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(de)主要不(bu)足，第一不(bu)是從副(fu)邊繞組直(zhi)接獲得取樣信號(hao)，因而(er)穩壓效(xiao)果(guo)不(bu)理想(xiang)；第二是輸出電(dian)(dian)(dian)流(liu)和電(dian)(dian)(dian)壓調(diao)節(jie)范(fan)(fan)圍窄，因而(er)只適用于固定負載。為(wei)此，本文介紹了一種(zhong)以單片機(ji)為(wei)控(kong)制器的(de)通用智能(neng)充(chong)(chong)電(dian)(dian)(dian)器的(de)設計方(fang)案。該裝置能(neng)根(gen)據蓄電(dian)(dian)(dian)池(chi)的(de)充(chong)(chong)電(dian)(dian)(dian)特性(xing)或實時監測到(dao)的(de)充(chong)(chong)電(dian)(dian)(dian)狀態，來智能(neng)化地(di)調(diao)節(jie)充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)壓和充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)，而(er)且調(diao)節(jie)范(fan)(fan)圍寬(kuan)，并具(ju)有過(guo)流(liu)、過(guo)壓、過(guo)溫等保護(hu)功(gong)能(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)(xian)示(shi)器可(ke)用于顯(xian)(xian)示(shi)單(dan)(dan)片機實時采樣到的蓄(xu)(xu)電(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)壓、充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)、已充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)時間和(he)蓄(xu)(xu)電(dian)(dian)(dian)(dian)(dian)池的溫(wen)度，鍵盤(pan)則(ze)用于設定充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓(充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)極限(xian)電(dian)(dian)(dian)(dian)(dian)壓)、恒流(liu)(liu)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(極限(xian)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu))和(he)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)時間。電(dian)(dian)(dian)(dian)(dian)路中的單(dan)(dan)片機可(ke)通過串口(kou)RS232和(he)上(shang)位機相連(lian)，以用于存儲(chu)數(shu)(shu)據(ju)和(he)虛擬顯(xian)(xian)示(shi)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)參數(shu)(shu)的設定。當(dang)檢測到充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)為(wei)零(ling)時，單(dan)(dan)片機轉入休(xiu)眠狀態。而當(dang)檢測到充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)不為(wei)零(ling)時，單(dan)(dan)片機被激活。

　　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)過流(liu)(liu)或短路(lu)時(shi)，內(nei)環(huan)(huan)(huan)取(qu)樣電(dian)(dian)(dian)(dian)(dian)(dian)阻R10兩端的電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)升(sheng)高。當(dang)3腳電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)超過1伏時(shi)，通(tong)過UC3842的內(nei)部調制可(ke)使(shi)其停止脈(mo)寬輸出(chu)，開關(guan)管截(jie)止，輸出(chu)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)和(he)(he)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)均為(wei)0，從(cong)而(er)(er)保(bao)(bao)護(hu)(hu)電(dian)(dian)(dian)(dian)(dian)(dian)源。過壓(ya)(ya)時(shi)，DW1和(he)(he)DW2會(hui)擊穿而(er)(er)短路(lu)，也會(hui)造成過流(liu)(liu)保(bao)(bao)護(hu)(hu)，DW2可(ke)用(yong)以保(bao)(bao)護(hu)(hu)場(chang)效應(ying)管和(he)(he)UC3842。而(er)(er)當(dang)發生(sheng)欠壓(ya)(ya)時(shi)，即(ji)當(dang)UC3842的7腳電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)降至10 V以下時(shi)，UC3842將啟動欠壓(ya)(ya)鎖定電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)而(er)(er)關(guan)閉開關(guan)控(kong)制器。內(nei)環(huan)(huan)(huan)的這(zhe)(zhe)種反饋調整是(shi)(shi)在輸出(chu)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)尚未發生(sheng)變化時(shi)，通(tong)過檢(jian)測內(nei)環(huan)(huan)(huan)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)使(shi)脈(mo)寬提前得(de)到調整，(前饋控(kong)制)，從(cong)而(er)(er)加(jia)快了變換器對(dui)異(yi)(yi)常(chang)情況的動態(tai)響(xiang)(xiang)應(ying)速度。以便更(geng)加(jia)快速有效地起到保(bao)(bao)護(hu)(hu)作用(yong)。當(dang)然，外(wai)(wai)環(huan)(huan)(huan)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)、電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)的取(qu)樣(Rs、Rw)亦(yi)可(ke)通(tong)過單片(pian)機的調節作用(yong)來(lai)達到對(dui)異(yi)(yi)常(chang)情況的保(bao)(bao)護(hu)(hu)，但響(xiang)(xiang)應(ying)速度比(bi)內(nei)環(huan)(huan)(huan)慢5～10個工頻周期，因此(ci)，外(wai)(wai)環(huan)(huan)(huan)取(qu)樣主要是(shi)(shi)調節充電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)和(he)(he)充電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)，兼作二次保(bao)(bao)護(hu)(hu)，而(er)(er)內(nei)環(huan)(huan)(huan)取(qu)樣則是(shi)(shi)主要的，它是(shi)(shi)一(yi)次的保(bao)(bao)護(hu)(hu)，這(zhe)(zhe)種雙環(huan)(huan)(huan)保(bao)(bao)護(hu)(hu)方式會(hui)更(geng)加(jia)安全可(ke)靠。

　　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(ben)文(wen)設計的過(guo)(guo)度放電(dian)(dian)(dian)(dian)(dian)(dian)預充(chong)(chong)、恒流快充(chong)(chong)、恒壓涓充(chong)(chong)、智能控(kong)制(zhi)的充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)方案，能很好地(di)解決(jue)電(dian)(dian)(dian)(dian)(dian)(dian)動(dong)自行車用(yong)電(dian)(dian)(dian)(dian)(dian)(dian)池在(zai)(zai)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)過(guo)(guo)程(cheng)中存在(zai)(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)不足和(he)發(fa)熱等問題，并(bing)能根據不同(tong)電(dian)(dian)(dian)(dian)(dian)(dian)池選擇不同(tong)的充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)方案。而且具(ju)有(you)通(tong)用(yong)性。能實時(shi)(shi)檢測并(bing)顯(xian)示充(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)(shi)間(jian)和(he)蓄電(dian)(dian)(dian)(dian)(dian)(dian)池溫度等參數。由于電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)具(ju)有(you)內外環控(kong)制(zhi)，符合最(zui)(zui)優控(kong)制(zhi)規律。最(zui)(zui)具(ju)有(you)過(guo)(guo)流、過(guo)(guo)壓和(he)超溫保(bao)護(hu)功能，同(tong)時(shi)(shi)由于UC3842采用(yong)穩壓供電(dian)(dian)(dian)(dian)(dian)(dian)，因(yin)此，不但(dan)諧波污染程(cheng)度低，原(yuan)副邊電(dian)(dian)(dian)(dian)(dian)(dian)氣隔離(li)安全(quan)可靠，同(tong)時(shi)(shi)還可根據負載(zai)情況通(tong)過(guo)(guo)單片機來進行控(kong)制(zhi)，并(bing)可實現跳周(zhou)期模式工作。故(gu)可提高電(dian)(dian)(dian)(dian)(dian)(dian)源的效(xiao)率(lv)。