開(kai)關(guan)電源以效(xiao)率高、電壓適應性(xing)強而得到廣泛應用。

     本文介紹一種插頭可伸縮的袖珍式開關電源充電器，其尺寸為６９ｍｍ×４７ｍｍ×２６ｍｍ。該充電器電(dian)(dian)(dian)路采用分立(li)元件(jian)(jian)和(he)貼片元件(jian)(jian)相結(jie)合，電(dian)(dian)(dian)路設計別(bie)致(zhi)新穎，元件(jian)(jian)布(bu)局(ju)嚴謹合理(li)。供電(dian)(dian)(dian)電(dian)(dian)(dian)壓原(yuan)為１１０Ｖ，可(ke)方便地改(gai)為９０～２５０Ｖ工作；輸(shu)出(chu)電(dian)(dian)(dian)壓５Ｖ，可(ke)改(gai)動為５～１２Ｖ輸(shu)出(chu)，特別(bie)適(shi)合無(wu)繩電(dian)(dian)(dian)話或手機的３．６Ｖ（或４～９Ｖ）電(dian)(dian)(dian)池作快速充(chong)電(dian)(dian)(dian)之(zhi)用。電(dian)(dian)(dian)路原(yuan)理(li)見附圖(tu)。其(qi)中Ｄ１、Ｌ１以及Ｃ２等(deng)組(zu)成市電(dian)(dian)(dian)輸(shu)入整(zheng)流(liu)濾波電(dian)(dian)(dian)路，Ｃ２兩(liang)端產生約(yue)３００Ｖ的直流(liu)高(gao)壓。

     ＶＴ１、ＶＴ２、Ｎ１、Ｎ２等組成自(zi)激式振蕩電路，Ｒ３、Ｒ４提供啟動偏(pian)置電流(liu)(liu)，使ＶＴ１加電時(shi)即導通(tong)，主回路Ｎ１中(zhong)有電流(liu)(liu)流(liu)(liu)過(guo)，Ｎ２上產生感應電壓。當此電壓峰值超過(guo)３Ｖ時(shi)，Ｄ５擊(ji)穿，通(tong)過(guo)Ｒ８向(xiang)ＶＴ２提供偏(pian)流(liu)(liu)，使ＶＴ２飽和導通(tong)，ＶＴ１因(yin)偏(pian)置電壓被短路而關斷。

     當Ｎ１中電(dian)(dian)流關斷時，Ｎ２感(gan)應電(dian)(dian)壓極(ji)性反(fan)相，經Ｄ５、Ｒ８加(jia)反(fan)向偏(pian)壓于ＶＴ２基極(ji)，ＶＴ２轉變為(wei)(wei)截止狀態，ＶＴ１經Ｒ３、Ｒ４偏(pian)置重新導通。如此循環往復，形成間歇(xie)自激(ji)振(zhen)蕩(dang)(dang)。Ｃ５、Ｒ６用以改善振(zhen)蕩(dang)(dang)波形，光(guang)電(dian)(dian)耦合器(qi)ＯＰＴ１用以調控振(zhen)蕩(dang)(dang)器(qi)脈(mo)沖(chong)寬度。Ｎ３、Ｌ２、Ｃ７等組(zu)成整流輸(shu)出電(dian)(dian)路(lu)，二極(ji)管３Ｓ９０作半波整流，ＲＫ１４作充(chong)電(dian)(dian)隔(ge)離，Ｒ１８為(wei)(wei)輸(shu)出電(dian)(dian)流采樣電(dian)(dian)阻(zu)。

    當輸出(chu)電(dian)流超載（大(da)(da)于(yu)０．８Ａ）或短路(lu)時，Ｒ１８上(shang)產生較大(da)(da)壓降，使ＯＰ１輸出(chu)電(dian)位(wei)急劇降低(di)，光電(dian)耦合器(qi)控(kong)制振蕩脈(mo)沖變窄，由(you)Ｎ１耦合到Ｎ３的平均能量(liang)也(ye)大(da)(da)幅度減少(shao)。即使輸出(chu)短路(lu)，輸出(chu)電(dian)流也(ye)僅(jin)有(you)十幾毫(hao)安，從而避免(mian)了輸出(chu)端超載甚(shen)至短路(lu)對開關電(dian)源自(zi)身造(zao)成的威脅。

     穩壓(ya)(ya)部分由ＴＬ４３１等周邊電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)組成，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)采樣點(dian)取(qu)自被(bei)充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池兩端，按圖中Ｒ１３＋Ｒ１４參數值，空載輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)為(wei)５．２５Ｖ，對(dui)于３．６Ｖ可充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池的(de)(de)最大(da)充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流為(wei)０．９５Ａ，適合對(dui)２Ａｈ以(yi)上的(de)(de)鎳鎘(ge)或鋰電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池直接充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)。若用它對(dui)０．７～１Ａｈ的(de)(de)鎳鎘(ge)或鋰電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)時，充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)回路(lu)內可串接一(yi)只(zhi)１．５～２．５Ω、功率０．５Ｗ的(de)(de)限(xian)流電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)，使(shi)充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流被(bei)限(xian)制(zhi)在(zai)０．３～０．４Ａ。經(jing)試驗，該(gai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源的(de)(de)輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)只(zhi)需經(jing)小改動，即可使(shi)輸(shu)(shu)出(chu)為(wei)５～１２Ｖ之(zhi)間的(de)(de)某一(yi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)值。方(fang)法(fa)是：更換帶 號(hao)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)，在(zai)２４ｋΩ～６２ｋΩ之(zhi)間取(qu)值。需要(yao)指出(chu)的(de)(de)是，輸(shu)(shu)出(chu)端濾波電(dian)(dian)(dian)(dian)(dian)(dian)(dian)解電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容器標稱(cheng)耐(nai)壓(ya)(ya)為(wei)１０Ｖ，需要(yao)改為(wei)１２Ｖ輸(shu)(shu)出(chu)時，請更換成耐(nai)壓(ya)(ya)為(wei)１６Ｖ的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)解電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容。在(zai)１２Ｖ時，其最大(da)輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流應控制(zhi)在(zai)０．７Ａ以(yi)內。輸(shu)(shu)出(chu)端帶有２米長黑白線，黑線為(wei)正極，白線為(wei)負極。