現代通(tong)訊設備、便攜式電(dian)(dian)(dian)子產品(pin)、筆記本(ben)電(dian)(dian)(dian)腦、電(dian)(dian)(dian)動汽(qi)車、小衛星等普遍使(shi)用蓄電(dian)(dian)(dian)池作為電(dian)(dian)(dian)源(yuan),應用非常廣泛(fan)。然而大多(duo)(duo)數(shu)設備中(zhong)的(de)(de)蓄電(dian)(dian)(dian)池,只能使(shi)用專用的(de)(de)充(chong)電(dian)(dian)(dian)器,而且(qie)普通(tong)的(de)(de)充(chong)電(dian)(dian)(dian)器大多(duo)(duo)充(chong)電(dian)(dian)(dian)時間長(chang),無(wu)法判斷其充(chong)電(dian)(dian)(dian)參數(shu)和剩余的(de)(de)充(chong)電(dian)(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(ke)以實時采集電(dian)(dian)(dian)(dian)池(chi)的(de)電(dian)(dian)(dian)(dian)壓、電(dian)(dian)(dian)(dian)流,對(dui)充(chong)電(dian)(dian)(dian)(dian)過程進(jin)行(xing)智能(neng)控制(zhi),計算電(dian)(dian)(dian)(dian)池(chi)已充(chong)的(de)電(dian)(dian)(dian)(dian)量(liang)和剩(sheng)余的(de)充(chong)電(dian)(dian)(dian)(dian)時間;還可(ke)以通過串口和上位機(ji)進(jin)行(xing)通訊并(bing)給用(yong)戶顯示必(bi)要的(de)信(xin)息(xi),有虛(xu)擬儀表的(de)作用(yong);另(ling)外,它也可(ke)以改變參數(shu),適應各種(zhong)(zhong)不同電(dian)(dian)(dian)(dian)池(chi)的(de)充(chong)電(dian)(dian)(dian)(dian)。這里列(lie)舉幾種(zhong)(zhong)不同的(de)電(dian)(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)(dian)試驗,來說明智能(neng)充(chong)電(dian)(dian)(dian)(dian)器的(de)實用(yong)價值。 

1 智能充電器的硬件設計 

　　主要包括電源變換電路、采樣電路、處理器(qi)、脈寬調制控制器(qi)和電池(chi)組等,形成了一個閉環系統(tong).

1．1 處(chu)理器(qi) 

　　處理(li)器采用(yong)51系(xi)列單片(pian)機(ji)(ji)89C51。單片(pian)機(ji)(ji)內部(bu)有(you)兩個(ge)定時器、兩個(ge)外(wai)部(bu)中斷和一(yi)個(ge)串口中斷、三個(ge)八路的(de)I/O口,采用(yong)11.0592MHz的(de)晶(jing)振。單片(pian)機(ji)(ji)的(de)任務(wu)是通過(guo)采樣電(dian)路實(shi)時采集電(dian)池的(de)充(chong)電(dian)狀態,通過(guo)計(ji)算(suan)決(jue)定下一(yi)階(jie)段的(de)充(chong)電(dian)電(dian)流,然后發(fa)送命令給控(kong)制器控(kong)制電(dian)流的(de)大小。單片(pian)機(ji)(ji)通過(guo)串口RS232和上位機(ji)(ji)相連,用(yong)于存儲數據和虛(xu)擬顯(xian)示。 

1．2 采樣部分 

　　電(dian)壓和電(dian)流(liu)采樣采用模/數(shu)轉換器AD574。AD574為±15V雙電(dian)源供電(dian),12位輸出,最大誤差為±4bit,合計電(dian)壓0.01V。 

　　充(chong)電(dian)(dian)電(dian)(dian)流通(tong)過(guo)(guo)電(dian)(dian)流傳感器(qi)MAX471轉換(huan)(huan)為(wei)電(dian)(dian)壓值。電(dian)(dian)流采樣的(de)電(dian)(dian)壓值和電(dian)(dian)池組的(de)端(duan)電(dian)(dian)壓值兩者經過(guo)(guo)模擬(ni)開關CD4051,再經過(guo)(guo)電(dian)(dian)壓跟隨器(qi)輸入(ru)到(dao)AD574,分(fen)別進(jin)行轉換(huan)(huan),其結果由單片機讀(du)取,并進(jin)行存儲和處(chu)理。

1．3 控制器(qi) 

