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)機(ji))中，對電(dian)(dian)(dian)(dian)(dian)源(yuan)的(de)(de)性能(neng)要(yao)求更高。在(zai)很多(duo)應(ying)用直流電(dian)(dian)(dian)(dian)(dian)機(ji)的(de)(de)場合中，要(yao)求為(wei)電(dian)(dian)(dian)(dian)(dian)機(ji)驅動電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)提(ti)供1個(ge)其輸出能(neng)從(cong)0 V開始(shi)連(lian)續可調(diao)(0～24 V)的(de)(de)直流電(dian)(dian)(dian)(dian)(dian)源(yuan)，并且(qie)要(yao)求電(dian)(dian)(dian)(dian)(dian)源(yuan)有(you)保護功能(neng)。實際上就是要(yao)求設(she)計(ji)(ji)一個(ge)具有(you)足(zu)夠調(diao)壓(ya)(ya)范圍和(he)帶負載(zai)能(neng)力的(de)(de)直流穩壓(ya)(ya)電(dian)(dian)(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)。該電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)的(de)(de)設(she)計(ji)(ji)關(guan)鍵在(zai)于穩壓(ya)(ya)電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)的(de)(de)設(she)計(ji)(ji)，其要(yao)求是輸出電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)從(cong)0 V開始(shi)連(lian)續可調(diao)；所選器件和(he)電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)必(bi)須達到在(zai)較寬范圍內(nei)輸出電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)可調(diao)；輸出電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)應(ying)能(neng)夠適(shi)應(ying)所帶負載(zai)的(de)(de)啟(qi)動性能(neng)。此(ci)外，電(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)還必(bi)須簡單可靠，能(neng)夠輸出足(zu)夠大(da)的(de)(de)電(dian)(dian)(dian)(dian)(dian)流。

可調直流電源電(dian)路的(de)設(she)計符合(he)上述要求(qiu)的(de)電(dian)源電(dian)路的(de)設(she)計方法有(you)很(hen)多種，比(bi)較簡單(dan)的(de)有(you)3種：

晶體管(guan)串聯式直(zhi)流穩壓(ya)(ya)電(dian)(dian)(dian)路(lu)。電(dian)(dian)(dian)路(lu)框圖(tu)如圖(tu)1所(suo)示，該(gai)電(dian)(dian)(dian)路(lu)中，輸(shu)出電(dian)(dian)(dian)壓(ya)(ya)UO經取(qu)(qu)樣電(dian)(dian)(dian)路(lu)取(qu)(qu)樣后得(de)到取(qu)(qu)樣電(dian)(dian)(dian)壓(ya)(ya)，取(qu)(qu)樣電(dian)(dian)(dian)壓(ya)(ya)與基準電(dian)(dian)(dian)壓(ya)(ya)進行比較得(de)到誤差(cha)電(dian)(dian)(dian)壓(ya)(ya)，該(gai)誤差(cha)電(dian)(dian)(dian)壓(ya)(ya)對調(diao)整(zheng)管(guan)的(de)工作狀態進行調(diao)整(zheng)，從而(er)(er)使輸(shu)出電(dian)(dian)(dian)壓(ya)(ya)發生變(bian)(bian)化，該(gai)變(bian)(bian)化與由于(yu)供電(dian)(dian)(dian)電(dian)(dian)(dian)壓(ya)(ya)UI發生變(bian)(bian)化引起的(de)輸(shu)出電(dian)(dian)(dian)壓(ya)(ya)的(de)變(bian)(bian)化正好相(xiang)反，從而(er)(er)保證(zheng)輸(shu)出電(dian)(dian)(dian)壓(ya)(ya)UO為恒定值(穩壓(ya)(ya)值)。因輸(shu)出電(dian)(dian)(dian)壓(ya)(ya)要求從0 V起實現(xian)連續(xu)可調(diao)，因此要在基準電(dian)(dian)(dian)壓(ya)(ya)處(chu)設計輔(fu)助(zhu)電(dian)(dian)(dian)源，用(yong)于(yu)控制輸(shu)出電(dian)(dian)(dian)壓(ya)(ya)能夠從0 V開始(shi)調(diao)節。