顧名(ming)思義，開(kai)關(guan)電源就是利(li)用電子開關器(qi)件(jian)(jian)（如晶體(ti)管、場效應管、可(ke)控硅(gui)閘(zha)流管等），通過控制(zhi)電路，使電子開關器(qi)件(jian)(jian)不(bu)停(ting)地“接(jie)通”和(he)“關斷”，讓電子開關器(qi)件(jian)(jian)對輸(shu)入電壓進(jin)行脈(mo)沖(chong)調(diao)(diao)制(zhi)，從而實(shi)現DC/AC、DC/DC電壓變換，以及輸(shu)出電壓可(ke)調(diao)(diao)和(he)自動(dong)穩(wen)壓。

工(gong)作模式
　　開(kai)關(guan)電(dian)(dian)(dian)源(yuan)(yuan)一(yi)般有(you)三(san)種工(gong)作(zuo)(zuo)模(mo)式(shi)(shi)(shi)：頻率(lv)(lv)、脈(mo)沖(chong)寬度(du)固(gu)定模(mo)式(shi)(shi)(shi)，頻率(lv)(lv)固(gu)定、脈(mo)沖(chong)寬度(du)可變(bian)模(mo)式(shi)(shi)(shi)，頻率(lv)(lv)、脈(mo)沖(chong)寬度(du)可變(bian)模(mo)式(shi)(shi)(shi)。前一(yi)種工(gong)作(zuo)(zuo)模(mo)式(shi)(shi)(shi)多用(yong)于(yu)(yu)DC/AC逆變(bian)電(dian)(dian)(dian)源(yuan)(yuan)，或DC/DC電(dian)(dian)(dian)壓(ya)(ya)(ya)變(bian)換；后(hou)兩種工(gong)作(zuo)(zuo)模(mo)式(shi)(shi)(shi)多用(yong)于(yu)(yu)開(kai)關(guan)穩(wen)壓(ya)(ya)(ya)電(dian)(dian)(dian)源(yuan)(yuan)。另(ling)外，開(kai)關(guan)電(dian)(dian)(dian)源(yuan)(yuan)輸出電(dian)(dian)(dian)壓(ya)(ya)(ya)也有(you)三(san)種工(gong)作(zuo)(zuo)方(fang)式(shi)(shi)(shi)：直接輸出電(dian)(dian)(dian)壓(ya)(ya)(ya)方(fang)式(shi)(shi)(shi)、平均值(zhi)輸出電(dian)(dian)(dian)壓(ya)(ya)(ya)方(fang)式(shi)(shi)(shi)、幅(fu)值(zhi)輸出電(dian)(dian)(dian)壓(ya)(ya)(ya)方(fang)式(shi)(shi)(shi)。同樣，前一(yi)種工(gong)作(zuo)(zuo)方(fang)式(shi)(shi)(shi)多用(yong)于(yu)(yu)DC/AC逆變(bian)電(dian)(dian)(dian)源(yuan)(yuan)，或DC/DC電(dian)(dian)(dian)壓(ya)(ya)(ya)變(bian)換；后(hou)兩種工(gong)作(zuo)(zuo)方(fang)式(shi)(shi)(shi)多用(yong)于(yu)(yu)開(kai)關(guan)穩(wen)壓(ya)(ya)(ya)電(dian)(dian)(dian)源(yuan)(yuan)。
　　根據開(kai)(kai)關(guan)(guan)(guan)器件在電(dian)(dian)路中連接(jie)的方式(shi)(shi)(shi)，開(kai)(kai)關(guan)(guan)(guan)電(dian)(dian)源(yuan)，大(da)體(ti)上可分(fen)為：串聯(lian)式(shi)(shi)(shi)開(kai)(kai)關(guan)(guan)(guan)電(dian)(dian)源(yuan)、并聯(lian)式(shi)(shi)(shi)開(kai)(kai)關(guan)(guan)(guan)電(dian)(dian)源(yuan)、變壓(ya)器式(shi)(shi)(shi)開(kai)(kai)關(guan)(guan)(guan)電(dian)(dian)源(yuan)等三大(da)類。其中，變壓(ya)器式(shi)(shi)(shi)開(kai)(kai)關(guan)(guan)(guan)電(dian)(dian)源(yuan)（后(hou)面簡稱(cheng)變壓(ya)器開(kai)(kai)關(guan)(guan)(guan)電(dian)(dian)源(yuan)）還可以進一步分(fen)成：推挽(wan)式(shi)(shi)(shi)、半橋式(shi)(shi)(shi)、全橋式(shi)(shi)(shi)等多(duo)種；根據變壓(ya)器的激(ji)勵和輸(shu)出電(dian)(dian)壓(ya)的相(xiang)位，又可以分(fen)成：正激(ji)式(shi)(shi)(shi)、反激(ji)式(shi)(shi)(shi)、單激(ji)式(shi)(shi)(shi)和雙(shuang)激(ji)式(shi)(shi)(shi)等多(duo)種；如果從用途上來分(fen)，還可以分(fen)成更多(duo)種類。
主要特點
　　1、體積小、重(zhong)量輕：由(you)于沒有工頻變壓(ya)器，所以體積和重(zhong)量只有線(xian)性電源的(de)20～30%。
　　2、功(gong)耗小、效率(lv)高：功(gong)率(lv)晶體(ti)管(guan)工作(zuo)在開關狀態，所以晶體(ti)管(guan)上的(de)功(gong)耗小，轉 化效率(lv)高，一般為(wei)60～70%，而線性電電源只有30～40%。