顧名思義，開(kai)關電源就是利(li)用(yong)電(dian)(dian)子(zi)開(kai)關(guan)(guan)器件（如(ru)晶體管(guan)(guan)、場效(xiao)應管(guan)(guan)、可控硅閘流管(guan)(guan)等），通過控制電(dian)(dian)路，使電(dian)(dian)子(zi)開(kai)關(guan)(guan)器件不(bu)停地“接通”和“關(guan)(guan)斷”，讓電(dian)(dian)子(zi)開(kai)關(guan)(guan)器件對輸入電(dian)(dian)壓(ya)進行脈沖調制，從而實現DC/AC、DC/DC電(dian)(dian)壓(ya)變換，以及輸出電(dian)(dian)壓(ya)可調和自(zi)動穩壓(ya)。

工作模(mo)式
　　開(kai)(kai)關(guan)電(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)一般有三種工(gong)作(zuo)(zuo)模式(shi)(shi)：頻率(lv)、脈沖寬(kuan)(kuan)度(du)(du)固(gu)定(ding)模式(shi)(shi)，頻率(lv)固(gu)定(ding)、脈沖寬(kuan)(kuan)度(du)(du)可變(bian)(bian)(bian)模式(shi)(shi)，頻率(lv)、脈沖寬(kuan)(kuan)度(du)(du)可變(bian)(bian)(bian)模式(shi)(shi)。前一種工(gong)作(zuo)(zuo)模式(shi)(shi)多(duo)(duo)用(yong)于DC/AC逆變(bian)(bian)(bian)電(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)，或DC/DC電(dian)(dian)(dian)壓變(bian)(bian)(bian)換；后兩種工(gong)作(zuo)(zuo)模式(shi)(shi)多(duo)(duo)用(yong)于開(kai)(kai)關(guan)穩壓電(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)。另(ling)外，開(kai)(kai)關(guan)電(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)輸(shu)出(chu)(chu)電(dian)(dian)(dian)壓也有三種工(gong)作(zuo)(zuo)方(fang)(fang)式(shi)(shi)：直接輸(shu)出(chu)(chu)電(dian)(dian)(dian)壓方(fang)(fang)式(shi)(shi)、平均值(zhi)輸(shu)出(chu)(chu)電(dian)(dian)(dian)壓方(fang)(fang)式(shi)(shi)、幅值(zhi)輸(shu)出(chu)(chu)電(dian)(dian)(dian)壓方(fang)(fang)式(shi)(shi)。同樣，前一種工(gong)作(zuo)(zuo)方(fang)(fang)式(shi)(shi)多(duo)(duo)用(yong)于DC/AC逆變(bian)(bian)(bian)電(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)，或DC/DC電(dian)(dian)(dian)壓變(bian)(bian)(bian)換；后兩種工(gong)作(zuo)(zuo)方(fang)(fang)式(shi)(shi)多(duo)(duo)用(yong)于開(kai)(kai)關(guan)穩壓電(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)。
　　根據開關(guan)器(qi)件在(zai)電(dian)路中連接的方式(shi)，開關(guan)電(dian)源(yuan)(yuan)，大(da)體(ti)上可分為：串聯式(shi)開關(guan)電(dian)源(yuan)(yuan)、并聯式(shi)開關(guan)電(dian)源(yuan)(yuan)、變壓(ya)器(qi)式(shi)開關(guan)電(dian)源(yuan)(yuan)等(deng)三(san)大(da)類。其中，變壓(ya)器(qi)式(shi)開關(guan)電(dian)源(yuan)(yuan)（后面簡稱變壓(ya)器(qi)開關(guan)電(dian)源(yuan)(yuan)）還可以進一步分成(cheng)：推(tui)挽式(shi)、半橋式(shi)、全橋式(shi)等(deng)多(duo)種(zhong)；根據變壓(ya)器(qi)的激勵(li)和輸出電(dian)壓(ya)的相位，又可以分成(cheng)：正激式(shi)、反激式(shi)、單(dan)激式(shi)和雙激式(shi)等(deng)多(duo)種(zhong)；如(ru)果從用(yong)途上來分，還可以分成(cheng)更多(duo)種(zhong)類。
主(zhu)要特點
　　1、體積小、重(zhong)量輕(qing)：由于沒有工頻變壓器(qi)，所以體積和(he)重(zhong)量只有線性電源的20～30%。
　　2、功(gong)耗小(xiao)、效率(lv)高：功(gong)率(lv)晶體管(guan)工作在開關狀態，所以晶體管(guan)上的功(gong)耗小(xiao)，轉(zhuan) 化效率(lv)高，一般(ban)為60～70%，而線性電(dian)電(dian)源只有30～40%。