現(xian)代通訊(xun)設(she)備(bei)、便攜式(shi)電(dian)子產品、筆記本電(dian)腦、電(dian)動汽車(che)、小衛(wei)星等(deng)普遍使(shi)用(yong)(yong)蓄電(dian)池(chi)作為電(dian)源,應用(yong)(yong)非常廣泛。然而(er)大多(duo)數設(she)備(bei)中的(de)蓄電(dian)池(chi),只(zhi)能使(shi)用(yong)(yong)專用(yong)(yong)的(de)充(chong)電(dian)器,而(er)且(qie)普通的(de)充(chong)電(dian)器大多(duo)充(chong)電(dian)時間長,無(wu)法(fa)判斷(duan)其充(chong)電(dian)參數和剩余的(de)充(chong)電(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(yi)(yi)實時(shi)(shi)采集(ji)電(dian)池(chi)的電(dian)壓、電(dian)流,對(dui)充(chong)(chong)(chong)電(dian)過(guo)程進(jin)行智(zhi)能控制,計算電(dian)池(chi)已充(chong)(chong)(chong)的電(dian)量和剩(sheng)余的充(chong)(chong)(chong)電(dian)時(shi)(shi)間;還可以(yi)(yi)通過(guo)串口(kou)和上位機進(jin)行通訊并給用戶(hu)顯(xian)示必要的信息,有虛(xu)擬儀(yi)表(biao)的作用;另外,它也可以(yi)(yi)改變參數,適(shi)應各種(zhong)不(bu)同(tong)電(dian)池(chi)的充(chong)(chong)(chong)電(dian)。這(zhe)里列舉幾種(zhong)不(bu)同(tong)的電(dian)池(chi)充(chong)(chong)(chong)電(dian)試驗,來說明(ming)智(zhi)能充(chong)(chong)(chong)電(dian)器的實用價值。 

1 智能充電器的硬件設計 

　　主要包括(kuo)電(dian)(dian)(dian)源變換電(dian)(dian)(dian)路、采樣(yang)電(dian)(dian)(dian)路、處理器、脈寬調(diao)制控制器和電(dian)(dian)(dian)池組等,形(xing)成了一個閉環(huan)系統.

1．1 處理器 

　　處理器采(cai)(cai)用(yong)(yong)51系列單片(pian)(pian)機(ji)89C51。單片(pian)(pian)機(ji)內部(bu)有(you)兩個(ge)(ge)定(ding)時(shi)器、兩個(ge)(ge)外部(bu)中(zhong)斷和一個(ge)(ge)串(chuan)口中(zhong)斷、三(san)個(ge)(ge)八路的(de)I/O口,采(cai)(cai)用(yong)(yong)11.0592MHz的(de)晶振。單片(pian)(pian)機(ji)的(de)任務(wu)是通(tong)過(guo)采(cai)(cai)樣電路實時(shi)采(cai)(cai)集電池的(de)充電狀態,通(tong)過(guo)計算決(jue)定(ding)下一階段(duan)的(de)充電電流,然后發(fa)送命令給控制器控制電流的(de)大小。單片(pian)(pian)機(ji)通(tong)過(guo)串(chuan)口RS232和上位機(ji)相(xiang)連,用(yong)(yong)于存儲數據和虛擬顯示。 

1．2 采樣部分 

　　電(dian)壓和電(dian)流(liu)采樣采用模(mo)/數轉(zhuan)換器AD574。AD574為(wei)±15V雙電(dian)源供(gong)電(dian),12位輸(shu)出,最大誤差為(wei)±4bit,合計電(dian)壓0.01V。 

　　充(chong)電(dian)電(dian)流通過電(dian)流傳感器MAX471轉換(huan)為電(dian)壓(ya)(ya)值(zhi)。電(dian)流采(cai)樣的電(dian)壓(ya)(ya)值(zhi)和(he)電(dian)池組的端(duan)電(dian)壓(ya)(ya)值(zhi)兩者經(jing)(jing)過模擬開關CD4051,再經(jing)(jing)過電(dian)壓(ya)(ya)跟隨器輸入到AD574,分別進(jin)行(xing)轉換(huan),其(qi)結(jie)果(guo)由單片機讀取(qu),并進(jin)行(xing)存儲(chu)和(he)處(chu)理。

1．3 控制(zhi)器(qi) 

