Optimum design of a high-power, high-frequency transformer

A procedure for optimum design of a high-power, high-frequency transformer is presented. The procedure is based on both electrical and thermal processes in the power transformer and identifies: (a) the VA-rating of ferrite cores in relation to the operating frequency; (b) the optimum flux density in the core; and (c) the optimum current densities of the windings providing maximum transformer efficiency. Since the transformer is the major contributor to the volume and weight of the power supply, the results of transformer analysis can be used for entire power supply optimization as well. Two high-power, high-frequency transformers are optimally designed, built, and tested. Practical results show good agreement with the theory     

高频反激变压器绕组模型优化设计

反激变换器中高频变压器是核心部件,其效率直接关系到变换器的效率,因此优化设计高频变压器就成为提高效率的关键。通过对反激变压器绕组采用不同结构时所带来不同的涡流损耗和漏感进行分析,得到本文所设计绕组结构二维模型。利用有限元分析软件进行数值仿真,获得的数据证明此模型是可行的。制作出实验样机对其进行实验比较,验证了所设计的高频变压器绕组结构合理,漏感小,效率高,输出的电压的谐波含量低。     

Analysis and design of a parallel resonant converter including theeffect of a high-frequency transformer

A high-frequency (HF)-link DC-DC parallel resonant converter (PRC) operating above resonance is analyzed using the state-space approach. The analysis includes the effect of the leakage and magnetizing inductances of the high-frequency transformer. Steady-state solutions are derived and used to obtain the design curves. A method of obtaining an optimum operating point under certain constraints is developed and used as the basis of a simple design procedure. The analysis shows that including an HF transformer introduces a new mode of operation in between the two general steady-state modes. Experimental results obtained with a MOSFET-based PRC for three different transformer turns ratios are presented to support the theory. Efficiencies of about 89% were obtained for 985 W, 115 V, and 230 V output converters, whereas an efficiency of about 86% was obtained for a 15 V, 63 A converter. It was observed that the introduction of the transformer considerably affected the performance, especially in the case of low output voltage and large load current converters     

A novel approach for minimizing high-frequency transformer copperlosses

A graphical and numerical method of calculating and minimizing losses in windings, that generalizes previous findings, has been introduced. Using electromagnetic theory and MMF diagrams in both space and time a method is proposed that provides insight into the mechanism of skin and proximity effect losses and that also yields quantitative results. Using this method, several winding geometries for various topologies are covered. The analysis and optimization process is experimentally verified using an interleaved flyback transformer. The mathematical treatment justifying the use of the field method and which is essential in arriving at any numerical result is presented are more general equations for the calculation of copper losses are derived. The relation between the fields in the transformer and copper losses is emphasized. Also, the tools necessary to derive optimization diagrams are provided     

Design of a high-frequency planar power transformer in multilayertechnology

A high-frequency power transformer using multilayer printed circuit board (ML-PCB) technology is presented for applications in switched-mode power supplies operating at frequencies up to several megahertz. The mechanical configuration of laboratory prototypes is discussed, as well as the electrical, parasitic, and thermal behavior. The focus is on the leakage inductance, since the analysis of other aspects is relatively simple. Test results show that the transformer has high efficiency, low leakage inductance, good thermal behavior, and good line insulation properties. The topology enables the designer to make a trade-off between leakage inductance and interwinding capacitance. Due to the well-defined geometry, parasitic interwinding capacitance and leakage inductance are reproducible and can be computed relatively easily     

高频变压器绕组涡流损耗等效因子分析

针对平面磁性元件,利用Dowell模型和有限元方法对绕组涡流损耗等效因子Δ进行研究。分别对单股、多股圆导线和其等截面积正方形导线进行仿真分析,得到当圆导线直径为2~6个集肤深度时,涡流损耗减小显著;当圆导线直径大于6个集肤深度时,涡流损耗趋于平稳。圆导线直径为2~6个集肤深度时,等效因子的值较为理想;圆导线直径大于6个集肤深度时,其值偏低。为了提高设计的精确性应尽量选择直径少于6个集肤深度的圆导线。     

