開關電源不同于線性電源適配器，前者(zhe)調整管(guan)(guan)工(gong)(gong)作(zuo)在通(tong)(tong)、斷狀(zhuang)(zhuang)態，后者(zhe)調整管(guan)(guan)工(gong)(gong)作(zuo)在線性狀(zhuang)(zhuang)態。電(dian)源(yuan)適(shi)配(pei)器(qi)(qi)(qi)通(tong)(tong)過(guo)控制調整管(guan)(guan)的通(tong)(tong)、斷時(shi)間(jian)實(shi)現穩壓(ya)。電(dian)源(yuan)適(shi)配(pei)器(qi)(qi)(qi)的優(you)點是體積小(xiao)(xiao)、重(zhong)量(liang)輕、功耗小(xiao)(xiao)、穩壓(ya)范圍寬(kuan)，效率可(ke)(ke)高達80%～90%。調整管(guan)(guan)功率損耗小(xiao)(xiao)，散熱器(qi)(qi)(qi)也隨(sui)之減小(xiao)(xiao)。英規(gui)電(dian)源(yuan)適(shi)配(pei)器(qi)(qi)(qi)工(gong)(gong)作(zuo)頻率在幾十千(qian)赫茲甚(shen)至幾百千(qian)赫茲，濾波電(dian)感、電(dian)容(rong)元(yuan)件可(ke)(ke)用較小(xiao)(xiao)的容(rong)量(liang)，允許(xu)的環境溫度也可(ke)(ke)以大(da)大(da)提高，廣泛應用在各(ge)種電(dian)子設備中(zhong)。本章(zhang)主要(yao)介紹電(dian)源(yuan)適(shi)配(pei)器(qi)(qi)(qi)的基本構成(cheng)、分類及(ji)工(gong)(gong)作(zuo)原理(li)，讓讀者(zhe)對(dui)電(dian)源(yuan)適(shi)配(pei)器(qi)(qi)(qi)有一(yi)個(ge)初步(bu)的認識。

　　穩壓電源適配器的比較

　　電(dian)(dian)子(zi)(zi)設(she)備(bei)(bei)離不開(kai)電(dian)(dian)源(yuan)適(shi)配(pei)(pei)器(qi)(qi)(qi)(qi)。電(dian)(dian)源(yuan)適(shi)配(pei)(pei)器(qi)(qi)(qi)(qi)供給電(dian)(dian)子(zi)(zi)設(she)備(bei)(bei)所需要的能(neng)(neng)量。電(dian)(dian)源(yuan)適(shi)配(pei)(pei)器(qi)(qi)(qi)(qi)的性能(neng)(neng)、質量直接影響著電(dian)(dian)子(zi)(zi)設(she)備(bei)(bei)的安全可靠運行，故此對電(dian)(dian)子(zi)(zi)設(she)備(bei)(bei)電(dian)(dian)源(yuan)適(shi)配(pei)(pei)器(qi)(qi)(qi)(qi)性能(neng)(neng)、質量的要求(qiu)也越(yue)來越(yue)高。現(xian)有(you)的電(dian)(dian)源(yuan)適(shi)配(pei)(pei)器(qi)(qi)(qi)(qi)主要有(you)兩(liang)大類(lei)：串聯(lian)線性穩壓電(dian)(dian)源(yuan)適(shi)配(pei)(pei)器(qi)(qi)(qi)(qi)(簡稱(cheng)(cheng)線性電(dian)(dian)源(yuan)適(shi)配(pei)(pei)器(qi)(qi)(qi)(qi))和開(kai)關穩壓電(dian)(dian)源(yuan)適(shi)配(pei)(pei)器(qi)(qi)(qi)(qi)(簡稱(cheng)(cheng)電(dian)(dian)源(yuan)適(shi)配(pei)(pei)器(qi)(qi)(qi)(qi))。這(zhe)兩(liang)類(lei)電(dian)(dian)源(yuan)適(shi)配(pei)(pei)器(qi)(qi)(qi)(qi)各具特色而被廣泛應用(yong)。

　　線性電源適配器的結構與特點

　　線性電(dian)源適(shi)配器通常(chang)都是(shi)由電(dian)網(wang)所提供的交流電(dian)，經過變壓(ya)、整(zheng)流、濾(lv)波和穩壓(ya)環節(jie)而得到。其各個部分(fen)電(dian)路的作用如下：

　　①電源適配器(qi)(qi)變(bian)壓器(qi)(qi)——將220V電網(wang)電壓轉換為整(zheng)流電路所(suo)需要的交流電壓值(zhi)，而(er)少部分電路采用電容降(jiang)壓，如遙(yao)控電風扇電路。

　　②整(zheng)流電(dian)路——將交流電(dian)壓轉換為(wei)脈(mo)動(dong)直流電(dian)壓。常用的(de)整(zheng)流電(dian)路有半波整(zheng)流電(dian)路、全(quan)波整(zheng)流電(dian)路和橋式整(zheng)流電(dian)路。

　　③濾(lv)(lv)(lv)波(bo)(bo)(bo)電(dian)路——將脈動直(zhi)流電(dian)壓轉換成較為平滑的(de)直(zhi)流電(dian)壓。線性(xing)電(dian)源適(shi)配器中常(chang)用的(de)濾(lv)(lv)(lv)波(bo)(bo)(bo)電(dian)路有電(dian)感濾(lv)(lv)(lv)波(bo)(bo)(bo)、電(dian)容濾(lv)(lv)(lv)波(bo)(bo)(bo)和阻容濾(lv)(lv)(lv)波(bo)(bo)(bo)，其中最常(chang)用的(de)是電(dian)容濾(lv)(lv)(lv)波(bo)(bo)(bo)。

　　④穩(wen)(wen)壓(ya)(ya)(ya)電(dian)(dian)路(lu)——將直流(liu)電(dian)(dian)源(yuan)(yuan)適配器的(de)輸出電(dian)(dian)壓(ya)(ya)(ya)穩(wen)(wen)定(ding)，基本不(bu)受電(dian)(dian)網電(dian)(dian)壓(ya)(ya)(ya)或負載的(de)影(ying)響。在線性電(dian)(dian)源(yuan)(yuan)適配器中常用的(de)穩(wen)(wen)壓(ya)(ya)(ya)電(dian)(dian)路(lu)有二極管(guan)穩(wen)(wen)壓(ya)(ya)(ya)、串聯穩(wen)(wen)壓(ya)(ya)(ya)。其(qi)中，串聯穩(wen)(wen)壓(ya)(ya)(ya)有現成(cheng)的(de)集成(cheng)電(dian)(dian)路(lu)，如固定(ding)電(dian)(dian)壓(ya)(ya)(ya)輸出的(de)集成(cheng)電(dian)(dian)路(lu)有LM78××，LM79××等，可調(diao)電(dian)(dian)壓(ya)(ya)(ya)輸出的(de)集成(cheng)電(dian)(dian)路(lu)有LM317和LM337等。

　　4個功能模塊的線性穩壓電源適配器

　　線性(xing)電(dian)源(yuan)適配器的優點是穩定(ding)性(xing)好、瞬態響應速度快(kuai)、可靠性(xing)高(gao)、輸(shu)(shu)出(chu)電(dian)壓精度高(gao)和(he)輸(shu)(shu)出(chu)紋波電(dian)壓小;缺點是工作頻率低，所(suo)采用的工頻變壓器、濾波器的體積和(he)重量都(dou)較大。調整管工作在(zai)線性(xing)狀態，功耗大、效率低，需要加(jia)裝散熱器。