隨著手機、MP3、PMP、DC/DV等手持電子產品越來越大眾化，鋰金屬（Li）和鋰離子電池使用(yong)越來越普遍，而配用(yong)的(de)(de)充(chong)電(dian)器無論是(shi)(shi)市售的(de)(de)15元手機(ji)充(chong)電(dian)器還是(shi)(shi)較高(gao)檔的(de)(de)DC/DV兼(jian)容(rong)充(chong)電(dian)器，絕大部分是(shi)(shi)采用(yong)LM324組成(cheng)的(de)(de)充(chong)電(dian)電(dian)壓檢測和控制線路(lu)，這些線路(lu)無論從控制精(jing)度還是(shi)(shi)功能方(fang)面都不(bu)能滿足鋰電(dian)池(chi)充(chong)電(dian)特性的(de)(de)要求，直接(jie)導致電(dian)池(chi)充(chong)不(bu)滿，電(dian)池(chi)壽命減(jian)短以及(ji)越來越多的(de)(de)電(dian)池(chi)損壞(huai)、爆(bao)炸(zha)等(deng)案例發生。而如果采用(yong)國(guo)外(wai)專用(yong)IC來設計，則其(qi)極其(qi)高(gao)昂的(de)(de)成(cheng)本實在令人無法接(jie)受(shou)。

     有鑒于此，筆者在此介紹兩款由國產新型IC組成的鋰電池充電器，在大(da)致相(xiang)當(dang)的(de)(de)總體成本下提(ti)供了遠(yuan)遠(yuan)超過LM324方案的(de)(de)性能，具有極高的(de)(de)新(xin)穎性和市(shi)場(chang)前景(jing)。

PT7M7433T是(shi)上海百(bai)利(li)通公司(si)最新設計(ji)的(de)極(ji)高(gao)精度的(de)一(yi)系列電(dian)壓檢測器的(de)其(qi)中一(yi)款(kuan)，其(qi)檢測精度在0-Vcc （5.5V）范圍內小(xiao)于1mV，而且其(qi)批(pi)量IC的(de)檢測值偏差(cha)<±2.5%，這樣完全保證了批(pi)量產品的(de)性(xing)能一(yi)致性(xing)和極(ji)高(gao)的(de)總體性(xing)能，我們(men)利(li)用其(qi)配合少量外部電(dian)路(lu)即可組成相當簡單的(de)鋰(li)電(dian)池充電(dian)線(xian)路(lu)。

該IC的內部框圖和簡單(dan)介紹如(ru)下：（圖一）

IC內含(han)一個高(gao)精(jing)度的(de)615mV基準電(dian)(dian)壓(ya)源、兩個比較(jiao)器(qi)、一個RS觸發器(qi)和其(qi)它一些邏(luo)輯電(dian)(dian)路，其(qi)大致功能是：VCC電(dian)(dian)壓(ya)或其(qi)它待(dai)檢測電(dian)(dian)壓(ya)通(tong)過R1-R3組成的(de)分壓(ya)網絡接(jie)在IC的(de)LTHIN /HTHIN檢測引(yin)(yin)腳(jiao)(jiao)，當待(dai)測電(dian)(dian)壓(ya)下降導(dao)(dao)致LTHIN引(yin)(yin)腳(jiao)(jiao)低(di)于615mV時，輸(shu)(shu)出(chu)腳(jiao)(jiao)LBO輸(shu)(shu)出(chu)低(di)電(dian)(dian)平，而如(ru)果待(dai)測電(dian)(dian)壓(ya)上升(sheng)導(dao)(dao)致HTHIN引(yin)(yin)腳(jiao)(jiao)高(gao)于615 mV時，經過內部邏(luo)輯判斷和簡單延時后(hou)，輸(shu)(shu)出(chu)腳(jiao)(jiao)LBO輸(shu)(shu)出(chu)高(gao)電(dian)(dian)平。

