現代通訊(xun)設備(bei)、便攜式電(dian)(dian)子產品、筆(bi)記本電(dian)(dian)腦、電(dian)(dian)動(dong)汽車(che)、小衛(wei)星(xing)等普(pu)遍使用(yong)蓄電(dian)(dian)池作(zuo)為電(dian)(dian)源,應用(yong)非常廣泛。然(ran)而(er)大(da)多數(shu)設備(bei)中(zhong)的(de)蓄電(dian)(dian)池,只能使用(yong)專用(yong)的(de)充電(dian)(dian)器,而(er)且普(pu)通的(de)充電(dian)(dian)器大(da)多充電(dian)(dian)時間長,無法(fa)判斷其充電(dian)(dian)參數(shu)和(he)剩余的(de)充電(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。充電器可以實時采集電(dian)(dian)(dian)池(chi)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)壓、電(dian)(dian)(dian)流,對充(chong)電(dian)(dian)(dian)過(guo)程進行(xing)智(zhi)能控制,計算(suan)電(dian)(dian)(dian)池(chi)已(yi)充(chong)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)量和剩(sheng)余的(de)(de)(de)(de)(de)充(chong)電(dian)(dian)(dian)時間(jian);還(huan)可以通過(guo)串口(kou)和上位(wei)機進行(xing)通訊并(bing)給用戶(hu)顯示必要的(de)(de)(de)(de)(de)信息,有虛擬儀表(biao)的(de)(de)(de)(de)(de)作用;另(ling)外,它也可以改(gai)變(bian)參數,適應各種不同電(dian)(dian)(dian)池(chi)的(de)(de)(de)(de)(de)充(chong)電(dian)(dian)(dian)。這里列舉幾種不同的(de)(de)(de)(de)(de)電(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)試驗,來說明智(zhi)能充(chong)電(dian)(dian)(dian)器的(de)(de)(de)(de)(de)實用價值。 

1 智能充電器的(de)硬(ying)件(jian)設計 

　　主要(yao)包括(kuo)電源(yuan)變換電路(lu)(lu)、采樣電路(lu)(lu)、處理器、脈寬調制控制器和電池組(zu)等,形成(cheng)了一個閉(bi)環系統.

1．1 處理器 

　　處理器(qi)采用(yong)51系(xi)列單(dan)(dan)片機89C51。單(dan)(dan)片機內部有兩個(ge)(ge)定(ding)時(shi)器(qi)、兩個(ge)(ge)外(wai)部中斷和(he)(he)(he)一(yi)個(ge)(ge)串(chuan)口中斷、三個(ge)(ge)八路的(de)(de)I/O口,采用(yong)11.0592MHz的(de)(de)晶振(zhen)。單(dan)(dan)片機的(de)(de)任務是通(tong)過采樣(yang)電路實時(shi)采集電池的(de)(de)充電狀態(tai),通(tong)過計算決定(ding)下一(yi)階段的(de)(de)充電電流,然后(hou)發送命(ming)令給控制(zhi)器(qi)控制(zhi)電流的(de)(de)大(da)小(xiao)。單(dan)(dan)片機通(tong)過串(chuan)口RS232和(he)(he)(he)上位機相(xiang)連,用(yong)于存儲數據和(he)(he)(he)虛擬顯示。 

1．2 采(cai)樣部分 

　　電壓和電流采(cai)樣(yang)采(cai)用模/數轉換器(qi)AD574。AD574為(wei)±15V雙電源供電,12位(wei)輸出,最大誤差為(wei)±4bit,合計電壓0.01V。 

　　充電(dian)(dian)電(dian)(dian)流通過電(dian)(dian)流傳感(gan)器(qi)(qi)MAX471轉(zhuan)換為電(dian)(dian)壓(ya)值(zhi)。電(dian)(dian)流采樣的電(dian)(dian)壓(ya)值(zhi)和電(dian)(dian)池組的端電(dian)(dian)壓(ya)值(zhi)兩者經過模擬開關(guan)CD4051,再經過電(dian)(dian)壓(ya)跟隨(sui)器(qi)(qi)輸入到AD574,分(fen)別進行轉(zhuan)換,其結(jie)果由單片機讀取,并進行存儲和處理。

1．3 控制器 

　　控(kong)制器(qi)采用(yong)脈寬調制(PWM)方(fang)(fang)式(shi)控(kong)制供電(dian)電(dian)流的(de)大(da)小。PWM發生器(qi)由(you)另一個(ge)20MHz的(de)單片機(ji)構成,主控(kong)制器(qi)和它采用(yong)中斷的(de)方(fang)(fang)式(shi)進行通訊(xun),控(kong)制其增大(da)或減小脈寬。PWM信號通過光電(dian)隔離驅動主回路上的(de)MOSFET。開關(guan)管、二極(ji)管、LC電(dian)路構成開關(guan)穩壓(ya)電(dian)源(yuan)(yuan)。用(yong)PWM方(fang)(fang)式(shi)控(kong)制的(de)開關(guan)電(dian)源(yuan)(yuan)可以減小功耗(hao),同(tong)時便于(yu)進行數(shu)字化(hua)控(kong)制,但母線的(de)紋波系數(shu)相對較(jiao)大(da)。

