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(jiao)流(liu)電(dian)經(jing)K1～K4及其相應(ying)阻容(rong)元(yuan)件組(zu)成的(de)4條并列支(zhi)路(lu)選擇或組(zu)合(he)，再經(jing)整(zheng)流(liu)堆(dui)D整(zheng)流(liu)后(hou)，通過(guo)電(dian)流(liu)表(biao)A，給(gei)蓄(xu)(xu)電(dian)池(chi)(chi)充(chong)電(dian)。在充(chong)電(dian)過(guo)程中，由于回路(lu)中蓄(xu)(xu)電(dian)池(chi)(chi)兩(liang)(liang)端電(dian)壓的(de)變(bian)化量相對于220V交(jiao)流(liu)電(dian)壓來說很小，電(dian)容(rong)兩(liang)(liang)端的(de)電(dian)壓降幾乎可認為(wei)是(shi)不(bu)變(bian)的(de)，所以，通過(guo)電(dian)容(rong)器的(de)電(dian)流(liu)也是(shi)不(bu)變(bian)的(de)，通過(guo)蓄(xu)(xu)電(dian)池(chi)(chi)內(nei)部的(de)充(chong)電(dian)電(dian)流(liu)自然也是(shi)恒定的(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(jiang)電(dian)(dian)(dian)容器上積(ji)存的(de)電(dian)(dian)(dian)荷放(fang)掉；K1、K2、K3、K4是支(zhi)路控制(zhi)(zhi)開關，通(tong)(tong)過(guo)開關通(tong)(tong)斷控制(zhi)(zhi)可(ke)以決定支(zhi)路是否并入電(dian)(dian)(dian)路；R5、LED組(zu)成空載(zai)報警(jing)指示電(dian)(dian)(dian)路(為了安全，充電(dian)(dian)(dian)器不(bu)可(ke)在空載(zai)狀態下插入220V交流(liu)電(dian)(dian)(dian)源(yuan))，LED亮時，說明空載(zai)。電(dian)(dian)(dian)流(liu)表(biao)A指示充電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)的(de)大小：電(dian)(dian)(dian)壓(ya)表(biao)V指示蓄電(dian)(dian)(dian)池(chi)兩端(duan)的(de)電(dian)(dian)(dian)壓(ya)(為防止空載(zai)時電(dian)(dian)(dian)壓(ya)高(gao)燒壞(huai)電(dian)(dian)(dian)壓(ya)表(biao)，電(dian)(dian)(dian)壓(ya)表(biao)的(de)接入與(yu)否受開關K5的(de)控制(zhi)(zhi))。

　　二、電路設計

　　該(gai)充(chong)電(dian)(dian)(dian)器的(de)限流(liu)電(dian)(dian)(dian)容器容量(liang)越大(da)(da)，容抗越小，充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)越大(da)(da)。反之，充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)越小。根(gen)據(ju)該(gai)原理，可采用調整(zheng)并聯電(dian)(dian)(dian)容的(de)方法來(lai)達到(dao)調整(zheng)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)大(da)(da)小的(de)目的(de)。以(yi)汽車、摩托車、電(dian)(dian)(dian)動(dong)自(zi)行車常(chang)用的(de)蓄電(dian)(dian)(dian)池(chi)為(wei)例(li)，該(gai)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)路設(she)置了相(xiang)鄰級差為(wei)1A的(de)1～15A的(de)15級可調充(chong)電(dian)(dian)(dian)，通過四(si)條支路的(de)不(bu)同(tong)并聯組(zu)合實現對畜電(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)的(de)調整(zheng)。

　　由純電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)交流(liu)(liu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路中(zhong)(圖(tu)中(zhong)各分流(liu)(liu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻的(de)(de)(de)(de)分流(liu)(liu)很小，可忽略不計(ji))電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓、電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)、容(rong)抗(kang)之間的(de)(de)(de)(de)關系(xi)得：I=U／Xc=2πfcU=2×3．14×50×210C=65940C(式中(zhong)，Xc表示(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)器的(de)(de)(de)(de)容(rong)抗(kang)，其單(dan)位為(wei)(wei)(wei)(wei)歐(ou)姆；U表示(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)器兩端的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓，其單(dan)位為(wei)(wei)(wei)(wei)伏(fu)特，其值(zhi)為(wei)(wei)(wei)(wei)：交流(liu)(liu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源的(de)(de)(de)(de)總(zong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓220V-蓄(xu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)(de)下限電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓10V=210V；C表示(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)器的(de)(de)(de)(de)容(rong)量，其單(dan)位為(wei)(wei)(wei)(wei)法(fa)拉(la)：f表示(shi)交流(liu)(liu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)(de)頻(pin)率，其單(dan)位為(wei)(wei)(wei)(wei)赫茲，我國公共電(dian)(dian)(dian)(dian)(dian)(dian)(dian)網的(de)(de)(de)(de)頻(pin)率為(wei)(wei)(wei)(wei)50赫茲；I表示(shi)通過(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)器的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)，其單(dan)位為(wei)(wei)(wei)(wei)安培；π取3．14)。

