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)機(ji)(ji))中(zhong)，對電(dian)(dian)(dian)源(yuan)的(de)(de)性(xing)能(neng)要(yao)求更高。在(zai)很多應(ying)用(yong)直(zhi)(zhi)流電(dian)(dian)(dian)機(ji)(ji)的(de)(de)場合中(zhong)，要(yao)求為電(dian)(dian)(dian)機(ji)(ji)驅動電(dian)(dian)(dian)路(lu)(lu)(lu)提供1個(ge)其輸出(chu)(chu)能(neng)從(cong)0 V開始連(lian)續(xu)可調(0～24 V)的(de)(de)直(zhi)(zhi)流電(dian)(dian)(dian)源(yuan)，并且要(yao)求電(dian)(dian)(dian)源(yuan)有(you)保(bao)護功(gong)能(neng)。實際(ji)上(shang)就是要(yao)求設計一個(ge)具有(you)足夠(gou)調壓范圍和帶負載(zai)能(neng)力的(de)(de)直(zhi)(zhi)流穩壓電(dian)(dian)(dian)源(yuan)電(dian)(dian)(dian)路(lu)(lu)(lu)。該電(dian)(dian)(dian)路(lu)(lu)(lu)的(de)(de)設計關鍵在(zai)于穩壓電(dian)(dian)(dian)路(lu)(lu)(lu)的(de)(de)設計，其要(yao)求是輸出(chu)(chu)電(dian)(dian)(dian)壓從(cong)0 V開始連(lian)續(xu)可調；所選器件和電(dian)(dian)(dian)路(lu)(lu)(lu)必須(xu)達到在(zai)較寬范圍內輸出(chu)(chu)電(dian)(dian)(dian)壓可調；輸出(chu)(chu)電(dian)(dian)(dian)壓應(ying)能(neng)夠(gou)適應(ying)所帶負載(zai)的(de)(de)啟動性(xing)能(neng)。此外，電(dian)(dian)(dian)路(lu)(lu)(lu)還必須(xu)簡(jian)單可靠，能(neng)夠(gou)輸出(chu)(chu)足夠(gou)大的(de)(de)電(dian)(dian)(dian)流。

可調直流電源電(dian)路的(de)設計符合上述要(yao)求的(de)電(dian)源電(dian)路的(de)設計方法有很(hen)多種(zhong)，比較簡單的(de)有3種(zhong)：

晶體管串(chuan)聯式直流穩壓(ya)(ya)(ya)電(dian)(dian)(dian)(dian)路(lu)。電(dian)(dian)(dian)(dian)路(lu)框圖如圖1所示，該(gai)電(dian)(dian)(dian)(dian)路(lu)中，輸(shu)出(chu)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)UO經取(qu)(qu)樣電(dian)(dian)(dian)(dian)路(lu)取(qu)(qu)樣后得(de)到取(qu)(qu)樣電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)，取(qu)(qu)樣電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)與基(ji)(ji)準電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)進行(xing)(xing)比較(jiao)得(de)到誤(wu)(wu)差電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)，該(gai)誤(wu)(wu)差電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)對調整(zheng)管的工作狀態進行(xing)(xing)調整(zheng)，從(cong)而(er)使輸(shu)出(chu)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)發生變(bian)化(hua)，該(gai)變(bian)化(hua)與由于供電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)UI發生變(bian)化(hua)引(yin)起(qi)的輸(shu)出(chu)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)的變(bian)化(hua)正好相反，從(cong)而(er)保證輸(shu)出(chu)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)UO為恒(heng)定值(穩壓(ya)(ya)(ya)值)。因輸(shu)出(chu)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)要(yao)求從(cong)0 V起(qi)實現連續可(ke)調，因此要(yao)在基(ji)(ji)準電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)處設計輔助電(dian)(dian)(dian)(dian)源，用于控制(zhi)輸(shu)出(chu)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)能夠從(cong)0 V開(kai)始調節(jie)。