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)池具(ju)有(you)(you)較(jiao)長的(de)(de)壽命。利用C8051F310單片(pian)機設計的(de)(de)智能充(chong)(chong)電(dian)(dian)器，具(ju)有(you)(you)較(jiao)高的(de)(de)測量精度(du)，可很(hen)好的(de)(de)控制充(chong)(chong)電(dian)(dian)電(dian)(dian)流的(de)(de)大小，適時的(de)(de)調整(zheng)，并可根(gen)據充(chong)(chong)電(dian)(dian)的(de)(de)狀(zhuang)態(tai)判斷(duan)充(chong)(chong)電(dian)(dian)的(de)(de)時間，及時終止充(chong)(chong)電(dian)(dian)，以(yi)避免電(dian)(dian)池的(de)(de)過充(chong)(chong)。

　　本文討論使(shi)用(yong)C8051F310器(qi)(qi)件設計鋰離(li)子電(dian)(dian)(dian)池(chi)(chi)充電(dian)(dian)(dian)器(qi)(qi)的(de)。利用(yong)PWM脈(mo)寬調制(zhi)產生可用(yong)軟件控制(zhi)的(de)充電(dian)(dian)(dian)電(dian)(dian)(dian)源，以適應不同(tong)階(jie)段的(de)充電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)的(de)要求。溫度(du)傳感器(qi)(qi)對電(dian)(dian)(dian)池(chi)(chi)溫度(du)進行監測，并通(tong)過AD轉換和相關計算(suan)檢測電(dian)(dian)(dian)池(chi)(chi)充電(dian)(dian)(dian)電(dian)(dian)(dian)壓和電(dian)(dian)(dian)流(liu)，以判斷電(dian)(dian)(dian)池(chi)(chi)到達哪個(ge)階(jie)段。使(shi)電(dian)(dian)(dian)池(chi)(chi)具有(you)更長的(de)使(shi)用(yong)壽命，更有(you)效的(de)充電(dian)(dian)(dian)方法。

　　設計過程

　　1 充電原理

　　電(dian)(dian)池(chi)的特性唯一地決定(ding)其安全性能(neng)和充(chong)(chong)電(dian)(dian)的效率。電(dian)(dian)池(chi)的最佳充(chong)(chong)電(dian)(dian)方法是由電(dian)(dian)池(chi)的化(hua)學成分決定(ding)的（鋰離子、鎳(nie)氫(qing)、鎳(nie)鎘還是SLA電(dian)(dian)池(chi)等）。盡(jin)管如此(ci)，大(da)多數充(chong)(chong)電(dian)(dian)方案都包含下面(mian)的三個(ge)階段：

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

　　所有電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)都是通過向自身傳輸電(dian)(dian)(dian)(dian)(dian)能的(de)方法進(jin)行(xing)充(chong)電(dian)(dian)(dian)(dian)(dian)的(de)，一(yi)節電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)的(de)最大充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)取決(jue)于(yu)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)的(de)額定容(rong)量(liang)（C）例如，一(yi)節容(rong)量(liang)為1000mAh的(de)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)在充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)為1000mA時(shi)，可以充(chong)電(dian)(dian)(dian)(dian)(dian)1C(電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)容(rong)量(liang)的(de)1倍)也可以用(yong)1/50C(20mA)或更低的(de)電(dian)(dian)(dian)(dian)(dian)流(liu)給電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)(dian)(dian)(dian)。盡管如此，這只(zhi)是一(yi)個普通的(de)低電(dian)(dian)(dian)(dian)(dian)流(liu)充(chong)電(dian)(dian)(dian)(dian)(dian)方式，不適(shi)用(yong)于(yu)要求短充(chong)電(dian)(dian)(dian)(dian)(dian)時(shi)間的(de)快速充(chong)電(dian)(dian)(dian)(dian)(dian)方案(an)。

