開關電源以效率高、電壓(ya)適應性強(qiang)而得到廣泛(fan)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)路采用分立元件(jian)和貼(tie)片元件(jian)相結合(he)(he)(he)，電(dian)(dian)(dian)路設(she)計別致新穎，元件(jian)布局嚴謹合(he)(he)(he)理(li)。供電(dian)(dian)(dian)電(dian)(dian)(dian)壓(ya)原為(wei)１１０Ｖ，可(ke)方便地改為(wei)９０～２５０Ｖ工作(zuo)；輸出電(dian)(dian)(dian)壓(ya)５Ｖ，可(ke)改動為(wei)５～１２Ｖ輸出，特別適合(he)(he)(he)無繩(sheng)電(dian)(dian)(dian)話或手機的３．６Ｖ（或４～９Ｖ）電(dian)(dian)(dian)池作(zuo)快速充電(dian)(dian)(dian)之用。電(dian)(dian)(dian)路原理(li)見附圖。其(qi)中Ｄ１、Ｌ１以及(ji)Ｃ２等組成市電(dian)(dian)(dian)輸入整流濾波電(dian)(dian)(dian)路，Ｃ２兩端產生約３００Ｖ的直流高壓(ya)。

     ＶＴ１、ＶＴ２、Ｎ１、Ｎ２等組成自激式(shi)振蕩電(dian)(dian)路(lu)，Ｒ３、Ｒ４提(ti)供啟動偏置(zhi)電(dian)(dian)流(liu)(liu)，使(shi)(shi)ＶＴ１加(jia)電(dian)(dian)時即導(dao)通，主回(hui)路(lu)Ｎ１中(zhong)有(you)電(dian)(dian)流(liu)(liu)流(liu)(liu)過(guo)，Ｎ２上(shang)產生感(gan)應電(dian)(dian)壓。當此電(dian)(dian)壓峰值超(chao)過(guo)３Ｖ時，Ｄ５擊穿，通過(guo)Ｒ８向ＶＴ２提(ti)供偏流(liu)(liu)，使(shi)(shi)ＶＴ２飽(bao)和導(dao)通，ＶＴ１因偏置(zhi)電(dian)(dian)壓被短路(lu)而(er)關斷(duan)。

     當Ｎ１中(zhong)電(dian)流(liu)關(guan)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轉變為截止狀(zhuang)態，ＶＴ１經Ｒ３、Ｒ４偏置重(zhong)新導通(tong)。如此(ci)循環(huan)往復，形成間歇自激振(zhen)蕩(dang)。Ｃ５、Ｒ６用以改(gai)善(shan)振(zhen)蕩(dang)波形，光(guang)電(dian)耦合器ＯＰＴ１用以調(diao)控振(zhen)蕩(dang)器脈(mo)沖寬(kuan)度(du)。Ｎ３、Ｌ２、Ｃ７等組成整流(liu)輸出電(dian)路，二極(ji)管(guan)３Ｓ９０作半(ban)波整流(liu)，ＲＫ１４作充(chong)電(dian)隔離，Ｒ１８為輸出電(dian)流(liu)采樣電(dian)阻。

    當輸出(chu)電(dian)流超載(zai)(zai)（大(da)于(yu)０．８Ａ）或短路(lu)時，Ｒ１８上產生較大(da)壓降，使ＯＰ１輸出(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Ｎ１耦合(he)到(dao)Ｎ３的平均能量(liang)也(ye)大(da)幅度減少(shao)。即使輸出(chu)短路(lu)，輸出(chu)電(dian)流也(ye)僅有(you)十幾毫安，從而避免了輸出(chu)端超載(zai)(zai)甚至短路(lu)對(dui)開關電(dian)源自身造(zao)成的威脅。

     穩壓(ya)部分由(you)ＴＬ４３１等周邊電(dian)(dian)(dian)(dian)路組成(cheng)，電(dian)(dian)(dian)(dian)壓(ya)采樣點(dian)取(qu)自被充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)池(chi)兩端(duan)，按圖中(zhong)Ｒ１３＋Ｒ１４參數值，空(kong)載輸(shu)出(chu)電(dian)(dian)(dian)(dian)壓(ya)為(wei)(wei)(wei)(wei)(wei)５．２５Ｖ，對于３．６Ｖ可充電(dian)(dian)(dian)(dian)池(chi)的(de)(de)最(zui)大(da)充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)為(wei)(wei)(wei)(wei)(wei)０．９５Ａ，適合對２Ａｈ以上的(de)(de)鎳(nie)(nie)鎘(ge)或鋰(li)(li)電(dian)(dian)(dian)(dian)池(chi)直(zhi)接(jie)充電(dian)(dian)(dian)(dian)。若(ruo)用它對０．７～１Ａｈ的(de)(de)鎳(nie)(nie)鎘(ge)或鋰(li)(li)電(dian)(dian)(dian)(dian)池(chi)充電(dian)(dian)(dian)(dian)時(shi)，充電(dian)(dian)(dian)(dian)回路內(nei)可串接(jie)一(yi)只１．５～２．５Ω、功(gong)率(lv)０．５Ｗ的(de)(de)限(xian)流(liu)電(dian)(dian)(dian)(dian)阻(zu)，使充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)被限(xian)制在(zai)０．３～０．４Ａ。經試(shi)驗，該電(dian)(dian)(dian)(dian)源(yuan)的(de)(de)輸(shu)出(chu)電(dian)(dian)(dian)(dian)壓(ya)只需(xu)經小改(gai)(gai)動(dong)，即(ji)可使輸(shu)出(chu)為(wei)(wei)(wei)(wei)(wei)５～１２Ｖ之間(jian)的(de)(de)某一(yi)電(dian)(dian)(dian)(dian)壓(ya)值。方法是：更(geng)換帶(dai) 號的(de)(de)電(dian)(dian)(dian)(dian)阻(zu)，在(zai)２４ｋΩ～６２ｋΩ之間(jian)取(qu)值。需(xu)要(yao)指出(chu)的(de)(de)是，輸(shu)出(chu)端(duan)濾(lv)波電(dian)(dian)(dian)(dian)解電(dian)(dian)(dian)(dian)容器標稱耐(nai)壓(ya)為(wei)(wei)(wei)(wei)(wei)１０Ｖ，需(xu)要(yao)改(gai)(gai)為(wei)(wei)(wei)(wei)(wei)１２Ｖ輸(shu)出(chu)時(shi)，請更(geng)換成(cheng)耐(nai)壓(ya)為(wei)(wei)(wei)(wei)(wei)１６Ｖ的(de)(de)電(dian)(dian)(dian)(dian)解電(dian)(dian)(dian)(dian)容。在(zai)１２Ｖ時(shi)，其最(zui)大(da)輸(shu)出(chu)電(dian)(dian)(dian)(dian)流(liu)應控(kong)制在(zai)０．７Ａ以內(nei)。輸(shu)出(chu)端(duan)帶(dai)有２米長黑白(bai)線(xian)，黑線(xian)為(wei)(wei)(wei)(wei)(wei)正極，白(bai)線(xian)為(wei)(wei)(wei)(wei)(wei)負極。