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(pu)遍，而(er)配用(yong)(yong)的(de)(de)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)器無論是市售的(de)(de)15元手機充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)器還(huan)是較高檔的(de)(de)DC/DV兼容充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)器，絕大(da)部(bu)分是采(cai)用(yong)(yong)LM324組成(cheng)的(de)(de)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓檢測(ce)和控制線(xian)(xian)路，這些線(xian)(xian)路無論從控制精度還(huan)是功能(neng)方面都不能(neng)滿(man)足鋰電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)特性的(de)(de)要求，直(zhi)接(jie)(jie)導致電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)不滿(man)，電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)壽命(ming)減(jian)短以及(ji)越(yue)來越(yue)多(duo)的(de)(de)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)損壞、爆(bao)炸等案例發生(sheng)。而(er)如果(guo)采(cai)用(yong)(yong)國外專用(yong)(yong)IC來設計(ji)，則其(qi)(qi)極(ji)其(qi)(qi)高昂的(de)(de)成(cheng)本實在(zai)令人無法接(jie)(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，在大致相當的(de)總體成(cheng)本下提供了(le)遠(yuan)遠(yuan)超過(guo)LM324方案(an)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(bai)利通公(gong)司(si)最(zui)新設計的(de)(de)極(ji)高精(jing)度的(de)(de)一系(xi)列電(dian)(dian)壓檢(jian)測器的(de)(de)其(qi)中(zhong)一款(kuan)，其(qi)檢(jian)測精(jing)度在0-Vcc （5.5V）范圍內小于1mV，而且其(qi)批量IC的(de)(de)檢(jian)測值偏差<±2.5%，這樣完全保證了批量產品的(de)(de)性能一致(zhi)性和極(ji)高的(de)(de)總體性能，我們利用其(qi)配合少量外部電(dian)(dian)路即可(ke)組成(cheng)相(xiang)當簡單的(de)(de)鋰電(dian)(dian)池充電(dian)(dian)線路。

該(gai)IC的內(nei)部(bu)框圖和簡(jian)單介紹如下：（圖一）

IC內含一個高(gao)精度(du)的615mV基準電壓(ya)源、兩(liang)個比較器(qi)、一個RS觸發器(qi)和其(qi)它(ta)一些邏輯電路，其(qi)大致(zhi)功(gong)能是：VCC電壓(ya)或其(qi)它(ta)待檢測電壓(ya)通(tong)過R1-R3組成(cheng)的分壓(ya)網(wang)絡接(jie)在(zai)IC的LTHIN /HTHIN檢測引腳，當待測電壓(ya)下降導(dao)致(zhi)LTHIN引腳低(di)于(yu)615mV時，輸出腳LBO輸出低(di)電平，而(er)如果(guo)待測電壓(ya)上升導(dao)致(zhi)HTHIN引腳高(gao)于(yu)615 mV時，經過內部邏輯判斷(duan)和簡(jian)單延時后，輸出腳LBO輸出高(gao)電平。

利用這個IC裝制的充電器電路如下（圖(tu)二(er)）

其(qi)(qi)工作流程(cheng)大(da)致是：當(dang)接上Li+電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)和供電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)源(yuan)時(shi)，IC通(tong)過(guo)R1/R2/R3組(zu)成(cheng)的(de)網絡檢測電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)壓(ya)，如果電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)壓(ya)低于3.3V（由R1-R3的(de)電(dian)(dian)(dian)(dian)(dian)阻(zu)值決(jue)定(ding)），或者按下按制SW1，此時(shi)IC3腳(jiao)(jiao)的(de)電(dian)(dian)(dian)(dian)(dian)壓(ya)低于615mV，則IC4腳(jiao)(jiao)輸(shu)出低電(dian)(dian)(dian)(dian)(dian)平，通(tong)過(guo)R5/D2拉低Q1的(de)柵極(ji)使之導(dao)(dao)通(tong)，從而(er)通(tong)過(guo)Q1/R9/D1給電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)進(jin)行大(da)電(dian)(dian)(dian)(dian)(dian)流充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)，當(dang)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)壓(ya)一路(lu)上升直至超(chao)過(guo)4.20V,此時(shi)IC的(de)1腳(jiao)(jiao)電(dian)(dian)(dian)(dian)(dian)壓(ya)高過(guo)615mV,IC內(nei)部經簡單判斷(duan)和延時(shi)，令(ling)(ling)4腳(jiao)(jiao)輸(shu)出高電(dian)(dian)(dian)(dian)(dian)平，從而(er)關閉(bi)大(da)電(dian)(dian)(dian)(dian)(dian)流充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)通(tong)道，但(dan)是4腳(jiao)(jiao)的(de)高電(dian)(dian)(dian)(dian)(dian)平同時(shi)給R7/C2的(de)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)回路(lu)供電(dian)(dian)(dian)(dian)(dian)，令(ling)(ling)到Q3的(de)柵極(ji)電(dian)(dian)(dian)(dian)(dian)壓(ya)慢慢升高，并給R8提供通(tong)路(lu)導(dao)(dao)致Q2導(dao)(dao)通(tong)，通(tong)過(guo)R10給Q1提供一個較(jiao)弱的(de)導(dao)(dao)通(tong)電(dian)(dian)(dian)(dian)(dian)流，使之微微導(dao)(dao)通(tong)，從而(er)為電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)提供一個較(jiao)少的(de)補充(chong)(chong)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流。按照圖中所示元(yuan)件(jian)參數將(jiang)于大(da)約十分鐘后，由于C2的(de)不斷(duan)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)，其(qi)(qi)端電(dian)(dian)(dian)(dian)(dian)壓(ya)即Q3的(de)柵極(ji)電(dian)(dian)(dian)(dian)(dian)壓(ya)不斷(duan)上升直至使Q3導(dao)(dao)通(tong)，從而(er)關閉(bi)Q2，令(ling)(ling)到整(zheng)個充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)過(guo)程(cheng)結(jie)束。

