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電池具有較長的壽命。利用C8051F310單片機設計的智能充電器，具(ju)有(you)較高的(de)(de)測量精度，可很(hen)好的(de)(de)控制充(chong)電電流的(de)(de)大小，適時的(de)(de)調整(zheng)，并可根據充(chong)電的(de)(de)狀態(tai)判斷充(chong)電的(de)(de)時間，及時終止充(chong)電，以避免電池的(de)(de)過充(chong)。

　　本文(wen)討論使(shi)(shi)用(yong)(yong)C8051F310器(qi)件設(she)計(ji)鋰(li)離子電(dian)(dian)(dian)(dian)池充電(dian)(dian)(dian)(dian)器(qi)的(de)(de)。利用(yong)(yong)PWM脈寬調制產生可用(yong)(yong)軟件控制的(de)(de)充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)源，以適應(ying)不(bu)同階(jie)段(duan)的(de)(de)充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流的(de)(de)要求。溫(wen)度傳感器(qi)對電(dian)(dian)(dian)(dian)池溫(wen)度進(jin)行(xing)監測，并通過(guo)AD轉換(huan)和(he)相關計(ji)算檢測電(dian)(dian)(dian)(dian)池充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)壓和(he)電(dian)(dian)(dian)(dian)流，以判(pan)斷電(dian)(dian)(dian)(dian)池到達哪(na)個階(jie)段(duan)。使(shi)(shi)電(dian)(dian)(dian)(dian)池具有(you)更(geng)長的(de)(de)使(shi)(shi)用(yong)(yong)壽命，更(geng)有(you)效的(de)(de)充電(dian)(dian)(dian)(dian)方(fang)法。

　　設計過程

　　1 充電原理

　　電池(chi)(chi)(chi)的(de)(de)特性唯一地決定(ding)其安全性能(neng)和(he)充電的(de)(de)效率。電池(chi)(chi)(chi)的(de)(de)最佳充電方法是由(you)電池(chi)(chi)(chi)的(de)(de)化學成分決定(ding)的(de)(de)（鋰離子、鎳(nie)氫、鎳(nie)鎘還(huan)是SLA電池(chi)(chi)(chi)等）。盡管如(ru)此，大多數充電方案都(dou)包(bao)含下面的(de)(de)三(san)個階(jie)段(duan)：

　　● 低電流調節階段

　　● 恒流階段

　　● 恒壓階(jie)段/充電終(zhong)止

　　所有電(dian)(dian)(dian)(dian)池(chi)都是(shi)通(tong)過向自身傳輸(shu)電(dian)(dian)(dian)(dian)能的(de)方(fang)法進行充電(dian)(dian)(dian)(dian)的(de)，一節電(dian)(dian)(dian)(dian)池(chi)的(de)最(zui)大(da)充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)取決于電(dian)(dian)(dian)(dian)池(chi)的(de)額定容(rong)量（C）例如(ru)(ru)，一節容(rong)量為1000mAh的(de)電(dian)(dian)(dian)(dian)池(chi)在充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)為1000mA時，可(ke)以(yi)充電(dian)(dian)(dian)(dian)1C（電(dian)(dian)(dian)(dian)池(chi)容(rong)量的(de)1倍）也可(ke)以(yi)用(yong)1/50C（20mA）或(huo)更低(di)的(de)電(dian)(dian)(dian)(dian)流(liu)(liu)給電(dian)(dian)(dian)(dian)池(chi)充電(dian)(dian)(dian)(dian)。盡管如(ru)(ru)此，這(zhe)只是(shi)一個普通(tong)的(de)低(di)電(dian)(dian)(dian)(dian)流(liu)(liu)充電(dian)(dian)(dian)(dian)方(fang)式，不適用(yong)于要求(qiu)短充電(dian)(dian)(dian)(dian)時間的(de)快速充電(dian)(dian)(dian)(dian)方(fang)案。

