現代(dai)通(tong)(tong)訊(xun)設備(bei)、便(bian)攜式電(dian)(dian)子產(chan)品、筆記本電(dian)(dian)腦(nao)、電(dian)(dian)動(dong)汽車、小衛星等普(pu)遍(bian)使用蓄(xu)電(dian)(dian)池作(zuo)為電(dian)(dian)源(yuan),應用非(fei)常廣泛(fan)。然而大(da)多數設備(bei)中的蓄(xu)電(dian)(dian)池,只(zhi)能使用專用的充(chong)電(dian)(dian)器,而且普(pu)通(tong)(tong)的充(chong)電(dian)(dian)器大(da)多充(chong)電(dian)(dian)時(shi)間長,無法判斷其充(chong)電(dian)(dian)參數和(he)剩余的充(chong)電(dian)(dian)時(shi)間。 

　　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(ke)以實時(shi)采集電(dian)(dian)池(chi)的(de)(de)電(dian)(dian)壓、電(dian)(dian)流,對充電(dian)(dian)過(guo)程進(jin)行智能控制,計算(suan)電(dian)(dian)池(chi)已充的(de)(de)電(dian)(dian)量和(he)剩(sheng)余的(de)(de)充電(dian)(dian)時(shi)間;還可(ke)以通過(guo)串口和(he)上位機進(jin)行通訊(xun)并給用(yong)戶顯示必要的(de)(de)信息,有虛擬(ni)儀表的(de)(de)作(zuo)用(yong);另外,它也可(ke)以改(gai)變參數,適應各種不同電(dian)(dian)池(chi)的(de)(de)充電(dian)(dian)。這里列(lie)舉幾(ji)種不同的(de)(de)電(dian)(dian)池(chi)充電(dian)(dian)試(shi)驗,來(lai)說(shuo)明(ming)智能充電(dian)(dian)器的(de)(de)實用(yong)價(jia)值。 

1 智能充電器的硬件設計 

　　主要包括電源變換電路、采樣電路、處理器(qi)、脈寬調制控(kong)制器(qi)和電池組等,形成(cheng)了一(yi)個閉環系統.

1．1 處理器 

　　處理器采用51系列單(dan)(dan)片機(ji)89C51。單(dan)(dan)片機(ji)內(nei)部有兩(liang)個(ge)定時(shi)(shi)器、兩(liang)個(ge)外部中(zhong)斷和一(yi)個(ge)串口(kou)中(zhong)斷、三(san)個(ge)八路的(de)I/O口(kou),采用11.0592MHz的(de)晶振。單(dan)(dan)片機(ji)的(de)任(ren)務是通(tong)過(guo)采樣電(dian)路實時(shi)(shi)采集電(dian)池的(de)充電(dian)狀態(tai),通(tong)過(guo)計算決定下一(yi)階段的(de)充電(dian)電(dian)流,然后發(fa)送命令給控制器控制電(dian)流的(de)大(da)小。單(dan)(dan)片機(ji)通(tong)過(guo)串口(kou)RS232和上位機(ji)相(xiang)連,用于存儲(chu)數據和虛(xu)擬顯示。 

1．2 采樣部分 

　　電(dian)(dian)壓(ya)和電(dian)(dian)流采樣采用模(mo)/數(shu)轉換器(qi)AD574。AD574為±15V雙電(dian)(dian)源(yuan)供(gong)電(dian)(dian),12位輸出,最大(da)誤(wu)差(cha)為±4bit,合計電(dian)(dian)壓(ya)0.01V。 

　　充電(dian)電(dian)流通過(guo)電(dian)流傳感器MAX471轉換為電(dian)壓值。電(dian)流采樣(yang)的電(dian)壓值和電(dian)池組(zu)的端電(dian)壓值兩者(zhe)經(jing)過(guo)模擬開關CD4051,再經(jing)過(guo)電(dian)壓跟隨器輸(shu)入到AD574,分別進行轉換,其(qi)結果由(you)單片機讀取,并進行存儲和處理。

1．3 控(kong)制器 

　　控制(zhi)(zhi)(zhi)(zhi)器采用脈寬(kuan)調制(zhi)(zhi)(zhi)(zhi)(PWM)方(fang)式(shi)控制(zhi)(zhi)(zhi)(zhi)供電電流的(de)大(da)小。PWM發生(sheng)器由(you)另一(yi)個20MHz的(de)單片(pian)機構成,主控制(zhi)(zhi)(zhi)(zhi)器和它采用中斷的(de)方(fang)式(shi)進(jin)行通訊,控制(zhi)(zhi)(zhi)(zhi)其增大(da)或減(jian)小脈寬(kuan)。PWM信號通過光電隔離驅動主回路上的(de)MOSFET。開關管、二(er)極管、LC電路構成開關穩壓(ya)電源(yuan)。用PWM方(fang)式(shi)控制(zhi)(zhi)(zhi)(zhi)的(de)開關電源(yuan)可以減(jian)小功(gong)耗,同時便于進(jin)行數(shu)字化控制(zhi)(zhi)(zhi)(zhi),但母線的(de)紋波(bo)系數(shu)相(xiang)對較大(da)。

