現代通(tong)訊設(she)備、便(bian)攜式電(dian)(dian)(dian)子(zi)產品、筆記本電(dian)(dian)(dian)腦、電(dian)(dian)(dian)動汽(qi)車、小衛(wei)星等普(pu)遍使用蓄電(dian)(dian)(dian)池(chi)作為電(dian)(dian)(dian)源(yuan),應用非常廣泛。然而(er)大(da)多(duo)數設(she)備中的蓄電(dian)(dian)(dian)池(chi),只能使用專用的充(chong)(chong)(chong)電(dian)(dian)(dian)器,而(er)且普(pu)通(tong)的充(chong)(chong)(chong)電(dian)(dian)(dian)器大(da)多(duo)充(chong)(chong)(chong)電(dian)(dian)(dian)時間(jian)長,無法判斷其充(chong)(chong)(chong)電(dian)(dian)(dian)參(can)數和剩(sheng)余的充(chong)(chong)(chong)電(dian)(dian)(dian)時間(jian)。 

　　本文介紹一種基于單片機的通用智能充電器的設計。充電器可以(yi)實(shi)時采集電(dian)(dian)池(chi)的電(dian)(dian)壓(ya)、電(dian)(dian)流,對充(chong)(chong)(chong)電(dian)(dian)過(guo)程(cheng)進(jin)行(xing)智(zhi)能控制,計算電(dian)(dian)池(chi)已充(chong)(chong)(chong)的電(dian)(dian)量和(he)剩余的充(chong)(chong)(chong)電(dian)(dian)時間;還(huan)可以(yi)通過(guo)串(chuan)口和(he)上位機進(jin)行(xing)通訊并給(gei)用(yong)戶顯示必(bi)要的信息,有虛擬儀表的作用(yong);另(ling)外(wai),它(ta)也可以(yi)改變參數(shu),適應各種不同電(dian)(dian)池(chi)的充(chong)(chong)(chong)電(dian)(dian)。這里列舉幾種不同的電(dian)(dian)池(chi)充(chong)(chong)(chong)電(dian)(dian)試驗,來說明智(zhi)能充(chong)(chong)(chong)電(dian)(dian)器的實(shi)用(yong)價值(zhi)。 

1 智能充電器的硬件設計 

　　主(zhu)要(yao)包(bao)括電源(yuan)變換電路(lu)、采樣電路(lu)、處(chu)理器、脈寬(kuan)調制控(kong)制器和電池(chi)組(zu)等,形成了一個(ge)閉環系統.

1．1 處理(li)器(qi) 

　　處理(li)器采用(yong)51系列單(dan)片機89C51。單(dan)片機內(nei)部(bu)有兩個(ge)定(ding)時(shi)器、兩個(ge)外部(bu)中(zhong)斷和(he)一個(ge)串(chuan)口(kou)(kou)中(zhong)斷、三(san)個(ge)八路的(de)(de)I/O口(kou)(kou),采用(yong)11.0592MHz的(de)(de)晶振。單(dan)片機的(de)(de)任務是通(tong)(tong)過(guo)采樣電路實時(shi)采集電池的(de)(de)充電狀(zhuang)態(tai),通(tong)(tong)過(guo)計算決定(ding)下(xia)一階段(duan)的(de)(de)充電電流,然后發送命令給控制(zhi)器控制(zhi)電流的(de)(de)大小。單(dan)片機通(tong)(tong)過(guo)串(chuan)口(kou)(kou)RS232和(he)上位(wei)機相(xiang)連,用(yong)于存(cun)儲數據和(he)虛擬顯示。 

1．2 采樣部分(fen) 

　　電壓(ya)(ya)和電流采樣(yang)采用模(mo)/數轉換器AD574。AD574為±15V雙電源供(gong)電,12位(wei)輸(shu)出(chu),最(zui)大誤差為±4bit,合(he)計電壓(ya)(ya)0.01V。 

　　充電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)通(tong)過(guo)電(dian)(dian)(dian)流(liu)傳(chuan)感器(qi)MAX471轉換(huan)為電(dian)(dian)(dian)壓值。電(dian)(dian)(dian)流(liu)采樣的(de)電(dian)(dian)(dian)壓值和(he)電(dian)(dian)(dian)池(chi)組的(de)端電(dian)(dian)(dian)壓值兩者經(jing)過(guo)模擬開關(guan)CD4051,再經(jing)過(guo)電(dian)(dian)(dian)壓跟隨器(qi)輸入到AD574,分別進(jin)(jin)行轉換(huan),其結果由單片機(ji)讀取,并進(jin)(jin)行存(cun)儲(chu)和(he)處(chu)理(li)。

