開關電源(yuan)以效率高、電壓適應性強而得到廣泛應用(yong)。

     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)路采用分立元件(jian)和(he)貼(tie)片元件(jian)相結合，電(dian)(dian)路設(she)計別致新(xin)穎，元件(jian)布局嚴謹合理。供電(dian)(dian)電(dian)(dian)壓(ya)原為１１０Ｖ，可(ke)(ke)方(fang)便地改為９０～２５０Ｖ工(gong)作；輸出電(dian)(dian)壓(ya)５Ｖ，可(ke)(ke)改動為５～１２Ｖ輸出，特別適合無(wu)繩電(dian)(dian)話或手機(ji)的３．６Ｖ（或４～９Ｖ）電(dian)(dian)池作快速(su)充電(dian)(dian)之用。電(dian)(dian)路原理見附(fu)圖。其中Ｄ１、Ｌ１以及Ｃ２等組成市(shi)電(dian)(dian)輸入整流濾(lv)波電(dian)(dian)路，Ｃ２兩端產生約３００Ｖ的直流高壓(ya)。

     ＶＴ１、ＶＴ２、Ｎ１、Ｎ２等組成(cheng)自激式振蕩電(dian)(dian)(dian)路，Ｒ３、Ｒ４提供啟動(dong)偏(pian)置電(dian)(dian)(dian)流(liu)(liu)(liu)，使(shi)ＶＴ１加電(dian)(dian)(dian)時即導通，主回路Ｎ１中(zhong)有電(dian)(dian)(dian)流(liu)(liu)(liu)流(liu)(liu)(liu)過，Ｎ２上產生感應(ying)電(dian)(dian)(dian)壓。當此電(dian)(dian)(dian)壓峰值(zhi)超過３Ｖ時，Ｄ５擊穿，通過Ｒ８向ＶＴ２提供偏(pian)流(liu)(liu)(liu)，使(shi)ＶＴ２飽和導通，ＶＴ１因偏(pian)置電(dian)(dian)(dian)壓被短(duan)路而(er)關斷。

     當Ｎ１中電(dian)(dian)(dian)流(liu)關斷時，Ｎ２感應電(dian)(dian)(dian)壓極(ji)性反(fan)相，經(jing)Ｄ５、Ｒ８加反(fan)向偏壓于ＶＴ２基極(ji)，ＶＴ２轉(zhuan)變(bian)為截(jie)止狀態，ＶＴ１經(jing)Ｒ３、Ｒ４偏置重(zhong)新導(dao)通。如此循(xun)環往(wang)復，形(xing)成間歇(xie)自(zi)激振蕩。Ｃ５、Ｒ６用以改善振蕩波形(xing)，光電(dian)(dian)(dian)耦合器(qi)ＯＰＴ１用以調控振蕩器(qi)脈沖寬度。Ｎ３、Ｌ２、Ｃ７等組(zu)成整流(liu)輸出(chu)電(dian)(dian)(dian)路(lu)，二極(ji)管３Ｓ９０作(zuo)半波整流(liu)，ＲＫ１４作(zuo)充電(dian)(dian)(dian)隔離，Ｒ１８為輸出(chu)電(dian)(dian)(dian)流(liu)采樣電(dian)(dian)(dian)阻(zu)。

    當輸出(chu)(chu)電(dian)流超載（大于０．８Ａ）或短(duan)路時(shi)，Ｒ１８上產生較大壓(ya)降，使(shi)ＯＰ１輸出(chu)(chu)電(dian)位急劇降低(di)，光電(dian)耦合(he)器控制振蕩脈沖變窄，由(you)Ｎ１耦合(he)到(dao)Ｎ３的平均能(neng)量也大幅度減少。即使(shi)輸出(chu)(chu)短(duan)路，輸出(chu)(chu)電(dian)流也僅有十幾毫安(an)，從而避免了輸出(chu)(chu)端超載甚至短(duan)路對開關電(dian)源自身造成(cheng)的威脅。

     穩壓部分(fen)由ＴＬ４３１等周邊電(dian)(dian)(dian)(dian)(dian)路組成，電(dian)(dian)(dian)(dian)(dian)壓采樣點(dian)取自被充電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)池(chi)兩端(duan)，按(an)圖中Ｒ１３＋Ｒ１４參(can)數值，空(kong)載(zai)輸(shu)(shu)出(chu)(chu)電(dian)(dian)(dian)(dian)(dian)壓為(wei)５．２５Ｖ，對于３．６Ｖ可充電(dian)(dian)(dian)(dian)(dian)池(chi)的(de)(de)(de)(de)(de)最大充電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)為(wei)０．９５Ａ，適合對２Ａｈ以上的(de)(de)(de)(de)(de)鎳鎘或鋰電(dian)(dian)(dian)(dian)(dian)池(chi)直接充電(dian)(dian)(dian)(dian)(dian)。若用它對０．７～１Ａｈ的(de)(de)(de)(de)(de)鎳鎘或鋰電(dian)(dian)(dian)(dian)(dian)池(chi)充電(dian)(dian)(dian)(dian)(dian)時，充電(dian)(dian)(dian)(dian)(dian)回路內(nei)可串接一(yi)(yi)只１．５～２．５Ω、功率０．５Ｗ的(de)(de)(de)(de)(de)限(xian)流(liu)(liu)(liu)電(dian)(dian)(dian)(dian)(dian)阻(zu)，使(shi)充電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)被限(xian)制(zhi)在０．３～０．４Ａ。經試(shi)驗，該電(dian)(dian)(dian)(dian)(dian)源(yuan)的(de)(de)(de)(de)(de)輸(shu)(shu)出(chu)(chu)電(dian)(dian)(dian)(dian)(dian)壓只需經小改動，即可使(shi)輸(shu)(shu)出(chu)(chu)為(wei)５～１２Ｖ之間的(de)(de)(de)(de)(de)某一(yi)(yi)電(dian)(dian)(dian)(dian)(dian)壓值。方(fang)法是(shi)：更(geng)換帶 號的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)阻(zu)，在２４ｋΩ～６２ｋΩ之間取值。需要(yao)指出(chu)(chu)的(de)(de)(de)(de)(de)是(shi)，輸(shu)(shu)出(chu)(chu)端(duan)濾波電(dian)(dian)(dian)(dian)(dian)解(jie)電(dian)(dian)(dian)(dian)(dian)容器(qi)標稱耐壓為(wei)１０Ｖ，需要(yao)改為(wei)１２Ｖ輸(shu)(shu)出(chu)(chu)時，請(qing)更(geng)換成耐壓為(wei)１６Ｖ的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)解(jie)電(dian)(dian)(dian)(dian)(dian)容。在１２Ｖ時，其最大輸(shu)(shu)出(chu)(chu)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)應控制(zhi)在０．７Ａ以內(nei)。輸(shu)(shu)出(chu)(chu)端(duan)帶有２米長黑白線(xian)，黑線(xian)為(wei)正極，白線(xian)為(wei)負極。