開(kai)(kai)關電源(yuan)是利用現代電力電子技術(shu)，控(kong)制開(kai)(kai)關晶體管開(kai)(kai)通和關斷的時間比率(lv)，維持(chi)穩定(ding)輸出(chu)電壓的一種電源(yuan)，開(kai)(kai)關電源(yuan)一般由脈沖寬度調(diao)制（PWM）控(kong)制IC和MOSFET構(gou)成。

開關電源的選用：

開(kai)(kai)關(guan)電(dian)(dian)(dian)源(yuan)在(zai)(zai)輸(shu)入抗干擾性能上，由(you)于其自身電(dian)(dian)(dian)路結構的(de)特點（多級串聯），一般的(de)輸(shu)入干擾如浪涌電(dian)(dian)(dian)壓(ya)很難(nan)通(tong)過，在(zai)(zai)輸(shu)出(chu)電(dian)(dian)(dian)壓(ya)穩定(ding)度(du)這(zhe)一技術指標上與(yu)線(xian)性電(dian)(dian)(dian)源(yuan)相(xiang)比具有較大(da)的(de)優勢(shi)，其輸(shu)出(chu)電(dian)(dian)(dian)壓(ya)穩定(ding)度(du)可達（0.5~1）%。開(kai)(kai)關(guan)電(dian)(dian)(dian)源(yuan)模塊作為一種電(dian)(dian)(dian)力電(dian)(dian)(dian)子集成(cheng)器件，在(zai)(zai)選(xuan)用中應注(zhu)意以下幾(ji)點：

1、輸出電流的選擇

Is=KIf式中：Is-開關電(dian)(dian)源的(de)額定(ding)輸出電(dian)(dian)流；If-用電(dian)(dian)設(she)備的(de)最大(da)吸收電(dian)(dian)流；K-裕量系(xi)數，一(yi)般取1.5~1.82、接地(di)

開關電(dian)(dian)源比線(xian)性電(dian)(dian)源會產(chan)生更多的(de)干(gan)擾，對共(gong)模干(gan)擾敏感的(de)用電(dian)(dian)設備(bei)，應采取接(jie)地和屏(ping)蔽措(cuo)施(shi)，按ICE1000、EN61000、FCC等EMC限制，開關電(dian)(dian)源均采取EMC電(dian)(dian)磁兼容(rong)措(cuo)施(shi)，因此開關電(dian)(dian)源一(yi)般應帶有EMC電(dian)(dian)磁兼容(rong)濾波器(qi)。如利德華福技術的(de)HA系列開關電(dian)(dian)源，將其FG端子接(jie)大地或接(jie)用戶機殼，方能滿(man)足上述電(dian)(dian)磁兼容(rong)的(de)要求。

3、保護電路

開關電(dian)(dian)(dian)(dian)源在設(she)(she)計中必(bi)須具有過流、過熱、短(duan)路等保(bao)護功(gong)能，故在設(she)(she)計時應(ying)首(shou)選保(bao)護功(gong)能齊備的開關電(dian)(dian)(dian)(dian)源模塊，并且(qie)其保(bao)護電(dian)(dian)(dian)(dian)路的技術參數(shu)應(ying)與用(yong)電(dian)(dian)(dian)(dian)設(she)(she)備的工作特性(xing)相匹配，以避(bi)免損壞用(yong)電(dian)(dian)(dian)(dian)設(she)(she)備或開關電(dian)(dian)(dian)(dian)源。

4、開關電源技(ji)術的發展動(dong)向

開(kai)關電(dian)源(yuan)的發展方向(xiang)是(shi)高頻、高可靠、低耗、低噪聲(sheng)、抗(kang)干擾和模塊化。