2 智(zhi)能充(chong)電器的軟件設計 

2．1 數據(ju)測(ce)量 

　　在(zai)單片(pian)機的(de)測(ce)(ce)(ce)量(liang)(liang)(liang)中,電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)壓(ya)值(zhi)和電(dian)(dian)(dian)流(liu)(liu)測(ce)(ce)(ce)量(liang)(liang)(liang)值(zhi)經過多路選擇器進行(xing)選擇,然(ran)后通過A/D轉換器轉換為16進制(zhi)數,直接存入單片(pian)機。電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)容(rong)量(liang)(liang)(liang)C則需要(yao)間接計算,由于每個循環 周期檢測(ce)(ce)(ce)電(dian)(dian)(dian)流(liu)(liu)一次(ci),故(gu)可(ke)(ke)以利用電(dian)(dian)(dian)流(liu)(liu)值(zhi)的(de)積分(fen)求出電(dian)(dian)(dian)容(rong)量(liang)(liang)(liang)C。考慮(lv)電(dian)(dian)(dian)池(chi)內阻r的(de)影響,可(ke)(ke)以得(de)到計算電(dian)(dian)(dian)容(rong)量(liang)(liang)(liang)的(de)計算公式為: 

　　Cn+1=Cn+I?t-I2?r?t 

　　充電(dian)(dian)(dian)時(shi)(shi)間和剩余充電(dian)(dian)(dian)時(shi)(shi)間由上位機進(jin)行計(ji)算,剩余充電(dian)(dian)(dian)時(shi)(shi)間等(deng)于預設(she)(she)的充電(dian)(dian)(dian)時(shi)(shi)間與已充電(dian)(dian)(dian)時(shi)(shi)間的差值。其中(zhong),預設(she)(she)時(shi)(shi)間可(ke)根據電(dian)(dian)(dian)池的型號預先得(de)到。 

2．2 單片機(ji)控制程(cheng)序設(she)計(ji) 

對于不(bu)同(tong)的(de)電(dian)(dian)(dian)(dian)(dian)池(chi)和不(bu)同(tong)的(de)參數,單片機需要(yao)設定不(bu)同(tong)的(de)充(chong)電(dian)(dian)(dian)(dian)(dian)參數,選擇不(bu)同(tong)的(de)充(chong)電(dian)(dian)(dian)(dian)(dian)策略。另外,程(cheng)(cheng)序需要(yao)在(zai)電(dian)(dian)(dian)(dian)(dian)池(chi)過(guo)電(dian)(dian)(dian)(dian)(dian)流(liu)、過(guo)電(dian)(dian)(dian)(dian)(dian)壓(ya)等異常情況(kuang)下(xia)強制終止充(chong)電(dian)(dian)(dian)(dian)(dian)。以鋰離子電(dian)(dian)(dian)(dian)(dian)池(chi)為例,一(yi)般采用恒流(liu)-恒壓(ya)充(chong)電(dian)(dian)(dian)(dian)(dian)方式,其充(chong)電(dian)(dian)(dian)(dian)(dian)過(guo)程(cheng)(cheng)包(bao)括小電(dian)(dian)(dian)(dian)(dian)流(liu)預充(chong)電(dian)(dian)(dian)(dian)(dian)、大電(dian)(dian)(dian)(dian)(dian)流(liu)充(chong)電(dian)(dian)(dian)(dian)(dian)、恒壓(ya)充(chong)電(dian)(dian)(dian)(dian)(dian)等幾部分。

　　在控制恒(heng)定(ding)電流(liu)(liu)(liu)和恒(heng)定(ding)電壓的(de)過(guo)程中,采用比例控制,即如果充電電流(liu)(liu)(liu)I大于設(she)定(ding)電流(liu)(liu)(liu)Is,就按照比例減小脈寬;反之按照比例增大脈寬。單片機(ji)還需要(yao)接收和處理上位(wei)機(ji)的(de)命令,并根據上位(wei)機(ji)的(de)要(yao)求將數據實時回送給(gei)上位(wei)機(ji)。兩(liang)者的(de)通(tong)訊協議要(yao)在程序中預先設(she)定(ding)。 

