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(ke)使電(dian)池(chi)具(ju)有較長的(de)(de)(de)壽命。利(li)用(yong)C8051F310單片機設計的(de)(de)(de)智能充(chong)(chong)(chong)電(dian)器，具(ju)有較高的(de)(de)(de)測量精(jing)度(du)，可(ke)很好的(de)(de)(de)控制充(chong)(chong)(chong)電(dian)電(dian)流的(de)(de)(de)大(da)小，適時的(de)(de)(de)調整，并可(ke)根(gen)據充(chong)(chong)(chong)電(dian)的(de)(de)(de)狀態判(pan)斷(duan)充(chong)(chong)(chong)電(dian)的(de)(de)(de)時間(jian)，及時終(zhong)止充(chong)(chong)(chong)電(dian)，以避免(mian)電(dian)池(chi)的(de)(de)(de)過充(chong)(chong)(chong)。

　　本文討(tao)論(lun)使(shi)用(yong)C8051F310器(qi)件設計(ji)鋰離子電(dian)(dian)(dian)池(chi)(chi)充電(dian)(dian)(dian)器(qi)的(de)。利用(yong)PWM脈寬調制(zhi)產生可用(yong)軟件控制(zhi)的(de)充電(dian)(dian)(dian)電(dian)(dian)(dian)源(yuan)，以適應(ying)不同階段的(de)充電(dian)(dian)(dian)電(dian)(dian)(dian)流的(de)要求。溫(wen)度傳感器(qi)對(dui)電(dian)(dian)(dian)池(chi)(chi)溫(wen)度進(jin)行(xing)監測(ce)，并通(tong)過AD轉換(huan)和相關計(ji)算(suan)檢測(ce)電(dian)(dian)(dian)池(chi)(chi)充電(dian)(dian)(dian)電(dian)(dian)(dian)壓和電(dian)(dian)(dian)流，以判斷電(dian)(dian)(dian)池(chi)(chi)到達哪個階段。使(shi)電(dian)(dian)(dian)池(chi)(chi)具有(you)(you)更長的(de)使(shi)用(yong)壽命，更有(you)(you)效的(de)充電(dian)(dian)(dian)方法。

　　設計過程

　　1 充電原理

　　電(dian)(dian)(dian)池(chi)的特(te)性唯一地(di)決定其安全性能和充電(dian)(dian)(dian)的效率。電(dian)(dian)(dian)池(chi)的最(zui)佳充電(dian)(dian)(dian)方法是由電(dian)(dian)(dian)池(chi)的化學成分(fen)決定的（鋰離子、鎳(nie)氫、鎳(nie)鎘還(huan)是SLA電(dian)(dian)(dian)池(chi)等）。盡管(guan)如(ru)此(ci)，大多數(shu)充電(dian)(dian)(dian)方案(an)都(dou)包含下(xia)面的三個(ge)階段：

　　● 低電流調節階段
　　● 恒流階段
　　● 恒(heng)壓(ya)階段/充電終止

　　所有電(dian)(dian)(dian)(dian)池(chi)都是通過向自身傳輸電(dian)(dian)(dian)(dian)能的(de)方(fang)法進行充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)的(de)，一(yi)節電(dian)(dian)(dian)(dian)池(chi)的(de)最大充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)取決于(yu)電(dian)(dian)(dian)(dian)池(chi)的(de)額定容(rong)量(liang)（C）例如(ru)，一(yi)節容(rong)量(liang)為(wei)(wei)1000mAh的(de)電(dian)(dian)(dian)(dian)池(chi)在(zai)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)為(wei)(wei)1000mA時，可以(yi)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)1C(電(dian)(dian)(dian)(dian)池(chi)容(rong)量(liang)的(de)1倍)也可以(yi)用1/50C(20mA)或更低(di)的(de)電(dian)(dian)(dian)(dian)流(liu)給(gei)電(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)。盡管(guan)如(ru)此，這只是一(yi)個普(pu)通的(de)低(di)電(dian)(dian)(dian)(dian)流(liu)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)方(fang)式，不適用于(yu)要求(qiu)短(duan)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)時間(jian)的(de)快速充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)方(fang)案。

