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)來越(yue)普遍，而(er)配用(yong)(yong)的(de)充(chong)電(dian)(dian)器(qi)無(wu)論是市售(shou)的(de)15元(yuan)手機充(chong)電(dian)(dian)器(qi)還是較高(gao)檔的(de)DC/DV兼容充(chong)電(dian)(dian)器(qi)，絕大部分是采用(yong)(yong)LM324組成(cheng)的(de)充(chong)電(dian)(dian)電(dian)(dian)壓檢測和控制(zhi)線(xian)路，這(zhe)些線(xian)路無(wu)論從控制(zhi)精度還是功(gong)能(neng)方面都(dou)不能(neng)滿(man)足鋰(li)電(dian)(dian)池(chi)充(chong)電(dian)(dian)特(te)性的(de)要求(qiu)，直接(jie)導致(zhi)電(dian)(dian)池(chi)充(chong)不滿(man)，電(dian)(dian)池(chi)壽命減短以及(ji)越(yue)來越(yue)多的(de)電(dian)(dian)池(chi)損壞、爆炸等案例發(fa)生(sheng)。而(er)如果采用(yong)(yong)國外專用(yong)(yong)IC來設計，則(ze)其極其高(gao)昂的(de)成(cheng)本實在令(ling)人無(wu)法接(jie)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，在大致(zhi)相當的總體成本(ben)下提供了遠遠超過(guo)LM324方案(an)的性能，具(ju)有極高的新穎性和市場前景。

PT7M7433T是上海(hai)百利(li)通公司最(zui)新設計的(de)(de)極高(gao)精度的(de)(de)一(yi)系列電(dian)(dian)(dian)(dian)壓檢測(ce)器的(de)(de)其中一(yi)款(kuan)，其檢測(ce)精度在0-Vcc （5.5V）范(fan)圍內小于(yu)1mV，而(er)且其批量IC的(de)(de)檢測(ce)值偏差<±2.5%，這樣完全保證了批量產品(pin)的(de)(de)性(xing)(xing)能一(yi)致性(xing)(xing)和極高(gao)的(de)(de)總體性(xing)(xing)能，我們利(li)用(yong)其配合少量外部電(dian)(dian)(dian)(dian)路(lu)即(ji)可組成相當簡(jian)單的(de)(de)鋰電(dian)(dian)(dian)(dian)池充電(dian)(dian)(dian)(dian)線路(lu)。

該IC的內部框圖(tu)和簡單介紹如下：（圖(tu)一）

IC內含(han)一個(ge)高精度的615mV基準電(dian)(dian)(dian)壓(ya)源(yuan)、兩個(ge)比較器(qi)、一個(ge)RS觸(chu)發(fa)器(qi)和其(qi)它一些邏輯電(dian)(dian)(dian)路，其(qi)大致功能是：VCC電(dian)(dian)(dian)壓(ya)或其(qi)它待檢測(ce)電(dian)(dian)(dian)壓(ya)通(tong)過(guo)R1-R3組成的分壓(ya)網絡接(jie)在(zai)IC的LTHIN /HTHIN檢測(ce)引(yin)(yin)腳，當(dang)待測(ce)電(dian)(dian)(dian)壓(ya)下(xia)降導致LTHIN引(yin)(yin)腳低于615mV時，輸(shu)出(chu)腳LBO輸(shu)出(chu)低電(dian)(dian)(dian)平(ping)，而如果待測(ce)電(dian)(dian)(dian)壓(ya)上(shang)升導致HTHIN引(yin)(yin)腳高于615 mV時，經過(guo)內部邏輯判(pan)斷和簡單延時后，輸(shu)出(chu)腳LBO輸(shu)出(chu)高電(dian)(dian)(dian)平(ping)。