2 智能充電(dian)器的軟(ruan)件設(she)計 

2．1 數據測量 

　　在單片(pian)機的測量(liang)(liang)(liang)中,電池(chi)電壓值(zhi)和(he)電流測量(liang)(liang)(liang)值(zhi)經過多路選擇器(qi)進行選擇,然后(hou)通過A/D轉換器(qi)轉換為16進制數,直接存入單片(pian)機。電池(chi)電容量(liang)(liang)(liang)C則需要間接計(ji)(ji)算(suan),由(you)于每個循環 周期檢測電流一(yi)次(ci),故(gu)可(ke)以利用(yong)電流值(zhi)的積(ji)分求出電容量(liang)(liang)(liang)C。考慮(lv)電池(chi)內阻r的影響,可(ke)以得到(dao)計(ji)(ji)算(suan)電容量(liang)(liang)(liang)的計(ji)(ji)算(suan)公式為: 

　　Cn+1=Cn+I?t-I2?r?t 

　　充(chong)(chong)(chong)(chong)電時(shi)(shi)間(jian)(jian)和剩(sheng)余充(chong)(chong)(chong)(chong)電時(shi)(shi)間(jian)(jian)由上位機進行計算,剩(sheng)余充(chong)(chong)(chong)(chong)電時(shi)(shi)間(jian)(jian)等(deng)于預設的充(chong)(chong)(chong)(chong)電時(shi)(shi)間(jian)(jian)與已充(chong)(chong)(chong)(chong)電時(shi)(shi)間(jian)(jian)的差值。其中,預設時(shi)(shi)間(jian)(jian)可根據(ju)電池的型號預先得到。 

2．2 單片機(ji)控制程序設(she)計 

對于不(bu)(bu)同的電(dian)(dian)(dian)(dian)池和不(bu)(bu)同的參數(shu),單片機(ji)需要設定(ding)不(bu)(bu)同的充(chong)電(dian)(dian)(dian)(dian)參數(shu),選擇(ze)不(bu)(bu)同的充(chong)電(dian)(dian)(dian)(dian)策略。另外,程序需要在電(dian)(dian)(dian)(dian)池過(guo)電(dian)(dian)(dian)(dian)流(liu)、過(guo)電(dian)(dian)(dian)(dian)壓(ya)等(deng)異常情況下(xia)強制終(zhong)止充(chong)電(dian)(dian)(dian)(dian)。以(yi)鋰(li)離子電(dian)(dian)(dian)(dian)池為例,一般采用恒(heng)流(liu)-恒(heng)壓(ya)充(chong)電(dian)(dian)(dian)(dian)方(fang)式,其(qi)充(chong)電(dian)(dian)(dian)(dian)過(guo)程包括小電(dian)(dian)(dian)(dian)流(liu)預充(chong)電(dian)(dian)(dian)(dian)、大電(dian)(dian)(dian)(dian)流(liu)充(chong)電(dian)(dian)(dian)(dian)、恒(heng)壓(ya)充(chong)電(dian)(dian)(dian)(dian)等(deng)幾部分(fen)。

　　在(zai)控制恒(heng)(heng)定(ding)電(dian)流和(he)恒(heng)(heng)定(ding)電(dian)壓的(de)過程中(zhong),采用(yong)比例(li)控制,即(ji)如果充電(dian)電(dian)流I大于設(she)定(ding)電(dian)流Is,就按(an)照(zhao)比例(li)減小脈(mo)寬(kuan);反之按(an)照(zhao)比例(li)增大脈(mo)寬(kuan)。單片(pian)機(ji)還需要(yao)接收和(he)處理上(shang)位(wei)機(ji)的(de)命令,并根據上(shang)位(wei)機(ji)的(de)要(yao)求將(jiang)數(shu)據實時回送給上(shang)位(wei)機(ji)。兩者的(de)通訊協議要(yao)在(zai)程序中(zhong)預(yu)先(xian)設(she)定(ding)。 

