開關電源以效率(lv)高、電壓適(shi)應(ying)性(xing)強而得到廣泛應(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(lu)采用(yong)分立元(yuan)件(jian)和貼片元(yuan)件(jian)相結合(he)，電(dian)路(lu)設計別(bie)致新穎，元(yuan)件(jian)布局嚴謹合(he)理。供(gong)電(dian)電(dian)壓原(yuan)為(wei)１１０Ｖ，可(ke)方便地(di)改為(wei)９０～２５０Ｖ工作；輸出電(dian)壓５Ｖ，可(ke)改動(dong)為(wei)５～１２Ｖ輸出，特(te)別(bie)適(shi)合(he)無繩(sheng)電(dian)話或手機的３．６Ｖ（或４～９Ｖ）電(dian)池(chi)作快速充電(dian)之用(yong)。電(dian)路(lu)原(yuan)理見附圖。其中Ｄ１、Ｌ１以及Ｃ２等組(zu)成市電(dian)輸入整流濾波電(dian)路(lu)，Ｃ２兩端產生約３００Ｖ的直流高壓。

     ＶＴ１、ＶＴ２、Ｎ１、Ｎ２等組成(cheng)自激式(shi)振蕩電路，Ｒ３、Ｒ４提(ti)供啟(qi)動(dong)偏(pian)置電流，使ＶＴ１加電時即導通(tong)，主回(hui)路Ｎ１中(zhong)有(you)電流流過，Ｎ２上產生感應(ying)電壓(ya)。當此電壓(ya)峰值超過３Ｖ時，Ｄ５擊穿，通(tong)過Ｒ８向ＶＴ２提(ti)供偏(pian)流，使ＶＴ２飽(bao)和導通(tong)，ＶＴ１因偏(pian)置電壓(ya)被短路而關斷。

     當Ｎ１中電流(liu)(liu)關斷(duan)時，Ｎ２感應電壓(ya)極(ji)(ji)性反(fan)相(xiang)，經Ｄ５、Ｒ８加反(fan)向偏壓(ya)于(yu)ＶＴ２基(ji)極(ji)(ji)，ＶＴ２轉(zhuan)變為截止狀態，ＶＴ１經Ｒ３、Ｒ４偏置(zhi)重(zhong)新導通。如此(ci)循環往復，形(xing)成(cheng)間歇(xie)自激振蕩(dang)。Ｃ５、Ｒ６用以改善振蕩(dang)波(bo)(bo)形(xing)，光(guang)電耦(ou)合器ＯＰＴ１用以調(diao)控振蕩(dang)器脈沖寬度。Ｎ３、Ｌ２、Ｃ７等組成(cheng)整(zheng)(zheng)流(liu)(liu)輸出電路(lu)，二極(ji)(ji)管３Ｓ９０作(zuo)半波(bo)(bo)整(zheng)(zheng)流(liu)(liu)，ＲＫ１４作(zuo)充電隔離，Ｒ１８為輸出電流(liu)(liu)采樣電阻。

    當輸(shu)出(chu)電流超(chao)載(zai)（大于０．８Ａ）或短(duan)(duan)路時，Ｒ１８上產生較大壓(ya)降(jiang)，使ＯＰ１輸(shu)出(chu)電位(wei)急劇降(jiang)低，光(guang)電耦合(he)器(qi)控制振蕩(dang)脈(mo)沖變窄，由Ｎ１耦合(he)到Ｎ３的(de)(de)平均能量(liang)也(ye)大幅度(du)減少。即使輸(shu)出(chu)短(duan)(duan)路，輸(shu)出(chu)電流也(ye)僅有十(shi)幾毫(hao)安，從(cong)而避(bi)免了輸(shu)出(chu)端超(chao)載(zai)甚至短(duan)(duan)路對(dui)開關電源自身造成的(de)(de)威(wei)脅。

     穩壓(ya)(ya)部分由ＴＬ４３１等周邊(bian)電(dian)(dian)(dian)(dian)(dian)路(lu)組成，電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)采(cai)樣點取自被充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)兩端，按(an)圖中Ｒ１３＋Ｒ１４參數(shu)值(zhi)，空載輸(shu)出(chu)(chu)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)為(wei)(wei)(wei)５．２５Ｖ，對(dui)于３．６Ｖ可(ke)(ke)充(chong)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)的(de)(de)最大充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)為(wei)(wei)(wei)０．９５Ａ，適合對(dui)２Ａｈ以(yi)上的(de)(de)鎳(nie)鎘或鋰(li)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)直接(jie)充(chong)電(dian)(dian)(dian)(dian)(dian)。若用它對(dui)０．７～１Ａｈ的(de)(de)鎳(nie)鎘或鋰(li)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)(dian)(dian)(dian)時(shi)(shi)，充(chong)電(dian)(dian)(dian)(dian)(dian)回(hui)路(lu)內(nei)(nei)可(ke)(ke)串接(jie)一只(zhi)１．５～２．５Ω、功率(lv)０．５Ｗ的(de)(de)限流(liu)電(dian)(dian)(dian)(dian)(dian)阻，使(shi)充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)被限制在(zai)０．３～０．４Ａ。經試驗(yan)，該電(dian)(dian)(dian)(dian)(dian)源的(de)(de)輸(shu)出(chu)(chu)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)只(zhi)需(xu)經小改動，即可(ke)(ke)使(shi)輸(shu)出(chu)(chu)為(wei)(wei)(wei)５～１２Ｖ之間的(de)(de)某(mou)一電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)值(zhi)。方(fang)法是：更換帶 號的(de)(de)電(dian)(dian)(dian)(dian)(dian)阻，在(zai)２４ｋΩ～６２ｋΩ之間取值(zhi)。需(xu)要指出(chu)(chu)的(de)(de)是，輸(shu)出(chu)(chu)端濾波電(dian)(dian)(dian)(dian)(dian)解(jie)電(dian)(dian)(dian)(dian)(dian)容(rong)器標稱耐(nai)(nai)壓(ya)(ya)為(wei)(wei)(wei)１０Ｖ，需(xu)要改為(wei)(wei)(wei)１２Ｖ輸(shu)出(chu)(chu)時(shi)(shi)，請更換成耐(nai)(nai)壓(ya)(ya)為(wei)(wei)(wei)１６Ｖ的(de)(de)電(dian)(dian)(dian)(dian)(dian)解(jie)電(dian)(dian)(dian)(dian)(dian)容(rong)。在(zai)１２Ｖ時(shi)(shi)，其最大輸(shu)出(chu)(chu)電(dian)(dian)(dian)(dian)(dian)流(liu)應控(kong)制在(zai)０．７Ａ以(yi)內(nei)(nei)。輸(shu)出(chu)(chu)端帶有(you)２米長黑(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)。