交流(liu)(liu)電(dian)(dian)(dian)網(wang)電(dian)(dian)(dian)壓(ya)的波動和(he)負載電(dian)(dian)(dian)流(liu)(liu)的變化(hua)都(dou)會使整流(liu)(liu)電(dian)(dian)(dian)源的輸出電(dian)(dian)(dian)壓(ya)和(he)電(dian)(dian)(dian)流(liu)(liu)隨之(zhi)變動，因此要(yao)求(qiu)較(jiao)高的電(dian)(dian)(dian)子電(dian)(dian)(dian)路必須使用穩壓(ya)電(dian)(dian)(dian)源。
(1 ）穩壓管(guan)并(bing)聯穩壓電路
用一個(ge)穩壓(ya)(ya)管(guan)和負載并聯的電路是(shi)最簡單的穩壓(ya)(ya)電路，見圖(tu) 4 （ a ）。圖(tu)中 R 是(shi)限流電阻。這個(ge)電路的輸出(chu)電流很(hen)小，它的輸出(chu)電壓(ya)(ya)等于穩壓(ya)(ya)管(guan)的穩定電壓(ya)(ya)值(zhi) V Z 。
(2 ）串聯型穩壓(ya)電路
有放大(da)和負反(fan)饋作用(yong)的(de)(de)(de)串聯型(xing)穩(wen)壓(ya)(ya)電(dian)(dian)(dian)(dian)(dian)路(lu)是(shi)(shi)最常用(yong)的(de)(de)(de)穩(wen)壓(ya)(ya)電(dian)(dian)(dian)(dian)(dian)路(lu)。它的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)路(lu)和框圖見圖 4 （ b ）、（ c ）。它是(shi)(shi)從取(qu)樣電(dian)(dian)(dian)(dian)(dian)路(lu)（ R3 、 R4 ）中檢(jian)測(ce)出(chu)輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)的(de)(de)(de)變動，與基(ji)準電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)（ V Z ）比(bi)較(jiao)并經放大(da)器（ VT2 ）放大(da)后加到調整(zheng)管（ VT1 ）上，使(shi)調整(zheng)管兩端的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)隨(sui)著變化。如果(guo)輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)下(xia)降(jiang)，就使(shi)調整(zheng)管管壓(ya)(ya)降(jiang)也降(jiang)低，于是(shi)(shi)輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)被提升；如果(guo)輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)上升，就使(shi)調整(zheng)管管壓(ya)(ya)降(jiang)也上升，于是(shi)(shi)輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)被壓(ya)(ya)低，結果(guo)就使(shi)輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)基(ji)本不變。在這個電(dian)(dian)(dian)(dian)(dian)路(lu)的(de)(de)(de)基(ji)礎上發展成很多變型(xing)電(dian)(dian)(dian)(dian)(dian)路(lu)或增(zeng)加一些輔助電(dian)(dian)(dian)(dian)(dian)路(lu)，如用(yong)復合管作調整(zheng)管，輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)可調的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)路(lu)，用(yong)運算放 大(da)器作比(bi)較(jiao)放大(da)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)路(lu)，以(yi)及增(zeng)加輔助電(dian)(dian)(dian)(dian)(dian)源和過流保(bao)護電(dian)(dian)(dian)(dian)(dian)路(lu)等(deng)。
