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)(dian)機)中(zhong)，對電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源的性(xing)能(neng)要(yao)求更(geng)高。在很多應(ying)用直流(liu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)機的場合中(zhong)，要(yao)求為(wei)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)機驅動(dong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路提供1個其輸出能(neng)從(cong)0 V開(kai)始連續(xu)可(ke)調(0～24 V)的直流(liu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源，并(bing)且要(yao)求電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源有保護功(gong)能(neng)。實際上就是(shi)要(yao)求設(she)計(ji)(ji)一個具有足(zu)夠調壓范圍(wei)和(he)(he)帶負載能(neng)力的直流(liu)穩壓電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路。該電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路的設(she)計(ji)(ji)關鍵在于(yu)穩壓電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路的設(she)計(ji)(ji)，其要(yao)求是(shi)輸出電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓從(cong)0 V開(kai)始連續(xu)可(ke)調；所(suo)選(xuan)器件和(he)(he)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路必(bi)須(xu)達到(dao)在較寬范圍(wei)內輸出電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓可(ke)調；輸出電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓應(ying)能(neng)夠適應(ying)所(suo)帶負載的啟動(dong)性(xing)能(neng)。此外，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路還(huan)必(bi)須(xu)簡(jian)單可(ke)靠，能(neng)夠輸出足(zu)夠大的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)。

可調直流電源電(dian)路的設(she)計符合上述要求(qiu)的電(dian)源電(dian)路的設(she)計方法(fa)有(you)很多種，比較簡單的有(you)3種：

晶體管串聯式直流穩(wen)壓(ya)(ya)(ya)(ya)(ya)電(dian)(dian)(dian)路。電(dian)(dian)(dian)路框圖如圖1所示，該(gai)(gai)電(dian)(dian)(dian)路中(zhong)，輸(shu)(shu)出(chu)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)UO經(jing)取(qu)樣(yang)電(dian)(dian)(dian)路取(qu)樣(yang)后(hou)得到(dao)(dao)取(qu)樣(yang)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)，取(qu)樣(yang)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)與基(ji)準(zhun)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)進行(xing)比較(jiao)得到(dao)(dao)誤差(cha)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)，該(gai)(gai)誤差(cha)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)對(dui)調整(zheng)管的(de)工(gong)作狀態進行(xing)調整(zheng)，從(cong)而使輸(shu)(shu)出(chu)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)發生(sheng)變(bian)化，該(gai)(gai)變(bian)化與由(you)于供(gong)電(dian)(dian)(dian)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)UI發生(sheng)變(bian)化引起的(de)輸(shu)(shu)出(chu)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)的(de)變(bian)化正好相反，從(cong)而保證輸(shu)(shu)出(chu)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)UO為恒(heng)定值(穩(wen)壓(ya)(ya)(ya)(ya)(ya)值)。因輸(shu)(shu)出(chu)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)要(yao)求從(cong)0 V起實現連(lian)續可調，因此要(yao)在基(ji)準(zhun)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)處(chu)設計輔助(zhu)電(dian)(dian)(dian)源，用于控制輸(shu)(shu)出(chu)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)能夠從(cong)0 V開始調節。