　　現在使用的大多數充電器在給電(dian)(dian)(dian)(dian)(dian)(dian)池充電(dian)(dian)(dian)(dian)(dian)(dian)時(shi)(shi)都(dou)是既使用(yong)低(di)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)充電(dian)(dian)(dian)(dian)(dian)(dian)方式又使用(yong)額定充電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)(de)(de)方法，即容積充電(dian)(dian)(dian)(dian)(dian)(dian)，低(di)充電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)通常使用(yong)在充電(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)(de)初(chu)始階段(duan)。在這(zhe)一(yi)階段(duan)，需要將(jiang)會導致充電(dian)(dian)(dian)(dian)(dian)(dian)過程終止的(de)(de)(de)(de)芯片初(chu)期的(de)(de)(de)(de)自熱效(xiao)應減小到最(zui)低(di)程度(du)，容積充電(dian)(dian)(dian)(dian)(dian)(dian)通常用(yong)在充電(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)(de)中級階段(duan)，電(dian)(dian)(dian)(dian)(dian)(dian)池的(de)(de)(de)(de)大(da)部分(fen)(fen)能(neng)量(liang)都(dou)是在這(zhe)一(yi)階段(duan)存儲(chu)的(de)(de)(de)(de)。在電(dian)(dian)(dian)(dian)(dian)(dian)池充電(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)(de)最(zui)后階段(duan)，通常充電(dian)(dian)(dian)(dian)(dian)(dian)時(shi)(shi)間的(de)(de)(de)(de)絕大(da)部分(fen)(fen)都(dou)是消耗在這(zhe)一(yi)階段(duan)，可以(yi)通過監測電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)、電(dian)(dian)(dian)(dian)(dian)(dian)壓或兩者的(de)(de)(de)(de)值(zhi)來(lai)決定何時(shi)(shi)結(jie)束充電(dian)(dian)(dian)(dian)(dian)(dian)。同樣，結(jie)束方案(an)依(yi)賴(lai)于電(dian)(dian)(dian)(dian)(dian)(dian)池的(de)(de)(de)(de)化(hua)學特性(xing)，例(li)如：大(da)多(duo)數鋰離子電(dian)(dian)(dian)(dian)(dian)(dian)池充電(dian)(dian)(dian)(dian)(dian)(dian)器都(dou)是將(jiang)電(dian)(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)(dian)壓保持在恒(heng)定值(zhi)，同時(shi)(shi)檢測最(zui)低(di)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)。鎳鎘、NiCd電(dian)(dian)(dian)(dian)(dian)(dian)池用(yong)電(dian)(dian)(dian)(dian)(dian)(dian)壓或溫(wen)度(du)的(de)(de)(de)(de)變化(hua)率來(lai)決定充電(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)(de)結(jie)束時(shi)(shi)間。

　　圖1 鋰離子電池充電模塊圖

　　充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)時部(bu)分(fen)電(dian)(dian)(dian)(dian)能(neng)被(bei)轉(zhuan)換(huan)成(cheng)熱能(neng)，直至電(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)(chong)(chong)(chong)(chong)滿(man)。而充(chong)(chong)(chong)(chong)(chong)(chong)滿(man)后，所(suo)(suo)有(you)的(de)電(dian)(dian)(dian)(dian)能(neng)將全(quan)部(bu)被(bei)轉(zhuan)換(huan)成(cheng)熱能(neng)。如果此時不終(zhong)止(zhi)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)，電(dian)(dian)(dian)(dian)池(chi)就(jiu)會被(bei)損壞或燒毀。快速充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)器電(dian)(dian)(dian)(dian)池(chi)（完全(quan)充(chong)(chong)(chong)(chong)(chong)(chong)滿(man)的(de)時間小于(yu)兩小時的(de)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)器）則可以解決這個(ge)問題(ti)，因(yin)為這些充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)器是(shi)使用高(gao)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流來(lai)縮(suo)短充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)時間的(de)。因(yin)此，對(dui)于(yu)鋰(li)離子電(dian)(dian)(dian)(dian)池(chi)來(lai)說，監(jian)測(ce)它的(de)溫(wen)度(du)(du)是(shi)至關重要的(de)，因(yin)為電(dian)(dian)(dian)(dian)池(chi)在過(guo)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)時會發生爆裂，在所(suo)(suo)有(you)的(de)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)階段都應該隨時監(jian)測(ce)溫(wen)度(du)(du)的(de)變(bian)化，并且在溫(wen)度(du)(du)超(chao)過(guo)最大設定值時立(li)即停(ting)止(zhi)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)。

