在(zai)電(dian)源適(shi)配(pei)器中(zhong)，電(dian)壓(ya)、電(dian)流波(bo)形均為突變的(de)(de)(de)脈沖(chong)狀(zhuang)態，元(yuan)(yuan)器件(jian)所承受電(dian)壓(ya)或電(dian)流除(chu)加在(zai)元(yuan)(yuan)器件(jian)上(shang)的(de)(de)(de)供(gong)電(dian)電(dian)壓(ya)以(yi)外，還有電(dian)路中(zhong)電(dian)感成分引(yin)起的(de)(de)(de)感應電(dian)壓(ya)、電(dian)容器的(de)(de)(de)充電(dian)電(dian)流等.使得(de)元(yuan)(yuan)器件(jian)的(de)(de)(de)選(xuan)擇變得(de)復雜化。

 實際(ji)(ji)上(shang)，電(dian)源(yuan)適(shi)配器(qi)屬(shu)有穩壓功能(neng)的AC/DC或DC/DC變(bian)換器(qi)，即使所謂DC/DC變(bian)換.其中間環(huan)節仍然要(yao)通過脈(mo)沖(chong)狀態作為轉換媒介。實際(ji)(ji)過程是(shi)，DC先逆變(bian)成脈(mo)沖(chong)狀態的AC，再(zai)由脈(mo)沖(chong)整(zheng)流濾(lv)波成為直流電(dian)壓。在(zai)此過程中，整(zheng)流、濾(lv)波元器(qi)件要(yao)求也與工頻整(zheng)流電(dian)路大(da)有區別。工頻正(zheng)弦波交(jiao)流電(dian)源(yuan)最大(da)值、平均值和有效值都按正(zheng)弦函數有固定的比(bi)例關系，可(ke)以對元器(qi)件的額定參數進行十分準確的計(ji)算。

但是(shi)(shi)，脈(mo)沖(chong)(chong)波、電(dian)壓、電(dian)流數值的(de)(de)(de)(de)關(guan)(guan)系不(bu)是(shi)(shi)一成不(bu)變的(de)(de)(de)(de)，而(er)是(shi)(shi)隨脈(mo)沖(chong)(chong)波形和負(fu)載(zai)性質(zhi)而(er)有(you)很大(da)的(de)(de)(de)(de)變化。即使(shi)采用積分法計(ji)算脈(mo)沖(chong)(chong)波形的(de)(de)(de)(de)平均值，要(yao)(yao)求(qiu)脈(mo)沖(chong)(chong)波形有(you)一定(ding)的(de)(de)(de)(de)規律，而(er)波形幅度與時間關(guan)(guan)系的(de)(de)(de)(de)不(bu)穩定(ding)性使(shi)這種計(ji)算往(wang)往(wang)難(nan)(nan)以(yi)(yi)準(zhun)確。尤其是(shi)(shi)脈(mo)沖(chong)(chong)波形的(de)(de)(de)(de)定(ding)量(liang)測(ce)量(liang)，也非(fei)一般簡單儀(yi)(yi)表(biao)所能準(zhun)確測(ce)量(liang)的(de)(de)(de)(de)，除了脈(mo)沖(chong)(chong)示波器(qi)以(yi)(yi)外(wai)，還(huan)沒(mei)有(you)更(geng)簡單的(de)(de)(de)(de)方(fang)(fang)式(shi)，例(li)如電(dian)源(yuan)適(shi)配器(qi)電(dian)源(yuan)適(shi)配器(qi)的(de)(de)(de)(de)反(fan)向(xiang)電(dian)壓值。至于某些情況(kuang)下要(yao)(yao)求(qiu)測(ce)出脈(mo)沖(chong)(chong)波的(de)(de)(de)(de)有(you)效值就更(geng)困難(nan)(nan)了。例(li)如，用行逆程脈(mo)沖(chong)(chong)向(xiang)CRT燈絲供電(dian)，要(yao)(yao)求(qiu)6.3V的(de)(de)(de)(de)有(you)效值，其準(zhun)確測(ce)量(liang)除用熱電(dian)偶傳感器(qi)組成的(de)(de)(de)(de)磁電(dian)式(shi)儀(yi)(yi)表(biao)或高頻率電(dian)動(dong)式(shi)儀(yi)(yi)表(biao)以(yi)(yi)外(wai)，似(si)乎還(huan)沒(mei)有(you)其他(ta)的(de)(de)(de)(de)方(fang)(fang)式(shi)。

也就(jiu)是(shi)說(shuo)，工作在脈(mo)沖電(dian)(dian)(dian)路中(zhong)的(de)(de)元(yuan)器(qi)(qi)(qi)件欲通過實測電(dian)(dian)(dian)壓、電(dian)(dian)(dian)流參(can)數(shu)選擇其(qi)性能(neng)是(shi)不可(ke)能(neng)的(de)(de)。至于(yu)理(li)論(lun)(lun)計(ji)算，也只能(neng)達到(dao)近(jin)似(si)估(gu)計(ji)的(de)(de)程度，具體參(can)數(shu)選擇是(shi)在計(ji)算結果的(de)(de)基礎(chu)上寬打窄(zhai)用。最明顯的(de)(de)例子是(shi)單端(duan)開關電(dian)(dian)(dian)路，從理(li)論(lun)(lun)上計(ji)算，其(qi)電(dian)(dian)(dian)源適(shi)(shi)配(pei)器(qi)(qi)(qi)反壓應(ying)為(wei)輸入電(dian)(dian)(dian)壓最大值(zhi)(zhi)的(de)(de)兩倍。而實際(ji)應(ying)用中(zhong)，加在電(dian)(dian)(dian)源適(shi)(shi)配(pei)器(qi)(qi)(qi)集(ji)電(dian)(dian)(dian)極的(de)(de)脈(mo)沖波(bo)形受儲能(neng)電(dian)(dian)(dian)感的(de)(de)集(ji)總參(can)數(shu)、分布參(can)數(shu)和電(dian)(dian)(dian)源負載性質(zhi)的(de)(de)影響(xiang)，電(dian)(dian)(dian)源適(shi)(shi)配(pei)器(qi)(qi)(qi)承受反壓值(zhi)(zhi)將超出理(li)論(lun)(lun)計(ji)算值(zhi)(zhi)范圍。