（ 3 ）開關型穩(wen)壓電路
近(jin)年來廣泛(fan)應用的(de)新型穩壓電源是開(kai)關型穩壓電源。它(ta)的(de)調整(zheng)管工作在開(kai)關狀態，本身(shen)功耗很小(xiao)，所以有效率高、體(ti)積小(xiao)等優(you)點，但電路比(bi)較復(fu)雜(za)。
開關(guan)穩(wen)(wen)壓電源從原(yuan)理上分有很多種。它的(de)基本原(yuan)理框圖(tu)(tu)見(jian)圖(tu)(tu) 4 （ d ）。圖(tu)(tu)中電感 L 和(he)電容 C 是儲能(neng)和(he)濾(lv)波(bo)元(yuan)件，二極管(guan) VD 是調整(zheng)管(guan)在關(guan)斷狀(zhuang)態時為 L 、 C 濾(lv)波(bo)器提(ti)供電流(liu)通(tong)路的(de)續(xu)流(liu)二極管(guan)。開關(guan)穩(wen)(wen)壓電源的(de)開關(guan)頻率(lv)都很高(gao)(gao)，一般為幾～幾十千赫，所(suo)以(yi)電感器的(de)體積(ji)不很大(da)，輸出電壓中的(de)高(gao)(gao)次諧波(bo)也不多。
它(ta)的(de)基本(ben)工作原理是 : 從(cong)取(qu)樣電(dian)(dian)路(lu)(lu)（ R3 、 R4 ）中檢測出(chu)(chu)取(qu)樣電(dian)(dian)壓(ya)(ya)經比(bi)較放大(da)后去控制(zhi)一個矩(ju)形(xing)波發(fa)生器。矩(ju)形(xing)波發(fa)生器的(de)輸出(chu)(chu)脈沖是控制(zhi)調整管(guan)（ VT ）的(de)導通和截止時(shi)間的(de)。如(ru)果輸出(chu)(chu)電(dian)(dian)壓(ya)(ya) U 0 因為電(dian)(dian)網電(dian)(dian)壓(ya)(ya)或負載電(dian)(dian)流的(de)變動而降低，就會(hui)使(shi)(shi)矩(ju)形(xing)波發(fa)生器的(de)輸出(chu)(chu)脈沖變寬，于是調整管(guan)導通時(shi)間增大(da)，使(shi)(shi) L 、 C 儲能電(dian)(dian)路(lu)(lu)得到更多的(de)能量，結果是使(shi)(shi)輸出(chu)(chu)電(dian)(dian)壓(ya)(ya) U 0 被提升(sheng)，達(da)到了(le)穩定輸出(chu)(chu)電(dian)(dian)壓(ya)(ya)的(de)目的(de)。
（ 4 ）集成化穩壓電路
近(jin)年(nian)來已(yi)有(you)大量集(ji)成穩(wen)壓(ya)(ya)器產品問(wen)世，品種(zhong)很多(duo)，結構也(ye)各不(bu)相同(tong)。目前用得(de)較多(duo)的有(you)三端集(ji)成穩(wen)壓(ya)(ya)器，有(you)輸(shu)(shu)出(chu)(chu)正電壓(ya)(ya)的 CW7800 系列和輸(shu)(shu)出(chu)(chu)負(fu)電壓(ya)(ya)的 CW7900 系列等產品。輸(shu)(shu)出(chu)(chu)電流從 0.1A ～ 3A ，輸(shu)(shu)出(chu)(chu)電壓(ya)(ya)有(you) 5V、 6V 、 9V 、 12V 、 15V 、 18V 、 24V 等多(duo)種(zhong)。
這種(zhong)集成穩壓器只(zhi)(zhi)有三個(ge)端(duan)子，穩壓電(dian)路(lu)的所有部分包括大功率調整(zheng)管以及(ji)保護(hu)電(dian)路(lu)等都已集成在芯(xin)片內(nei)。使用時只(zhi)(zhi)要加上散(san)熱片后(hou)接到整(zheng)流濾波電(dian)路(lu)后(hou)面就行了。外圍(wei)元件(jian)少，穩壓精(jing)度高，工作可靠(kao)，一般不需調試。
（ e ）是(shi)(shi)一個三(san)端穩壓器電(dian)路。圖中 C 是(shi)(shi)主濾(lv)波電(dian)容， C1 、 C2 是(shi)(shi)消除寄(ji)生振蕩的電(dian)容 ,VD 是(shi)(shi)為防止輸入短(duan)路燒壞集成塊而使用的保護二極(ji)管。
