電子電路要正常工作，可調直流電源必不可少，并且電源性能對電路、電子儀器和電子設備的使用壽命、使用性能等影響很大，尤其在帶有感性負載的電路和設備(如電(dian)(dian)(dian)(dian)(dian)(dian)機)中，對電(dian)(dian)(dian)(dian)(dian)(dian)源的(de)性能(neng)(neng)(neng)要(yao)(yao)求更高。在很多應(ying)用直(zhi)(zhi)流(liu)(liu)(liu)電(dian)(dian)(dian)(dian)(dian)(dian)機的(de)場合中，要(yao)(yao)求為電(dian)(dian)(dian)(dian)(dian)(dian)機驅動電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)(lu)提供1個(ge)其(qi)輸(shu)出能(neng)(neng)(neng)從(cong)(cong)0 V開始連續(xu)可(ke)調(0～24 V)的(de)直(zhi)(zhi)流(liu)(liu)(liu)電(dian)(dian)(dian)(dian)(dian)(dian)源，并且要(yao)(yao)求電(dian)(dian)(dian)(dian)(dian)(dian)源有(you)保(bao)護(hu)功能(neng)(neng)(neng)。實際(ji)上就是要(yao)(yao)求設(she)(she)計(ji)一個(ge)具(ju)有(you)足(zu)夠(gou)(gou)調壓范(fan)圍和(he)帶負載能(neng)(neng)(neng)力(li)的(de)直(zhi)(zhi)流(liu)(liu)(liu)穩壓電(dian)(dian)(dian)(dian)(dian)(dian)源電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)(lu)。該電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)(lu)的(de)設(she)(she)計(ji)關鍵在于穩壓電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)(lu)的(de)設(she)(she)計(ji)，其(qi)要(yao)(yao)求是輸(shu)出電(dian)(dian)(dian)(dian)(dian)(dian)壓從(cong)(cong)0 V開始連續(xu)可(ke)調；所選器件(jian)和(he)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)(lu)必(bi)須(xu)達到在較(jiao)寬范(fan)圍內輸(shu)出電(dian)(dian)(dian)(dian)(dian)(dian)壓可(ke)調；輸(shu)出電(dian)(dian)(dian)(dian)(dian)(dian)壓應(ying)能(neng)(neng)(neng)夠(gou)(gou)適應(ying)所帶負載的(de)啟動性能(neng)(neng)(neng)。此外，電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)(lu)(lu)還必(bi)須(xu)簡單可(ke)靠，能(neng)(neng)(neng)夠(gou)(gou)輸(shu)出足(zu)夠(gou)(gou)大的(de)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)。

可調直流電源電路(lu)的設計符合(he)上述要求的電源電路(lu)的設計方法(fa)有很多種，比較簡單的有3種：

晶體管(guan)串聯(lian)式直流穩(wen)壓(ya)電(dian)(dian)(dian)路(lu)。電(dian)(dian)(dian)路(lu)框圖(tu)如圖(tu)1所示，該電(dian)(dian)(dian)路(lu)中(zhong)，輸(shu)出(chu)(chu)電(dian)(dian)(dian)壓(ya)UO經(jing)取(qu)樣電(dian)(dian)(dian)路(lu)取(qu)樣后得到(dao)取(qu)樣電(dian)(dian)(dian)壓(ya)，取(qu)樣電(dian)(dian)(dian)壓(ya)與基準電(dian)(dian)(dian)壓(ya)進行比較得到(dao)誤差(cha)(cha)電(dian)(dian)(dian)壓(ya)，該誤差(cha)(cha)電(dian)(dian)(dian)壓(ya)對調(diao)整管(guan)的(de)工作狀(zhuang)態進行調(diao)整，從而(er)(er)使(shi)輸(shu)出(chu)(chu)電(dian)(dian)(dian)壓(ya)發生變化，該變化與由于供電(dian)(dian)(dian)電(dian)(dian)(dian)壓(ya)UI發生變化引(yin)起的(de)輸(shu)出(chu)(chu)電(dian)(dian)(dian)壓(ya)的(de)變化正好(hao)相(xiang)反(fan)，從而(er)(er)保證(zheng)輸(shu)出(chu)(chu)電(dian)(dian)(dian)壓(ya)UO為(wei)恒定值(穩(wen)壓(ya)值)。因(yin)輸(shu)出(chu)(chu)電(dian)(dian)(dian)壓(ya)要(yao)求從0 V起實現(xian)連續(xu)可調(diao)，因(yin)此要(yao)在基準電(dian)(dian)(dian)壓(ya)處(chu)設計輔(fu)助電(dian)(dian)(dian)源，用于控制輸(shu)出(chu)(chu)電(dian)(dian)(dian)壓(ya)能夠(gou)從0 V開始(shi)調(diao)節。