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(lai)越普遍，而(er)配用(yong)的(de)充(chong)(chong)電(dian)(dian)器無論是(shi)市售的(de)15元手機充(chong)(chong)電(dian)(dian)器還是(shi)較高檔的(de)DC/DV兼容充(chong)(chong)電(dian)(dian)器，絕大部分是(shi)采用(yong)LM324組成的(de)充(chong)(chong)電(dian)(dian)電(dian)(dian)壓檢測(ce)和(he)控制(zhi)線路，這些線路無論從(cong)控制(zhi)精度還是(shi)功能方面(mian)都(dou)不能滿(man)足鋰電(dian)(dian)池充(chong)(chong)電(dian)(dian)特性的(de)要求，直接(jie)(jie)導致電(dian)(dian)池充(chong)(chong)不滿(man)，電(dian)(dian)池壽(shou)命(ming)減短以(yi)及越來(lai)越多的(de)電(dian)(dian)池損壞(huai)、爆炸等案(an)例發生(sheng)。而(er)如果采用(yong)國外專用(yong)IC來(lai)設計，則其極其高昂(ang)的(de)成本(ben)實在令人(ren)無法接(jie)(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，在大致相當的總體成本(ben)下提(ti)供了遠遠超過(guo)LM324方案的性(xing)能，具有極高(gao)的新穎性(xing)和市場前景(jing)。

PT7M7433T是上海百利通公司最新設計的(de)(de)(de)(de)極高精(jing)(jing)度的(de)(de)(de)(de)一系列(lie)電(dian)壓檢測器的(de)(de)(de)(de)其(qi)中一款，其(qi)檢測精(jing)(jing)度在0-Vcc （5.5V）范圍(wei)內小于1mV，而且(qie)其(qi)批量IC的(de)(de)(de)(de)檢測值偏差<±2.5%，這(zhe)樣(yang)完全保(bao)證了批量產品的(de)(de)(de)(de)性能一致(zhi)性和極高的(de)(de)(de)(de)總體性能，我們利用(yong)其(qi)配(pei)合少量外部(bu)電(dian)路(lu)即可組成(cheng)相當(dang)簡單的(de)(de)(de)(de)鋰電(dian)池(chi)充(chong)電(dian)線路(lu)。

該IC的內部框圖和(he)簡單介紹如下(xia)：（圖一）

IC內含一個(ge)高(gao)精(jing)度的615mV基準電(dian)壓源、兩(liang)個(ge)比較器、一個(ge)RS觸發器和其它(ta)一些(xie)邏輯電(dian)路，其大致(zhi)(zhi)功能是：VCC電(dian)壓或其它(ta)待(dai)檢測電(dian)壓通過R1-R3組成的分壓網絡(luo)接在IC的LTHIN /HTHIN檢測引(yin)腳(jiao)，當(dang)待(dai)測電(dian)壓下(xia)降導致(zhi)(zhi)LTHIN引(yin)腳(jiao)低于(yu)(yu)615mV時，輸(shu)(shu)(shu)出(chu)腳(jiao)LBO輸(shu)(shu)(shu)出(chu)低電(dian)平，而(er)如(ru)果(guo)待(dai)測電(dian)壓上升導致(zhi)(zhi)HTHIN引(yin)腳(jiao)高(gao)于(yu)(yu)615 mV時，經過內部邏輯判斷(duan)和簡單延時后(hou)，輸(shu)(shu)(shu)出(chu)腳(jiao)LBO輸(shu)(shu)(shu)出(chu)高(gao)電(dian)平。

