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)(yong)越(yue)(yue)來(lai)越(yue)(yue)普遍，而配用(yong)(yong)的(de)(de)充(chong)(chong)電(dian)(dian)(dian)器無(wu)(wu)論是(shi)市售的(de)(de)15元手機充(chong)(chong)電(dian)(dian)(dian)器還是(shi)較高檔的(de)(de)DC/DV兼容(rong)充(chong)(chong)電(dian)(dian)(dian)器，絕大部(bu)分是(shi)采用(yong)(yong)LM324組成(cheng)的(de)(de)充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)壓(ya)檢測(ce)和控制線(xian)路，這些線(xian)路無(wu)(wu)論從(cong)控制精度還是(shi)功能(neng)方面都不(bu)能(neng)滿(man)(man)足鋰電(dian)(dian)(dian)池充(chong)(chong)電(dian)(dian)(dian)特性的(de)(de)要求(qiu)，直接導(dao)致電(dian)(dian)(dian)池充(chong)(chong)不(bu)滿(man)(man)，電(dian)(dian)(dian)池壽命減短以及越(yue)(yue)來(lai)越(yue)(yue)多(duo)的(de)(de)電(dian)(dian)(dian)池損壞、爆炸(zha)等(deng)案例發生。而如果采用(yong)(yong)國外(wai)專用(yong)(yong)IC來(lai)設計，則其極(ji)其高昂的(de)(de)成(cheng)本實在令(ling)人無(wu)(wu)法接受。

     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(zai)大致相(xiang)當的總體成本下提(ti)供了遠遠超過LM324方(fang)案的性(xing)能，具有極高的新穎性(xing)和(he)市場前景。

PT7M7433T是上(shang)海(hai)百(bai)利通公(gong)司最新設計的(de)(de)極(ji)高(gao)精度的(de)(de)一(yi)(yi)系列電壓檢測(ce)器的(de)(de)其中一(yi)(yi)款，其檢測(ce)精度在(zai)0-Vcc （5.5V）范圍內小于1mV，而(er)且(qie)其批量IC的(de)(de)檢測(ce)值偏差<±2.5%，這樣(yang)完全保(bao)證(zheng)了(le)批量產品的(de)(de)性能(neng)一(yi)(yi)致性和極(ji)高(gao)的(de)(de)總體性能(neng)，我們利用其配合少(shao)量外部電路(lu)即(ji)可組(zu)成相(xiang)當簡單(dan)的(de)(de)鋰(li)電池充電線路(lu)。

該IC的內部框圖和簡單介紹如(ru)下(xia)：（圖一）

IC內含(han)一個(ge)高(gao)精度的615mV基準電(dian)壓(ya)源、兩個(ge)比較器(qi)、一個(ge)RS觸發器(qi)和(he)其(qi)它(ta)一些邏輯(ji)電(dian)路，其(qi)大致(zhi)(zhi)功能是：VCC電(dian)壓(ya)或(huo)其(qi)它(ta)待檢(jian)測電(dian)壓(ya)通過(guo)R1-R3組(zu)成的分壓(ya)網絡接在(zai)IC的LTHIN /HTHIN檢(jian)測引(yin)腳(jiao)，當(dang)待測電(dian)壓(ya)下降導致(zhi)(zhi)LTHIN引(yin)腳(jiao)低于615mV時(shi)，輸出腳(jiao)LBO輸出低電(dian)平，而如果待測電(dian)壓(ya)上升導致(zhi)(zhi)HTHIN引(yin)腳(jiao)高(gao)于615 mV時(shi)，經過(guo)內部邏輯(ji)判斷(duan)和(he)簡單(dan)延時(shi)后，輸出腳(jiao)LBO輸出高(gao)電(dian)平。

