現代通(tong)訊(xun)設(she)備、便攜式電(dian)(dian)(dian)子(zi)產品(pin)、筆記本電(dian)(dian)(dian)腦、電(dian)(dian)(dian)動(dong)汽(qi)車(che)、小衛(wei)星等普遍使用(yong)蓄(xu)電(dian)(dian)(dian)池作為電(dian)(dian)(dian)源,應用(yong)非常(chang)廣泛。然(ran)而(er)(er)大多數(shu)設(she)備中(zhong)的(de)蓄(xu)電(dian)(dian)(dian)池,只能使用(yong)專用(yong)的(de)充(chong)電(dian)(dian)(dian)器,而(er)(er)且(qie)普通(tong)的(de)充(chong)電(dian)(dian)(dian)器大多充(chong)電(dian)(dian)(dian)時間(jian)長,無法判斷其(qi)充(chong)電(dian)(dian)(dian)參數(shu)和剩余的(de)充(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(ke)以(yi)實時采集(ji)電池的(de)電壓、電流,對充(chong)電過程進(jin)行智能控(kong)制,計算(suan)電池已充(chong)的(de)電量(liang)和剩余的(de)充(chong)電時間(jian);還可(ke)以(yi)通過串(chuan)口和上位機(ji)進(jin)行通訊并給用戶顯示必要的(de)信息,有虛擬儀表(biao)的(de)作用;另外,它也可(ke)以(yi)改變參數(shu),適應各種不同電池的(de)充(chong)電。這里列舉幾種不同的(de)電池充(chong)電試驗(yan),來說(shuo)明智能充(chong)電器的(de)實用價值。 

1 智能充電器的硬件設計 

　　主要包括(kuo)電(dian)源(yuan)變換電(dian)路、采樣電(dian)路、處理器、脈寬調制控(kong)制器和電(dian)池(chi)組等,形成了一個(ge)閉環系統.

1．1 處(chu)理器 

　　處(chu)理器(qi)采用(yong)51系列單片(pian)(pian)(pian)(pian)機89C51。單片(pian)(pian)(pian)(pian)機內部(bu)有兩個定時(shi)器(qi)、兩個外部(bu)中斷和一個串口中斷、三(san)個八路的(de)I/O口,采用(yong)11.0592MHz的(de)晶振。單片(pian)(pian)(pian)(pian)機的(de)任務是通過采樣電(dian)路實時(shi)采集電(dian)池的(de)充(chong)電(dian)狀態,通過計(ji)算決(jue)定下一階(jie)段的(de)充(chong)電(dian)電(dian)流,然后(hou)發送(song)命令給控(kong)制器(qi)控(kong)制電(dian)流的(de)大(da)小。單片(pian)(pian)(pian)(pian)機通過串口RS232和上位機相(xiang)連,用(yong)于存儲數據(ju)和虛擬顯示。 

1．2 采樣部分 

　　電壓和電流采(cai)樣(yang)采(cai)用模(mo)/數轉換(huan)器AD574。AD574為(wei)±15V雙(shuang)電源(yuan)供電,12位輸出,最(zui)大(da)誤差(cha)為(wei)±4bit,合計電壓0.01V。 

　　充電(dian)電(dian)流(liu)通過電(dian)流(liu)傳感器MAX471轉(zhuan)換(huan)為電(dian)壓(ya)(ya)值(zhi)。電(dian)流(liu)采樣的(de)電(dian)壓(ya)(ya)值(zhi)和電(dian)池組的(de)端電(dian)壓(ya)(ya)值(zhi)兩者(zhe)經過模擬(ni)開關CD4051,再經過電(dian)壓(ya)(ya)跟隨(sui)器輸入到AD574,分別進行轉(zhuan)換(huan),其結(jie)果由單片機讀取,并進行存儲和處(chu)理。

1．3 控制器(qi) 

