用6V免維護電瓶供電的應急手提燈在農村應用非常廣泛，其配用的充電器是一(yi)個變壓(ya)器降壓(ya)、單(dan)二(er)極管半(ban)波整(zheng)流(liu)裝置，充電(dian)(dian)(dian)(dian)時間很難掌握。由于電(dian)(dian)(dian)(dian)池(chi)虧電(dian)(dian)(dian)(dian)或過充電(dian)(dian)(dian)(dian)往(wang)往(wang)會造成(cheng)電(dian)(dian)(dian)(dian)池(chi)壽命縮(suo)短，本人設計制作(zuo)了一(yi)個簡易自動充電(dian)(dian)(dian)(dian)裝置，可有效延(yan)長電(dian)(dian)(dian)(dian)池(chi)壽命。

        元件選用與制(zhi)作(zuo)

　　T1可使(shi)用10VA左右，次級(ji)有9V和12V輸(shu)出(chu)的(de)電(dian)源變壓(ya)(ya)(ya)器(qi)(qi)，若使(shi)用原配變壓(ya)(ya)(ya)器(qi)(qi)(次級(ji)輸(shu)出(chu)9V)時，繼(ji)電(dian)器(qi)(qi)K1工作(zuo)電(dian)壓(ya)(ya)(ya)也應(ying)選9V。繼(ji)電(dian)器(qi)(qi)選用4088、4089、JRX-13F等(deng)12V繼(ji)電(dian)器(qi)(qi)。VT使(shi)用9013、9014、8050等(deng)小(xiao)功率晶體管，要(yao)(yao)求穿透電(dian)流(liu)要(yao)(yao)小(xiao)，開關(guan)特性好，β=100～1500光耦(ou)合器(qi)(qi)IC可用4N23、4N25、4N33等(deng)型號。C1的(de)耐壓(ya)(ya)(ya)不得小(xiao)于(yu)450V，容量取220nF～470nF，容量越大(da)，LED1越亮。調(diao)試時，先(xian)斷開VD2，在X1、X2兩(liang)端加7.5V直流(liu)電(dian)壓(ya)(ya)(ya)，從大(da)到小(xiao)調(diao)電(dian)位器(qi)(qi)RP，使(shi)4N250⑤腳電(dian)位突然(ran)下(xia)降(jiang)(K1釋放)即可。

　　工作原理

　　電路如圖1所示。GB為待充電電池，平時只要不再使用，就將充電器插頭X1、X2插入手提燈的充電插孔內。按一下啟動按鈕SB，220V交流市電經保險Fu、SB加在電源變壓器T1初級。其次級輸出兩路交流電壓：交流12V經VD1半波整流、C2平滑濾波，使VT導通。繼電器K1吸合，K1-1閉合。此時松手使SB斷開后，充電器仍然工(gong)作。圖中，R2是VT的偏(pian)置電(dian)阻(zu);C1是降壓電(dian)容，LED1(紅)為市電(dian)電(dian)源(yuan)指(zhi)示管;啟(qi)動完(wan)成后，交流(liu)9V電(dian)壓經(jing)VD2整流(liu)為電(dian)瓶GB充(chong)電(dian)，LED2(綠)為充(chong)電(dian)指(zhi)示管。隨(sui)著充(chong)電(dian)過程的進行，電(dian)瓶兩端電(dian)壓不斷上升，當升至(zhi)極限(xian)電(dian)壓值(約7.5V)時，穩(wen)壓管VD3反向擊穿導通，光(guang)(guang)耦合器4N25①、②腳內發(fa)光(guang)(guang)二極管發(fa)光(guang)(guang)，④、⑤腳內光(guang)(guang)電(dian)管受光(guang)(guang)后隨(sui)之(zhi)導通，VT基極被下拉(la)(約0V)而(er)失去(qu)正偏(pian)壓，所以VT截止，K1釋放(fang)使K1-1斷開，停止充(chong)電(dian)，充(chong)電(dian)指(zhi)示管LED2熄滅。