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(ju)有較高(gao)的(de)測(ce)量精(jing)度(du)，可(ke)很好的(de)控制充(chong)電(dian)電(dian)流(liu)的(de)大小，適時的(de)調整(zheng)，并可(ke)根據充(chong)電(dian)的(de)狀態判斷充(chong)電(dian)的(de)時間(jian)，及(ji)時終止充(chong)電(dian)，以避(bi)免(mian)電(dian)池的(de)過充(chong)。

　　本文討(tao)論(lun)使(shi)(shi)用(yong)C8051F310器(qi)件設計鋰(li)離子(zi)電(dian)(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)(dian)器(qi)的(de)。利用(yong)PWM脈寬調制(zhi)產生(sheng)可用(yong)軟件控制(zhi)的(de)充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)源，以適應不同階(jie)段的(de)充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流的(de)要求。溫(wen)度傳感(gan)器(qi)對(dui)電(dian)(dian)(dian)(dian)池(chi)溫(wen)度進行監測，并通過AD轉換(huan)和相關計算檢測電(dian)(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)壓(ya)和電(dian)(dian)(dian)(dian)流，以判斷電(dian)(dian)(dian)(dian)池(chi)到達哪個階(jie)段。使(shi)(shi)電(dian)(dian)(dian)(dian)池(chi)具有更長的(de)使(shi)(shi)用(yong)壽命，更有效(xiao)的(de)充(chong)電(dian)(dian)(dian)(dian)方法。

　　設計過程

　　1 充電原理

　　電(dian)池的(de)(de)(de)特性唯一地決定其(qi)安全性能和充電(dian)的(de)(de)(de)效率。電(dian)池的(de)(de)(de)最佳充電(dian)方法是(shi)由電(dian)池的(de)(de)(de)化學(xue)成分決定的(de)(de)(de)（鋰(li)離子、鎳氫、鎳鎘還是(shi)SLA電(dian)池等）。盡(jin)管如此，大多數充電(dian)方案都包含下面的(de)(de)(de)三個(ge)階段：

　　● 低電(dian)流調節(jie)階段

　　● 恒流階段

　　● 恒壓階段/充電終止

　　所有電(dian)(dian)(dian)(dian)(dian)(dian)池都是(shi)(shi)通過向(xiang)自(zi)身(shen)傳輸電(dian)(dian)(dian)(dian)(dian)(dian)能的(de)方法進行充(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)取(qu)決(jue)于電(dian)(dian)(dian)(dian)(dian)(dian)池的(de)額定容量（C）例如，一節容量為1000mAh的(de)電(dian)(dian)(dian)(dian)(dian)(dian)池在(zai)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)為1000mA時，可(ke)以(yi)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)1C（電(dian)(dian)(dian)(dian)(dian)(dian)池容量的(de)1倍）也可(ke)以(yi)用(yong)1/50C（20mA）或(huo)更(geng)低(di)(di)的(de)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)給(gei)電(dian)(dian)(dian)(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)。盡管如此，這只是(shi)(shi)一個(ge)普通的(de)低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)方式，不適用(yong)于要(yao)求短充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)時間的(de)快速充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)方案。

　　現在使用的大多數充電器在(zai)(zai)(zai)(zai)給電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)時都是既使用(yong)低(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)方式又(you)使用(yong)額定充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)(de)方法，即(ji)容積(ji)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，低(di)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)通常(chang)使用(yong)在(zai)(zai)(zai)(zai)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)初(chu)(chu)始階(jie)(jie)段(duan)(duan)(duan)(duan)。在(zai)(zai)(zai)(zai)這一階(jie)(jie)段(duan)(duan)(duan)(duan)，需要將會導致(zhi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)過程終止的(de)(de)(de)芯(xin)片(pian)初(chu)(chu)期(qi)的(de)(de)(de)自熱(re)效應減小到最低(di)程度，容積(ji)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)通常(chang)用(yong)在(zai)(zai)(zai)(zai)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)中(zhong)級階(jie)(jie)段(duan)(duan)(duan)(duan)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池的(de)(de)(de)大部分(fen)能量都是在(zai)(zai)(zai)(zai)這一階(jie)(jie)段(duan)(duan)(duan)(duan)存儲的(de)(de)(de)。在(zai)(zai)(zai)(zai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)最后階(jie)(jie)段(duan)(duan)(duan)(duan)，通常(chang)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)時間的(de)(de)(de)絕大部分(fen)都是消(xiao)耗(hao)在(zai)(zai)(zai)(zai)這一階(jie)(jie)段(duan)(duan)(duan)(duan)，可以通過監測電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)、電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓或兩者(zhe)的(de)(de)(de)值(zhi)來(lai)決定何時結束充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。同(tong)樣，結束方案依賴于電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池的(de)(de)(de)化學特(te)性，例如：大多數鋰離子電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器都是將電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓保(bao)持在(zai)(zai)(zai)(zai)恒定值(zhi)，同(tong)時檢測最低(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)。鎳鎘、NiCd電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池用(yong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓或溫度的(de)(de)(de)變化率來(lai)決定充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)結束時間。

