C8051F310器(qi)件設計(ji)鋰(li)離子電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)充(chong)電(dian)(dian)(dian)(dian)(dian)器(qi)。利用(yong)PWM脈(mo)寬調制產生可用(yong)軟件控制的(de)(de)充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)源，以適應不同階段的(de)(de)充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流的(de)(de)要求。溫(wen)度(du)傳感器(qi)對電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)溫(wen)度(du)進行監測，并(bing)通(tong)過AD轉換和(he)相關計(ji)算檢(jian)測電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓和(he)電(dian)(dian)(dian)(dian)(dian)流，以判斷(duan)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)到達哪個階段。使(shi)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)具(ju)有更長的(de)(de)使(shi)用(yong)壽命。

設計過程

1  充電原理

　　電池(chi)(chi)的(de)(de)(de)特性唯一(yi)地(di)決定其安全性能和(he)充電的(de)(de)(de)效率(lv)。電池(chi)(chi)的(de)(de)(de)最佳充電方法是(shi)由(you)電池(chi)(chi)的(de)(de)(de)化學成分(fen)決定的(de)(de)(de)（鋰離子、鎳氫、鎳鎘還(huan)是(shi)SLA電池(chi)(chi)等(deng)）。盡(jin)管如此，大多數充電方案都包(bao)含下面的(de)(de)(de)三個階段：

　　低電流調節階段

　　恒流階段

　　恒(heng)壓階(jie)段(duan)/充電終止

　　所有(you)電(dian)池(chi)(chi)都是通(tong)過向自身傳輸電(dian)能的(de)(de)方法進行充(chong)(chong)電(dian)的(de)(de)，一節(jie)電(dian)池(chi)(chi)的(de)(de)最大充(chong)(chong)電(dian)電(dian)流(liu)取決于電(dian)池(chi)(chi)的(de)(de)額定容(rong)量(liang)(liang)（C）例如，一節(jie)容(rong)量(liang)(liang)為1000mAh的(de)(de)電(dian)池(chi)(chi)在充(chong)(chong)電(dian)電(dian)流(liu)為1000mA時，可(ke)以充(chong)(chong)電(dian)1C（電(dian)池(chi)(chi)容(rong)量(liang)(liang)的(de)(de)1倍）也可(ke)以用1/50C（20mA）或更(geng)低的(de)(de)電(dian)流(liu)給電(dian)池(chi)(chi)充(chong)(chong)電(dian)。

　　現在使用的大多數充電器在(zai)給電(dian)(dian)(dian)池(chi)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)時都是既使(shi)用低(di)電(dian)(dian)(dian)流充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)方(fang)式又使(shi)用額定充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流的(de)(de)(de)方(fang)法，即容積(ji)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)，低(di)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流通常(chang)(chang)使(shi)用在(zai)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)的(de)(de)(de)初始(shi)階(jie)(jie)段(duan)(duan)。在(zai)這一(yi)階(jie)(jie)段(duan)(duan)，需(xu)要將會導致充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)過程終止的(de)(de)(de)芯片初期的(de)(de)(de)自熱效應減小(xiao)到最(zui)低(di)程度(du)，容積(ji)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)通常(chang)(chang)用在(zai)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)的(de)(de)(de)中級(ji)階(jie)(jie)段(duan)(duan)，電(dian)(dian)(dian)池(chi)的(de)(de)(de)大部分能量都是在(zai)這一(yi)階(jie)(jie)段(duan)(duan)存儲的(de)(de)(de)。

