The relationship between size and power dissipation in a 1-10 MHztransformer

The trade-off between size and power dissipation in the design of low-profile 1-10 MHz transformers with planar spiral windings is considered. For a fixed power loss and number of conductor layers, the transformer with the smallest possible footprint can be designed by a trade-off of core and copper loss. The relationship between the marginal reduction of the transformer footprint and the associated marginal increase in power dissipation and/or number of conductor layers for the design of the smallest possible transformer is discussed     

平面型PCB变压器的设计

根据变压器工作原理和平面型PCB变压器的自身特点,对PCB变压器进行了研究.得出了变压器PCB板绕组的最优布置方式;在绕组损耗和磁芯损耗的数学模型基础上,找出最适当的磁芯几何形状,使变压器的损耗为最小,达到优化设计的目的.     

行波管高压电源中变压器的优化设计

研究了行波管高压电源中变压器的铁芯损耗、绕组损耗(铜损)和工作频率,主要通过理论推导和仿真对磁性元件的设计进行了优化分析,并用PC95材质PQ40/40磁芯设计了一种输出电压10kV、输出功率450 W的行波管高压电源变压器。变压器设计结果满足电源要求,实验结果验证了理论分析。     

Design issues for the transformer in a low-voltage power supplywith high efficiency and high power density

Circuit model, design feasibility, and design tradeoffs are investigated for the transformer in 1.5-5 V power supplies with high efficiency and high power density. The transformer is constructed from a single or a matrix of pot cores and from interleaved planar windings. It has been determined theoretically and verified experimentally that such a transformer is realizable as long as the loss constraint is not severe (e.g. less than 0.5 W transformer loss per 100 W output). The primary source of loss is the winding, not the core, in 1.5 V/turn design. Measures to reduce the transformer height tend to increase transformer loss or volume     

A leakage-inductance-based ZVS two-inductor boost converter with integrated magnetics

A two-inductor boost converter topology has conduction loss and transformer utilization advantages in converting low-voltage higher current inputs to high output voltages. In this letter, a new zero-voltage switching (ZVS) two-inductor boost converter with integrated magnetics is proposed. In the new topology, the two current source inductors, a resonant inductor and a two-winding transformer, are integrated into one single magnetic core with three windings. Two windings simultaneously perform the functions of the current source inductors and the transformer primary. The transformer leakage inductance forms the resonant inductance. This leads to a much more compact converter design with a significant reduction in the number of core and winding components. A theoretical analysis establishes the operating point of the ZVS converter. Both of the theoretical and experimental waveforms, including flux waveforms for the legs of the integrated core structure, are presented at the end of the letter.     

Design aspects of planar and conventional SMPS transformer: a cost benefit analysis

The intent of this paper is to design a high-frequency transformer that is to be incorporated into the DC/DC pulsewidth-modulated switch-mode power supplies by two different technical approaches: a conventional wound-coil magnetic using copper wires, and a planar magnetic with layered copper tracks on laminated printed circuit board. Comparisons will be made between the two approaches in terms of profile: mounting height and surface area, and performance: power losses and efficiency. Other indicators like temperature rise and leakage inductance that causes electromagnetic interference, and cost, materials, and process fluency are also to be looked into. A sandwiched configuration for primary and secondary windings is proposed for the planar type. Issues arising and typical phenomena encountered will be discussed in detail. Primarily, the dominating factor in performance, cost effectiveness, or circuit compactness that restrains the choice of a particular type is to be evaluated.     

Coupled Input-Series and Output-Parallel Dual Interleaved Flyback Converter for High Input Voltage Application

This paper proposes an integrated magnetic dc-dc converter suitable for high input voltage application. The converter is based on a coupled input-series and output-parallel dual interleaved Flyback converter concept. All the center and outer legs are gapped, and the transformers are integrated into one magnetic core with not so tight coupling. The gap is beneficial for suppressing current spike caused by the voltage mismatch between the windings. The two transformers are inversely coupled, and current ripple reduction can be achieved with suitable coupling design. A prototype with 350-450-V input and 24-V/4-A output is built. Experimental results verify the performance of the new topology.     

