顧名思義，開(kai)關(guan)電源就是利(li)用電(dian)(dian)子開關(guan)(guan)器(qi)件（如晶體管、場效應管、可控硅閘流(liu)管等），通(tong)過控制電(dian)(dian)路，使電(dian)(dian)子開關(guan)(guan)器(qi)件不停地“接通(tong)”和(he)“關(guan)(guan)斷(duan)”，讓電(dian)(dian)子開關(guan)(guan)器(qi)件對輸入電(dian)(dian)壓(ya)進(jin)行脈沖調制，從而實(shi)現DC/AC、DC/DC電(dian)(dian)壓(ya)變換(huan)，以(yi)及輸出(chu)電(dian)(dian)壓(ya)可調和(he)自動穩(wen)壓(ya)。

工作模(mo)式
　　開關電(dian)(dian)(dian)(dian)源(yuan)一般有三種工作模(mo)(mo)式(shi)(shi)：頻率、脈沖(chong)(chong)寬(kuan)度(du)固定模(mo)(mo)式(shi)(shi)，頻率固定、脈沖(chong)(chong)寬(kuan)度(du)可(ke)變(bian)模(mo)(mo)式(shi)(shi)，頻率、脈沖(chong)(chong)寬(kuan)度(du)可(ke)變(bian)模(mo)(mo)式(shi)(shi)。前(qian)一種工作模(mo)(mo)式(shi)(shi)多(duo)用(yong)于(yu)(yu)DC/AC逆(ni)變(bian)電(dian)(dian)(dian)(dian)源(yuan)，或DC/DC電(dian)(dian)(dian)(dian)壓(ya)(ya)變(bian)換；后兩種工作模(mo)(mo)式(shi)(shi)多(duo)用(yong)于(yu)(yu)開關穩壓(ya)(ya)電(dian)(dian)(dian)(dian)源(yuan)。另外，開關電(dian)(dian)(dian)(dian)源(yuan)輸(shu)出電(dian)(dian)(dian)(dian)壓(ya)(ya)也(ye)有三種工作方(fang)(fang)式(shi)(shi)：直接(jie)輸(shu)出電(dian)(dian)(dian)(dian)壓(ya)(ya)方(fang)(fang)式(shi)(shi)、平(ping)均值(zhi)輸(shu)出電(dian)(dian)(dian)(dian)壓(ya)(ya)方(fang)(fang)式(shi)(shi)、幅值(zhi)輸(shu)出電(dian)(dian)(dian)(dian)壓(ya)(ya)方(fang)(fang)式(shi)(shi)。同樣，前(qian)一種工作方(fang)(fang)式(shi)(shi)多(duo)用(yong)于(yu)(yu)DC/AC逆(ni)變(bian)電(dian)(dian)(dian)(dian)源(yuan)，或DC/DC電(dian)(dian)(dian)(dian)壓(ya)(ya)變(bian)換；后兩種工作方(fang)(fang)式(shi)(shi)多(duo)用(yong)于(yu)(yu)開關穩壓(ya)(ya)電(dian)(dian)(dian)(dian)源(yuan)。
　　根(gen)據開(kai)(kai)關器(qi)件(jian)在電(dian)(dian)(dian)(dian)路中(zhong)連接(jie)的方式，開(kai)(kai)關電(dian)(dian)(dian)(dian)源(yuan)，大體上(shang)(shang)可分為：串聯(lian)式開(kai)(kai)關電(dian)(dian)(dian)(dian)源(yuan)、并聯(lian)式開(kai)(kai)關電(dian)(dian)(dian)(dian)源(yuan)、變壓器(qi)式開(kai)(kai)關電(dian)(dian)(dian)(dian)源(yuan)等(deng)三大類。其中(zhong)，變壓器(qi)式開(kai)(kai)關電(dian)(dian)(dian)(dian)源(yuan)（后面簡稱變壓器(qi)開(kai)(kai)關電(dian)(dian)(dian)(dian)源(yuan)）還可以(yi)進一步(bu)分成：推挽(wan)式、半橋式、全(quan)橋式等(deng)多(duo)種；根(gen)據變壓器(qi)的激(ji)勵和(he)輸(shu)出電(dian)(dian)(dian)(dian)壓的相位，又(you)可以(yi)分成：正(zheng)激(ji)式、反(fan)激(ji)式、單激(ji)式和(he)雙(shuang)激(ji)式等(deng)多(duo)種；如果從(cong)用途上(shang)(shang)來(lai)分，還可以(yi)分成更(geng)多(duo)種類。
主要特(te)點
　　1、體積小、重量(liang)輕(qing)：由(you)于沒有工頻變(bian)壓器，所以體積和重量(liang)只有線性(xing)電(dian)源的20～30%。
　　2、功耗(hao)小、效(xiao)率高：功率晶體管(guan)(guan)工作在開(kai)關狀(zhuang)態，所以晶體管(guan)(guan)上的功耗(hao)小，轉 化(hua)效(xiao)率高，一般為60～70%，而線性(xing)電電源只有30～40%。