　　充電(dian)(dian)(dian)時部(bu)分電(dian)(dian)(dian)能(neng)(neng)被(bei)轉換成熱(re)能(neng)(neng)，直至電(dian)(dian)(dian)池充滿(man)。而(er)充滿(man)后，所有的電(dian)(dian)(dian)能(neng)(neng)將(jiang)全部(bu)被(bei)轉換成熱(re)能(neng)(neng)。如(ru)果此(ci)時不終止(zhi)充電(dian)(dian)(dian)，電(dian)(dian)(dian)池就會被(bei)損壞(huai)或燒毀。快速充電(dian)(dian)(dian)器電(dian)(dian)(dian)池則可以(yi)解決這個問題，因(yin)為(wei)這些充電(dian)(dian)(dian)器是使用高充電(dian)(dian)(dian)電(dian)(dian)(dian)流來縮(suo)短充電(dian)(dian)(dian)時間的。

2  總體設計

　　充電(dian)電(dian)路由三(san)部(bu)分：控制部(bu)分，檢(jian)測(ce)部(bu)分及充電(dian)部(bu)分組(zu)成。

　　如圖1所示，采用F310單(dan)片機(ji)進行充電控制，單(dan)片機(ji)本(ben)身具(ju)有(you)(you)脈(mo)寬調制PWM型開關穩(wen)壓(ya)電源所需的(de)全(quan)部功能，具(ju)有(you)(you)10位A/D轉換器。

　　利用單片機A/D端口，構成電(dian)池電(dian)壓，電(dian)流，溫度檢測電(dian)路。

 

 

 

    圖(tu)(tu)1  鋰離子(zi)電(dian)(dian)池充電(dian)(dian)模塊圖(tu)(tu)

    單片(pian)機(ji)通(tong)過電(dian)(dian)壓反饋(kui)和電(dian)(dian)流反饋(kui)信號，直接利用(yong)PWM輸出將數字(zi)電(dian)(dian)壓信號并轉化成模擬電(dian)(dian)壓信號，能夠保證(zheng)控制精度(du)。

3  控制部分電路設計

　　C8051F310單片(pian)機

　　①模擬外設

　　a.10位(wei)ADC：轉(zhuan)換(huan)(huan)速度可達200ks/s,可多達21或17個外部(bu)(bu)單端或差分輸入，VREF可在外部(bu)(bu)引腳或VDD中選擇，內置溫度傳感器（±3℃），外部(bu)(bu)轉(zhuan)換(huan)(huan)啟動輸入；

　　b.兩個模擬比較器(qi)：可編程(cheng)回差電壓和響應時間，可配置為(wei)中斷或復位源，小電流（〈0.5μA）。

　　②供電電壓

　　a.典(dian)型工(gong)作電流：5mA、25MHz；

　　b.典型停(ting)機電流：0.1μA；

　　c.溫度(du)范圍(wei)：-40～+85℃。

　　③高(gao)速(su)8051微控制(zhi)器(qi)內核

　　a.流水線指令結構：70%的指令的執行時間(jian)為一個(ge)(ge)或兩個(ge)(ge)系統時鐘周期；

　　b.速度可達25MI/s（時鐘頻率為(wei)25MHz時）；

　　c.擴展的中斷系(xi)統(tong)。

　　④數字外設

　　a.29/25個端口I/O：所有(you)的(de)口線(xian)均耐5V電(dian)壓；

　　b.4個通用16位計數器(qi)/定時器(qi)；

　　c.16位可編程計數器/定時(shi)器陣列（PCA），有5個捕捉/比較模塊；

　　d.使用PCA或定時(shi)器和(he)外(wai)部(bu)時(shi)鐘(zhong)源的實時(shi)時(shi)鐘(zhong)方(fang)式(shi)。

　　控制電路(lu)中如圖2所示，P0.3口(kou)提供充(chong)電電源，P0.6口(kou)檢(jian)測充(chong)電電壓的(de)大小(xiao)，P0.5口(kou)檢(jian)測充(chong)電電流(liu)的(de)大小(xiao)，P0.4口(kou)檢(jian)測電池的(de)溫度(du)。

  

 

