C8051F310器件設計鋰離子電(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)(dian)(dian)器。利用(yong)(yong)PWM脈寬(kuan)調制產生(sheng)可用(yong)(yong)軟件控制的(de)充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)源(yuan)，以適應不同階段(duan)的(de)充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流的(de)要求。溫度(du)傳感器對電(dian)(dian)(dian)(dian)池(chi)(chi)溫度(du)進行監測，并通過AD轉換和相關計算檢(jian)測電(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)壓和電(dian)(dian)(dian)(dian)流，以判(pan)斷電(dian)(dian)(dian)(dian)池(chi)(chi)到達哪個階段(duan)。使電(dian)(dian)(dian)(dian)池(chi)(chi)具有更(geng)長(chang)的(de)使用(yong)(yong)壽命。

設計過程

1  充電原理

　　電(dian)(dian)池(chi)的(de)特性唯一地(di)決(jue)(jue)定其安全性能和充電(dian)(dian)的(de)效率。電(dian)(dian)池(chi)的(de)最佳充電(dian)(dian)方法是(shi)(shi)由電(dian)(dian)池(chi)的(de)化學成(cheng)分(fen)決(jue)(jue)定的(de)（鋰離(li)子、鎳(nie)氫、鎳(nie)鎘還(huan)是(shi)(shi)SLA電(dian)(dian)池(chi)等）。盡(jin)管(guan)如此，大多數充電(dian)(dian)方案都包含(han)下面的(de)三個(ge)階段：

　　低電流調節階段

　　恒流階段

　　恒壓(ya)階段/充電(dian)終止

　　所有電(dian)(dian)(dian)(dian)池(chi)都是通(tong)過向自身傳輸(shu)電(dian)(dian)(dian)(dian)能的(de)方(fang)法進行充電(dian)(dian)(dian)(dian)的(de)，一節電(dian)(dian)(dian)(dian)池(chi)的(de)最(zui)大(da)充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)取決于電(dian)(dian)(dian)(dian)池(chi)的(de)額定(ding)容(rong)量（C）例如，一節容(rong)量為1000mAh的(de)電(dian)(dian)(dian)(dian)池(chi)在充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)為1000mA時(shi)，可(ke)(ke)以充電(dian)(dian)(dian)(dian)1C（電(dian)(dian)(dian)(dian)池(chi)容(rong)量的(de)1倍(bei)）也可(ke)(ke)以用(yong)1/50C（20mA）或更低(di)的(de)電(dian)(dian)(dian)(dian)流(liu)(liu)給電(dian)(dian)(dian)(dian)池(chi)充電(dian)(dian)(dian)(dian)。

　　現在使用的大多數充電器在(zai)(zai)給電(dian)(dian)(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)(dian)(dian)時都(dou)是既使用(yong)(yong)低電(dian)(dian)(dian)(dian)(dian)流充(chong)電(dian)(dian)(dian)(dian)(dian)方式又使用(yong)(yong)額(e)定充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流的(de)(de)方法，即容積充(chong)電(dian)(dian)(dian)(dian)(dian)，低充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流通(tong)常使用(yong)(yong)在(zai)(zai)充(chong)電(dian)(dian)(dian)(dian)(dian)的(de)(de)初始(shi)階(jie)段(duan)。在(zai)(zai)這一(yi)(yi)階(jie)段(duan)，需要將會(hui)導致充(chong)電(dian)(dian)(dian)(dian)(dian)過程終止的(de)(de)芯(xin)片初期的(de)(de)自熱效應減小到最低程度，容積充(chong)電(dian)(dian)(dian)(dian)(dian)通(tong)常用(yong)(yong)在(zai)(zai)充(chong)電(dian)(dian)(dian)(dian)(dian)的(de)(de)中級階(jie)段(duan)，電(dian)(dian)(dian)(dian)(dian)池的(de)(de)大(da)部分能量都(dou)是在(zai)(zai)這一(yi)(yi)階(jie)段(duan)存儲的(de)(de)。