基于ANSYS的高频高压变压器的漏感研究

大功率高频高压变压器作为静电除尘高频电源系统的关键部分之一,其分布参数不仅直接影响系统特性,也是设计LCC串并联谐振电路的关键.为了准确计算出变压器漏感数值,本文首先对静电除尘用72kV/85kW高频高压变压器进行建模并利用有限元分析软件ANSYS对其三维磁场进行仿真,然后利用能量公式计算出其漏感数值,最后通过与实际测量数值进行比对,证明了有限元仿真方法的可行性.     

反激式变压器设计方法的改进

分析了单端反激式开关电源变压器的能量转换过程,提出了一种连续导通模式下反激式变压器的改进设计方法,给出了关键参数的推导过程。该方法简化了反激式变压器的设计步骤,提高了设计效率。大量实践表明该设计方法的可行性与准确性。     

光纤电子式电流互感器的优化设计

新型光纤数字化电子式电流互感器(ECT)是在普通ECT的基础上改进其存在的一些不足,使之精度更高,功耗更低,功能更完善,适用于数字化变电站的要求.文章首先介绍了新型光纤数字化ECT的总体设计,然后分别介绍了组成新型数字化ECT的高压侧数据采集器和低压侧合并单元(MU),最后介绍了新型数字化ECT的供能方案.     

基于有限元法的高频开关电源变压器绕组损耗分析

应用有限元法对高频开关电源变压器绕组损耗进行分析,分别对单股粗导线构成的绕组和由多股细导线并绕构成的绕组进行仿真,得到其绝缘损耗、磁滞损耗、欧姆损耗以及能量分布等参数。仿真结果表明,虽然单股粗导线构成的绕组绝缘损耗较小,但是其磁滞损耗和欧姆损耗比由多股细导线并绕构成的绕组要大得多,导致整体绕组损耗要大于由多股细导线并绕构成的绕组。所以用多股细导线并绕来代替单股的粗导线,可以有效地减小高频变压器绕组损耗。     

环氧浇注高压电子变压器的绝缘设计

为了提高高压电子变压器的绝缘性能,变压器高压绕组宜采用心式、单线包结构形式,用环氧树脂进行浇注,在实际应用中,浇注厚度是理论值的1／3-1／4。同时为避免出现爬电或飞弧现象,在良好室内环境条件下,外绝缘距离的设计一般为400V／mm。然后再通过提高浇注工艺水平和调整固化方法以提高变压器绕组抗开裂性和降低局部放电,使变压器的绝缘性能达到要求,变压器能够安全、稳定、可靠地运行。     

Optimized design of parallel carry-select adders

In this paper, a novel gate-level strategy for designing Carry-Select adders is proposed. The strategy is more general than the previously proposed techniques, and accounts for the dependence of multiplexer delay on its fan-out. Moreover the strategy is simple and systematic, and is helpful for designing Carry-Select adders with a pencil-and-paper approach. An approximate expression of the minimum delay achievable is derived to estimate performance before carrying out the design.The proposed strategy is validated in more than 1000 adders. Analysis confirms that the strategy leads to a delay which is minimal in most cases, and always within 5.7%.     

多波长光交叉连接节点的优化设计

在WDM光网络中，光交叉连接（OXC）节点的串扰是限制网络规模的关键因素，提高光开关的隔离度是降低OXC串扰的一条途径，文章比较了3种不同结构的光开关矩阵的串扰特性，在此基础上对OXC节点进行了优化设计，改进后的OXC节点的串扰性能大的改善，网络规模也因此而得到了极大地扩展。     