　　控(kong)制(zhi)(zhi)器采用(yong)脈寬調制(zhi)(zhi)(PWM)方式(shi)控(kong)制(zhi)(zhi)供電電流的(de)(de)大小(xiao)。PWM發生器由另一個20MHz的(de)(de)單片機(ji)構成,主控(kong)制(zhi)(zhi)器和它采用(yong)中斷的(de)(de)方式(shi)進行通訊(xun),控(kong)制(zhi)(zhi)其(qi)增(zeng)大或減小(xiao)脈寬。PWM信號通過光電隔(ge)離驅動主回(hui)路(lu)上的(de)(de)MOSFET。開(kai)關(guan)管(guan)、二極管(guan)、LC電路(lu)構成開(kai)關(guan)穩壓電源。用(yong)PWM方式(shi)控(kong)制(zhi)(zhi)的(de)(de)開(kai)關(guan)電源可以減小(xiao)功耗,同時(shi)便于(yu)進行數(shu)字化控(kong)制(zhi)(zhi),但母(mu)線的(de)(de)紋波系數(shu)相對較大。

2 智能充(chong)電器的軟(ruan)件設計 

2．1 數據測(ce)量 

　　在單(dan)(dan)片(pian)機的(de)(de)測(ce)量中,電(dian)池(chi)電(dian)壓值和電(dian)流(liu)測(ce)量值經過(guo)多路選(xuan)擇器進(jin)行選(xuan)擇,然后通過(guo)A/D轉換器轉換為16進(jin)制(zhi)數,直接存入(ru)單(dan)(dan)片(pian)機。電(dian)池(chi)電(dian)容(rong)量C則需要間接計(ji)算(suan),由于(yu)每個(ge)循環(huan) 周期檢測(ce)電(dian)流(liu)一(yi)次,故可(ke)以(yi)利用電(dian)流(liu)值的(de)(de)積分求出電(dian)容(rong)量C。考慮電(dian)池(chi)內阻r的(de)(de)影響,可(ke)以(yi)得到計(ji)算(suan)電(dian)容(rong)量的(de)(de)計(ji)算(suan)公式為: 

　　Cn+1=Cn+I?t-I2?r?t 

　　充(chong)(chong)電時(shi)間(jian)和剩(sheng)余充(chong)(chong)電時(shi)間(jian)由(you)上(shang)位(wei)機(ji)進行計算,剩(sheng)余充(chong)(chong)電時(shi)間(jian)等于(yu)預(yu)(yu)設(she)的(de)充(chong)(chong)電時(shi)間(jian)與已充(chong)(chong)電時(shi)間(jian)的(de)差值。其中,預(yu)(yu)設(she)時(shi)間(jian)可根據(ju)電池的(de)型號(hao)預(yu)(yu)先得到。 

2．2 單片(pian)機控制程序設計 

對于不同的電(dian)(dian)(dian)(dian)池和不同的參(can)數,單片機需(xu)要(yao)設定不同的充(chong)(chong)電(dian)(dian)(dian)(dian)參(can)數,選擇不同的充(chong)(chong)電(dian)(dian)(dian)(dian)策略。另外(wai),程序需(xu)要(yao)在電(dian)(dian)(dian)(dian)池過電(dian)(dian)(dian)(dian)流(liu)、過電(dian)(dian)(dian)(dian)壓等(deng)異常情況(kuang)下強制終(zhong)止充(chong)(chong)電(dian)(dian)(dian)(dian)。以鋰(li)離子(zi)電(dian)(dian)(dian)(dian)池為例,一般采用(yong)恒(heng)流(liu)-恒(heng)壓充(chong)(chong)電(dian)(dian)(dian)(dian)方式(shi),其充(chong)(chong)電(dian)(dian)(dian)(dian)過程包括小電(dian)(dian)(dian)(dian)流(liu)預充(chong)(chong)電(dian)(dian)(dian)(dian)、大電(dian)(dian)(dian)(dian)流(liu)充(chong)(chong)電(dian)(dian)(dian)(dian)、恒(heng)壓充(chong)(chong)電(dian)(dian)(dian)(dian)等(deng)幾部分(fen)。

　　在控(kong)制恒定電流和恒定電壓的(de)過程(cheng)中(zhong),采用比(bi)例控(kong)制,即如(ru)果充電電流I大于設(she)(she)定電流Is,就按照(zhao)比(bi)例減小脈寬(kuan);反(fan)之按照(zhao)比(bi)例增大脈寬(kuan)。單(dan)片機(ji)還需要(yao)(yao)接收(shou)和處理(li)上位(wei)機(ji)的(de)命令(ling),并根據上位(wei)機(ji)的(de)要(yao)(yao)求將數據實(shi)時回送給上位(wei)機(ji)。兩(liang)者的(de)通訊(xun)協議要(yao)(yao)在程(cheng)序中(zhong)預(yu)先設(she)(she)定。 

