開關電源以效率高(gao)、電壓適應性強而得到(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(yong)(yong)分立元件(jian)和貼片(pian)元件(jian)相結合，電(dian)(dian)(dian)(dian)路(lu)(lu)設計(ji)別(bie)(bie)致新穎(ying)，元件(jian)布局(ju)嚴謹合理。供電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)壓原(yuan)為１１０Ｖ，可方便地(di)改為９０～２５０Ｖ工作；輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)壓５Ｖ，可改動為５～１２Ｖ輸(shu)(shu)出(chu)，特別(bie)(bie)適合無繩電(dian)(dian)(dian)(dian)話或(huo)手(shou)機的(de)３．６Ｖ（或(huo)４～９Ｖ）電(dian)(dian)(dian)(dian)池作快速充(chong)電(dian)(dian)(dian)(dian)之用(yong)(yong)。電(dian)(dian)(dian)(dian)路(lu)(lu)原(yuan)理見附圖。其中Ｄ１、Ｌ１以及Ｃ２等組(zu)成市(shi)電(dian)(dian)(dian)(dian)輸(shu)(shu)入整流濾(lv)波電(dian)(dian)(dian)(dian)路(lu)(lu)，Ｃ２兩(liang)端(duan)產生約(yue)３００Ｖ的(de)直流高壓。

     ＶＴ１、ＶＴ２、Ｎ１、Ｎ２等組成自激式振蕩電(dian)(dian)(dian)路(lu)，Ｒ３、Ｒ４提供啟動偏(pian)置電(dian)(dian)(dian)流(liu)，使ＶＴ１加電(dian)(dian)(dian)時(shi)即導(dao)通，主回路(lu)Ｎ１中(zhong)有(you)電(dian)(dian)(dian)流(liu)流(liu)過，Ｎ２上產生感應電(dian)(dian)(dian)壓。當此電(dian)(dian)(dian)壓峰值(zhi)超過３Ｖ時(shi)，Ｄ５擊穿，通過Ｒ８向ＶＴ２提供偏(pian)流(liu)，使ＶＴ２飽和導(dao)通，ＶＴ１因(yin)偏(pian)置電(dian)(dian)(dian)壓被(bei)短路(lu)而關斷(duan)。

     當Ｎ１中電(dian)(dian)流關斷時，Ｎ２感應電(dian)(dian)壓極(ji)性反(fan)相，經Ｄ５、Ｒ８加反(fan)向(xiang)偏壓于ＶＴ２基極(ji)，ＶＴ２轉變為(wei)截止狀態，ＶＴ１經Ｒ３、Ｒ４偏置重新導通。如此(ci)循(xun)環往復(fu)，形(xing)成(cheng)間歇自激振(zhen)蕩(dang)。Ｃ５、Ｒ６用(yong)以(yi)改善振(zhen)蕩(dang)波形(xing)，光(guang)電(dian)(dian)耦合(he)器ＯＰＴ１用(yong)以(yi)調控振(zhen)蕩(dang)器脈沖寬度。Ｎ３、Ｌ２、Ｃ７等組成(cheng)整(zheng)流輸(shu)出電(dian)(dian)路，二極(ji)管３Ｓ９０作半波整(zheng)流，ＲＫ１４作充(chong)電(dian)(dian)隔離，Ｒ１８為(wei)輸(shu)出電(dian)(dian)流采樣(yang)電(dian)(dian)阻。

    當輸出電流超載（大于(yu)０．８Ａ）或短(duan)(duan)路時，Ｒ１８上(shang)產生較大壓降，使ＯＰ１輸出電位(wei)急劇降低，光電耦合器(qi)控制振蕩脈沖變窄(zhai)，由(you)Ｎ１耦合到Ｎ３的平均能量也(ye)(ye)大幅度減(jian)少。即使輸出短(duan)(duan)路，輸出電流也(ye)(ye)僅有(you)十幾(ji)毫安，從而避(bi)免(mian)了輸出端超載甚至短(duan)(duan)路對開關電源自身造成的威脅。

     穩壓(ya)部分由ＴＬ４３１等(deng)周邊電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)組成，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)采(cai)樣點取(qu)自(zi)被(bei)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池兩端，按(an)圖(tu)中Ｒ１３＋Ｒ１４參數(shu)值，空(kong)載輸(shu)出電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)為(wei)(wei)(wei)５．２５Ｖ，對于３．６Ｖ可充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池的最大充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)為(wei)(wei)(wei)０．９５Ａ，適合對２Ａｈ以上(shang)的鎳鎘或鋰(li)(li)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池直(zhi)接充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)。若(ruo)用它對０．７～１Ａｈ的鎳鎘或鋰(li)(li)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)時，充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)回路(lu)內(nei)可串接一只１．５～２．５Ω、功率０．５Ｗ的限流(liu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻，使(shi)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)被(bei)限制在０．３～０．４Ａ。經試驗，該(gai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)的輸(shu)出電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)只需(xu)經小改動，即可使(shi)輸(shu)出為(wei)(wei)(wei)５～１２Ｖ之間(jian)的某一電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)值。方法是(shi)：更換帶 號的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻，在２４ｋΩ～６２ｋΩ之間(jian)取(qu)值。需(xu)要(yao)指出的是(shi)，輸(shu)出端濾波電(dian)(dian)(dian)(dian)(dian)(dian)(dian)解電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容器標稱耐壓(ya)為(wei)(wei)(wei)１０Ｖ，需(xu)要(yao)改為(wei)(wei)(wei)１２Ｖ輸(shu)出時，請(qing)更換成耐壓(ya)為(wei)(wei)(wei)１６Ｖ的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)解電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容。在１２Ｖ時，其最大輸(shu)出電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)應控制在０．７Ａ以內(nei)。輸(shu)出端帶有２米長黑白線，黑線為(wei)(wei)(wei)正極(ji)，白線為(wei)(wei)(wei)負極(ji)。