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(shi)電(dian)(dian)(dian)池具有較長的(de)壽(shou)命。利(li)用C8051F310單片機設計的(de)智能充(chong)電(dian)(dian)(dian)器，具有較高的(de)測量(liang)精度，可很好的(de)控制(zhi)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流的(de)大(da)小，適時(shi)的(de)調整，并可根據充(chong)電(dian)(dian)(dian)的(de)狀態判斷充(chong)電(dian)(dian)(dian)的(de)時(shi)間，及時(shi)終止(zhi)充(chong)電(dian)(dian)(dian)，以避免(mian)電(dian)(dian)(dian)池的(de)過充(chong)。

　　本文討(tao)論使用C8051F310器件設計(ji)鋰離子電(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)器的。利用PWM脈寬調(diao)制產生(sheng)可用軟件控制的充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)源，以適應不同階段的充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流的要求。溫度(du)傳感(gan)器對電(dian)(dian)(dian)(dian)池(chi)(chi)溫度(du)進行(xing)監(jian)測，并(bing)通過AD轉(zhuan)換(huan)和相關計(ji)算檢測電(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)(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(da)哪(na)個階段。使電(dian)(dian)(dian)(dian)池(chi)(chi)具(ju)有更長的使用壽命，更有效的充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)方法。

　　設計過程

　　1 充電原理

　　電(dian)(dian)(dian)池的(de)(de)(de)特性唯一地決定其(qi)安全性能和(he)充電(dian)(dian)(dian)的(de)(de)(de)效率(lv)。電(dian)(dian)(dian)池的(de)(de)(de)最佳充電(dian)(dian)(dian)方法是(shi)由(you)電(dian)(dian)(dian)池的(de)(de)(de)化學成(cheng)分決定的(de)(de)(de)（鋰離子、鎳氫、鎳鎘還(huan)是(shi)SLA電(dian)(dian)(dian)池等）。盡管(guan)如(ru)此(ci)，大多數充電(dian)(dian)(dian)方案(an)都(dou)包含(han)下面的(de)(de)(de)三個(ge)階段(duan)：

　　● 低電流調節階段
　　● 恒流階段
　　● 恒壓階段/充電終止

　　所有電(dian)(dian)池(chi)都是通(tong)過向自身傳輸(shu)電(dian)(dian)能(neng)的(de)方(fang)法進行充(chong)(chong)(chong)電(dian)(dian)的(de)，一(yi)節電(dian)(dian)池(chi)的(de)最(zui)大充(chong)(chong)(chong)電(dian)(dian)電(dian)(dian)流(liu)取決于電(dian)(dian)池(chi)的(de)額定(ding)容(rong)量（C）例如，一(yi)節容(rong)量為1000mAh的(de)電(dian)(dian)池(chi)在充(chong)(chong)(chong)電(dian)(dian)電(dian)(dian)流(liu)為1000mA時，可以充(chong)(chong)(chong)電(dian)(dian)1C(電(dian)(dian)池(chi)容(rong)量的(de)1倍)也可以用1/50C(20mA)或更低的(de)電(dian)(dian)流(liu)給電(dian)(dian)池(chi)充(chong)(chong)(chong)電(dian)(dian)。盡管如此，這只(zhi)是一(yi)個普通(tong)的(de)低電(dian)(dian)流(liu)充(chong)(chong)(chong)電(dian)(dian)方(fang)式，不適(shi)用于要求短充(chong)(chong)(chong)電(dian)(dian)時間的(de)快速充(chong)(chong)(chong)電(dian)(dian)方(fang)案(an)。

