C8051F310器件設計鋰離子電(dian)(dian)(dian)(dian)池(chi)充電(dian)(dian)(dian)(dian)器。利用PWM脈寬調制(zhi)產生可用軟件控制(zhi)的(de)(de)充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)源，以適應不同階(jie)段的(de)(de)充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流的(de)(de)要求。溫度傳感(gan)器對(dui)電(dian)(dian)(dian)(dian)池(chi)溫度進行監測，并(bing)通過AD轉換(huan)和(he)相關計算檢測電(dian)(dian)(dian)(dian)池(chi)充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)壓(ya)和(he)電(dian)(dian)(dian)(dian)流，以判斷電(dian)(dian)(dian)(dian)池(chi)到達哪個階(jie)段。使電(dian)(dian)(dian)(dian)池(chi)具有更(geng)長的(de)(de)使用壽命。

設計過程

1  充電原理

　　電池(chi)的(de)特性唯一(yi)地決(jue)定其安全(quan)性能和充電的(de)效率(lv)。電池(chi)的(de)最(zui)佳充電方(fang)法(fa)是(shi)由電池(chi)的(de)化學(xue)成分決(jue)定的(de)（鋰離子、鎳氫、鎳鎘(ge)還(huan)是(shi)SLA電池(chi)等）。盡管如此，大多(duo)數充電方(fang)案都(dou)包含(han)下(xia)面的(de)三個階段：

　　低電流調節階段

　　恒流階段

　　恒壓階段/充(chong)電終止(zhi)

　　所有(you)電(dian)(dian)(dian)(dian)(dian)池(chi)都是通過向自身傳輸電(dian)(dian)(dian)(dian)(dian)能的(de)方法進行充(chong)電(dian)(dian)(dian)(dian)(dian)的(de)，一(yi)節電(dian)(dian)(dian)(dian)(dian)池(chi)的(de)最(zui)大充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流取(qu)決于(yu)電(dian)(dian)(dian)(dian)(dian)池(chi)的(de)額(e)定(ding)容(rong)(rong)量（C）例如，一(yi)節容(rong)(rong)量為1000mAh的(de)電(dian)(dian)(dian)(dian)(dian)池(chi)在充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流為1000mA時，可以充(chong)電(dian)(dian)(dian)(dian)(dian)1C（電(dian)(dian)(dian)(dian)(dian)池(chi)容(rong)(rong)量的(de)1倍）也可以用1/50C（20mA）或更低的(de)電(dian)(dian)(dian)(dian)(dian)流給電(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)(dian)(dian)。

　　現在使用的大多數充電器在(zai)給電(dian)(dian)(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)(dian)(dian)時(shi)都(dou)是既使(shi)(shi)(shi)用低電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)充(chong)電(dian)(dian)(dian)(dian)(dian)方式又使(shi)(shi)(shi)用額定充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)的(de)方法(fa)，即容(rong)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(liu)(liu)通(tong)常(chang)使(shi)(shi)(shi)用在(zai)充(chong)電(dian)(dian)(dian)(dian)(dian)的(de)初始階(jie)(jie)段。在(zai)這一(yi)階(jie)(jie)段，需要將會導致充(chong)電(dian)(dian)(dian)(dian)(dian)過程終止的(de)芯(xin)片初期的(de)自熱效應(ying)減(jian)小到(dao)最低程度，容(rong)積充(chong)電(dian)(dian)(dian)(dian)(dian)通(tong)常(chang)用在(zai)充(chong)電(dian)(dian)(dian)(dian)(dian)的(de)中級階(jie)(jie)段，電(dian)(dian)(dian)(dian)(dian)池的(de)大部分能量都(dou)是在(zai)這一(yi)階(jie)(jie)段存(cun)儲的(de)。

