交流電(dian)網電(dian)壓的波動和負載電(dian)流的變化都會(hui)使整(zheng)流電(dian)源的輸出電(dian)壓和電(dian)流隨之變動，因(yin)此要求(qiu)較高的電(dian)子電(dian)路必須(xu)使用穩壓電(dian)源。
(1 ）穩壓管并聯穩壓電路(lu)
用一個穩(wen)壓(ya)管(guan)和負載并聯的電(dian)(dian)(dian)路(lu)是最(zui)簡(jian)單(dan)的穩(wen)壓(ya)電(dian)(dian)(dian)路(lu)，見圖 4 （ a ）。圖中 R 是限流電(dian)(dian)(dian)阻。這(zhe)個電(dian)(dian)(dian)路(lu)的輸(shu)出電(dian)(dian)(dian)流很小(xiao)，它(ta)的輸(shu)出電(dian)(dian)(dian)壓(ya)等于穩(wen)壓(ya)管(guan)的穩(wen)定電(dian)(dian)(dian)壓(ya)值 V Z 。
(2 ）串聯型穩壓電路
有放(fang)大和(he)負反饋(kui)作(zuo)(zuo)用的(de)串(chuan)聯(lian)型(xing)穩壓(ya)(ya)(ya)電(dian)(dian)(dian)(dian)(dian)路(lu)是(shi)最常用的(de)穩壓(ya)(ya)(ya)電(dian)(dian)(dian)(dian)(dian)路(lu)。它的(de)電(dian)(dian)(dian)(dian)(dian)路(lu)和(he)框圖(tu)見圖(tu) 4 （ b ）、（ c ）。它是(shi)從取樣電(dian)(dian)(dian)(dian)(dian)路(lu)（ R3 、 R4 ）中檢測出輸出電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)的(de)變(bian)動(dong)，與基準電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)（ V Z ）比(bi)較(jiao)并經放(fang)大器（ VT2 ）放(fang)大后加(jia)到調(diao)整(zheng)管（ VT1 ）上(shang)(shang)，使(shi)調(diao)整(zheng)管兩端的(de)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)隨著變(bian)化。如果輸出電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)下降(jiang)，就(jiu)使(shi)調(diao)整(zheng)管管壓(ya)(ya)(ya)降(jiang)也降(jiang)低，于是(shi)輸出電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)被(bei)提升(sheng)；如果輸出電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)上(shang)(shang)升(sheng)，就(jiu)使(shi)調(diao)整(zheng)管管壓(ya)(ya)(ya)降(jiang)也上(shang)(shang)升(sheng)，于是(shi)輸出電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)被(bei)壓(ya)(ya)(ya)低，結果就(jiu)使(shi)輸出電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)基本不變(bian)。在這個電(dian)(dian)(dian)(dian)(dian)路(lu)的(de)基礎(chu)上(shang)(shang)發(fa)展成很多變(bian)型(xing)電(dian)(dian)(dian)(dian)(dian)路(lu)或增(zeng)加(jia)一些輔助電(dian)(dian)(dian)(dian)(dian)路(lu)，如用復合管作(zuo)(zuo)調(diao)整(zheng)管，輸出電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)可調(diao)的(de)電(dian)(dian)(dian)(dian)(dian)路(lu)，用運算放(fang) 大器作(zuo)(zuo)比(bi)較(jiao)放(fang)大的(de)電(dian)(dian)(dian)(dian)(dian)路(lu)，以及增(zeng)加(jia)輔助電(dian)(dian)(dian)(dian)(dian)源和(he)過流保護電(dian)(dian)(dian)(dian)(dian)路(lu)等。
