開關電源不同于線性電源適配器，前者(zhe)調(diao)整管工(gong)作(zuo)在通(tong)(tong)(tong)、斷狀(zhuang)態，后者(zhe)調(diao)整管工(gong)作(zuo)在線性狀(zhuang)態。電(dian)源(yuan)適配(pei)器(qi)(qi)通(tong)(tong)(tong)過控(kong)制(zhi)調(diao)整管的(de)(de)通(tong)(tong)(tong)、斷時間(jian)實現穩壓。電(dian)源(yuan)適配(pei)器(qi)(qi)的(de)(de)優點是體積小(xiao)、重量輕(qing)、功耗小(xiao)、穩壓范圍寬，效(xiao)率可高達80%～90%。調(diao)整管功率損耗小(xiao)，散(san)熱器(qi)(qi)也隨之減(jian)小(xiao)。英規電(dian)源(yuan)適配(pei)器(qi)(qi)工(gong)作(zuo)頻(pin)率在幾十千(qian)赫(he)茲(zi)甚(shen)至(zhi)幾百千(qian)赫(he)茲(zi)，濾波(bo)電(dian)感、電(dian)容元件可用(yong)較小(xiao)的(de)(de)容量，允許的(de)(de)環(huan)境溫度(du)也可以大大提高，廣泛應用(yong)在各(ge)種(zhong)電(dian)子設備中。本章(zhang)主要介紹電(dian)源(yuan)適配(pei)器(qi)(qi)的(de)(de)基本構成、分類(lei)及工(gong)作(zuo)原理，讓讀者(zhe)對電(dian)源(yuan)適配(pei)器(qi)(qi)有一個初步(bu)的(de)(de)認識。

　　穩壓電源適配器的比較

　　電(dian)(dian)(dian)(dian)(dian)(dian)子設(she)備離不(bu)開(kai)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)適(shi)(shi)配(pei)(pei)(pei)器(qi)。電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)適(shi)(shi)配(pei)(pei)(pei)器(qi)供給電(dian)(dian)(dian)(dian)(dian)(dian)子設(she)備所需要(yao)的(de)能(neng)量(liang)。電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)適(shi)(shi)配(pei)(pei)(pei)器(qi)的(de)性(xing)能(neng)、質量(liang)直接(jie)影響著電(dian)(dian)(dian)(dian)(dian)(dian)子設(she)備的(de)安全可靠運行，故此對電(dian)(dian)(dian)(dian)(dian)(dian)子設(she)備電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)適(shi)(shi)配(pei)(pei)(pei)器(qi)性(xing)能(neng)、質量(liang)的(de)要(yao)求也(ye)越(yue)來越(yue)高。現有的(de)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)適(shi)(shi)配(pei)(pei)(pei)器(qi)主要(yao)有兩(liang)大(da)類(lei)(lei)：串聯線性(xing)穩壓(ya)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)適(shi)(shi)配(pei)(pei)(pei)器(qi)(簡稱線性(xing)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)適(shi)(shi)配(pei)(pei)(pei)器(qi))和開(kai)關(guan)穩壓(ya)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)適(shi)(shi)配(pei)(pei)(pei)器(qi)(簡稱電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)適(shi)(shi)配(pei)(pei)(pei)器(qi))。這兩(liang)類(lei)(lei)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)適(shi)(shi)配(pei)(pei)(pei)器(qi)各具特色而被廣泛應用。

　　線性電源適配器的結構與特點

　　線(xian)性電源適配(pei)器通(tong)常都(dou)是由電網所提供的交流(liu)(liu)電，經過變壓(ya)、整流(liu)(liu)、濾波和穩壓(ya)環節而得到(dao)。其(qi)各個部分電路(lu)的作用如(ru)下：

　　①電源適配(pei)器變壓(ya)(ya)(ya)器——將220V電網電壓(ya)(ya)(ya)轉換為整流電路(lu)所需(xu)要的交流電壓(ya)(ya)(ya)值，而少部分(fen)電路(lu)采用電容降壓(ya)(ya)(ya)，如遙控(kong)電風扇電路(lu)。

　　②整(zheng)流(liu)電(dian)路——將交(jiao)流(liu)電(dian)壓轉換為(wei)脈動直流(liu)電(dian)壓。常用的(de)整(zheng)流(liu)電(dian)路有半波整(zheng)流(liu)電(dian)路、全(quan)波整(zheng)流(liu)電(dian)路和橋式(shi)整(zheng)流(liu)電(dian)路。

　　③濾(lv)波(bo)電(dian)路(lu)——將脈動(dong)直(zhi)流電(dian)壓(ya)(ya)轉換成較為平滑的(de)直(zhi)流電(dian)壓(ya)(ya)。線性(xing)電(dian)源(yuan)適配器中常(chang)用的(de)濾(lv)波(bo)電(dian)路(lu)有(you)電(dian)感濾(lv)波(bo)、電(dian)容(rong)濾(lv)波(bo)和阻容(rong)濾(lv)波(bo)，其中最常(chang)用的(de)是電(dian)容(rong)濾(lv)波(bo)。

　　④穩壓(ya)(ya)(ya)(ya)電(dian)(dian)路(lu)——將直流電(dian)(dian)源適配(pei)器(qi)的(de)輸出(chu)(chu)電(dian)(dian)壓(ya)(ya)(ya)(ya)穩定，基(ji)本不受電(dian)(dian)網(wang)電(dian)(dian)壓(ya)(ya)(ya)(ya)或負(fu)載的(de)影(ying)響(xiang)。在線性電(dian)(dian)源適配(pei)器(qi)中(zhong)常用的(de)穩壓(ya)(ya)(ya)(ya)電(dian)(dian)路(lu)有(you)二極管穩壓(ya)(ya)(ya)(ya)、串聯(lian)穩壓(ya)(ya)(ya)(ya)。其中(zhong)，串聯(lian)穩壓(ya)(ya)(ya)(ya)有(you)現成(cheng)的(de)集(ji)成(cheng)電(dian)(dian)路(lu)，如固定電(dian)(dian)壓(ya)(ya)(ya)(ya)輸出(chu)(chu)的(de)集(ji)成(cheng)電(dian)(dian)路(lu)有(you)LM78××，LM79××等(deng)，可調電(dian)(dian)壓(ya)(ya)(ya)(ya)輸出(chu)(chu)的(de)集(ji)成(cheng)電(dian)(dian)路(lu)有(you)LM317和LM337等(deng)。

　　4個功能模塊的線性穩壓電源適配器

　　線(xian)性(xing)(xing)電源適配(pei)器的(de)優點是穩定性(xing)(xing)好、瞬態(tai)響應速度快、可靠性(xing)(xing)高(gao)(gao)、輸出電壓(ya)精度高(gao)(gao)和(he)(he)輸出紋波電壓(ya)小;缺點是工作(zuo)頻率(lv)低，所(suo)采用的(de)工頻變壓(ya)器、濾波器的(de)體積和(he)(he)重量都較(jiao)大。調整管(guan)工作(zuo)在線(xian)性(xing)(xing)狀(zhuang)態(tai)，功耗大、效率(lv)低，需要加裝散熱器。