利(li)用這個IC裝制的充電器電路如下(xia)（圖二）

其工作流程大(da)致(zhi)是：當接上Li+電(dian)(dian)(dian)(dian)(dian)(dian)池和供電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)源時(shi)，IC通(tong)(tong)(tong)過R1/R2/R3組成(cheng)的(de)網絡檢測電(dian)(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)(dian)壓，如果(guo)電(dian)(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)(dian)壓低(di)于(yu)3.3V（由R1-R3的(de)電(dian)(dian)(dian)(dian)(dian)(dian)阻值決(jue)定），或者按(an)下按(an)制(zhi)SW1，此(ci)時(shi)IC3腳的(de)電(dian)(dian)(dian)(dian)(dian)(dian)壓低(di)于(yu)615mV，則IC4腳輸(shu)出低(di)電(dian)(dian)(dian)(dian)(dian)(dian)平，通(tong)(tong)(tong)過R5/D2拉低(di)Q1的(de)柵(zha)(zha)極(ji)使(shi)(shi)之(zhi)導(dao)(dao)通(tong)(tong)(tong)，從而(er)通(tong)(tong)(tong)過Q1/R9/D1給(gei)電(dian)(dian)(dian)(dian)(dian)(dian)池進(jin)行大(da)電(dian)(dian)(dian)(dian)(dian)(dian)流充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)，當電(dian)(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)(dian)壓一路(lu)(lu)上升(sheng)(sheng)直至(zhi)超過4.20V,此(ci)時(shi)IC的(de)1腳電(dian)(dian)(dian)(dian)(dian)(dian)壓高過615mV,IC內部經簡單判斷(duan)和延時(shi)，令4腳輸(shu)出高電(dian)(dian)(dian)(dian)(dian)(dian)平，從而(er)關(guan)閉大(da)電(dian)(dian)(dian)(dian)(dian)(dian)流充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)通(tong)(tong)(tong)道，但是4腳的(de)高電(dian)(dian)(dian)(dian)(dian)(dian)平同時(shi)給(gei)R7/C2的(de)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)回路(lu)(lu)供電(dian)(dian)(dian)(dian)(dian)(dian)，令到Q3的(de)柵(zha)(zha)極(ji)電(dian)(dian)(dian)(dian)(dian)(dian)壓慢(man)慢(man)升(sheng)(sheng)高，并給(gei)R8提(ti)供通(tong)(tong)(tong)路(lu)(lu)導(dao)(dao)致(zhi)Q2導(dao)(dao)通(tong)(tong)(tong)，通(tong)(tong)(tong)過R10給(gei)Q1提(ti)供一個較弱的(de)導(dao)(dao)通(tong)(tong)(tong)電(dian)(dian)(dian)(dian)(dian)(dian)流，使(shi)(shi)之(zhi)微(wei)微(wei)導(dao)(dao)通(tong)(tong)(tong)，從而(er)為(wei)電(dian)(dian)(dian)(dian)(dian)(dian)池提(ti)供一個較少的(de)補充(chong)(chong)(chong)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流。按(an)照(zhao)圖中所(suo)示元件參數將(jiang)于(yu)大(da)約十分(fen)鐘(zhong)后，由于(yu)C2的(de)不斷(duan)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)，其端(duan)電(dian)(dian)(dian)(dian)(dian)(dian)壓即(ji)Q3的(de)柵(zha)(zha)極(ji)電(dian)(dian)(dian)(dian)(dian)(dian)壓不斷(duan)上升(sheng)(sheng)直至(zhi)使(shi)(shi)Q3導(dao)(dao)通(tong)(tong)(tong)，從而(er)關(guan)閉Q2，令到整(zheng)個充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)過程結束(shu)。

上(shang)面的(de)(de)方(fang)案(an)還存在一(yi)(yi)(yi)些不(bu)足之處(chu)，例如檢測精度(du)由(you)外接電(dian)(dian)(dian)阻R1/R2/R3的(de)(de)精度(du)決定，對(dui)于(yu)過(guo)放電(dian)(dian)(dian)的(de)(de)電(dian)(dian)(dian)池(chi)（電(dian)(dian)(dian)池(chi)端電(dian)(dian)(dian)壓(ya)低于(yu)2.8V）沒有一(yi)(yi)(yi)個小電(dian)(dian)(dian)流預充(chong)的(de)(de)過(guo)程，另(ling)外該方(fang)案(an)的(de)(de)10分鐘補充(chong)充(chong)電(dian)(dian)(dian)時間對(dui)于(yu)較(jiao)大容(rong)量的(de)(de)電(dian)(dian)(dian)池(chi)來說不(bu)是太足夠，因此針(zhen)對(dui)上(shang)述不(bu)足之處(chu)，我們還提供一(yi)(yi)(yi)個成本稍高一(yi)(yi)(yi)點，性能(neng)更加完(wan)善的(de)(de)方(fang)案(an)：（圖(tu)三）

