開關電源以效率高、電壓適應(ying)性(xing)強而得(de)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)(dian)(dian)(dian)路(lu)采用分立(li)元件(jian)和貼片元件(jian)相結合，電(dian)(dian)(dian)(dian)路(lu)設(she)計別致新穎，元件(jian)布局嚴謹合理。供電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)壓原(yuan)為１１０Ｖ，可方便地改為９０～２５０Ｖ工作；輸出電(dian)(dian)(dian)(dian)壓５Ｖ，可改動為５～１２Ｖ輸出，特別適合無繩電(dian)(dian)(dian)(dian)話或(huo)手機的３．６Ｖ（或(huo)４～９Ｖ）電(dian)(dian)(dian)(dian)池(chi)作快速充電(dian)(dian)(dian)(dian)之用。電(dian)(dian)(dian)(dian)路(lu)原(yuan)理見附圖。其中Ｄ１、Ｌ１以(yi)及Ｃ２等組成市(shi)電(dian)(dian)(dian)(dian)輸入整流(liu)濾波電(dian)(dian)(dian)(dian)路(lu)，Ｃ２兩端(duan)產生約３００Ｖ的直流(liu)高壓。

     ＶＴ１、ＶＴ２、Ｎ１、Ｎ２等組成自激式振蕩電(dian)(dian)路，Ｒ３、Ｒ４提(ti)供啟動偏置(zhi)電(dian)(dian)流(liu)，使ＶＴ１加電(dian)(dian)時(shi)即(ji)導通(tong)，主回路Ｎ１中有電(dian)(dian)流(liu)流(liu)過(guo)，Ｎ２上產生感應電(dian)(dian)壓(ya)。當此電(dian)(dian)壓(ya)峰值超(chao)過(guo)３Ｖ時(shi)，Ｄ５擊穿，通(tong)過(guo)Ｒ８向ＶＴ２提(ti)供偏流(liu)，使ＶＴ２飽和導通(tong)，ＶＴ１因偏置(zhi)電(dian)(dian)壓(ya)被短路而關斷。

     當Ｎ１中電(dian)流關(guan)斷(duan)時，Ｎ２感應電(dian)壓極性反(fan)相，經(jing)Ｄ５、Ｒ８加反(fan)向偏壓于ＶＴ２基極，ＶＴ２轉變為截(jie)止狀態(tai)，ＶＴ１經(jing)Ｒ３、Ｒ４偏置重新(xin)導(dao)通。如(ru)此(ci)循環往復，形成間歇自激振蕩(dang)(dang)。Ｃ５、Ｒ６用以(yi)改(gai)善振蕩(dang)(dang)波形，光電(dian)耦合(he)器ＯＰＴ１用以(yi)調控振蕩(dang)(dang)器脈沖寬(kuan)度。Ｎ３、Ｌ２、Ｃ７等組成整(zheng)流輸出(chu)電(dian)路(lu)，二極管３Ｓ９０作半波整(zheng)流，ＲＫ１４作充電(dian)隔離，Ｒ１８為輸出(chu)電(dian)流采樣電(dian)阻。

    當(dang)輸(shu)(shu)出電(dian)流(liu)超(chao)載（大(da)于(yu)０．８Ａ）或短(duan)路時，Ｒ１８上產生較大(da)壓降(jiang)，使ＯＰ１輸(shu)(shu)出電(dian)位急(ji)劇降(jiang)低，光電(dian)耦合器控制振蕩脈沖(chong)變窄，由Ｎ１耦合到Ｎ３的平均能量也(ye)大(da)幅(fu)度減少。即使輸(shu)(shu)出短(duan)路，輸(shu)(shu)出電(dian)流(liu)也(ye)僅有十幾毫(hao)安，從而(er)避免了(le)輸(shu)(shu)出端超(chao)載甚至(zhi)短(duan)路對開關(guan)電(dian)源自身造成的威(wei)脅。

     穩壓部分由ＴＬ４３１等周邊(bian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路組(zu)成，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓采(cai)樣點取自被充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)兩端，按(an)圖中Ｒ１３＋Ｒ１４參數值，空載輸(shu)(shu)(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓為５．２５Ｖ，對(dui)(dui)于３．６Ｖ可(ke)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)的(de)(de)最大充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流為０．９５Ａ，適合對(dui)(dui)２Ａｈ以上的(de)(de)鎳鎘或鋰電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)直接(jie)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)。若(ruo)用(yong)它對(dui)(dui)０．７～１Ａｈ的(de)(de)鎳鎘或鋰電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)時，充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)回路內可(ke)串接(jie)一只(zhi)１．５～２．５Ω、功(gong)率(lv)０．５Ｗ的(de)(de)限流電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻，使(shi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流被限制(zhi)在(zai)０．３～０．４Ａ。經(jing)試驗，該(gai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源的(de)(de)輸(shu)(shu)(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓只(zhi)需經(jing)小改動，即可(ke)使(shi)輸(shu)(shu)(shu)(shu)出(chu)為５～１２Ｖ之(zhi)間(jian)的(de)(de)某(mou)一電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓值。方(fang)法(fa)是：更(geng)換(huan)帶 號的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻，在(zai)２４ｋΩ～６２ｋΩ之(zhi)間(jian)取值。需要(yao)指(zhi)出(chu)的(de)(de)是，輸(shu)(shu)(shu)(shu)出(chu)端濾波電(dian)(dian)(dian)(dian)(dian)(dian)(dian)解電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容器標稱(cheng)耐(nai)壓為１０Ｖ，需要(yao)改為１２Ｖ輸(shu)(shu)(shu)(shu)出(chu)時，請(qing)更(geng)換(huan)成耐(nai)壓為１６Ｖ的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)解電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容。在(zai)１２Ｖ時，其最大輸(shu)(shu)(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流應(ying)控制(zhi)在(zai)０．７Ａ以內。輸(shu)(shu)(shu)(shu)出(chu)端帶有２米(mi)長黑白(bai)線，黑線為正極，白(bai)線為負極。