利用這個IC裝制的(de)充電(dian)(dian)器電(dian)(dian)路如(ru)下（圖(tu)二）

其工(gong)作流程大致(zhi)是：當(dang)接上Li+電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)和供電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源時，IC通(tong)(tong)(tong)(tong)過(guo)R1/R2/R3組成的網絡檢測電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)，如果(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)低(di)于(yu)3.3V（由(you)R1-R3的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻值決定），或者按下按制(zhi)SW1，此時IC3腳的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)低(di)于(yu)615mV，則IC4腳輸出低(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)，通(tong)(tong)(tong)(tong)過(guo)R5/D2拉低(di)Q1的柵極使(shi)之導(dao)(dao)通(tong)(tong)(tong)(tong)，從(cong)而通(tong)(tong)(tong)(tong)過(guo)Q1/R9/D1給電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)進行大電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)，當(dang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)一路(lu)上升(sheng)直(zhi)至超過(guo)4.20V,此時IC的1腳電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)高(gao)(gao)(gao)過(guo)615mV,IC內部經簡單(dan)判斷和延(yan)時，令4腳輸出高(gao)(gao)(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)，從(cong)而關閉大電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)通(tong)(tong)(tong)(tong)道，但是4腳的高(gao)(gao)(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)同(tong)時給R7/C2的充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)回路(lu)供電(dian)(dian)(dian)(dian)(dian)(dian)(dian)，令到Q3的柵極電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)慢(man)慢(man)升(sheng)高(gao)(gao)(gao)，并給R8提供通(tong)(tong)(tong)(tong)路(lu)導(dao)(dao)致(zhi)Q2導(dao)(dao)通(tong)(tong)(tong)(tong)，通(tong)(tong)(tong)(tong)過(guo)R10給Q1提供一個較(jiao)(jiao)弱的導(dao)(dao)通(tong)(tong)(tong)(tong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流，使(shi)之微微導(dao)(dao)通(tong)(tong)(tong)(tong)，從(cong)而為電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)提供一個較(jiao)(jiao)少的補充(chong)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流。按照圖(tu)中所示元件參數將于(yu)大約十分鐘后(hou)，由(you)于(yu)C2的不斷充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)，其端電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)即Q3的柵極電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)不斷上升(sheng)直(zhi)至使(shi)Q3導(dao)(dao)通(tong)(tong)(tong)(tong)，從(cong)而關閉Q2，令到整個充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)過(guo)程結束。

上(shang)面的(de)(de)方(fang)案(an)(an)還(huan)存在一些不(bu)足之處，例如檢測精度由外接電(dian)(dian)(dian)阻(zu)R1/R2/R3的(de)(de)精度決定(ding)，對于(yu)過放(fang)電(dian)(dian)(dian)的(de)(de)電(dian)(dian)(dian)池（電(dian)(dian)(dian)池端(duan)電(dian)(dian)(dian)壓低于(yu)2.8V）沒(mei)有一個(ge)小電(dian)(dian)(dian)流預充(chong)的(de)(de)過程，另外該方(fang)案(an)(an)的(de)(de)10分(fen)鐘(zhong)補充(chong)充(chong)電(dian)(dian)(dian)時間對于(yu)較大(da)容量的(de)(de)電(dian)(dian)(dian)池來(lai)說不(bu)是太(tai)足夠，因此針(zhen)對上(shang)述不(bu)足之處，我們還(huan)提供一個(ge)成本稍高一點(dian)，性能更加完善的(de)(de)方(fang)案(an)(an)：（圖三）

乍看之下，這(zhe)個(ge)(ge)方(fang)案采用(yong)(yong)了三(san)個(ge)(ge)IC，可是U1和U2是采用(yong)(yong)的SOT-23或者TO-92封裝，就(jiu)好像(xiang)普通(tong)三(san)極管一樣，其價格也(ye)(ye)就(jiu)是2-3個(ge)(ge)三(san)極管的價格，而U3（PT8A2513NE）也(ye)(ye)是采用(yong)(yong)的TO-94封裝，外形和三(san)極管很相似，價錢也(ye)(ye)相當便宜，不過，這(zhe)個(ge)(ge)電(dian)路可以實現智能判斷電(dian)池是否(fou)過放電(dian)，決定是否(fou)在開始充(chong)電(dian)時采用(yong)(yong)小(xiao)電(dian)流(liu)預充(chong)，另(ling)外，采用(yong)(yong)U3后也(ye)(ye)將(jiang)充(chong)電(dian)后期的補充(chong)充(chong)電(dian)過程延長到大(da)約一個(ge)(ge)小(xiao)時！

首先讓我們介(jie)紹一下(xia)該電路中(zhong)幾個IC的功能：

（圖四）是U1/U2的(de)(de)內部(bu)框圖，這兩個IC只是內部(bu)電阻R1/R2的(de)(de)數值(zhi)不(bu)(bu)同(tong)而已，它們的(de)(de)功能也(ye)很簡(jian)單：當(dang)Vcc低(di)于(yu)IC的(de)(de)設定值(zhi)時（根據IC編號不(bu)(bu)同(tong)，內部(bu)R3/R4阻值(zhi)也(ye)不(bu)(bu)同(tong)從而導致檢測電壓值(zhi)不(bu)(bu)同(tong)，對于(yu)PT7M6128指的(de)(de)是2.80V），RST引腳輸(shu)出低(di)電平，反之(zhi)當(dang)Vcc 高于(yu)1.05倍標稱值(zhi)時（例(li)如對于(yu)PT7M6140，此數值(zhi)為1.05x4.0 =4.20V）則RST引腳輸(shu)出高電平。

