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很寬的(de)溫(wen)度(du)范圍內精確充電， 延長蓄電池(chi)的(de)使用壽命(ming); 可(ke)以(yi)消(xiao)除充電過程(cheng)中的(de)極化現(xian)象， 提高充電效率。

　　1 UC3906的結構及(ji)工作原(yuan)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(de)輸出電壓與電流(liu)(liu)。電壓和(he)電流(liu)(liu)檢測(ce)比較器(qi)檢測(ce)蓄電池的(de)充電狀態， 并控(kong)制狀態邏(luo)輯電路的(de)輸入信號。

　　

 

　　圖1 UC3906內部結構(gou)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，避免(mian)了因充電(dian)電(dian)流過大而損(sun)壞蓄電(dian)池。

　　蓄(xu)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)與(yu)環(huan)(huan)境(jing)溫(wen)(wen)度(du)(du)有(you)(you)關， 溫(wen)(wen)度(du)(du)每升高1 ℃， 蓄(xu)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)單(dan)格電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)下降4 mV, 也(ye)就是說蓄(xu)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)的(de)(de)(de)(de)(de)浮充電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)有(you)(you)負的(de)(de)(de)(de)(de)溫(wen)(wen)度(du)(du)系(xi)數(shu)- 4 mV/℃。普(pu)通充電(dian)(dian)(dian)(dian)(dian)(dian)器如果在25 ℃處(chu)于最佳工作狀態， 在環(huan)(huan)境(jing)溫(wen)(wen)度(du)(du)為0 ℃就會(hui)(hui)充電(dian)(dian)(dian)(dian)(dian)(dian)不(bu)足， 而在溫(wen)(wen)度(du)(du)為45 ℃時(shi)可(ke)(ke)能因嚴重過充電(dian)(dian)(dian)(dian)(dian)(dian)而縮短蓄(xu)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)的(de)(de)(de)(de)(de)使用(yong)壽命。而UC3906的(de)(de)(de)(de)(de)最重要的(de)(de)(de)(de)(de)特(te)性(xing)(xing)是具有(you)(you)精確的(de)(de)(de)(de)(de)基準電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)， 其基準電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)的(de)(de)(de)(de)(de)大小隨環(huan)(huan)境(jing)溫(wen)(wen)度(du)(du)而變化(hua)， 且(qie)變化(hua)規律與(yu)鉛(qian)酸蓄(xu)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)的(de)(de)(de)(de)(de)溫(wen)(wen)度(du)(du)特(te)性(xing)(xing)一(yi)致。同時(shi)芯片只需(xu)1.7 mA的(de)(de)(de)(de)(de)輸入電(dian)(dian)(dian)(dian)(dian)(dian)流就可(ke)(ke)工作， 這樣可(ke)(ke)以(yi)盡(jin)量減小芯片的(de)(de)(de)(de)(de)功耗(hao)， 實現對環(huan)(huan)境(jing)溫(wen)(wen)度(du)(du)的(de)(de)(de)(de)(de)準確檢(jian)測。在0~70 ℃溫(wen)(wen)度(du)(du)范(fan)圍內可(ke)(ke)以(yi)保證蓄(xu)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)既充足電(dian)(dian)(dian)(dian)(dian)(dian)又不(bu)會(hui)(hui)出現過充電(dian)(dian)(dian)(dian)(dian)(dian)現象(xiang)， 完全滿足蓄(xu)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充電(dian)(dian)(dian)(dian)(dian)(dian)需(xu)要。

　　UC3906可構成雙電平浮充充電器， 充(chong)(chong)電(dian)(dian)過程分為3個充(chong)(chong)電(dian)(dian)狀(zhuang)態(tai)(tai)， 如圖(tu)2所(suo)示(shi)： 大電(dian)(dian)流恒(heng)流充(chong)(chong)電(dian)(dian)狀(zhuang)態(tai)(tai)， 高電(dian)(dian)壓(ya)過充(chong)(chong)電(dian)(dian)狀(zhuang)態(tai)(tai)和低電(dian)(dian)壓(ya)恒(heng)壓(ya)浮(fu)充(chong)(chong)狀(zhuang)態(tai)(tai)。

　　

 

　　圖2 雙電(dian)平浮充充電(dian)狀態曲線

　　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% ,充電器輸出電壓下降(jiang)到較(jiao)低的浮充(chong)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。充電器主電路由功率(lv)MOSFET ( IRF9503) 、續流二(er)極管( UES2402) 和(he)濾(lv)波電感( 130 μH) 等(deng)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)壓電(dian)流控(kong)制回路與電(dian)池充電(dian)邏(luo)輯(ji)狀態電(dian)路