Optimal air-gap design in high-frequency foil windings

High-frequency AC losses are normally induced in transformer and inductor windings due to skin, proximity, fringing and other AC effects. In addition, the winding structure greatly affects the distribution of losses within the windings. Air gaps are usually placed in the core of magnetic devices to support the high magnetomotive force (MMF). Fringing fields can cause additional AC winding losses, and care must be taken to minimize these losses. In this paper, the effect of air-gap design on the induced losses is investigated. In particular, three air-gap designs-lumped, discretely distributed and uniformly distributed-are investigated and evaluated. Both one-dimensional (1-D) and finite-element analyses (FEAs) are used to investigate the different design structures     

A novel soft-switching high-frequency transformer isolated three-phase AC-to-DC converter with low harmonic distortion

A high-frequency transformer isolated, fixed-frequency, 3-/spl phi/ single-stage ac-to-dc converter using a boost-integrated bridge converter that employs a new gating scheme is proposed. This converter enjoys natural power factor correction with low line current harmonic distortion and symmetric high frequency voltage and current waveforms while ensuring zero-voltage switching for all the switches for a wide variation in load and line voltage. Various operating modes of the converter are presented and analyzed. Based on the analysis, design curves are obtained and an optimum design is given. A design example is presented. Results obtained from SPICE simulation and a 500 W output experimental prototype are given to verify the performance of the proposed converter for varying load as well as line voltage.     

Analysis and design of a low-voltage high-frequency LDMOStransistor

For a low voltage lateral double-diffused MOS (LDMOS) transistor, the output performance has been improved in terms of f_MAX. This is done by decreasing the output capacitance and thus decreasing the total output conductance. Extraction of the model parameters has been made and the most efficient parameter to improve was identified and linked to a specific part of the transistor structure. Layout changes in the n-well/p-base region were done as the result of the model analyses and finally, the modified devices were processed. Measurements on the improved devices showed results that closely, matched the expected, and f_MAX was increased with 30% and only a slight decrease in f _T. Finally, the capacitance reduction in the n-well/p-base junction was measured by direct. measurements     

宽带传输线变压器的分析与设计

研究了变换比为1：n^2(n为整数）的宽频带传输线变压器,给出了考虑线圈互耦的等效电路模型,分析了其阻抗变换特性。然后在此基础上,通过实验调试,研制了工作频带为30MHz-450MHz、变换比为1：1．6的传输线变压器,总结出设计任意变换比传输线变压器的一些结论。     

Optimized spinning design for low PMD fibers: an analyticalapproach

It is known that the differential group delay (DGD) due to polarization mode dispersion (PMD) can be effectively reduced by spinning the fiber during drawing. In this paper, we propose an analytical approach that allows optimization of the spinning design. The fundamental idea is that, in the absence of polarization coupling, an optimized spinning profile can balance the effects of the intrinsic linear birefringence so that the differential group delay can be forced to be periodic and, consequently, have a limited amplitude as a function of distance. Our approach Is independent of the spin profile. In other words, with a fixed set of parameters that characterize a particular spin function, we are able to find analytically the values corresponding to a periodic DGD in a deterministic regime. Numerical results based on waveplate model confirm the analytical prediction and show that PMD can be reduced by about two orders of magnitude with respect to the same fiber without spinning, even after the introduction of random polarization coupling     

全景图像自动拼接算法的优化设计

提出了一种结合空域和频域进行全景图像序列自动拼接融合的优化算法。首先利用改进的相位相关法对全景序列图像进行自动排序并确定重叠区域,根据重叠区域像素均值进行图像整体亮度差异自动调整以降低角点的误匹配率;然后使用改进的Harris 算子在空间域提取图像角点（无需人工设定阈值）,通过双向最大互相关系数匹配获得初始特征点对,并用RANSAC 算法实现精确匹配;最后采用非线性平滑算法对图像重叠区域进行融合处理。实验结果表明,该优化算法排序过程简单有效,特征点提取匹配过程的成功率和效率都较现有算法有很大提高,拼接的图像清晰度高,具有较高的稳健性和拼接精度。