固定变比为1/3的双桥臂开关电容变换器的研究

摘要：开关电容变换器一直是一个重要的研究领域。近年来,随着交流场合应用的需要,AC-AC开关电容变换器在逐渐发展,主要集中在单桥臂的研究,对于双桥臂的研究较少,尤其在高频工作过程方面还有待发展。通过对各种直流、单相交流开关电容变换器的研究,发现所研究的开关电容变换器主要集中在对单桥臂实验波形、效率和等效电阻的分析,由于双桥臂的电路结构、工作过程比单桥臂要复杂,对其暂态工作过程的研究很少,而开关电容变换器的工作过程和等效电阻的研究对设计双桥臂开关电容变换器以及提高电路的稳态特性有着重要作用。为了更好的提升电路的性能和稳态特性,对1-2升压型双桥臂开关电容变换器在低频、高频的工作过程和换向过程进行了深入研究,给出了开关电容变换器的控制驱动方式,并通过高频分析进行暂态建模得到了等效内阻的表达式。最后通过仿真对分析结果进行了验证。     

集成开关电容DC—DC变换器

本文研究了一种仅由MOSFET开关和电容以及控制电路构成的开关电容DC－DC变换器，因不含电感所以便于集成。文中讨论了采用逐压反馈控制取代PWM调节改善变换器性能的方法以及采用适当电容组合实现任意电压变比并提高效率的方法。     

基于CMOS的开关电容DC-DC降压变换器

在标准CMOS工艺的基础上,分析了基本串并电容组合开关电容DC-DC降压变换器的工作原理和集成方法.采用两个单端开关电容变换器反相并联联结,降低了输出电压波纹.利用电路内部节点电压驱动MOS开关管,避免了每个开关管都必须单独驱动.用SPICE软件对电路进行了瞬态分析,给出了分析结果.     

一种基于PWM控制方法的开关电容DC-DC变换器

本文介绍了一种新型的开关电容升压DC-DC变换器拓扑结构，并利用状态空间平均法进行了稳态分析，最后用PWM控制方法进行了仿真，仿真结果验证了理论分析的正确性。     

降压型双桥臂交流开关电容变换器研究

开关电容变换器研究主要集中在对单桥臂试验波形、效率和等效电阻的分析。随着交流场合应用需求的增加,双桥臂ACAC开关电容变换器逐渐发展。由于双桥臂的电路结构、工作过程较复杂,目前对其暂态工作过程的研究甚少。为了提升电路性能,对AC-AC开关电容变换器在低频、高频的工作过程和换向过程进行了深入研究。给出了该变换器的控制驱动方式,并对高频工作过程进行了理论分析。最后通过仿真对该变换器进行了验证。该变换器各功率开关管以及电容的电压应力研究,对于开关电容变换器在双桥臂领域的电路参数选择具有重要的参考价值。开关电容变换器的工作过程和换向规律,为双桥臂开关电容变换器的进一步研究奠定了基础。     

电容类传感器的开关-电容接口

本文介绍了一个以双斜式A/D转换技术为基础的SC(开关—电容)接口。这个接口由SC积分器、比较器和数字控制电路组成。由于它具有自动调整量程的功能,所以它的动态范围很宽。实验表明它所测电容的量程比是1:40,精度高于1％。     

直接AC-AC变换器在感应加热中的研究

在感应淬火设备优化的研究中,要求感应淬火设备在宽的频率范围内实现精确的功率控制并且具有高效率.传统的解决方案是AC-DC-AC组合,但效率低且成本高.为解决上述问题,提出一种直接AC-AC变换器,以减少元件的数量,降低成本,提高可靠性,并提高效率.提出的变换器是电压源串联谐振变换器,通过调制策略可以实现线性输出功率控制,减少控制复杂性.另外,变换器在导通和关断过程中实现软开关,进一步提高了效率.采用Saber对一个3.3kW的变换器进行了仿真,仿真结果验证了方案的可行性和预期的性能.     

基于全桥变换器滞后臂零电压开关的研究

全桥零电压变换器性能优异,相对突出的是滞后臂轻载时零电压开关问题,同时发生占空比丢失。究其原因是滞后臂开关过程中只有原边电感参与谐振。本文通过探索在滞后臂并联谐振电感及加入输出电感和续流二极管两种方法解决全桥零电压变换器滞后臂轻载时零电压开关问题。     

矿用本安电源开关变换器滤波电容消解方案

针对矿用本安电源因开关变换器滤波电容较大而导致输出电压纹波较大、本安性能较差等问题,提出采用有源电容技术消解本安电源开关变换器滤波电容的方案,对有源电容的工作原理、控制策略和数学模型进行了分析.有源电容技术通过控制内部全桥变换器,将直流母线瞬时功率差转移给非直流母线电容进行能量平衡,从而实现直流母线滤波电容容量消解.以基于Buck变换器的电源为例,介绍了有源电容技术在矿用本安电源中的应用,并通过仿真和试验验证了采用有源电容技术可以较小的电容达到输出本安要求.     

