pdf

网络变压器设计资料 23页

  • 1星
  • 日期: 2015-12-22
  • 大小: 123.69KB
  • 所需积分:0分
  • 下载次数:8
  • favicon收藏
  • rep举报
  • 分享
  • free评论
标签: 变压器

网络变压器设计资料 23页

文档内容节选

APPLICATION NOTE Design of HF wideband power transformers ECO6907 Philips Semiconductors Design of HF wideband power transformers CONTENTS Application Note ECO6907 1 2 3 31 32 4 41 42 5 51 52 6 61 62 63 64 65 66 67 68 681 682 7 71 72 8 INTRODUCTION TRANSFORMER SPECIFICATION INFLUENCE OF THE CORE ON PERFORMANCE Primary Inductance Core Losses INFLUENCE OF THE TRANSMISSION LINE ON PERFORMANCE Resistive Loss and Power Handling Mismatch loss COMPENSATION TECHNIQUES Compensation at Low Frequencies Com......

APPLICATION NOTE Design of HF wideband power transformers ECO6907 Philips Semiconductors Design of HF wideband power transformers CONTENTS Application Note ECO6907 1 2 3 3.1 3.2 4 4.1 4.2 5 5.1 5.2 6 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.8.1 6.8.2 7 7.1 7.2 8 INTRODUCTION TRANSFORMER SPECIFICATION INFLUENCE OF THE CORE ON PERFORMANCE Primary Inductance Core Losses INFLUENCE OF THE TRANSMISSION LINE ON PERFORMANCE Resistive Loss and Power Handling Mismatch loss COMPENSATION TECHNIQUES Compensation at Low Frequencies Compensation at High Frequencies TRANSFORMER CONFIGURATION Phase Reversing Transformer Balanced to Unbalanced Transformer Symmetrical 1 : 4 Impedance Transformer Asymmetrical 1 : 4 Impedance Transformer Symmetrical 9 : 1 Impedance Transformer Asymmetrical 1 : 9 Impedance Transformer Single-ended Hybrid Push-pull Hybrid Impedance Step-up Type Impedance Step-Down Type PRACTICAL EXAMPLES 12.5 W Transformer 50 W Transformer REFERENCES Unbalanced to 5.55 W Balanced Balanced to 50 W Unbalanced 1998 Mar 23 2 Philips Semiconductors Design of HF wideband power transformers 1 INTRODUCTION Application Note ECO6907 Transmission line power transformers can be used to perform a variety of functions, among which are phase reversal, balanced to unbalanced coupling, impedance transformation and hybrid functions. Such transformers find many applications in wide-band power amplifiers for both s.s.b. transmitters in the h.f. region and f.m. transmitters in the lower v.h.f. region. The properties of a practical h.f. power transformer are discussed here and their effect on transformer performance is analysed. Since losses must be kept low, in practice the transformer will use a ferrite core. Further, we have limited the discussion to cores without an air-gap since these have a low stray magnetic field, a high permeability, and can cover the power range (up to 80 W) dealt with here. Data (dimensions, permeability values etc.) on all core types can be found in our Data Handbook “Soft Ferrites”, MA01. A glance through the Handbook will show the wide range of materials, dimensions and types from which the designer may choose. It must be remembered, of course, that when cores constructed in two parts (pot-cores and cross-cores, for example) are used, the type without an air-gap must be selected. Throughout we have aimed at giving practical solutions to the problems posed by material and design limitations. In particular, compensating techniques for extending the frequency range of a number of transformer configurations are discussed. To give an idea of some application possibilities, practical examples in several transformer configurations have been worked, using transformer cores from our range of ferrites. 2 TRANSFORMER SPECIFICATION The transformer design considerations dealt with in this publication are: • Maximum power level to be handled • Frequency range • Input and output impedance • Allowable reflection and resistive losses. How a transformer can meet the above considerations for a particular application is analysed in the following three sections. The first two sections deal with the influence of the core and transmission line respectively on transformer performance, and the third with mismatch compensation techniques. 3 INFLUENCE OF THE CORE ON PERFORMANCE 3.1 Primary Inductance This inductance determines the amount of reflection at the low frequency end of the band. It can be calculated using the formula: L = m om in which: rn2 A/l L = inductance in H m o = 4 p 10-7 (rationalised M.K.S. units) r = relative permeability A = average ferrite cross section in m2 l = average length of the lines of force in m n = number of turns between the input connections. 