　　現在(zai)使(shi)用(yong)的(de)(de)(de)大(da)多(duo)數充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器在(zai)給(gei)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)時都是既使(shi)用(yong)低(di)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)方(fang)(fang)式又使(shi)用(yong)額(e)定(ding)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)的(de)(de)(de)方(fang)(fang)法，即容(rong)積充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)，低(di)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)通(tong)常(chang)(chang)使(shi)用(yong)在(zai)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)初始階(jie)(jie)(jie)(jie)段(duan)。在(zai)這(zhe)一(yi)(yi)階(jie)(jie)(jie)(jie)段(duan)，需要將會導致充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)過程(cheng)終止的(de)(de)(de)芯片初期(qi)的(de)(de)(de)自熱效(xiao)應(ying)減小(xiao)到(dao)最低(di)程(cheng)度，容(rong)積充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)通(tong)常(chang)(chang)用(yong)在(zai)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)中級階(jie)(jie)(jie)(jie)段(duan)，電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)的(de)(de)(de)大(da)部分能量都是在(zai)這(zhe)一(yi)(yi)階(jie)(jie)(jie)(jie)段(duan)存儲(chu)的(de)(de)(de)。在(zai)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)最后(hou)階(jie)(jie)(jie)(jie)段(duan)，通(tong)常(chang)(chang)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)時間(jian)的(de)(de)(de)絕大(da)部分都是消耗在(zai)這(zhe)一(yi)(yi)階(jie)(jie)(jie)(jie)段(duan)，可以通(tong)過監測電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)、電(dian)(dian)(dian)(dian)(dian)(dian)壓或兩者的(de)(de)(de)值來決定(ding)何(he)時結束充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)。同樣(yang)，結束方(fang)(fang)案依賴于(yu)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)的(de)(de)(de)化(hua)學(xue)特性(xing)，例(li)如：大(da)多(duo)數鋰(li)離子電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器都是將電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)壓保持在(zai)恒定(ding)值，同時檢(jian)測最低(di)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)。鎳鎘、NiCd電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)用(yong)電(dian)(dian)(dian)(dian)(dian)(dian)壓或溫度的(de)(de)(de)變化(hua)率來決定(ding)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)結束時間(jian)。

      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(de)溫度(du)是至關重要的(de)，因為(wei)電(dian)(dian)池在(zai)過充(chong)電(dian)(dian)時(shi)會發生爆裂，在(zai)所有的(de)充(chong)電(dian)(dian)階段都應該隨時(shi)監(jian)測溫度(du)的(de)變化，并且在(zai)溫度(du)超過最大設定(ding)值時(shi)立即停止充(chong)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)用單片機A/D端口，構成電(dian)池電(dian)壓，電(dian)流，溫度檢測電(dian)路。

　　單片(pian)機通過電壓(ya)反饋和(he)電流反饋信(xin)號，直(zhi)接利(li)用PWM輸出將數字(zi)電壓(ya)信(xin)號并轉化(hua)成(cheng)模擬電壓(ya)信(xin)號，能夠保證控制精度。

　　3 控(kong)制(zhi)部(bu)分電路設計(ji) 

　　C8051F310單片機

　　①模擬外設

　　a.10位ADC：轉換(huan)(huan)速度可(ke)達(da)200ks/s,可(ke)多達(da)21或17個外部單端(duan)或差分輸入，VREF可(ke)在外部引腳或VDD中選擇，內置溫度傳感器（±3℃），外部轉換(huan)(huan)啟(qi)動(dong)輸入；

　　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：-40～+85℃。

　　③高速8051微控制(zhi)器(qi)內核(he)

　　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(kuo)展(zhan)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)器(qi)和外部時(shi)(shi)鐘(zhong)源的實時(shi)(shi)時(shi)(shi)鐘(zhong)方式。

　　控制電(dian)(dian)(dian)路中如圖2所示(shi)，P0.3口(kou)提供充電(dian)(dian)(dian)電(dian)(dian)(dian)源，P0.6口(kou)檢(jian)測(ce)(ce)充電(dian)(dian)(dian)電(dian)(dian)(dian)壓的(de)大小，P0.5口(kou)檢(jian)測(ce)(ce)充電(dian)(dian)(dian)電(dian)(dian)(dian)流的(de)大小，P0.4口(kou)檢(jian)測(ce)(ce)電(dian)(dian)(dian)池的(de)溫度。

　　充電電流由單(dan)片(pian)機脈寬調制PWM產(chan)生，充電電流由AD轉(zhuan)換再經過計算得出。

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

　　②快速轉換器

　　實(shi)現漸弱終止充電(dian)(dian)器的(de)(de)(de)(de)最(zui)經濟的(de)(de)(de)(de)方(fang)法就是(shi)用(yong)一個(ge)快(kuai)速轉(zhuan)換(huan)器。快(kuai)速轉(zhuan)換(huan)器是(shi)用(yong)一個(ge)電(dian)(dian)感和/或一個(ge)變(bian)壓器（需要(yao)隔離的(de)(de)(de)(de)時(shi)候用(yong)變(bian)壓器）作(zuo)為能量存(cun)儲單元(yuan)以(yi)離散(san)的(de)(de)(de)(de)能量包的(de)(de)(de)(de)形式(shi)將能量從輸入傳輸至輸出的(de)(de)(de)(de)開關(guan)調(diao)(diao)節器反饋電(dian)(dian)路，通過晶體管(guan)來調(diao)(diao)節能量的(de)(de)(de)(de)傳輸，同時(shi)也作(zuo)為過濾開關(guan)，以(yi)確(que)保電(dian)(dian)壓或電(dian)(dian)流(liu)在(zai)負載時(shi)保持(chi)恒(heng)定。

　　快速調節(jie)器的(de)(de)(de)操作(zuo)是通過控(kong)制一個晶體(ti)管(guan)開(kai)關的(de)(de)(de)占空比(bi)來實現(xian)的(de)(de)(de)。占空比(bi)會自動增(zeng)加以(yi)使電(dian)池流入更(geng)多的(de)(de)(de)電(dian)流。當VBATT