利(li)用這個IC裝(zhuang)制的充(chong)電器電路(lu)如下（圖二）

其(qi)工(gong)作流程大致(zhi)是：當(dang)接上(shang)(shang)Li+電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)和供(gong)(gong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源時，IC通(tong)(tong)(tong)(tong)過(guo)(guo)R1/R2/R3組成的網絡(luo)檢測電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)，如果電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)低(di)于(yu)3.3V（由R1-R3的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻值(zhi)決定），或者(zhe)按(an)(an)下(xia)按(an)(an)制SW1，此時IC3腳的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)低(di)于(yu)615mV，則IC4腳輸出(chu)低(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平，通(tong)(tong)(tong)(tong)過(guo)(guo)R5/D2拉低(di)Q1的柵(zha)極使之導(dao)(dao)通(tong)(tong)(tong)(tong)，從而通(tong)(tong)(tong)(tong)過(guo)(guo)Q1/R9/D1給(gei)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)進行大電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，當(dang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)一路上(shang)(shang)升(sheng)直至超(chao)過(guo)(guo)4.20V,此時IC的1腳電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)高(gao)過(guo)(guo)615mV,IC內部經簡單判(pan)斷和延時，令(ling)4腳輸出(chu)高(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平，從而關(guan)閉大電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)通(tong)(tong)(tong)(tong)道，但是4腳的高(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平同時給(gei)R7/C2的充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)回(hui)路供(gong)(gong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，令(ling)到Q3的柵(zha)極電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)慢(man)慢(man)升(sheng)高(gao)，并給(gei)R8提(ti)供(gong)(gong)通(tong)(tong)(tong)(tong)路導(dao)(dao)致(zhi)Q2導(dao)(dao)通(tong)(tong)(tong)(tong)，通(tong)(tong)(tong)(tong)過(guo)(guo)R10給(gei)Q1提(ti)供(gong)(gong)一個較弱的導(dao)(dao)通(tong)(tong)(tong)(tong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流，使之微微導(dao)(dao)通(tong)(tong)(tong)(tong)，從而為電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)提(ti)供(gong)(gong)一個較少的補充充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流。按(an)(an)照圖(tu)中所示元(yuan)件參數將于(yu)大約十分(fen)鐘后(hou)，由于(yu)C2的不(bu)斷充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，其(qi)端電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)即Q3的柵(zha)極電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)不(bu)斷上(shang)(shang)升(sheng)直至使Q3導(dao)(dao)通(tong)(tong)(tong)(tong)，從而關(guan)閉Q2，令(ling)到整個充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)過(guo)(guo)程結束。

上(shang)面的(de)(de)方案(an)還存在(zai)一些不足(zu)之處，例如檢測(ce)精度由外接電(dian)(dian)(dian)(dian)(dian)阻R1/R2/R3的(de)(de)精度決定，對于(yu)過放電(dian)(dian)(dian)(dian)(dian)的(de)(de)電(dian)(dian)(dian)(dian)(dian)池（電(dian)(dian)(dian)(dian)(dian)池端(duan)電(dian)(dian)(dian)(dian)(dian)壓低于(yu)2.8V）沒(mei)有一個小電(dian)(dian)(dian)(dian)(dian)流預充的(de)(de)過程，另(ling)外該方案(an)的(de)(de)10分鐘補充充電(dian)(dian)(dian)(dian)(dian)時間對于(yu)較大容量的(de)(de)電(dian)(dian)(dian)(dian)(dian)池來說不是(shi)太足(zu)夠，因此針對上(shang)述(shu)不足(zu)之處，我(wo)們還提供(gong)一個成本稍高一點，性能更加(jia)完善的(de)(de)方案(an)：（圖三）

乍(zha)看之下，這個(ge)(ge)方案采(cai)用(yong)(yong)了(le)三(san)個(ge)(ge)IC，可是(shi)(shi)U1和(he)U2是(shi)(shi)采(cai)用(yong)(yong)的SOT-23或者TO-92封裝(zhuang)，就(jiu)好(hao)像普通三(san)極管(guan)(guan)一(yi)樣(yang)，其價格(ge)也就(jiu)是(shi)(shi)2-3個(ge)(ge)三(san)極管(guan)(guan)的價格(ge)，而(er)U3（PT8A2513NE）也是(shi)(shi)采(cai)用(yong)(yong)的TO-94封裝(zhuang)，外形和(he)三(san)極管(guan)(guan)很(hen)相似，價錢也相當便宜，不過(guo)，這個(ge)(ge)電(dian)路可以實(shi)現(xian)智能判(pan)斷電(dian)池是(shi)(shi)否(fou)(fou)過(guo)放(fang)電(dian)，決(jue)定是(shi)(shi)否(fou)(fou)在開(kai)始充電(dian)時采(cai)用(yong)(yong)小電(dian)流(liu)預(yu)充，另外，采(cai)用(yong)(yong)U3后也將充電(dian)后期的補充充電(dian)過(guo)程延長到大(da)約一(yi)個(ge)(ge)小時！

首(shou)先(xian)讓我們介紹一下該電路中幾(ji)個IC的(de)功能：

（圖四）是U1/U2的內(nei)部框圖，這兩個IC只是內(nei)部電(dian)(dian)阻(zu)(zu)R1/R2的數值(zhi)不(bu)同(tong)而已，它(ta)們的功能也很簡單：當(dang)Vcc低(di)于IC的設定值(zhi)時(shi)（根據IC編號不(bu)同(tong)，內(nei)部R3/R4阻(zu)(zu)值(zhi)也不(bu)同(tong)從(cong)而導致檢測電(dian)(dian)壓值(zhi)不(bu)同(tong)，對(dui)(dui)于PT7M6128指的是2.80V），RST引腳輸(shu)出低(di)電(dian)(dian)平(ping)，反之當(dang)Vcc 高(gao)于1.05倍標稱值(zhi)時(shi)（例如(ru)對(dui)(dui)于PT7M6140，此數值(zhi)為(wei)1.05x4.0 =4.20V）則(ze)RST引腳輸(shu)出高(gao)電(dian)(dian)平(ping)。

