現代通訊設備、便攜(xie)式電(dian)(dian)子(zi)產品(pin)、筆記本電(dian)(dian)腦(nao)、電(dian)(dian)動汽(qi)車、小(xiao)衛(wei)星等普遍使(shi)用蓄電(dian)(dian)池作(zuo)為電(dian)(dian)源,應用非常廣(guang)泛。然(ran)而大(da)多(duo)數設備中的蓄電(dian)(dian)池,只(zhi)能(neng)使(shi)用專(zhuan)用的充(chong)電(dian)(dian)器(qi),而且普通的充(chong)電(dian)(dian)器(qi)大(da)多(duo)充(chong)電(dian)(dian)時(shi)間長,無(wu)法判斷其充(chong)電(dian)(dian)參數和剩余(yu)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。充電器可以實時采(cai)集電(dian)(dian)(dian)(dian)池的(de)(de)(de)電(dian)(dian)(dian)(dian)壓、電(dian)(dian)(dian)(dian)流(liu),對充(chong)(chong)電(dian)(dian)(dian)(dian)過程進行智能(neng)控(kong)制,計算(suan)電(dian)(dian)(dian)(dian)池已充(chong)(chong)的(de)(de)(de)電(dian)(dian)(dian)(dian)量和剩(sheng)余(yu)的(de)(de)(de)充(chong)(chong)電(dian)(dian)(dian)(dian)時間;還可以通(tong)過串口(kou)和上(shang)位機進行通(tong)訊(xun)并給用(yong)戶顯示(shi)必(bi)要的(de)(de)(de)信息(xi),有虛(xu)擬儀(yi)表的(de)(de)(de)作用(yong);另外,它也可以改變參數,適應(ying)各種(zhong)不(bu)同電(dian)(dian)(dian)(dian)池的(de)(de)(de)充(chong)(chong)電(dian)(dian)(dian)(dian)。這里列舉幾種(zhong)不(bu)同的(de)(de)(de)電(dian)(dian)(dian)(dian)池充(chong)(chong)電(dian)(dian)(dian)(dian)試驗,來說明智能(neng)充(chong)(chong)電(dian)(dian)(dian)(dian)器的(de)(de)(de)實用(yong)價值(zhi)。 

1 智能充電器的硬件設計(ji) 

　　主要包括電源變換電路、采樣電路、處理(li)器(qi)(qi)、脈寬(kuan)調制控制器(qi)(qi)和電池組等,形成(cheng)了一個閉環系統(tong).

1．1 處理器(qi) 

　　處理器采(cai)(cai)用(yong)51系列單(dan)(dan)(dan)片(pian)機(ji)89C51。單(dan)(dan)(dan)片(pian)機(ji)內部(bu)有兩個(ge)定時器、兩個(ge)外部(bu)中斷(duan)和一個(ge)串口(kou)中斷(duan)、三個(ge)八路的I/O口(kou),采(cai)(cai)用(yong)11.0592MHz的晶(jing)振。單(dan)(dan)(dan)片(pian)機(ji)的任務(wu)是通(tong)過(guo)采(cai)(cai)樣(yang)電(dian)路實時采(cai)(cai)集電(dian)池的充(chong)電(dian)狀態,通(tong)過(guo)計算(suan)決定下一階(jie)段的充(chong)電(dian)電(dian)流,然(ran)后發送命令給控(kong)(kong)制器控(kong)(kong)制電(dian)流的大小。單(dan)(dan)(dan)片(pian)機(ji)通(tong)過(guo)串口(kou)RS232和上位(wei)機(ji)相連,用(yong)于存(cun)儲數據和虛(xu)擬(ni)顯示。 

1．2 采(cai)樣部分 

　　電(dian)(dian)(dian)壓(ya)和電(dian)(dian)(dian)流采(cai)樣(yang)采(cai)用模/數轉換器AD574。AD574為±15V雙電(dian)(dian)(dian)源供電(dian)(dian)(dian),12位輸(shu)出,最(zui)大誤差為±4bit,合計電(dian)(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(wei)電(dian)壓值(zhi)。電(dian)流采樣的(de)電(dian)壓值(zhi)和(he)電(dian)池組的(de)端電(dian)壓值(zhi)兩(liang)者經過(guo)模擬(ni)開關(guan)CD4051,再經過(guo)電(dian)壓跟隨器輸入到AD574,分別進(jin)行(xing)轉換,其結(jie)果由單片機讀(du)取(qu),并進(jin)行(xing)存儲和(he)處理。