　　充(chong)(chong)電(dian)時(shi)部(bu)分電(dian)能(neng)被(bei)轉換成(cheng)(cheng)熱能(neng)，直(zhi)至(zhi)電(dian)池充(chong)(chong)滿。而(er)充(chong)(chong)滿后，所有的電(dian)能(neng)將(jiang)全部(bu)被(bei)轉換成(cheng)(cheng)熱能(neng)。如果此時(shi)不(bu)終止(zhi)充(chong)(chong)電(dian)，電(dian)池就會被(bei)損壞(huai)或燒毀。快速(su)充(chong)(chong)電(dian)器電(dian)池則(ze)可以解(jie)決這個(ge)問題，因為這些充(chong)(chong)電(dian)器是使用高充(chong)(chong)電(dian)電(dian)流來縮短(duan)充(chong)(chong)電(dian)時(shi)間(jian)的。

2  總體設計

　　充(chong)電(dian)電(dian)路由三部(bu)(bu)分：控制(zhi)部(bu)(bu)分，檢(jian)測部(bu)(bu)分及充(chong)電(dian)部(bu)(bu)分組(zu)成。

　　如圖1所示(shi)，采用F310單片機進行充(chong)電控制，單片機本(ben)身具(ju)有(you)脈寬調制PWM型開關穩壓電源所需(xu)的全部功能，具(ju)有(you)10位A/D轉換器(qi)。

　　利用(yong)單片(pian)機A/D端口，構成(cheng)電池電壓，電流，溫度檢測電路。

 

 

 

    圖(tu)1  鋰離子電池充電模塊圖(tu)

    單片機(ji)通(tong)過電(dian)(dian)壓(ya)(ya)反(fan)(fan)饋和電(dian)(dian)流反(fan)(fan)饋信號，直接利用PWM輸出將(jiang)數字電(dian)(dian)壓(ya)(ya)信號并轉化成(cheng)模(mo)擬電(dian)(dian)壓(ya)(ya)信號，能(neng)夠保(bao)證控(kong)制精度。

3  控制部分電路設計

　　C8051F310單片機

　　①模擬外設

　　a.10位(wei)ADC：轉(zhuan)換速度(du)可(ke)達200ks/s,可(ke)多達21或(huo)(huo)17個外部單(dan)端或(huo)(huo)差分輸(shu)入，VREF可(ke)在外部引(yin)腳(jiao)或(huo)(huo)VDD中(zhong)選擇，內(nei)置溫度(du)傳感(gan)器（±3℃），外部轉(zhuan)換啟動(dong)輸(shu)入；

　　b.兩個模(mo)擬比較器：可(ke)編程回差電壓和響應時間，可(ke)配(pei)置為中斷或復位源，小(xiao)電流(liu)（〈0.5μA）。

　　②供電電壓

　　a.典型(xing)工作電流：5mA、25MHz；

　　b.典型(xing)停機電流：0.1μA；

　　c.溫度范(fan)圍(wei)：-40～+85℃。

　　③高速8051微控(kong)制(zhi)器內核

　　a.流水線(xian)指(zhi)令(ling)結構：70%的指(zhi)令(ling)的執(zhi)行時(shi)間為(wei)一個或兩(liang)個系統時(shi)鐘周期；

　　b.速度(du)可達(da)25MI/s（時(shi)(shi)鐘(zhong)頻(pin)率為(wei)25MHz時(shi)(shi)）；

　　c.擴展(zhan)的中斷系(xi)統。

　　④數字外設

　　a.29/25個(ge)端口(kou)I/O：所有的口(kou)線(xian)均耐5V電壓；

　　b.4個通(tong)用16位(wei)計數器(qi)/定時器(qi)；

　　c.16位可(ke)編程計(ji)數器/定時器陣列（PCA），有5個(ge)捕捉/比較模塊；

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

　　控(kong)制(zhi)電(dian)路中如圖(tu)2所示，P0.3口(kou)提供(gong)充(chong)電(dian)電(dian)源，P0.6口(kou)檢測(ce)充(chong)電(dian)電(dian)壓的大小，P0.5口(kou)檢測(ce)充(chong)電(dian)電(dian)流(liu)的大小，P0.4口(kou)檢測(ce)電(dian)池的溫(wen)度。

  

 

    圖(tu)2  控制電路接線圖(tu)

