利盈娱乐(中国)创新平台有限公司

开关(guan)电源(yuan)简介—— 开关(guan)电源(yuan)常用的(de)基本(ben)拓扑约有14种。

开关电(dian)源常用(yong)的(de)基(ji)本拓扑(pu)约有(you)14种每种拓扑(pu)都(dou)有(you)其自(zi)身的(de)特(te)点和适用(yong)场合。一些拓扑(pu)适用(yong)于离线式（电(dian)网供(gong)电(dian)的(de)）AC/DC变(bian)换器(qi)。其中(zhong)有(you)些适合小功率输(shu)(shu)出(<200W)，有(you)些适合大功率输(shu)(shu)出：有(you)些适合高压(ya)输(shu)(shu)入(ru)(≥220V AC)，有(you)些适合120V AC或(huo)者(zhe)更低输(shu)(shu)入(ru)的(de)场合：有(you)些在(zai)(zai)高压(ya)直流(liu)输(shu)(shu)出（>～200V）或(huo)者(zhe)多组(zu)（4-5组(zu)以上）输(shu)(shu)出场合有(you)较大的(de)优势；有(you)些在(zai)(zai)相(xiang)同输(shu)(shu)出功率下使用(yong)器(qi)件较少或(huo)是在(zai)(zai)器(qi)件数与(yu)可靠(kao)性之间有(you)较好的(de)折中(zhong)。较小的(de)输(shu)(shu)入(ru)／输(shu)(shu)出纹(wen)波和噪声也是选择拓扑(pu)经常考虑的(de)因素。

一些拓扑(pu)(pu)更适(shi)用于DC/DC变换器。选择时(shi)还要(yao)看是(shi)大功(gong)率还是(shi)小功(gong)率，高压输(shu)出(chu)还是(shi)低压输(shu)出(chu)，以及是(shi)否要(yao)求器件尽量(liang)少等。另外，有些拓扑(pu)(pu)自身有缺(que)陷，需要(yao)附加复杂且难以定(ding)量(liang)分析的电(dian)路(lu)才能工作。

因此，要(yao)恰当选择拓扑，熟悉各(ge)种不(bu)同拓扑的(de)优(you)缺点及适用范围是(shi)非常重要(yao)的(de)。错误的(de)选择会使电源设计一开始就注(zhu)定失败(bai)。

本(ben)(ben)章(zhang)将介绍几种早期(qi)的(de)基(ji)本(ben)(ben)拓扑-buck、boost及(ji)(ji)(ji)反极性调(diao)整器并讨论其基(ji)本(ben)(ben)工作原理、典型波(bo)形、优(you)缺点以及(ji)(ji)(ji)应(ying)用场(chang)合。不同(tong)输出(chu)功率、不同(tong)输入电(dian)(dian)压及(ji)(ji)(ji)其波(bo)动(dong)范围下晶(jing)体管(guan)的(de)峰值(zhi)电(dian)(dian)流电(dian)(dian)压应(ying)力，输入电(dian)(dian)流与输出(chu)功率和输入电(dian)(dian)压之间(jian)的(de)关系，以及(ji)(ji)(ji)效率及(ji)(ji)(ji)DC导通损

耗和AC开关(guan)损耗，都将在本(ben)章介绍(shao)。

为说明开关(guan)型调整(zheng)器的由来(lai)，下面先(xian)讨论其前身——线性调整(zheng)器（或称串联型调整(zheng)器）。

1.2  线(xian)性调(diao)整(zheng)器(qi)——开(kai)关调(diao)整(zheng)器(qi)的原型

1.2.1

开(kai)关(guan)电源 基本工作(zuo)原理及优缺点

线性调整器的基本电(dian)路如图1.1(a)所示，它由一(yi)个工作(zuo)在线性区的晶(jing)体管与负载串联构成(cheng)。晶(jing)体管相(xiang)当(dang)于一(yi)个可变电(dian)阻。首(shou)先(xian)，R1和R2组(zu)成(cheng)的分(fen)压(ya)(ya)网络对输(shu)出电(dian)压(ya)(ya)采样：然后，采样电(dian)压(ya)(ya)输(shu)入到误(wu)差(cha)放大(da)器同参考电(dian)压(ya)(ya)进(jin)行(xing)比较：最(zui)后，误(wu)差(cha)放大(da)器输(shu)出电(dian)压(ya)(ya)经电(dian)流(liu)放大(da)器驱动串联的功率晶(jing)体管。

