開關電(dian)源以效率高、電(dian)壓適應性強而得到(dao)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)(dian)路(lu)(lu)采用分立元件(jian)和貼片元件(jian)相結(jie)合，電(dian)(dian)(dian)(dian)路(lu)(lu)設計(ji)別致(zhi)新穎，元件(jian)布局嚴(yan)謹合理。供電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)壓(ya)原為(wei)１１０Ｖ，可方便(bian)地改為(wei)９０～２５０Ｖ工作；輸出電(dian)(dian)(dian)(dian)壓(ya)５Ｖ，可改動為(wei)５～１２Ｖ輸出，特別適(shi)合無繩(sheng)電(dian)(dian)(dian)(dian)話或(huo)手機的３．６Ｖ（或(huo)４～９Ｖ）電(dian)(dian)(dian)(dian)池作快速(su)充電(dian)(dian)(dian)(dian)之用。電(dian)(dian)(dian)(dian)路(lu)(lu)原理見附圖。其中(zhong)Ｄ１、Ｌ１以及Ｃ２等(deng)組成市電(dian)(dian)(dian)(dian)輸入(ru)整流濾波(bo)電(dian)(dian)(dian)(dian)路(lu)(lu)，Ｃ２兩端產生約３００Ｖ的直流高(gao)壓(ya)。

     ＶＴ１、ＶＴ２、Ｎ１、Ｎ２等組(zu)成自(zi)激式振蕩電(dian)(dian)(dian)路(lu)，Ｒ３、Ｒ４提供啟動偏置電(dian)(dian)(dian)流(liu)，使ＶＴ１加電(dian)(dian)(dian)時(shi)即導通，主回路(lu)Ｎ１中有電(dian)(dian)(dian)流(liu)流(liu)過，Ｎ２上產生感應電(dian)(dian)(dian)壓(ya)。當此電(dian)(dian)(dian)壓(ya)峰值超過３Ｖ時(shi)，Ｄ５擊穿，通過Ｒ８向(xiang)ＶＴ２提供偏流(liu)，使ＶＴ２飽和導通，ＶＴ１因偏置電(dian)(dian)(dian)壓(ya)被短路(lu)而(er)關斷。

     當Ｎ１中電(dian)流(liu)關斷時，Ｎ２感應電(dian)壓(ya)極(ji)性反(fan)(fan)相，經Ｄ５、Ｒ８加反(fan)(fan)向偏壓(ya)于ＶＴ２基極(ji)，ＶＴ２轉變(bian)為截止狀態，ＶＴ１經Ｒ３、Ｒ４偏置重新導(dao)通。如(ru)此(ci)循(xun)環(huan)往復，形成(cheng)(cheng)間(jian)歇(xie)自激振蕩(dang)(dang)。Ｃ５、Ｒ６用以(yi)改善振蕩(dang)(dang)波形，光電(dian)耦合器(qi)(qi)ＯＰＴ１用以(yi)調控振蕩(dang)(dang)器(qi)(qi)脈(mo)沖(chong)寬度(du)。Ｎ３、Ｌ２、Ｃ７等組成(cheng)(cheng)整(zheng)流(liu)輸(shu)出電(dian)路，二極(ji)管(guan)３Ｓ９０作半波整(zheng)流(liu)，ＲＫ１４作充(chong)電(dian)隔離(li)，Ｒ１８為輸(shu)出電(dian)流(liu)采樣電(dian)阻。

    當輸(shu)(shu)出(chu)電(dian)流超(chao)載（大(da)于０．８Ａ）或短(duan)路時，Ｒ１８上產生較大(da)壓(ya)降，使ＯＰ１輸(shu)(shu)出(chu)電(dian)位急(ji)劇(ju)降低，光電(dian)耦合器(qi)控(kong)制振(zhen)蕩(dang)脈沖(chong)變窄，由Ｎ１耦合到Ｎ３的(de)平均(jun)能量(liang)也(ye)大(da)幅度減少(shao)。即使輸(shu)(shu)出(chu)短(duan)路，輸(shu)(shu)出(chu)電(dian)流也(ye)僅有(you)十幾毫(hao)安(an)，從而(er)避(bi)免(mian)了(le)輸(shu)(shu)出(chu)端超(chao)載甚至短(duan)路對開關電(dian)源(yuan)自身(shen)造(zao)成的(de)威脅。

     穩(wen)壓(ya)部分(fen)由ＴＬ４３１等周(zhou)邊電(dian)(dian)(dian)(dian)(dian)路組成(cheng)，電(dian)(dian)(dian)(dian)(dian)壓(ya)采樣點取自被(bei)充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)池(chi)兩端(duan)，按圖中Ｒ１３＋Ｒ１４參數值，空載輸(shu)(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)壓(ya)為(wei)(wei)(wei)５．２５Ｖ，對(dui)于３．６Ｖ可充(chong)電(dian)(dian)(dian)(dian)(dian)池(chi)的最大(da)(da)充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)為(wei)(wei)(wei)０．９５Ａ，適合對(dui)２Ａｈ以上的鎳鎘或鋰電(dian)(dian)(dian)(dian)(dian)池(chi)直接(jie)充(chong)電(dian)(dian)(dian)(dian)(dian)。若用它對(dui)０．７～１Ａｈ的鎳鎘或鋰電(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)(dian)(dian)時，充(chong)電(dian)(dian)(dian)(dian)(dian)回(hui)路內(nei)(nei)可串接(jie)一只１．５～２．５Ω、功率０．５Ｗ的限流(liu)(liu)電(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)，使(shi)充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)被(bei)限制(zhi)在(zai)(zai)０．３～０．４Ａ。經試驗(yan)，該(gai)電(dian)(dian)(dian)(dian)(dian)源的輸(shu)(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)壓(ya)只需(xu)(xu)經小改(gai)動，即可使(shi)輸(shu)(shu)(shu)出(chu)為(wei)(wei)(wei)５～１２Ｖ之間的某一電(dian)(dian)(dian)(dian)(dian)壓(ya)值。方法是(shi)：更(geng)換帶(dai) 號的電(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)，在(zai)(zai)２４ｋΩ～６２ｋΩ之間取值。需(xu)(xu)要指出(chu)的是(shi)，輸(shu)(shu)(shu)出(chu)端(duan)濾波電(dian)(dian)(dian)(dian)(dian)解電(dian)(dian)(dian)(dian)(dian)容器標稱耐壓(ya)為(wei)(wei)(wei)１０Ｖ，需(xu)(xu)要改(gai)為(wei)(wei)(wei)１２Ｖ輸(shu)(shu)(shu)出(chu)時，請(qing)更(geng)換成(cheng)耐壓(ya)為(wei)(wei)(wei)１６Ｖ的電(dian)(dian)(dian)(dian)(dian)解電(dian)(dian)(dian)(dian)(dian)容。在(zai)(zai)１２Ｖ時，其最大(da)(da)輸(shu)(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)應控制(zhi)在(zai)(zai)０．７Ａ以內(nei)(nei)。輸(shu)(shu)(shu)出(chu)端(duan)帶(dai)有２米(mi)長黑(hei)白線(xian)，黑(hei)線(xian)為(wei)(wei)(wei)正極(ji)，白線(xian)為(wei)(wei)(wei)負(fu)極(ji)。