設計了一種基于UC3906與UC3823的免維護鉛酸蓄電池開關型雙電平智能充電器， 這種充電器可保證蓄電池在(zai)很(hen)寬的溫度范圍內(nei)精確充(chong)電(dian)， 延(yan)長蓄電(dian)池的使(shi)用壽命; 可以消除充(chong)電(dian)過程中的極化現象， 提高充(chong)電(dian)效率。

　　1 UC3906的結(jie)構及工作原理。

　　UC3906內部框圖如圖1所示，該芯片內含有獨立的電壓控制電路和限流放大器， 它可以控制芯片內的驅動器， 驅動器提供的輸出電流達25 mA, 可直接驅動外部串聯的調整管， 從而調整充電器的輸出電(dian)(dian)(dian)(dian)壓與電(dian)(dian)(dian)(dian)流。電(dian)(dian)(dian)(dian)壓和電(dian)(dian)(dian)(dian)流檢(jian)測(ce)比較器檢(jian)測(ce)蓄電(dian)(dian)(dian)(dian)池的充電(dian)(dian)(dian)(dian)狀態， 并控(kong)制狀態邏輯電(dian)(dian)(dian)(dian)路的輸入(ru)信號。

　　

 

　　圖1 UC3906內部結構框圖

　　當蓄電池電壓或電流過低時， 充電起動比較器控制充電器進入涓流充電狀態， 當驅動器截止時，該比較器還能輸出25 mA涓流充電電流。這樣， 當蓄電池短路或反接時， 充電器只能以小電流充電，避(bi)免了因充電電流過(guo)大而損壞蓄電池。

　　蓄(xu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓與環境溫(wen)度(du)(du)有關， 溫(wen)度(du)(du)每升高(gao)1 ℃， 蓄(xu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)單(dan)格電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓下降4 mV, 也(ye)就(jiu)是(shi)說蓄(xu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)的(de)(de)(de)浮(fu)充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓有負的(de)(de)(de)溫(wen)度(du)(du)系數- 4 mV/℃。普通充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)器如果在(zai)25 ℃處于(yu)最(zui)佳工作(zuo)狀態， 在(zai)環境溫(wen)度(du)(du)為0 ℃就(jiu)會充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)不(bu)足(zu)， 而(er)(er)在(zai)溫(wen)度(du)(du)為45 ℃時可(ke)能因嚴重過(guo)充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)而(er)(er)縮短蓄(xu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)的(de)(de)(de)使用壽命。而(er)(er)UC3906的(de)(de)(de)最(zui)重要的(de)(de)(de)特(te)性是(shi)具有精確(que)(que)的(de)(de)(de)基準(zhun)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓， 其基準(zhun)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓的(de)(de)(de)大小(xiao)隨環境溫(wen)度(du)(du)而(er)(er)變化(hua)， 且(qie)變化(hua)規(gui)律與鉛酸蓄(xu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)的(de)(de)(de)溫(wen)度(du)(du)特(te)性一(yi)致。同時芯(xin)片(pian)只需(xu)1.7 mA的(de)(de)(de)輸入電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流就(jiu)可(ke)工作(zuo)， 這樣(yang)可(ke)以盡(jin)量減小(xiao)芯(xin)片(pian)的(de)(de)(de)功耗， 實現對環境溫(wen)度(du)(du)的(de)(de)(de)準(zhun)確(que)(que)檢測。在(zai)0~70 ℃溫(wen)度(du)(du)范圍內可(ke)以保證蓄(xu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)既充足(zu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)又不(bu)會出(chu)現過(guo)充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)現象， 完(wan)全滿足(zu)蓄(xu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)需(xu)要。

　　UC3906可構成雙電平浮充充電器， 充(chong)電(dian)(dian)過程(cheng)分為3個充(chong)電(dian)(dian)狀態(tai)， 如(ru)圖2所示： 大電(dian)(dian)流(liu)恒(heng)流(liu)充(chong)電(dian)(dian)狀態(tai)， 高電(dian)(dian)壓(ya)過充(chong)電(dian)(dian)狀態(tai)和(he)低電(dian)(dian)壓(ya)恒(heng)壓(ya)浮充(chong)狀態(tai)。

