開關電源不同于線性電源適配器，前者調(diao)(diao)整(zheng)管(guan)工(gong)作在通、斷狀態，后(hou)者調(diao)(diao)整(zheng)管(guan)工(gong)作在線性狀態。電(dian)(dian)(dian)源(yuan)(yuan)適(shi)(shi)配(pei)(pei)(pei)(pei)器通過控制調(diao)(diao)整(zheng)管(guan)的(de)(de)通、斷時間(jian)實現(xian)穩壓。電(dian)(dian)(dian)源(yuan)(yuan)適(shi)(shi)配(pei)(pei)(pei)(pei)器的(de)(de)優點是體(ti)積小(xiao)(xiao)、重量輕、功(gong)耗小(xiao)(xiao)、穩壓范圍寬(kuan)，效(xiao)率(lv)(lv)可(ke)(ke)高達80%～90%。調(diao)(diao)整(zheng)管(guan)功(gong)率(lv)(lv)損耗小(xiao)(xiao)，散熱器也隨之減小(xiao)(xiao)。英(ying)規(gui)電(dian)(dian)(dian)源(yuan)(yuan)適(shi)(shi)配(pei)(pei)(pei)(pei)器工(gong)作頻率(lv)(lv)在幾(ji)十千(qian)赫(he)茲甚至幾(ji)百千(qian)赫(he)茲，濾波電(dian)(dian)(dian)感、電(dian)(dian)(dian)容元(yuan)件可(ke)(ke)用較小(xiao)(xiao)的(de)(de)容量，允許的(de)(de)環境溫(wen)度也可(ke)(ke)以大(da)大(da)提高，廣(guang)泛應用在各種電(dian)(dian)(dian)子(zi)設備中。本(ben)章主(zhu)要介紹電(dian)(dian)(dian)源(yuan)(yuan)適(shi)(shi)配(pei)(pei)(pei)(pei)器的(de)(de)基本(ben)構成、分類及工(gong)作原(yuan)理(li)，讓讀者對電(dian)(dian)(dian)源(yuan)(yuan)適(shi)(shi)配(pei)(pei)(pei)(pei)器有(you)一個(ge)初步的(de)(de)認(ren)識。

　　穩壓電源適配器的比較

　　電(dian)(dian)子(zi)(zi)設備(bei)(bei)離不開電(dian)(dian)源(yuan)(yuan)(yuan)(yuan)適(shi)(shi)配(pei)器(qi)(qi)。電(dian)(dian)源(yuan)(yuan)(yuan)(yuan)適(shi)(shi)配(pei)器(qi)(qi)供給電(dian)(dian)子(zi)(zi)設備(bei)(bei)所需要的(de)能量(liang)。電(dian)(dian)源(yuan)(yuan)(yuan)(yuan)適(shi)(shi)配(pei)器(qi)(qi)的(de)性(xing)能、質(zhi)量(liang)直(zhi)接影響著電(dian)(dian)子(zi)(zi)設備(bei)(bei)的(de)安全(quan)可(ke)靠運行，故(gu)此對電(dian)(dian)子(zi)(zi)設備(bei)(bei)電(dian)(dian)源(yuan)(yuan)(yuan)(yuan)適(shi)(shi)配(pei)器(qi)(qi)性(xing)能、質(zhi)量(liang)的(de)要求也越(yue)來越(yue)高(gao)。現有的(de)電(dian)(dian)源(yuan)(yuan)(yuan)(yuan)適(shi)(shi)配(pei)器(qi)(qi)主要有兩大類(lei)：串聯線(xian)性(xing)穩壓電(dian)(dian)源(yuan)(yuan)(yuan)(yuan)適(shi)(shi)配(pei)器(qi)(qi)(簡稱(cheng)(cheng)線(xian)性(xing)電(dian)(dian)源(yuan)(yuan)(yuan)(yuan)適(shi)(shi)配(pei)器(qi)(qi))和(he)開關穩壓電(dian)(dian)源(yuan)(yuan)(yuan)(yuan)適(shi)(shi)配(pei)器(qi)(qi)(簡稱(cheng)(cheng)電(dian)(dian)源(yuan)(yuan)(yuan)(yuan)適(shi)(shi)配(pei)器(qi)(qi))。這兩類(lei)電(dian)(dian)源(yuan)(yuan)(yuan)(yuan)適(shi)(shi)配(pei)器(qi)(qi)各具特色而被廣泛應用。