　　圖1 鋰離子電池充電模塊圖

　　充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)時(shi)(shi)(shi)部分電(dian)(dian)(dian)(dian)(dian)(dian)能(neng)被轉換成(cheng)熱(re)能(neng)，直至電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)(chong)滿(man)。而充(chong)(chong)(chong)滿(man)后，所有(you)(you)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)能(neng)將全部被轉換成(cheng)熱(re)能(neng)。如(ru)果(guo)此時(shi)(shi)(shi)不終止(zhi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)，電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)就會被損壞或燒毀。快速充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器(qi)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)（完全充(chong)(chong)(chong)滿(man)的(de)(de)時(shi)(shi)(shi)間小(xiao)于(yu)兩(liang)小(xiao)時(shi)(shi)(shi)的(de)(de)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器(qi)）則可以(yi)解決這個問題(ti)，因為(wei)這些充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器(qi)是(shi)使用高充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流來(lai)(lai)縮短充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)時(shi)(shi)(shi)間的(de)(de)。因此，對于(yu)鋰離子電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)來(lai)(lai)說(shuo)，監測它(ta)的(de)(de)溫(wen)度是(shi)至關重要的(de)(de)，因為(wei)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)在(zai)過充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)時(shi)(shi)(shi)會發(fa)生(sheng)爆裂，在(zai)所有(you)(you)的(de)(de)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)階段都應(ying)該隨時(shi)(shi)(shi)監測溫(wen)度的(de)(de)變化，并且在(zai)溫(wen)度超(chao)過最大設(she)定值(zhi)時(shi)(shi)(shi)立(li)即停止(zhi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)。

　　2 總體設計

　　充(chong)電(dian)電(dian)路(lu)由(you)三部(bu)(bu)分：控制(zhi)(zhi)部(bu)(bu)分，檢測(ce)部(bu)(bu)分及充(chong)電(dian)部(bu)(bu)分組(zu)成。如(ru)圖1所示，采用(yong)F310單(dan)片機進行充(chong)電(dian)控制(zhi)(zhi)，單(dan)片機本身具有脈(mo)寬調制(zhi)(zhi)PWM型開關穩壓(ya)電(dian)源所需的全部(bu)(bu)功能，具有10位A/D轉換器。利用(yong)單(dan)片機A/D端口，構成電(dian)池電(dian)壓(ya)，電(dian)流，溫度(du)檢測(ce)電(dian)路(lu)。

　　單片機通過電(dian)壓反(fan)饋和電(dian)流(liu)反(fan)饋信(xin)號，直接(jie)利(li)用PWM輸出將數(shu)字(zi)電(dian)壓信(xin)號并轉(zhuan)化成模擬(ni)電(dian)壓信(xin)號，能夠(gou)保(bao)證控制精度。

　　3 控制部(bu)分電路(lu)設計

　　C8051F310單片機

　　①模擬外設

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

　　b.兩個(ge)模擬比較器：可(ke)編程回差(cha)電(dian)壓和響應時間，可(ke)配置為中斷或復位源，小電(dian)流（〈0.5μA）。

　　②供電電壓

　　a.典型工作(zuo)電流：5mA、25MHz；

　　b.典型停機電(dian)流：0.1μA；

　　c.溫(wen)度范(fan)圍：-40～+85℃。

　　③高速8051微控制器內核

　　a.流水線指令結(jie)構(gou)：70%的(de)指令的(de)執行時間為一個或兩個系統時鐘周期；

　　b.速度可(ke)達25MI/s（時(shi)鐘頻(pin)率為25MHz時(shi)）；

　　c.擴(kuo)展(zhan)的中斷系統。

　　④數字外設

　　a.29/25個(ge)端口(kou)I/O：所(suo)有的(de)口(kou)線均耐5V電壓；

　　b.4個通用16位計數(shu)器(qi)/定時(shi)器(qi)；

　　c.16位(wei)可編程計(ji)數(shu)器/定時器陣列（PCA），有(you)5個捕捉/比較模(mo)塊；

　　d.使用PCA或定時(shi)器和外部時(shi)鐘源的實(shi)時(shi)時(shi)鐘方式。

　　控制電(dian)路中如圖2所示，P0.3口提供充電(dian)電(dian)源，P0.6口檢(jian)測(ce)(ce)充電(dian)電(dian)壓的大小(xiao)，P0.5口檢(jian)測(ce)(ce)充電(dian)電(dian)流(liu)的大小(xiao)，P0.4口檢(jian)測(ce)(ce)電(dian)池的溫度。