　　現在使(shi)用的(de)(de)(de)大(da)多數充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器在給電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)時(shi)(shi)都是(shi)既使(shi)用低電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)方(fang)(fang)式又(you)使(shi)用額定(ding)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)的(de)(de)(de)方(fang)(fang)法，即(ji)容(rong)積(ji)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，低充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)通(tong)常(chang)使(shi)用在充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)初始階(jie)段(duan)(duan)(duan)(duan)。在這(zhe)一階(jie)段(duan)(duan)(duan)(duan)，需要將(jiang)會導(dao)致(zhi)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)過(guo)程終止的(de)(de)(de)芯片初期的(de)(de)(de)自熱效應減(jian)小到最低程度(du)，容(rong)積(ji)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)通(tong)常(chang)用在充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)中(zhong)級階(jie)段(duan)(duan)(duan)(duan)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)的(de)(de)(de)大(da)部分能(neng)量都是(shi)在這(zhe)一階(jie)段(duan)(duan)(duan)(duan)存儲(chu)的(de)(de)(de)。在電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)最后(hou)階(jie)段(duan)(duan)(duan)(duan)，通(tong)常(chang)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)時(shi)(shi)間(jian)的(de)(de)(de)絕大(da)部分都是(shi)消耗在這(zhe)一階(jie)段(duan)(duan)(duan)(duan)，可(ke)以通(tong)過(guo)監測電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)、電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓或兩者的(de)(de)(de)值(zhi)來決定(ding)何時(shi)(shi)結束(shu)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。同(tong)樣，結束(shu)方(fang)(fang)案依賴于電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)的(de)(de)(de)化學特(te)性，例如：大(da)多數鋰離子電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器都是(shi)將(jiang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓保持在恒定(ding)值(zhi)，同(tong)時(shi)(shi)檢測最低電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)。鎳鎘、NiCd電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)用電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓或溫度(du)的(de)(de)(de)變化率來決定(ding)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)結束(shu)時(shi)(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，對于鋰離子電池來說,監(jian)測它(ta)的(de)(de)溫度是(shi)至關重要的(de)(de)，因(yin)為電(dian)(dian)池在(zai)過充(chong)電(dian)(dian)時會發生爆裂(lie)，在(zai)所(suo)有的(de)(de)充(chong)電(dian)(dian)階(jie)段都應該隨(sui)時監(jian)測溫度的(de)(de)變(bian)化，并且在(zai)溫度超過最(zui)大設定(ding)值(zhi)時立即(ji)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(ji)A/D端口，構成電池(chi)電壓，電流，溫度檢(jian)測電路。

　　單片(pian)機通(tong)過電壓(ya)反饋和電流反饋信號，直(zhi)接(jie)利用PWM輸出(chu)將數字(zi)電壓(ya)信號并轉化成(cheng)模擬電壓(ya)信號，能(neng)夠保(bao)證控制精度(du)。

　　3 控制部分電(dian)路設計 

　　C8051F310單片機

　　①模擬外設

　　a.10位(wei)ADC：轉換速度可達200ks/s,可多達21或17個(ge)外(wai)部單端或差分輸入，VREF可在外(wai)部引腳(jiao)或VDD中選擇，內置溫(wen)度傳感器（±3℃），外(wai)部轉換啟動輸入；

　　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(du)范圍：-40～+85℃。

　　③高速(su)8051微控制器內(nei)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(kuo)展的中(zhong)斷系統(tong)。

　　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(shi)器和外部時(shi)鐘(zhong)源(yuan)的實時(shi)時(shi)鐘(zhong)方式。

　　控制電(dian)路中如圖2所示，P0.3口(kou)提供充(chong)電(dian)電(dian)源，P0.6口(kou)檢測(ce)充(chong)電(dian)電(dian)壓的(de)大小(xiao)，P0.5口(kou)檢測(ce)充(chong)電(dian)電(dian)流的(de)大小(xiao)，P0.4口(kou)檢測(ce)電(dian)池(chi)的(de)溫度。

　　充電(dian)電(dian)流由(you)單片機脈(mo)寬調制PWM產生，充電(dian)電(dian)流由(you)AD轉換再(zai)經(jing)過計算得(de)出。

　　4 充(chong)電(dian)部(bu)(bu)分及檢測部(bu)(bu)分電(dian)路設(she)計

　　②快速轉換器

　　實現漸弱終(zhong)止充電器(qi)的(de)(de)(de)(de)最經(jing)濟(ji)的(de)(de)(de)(de)方法(fa)就是用一個(ge)(ge)快速轉換器(qi)。快速轉換器(qi)是用一個(ge)(ge)電感和(he)/或(huo)(huo)一個(ge)(ge)變(bian)壓器(qi)（需要隔離的(de)(de)(de)(de)時(shi)候用變(bian)壓器(qi)）作為能(neng)量存儲單元以(yi)離散的(de)(de)(de)(de)能(neng)量包(bao)的(de)(de)(de)(de)形式(shi)將能(neng)量從輸(shu)(shu)入傳(chuan)輸(shu)(shu)至輸(shu)(shu)出的(de)(de)(de)(de)開關調節器(qi)反饋(kui)電路，通過晶體管來調節能(neng)量的(de)(de)(de)(de)傳(chuan)輸(shu)(shu)，同時(shi)也作為過濾開關，以(yi)確(que)保(bao)電壓或(huo)(huo)電流在負(fu)載時(shi)保(bao)持恒定。

　　快速調節器的操作是(shi)通過控(kong)制一個晶(jing)體管開關的占空比來實現的。占空比會(hui)自動增(zeng)加以使電池(chi)流入更多的電流。當(dang)VBATT

