C8051F310器件(jian)設計鋰(li)離(li)子電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充電(dian)(dian)(dian)(dian)(dian)器。利用PWM脈寬調制產生可用軟件(jian)控制的充電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)源，以(yi)適應不(bu)同階(jie)段的充電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)的要(yao)求。溫度(du)傳感器對電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)溫度(du)進行監(jian)測，并通過AD轉換和相關計算檢測電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓和電(dian)(dian)(dian)(dian)(dian)流(liu)，以(yi)判斷電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)到達(da)哪個(ge)階(jie)段。使電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)具有更長的使用壽(shou)命。

設計過程

1  充電原理

　　電(dian)(dian)(dian)(dian)池的(de)(de)(de)特性(xing)唯(wei)一地決(jue)定其安(an)全性(xing)能和充電(dian)(dian)(dian)(dian)的(de)(de)(de)效率。電(dian)(dian)(dian)(dian)池的(de)(de)(de)最佳充電(dian)(dian)(dian)(dian)方法是由電(dian)(dian)(dian)(dian)池的(de)(de)(de)化學成分決(jue)定的(de)(de)(de)（鋰離子、鎳氫、鎳鎘(ge)還是SLA電(dian)(dian)(dian)(dian)池等）。盡管如此，大(da)多(duo)數充電(dian)(dian)(dian)(dian)方案(an)都包含下面(mian)的(de)(de)(de)三個階段(duan)：

　　低電流調節階段

　　恒流階段

　　恒(heng)壓階段/充電終(zhong)止

　　所有電(dian)(dian)(dian)(dian)池都是通(tong)過向自身傳輸電(dian)(dian)(dian)(dian)能的(de)方法進行充(chong)(chong)電(dian)(dian)(dian)(dian)的(de)，一節(jie)電(dian)(dian)(dian)(dian)池的(de)最大充(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)取決于(yu)電(dian)(dian)(dian)(dian)池的(de)額定(ding)容(rong)量（C）例如，一節(jie)容(rong)量為1000mAh的(de)電(dian)(dian)(dian)(dian)池在充(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)為1000mA時，可(ke)以充(chong)(chong)電(dian)(dian)(dian)(dian)1C（電(dian)(dian)(dian)(dian)池容(rong)量的(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(gei)電(dian)(dian)(dian)(dian)池充(chong)(chong)電(dian)(dian)(dian)(dian)。

　　現在使用的大多數充電器在(zai)給電(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)時(shi)都(dou)是(shi)既使(shi)用低電(dian)(dian)(dian)流充(chong)電(dian)(dian)(dian)方式又使(shi)用額定充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流的(de)方法(fa)，即容積充(chong)電(dian)(dian)(dian)，低充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流通常(chang)使(shi)用在(zai)充(chong)電(dian)(dian)(dian)的(de)初(chu)始階(jie)段。在(zai)這一(yi)階(jie)段，需要將會導致充(chong)電(dian)(dian)(dian)過程終止的(de)芯片(pian)初(chu)期的(de)自熱效(xiao)應(ying)減小到最(zui)低程度，容積充(chong)電(dian)(dian)(dian)通常(chang)用在(zai)充(chong)電(dian)(dian)(dian)的(de)中級階(jie)段，電(dian)(dian)(dian)池的(de)大部分能量(liang)都(dou)是(shi)在(zai)這一(yi)階(jie)段存儲(chu)的(de)。

　　充(chong)電(dian)(dian)(dian)(dian)時(shi)部(bu)分電(dian)(dian)(dian)(dian)能被轉(zhuan)換成熱能，直至(zhi)電(dian)(dian)(dian)(dian)池充(chong)滿。而充(chong)滿后，所有的電(dian)(dian)(dian)(dian)能將全部(bu)被轉(zhuan)換成熱能。如果此時(shi)不終止(zhi)充(chong)電(dian)(dian)(dian)(dian)，電(dian)(dian)(dian)(dian)池就會被損壞或燒毀。快速(su)充(chong)電(dian)(dian)(dian)(dian)器電(dian)(dian)(dian)(dian)池則可以解(jie)決這(zhe)個問題，因為這(zhe)些充(chong)電(dian)(dian)(dian)(dian)器是(shi)使用高充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流來縮短充(chong)電(dian)(dian)(dian)(dian)時(shi)間的。