　　充電電流(liu)(liu)由單片機脈寬調制PWM產生，充電電流(liu)(liu)由AD轉(zhuan)換再經過(guo)計算得(de)出(chu)。

　　4 充電部分及(ji)檢(jian)測部分電路設計(ji)

　　圖(tu)2 控(kong)制電路接線圖(tu)

　　圖3 充電(dian)電(dian)路與檢(jian)測電(dian)路圖

　　圖3為充電(dian)電(dian)路與檢測電(dian)路圖。

　　①充電過程曲線

　　圖4 鋰(li)電(dian)(dian)池(chi)充電(dian)(dian)曲線

　　如圖4所示，充電(dian)過(guo)程由(you)預充狀(zhuang)態(tai)，恒流充電(dian)狀(zhuang)態(tai)和恒壓充電(dian)狀(zhuang)態(tai)組成。

　　②快速轉換器

　　實現漸弱終止充電器的最經濟的方法(fa)就(jiu)是用一個(ge)(ge)快速轉(zhuan)換(huan)器。快速轉(zhuan)換(huan)器是用一個(ge)(ge)電(dian)感和(he)/或(huo)一個(ge)(ge)變壓器（需要隔離的時(shi)候用變壓器）作(zuo)(zuo)為(wei)能(neng)量存(cun)儲(chu)單(dan)元(yuan)以離散的能(neng)量包的形式(shi)將(jiang)能(neng)量從輸(shu)入傳輸(shu)至輸(shu)出(chu)的開關調節(jie)器反饋電(dian)路(lu)，通過(guo)晶(jing)體(ti)管來調節(jie)能(neng)量的傳輸(shu)，同時(shi)也(ye)作(zuo)(zuo)為(wei)過(guo)濾開關，以確(que)保(bao)電(dian)壓或(huo)電(dian)流在負載時(shi)保(bao)持恒定。

　　如圖(tu)a開關閉合(he)

　　如圖(tu)b開(kai)關打開(kai)

　　快速(su)調(diao)節器(qi)的操作(zuo)是(shi)通過控(kong)制一個(ge)晶體管開關的占空比來(lai)實現的。占空比會(hui)自動增加以使電池流入更多的電流。當(dang)VBATT

　　③電感的確定

　　電(dian)(dian)(dian)(dian)(dian)感(gan)對(dui)交(jiao)(jiao)流(liu)(liu)電(dian)(dian)(dian)(dian)(dian)是有阻礙作(zuo)用的(de)。在(zai)交(jiao)(jiao)流(liu)(liu)電(dian)(dian)(dian)(dian)(dian)頻率(lv)一(yi)(yi)定(ding)的(de)情(qing)況(kuang)下，電(dian)(dian)(dian)(dian)(dian)感(gan)量(liang)越(yue)(yue)大，對(dui)交(jiao)(jiao)流(liu)(liu)電(dian)(dian)(dian)(dian)(dian)的(de)阻礙能(neng)力越(yue)(yue)強，電(dian)(dian)(dian)(dian)(dian)感(gan)量(liang)越(yue)(yue)小，其阻礙能(neng)力越(yue)(yue)小。另外，在(zai)電(dian)(dian)(dian)(dian)(dian)感(gan)量(liang)一(yi)(yi)定(ding)的(de)情(qing)況(kuang)下，交(jiao)(jiao)流(liu)(liu)電(dian)(dian)(dian)(dian)(dian)的(de)頻率(lv)越(yue)(yue)高(gao)，電(dian)(dian)(dian)(dian)(dian)感(gan)對(dui)交(jiao)(jiao)流(liu)(liu)電(dian)(dian)(dian)(dian)(dian)的(de)阻礙能(neng)力越(yue)(yue)大，頻率(lv)越(yue)(yue)低，電(dian)(dian)(dian)(dian)(dian)感(gan)對(dui)交(jiao)(jiao)流(liu)(liu)電(dian)(dian)(dian)(dian)(dian)的(de)阻礙能(neng)力越(yue)(yue)小。也就是說，電(dian)(dian)(dian)(dian)(dian)感(gan)有阻止交(jiao)(jiao)流(liu)(liu)電(dian)(dian)(dian)(dian)(dian)通(tong)過的(de)特(te)性(xing)。