　　③電感的確定

　　電(dian)感(gan)對(dui)交(jiao)流(liu)電(dian)是有阻(zu)(zu)(zu)礙(ai)作用的(de)(de)(de)。在交(jiao)流(liu)電(dian)頻率(lv)一定(ding)的(de)(de)(de)情(qing)況(kuang)下，電(dian)感(gan)量越(yue)(yue)大(da)，對(dui)交(jiao)流(liu)電(dian)的(de)(de)(de)阻(zu)(zu)(zu)礙(ai)能力(li)越(yue)(yue)強??一定(ding)的(de)(de)(de)情(qing)況(kuang)下，交(jiao)流(liu)電(dian)的(de)(de)(de)頻率(lv)越(yue)(yue)高，電(dian)感(gan)對(dui)交(jiao)流(liu)電(dian)的(de)(de)(de)阻(zu)(zu)(zu)礙(ai)能力(li)越(yue)(yue)大(da)，頻率(lv)越(yue)(yue)低，電(dian)感(gan)對(dui)交(jiao)流(liu)電(dian)的(de)(de)(de)阻(zu)(zu)(zu)礙(ai)能力(li)越(yue)(yue)小(xiao)。也就是說，電(dian)感(gan)有阻(zu)(zu)(zu)止交(jiao)流(liu)電(dian)通過的(de)(de)(de)特(te)性。

　　其工作(zuo)原理是(shi)這(zhe)樣的(de)(de)(de)：當負(fu)(fu)載(zai)兩端的(de)(de)(de)電(dian)(dian)(dian)(dian)壓(ya)(ya)要降低時(shi)(shi)，通過(guo)MOSFET場(chang)(chang)效(xiao)應(ying)管(guan)的(de)(de)(de)開關(guan)(guan)(guan)作(zuo)用(yong)，外(wai)部(bu)(bu)電(dian)(dian)(dian)(dian)源(yuan)對(dui)電(dian)(dian)(dian)(dian)感(gan)進行充(chong)電(dian)(dian)(dian)(dian)并達到所需(xu)的(de)(de)(de)額定電(dian)(dian)(dian)(dian)壓(ya)(ya)。當負(fu)(fu)載(zai)兩端地(di)電(dian)(dian)(dian)(dian)壓(ya)(ya)升(sheng)高(gao)時(shi)(shi)，通過(guo)MOSFET場(chang)(chang)效(xiao)應(ying)管(guan)的(de)(de)(de)開關(guan)(guan)(guan)作(zuo)用(yong)，外(wai)部(bu)(bu)電(dian)(dian)(dian)(dian)源(yuan)供(gong)電(dian)(dian)(dian)(dian)斷(duan)開，電(dian)(dian)(dian)(dian)感(gan)釋(shi)放(fang)出剛才充(chong)入的(de)(de)(de)能(neng)(neng)量(liang)，這(zhe)時(shi)(shi)電(dian)(dian)(dian)(dian)感(gan)就變成了電(dian)(dian)(dian)(dian)源(yuan)繼續(xu)對(dui)負(fu)(fu)載(zai)供(gong)電(dian)(dian)(dian)(dian)。隨(sui)著(zhu)電(dian)(dian)(dian)(dian)感(gan)上存(cun)儲(chu)的(de)(de)(de)能(neng)(neng)量(liang)地(di)消耗。負(fu)(fu)載(zai)兩端的(de)(de)(de)電(dian)(dian)(dian)(dian)壓(ya)(ya)開始逐漸(jian)降低，外(wai)部(bu)(bu)電(dian)(dian)(dian)(dian)源(yuan)通過(guo)MOSFET場(chang)(chang)效(xiao)應(ying)管(guan)的(de)(de)(de)開關(guan)(guan)(guan)作(zuo)用(yong)又(you)要充(chong)電(dian)(dian)(dian)(dian)。依次類推在不(bu)斷(duan)的(de)(de)(de)充(chong)電(dian)(dian)(dian)(dian)和放(fang)電(dian)(dian)(dian)(dian)的(de)(de)(de)過(guo)程中形(xing)成了一種穩定的(de)(de)(de)電(dian)(dian)(dian)(dian)壓(ya)(ya)，永遠(yuan)使(shi)負(fu)(fu)載(zai)兩端地(di)電(dian)(dian)(dian)(dian)壓(ya)(ya)不(bu)會升(sheng)高(gao)也(ye)不(bu)會降低，這(zhe)就是(shi)開關(guan)(guan)(guan)電(dian)(dian)(dian)(dian)源(yuan)的(de)(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)例中T=10.5s）

　　占空比=ton/T （1）

　　至此就可以(yi)選擇一個PWM的轉換頻(pin)率(lv)（如方程式2所示）PWM的轉換頻(pin)率(lv)越大，則電感的值(zhi)越小，也越節(jie)約成本。

　　我的示(shi)例代碼配置F310的8位硬件PWM是使用內部24.5MHz主時鐘的256分頻來產生一(yi)個95.7kHz的轉換速率。

　　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)是(shi)：在本(ben)電路中的(de)電容僅(jin)僅(jin)是(shi)一個紋波衰減(jian)(jian)器(qi)，因為紋波與電容的(de)大小成反比例關(guan)系(xi)，所以(yi)電容的(de)值越(yue)(yue)大，衰減(jian)(jian)效果越(yue)(yue)好。