傳統的(de)(de)輸(shu)入浪涌電(dian)(dian)流限(xian)(xian)制方法(fa)是串聯負溫(wen)度(du)系數熱敏(min)限(xian)(xian)流電(dian)(dian)阻器(NTC)，然而(er)這種簡(jian)單的(de)(de)方法(fa)具有(you)很多缺點：如NTC電(dian)(dian)阻器的(de)(de)限(xian)(xian)流效果受環(huan)境溫(wen)度(du)影響較(jiao)大、限(xian)(xian)流效果在短暫的(de)(de)輸(shu)入主電(dian)(dian)網中斷(約幾百毫秒數量(liang)級)時只能部分地達(da)到(dao)、NTC電(dian)(dian)阻器的(de)(de)功(gong)率損耗降(jiang)低了(le)開(kai)關電(dian)(dian)源的(de)(de)轉換效率……。其(qi)實上面提出的(de)(de)這兩個(ge)問題可(ke)以通過(guo)一(yi)個(ge)“軟啟動(dong)電(dian)(dian)路”來解決(jue)，下(xia)面詳(xiang)細介紹之。

　　1 開關(guan)電源浪涌電流產生的原因

　　開(kai)(kai)關(guan)(guan)(guan)電(dian)(dian)(dian)(dian)(dian)源(yuan)的(de)輸(shu)入(ru)電(dian)(dian)(dian)(dian)(dian)路大(da)(da)(da)都采用(yong)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)濾波型整流(liu)電(dian)(dian)(dian)(dian)(dian)路，在進(jin)線電(dian)(dian)(dian)(dian)(dian)源(yuan)合(he)閘(zha)瞬(shun)間，由于(yu)電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)上(shang)的(de)初始(shi)電(dian)(dian)(dian)(dian)(dian)壓為零，電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)充電(dian)(dian)(dian)(dian)(dian)瞬(shun)間會(hui)(hui)形成(cheng)很(hen)大(da)(da)(da)的(de)浪涌(yong)電(dian)(dian)(dian)(dian)(dian)流(liu)，特(te)別是大(da)(da)(da)功率開(kai)(kai)關(guan)(guan)(guan)電(dian)(dian)(dian)(dian)(dian)源(yuan)，采用(yong)容(rong)(rong)量較大(da)(da)(da)的(de)濾波電(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)，使(shi)浪涌(yong)電(dian)(dian)(dian)(dian)(dian)流(liu)達(da)100A以(yi)上(shang)。在電(dian)(dian)(dian)(dian)(dian)源(yuan)接通瞬(shun)間如此大(da)(da)(da)的(de)浪涌(yong)電(dian)(dian)(dian)(dian)(dian)流(liu)，重者(zhe)往往會(hui)(hui)導(dao)致輸(shu)入(ru)熔斷器(qi)燒斷或合(he)閘(zha)開(kai)(kai)關(guan)(guan)(guan)的(de)觸(chu)點燒壞(huai)(huai)，整流(liu)橋(qiao)過(guo)流(liu)損壞(huai)(huai);輕者(zhe)也會(hui)(hui)使(shi)空氣開(kai)(kai)關(guan)(guan)(guan)合(he)不上(shang)閘(zha)。上(shang)述現象均(jun)會(hui)(hui)造成(cheng)開(kai)(kai)關(guan)(guan)(guan)電(dian)(dian)(dian)(dian)(dian)源(yuan)無(wu)法(fa)正常工(gong)作，為此幾乎所(suo)有的(de)開(kai)(kai)關(guan)(guan)(guan)電(dian)(dian)(dian)(dian)(dian)源(yuan)都設置了防止流(liu)涌(yong)電(dian)(dian)(dian)(dian)(dian)流(liu)的(de)軟啟動電(dian)(dian)(dian)(dian)(dian)路，以(yi)保證二(er)手機(ji)器(qi)人(ren)電(dian)(dian)(dian)(dian)(dian)源(yuan)正常而可靠運行。

　　2 軟(ruan)啟動(dong)電(dian)路電(dian)氣工作(zuo)原理

　　如果采用“軟啟動電路”來消除開關電源啟(qi)(qi)動(dong)(dong)時的(de)(de)浪(lang)涌電(dian)(dian)(dian)流，可(ke)以很好地(di)避(bi)免上述(shu)傳(chuan)統浪(lang)涌電(dian)(dian)(dian)流限制方法的(de)(de)缺點。通過“軟啟(qi)(qi)動(dong)(dong)”來控制開(kai)關(guan)電(dian)(dian)(dian)源的(de)(de)啟(qi)(qi)動(dong)(dong)以消(xiao)除(chu)浪(lang)涌電(dian)(dian)(dian)流，包含這(zhe)(zhe)樣兩(liang)條設計(ji)原則：即(ji)在(zai)加電(dian)(dian)(dian)瞬間除(chu)去(qu)負載(zai)、同時限制有(you)用(yong)的(de)(de)電(dian)(dian)(dian)流。如果不驅動(dong)(dong)負載(zai)，開(kai)關(guan)電(dian)(dian)(dian)源啟(qi)(qi)動(dong)(dong)時一(yi)般電(dian)(dian)(dian)流很小(xiao)。在(zai)很多(duo)情況下(xia)，啟(qi)(qi)動(dong)(dong)電(dian)(dian)(dian)流實際有(you)可(ke)能要比利用(yong)這(zhe)(zhe)種方法保持的(de)(de)穩態工(gong)作電(dian)(dian)(dian)流小(xiao)。