上面(mian)的(de)(de)方案還存在一(yi)些不足之(zhi)(zhi)處，例如檢(jian)測精(jing)度由外接電(dian)阻R1/R2/R3的(de)(de)精(jing)度決定，對于過(guo)放(fang)電(dian)的(de)(de)電(dian)池（電(dian)池端電(dian)壓低于2.8V）沒有一(yi)個小電(dian)流預充(chong)的(de)(de)過(guo)程，另外該(gai)方案的(de)(de)10分(fen)鐘補充(chong)充(chong)電(dian)時間(jian)對于較大容量的(de)(de)電(dian)池來說不是太足夠，因此針(zhen)對上述不足之(zhi)(zhi)處，我們還提供一(yi)個成本(ben)稍高一(yi)點，性能更(geng)加完善(shan)的(de)(de)方案：（圖三）

乍看之下(xia)，這(zhe)個方案采(cai)(cai)用(yong)了(le)三(san)個IC，可(ke)是(shi)(shi)U1和U2是(shi)(shi)采(cai)(cai)用(yong)的(de)SOT-23或者TO-92封(feng)裝，就好(hao)像普通三(san)極(ji)管(guan)一樣(yang)，其價格也就是(shi)(shi)2-3個三(san)極(ji)管(guan)的(de)價格，而(er)U3（PT8A2513NE）也是(shi)(shi)采(cai)(cai)用(yong)的(de)TO-94封(feng)裝，外形和三(san)極(ji)管(guan)很相似，價錢也相當便宜(yi)，不過(guo)，這(zhe)個電(dian)(dian)(dian)路(lu)可(ke)以(yi)實現智(zhi)能判斷(duan)電(dian)(dian)(dian)池(chi)是(shi)(shi)否(fou)過(guo)放電(dian)(dian)(dian)，決定是(shi)(shi)否(fou)在開(kai)始充(chong)電(dian)(dian)(dian)時(shi)采(cai)(cai)用(yong)小(xiao)電(dian)(dian)(dian)流預充(chong)，另(ling)外，采(cai)(cai)用(yong)U3后也將充(chong)電(dian)(dian)(dian)后期(qi)的(de)補充(chong)充(chong)電(dian)(dian)(dian)過(guo)程(cheng)延長到大(da)約(yue)一個小(xiao)時(shi)！

首先讓我(wo)們介紹一下該電路中幾個IC的功能：

（圖四）是U1/U2的(de)內部(bu)(bu)框圖，這(zhe)兩個IC只是內部(bu)(bu)電(dian)阻(zu)R1/R2的(de)數值(zhi)不(bu)同(tong)(tong)(tong)而(er)已，它們的(de)功能也很簡(jian)單：當Vcc低于IC的(de)設定(ding)值(zhi)時（根據IC編號(hao)不(bu)同(tong)(tong)(tong)，內部(bu)(bu)R3/R4阻(zu)值(zhi)也不(bu)同(tong)(tong)(tong)從而(er)導致檢測電(dian)壓(ya)值(zhi)不(bu)同(tong)(tong)(tong)，對于PT7M6128指的(de)是2.80V），RST引腳輸出低電(dian)平，反之當Vcc 高(gao)于1.05倍標稱值(zhi)時（例如對于PT7M6140，此數值(zhi)為1.05x4.0 =4.20V）則RST引腳輸出高(gao)電(dian)平。

