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(kuan)的(de)溫度范(fan)圍內精確充(chong)電(dian)， 延長蓄(xu)電(dian)池的(de)使(shi)用壽命; 可以消除充(chong)電(dian)過程(cheng)中(zhong)的(de)極(ji)化(hua)現象， 提高充(chong)電(dian)效率(lv)。

　　1 UC3906的結構及工作原理。

　　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(shu)出(chu)電(dian)(dian)壓(ya)(ya)與電(dian)(dian)流。電(dian)(dian)壓(ya)(ya)和電(dian)(dian)流檢測比較(jiao)器檢測蓄電(dian)(dian)池的充電(dian)(dian)狀(zhuang)態， 并控制狀(zhuang)態邏輯電(dian)(dian)路(lu)的輸(shu)入(ru)信號。

　　

 

　　圖1 UC3906內(nei)部(bu)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，避免了(le)因(yin)充電(dian)電(dian)流過大(da)而損壞蓄(xu)電(dian)池。

　　蓄(xu)(xu)電(dian)(dian)(dian)(dian)池(chi)的(de)(de)電(dian)(dian)(dian)(dian)壓(ya)(ya)與環(huan)境(jing)(jing)(jing)溫(wen)(wen)(wen)度(du)(du)有(you)關， 溫(wen)(wen)(wen)度(du)(du)每升高(gao)1 ℃， 蓄(xu)(xu)電(dian)(dian)(dian)(dian)池(chi)單(dan)格電(dian)(dian)(dian)(dian)壓(ya)(ya)下降4 mV, 也就是說(shuo)蓄(xu)(xu)電(dian)(dian)(dian)(dian)池(chi)的(de)(de)浮充(chong)電(dian)(dian)(dian)(dian)壓(ya)(ya)有(you)負(fu)的(de)(de)溫(wen)(wen)(wen)度(du)(du)系數- 4 mV/℃。普(pu)通充(chong)電(dian)(dian)(dian)(dian)器如果在25 ℃處于最(zui)佳(jia)工(gong)作狀態， 在環(huan)境(jing)(jing)(jing)溫(wen)(wen)(wen)度(du)(du)為(wei)0 ℃就會充(chong)電(dian)(dian)(dian)(dian)不足(zu)， 而在溫(wen)(wen)(wen)度(du)(du)為(wei)45 ℃時(shi)可能因嚴(yan)重(zhong)(zhong)過充(chong)電(dian)(dian)(dian)(dian)而縮(suo)短蓄(xu)(xu)電(dian)(dian)(dian)(dian)池(chi)的(de)(de)使用壽命(ming)。而UC3906的(de)(de)最(zui)重(zhong)(zhong)要(yao)的(de)(de)特性是具有(you)精確的(de)(de)基準電(dian)(dian)(dian)(dian)壓(ya)(ya)， 其基準電(dian)(dian)(dian)(dian)壓(ya)(ya)的(de)(de)大小(xiao)隨環(huan)境(jing)(jing)(jing)溫(wen)(wen)(wen)度(du)(du)而變化， 且變化規律與鉛酸蓄(xu)(xu)電(dian)(dian)(dian)(dian)池(chi)的(de)(de)溫(wen)(wen)(wen)度(du)(du)特性一致。同時(shi)芯片(pian)只需1.7 mA的(de)(de)輸入電(dian)(dian)(dian)(dian)流就可工(gong)作， 這樣可以盡量減小(xiao)芯片(pian)的(de)(de)功耗， 實現對(dui)環(huan)境(jing)(jing)(jing)溫(wen)(wen)(wen)度(du)(du)的(de)(de)準確檢(jian)測。在0~70 ℃溫(wen)(wen)(wen)度(du)(du)范圍內可以保證蓄(xu)(xu)電(dian)(dian)(dian)(dian)池(chi)既充(chong)足(zu)電(dian)(dian)(dian)(dian)又不會出現過充(chong)電(dian)(dian)(dian)(dian)現象， 完(wan)全滿足(zu)蓄(xu)(xu)電(dian)(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)(dian)需要(yao)。