利(li)用這(zhe)個IC裝制的(de)充電器電路如(ru)下(xia)（圖(tu)二）

其(qi)工作流(liu)(liu)程(cheng)大(da)致(zhi)是：當(dang)(dang)接上(shang)Li+電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)和供電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源時，IC通(tong)(tong)(tong)(tong)過R1/R2/R3組成(cheng)的(de)(de)網絡檢測(ce)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)，如果電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)低(di)于(yu)(yu)3.3V（由R1-R3的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)值決定），或者按下按制(zhi)SW1，此時IC3腳(jiao)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)低(di)于(yu)(yu)615mV，則IC4腳(jiao)輸(shu)出低(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)，通(tong)(tong)(tong)(tong)過R5/D2拉(la)低(di)Q1的(de)(de)柵極(ji)使(shi)之導(dao)(dao)通(tong)(tong)(tong)(tong)，從(cong)而(er)通(tong)(tong)(tong)(tong)過Q1/R9/D1給(gei)(gei)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)進行大(da)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，當(dang)(dang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)一路上(shang)升(sheng)直至(zhi)超過4.20V,此時IC的(de)(de)1腳(jiao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)高過615mV,IC內(nei)部(bu)經(jing)簡單判(pan)斷和延時，令4腳(jiao)輸(shu)出高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)，從(cong)而(er)關閉大(da)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)通(tong)(tong)(tong)(tong)道，但(dan)是4腳(jiao)的(de)(de)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)同(tong)時給(gei)(gei)R7/C2的(de)(de)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)回路供電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，令到(dao)(dao)Q3的(de)(de)柵極(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)慢(man)慢(man)升(sheng)高，并給(gei)(gei)R8提供通(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R10給(gei)(gei)Q1提供一個(ge)較弱的(de)(de)導(dao)(dao)通(tong)(tong)(tong)(tong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)，使(shi)之微微導(dao)(dao)通(tong)(tong)(tong)(tong)，從(cong)而(er)為電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)提供一個(ge)較少(shao)的(de)(de)補充(chong)(chong)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)。按照圖(tu)中所示元件參數將于(yu)(yu)大(da)約十分(fen)鐘后，由于(yu)(yu)C2的(de)(de)不斷充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，其(qi)端(duan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)即(ji)Q3的(de)(de)柵極(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)不斷上(shang)升(sheng)直至(zhi)使(shi)Q3導(dao)(dao)通(tong)(tong)(tong)(tong)，從(cong)而(er)關閉Q2，令到(dao)(dao)整個(ge)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)過程(cheng)結束(shu)。

上面的(de)方(fang)(fang)案(an)還(huan)存在(zai)一(yi)些不(bu)足之處，例如(ru)檢(jian)測精(jing)度(du)由外(wai)接電(dian)(dian)阻R1/R2/R3的(de)精(jing)度(du)決定，對于(yu)過(guo)放電(dian)(dian)的(de)電(dian)(dian)池（電(dian)(dian)池端(duan)電(dian)(dian)壓低(di)于(yu)2.8V）沒有一(yi)個小電(dian)(dian)流預(yu)充(chong)的(de)過(guo)程，另外(wai)該方(fang)(fang)案(an)的(de)10分鐘補充(chong)充(chong)電(dian)(dian)時間(jian)對于(yu)較大容(rong)量(liang)的(de)電(dian)(dian)池來說不(bu)是(shi)太足夠，因此針對上述(shu)不(bu)足之處，我們還(huan)提供一(yi)個成本稍高一(yi)點，性能更加完善的(de)方(fang)(fang)案(an)：（圖三）

乍看之下，這個(ge)(ge)方案采(cai)(cai)用(yong)了三個(ge)(ge)IC，可是U1和(he)U2是采(cai)(cai)用(yong)的SOT-23或者(zhe)TO-92封裝(zhuang)，就(jiu)好像(xiang)普通三極(ji)管一樣，其(qi)價格也(ye)就(jiu)是2-3個(ge)(ge)三極(ji)管的價格，而U3（PT8A2513NE）也(ye)是采(cai)(cai)用(yong)的TO-94封裝(zhuang)，外形和(he)三極(ji)管很相似，價錢也(ye)相當便宜(yi)，不(bu)過，這個(ge)(ge)電(dian)路可以實現智能(neng)判(pan)斷電(dian)池是否(fou)過放電(dian)，決定是否(fou)在開始充(chong)電(dian)時(shi)采(cai)(cai)用(yong)小電(dian)流預充(chong)，另外，采(cai)(cai)用(yong)U3后也(ye)將充(chong)電(dian)后期的補充(chong)充(chong)電(dian)過程延(yan)長到大約一個(ge)(ge)小時(shi)！

首先(xian)讓(rang)我們介紹一下該電路中幾個IC的功能：

（圖四）是(shi)U1/U2的(de)內部(bu)框圖，這兩個(ge)IC只是(shi)內部(bu)電(dian)阻R1/R2的(de)數(shu)值(zhi)(zhi)(zhi)不(bu)同(tong)而已，它們(men)的(de)功能(neng)也很簡(jian)單(dan)：當(dang)Vcc低于(yu)IC的(de)設定值(zhi)(zhi)(zhi)時(shi)（根據(ju)IC編號不(bu)同(tong)，內部(bu)R3/R4阻值(zhi)(zhi)(zhi)也不(bu)同(tong)從(cong)而導致檢測電(dian)壓值(zhi)(zhi)(zhi)不(bu)同(tong)，對(dui)于(yu)PT7M6128指的(de)是(shi)2.80V），RST引(yin)腳輸(shu)出(chu)低電(dian)平，反(fan)之(zhi)當(dang)Vcc 高于(yu)1.05倍標稱值(zhi)(zhi)(zhi)時(shi)（例如對(dui)于(yu)PT7M6140，此數(shu)值(zhi)(zhi)(zhi)為1.05x4.0 =4.20V）則RST引(yin)腳輸(shu)出(chu)高電(dian)平。

