開關電源不同于線性電源適配器，前(qian)者(zhe)調(diao)(diao)(diao)整管(guan)(guan)工(gong)(gong)作在通、斷狀態(tai)，后者(zhe)調(diao)(diao)(diao)整管(guan)(guan)工(gong)(gong)作在線(xian)性狀態(tai)。電(dian)(dian)(dian)源適(shi)配(pei)器(qi)通過控制(zhi)調(diao)(diao)(diao)整管(guan)(guan)的通、斷時間實現穩壓。電(dian)(dian)(dian)源適(shi)配(pei)器(qi)的優(you)點(dian)是體積小(xiao)(xiao)、重量(liang)輕、功耗小(xiao)(xiao)、穩壓范圍寬，效率可(ke)(ke)高達80%～90%。調(diao)(diao)(diao)整管(guan)(guan)功率損耗小(xiao)(xiao)，散熱器(qi)也隨之減小(xiao)(xiao)。英規(gui)電(dian)(dian)(dian)源適(shi)配(pei)器(qi)工(gong)(gong)作頻率在幾十(shi)千赫茲甚至(zhi)幾百(bai)千赫茲，濾波電(dian)(dian)(dian)感、電(dian)(dian)(dian)容元(yuan)件可(ke)(ke)用較小(xiao)(xiao)的容量(liang)，允許的環境溫度也可(ke)(ke)以大大提(ti)高，廣泛應用在各種電(dian)(dian)(dian)子設備中。本章主要介紹電(dian)(dian)(dian)源適(shi)配(pei)器(qi)的基本構成、分類及工(gong)(gong)作原(yuan)理(li)，讓讀者(zhe)對電(dian)(dian)(dian)源適(shi)配(pei)器(qi)有(you)一(yi)個初(chu)步的認識。

　　穩壓電源適配器的比較

　　電(dian)(dian)子(zi)設(she)備離不開電(dian)(dian)源(yuan)適(shi)(shi)(shi)配器(qi)(qi)(qi)。電(dian)(dian)源(yuan)適(shi)(shi)(shi)配器(qi)(qi)(qi)供給電(dian)(dian)子(zi)設(she)備所(suo)需要的(de)能(neng)量(liang)。電(dian)(dian)源(yuan)適(shi)(shi)(shi)配器(qi)(qi)(qi)的(de)性(xing)(xing)能(neng)、質量(liang)直接影(ying)響著電(dian)(dian)子(zi)設(she)備的(de)安全可靠運行(xing)，故此對電(dian)(dian)子(zi)設(she)備電(dian)(dian)源(yuan)適(shi)(shi)(shi)配器(qi)(qi)(qi)性(xing)(xing)能(neng)、質量(liang)的(de)要求(qiu)也越來(lai)越高(gao)。現有的(de)電(dian)(dian)源(yuan)適(shi)(shi)(shi)配器(qi)(qi)(qi)主要有兩大(da)類(lei)(lei)：串(chuan)聯線性(xing)(xing)穩(wen)壓電(dian)(dian)源(yuan)適(shi)(shi)(shi)配器(qi)(qi)(qi)(簡稱(cheng)(cheng)線性(xing)(xing)電(dian)(dian)源(yuan)適(shi)(shi)(shi)配器(qi)(qi)(qi))和開關穩(wen)壓電(dian)(dian)源(yuan)適(shi)(shi)(shi)配器(qi)(qi)(qi)(簡稱(cheng)(cheng)電(dian)(dian)源(yuan)適(shi)(shi)(shi)配器(qi)(qi)(qi))。這兩類(lei)(lei)電(dian)(dian)源(yuan)適(shi)(shi)(shi)配器(qi)(qi)(qi)各具特色而被(bei)廣泛應用。

　　線性電源適配器的結構與特點

　　線性電(dian)源適配器通常(chang)都是由(you)電(dian)網所提(ti)供(gong)的交流電(dian)，經過(guo)變壓、整流、濾(lv)波和(he)穩(wen)壓環節(jie)而得到。其各(ge)個部分(fen)電(dian)路的作用如下(xia)：

　　①電源(yuan)適配器變壓器——將220V電網電壓轉(zhuan)換為整流電路(lu)(lu)所需要的交流電壓值，而少部分電路(lu)(lu)采(cai)用電容(rong)降壓，如遙控電風扇(shan)電路(lu)(lu)。

　　②整(zheng)(zheng)(zheng)(zheng)流(liu)(liu)電(dian)路(lu)(lu)——將交流(liu)(liu)電(dian)壓轉換為脈動直流(liu)(liu)電(dian)壓。常用(yong)的整(zheng)(zheng)(zheng)(zheng)流(liu)(liu)電(dian)路(lu)(lu)有半波(bo)整(zheng)(zheng)(zheng)(zheng)流(liu)(liu)電(dian)路(lu)(lu)、全波(bo)整(zheng)(zheng)(zheng)(zheng)流(liu)(liu)電(dian)路(lu)(lu)和橋式整(zheng)(zheng)(zheng)(zheng)流(liu)(liu)電(dian)路(lu)(lu)。

　　③濾(lv)(lv)波(bo)電(dian)(dian)路——將脈動直流電(dian)(dian)壓轉換(huan)成較為平(ping)滑的直流電(dian)(dian)壓。線(xian)性電(dian)(dian)源適配器中常用(yong)的濾(lv)(lv)波(bo)電(dian)(dian)路有電(dian)(dian)感濾(lv)(lv)波(bo)、電(dian)(dian)容濾(lv)(lv)波(bo)和阻容濾(lv)(lv)波(bo)，其(qi)中最常用(yong)的是電(dian)(dian)容濾(lv)(lv)波(bo)。

　　④穩(wen)壓(ya)(ya)(ya)電(dian)路(lu)(lu)——將直流電(dian)源適(shi)配(pei)器的(de)輸出(chu)電(dian)壓(ya)(ya)(ya)穩(wen)定，基本不受電(dian)網電(dian)壓(ya)(ya)(ya)或(huo)負載的(de)影響。在線性電(dian)源適(shi)配(pei)器中常用(yong)的(de)穩(wen)壓(ya)(ya)(ya)電(dian)路(lu)(lu)有(you)(you)二極管穩(wen)壓(ya)(ya)(ya)、串聯穩(wen)壓(ya)(ya)(ya)。其(qi)中，串聯穩(wen)壓(ya)(ya)(ya)有(you)(you)現成(cheng)的(de)集成(cheng)電(dian)路(lu)(lu)，如固定電(dian)壓(ya)(ya)(ya)輸出(chu)的(de)集成(cheng)電(dian)路(lu)(lu)有(you)(you)LM78××，LM79××等(deng)，可調(diao)電(dian)壓(ya)(ya)(ya)輸出(chu)的(de)集成(cheng)電(dian)路(lu)(lu)有(you)(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(pei)器(qi)的(de)優點(dian)是穩定性(xing)好、瞬態(tai)(tai)響應速(su)度快、可靠性(xing)高、輸(shu)出(chu)電壓精度高和輸(shu)出(chu)紋(wen)波(bo)電壓小;缺點(dian)是工作頻(pin)率低，所采用的(de)工頻(pin)變壓器(qi)、濾波(bo)器(qi)的(de)體(ti)積和重(zhong)量都較(jiao)大。調整管工作在(zai)線性(xing)狀態(tai)(tai)，功耗大、效(xiao)率低，需要(yao)加裝散熱(re)器(qi)。