　　

 

　　圖2 雙電平浮充(chong)充(chong)電狀態曲線(xian)

　　充電過程從大電流恒流充電狀態開始， 在這種狀態下充電器輸出恒定的充電電流Imax, 同時充電器連續監控蓄電池組的兩端電壓， 當蓄電池的電壓達到轉換電壓U12時， 其電量已恢復到放電容量的70%~90%, 充電器轉入過充電狀態。在此狀態下， 充電器輸出電壓升高到Uoc; 由于充電器輸出電壓保持恒定不變， 所以充電電流連續下降， 當電流下降到Ioct時， 蓄電池的容量已達到額定容量的100% ,充電器輸出電壓下(xia)降到較低(di)的浮充電壓UF.

　　2 電路設計。

　　對于較大容量的鉛酸蓄電池， 為了提高充電效率， 通常選用開關型充電器。設計的24V20Ah鉛酸蓄電池開關型充電器實際電路見圖3, 在該電路中，用兩只專用集成電路UC3906與UC3823和一只通用運放即可完成全部控制功能。充電器主電(dian)路由(you)功率MOSFET ( IRF9503) 、續流二(er)極管( UES2402) 和濾波電(dian)感( 130 μH) 等元件組(zu)成。

　　

 

　　圖3 24 V 20 Ah鉛酸蓄電池開關型雙電平浮充智能充電器電路圖

2.1 電(dian)壓(ya)電(dian)流控制(zhi)回路與電(dian)池充電(dian)邏輯狀態電(dian)路

 

　　對小(xiao)容量蓄(xu)(xu)電(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)器可采用(yong)線性(xing)串(chuan)聯(lian)調整管(guan)來控制充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流， 而對于(yu)開(kai)關型充(chong)電(dian)(dian)(dian)器， UC3906鉛酸蓄(xu)(xu)電(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)控制集(ji)成電(dian)(dian)(dian)路具有(you)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)壓控制和充(chong)電(dian)(dian)(dian)邏(luo)輯狀(zhuang)態控制的(de)功(gong)能(neng)(neng)(neng)， 并能(neng)(neng)(neng)提供充(chong)電(dian)(dian)(dian)的(de)溫度(du)補(bu)償(chang)控制功(gong)能(neng)(neng)(neng)。

　　蓄電(dian)(dian)(dian)(dian)池(chi)兩端(duan)的(de)分(fen)壓(ya)電(dian)(dian)(dian)(dian)阻(zu)監控蓄電(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)壓(ya)， 分(fen)壓(ya)電(dian)(dian)(dian)(dian)阻(zu)的(de)阻(zu)值(zhi)確定浮充(chong)電(dian)(dian)(dian)(dian)壓(ya)、過(guo)充(chong)電(dian)(dian)(dian)(dian)壓(ya)和涓流充(chong)電(dian)(dian)(dian)(dian)門(men)限電(dian)(dian)(dian)(dian)壓(ya)。差動(dong)電(dian)(dian)(dian)(dian)流取樣(yang)比較器(qi)產生過(guo)充(chong)電(dian)(dian)(dian)(dian)狀態(tai)的(de)轉換信號， 電(dian)(dian)(dian)(dian)壓(ya)放大(da)器(qi)放大(da)補償電(dian)(dian)(dian)(dian)壓(ya)回路的(de)信號。

　　在溫度(du)為(wei)25 ℃， Uref值為(wei)2.3 V時：

　　過充電壓：

　　

 

　　浮充電壓：

　　

 

　　過充(chong)轉換電壓：U12=0.95Uoc=28.03 V

　　浮充轉換(huan)電壓：U13=0.9UF=24.8 V

　　最大充電電流：

　　

