一、電路原理

　　如圖所示，該充電器屬于電容限流式無電源變壓器恒流充電器。220V交流(liu)(liu)電(dian)(dian)(dian)(dian)經K1～K4及其(qi)相應(ying)阻容(rong)(rong)元件組成(cheng)的(de)4條并列支路選(xuan)擇或組合，再經整流(liu)(liu)堆D整流(liu)(liu)后，通過(guo)電(dian)(dian)(dian)(dian)流(liu)(liu)表A，給蓄電(dian)(dian)(dian)(dian)池(chi)(chi)充電(dian)(dian)(dian)(dian)。在充電(dian)(dian)(dian)(dian)過(guo)程中，由于回路中蓄電(dian)(dian)(dian)(dian)池(chi)(chi)兩端(duan)(duan)電(dian)(dian)(dian)(dian)壓的(de)變化量相對(dui)于220V交流(liu)(liu)電(dian)(dian)(dian)(dian)壓來說很小，電(dian)(dian)(dian)(dian)容(rong)(rong)兩端(duan)(duan)的(de)電(dian)(dian)(dian)(dian)壓降幾乎可(ke)認為(wei)是(shi)不變的(de)，所以(yi)，通過(guo)電(dian)(dian)(dian)(dian)容(rong)(rong)器的(de)電(dian)(dian)(dian)(dian)流(liu)(liu)也是(shi)不變的(de)，通過(guo)蓄電(dian)(dian)(dian)(dian)池(chi)(chi)內部的(de)充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)自然也是(shi)恒定(ding)的(de)。

　　圖中，L為220V交流電源指示燈，R1、R2、R3、R4分別是電容器C1、C2、C3、C4的泄放電阻，在不用充電器時，能及時將電(dian)(dian)(dian)(dian)容器上積存的(de)電(dian)(dian)(dian)(dian)荷放(fang)掉；K1、K2、K3、K4是(shi)支(zhi)路(lu)控制開(kai)關(guan)，通(tong)過開(kai)關(guan)通(tong)斷控制可(ke)以決定支(zhi)路(lu)是(shi)否(fou)并(bing)入(ru)電(dian)(dian)(dian)(dian)路(lu)；R5、LED組(zu)成(cheng)空載報警指(zhi)示(shi)電(dian)(dian)(dian)(dian)路(lu)(為了安(an)全，充(chong)電(dian)(dian)(dian)(dian)器不(bu)可(ke)在空載狀態下插入(ru)220V交流電(dian)(dian)(dian)(dian)源)，LED亮(liang)時，說明空載。電(dian)(dian)(dian)(dian)流表(biao)A指(zhi)示(shi)充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流的(de)大小(xiao)：電(dian)(dian)(dian)(dian)壓表(biao)V指(zhi)示(shi)蓄(xu)電(dian)(dian)(dian)(dian)池兩(liang)端的(de)電(dian)(dian)(dian)(dian)壓(為防止(zhi)空載時電(dian)(dian)(dian)(dian)壓高燒(shao)壞電(dian)(dian)(dian)(dian)壓表(biao)，電(dian)(dian)(dian)(dian)壓表(biao)的(de)接入(ru)與否(fou)受開(kai)關(guan)K5的(de)控制)。

　　二、電路設計

　　該(gai)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器(qi)的(de)(de)(de)限流電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)器(qi)容(rong)量越(yue)大(da)，容(rong)抗越(yue)小，充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流越(yue)大(da)。反之，充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流越(yue)小。根(gen)據該(gai)原(yuan)理，可采用調整并聯電(dian)(dian)(dian)(dian)(dian)(dian)容(rong)的(de)(de)(de)方法來達(da)到(dao)調整充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流大(da)小的(de)(de)(de)目的(de)(de)(de)。以汽車(che)、摩托(tuo)車(che)、電(dian)(dian)(dian)(dian)(dian)(dian)動(dong)自行車(che)常用的(de)(de)(de)蓄電(dian)(dian)(dian)(dian)(dian)(dian)池為例(li)，該(gai)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)路設置了相鄰級差(cha)為1A的(de)(de)(de)1～15A的(de)(de)(de)15級可調充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)，通過四條支路的(de)(de)(de)不同(tong)并聯組(zu)合實(shi)現對畜電(dian)(dian)(dian)(dian)(dian)(dian)池充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流的(de)(de)(de)調整。

　　由純電(dian)(dian)(dian)(dian)容(rong)(rong)交流(liu)電(dian)(dian)(dian)(dian)路(lu)中(圖中各分流(liu)電(dian)(dian)(dian)(dian)阻(zu)的(de)(de)分流(liu)很小，可忽略不計(ji))電(dian)(dian)(dian)(dian)壓、電(dian)(dian)(dian)(dian)流(liu)、容(rong)(rong)抗(kang)之間的(de)(de)關(guan)系得(de)：I=U／Xc=2πfcU=2×3．14×50×210C=65940C(式中，Xc表示電(dian)(dian)(dian)(dian)容(rong)(rong)器的(de)(de)容(rong)(rong)抗(kang)，其(qi)(qi)單位為(wei)(wei)歐(ou)姆；U表示電(dian)(dian)(dian)(dian)容(rong)(rong)器兩端的(de)(de)電(dian)(dian)(dian)(dian)壓，其(qi)(qi)單位為(wei)(wei)伏特，其(qi)(qi)值為(wei)(wei)：交流(liu)電(dian)(dian)(dian)(dian)源(yuan)的(de)(de)總(zong)電(dian)(dian)(dian)(dian)壓220V-蓄(xu)電(dian)(dian)(dian)(dian)池(chi)放電(dian)(dian)(dian)(dian)的(de)(de)下限電(dian)(dian)(dian)(dian)壓10V=210V；C表示電(dian)(dian)(dian)(dian)容(rong)(rong)器的(de)(de)容(rong)(rong)量，其(qi)(qi)單位為(wei)(wei)法拉：f表示交流(liu)電(dian)(dian)(dian)(dian)的(de)(de)頻(pin)率(lv)，其(qi)(qi)單位為(wei)(wei)赫茲(zi)(zi)，我國公共電(dian)(dian)(dian)(dian)網的(de)(de)頻(pin)率(lv)為(wei)(wei)50赫茲(zi)(zi)；I表示通(tong)過(guo)電(dian)(dian)(dian)(dian)容(rong)(rong)器的(de)(de)電(dian)(dian)(dian)(dian)流(liu)，其(qi)(qi)單位為(wei)(wei)安培；π取3．14)。

