隨著油價的不斷上漲和人們環保意識的增強，電動自行車以其價格低、綠色環保，使用安全方便等優點越來越受到消費者的喜愛。評價電動自行車質量好壞的重要參數之一是其蓄電池的使用壽命。而蓄電池的充電過程對其壽命影響最大。研究表明：過充電，可使蓄電池發熱，電解液失水；而充電不足，則可使蓄電池內化學反應不充分，長期充電不足會導致蓄電池容量下降。由此可見，充電器性能的好壞直接影響著蓄電池的使用效果和使用壽命。目前市場上的充電器存在的主要不(bu)足，第(di)一(yi)不(bu)是從(cong)副邊繞(rao)組直(zhi)接(jie)獲得取樣信號，因(yin)(yin)而穩壓效果不(bu)理想；第(di)二(er)是輸(shu)出電流和電壓調(diao)節(jie)范圍窄，因(yin)(yin)而只適(shi)用(yong)(yong)于固定負載(zai)。為(wei)此，本文介紹了一(yi)種以單片機為(wei)控制(zhi)器(qi)的通用(yong)(yong)智能(neng)(neng)充(chong)(chong)電器(qi)的設計方案。該裝置能(neng)(neng)根(gen)據蓄電池的充(chong)(chong)電特性(xing)或實時監測到(dao)的充(chong)(chong)電狀態，來智能(neng)(neng)化地調(diao)節(jie)充(chong)(chong)電電壓和充(chong)(chong)電電流，而且調(diao)節(jie)范圍寬(kuan)，并具有過(guo)流、過(guo)壓、過(guo)溫等保護功(gong)能(neng)(neng)。

　　1、系統結構
　　該系統主要由電源變換電路、采樣電路、微處理器，脈寬調制器、鍵盤、顯示器和溫度傳感器等部分組成，是一個閉環的智能充電系統。
　　2、硬件電路
　　本智能充電器的硬件電路分為開關電源部分、以單片機為主的控制電路和以UC3842為核心的脈寬調制電路三部分。
　　2．1開關電源設計
本設計采用電流控制型脈寬調制方式。其整個工作過程是將交流輸入經濾波、整流后變為直流高壓，再由開關管斬波、高頻變壓器降壓后得到高頻矩形電壓，最后經過輸出整流濾波獲得所需要的直流輸出電壓。系統對開關電源的要求是其交流輸入電壓范圍為90～270 V，能同時輸出+5V(作為控制部分電源)及12～60 V(主回路)的電壓。輸出電流為1～3 A。　
2．2單片機控制電路設計
　　單片機控制電路主要由單片機AT89S52、ADC(TLC0832)、多路選擇開關(CD4051)、數字電位器(X9C102)、數字溫度傳感器DSl8820、取樣電阻Rs和Rw、2×4鍵盤、液晶顯示(CONl6)等組成。
　
　　本部分設計時應先根據蓄電池的型號參數，來通過鍵盤設計與之對應的充電電流、充電電壓以及充電時間，當電路接上蓄電池后，充電過程開始，此后由單片機通過取樣電阻RM檢測電池電壓，若檢測到蓄電池因過渡放電而使電壓低于正常范圍。那么，為了避免充電電流過大而造成蓄電池損壞，應先對蓄電池實行穩定的小電流充電(本設計程序中設為l／5的設定充電電流)，同時，單片機開始計時，之后單片機將不斷檢測電池電壓和充電電流并顯示在液晶屏上，隨著充電的進行，電池電壓不斷上升，當上升到正常范圍時，單片機可通過控制數字電位器來調節輸出電壓，從而轉入大電流恒流充電(即設定電流)方式，此后，單片機一直保持不停地檢測電池電壓，當電壓達到設定值時，單片機發出指令，以增大數字電位器的阻值，并通過脈寬調制減小輸出電壓。從而使充電電流減小，當充電電流減小到1／5的設定電流時，再轉為涓流充電，最后在充電時間到時關閉電源，這樣就避免了因電池溫升過快或嚴重極化而影響充電質量，提高蓄電池的使用壽命。當檢測到電池電壓、充電電流和溫度超過設定值的1／10倍時(由程序設定)，單片機立即輸出報警信號報警。同時使繼電器動作并切斷總電源，以提高充電的安全性和可靠性。
　　顯(xian)示(shi)器可(ke)(ke)用(yong)于(yu)顯(xian)示(shi)單片機(ji)實時(shi)采樣(yang)到的蓄(xu)電(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)壓(ya)、充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)、已(yi)充(chong)電(dian)(dian)(dian)(dian)時(shi)間和蓄(xu)電(dian)(dian)(dian)(dian)池(chi)的溫度，鍵盤則(ze)用(yong)于(yu)設(she)定充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)壓(ya)(充(chong)電(dian)(dian)(dian)(dian)極(ji)(ji)限電(dian)(dian)(dian)(dian)壓(ya))、恒流(liu)充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(極(ji)(ji)限充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu))和充(chong)電(dian)(dian)(dian)(dian)時(shi)間。電(dian)(dian)(dian)(dian)路中(zhong)的單片機(ji)可(ke)(ke)通過串(chuan)口RS232和上位機(ji)相連，以用(yong)于(yu)存儲數據和虛擬顯(xian)示(shi)充(chong)電(dian)(dian)(dian)(dian)參數的設(she)定。當(dang)檢測到充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)為零時(shi)，單片機(ji)轉(zhuan)入休眠狀態(tai)。而(er)當(dang)檢測到充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)不為零時(shi)，單片機(ji)被激活。

