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池具有較長的壽命。利用C8051F310單片機設計的智能充電器，具有較(jiao)高的(de)測量精度，可很好的(de)控制充電電流的(de)大(da)小，適時的(de)調整，并可根據充電的(de)狀(zhuang)態判斷充電的(de)時間，及時終止(zhi)充電，以避免電池的(de)過充。

　　本文討論(lun)使(shi)用(yong)(yong)C8051F310器件設計(ji)(ji)鋰離子電(dian)(dian)(dian)池(chi)充電(dian)(dian)(dian)器的。利用(yong)(yong)PWM脈寬調制產生可用(yong)(yong)軟件控制的充電(dian)(dian)(dian)電(dian)(dian)(dian)源，以(yi)適(shi)應(ying)不(bu)同階段的充電(dian)(dian)(dian)電(dian)(dian)(dian)流的要求(qiu)。溫(wen)度傳(chuan)感(gan)器對電(dian)(dian)(dian)池(chi)溫(wen)度進行監測(ce)，并通(tong)過AD轉換和相關計(ji)(ji)算檢(jian)測(ce)電(dian)(dian)(dian)池(chi)充電(dian)(dian)(dian)電(dian)(dian)(dian)壓和電(dian)(dian)(dian)流，以(yi)判斷電(dian)(dian)(dian)池(chi)到達哪(na)個階段。使(shi)電(dian)(dian)(dian)池(chi)具有(you)更(geng)(geng)長的使(shi)用(yong)(yong)壽命，更(geng)(geng)有(you)效的充電(dian)(dian)(dian)方法。

　　設計過程

　　1 充電原理

　　電(dian)池(chi)(chi)的(de)(de)特性唯一地決(jue)定其安全性能和充電(dian)的(de)(de)效(xiao)率。電(dian)池(chi)(chi)的(de)(de)最佳充電(dian)方法是(shi)由電(dian)池(chi)(chi)的(de)(de)化學成分決(jue)定的(de)(de)（鋰離子、鎳氫、鎳鎘(ge)還是(shi)SLA電(dian)池(chi)(chi)等）。盡管如此，大(da)多數充電(dian)方案都包含下(xia)面的(de)(de)三個階段：

　　● 低(di)電流調節(jie)階(jie)段

　　● 恒流階段

　　● 恒壓(ya)階段/充電終(zhong)止

　　所有(you)電(dian)(dian)(dian)(dian)池都是(shi)通過(guo)向自身傳輸電(dian)(dian)(dian)(dian)能的(de)方(fang)法進(jin)行(xing)充電(dian)(dian)(dian)(dian)的(de)，一(yi)節電(dian)(dian)(dian)(dian)池的(de)最大充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)取決于電(dian)(dian)(dian)(dian)池的(de)額定容(rong)量(liang)（C）例如，一(yi)節容(rong)量(liang)為(wei)1000mAh的(de)電(dian)(dian)(dian)(dian)池在充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)為(wei)1000mA時，可(ke)以充電(dian)(dian)(dian)(dian)1C（電(dian)(dian)(dian)(dian)池容(rong)量(liang)的(de)1倍）也可(ke)以用1/50C（20mA）或(huo)更低的(de)電(dian)(dian)(dian)(dian)流(liu)給電(dian)(dian)(dian)(dian)池充電(dian)(dian)(dian)(dian)。盡(jin)管如此，這只是(shi)一(yi)個普通的(de)低電(dian)(dian)(dian)(dian)流(liu)充電(dian)(dian)(dian)(dian)方(fang)式，不適用于要求短充電(dian)(dian)(dian)(dian)時間的(de)快(kuai)速充電(dian)(dian)(dian)(dian)方(fang)案。