　　③電感的確定

　　電(dian)(dian)(dian)感(gan)(gan)對(dui)(dui)交(jiao)流(liu)電(dian)(dian)(dian)是(shi)有(you)阻礙(ai)作用的(de)(de)。在交(jiao)流(liu)電(dian)(dian)(dian)頻率(lv)一(yi)定的(de)(de)情(qing)況下(xia)，電(dian)(dian)(dian)感(gan)(gan)量越大(da)，對(dui)(dui)交(jiao)流(liu)電(dian)(dian)(dian)的(de)(de)阻礙(ai)能力越強??一(yi)定的(de)(de)情(qing)況下(xia)，交(jiao)流(liu)電(dian)(dian)(dian)的(de)(de)頻率(lv)越高(gao)，電(dian)(dian)(dian)感(gan)(gan)對(dui)(dui)交(jiao)流(liu)電(dian)(dian)(dian)的(de)(de)阻礙(ai)能力越大(da)，頻率(lv)越低，電(dian)(dian)(dian)感(gan)(gan)對(dui)(dui)交(jiao)流(liu)電(dian)(dian)(dian)的(de)(de)阻礙(ai)能力越小。也就是(shi)說，電(dian)(dian)(dian)感(gan)(gan)有(you)阻止(zhi)交(jiao)流(liu)電(dian)(dian)(dian)通過的(de)(de)特(te)性(xing)。

　　其工作原理是這樣的(de)(de)(de)(de)：當負(fu)載兩端的(de)(de)(de)(de)電(dian)(dian)(dian)壓要(yao)降(jiang)(jiang)(jiang)低(di)時，通(tong)(tong)過MOSFET場(chang)效應(ying)管(guan)的(de)(de)(de)(de)開(kai)關(guan)(guan)作用，外部(bu)電(dian)(dian)(dian)源(yuan)對電(dian)(dian)(dian)感(gan)進(jin)行充(chong)電(dian)(dian)(dian)并達到所需的(de)(de)(de)(de)額定電(dian)(dian)(dian)壓。當負(fu)載兩端地電(dian)(dian)(dian)壓升高(gao)時，通(tong)(tong)過MOSFET場(chang)效應(ying)管(guan)的(de)(de)(de)(de)開(kai)關(guan)(guan)作用，外部(bu)電(dian)(dian)(dian)源(yuan)供電(dian)(dian)(dian)斷(duan)開(kai)，電(dian)(dian)(dian)感(gan)釋(shi)放出剛才充(chong)入的(de)(de)(de)(de)能量，這時電(dian)(dian)(dian)感(gan)就(jiu)變成(cheng)了電(dian)(dian)(dian)源(yuan)繼續對負(fu)載供電(dian)(dian)(dian)。隨著電(dian)(dian)(dian)感(gan)上存儲的(de)(de)(de)(de)能量地消耗。負(fu)載兩端的(de)(de)(de)(de)電(dian)(dian)(dian)壓開(kai)始(shi)逐(zhu)漸降(jiang)(jiang)(jiang)低(di)，外部(bu)電(dian)(dian)(dian)源(yuan)通(tong)(tong)過MOSFET場(chang)效應(ying)管(guan)的(de)(de)(de)(de)開(kai)關(guan)(guan)作用又要(yao)充(chong)電(dian)(dian)(dian)。依次(ci)類(lei)推在不(bu)斷(duan)的(de)(de)(de)(de)充(chong)電(dian)(dian)(dian)和放電(dian)(dian)(dian)的(de)(de)(de)(de)過程中形成(cheng)了一種穩定的(de)(de)(de)(de)電(dian)(dian)(dian)壓，永遠使負(fu)載兩端地電(dian)(dian)(dian)壓不(bu)會(hui)(hui)升高(gao)也不(bu)會(hui)(hui)降(jiang)(jiang)(jiang)低(di)，這就(jiu)是開(kai)關(guan)(guan)電(dian)(dian)(dian)源(yuan)的(de)(de)(de)(de)最大優勢。

　　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：
　　（其中T是PWM的周期在程序示例中T=10.5s）

　　占空比(bi)=ton/T （1）

　　至(zhi)此就可以選擇一個PWM的(de)轉換頻率(lv)（如(ru)方程式2所示(shi)）PWM的(de)轉換頻率(lv)越大，則電感的(de)值越小，也越節約成(cheng)本(ben)。

　　我的(de)(de)示例代碼配(pei)置F310的(de)(de)8位硬(ying)件PWM是使用內部24.5MHz主時鐘的(de)(de)256分頻來(lai)產生一個95.7kHz的(de)(de)轉(zhuan)換(huan)速率(lv)。

　　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。
需要注意的是：在本電(dian)(dian)(dian)路中的電(dian)(dian)(dian)容僅僅是一個紋(wen)波(bo)衰減(jian)(jian)器，因為紋(wen)波(bo)與(yu)電(dian)(dian)(dian)容的大(da)小(xiao)成反比例關系，所以電(dian)(dian)(dian)容的值越大(da)，衰減(jian)(jian)效果越好。