　　控制器(qi)采用脈(mo)寬調制(PWM)方式(shi)控制供(gong)電電流的大(da)小(xiao)。PWM發生器(qi)由另一個(ge)20MHz的單(dan)片機構(gou)成,主(zhu)控制器(qi)和它采用中斷的方式(shi)進行通訊,控制其增(zeng)大(da)或減小(xiao)脈(mo)寬。PWM信(xin)號(hao)通過(guo)光電隔離驅動主(zhu)回路(lu)上(shang)的MOSFET。開關管、二(er)極(ji)管、LC電路(lu)構(gou)成開關穩壓電源(yuan)。用PWM方式(shi)控制的開關電源(yuan)可以減小(xiao)功耗,同時便于進行數(shu)字(zi)化控制,但母線的紋波系(xi)數(shu)相對(dui)較大(da)。

2 智能充(chong)電器(qi)的軟件設(she)計 

2．1 數據測量(liang) 

　　在單片機(ji)的測(ce)量(liang)中(zhong),電(dian)(dian)池電(dian)(dian)壓值和電(dian)(dian)流(liu)測(ce)量(liang)值經(jing)過多(duo)路選擇器進行選擇,然后通過A/D轉換(huan)器轉換(huan)為16進制數,直接存入單片機(ji)。電(dian)(dian)池電(dian)(dian)容(rong)量(liang)C則需要間接計(ji)算,由于每個(ge)循環 周期檢測(ce)電(dian)(dian)流(liu)一(yi)次,故可以(yi)利用電(dian)(dian)流(liu)值的積分求出電(dian)(dian)容(rong)量(liang)C。考(kao)慮電(dian)(dian)池內阻(zu)r的影響,可以(yi)得到計(ji)算電(dian)(dian)容(rong)量(liang)的計(ji)算公(gong)式為: 

　　Cn+1=Cn+I?t-I2?r?t 

　　充(chong)(chong)電(dian)時間和剩余充(chong)(chong)電(dian)時間由上(shang)位機進行計(ji)算,剩余充(chong)(chong)電(dian)時間等于(yu)預設的充(chong)(chong)電(dian)時間與已充(chong)(chong)電(dian)時間的差值。其中(zhong),預設時間可(ke)根(gen)據(ju)電(dian)池(chi)的型號預先(xian)得到。 

2．2 單片(pian)機控制程序設計 

對于不(bu)(bu)同(tong)(tong)(tong)的(de)(de)電(dian)(dian)池和不(bu)(bu)同(tong)(tong)(tong)的(de)(de)參(can)數,單片機需(xu)要設定不(bu)(bu)同(tong)(tong)(tong)的(de)(de)充(chong)(chong)(chong)電(dian)(dian)參(can)數,選擇不(bu)(bu)同(tong)(tong)(tong)的(de)(de)充(chong)(chong)(chong)電(dian)(dian)策略。另(ling)外,程(cheng)序需(xu)要在電(dian)(dian)池過電(dian)(dian)流(liu)、過電(dian)(dian)壓等(deng)異常情(qing)況下強制終止充(chong)(chong)(chong)電(dian)(dian)。以鋰(li)離(li)子電(dian)(dian)池為(wei)例,一般采用恒流(liu)-恒壓充(chong)(chong)(chong)電(dian)(dian)方式(shi),其充(chong)(chong)(chong)電(dian)(dian)過程(cheng)包括小電(dian)(dian)流(liu)預(yu)充(chong)(chong)(chong)電(dian)(dian)、大電(dian)(dian)流(liu)充(chong)(chong)(chong)電(dian)(dian)、恒壓充(chong)(chong)(chong)電(dian)(dian)等(deng)幾(ji)部分。

　　在控制恒(heng)(heng)定電(dian)(dian)(dian)流(liu)和恒(heng)(heng)定電(dian)(dian)(dian)壓(ya)的(de)過程(cheng)(cheng)中,采用比例(li)控制,即如果(guo)充電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)I大(da)于設定電(dian)(dian)(dian)流(liu)Is,就按照比例(li)減小脈寬(kuan);反之按照比例(li)增大(da)脈寬(kuan)。單片機(ji)還需(xu)要(yao)接收和處理(li)上位機(ji)的(de)命令,并根(gen)據上位機(ji)的(de)要(yao)求(qiu)將數據實時回送給上位機(ji)。兩者的(de)通訊協議要(yao)在程(cheng)(cheng)序中預(yu)先設定。 

2．3 上位(wei)機(ji)處理程序設計(ji) 