　　2．3 PWM控制器設計
　　PW M控制器部分是以UC3842為核心。UC3842芯片內含有5.0 V基準電壓穩壓器、高增益誤差放大器和脈沖寬度比較器，它可以控制芯片內的驅動器。而驅動器則可提供25 mA的輸出電流．可直接驅動NOSFET調整管，從而調整充電器的輸出電壓和電流。由于該驅動器同時具有過流、過壓保護，工作電源電壓可以在8～40 V，而啟動電流小于1 mA，工作溫度為O～70℃，因而是目前較理想的新型脈寬調制器。
　　該PWM控制器在啟動時，是由R1、Rw。為UC3842提供啟動電壓，待其工作后，其輔助繞組3、4端的電壓經D1整流、C4、C5濾波、DW1穩壓后得到的16 V直流電壓，一路加到UC38427的7腳為其供電，另一路經R3和數字電位器X9C102分壓后加到UC3842的2腳。以作為脈寬調制的輸入信號。一般在這類電源的設計中，輸出電壓取樣可與UC3842的供電電壓相連。為了反映輸出電壓變化，本設計沒有加穩壓管，但這會使UC3842的工作電壓不穩，輸出諧波成分增多，為了克服此不足，本設計中UC3842的供電電壓采用由3、4繞組端壓單獨整流、濾波、穩壓后，提供給UC3842芯片16 V的穩定電壓。充電電壓的調節是將電池電壓經外環電壓取樣電路R12、RM取樣，再經多路電子開關選擇、MD變換，單片機處理后，送入數字電位器，以控制數字電位器的有效電阻。從而間接控制UC3842的2腳電壓，進而控制脈沖占空比，以改變充電電壓。
　　當充電器輸出電壓偏高時，反饋回UC3842的2腳電壓也升高(超過參考電壓2.5 V)之后，驅動信號的脈沖占空比減小，使輸出電壓下降，從而達到穩壓的目的。充電電流的調節主要是先將充電電流經外環電流取樣電阻Rs取樣和LM358放大(可用R1調節放大倍數)、多路電子開關選擇、MD變換，再送單片機處理，然后調節數字電位器的阻值。其調節過程與電壓調節相似，實際上，電流調節也是通過電壓調節實現的。
2．4．保護電路設計
　　當(dang)過(guo)(guo)流(liu)(liu)(liu)或短路時(shi)(shi)，內(nei)(nei)環(huan)(huan)取(qu)(qu)樣(yang)(yang)電(dian)(dian)(dian)(dian)(dian)阻R10兩(liang)端(duan)的電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)升高。當(dang)3腳電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)超(chao)過(guo)(guo)1伏時(shi)(shi)，通(tong)過(guo)(guo)UC3842的內(nei)(nei)部(bu)調(diao)(diao)(diao)制(zhi)可(ke)使(shi)其停止(zhi)脈寬輸(shu)出(chu)，開關(guan)(guan)管截止(zhi)，輸(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)和電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)均為0，從(cong)而(er)保(bao)(bao)護(hu)(hu)電(dian)(dian)(dian)(dian)(dian)源。過(guo)(guo)壓(ya)(ya)(ya)時(shi)(shi)，DW1和DW2會(hui)擊穿而(er)短路，也(ye)會(hui)造成(cheng)過(guo)(guo)流(liu)(liu)(liu)保(bao)(bao)護(hu)(hu)，DW2可(ke)用(yong)以保(bao)(bao)護(hu)(hu)場效(xiao)應(ying)管和UC3842。而(er)當(dang)發(fa)(fa)生欠(qian)(qian)壓(ya)(ya)(ya)時(shi)(shi)，即當(dang)UC3842的7腳電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)降至10 V以下時(shi)(shi)，UC3842將啟動欠(qian)(qian)壓(ya)(ya)(ya)鎖定電(dian)(dian)(dian)(dian)(dian)路而(er)關(guan)(guan)閉開關(guan)(guan)控(kong)制(zhi)器。內(nei)(nei)環(huan)(huan)的這種反饋(kui)調(diao)(diao)(diao)整是(shi)(shi)在(zai)輸(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)尚未發(fa)(fa)生變化時(shi)(shi)，通(tong)過(guo)(guo)檢測(ce)內(nei)(nei)環(huan)(huan)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)使(shi)脈寬提前得到調(diao)(diao)(diao)整，(前饋(kui)控(kong)制(zhi))，從(cong)而(er)加(jia)(jia)快了(le)變換(huan)器對異(yi)常(chang)情(qing)況(kuang)的動態響應(ying)速度(du)。以便更加(jia)(jia)快速有(you)效(xiao)地起到保(bao)(bao)護(hu)(hu)作用(yong)。