現代(dai)通(tong)訊設備、便攜式電(dian)(dian)子產品、筆(bi)記本電(dian)(dian)腦、電(dian)(dian)動汽車(che)、小(xiao)衛星等普遍(bian)使(shi)用(yong)(yong)蓄電(dian)(dian)池作為(wei)電(dian)(dian)源,應用(yong)(yong)非常(chang)廣泛(fan)。然而大多數(shu)設備中的蓄電(dian)(dian)池,只能使(shi)用(yong)(yong)專(zhuan)用(yong)(yong)的充(chong)電(dian)(dian)器,而且普通(tong)的充(chong)電(dian)(dian)器大多充(chong)電(dian)(dian)時間長,無法判(pan)斷其充(chong)電(dian)(dian)參數(shu)和剩余的充(chong)電(dian)(dian)時間。 

　　本文介紹一種基于單片機的通用智能充電器的設計。充電器可以實(shi)時(shi)采集電(dian)池的電(dian)壓、電(dian)流,對充(chong)(chong)電(dian)過程(cheng)進行(xing)智能控制,計算電(dian)池已充(chong)(chong)的電(dian)量和剩余的充(chong)(chong)電(dian)時(shi)間;還可以通過串口和上位(wei)機(ji)進行(xing)通訊并(bing)給用(yong)戶顯示必要的信息,有虛擬儀表的作用(yong);另外,它(ta)也可以改變(bian)參數(shu),適應各(ge)種(zhong)不同電(dian)池的充(chong)(chong)電(dian)。這里(li)列舉幾(ji)種(zhong)不同的電(dian)池充(chong)(chong)電(dian)試驗,來(lai)說(shuo)明智能充(chong)(chong)電(dian)器的實(shi)用(yong)價值。 

1 智能充電器的(de)硬(ying)件設計 

　　主要(yao)包括電(dian)源變換電(dian)路(lu)、采(cai)樣(yang)電(dian)路(lu)、處(chu)理器、脈(mo)寬調(diao)制(zhi)控制(zhi)器和電(dian)池組等(deng),形成了一個閉環系(xi)統.

1．1 處理器 

　　處理器采用51系列單(dan)(dan)片(pian)機89C51。單(dan)(dan)片(pian)機內部有兩個(ge)(ge)定(ding)時(shi)器、兩個(ge)(ge)外部中(zhong)斷(duan)和一個(ge)(ge)串口(kou)中(zhong)斷(duan)、三個(ge)(ge)八路(lu)的(de)I/O口(kou),采用11.0592MHz的(de)晶振。單(dan)(dan)片(pian)機的(de)任務是通(tong)過采樣電(dian)路(lu)實時(shi)采集電(dian)池的(de)充電(dian)狀態,通(tong)過計算決(jue)定(ding)下一階段的(de)充電(dian)電(dian)流,然后發送命令給控制(zhi)器控制(zhi)電(dian)流的(de)大小。單(dan)(dan)片(pian)機通(tong)過串口(kou)RS232和上位機相(xiang)連(lian),用于存儲數據和虛擬(ni)顯示(shi)。 

1．2 采樣部(bu)分 

　　電壓和電流采(cai)樣采(cai)用模/數轉換(huan)器AD574。AD574為±15V雙電源供電,12位輸出,最大誤差(cha)為±4bit,合計電壓0.01V。 

　　充電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)通過(guo)電(dian)(dian)(dian)流(liu)傳(chuan)感器MAX471轉換(huan)為電(dian)(dian)(dian)壓(ya)值。電(dian)(dian)(dian)流(liu)采樣的電(dian)(dian)(dian)壓(ya)值和電(dian)(dian)(dian)池組(zu)的端電(dian)(dian)(dian)壓(ya)值兩者經過(guo)模擬開(kai)關CD4051,再經過(guo)電(dian)(dian)(dian)壓(ya)跟隨器輸入(ru)到AD574,分別進(jin)行轉換(huan),其結果由(you)單片機讀取,并(bing)進(jin)行存儲(chu)和處理。

