噪比进行了测试,并对测试结果进行了分析。     

Increasing flow efficiency of high-pressure and low-pressure steam turbine stages from numerical optimization of 3D blading

3D blading of a high-pressure and low-pressure steam turbine stage is optimized using Nelder–Mead method of deformed polyhedron. Values of the minimized objective function, i.e. stage losses with the exit energy are found from 3D viscous compressible flow computations, including turbulence effects. Among the optimized parameters are stator and rotor blade numbers and stagger angles, rotor blade twist angle, stator blade sweep and lean, both straight and compound. The blade sections (profiles) are assumed not to change during the optimization. There are constraints imposed on the design parameters, including the mass flow rate and stage reaction. Optimization gives designs with new 3D blade stacking lines, and with increased efficiencies, compared with the original design.     

外腔式半导体激光器的输出光谱

用射线法导出了两段式激光器的输出谱公式，分析了外腔式半导体激光器的输出光谱，计算了ＥＣＬＤ被调二极管模式的不同波长处振时的阈值，获得了ＥＣＬＤ模式的波长表达式，讨论了二极管靠近光栅的一面的反射率的波长特性对输出的影响。