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）和鋰離子電池使用越來越普遍，而(er)配用的(de)(de)充(chong)電(dian)(dian)器無(wu)論是(shi)市售(shou)的(de)(de)15元手機充(chong)電(dian)(dian)器還(huan)是(shi)較高檔的(de)(de)DC/DV兼容(rong)充(chong)電(dian)(dian)器，絕大部分是(shi)采用LM324組成(cheng)的(de)(de)充(chong)電(dian)(dian)電(dian)(dian)壓檢測和控(kong)制線路，這些線路無(wu)論從(cong)控(kong)制精度還(huan)是(shi)功能(neng)(neng)方面都不能(neng)(neng)滿足鋰電(dian)(dian)池充(chong)電(dian)(dian)特性的(de)(de)要求，直接導致電(dian)(dian)池充(chong)不滿，電(dian)(dian)池壽命減短以及越來越多的(de)(de)電(dian)(dian)池損壞(huai)、爆炸(zha)等案(an)例發(fa)生(sheng)。而(er)如果采用國外專用IC來設計，則其(qi)極其(qi)高昂的(de)(de)成(cheng)本實在令人無(wu)法(fa)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(da)致相當的(de)總體成本下提供了遠遠超過LM324方案的(de)性(xing)能，具有極高的(de)新穎性(xing)和(he)市場前景。

PT7M7433T是上海百利通公司最新設計的(de)極(ji)高精(jing)度(du)的(de)一(yi)(yi)系列電壓檢測器的(de)其(qi)中一(yi)(yi)款，其(qi)檢測精(jing)度(du)在0-Vcc （5.5V）范(fan)圍內小于1mV，而且其(qi)批量(liang)IC的(de)檢測值偏差<±2.5%，這(zhe)樣完全保證了批量(liang)產品的(de)性能(neng)(neng)一(yi)(yi)致性和極(ji)高的(de)總體性能(neng)(neng)，我(wo)們利用其(qi)配合(he)少(shao)量(liang)外部(bu)電路即可組(zu)成相當簡(jian)單的(de)鋰電池(chi)充電線路。

該IC的內部(bu)框圖和簡(jian)單介紹如下：（圖一(yi)）

IC內含一(yi)個高(gao)精度的615mV基準電(dian)壓(ya)(ya)源(yuan)、兩個比較器、一(yi)個RS觸(chu)發(fa)器和(he)其(qi)它(ta)一(yi)些邏輯電(dian)路，其(qi)大致功能是(shi)：VCC電(dian)壓(ya)(ya)或(huo)其(qi)它(ta)待檢測(ce)電(dian)壓(ya)(ya)通過(guo)R1-R3組成的分壓(ya)(ya)網絡(luo)接在IC的LTHIN /HTHIN檢測(ce)引腳(jiao)(jiao)(jiao)，當待測(ce)電(dian)壓(ya)(ya)下(xia)降導(dao)致LTHIN引腳(jiao)(jiao)(jiao)低于615mV時(shi)，輸(shu)出(chu)腳(jiao)(jiao)(jiao)LBO輸(shu)出(chu)低電(dian)平(ping)，而(er)如果待測(ce)電(dian)壓(ya)(ya)上升導(dao)致HTHIN引腳(jiao)(jiao)(jiao)高(gao)于615 mV時(shi)，經(jing)過(guo)內部(bu)邏輯判斷(duan)和(he)簡(jian)單延(yan)時(shi)后，輸(shu)出(chu)腳(jiao)(jiao)(jiao)LBO輸(shu)出(chu)高(gao)電(dian)平(ping)。

利用這個(ge)IC裝(zhuang)制(zhi)的充(chong)電(dian)器電(dian)路如下(xia)（圖二）

其工作(zuo)流(liu)(liu)(liu)程大(da)致是(shi)：當(dang)接(jie)上(shang)Li+電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)和供(gong)(gong)(gong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)時，IC通(tong)(tong)過(guo)(guo)(guo)R1/R2/R3組成的(de)(de)網絡檢測電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)，如果(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)低(di)于3.3V（由R1-R3的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻值決定），或者按(an)下按(an)制SW1，此時IC3腳的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)低(di)于615mV，則IC4腳輸出(chu)(chu)低(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平，通(tong)(tong)過(guo)(guo)(guo)R5/D2拉低(di)Q1的(de)(de)柵極(ji)(ji)使(shi)之導(dao)通(tong)(tong)，從而(er)通(tong)(tong)過(guo)(guo)(guo)Q1/R9/D1給電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)進行大(da)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，當(dang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)一路上(shang)升直(zhi)至(zhi)(zhi)超過(guo)(guo)(guo)4.20V,此時IC的(de)(de)1腳電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)高(gao)過(guo)(guo)(guo)615mV,IC內部經簡單判斷和延時，令4腳輸出(chu)(chu)高(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平，從而(er)關(guan)閉大(da)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)通(tong)(tong)道(dao)，但是(shi)4腳的(de)(de)高(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平同時給R7/C2的(de)(de)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)回路供(gong)(gong)(gong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，令到(dao)Q3的(de)(de)柵極(ji)(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)慢(man)慢(man)升高(gao)，并給R8提供(gong)(gong)(gong)通(tong)(tong)路導(dao)致Q2導(dao)通(tong)(tong)，通(tong)(tong)過(guo)(guo)(guo)R10給Q1提供(gong)(gong)(gong)一個較弱的(de)(de)導(dao)通(tong)(tong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)，使(shi)之微(wei)微(wei)導(dao)通(tong)(tong)，從而(er)為電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)提供(gong)(gong)(gong)一個較少(shao)的(de)(de)補(bu)充(chong)(chong)(chong)(chong)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)。按(an)照圖(tu)中所示元件(jian)參數將于大(da)約十分鐘后，由于C2的(de)(de)不斷充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，其端電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)即Q3的(de)(de)柵極(ji)(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)不斷上(shang)升直(zhi)至(zhi)(zhi)使(shi)Q3導(dao)通(tong)(tong)，從而(er)關(guan)閉Q2，令到(dao)整個充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)過(guo)(guo)(guo)程結束。

