開關電(dian)源以效率高、電(dian)壓適應(ying)性(xing)強(qiang)而得到廣泛應(ying)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)路采用分立元件(jian)和貼片元件(jian)相結合，電(dian)路設計(ji)別(bie)致新穎，元件(jian)布局(ju)嚴謹(jin)合理。供電(dian)電(dian)壓(ya)(ya)原(yuan)為１１０Ｖ，可(ke)方(fang)便地改為９０～２５０Ｖ工作；輸(shu)出電(dian)壓(ya)(ya)５Ｖ，可(ke)改動為５～１２Ｖ輸(shu)出，特別(bie)適合無繩(sheng)電(dian)話或手機的(de)３．６Ｖ（或４～９Ｖ）電(dian)池作快速充電(dian)之(zhi)用。電(dian)路原(yuan)理見附圖。其中Ｄ１、Ｌ１以及Ｃ２等(deng)組成市電(dian)輸(shu)入整流濾(lv)波電(dian)路，Ｃ２兩端產生約３００Ｖ的(de)直(zhi)流高壓(ya)(ya)。

     ＶＴ１、ＶＴ２、Ｎ１、Ｎ２等組成自激式振蕩電(dian)路(lu)，Ｒ３、Ｒ４提供啟動(dong)偏置電(dian)流(liu)，使ＶＴ１加(jia)電(dian)時即導通(tong)(tong)，主回路(lu)Ｎ１中有(you)電(dian)流(liu)流(liu)過，Ｎ２上產生感應電(dian)壓(ya)。當此電(dian)壓(ya)峰值(zhi)超過３Ｖ時，Ｄ５擊(ji)穿，通(tong)(tong)過Ｒ８向ＶＴ２提供偏流(liu)，使ＶＴ２飽和導通(tong)(tong)，ＶＴ１因偏置電(dian)壓(ya)被(bei)短路(lu)而關(guan)斷(duan)。

     當Ｎ１中電(dian)(dian)(dian)流關斷時(shi)，Ｎ２感應電(dian)(dian)(dian)壓極(ji)性反相(xiang)，經Ｄ５、Ｒ８加反向偏(pian)壓于(yu)ＶＴ２基極(ji)，ＶＴ２轉變為截(jie)止狀態(tai)，ＶＴ１經Ｒ３、Ｒ４偏(pian)置重(zhong)新導(dao)通。如(ru)此循環往復，形成間歇自激振(zhen)蕩。Ｃ５、Ｒ６用以改善振(zhen)蕩波形，光電(dian)(dian)(dian)耦(ou)合器ＯＰＴ１用以調控振(zhen)蕩器脈(mo)沖(chong)寬(kuan)度。Ｎ３、Ｌ２、Ｃ７等組成整(zheng)流輸出電(dian)(dian)(dian)路，二極(ji)管３Ｓ９０作半波整(zheng)流，ＲＫ１４作充電(dian)(dian)(dian)隔離(li)，Ｒ１８為輸出電(dian)(dian)(dian)流采樣(yang)電(dian)(dian)(dian)阻。

    當輸出(chu)電(dian)(dian)(dian)(dian)流超(chao)載（大于０．８Ａ）或短路時，Ｒ１８上(shang)產生較大壓降(jiang)，使ＯＰ１輸出(chu)電(dian)(dian)(dian)(dian)位急(ji)劇(ju)降(jiang)低，光電(dian)(dian)(dian)(dian)耦合器控制振蕩脈(mo)沖(chong)變(bian)窄(zhai)，由Ｎ１耦合到Ｎ３的平均(jun)能(neng)量也大幅度(du)減少。即使輸出(chu)短路，輸出(chu)電(dian)(dian)(dian)(dian)流也僅有十(shi)幾(ji)毫安，從(cong)而避免了輸出(chu)端超(chao)載甚至短路對開關電(dian)(dian)(dian)(dian)源自身造成的威脅(xie)。

     穩(wen)壓(ya)(ya)部(bu)分由(you)ＴＬ４３１等周邊電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)組成，電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)采樣點取自被(bei)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)池兩(liang)端(duan)，按圖中Ｒ１３＋Ｒ１４參數(shu)值(zhi)，空載輸(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)為(wei)５．２５Ｖ，對于３．６Ｖ可(ke)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)池的(de)最大(da)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流為(wei)０．９５Ａ，適合對２Ａｈ以上的(de)鎳(nie)鎘(ge)或(huo)鋰電(dian)(dian)(dian)(dian)(dian)(dian)池直接充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)。若用它對０．７～１Ａｈ的(de)鎳(nie)鎘(ge)或(huo)鋰電(dian)(dian)(dian)(dian)(dian)(dian)池充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)時，充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)回路(lu)內可(ke)串(chuan)接一只１．５～２．５Ω、功率(lv)０．５Ｗ的(de)限流電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)，使充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流被(bei)限制在(zai)(zai)０．３～０．４Ａ。經試(shi)驗(yan)，該電(dian)(dian)(dian)(dian)(dian)(dian)源的(de)輸(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)只需(xu)經小改動(dong)，即可(ke)使輸(shu)出(chu)為(wei)５～１２Ｖ之間(jian)的(de)某一電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)值(zhi)。方法是(shi)：更換(huan)(huan)帶 號的(de)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)，在(zai)(zai)２４ｋΩ～６２ｋΩ之間(jian)取值(zhi)。需(xu)要指(zhi)出(chu)的(de)是(shi)，輸(shu)出(chu)端(duan)濾波電(dian)(dian)(dian)(dian)(dian)(dian)解(jie)電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)器標稱耐(nai)壓(ya)(ya)為(wei)１０Ｖ，需(xu)要改為(wei)１２Ｖ輸(shu)出(chu)時，請(qing)更換(huan)(huan)成耐(nai)壓(ya)(ya)為(wei)１６Ｖ的(de)電(dian)(dian)(dian)(dian)(dian)(dian)解(jie)電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)。在(zai)(zai)１２Ｖ時，其最大(da)輸(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)(dian)流應控制在(zai)(zai)０．７Ａ以內。輸(shu)出(chu)端(duan)帶有２米長黑(hei)白線，黑(hei)線為(wei)正(zheng)極，白線為(wei)負極。