　　控(kong)制(zhi)(zhi)(zhi)器(qi)采用脈(mo)寬(kuan)(kuan)調制(zhi)(zhi)(zhi)(PWM)方式控(kong)制(zhi)(zhi)(zhi)供電電流的(de)(de)(de)大(da)小。PWM發(fa)生器(qi)由另一個20MHz的(de)(de)(de)單片機構(gou)成,主控(kong)制(zhi)(zhi)(zhi)器(qi)和它采用中(zhong)斷的(de)(de)(de)方式進行通訊,控(kong)制(zhi)(zhi)(zhi)其(qi)增大(da)或減小脈(mo)寬(kuan)(kuan)。PWM信號通過光電隔離驅動主回路上(shang)的(de)(de)(de)MOSFET。開(kai)(kai)關管、二(er)極管、LC電路構(gou)成開(kai)(kai)關穩壓電源。用PWM方式控(kong)制(zhi)(zhi)(zhi)的(de)(de)(de)開(kai)(kai)關電源可以減小功耗,同時便(bian)于(yu)進行數字化控(kong)制(zhi)(zhi)(zhi),但(dan)母線的(de)(de)(de)紋(wen)波系數相對較大(da)。

2 智能(neng)充電器的軟(ruan)件(jian)設計(ji) 

2．1 數據測量 

　　在單片(pian)機的(de)測量(liang)中,電(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)壓值和電(dian)(dian)(dian)(dian)流(liu)測量(liang)值經過多路選擇器進行選擇,然后通(tong)過A/D轉換器轉換為16進制數(shu),直(zhi)接(jie)存入單片(pian)機。電(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)容量(liang)C則需要間(jian)接(jie)計(ji)算(suan),由于(yu)每個循環 周期檢測電(dian)(dian)(dian)(dian)流(liu)一次,故可以(yi)利用電(dian)(dian)(dian)(dian)流(liu)值的(de)積(ji)分求出電(dian)(dian)(dian)(dian)容量(liang)C。考慮電(dian)(dian)(dian)(dian)池內阻r的(de)影(ying)響,可以(yi)得到計(ji)算(suan)電(dian)(dian)(dian)(dian)容量(liang)的(de)計(ji)算(suan)公式為: 

　　Cn+1=Cn+I?t-I2?r?t 

　　充電(dian)(dian)時(shi)(shi)間(jian)(jian)和剩余(yu)充電(dian)(dian)時(shi)(shi)間(jian)(jian)由上(shang)位機進行(xing)計算(suan),剩余(yu)充電(dian)(dian)時(shi)(shi)間(jian)(jian)等于(yu)預(yu)(yu)設的(de)充電(dian)(dian)時(shi)(shi)間(jian)(jian)與已充電(dian)(dian)時(shi)(shi)間(jian)(jian)的(de)差值。其中,預(yu)(yu)設時(shi)(shi)間(jian)(jian)可根據電(dian)(dian)池(chi)的(de)型號預(yu)(yu)先得到。 

2．2 單(dan)片機(ji)控制程序設計 

對于不同(tong)(tong)的(de)電(dian)(dian)(dian)(dian)(dian)(dian)池和不同(tong)(tong)的(de)參數,單片機需要(yao)設定不同(tong)(tong)的(de)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)參數,選擇不同(tong)(tong)的(de)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)策略。另外,程(cheng)序需要(yao)在電(dian)(dian)(dian)(dian)(dian)(dian)池過(guo)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)、過(guo)電(dian)(dian)(dian)(dian)(dian)(dian)壓等異常(chang)情況下強(qiang)制終止充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)。以鋰(li)離子電(dian)(dian)(dian)(dian)(dian)(dian)池為例,一(yi)般(ban)采用(yong)恒(heng)流(liu)-恒(heng)壓充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)方式,其充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)過(guo)程(cheng)包括小電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)預(yu)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)、大電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)、恒(heng)壓充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)等幾(ji)部分(fen)。

　　在控(kong)制恒定(ding)電(dian)(dian)(dian)流(liu)(liu)和恒定(ding)電(dian)(dian)(dian)壓的(de)過程中,采(cai)用比(bi)(bi)例控(kong)制,即(ji)如果充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)I大于設定(ding)電(dian)(dian)(dian)流(liu)(liu)Is,就(jiu)按照(zhao)比(bi)(bi)例減小(xiao)脈(mo)(mo)寬;反(fan)之(zhi)按照(zhao)比(bi)(bi)例增(zeng)大脈(mo)(mo)寬。單片(pian)機(ji)(ji)還需要(yao)(yao)接收和處理(li)上(shang)位(wei)機(ji)(ji)的(de)命令,并根據(ju)上(shang)位(wei)機(ji)(ji)的(de)要(yao)(yao)求(qiu)將數(shu)據(ju)實時回送給上(shang)位(wei)機(ji)(ji)。兩者的(de)通訊協議要(yao)(yao)在程序中預先設定(ding)。 

2．3 上位機處理程(cheng)序設計(ji) 