 

　　過充終止電流：

　　

 

　　2.2 開關型電流源控制(zhi)回路

　　輸入電(dian)壓(ya)( 35 /50 V) 經10 kΩ電(dian)阻與1N4744穩(wen)(wen)壓(ya)管組成的穩(wen)(wen)壓(ya)電(dian)路穩(wen)(wen)壓(ya)后， 又經TIP31晶體管射隨器輸出+14 V電(dian)壓(ya)， 作為控制電(dian)路的電(dian)源電(dian)壓(ya)。

　　PWM頻率設定(ding)為100 kHz, 以減小輸出(chu)濾波器的(de)體積， 蓄電池充電電流從0.1 Ω/5 W電阻上取(qu)樣(yang)， 差動放大增(zeng)益為5。

　　開(kai)關型電(dian)(dian)流(liu)(liu)(liu)源控(kong)(kong)(kong)制回路(lu)的(de)性(xing)能對充電(dian)(dian)狀態(tai)控(kong)(kong)(kong)制轉換有很(hen)大(da)的(de)影響， 在(zai)大(da)電(dian)(dian)流(liu)(liu)(liu)快速(su)充電(dian)(dian)狀態(tai)下， 充電(dian)(dian)器(qi)要能提(ti)供最大(da)的(de)充電(dian)(dian)電(dian)(dian)流(liu)(liu)(liu); 在(zai)浮充狀態(tai)下， 充電(dian)(dian)器(qi)輸出(chu)電(dian)(dian)流(liu)(liu)(liu)很(hen)小。因(yin)此， 充電(dian)(dian)器(qi)電(dian)(dian)流(liu)(liu)(liu)控(kong)(kong)(kong)制回路(lu)的(de)增(zeng)益變化范(fan)圍應大(da)于(yu)60 db, 采(cai)(cai)用(yong)普通的(de)峰(feng)值(zhi)電(dian)(dian)流(liu)(liu)(liu)反饋(kui)(kui)很(hen)難滿足要求， 24 V20 Ah鉛(qian)酸蓄電(dian)(dian)池開(kai)關型充電(dian)(dian)器(qi)采(cai)(cai)用(yong)平均(jun)(jun)電(dian)(dian)流(liu)(liu)(liu)反饋(kui)(kui)回路(lu)見圖4.它(ta)比(bi)峰(feng)值(zhi)電(dian)(dian)流(liu)(liu)(liu)反饋(kui)(kui)控(kong)(kong)(kong)制相對復雜， 利用(yong)平均(jun)(jun)電(dian)(dian)流(liu)(liu)(liu)反饋(kui)(kui)控(kong)(kong)(kong)制回路(lu)可以(yi)使充電(dian)(dian)器(qi)電(dian)(dian)路(lu)在(zai)以(yi)下幾方(fang)面有所改進： ①由于(yu)誤差放大(da)在(zai)較(jiao)低工(gong)作(zuo)頻率范(fan)圍內的(de)高(gao)增(zeng)益， 從而使閉環(huan)電(dian)(dian)流(liu)(liu)(liu)的(de)控(kong)(kong)(kong)制精度得到(dao)了提(ti)高(gao); ②在(zai)大(da)電(dian)(dian)流(liu)(liu)(liu)充電(dian)(dian)的(de)工(gong)作(zuo)狀態(tai)下， 當電(dian)(dian)感電(dian)(dian)流(liu)(liu)(liu)不(bu)連續時(shi)， 可以(yi)改善大(da)電(dian)(dian)流(liu)(liu)(liu)輸出(chu)級的(de)非線性(xing); ③可以(yi)提(ti)高(gao)充電(dian)(dian)器(qi)電(dian)(dian)路(lu)在(zai)很(hen)小的(de)脈沖占空比(bi)工(gong)作(zuo)條件下的(de)抗開(kai)關峰(feng)值(zhi)噪聲的(de)能力。

　　

 