1．3 控制器 

　　控(kong)制(zhi)(zhi)(zhi)器采用(yong)脈(mo)寬(kuan)調制(zhi)(zhi)(zhi)(PWM)方(fang)(fang)式(shi)控(kong)制(zhi)(zhi)(zhi)供(gong)電(dian)(dian)電(dian)(dian)流(liu)的大(da)小。PWM發生器由另一個20MHz的單片機構成,主控(kong)制(zhi)(zhi)(zhi)器和(he)它采用(yong)中斷的方(fang)(fang)式(shi)進(jin)行通(tong)訊,控(kong)制(zhi)(zhi)(zhi)其增大(da)或減小脈(mo)寬(kuan)。PWM信號通(tong)過光電(dian)(dian)隔離驅動主回(hui)路上的MOSFET。開(kai)(kai)關(guan)管、二(er)極管、LC電(dian)(dian)路構成開(kai)(kai)關(guan)穩(wen)壓(ya)電(dian)(dian)源(yuan)。用(yong)PWM方(fang)(fang)式(shi)控(kong)制(zhi)(zhi)(zhi)的開(kai)(kai)關(guan)電(dian)(dian)源(yuan)可以減小功耗,同時便于進(jin)行數字化控(kong)制(zhi)(zhi)(zhi),但(dan)母線的紋波(bo)系數相對較大(da)。

2 智能充電器的(de)軟件(jian)設計 

2．1 數據測量 

　　在單(dan)片(pian)機的測(ce)量(liang)中,電池電壓值(zhi)(zhi)(zhi)和電流(liu)測(ce)量(liang)值(zhi)(zhi)(zhi)經過多路選(xuan)擇器(qi)進行(xing)選(xuan)擇,然后通過A/D轉換器(qi)轉換為16進制數,直(zhi)接(jie)存入單(dan)片(pian)機。電池電容量(liang)C則需要間(jian)接(jie)計算,由于每個循環 周期檢測(ce)電流(liu)一次,故可以利用(yong)電流(liu)值(zhi)(zhi)(zhi)的積分求出(chu)電容量(liang)C。考(kao)慮電池內(nei)阻r的影(ying)響,可以得到計算電容量(liang)的計算公式為: 

　　Cn+1=Cn+I?t-I2?r?t 

　　充(chong)電(dian)時(shi)(shi)(shi)間和(he)剩余(yu)充(chong)電(dian)時(shi)(shi)(shi)間由上位(wei)機進行計算,剩余(yu)充(chong)電(dian)時(shi)(shi)(shi)間等于預(yu)設(she)的充(chong)電(dian)時(shi)(shi)(shi)間與(yu)已充(chong)電(dian)時(shi)(shi)(shi)間的差值(zhi)。其(qi)中,預(yu)設(she)時(shi)(shi)(shi)間可根據電(dian)池的型號預(yu)先(xian)得到(dao)。 

2．2 單(dan)片(pian)機控(kong)制(zhi)程序設計(ji) 

對(dui)于(yu)不同(tong)的(de)電(dian)池和不同(tong)的(de)參(can)數,單片機(ji)需要(yao)(yao)設定不同(tong)的(de)充(chong)電(dian)參(can)數,選擇不同(tong)的(de)充(chong)電(dian)策略。另外,程(cheng)序(xu)需要(yao)(yao)在電(dian)池過電(dian)流(liu)(liu)、過電(dian)壓(ya)等異常情況下強制終止充(chong)電(dian)。以(yi)鋰離子電(dian)池為例,一般(ban)采用(yong)恒流(liu)(liu)-恒壓(ya)充(chong)電(dian)方式,其充(chong)電(dian)過程(cheng)包括(kuo)小電(dian)流(liu)(liu)預充(chong)電(dian)、大電(dian)流(liu)(liu)充(chong)電(dian)、恒壓(ya)充(chong)電(dian)等幾部分。

　　在控制恒定電流(liu)(liu)和(he)恒定電壓的(de)過程(cheng)中(zhong),采用比例控制,即如果充電電流(liu)(liu)I大于設定電流(liu)(liu)Is,就(jiu)按(an)(an)照(zhao)(zhao)比例減小脈寬;反(fan)之按(an)(an)照(zhao)(zhao)比例增大脈寬。單片機(ji)(ji)還需要(yao)接收(shou)和(he)處理上位(wei)機(ji)(ji)的(de)命令(ling),并根據(ju)上位(wei)機(ji)(ji)的(de)要(yao)求將數據(ju)實時回送給上位(wei)機(ji)(ji)。兩者的(de)通訊協議要(yao)在程(cheng)序中(zhong)預先設定。 

2．3 上位機處理程(cheng)序設計(ji) 

