開關電源不同于線性電源適配器，前者調(diao)(diao)整管(guan)(guan)工作(zuo)(zuo)在通、斷狀(zhuang)態(tai)，后者調(diao)(diao)整管(guan)(guan)工作(zuo)(zuo)在線性(xing)狀(zhuang)態(tai)。電(dian)源(yuan)適配(pei)器(qi)(qi)通過控制調(diao)(diao)整管(guan)(guan)的(de)通、斷時間實現穩壓。電(dian)源(yuan)適配(pei)器(qi)(qi)的(de)優點(dian)是體積小(xiao)(xiao)、重(zhong)量輕、功耗(hao)小(xiao)(xiao)、穩壓范圍寬，效率可(ke)高(gao)達(da)80%～90%。調(diao)(diao)整管(guan)(guan)功率損耗(hao)小(xiao)(xiao)，散熱器(qi)(qi)也隨之減小(xiao)(xiao)。英(ying)規(gui)電(dian)源(yuan)適配(pei)器(qi)(qi)工作(zuo)(zuo)頻(pin)率在幾十千(qian)赫(he)茲甚(shen)至幾百千(qian)赫(he)茲，濾波電(dian)感、電(dian)容元件可(ke)用(yong)較小(xiao)(xiao)的(de)容量，允許的(de)環(huan)境溫度(du)也可(ke)以大大提高(gao)，廣泛應用(yong)在各種電(dian)子(zi)設備中。本(ben)(ben)章主要介(jie)紹電(dian)源(yuan)適配(pei)器(qi)(qi)的(de)基本(ben)(ben)構成、分類(lei)及(ji)工作(zuo)(zuo)原理，讓讀者對電(dian)源(yuan)適配(pei)器(qi)(qi)有一個初步的(de)認(ren)識(shi)。

　　穩壓電源適配器的比較

　　電(dian)(dian)(dian)子(zi)(zi)設(she)備離不開電(dian)(dian)(dian)源(yuan)(yuan)(yuan)適(shi)配(pei)(pei)(pei)(pei)器(qi)(qi)(qi)(qi)。電(dian)(dian)(dian)源(yuan)(yuan)(yuan)適(shi)配(pei)(pei)(pei)(pei)器(qi)(qi)(qi)(qi)供給電(dian)(dian)(dian)子(zi)(zi)設(she)備所需要(yao)的(de)能(neng)量。電(dian)(dian)(dian)源(yuan)(yuan)(yuan)適(shi)配(pei)(pei)(pei)(pei)器(qi)(qi)(qi)(qi)的(de)性能(neng)、質(zhi)量直接影(ying)響著(zhu)電(dian)(dian)(dian)子(zi)(zi)設(she)備的(de)安全(quan)可靠運行，故此對電(dian)(dian)(dian)子(zi)(zi)設(she)備電(dian)(dian)(dian)源(yuan)(yuan)(yuan)適(shi)配(pei)(pei)(pei)(pei)器(qi)(qi)(qi)(qi)性能(neng)、質(zhi)量的(de)要(yao)求也(ye)越(yue)來越(yue)高。現(xian)有的(de)電(dian)(dian)(dian)源(yuan)(yuan)(yuan)適(shi)配(pei)(pei)(pei)(pei)器(qi)(qi)(qi)(qi)主要(yao)有兩大(da)類(lei)(lei)：串聯線(xian)(xian)性穩壓(ya)電(dian)(dian)(dian)源(yuan)(yuan)(yuan)適(shi)配(pei)(pei)(pei)(pei)器(qi)(qi)(qi)(qi)(簡(jian)稱線(xian)(xian)性電(dian)(dian)(dian)源(yuan)(yuan)(yuan)適(shi)配(pei)(pei)(pei)(pei)器(qi)(qi)(qi)(qi))和開關穩壓(ya)電(dian)(dian)(dian)源(yuan)(yuan)(yuan)適(shi)配(pei)(pei)(pei)(pei)器(qi)(qi)(qi)(qi)(簡(jian)稱電(dian)(dian)(dian)源(yuan)(yuan)(yuan)適(shi)配(pei)(pei)(pei)(pei)器(qi)(qi)(qi)(qi))。這(zhe)兩類(lei)(lei)電(dian)(dian)(dian)源(yuan)(yuan)(yuan)適(shi)配(pei)(pei)(pei)(pei)器(qi)(qi)(qi)(qi)各具(ju)特(te)色而被廣泛應用(yong)。