乍看之下，這個方案采用了三個IC，可是(shi)U1和U2是(shi)采用的(de)SOT-23或(huo)者(zhe)TO-92封裝，就好像(xiang)普通三極(ji)管一樣，其價(jia)(jia)(jia)格(ge)也(ye)就是(shi)2-3個三極(ji)管的(de)價(jia)(jia)(jia)格(ge)，而(er)U3（PT8A2513NE）也(ye)是(shi)采用的(de)TO-94封裝，外形和三極(ji)管很(hen)相似，價(jia)(jia)(jia)錢也(ye)相當便(bian)宜，不過，這個電路可以實現智(zhi)能(neng)判斷電池是(shi)否過放電，決定是(shi)否在開始充(chong)(chong)電時采用小(xiao)(xiao)電流預充(chong)(chong)，另外，采用U3后也(ye)將充(chong)(chong)電后期的(de)補充(chong)(chong)充(chong)(chong)電過程(cheng)延長到大約一個小(xiao)(xiao)時！

首先讓我們(men)介紹一下該(gai)電路中幾個IC的功能：

（圖四(si)）是U1/U2的(de)內部框圖，這兩個IC只(zhi)是內部電阻(zu)R1/R2的(de)數值(zhi)(zhi)不(bu)同(tong)而(er)已，它(ta)們的(de)功(gong)能也很簡單(dan)：當Vcc低于(yu)IC的(de)設定(ding)值(zhi)(zhi)時(shi)（根據IC編號不(bu)同(tong)，內部R3/R4阻(zu)值(zhi)(zhi)也不(bu)同(tong)從而(er)導致(zhi)檢測電壓值(zhi)(zhi)不(bu)同(tong)，對(dui)于(yu)PT7M6128指的(de)是2.80V），RST引(yin)(yin)腳(jiao)輸出低電平(ping)，反(fan)之當Vcc 高(gao)于(yu)1.05倍(bei)標稱值(zhi)(zhi)時(shi)（例(li)如對(dui)于(yu)PT7M6140，此數值(zhi)(zhi)為1.05x4.0 =4.20V）則(ze)RST引(yin)(yin)腳(jiao)輸出高(gao)電平(ping)。

上(shang)面(mian)電(dian)路的(de)(de)另外(wai)一(yi)(yi)個IC（PT8A25 13）則是(shi)一(yi)(yi)個極簡(jian)單卻極穩定的(de)(de)延時(shi)IC，其延時(shi)時(shi)間僅(jin)僅(jin)取(qu)決(jue)于 OSC腳的(de)(de)頻(pin)(pin)(pin)率。事實上(shang)該IC就是(shi)將OSC震蕩頻(pin)(pin)(pin)率進行32768次分(fen)頻(pin)(pin)(pin)后(hou)用(yong)(yong)來(lai)控制輸出(chu)的(de)(de)。之所以采用(yong)(yong)這(zhe)個電(dian)路而(er)不(bu)采用(yong)(yong)LM555或(huo)者CD4060等通用(yong)(yong)IC的(de)(de)原因就是(shi)因為它相對而(er)言定時(shi)精度更(geng)(geng)高（其它IC不(bu)分(fen)頻(pin)(pin)(pin)），定時(shi)時(shi)間更(geng)(geng)長（可達數小(xiao)時(shi)）。并且電(dian)路更(geng)(geng)加簡(jian)單，采用(yong)(yong)TO-94或(huo)SOT-23-4封裝(zhuang)，就像一(yi)(yi)個三(san)極管一(yi)(yi)樣。而(er)價錢也(ye)跟CD4060差不(bu)多(duo)，使(shi)用(yong)(yong)效果可就好的(de)(de)太多(duo)了。