　　現在使用的大多數充電器在(zai)(zai)給電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)時都(dou)是(shi)既使(shi)用(yong)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)方式又使(shi)用(yong)額定(ding)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)的(de)(de)(de)方法，即容積(ji)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，低(di)(di)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)通(tong)常使(shi)用(yong)在(zai)(zai)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)初始階(jie)段(duan)(duan)。在(zai)(zai)這一階(jie)段(duan)(duan)，需要將會(hui)導致充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)過程終止(zhi)的(de)(de)(de)芯片初期的(de)(de)(de)自熱效應(ying)減小到最低(di)(di)程度(du)，容積(ji)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)通(tong)常用(yong)在(zai)(zai)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)中級階(jie)段(duan)(duan)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)的(de)(de)(de)大(da)部分能量都(dou)是(shi)在(zai)(zai)這一階(jie)段(duan)(duan)存儲的(de)(de)(de)。在(zai)(zai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)最后階(jie)段(duan)(duan)，通(tong)常充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)時間(jian)的(de)(de)(de)絕大(da)部分都(dou)是(shi)消耗在(zai)(zai)這一階(jie)段(duan)(duan)，可以通(tong)過監測電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)、電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓或(huo)兩者的(de)(de)(de)值(zhi)來決定(ding)何時結(jie)束(shu)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。同樣，結(jie)束(shu)方案依賴于電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)的(de)(de)(de)化(hua)學(xue)特(te)性，例如(ru)：大(da)多數鋰離子電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器都(dou)是(shi)將電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓保持(chi)在(zai)(zai)恒定(ding)值(zhi)，同時檢測最低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)。鎳鎘(ge)、NiCd電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)用(yong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓或(huo)溫度(du)的(de)(de)(de)變化(hua)率(lv)來決定(ding)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)結(jie)束(shu)時間(jian)。

　　圖1 鋰離子電池充電模塊圖

　　充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)時(shi)部分電(dian)能被轉換(huan)成熱(re)能，直至(zhi)電(dian)池充(chong)(chong)(chong)(chong)(chong)(chong)滿(man)。而充(chong)(chong)(chong)(chong)(chong)(chong)滿(man)后，所(suo)(suo)有的(de)電(dian)能將(jiang)全(quan)部被轉換(huan)成熱(re)能。如果此(ci)時(shi)不(bu)終止充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)，電(dian)池就會(hui)被損壞或燒毀。快速(su)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)器(qi)電(dian)池（完全(quan)充(chong)(chong)(chong)(chong)(chong)(chong)滿(man)的(de)時(shi)間(jian)小于(yu)兩(liang)小時(shi)的(de)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)器(qi)）則可以解決這個問題，因(yin)為(wei)這些充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)器(qi)是(shi)(shi)使用高充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)電(dian)流來縮(suo)短充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)時(shi)間(jian)的(de)。因(yin)此(ci)，對于(yu)鋰離子電(dian)池來說(shuo)，監測它(ta)的(de)溫度是(shi)(shi)至(zhi)關重(zhong)要的(de)，因(yin)為(wei)電(dian)池在(zai)(zai)過(guo)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)時(shi)會(hui)發生爆裂，在(zai)(zai)所(suo)(suo)有的(de)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)階段都應該隨時(shi)監測溫度的(de)變化，并且在(zai)(zai)溫度超過(guo)最大設定值時(shi)立即停(ting)止充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)。

　　2 總體設計

　　充(chong)(chong)電(dian)(dian)電(dian)(dian)路由三(san)部(bu)分：控制部(bu)分，檢測(ce)部(bu)分及(ji)充(chong)(chong)電(dian)(dian)部(bu)分組成(cheng)。如圖1所(suo)示，采用F310單片機(ji)進行(xing)充(chong)(chong)電(dian)(dian)控制，單片機(ji)本(ben)身具(ju)有脈(mo)寬調制PWM型(xing)開關穩壓(ya)電(dian)(dian)源所(suo)需的全部(bu)功能，具(ju)有10位(wei)A/D轉(zhuan)換器(qi)。利用單片機(ji)A/D端口，構成(cheng)電(dian)(dian)池電(dian)(dian)壓(ya)，電(dian)(dian)流，溫(wen)度檢測(ce)電(dian)(dian)路。

