現(xian)代通(tong)訊設(she)備、便攜式電(dian)(dian)(dian)(dian)子產品、筆記本電(dian)(dian)(dian)(dian)腦、電(dian)(dian)(dian)(dian)動(dong)汽車(che)、小衛(wei)星等(deng)普遍使用蓄電(dian)(dian)(dian)(dian)池(chi)作為電(dian)(dian)(dian)(dian)源,應用非常(chang)廣泛。然而(er)大(da)多(duo)數(shu)設(she)備中的(de)(de)蓄電(dian)(dian)(dian)(dian)池(chi),只能(neng)使用專(zhuan)用的(de)(de)充電(dian)(dian)(dian)(dian)器,而(er)且普通(tong)的(de)(de)充電(dian)(dian)(dian)(dian)器大(da)多(duo)充電(dian)(dian)(dian)(dian)時(shi)間長,無法判斷(duan)其充電(dian)(dian)(dian)(dian)參數(shu)和剩(sheng)余的(de)(de)充電(dian)(dian)(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(yi)實(shi)時采集電(dian)(dian)(dian)(dian)池(chi)的電(dian)(dian)(dian)(dian)壓、電(dian)(dian)(dian)(dian)流,對充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)過(guo)程進行(xing)智能控制,計算電(dian)(dian)(dian)(dian)池(chi)已(yi)充(chong)(chong)(chong)的電(dian)(dian)(dian)(dian)量和(he)剩余的充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)時間;還可以(yi)通(tong)(tong)過(guo)串口(kou)和(he)上(shang)位機進行(xing)通(tong)(tong)訊并給用(yong)戶顯示必(bi)要(yao)的信(xin)息(xi),有虛擬儀表的作用(yong);另外,它也可以(yi)改變參(can)數,適應(ying)各種不(bu)同電(dian)(dian)(dian)(dian)池(chi)的充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)。這里列舉(ju)幾(ji)種不(bu)同的電(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)試驗,來說明智能充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)器的實(shi)用(yong)價值。 

1 智能充電器的硬件設計 

　　主(zhu)要(yao)包括電(dian)(dian)(dian)源變換(huan)電(dian)(dian)(dian)路、采樣電(dian)(dian)(dian)路、處理器(qi)、脈寬調制控制器(qi)和電(dian)(dian)(dian)池組等,形成了一個閉環系統.

1．1 處(chu)理(li)器 

　　處理器采用(yong)51系列(lie)單片(pian)機(ji)89C51。單片(pian)機(ji)內部有兩個(ge)定時(shi)器、兩個(ge)外(wai)部中斷和(he)一(yi)(yi)個(ge)串口中斷、三個(ge)八(ba)路的(de)(de)I/O口,采用(yong)11.0592MHz的(de)(de)晶振。單片(pian)機(ji)的(de)(de)任務是(shi)通過(guo)采樣電路實時(shi)采集電池的(de)(de)充(chong)(chong)電狀態,通過(guo)計(ji)算決(jue)定下(xia)一(yi)(yi)階段的(de)(de)充(chong)(chong)電電流(liu),然后發送命令給控制(zhi)器控制(zhi)電流(liu)的(de)(de)大小。單片(pian)機(ji)通過(guo)串口RS232和(he)上位機(ji)相連,用(yong)于存儲數據和(he)虛擬顯示(shi)。 

1．2 采樣部分(fen) 

　　電壓和電流采(cai)樣(yang)采(cai)用模/數轉換器AD574。AD574為±15V雙(shuang)電源供電,12位輸(shu)出,最(zui)大誤差(cha)為±4bit,合(he)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)傳感(gan)器(qi)MAX471轉換為電(dian)(dian)(dian)壓(ya)(ya)值。電(dian)(dian)(dian)流(liu)采樣的(de)電(dian)(dian)(dian)壓(ya)(ya)值和電(dian)(dian)(dian)池組的(de)端電(dian)(dian)(dian)壓(ya)(ya)值兩者經過(guo)模擬開(kai)關CD4051,再(zai)經過(guo)電(dian)(dian)(dian)壓(ya)(ya)跟隨器(qi)輸入到AD574,分別進行轉換,其結果由單片(pian)機讀取(qu),并進行存儲和處理。