1998 Mar 23 3 m Philips Semiconductors Design of HF wideband power transformers Application Note ECO6907 In a simple example, like the phase reversing transformer, this relation holds. Other cases may require a transformation (see Section 7.1). If degrading of performance at the high end of the band is to be avoided, the value of L must not be higher than really necessary. A good practical value is: L = 4R/w min in which: R = midband input resistance in W w min = 2p times the minimum frequency in Hz. Where requirements are severe the compensation technique described in Section 5.1 may be used. 3.2 Core Losses r The losses caused by the core material will be represented here as a resistance (Rp) in parallel with the input. This resistance depends on: • The sort of ferrite material • The frequency • The quantity L/m • The maximum flux density Bmax. In the small signal case (Bmax fi 0), Rp can be calculated with the aid of curves of the type shown in Fig.1(1). In these curves a comparison is made between different core materials based on equal core dimensions and equal number of turns. It can be seen that 4C4 and 4C6 are the best materials for frequencies above approximately 2.5 MHz. In the high v.h.f. region IZ2 ferroxplana shows interesting properties as can be seen from the same figure. The power handling capability of a transformer is closely dependent on the behaviour of Rp as a function of Bmax. For the section of the B-H curve with which we are dealing, Bmax can be calculated using the formula: Bmax = Vmax/w in which: A · n Bmax = maximum flux density in T(2) w = 2p times frequency in Hz A = ferrite cross section in m2 n = number of turns Vmax = maximum value of voltage across n turns in V. (1) The curves of Figs 1 to 7 have been drawn from measurements on single samples of the ferrite materials. Thus the average curves may differ somewhat from those shown. (2) The letter T stands for Tesla, the unit of magnetic flux density in the SI unit system. The following relationship holds: 1T = 1 Wb/m2 = 1 Vsec/m2 = 10000 gauss. 1998 Mar 23 4 · Philips Semiconductors Design of HF wideband power transformers 1012 handbook, full pagewidth m rRp L (sec- 1) 1011 1010 1 Application Note ECO6907 MGL235 1Z2 4C4 4C6 4B1 4A4 3H1 10 102 f (MHz) 103 Fig.1 Curves of m rRp/L plotted against frequency for our various ferrites. The curves have been plotted for small signal conditions (Bmax fi 0). In Figs 2 to 7 the quantity m rRp/L is given for different ferrite materials as a function of the product Bmax · ƒ with the frequency as a parameter. The product Bmax · ƒ has been chosen because, for most transformers, its value remains constant for changing frequency. From Figs 2 to 7 it can be seen that Rp decreases as Bmax increases, especially at lower frequencies. This forms the primary limit on the power handling capability of these transformers. If 4C4 material (Fig.5) is used in the h.f. region, the Bmax · ƒ product must not be higher than approx. 2 · 104 T.Hz. Combining this with the choice of L according to the second equation in Section 3.1, we find that the power loss caused by the core material will be no more than 1%. At frequencies of 30 MHz and higher it seems that higher Bmax · ƒ products, perhaps up to 105 T.Hz, can be used. For IZ2 ferroxplana this has already been confirmed by measurements at 165 MHz. A very conservative choice of the Bmax value must also be avoided because this leads to a greater length of the transmission line and consequently more loss at the high end of the band. 4 INFLUENCE OF THE TRANSMISSION LINE ON PERFORMANCE 4.1 Resistive Loss and Power Handling The power loss in the transmission line depends on: • The type of line • The frequency • The length. Data on power loss in some 50 W temperature restrict the power handling of the cable. The maximum power which can be transmitted depends on the type of cable and the frequency; data is given in Fig.9. coaxial cables is given in Fig.8. This power loss and the allowable maximum cable 1998 Mar 23 5
更多简介内容