　　圖4 平均電(dian)流反饋電(dian)路圖

　　電(dian)(dian)(dian)流控(kong)(kong)制(zhi)回路(lu)選用UC3823PWM控(kong)(kong)制(zhi)器， 因為它在非常小的(de)脈(mo)(mo)沖(chong)占(zhan)(zhan)空(kong)比(bi)(bi)到100%的(de)脈(mo)(mo)沖(chong)占(zhan)(zhan)空(kong)比(bi)(bi)的(de)變化范圍內能(neng)夠線性工(gong)作; UC3823PWM控(kong)(kong)制(zhi)器的(de)帶(dai)寬和(he)電(dian)(dian)(dian)路(lu)結構(gou)完全(quan)滿足平均(jun)電(dian)(dian)(dian)流控(kong)(kong)制(zhi)回路(lu)的(de)要(yao)求(qiu); UC3823PWM控(kong)(kong)制(zhi)器輸(shu)(shu)出驅動(dong)級與開關電(dian)(dian)(dian)流源(yuan)輸(shu)(shu)出功率(lv)級連接簡(jian)單(dan)。運放當作差動(dong)放大(da)器使用，用以檢測開關電(dian)(dian)(dian)流源(yuan)的(de)輸(shu)(shu)出電(dian)(dian)(dian)流， 并把(ba)該電(dian)(dian)(dian)流信號變換為適當的(de)電(dian)(dian)(dian)壓信號。

　　2.3 功率輸出級

　　功率輸(shu)出(chu)級采(cai)用降(jiang)壓(ya)式開關電(dian)流源。為了簡化UC3823的高端驅(qu)動(dong)電(dian)路， 輸(shu)出(chu)開關管(guan)采(cai)用直(zhi)接耦合(he)P溝道MOSFET.流入MOSFET的開關電(dian)流提供柵(zha)極(ji)(ji)電(dian)荷， 使(shi)MOSFET導通， 接在柵(zha)極(ji)(ji)與源極(ji)(ji)的穩壓(ya)管(guan)將柵(zha)極(ji)(ji)電(dian)壓(ya)限制在12 V.PNP管(guan)的作用是釋放柵(zha)極(ji)(ji)電(dian)荷， 從而使(shi)MOSFET加(jia)速關斷(duan)(duan)。在續(xu)流二極(ji)(ji)管(guan)兩端加(jia)入RC緩沖器(qi)(qi)， 可(ke)以(yi)(yi)抑制電(dian)路寄生參數引起的高頻自激振蕩(dang)。在輸(shu)出(chu)電(dian)路中(zhong)加(jia)入整流管(guan)， 可(ke)以(yi)(yi)避免在電(dian)源中(zhong)斷(duan)(duan)后蓄電(dian)池組對充電(dian)器(qi)(qi)放電(dian)。

　　1) UC3906內部(bu)基準電(dian)(dian)壓的(de)溫(wen)度系(xi)數(shu)與鉛(qian)酸蓄(xu)(xu)電(dian)(dian)池(chi)的(de)溫(wen)度系(xi)數(shu)相同， 從(cong)而保證了蓄(xu)(xu)電(dian)(dian)池(chi)在較寬的(de)溫(wen)度范(fan)圍內實(shi)現蓄(xu)(xu)電(dian)(dian)池(chi)的(de)精(jing)確(que)快速充(chong)(chong)電(dian)(dian)， 且不會過充(chong)(chong)影響蓄(xu)(xu)電(dian)(dian)池(chi)壽(shou)命。

　　2) UC3823PWM控(kong)制器在非常(chang)小(xiao)的(de)(de)脈(mo)(mo)沖占空比到100%的(de)(de)脈(mo)(mo)沖占空比的(de)(de)變化范圍(wei)內能夠線(xian)性工作(zuo);UC3823PWM控(kong)制器的(de)(de)帶(dai)寬和電路結構完(wan)全滿足平均電流控(kong)制回路的(de)(de)要(yao)求。