顧名思義，開(kai)關電(dian)源(yuan)就是利用(yong)電(dian)(dian)子(zi)開(kai)關器件(jian)（如晶體管(guan)、場效應管(guan)、可控硅閘流管(guan)等），通過(guo)控制電(dian)(dian)路(lu)，使電(dian)(dian)子(zi)開(kai)關器件(jian)不停地“接(jie)通”和(he)“關斷(duan)”，讓電(dian)(dian)子(zi)開(kai)關器件(jian)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，以及輸出電(dian)(dian)壓(ya)(ya)可調和(he)自動穩壓(ya)(ya)。

工作模(mo)式(shi)
　　開(kai)(kai)關(guan)電(dian)(dian)源一般有(you)三(san)種(zhong)工作模(mo)式：頻率、脈(mo)(mo)沖寬(kuan)度(du)(du)固(gu)定模(mo)式，頻率固(gu)定、脈(mo)(mo)沖寬(kuan)度(du)(du)可(ke)變(bian)(bian)(bian)模(mo)式，頻率、脈(mo)(mo)沖寬(kuan)度(du)(du)可(ke)變(bian)(bian)(bian)模(mo)式。前一種(zhong)工作模(mo)式多用于(yu)(yu)DC/AC逆變(bian)(bian)(bian)電(dian)(dian)源，或DC/DC電(dian)(dian)壓(ya)變(bian)(bian)(bian)換；后兩(liang)種(zhong)工作模(mo)式多用于(yu)(yu)開(kai)(kai)關(guan)穩壓(ya)電(dian)(dian)源。另外，開(kai)(kai)關(guan)電(dian)(dian)源輸(shu)(shu)(shu)出(chu)(chu)電(dian)(dian)壓(ya)也有(you)三(san)種(zhong)工作方(fang)(fang)(fang)式：直接(jie)輸(shu)(shu)(shu)出(chu)(chu)電(dian)(dian)壓(ya)方(fang)(fang)(fang)式、平均值輸(shu)(shu)(shu)出(chu)(chu)電(dian)(dian)壓(ya)方(fang)(fang)(fang)式、幅值輸(shu)(shu)(shu)出(chu)(chu)電(dian)(dian)壓(ya)方(fang)(fang)(fang)式。同樣，前一種(zhong)工作方(fang)(fang)(fang)式多用于(yu)(yu)DC/AC逆變(bian)(bian)(bian)電(dian)(dian)源，或DC/DC電(dian)(dian)壓(ya)變(bian)(bian)(bian)換；后兩(liang)種(zhong)工作方(fang)(fang)(fang)式多用于(yu)(yu)開(kai)(kai)關(guan)穩壓(ya)電(dian)(dian)源。
　　根據(ju)開(kai)關器(qi)(qi)件在電(dian)(dian)路中連(lian)接的方式(shi)(shi)(shi)(shi)，開(kai)關電(dian)(dian)源(yuan)，大(da)體上(shang)可(ke)分(fen)(fen)為：串(chuan)聯式(shi)(shi)(shi)(shi)開(kai)關電(dian)(dian)源(yuan)、并聯式(shi)(shi)(shi)(shi)開(kai)關電(dian)(dian)源(yuan)、變(bian)壓(ya)器(qi)(qi)式(shi)(shi)(shi)(shi)開(kai)關電(dian)(dian)源(yuan)等(deng)三大(da)類。其中，變(bian)壓(ya)器(qi)(qi)式(shi)(shi)(shi)(shi)開(kai)關電(dian)(dian)源(yuan)（后面簡稱變(bian)壓(ya)器(qi)(qi)開(kai)關電(dian)(dian)源(yuan)）還(huan)可(ke)以(yi)進一步分(fen)(fen)成(cheng)：推挽式(shi)(shi)(shi)(shi)、半橋式(shi)(shi)(shi)(shi)、全橋式(shi)(shi)(shi)(shi)等(deng)多種；根據(ju)變(bian)壓(ya)器(qi)(qi)的激(ji)勵和(he)輸出電(dian)(dian)壓(ya)的相位，又可(ke)以(yi)分(fen)(fen)成(cheng)：正激(ji)式(shi)(shi)(shi)(shi)、反激(ji)式(shi)(shi)(shi)(shi)、單激(ji)式(shi)(shi)(shi)(shi)和(he)雙(shuang)激(ji)式(shi)(shi)(shi)(shi)等(deng)多種；如果(guo)從用(yong)途上(shang)來分(fen)(fen)，還(huan)可(ke)以(yi)分(fen)(fen)成(cheng)更(geng)多種類。
主要特點
　　1、體積小、重量輕：由于沒有工頻變壓器，所(suo)以體積和重量只有線性電(dian)源的20～30%。
　　2、功(gong)(gong)耗小(xiao)(xiao)、效(xiao)率高：功(gong)(gong)率晶體(ti)管工(gong)作在(zai)開關(guan)狀態(tai)，所以(yi)晶體(ti)管上的(de)功(gong)(gong)耗小(xiao)(xiao)，轉(zhuan) 化效(xiao)率高，一般為60～70%，而線(xian)性電電源(yuan)只(zhi)有30～40%。