　　其(qi)工作(zuo)原理是這樣的(de)(de)：當負(fu)載(zai)(zai)(zai)兩(liang)(liang)(liang)端(duan)的(de)(de)電(dian)(dian)(dian)(dian)壓(ya)要降低時，通過MOSFET場(chang)效(xiao)應(ying)管的(de)(de)開(kai)(kai)關(guan)(guan)作(zuo)用(yong)，外部(bu)電(dian)(dian)(dian)(dian)源對電(dian)(dian)(dian)(dian)感進(jin)行(xing)充電(dian)(dian)(dian)(dian)并達到所需的(de)(de)額定電(dian)(dian)(dian)(dian)壓(ya)。當負(fu)載(zai)(zai)(zai)兩(liang)(liang)(liang)端(duan)地(di)電(dian)(dian)(dian)(dian)壓(ya)升高時，通過MOSFET場(chang)效(xiao)應(ying)管的(de)(de)開(kai)(kai)關(guan)(guan)作(zuo)用(yong)，外部(bu)電(dian)(dian)(dian)(dian)源供電(dian)(dian)(dian)(dian)斷開(kai)(kai)，電(dian)(dian)(dian)(dian)感釋放出剛(gang)才充入的(de)(de)能量，這時電(dian)(dian)(dian)(dian)感就(jiu)變(bian)成了電(dian)(dian)(dian)(dian)源繼續對負(fu)載(zai)(zai)(zai)供電(dian)(dian)(dian)(dian)。隨著電(dian)(dian)(dian)(dian)感上存儲的(de)(de)能量地(di)消耗(hao)。負(fu)載(zai)(zai)(zai)兩(liang)(liang)(liang)端(duan)的(de)(de)電(dian)(dian)(dian)(dian)壓(ya)開(kai)(kai)始逐(zhu)漸降低，外部(bu)電(dian)(dian)(dian)(dian)源通過MOSFET場(chang)效(xiao)應(ying)管的(de)(de)開(kai)(kai)關(guan)(guan)作(zuo)用(yong)又要充電(dian)(dian)(dian)(dian)。依(yi)次類(lei)推在(zai)不(bu)斷的(de)(de)充電(dian)(dian)(dian)(dian)和(he)放電(dian)(dian)(dian)(dian)的(de)(de)過程中(zhong)形成了一種穩定的(de)(de)電(dian)(dian)(dian)(dian)壓(ya)，永(yong)遠使負(fu)載(zai)(zai)(zai)兩(liang)(liang)(liang)端(duan)地(di)電(dian)(dian)(dian)(dian)壓(ya)不(bu)會升高也不(bu)會降低，這就(jiu)是開(kai)(kai)關(guan)(guan)電(dian)(dian)(dian)(dian)源的(de)(de)最大優勢。

　　要確定快速轉(zhuan)換(huan)器(qi)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(zhuan)換(huan)器(qi)操(cao)作操(cao)作效(xiao)率最高。占空比由方程式1給出(chu)：

　　（其中(zhong)T是PWM的周期在(zai)程序示例中(zhong)T=10.5s）

　　占空(kong)比=ton/T （1）

　　至此就可(ke)以選擇一個PWM的(de)轉換(huan)頻率（如方程式2所(suo)示）PWM的(de)轉換(huan)頻率越(yue)大，則電感的(de)值越(yue)小，也越(yue)節約成(cheng)本。

　　我的(de)示例代碼配置F310的(de)8位硬件PWM是使用內部(bu)24.5MHz主時鐘的(de)256分(fen)頻(pin)來產生一個95.7kHz的(de)轉換速率(lv)。

　　L=（Vi-Vsat-Voton）/2Iomax （2）

　　現在我(wo)們(men)可(ke)以計(ji)算電(dian)(dian)感(gan)的(de)大小了，假(jia)定充電(dian)(dian)電(dian)(dian)壓Vi的(de)值為(wei)(wei)15V，飽和電(dian)(dian)壓Vsat的(de)值為(wei)(wei)0.5V，需要獲得(de)的(de)輸出(chu)電(dian)(dian)壓值為(wei)(wei)4.2V,并且(qie)最大輸出(chu)電(dian)(dian)流IＯMAX為(wei)(wei)1500mA，那么(me)，電(dian)(dian)感(gan)的(de)值至少應選為(wei)(wei)18H。

　　需(xu)要(yao)注意的(de)是：在本(ben)電(dian)路(lu)中的(de)電(dian)容僅(jin)僅(jin)是一個紋波衰減(jian)器，因為紋波與電(dian)容的(de)大小成(cheng)反比例(li)關系，所以電(dian)容的(de)值越(yue)大，衰減(jian)效果(guo)越(yue)好。