　　單片(pian)機通過電壓(ya)反饋(kui)(kui)和電流(liu)反饋(kui)(kui)信(xin)(xin)號，直接(jie)利用PWM輸出將數字電壓(ya)信(xin)(xin)號并轉化成模擬電壓(ya)信(xin)(xin)號，能夠保證控制精度。

　　3 控(kong)制部分電路(lu)設計

　　C8051F310單(dan)片機

　　①模擬外設

　　a.10位ADC：轉換(huan)速度可(ke)(ke)達(da)200ks/s,可(ke)(ke)多達(da)21或17個外部單端或差分輸入(ru)，VREF可(ke)(ke)在外部引腳或VDD中選擇，內置溫度傳感器（±3℃），外部轉換(huan)啟(qi)動輸入(ru)；

　　b.兩個模擬比較器(qi)：可編程回差電(dian)壓(ya)和響應時間，可配(pei)置為中斷或復位源，小電(dian)流（〈0.5μA）。

　　②供電電壓

　　a.典(dian)型工作(zuo)電(dian)流：5mA、25MHz；

　　b.典型停機(ji)電流：0.1μA；

　　c.溫度范圍：-40～+85℃。

　　③高速(su)8051微控制(zhi)器內核

　　a.流水線指令結構：70%的指令的執行時間為一個(ge)或(huo)兩個(ge)系統時鐘周期；

　　b.速度可達25MI/s（時(shi)鐘頻率為25MHz時(shi)）；

　　c.擴(kuo)展(zhan)的中(zhong)斷系(xi)統(tong)。

　　④數字外設

　　a.29/25個端(duan)口(kou)I/O：所有的口(kou)線(xian)均耐(nai)5V電(dian)壓；

　　b.4個通用16位(wei)計(ji)數器/定時器；

　　c.16位(wei)可編程計數器(qi)/定(ding)時器(qi)陣列（PCA），有5個捕捉/比(bi)較(jiao)模塊；

　　d.使用PCA或定時(shi)(shi)器和外(wai)部時(shi)(shi)鐘(zhong)(zhong)源的實時(shi)(shi)時(shi)(shi)鐘(zhong)(zhong)方式。

　　控制電(dian)(dian)(dian)路中如圖2所示，P0.3口提(ti)供充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)源，P0.6口檢(jian)測充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)壓的(de)大小(xiao)，P0.5口檢(jian)測充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流的(de)大小(xiao)，P0.4口檢(jian)測電(dian)(dian)(dian)池(chi)的(de)溫度。

　　充(chong)電電流由(you)單片機脈(mo)寬調制PWM產生，充(chong)電電流由(you)AD轉(zhuan)換(huan)再(zai)經過計(ji)算得(de)出。

　　4 充電部(bu)分(fen)及(ji)檢測部(bu)分(fen)電路設計(ji)

　　圖(tu)2 控制電路接線圖(tu)