（ 3 ）開關型(xing)穩壓(ya)電路
近(jin)年(nian)來廣泛應用(yong)的(de)新(xin)型穩壓(ya)電(dian)(dian)源(yuan)是開關型穩壓(ya)電(dian)(dian)源(yuan)。它的(de)調整管工(gong)作(zuo)在(zai)開關狀態，本身功耗很小，所(suo)以(yi)有效(xiao)率(lv)高(gao)、體積(ji)小等(deng)優點，但電(dian)(dian)路比較復雜。
開關(guan)穩壓(ya)(ya)電(dian)源從原理(li)上分有很多種。它的(de)基本原理(li)框圖見(jian)圖 4 （ d ）。圖中電(dian)感(gan) L 和電(dian)容 C 是儲能和濾(lv)波(bo)元件，二(er)極管(guan)(guan) VD 是調(diao)整管(guan)(guan)在關(guan)斷狀態時為 L 、 C 濾(lv)波(bo)器提供電(dian)流通(tong)路的(de)續(xu)流二(er)極管(guan)(guan)。開關(guan)穩壓(ya)(ya)電(dian)源的(de)開關(guan)頻率(lv)都很高，一般為幾(ji)～幾(ji)十千赫，所以電(dian)感(gan)器的(de)體積不很大，輸出電(dian)壓(ya)(ya)中的(de)高次(ci)諧波(bo)也不多。
它的(de)(de)(de)基本工作原理(li)是 : 從取樣(yang)(yang)電(dian)路（ R3 、 R4 ）中檢測出(chu)取樣(yang)(yang)電(dian)壓(ya)經比較放大(da)后去(qu)控制一個矩形(xing)(xing)波(bo)(bo)發生器。矩形(xing)(xing)波(bo)(bo)發生器的(de)(de)(de)輸出(chu)脈沖(chong)是控制調(diao)整(zheng)管(guan)（ VT ）的(de)(de)(de)導通和截止(zhi)時(shi)間(jian)的(de)(de)(de)。如果輸出(chu)電(dian)壓(ya) U 0 因為電(dian)網電(dian)壓(ya)或負載電(dian)流的(de)(de)(de)變(bian)動而降低，就會使(shi)矩形(xing)(xing)波(bo)(bo)發生器的(de)(de)(de)輸出(chu)脈沖(chong)變(bian)寬，于是調(diao)整(zheng)管(guan)導通時(shi)間(jian)增大(da)，使(shi) L 、 C 儲能電(dian)路得到更多的(de)(de)(de)能量，結果是使(shi)輸出(chu)電(dian)壓(ya) U 0 被提(ti)升(sheng)，達到了(le)穩定(ding)輸出(chu)電(dian)壓(ya)的(de)(de)(de)目的(de)(de)(de)。
（ 4 ）集(ji)成化穩(wen)壓(ya)電路
近年來已有(you)大量集(ji)成穩壓器產品問世，品種(zhong)很多(duo)，結構(gou)也(ye)各(ge)不相同。目前用(yong)得較(jiao)多(duo)的(de)(de)有(you)三端集(ji)成穩壓器，有(you)輸出(chu)正電(dian)壓的(de)(de) CW7800 系(xi)列和輸出(chu)負電(dian)壓的(de)(de) CW7900 系(xi)列等(deng)產品。輸出(chu)電(dian)流從 0.1A ～ 3A ，輸出(chu)電(dian)壓有(you) 5V、 6V 、 9V 、 12V 、 15V 、 18V 、 24V 等(deng)多(duo)種(zhong)。
這種(zhong)集成穩壓器只(zhi)有三個端子，穩壓電路的所有部分包括大功率(lv)調整(zheng)管以(yi)及保護電路等都(dou)已集成在芯片(pian)內。使用時只(zhi)要(yao)加上散熱(re)片(pian)后(hou)接(jie)到整(zheng)流(liu)濾波(bo)電路后(hou)面就(jiu)行了。外(wai)圍元(yuan)件少，穩壓精度高，工作可靠(kao)，一般不需調試。
（ e ）是一個三端穩(wen)壓器電(dian)路。圖中(zhong) C 是主(zhu)濾波電(dian)容， C1 、 C2 是消(xiao)除寄生振蕩的電(dian)容 ,VD 是為防(fang)止輸入短路燒(shao)壞集(ji)成塊(kuai)而使用的保護二極(ji)管。