　　現(xian)在(zai)使(shi)用(yong)的(de)(de)(de)大(da)(da)(da)多數充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)在(zai)給電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)時(shi)都(dou)(dou)是既使(shi)用(yong)低(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)方式(shi)又使(shi)用(yong)額(e)定充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)(de)方法，即容積充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)，低(di)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)通(tong)(tong)常(chang)(chang)使(shi)用(yong)在(zai)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)初(chu)始階段(duan)(duan)(duan)。在(zai)這(zhe)(zhe)一(yi)階段(duan)(duan)(duan)，需要(yao)將會導致(zhi)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)過程(cheng)終止的(de)(de)(de)芯(xin)片初(chu)期(qi)的(de)(de)(de)自熱(re)效應減小到最低(di)程(cheng)度，容積充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)通(tong)(tong)常(chang)(chang)用(yong)在(zai)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)中(zhong)級(ji)階段(duan)(duan)(duan)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)的(de)(de)(de)大(da)(da)(da)部分能量都(dou)(dou)是在(zai)這(zhe)(zhe)一(yi)階段(duan)(duan)(duan)存儲的(de)(de)(de)。在(zai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)最后(hou)階段(duan)(duan)(duan)，通(tong)(tong)常(chang)(chang)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)時(shi)間的(de)(de)(de)絕大(da)(da)(da)部分都(dou)(dou)是消(xiao)耗在(zai)這(zhe)(zhe)一(yi)階段(duan)(duan)(duan)，可以通(tong)(tong)過監(jian)測電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)、電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)或(huo)兩者的(de)(de)(de)值(zhi)(zhi)來決(jue)(jue)定何(he)時(shi)結(jie)束(shu)(shu)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)。同樣，結(jie)束(shu)(shu)方案依賴于(yu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)的(de)(de)(de)化學特性，例如：大(da)(da)(da)多數鋰離子電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)都(dou)(dou)是將電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)保持在(zai)恒定值(zhi)(zhi)，同時(shi)檢測最低(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)。鎳鎘、NiCd電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)用(yong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)或(huo)溫度的(de)(de)(de)變化率來決(jue)(jue)定充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)結(jie)束(shu)(shu)時(shi)間。

      充電時部分電能被轉換成熱能，直至電池充滿。而充滿后，所有的電能將全部被轉換成熱能。如果此時不終止充電，電池就會被損壞或燒毀。快速充電器電池（完全充滿的時間小于兩小時的充電器）則可以解決這個問題，因為這些充電器是使用高充電電流來縮短充電時間的。因此，對于鋰離子電池來說,監(jian)測它的溫(wen)度是(shi)至關重要(yao)的，因為電(dian)(dian)池在(zai)過充電(dian)(dian)時(shi)會(hui)發生(sheng)爆裂，在(zai)所有(you)的充電(dian)(dian)階段都應該(gai)隨時(shi)監(jian)測溫(wen)度的變(bian)化，并(bing)且(qie)在(zai)溫(wen)度超過最大設定(ding)值時(shi)立即停止(zhi)充電(dian)(dian)。

　　2 總體設計 
　
　　充電電路由三部分：控制部分，檢測部分及充電部分組成。如圖1所示，采用F310單片機進行充電控制，單片機本身具有脈寬調制PWM型開關穩壓電源所需的全部功能，具有10位A/D轉換器。利(li)用單片(pian)機A/D端口，構(gou)成電池電壓，電流，溫度(du)檢測(ce)電路。

　　單片機通過電壓反饋和電流反饋信(xin)號，直接利用PWM輸(shu)出將數字電壓信(xin)號并轉(zhuan)化成模(mo)擬電壓信(xin)號，能夠保證控制(zhi)精(jing)度。