　　2 總體設計

　　充(chong)電(dian)(dian)電(dian)(dian)路(lu)由(you)三部(bu)(bu)分(fen)(fen)：控制(zhi)部(bu)(bu)分(fen)(fen)，檢測部(bu)(bu)分(fen)(fen)及充(chong)電(dian)(dian)部(bu)(bu)分(fen)(fen)組(zu)成。如圖1所示(shi)，采用(yong)F310單(dan)(dan)片機(ji)進行充(chong)電(dian)(dian)控制(zhi)，單(dan)(dan)片機(ji)本身(shen)具有(you)脈寬調制(zhi)PWM型開關穩(wen)壓電(dian)(dian)源(yuan)所需的(de)全部(bu)(bu)功能，具有(you)10位A/D轉換(huan)器。利用(yong)單(dan)(dan)片機(ji)A/D端口，構(gou)成電(dian)(dian)池(chi)電(dian)(dian)壓，電(dian)(dian)流(liu)，溫度檢測電(dian)(dian)路(lu)。

　　單片機通過電壓(ya)反(fan)饋和電流反(fan)饋信號，直接利用PWM輸(shu)出將數(shu)字(zi)電壓(ya)信號并轉化成模擬電壓(ya)信號，能夠(gou)保證控制精度。

　　3 控制部(bu)分電路設計

　　C8051F310單片機

　　①模擬外設

　　a.10位ADC：轉換速度可達200ks/s,可多達21或(huo)17個外(wai)(wai)部(bu)單端或(huo)差分(fen)輸入，VREF可在(zai)外(wai)(wai)部(bu)引腳或(huo)VDD中選擇，內(nei)置(zhi)溫(wen)度傳感器（±3℃），外(wai)(wai)部(bu)轉換啟動輸入；

　　b.兩個模擬比較(jiao)器：可編程回差電(dian)壓(ya)和(he)響(xiang)應時間(jian)，可配置(zhi)為(wei)中斷或復位源，小(xiao)電(dian)流（〈0.5μA）。

　　②供電電壓

　　a.典(dian)型工作電流：5mA、25MHz；

　　b.典型停機電流：0.1μA；

　　c.溫度范圍：-40～+85℃。

　　③高速8051微控制器(qi)內核

　　a.流水線指令(ling)結構(gou)：70%的指令(ling)的執(zhi)行時(shi)間為一個或兩個系統時(shi)鐘(zhong)周期(qi)；

　　b.速度可達25MI/s（時鐘頻率為25MHz時）；

　　c.擴展的中斷(duan)系(xi)統(tong)。

　　④數字外設

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

　　b.4個通用16位計數器/定時器；

　　c.16位(wei)可編程計數器/定時器陣列(lie)（PCA），有5個捕捉/比較(jiao)模(mo)塊；

　　d.使用PCA或(huo)定時(shi)器(qi)和外部(bu)時(shi)鐘源的實時(shi)時(shi)鐘方式。

　　控制電(dian)(dian)路(lu)中(zhong)如圖2所示，P0.3口(kou)提(ti)供充電(dian)(dian)電(dian)(dian)源，P0.6口(kou)檢(jian)測充電(dian)(dian)電(dian)(dian)壓(ya)的(de)(de)大小，P0.5口(kou)檢(jian)測充電(dian)(dian)電(dian)(dian)流的(de)(de)大小，P0.4口(kou)檢(jian)測電(dian)(dian)池的(de)(de)溫度。

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

　　4 充電(dian)部(bu)分及檢測部(bu)分電(dian)路(lu)設計(ji)

　　圖(tu)2 控制電路接線圖(tu)

　　圖3 充(chong)電電路(lu)(lu)與(yu)檢測電路(lu)(lu)圖

　　圖3為充(chong)電(dian)(dian)電(dian)(dian)路與檢測(ce)電(dian)(dian)路圖。

　　①充電過程曲線

　　圖4 鋰電池充(chong)電曲(qu)線

　　如圖4所示，充(chong)(chong)電(dian)(dian)過程由預充(chong)(chong)狀態，恒流(liu)充(chong)(chong)電(dian)(dian)狀態和恒壓充(chong)(chong)電(dian)(dian)狀態組成(cheng)。

