開關電源不同于線性電源適配器，前者調(diao)整(zheng)管(guan)工(gong)(gong)作(zuo)在通、斷狀態，后(hou)者調(diao)整(zheng)管(guan)工(gong)(gong)作(zuo)在線性狀態。電(dian)源適配器(qi)通過(guo)控制調(diao)整(zheng)管(guan)的(de)通、斷時間實(shi)現穩壓。電(dian)源適配器(qi)的(de)優點是體積小(xiao)、重量輕、功耗小(xiao)、穩壓范圍寬，效率(lv)(lv)可(ke)高達(da)80%～90%。調(diao)整(zheng)管(guan)功率(lv)(lv)損耗小(xiao)，散熱器(qi)也(ye)隨之減(jian)小(xiao)。英規電(dian)源適配器(qi)工(gong)(gong)作(zuo)頻率(lv)(lv)在幾(ji)十(shi)千(qian)赫茲甚至幾(ji)百千(qian)赫茲，濾波電(dian)感、電(dian)容(rong)(rong)元(yuan)件可(ke)用(yong)較小(xiao)的(de)容(rong)(rong)量，允許的(de)環境溫度也(ye)可(ke)以大大提高，廣(guang)泛應用(yong)在各種電(dian)子(zi)設備(bei)中。本章(zhang)主要介紹電(dian)源適配器(qi)的(de)基本構成(cheng)、分類及(ji)工(gong)(gong)作(zuo)原理，讓(rang)讀者對(dui)電(dian)源適配器(qi)有(you)一個初步(bu)的(de)認識。

　　穩壓電源適配器的比較

　　電(dian)(dian)(dian)(dian)(dian)子(zi)設備(bei)離(li)不(bu)開(kai)電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)適(shi)(shi)(shi)(shi)(shi)配(pei)器(qi)(qi)。電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)適(shi)(shi)(shi)(shi)(shi)配(pei)器(qi)(qi)供給電(dian)(dian)(dian)(dian)(dian)子(zi)設備(bei)所需要的(de)能量(liang)(liang)。電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)適(shi)(shi)(shi)(shi)(shi)配(pei)器(qi)(qi)的(de)性能、質量(liang)(liang)直接影響著電(dian)(dian)(dian)(dian)(dian)子(zi)設備(bei)的(de)安全可靠運行，故(gu)此(ci)對電(dian)(dian)(dian)(dian)(dian)子(zi)設備(bei)電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)適(shi)(shi)(shi)(shi)(shi)配(pei)器(qi)(qi)性能、質量(liang)(liang)的(de)要求也越(yue)來越(yue)高。現有的(de)電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)適(shi)(shi)(shi)(shi)(shi)配(pei)器(qi)(qi)主要有兩(liang)大類：串(chuan)聯線(xian)性穩壓電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)適(shi)(shi)(shi)(shi)(shi)配(pei)器(qi)(qi)(簡稱線(xian)性電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)適(shi)(shi)(shi)(shi)(shi)配(pei)器(qi)(qi))和開(kai)關穩壓電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)適(shi)(shi)(shi)(shi)(shi)配(pei)器(qi)(qi)(簡稱電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)適(shi)(shi)(shi)(shi)(shi)配(pei)器(qi)(qi))。這兩(liang)類電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)適(shi)(shi)(shi)(shi)(shi)配(pei)器(qi)(qi)各(ge)具特色(se)而(er)被廣泛(fan)應用。

　　線性電源適配器的結構與特點

　　線(xian)性(xing)電源適配(pei)器通常都是由電網所提供的交(jiao)流電，經過(guo)變壓、整流、濾波和穩壓環節而得(de)到(dao)。其各(ge)個部分電路的作用如(ru)下：

　　①電(dian)源適配器變壓(ya)(ya)器——將(jiang)220V電(dian)網電(dian)壓(ya)(ya)轉(zhuan)換為整(zheng)流電(dian)路所需要的交流電(dian)壓(ya)(ya)值，而少部(bu)分電(dian)路采用電(dian)容降壓(ya)(ya)，如(ru)遙(yao)控電(dian)風(feng)扇電(dian)路。

　　②整(zheng)(zheng)流(liu)(liu)電(dian)(dian)(dian)路——將交流(liu)(liu)電(dian)(dian)(dian)壓(ya)轉換為脈動直(zhi)流(liu)(liu)電(dian)(dian)(dian)壓(ya)。常(chang)用的整(zheng)(zheng)流(liu)(liu)電(dian)(dian)(dian)路有(you)半(ban)波整(zheng)(zheng)流(liu)(liu)電(dian)(dian)(dian)路、全波整(zheng)(zheng)流(liu)(liu)電(dian)(dian)(dian)路和橋式整(zheng)(zheng)流(liu)(liu)電(dian)(dian)(dian)路。

　　③濾(lv)(lv)(lv)波(bo)電路——將脈(mo)動直(zhi)流電壓轉(zhuan)換成(cheng)較為平滑的(de)直(zhi)流電壓。線性電源適配器中常用的(de)濾(lv)(lv)(lv)波(bo)電路有電感濾(lv)(lv)(lv)波(bo)、電容(rong)濾(lv)(lv)(lv)波(bo)和阻容(rong)濾(lv)(lv)(lv)波(bo)，其中最常用的(de)是電容(rong)濾(lv)(lv)(lv)波(bo)。

　　④穩壓(ya)電(dian)(dian)(dian)(dian)路——將直流(liu)電(dian)(dian)(dian)(dian)源(yuan)適(shi)(shi)配器的輸(shu)出(chu)電(dian)(dian)(dian)(dian)壓(ya)穩定，基本不(bu)受(shou)電(dian)(dian)(dian)(dian)網電(dian)(dian)(dian)(dian)壓(ya)或負載的影響。在線(xian)性電(dian)(dian)(dian)(dian)源(yuan)適(shi)(shi)配器中常用的穩壓(ya)電(dian)(dian)(dian)(dian)路有(you)二(er)極(ji)管穩壓(ya)、串聯穩壓(ya)。其中，串聯穩壓(ya)有(you)現成(cheng)的集(ji)(ji)成(cheng)電(dian)(dian)(dian)(dian)路，如固(gu)定電(dian)(dian)(dian)(dian)壓(ya)輸(shu)出(chu)的集(ji)(ji)成(cheng)電(dian)(dian)(dian)(dian)路有(you)LM78××，LM79××等(deng)，可調(diao)電(dian)(dian)(dian)(dian)壓(ya)輸(shu)出(chu)的集(ji)(ji)成(cheng)電(dian)(dian)(dian)(dian)路有(you)LM317和LM337等(deng)。

　　4個功能模塊的線性穩壓電源適配器

　　線性(xing)電源適(shi)配器(qi)(qi)的(de)(de)優點是穩定性(xing)好、瞬態響應速(su)度(du)快、可靠性(xing)高(gao)、輸(shu)出電壓(ya)精度(du)高(gao)和輸(shu)出紋波電壓(ya)小;缺(que)點是工作頻率低(di)，所采用的(de)(de)工頻變壓(ya)器(qi)(qi)、濾波器(qi)(qi)的(de)(de)體(ti)積和重量(liang)都較大。調整管(guan)工作在線性(xing)狀(zhuang)態，功耗大、效率低(di)，需要加裝散熱器(qi)(qi)。