　　3 控制部分電路設計 

　　C8051F310單片機

　　①模擬外設

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

　　b.兩個模擬比較器：可編程回差電壓和響應時間，可配置為中斷或復位源，小電流（〈0.5μA）。
　　
　　②供電電壓

　　a.典型工作電流：5mA、25MHz；
　　b.典型停機電流：0.1μA；
　　c.溫度范圍(wei)：-40～+85℃。

　　③高速8051微控(kong)制器內核

　　a.流水線指令結構：70%的指令的執行時間為一個或兩個系統時鐘周期；
　　b.速度可達25MI/s（時鐘頻率為25MHz時）；
　　c.擴展的中斷(duan)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16位計數器/定時器；
　　c.16位可編程計數器/定時器陣列（PCA），有5個捕捉/比較模塊；
　　d.使用PCA或定時(shi)(shi)(shi)器和外部時(shi)(shi)(shi)鐘源的實時(shi)(shi)(shi)時(shi)(shi)(shi)鐘方式。

　　控制電路中如圖2所示，P0.3口(kou)提(ti)供(gong)充電電源，P0.6口(kou)檢測充電電壓(ya)的大小，P0.5口(kou)檢測充電電流(liu)的大小，P0.4口(kou)檢測電池(chi)的溫(wen)度。

　　充電(dian)電(dian)流(liu)由(you)單(dan)片機脈寬調(diao)制(zhi)PWM產生(sheng)，充電(dian)電(dian)流(liu)由(you)AD轉換再(zai)經過計算得出。

　　4 充電(dian)部分及檢(jian)測部分電(dian)路設(she)計

　　②快速轉換器

　　實現(xian)漸弱(ruo)終止充電(dian)器(qi)(qi)的(de)(de)最經濟的(de)(de)方法就是用(yong)一個(ge)快速(su)轉換器(qi)(qi)。快速(su)轉換器(qi)(qi)是用(yong)一個(ge)電(dian)感和/或一個(ge)變壓(ya)器(qi)(qi)（需要隔(ge)離的(de)(de)時(shi)候(hou)用(yong)變壓(ya)器(qi)(qi)）作為(wei)能(neng)(neng)量(liang)(liang)存儲單元以離散的(de)(de)能(neng)(neng)量(liang)(liang)包(bao)的(de)(de)形式將能(neng)(neng)量(liang)(liang)從輸入傳(chuan)輸至輸出(chu)的(de)(de)開關(guan)調(diao)(diao)節器(qi)(qi)反饋電(dian)路(lu)，通過(guo)晶體管來調(diao)(diao)節能(neng)(neng)量(liang)(liang)的(de)(de)傳(chuan)輸，同(tong)時(shi)也作為(wei)過(guo)濾開關(guan)，以確保電(dian)壓(ya)或電(dian)流在負載時(shi)保持恒定。

　　快速(su)調節器的(de)操(cao)作(zuo)是(shi)通過控制一(yi)個晶體(ti)管開(kai)關的(de)占空(kong)比來實現的(de)。占空(kong)比會自動增(zeng)加以使電(dian)池流(liu)入更(geng)多(duo)的(de)電(dian)流(liu)。當VBATT

　　③電感的確定

　　電(dian)(dian)(dian)(dian)感(gan)對交(jiao)(jiao)流電(dian)(dian)(dian)(dian)是有阻(zu)(zu)(zu)(zu)(zu)礙(ai)作用的。在(zai)交(jiao)(jiao)流電(dian)(dian)(dian)(dian)頻率(lv)一定的情況下，電(dian)(dian)(dian)(dian)感(gan)量越(yue)大(da)，對交(jiao)(jiao)流電(dian)(dian)(dian)(dian)的阻(zu)(zu)(zu)(zu)(zu)礙(ai)能力(li)越(yue)強??一定的情況下，交(jiao)(jiao)流電(dian)(dian)(dian)(dian)的頻率(lv)越(yue)高，電(dian)(dian)(dian)(dian)感(gan)對交(jiao)(jiao)流電(dian)(dian)(dian)(dian)的阻(zu)(zu)(zu)(zu)(zu)礙(ai)能力(li)越(yue)大(da)，頻率(lv)越(yue)低，電(dian)(dian)(dian)(dian)感(gan)對交(jiao)(jiao)流電(dian)(dian)(dian)(dian)的阻(zu)(zu)(zu)(zu)(zu)礙(ai)能力(li)越(yue)小。也就是說(shuo)，電(dian)(dian)(dian)(dian)感(gan)有阻(zu)(zu)(zu)(zu)(zu)止交(jiao)(jiao)流電(dian)(dian)(dian)(dian)通過的特(te)性。

