傳統的(de)(de)輸入浪(lang)涌電(dian)(dian)流(liu)(liu)限(xian)制方法是串聯負(fu)溫度系數熱敏限(xian)流(liu)(liu)電(dian)(dian)阻器(NTC)，然而這(zhe)種簡單(dan)的(de)(de)方法具有(you)很多缺點(dian)：如(ru)NTC電(dian)(dian)阻器的(de)(de)限(xian)流(liu)(liu)效果受環境(jing)溫度影響較大、限(xian)流(liu)(liu)效果在短暫的(de)(de)輸入主電(dian)(dian)網中斷(duan)(約幾百毫(hao)秒數量級)時只(zhi)能部分地達(da)到、NTC電(dian)(dian)阻器的(de)(de)功率損耗降低了開關(guan)電(dian)(dian)源(yuan)的(de)(de)轉(zhuan)換(huan)效率……。其實上(shang)面(mian)提出的(de)(de)這(zhe)兩個問題(ti)可以通過一個“軟啟(qi)動電(dian)(dian)路”來(lai)解決，下面(mian)詳(xiang)細介紹之。

　　1 開關電(dian)源浪涌電(dian)流(liu)產生的(de)原(yuan)因

　　開(kai)關(guan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)的(de)(de)輸(shu)入電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)大(da)(da)都(dou)(dou)采用電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)濾(lv)波(bo)型(xing)整流電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)，在(zai)進線電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)合閘(zha)瞬間，由于電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)上(shang)(shang)的(de)(de)初(chu)始電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓為零，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)瞬間會形成很大(da)(da)的(de)(de)浪(lang)(lang)涌電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流，特別是大(da)(da)功率開(kai)關(guan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)，采用容(rong)(rong)量較大(da)(da)的(de)(de)濾(lv)波(bo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)(qi)，使(shi)浪(lang)(lang)涌電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流達100A以(yi)上(shang)(shang)。在(zai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)接通(tong)瞬間如此(ci)大(da)(da)的(de)(de)浪(lang)(lang)涌電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流，重者(zhe)往往會導致輸(shu)入熔斷器(qi)(qi)(qi)燒(shao)斷或合閘(zha)開(kai)關(guan)的(de)(de)觸點燒(shao)壞，整流橋過流損壞;輕者(zhe)也會使(shi)空氣開(kai)關(guan)合不上(shang)(shang)閘(zha)。上(shang)(shang)述(shu)現象(xiang)均會造(zao)成開(kai)關(guan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)無(wu)法正(zheng)常(chang)(chang)工作，為此(ci)幾乎所有的(de)(de)開(kai)關(guan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)都(dou)(dou)設置(zhi)了防止流涌電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流的(de)(de)軟啟動電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)，以(yi)保證(zheng)二手機器(qi)(qi)(qi)人電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)正(zheng)常(chang)(chang)而可(ke)靠運行。

　　2 軟(ruan)啟動電(dian)路電(dian)氣(qi)工作原(yuan)理(li)

　　如果采用“軟啟動電路”來消除開關電源啟動(dong)時的浪涌(yong)電(dian)流(liu)(liu)，可以很(hen)(hen)好地避免上述傳統(tong)浪涌(yong)電(dian)流(liu)(liu)限制方法的缺點(dian)。通(tong)過“軟啟動(dong)”來控制開關(guan)電(dian)源的啟動(dong)以消除浪涌(yong)電(dian)流(liu)(liu)，包含這樣兩條設計原則：即(ji)在加電(dian)瞬(shun)間除去負載、同(tong)時限制有用的電(dian)流(liu)(liu)。如果不(bu)驅(qu)動(dong)負載，開關(guan)電(dian)源啟動(dong)時一般電(dian)流(liu)(liu)很(hen)(hen)小。在很(hen)(hen)多(duo)情況下，啟動(dong)電(dian)流(liu)(liu)實際有可能要比利用這種方法保持(chi)的穩(wen)態工作電(dian)流(liu)(liu)小。