上面電路的另外一(yi)個IC（PT8A25 13）則(ze)是一(yi)個極(ji)簡單卻極(ji)穩(wen)定(ding)的延(yan)時(shi)IC，其延(yan)時(shi)時(shi)間(jian)僅僅取決于 OSC腳(jiao)的頻率(lv)。事(shi)實上該(gai)IC就(jiu)(jiu)是將(jiang)OSC震蕩頻率(lv)進行32768次分(fen)頻后用(yong)來(lai)控(kong)制輸出的。之所(suo)以采用(yong)這個電路而不(bu)采用(yong)LM555或(huo)者CD4060等(deng)通(tong)用(yong)IC的原(yuan)因就(jiu)(jiu)是因為它(ta)相對而言(yan)定(ding)時(shi)精度(du)更高（其它(ta)IC不(bu)分(fen)頻），定(ding)時(shi)時(shi)間(jian)更長(chang)（可達數小時(shi)）。并且電路更加簡單，采用(yong)TO-94或(huo)SOT-23-4封裝，就(jiu)(jiu)像一(yi)個三極(ji)管一(yi)樣。而價錢也跟CD4060差不(bu)多，使(shi)用(yong)效(xiao)果可就(jiu)(jiu)好的太多了。

至(zhi)此(ci)大(da)家(jia)想必(bi)也(ye)大(da)致了(le)(le)解了(le)(le)圖(tu)三的工作(zuo)流(liu)程了(le)(le)：接上電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)和(he)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器，如果電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)低(di)于(yu)2.8V，則U1輸(shu)(shu)出為低(di)（U2輸(shu)(shu)出也(ye)是(shi)低(di)），這(zhe)樣(yang)R3和(he)R4的回(hui)路(lu)(lu)都不通(tong)，只有R2回(hui)路(lu)(lu)導(dao)(dao)(dao)通(tong)，給(gei)Q1提供(gong)微弱的導(dao)(dao)(dao)通(tong)，使之輸(shu)(shu)出約(yue)數毫安(an)的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)給(gei)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)進行預充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，當電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)上升到超過(guo)2.94V（1.05X2.8）時(shi)(shi)(shi)或者剛接上電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)就超過(guo)2.94V時(shi)(shi)(shi)，U1輸(shu)(shu)出高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)而U2繼續(xu)輸(shu)(shu)出低(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)（電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)還沒達(da)到4.2V J），這(zhe)時(shi)(shi)(shi)R2通(tong)路(lu)(lu)截止而R3通(tong)路(lu)(lu)導(dao)(dao)(dao)通(tong)（因(yin)為Q4導(dao)(dao)(dao)通(tong)且其源極電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)為低(di)-因(yin)U1輸(shu)(shu)出拉低(di)），從(cong)而由較小阻值的R3令(ling)Q1完(wan)全(quan)導(dao)(dao)(dao)通(tong)，提供(gong)一(yi)個(ge)數百毫安(an)的大(da)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)恒流(liu)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，而當這(zhe)個(ge)恒流(liu)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)過(guo)程慢慢令(ling)到被(bei)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的Li+電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)端(duan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)上升到4.2V時(shi)(shi)(shi)，U2也(ye)輸(shu)(shu)出高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)從(cong)而關(guan)閉(bi)Q4,但是(shi)它同時(shi)(shi)(shi)也(ye)給(gei)U3提供(gong)了(le)(le)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源導(dao)(dao)(dao)致U3開始工作(zuo)，這(zhe)樣(yang)U3觸發Q3使R4導(dao)(dao)(dao)通(tong)提供(gong)一(yi)個(ge)很小的補充(chong)(chong)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)，直至(zhi)U3達(da)到定時(shi)(shi)(shi)時(shi)(shi)(shi)間(jian)從(cong)而關(guan)閉(bi)Q3，這(zhe)時(shi)(shi)(shi)整個(ge)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)過(guo)程才完(wan)全(quan)結束。

相比而言，第二個(ge)方(fang)案(an)增加了前期智能(neng)判斷電池(chi)狀態和(he)自(zi)動預充(chong)(chong)電過程(cheng)，以及延長了末尾(wei)的補充(chong)(chong)充(chong)(chong)電過程(cheng)的時(shi)(shi)間(jian)，各個(ge)階(jie)段的充(chong)(chong)電電流可調并且補充(chong)(chong)充(chong)(chong)電時(shi)(shi)間(jian)可調（數(shu)分(fen)鐘至數(shu)小時(shi)(shi)），因此該(gai)方(fang)案(an)對鋰電池(chi)充(chong)(chong)電具有更(geng)好的精確性和(he)安全性，加上價錢便宜，功能(neng)也比較完善，相信很(hen)快會(hui)取代市面中低檔的充(chong)(chong)電器(qi)特別是那些廉價的手(shou)機電池(chi)充(chong)(chong)電器(qi)。