當(dang)然，外環(huan)(huan)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)、電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)的取(qu)(qu)樣(yang)(yang)(Rs、Rw)亦可(ke)通(tong)過(guo)(guo)單片機的調(diao)(diao)(diao)節作用(yong)來(lai)達到對異(yi)常(chang)情(qing)況(kuang)的保(bao)(bao)護(hu)(hu)，但響應(ying)速度(du)比內(nei)(nei)環(huan)(huan)慢5～10個(ge)工頻周期，因此，外環(huan)(huan)取(qu)(qu)樣(yang)(yang)主要是(shi)(shi)調(diao)(diao)(diao)節充電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)和充電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)，兼作二次(ci)(ci)保(bao)(bao)護(hu)(hu)，而(er)內(nei)(nei)環(huan)(huan)取(qu)(qu)樣(yang)(yang)則是(shi)(shi)主要的，它是(shi)(shi)一(yi)次(ci)(ci)的保(bao)(bao)護(hu)(hu)，這種雙環(huan)(huan)保(bao)(bao)護(hu)(hu)方式(shi)會(hui)更加(jia)(jia)安全可(ke)靠(kao)。

　　3、軟件設計

　　在程序的初始階段，首先是對單片機進行初始化，即根據不同的電池設定不同的充電參數，選擇不同的充電策略。其后是判斷電池是否連接正確，根據電池電壓值判斷應該進入哪一個充電階段(即小電流預充電，大電流恒流充電或恒壓涓流充電方式)。在預充階段，應降低充電電壓，而在恒流方式時，應不斷檢測充電電流是否達到恒定電流(如1.8 A)，如果小于1.8 A，則抬高電池兩端的電壓，使之達到1.8 A，以上調節過程均可采用比例控制。在電池兩端電壓達到設定值后，系統再進入涓流充電模式。該充電器的程序流程如圖3所示。圖3中，Is為設定的充電電流(即恒流充電電流)，Umin為蓄電池的放電極限電壓，Umax為蓄電池的充電極限電壓。
　　4、應用試驗
　　本設計選用了電動自行車常用的36 V／12 Ah鉛酸蓄電池作為測試對象，其恒壓充電電壓設定為43 V，恒流充電電流Is為1.8 A，起始時，隨著充電的進行，充電電流幾乎維持1.8 A不變，但電池電壓不斷升高，當充電3小時后。電壓上升減慢；當充電到4小時后，充電電壓接近43 V；之后電壓上升更加緩慢。而且充電下降較快。當充到43 V時，充電器自動停止。從測試數據來看，該設計達到了恒流快充，恒壓涓充，充滿自行關斷的設計要求。
　　5、結束語
　　本文設計的過(guo)(guo)度(du)放電(dian)(dian)(dian)(dian)(dian)(dian)預(yu)充(chong)(chong)、恒流快充(chong)(chong)、恒壓涓充(chong)(chong)、智能控制(zhi)(zhi)的充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)方(fang)(fang)案，能很好地(di)解決(jue)電(dian)(dian)(dian)(dian)(dian)(dian)動自行車用(yong)(yong)電(dian)(dian)(dian)(dian)(dian)(dian)池在(zai)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)過(guo)(guo)程中存在(zai)的過(guo)(guo)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)、充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)不(bu)足和發熱等(deng)問題，并(bing)能根(gen)據(ju)不(bu)同(tong)電(dian)(dian)(dian)(dian)(dian)(dian)池選(xuan)擇不(bu)同(tong)的充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)方(fang)(fang)案。而且具有(you)(you)通用(yong)(yong)性。能實時(shi)檢(jian)測并(bing)顯示(shi)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流、充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)壓、充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)時(shi)間和蓄電(dian)(dian)(dian)(dian)(dian)(dian)池溫度(du)等(deng)參(can)數。由于電(dian)(dian)(dian)(dian)(dian)(dian)路具有(you)(you)內外環控制(zhi)(zhi)，符合(he)最(zui)優控制(zhi)(zhi)規律(lv)。最(zui)具有(you)(you)過(guo)(guo)流、過(guo)(guo)壓和超溫保護功能，同(tong)時(shi)由于UC3842采用(yong)(yong)穩壓供(gong)電(dian)(dian)(dian)(dian)(dian)(dian)，因此，不(bu)但諧波污染程度(du)低，原副邊(bian)電(dian)(dian)(dian)(dian)(dian)(dian)氣隔離安全可(ke)靠，同(tong)時(shi)還可(ke)根(gen)據(ju)負載情況通過(guo)(guo)單片機(ji)來進行控制(zhi)(zhi)，并(bing)可(ke)實現跳周(zhou)期模式工作。故可(ke)提高電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)的效率。