　　②快速轉換器

　　實現漸弱終止充電器的(de)(de)最經濟的(de)(de)方法就是(shi)用(yong)一個快(kuai)速轉(zhuan)換器(qi)。快(kuai)速轉(zhuan)換器(qi)是(shi)用(yong)一個電(dian)(dian)(dian)(dian)感(gan)和/或(huo)一個變壓器(qi)（需要隔離的(de)(de)時候用(yong)變壓器(qi)）作(zuo)為能(neng)量(liang)存儲單元以離散的(de)(de)能(neng)量(liang)包(bao)的(de)(de)形式將能(neng)量(liang)從輸(shu)入傳(chuan)輸(shu)至(zhi)輸(shu)出的(de)(de)開(kai)關調節器(qi)反饋電(dian)(dian)(dian)(dian)路，通過晶體管來(lai)調節能(neng)量(liang)的(de)(de)傳(chuan)輸(shu)，同時也作(zuo)為過濾(lv)開(kai)關，以確保電(dian)(dian)(dian)(dian)壓或(huo)電(dian)(dian)(dian)(dian)流在負載時保持恒定。

　　如(ru)圖a開關閉合

　　如圖b開關打開

　　快(kuai)速調節器的(de)(de)(de)操作是通過控制一個(ge)晶體管開(kai)關的(de)(de)(de)占(zhan)(zhan)空(kong)(kong)比來實現的(de)(de)(de)。占(zhan)(zhan)空(kong)(kong)比會自動增加以使電(dian)池流(liu)入(ru)更(geng)多的(de)(de)(de)電(dian)流(liu)。當VBATT

　　③電感的確定

　　電(dian)(dian)感(gan)對交(jiao)(jiao)流(liu)(liu)電(dian)(dian)是(shi)有阻(zu)礙(ai)作用的(de)(de)。在(zai)(zai)交(jiao)(jiao)流(liu)(liu)電(dian)(dian)頻率(lv)一(yi)(yi)定(ding)的(de)(de)情(qing)況下，電(dian)(dian)感(gan)量(liang)越(yue)大，對交(jiao)(jiao)流(liu)(liu)電(dian)(dian)的(de)(de)阻(zu)礙(ai)能力(li)越(yue)強，電(dian)(dian)感(gan)量(liang)越(yue)小，其阻(zu)礙(ai)能力(li)越(yue)小。另外(wai)，在(zai)(zai)電(dian)(dian)感(gan)量(liang)一(yi)(yi)定(ding)的(de)(de)情(qing)況下，交(jiao)(jiao)流(liu)(liu)電(dian)(dian)的(de)(de)頻率(lv)越(yue)高，電(dian)(dian)感(gan)對交(jiao)(jiao)流(liu)(liu)電(dian)(dian)的(de)(de)阻(zu)礙(ai)能力(li)越(yue)大，頻率(lv)越(yue)低，電(dian)(dian)感(gan)對交(jiao)(jiao)流(liu)(liu)電(dian)(dian)的(de)(de)阻(zu)礙(ai)能力(li)越(yue)小。也就是(shi)說，電(dian)(dian)感(gan)有阻(zu)止(zhi)交(jiao)(jiao)流(liu)(liu)電(dian)(dian)通過的(de)(de)特性(xing)。

