鋰離子電池具有較高的能量重量和能量體積比，無記憶效應，可重復充電次數多，使用壽命長，價格也越來越低。一個良好的充電器可使電(dian)(dian)(dian)(dian)池(chi)具有較(jiao)長的(de)壽命(ming)。利用C8051F310單片機(ji)設計的(de)智能充(chong)電(dian)(dian)(dian)(dian)器(qi)，具有較(jiao)高的(de)測(ce)量精度，可很(hen)好的(de)控制充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流的(de)大小(xiao)，適時的(de)調整(zheng)，并(bing)可根據充(chong)電(dian)(dian)(dian)(dian)的(de)狀態判斷充(chong)電(dian)(dian)(dian)(dian)的(de)時間，及時終止充(chong)電(dian)(dian)(dian)(dian)，以避免電(dian)(dian)(dian)(dian)池(chi)的(de)過充(chong)。

　　本文(wen)討(tao)論(lun)使(shi)用C8051F310器件設(she)計鋰離子電(dian)(dian)池(chi)充(chong)(chong)電(dian)(dian)器的(de)。利用PWM脈寬調制產(chan)生可用軟件控制的(de)充(chong)(chong)電(dian)(dian)電(dian)(dian)源，以適(shi)應不同階段的(de)充(chong)(chong)電(dian)(dian)電(dian)(dian)流的(de)要(yao)求。溫(wen)度(du)傳感器對電(dian)(dian)池(chi)溫(wen)度(du)進行(xing)監測，并(bing)通過(guo)AD轉換和相(xiang)關計算檢(jian)測電(dian)(dian)池(chi)充(chong)(chong)電(dian)(dian)電(dian)(dian)壓和電(dian)(dian)流，以判斷(duan)電(dian)(dian)池(chi)到達哪(na)個階段。使(shi)電(dian)(dian)池(chi)具有更(geng)長的(de)使(shi)用壽命，更(geng)有效(xiao)的(de)充(chong)(chong)電(dian)(dian)方法(fa)。

　　設計過程

　　1 充電原理

　　電(dian)池(chi)(chi)的特性唯一地決定其安全性能和充電(dian)的效率。電(dian)池(chi)(chi)的最佳(jia)充電(dian)方(fang)法是由電(dian)池(chi)(chi)的化學成分決定的（鋰(li)離子、鎳氫、鎳鎘(ge)還是SLA電(dian)池(chi)(chi)等(deng)）。盡管(guan)如此，大(da)多數(shu)充電(dian)方(fang)案都包含下面的三(san)個階段：

　　● 低電流調節階段
　　● 恒流階段
　　● 恒(heng)壓(ya)階段/充電終止(zhi)

　　所有電(dian)(dian)(dian)(dian)(dian)(dian)池都是通過向自身傳輸(shu)電(dian)(dian)(dian)(dian)(dian)(dian)能的(de)方(fang)(fang)法進行(xing)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)的(de)，一節電(dian)(dian)(dian)(dian)(dian)(dian)池的(de)最大(da)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)取決于(yu)電(dian)(dian)(dian)(dian)(dian)(dian)池的(de)額定容(rong)量(liang)（C）例(li)如，一節容(rong)量(liang)為1000mAh的(de)電(dian)(dian)(dian)(dian)(dian)(dian)池在充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)為1000mA時，可以充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)1C(電(dian)(dian)(dian)(dian)(dian)(dian)池容(rong)量(liang)的(de)1倍)也可以用1/50C(20mA)或(huo)更低(di)的(de)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)給電(dian)(dian)(dian)(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)。盡管如此(ci)，這只是一個普通的(de)低(di)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)方(fang)(fang)式，不適用于(yu)要求短(duan)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)時間的(de)快速充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)方(fang)(fang)案(an)。