　　上位(wei)機程序由VisualC++編寫。其任務(wu)是(shi)每隔1秒鐘向串口(kou)發送一個(ge)查詢(xun)命令,并讀取單片機回送的(de)(de)信息,提取充(chong)電(dian)(dian)電(dian)(dian)流、充(chong)電(dian)(dian)電(dian)(dian)壓、工作狀態等參數。參數經過(guo)數制轉(zhuan)換和計算后進行顯示。軟(ruan)件(jian)有著(zhu)良好(hao)的(de)(de)用戶界面,可(ke)以方便地觀(guan)測電(dian)(dian)池目(mu)前的(de)(de)工作狀態以及剩(sheng)余充(chong)電(dian)(dian)時間等信息。上位(wei)機程序會同(tong)時把讀到(dao)的(de)(de)數據存(cun)儲到(dao)文件(jian)中,這些(xie)數據可(ke)以利用其它(ta)數學軟(ruan)件(jian)(如Matlab)進行處理(li)。 

　　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(can)數一般包括充(chong)電(dian)電(dian)池(chi)的種類(lei)(鋰離子電(dian)池(chi)、鎳鎘(ge)電(dian)池(chi))、充(chong)電(dian)電(dian)池(chi)的容(rong)量(單(dan)(dan)位為mAh)等。根據不(bu)同的電(dian)池(chi)型號,單(dan)(dan)片(pian)機可以設定不(bu)同的充(chong)電(dian)參(can)數,程序可以直接(jie)控制單(dan)(dan)片(pian)機的運行與停止。 

3智能充(chong)電器(qi)的應(ying)用試驗 

3．1充電性能試驗 

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

　　充(chong)電(dian)(dian)(dian)(dian)(dian)時(shi)間(jian)約(yue)為240分鐘(zhong),如(ru)果(guo)需(xu)要進一步縮短充(chong)電(dian)(dian)(dian)(dian)(dian)時(shi)間(jian),只需(xu)在初(chu)始化時(shi)設定更大的(de)充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流即可。因為采用PWM控制器,所以電(dian)(dian)(dian)(dian)(dian)源(yuan)供(gong)(gong)電(dian)(dian)(dian)(dian)(dian)的(de)效(xiao)率高(gao),從(cong)供(gong)(gong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)源(yuan)到(dao)充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)池的(de)工作效(xiao)率,最低時(shi)在85%左(zuo)右。充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流波動較大,波動系數約(yue)為5%。 

3．2 智能充電器通用(yong)性試驗 

　　選用NOKIA6100鋰離子電(dian)池(額定容量為(wei)(wei)550mAh),用恒流-恒壓充電(dian)方式進行充電(dian),取恒流充電(dian)電(dian)流為(wei)(wei)0.15A,截止電(dian)壓為(wei)(wei)4.2V,充電(dian)曲線如圖(tu)6所示。 

　　從充(chong)電(dian)(dian)(dian)(dian)曲線(xian)來看,電(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)壓達到(dao)3.96V時(shi)(shi)就不再(zai)上(shang)升了(le)(le),充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)也(ye)不再(zai)下降了(le)(le)。可以判斷商(shang)用(yong)電(dian)(dian)(dian)(dian)池內部有保護電(dian)(dian)(dian)(dian)路,將多余(yu)的(de)電(dian)(dian)(dian)(dian)流(liu)旁(pang)路了(le)(le),這樣的(de)保護電(dian)(dian)(dian)(dian)路使充(chong)電(dian)(dian)(dian)(dian)過(guo)程(cheng)中能(neng)量(liang)損耗很大。試(shi)驗曲線(xian)顯示在四小時(shi)(shi)時(shi)(shi)電(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)量(liang)已(yi)經達到(dao)550mAh,但實(shi)(shi)際上(shang)并沒有達到(dao)滿充(chong)。此實(shi)(shi)驗證明,此充(chong)電(dian)(dian)(dian)(dian)器可以作(zuo)為一般的(de)商(shang)用(yong)電(dian)(dian)(dian)(dian)池的(de)通用(yong)充(chong)電(dian)(dian)(dian)(dian)器,充(chong)電(dian)(dian)(dian)(dian)速度快,效果良好。不足的(de)是它與實(shi)(shi)際的(de)充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)池在機械(xie)接口(kou)上(shang)還(huan)不能(neng)匹配,需要進一步改進。