　　其工(gong)作(zuo)原理(li)是這樣的(de)(de)(de)(de)(de)：當負(fu)(fu)載(zai)兩端(duan)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)壓要降(jiang)(jiang)(jiang)低(di)時(shi)，通過(guo)MOSFET場(chang)(chang)效(xiao)應(ying)管(guan)(guan)的(de)(de)(de)(de)(de)開(kai)關作(zuo)用，外部電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)對電(dian)(dian)(dian)(dian)(dian)(dian)感進行充電(dian)(dian)(dian)(dian)(dian)(dian)并達(da)到所需的(de)(de)(de)(de)(de)額(e)定電(dian)(dian)(dian)(dian)(dian)(dian)壓。當負(fu)(fu)載(zai)兩端(duan)地電(dian)(dian)(dian)(dian)(dian)(dian)壓升高時(shi)，通過(guo)MOSFET場(chang)(chang)效(xiao)應(ying)管(guan)(guan)的(de)(de)(de)(de)(de)開(kai)關作(zuo)用，外部電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)供電(dian)(dian)(dian)(dian)(dian)(dian)斷(duan)(duan)開(kai)，電(dian)(dian)(dian)(dian)(dian)(dian)感釋放出剛才充入(ru)的(de)(de)(de)(de)(de)能量，這時(shi)電(dian)(dian)(dian)(dian)(dian)(dian)感就變成(cheng)了電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)繼(ji)續對負(fu)(fu)載(zai)供電(dian)(dian)(dian)(dian)(dian)(dian)。隨著電(dian)(dian)(dian)(dian)(dian)(dian)感上(shang)存(cun)儲的(de)(de)(de)(de)(de)能量地消(xiao)耗。負(fu)(fu)載(zai)兩端(duan)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)壓開(kai)始逐漸降(jiang)(jiang)(jiang)低(di)，外部電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)通過(guo)MOSFET場(chang)(chang)效(xiao)應(ying)管(guan)(guan)的(de)(de)(de)(de)(de)開(kai)關作(zuo)用又要充電(dian)(dian)(dian)(dian)(dian)(dian)。依次類推在不(bu)斷(duan)(duan)的(de)(de)(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)(de)(de)過(guo)程中形成(cheng)了一(yi)種穩定的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)壓，永遠使負(fu)(fu)載(zai)兩端(duan)地電(dian)(dian)(dian)(dian)(dian)(dian)壓不(bu)會升高也不(bu)會降(jiang)(jiang)(jiang)低(di)，這就是開(kai)關電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)的(de)(de)(de)(de)(de)最大(da)優勢(shi)。

　　要(yao)確定快速轉換器(qi)中電感的(de)大小首先應假定晶體管的(de)占空比為(wei)50%，因為(wei)此時的(de)轉換器(qi)操(cao)作操(cao)作效率最(zui)高。占空比由方程式1給出(chu)：

　　（其中(zhong)T是PWM的周期在程(cheng)序示例(li)中(zhong)T=10.5s）

　　占空(kong)比=ton/T （1）

　　至(zhi)此就可以選(xuan)擇一個PWM的(de)轉換頻(pin)率（如方程式(shi)2所示）PWM的(de)轉換頻(pin)率越(yue)大(da)，則電感(gan)的(de)值(zhi)越(yue)小(xiao)，也越(yue)節約成本(ben)。

　　我的示例代碼配置F310的8位(wei)硬件PWM是使用(yong)內部24.5MHz主時鐘(zhong)的256分頻(pin)來產生一個(ge)95.7kHz的轉換速率。

　　L=（Vi-Vsat-Voton）/2Iomax （2）

　　現在(zai)我們可(ke)以計算電(dian)(dian)感的大小(xiao)了，假(jia)定(ding)充電(dian)(dian)電(dian)(dian)壓(ya)(ya)Vi的值(zhi)(zhi)為(wei)(wei)15V，飽和電(dian)(dian)壓(ya)(ya)Vsat的值(zhi)(zhi)為(wei)(wei)0.5V，需要獲得的輸出電(dian)(dian)壓(ya)(ya)值(zhi)(zhi)為(wei)(wei)4.2V,并且(qie)最大輸出電(dian)(dian)流IＯMAX為(wei)(wei)1500mA，那么，電(dian)(dian)感的值(zhi)(zhi)至少應選為(wei)(wei)18H。

　　需要注意(yi)的(de)是(shi)：在本電路中的(de)電容僅僅是(shi)一個(ge)紋波(bo)衰減(jian)器，因為(wei)紋波(bo)與電容的(de)大(da)小成反比例關系，所以(yi)電容的(de)值越大(da)，衰減(jian)效(xiao)果越好。