上(shang)面電路(lu)的(de)另外一(yi)個IC（PT8A25 13）則是(shi)一(yi)個極(ji)簡單卻極(ji)穩定的(de)延時(shi)IC，其延時(shi)時(shi)間僅僅取決于 OSC腳的(de)頻(pin)(pin)率。事實(shi)上(shang)該IC就(jiu)(jiu)是(shi)將(jiang)OSC震蕩(dang)頻(pin)(pin)率進行32768次分(fen)頻(pin)(pin)后用(yong)(yong)來控制輸出的(de)。之所以采用(yong)(yong)這個電路(lu)而(er)不(bu)采用(yong)(yong)LM555或(huo)者CD4060等通用(yong)(yong)IC的(de)原因就(jiu)(jiu)是(shi)因為它相(xiang)對而(er)言定時(shi)精度更高(gao)（其它IC不(bu)分(fen)頻(pin)(pin)），定時(shi)時(shi)間更長(chang)（可(ke)達(da)數小時(shi)）。并且電路(lu)更加簡單，采用(yong)(yong)TO-94或(huo)SOT-23-4封裝，就(jiu)(jiu)像一(yi)個三極(ji)管一(yi)樣(yang)。而(er)價錢也跟CD4060差不(bu)多(duo)，使用(yong)(yong)效果可(ke)就(jiu)(jiu)好的(de)太多(duo)了。

至此大家(jia)想必也大致了解了圖(tu)三的(de)工作(zuo)流(liu)程了：接(jie)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)壓低(di)于2.8V，則(ze)U1輸(shu)(shu)出(chu)為低(di)（U2輸(shu)(shu)出(chu)也是低(di)），這(zhe)(zhe)樣(yang)R3和(he)R4的(de)回(hui)(hui)路(lu)都不(bu)通(tong)(tong)，只(zhi)有R2回(hui)(hui)路(lu)導(dao)(dao)(dao)通(tong)(tong)，給Q1提(ti)供(gong)(gong)微弱的(de)導(dao)(dao)(dao)通(tong)(tong)，使之輸(shu)(shu)出(chu)約數(shu)毫安的(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)給電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)進行預(yu)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)壓上升到超過2.94V（1.05X2.8）時或者剛接(jie)上電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓就超過2.94V時，U1輸(shu)(shu)出(chu)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)而(er)(er)(er)U2繼續輸(shu)(shu)出(chu)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)壓還沒達到4.2V J），這(zhe)(zhe)時R2通(tong)(tong)路(lu)截止而(er)(er)(er)R3通(tong)(tong)路(lu)導(dao)(dao)(dao)通(tong)(tong)（因為Q4導(dao)(dao)(dao)通(tong)(tong)且其源極電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)為低(di)-因U1輸(shu)(shu)出(chu)拉(la)低(di)），從而(er)(er)(er)由較小阻值的(de)R3令Q1完全導(dao)(dao)(dao)通(tong)(tong)，提(ti)供(gong)(gong)一個數(shu)百毫安的(de)大電(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(er)(er)(er)當這(zhe)(zhe)個恒流(liu)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)過程慢慢令到被(bei)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)Li+電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)端(duan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓上升到4.2V時，U2也輸(shu)(shu)出(chu)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)從而(er)(er)(er)關(guan)閉Q4,但是它同時也給U3提(ti)供(gong)(gong)了電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源導(dao)(dao)(dao)致U3開始工作(zuo)，這(zhe)(zhe)樣(yang)U3觸發Q3使R4導(dao)(dao)(dao)通(tong)(tong)提(ti)供(gong)(gong)一個很(hen)小的(de)補(bu)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U3達到定(ding)時時間從而(er)(er)(er)關(guan)閉Q3，這(zhe)(zhe)時整個充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)過程才完全結束。

相(xiang)比(bi)而言，第二個(ge)方(fang)案增加了前(qian)期智能(neng)判(pan)斷電(dian)(dian)(dian)池(chi)(chi)(chi)狀態和自動預充(chong)電(dian)(dian)(dian)過(guo)程(cheng)，以及延長了末尾的(de)補充(chong)充(chong)電(dian)(dian)(dian)過(guo)程(cheng)的(de)時(shi)間，各個(ge)階段的(de)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流可調(diao)并(bing)且補充(chong)充(chong)電(dian)(dian)(dian)時(shi)間可調(diao)（數分鐘至數小時(shi)），因(yin)此該方(fang)案對鋰電(dian)(dian)(dian)池(chi)(chi)(chi)充(chong)電(dian)(dian)(dian)具有更好的(de)精確性(xing)(xing)和安全(quan)性(xing)(xing)，加上(shang)價錢便宜，功能(neng)也比(bi)較完(wan)善，相(xiang)信很快會取代市面中(zhong)低檔(dang)的(de)充(chong)電(dian)(dian)(dian)器特別是那些廉(lian)價的(de)手機電(dian)(dian)(dian)池(chi)(chi)(chi)充(chong)電(dian)(dian)(dian)器。