　　由以上計算結果(guo)可(ke)(ke)(ke)知，當(dang)電容(rong)(rong)器(qi)C取15微法(fa)(即0．000015法(fa)拉)時，I=65940C=65940×0．000015≈1(A)。C1=15微法(fa)、C2=30微法(fa)、C3=60微法(fa)、C4=120微法(fa)，對應的(de)各(ge)支路(lu)電流分(fen)(fen)別(bie)為1A、2A、4A、8A。通過各(ge)控(kong)制(zhi)(zhi)開(kai)關將以上四個電容(rong)(rong)器(qi)進行(xing)適當(dang)的(de)并(bing)(bing)聯(lian)(lian)組(zu)合(he)便可(ke)(ke)(ke)得到(dao)1A、2A、3A……15A的(de)15組(zu)可(ke)(ke)(ke)調充(chong)(chong)(chong)電電流。如果(guo)想將電流調得更(geng)精細些，可(ke)(ke)(ke)增加(jia)并(bing)(bing)聯(lian)(lian)支路(lu)。如增加(jia)7．5微法(fa)支路(lu)可(ke)(ke)(ke)得到(dao)相(xiang)鄰級(ji)(ji)差(cha)為0．5A的(de)0．5A～15．5A的(de)31級(ji)(ji)可(ke)(ke)(ke)調充(chong)(chong)(chong)電控(kong)制(zhi)(zhi)系(xi)統，上述各(ge)支路(lu)電容(rong)(rong)器(qi)的(de)容(rong)(rong)量若只取其十分(fen)(fen)之(zhi)一，便可(ke)(ke)(ke)得到(dao)相(xiang)鄰級(ji)(ji)差(cha)為O．1A的(de)0．1～1．5A的(de)15級(ji)(ji)可(ke)(ke)(ke)調并(bing)(bing)聯(lian)(lian)組(zu)合(he)充(chong)(chong)(chong)電控(kong)制(zhi)(zhi)系(xi)統；若只取其容(rong)(rong)量的(de)百分(fen)(fen)之(zhi)一，便可(ke)(ke)(ke)得到(dao)相(xiang)鄰級(ji)(ji)差(cha)為140mA的(de)15級(ji)(ji)可(ke)(ke)(ke)調并(bing)(bing)聯(lian)(lian)組(zu)合(he)充(chong)(chong)(chong)電控(kong)制(zhi)(zhi)系(xi)統。

　　三、制作方法

　　指(zhi)示(shi)燈(deng)L應(ying)選(xuan)(xuan)用(yong)額定工(gong)(gong)作(zuo)電(dian)壓為220V的(de)(de)體積較小(xiao)(xiao)(xiao)些的(de)(de)燈(deng)泡，也(ye)可以用(yong)10kΩ的(de)(de)電(dian)阻和(he)一個小(xiao)(xiao)(xiao)功(gong)率發光二極管(guan)串(chuan)聯代替；控(kong)(kong)制開關(guan)K1、K2、K3、K4應(ying)分別(bie)選(xuan)(xuan)用(yong)額定工(gong)(gong)作(zuo)電(dian)流(liu)(liu)不(bu)小(xiao)(xiao)(xiao)于(yu)1．5A、3A、6A、12A的(de)(de)；電(dian)容(rong)器C1、C2、C3、C4均選(xuan)(xuan)用(yong)耐(nai)壓不(bu)小(xiao)(xiao)(xiao)于(yu)400V規(gui)格的(de)(de)；泄放電(dian)阻R1、R2、R3、R4均選(xuan)(xuan)用(yong)220kΩ，1／2W規(gui)格的(de)(de)；整流(liu)(liu)堆D應(ying)選(xuan)(xuan)用(yong)額定工(gong)(gong)作(zuo)電(dian)流(liu)(liu)不(bu)小(xiao)(xiao)(xiao)于(yu)50A，耐(nai)壓不(bu)小(xiao)(xiao)(xiao)于(yu)400V規(gui)格的(de)(de)；電(dian)流(liu)(liu)表A選(xuan)(xuan)用(yong)量程為20A或30A規(gui)格的(de)(de)直流(liu)(liu)電(dian)流(liu)(liu)表；電(dian)壓表V應(ying)選(xuan)(xuan)用(yong)量程為50V規(gui)格的(de)(de)直流(liu)(liu)電(dian)壓表；R5選(xuan)(xuan)用(yong)10kΩ／6W的(de)(de)電(dian)阻；LED選(xuan)(xuan)用(yong)普通小(xiao)(xiao)(xiao)功(gong)率發光二極管(guan)；K5選(xuan)(xuan)用(yong)普通按鍵式開關(guan)，工(gong)(gong)作(zuo)電(dian)流(liu)(liu)大小(xiao)(xiao)(xiao)不(bu)作(zuo)要求(qiu)。將控(kong)(kong)制開關(guan)K1