1．3 控制器 

　　控(kong)制(zhi)(zhi)器(qi)采用(yong)(yong)(yong)脈(mo)寬調制(zhi)(zhi)(PWM)方(fang)式(shi)控(kong)制(zhi)(zhi)供電(dian)電(dian)流(liu)的(de)大(da)小。PWM發生器(qi)由(you)另一個20MHz的(de)單片(pian)機構成(cheng),主控(kong)制(zhi)(zhi)器(qi)和(he)它(ta)采用(yong)(yong)(yong)中斷的(de)方(fang)式(shi)進行(xing)通(tong)訊,控(kong)制(zhi)(zhi)其(qi)增大(da)或(huo)減小脈(mo)寬。PWM信號通(tong)過光電(dian)隔離驅動主回(hui)路上(shang)的(de)MOSFET。開關管、二極管、LC電(dian)路構成(cheng)開關穩壓電(dian)源。用(yong)(yong)(yong)PWM方(fang)式(shi)控(kong)制(zhi)(zhi)的(de)開關電(dian)源可以減小功(gong)耗(hao),同時便于進行(xing)數(shu)字(zi)化控(kong)制(zhi)(zhi),但母線的(de)紋波系數(shu)相對較大(da)。

2 智能充(chong)電器的(de)軟件設計 

2．1 數(shu)據測量(liang) 

　　在單片機的(de)(de)測量(liang)中,電池電壓(ya)值和電流測量(liang)值經(jing)過多路選擇(ze)器(qi)進(jin)(jin)行選擇(ze),然后通(tong)過A/D轉(zhuan)換(huan)器(qi)轉(zhuan)換(huan)為(wei)16進(jin)(jin)制數(shu),直接(jie)(jie)存(cun)入單片機。電池電容量(liang)C則需要間接(jie)(jie)計算(suan),由于每(mei)個循(xun)環 周期檢測電流一(yi)次,故可(ke)以利用電流值的(de)(de)積分求出電容量(liang)C。考(kao)慮電池內(nei)阻r的(de)(de)影響(xiang),可(ke)以得到計算(suan)電容量(liang)的(de)(de)計算(suan)公式為(wei): 

　　Cn+1=Cn+I?t-I2?r?t 

　　充(chong)電(dian)(dian)時(shi)間和剩余(yu)充(chong)電(dian)(dian)時(shi)間由上位機(ji)進行計算,剩余(yu)充(chong)電(dian)(dian)時(shi)間等于預設(she)(she)的(de)充(chong)電(dian)(dian)時(shi)間與已(yi)充(chong)電(dian)(dian)時(shi)間的(de)差值。其中(zhong),預設(she)(she)時(shi)間可根據電(dian)(dian)池(chi)的(de)型(xing)號預先得到(dao)。 

2．2 單(dan)片機控制程序設計(ji) 

對于(yu)不同(tong)(tong)(tong)的電(dian)池和不同(tong)(tong)(tong)的參數(shu),單片機需(xu)要設定(ding)不同(tong)(tong)(tong)的充(chong)電(dian)參數(shu),選擇不同(tong)(tong)(tong)的充(chong)電(dian)策(ce)略。另外,程(cheng)序需(xu)要在電(dian)池過電(dian)流、過電(dian)壓(ya)(ya)等異(yi)常(chang)情況下強(qiang)制終止(zhi)充(chong)電(dian)。以鋰(li)離子(zi)電(dian)池為例,一般采(cai)用恒(heng)流-恒(heng)壓(ya)(ya)充(chong)電(dian)方式(shi),其充(chong)電(dian)過程(cheng)包(bao)括小(xiao)電(dian)流預(yu)充(chong)電(dian)、大電(dian)流充(chong)電(dian)、恒(heng)壓(ya)(ya)充(chong)電(dian)等幾部分(fen)。

　　在(zai)控(kong)制(zhi)恒定(ding)(ding)電流(liu)和恒定(ding)(ding)電壓的(de)過程中,采用比例控(kong)制(zhi),即如果(guo)充電電流(liu)I大于設(she)定(ding)(ding)電流(liu)Is,就(jiu)按(an)照比例減(jian)小脈寬(kuan);反(fan)之按(an)照比例增大脈寬(kuan)。單(dan)片機(ji)還(huan)需要接收和處理上位機(ji)的(de)命令,并根據上位機(ji)的(de)要求將數(shu)據實時回送給上位機(ji)。兩者的(de)通(tong)訊協(xie)議要在(zai)程序中預先設(she)定(ding)(ding)。 

2．3 上位機處理程序設計(ji) 