2．3 上位機(ji)處理程序設計 

　　上(shang)位機(ji)程序由(you)VisualC++編寫。其任務(wu)是(shi)每隔1秒鐘向串口發送一個查詢命(ming)令,并讀取單片(pian)機(ji)回(hui)送的(de)(de)信(xin)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(tai)等(deng)(deng)參數(shu)。參數(shu)經(jing)過數(shu)制轉換和計算(suan)后進行顯示。軟件(jian)(jian)有(you)著(zhu)良好的(de)(de)用戶界面,可(ke)以(yi)(yi)方便地觀測電(dian)(dian)池目前的(de)(de)工作狀態(tai)以(yi)(yi)及剩余充(chong)電(dian)(dian)時間等(deng)(deng)信(xin)息。上(shang)位機(ji)程序會同(tong)時把讀到(dao)的(de)(de)數(shu)據(ju)存儲到(dao)文件(jian)(jian)中,這些數(shu)據(ju)可(ke)以(yi)(yi)利用其它數(shu)學軟件(jian)(jian)(如(ru)Matlab)進行處理。 

　　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(bao)括充電(dian)電(dian)池的種類(鋰離子電(dian)池、鎳鎘電(dian)池)、充電(dian)電(dian)池的容(rong)量(單(dan)(dan)位為mAh)等。根據不同的電(dian)池型號,單(dan)(dan)片(pian)機(ji)可以(yi)設定(ding)不同的充電(dian)參數,程序可以(yi)直(zhi)接控制單(dan)(dan)片(pian)機(ji)的運行與停(ting)止。 

3智能充電器的應用試驗 

3．1充(chong)電性能(neng)試(shi)驗 

　　這里選用型號為US18650的(de)SONY鋰離子電(dian)(dian)(dian)池(chi),其(qi)額定(ding)容量為1800mAh;經過(guo)測量,電(dian)(dian)(dian)池(chi)在4.2V左右時的(de)內阻約(yue)為0.3Ω。取恒流(liu)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)為1/3C=0.6A,截止電(dian)(dian)(dian)壓為4.2V,充(chong)電(dian)(dian)(dian)結(jie)束標志電(dian)(dian)(dian)流(liu)為0.06A,進行(xing)充(chong)電(dian)(dian)(dian)試驗。

　　充電(dian)(dian)(dian)(dian)時(shi)間約(yue)為240分鐘,如果需要(yao)進一步(bu)縮短充電(dian)(dian)(dian)(dian)時(shi)間,只需在初始化時(shi)設定更大的充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)即可。因(yin)為采用PWM控制(zhi)器,所以(yi)電(dian)(dian)(dian)(dian)源供電(dian)(dian)(dian)(dian)的效(xiao)率高,從供電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)源到充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)池的工作(zuo)效(xiao)率,最(zui)低(di)時(shi)在85%左右(you)。充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)波動較大,波動系數約(yue)為5%。 

3．2 智能(neng)充電(dian)器通用性試驗(yan) 

　　選用(yong)NOKIA6100鋰離(li)子電(dian)(dian)池(額定容量(liang)為550mAh),用(yong)恒(heng)流(liu)-恒(heng)壓(ya)充(chong)(chong)電(dian)(dian)方式(shi)進行充(chong)(chong)電(dian)(dian),取恒(heng)流(liu)充(chong)(chong)電(dian)(dian)電(dian)(dian)流(liu)為0.15A,截止電(dian)(dian)壓(ya)為4.2V,充(chong)(chong)電(dian)(dian)曲線(xian)如圖(tu)6所示。 

　　從充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)曲(qu)線(xian)來(lai)看,電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)壓達到3.96V時(shi)就不再上升了(le),充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流也不再下降了(le)。可以(yi)判斷商用(yong)(yong)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)內部有保護(hu)電(dian)(dian)(dian)(dian)(dian)(dian)路,將多余的電(dian)(dian)(dian)(dian)(dian)(dian)流旁路了(le),這樣的保護(hu)電(dian)(dian)(dian)(dian)(dian)(dian)路使充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)過程中(zhong)能(neng)量損耗很(hen)大。試(shi)驗曲(qu)線(xian)顯示(shi)在四(si)小時(shi)時(shi)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)量已經達到550mAh,但實(shi)際上并沒有達到滿充(chong)。此(ci)實(shi)驗證明,此(ci)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器(qi)可以(yi)作為一般(ban)的商用(yong)(yong)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)的通(tong)用(yong)(yong)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器(qi),充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)速度快,效果良好(hao)。不足(zu)的是(shi)它(ta)與實(shi)際的充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)在機(ji)械(xie)接口上還不能(neng)匹(pi)配,需要(yao)進一步改進。