　　上位(wei)機程序由VisualC++編寫。其任務是每隔1秒鐘(zhong)向串口發送一個查詢命令,并讀取單片機回送的信息(xi),提(ti)取充電電流、充電電壓(ya)、工作狀態等參(can)數。參(can)數經(jing)過數制(zhi)轉換和計(ji)算后進(jin)(jin)行(xing)顯示。軟(ruan)件有(you)著良好的用(yong)戶界面,可以方便地觀測電池目前的工作狀態以及剩余(yu)充電時間等信息(xi)。上位(wei)機程序會(hui)同時把讀到的數據存儲到文件中,這些數據可以利用(yong)其它數學軟(ruan)件(如Matlab)進(jin)(jin)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(can)數一般包括充(chong)電(dian)電(dian)池的(de)(de)(de)種類(鋰離子電(dian)池、鎳鎘電(dian)池)、充(chong)電(dian)電(dian)池的(de)(de)(de)容量(單位為(wei)mAh)等。根據不同(tong)的(de)(de)(de)電(dian)池型(xing)號(hao),單片機可以(yi)(yi)設定(ding)不同(tong)的(de)(de)(de)充(chong)電(dian)參(can)數,程序可以(yi)(yi)直接(jie)控制單片機的(de)(de)(de)運行(xing)與停止。 

3智能充電器的應用(yong)試(shi)驗 

3．1充電性(xing)能試驗 

　　這里(li)選(xuan)用型號為(wei)(wei)(wei)US18650的SONY鋰離子(zi)電池(chi),其額定容量(liang)(liang)為(wei)(wei)(wei)1800mAh;經過測量(liang)(liang),電池(chi)在(zai)4.2V左(zuo)右時的內阻約為(wei)(wei)(wei)0.3Ω。取恒流(liu)(liu)充電電流(liu)(liu)為(wei)(wei)(wei)1/3C=0.6A,截(jie)止電壓(ya)為(wei)(wei)(wei)4.2V,充電結(jie)束標(biao)志電流(liu)(liu)為(wei)(wei)(wei)0.06A,進(jin)行充電試驗。

　　充(chong)(chong)電(dian)時間約(yue)為240分鐘(zhong),如(ru)果(guo)需(xu)要進一(yi)步縮短充(chong)(chong)電(dian)時間,只需(xu)在初始化時設定更大的充(chong)(chong)電(dian)電(dian)流(liu)即可(ke)。因為采(cai)用(yong)PWM控制器,所以電(dian)源供電(dian)的效(xiao)率高,從供電(dian)電(dian)源到充(chong)(chong)電(dian)電(dian)池的工作效(xiao)率,最(zui)低時在85%左右。充(chong)(chong)電(dian)電(dian)流(liu)波動較(jiao)大,波動系(xi)數約(yue)為5%。 

3．2 智能充電器通用性試驗 

　　選(xuan)用(yong)NOKIA6100鋰離子電池(chi)(額定容量為550mAh),用(yong)恒(heng)流-恒(heng)壓(ya)充(chong)(chong)電方式進行充(chong)(chong)電,取恒(heng)流充(chong)(chong)電電流為0.15A,截止電壓(ya)為4.2V,充(chong)(chong)電曲線如圖6所(suo)示。 

　　從充(chong)電(dian)(dian)(dian)曲(qu)線來看,電(dian)(dian)(dian)池電(dian)(dian)(dian)壓達(da)(da)到3.96V時(shi)就不(bu)再(zai)上升了(le)(le),充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流也(ye)不(bu)再(zai)下(xia)降(jiang)了(le)(le)。可以(yi)判斷(duan)商用電(dian)(dian)(dian)池內部有(you)保(bao)護(hu)電(dian)(dian)(dian)路,將多余(yu)的(de)電(dian)(dian)(dian)流旁路了(le)(le),這(zhe)樣的(de)保(bao)護(hu)電(dian)(dian)(dian)路使充(chong)電(dian)(dian)(dian)過程中能量損耗(hao)很(hen)大。試(shi)驗曲(qu)線顯(xian)示在四小時(shi)時(shi)電(dian)(dian)(dian)池電(dian)(dian)(dian)量已經達(da)(da)到550mAh,但實際上并沒有(you)達(da)(da)到滿充(chong)。此(ci)實驗證明,此(ci)充(chong)電(dian)(dian)(dian)器可以(yi)作為一(yi)般(ban)的(de)商用電(dian)(dian)(dian)池的(de)通用充(chong)電(dian)(dian)(dian)器,充(chong)電(dian)(dian)(dian)速度快,效(xiao)果良好。不(bu)足的(de)是它與實際的(de)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)池在機械(xie)接口上還不(bu)能匹(pi)配,需要進(jin)一(yi)步改(gai)進(jin)。