至此大家想必也大致了解了圖三的工(gong)作(zuo)流(liu)(liu)程了：接(jie)上電(dian)(dian)(dian)(dian)池(chi)和充電(dian)(dian)(dian)(dian)器(qi)，如(ru)果電(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)壓低(di)(di)(di)于(yu)2.8V，則U1輸(shu)(shu)(shu)出(chu)為低(di)(di)(di)（U2輸(shu)(shu)(shu)出(chu)也是低(di)(di)(di)），這樣R3和R4的回(hui)路都不通(tong)(tong)，只有R2回(hui)路導(dao)(dao)通(tong)(tong)，給Q1提(ti)供(gong)(gong)微弱的導(dao)(dao)通(tong)(tong)，使之輸(shu)(shu)(shu)出(chu)約數毫(hao)安(an)的電(dian)(dian)(dian)(dian)流(liu)(liu)給電(dian)(dian)(dian)(dian)池(chi)進行預充電(dian)(dian)(dian)(dian)，當電(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)壓上升(sheng)到超(chao)過(guo)2.94V（1.05X2.8）時(shi)或者(zhe)剛接(jie)上電(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)壓就超(chao)過(guo)2.94V時(shi)，U1輸(shu)(shu)(shu)出(chu)高電(dian)(dian)(dian)(dian)平(ping)而(er)(er)U2繼續輸(shu)(shu)(shu)出(chu)低(di)(di)(di)電(dian)(dian)(dian)(dian)平(ping)（電(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)壓還沒達到4.2V J），這時(shi)R2通(tong)(tong)路截止而(er)(er)R3通(tong)(tong)路導(dao)(dao)通(tong)(tong)（因(yin)為Q4導(dao)(dao)通(tong)(tong)且(qie)其源(yuan)極電(dian)(dian)(dian)(dian)平(ping)為低(di)(di)(di)-因(yin)U1輸(shu)(shu)(shu)出(chu)拉(la)低(di)(di)(di)），從(cong)而(er)(er)由較小(xiao)(xiao)阻值的R3令Q1完全導(dao)(dao)通(tong)(tong)，提(ti)供(gong)(gong)一個數百(bai)毫(hao)安(an)的大電(dian)(dian)(dian)(dian)流(liu)(liu)恒流(liu)(liu)充電(dian)(dian)(dian)(dian)，而(er)(er)當這個恒流(liu)(liu)充電(dian)(dian)(dian)(dian)過(guo)程慢(man)慢(man)令到被充電(dian)(dian)(dian)(dian)的Li+電(dian)(dian)(dian)(dian)池(chi)端電(dian)(dian)(dian)(dian)壓上升(sheng)到4.2V時(shi)，U2也輸(shu)(shu)(shu)出(chu)高電(dian)(dian)(dian)(dian)平(ping)從(cong)而(er)(er)關閉Q4,但是它同時(shi)也給U3提(ti)供(gong)(gong)了電(dian)(dian)(dian)(dian)源(yuan)導(dao)(dao)致U3開始工(gong)作(zuo)，這樣U3觸發Q3使R4導(dao)(dao)通(tong)(tong)提(ti)供(gong)(gong)一個很小(xiao)(xiao)的補充充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)，直至U3達到定時(shi)時(shi)間(jian)從(cong)而(er)(er)關閉Q3，這時(shi)整個充電(dian)(dian)(dian)(dian)過(guo)程才完全結束。

相比而言，第二個(ge)方案(an)增加了前期智(zhi)能判斷電池(chi)(chi)狀(zhuang)態和自動(dong)預充(chong)(chong)(chong)電過程，以及延長了末尾的(de)(de)補充(chong)(chong)(chong)充(chong)(chong)(chong)電過程的(de)(de)時(shi)(shi)間，各個(ge)階段的(de)(de)充(chong)(chong)(chong)電電流可調并且(qie)補充(chong)(chong)(chong)充(chong)(chong)(chong)電時(shi)(shi)間可調（數(shu)分鐘至數(shu)小時(shi)(shi)），因此該方案(an)對(dui)鋰電池(chi)(chi)充(chong)(chong)(chong)電具(ju)有更好的(de)(de)精確性和安全性，加上(shang)價(jia)錢便宜，功能也比較完(wan)善，相信很快會取代市面(mian)中(zhong)低檔(dang)的(de)(de)充(chong)(chong)(chong)電器(qi)特(te)別是那些(xie)廉(lian)價(jia)的(de)(de)手機電池(chi)(chi)充(chong)(chong)(chong)電器(qi)。