　　UC3906可構成雙電平浮充充電器， 充(chong)電(dian)過程分為3個充(chong)電(dian)狀(zhuang)態(tai)， 如圖2所示： 大電(dian)流(liu)恒流(liu)充(chong)電(dian)狀(zhuang)態(tai)， 高電(dian)壓(ya)過充(chong)電(dian)狀(zhuang)態(tai)和(he)低電(dian)壓(ya)恒壓(ya)浮充(chong)狀(zhuang)態(tai)。

　　

 

　　圖2 雙電平浮充充電狀態曲線(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(ya)下降到較(jiao)低的浮充電壓(ya)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MOSFET ( IRF9503) 、續流二(er)極管( UES2402) 和濾波電感( 130 μH) 等元件組成(cheng)。

　　

 

　　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(liu)控制回(hui)路(lu)(lu)與電(dian)池充電(dian)邏輯狀態電(dian)路(lu)(lu)

 

　　對(dui)小容(rong)量蓄電(dian)(dian)池(chi)充(chong)電(dian)(dian)器可采(cai)用(yong)線性(xing)串(chuan)聯調整管來(lai)控制(zhi)(zhi)(zhi)充(chong)電(dian)(dian)電(dian)(dian)流， 而(er)對(dui)于開關型(xing)充(chong)電(dian)(dian)器， UC3906鉛酸蓄電(dian)(dian)池(chi)充(chong)電(dian)(dian)控制(zhi)(zhi)(zhi)集成電(dian)(dian)路具有充(chong)電(dian)(dian)電(dian)(dian)壓控制(zhi)(zhi)(zhi)和充(chong)電(dian)(dian)邏輯狀態(tai)控制(zhi)(zhi)(zhi)的(de)功能， 并能提供充(chong)電(dian)(dian)的(de)溫度補償(chang)控制(zhi)(zhi)(zhi)功能。

　　蓄(xu)電(dian)(dian)(dian)池兩端的(de)分壓(ya)(ya)電(dian)(dian)(dian)阻(zu)監控蓄(xu)電(dian)(dian)(dian)池電(dian)(dian)(dian)壓(ya)(ya)， 分壓(ya)(ya)電(dian)(dian)(dian)阻(zu)的(de)阻(zu)值確定(ding)浮充(chong)電(dian)(dian)(dian)壓(ya)(ya)、過充(chong)電(dian)(dian)(dian)壓(ya)(ya)和涓流充(chong)電(dian)(dian)(dian)門限電(dian)(dian)(dian)壓(ya)(ya)。差動電(dian)(dian)(dian)流取樣比較器產生過充(chong)電(dian)(dian)(dian)狀態(tai)的(de)轉換信號(hao)， 電(dian)(dian)(dian)壓(ya)(ya)放大器放大補(bu)償電(dian)(dian)(dian)壓(ya)(ya)回路的(de)信號(hao)。

　　在溫度為25 ℃， Uref值(zhi)為2.3 V時：

　　過充電壓：

　　

 

　　浮充電壓：

　　

 

　　過(guo)充轉換電壓(ya)：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(guan)型電流源控制回路

　　輸入電(dian)壓( 35 /50 V) 經(jing)10 kΩ電(dian)阻與1N4744穩(wen)壓管(guan)組成的(de)(de)穩(wen)壓電(dian)路(lu)穩(wen)壓后(hou)， 又經(jing)TIP31晶體管(guan)射隨器輸出+14 V電(dian)壓， 作為控制電(dian)路(lu)的(de)(de)電(dian)源電(dian)壓。

