顧名思義(yi)，開關電源就是利用電(dian)(dian)(dian)子(zi)開關器(qi)件(jian)（如晶體管(guan)、場效(xiao)應管(guan)、可(ke)控硅閘流管(guan)等(deng)），通過控制電(dian)(dian)(dian)路，使(shi)電(dian)(dian)(dian)子(zi)開關器(qi)件(jian)不停(ting)地“接通”和“關斷”，讓(rang)電(dian)(dian)(dian)子(zi)開關器(qi)件(jian)對輸入電(dian)(dian)(dian)壓進行(xing)脈沖調制，從而實現DC/AC、DC/DC電(dian)(dian)(dian)壓變換(huan)，以及輸出電(dian)(dian)(dian)壓可(ke)調和自動(dong)穩(wen)壓。

工作(zuo)模式
　　開(kai)關電(dian)(dian)(dian)(dian)源(yuan)一般有三種工(gong)作模式(shi)：頻率(lv)、脈(mo)沖(chong)寬度(du)固定(ding)(ding)模式(shi)，頻率(lv)固定(ding)(ding)、脈(mo)沖(chong)寬度(du)可變(bian)模式(shi)，頻率(lv)、脈(mo)沖(chong)寬度(du)可變(bian)模式(shi)。前(qian)一種工(gong)作模式(shi)多用于(yu)DC/AC逆變(bian)電(dian)(dian)(dian)(dian)源(yuan)，或(huo)DC/DC電(dian)(dian)(dian)(dian)壓(ya)變(bian)換；后兩(liang)種工(gong)作模式(shi)多用于(yu)開(kai)關穩壓(ya)電(dian)(dian)(dian)(dian)源(yuan)。另(ling)外，開(kai)關電(dian)(dian)(dian)(dian)源(yuan)輸(shu)出電(dian)(dian)(dian)(dian)壓(ya)也有三種工(gong)作方(fang)式(shi)：直(zhi)接(jie)輸(shu)出電(dian)(dian)(dian)(dian)壓(ya)方(fang)式(shi)、平均值輸(shu)出電(dian)(dian)(dian)(dian)壓(ya)方(fang)式(shi)、幅(fu)值輸(shu)出電(dian)(dian)(dian)(dian)壓(ya)方(fang)式(shi)。同樣，前(qian)一種工(gong)作方(fang)式(shi)多用于(yu)DC/AC逆變(bian)電(dian)(dian)(dian)(dian)源(yuan)，或(huo)DC/DC電(dian)(dian)(dian)(dian)壓(ya)變(bian)換；后兩(liang)種工(gong)作方(fang)式(shi)多用于(yu)開(kai)關穩壓(ya)電(dian)(dian)(dian)(dian)源(yuan)。
　　根據開(kai)(kai)(kai)關(guan)器件在(zai)電路中連接(jie)的(de)方式(shi)(shi)，開(kai)(kai)(kai)關(guan)電源(yuan)(yuan)，大(da)體上(shang)可(ke)(ke)分為：串聯(lian)式(shi)(shi)開(kai)(kai)(kai)關(guan)電源(yuan)(yuan)、并聯(lian)式(shi)(shi)開(kai)(kai)(kai)關(guan)電源(yuan)(yuan)、變(bian)(bian)壓(ya)器式(shi)(shi)開(kai)(kai)(kai)關(guan)電源(yuan)(yuan)等三大(da)類。其中，變(bian)(bian)壓(ya)器式(shi)(shi)開(kai)(kai)(kai)關(guan)電源(yuan)(yuan)（后面(mian)簡稱變(bian)(bian)壓(ya)器開(kai)(kai)(kai)關(guan)電源(yuan)(yuan)）還可(ke)(ke)以進(jin)一步(bu)分成：推(tui)挽式(shi)(shi)、半(ban)橋式(shi)(shi)、全(quan)橋式(shi)(shi)等多種(zhong)；根據變(bian)(bian)壓(ya)器的(de)激(ji)勵和輸出電壓(ya)的(de)相位，又可(ke)(ke)以分成：正激(ji)式(shi)(shi)、反激(ji)式(shi)(shi)、單(dan)激(ji)式(shi)(shi)和雙(shuang)激(ji)式(shi)(shi)等多種(zhong)；如果從用途上(shang)來分，還可(ke)(ke)以分成更多種(zhong)類。
主要特(te)點
　　1、體(ti)積小(xiao)、重量輕：由于沒有工頻變壓器，所以體(ti)積和重量只有線(xian)性電源的20～30%。
　　2、功耗小、效率高：功率晶(jing)(jing)體管工作在(zai)開關狀態，所(suo)以晶(jing)(jing)體管上的功耗小，轉 化效率高，一(yi)般為60～70%，而線性電(dian)電(dian)源只有(you)30～40%。