　　圖3 充電(dian)電(dian)路與檢測電(dian)路圖

　　圖(tu)3為充電電路與檢測電路圖(tu)。

　　①充電過程曲線

　　圖4 鋰電(dian)池充電(dian)曲線

　　如圖4所示，充電過程由預充狀態(tai)，恒流(liu)充電狀態(tai)和(he)恒壓充電狀態(tai)組成(cheng)。

　　②快速轉換器

　　實現漸弱終止充電器的(de)(de)最經濟的(de)(de)方法就是(shi)用(yong)一個快(kuai)速(su)轉(zhuan)換器(qi)(qi)。快(kuai)速(su)轉(zhuan)換器(qi)(qi)是(shi)用(yong)一個電(dian)(dian)感和/或一個變壓器(qi)(qi)（需要隔離的(de)(de)時候用(yong)變壓器(qi)(qi)）作為能量存(cun)儲單元以(yi)離散的(de)(de)能量包的(de)(de)形式(shi)將(jiang)能量從輸(shu)(shu)入傳(chuan)輸(shu)(shu)至輸(shu)(shu)出的(de)(de)開關調節(jie)器(qi)(qi)反饋電(dian)(dian)路，通(tong)過(guo)晶體管來(lai)調節(jie)能量的(de)(de)傳(chuan)輸(shu)(shu)，同時也作為過(guo)濾開關，以(yi)確保(bao)電(dian)(dian)壓或電(dian)(dian)流在(zai)負載時保(bao)持恒(heng)定。

　　如(ru)圖a開關閉合(he)

　　如圖b開(kai)關(guan)打開(kai)

　　快(kuai)速(su)調(diao)節器的(de)操作(zuo)是通(tong)過控(kong)制一個晶體管開關的(de)占空比(bi)來實現的(de)。占空比(bi)會自動增加以使電(dian)池流入更多的(de)電(dian)流。當VBATT

　　③電感的確定

　　電(dian)(dian)(dian)(dian)(dian)(dian)感對(dui)交(jiao)流(liu)電(dian)(dian)(dian)(dian)(dian)(dian)是有阻(zu)(zu)礙(ai)作(zuo)用的(de)。在交(jiao)流(liu)電(dian)(dian)(dian)(dian)(dian)(dian)頻(pin)率(lv)(lv)一(yi)定的(de)情況(kuang)下，電(dian)(dian)(dian)(dian)(dian)(dian)感量越大，對(dui)交(jiao)流(liu)電(dian)(dian)(dian)(dian)(dian)(dian)的(de)阻(zu)(zu)礙(ai)能(neng)力(li)越強，電(dian)(dian)(dian)(dian)(dian)(dian)感量越小，其阻(zu)(zu)礙(ai)能(neng)力(li)越小。另(ling)外，在電(dian)(dian)(dian)(dian)(dian)(dian)感量一(yi)定的(de)情況(kuang)下，交(jiao)流(liu)電(dian)(dian)(dian)(dian)(dian)(dian)的(de)頻(pin)率(lv)(lv)越高(gao)，電(dian)(dian)(dian)(dian)(dian)(dian)感對(dui)交(jiao)流(liu)電(dian)(dian)(dian)(dian)(dian)(dian)的(de)阻(zu)(zu)礙(ai)能(neng)力(li)越大，頻(pin)率(lv)(lv)越低，電(dian)(dian)(dian)(dian)(dian)(dian)感對(dui)交(jiao)流(liu)電(dian)(dian)(dian)(dian)(dian)(dian)的(de)阻(zu)(zu)礙(ai)能(neng)力(li)越小。也就是說，電(dian)(dian)(dian)(dian)(dian)(dian)感有阻(zu)(zu)止交(jiao)流(liu)電(dian)(dian)(dian)(dian)(dian)(dian)通過(guo)的(de)特性。