 

　　對小容量蓄電(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)電(dian)(dian)(dian)器可采用線性串聯(lian)調整管來控(kong)(kong)制(zhi)充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流， 而(er)對于(yu)開關型充(chong)(chong)電(dian)(dian)(dian)器， UC3906鉛酸蓄電(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)電(dian)(dian)(dian)控(kong)(kong)制(zhi)集成電(dian)(dian)(dian)路具有(you)充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)壓控(kong)(kong)制(zhi)和充(chong)(chong)電(dian)(dian)(dian)邏輯狀態控(kong)(kong)制(zhi)的功能， 并(bing)能提供充(chong)(chong)電(dian)(dian)(dian)的溫度(du)補償(chang)控(kong)(kong)制(zhi)功能。

　　蓄(xu)電(dian)池兩端的分(fen)壓(ya)(ya)電(dian)阻監控(kong)蓄(xu)電(dian)池電(dian)壓(ya)(ya)， 分(fen)壓(ya)(ya)電(dian)阻的阻值確定浮充(chong)(chong)(chong)電(dian)壓(ya)(ya)、過充(chong)(chong)(chong)電(dian)壓(ya)(ya)和涓流(liu)(liu)充(chong)(chong)(chong)電(dian)門(men)限(xian)電(dian)壓(ya)(ya)。差動(dong)電(dian)流(liu)(liu)取(qu)樣比(bi)較器產生過充(chong)(chong)(chong)電(dian)狀態的轉換信(xin)號， 電(dian)壓(ya)(ya)放(fang)大器放(fang)大補償電(dian)壓(ya)(ya)回路的信(xin)號。

　　在溫度為(wei)25 ℃， Uref值為(wei)2.3 V時：

　　過充電壓：

　　

 

　　浮充電壓：

　　

 

　　過充轉(zhuan)換電壓：U12=0.95Uoc=28.03 V

　　浮(fu)充轉換電壓：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(liu)源控制回路

　　輸入電(dian)(dian)壓(ya)(ya)( 35 /50 V) 經10 kΩ電(dian)(dian)阻與1N4744穩壓(ya)(ya)管組成(cheng)的穩壓(ya)(ya)電(dian)(dian)路(lu)穩壓(ya)(ya)后， 又(you)經TIP31晶體管射隨器輸出(chu)+14 V電(dian)(dian)壓(ya)(ya)， 作為控制(zhi)電(dian)(dian)路(lu)的電(dian)(dian)源電(dian)(dian)壓(ya)(ya)。

　　PWM頻率(lv)設定為100 kHz, 以減(jian)小輸(shu)出(chu)濾波器的體積， 蓄電(dian)池(chi)充電(dian)電(dian)流從0.1 Ω/5 W電(dian)阻上取樣， 差動放大增益為5。

　　開(kai)(kai)(kai)關型電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)源控制(zhi)回(hui)(hui)路(lu)的(de)(de)(de)性能(neng)對(dui)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)狀(zhuang)態(tai)控制(zhi)轉換有很(hen)大(da)的(de)(de)(de)影響， 在(zai)(zai)大(da)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)快速充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)狀(zhuang)態(tai)下(xia)(xia)(xia)， 充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器要(yao)能(neng)提供最(zui)大(da)的(de)(de)(de)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu); 在(zai)(zai)浮充(chong)(chong)狀(zhuang)態(tai)下(xia)(xia)(xia)， 充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器輸(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)很(hen)小(xiao)。因此， 充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)控制(zhi)回(hui)(hui)路(lu)的(de)(de)(de)增益變化范圍(wei)應大(da)于(yu)60 db, 采(cai)用(yong)普通的(de)(de)(de)峰值電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)反饋(kui)很(hen)難滿足要(yao)求， 24 V20 Ah鉛酸蓄電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池開(kai)(kai)(kai)關型充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器采(cai)用(yong)平均電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)反饋(kui)回(hui)(hui)路(lu)見圖4.它比峰值電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)反饋(kui)控制(zhi)相對(dui)復雜， 利用(yong)平均電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)反饋(kui)控制(zhi)回(hui)(hui)路(lu)可(ke)以使充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)在(zai)(zai)以下(xia)(xia)(xia)幾(ji)方(fang)面有所改進： ①由(you)于(yu)誤差放大(da)在(zai)(zai)較低工作頻率(lv)范圍(wei)內(nei)的(de)(de)(de)高(gao)增益， 從而(er)使閉環電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)的(de)(de)(de)控制(zhi)精度得到了提高(gao); ②在(zai)(zai)大(da)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)工作狀(zhuang)態(tai)下(xia)(xia)(xia)， 當(dang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)感電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)不連續時(shi)， 可(ke)以改善大(da)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)輸(shu)出(chu)級的(de)(de)(de)非線性; ③可(ke)以提高(gao)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)在(zai)(zai)很(hen)小(xiao)的(de)(de)(de)脈沖(chong)占(zhan)空比工作條件下(xia)(xia)(xia)的(de)(de)(de)抗(kang)開(kai)(kai)(kai)關峰值噪聲的(de)(de)(de)能(neng)力。

