壓力(li)校驗儀簡單的穩壓電路原理說明

穩壓電路

濾(lv)波(bo)電(dian)(dian)路可以將整流(liu)輸(shu)出波(bo)動(dong)(dong)大(da)的(de)脈動(dong)(dong)直(zhi)流(liu)電(dian)(dian)壓(ya)(ya)(ya)(ya)平滑成波(bo)動(dong)(dong)小的(de)直(zhi)流(liu)電(dian)(dian)壓(ya)(ya)(ya)(ya)，但(dan)如果(guo)因供(gong)(gong)電(dian)(dian)原(yuan)因引起(qi)220v電(dian)(dian)壓(ya)(ya)(ya)(ya)大(da)小變化時（如220v上升至240v），經(jing)整流(liu)得到的(de)脈動(dong)(dong)直(zhi)流(liu)電(dian)(dian)壓(ya)(ya)(ya)(ya)平均值隨(sui)之(zhi)(zhi)會(hui)變化（升高），濾(lv)波(bo)供(gong)(gong)給(gei)負載的(de)直(zhi)流(liu)電(dian)(dian)壓(ya)(ya)(ya)(ya)也會(hui)變化（升高）。為(wei)了保證(zheng)在市電(dian)(dian)電(dian)(dian)壓(ya)(ya)(ya)(ya)大(da)小發生(sheng)變化時，提供(gong)(gong)給(gei)負載的(de)直(zhi)流(liu)電(dian)(dian)壓(ya)(ya)(ya)(ya)始終保持(chi)穩(wen)定，還(huan)需要在整流(liu)濾(lv)波(bo)電(dian)(dian)路之(zhi)(zhi)后增加穩(wen)壓(ya)(ya)(ya)(ya)電(dian)(dian)路。

穩(wen)壓(ya)(ya)(ya)二(er)極管是一種(zhong)具有(you)穩(wen)壓(ya)(ya)(ya)功(gong)能(neng)的器件，采用(yong)穩(wen)壓(ya)(ya)(ya)二(er)極管

和限流電阻可以組成簡(jian)單(dan)的(de)穩壓電路(lu)。簡(jian)單(dan)穩壓電路(lu)如圖

所示，它由穩(wen)壓二極管vd和(he)限流電阻r組成。

輸入電壓(ya)(ya) u經限流電阻 r 送到穩壓(ya)(ya)二(er)極管(guan) vz兩端，vz

被反向擊穿，有電流流過r和(he)vz，r兩端的(de)電壓(ya)為up，vz 兩端的(de)電壓(ya)為u。，u’、u和(he)u。三者滿足u=uu。

如果輸(shu)入電(dian)壓u4升高，流過r和vz的電(dian)流增(zeng)大，r兩端(duan)

的電壓(ya)(ya)(ya)(ya)(ya) ug增大(da)（un=la，增大(da)，故 ur也增大(da)），由(you)于穩(wen)壓(ya)(ya)(ya)(ya)(ya)二極管具有(you)“擊穿后兩端電壓(ya)(ya)(ya)(ya)(ya)保(bao)持不變(bian)"的特點(dian)，所以u。電壓(ya)(ya)(ya)(ya)(ya)保(bao)持不變(bian)，從而實現(xian)了輸入電壓(ya)(ya)(ya)(ya)(ya)u升高時輸出(chu)電壓(ya)(ya)(ya)(ya)(ya)u。保(bao)持不變(bian)的穩(wen)壓(ya)(ya)(ya)(ya)(ya)功(gong)能(neng)。

如(ru)果(guo)輸(shu)(shu)入(ru)電(dian)(dian)壓 u4下(xia)降，只(zhi)要 u電(dian)(dian)壓大于(yu)穩壓二極管(guan)的(de)穩壓值，穩壓二極管(guan)就仍(reng)處于(yu)反向(xiang)導通狀態（擊穿狀態），由于(yu)u'下(xia)降，流過r和vz的(de)電(dian)(dian)流減小，r兩端的(de)電(dian)(dian)壓 ur減小，穩壓二極管(guan)兩端電(dian)(dian)壓保(bao)持(chi)不變(bian)，即u。電(dian)(dian)壓仍(reng)保(bao)持(chi)不變(bian)，從而實現了輸(shu)(shu)入(ru)電(dian)(dian)壓 u下(xia)降時讓輸(shu)(shu)出電(dian)(dian)壓u。保(bao)持(chi)不變(bian)的(de)穩壓功能。

要讓穩壓二(er)極管在電路(lu)中能(neng)夠穩壓，須(xu)滿足以(yi)下兩點。

①穩(wen)壓二極管在電路中需要反接(jie)（即正極接(jie)低電位(wei)，負極接(jie)高電位(wei)）。

② 加到穩壓(ya)二極管兩(liang)端的(de)電壓(ya)不(bu)能小于它(ta)的(de)擊穿電壓(ya)（也即穩壓(ya)值）。

例如圖(tu)8-15所示電路中(zhong)的(de)穩(wen)壓(ya)(ya)二(er)(er)極(ji)管(guan)(guan)vz的(de)穩(wen)壓(ya)(ya)值為(wei)6v，當(dang)輸入電壓(ya)(ya)u=9v時(shi)，vz處于擊(ji)穿狀態，u，=6v，ux=3v；若u由(you)9v上升(sheng)到(dao)(dao)(dao)12v，u。仍為(wei)6v，而(er)ux則(ze)由(you)3v升(sheng)高到(dao)(dao)(dao)6v（因(yin)輸入電壓(ya)(ya)升(sheng)高使流過r的(de)電流增大而(er)導致ur升(sheng)高）；若u由(you)9v下降(jiang)到(dao)(dao)(dao)5v，穩(wen)壓(ya)(ya)二(er)(er)極(ji)管(guan)(guan)無法擊(ji)穿，限流電阻r無電流通(tong)過，ux=0v，u。=5v，此(ci)時(shi)穩(wen)壓(ya)(ya)二(er)(er)極(ji)管(guan)(guan)無穩(wen)壓(ya)(ya)功能。

圖(tu) 簡單穩壓電路