顧(gu)名思(si)義(yi)，開(kai)關電源就是利用電子(zi)開關器(qi)(qi)件（如(ru)晶體管、場效應管、可(ke)(ke)控硅閘流管等），通過控制(zhi)電路，使(shi)電子(zi)開關器(qi)(qi)件不停(ting)地“接通”和“關斷”，讓電子(zi)開關器(qi)(qi)件對輸入電壓(ya)進行脈沖(chong)調(diao)制(zhi)，從而(er)實現DC/AC、DC/DC電壓(ya)變換，以及輸出電壓(ya)可(ke)(ke)調(diao)和自(zi)動穩壓(ya)。

工作模式
　　開關電(dian)(dian)(dian)(dian)源(yuan)一般有三種(zhong)(zhong)工作(zuo)模(mo)式(shi)(shi)(shi)：頻(pin)率、脈沖(chong)(chong)(chong)寬(kuan)度固(gu)定模(mo)式(shi)(shi)(shi)，頻(pin)率固(gu)定、脈沖(chong)(chong)(chong)寬(kuan)度可(ke)變(bian)(bian)模(mo)式(shi)(shi)(shi)，頻(pin)率、脈沖(chong)(chong)(chong)寬(kuan)度可(ke)變(bian)(bian)模(mo)式(shi)(shi)(shi)。前(qian)一種(zhong)(zhong)工作(zuo)模(mo)式(shi)(shi)(shi)多用(yong)(yong)于DC/AC逆變(bian)(bian)電(dian)(dian)(dian)(dian)源(yuan)，或(huo)DC/DC電(dian)(dian)(dian)(dian)壓(ya)變(bian)(bian)換；后兩種(zhong)(zhong)工作(zuo)模(mo)式(shi)(shi)(shi)多用(yong)(yong)于開關穩壓(ya)電(dian)(dian)(dian)(dian)源(yuan)。另外，開關電(dian)(dian)(dian)(dian)源(yuan)輸出(chu)(chu)(chu)電(dian)(dian)(dian)(dian)壓(ya)也有三種(zhong)(zhong)工作(zuo)方式(shi)(shi)(shi)：直接輸出(chu)(chu)(chu)電(dian)(dian)(dian)(dian)壓(ya)方式(shi)(shi)(shi)、平(ping)均(jun)值輸出(chu)(chu)(chu)電(dian)(dian)(dian)(dian)壓(ya)方式(shi)(shi)(shi)、幅值輸出(chu)(chu)(chu)電(dian)(dian)(dian)(dian)壓(ya)方式(shi)(shi)(shi)。同樣(yang)，前(qian)一種(zhong)(zhong)工作(zuo)方式(shi)(shi)(shi)多用(yong)(yong)于DC/AC逆變(bian)(bian)電(dian)(dian)(dian)(dian)源(yuan)，或(huo)DC/DC電(dian)(dian)(dian)(dian)壓(ya)變(bian)(bian)換；后兩種(zhong)(zhong)工作(zuo)方式(shi)(shi)(shi)多用(yong)(yong)于開關穩壓(ya)電(dian)(dian)(dian)(dian)源(yuan)。
　　根據開(kai)(kai)(kai)關(guan)(guan)(guan)器(qi)(qi)件在(zai)電路中(zhong)連(lian)接(jie)的方式(shi)(shi)(shi)，開(kai)(kai)(kai)關(guan)(guan)(guan)電源(yuan)，大體上(shang)可分為：串(chuan)聯(lian)式(shi)(shi)(shi)開(kai)(kai)(kai)關(guan)(guan)(guan)電源(yuan)、并(bing)聯(lian)式(shi)(shi)(shi)開(kai)(kai)(kai)關(guan)(guan)(guan)電源(yuan)、變壓(ya)器(qi)(qi)式(shi)(shi)(shi)開(kai)(kai)(kai)關(guan)(guan)(guan)電源(yuan)等(deng)三大類。其中(zhong)，變壓(ya)器(qi)(qi)式(shi)(shi)(shi)開(kai)(kai)(kai)關(guan)(guan)(guan)電源(yuan)（后面簡(jian)稱變壓(ya)器(qi)(qi)開(kai)(kai)(kai)關(guan)(guan)(guan)電源(yuan)）還可以(yi)進(jin)一步分成(cheng)：推挽(wan)式(shi)(shi)(shi)、半橋式(shi)(shi)(shi)、全橋式(shi)(shi)(shi)等(deng)多種；根據變壓(ya)器(qi)(qi)的激(ji)勵(li)和輸出電壓(ya)的相位，又可以(yi)分成(cheng)：正(zheng)激(ji)式(shi)(shi)(shi)、反(fan)激(ji)式(shi)(shi)(shi)、單激(ji)式(shi)(shi)(shi)和雙激(ji)式(shi)(shi)(shi)等(deng)多種；如(ru)果從用途上(shang)來分，還可以(yi)分成(cheng)更多種類。
主要特點(dian)
　　1、體(ti)積小(xiao)、重量輕(qing)：由于沒(mei)有工頻變(bian)壓器，所以體(ti)積和(he)重量只有線(xian)性電源的20～30%。
　　2、功耗小、效率(lv)高(gao)：功率(lv)晶(jing)體管工作(zuo)在開關狀態，所以晶(jing)體管上的功耗小，轉 化效率(lv)高(gao)，一般為60～70%，而(er)線性電(dian)電(dian)源只有30～40%。