開關電源不同于線性茄子視頻APP:電源適配器，前者調整管工作在通、斷狀態，后者調整管工作在線性狀態。電源適配器通過控制調整管的通、斷時間實現穩壓。電源適配器的優點是體積小、重量輕、功耗小、穩壓范圍寬，效率可高達80%～90%。調整管功率損耗小，散熱器也隨之減小。英規電源適配器工作頻率在幾十千赫茲甚至幾百千赫茲，濾波電感、電容元件可用較小的容量，允許的環境溫度也可以大大提高，廣泛應用在各種電子設備中。本章主要介紹電源適配器的基本構成、分類及工作原理，讓讀者對電源適配器有一個初步的認識。

　　穩壓電源適配器的比較

　　電(dian)(dian)(dian)(dian)子(zi)設備(bei)離不開電(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)適(shi)(shi)配器。電(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)適(shi)(shi)配器供(gong)給(gei)電(dian)(dian)(dian)(dian)子(zi)設備(bei)所需要(yao)的能量(liang)。電(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)適(shi)(shi)配器的性能、質(zhi)量(liang)直接影響著電(dian)(dian)(dian)(dian)子(zi)設備(bei)的安全可(ke)靠運行，故此對(dui)電(dian)(dian)(dian)(dian)子(zi)設備(bei)電(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)適(shi)(shi)配器性能、質(zhi)量(liang)的要(yao)求(qiu)也越來越高。現有的電(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)適(shi)(shi)配器主(zhu)要(yao)有兩(liang)(liang)大類(lei)：串(chuan)聯線性穩壓(ya)電(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)適(shi)(shi)配器(簡稱(cheng)線性電(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)適(shi)(shi)配器)和開關穩壓(ya)電(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)適(shi)(shi)配器(簡稱(cheng)電(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)適(shi)(shi)配器)。這(zhe)兩(liang)(liang)類(lei)電(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)適(shi)(shi)配器各具(ju)特色而被廣(guang)泛應用。

　　線性電源適配器的結構與特點

　　線性電源(yuan)適配(pei)器通常都(dou)是由(you)電網所提供的交流電，經過變(bian)壓、整(zheng)流、濾波和(he)穩壓環節(jie)而得到。其各個部分(fen)電路的作(zuo)用如(ru)下：

　　①電(dian)源適配器(qi)(qi)變壓(ya)(ya)(ya)器(qi)(qi)——將220V電(dian)網(wang)電(dian)壓(ya)(ya)(ya)轉換為整流電(dian)路(lu)所(suo)需要的交(jiao)流電(dian)壓(ya)(ya)(ya)值，而(er)少部分電(dian)路(lu)采用(yong)電(dian)容降(jiang)壓(ya)(ya)(ya)，如遙控電(dian)風(feng)扇電(dian)路(lu)。

　　②整流(liu)(liu)電(dian)(dian)(dian)路——將交流(liu)(liu)電(dian)(dian)(dian)壓轉換為脈(mo)動(dong)直流(liu)(liu)電(dian)(dian)(dian)壓。常用的(de)整流(liu)(liu)電(dian)(dian)(dian)路有(you)半波(bo)整流(liu)(liu)電(dian)(dian)(dian)路、全波(bo)整流(liu)(liu)電(dian)(dian)(dian)路和橋式整流(liu)(liu)電(dian)(dian)(dian)路。

　　③濾(lv)波(bo)(bo)(bo)電(dian)(dian)路(lu)(lu)——將(jiang)脈動直流(liu)電(dian)(dian)壓(ya)轉換成較為平(ping)滑(hua)的直流(liu)電(dian)(dian)壓(ya)。線性(xing)電(dian)(dian)源適(shi)配器中常用的濾(lv)波(bo)(bo)(bo)電(dian)(dian)路(lu)(lu)有(you)電(dian)(dian)感濾(lv)波(bo)(bo)(bo)、電(dian)(dian)容濾(lv)波(bo)(bo)(bo)和阻容濾(lv)波(bo)(bo)(bo)，其中最常用的是電(dian)(dian)容濾(lv)波(bo)(bo)(bo)。

　　④穩壓(ya)(ya)(ya)(ya)電(dian)路(lu)(lu)——將直流電(dian)源適(shi)配器的(de)輸出電(dian)壓(ya)(ya)(ya)(ya)穩定，基本不受電(dian)網(wang)電(dian)壓(ya)(ya)(ya)(ya)或(huo)負載(zai)的(de)影(ying)響。在線性電(dian)源適(shi)配器中常用的(de)穩壓(ya)(ya)(ya)(ya)電(dian)路(lu)(lu)有二極管(guan)穩壓(ya)(ya)(ya)(ya)、串聯(lian)(lian)穩壓(ya)(ya)(ya)(ya)。其中，串聯(lian)(lian)穩壓(ya)(ya)(ya)(ya)有現成的(de)集(ji)(ji)成電(dian)路(lu)(lu)，如固定電(dian)壓(ya)(ya)(ya)(ya)輸出的(de)集(ji)(ji)成電(dian)路(lu)(lu)有LM78××，LM79××等，可調電(dian)壓(ya)(ya)(ya)(ya)輸出的(de)集(ji)(ji)成電(dian)路(lu)(lu)有LM317和LM337等。

　　4個功能模塊的線性穩壓電源適配器

　　線(xian)性電(dian)源適配(pei)器(qi)的優點是穩定性好、瞬態(tai)響應(ying)速度(du)快、可靠(kao)性高(gao)、輸出(chu)(chu)電(dian)壓(ya)精度(du)高(gao)和(he)輸出(chu)(chu)紋波電(dian)壓(ya)小(xiao);缺點是工作頻(pin)率(lv)低(di)，所采用的工頻(pin)變壓(ya)器(qi)、濾波器(qi)的體積和(he)重量(liang)都較大。調整管工作在(zai)線(xian)性狀(zhuang)態(tai)，功(gong)耗大、效(xiao)率(lv)低(di)，需要(yao)加(jia)裝散熱器(qi)。