　　其(qi)工作(zuo)原(yuan)理(li)是這(zhe)樣的(de)(de)(de)：當負(fu)(fu)(fu)載兩端(duan)的(de)(de)(de)電(dian)(dian)(dian)壓(ya)(ya)要降低時(shi)(shi)，通(tong)過(guo)MOSFET場(chang)效(xiao)應管的(de)(de)(de)開(kai)(kai)關(guan)作(zuo)用(yong)(yong)，外(wai)部電(dian)(dian)(dian)源對電(dian)(dian)(dian)感進行充(chong)(chong)電(dian)(dian)(dian)并達到所需(xu)的(de)(de)(de)額定電(dian)(dian)(dian)壓(ya)(ya)。當負(fu)(fu)(fu)載兩端(duan)地電(dian)(dian)(dian)壓(ya)(ya)升(sheng)高時(shi)(shi)，通(tong)過(guo)MOSFET場(chang)效(xiao)應管的(de)(de)(de)開(kai)(kai)關(guan)作(zuo)用(yong)(yong)，外(wai)部電(dian)(dian)(dian)源供電(dian)(dian)(dian)斷(duan)開(kai)(kai)，電(dian)(dian)(dian)感釋放(fang)出剛才充(chong)(chong)入的(de)(de)(de)能量，這(zhe)時(shi)(shi)電(dian)(dian)(dian)感就變成了電(dian)(dian)(dian)源繼續(xu)對負(fu)(fu)(fu)載供電(dian)(dian)(dian)。隨著(zhu)電(dian)(dian)(dian)感上存儲的(de)(de)(de)能量地消(xiao)耗。負(fu)(fu)(fu)載兩端(duan)的(de)(de)(de)電(dian)(dian)(dian)壓(ya)(ya)開(kai)(kai)始逐漸降低，外(wai)部電(dian)(dian)(dian)源通(tong)過(guo)MOSFET場(chang)效(xiao)應管的(de)(de)(de)開(kai)(kai)關(guan)作(zuo)用(yong)(yong)又要充(chong)(chong)電(dian)(dian)(dian)。依次類(lei)推在不斷(duan)的(de)(de)(de)充(chong)(chong)電(dian)(dian)(dian)和放(fang)電(dian)(dian)(dian)的(de)(de)(de)過(guo)程中形成了一(yi)種穩定的(de)(de)(de)電(dian)(dian)(dian)壓(ya)(ya)，永(yong)遠(yuan)使(shi)負(fu)(fu)(fu)載兩端(duan)地電(dian)(dian)(dian)壓(ya)(ya)不會(hui)升(sheng)高也(ye)不會(hui)降低，這(zhe)就是開(kai)(kai)關(guan)電(dian)(dian)(dian)源的(de)(de)(de)最(zui)大優勢。

　　要確定快速轉(zhuan)換(huan)器中(zhong)電感的大(da)小首先應(ying)假定晶體管的占空比為50%，因為此時的轉(zhuan)換(huan)器操作操作效(xiao)率最(zui)高。占空比由方程式1給出：

　　（其(qi)中T是PWM的周期在程(cheng)序示(shi)例中T=10.5s）

　　占空比(bi)=ton/T （1）

　　至此(ci)就可以選擇一(yi)個PWM的(de)(de)轉換頻率（如方(fang)程(cheng)式(shi)2所示）PWM的(de)(de)轉換頻率越(yue)大，則電感的(de)(de)值越(yue)小，也越(yue)節約成本。

　　我的(de)示例(li)代(dai)碼配置F310的(de)8位(wei)硬件PWM是使用(yong)內部(bu)24.5MHz主時鐘的(de)256分頻來產(chan)生(sheng)一個95.7kHz的(de)轉換速率。

　　L=（Vi-Vsat-Voton）/2Iomax （2）

　　現在我們(men)可以計(ji)算電(dian)感的大(da)小了，假(jia)定充電(dian)電(dian)壓Vi的值(zhi)(zhi)(zhi)為(wei)(wei)15V，飽和電(dian)壓Vsat的值(zhi)(zhi)(zhi)為(wei)(wei)0.5V，需要獲得(de)的輸出電(dian)壓值(zhi)(zhi)(zhi)為(wei)(wei)4.2V,并且最大(da)輸出電(dian)流IＯMAX為(wei)(wei)1500mA，那么(me)，電(dian)感的值(zhi)(zhi)(zhi)至(zhi)少應選為(wei)(wei)18H。

　　需要注意的(de)(de)是：在本電路中的(de)(de)電容(rong)(rong)僅僅是一個(ge)紋波(bo)衰減(jian)器(qi)，因為紋波(bo)與電容(rong)(rong)的(de)(de)大(da)小成反(fan)比例關(guan)系，所以電容(rong)(rong)的(de)(de)值越大(da)，衰減(jian)效果越好。