2  總體設計

　　充(chong)電(dian)電(dian)路由三部分：控制部分，檢測部分及充(chong)電(dian)部分組成。

　　如(ru)圖1所(suo)示，采用F310單片機進行充(chong)電(dian)控制，單片機本身具(ju)有脈寬調制PWM型開(kai)關穩壓電(dian)源(yuan)所(suo)需(xu)的全(quan)部功能，具(ju)有10位A/D轉換器。

　　利用單(dan)片機A/D端(duan)口，構成電(dian)池電(dian)壓(ya)，電(dian)流(liu)，溫度(du)檢測電(dian)路(lu)。

 

 

 

    圖1  鋰離子電池(chi)充電模塊(kuai)圖

    單片機通(tong)過(guo)電壓反饋和電流反饋信(xin)號，直接利用PWM輸出將(jiang)數字電壓信(xin)號并轉化成模擬電壓信(xin)號，能夠保(bao)證(zheng)控制(zhi)精度。

3  控制部分電路設計

　　C8051F310單(dan)片機

　　①模擬外設

　　a.10位ADC：轉換速度可(ke)(ke)達200ks/s,可(ke)(ke)多(duo)達21或17個外(wai)部(bu)單(dan)端或差(cha)分(fen)輸(shu)(shu)入，VREF可(ke)(ke)在(zai)外(wai)部(bu)引腳或VDD中選擇，內置(zhi)溫度傳感器（±3℃），外(wai)部(bu)轉換啟(qi)動輸(shu)(shu)入；

　　b.兩個模擬(ni)比較器：可編程回差(cha)電(dian)壓和響(xiang)應時間，可配置為中斷或復位(wei)源，小(xiao)電(dian)流（〈0.5μA）。

　　②供電電壓

　　a.典(dian)型工作電流：5mA、25MHz；

　　b.典型停機(ji)電流：0.1μA；

　　c.溫度(du)范圍：-40～+85℃。

　　③高速8051微控制器內核

　　a.流水(shui)線指(zhi)令結構：70%的(de)指(zhi)令的(de)執行時(shi)間為一個或(huo)兩個系(xi)統時(shi)鐘(zhong)周期；

　　b.速度可達25MI/s（時鐘頻率(lv)為25MHz時）；

　　c.擴展的中斷系(xi)統。

　　④數字外設

　　a.29/25個端(duan)口(kou)I/O：所有(you)的口(kou)線均耐5V電壓；

　　b.4個通用16位計數(shu)器/定時器；

　　c.16位可編程計(ji)數器(qi)/定(ding)時器(qi)陣列（PCA），有5個(ge)捕(bu)捉/比較模塊；

　　d.使用PCA或定時(shi)器和外(wai)部時(shi)鐘源的(de)實時(shi)時(shi)鐘方(fang)式。

　　控制電(dian)(dian)(dian)(dian)(dian)路中如圖2所示，P0.3口(kou)提供充電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)源，P0.6口(kou)檢測充電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓的(de)大(da)小(xiao)，P0.5口(kou)檢測充電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流的(de)大(da)小(xiao)，P0.4口(kou)檢測電(dian)(dian)(dian)(dian)(dian)池的(de)溫(wen)度。

  

 

    圖2  控制(zhi)電路接(jie)線(xian)圖

　　充(chong)電(dian)電(dian)流由單片機脈寬調制PWM產生，充(chong)電(dian)電(dian)流由AD轉換再經過計算得出。

  

4  充(chong)電部(bu)分(fen)及檢測(ce)部(bu)分(fen)電路設計(ji)