　　充(chong)(chong)電時部(bu)(bu)分電能(neng)被(bei)轉換(huan)成熱能(neng)，直至電池充(chong)(chong)滿。而充(chong)(chong)滿后(hou)，所有(you)的電能(neng)將(jiang)全部(bu)(bu)被(bei)轉換(huan)成熱能(neng)。如果(guo)此時不終止充(chong)(chong)電，電池就會被(bei)損壞或燒毀。快(kuai)速充(chong)(chong)電器電池則可以解決這個(ge)問(wen)題，因為這些充(chong)(chong)電器是使用高(gao)充(chong)(chong)電電流來縮(suo)短充(chong)(chong)電時間的。

2  總體設計

　　充(chong)電(dian)電(dian)路由三部(bu)(bu)分(fen)(fen)(fen)：控制部(bu)(bu)分(fen)(fen)(fen)，檢(jian)測部(bu)(bu)分(fen)(fen)(fen)及充(chong)電(dian)部(bu)(bu)分(fen)(fen)(fen)組成。

　　如(ru)圖1所(suo)示，采用F310單(dan)片(pian)機進(jin)行充電控制(zhi)，單(dan)片(pian)機本身(shen)具(ju)有脈寬調制(zhi)PWM型開關穩壓(ya)電源所(suo)需的全部功能，具(ju)有10位(wei)A/D轉換器。

　　利用單片(pian)機A/D端口，構成電池(chi)電壓，電流，溫度檢測電路。

 

 

 

    圖1  鋰離子電池充電模塊圖

    單(dan)片機通(tong)過電(dian)壓(ya)反饋和(he)電(dian)流反饋信(xin)號(hao)，直接利用PWM輸出將(jiang)數(shu)字(zi)電(dian)壓(ya)信(xin)號(hao)并轉化(hua)成(cheng)模擬(ni)電(dian)壓(ya)信(xin)號(hao)，能夠保(bao)證控制精(jing)度。

3  控制部分電路設計

　　C8051F310單(dan)片(pian)機

　　①模擬外設

　　a.10位ADC：轉換速度可(ke)達(da)200ks/s,可(ke)多達(da)21或17個外部單端或差分(fen)輸(shu)入(ru)(ru)，VREF可(ke)在外部引腳(jiao)或VDD中選(xuan)擇，內置溫度傳感(gan)器（±3℃），外部轉換啟動輸(shu)入(ru)(ru)；

　　b.兩(liang)個(ge)模擬比較器：可(ke)編(bian)程回差(cha)電(dian)壓和響應(ying)時間，可(ke)配置(zhi)為中斷或復位源，小電(dian)流（〈0.5μA）。

　　②供電電壓

　　a.典型工作電流：5mA、25MHz；

　　b.典型停機電流(liu)：0.1μA；

　　c.溫度(du)范圍(wei)：-40～+85℃。

　　③高(gao)速8051微控(kong)制器內核(he)

　　a.流水(shui)線(xian)指令結構：70%的(de)指令的(de)執行(xing)時間為一個或兩(liang)個系統(tong)時鐘周期；

　　b.速度(du)可(ke)達25MI/s（時鐘頻率為25MHz時）；

　　c.擴展的(de)中斷系統。

　　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(yong)16位計(ji)數器/定時器；

　　c.16位可編程計數器(qi)/定時器(qi)陣列（PCA），有5個(ge)捕捉/比較模(mo)塊；

　　d.使用PCA或定時器(qi)和外部(bu)時鐘源的實(shi)時時鐘方式。

　　控(kong)制電(dian)路中如圖2所(suo)示，P0.3口(kou)提供(gong)充電(dian)電(dian)源(yuan)，P0.6口(kou)檢(jian)測充電(dian)電(dian)壓(ya)的(de)大(da)小(xiao)，P0.5口(kou)檢(jian)測充電(dian)電(dian)流的(de)大(da)小(xiao)，P0.4口(kou)檢(jian)測電(dian)池(chi)的(de)溫度。

  

 

    圖2  控制電路接線(xian)圖

　　充(chong)電電流由(you)單片(pian)機脈寬調制(zhi)PWM產生，充(chong)電電流由(you)AD轉換再經過計算得(de)出。

  

4  充電(dian)部分及檢測部分電(dian)路設(she)計

　　圖3為(wei)充電電路與檢測電路圖。

  

 

    圖(tu)3  充(chong)電電路與檢(jian)測電路圖(tu)