调整(zheng)原理如下：直(zhi)流(liu)(liu)输(shu)(shu)出电(dian)(dian)(dian)(dian)(dian)压(ya)(ya)由于输(shu)(shu)入电(dian)(dian)(dian)(dian)(dian)压(ya)(ya)升(sheng)(sheng)高(gao)或输(shu)(shu)出负(fu)载电(dian)(dian)(dian)(dian)(dian)流(liu)(liu)减小(xiao)(xiao)而升(sheng)(sheng)高(gao)时(shi)，串(chuan)接晶(jing)体管（设为NPN型）基极(ji)电(dian)(dian)(dian)(dian)(dian)压(ya)(ya)下降(jiang)(jiang)(jiang)，其等效电(dian)(dian)(dian)(dian)(dian)阻阻值加大，使输(shu)(shu)出电(dian)(dian)(dian)(dian)(dian)压(ya)(ya)降(jiang)(jiang)(jiang)低(di)，从而保持采样(yang)电(dian)(dian)(dian)(dian)(dian)压(ya)(ya)等于参考(kao)电(dian)(dian)(dian)(dian)(dian)压(ya)(ya)。这种负(fu)反(fan)馈控制在输(shu)(shu)出电(dian)(dian)(dian)(dian)(dian)压(ya)(ya)由于输(shu)(shu)入电(dian)(dian)(dian)(dian)(dian)压(ya)(ya)下降(jiang)(jiang)(jiang)或负(fu)载电(dian)(dian)(dian)(dian)(dian)流(liu)(liu)增(zeng)加而下降(jiang)(jiang)(jiang)时(shi)也同(tong)样(yang)起(qi)作用。此时(shi)，误差放大器输(shu)(shu)出会使串(chuan)接晶(jing)体管基极(ji)电(dian)(dian)(dian)(dian)(dian)压(ya)(ya)上升(sheng)(sheng)，集射极(ji)电(dian)(dian)(dian)(dian)(dian)阻减小(xiao)(xiao)，直(zhi)流(liu)(liu)输(shu)(shu)出电(dian)(dian)(dian)(dian)(dian)压(ya)(ya)升(sheng)(sheng)高(gao)，使采样(yang)电(dian)(dian)(dian)(dian)(dian)压(ya)(ya)等于参考(kao)电(dian)(dian)(dian)(dian)(dian)压(ya)(ya)。

实质(zhi)上，输(shu)入电(dian)压(ya)的(de)任何变(bian)化(hua)（不管是由于交流输(shu)入网压(ya)的(de)纹(wen)波(bo)，还(hai)是由于输(shu)入电(dian)压(ya)规定范围内的(de)稳态(tai)波(bo)动，或是由于负(fu)载瞬(shun)变(bian)造(zao)成的(de)输(shu)入电(dian)压(ya)瞬(shun)态(tai)变(bian)化(hua)）都会(hui)被串(chuan)联(lian)晶体管等效电(dian)阻(zu)所调整.使输(shu)出电(dian)压(ya)保(bao)持不变(bian)暗，其恒定程度与反馈放大器的(de)的(de)开环(huan)增益相关

图1.1(a)Ql与(yu)负(fu)载(zai)串联起可变电(dian)阻作用：负(fu)反馈环通(tong)过改变其阻值(zhi)以保持输出(chu)电(dian)压(ya)(ya)(ya)Vo的(de)(de)稳(wen)定(ding)。(b)线性调整(zheng)器的(de)(de)压(ya)(ya)(ya)差。若(ruo)串联NPN型晶(jing)体(ti)管，则应(ying)保证(zheng)交流(liu)(liu)输入(ru)电(dian)压(ya)(ya)(ya)Vac最低时(shi)对(dui)应(ying)的(de)(de)直(zhi)流(liu)(liu)电(dian)压(ya)(ya)(ya)的(de)(de)纹波谷值(zhi)与(yu)输出(chu)电(dian)压(ya)(ya)(ya)Vo之间(jian)有2.5V的(de)(de)压(ya)(ya)(ya)差反馈回路(lu)完全是直(zhi)流(liu)(liu)耦(ou)合(he)。由(you)于整(zheng)个回路(lu)没(mei)有开(kai)关器件(jian)，所(suo)以回路(lu)各点的(de)(de)直(zhi)流(liu)(liu)电(dian)压(ya)(ya)(ya)都(dou)可预测和计(ji)算。电(dian)路(lu)中没(mei)有变压(ya)(ya)(ya)器并且(qie)不(bu)存在引起RFI噪声(sheng)的(de)(de)瞬态尖峰电(dian)压(ya)(ya)(ya)或电(dian)流(liu)(liu)。由(you)于晶(jing)体(ti)管不(bu)工作在开(kai)关状态，所(suo)以不(bu)存在晶(jing)体(ti)管的(de)(de)下降电(dian)流(liu)(liu)和上升电(dian)压(ya)(ya)(ya)瞬时(shi)重(zhong)叠造成的(de)(de)交流(liu)(liu)开(kai)关损耗(hao)(hao)。所(suo)有功耗(hao)(hao)只(zhi)是电(dian)路(lu)各元件(jian)的(de)(de)直(zhi)流(liu)(liu)损耗(hao)(hao)，很(hen)容易计(ji)算。

1.2.2

线性调(diao)整器的缺点(dian)

直(zhi)(zhi)到20世纪(ji)60年代初(chu)期，这种简单的(de)(de)直(zhi)(zhi)流耦(ou)合串联型调(diao)整器(qi)一直(zhi)(zhi)是(shi)数十亿美元产(chan)值的(de)(de)电(dian)源工(gong)业的(de)(de)主要产(chan)品(pin)。但是(shi)，这种电(dian)源只(zhi)能降压(ya)(ya)，而(er)且它(ta)的(de)(de)输(shu)(shu)出与输(shu)(shu)入之间有公共端，通(tong)常需要另加电(dian)路实现输(shu)(shu)出与输(shu)(shu)入的(de)(de)隔离(li)。此外，其初(chu)始直(zhi)(zhi)流输(shu)(shu)入电(dian)压(ya)(ya)，即图1.1(a)中(zhong)的(de)(de)V，一般(ban)由工(gong)频变压(ya)(ya)器(qi)次级整流获得，而(er)工(gong)频变压(ya)(ya)器(qi)的(de)(de)体积和(he)重量限制了它(ta)的(de)(de)推广应用。

联系方式：邹先生

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