上(shang)面的方(fang)(fang)(fang)案(an)還存在一些不(bu)足(zu)(zu)之處，例(li)如(ru)檢測精(jing)度由外(wai)接電(dian)阻R1/R2/R3的精(jing)度決定，對(dui)(dui)于過放(fang)電(dian)的電(dian)池(chi)（電(dian)池(chi)端電(dian)壓低于2.8V）沒有一個小電(dian)流預充的過程，另外(wai)該方(fang)(fang)(fang)案(an)的10分鐘補充充電(dian)時間對(dui)(dui)于較大容量的電(dian)池(chi)來說不(bu)是太(tai)足(zu)(zu)夠(gou)，因(yin)此針對(dui)(dui)上(shang)述不(bu)足(zu)(zu)之處，我們還提(ti)供一個成本稍高一點，性能更加(jia)完(wan)善的方(fang)(fang)(fang)案(an)：（圖三）

乍看之下，這個(ge)(ge)(ge)方案采(cai)用(yong)(yong)了三個(ge)(ge)(ge)IC，可是U1和U2是采(cai)用(yong)(yong)的(de)(de)SOT-23或者TO-92封裝(zhuang)，就好(hao)像普通(tong)三極管一(yi)(yi)樣，其價格也就是2-3個(ge)(ge)(ge)三極管的(de)(de)價格，而U3（PT8A2513NE）也是采(cai)用(yong)(yong)的(de)(de)TO-94封裝(zhuang)，外(wai)形和三極管很相似(si)，價錢(qian)也相當(dang)便宜，不過，這個(ge)(ge)(ge)電(dian)路(lu)可以實現智能判斷電(dian)池是否過放電(dian)，決定是否在(zai)開始充(chong)電(dian)時(shi)(shi)采(cai)用(yong)(yong)小電(dian)流預充(chong)，另(ling)外(wai)，采(cai)用(yong)(yong)U3后(hou)也將(jiang)充(chong)電(dian)后(hou)期的(de)(de)補充(chong)充(chong)電(dian)過程延長(chang)到大約一(yi)(yi)個(ge)(ge)(ge)小時(shi)(shi)！

首先讓我(wo)們介紹一下該電路中(zhong)幾個(ge)IC的功能：

（圖四）是(shi)(shi)U1/U2的(de)內部框圖，這(zhe)兩個IC只是(shi)(shi)內部電阻R1/R2的(de)數(shu)值(zhi)不(bu)(bu)(bu)同而已，它們的(de)功能也很簡(jian)單：當Vcc低(di)于(yu)(yu)IC的(de)設定值(zhi)時（根(gen)據IC編號不(bu)(bu)(bu)同，內部R3/R4阻值(zhi)也不(bu)(bu)(bu)同從(cong)而導致檢測電壓值(zhi)不(bu)(bu)(bu)同，對于(yu)(yu)PT7M6128指的(de)是(shi)(shi)2.80V），RST引腳輸(shu)出(chu)低(di)電平，反之當Vcc 高(gao)于(yu)(yu)1.05倍(bei)標稱值(zhi)時（例(li)如對于(yu)(yu)PT7M6140，此數(shu)值(zhi)為(wei)1.05x4.0 =4.20V）則RST引腳輸(shu)出(chu)高(gao)電平。

上(shang)面(mian)電(dian)(dian)路(lu)的(de)(de)(de)另外(wai)一(yi)個IC（PT8A25 13）則是(shi)一(yi)個極簡單卻極穩(wen)定(ding)的(de)(de)(de)延(yan)時(shi)IC，其(qi)延(yan)時(shi)時(shi)間(jian)(jian)僅僅取決于(yu) OSC腳的(de)(de)(de)頻率(lv)。事實上(shang)該IC就(jiu)(jiu)是(shi)將OSC震蕩頻率(lv)進(jin)行32768次分頻后用(yong)來控制輸出(chu)的(de)(de)(de)。之(zhi)所以采用(yong)這個電(dian)(dian)路(lu)而不(bu)采用(yong)LM555或者CD4060等通用(yong)IC的(de)(de)(de)原因就(jiu)(jiu)是(shi)因為它相對而言(yan)定(ding)時(shi)精度更高（其(qi)它IC不(bu)分頻），定(ding)時(shi)時(shi)間(jian)(jian)更長（可達(da)數(shu)小時(shi)）。并且電(dian)(dian)路(lu)更加簡單，采用(yong)TO-94或SOT-23-4封裝，就(jiu)(jiu)像一(yi)個三(san)極管一(yi)樣。而價錢也跟CD4060差不(bu)多(duo)，使用(yong)效果可就(jiu)(jiu)好的(de)(de)(de)太多(duo)了。