1．3 控制器 

　　控制(zhi)(zhi)器采(cai)用(yong)脈寬調制(zhi)(zhi)(PWM)方式(shi)(shi)控制(zhi)(zhi)供電(dian)電(dian)流的(de)(de)大小。PWM發生器由另(ling)一個20MHz的(de)(de)單(dan)片機構成,主(zhu)控制(zhi)(zhi)器和它采(cai)用(yong)中斷的(de)(de)方式(shi)(shi)進行通(tong)訊,控制(zhi)(zhi)其增大或減小脈寬。PWM信(xin)號(hao)通(tong)過(guo)光電(dian)隔離(li)驅動主(zhu)回路上的(de)(de)MOSFET。開(kai)(kai)關管、二(er)極管、LC電(dian)路構成開(kai)(kai)關穩(wen)壓電(dian)源(yuan)。用(yong)PWM方式(shi)(shi)控制(zhi)(zhi)的(de)(de)開(kai)(kai)關電(dian)源(yuan)可以減小功耗(hao),同時便于(yu)進行數(shu)字(zi)化控制(zhi)(zhi),但母(mu)線的(de)(de)紋波系數(shu)相對較大。

2 智能充電器的軟件(jian)設計(ji) 

2．1 數(shu)據測量 

　　在單片機(ji)的(de)測(ce)量(liang)中,電(dian)(dian)(dian)池電(dian)(dian)(dian)壓值和電(dian)(dian)(dian)流測(ce)量(liang)值經過(guo)多路選擇器(qi)(qi)進行選擇,然后通過(guo)A/D轉換(huan)器(qi)(qi)轉換(huan)為16進制數,直(zhi)接存入單片機(ji)。電(dian)(dian)(dian)池電(dian)(dian)(dian)容(rong)量(liang)C則(ze)需要(yao)間接計(ji)(ji)算,由于每個循環 周(zhou)期檢測(ce)電(dian)(dian)(dian)流一次,故可(ke)以利用(yong)電(dian)(dian)(dian)流值的(de)積分求出電(dian)(dian)(dian)容(rong)量(liang)C。考慮電(dian)(dian)(dian)池內阻r的(de)影響,可(ke)以得到計(ji)(ji)算電(dian)(dian)(dian)容(rong)量(liang)的(de)計(ji)(ji)算公式為: 

　　Cn+1=Cn+I?t-I2?r?t 

　　充(chong)(chong)電時間(jian)和剩(sheng)余充(chong)(chong)電時間(jian)由上(shang)位機進行計算,剩(sheng)余充(chong)(chong)電時間(jian)等(deng)于預(yu)設的(de)充(chong)(chong)電時間(jian)與已充(chong)(chong)電時間(jian)的(de)差(cha)值。其中,預(yu)設時間(jian)可根據電池的(de)型號預(yu)先得到。 

2．2 單片機(ji)控制程序設(she)計(ji) 

對(dui)于(yu)不同(tong)的(de)電(dian)(dian)池(chi)和(he)不同(tong)的(de)參數,單(dan)片機需要(yao)設定不同(tong)的(de)充電(dian)(dian)參數,選擇不同(tong)的(de)充電(dian)(dian)策略。另外,程序需要(yao)在電(dian)(dian)池(chi)過電(dian)(dian)流(liu)(liu)、過電(dian)(dian)壓等(deng)異常(chang)情況(kuang)下強制終止充電(dian)(dian)。以(yi)鋰離子(zi)電(dian)(dian)池(chi)為例,一(yi)般(ban)采(cai)用恒流(liu)(liu)-恒壓充電(dian)(dian)方式(shi),其充電(dian)(dian)過程包括小電(dian)(dian)流(liu)(liu)預充電(dian)(dian)、大(da)電(dian)(dian)流(liu)(liu)充電(dian)(dian)、恒壓充電(dian)(dian)等(deng)幾(ji)部分。

　　在控(kong)(kong)制恒定電(dian)(dian)流(liu)和恒定電(dian)(dian)壓的過(guo)程中,采用比例(li)控(kong)(kong)制,即如果充電(dian)(dian)電(dian)(dian)流(liu)I大于設(she)定電(dian)(dian)流(liu)Is,就按照(zhao)比例(li)減小脈(mo)寬(kuan);反之按照(zhao)比例(li)增大脈(mo)寬(kuan)。單片機(ji)還需要(yao)接收和處理(li)上位(wei)機(ji)的命令,并根據(ju)上位(wei)機(ji)的要(yao)求將數(shu)據(ju)實時回(hui)送給上位(wei)機(ji)。兩者的通訊協議要(yao)在程序中預先設(she)定。 

