筆記本是一種電容輸入(ru)型(xing)電路(lu)，其電流(liu)和電壓之間的(de)(de)相位差會造(zao)成(cheng)交換功率的(de)(de)損失，此時便需(xu)要PFC電路(lu)提高功率因(yin)數。目前的(de)(de)PFC有兩種，一種為被動式(shi)PFC（也稱(cheng)無(wu)源PFC）和主動式(shi)PFC（也稱(cheng)有源式(shi)PFC）

被動式(shi)PFC編(bian)輯

被(bei)動(dong)式(shi)PFC一般分(fen)“電感補償式(shi)”和“填谷電路式(shi)(Valley FillCircuit)”

“電(dian)感(gan)補(bu)償(chang)式”是使(shi)交流輸入(ru)的(de)基波(bo)電(dian)流與電(dian)壓(ya)之間相位差減小來提高(gao)功(gong)率因數，“電(dian)感(gan)補(bu)償(chang)式”包(bao)括靜音(yin)式和非靜音(yin)式。“電(dian)感(gan)補(bu)償(chang)式”的(de)功(gong)率因數只(zhi)能達(da)到(dao)0.7～0.8，它一(yi)般在高(gao)壓(ya)濾波(bo)電(dian)容附近(jin)。

“填谷(gu)電(dian)(dian)(dian)路(lu)式(shi)”屬(shu)于一(yi)種新(xin)型無源功率(lv)(lv)因數(shu)校正電(dian)(dian)(dian)路(lu)，其特點是利用(yong)(yong)整流橋(qiao)后面的(de)(de)填谷(gu)電(dian)(dian)(dian)路(lu)來大幅度增加整流管的(de)(de)導通角，通過填平谷(gu)點，使輸入(ru)電(dian)(dian)(dian)流從(cong)尖峰脈(mo)沖變(bian)為接近于正弦(xian)波(bo)的(de)(de)波(bo)形(xing)，將(jiang)功率(lv)(lv)因數(shu)提高(gao)到0.9左右(you)，顯著降低總諧波(bo)失(shi)真。與傳統的(de)(de)電(dian)(dian)(dian)感式(shi)無源功率(lv)(lv)因數(shu)校正電(dian)(dian)(dian)路(lu)相比，其優(you)點是電(dian)(dian)(dian)路(lu)簡單(dan)，功率(lv)(lv)因素(su)補償效果(guo)顯著，并且在(zai)輸入(ru)電(dian)(dian)(dian)路(lu)中不需(xu)要(yao)使用(yong)(yong)體(ti)積大重量(liang)沉(chen)的(de)(de)大電(dian)(dian)(dian)感器。

主(zhu)動式PFC編輯

而主動(dong)(dong)式(shi)PFC則由電(dian)(dian)感電(dian)(dian)容及(ji)電(dian)(dian)子元器件組成(cheng)，體積(ji)小、通過專用(yong)IC去調整電(dian)(dian)流(liu)的(de)波形，對電(dian)(dian)流(liu)電(dian)(dian)壓(ya)(ya)間的(de)相(xiang)位差進行(xing)補償。主動(dong)(dong)式(shi)PFC可(ke)以達(da)到(dao)較高的(de)功率因數──通常可(ke)達(da)98%以上，但成(cheng)本(ben)也相(xiang)對較高。此外，主動(dong)(dong)式(shi)PFC還可(ke)用(yong)作，因此在使(shi)用(yong)主動(dong)(dong)式(shi)PFC電(dian)(dian)路中，往(wang)(wang)往(wang)(wang)不(bu)需要待機(ji)變壓(ya)(ya)器，而且主動(dong)(dong)式(shi)PFC輸出直流(liu)電(dian)(dian)壓(ya)(ya)的(de)紋波很(hen)小，這種電(dian)(dian)源不(bu)必采(cai)用(yong)很(hen)大(da)容量的(de)濾波電(dian)(dian)容。