    圖2  控制(zhi)電路(lu)接線圖

　　充電(dian)(dian)電(dian)(dian)流由(you)單片機脈(mo)寬調制PWM產(chan)生，充電(dian)(dian)電(dian)(dian)流由(you)AD轉換再(zai)經(jing)過計算得出。

  

4  充電部(bu)分(fen)及檢測部(bu)分(fen)電路(lu)設計(ji)

　　圖3為充電電路(lu)與檢測電路(lu)圖。

  

 

    圖(tu)3  充電電路與檢測(ce)電路圖(tu)

 　　①充電(dian)過(guo)程曲線

　　如圖4所示，充電過程由(you)預充狀態(tai)(tai)，恒流充電狀態(tai)(tai)和恒壓(ya)充電狀態(tai)(tai)組成。

  

 

    圖4  鋰電(dian)(dian)池充電(dian)(dian)曲線

　　②快速轉換器

　　實現漸弱(ruo)終(zhong)止充電器的最經濟的方法就是用(yong)(yong)一個(ge)(ge)快速轉換器。快速轉換器是用(yong)(yong)一個(ge)(ge)電感和/或一個(ge)(ge)變壓器（需要隔(ge)離的時候用(yong)(yong)變壓器）作(zuo)為能(neng)(neng)(neng)量存儲單元(yuan)以離散的能(neng)(neng)(neng)量包的形式將能(neng)(neng)(neng)量從輸(shu)入傳輸(shu)至輸(shu)出的開(kai)關調(diao)節器反(fan)饋電路，通(tong)過(guo)晶體(ti)管來調(diao)節能(neng)(neng)(neng)量的傳輸(shu)，同時也(ye)作(zuo)為過(guo)濾(lv)開(kai)關，以確保(bao)電壓或電流(liu)在負(fu)載(zai)時保(bao)持恒定。

　　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  開關打開

    圖(tu)5  快速轉換器操作

　　③電感的確定

　　電感(gan)對交(jiao)(jiao)流電是有阻礙(ai)作用的(de)。在交(jiao)(jiao)流電頻率一定的(de)情(qing)況下，電感(gan)量越(yue)大，對交(jiao)(jiao)流電的(de)阻礙(ai)能力(li)越(yue)強，電感(gan)量越(yue)小，其阻礙(ai)能力(li)越(yue)小。

　　其工作(zuo)原(yuan)理是這樣(yang)的(de)：當負(fu)載兩端的(de)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)要(yao)降(jiang)低時(shi)(shi)，通過MOSFET場(chang)效應管(guan)的(de)開(kai)(kai)(kai)關(guan)作(zuo)用，外部(bu)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)對電(dian)(dian)(dian)(dian)(dian)(dian)感進行充電(dian)(dian)(dian)(dian)(dian)(dian)并(bing)達(da)到所需的(de)額(e)定電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)。當負(fu)載兩端地(di)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)升(sheng)高時(shi)(shi)，通過MOSFET場(chang)效應管(guan)的(de)開(kai)(kai)(kai)關(guan)作(zuo)用，外部(bu)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)供電(dian)(dian)(dian)(dian)(dian)(dian)斷開(kai)(kai)(kai)，電(dian)(dian)(dian)(dian)(dian)(dian)感釋放出剛才充入(ru)的(de)能量(liang)，這時(shi)(shi)電(dian)(dian)(dian)(dian)(dian)(dian)感就變(bian)成(cheng)了電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)繼續(xu)對負(fu)載供電(dian)(dian)(dian)(dian)(dian)(dian)。隨著(zhu)電(dian)(dian)(dian)(dian)(dian)(dian)感上存儲的(de)能量(liang)地(di)消耗。負(fu)載兩端的(de)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)開(kai)(kai)(kai)始逐漸降(jiang)低，外部(bu)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)通過MOSFET場(chang)效應管(guan)的(de)開(kai)(kai)(kai)關(guan)作(zuo)用又要(yao)充電(dian)(dian)(dian)(dian)(dian)(dian)。