電動車充電器直流電壓輸出過低，根據維修經驗，除穩壓控制電路會引起輸出電壓過低外，還有以下幾點原因：
   （1）輸出電壓端整流三極莒、濾波電容失效，可以通過代換法進行判斷。
   （2）開關功率管的性能下降，導致開關管不能正常導通，使電源的內阻增加，帶負載能力下降。
   （3）開關功率管的源極通常接一個阻值很小但功率很大的電阻，作為過流吳護檢測電阻。該電阻的阻值—般在0.2～o.8ω。如該電阻變值或開焊、接觸不良也會造成輸出電壓過低。
   （4）高頻脈沖變壓器不良，不但造成輸出黽壓下降，還會造成開關功率管激勵不足從而屢損開關管。
   （5）高壓直流濾波電容不良，造成電源帶負載能力差。
   （6）電源輸出線接觸不良，有—定的接觸電阻，造成輸出電壓過低。
   （7）電(dian)(dian)網(wang)電(dian)(dian)壓(ya)(ya)過(guo)(guo)(guo)低(di)(di)。雖然充(chong)(chong)(chong)(chong)電(dian)(dian)器(qi)在低(di)(di)玉(yu)下(xia)(xia)(xia)仍然可以輸(shu)出(chu)額定的充(chong)(chong)(chong)(chong)咆電(dian)(dian)壓(ya)(ya)，但當電(dian)(dian)網(wang)電(dian)(dian)壓(ya)(ya)低(di)(di)于充(chong)(chong)(chong)(chong)電(dian)(dian)器(qi)的最低(di)(di)電(dian)(dian)壓(ya)(ya)限定值(zhi)時，也會使輸(shu)出(chu)電(dian)(dian)壓(ya)(ya)過(guo)(guo)(guo)低(di)(di)。　維(wei)修方法∶首先用萬用表檢查—下(xia)(xia)(xia)高壓(ya)(ya)直流濾(lv)波電(dian)(dian)容(rong)是(shi)否(fou)變質(zhi)、容(rong)量(liang)是(shi)否(fou)下(xia)(xia)(xia)降(jiang)、能否(fou)正常充(chong)(chong)(chong)(chong)放(fang)電(dian)(dian)。如(ru)無以上問題，則測(ce)量(liang)一下(xia)(xia)(xia)開關功(gong)率(lv)管(guan)的電(dian)(dian)極的限流電(dian)(dian)阻(zu)以及(ji)源極的過(guo)(guo)(guo)流保(bao)護殮測(ce)電(dian)(dian)阻(zu)是(shi)否(fou)變值(zhi)、變質(zhi)或(huo)開焊(han)、接觸不良。若無問題，再檢查—下(xia)(xia)(xia)高頻變壓(ya)(ya)器(qi)的鐵芯是(shi)否(fou)完(wan)好(hao)無損。除(chu)此(ci)z外還有可能就是(shi)輸(shu)出(chu)濾(lv)波電(dian)(dian)容(rong)容(rong)量(liang)降(jiang)低(di)(di)，或(huo)開焊(han)、虛接;電(dian)(dian)源輸(shu)出(chu)限流電(dian)(dian)阻(zu)變值(zhi)或(huo)虛接;電(dian)(dian)源輸(shu)出(chu)線虛接等困素都不要放(fang)過(guo)(guo)(guo)，都應(ying)仔(zi)細檢查，確保(bao)萬無—失。