推荐帖子

LOTO课1:RC阻容实践 --- 低通滤波器PWM变直流
    实践用到的资源:1.5K电阻, 22u电容,LOTO示波器,可调PWM波。 备注:阻值和容值的选择并不需要准确,其实就是组合出一个截止频率很低的低通滤波器就可以了。比如我们上面的选值相当于一个截止频率4.8Hz的低通滤波。       视频中阐述并实践了两种方法,第一种是软件控制OSC482自带PWM的占空比调节RC滤波产生直流的大
LOTO2018 移动便携
keil中针对printf和scanf的实现机理
最开始学习C语言时,使用printf和scanf进行格式化输入输出十分方便。 学习单片机有很长时间了,之前要再屏幕上显示一个变量或者通过串口传出一些变量值观测的话,需要进行一系列的取余取整运算,很是麻烦。 最近又研究了一下keil中针对printf和scanf的实现机理,做了一些改动,实现了标准格式化输入输出,共大家参考。 1.printf函数在格式化输出时,向下调用了char
fish001 【微控制器 MCU】
为啥镀银线比漆包线的Q值要高?---频率的变化对 L 和 Q 的变化? 实测对比
本帖最后由 btty038 于 2020-5-22 15:45 编辑     一,这是漆包线的实际原模型,         漆包线绕制线圈   二,这是镀银线的实际原模型,             镀银线绕制线圈   三,这是需要的效果,      
btty038 RF/无线
下资料 看视频 抽大奖!泰克汽车电子测试解决方案
毫米波雷达市场空间广阔,由于各国汽车安全标准的不断提高,导致主动安全技术高级驾驶辅助系统(ADAS)近年来呈快速发展趋势。汽车毫米波雷达因能够全天候工作,已成为汽车电子厂商公认的主流选择,拥有巨大的市场需求。2014年全球汽车毫米波雷达市场出货量在1900万个,据市场研究机构预测,预计到2020年全球汽车毫米波雷达将近7000万个,2015-2020年的年均复合增速约为24%。  
zqy1111 【测试/测量】
【 ST NUCLEO-H743ZI测评】+ USB OTG+FATFS
本帖最后由 sylar^z 于 2020-5-19 00:38 编辑     NUCLEO-H743ZI板子自带USB接口,既可以作为设备USB口,也可以作为主USB口来外接U盘、HID设备等。   一、硬件原理图     NUCLEO-H743ZI板子USB接口的硬件电路。USB_VBUS、USB_DM、USB_DP、USB_ID、GND为USB5个引脚。USB_Powe
sylar^z 【stm32/stm8】
分享一份射频功放设计指南
射频功放设计规范和指南 第一章 射频功放设计步骤 1 1.1 定设计方案 1 1.1.1 GSM及PHS基站系统 1 1.1.2 CDMA及WCDMA基站系统 3 1.2 选择确定具体线路形式及关键器件 5 1.2.1 射频放大链路形式与关键器件选择及确定 5 1.2.2 控制电路的确定 8 1.3 进行专题实验或一板实验 9 1.4 结构设计
Stephenhu1984 RF/无线

评论

登录/注册

意见反馈

求资源

回顶部

datasheet推荐 换一换

About Us 关于我们 客户服务 联系方式 器件索引 网站地图 最新更新 手机版 版权声明

北京市海淀区知春路23号集成电路设计园量子银座1305 电话:(010)82350740 邮编:100191

电子工程世界版权所有 京ICP证060456号 京ICP备10001474号 电信业务审批[2006]字第258号函 京公海网安备110108001534 Copyright © 2005-2020 EEWORLD.com.cn, Inc. All rights reserved
$(function(){ var appid = $(".select li a").data("channel"); $(".select li a").click(function(){ var appid = $(this).data("channel"); $('.select dt').html($(this).html()); $('#channel').val(appid); }) })