　　充電(dian)電(dian)流(liu)由(you)單片機(ji)脈寬調制PWM產生，充電(dian)電(dian)流(liu)由(you)AD轉換(huan)再經過計算得出。

  

4  充電部分及檢測部分電路設計(ji)

　　圖3為充電(dian)電(dian)路(lu)與檢(jian)測電(dian)路(lu)圖。

  

 

    圖3  充電(dian)電(dian)路(lu)與檢測(ce)電(dian)路(lu)圖

 　　①充電過程曲線(xian)

　　如圖4所(suo)示，充(chong)電(dian)(dian)(dian)過(guo)程(cheng)由(you)預充(chong)狀態(tai)(tai)，恒流(liu)充(chong)電(dian)(dian)(dian)狀態(tai)(tai)和恒壓充(chong)電(dian)(dian)(dian)狀態(tai)(tai)組成(cheng)。

  

 

    圖4  鋰(li)電(dian)池充(chong)電(dian)曲線

　　②快速轉換器

　　實現漸弱終(zhong)止充電器的最經濟(ji)的方法就是用一個(ge)快速(su)轉換器。快速(su)轉換器是用一個(ge)電感和/或一個(ge)變壓器（需要隔離(li)的時候(hou)用變壓器）作(zuo)為能量存儲(chu)單(dan)元以離(li)散的能量包的形式將能量從(cong)輸(shu)(shu)入(ru)傳輸(shu)(shu)至(zhi)輸(shu)(shu)出的開(kai)關(guan)調節器反饋電路，通過(guo)晶體管來(lai)調節能量的傳輸(shu)(shu)，同時也作(zuo)為過(guo)濾開(kai)關(guan)，以確保電壓或電流(liu)在負載時保持(chi)恒定(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  開關(guan)閉合

 

  

b  開關打開

    圖5  快速轉(zhuan)換器(qi)操(cao)作

　　③電感的確定

　　電感(gan)對交(jiao)流(liu)電是有阻礙(ai)作用的(de)。在交(jiao)流(liu)電頻率一定的(de)情況下，電感(gan)量(liang)(liang)越大，對交(jiao)流(liu)電的(de)阻礙(ai)能(neng)(neng)力(li)(li)越強，電感(gan)量(liang)(liang)越小(xiao)，其阻礙(ai)能(neng)(neng)力(li)(li)越小(xiao)。

　　其工作(zuo)(zuo)原理是(shi)這樣的(de)：當負載(zai)(zai)兩端(duan)的(de)電(dian)(dian)(dian)壓要降低(di)時，通過MOSFET場效(xiao)(xiao)應管的(de)開關作(zuo)(zuo)用，外部(bu)(bu)電(dian)(dian)(dian)源(yuan)對電(dian)(dian)(dian)感進(jin)行充電(dian)(dian)(dian)并(bing)達到(dao)所(suo)需的(de)額(e)定(ding)電(dian)(dian)(dian)壓。當負載(zai)(zai)兩端(duan)地電(dian)(dian)(dian)壓升(sheng)高時，通過MOSFET場效(xiao)(xiao)應管的(de)開關作(zuo)(zuo)用，外部(bu)(bu)電(dian)(dian)(dian)源(yuan)供電(dian)(dian)(dian)斷開，電(dian)(dian)(dian)感釋放出剛才充入的(de)能量(liang)(liang)，這時電(dian)(dian)(dian)感就(jiu)變成(cheng)了電(dian)(dian)(dian)源(yuan)繼續對負載(zai)(zai)供電(dian)(dian)(dian)。隨著電(dian)(dian)(dian)感上存儲的(de)能量(liang)(liang)地消耗。負載(zai)(zai)兩端(duan)的(de)電(dian)(dian)(dian)壓開始(shi)逐漸降低(di)，外部(bu)(bu)電(dian)(dian)(dian)源(yuan)通過MOSFET場效(xiao)(xiao)應管的(de)開關作(zuo)(zuo)用又(you)要充電(dian)(dian)(dian)。