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(ru)電(dian)(dian)機)中，對電(dian)(dian)源的性(xing)能要求(qiu)更高(gao)。在很多應(ying)用(yong)直(zhi)(zhi)流(liu)電(dian)(dian)機的場合中，要求(qiu)為電(dian)(dian)機驅(qu)動電(dian)(dian)路(lu)提(ti)供(gong)1個(ge)其輸(shu)出能從0 V開始連續(xu)可(ke)調(0～24 V)的直(zhi)(zhi)流(liu)電(dian)(dian)源，并且要求(qiu)電(dian)(dian)源有(you)保護功能。實際(ji)上就是(shi)要求(qiu)設計(ji)一個(ge)具(ju)有(you)足夠調壓范(fan)(fan)圍和帶(dai)負(fu)載能力的直(zhi)(zhi)流(liu)穩(wen)壓電(dian)(dian)源電(dian)(dian)路(lu)。該電(dian)(dian)路(lu)的設計(ji)關(guan)鍵在于穩(wen)壓電(dian)(dian)路(lu)的設計(ji)，其要求(qiu)是(shi)輸(shu)出電(dian)(dian)壓從0 V開始連續(xu)可(ke)調；所選(xuan)器(qi)件和電(dian)(dian)路(lu)必須達到(dao)在較寬范(fan)(fan)圍內輸(shu)出電(dian)(dian)壓可(ke)調；輸(shu)出電(dian)(dian)壓應(ying)能夠適(shi)應(ying)所帶(dai)負(fu)載的啟動性(xing)能。此外，電(dian)(dian)路(lu)還必須簡單可(ke)靠，能夠輸(shu)出足夠大的電(dian)(dian)流(liu)。

可調直流電源電(dian)路(lu)的(de)設計(ji)符合上述(shu)要求的(de)電(dian)源電(dian)路(lu)的(de)設計(ji)方法有很多種(zhong)，比較簡單(dan)的(de)有3種(zhong)：

晶(jing)體管串(chuan)聯式直流穩壓(ya)(ya)電(dian)(dian)(dian)(dian)路(lu)。電(dian)(dian)(dian)(dian)路(lu)框圖(tu)如圖(tu)1所(suo)示，該電(dian)(dian)(dian)(dian)路(lu)中，輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)壓(ya)(ya)UO經取樣電(dian)(dian)(dian)(dian)路(lu)取樣后得(de)到取樣電(dian)(dian)(dian)(dian)壓(ya)(ya)，取樣電(dian)(dian)(dian)(dian)壓(ya)(ya)與基準電(dian)(dian)(dian)(dian)壓(ya)(ya)進(jin)行(xing)比較得(de)到誤差電(dian)(dian)(dian)(dian)壓(ya)(ya)，該誤差電(dian)(dian)(dian)(dian)壓(ya)(ya)對調(diao)(diao)整(zheng)管的工(gong)作狀態進(jin)行(xing)調(diao)(diao)整(zheng)，從(cong)而使輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)壓(ya)(ya)發生變(bian)化(hua)，該變(bian)化(hua)與由于(yu)供(gong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)壓(ya)(ya)UI發生變(bian)化(hua)引起(qi)的輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)壓(ya)(ya)的變(bian)化(hua)正好相反，從(cong)而保證輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)壓(ya)(ya)UO為恒定值(zhi)(穩壓(ya)(ya)值(zhi))。因輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)壓(ya)(ya)要求從(cong)0 V起(qi)實現連續可調(diao)(diao)，因此要在(zai)基準電(dian)(dian)(dian)(dian)壓(ya)(ya)處設計輔助電(dian)(dian)(dian)(dian)源，用于(yu)控制輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)壓(ya)(ya)能(neng)夠(gou)從(cong)0 V開始調(diao)(diao)節。