浅谈开关电源中的平面变压器

与传统变压器相比较,使用平面变压器可以提高开关电源的功率密度,减小开关电源中磁性元件的体积。因此,近年来平面变压器被广泛地研究。文章介绍了平面变压器的结构,将平面变压器与传统变压器进行比较,分析综述了平面变压器在当今开关电源发展应用的优势和前景,并进一步说明了平面变压器中绕组间距选择,绕组交叉技术及PCB绕组设计等要点。     

Integrated magnetic full wave converter with flexible output inductor

A new integrated magnetic full wave DC/DC power converter that provides flexible transformer design by incorporating an independent output inductor winding is introduced. The transformer is implemented on a traditional three-leg magnetic core. The inductor winding can be separately designed to control the output current ripple. The cross-sectional area of the inductor core leg can be reduced dramatically. The operation and performance of the proposed circuit are verified on a 100 W prototype converter.     

多层片式微磁变压器设计工艺及应用研究

采用LTCC低温共烧陶瓷技术制作的多层片式微磁变压器可以满足表面组装技术的需求,介绍了微磁变压器的特点、磁芯材料选择、设计方案、关键工艺及应用前景.     

HF Characterization and Nonlinear Modeling of a Gapped Toroidal Magnetic Structure

The frequency dependent characteristics of a gapped toroidal structure are extracted empirically over a bandwidth that exceeds 30MHz. The analysis is complicated due to nonlinear flux distributions, magnetic properties of the core material, leakage inductance, stray capacitances, and eddy currents in the windings. A permeance model of the core is implemented to model the magnetic circuit. The model includes a linear lumped element equivalent circuit to approximate the nonlinear complex permeability of the core, which was measured empirically. Stray capacitance and inductance of the winding are also modeled. A gyrator is used to couple the electric and magnetic models for circuit simulation. The measured and simulated results of open-circuit impedance from the secondary winding and the transimpedance gain (V/A) of the current sensor are compared and discussed.     

Transformer miniaturization for transcutaneous current/voltage pulse applications

A general procedure for the design of a miniaturized step up transformer to be used in the context of surface electrode based current/voltage pulse generation is presented. It has been shown that the optimum secondary current pulse width is 4.5 tau, where tau is the time constant associated with the pulse forming network associated with the transformer/electrode interaction. This criteria has been shown to produce the highest peak to average current ratio for the secondary current pulse. The design procedure allows for the calculation of the optimum turns ratio, primary turns, and secondary turns for a given electrode load/tissue and magnetic core parameters. Two design examples for transformer optimization are presented.     

Issues related to 1-10-MHz transformer design

Issues related to the design of high-frequency transformers are discussed. An analysis of skin and proximity effects in the conductors and measurements of permeability and hysteresis loss in the magnetic material are combined in a computer-assisted study of the relationships between size, efficiency, and frequency. Experimental data are presented for a prototype transformer     

高能量密度微电磁驱动器的制作方法

提出了一种非闭合磁路型高能量密度微电磁驱动器的制作方法,即利用MEMS工艺在单位面积硅基体上制作多匝、高深宽比的平面线圈和高厚度的磁芯.通过先面电铸再线电铸的方式,以及动态控制电铸电流密度的方法进行平面线圈的制作;通过改变衬底表面粗糙度和种子层厚度的方法,改善合金镀层与衬底的粘附性能,可以在单位面积的硅片上,制作出厚度更大的磁性合金镀层.初步实验结果表明：该微型电磁驱动器在相同的输入功率下,比同类其他微电磁驱动器,能产生更大的电磁驱动力,具有更高的能量密度.     