　　圖3為充電(dian)(dian)電(dian)(dian)路與(yu)檢測(ce)電(dian)(dian)路圖。

  

 

    圖3  充電電路(lu)與檢測電路(lu)圖

 　　①充(chong)電過程曲線

　　如圖4所示，充電過程由預充狀態，恒(heng)流(liu)充電狀態和恒(heng)壓充電狀態組成。

  

 

    圖4  鋰電池充電曲線(xian)

　　②快速轉換器

　　實現(xian)漸弱終止充電(dian)(dian)(dian)器(qi)(qi)的(de)最經(jing)濟的(de)方法就(jiu)是用(yong)一個(ge)快(kuai)速(su)轉換器(qi)(qi)。快(kuai)速(su)轉換器(qi)(qi)是用(yong)一個(ge)電(dian)(dian)(dian)感和(he)/或一個(ge)變(bian)壓器(qi)(qi)（需(xu)要隔離的(de)時候(hou)用(yong)變(bian)壓器(qi)(qi)）作為能(neng)量(liang)(liang)存儲單元以離散的(de)能(neng)量(liang)(liang)包的(de)形(xing)式將能(neng)量(liang)(liang)從輸(shu)入傳(chuan)輸(shu)至(zhi)輸(shu)出的(de)開(kai)關(guan)調(diao)節(jie)器(qi)(qi)反饋(kui)電(dian)(dian)(dian)路，通過晶體管來(lai)調(diao)節(jie)能(neng)量(liang)(liang)的(de)傳(chuan)輸(shu)，同(tong)時也(ye)作為過濾開(kai)關(guan)，以確保電(dian)(dian)(dian)壓或電(dian)(dian)(dian)流在負載(zai)時保持恒(heng)定。

　　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  開關閉合

 

  

b  開(kai)(kai)關打開(kai)(kai)

    圖5  快速(su)轉(zhuan)換器操作

　　③電感的確定

　　電(dian)感對(dui)交流(liu)(liu)電(dian)是有(you)阻礙(ai)作用(yong)的(de)。在交流(liu)(liu)電(dian)頻率一(yi)定的(de)情況(kuang)下，電(dian)感量越大，對(dui)交流(liu)(liu)電(dian)的(de)阻礙(ai)能力越強(qiang)，電(dian)感量越小，其(qi)阻礙(ai)能力越小。

　　其工作(zuo)(zuo)原理是這樣(yang)的：當(dang)負載(zai)兩(liang)端的電(dian)(dian)壓(ya)要降(jiang)低時(shi)(shi)，通(tong)過MOSFET場效(xiao)應管(guan)的開(kai)關作(zuo)(zuo)用(yong)(yong)，外(wai)部電(dian)(dian)源對(dui)電(dian)(dian)感進行充電(dian)(dian)并達到所需(xu)的額(e)定電(dian)(dian)壓(ya)。當(dang)負載(zai)兩(liang)端地(di)電(dian)(dian)壓(ya)升(sheng)高(gao)時(shi)(shi)，通(tong)過MOSFET場效(xiao)應管(guan)的開(kai)關作(zuo)(zuo)用(yong)(yong)，外(wai)部電(dian)(dian)源供(gong)電(dian)(dian)斷(duan)開(kai)，電(dian)(dian)感釋放出剛才充入的能量，這時(shi)(shi)電(dian)(dian)感就變(bian)成了(le)電(dian)(dian)源繼續(xu)對(dui)負載(zai)供(gong)電(dian)(dian)。隨著電(dian)(dian)感上(shang)存儲的能量地(di)消耗。負載(zai)兩(liang)端的電(dian)(dian)壓(ya)開(kai)始(shi)逐漸降(jiang)低，外(wai)部電(dian)(dian)源通(tong)過MOSFET場效(xiao)應管(guan)的開(kai)關作(zuo)(zuo)用(yong)(yong)又要充電(dian)(dian)。