　　其(qi)工作(zuo)(zuo)原理是這(zhe)樣的(de)(de)(de)：當(dang)負(fu)載兩(liang)(liang)端(duan)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)要(yao)降(jiang)低(di)時，通(tong)過(guo)MOSFET場(chang)效(xiao)應管(guan)的(de)(de)(de)開關作(zuo)(zuo)用，外部電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)對電(dian)(dian)(dian)(dian)(dian)(dian)感(gan)進行充電(dian)(dian)(dian)(dian)(dian)(dian)并達到所需(xu)的(de)(de)(de)額定電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)。當(dang)負(fu)載兩(liang)(liang)端(duan)地(di)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)升高時，通(tong)過(guo)MOSFET場(chang)效(xiao)應管(guan)的(de)(de)(de)開關作(zuo)(zuo)用，外部電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)供電(dian)(dian)(dian)(dian)(dian)(dian)斷(duan)開，電(dian)(dian)(dian)(dian)(dian)(dian)感(gan)釋放出剛(gang)才充入(ru)的(de)(de)(de)能量，這(zhe)時電(dian)(dian)(dian)(dian)(dian)(dian)感(gan)就變成了電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)繼續(xu)對負(fu)載供電(dian)(dian)(dian)(dian)(dian)(dian)。隨著電(dian)(dian)(dian)(dian)(dian)(dian)感(gan)上存儲的(de)(de)(de)能量地(di)消耗。負(fu)載兩(liang)(liang)端(duan)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)開始(shi)逐漸(jian)降(jiang)低(di)，外部電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)通(tong)過(guo)MOSFET場(chang)效(xiao)應管(guan)的(de)(de)(de)開關作(zuo)(zuo)用又要(yao)充電(dian)(dian)(dian)(dian)(dian)(dian)。依(yi)次類推在不斷(duan)的(de)(de)(de)充電(dian)(dian)(dian)(dian)(dian)(dian)和(he)放電(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)過(guo)程中形成了一種穩(wen)定的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)，永(yong)遠使負(fu)載兩(liang)(liang)端(duan)地(di)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)不會升高也不會降(jiang)低(di)，這(zhe)就是開關電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)的(de)(de)(de)最大優(you)勢。

　　要確定快速轉換器中電感的大小首先應假定晶體管的占空比為50%，因為此時的轉換器操作操作效率最高。占空比由方程式1給出：
　　（其(qi)中(zhong)T是PWM的周期在(zai)程序(xu)示例中(zhong)T=10.5s）

　　占空比=ton/T （1）

　　至此就可(ke)以選擇一個PWM的轉換頻率(lv)（如方(fang)程式2所示）PWM的轉換頻率(lv)越大，則電(dian)感的值越小(xiao)，也越節(jie)約成本。

　　我(wo)的(de)示(shi)例代碼配置F310的(de)8位硬件(jian)PWM是使用內部24.5MHz主時鐘的(de)256分頻來產生一個95.7kHz的(de)轉換速率。

　　L=（Vi-Vsat-Voton）/2Iomax （2）

　　現在我們可以計算電感的大小了，假定充電電壓Vi的值為15V，飽和電壓Vsat的值為0.5V，需要獲得的輸出電壓值為4.2V,并且最大輸出電流IＯMAX為1500mA，那么，電感的值至少應選為18H。
需要注意的(de)是：在本(ben)電路中的(de)電容僅僅是一個紋波衰減器，因為紋波與電容的(de)大小成反比例(li)關(guan)系，所以電容的(de)值越大，衰減效(xiao)果越好。