　　PWM頻(pin)率設定為(wei)100 kHz, 以減(jian)小輸(shu)出濾波器的體積(ji)， 蓄(xu)電(dian)(dian)池充(chong)電(dian)(dian)電(dian)(dian)流從0.1 Ω/5 W電(dian)(dian)阻上取樣， 差(cha)動放大增益(yi)為(wei)5。

　　開關型電(dian)(dian)(dian)(dian)流(liu)(liu)源(yuan)控(kong)(kong)制(zhi)(zhi)回(hui)路(lu)的(de)(de)(de)(de)(de)性(xing)能對充(chong)(chong)電(dian)(dian)(dian)(dian)狀(zhuang)態控(kong)(kong)制(zhi)(zhi)轉換有很大(da)的(de)(de)(de)(de)(de)影響(xiang)， 在(zai)大(da)電(dian)(dian)(dian)(dian)流(liu)(liu)快速充(chong)(chong)電(dian)(dian)(dian)(dian)狀(zhuang)態下， 充(chong)(chong)電(dian)(dian)(dian)(dian)器(qi)要能提(ti)供最大(da)的(de)(de)(de)(de)(de)充(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu); 在(zai)浮充(chong)(chong)狀(zhuang)態下， 充(chong)(chong)電(dian)(dian)(dian)(dian)器(qi)輸出電(dian)(dian)(dian)(dian)流(liu)(liu)很小(xiao)。因(yin)此， 充(chong)(chong)電(dian)(dian)(dian)(dian)器(qi)電(dian)(dian)(dian)(dian)流(liu)(liu)控(kong)(kong)制(zhi)(zhi)回(hui)路(lu)的(de)(de)(de)(de)(de)增益(yi)變化(hua)范圍應大(da)于60 db, 采用普(pu)通的(de)(de)(de)(de)(de)峰(feng)值(zhi)電(dian)(dian)(dian)(dian)流(liu)(liu)反(fan)(fan)饋很難(nan)滿足要求， 24 V20 Ah鉛酸蓄電(dian)(dian)(dian)(dian)池開關型充(chong)(chong)電(dian)(dian)(dian)(dian)器(qi)采用平均(jun)電(dian)(dian)(dian)(dian)流(liu)(liu)反(fan)(fan)饋回(hui)路(lu)見圖4.它比峰(feng)值(zhi)電(dian)(dian)(dian)(dian)流(liu)(liu)反(fan)(fan)饋控(kong)(kong)制(zhi)(zhi)相(xiang)對復雜， 利用平均(jun)電(dian)(dian)(dian)(dian)流(liu)(liu)反(fan)(fan)饋控(kong)(kong)制(zhi)(zhi)回(hui)路(lu)可以(yi)(yi)使充(chong)(chong)電(dian)(dian)(dian)(dian)器(qi)電(dian)(dian)(dian)(dian)路(lu)在(zai)以(yi)(yi)下幾方面(mian)有所改進： ①由于誤差(cha)放大(da)在(zai)較低(di)工作(zuo)頻(pin)率范圍內的(de)(de)(de)(de)(de)高(gao)增益(yi)， 從而使閉環電(dian)(dian)(dian)(dian)流(liu)(liu)的(de)(de)(de)(de)(de)控(kong)(kong)制(zhi)(zhi)精度得到了提(ti)高(gao); ②在(zai)大(da)電(dian)(dian)(dian)(dian)流(liu)(liu)充(chong)(chong)電(dian)(dian)(dian)(dian)的(de)(de)(de)(de)(de)工作(zuo)狀(zhuang)態下， 當電(dian)(dian)(dian)(dian)感電(dian)(dian)(dian)(dian)流(liu)(liu)不連續時(shi)， 可以(yi)(yi)改善大(da)電(dian)(dian)(dian)(dian)流(liu)(liu)輸出級的(de)(de)(de)(de)(de)非線性(xing); ③可以(yi)(yi)提(ti)高(gao)充(chong)(chong)電(dian)(dian)(dian)(dian)器(qi)電(dian)(dian)(dian)(dian)路(lu)在(zai)很小(xiao)的(de)(de)(de)(de)(de)脈(mo)沖占空(kong)比工作(zuo)條(tiao)件(jian)下的(de)(de)(de)(de)(de)抗開關峰(feng)值(zhi)噪聲的(de)(de)(de)(de)(de)能力。

