開(kai)關(guan)(guan)電(dian)(dian)源(yuan)(yuan)具(ju)有效率高、重量輕、體(ti)積小，穩(wen)壓(ya)范(fan)圍寬等突出(chu)優(you)點，從20世(shi)紀中(zhong)期問(wen)世(shi)以來，發展極其迅猛，在(zai)計算(suan)機、通信、航(hang)天(tian)、辦公和家用(yong)電(dian)(dian)器等方(fang)面得到了廣泛的(de)(de)(de)應用(yong)，大有取代線性穩(wen)壓(ya)電(dian)(dian)源(yuan)(yuan)之(zhi)勢(shi)。提高電(dian)(dian)路的(de)(de)(de)集成(cheng)化是(shi)(shi)開(kai)關(guan)(guan)電(dian)(dian)源(yuan)(yuan)的(de)(de)(de)追求之(zhi)一，對中(zhong)小功率開(kai)關(guan)(guan)電(dian)(dian)源(yuan)(yuan)來說是(shi)(shi)實現(xian)單(dan)片集成(cheng)化。開(kai)關(guan)(guan)集成(cheng)穩(wen)壓(ya)器是(shi)(shi)指(zhi)將(jiang)控制電(dian)(dian)路、功率開(kai)關(guan)(guan)管(guan)和保(bao)護電(dian)(dian)路等集成(cheng)在(zai)一個芯(xin)片內(nei)，而由開(kai)關(guan)(guan)集成(cheng)穩(wen)壓(ya)器構(gou)成(cheng)的(de)(de)(de)開(kai)關(guan)(guan)電(dian)(dian)源(yuan)(yuan)就稱之(zhi)為單(dan)片開(kai)關(guan)(guan)電(dian)(dian)源(yuan)(yuan)。美國PI公司的(de)(de)(de)單(dan)片開(kai)關(guan)(guan)電(dian)(dian)源(yuan)(yuan)系列是(shi)(shi)其顯著的(de)(de)(de)代表(biao)。  
    TOPSwitch—GX設(she)計的(de)(de)250W開(kai)(kai)關(guan)電(dian)(dian)(dian)源電(dian)(dian)(dian)路(lu)如圖(tu)1所示。直(zhi)流(liu)(liu)(liu)電(dian)(dian)(dian)壓(ya)經(jing)變壓(ya)器(qi)的(de)(de)原邊(bian)加到(dao)TOPSwitch—GX的(de)(de)漏(lou)極(ji)D；頻(pin)(pin)(pin)率(lv)選(xuan)擇端(duan)(duan)F和(he)極(ji)限電(dian)(dian)(dian)流(liu)(liu)(liu)設(she)定(ding)端(duan)(duan)X與(yu)源極(ji)S相(xiang)連，則該兩端(duan)(duan)的(de)(de)功(gong)能(neng)都(dou)沒用，即(ji)不(bu)從外部(bu)(bu)設(she)定(ding)極(ji)限電(dian)(dian)(dian)流(liu)(liu)(liu)，內部(bu)(bu)自動(dong)設(she)定(ding)自保(bao)護電(dian)(dian)(dian)流(liu)(liu)(liu)ILIMIT，開(kai)(kai)關(guan)工作頻(pin)(pin)(pin)率(lv)為132K；控制(zhi)極(ji)和(he)光耦LTV817相(xiang)連，接(jie)受反(fan)饋(kui)信號以(yi)(yi)(yi)實(shi)現對內部(bu)(bu)集成(cheng)的(de)(de)高壓(ya)功(gong)率(lv)MOS管占空比的(de)(de)控制(zhi)；線(xian)路(lu)檢測端(duan)(duan)L通(tong)過(guo)(guo)一2MΩ的(de)(de)電(dian)(dian)(dian)阻(zu)和(he)直(zhi)流(liu)(liu)(liu)高壓(ya)輸(shu)入(ru)(ru)的(de)(de)正端(duan)(duan)相(xiang)連以(yi)(yi)(yi)實(shi)現過(guo)(guo)壓(ya)、欠壓(ya)線(xian)電(dian)(dian)(dian)壓(ya)前饋(kui)的(de)(de)線(xian)電(dian)(dian)(dian)壓(ya)檢測。電(dian)(dian)(dian)容C1為高頻(pin)(pin)(pin)濾波電(dian)(dian)(dian)容；瞬態電(dian)(dian)(dian)壓(ya)抑(yi)制(zhi)器(qi)P6KE200和(he)超快恢復二極(ji)管BYV26C構(gou)成(cheng)鉗位(wei)電(dian)(dian)(dian)路(lu)，并在其中串(chuan)入(ru)(ru)RC吸(xi)收(shou)電(dian)(dian)(dian)路(lu)(由R2，R3和(he)C6組(zu)成(cheng))，這樣除了(le)可以(yi)(yi)(yi)吸(xi)收(shou)部(bu)(bu)分漏(lou)感中的(de)(de)能(neng)量(liang)以(yi)(yi)(yi)外，還可將(jiang)電(dian)(dian)(dian)壓(ya)鉗位(wei)在200V，可使開(kai)(kai)關(guan)電(dian)(dian)(dian)源在啟(qi)動(dong)或過(guo)(guo)載的(de)(de)情(qing)況下(xia)TOPSwitch—GX內部(bu)(bu)集成(cheng)MOS管的(de)(de)漏(lou)極(ji)電(dian)(dian)(dian)壓(ya)不(bu)超過(guo)(guo)700V；高頻(pin)(pin)(pin)變壓(ya)器(qi)T1的(de)(de)副邊(bian)輸(shu)出經(jing)過(guo)(guo)MURl640CT整流(liu)(liu)(liu)和(he)C9，C10和(he)C11濾波，再經(jing)過(guo)(guo)磁(ci)珠L1和(he)C12濾掉(diao)開(kai)(kai)關(guan)噪聲后，得(de)到(dao)輸(shu)出電(dian)(dian)(dian)壓(ya)；VD4和(he)C14構(gou)成(cheng)軟(ruan)啟(qi)動(dong)電(dian)(dian)(dian)路(lu)。  
    單片開(kai)關(guan)電(dian)(dian)源具有單片集成化、最簡外圍(wei)電(dian)(dian)路、最佳性能指標(biao)、能以無工頻變(bian)壓器電(dian)(dian)器實現完全隔離等顯(xian)著優(you)點，是我們(men)設計290W以下開(kai)關(guan)電(dian)(dian)源的理想選擇。