上面電(dian)路(lu)(lu)的(de)另外一(yi)個(ge)IC（PT8A25 13）則(ze)是(shi)一(yi)個(ge)極簡單(dan)卻極穩(wen)定(ding)的(de)延(yan)時(shi)IC，其(qi)延(yan)時(shi)時(shi)間(jian)僅僅取決(jue)于 OSC腳的(de)頻(pin)(pin)率。事實上該IC就是(shi)將OSC震(zhen)蕩(dang)頻(pin)(pin)率進(jin)行(xing)32768次(ci)分(fen)頻(pin)(pin)后用(yong)來控制輸(shu)出的(de)。之(zhi)所以采用(yong)這個(ge)電(dian)路(lu)(lu)而(er)不采用(yong)LM555或者(zhe)CD4060等通用(yong)IC的(de)原因就是(shi)因為它相對而(er)言定(ding)時(shi)精(jing)度(du)更高（其(qi)它IC不分(fen)頻(pin)(pin)），定(ding)時(shi)時(shi)間(jian)更長（可達數小時(shi)）。并(bing)且電(dian)路(lu)(lu)更加簡單(dan)，采用(yong)TO-94或SOT-23-4封裝，就像(xiang)一(yi)個(ge)三極管一(yi)樣。而(er)價錢也跟CD4060差(cha)不多，使用(yong)效(xiao)果可就好(hao)的(de)太多了。

至(zhi)此大(da)家想必也(ye)大(da)致(zhi)了(le)解了(le)圖三(san)的工作流(liu)程(cheng)(cheng)了(le)：接(jie)上(shang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)和充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)器，如果(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)低(di)于2.8V，則U1輸(shu)出(chu)為(wei)低(di)（U2輸(shu)出(chu)也(ye)是(shi)(shi)低(di)），這樣R3和R4的回路都不(bu)通(tong)(tong)(tong)，只有R2回路導通(tong)(tong)(tong)，給(gei)(gei)Q1提(ti)供(gong)微弱的導通(tong)(tong)(tong)，使(shi)之輸(shu)出(chu)約(yue)數毫安的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)給(gei)(gei)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)進行預充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)，當電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)上(shang)升到(dao)超過(guo)2.94V（1.05X2.8）時(shi)(shi)或者剛(gang)接(jie)上(shang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)就超過(guo)2.94V時(shi)(shi)，U1輸(shu)出(chu)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)而(er)U2繼續輸(shu)出(chu)低(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)（電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)還沒達到(dao)4.2V J），這時(shi)(shi)R2通(tong)(tong)(tong)路截止(zhi)而(er)R3通(tong)(tong)(tong)路導通(tong)(tong)(tong)（因為(wei)Q4導通(tong)(tong)(tong)且其源極電(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)為(wei)低(di)-因U1輸(shu)出(chu)拉低(di)），從(cong)而(er)由較小阻值(zhi)的R3令Q1完(wan)(wan)全導通(tong)(tong)(tong)，提(ti)供(gong)一(yi)(yi)個(ge)(ge)數百毫安的大(da)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)恒(heng)流(liu)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)，而(er)當這個(ge)(ge)恒(heng)流(liu)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)過(guo)程(cheng)(cheng)慢慢令到(dao)被充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)的Li+電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)端電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)上(shang)升到(dao)4.2V時(shi)(shi)，U2也(ye)輸(shu)出(chu)高電(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)從(cong)而(er)關閉Q4,但是(shi)(shi)它同時(shi)(shi)也(ye)給(gei)(gei)U3提(ti)供(gong)了(le)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源導致(zhi)U3開始(shi)工作，這樣U3觸發(fa)Q3使(shi)R4導通(tong)(tong)(tong)提(ti)供(gong)一(yi)(yi)個(ge)(ge)很(hen)小的補充(chong)(chong)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)，直至(zhi)U3達到(dao)定(ding)時(shi)(shi)時(shi)(shi)間從(cong)而(er)關閉Q3，這時(shi)(shi)整個(ge)(ge)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)過(guo)程(cheng)(cheng)才(cai)完(wan)(wan)全結束。

相比而言，第(di)二個(ge)(ge)方案增(zeng)加(jia)了(le)前(qian)期智能判斷電(dian)池(chi)狀態和(he)自動預充(chong)(chong)(chong)電(dian)過程，以及延(yan)長了(le)末尾的(de)補(bu)(bu)充(chong)(chong)(chong)充(chong)(chong)(chong)電(dian)過程的(de)時(shi)間(jian)，各個(ge)(ge)階段的(de)充(chong)(chong)(chong)電(dian)電(dian)流可(ke)(ke)調并且補(bu)(bu)充(chong)(chong)(chong)充(chong)(chong)(chong)電(dian)時(shi)間(jian)可(ke)(ke)調（數分鐘(zhong)至數小時(shi)），因此該(gai)方案對鋰電(dian)池(chi)充(chong)(chong)(chong)電(dian)具有更(geng)好的(de)精確性和(he)安全性，加(jia)上價錢便宜，功能也(ye)比較完善，相信很快會取代市面(mian)中低檔的(de)充(chong)(chong)(chong)電(dian)器(qi)特別是那些廉(lian)價的(de)手機電(dian)池(chi)充(chong)(chong)(chong)電(dian)器(qi)。