2．3 上位機處理程序設計 

　　上位機(ji)程序(xu)由(you)VisualC++編寫。其任務(wu)是(shi)每隔(ge)1秒鐘向串口發(fa)送(song)一(yi)個(ge)查詢命(ming)令,并讀取單片機(ji)回送(song)的(de)(de)(de)信(xin)息,提(ti)取充電(dian)電(dian)流、充電(dian)電(dian)壓(ya)、工(gong)作(zuo)狀態等(deng)參數(shu)。參數(shu)經過數(shu)制轉換(huan)和計(ji)算(suan)后(hou)進行(xing)顯示。軟件有著良好(hao)的(de)(de)(de)用(yong)(yong)戶(hu)界(jie)面,可(ke)以(yi)方(fang)便地(di)觀測電(dian)池目前的(de)(de)(de)工(gong)作(zuo)狀態以(yi)及剩余充電(dian)時間等(deng)信(xin)息。上位機(ji)程序(xu)會同時把讀到(dao)的(de)(de)(de)數(shu)據(ju)存儲(chu)到(dao)文件中(zhong),這些數(shu)據(ju)可(ke)以(yi)利用(yong)(yong)其它數(shu)學軟件(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(kuo)充電(dian)電(dian)池的(de)種類(鋰離子電(dian)池、鎳鎘(ge)電(dian)池)、充電(dian)電(dian)池的(de)容量(liang)(單位為mAh)等。根據不同(tong)的(de)電(dian)池型號,單片機可(ke)以設定不同(tong)的(de)充電(dian)參數,程序(xu)可(ke)以直接控制單片機的(de)運行與停止。 

3智能充電器的應用試驗(yan) 

3．1充(chong)電(dian)性能(neng)試(shi)驗 

　　這里選(xuan)用(yong)型號為(wei)(wei)(wei)US18650的SONY鋰離子電(dian)(dian)池(chi),其額定(ding)容量(liang)為(wei)(wei)(wei)1800mAh;經(jing)過測量(liang),電(dian)(dian)池(chi)在4.2V左右時的內阻約為(wei)(wei)(wei)0.3Ω。取恒流(liu)充(chong)電(dian)(dian)電(dian)(dian)流(liu)為(wei)(wei)(wei)1/3C=0.6A,截止電(dian)(dian)壓為(wei)(wei)(wei)4.2V,充(chong)電(dian)(dian)結(jie)束標志(zhi)電(dian)(dian)流(liu)為(wei)(wei)(wei)0.06A,進行充(chong)電(dian)(dian)試驗。

　　充(chong)電(dian)(dian)時間約(yue)(yue)為(wei)240分鐘,如(ru)果需要進一步縮(suo)短充(chong)電(dian)(dian)時間,只需在初始化時設定更(geng)大的(de)充(chong)電(dian)(dian)電(dian)(dian)流即可。因為(wei)采(cai)用PWM控制器,所(suo)以電(dian)(dian)源供電(dian)(dian)的(de)效(xiao)率(lv)(lv)高(gao),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(lv)(lv),最低時在85%左右。充(chong)電(dian)(dian)電(dian)(dian)流波動較(jiao)大,波動系數約(yue)(yue)為(wei)5%。 

3．2 智能充電(dian)器通(tong)用性試驗 

　　選用NOKIA6100鋰離(li)子電(dian)(dian)池(額(e)定容量為550mAh),用恒(heng)流-恒(heng)壓充(chong)電(dian)(dian)方(fang)式進行充(chong)電(dian)(dian),取恒(heng)流充(chong)電(dian)(dian)電(dian)(dian)流為0.15A,截止電(dian)(dian)壓為4.2V,充(chong)電(dian)(dian)曲線如圖(tu)6所示。 

　　從充(chong)電(dian)(dian)(dian)(dian)曲線(xian)來(lai)看,電(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)壓(ya)達(da)到(dao)3.96V時就不(bu)再(zai)(zai)上(shang)升了,充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流也不(bu)再(zai)(zai)下降(jiang)了。可(ke)以判斷(duan)商(shang)用(yong)電(dian)(dian)(dian)(dian)池(chi)內部有保(bao)護電(dian)(dian)(dian)(dian)路(lu),將多余的(de)電(dian)(dian)(dian)(dian)流旁路(lu)了,這樣的(de)保(bao)護電(dian)(dian)(dian)(dian)路(lu)使充(chong)電(dian)(dian)(dian)(dian)過程中(zhong)能(neng)(neng)量損耗很大(da)。試(shi)驗曲線(xian)顯示(shi)在四(si)小時時電(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)量已經達(da)到(dao)550mAh,但實(shi)際(ji)上(shang)并沒有達(da)到(dao)滿充(chong)。此實(shi)驗證明,此充(chong)電(dian)(dian)(dian)(dian)器可(ke)以作為一(yi)般的(de)商(shang)用(yong)電(dian)(dian)(dian)(dian)池(chi)的(de)通用(yong)充(chong)電(dian)(dian)(dian)(dian)器,充(chong)電(dian)(dian)(dian)(dian)速度快,效(xiao)果良好。不(bu)足的(de)是它(ta)與實(shi)際(ji)的(de)充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)池(chi)在機械接口上(shang)還(huan)不(bu)能(neng)(neng)匹配,需要進一(yi)步改(gai)進。