上(shang)面電路的另外一(yi)個IC（PT8A25 13）則是一(yi)個極簡單(dan)卻極穩定的延(yan)時IC，其(qi)延(yan)時時間(jian)僅(jin)僅(jin)取決(jue)于 OSC腳的頻(pin)率。事實(shi)上(shang)該IC就(jiu)是將OSC震蕩(dang)頻(pin)率進(jin)行32768次(ci)分頻(pin)后(hou)用(yong)來控制輸出的。之所以采(cai)用(yong)這個電路而不采(cai)用(yong)LM555或者CD4060等通用(yong)IC的原因就(jiu)是因為它相對而言定時精度更高（其(qi)它IC不分頻(pin)），定時時間(jian)更長（可達數(shu)小時）。并且電路更加簡單(dan)，采(cai)用(yong)TO-94或SOT-23-4封(feng)裝，就(jiu)像(xiang)一(yi)個三極管一(yi)樣。而價錢也(ye)跟CD4060差(cha)不多，使用(yong)效果可就(jiu)好的太多了。

至(zhi)此大家(jia)想必(bi)也(ye)(ye)大致(zhi)了(le)解了(le)圖三的(de)(de)(de)(de)工(gong)作(zuo)流(liu)程(cheng)了(le)：接上(shang)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)和(he)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)器，如果電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)壓低(di)于2.8V，則(ze)U1輸出(chu)(chu)(chu)為(wei)低(di)（U2輸出(chu)(chu)(chu)也(ye)(ye)是低(di)），這(zhe)(zhe)樣R3和(he)R4的(de)(de)(de)(de)回路都不通(tong)(tong)(tong)，只有R2回路導(dao)通(tong)(tong)(tong)，給Q1提(ti)供(gong)微(wei)弱(ruo)的(de)(de)(de)(de)導(dao)通(tong)(tong)(tong)，使之輸出(chu)(chu)(chu)約數(shu)毫安的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)流(liu)給電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)進行預充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)，當電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)壓上(shang)升到(dao)(dao)超過2.94V（1.05X2.8）時或者剛(gang)接上(shang)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)壓就超過2.94V時，U1輸出(chu)(chu)(chu)高電(dian)(dian)(dian)(dian)(dian)平(ping)(ping)而(er)(er)(er)U2繼續輸出(chu)(chu)(chu)低(di)電(dian)(dian)(dian)(dian)(dian)平(ping)(ping)（電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)壓還沒達到(dao)(dao)4.2V J），這(zhe)(zhe)時R2通(tong)(tong)(tong)路截止而(er)(er)(er)R3通(tong)(tong)(tong)路導(dao)通(tong)(tong)(tong)（因為(wei)Q4導(dao)通(tong)(tong)(tong)且其(qi)源極電(dian)(dian)(dian)(dian)(dian)平(ping)(ping)為(wei)低(di)-因U1輸出(chu)(chu)(chu)拉(la)低(di)），從(cong)而(er)(er)(er)由較(jiao)小阻(zu)值的(de)(de)(de)(de)R3令Q1完全(quan)導(dao)通(tong)(tong)(tong)，提(ti)供(gong)一個數(shu)百毫安的(de)(de)(de)(de)大電(dian)(dian)(dian)(dian)(dian)流(liu)恒流(liu)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)，而(er)(er)(er)當這(zhe)(zhe)個恒流(liu)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)過程(cheng)慢慢令到(dao)(dao)被充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)(de)Li+電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)端電(dian)(dian)(dian)(dian)(dian)壓上(shang)升到(dao)(dao)4.2V時，U2也(ye)(ye)輸出(chu)(chu)(chu)高電(dian)(dian)(dian)(dian)(dian)平(ping)(ping)從(cong)而(er)(er)(er)關閉Q4,但是它同時也(ye)(ye)給U3提(ti)供(gong)了(le)電(dian)(dian)(dian)(dian)(dian)源導(dao)致(zhi)U3開始工(gong)作(zuo)，這(zhe)(zhe)樣U3觸(chu)發Q3使R4導(dao)通(tong)(tong)(tong)提(ti)供(gong)一個很小的(de)(de)(de)(de)補充(chong)(chong)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)，直至(zhi)U3達到(dao)(dao)定時時間從(cong)而(er)(er)(er)關閉Q3，這(zhe)(zhe)時整個充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)過程(cheng)才完全(quan)結束。

相比(bi)而言，第二個(ge)(ge)方案增加了(le)前期智能判(pan)斷電池狀(zhuang)態和自動(dong)預充(chong)電過(guo)程，以及延長了(le)末尾的(de)補充(chong)充(chong)電過(guo)程的(de)時(shi)(shi)間(jian)，各(ge)個(ge)(ge)階段的(de)充(chong)電電流可調(diao)并(bing)且補充(chong)充(chong)電時(shi)(shi)間(jian)可調(diao)（數分(fen)鐘(zhong)至數小(xiao)時(shi)(shi)），因此該方案對鋰電池充(chong)電具有(you)更(geng)好(hao)的(de)精(jing)確性和安全性，加上價錢便宜，功能也比(bi)較完(wan)善(shan)，相信很快會取代市面中低檔的(de)充(chong)電器(qi)特(te)別是那些(xie)廉(lian)價的(de)手機電池充(chong)電器(qi)。