　　上(shang)位(wei)機程(cheng)序由VisualC++編寫。其任務是每隔1秒鐘(zhong)向串口發(fa)送一個(ge)查(cha)詢命令,并(bing)讀取(qu)單片機回送的(de)信(xin)息(xi),提取(qu)充(chong)電(dian)(dian)電(dian)(dian)流(liu)、充(chong)電(dian)(dian)電(dian)(dian)壓、工作狀態(tai)等(deng)(deng)參數(shu)(shu)。參數(shu)(shu)經過(guo)數(shu)(shu)制轉換和計算后進行(xing)顯示。軟件有著良好(hao)的(de)用戶界面,可(ke)以方便地觀測(ce)電(dian)(dian)池目前的(de)工作狀態(tai)以及剩余充(chong)電(dian)(dian)時(shi)間等(deng)(deng)信(xin)息(xi)。上(shang)位(wei)機程(cheng)序會(hui)同(tong)時(shi)把讀到的(de)數(shu)(shu)據存儲(chu)到文件中(zhong),這些(xie)數(shu)(shu)據可(ke)以利用其它數(shu)(shu)學軟件(如(ru)Matlab)進行(xing)處理。 

　　另外,程序在初始化時要把充電電池的型號參數發送給智能充電器,參數一般包括充(chong)(chong)電電池的(de)種類(鋰離子(zi)電池、鎳(nie)鎘電池)、充(chong)(chong)電電池的(de)容量(單位為(wei)mAh)等。根據(ju)不同(tong)的(de)電池型(xing)號,單片機可以設定不同(tong)的(de)充(chong)(chong)電參數,程序(xu)可以直接控制單片機的(de)運(yun)行與停止(zhi)。 

3智(zhi)能充(chong)電器的(de)應用試(shi)驗(yan) 

3．1充電(dian)性能(neng)試(shi)驗 

　　這里(li)選用型號為(wei)US18650的SONY鋰離子電(dian)(dian)(dian)池(chi)(chi),其額定容量(liang)為(wei)1800mAh;經過測量(liang),電(dian)(dian)(dian)池(chi)(chi)在4.2V左右時的內阻約為(wei)0.3Ω。取恒流(liu)充電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)為(wei)1/3C=0.6A,截止電(dian)(dian)(dian)壓(ya)為(wei)4.2V,充電(dian)(dian)(dian)結束標志電(dian)(dian)(dian)流(liu)為(wei)0.06A,進行充電(dian)(dian)(dian)試驗(yan)。

　　充(chong)(chong)電(dian)時間約為(wei)240分鐘,如果需要進一步縮短充(chong)(chong)電(dian)時間,只需在(zai)初始(shi)化時設(she)定更(geng)大(da)的(de)充(chong)(chong)電(dian)電(dian)流即可。因為(wei)采(cai)用(yong)PWM控制器,所以(yi)電(dian)源供電(dian)的(de)效(xiao)(xiao)率(lv)高,從(cong)供電(dian)電(dian)源到充(chong)(chong)電(dian)電(dian)池(chi)的(de)工作效(xiao)(xiao)率(lv),最低時在(zai)85%左右。充(chong)(chong)電(dian)電(dian)流波動(dong)較大(da),波動(dong)系數(shu)約為(wei)5%。 

3．2 智(zhi)能充電器通(tong)用性試驗 

　　選用NOKIA6100鋰(li)離子電池(chi)(額(e)定容量為550mAh),用恒(heng)流(liu)-恒(heng)壓充電方式進行(xing)充電,取(qu)恒(heng)流(liu)充電電流(liu)為0.15A,截止電壓為4.2V,充電曲線如圖6所(suo)示。 

　　從充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)曲線來看,電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)壓達(da)到(dao)(dao)3.96V時就不(bu)(bu)再上升(sheng)了(le)(le),充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)也不(bu)(bu)再下降了(le)(le)。可以(yi)(yi)判斷商用電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)內部有(you)(you)保(bao)護電(dian)(dian)(dian)(dian)(dian)(dian)路,將多余的電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)旁(pang)路了(le)(le),這(zhe)樣的保(bao)護電(dian)(dian)(dian)(dian)(dian)(dian)路使充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)過程中能量損(sun)耗很大。試(shi)驗曲線顯示在(zai)四小時時電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)量已(yi)經達(da)到(dao)(dao)550mAh,但(dan)實際上并沒有(you)(you)達(da)到(dao)(dao)滿充(chong)。此實驗證明,此充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器(qi)可以(yi)(yi)作(zuo)為一(yi)般的商用電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)的通用充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器(qi),充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)速度快,效(xiao)果良(liang)好。不(bu)(bu)足(zu)的是它與實際的充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)在(zai)機(ji)械接口上還(huan)不(bu)(bu)能匹配,需(xu)要進(jin)一(yi)步改進(jin)。