　　由以上(shang)計算(suan)結果可(ke)(ke)(ke)知，當(dang)電(dian)(dian)容(rong)器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)(de)各(ge)支路(lu)電(dian)(dian)流分(fen)別(bie)為(wei)1A、2A、4A、8A。通過各(ge)控(kong)(kong)(kong)制開關將(jiang)以上(shang)四個電(dian)(dian)容(rong)器進行(xing)適(shi)當(dang)的(de)(de)并聯(lian)組合(he)便(bian)可(ke)(ke)(ke)得到1A、2A、3A……15A的(de)(de)15組可(ke)(ke)(ke)調(diao)充電(dian)(dian)電(dian)(dian)流。如果想將(jiang)電(dian)(dian)流調(diao)得更精細些，可(ke)(ke)(ke)增(zeng)加(jia)并聯(lian)支路(lu)。如增(zeng)加(jia)7．5微法(fa)支路(lu)可(ke)(ke)(ke)得到相鄰級(ji)(ji)差(cha)為(wei)0．5A的(de)(de)0．5A～15．5A的(de)(de)31級(ji)(ji)可(ke)(ke)(ke)調(diao)充電(dian)(dian)控(kong)(kong)(kong)制系(xi)統，上(shang)述(shu)各(ge)支路(lu)電(dian)(dian)容(rong)器的(de)(de)容(rong)量(liang)若(ruo)只取其十分(fen)之一，便(bian)可(ke)(ke)(ke)得到相鄰級(ji)(ji)差(cha)為(wei)O．1A的(de)(de)0．1～1．5A的(de)(de)15級(ji)(ji)可(ke)(ke)(ke)調(diao)并聯(lian)組合(he)充電(dian)(dian)控(kong)(kong)(kong)制系(xi)統；若(ruo)只取其容(rong)量(liang)的(de)(de)百分(fen)之一，便(bian)可(ke)(ke)(ke)得到相鄰級(ji)(ji)差(cha)為(wei)140mA的(de)(de)15級(ji)(ji)可(ke)(ke)(ke)調(diao)并聯(lian)組合(he)充電(dian)(dian)控(kong)(kong)(kong)制系(xi)統。

　　三、制作方法

　　指示燈L應選(xuan)(xuan)用額(e)(e)定工(gong)作電(dian)(dian)壓(ya)為(wei)(wei)220V的(de)體積較小些的(de)燈泡，也可以用10kΩ的(de)電(dian)(dian)阻和一個小功率(lv)發光二極管串聯代(dai)替；控(kong)制(zhi)開關K1、K2、K3、K4應分別選(xuan)(xuan)用額(e)(e)定工(gong)作電(dian)(dian)流(liu)不小于(yu)1．5A、3A、6A、12A的(de)；電(dian)(dian)容器C1、C2、C3、C4均選(xuan)(xuan)用耐壓(ya)不小于(yu)400V規(gui)(gui)格(ge)(ge)的(de)；泄放電(dian)(dian)阻R1、R2、R3、R4均選(xuan)(xuan)用220kΩ，1／2W規(gui)(gui)格(ge)(ge)的(de)；整(zheng)流(liu)堆(dui)D應選(xuan)(xuan)用額(e)(e)定工(gong)作電(dian)(dian)流(liu)不小于(yu)50A，耐壓(ya)不小于(yu)400V規(gui)(gui)格(ge)(ge)的(de)；電(dian)(dian)流(liu)表(biao)A選(xuan)(xuan)用量程為(wei)(wei)20A或(huo)30A規(gui)(gui)格(ge)(ge)的(de)直流(liu)電(dian)(dian)流(liu)表(biao)；電(dian)(dian)壓(ya)表(biao)V應選(xuan)(xuan)用量程為(wei)(wei)50V規(gui)(gui)格(ge)(ge)的(de)直流(liu)電(dian)(dian)壓(ya)表(biao)；R5選(xuan)(xuan)用10kΩ／6W的(de)電(dian)(dian)阻；LED選(xuan)(xuan)用普(pu)通小功率(lv)發光二極管；K5選(xuan)(xuan)用普(pu)通按鍵(jian)式開關，工(gong)作電(dian)(dian)流(liu)大小不作要求(qiu)。將控(kong)制(zhi)開關K1