　　現在(zai)(zai)使用(yong)(yong)的(de)(de)大多數充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)器(qi)在(zai)(zai)給電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)時(shi)都(dou)(dou)是(shi)既(ji)使用(yong)(yong)低電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)方(fang)式又使用(yong)(yong)額定(ding)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)的(de)(de)方(fang)法，即容積(ji)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)，低充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)通(tong)(tong)常(chang)使用(yong)(yong)在(zai)(zai)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)的(de)(de)初(chu)始階(jie)段(duan)(duan)。在(zai)(zai)這一階(jie)段(duan)(duan)，需(xu)要將會導致充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)過(guo)程終止的(de)(de)芯片初(chu)期的(de)(de)自熱效應減小到最低程度，容積(ji)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)通(tong)(tong)常(chang)用(yong)(yong)在(zai)(zai)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)的(de)(de)中級階(jie)段(duan)(duan)，電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的(de)(de)大部分能量(liang)都(dou)(dou)是(shi)在(zai)(zai)這一階(jie)段(duan)(duan)存(cun)儲的(de)(de)。在(zai)(zai)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)的(de)(de)最后階(jie)段(duan)(duan)，通(tong)(tong)常(chang)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)時(shi)間(jian)的(de)(de)絕大部分都(dou)(dou)是(shi)消耗在(zai)(zai)這一階(jie)段(duan)(duan)，可以通(tong)(tong)過(guo)監測電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)、電(dian)(dian)(dian)(dian)(dian)壓或兩(liang)者的(de)(de)值(zhi)來決(jue)定(ding)何時(shi)結束(shu)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)。同(tong)樣，結束(shu)方(fang)案依(yi)賴于電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的(de)(de)化學特性，例如：大多數鋰離子電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)器(qi)都(dou)(dou)是(shi)將電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)壓保(bao)持在(zai)(zai)恒定(ding)值(zhi)，同(tong)時(shi)檢測最低電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)。鎳鎘(ge)、NiCd電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)用(yong)(yong)電(dian)(dian)(dian)(dian)(dian)壓或溫度的(de)(de)變化率來決(jue)定(ding)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)的(de)(de)結束(shu)時(shi)間(jian)。

      充電時部分電能被轉換成熱能，直至電池充滿。而充滿后，所有的電能將全部被轉換成熱能。如果此時不終止充電，電池就會被損壞或燒毀。快速充電器電池（完全充滿的時間小于兩小時的充電器）則可以解決這個問題，因為這些充電器是使用高充電電流來縮短充電時間的。因此，對于鋰離子電池來(lai)說,監(jian)(jian)測它(ta)的溫度(du)(du)是至關(guan)重(zhong)要的，因為電(dian)(dian)池在(zai)(zai)過充(chong)電(dian)(dian)時(shi)會發生爆裂，在(zai)(zai)所有(you)的充(chong)電(dian)(dian)階段都(dou)應(ying)該隨(sui)時(shi)監(jian)(jian)測溫度(du)(du)的變化，并(bing)且在(zai)(zai)溫度(du)(du)超過最大設定(ding)值時(shi)立即停止充(chong)電(dian)(dian)。

　　2 總體設計 
　
　　充電電路由三部分：控制部分，檢測部分及充電部分組成。如圖1所示，采用F310單片機進行充電控制，單片機本身具有脈寬調制PWM型開關穩壓電源所需的全部功能，具有10位A/D轉換器。利用單片機A/D端口，構成(cheng)電(dian)池電(dian)壓，電(dian)流(liu)，溫度檢測電(dian)路。

　　單片(pian)機(ji)通過(guo)電壓反饋(kui)(kui)和電流反饋(kui)(kui)信號，直接利用PWM輸出將數字電壓信號并轉化成模擬電壓信號，能夠保(bao)證(zheng)控制精度。