2．3 上位機(ji)處理(li)程序設計 

　　上位機程(cheng)序由VisualC++編寫。其(qi)任務是每隔1秒鐘向串(chuan)口(kou)發送(song)一個(ge)查詢(xun)命(ming)令,并讀(du)取單(dan)片(pian)機回送(song)的(de)信(xin)息,提取充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)、充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)壓(ya)、工作(zuo)狀態等參數。參數經過數制轉換和計(ji)算后進(jin)行顯示(shi)。軟(ruan)(ruan)件(jian)有著(zhu)良好的(de)用戶界面(mian),可(ke)以(yi)(yi)方便地觀測(ce)電(dian)(dian)(dian)池目前的(de)工作(zuo)狀態以(yi)(yi)及(ji)剩余充(chong)電(dian)(dian)(dian)時間(jian)等信(xin)息。上位機程(cheng)序會同時把讀(du)到的(de)數據(ju)存儲(chu)到文件(jian)中,這些(xie)數據(ju)可(ke)以(yi)(yi)利用其(qi)它(ta)數學軟(ruan)(ruan)件(jian)(如Matlab)進(jin)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)數一般包括充電(dian)電(dian)池的(de)種類(鋰(li)離子(zi)電(dian)池、鎳鎘電(dian)池)、充電(dian)電(dian)池的(de)容量(單位為mAh)等(deng)。根(gen)據不(bu)同(tong)的(de)電(dian)池型號(hao),單片機(ji)可以設定不(bu)同(tong)的(de)充電(dian)參(can)數,程序(xu)可以直接(jie)控(kong)制單片機(ji)的(de)運行與停(ting)止。 

3智(zhi)能充電器的應用(yong)試驗 

3．1充電性(xing)能(neng)試驗 

　　這里選用型號(hao)為(wei)(wei)US18650的(de)SONY鋰(li)離子電(dian)池,其額定容量為(wei)(wei)1800mAh;經(jing)過測量,電(dian)池在4.2V左右時的(de)內阻約為(wei)(wei)0.3Ω。取恒(heng)流(liu)充(chong)電(dian)電(dian)流(liu)為(wei)(wei)1/3C=0.6A,截(jie)止電(dian)壓為(wei)(wei)4.2V,充(chong)電(dian)結束標志電(dian)流(liu)為(wei)(wei)0.06A,進行充(chong)電(dian)試驗。

　　充(chong)電(dian)(dian)時間約為(wei)240分鐘,如果需要(yao)進一(yi)步縮短充(chong)電(dian)(dian)時間,只(zhi)需在(zai)初始化(hua)時設定更(geng)大(da)的充(chong)電(dian)(dian)電(dian)(dian)流(liu)即可。因為(wei)采用PWM控(kong)制(zhi)器,所以電(dian)(dian)源供電(dian)(dian)的效率(lv)高(gao),從供電(dian)(dian)電(dian)(dian)源到充(chong)電(dian)(dian)電(dian)(dian)池的工作效率(lv),最(zui)低時在(zai)85%左右。充(chong)電(dian)(dian)電(dian)(dian)流(liu)波動較大(da),波動系數(shu)約為(wei)5%。 

3．2 智能充電器通用性試驗 

　　選用(yong)NOKIA6100鋰(li)離(li)子電(dian)池(額定容量為(wei)550mAh),用(yong)恒(heng)流-恒(heng)壓(ya)充電(dian)方式(shi)進行充電(dian),取恒(heng)流充電(dian)電(dian)流為(wei)0.15A,截止電(dian)壓(ya)為(wei)4.2V,充電(dian)曲線如圖6所示。 

　　從充(chong)電(dian)(dian)曲線來看,電(dian)(dian)池電(dian)(dian)壓(ya)達到(dao)3.96V時(shi)(shi)就不再上(shang)升了(le),充(chong)電(dian)(dian)電(dian)(dian)流也不再下降(jiang)了(le)。可(ke)以判斷商(shang)(shang)用電(dian)(dian)池內部有(you)保(bao)護電(dian)(dian)路(lu),將多余的電(dian)(dian)流旁路(lu)了(le),這樣的保(bao)護電(dian)(dian)路(lu)使(shi)充(chong)電(dian)(dian)過程中(zhong)能(neng)量損(sun)耗很大。試驗曲線顯示在四小時(shi)(shi)時(shi)(shi)電(dian)(dian)池電(dian)(dian)量已(yi)經達到(dao)550mAh,但實(shi)(shi)際上(shang)并(bing)沒(mei)有(you)達到(dao)滿充(chong)。此(ci)實(shi)(shi)驗證明(ming),此(ci)充(chong)電(dian)(dian)器可(ke)以作為一(yi)般的商(shang)(shang)用電(dian)(dian)池的通用充(chong)電(dian)(dian)器,充(chong)電(dian)(dian)速度快(kuai),效果良(liang)好。不足的是它與實(shi)(shi)際的充(chong)電(dian)(dian)電(dian)(dian)池在機械接口上(shang)還不能(neng)匹配,需要進一(yi)步改進。