　　

 

　　圖(tu)(tu)4 平(ping)均電(dian)流反饋電(dian)路圖(tu)(tu)

　　電(dian)(dian)流控(kong)制(zhi)回(hui)路選用(yong)UC3823PWM控(kong)制(zhi)器， 因為它在非常小(xiao)的脈沖占(zhan)空(kong)比到100%的脈沖占(zhan)空(kong)比的變(bian)化范圍內能(neng)夠線(xian)性工作; UC3823PWM控(kong)制(zhi)器的帶寬和電(dian)(dian)路結構(gou)完全滿足平(ping)均電(dian)(dian)流控(kong)制(zhi)回(hui)路的要求; UC3823PWM控(kong)制(zhi)器輸出驅動級與(yu)開(kai)關電(dian)(dian)流源輸出功率(lv)級連接(jie)簡單。運(yun)放(fang)當作差動放(fang)大器使(shi)用(yong)，用(yong)以檢測開(kai)關電(dian)(dian)流源的輸出電(dian)(dian)流， 并把該電(dian)(dian)流信號變(bian)換(huan)為適(shi)當的電(dian)(dian)壓信號。

　　2.3 功率輸出級

　　功(gong)率輸(shu)(shu)出級采用降壓(ya)式(shi)開關(guan)電(dian)(dian)流源。為(wei)了簡化(hua)UC3823的高端(duan)驅動電(dian)(dian)路(lu)， 輸(shu)(shu)出開關(guan)管采用直(zhi)接耦合P溝道MOSFET.流入(ru)MOSFET的開關(guan)電(dian)(dian)流提(ti)供(gong)柵(zha)極電(dian)(dian)荷， 使MOSFET導通， 接在(zai)柵(zha)極與源極的穩壓(ya)管將柵(zha)極電(dian)(dian)壓(ya)限(xian)制(zhi)在(zai)12 V.PNP管的作用是釋(shi)放柵(zha)極電(dian)(dian)荷， 從而使MOSFET加速關(guan)斷。在(zai)續流二(er)極管兩端(duan)加入(ru)RC緩沖器(qi)， 可以抑制(zhi)電(dian)(dian)路(lu)寄生參(can)數引起的高頻自激振(zhen)蕩(dang)。在(zai)輸(shu)(shu)出電(dian)(dian)路(lu)中(zhong)(zhong)加入(ru)整流管， 可以避免(mian)在(zai)電(dian)(dian)源中(zhong)(zhong)斷后蓄電(dian)(dian)池組對充電(dian)(dian)器(qi)放電(dian)(dian)。

　　1) UC3906內部(bu)基準電(dian)(dian)壓的(de)溫度(du)系(xi)數與鉛酸(suan)蓄電(dian)(dian)池的(de)溫度(du)系(xi)數相同(tong)， 從(cong)而保(bao)證了蓄電(dian)(dian)池在較寬的(de)溫度(du)范圍內實(shi)現(xian)蓄電(dian)(dian)池的(de)精確快速(su)充電(dian)(dian)， 且不會過充影響蓄電(dian)(dian)池壽命。

　　2) UC3823PWM控制器(qi)(qi)在非常小的(de)脈(mo)沖占空(kong)比到(dao)100%的(de)脈(mo)沖占空(kong)比的(de)變化范圍內能夠線(xian)性(xing)工(gong)作;UC3823PWM控制器(qi)(qi)的(de)帶寬和電(dian)路結(jie)構完全滿足(zu)平均電(dian)流控制回路的(de)要(yao)求。