顧名(ming)思(si)義，開關(guan)電源就(jiu)是(shi)利用電(dian)(dian)子(zi)開(kai)關(guan)(guan)(guan)器(qi)件（如晶體管(guan)、場效(xiao)應管(guan)、可控硅(gui)閘流管(guan)等），通過控制電(dian)(dian)路，使(shi)電(dian)(dian)子(zi)開(kai)關(guan)(guan)(guan)器(qi)件不停地“接通”和(he)(he)“關(guan)(guan)(guan)斷”，讓電(dian)(dian)子(zi)開(kai)關(guan)(guan)(guan)器(qi)件對輸入電(dian)(dian)壓(ya)(ya)進行脈(mo)沖(chong)調制，從而實現DC/AC、DC/DC電(dian)(dian)壓(ya)(ya)變換(huan)，以及輸出電(dian)(dian)壓(ya)(ya)可調和(he)(he)自(zi)動穩壓(ya)(ya)。

工作模式
　　開關(guan)(guan)電(dian)源(yuan)一般有三種(zhong)(zhong)工作(zuo)模(mo)式(shi)(shi)(shi)(shi)：頻率、脈沖(chong)寬度(du)固(gu)(gu)定模(mo)式(shi)(shi)(shi)(shi)，頻率固(gu)(gu)定、脈沖(chong)寬度(du)可變模(mo)式(shi)(shi)(shi)(shi)，頻率、脈沖(chong)寬度(du)可變模(mo)式(shi)(shi)(shi)(shi)。前一種(zhong)(zhong)工作(zuo)模(mo)式(shi)(shi)(shi)(shi)多用(yong)于(yu)DC/AC逆變電(dian)源(yuan)，或DC/DC電(dian)壓(ya)(ya)變換；后(hou)兩(liang)種(zhong)(zhong)工作(zuo)模(mo)式(shi)(shi)(shi)(shi)多用(yong)于(yu)開關(guan)(guan)穩壓(ya)(ya)電(dian)源(yuan)。另外，開關(guan)(guan)電(dian)源(yuan)輸(shu)(shu)出(chu)(chu)電(dian)壓(ya)(ya)也有三種(zhong)(zhong)工作(zuo)方(fang)式(shi)(shi)(shi)(shi)：直接輸(shu)(shu)出(chu)(chu)電(dian)壓(ya)(ya)方(fang)式(shi)(shi)(shi)(shi)、平均值輸(shu)(shu)出(chu)(chu)電(dian)壓(ya)(ya)方(fang)式(shi)(shi)(shi)(shi)、幅值輸(shu)(shu)出(chu)(chu)電(dian)壓(ya)(ya)方(fang)式(shi)(shi)(shi)(shi)。同樣，前一種(zhong)(zhong)工作(zuo)方(fang)式(shi)(shi)(shi)(shi)多用(yong)于(yu)DC/AC逆變電(dian)源(yuan)，或DC/DC電(dian)壓(ya)(ya)變換；后(hou)兩(liang)種(zhong)(zhong)工作(zuo)方(fang)式(shi)(shi)(shi)(shi)多用(yong)于(yu)開關(guan)(guan)穩壓(ya)(ya)電(dian)源(yuan)。
　　根據開(kai)(kai)關(guan)器件在電(dian)(dian)(dian)(dian)路中連接的方(fang)式(shi)(shi)(shi)，開(kai)(kai)關(guan)電(dian)(dian)(dian)(dian)源(yuan)(yuan)，大體上可分(fen)(fen)為：串聯(lian)(lian)式(shi)(shi)(shi)開(kai)(kai)關(guan)電(dian)(dian)(dian)(dian)源(yuan)(yuan)、并聯(lian)(lian)式(shi)(shi)(shi)開(kai)(kai)關(guan)電(dian)(dian)(dian)(dian)源(yuan)(yuan)、變(bian)壓(ya)(ya)器式(shi)(shi)(shi)開(kai)(kai)關(guan)電(dian)(dian)(dian)(dian)源(yuan)(yuan)等三大類(lei)。其中，變(bian)壓(ya)(ya)器式(shi)(shi)(shi)開(kai)(kai)關(guan)電(dian)(dian)(dian)(dian)源(yuan)(yuan)（后面(mian)簡稱變(bian)壓(ya)(ya)器開(kai)(kai)關(guan)電(dian)(dian)(dian)(dian)源(yuan)(yuan)）還可以(yi)進一(yi)步分(fen)(fen)成：推挽式(shi)(shi)(shi)、半(ban)橋式(shi)(shi)(shi)、全橋式(shi)(shi)(shi)等多(duo)種；根據變(bian)壓(ya)(ya)器的激(ji)(ji)勵和輸出電(dian)(dian)(dian)(dian)壓(ya)(ya)的相位，又可以(yi)分(fen)(fen)成：正激(ji)(ji)式(shi)(shi)(shi)、反激(ji)(ji)式(shi)(shi)(shi)、單激(ji)(ji)式(shi)(shi)(shi)和雙激(ji)(ji)式(shi)(shi)(shi)等多(duo)種；如果(guo)從用途上來分(fen)(fen)，還可以(yi)分(fen)(fen)成更多(duo)種類(lei)。
主要特點
　　1、體積小、重量(liang)輕：由(you)于沒有工頻(pin)變壓(ya)器，所以體積和重量(liang)只有線性(xing)電源的(de)20～30%。
　　2、功(gong)耗小、效率(lv)高：功(gong)率(lv)晶(jing)體管(guan)工作在開關(guan)狀(zhuang)態(tai)，所以晶(jing)體管(guan)上的功(gong)耗小，轉(zhuan) 化效率(lv)高，一般為60～70%，而線性(xing)電電源(yuan)只(zhi)有30～40%。