　　線性電源適配器的結構與特點

　　線(xian)性電(dian)(dian)源適配器通常都是由電(dian)(dian)網所提供的交流電(dian)(dian)，經過變(bian)壓、整流、濾(lv)波和穩(wen)壓環節而(er)得(de)到。其各(ge)個部分(fen)電(dian)(dian)路的作(zuo)用如下：

　　①電(dian)(dian)(dian)源適配器變(bian)壓(ya)器——將220V電(dian)(dian)(dian)網電(dian)(dian)(dian)壓(ya)轉換(huan)為(wei)整流(liu)電(dian)(dian)(dian)路所需要的交流(liu)電(dian)(dian)(dian)壓(ya)值，而少部(bu)分(fen)電(dian)(dian)(dian)路采用電(dian)(dian)(dian)容降壓(ya)，如遙控(kong)電(dian)(dian)(dian)風扇電(dian)(dian)(dian)路。

　　②整流電路(lu)——將交流電壓(ya)轉換(huan)為脈(mo)動(dong)直流電壓(ya)。常用的整流電路(lu)有半波整流電路(lu)、全(quan)波整流電路(lu)和橋式整流電路(lu)。

　　③濾(lv)(lv)波(bo)(bo)電(dian)(dian)(dian)路——將脈動直(zhi)流電(dian)(dian)(dian)壓轉(zhuan)換成較為(wei)平滑的(de)直(zhi)流電(dian)(dian)(dian)壓。線性(xing)電(dian)(dian)(dian)源(yuan)適配器中(zhong)常用的(de)濾(lv)(lv)波(bo)(bo)電(dian)(dian)(dian)路有電(dian)(dian)(dian)感濾(lv)(lv)波(bo)(bo)、電(dian)(dian)(dian)容(rong)(rong)濾(lv)(lv)波(bo)(bo)和阻容(rong)(rong)濾(lv)(lv)波(bo)(bo)，其中(zhong)最常用的(de)是電(dian)(dian)(dian)容(rong)(rong)濾(lv)(lv)波(bo)(bo)。

　　④穩(wen)(wen)壓(ya)(ya)電(dian)(dian)(dian)(dian)(dian)路(lu)——將直流電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)適配(pei)器(qi)的(de)(de)(de)輸(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)穩(wen)(wen)定，基本不(bu)受(shou)電(dian)(dian)(dian)(dian)(dian)網電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)或(huo)負(fu)載(zai)的(de)(de)(de)影響。在線性(xing)電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)適配(pei)器(qi)中常(chang)用(yong)的(de)(de)(de)穩(wen)(wen)壓(ya)(ya)電(dian)(dian)(dian)(dian)(dian)路(lu)有(you)(you)二極管穩(wen)(wen)壓(ya)(ya)、串聯穩(wen)(wen)壓(ya)(ya)。其(qi)中，串聯穩(wen)(wen)壓(ya)(ya)有(you)(you)現成(cheng)(cheng)的(de)(de)(de)集成(cheng)(cheng)電(dian)(dian)(dian)(dian)(dian)路(lu)，如固定電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)輸(shu)出(chu)的(de)(de)(de)集成(cheng)(cheng)電(dian)(dian)(dian)(dian)(dian)路(lu)有(you)(you)LM78××，LM79××等，可調(diao)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)輸(shu)出(chu)的(de)(de)(de)集成(cheng)(cheng)電(dian)(dian)(dian)(dian)(dian)路(lu)有(you)(you)LM317和LM337等。

　　4個功能模塊的線性穩壓電源適配器

　　線性(xing)(xing)電(dian)源適配器(qi)的優點是(shi)穩定性(xing)(xing)好(hao)、瞬態(tai)響應速度快、可靠(kao)性(xing)(xing)高(gao)、輸出電(dian)壓(ya)精度高(gao)和輸出紋波電(dian)壓(ya)小(xiao);缺(que)點是(shi)工(gong)作頻率低，所采用的工(gong)頻變壓(ya)器(qi)、濾波器(qi)的體積和重量都較大。調整(zheng)管工(gong)作在線性(xing)(xing)狀態(tai)，功耗大、效率低，需要加裝散熱器(qi)。