1．3 控制器 

　　控(kong)制器采用脈寬(kuan)調制(PWM)方(fang)式(shi)控(kong)制供電(dian)電(dian)流的(de)(de)大小。PWM發生(sheng)器由另一個20MHz的(de)(de)單(dan)片機構成,主控(kong)制器和(he)它采用中斷的(de)(de)方(fang)式(shi)進行通訊,控(kong)制其增大或減(jian)(jian)小脈寬(kuan)。PWM信號通過(guo)光電(dian)隔離(li)驅動主回路(lu)上的(de)(de)MOSFET。開(kai)關管、二極管、LC電(dian)路(lu)構成開(kai)關穩(wen)壓電(dian)源。用PWM方(fang)式(shi)控(kong)制的(de)(de)開(kai)關電(dian)源可以減(jian)(jian)小功(gong)耗,同(tong)時便于進行數字化控(kong)制,但母線的(de)(de)紋波系數相(xiang)對較(jiao)大。

2 智(zhi)能充電(dian)器(qi)的軟件設計 

2．1 數據(ju)測量(liang) 

　　在單(dan)(dan)片機的(de)測(ce)量(liang)中,電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)壓值(zhi)(zhi)和電(dian)(dian)(dian)流(liu)測(ce)量(liang)值(zhi)(zhi)經過(guo)多路選擇器進(jin)行選擇,然后通過(guo)A/D轉(zhuan)(zhuan)換(huan)(huan)器轉(zhuan)(zhuan)換(huan)(huan)為16進(jin)制數(shu),直接(jie)存入單(dan)(dan)片機。電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)容(rong)量(liang)C則需要(yao)間接(jie)計算(suan),由于每個循環(huan) 周期檢測(ce)電(dian)(dian)(dian)流(liu)一次,故可(ke)以利用電(dian)(dian)(dian)流(liu)值(zhi)(zhi)的(de)積分求(qiu)出電(dian)(dian)(dian)容(rong)量(liang)C。考慮電(dian)(dian)(dian)池(chi)內(nei)阻r的(de)影響,可(ke)以得到計算(suan)電(dian)(dian)(dian)容(rong)量(liang)的(de)計算(suan)公式為: 

　　Cn+1=Cn+I?t-I2?r?t 

　　充電時(shi)(shi)間(jian)(jian)和剩(sheng)余充電時(shi)(shi)間(jian)(jian)由上位(wei)機進行計算(suan),剩(sheng)余充電時(shi)(shi)間(jian)(jian)等于預(yu)設(she)的(de)充電時(shi)(shi)間(jian)(jian)與已充電時(shi)(shi)間(jian)(jian)的(de)差(cha)值。其(qi)中,預(yu)設(she)時(shi)(shi)間(jian)(jian)可根(gen)據電池的(de)型號(hao)預(yu)先得到。 

2．2 單片機控制程序設計 

對于不(bu)同的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)和不(bu)同的參數(shu),單片機需要設定不(bu)同的充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)參數(shu),選擇不(bu)同的充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)策(ce)略。另外,程序需要在電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)過電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)、過電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)等(deng)異常(chang)情況下強制終(zhong)止充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。以(yi)鋰(li)離子電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)為(wei)例(li),一般采用恒(heng)流(liu)(liu)-恒(heng)壓(ya)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)方式,其充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)過程包括小電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)預充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)、大電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)、恒(heng)壓(ya)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)等(deng)幾(ji)部分(fen)。

　　在控(kong)制(zhi)(zhi)恒定(ding)電流和恒定(ding)電壓的(de)過程(cheng)中,采(cai)用比(bi)例控(kong)制(zhi)(zhi),即(ji)如(ru)果充電電流I大于設定(ding)電流Is,就按(an)(an)照比(bi)例減(jian)小脈寬(kuan)(kuan);反之按(an)(an)照比(bi)例增大脈寬(kuan)(kuan)。單(dan)片機(ji)還(huan)需(xu)要(yao)接收(shou)和處(chu)理(li)上(shang)位(wei)(wei)機(ji)的(de)命令,并根據(ju)上(shang)位(wei)(wei)機(ji)的(de)要(yao)求(qiu)將數(shu)據(ju)實時回送給(gei)上(shang)位(wei)(wei)機(ji)。兩者的(de)通訊協議要(yao)在程(cheng)序中預先設定(ding)。 

