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)機)中，對電(dian)(dian)(dian)(dian)源的(de)性能(neng)(neng)要求更高。在(zai)很多應(ying)用直流(liu)電(dian)(dian)(dian)(dian)機的(de)場合(he)中，要求為電(dian)(dian)(dian)(dian)機驅(qu)動電(dian)(dian)(dian)(dian)路(lu)(lu)提供1個其輸(shu)(shu)出(chu)能(neng)(neng)從(cong)(cong)0 V開(kai)始連續可(ke)調(0～24 V)的(de)直流(liu)電(dian)(dian)(dian)(dian)源，并且要求電(dian)(dian)(dian)(dian)源有(you)保護功(gong)能(neng)(neng)。實際上就(jiu)是要求設計(ji)一個具(ju)有(you)足夠調壓(ya)(ya)范圍和帶負(fu)載能(neng)(neng)力的(de)直流(liu)穩(wen)壓(ya)(ya)電(dian)(dian)(dian)(dian)源電(dian)(dian)(dian)(dian)路(lu)(lu)。該(gai)電(dian)(dian)(dian)(dian)路(lu)(lu)的(de)設計(ji)關鍵在(zai)于穩(wen)壓(ya)(ya)電(dian)(dian)(dian)(dian)路(lu)(lu)的(de)設計(ji)，其要求是輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)壓(ya)(ya)從(cong)(cong)0 V開(kai)始連續可(ke)調；所(suo)選(xuan)器件和電(dian)(dian)(dian)(dian)路(lu)(lu)必須(xu)達到在(zai)較寬范圍內輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)壓(ya)(ya)可(ke)調；輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)壓(ya)(ya)應(ying)能(neng)(neng)夠適應(ying)所(suo)帶負(fu)載的(de)啟動性能(neng)(neng)。此外，電(dian)(dian)(dian)(dian)路(lu)(lu)還必須(xu)簡單可(ke)靠，能(neng)(neng)夠輸(shu)(shu)出(chu)足夠大(da)的(de)電(dian)(dian)(dian)(dian)流(liu)。

可調直流電源電路的(de)設(she)計符(fu)合上(shang)述要求的(de)電源電路的(de)設(she)計方(fang)法有很多(duo)種，比較(jiao)簡單(dan)的(de)有3種：

晶體管串聯式直流穩壓(ya)(ya)(ya)電(dian)(dian)(dian)路。電(dian)(dian)(dian)路框圖(tu)如圖(tu)1所示，該電(dian)(dian)(dian)路中(zhong)，輸(shu)出電(dian)(dian)(dian)壓(ya)(ya)(ya)UO經取樣(yang)電(dian)(dian)(dian)路取樣(yang)后得到(dao)取樣(yang)電(dian)(dian)(dian)壓(ya)(ya)(ya)，取樣(yang)電(dian)(dian)(dian)壓(ya)(ya)(ya)與基準電(dian)(dian)(dian)壓(ya)(ya)(ya)進行比(bi)較(jiao)得到(dao)誤差電(dian)(dian)(dian)壓(ya)(ya)(ya)，該誤差電(dian)(dian)(dian)壓(ya)(ya)(ya)對(dui)調(diao)整管的工作狀態進行調(diao)整，從而使輸(shu)出電(dian)(dian)(dian)壓(ya)(ya)(ya)發(fa)生(sheng)變化(hua)，該變化(hua)與由于供電(dian)(dian)(dian)電(dian)(dian)(dian)壓(ya)(ya)(ya)UI發(fa)生(sheng)變化(hua)引起的輸(shu)出電(dian)(dian)(dian)壓(ya)(ya)(ya)的變化(hua)正好(hao)相反，從而保證輸(shu)出電(dian)(dian)(dian)壓(ya)(ya)(ya)UO為(wei)恒定值(zhi)(穩壓(ya)(ya)(ya)值(zhi))。因(yin)輸(shu)出電(dian)(dian)(dian)壓(ya)(ya)(ya)要求從0 V起實現(xian)連續可調(diao)，因(yin)此(ci)要在(zai)基準電(dian)(dian)(dian)壓(ya)(ya)(ya)處設計輔助(zhu)電(dian)(dian)(dian)源(yuan)，用于控制輸(shu)出電(dian)(dian)(dian)壓(ya)(ya)(ya)能夠從0 V開(kai)始調(diao)節。