 　　①充電(dian)過(guo)程曲線

　　如圖4所示，充電過(guo)程由(you)預充狀態(tai)(tai)，恒(heng)流充電狀態(tai)(tai)和恒(heng)壓充電狀態(tai)(tai)組成。

  

 

    圖4  鋰(li)電池充(chong)電曲線

　　②快速轉換器

　　實(shi)現漸弱終止充(chong)電(dian)器(qi)(qi)的(de)最(zui)經濟的(de)方法就是用一(yi)個(ge)(ge)快(kuai)速轉換器(qi)(qi)。快(kuai)速轉換器(qi)(qi)是用一(yi)個(ge)(ge)電(dian)感和/或一(yi)個(ge)(ge)變壓器(qi)(qi)（需要隔離的(de)時候用變壓器(qi)(qi)）作(zuo)為(wei)能(neng)量存儲單(dan)元以(yi)離散的(de)能(neng)量包(bao)的(de)形式將(jiang)能(neng)量從輸(shu)入傳(chuan)輸(shu)至輸(shu)出(chu)的(de)開(kai)關調節(jie)器(qi)(qi)反饋電(dian)路，通(tong)過晶體管(guan)來調節(jie)能(neng)量的(de)傳(chuan)輸(shu)，同時也作(zuo)為(wei)過濾開(kai)關，以(yi)確保電(dian)壓或電(dian)流(liu)在負(fu)載時保持(chi)恒(heng)定(ding)。

　　快速調節器的操作是通過控制一個晶體管開關的占空比來實現的。占空比會自動增加以使電池流入更多的電流。當VBATT

 

 

  

a  開(kai)關閉合

 

  

b  開(kai)關打開(kai)

    圖5  快(kuai)速轉換器操作(zuo)

　　③電感的確定

　　電感對交(jiao)流電是(shi)有阻(zu)礙(ai)作用的。在(zai)交(jiao)流電頻率一定的情況下，電感量越(yue)大，對交(jiao)流電的阻(zu)礙(ai)能力(li)越(yue)強，電感量越(yue)小，其阻(zu)礙(ai)能力(li)越(yue)小。

　　其工作(zuo)原(yuan)理是這樣的(de)：當負(fu)載(zai)兩(liang)端的(de)電(dian)(dian)(dian)(dian)(dian)壓要(yao)降低(di)時，通(tong)過MOSFET場(chang)效(xiao)(xiao)應管的(de)開(kai)(kai)關(guan)作(zuo)用(yong)，外部(bu)(bu)電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)對(dui)(dui)電(dian)(dian)(dian)(dian)(dian)感(gan)(gan)進行充電(dian)(dian)(dian)(dian)(dian)并達(da)到所需的(de)額定電(dian)(dian)(dian)(dian)(dian)壓。當負(fu)載(zai)兩(liang)端地(di)電(dian)(dian)(dian)(dian)(dian)壓升高時，通(tong)過MOSFET場(chang)效(xiao)(xiao)應管的(de)開(kai)(kai)關(guan)作(zuo)用(yong)，外部(bu)(bu)電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)供(gong)電(dian)(dian)(dian)(dian)(dian)斷開(kai)(kai)，電(dian)(dian)(dian)(dian)(dian)感(gan)(gan)釋放(fang)出(chu)剛才(cai)充入的(de)能(neng)量(liang)(liang)，這時電(dian)(dian)(dian)(dian)(dian)感(gan)(gan)就(jiu)變成了(le)電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)繼續對(dui)(dui)負(fu)載(zai)供(gong)電(dian)(dian)(dian)(dian)(dian)。隨著(zhu)電(dian)(dian)(dian)(dian)(dian)感(gan)(gan)上存儲的(de)能(neng)量(liang)(liang)地(di)消(xiao)耗。負(fu)載(zai)兩(liang)端的(de)電(dian)(dian)(dian)(dian)(dian)壓開(kai)(kai)始逐漸降低(di)，外部(bu)(bu)電(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)通(tong)過MOSFET場(chang)效(xiao)(xiao)應管的(de)開(kai)(kai)關(guan)作(zuo)用(yong)又要(yao)充電(dian)(dian)(dian)(dian)(dian)。