開關電源不同于線性電源適配器，前(qian)者(zhe)調整管(guan)工作在通、斷(duan)狀(zhuang)態(tai)，后者(zhe)調整管(guan)工作在線性狀(zhuang)態(tai)。電(dian)源(yuan)適(shi)(shi)配器(qi)通過控(kong)制調整管(guan)的(de)通、斷(duan)時間實現穩壓。電(dian)源(yuan)適(shi)(shi)配器(qi)的(de)優點是體積小(xiao)、重量(liang)(liang)輕、功耗小(xiao)、穩壓范(fan)圍寬，效率可高達80%～90%。調整管(guan)功率損耗小(xiao)，散熱器(qi)也隨之減小(xiao)。英規電(dian)源(yuan)適(shi)(shi)配器(qi)工作頻率在幾十千赫茲甚至(zhi)幾百千赫茲，濾波電(dian)感(gan)、電(dian)容(rong)元件可用(yong)(yong)較(jiao)小(xiao)的(de)容(rong)量(liang)(liang)，允許的(de)環(huan)境溫度也可以大大提高，廣泛應用(yong)(yong)在各種電(dian)子設備中。本章主要介紹電(dian)源(yuan)適(shi)(shi)配器(qi)的(de)基本構(gou)成(cheng)、分(fen)類(lei)及工作原理，讓讀者(zhe)對(dui)電(dian)源(yuan)適(shi)(shi)配器(qi)有一個初步(bu)的(de)認識(shi)。

　　穩壓電源適配器的比較

　　電(dian)(dian)(dian)子(zi)設(she)備(bei)離(li)不開電(dian)(dian)(dian)源(yuan)適(shi)配(pei)器(qi)(qi)。電(dian)(dian)(dian)源(yuan)適(shi)配(pei)器(qi)(qi)供給(gei)電(dian)(dian)(dian)子(zi)設(she)備(bei)所需(xu)要(yao)的能(neng)量。電(dian)(dian)(dian)源(yuan)適(shi)配(pei)器(qi)(qi)的性(xing)(xing)能(neng)、質量直接影響著電(dian)(dian)(dian)子(zi)設(she)備(bei)的安全可靠(kao)運行，故此(ci)對電(dian)(dian)(dian)子(zi)設(she)備(bei)電(dian)(dian)(dian)源(yuan)適(shi)配(pei)器(qi)(qi)性(xing)(xing)能(neng)、質量的要(yao)求也越來越高。現(xian)有的電(dian)(dian)(dian)源(yuan)適(shi)配(pei)器(qi)(qi)主要(yao)有兩(liang)大類：串(chuan)聯線性(xing)(xing)穩(wen)壓電(dian)(dian)(dian)源(yuan)適(shi)配(pei)器(qi)(qi)(簡稱線性(xing)(xing)電(dian)(dian)(dian)源(yuan)適(shi)配(pei)器(qi)(qi))和開關穩(wen)壓電(dian)(dian)(dian)源(yuan)適(shi)配(pei)器(qi)(qi)(簡稱電(dian)(dian)(dian)源(yuan)適(shi)配(pei)器(qi)(qi))。這兩(liang)類電(dian)(dian)(dian)源(yuan)適(shi)配(pei)器(qi)(qi)各具(ju)特色而被(bei)廣(guang)泛應用。

　　線性電源適配器的結構與特點

　　線性(xing)電(dian)(dian)源(yuan)適(shi)配器通常都是(shi)由電(dian)(dian)網所提供的(de)交流電(dian)(dian)，經過(guo)變壓(ya)(ya)、整流、濾(lv)波(bo)和穩壓(ya)(ya)環節而得到。其(qi)各個部(bu)分(fen)電(dian)(dian)路(lu)的(de)作用(yong)如下：

　　①電(dian)(dian)源適配器(qi)變壓器(qi)——將220V電(dian)(dian)網電(dian)(dian)壓轉(zhuan)換為整流電(dian)(dian)路所需要的(de)交(jiao)流電(dian)(dian)壓值，而少部(bu)分電(dian)(dian)路采用電(dian)(dian)容降壓，如遙控(kong)電(dian)(dian)風扇(shan)電(dian)(dian)路。

　　②整(zheng)流(liu)(liu)電(dian)路(lu)——將交流(liu)(liu)電(dian)壓轉(zhuan)換(huan)為(wei)脈動(dong)直(zhi)流(liu)(liu)電(dian)壓。常用的(de)整(zheng)流(liu)(liu)電(dian)路(lu)有半波(bo)整(zheng)流(liu)(liu)電(dian)路(lu)、全波(bo)整(zheng)流(liu)(liu)電(dian)路(lu)和橋式整(zheng)流(liu)(liu)電(dian)路(lu)。

　　③濾波(bo)電路——將脈動直流(liu)電壓轉換(huan)成較為平滑的(de)直流(liu)電壓。線性電源適配器(qi)中常用的(de)濾波(bo)電路有電感(gan)濾波(bo)、電容濾波(bo)和阻(zu)容濾波(bo)，其(qi)中最常用的(de)是電容濾波(bo)。

　　④穩壓(ya)電(dian)(dian)路——將直(zhi)流電(dian)(dian)源適配器的輸出電(dian)(dian)壓(ya)穩定(ding)，基本不受電(dian)(dian)網電(dian)(dian)壓(ya)或負載(zai)的影響。在(zai)線(xian)性電(dian)(dian)源適配器中常(chang)用的穩壓(ya)電(dian)(dian)路有(you)二(er)極管穩壓(ya)、串聯穩壓(ya)。其(qi)中，串聯穩壓(ya)有(you)現(xian)成(cheng)的集(ji)(ji)成(cheng)電(dian)(dian)路，如固(gu)定(ding)電(dian)(dian)壓(ya)輸出的集(ji)(ji)成(cheng)電(dian)(dian)路有(you)LM78××，LM79××等，可調(diao)電(dian)(dian)壓(ya)輸出的集(ji)(ji)成(cheng)電(dian)(dian)路有(you)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)源適配器的(de)優點(dian)(dian)是(shi)穩定性(xing)好、瞬(shun)態(tai)響應速度(du)快、可靠性(xing)高、輸(shu)出(chu)電(dian)壓(ya)精度(du)高和輸(shu)出(chu)紋(wen)波電(dian)壓(ya)小;缺點(dian)(dian)是(shi)工(gong)(gong)作頻率(lv)低，所(suo)采(cai)用的(de)工(gong)(gong)頻變壓(ya)器、濾波器的(de)體積(ji)和重量都(dou)較大(da)。調整管工(gong)(gong)作在線性(xing)狀(zhuang)態(tai)，功耗(hao)大(da)、效率(lv)低，需要加裝散熱器。