　　上位(wei)機(ji)程(cheng)序(xu)由VisualC++編寫(xie)。其任務(wu)是每(mei)隔1秒鐘(zhong)向串口發(fa)送(song)一(yi)個查詢命令,并讀取單片機(ji)回(hui)送(song)的信(xin)息,提(ti)取充電電流、充電電壓(ya)、工作狀(zhuang)態等參數。參數經過數制轉換(huan)和計算后進(jin)行顯(xian)示(shi)。軟件有(you)著良(liang)好的用戶(hu)界(jie)面,可以方便地觀測電池目前的工作狀(zhuang)態以及剩余充電時間等信(xin)息。上位(wei)機(ji)程(cheng)序(xu)會同時把讀到(dao)的數據存儲到(dao)文件中,這些數據可以利用其它數學軟件(如Matlab)進(jin)行處理。 

　　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)電(dian)(dian)電(dian)(dian)池(chi)的(de)(de)(de)種類(lei)(鋰離(li)子電(dian)(dian)池(chi)、鎳鎘電(dian)(dian)池(chi))、充(chong)電(dian)(dian)電(dian)(dian)池(chi)的(de)(de)(de)容量(單(dan)位為(wei)mAh)等。根據不同的(de)(de)(de)電(dian)(dian)池(chi)型號,單(dan)片機可以設定不同的(de)(de)(de)充(chong)電(dian)(dian)參數,程序可以直接(jie)控制單(dan)片機的(de)(de)(de)運(yun)行與停止。 

3智(zhi)能充電器的應用試驗(yan) 

3．1充(chong)電性能試驗(yan) 

　　這里(li)選用型號為(wei)(wei)(wei)US18650的SONY鋰離子(zi)電池,其額(e)定容量(liang)為(wei)(wei)(wei)1800mAh;經過測量(liang),電池在4.2V左右(you)時的內阻約為(wei)(wei)(wei)0.3Ω。取恒流(liu)充(chong)(chong)電電流(liu)為(wei)(wei)(wei)1/3C=0.6A,截止(zhi)電壓為(wei)(wei)(wei)4.2V,充(chong)(chong)電結束(shu)標志電流(liu)為(wei)(wei)(wei)0.06A,進行充(chong)(chong)電試驗。

　　充(chong)電(dian)(dian)時(shi)間(jian)約為240分鐘,如果(guo)需要進一(yi)步(bu)縮短充(chong)電(dian)(dian)時(shi)間(jian),只需在(zai)初始化時(shi)設定(ding)更(geng)大的(de)充(chong)電(dian)(dian)電(dian)(dian)流(liu)即(ji)可。因為采用PWM控制器,所以電(dian)(dian)源供電(dian)(dian)的(de)效(xiao)率高,從供電(dian)(dian)電(dian)(dian)源到充(chong)電(dian)(dian)電(dian)(dian)池(chi)的(de)工作效(xiao)率,最低(di)時(shi)在(zai)85%左右。充(chong)電(dian)(dian)電(dian)(dian)流(liu)波動較大,波動系數(shu)約為5%。 

3．2 智能充電(dian)器通用性(xing)試驗 

　　選用NOKIA6100鋰離子電池(額(e)定(ding)容量為(wei)550mAh),用恒流-恒壓充(chong)電方式進行充(chong)電,取恒流充(chong)電電流為(wei)0.15A,截止電壓為(wei)4.2V,充(chong)電曲線如(ru)圖6所示。 

　　從充電(dian)(dian)曲線(xian)來看,電(dian)(dian)池電(dian)(dian)壓達到3.96V時就不再上升了,充電(dian)(dian)電(dian)(dian)流也不再下降了。可以(yi)判斷商用電(dian)(dian)池內部(bu)有(you)保護(hu)電(dian)(dian)路(lu),將(jiang)多余的電(dian)(dian)流旁路(lu)了,這樣(yang)的保護(hu)電(dian)(dian)路(lu)使充電(dian)(dian)過(guo)程中能量損耗很大。試驗(yan)曲線(xian)顯示在四(si)小時時電(dian)(dian)池電(dian)(dian)量已經達到550mAh,但實際上并沒有(you)達到滿(man)充。此實驗(yan)證(zheng)明,此充電(dian)(dian)器可以(yi)作為(wei)一般的商用電(dian)(dian)池的通用充電(dian)(dian)器,充電(dian)(dian)速度快,效果(guo)良好。不足的是它與實際的充電(dian)(dian)電(dian)(dian)池在機(ji)械接口(kou)上還不能匹配,需要進一步(bu)改進。