至(zhi)此大(da)家想必也(ye)大(da)致(zhi)了(le)解了(le)圖三的工作流程了(le)：接上(shang)電(dian)(dian)(dian)池(chi)和充(chong)電(dian)(dian)(dian)器，如果電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)壓(ya)低(di)(di)于(yu)2.8V，則U1輸(shu)出(chu)為(wei)低(di)(di)（U2輸(shu)出(chu)也(ye)是低(di)(di)），這(zhe)(zhe)樣R3和R4的回路都不通(tong)，只有R2回路導(dao)(dao)通(tong)，給Q1提供(gong)微弱的導(dao)(dao)通(tong)，使(shi)之輸(shu)出(chu)約數(shu)毫(hao)安的電(dian)(dian)(dian)流給電(dian)(dian)(dian)池(chi)進行預充(chong)電(dian)(dian)(dian)，當電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)壓(ya)上(shang)升(sheng)到(dao)超(chao)過2.94V（1.05X2.8）時(shi)(shi)或者剛接上(shang)電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)壓(ya)就(jiu)超(chao)過2.94V時(shi)(shi)，U1輸(shu)出(chu)高電(dian)(dian)(dian)平(ping)(ping)而(er)(er)(er)U2繼續輸(shu)出(chu)低(di)(di)電(dian)(dian)(dian)平(ping)(ping)（電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)壓(ya)還沒達到(dao)4.2V J），這(zhe)(zhe)時(shi)(shi)R2通(tong)路截(jie)止而(er)(er)(er)R3通(tong)路導(dao)(dao)通(tong)（因為(wei)Q4導(dao)(dao)通(tong)且其源極(ji)電(dian)(dian)(dian)平(ping)(ping)為(wei)低(di)(di)-因U1輸(shu)出(chu)拉低(di)(di)），從而(er)(er)(er)由較小阻值的R3令Q1完(wan)全(quan)導(dao)(dao)通(tong)，提供(gong)一個(ge)數(shu)百毫(hao)安的大(da)電(dian)(dian)(dian)流恒(heng)(heng)流充(chong)電(dian)(dian)(dian)，而(er)(er)(er)當這(zhe)(zhe)個(ge)恒(heng)(heng)流充(chong)電(dian)(dian)(dian)過程慢慢令到(dao)被充(chong)電(dian)(dian)(dian)的Li+電(dian)(dian)(dian)池(chi)端電(dian)(dian)(dian)壓(ya)上(shang)升(sheng)到(dao)4.2V時(shi)(shi)，U2也(ye)輸(shu)出(chu)高電(dian)(dian)(dian)平(ping)(ping)從而(er)(er)(er)關(guan)閉Q4,但是它同(tong)時(shi)(shi)也(ye)給U3提供(gong)了(le)電(dian)(dian)(dian)源導(dao)(dao)致(zhi)U3開始(shi)工作，這(zhe)(zhe)樣U3觸發Q3使(shi)R4導(dao)(dao)通(tong)提供(gong)一個(ge)很小的補充(chong)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流，直至(zhi)U3達到(dao)定時(shi)(shi)時(shi)(shi)間從而(er)(er)(er)關(guan)閉Q3，這(zhe)(zhe)時(shi)(shi)整個(ge)充(chong)電(dian)(dian)(dian)過程才完(wan)全(quan)結束。

相(xiang)比(bi)而言(yan)，第二個方案(an)增加了前期智(zhi)能判斷電(dian)(dian)(dian)(dian)池狀(zhuang)態和自動預充(chong)(chong)電(dian)(dian)(dian)(dian)過程，以及延長了末(mo)尾的(de)(de)補充(chong)(chong)充(chong)(chong)電(dian)(dian)(dian)(dian)過程的(de)(de)時間，各個階段的(de)(de)充(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流可調并且補充(chong)(chong)充(chong)(chong)電(dian)(dian)(dian)(dian)時間可調（數分(fen)鐘至數小時），因此(ci)該方案(an)對鋰電(dian)(dian)(dian)(dian)池充(chong)(chong)電(dian)(dian)(dian)(dian)具有更(geng)好的(de)(de)精確性和安全性，加上價(jia)錢(qian)便宜，功(gong)能也比(bi)較完善，相(xiang)信很快會取代市面中低檔的(de)(de)充(chong)(chong)電(dian)(dian)(dian)(dian)器特別是那(nei)些廉價(jia)的(de)(de)手機電(dian)(dian)(dian)(dian)池充(chong)(chong)電(dian)(dian)(dian)(dian)器。