　　

 

　　圖4 平均電流反饋(kui)電路圖

　　電(dian)流控(kong)制(zhi)回(hui)路(lu)(lu)選用(yong)UC3823PWM控(kong)制(zhi)器， 因為它(ta)在(zai)非常小的(de)脈(mo)沖占(zhan)空比(bi)到100%的(de)脈(mo)沖占(zhan)空比(bi)的(de)變化范(fan)圍內能夠線性工作(zuo); UC3823PWM控(kong)制(zhi)器的(de)帶(dai)寬和電(dian)路(lu)(lu)結構完全(quan)滿(man)足平均(jun)電(dian)流控(kong)制(zhi)回(hui)路(lu)(lu)的(de)要(yao)求(qiu); UC3823PWM控(kong)制(zhi)器輸出驅動(dong)(dong)級與開關(guan)電(dian)流源(yuan)輸出功率級連接(jie)簡單。運放當作(zuo)差動(dong)(dong)放大器使用(yong)，用(yong)以檢(jian)測開關(guan)電(dian)流源(yuan)的(de)輸出電(dian)流， 并把該電(dian)流信號變換為適(shi)當的(de)電(dian)壓信號。

　　2.3 功率輸出級

　　功率輸出級采用降(jiang)壓(ya)(ya)式開(kai)關(guan)電(dian)(dian)(dian)流(liu)源(yuan)。為了簡化(hua)UC3823的高端驅動電(dian)(dian)(dian)路， 輸出開(kai)關(guan)管采用直(zhi)接(jie)耦合P溝道MOSFET.流(liu)入(ru)(ru)MOSFET的開(kai)關(guan)電(dian)(dian)(dian)流(liu)提供柵(zha)(zha)極(ji)電(dian)(dian)(dian)荷(he)(he)， 使MOSFET導通， 接(jie)在柵(zha)(zha)極(ji)與源(yuan)極(ji)的穩壓(ya)(ya)管將柵(zha)(zha)極(ji)電(dian)(dian)(dian)壓(ya)(ya)限制在12 V.PNP管的作用是釋放柵(zha)(zha)極(ji)電(dian)(dian)(dian)荷(he)(he)， 從而使MOSFET加速關(guan)斷(duan)。在續(xu)流(liu)二(er)極(ji)管兩(liang)端加入(ru)(ru)RC緩沖(chong)器(qi)， 可以(yi)抑制電(dian)(dian)(dian)路寄生參數引(yin)起(qi)的高頻(pin)自激振(zhen)蕩。在輸出電(dian)(dian)(dian)路中(zhong)加入(ru)(ru)整流(liu)管， 可以(yi)避免在電(dian)(dian)(dian)源(yuan)中(zhong)斷(duan)后蓄電(dian)(dian)(dian)池組對(dui)充電(dian)(dian)(dian)器(qi)放電(dian)(dian)(dian)。

　　1) UC3906內部基準電(dian)(dian)壓的(de)溫(wen)度系數與鉛酸蓄(xu)(xu)電(dian)(dian)池的(de)溫(wen)度系數相同， 從而保(bao)證了蓄(xu)(xu)電(dian)(dian)池在較寬的(de)溫(wen)度范圍內實現蓄(xu)(xu)電(dian)(dian)池的(de)精確快速充(chong)電(dian)(dian)， 且不會過充(chong)影響蓄(xu)(xu)電(dian)(dian)池壽(shou)命。

　　2) UC3823PWM控制器在(zai)非(fei)常小的(de)脈沖占空比到100%的(de)脈沖占空比的(de)變(bian)化范圍內能夠(gou)線性工(gong)作;UC3823PWM控制器的(de)帶寬和(he)電路(lu)結構完全滿(man)足平均電流控制回路(lu)的(de)要求。