2．3 上位機處理程(cheng)序設計 

　　上(shang)位(wei)機(ji)程序由VisualC++編寫。其任務是每隔1秒鐘(zhong)向串口發送一個查詢命令,并讀取單片機(ji)回送的(de)(de)信息,提取充(chong)(chong)電(dian)(dian)電(dian)(dian)流、充(chong)(chong)電(dian)(dian)電(dian)(dian)壓、工作狀態(tai)(tai)等(deng)參數(shu)。參數(shu)經過數(shu)制轉換(huan)和計算(suan)后進行(xing)顯示。軟(ruan)件有著良好的(de)(de)用(yong)戶界面,可(ke)(ke)以方便地觀測電(dian)(dian)池(chi)目前(qian)的(de)(de)工作狀態(tai)(tai)以及剩余充(chong)(chong)電(dian)(dian)時間等(deng)信息。上(shang)位(wei)機(ji)程序會同時把讀到的(de)(de)數(shu)據存儲到文件中,這些數(shu)據可(ke)(ke)以利用(yong)其它(ta)數(shu)學軟(ruan)件(如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(bao)括充電(dian)(dian)電(dian)(dian)池的種(zhong)類(鋰離子(zi)電(dian)(dian)池、鎳(nie)鎘電(dian)(dian)池)、充電(dian)(dian)電(dian)(dian)池的容量(單位為mAh)等。根據不同(tong)的電(dian)(dian)池型號,單片機(ji)可(ke)以設(she)定(ding)不同(tong)的充電(dian)(dian)參數,程序可(ke)以直接控(kong)制(zhi)單片機(ji)的運行與停止。 

3智能充電(dian)器(qi)的(de)應(ying)用試驗 

3．1充(chong)電(dian)性能試驗 

　　這里選用型號為(wei)US18650的SONY鋰離(li)子電(dian)池,其額(e)定容量為(wei)1800mAh;經過測量,電(dian)池在4.2V左右時的內阻約為(wei)0.3Ω。取恒流(liu)(liu)充(chong)(chong)電(dian)電(dian)流(liu)(liu)為(wei)1/3C=0.6A,截止電(dian)壓為(wei)4.2V,充(chong)(chong)電(dian)結束(shu)標志(zhi)電(dian)流(liu)(liu)為(wei)0.06A,進行充(chong)(chong)電(dian)試驗(yan)。

　　充(chong)電(dian)時間約為240分鐘,如(ru)果需要進一步縮(suo)短(duan)充(chong)電(dian)時間,只需在初始化(hua)時設定更(geng)大(da)的(de)(de)充(chong)電(dian)電(dian)流即可。因為采用PWM控制器,所以(yi)電(dian)源(yuan)供電(dian)的(de)(de)效率高,從供電(dian)電(dian)源(yuan)到充(chong)電(dian)電(dian)池的(de)(de)工作效率,最低時在85%左右。充(chong)電(dian)電(dian)流波動較(jiao)大(da),波動系數(shu)約為5%。 

3．2 智能充(chong)電(dian)器通用性試驗 

　　選(xuan)用(yong)(yong)NOKIA6100鋰離(li)子電(dian)池(額(e)定容量(liang)為(wei)550mAh),用(yong)(yong)恒流-恒壓充(chong)電(dian)方式進行(xing)充(chong)電(dian),取(qu)恒流充(chong)電(dian)電(dian)流為(wei)0.15A,截止電(dian)壓為(wei)4.2V,充(chong)電(dian)曲線如圖6所示。 

　　從充(chong)電(dian)(dian)(dian)(dian)(dian)曲(qu)線(xian)來看,電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)(dian)壓達(da)到3.96V時就不再(zai)上(shang)升了(le),充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流也不再(zai)下降了(le)。可以(yi)判(pan)斷商用(yong)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)內部有保護(hu)電(dian)(dian)(dian)(dian)(dian)路,將多余的(de)(de)電(dian)(dian)(dian)(dian)(dian)流旁路了(le),這樣的(de)(de)保護(hu)電(dian)(dian)(dian)(dian)(dian)路使充(chong)電(dian)(dian)(dian)(dian)(dian)過(guo)程中能量(liang)損耗很大。試驗曲(qu)線(xian)顯(xian)示在四小時時電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)(dian)量(liang)已經達(da)到550mAh,但(dan)實際上(shang)并沒(mei)有達(da)到滿充(chong)。此實驗證明,此充(chong)電(dian)(dian)(dian)(dian)(dian)器可以(yi)作為一般的(de)(de)商用(yong)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)的(de)(de)通用(yong)充(chong)電(dian)(dian)(dian)(dian)(dian)器,充(chong)電(dian)(dian)(dian)(dian)(dian)速度快,效(xiao)果(guo)良好。不足的(de)(de)是它與(yu)實際的(de)(de)充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)在機械接口上(shang)還不能匹配(pei),需要進(jin)一步改進(jin)。