　　3 控制部分電(dian)路設(she)計 

　　C8051F310單(dan)片機

　　①模擬外設

　　a.10位ADC：轉換(huan)速度可(ke)(ke)達200ks/s,可(ke)(ke)多達21或17個外部(bu)單端(duan)或差分輸入，VREF可(ke)(ke)在外部(bu)引腳或VDD中(zhong)選擇，內置(zhi)溫度傳感器（±3℃），外部(bu)轉換(huan)啟動輸入；

　　b.兩個模擬比較器：可編程回差電壓和響應時間，可配置為中斷或復位源，小電流（〈0.5μA）。
　　
　　②供電電壓

　　a.典型工作電流：5mA、25MHz；
　　b.典型停機電流：0.1μA；
　　c.溫度范圍：-40～+85℃。

　　③高速8051微控制器內核

　　a.流水線指令結構：70%的指令的執行時間為一個或兩個系統時鐘周期；
　　b.速度可達25MI/s（時鐘頻率為25MHz時）；
　　c.擴展的(de)中斷(duan)系統。

　　④數字外設

　　a.29/25個端口I/O：所有的口線均耐5V電壓；
　　b.4個通用16位計數器/定時器；
　　c.16位可編程計數器/定時器陣列（PCA），有5個捕捉/比較模塊；
　　d.使用PCA或定時器和外部時鐘(zhong)源的實時時鐘(zhong)方式。

　　控制電路中如圖2所(suo)示，P0.3口提(ti)供充(chong)電電源，P0.6口檢測(ce)充(chong)電電壓的大(da)(da)小，P0.5口檢測(ce)充(chong)電電流的大(da)(da)小，P0.4口檢測(ce)電池(chi)的溫度。

　　充電(dian)電(dian)流由單(dan)片(pian)機脈寬調(diao)制PWM產生，充電(dian)電(dian)流由AD轉換(huan)再經過計算得出(chu)。

　　4 充電(dian)部分及(ji)檢測部分電(dian)路設計

　　②快速轉換器

　　實現(xian)漸弱終止充電(dian)(dian)器的(de)(de)(de)(de)最經濟(ji)的(de)(de)(de)(de)方法就(jiu)是用一(yi)個快速轉(zhuan)換器。快速轉(zhuan)換器是用一(yi)個電(dian)(dian)感和/或一(yi)個變壓(ya)器（需(xu)要隔離(li)的(de)(de)(de)(de)時(shi)(shi)候(hou)用變壓(ya)器）作為(wei)能量(liang)存儲單(dan)元以離(li)散的(de)(de)(de)(de)能量(liang)包的(de)(de)(de)(de)形式將能量(liang)從(cong)輸入傳輸至輸出(chu)的(de)(de)(de)(de)開(kai)關調(diao)節器反饋(kui)電(dian)(dian)路(lu)，通(tong)過晶(jing)體(ti)管來調(diao)節能量(liang)的(de)(de)(de)(de)傳輸，同(tong)時(shi)(shi)也(ye)作為(wei)過濾(lv)開(kai)關，以確保電(dian)(dian)壓(ya)或電(dian)(dian)流在(zai)負載時(shi)(shi)保持恒定。

　　快速調節器的(de)(de)操(cao)作是(shi)通過(guo)控制(zhi)一個晶(jing)體管開關的(de)(de)占空比來實現的(de)(de)。占空比會自動增加以使電池流入更多(duo)的(de)(de)電流。當VBATT

　　③電感的確定

　　電感對(dui)交流(liu)(liu)電是有阻礙作(zuo)用的(de)。在交流(liu)(liu)電頻率一定(ding)的(de)情況(kuang)下，電感量越(yue)大(da)，對(dui)交流(liu)(liu)電的(de)阻礙能(neng)(neng)力越(yue)強(qiang)??一定(ding)的(de)情況(kuang)下，交流(liu)(liu)電的(de)頻率越(yue)高，電感對(dui)交流(liu)(liu)電的(de)阻礙能(neng)(neng)力越(yue)大(da)，頻率越(yue)低，電感對(dui)交流(liu)(liu)電的(de)阻礙能(neng)(neng)力越(yue)小。也就是說(shuo)，電感有阻止交流(liu)(liu)電通過的(de)特(te)性。