　　線性電源適配器的結構與特點

　　線性電(dian)源適配(pei)器(qi)通常(chang)都(dou)是(shi)由電(dian)網所(suo)提供(gong)的交流(liu)電(dian)，經過變壓、整流(liu)、濾波和(he)穩(wen)壓環節(jie)而得到。其各個(ge)部分電(dian)路的作用如下：

　　①電(dian)(dian)(dian)(dian)源(yuan)適配器變壓(ya)器——將220V電(dian)(dian)(dian)(dian)網電(dian)(dian)(dian)(dian)壓(ya)轉換(huan)為整流電(dian)(dian)(dian)(dian)路所需要的交流電(dian)(dian)(dian)(dian)壓(ya)值(zhi)，而(er)少部分電(dian)(dian)(dian)(dian)路采用電(dian)(dian)(dian)(dian)容降壓(ya)，如遙控電(dian)(dian)(dian)(dian)風扇電(dian)(dian)(dian)(dian)路。

　　②整流(liu)電(dian)路(lu)(lu)(lu)——將交流(liu)電(dian)壓轉換為脈動直流(liu)電(dian)壓。常用的整流(liu)電(dian)路(lu)(lu)(lu)有半(ban)波(bo)整流(liu)電(dian)路(lu)(lu)(lu)、全波(bo)整流(liu)電(dian)路(lu)(lu)(lu)和橋式整流(liu)電(dian)路(lu)(lu)(lu)。

　　③濾(lv)(lv)波(bo)電(dian)路——將脈動直(zhi)流電(dian)壓轉換成較(jiao)為平滑的(de)直(zhi)流電(dian)壓。線性(xing)電(dian)源適配器中常(chang)用(yong)的(de)濾(lv)(lv)波(bo)電(dian)路有電(dian)感濾(lv)(lv)波(bo)、電(dian)容濾(lv)(lv)波(bo)和阻(zu)容濾(lv)(lv)波(bo)，其中最常(chang)用(yong)的(de)是電(dian)容濾(lv)(lv)波(bo)。

　　④穩(wen)(wen)(wen)壓(ya)(ya)(ya)電(dian)(dian)路——將直流電(dian)(dian)源適配器的(de)(de)輸(shu)出電(dian)(dian)壓(ya)(ya)(ya)穩(wen)(wen)(wen)定，基(ji)本(ben)不受(shou)電(dian)(dian)網電(dian)(dian)壓(ya)(ya)(ya)或負(fu)載的(de)(de)影(ying)響。在線性(xing)電(dian)(dian)源適配器中常用的(de)(de)穩(wen)(wen)(wen)壓(ya)(ya)(ya)電(dian)(dian)路有(you)二極(ji)管(guan)穩(wen)(wen)(wen)壓(ya)(ya)(ya)、串聯(lian)穩(wen)(wen)(wen)壓(ya)(ya)(ya)。其中，串聯(lian)穩(wen)(wen)(wen)壓(ya)(ya)(ya)有(you)現成的(de)(de)集成電(dian)(dian)路，如(ru)固定電(dian)(dian)壓(ya)(ya)(ya)輸(shu)出的(de)(de)集成電(dian)(dian)路有(you)LM78××，LM79××等(deng)，可調電(dian)(dian)壓(ya)(ya)(ya)輸(shu)出的(de)(de)集成電(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

　　線性電源(yuan)適配器的優點是穩定性好、瞬(shun)態響應速(su)度快、可靠性高、輸出電壓(ya)精度高和輸出紋波電壓(ya)小(xiao);缺(que)點是工(gong)作(zuo)頻(pin)率低(di)，所采用的工(gong)頻(pin)變壓(ya)器、濾波器的體積和重量(liang)都較大(da)。調(diao)整管工(gong)作(zuo)在線性狀態，功耗大(da)、效率低(di)，需要加(jia)裝散熱器。