傳統的(de)輸入浪涌電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)限制方(fang)法(fa)是串聯負溫(wen)度(du)系數(shu)熱敏限流(liu)(liu)(liu)電(dian)(dian)(dian)(dian)阻(zu)(zu)器(NTC)，然(ran)而(er)這種(zhong)簡單的(de)方(fang)法(fa)具有很多缺點(dian)：如NTC電(dian)(dian)(dian)(dian)阻(zu)(zu)器的(de)限流(liu)(liu)(liu)效(xiao)果(guo)(guo)受環境(jing)溫(wen)度(du)影響較大、限流(liu)(liu)(liu)效(xiao)果(guo)(guo)在短暫(zan)的(de)輸入主(zhu)電(dian)(dian)(dian)(dian)網中(zhong)斷(duan)(約幾百(bai)毫(hao)秒數(shu)量級(ji))時只(zhi)能部分地達到、NTC電(dian)(dian)(dian)(dian)阻(zu)(zu)器的(de)功率損耗降低了開(kai)關電(dian)(dian)(dian)(dian)源的(de)轉換效(xiao)率……。其實上面提出的(de)這兩個問題可以(yi)通過一個“軟啟動(dong)電(dian)(dian)(dian)(dian)路”來(lai)解決，下面詳細(xi)介紹之。

　　1 開(kai)關電源浪涌(yong)電流產生(sheng)的原因

　　開關(guan)(guan)(guan)電(dian)(dian)(dian)源的(de)(de)輸入(ru)(ru)電(dian)(dian)(dian)路大(da)(da)都(dou)采用電(dian)(dian)(dian)容(rong)(rong)濾波(bo)型整流(liu)(liu)電(dian)(dian)(dian)路，在進線電(dian)(dian)(dian)源合閘瞬(shun)間(jian)(jian)，由(you)于電(dian)(dian)(dian)容(rong)(rong)器(qi)上的(de)(de)初始電(dian)(dian)(dian)壓為(wei)零(ling)，電(dian)(dian)(dian)容(rong)(rong)器(qi)充電(dian)(dian)(dian)瞬(shun)間(jian)(jian)會形成(cheng)很大(da)(da)的(de)(de)浪(lang)涌電(dian)(dian)(dian)流(liu)(liu)，特別(bie)是大(da)(da)功率開關(guan)(guan)(guan)電(dian)(dian)(dian)源，采用容(rong)(rong)量較大(da)(da)的(de)(de)濾波(bo)電(dian)(dian)(dian)容(rong)(rong)器(qi)，使(shi)浪(lang)涌電(dian)(dian)(dian)流(liu)(liu)達100A以(yi)(yi)上。在電(dian)(dian)(dian)源接通瞬(shun)間(jian)(jian)如此大(da)(da)的(de)(de)浪(lang)涌電(dian)(dian)(dian)流(liu)(liu)，重(zhong)者往(wang)往(wang)會導致輸入(ru)(ru)熔斷器(qi)燒(shao)斷或合閘開關(guan)(guan)(guan)的(de)(de)觸點燒(shao)壞(huai)，整流(liu)(liu)橋過流(liu)(liu)損壞(huai);輕者也會使(shi)空氣(qi)開關(guan)(guan)(guan)合不上閘。上述(shu)現象均會造成(cheng)開關(guan)(guan)(guan)電(dian)(dian)(dian)源無法正(zheng)常工(gong)作，為(wei)此幾乎所有的(de)(de)開關(guan)(guan)(guan)電(dian)(dian)(dian)源都(dou)設置了防止流(liu)(liu)涌電(dian)(dian)(dian)流(liu)(liu)的(de)(de)軟啟動電(dian)(dian)(dian)路，以(yi)(yi)保證二手機器(qi)人電(dian)(dian)(dian)源正(zheng)常而(er)可(ke)靠運行。

　　2 軟(ruan)啟(qi)動電(dian)路電(dian)氣(qi)工作原理

　　如果采用“軟啟動電路”來消除開關電源啟(qi)動(dong)(dong)(dong)時(shi)的(de)浪(lang)涌電(dian)(dian)(dian)流(liu)(liu)(liu)，可(ke)以很(hen)好(hao)地避免(mian)上述傳統浪(lang)涌電(dian)(dian)(dian)流(liu)(liu)(liu)限制(zhi)方(fang)法(fa)(fa)的(de)缺(que)點。通過“軟啟(qi)動(dong)(dong)(dong)”來控制(zhi)開(kai)關電(dian)(dian)(dian)源的(de)啟(qi)動(dong)(dong)(dong)以消除(chu)浪(lang)涌電(dian)(dian)(dian)流(liu)(liu)(liu)，包含這(zhe)樣兩(liang)條(tiao)設計(ji)原則：即(ji)在加電(dian)(dian)(dian)瞬間(jian)除(chu)去負(fu)載(zai)、同時(shi)限制(zhi)有(you)用的(de)電(dian)(dian)(dian)流(liu)(liu)(liu)。如果(guo)不驅(qu)動(dong)(dong)(dong)負(fu)載(zai)，開(kai)關電(dian)(dian)(dian)源啟(qi)動(dong)(dong)(dong)時(shi)一般電(dian)(dian)(dian)流(liu)(liu)(liu)很(hen)小。在很(hen)多情(qing)況下，啟(qi)動(dong)(dong)(dong)電(dian)(dian)(dian)流(liu)(liu)(liu)實際(ji)有(you)可(ke)能要比利用這(zhe)種方(fang)法(fa)(fa)保持的(de)穩態工作(zuo)電(dian)(dian)(dian)流(liu)(liu)(liu)小。