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(ge)變(bian)壓器降壓、單二極管半波整流裝置(zhi)，充(chong)(chong)電(dian)時間很難(nan)掌握。由于電(dian)池虧電(dian)或過(guo)充(chong)(chong)電(dian)往往會(hui)造成電(dian)池壽命(ming)縮短，本人設計制作了一(yi)個(ge)簡易自(zi)動充(chong)(chong)電(dian)裝置(zhi)，可有(you)效延長電(dian)池壽命(ming)。

        元件選用與制作

　　T1可使用10VA左右(you)，次級有9V和12V輸出的(de)電(dian)(dian)(dian)(dian)源變壓(ya)器(qi)(qi)(qi)(qi)，若(ruo)使用原配變壓(ya)器(qi)(qi)(qi)(qi)(次級輸出9V)時(shi)，繼電(dian)(dian)(dian)(dian)器(qi)(qi)(qi)(qi)K1工作電(dian)(dian)(dian)(dian)壓(ya)也(ye)應選(xuan)9V。繼電(dian)(dian)(dian)(dian)器(qi)(qi)(qi)(qi)選(xuan)用4088、4089、JRX-13F等(deng)12V繼電(dian)(dian)(dian)(dian)器(qi)(qi)(qi)(qi)。VT使用9013、9014、8050等(deng)小功(gong)率晶體管(guan)，要(yao)求穿透電(dian)(dian)(dian)(dian)流(liu)要(yao)小，開關特性好(hao)，β=100～1500光耦合(he)器(qi)(qi)(qi)(qi)IC可用4N23、4N25、4N33等(deng)型號。C1的(de)耐壓(ya)不得小于450V，容(rong)量取220nF～470nF，容(rong)量越大(da)，LED1越亮。調試時(shi)，先斷開VD2，在X1、X2兩端加7.5V直流(liu)電(dian)(dian)(dian)(dian)壓(ya)，從大(da)到小調電(dian)(dian)(dian)(dian)位器(qi)(qi)(qi)(qi)RP，使4N250⑤腳電(dian)(dian)(dian)(dian)位突然下降(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(tu)中，R2是(shi)VT的偏(pian)置電(dian)阻;C1是(shi)降壓電(dian)容(rong)，LED1(紅)為市電(dian)電(dian)源(yuan)指示(shi)管(guan);啟動完成后，交(jiao)流9V電(dian)壓經VD2整(zheng)流為電(dian)瓶GB充電(dian)，LED2(綠)為充電(dian)指示(shi)管(guan)。隨著充電(dian)過程的進行(xing)，電(dian)瓶兩端(duan)電(dian)壓不斷上升，當(dang)升至極限電(dian)壓值(約7.5V)時，穩壓管(guan)VD3反向(xiang)擊穿導通(tong)，光(guang)耦合(he)器4N25①、②腳內發(fa)光(guang)二極管(guan)發(fa)光(guang)，④、⑤腳內光(guang)電(dian)管(guan)受光(guang)后隨之(zhi)導通(tong)，VT基極被下拉(la)(約0V)而失去正偏(pian)壓，所以(yi)VT截止，K1釋放(fang)使(shi)K1-1斷開，停止充電(dian)，充電(dian)指示(shi)管(guan)LED2熄(xi)滅。