　　其工作原理是這樣的(de)(de)：當(dang)負(fu)載(zai)(zai)兩(liang)(liang)端(duan)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)要降(jiang)低(di)時(shi)，通(tong)過MOSFET場效應(ying)管(guan)的(de)(de)開(kai)關(guan)作用，外部電(dian)(dian)(dian)(dian)(dian)(dian)源對(dui)電(dian)(dian)(dian)(dian)(dian)(dian)感進行充電(dian)(dian)(dian)(dian)(dian)(dian)并達(da)到(dao)所需的(de)(de)額定電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)。當(dang)負(fu)載(zai)(zai)兩(liang)(liang)端(duan)地(di)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)升(sheng)高時(shi)，通(tong)過MOSFET場效應(ying)管(guan)的(de)(de)開(kai)關(guan)作用，外部電(dian)(dian)(dian)(dian)(dian)(dian)源供電(dian)(dian)(dian)(dian)(dian)(dian)斷(duan)開(kai)，電(dian)(dian)(dian)(dian)(dian)(dian)感釋放出剛才充入的(de)(de)能量，這時(shi)電(dian)(dian)(dian)(dian)(dian)(dian)感就變成了(le)電(dian)(dian)(dian)(dian)(dian)(dian)源繼續對(dui)負(fu)載(zai)(zai)供電(dian)(dian)(dian)(dian)(dian)(dian)。隨著電(dian)(dian)(dian)(dian)(dian)(dian)感上存儲的(de)(de)能量地(di)消(xiao)耗。負(fu)載(zai)(zai)兩(liang)(liang)端(duan)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)開(kai)始(shi)逐漸降(jiang)低(di)，外部電(dian)(dian)(dian)(dian)(dian)(dian)源通(tong)過MOSFET場效應(ying)管(guan)的(de)(de)開(kai)關(guan)作用又要充電(dian)(dian)(dian)(dian)(dian)(dian)。依次類推在不斷(duan)的(de)(de)充電(dian)(dian)(dian)(dian)(dian)(dian)和放電(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)過程中形成了(le)一(yi)種穩定的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)，永遠使負(fu)載(zai)(zai)兩(liang)(liang)端(duan)地(di)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)不會(hui)升(sheng)高也不會(hui)降(jiang)低(di)，這就是開(kai)關(guan)電(dian)(dian)(dian)(dian)(dian)(dian)源的(de)(de)最大優勢(shi)。

　　要確定快速轉換器中電感的大小首先應假定晶體管的占空比為50%，因為此時的轉換器操作操作效率最高。占空比由方程式1給出：
　　（其中T是PWM的周期在程序示(shi)例(li)中T=10.5s）

　　占空比=ton/T （1）

　　至(zhi)此就可以選(xuan)擇一(yi)個PWM的轉換(huan)頻(pin)率(lv)（如(ru)方程式2所示）PWM的轉換(huan)頻(pin)率(lv)越大，則電感(gan)的值(zhi)越小，也越節約成本。

　　我(wo)的示例(li)代(dai)碼配(pei)置F310的8位硬件PWM是(shi)使用內部(bu)24.5MHz主時(shi)鐘的256分(fen)頻來產生一個95.7kHz的轉換速(su)率。

　　L=（Vi-Vsat-Voton）/2Iomax （2）

　　現在我們可以計算電感的大小了，假定充電電壓Vi的值為15V，飽和電壓Vsat的值為0.5V，需要獲得的輸出電壓值為4.2V,并且最大輸出電流IＯMAX為1500mA，那么，電感的值至少應選為18H。
需要注意的(de)(de)是：在本電(dian)路中(zhong)的(de)(de)電(dian)容(rong)(rong)僅僅是一個紋波衰(shuai)減器，因為紋波與電(dian)容(rong)(rong)的(de)(de)大(da)小成反比例關(guan)系，所以電(dian)容(rong)(rong)的(de)(de)值越大(da)，衰(shuai)減效(xiao)果(guo)越好。