2．3 上位機(ji)處理程序(xu)設(she)計 

　　上(shang)位機程(cheng)序(xu)由VisualC++編寫(xie)。其(qi)任務是每隔1秒鐘向串口發送一(yi)個(ge)查詢命(ming)令,并讀取單片機回送的(de)信息,提取充(chong)電(dian)電(dian)流、充(chong)電(dian)電(dian)壓、工(gong)作(zuo)狀態(tai)等(deng)參(can)數。參(can)數經(jing)過數制(zhi)轉換和(he)計算后(hou)進行(xing)顯示。軟件(jian)(jian)有著良好的(de)用戶界面,可以方便(bian)地觀測電(dian)池目前的(de)工(gong)作(zuo)狀態(tai)以及(ji)剩余充(chong)電(dian)時間等(deng)信息。上(shang)位機程(cheng)序(xu)會同時把讀到的(de)數據(ju)存儲到文件(jian)(jian)中,這些數據(ju)可以利用其(qi)它數學(xue)軟件(jian)(jian)(如(ru)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(can)數一般包(bao)括充(chong)電(dian)(dian)電(dian)(dian)池(chi)(chi)的(de)(de)(de)種類(鋰離子電(dian)(dian)池(chi)(chi)、鎳鎘電(dian)(dian)池(chi)(chi))、充(chong)電(dian)(dian)電(dian)(dian)池(chi)(chi)的(de)(de)(de)容(rong)量(單位(wei)為mAh)等。根據不同(tong)的(de)(de)(de)電(dian)(dian)池(chi)(chi)型號(hao),單片(pian)機可以設定不同(tong)的(de)(de)(de)充(chong)電(dian)(dian)參(can)數,程序可以直接(jie)控(kong)制(zhi)單片(pian)機的(de)(de)(de)運行與停止(zhi)。 

3智能充電器的應用試驗(yan) 

3．1充電性能試驗 

　　這(zhe)里選用型號為(wei)US18650的SONY鋰離子電(dian)池,其(qi)額定容(rong)量(liang)(liang)為(wei)1800mAh;經過測量(liang)(liang),電(dian)池在4.2V左右(you)時的內阻(zu)約為(wei)0.3Ω。取恒流(liu)(liu)充(chong)電(dian)電(dian)流(liu)(liu)為(wei)1/3C=0.6A,截止電(dian)壓為(wei)4.2V,充(chong)電(dian)結束標志(zhi)電(dian)流(liu)(liu)為(wei)0.06A,進行(xing)充(chong)電(dian)試驗。

　　充(chong)電(dian)(dian)(dian)時(shi)間約為240分鐘(zhong),如果需要進一步縮短充(chong)電(dian)(dian)(dian)時(shi)間,只需在初(chu)始化時(shi)設(she)定更大的(de)(de)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)即可。因為采用PWM控制(zhi)器,所以電(dian)(dian)(dian)源(yuan)(yuan)供電(dian)(dian)(dian)的(de)(de)效率高,從供電(dian)(dian)(dian)電(dian)(dian)(dian)源(yuan)(yuan)到(dao)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)池(chi)的(de)(de)工作效率,最低時(shi)在85%左(zuo)右。充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)波(bo)動(dong)較大,波(bo)動(dong)系數約為5%。 

3．2 智能充電器通用性(xing)試驗 

　　選(xuan)用NOKIA6100鋰離子電池(額定容量為(wei)550mAh),用恒流(liu)-恒壓充(chong)(chong)電方式進(jin)行(xing)充(chong)(chong)電,取(qu)恒流(liu)充(chong)(chong)電電流(liu)為(wei)0.15A,截止電壓為(wei)4.2V,充(chong)(chong)電曲線如圖(tu)6所(suo)示。 

　　從充電(dian)(dian)曲線來看,電(dian)(dian)池(chi)電(dian)(dian)壓達到3.96V時就(jiu)不(bu)再上升了,充電(dian)(dian)電(dian)(dian)流也不(bu)再下降了。可(ke)以判斷商用(yong)(yong)電(dian)(dian)池(chi)內部有保護電(dian)(dian)路(lu),將多余的(de)電(dian)(dian)流旁路(lu)了,這樣(yang)的(de)保護電(dian)(dian)路(lu)使充電(dian)(dian)過程中能(neng)量(liang)損耗很大。試驗(yan)曲線顯示在四小時時電(dian)(dian)池(chi)電(dian)(dian)量(liang)已經達到550mAh,但實(shi)際上并沒有達到滿充。此實(shi)驗(yan)證明,此充電(dian)(dian)器可(ke)以作為(wei)一(yi)般(ban)的(de)商用(yong)(yong)電(dian)(dian)池(chi)的(de)通用(yong)(yong)充電(dian)(dian)器,充電(dian)(dian)速度快,效果(guo)良好。不(bu)足的(de)是它與實(shi)際的(de)充電(dian)(dian)電(dian)(dian)池(chi)在機械接(jie)口上還(huan)不(bu)能(neng)匹配,需要(yao)進一(yi)步改進。