一种新型方位传感器

简述了二次谐波法磁通门磁强计的工作原理。以高导磁材料坡莫合金丝作探头铁芯 ,试制了一种以正交的双轴磁通门磁强计为基本结构的摆式航向传感器。该传感器体积小 ,分辨率高 ,精度达到 0 .2°。     

Design and performance analysis of double cantilever type capacitive shunt RF MEMS switch

This paper presents a novel structure of capacitance shunt type RF switch for 5G applications. The proposed RF MEMS switch is having Cantilever type designed with optimized dimensions to operate in V-band applications. The electromechanical analysis is done by using the COMSOL tool. The actuation voltage of the proposed switch is 10.5 V with the air gap of 1 µm and gold as a beam material. The proposed switch with the meanders and perforations show the scattering parameters in HFSS software such as insertion loss (S₁₂) of − 0.033 dB and return loss (S₁₁) less than − 48 dB and the isolation (S₂₁) calculated in off-state as − 62 dB at 50 GHz.

     

A lotus 1-2-3 based cash flow forecasting system

The role of Industrial Engineers within financial institutions has expanded significantly through the current emphasis on cash management related services. This paper discusses an automated cash flow forecasting system developed in conjunction with Citibank Panama's Cash Management Group. Features of Lotus 1-2-3 software are combined with a regression based multiplicative approach to yield an effective forecasting tool for financial treasury personnel. Development of the system is illustrated through a case study.     

A local minimum for the 2-3-1 XOR network.

It was assumed proven that two-layer feedforward neural networks with t-1 hidden nodes, when presented with t input patterns, can not have any suboptimal local minima on the error surface. In this paper, however, we shall give a counterexample to this assumption. This counterexample consists of a region of local minima with nonzero error on the error surface of a neural network with three hidden nodes when presented with four patterns (the XOR problem). We will also show that the original proof is valid only when an unusual definition of local minimum is used.     

A lotus 1-2-3 model for airline level of operations planning

In this paper a Lotus 1-2-3 model that forecasts operating statistics for an airline is presented. The Level of Operations Model is useful in long range planning because a schedule is not required to produce the forecasts. The paper lists the key formulas and required data. Successful applications of the model such as fleet planning, and pilot pay studies are discussed.     

The local minima of the error surface of the 2-2-1 XOR network

All local minima of the error surface of the 2-2-1 XOR network are described. A local minimum is defined as a point such that all points in a neighbourhood have an error value greater than or equal to the error value in that point. It is proved that the error surface of the two-layer XOR network with two hidden units has a number of regions with local minima. These regions of local minima occur for combinations of the weights from the inputs to the hidden nodes such that one or both hidden nodes are saturated for at least two patterns. However, boundary points of these regions of local minima are saddle points. It will be concluded that from each finite point in weight space a strictly decreasing path exists to a point with error zero. This also explains why experiments using higher numerical precision find less “local minima”. This revised version was published online in June 2006 with corrections to the Cover Date.     

Performance analysis of a 3-2-1 pose estimation device

This paper deals with the problem of estimating the pose of a moving rigid body by measuring the length of six wires attached to it. Since wires can be seen as extensible legs, this problem is equivalent to that of solving the forward kinematics of a six-degree-of-freedom parallel manipulator. Among all possible locations for the attachments on the moving object, the "3-2-1" configuration is shown to exhibit a large number of favorable properties. The performance analysis of this particular configuration is addressed by finding analytic expressions for the estimated pose covariance matrix and the expected value of the pose estimation error, or bias error, which has been omitted in the previous analysis of wire-based tracking devices. This analysis takes advantage of a formulation for trilateration based on Cayley-Menger determinants, which is mathematically more tractable compared to previous ones, because all terms involved are determinants with geometric meaning. This accommodates a more thorough investigation of the properties of the device.     

一种具有双层信息损失优化结构的遥感图像检索方法*

当前主流的图像检索方法在处理遥感图像时不能针对遥感图像信息丰富、特征维度高的特点,并且通过传统的特征提取方法得到的图像特征表达能力弱、信息损失严重,因此不能取得较高精度的检索结果。针对上述问题,提出具有双层信息损失优化结构的哈希编码方法用于遥感图像检索。首先,将经过傅里叶变换滤波降噪处理后的遥感图像数据输入卷积网络（Convolutional Neural Network, CNN）,通过多层卷积得到表达图像的深层特征向量;然后利用K-means算法对图像特征聚类,再在每个聚类内寻找最优的哈希函数,进而得到图像对应的二进制哈希码。最后利用汉明距离对图像进行相似性比较,完成对图像数据的有效检索。实验结果表明,对比于其他算法,本文方法提高了检索的查准率,查全率以及平均检索精度,对于遥感图像有较好的适用性。