High-Performance Planar Isolated Current Sensor for Power Electronics Applications

A planar current sensor, comprised of a magnetic current transformer and a hall-effect element, is presented. The sensor has a broad frequency bandwidth from dc up to 30 MHz, a high current rating (40-A dc), superior linearity, high EMI immunity, small size, robustness, and low realization cost. The main design formulations are given analytically; simulations and finite-element results are presented for verification. Experimental results of current step response and dv/dt immunity are included.     

高能量密度微电磁驱动器的制作方法

提出了一种非闭合磁路型高能量密度微电磁驱动器的制作方法,即利用MEMS工艺在单位面积硅基体上制作多匝、高深宽比.的平面线圈和高厚度的磁芯.通过先面电铸再线电铸的方式,以及动态控制电铸电流密度的方法进行平面线圈的制作;通过改变衬底表面粗糙度和种子层厚度的方法,改善合金镀层与衬底的粘附性能.可以在单位面积的硅片上,制作出厚度更大的磁性合金镀层.初步实验结果表明:该微型电磁驱动器在相同的输入功率下,比同类其他微电磁驱动器,能产生更大的电磁驱动力,具有更高的能量密度.     

一种薄膜PCB平面变压器的研究

采用现代化印刷版技术,首先设计制作出一种基于柔性PCB板、线圈宽度为0.2mm、线间距为0.3mm、匝数比为6:18的空心变压器,然后采用直流磁控溅射在其上下表面镀上软磁薄膜,而最终制成了一种薄膜PCB平面变压器。研究了薄膜材料、膜厚等因素对该种变压器性能的影响。结果表明,制得的薄膜PCB平面变压器可以有效工作于4～14MHz的频率范围。采用上述方法制备变压器,可以把变压器从三维变成两维,从而为器件的表面贴装打下基础,并同时满足"更小,更轻,更薄"的要求。     

An Inductive Conductivity Meter for Monitoring the Salinity of Dialysis Water

An inductive conductivity meter is described, especially adapted as a salinity monitor for dialysis water. Salinity are given. The principal problems of the inductive conductivity meter result from the low conductivity of electrolytes. The weak coupling due to the electrolyte means that stray coupling must be reduced to a very low level. This has been accomplished by means of a heavy copper eddy-current shield, which reduces the unwanted coupling to a level corresponding to a conductivity increment of the order of 10-8 ?-1. cm-1. The effect of parasitic impedances in the receiver core are minimized by designing this core as a current transformer, rather than a voltage transformer. The operating frequency is 5600 Hz. The circuits are described, including the oscillator, current-sensitive preamplifier, phase-sensitive detector, dc amplifiers, and alarm circuits. The phase-sensitive detector uses ordinary planar transistors and does not require a square wave reference signal.     

Optimized transformer design: inclusive of high-frequency effects

Switching circuits, operating at high frequencies, have led to considerable reductions in the size of magnetic components and power supplies. Nonsinusoidal voltage and current waveforms and high-frequency skin and proximity effects contribute to power transformer losses. Traditionally, power transformer design has been based on sinusoidal voltage and current waveforms operating at low frequencies. The physical and electrical properties of the transformer form the basis of a new design methodology while taking full account of the current and voltage waveforms and high-frequency effects. Core selection is based on the optimum throughput of energy with minimum losses. The optimum core is found directly from the following transformer specifications: frequency; power output; and temperature rise. The design methodology is illustrated with a detailed design of a push-pull power converter     

高频变压器铜损的三维模拟仿真与分析

对高频变压器建立三维电磁分析模型,采用有限元法对变压器铜损进行数值求解.模拟分析次级绕组段间距、初级绕组以及磁芯漏磁对次级绕组损耗的影响,并引入了矩形导线和圆导线之间的等效因子.分析表明,在考虑次级绕组段间距、初级绕组以及磁芯漏磁后,高频变压器次级铜损为246.086W,大于Dowell模型的理论计算值107.500W,这为变压器的优化设计提供了参考.