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溫度范圍內精確充電(dian)(dian)， 延長蓄(xu)電(dian)(dian)池的使用壽命; 可(ke)以消除充電(dian)(dian)過程中的極化現(xian)象， 提(ti)高充電(dian)(dian)效率。

　　1 UC3906的結(jie)構及工(gong)作原理(li)。

　　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)出電(dian)壓(ya)與(yu)電(dian)流。電(dian)壓(ya)和電(dian)流檢測(ce)比較器檢測(ce)蓄電(dian)池(chi)的充電(dian)狀態， 并控制狀態邏(luo)輯電(dian)路的輸(shu)入信號。

　　

 

　　圖(tu)1 UC3906內部結(jie)構(gou)框圖(tu)

　　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(chong)電(dian)電(dian)流(liu)過大而損壞蓄電(dian)池。

　　蓄(xu)(xu)電(dian)(dian)池(chi)(chi)的(de)(de)(de)電(dian)(dian)壓(ya)與(yu)環(huan)(huan)境溫(wen)度有關， 溫(wen)度每(mei)升高(gao)1 ℃， 蓄(xu)(xu)電(dian)(dian)池(chi)(chi)單格電(dian)(dian)壓(ya)下降4 mV, 也就(jiu)(jiu)是說蓄(xu)(xu)電(dian)(dian)池(chi)(chi)的(de)(de)(de)浮充(chong)電(dian)(dian)壓(ya)有負的(de)(de)(de)溫(wen)度系(xi)數- 4 mV/℃。普通充(chong)電(dian)(dian)器(qi)如果(guo)在(zai)25 ℃處于最佳工(gong)作(zuo)狀態， 在(zai)環(huan)(huan)境溫(wen)度為0 ℃就(jiu)(jiu)會充(chong)電(dian)(dian)不(bu)足， 而在(zai)溫(wen)度為45 ℃時(shi)可(ke)(ke)能(neng)因(yin)嚴重過充(chong)電(dian)(dian)而縮短蓄(xu)(xu)電(dian)(dian)池(chi)(chi)的(de)(de)(de)使(shi)用壽命。而UC3906的(de)(de)(de)最重要(yao)的(de)(de)(de)特性是具有精(jing)確的(de)(de)(de)基準(zhun)電(dian)(dian)壓(ya)， 其基準(zhun)電(dian)(dian)壓(ya)的(de)(de)(de)大小隨環(huan)(huan)境溫(wen)度而變化， 且變化規律與(yu)鉛(qian)酸蓄(xu)(xu)電(dian)(dian)池(chi)(chi)的(de)(de)(de)溫(wen)度特性一致。同(tong)時(shi)芯(xin)(xin)片只需1.7 mA的(de)(de)(de)輸入電(dian)(dian)流就(jiu)(jiu)可(ke)(ke)工(gong)作(zuo)， 這樣可(ke)(ke)以盡量減小芯(xin)(xin)片的(de)(de)(de)功耗， 實現對環(huan)(huan)境溫(wen)度的(de)(de)(de)準(zhun)確檢測。在(zai)0~70 ℃溫(wen)度范圍內可(ke)(ke)以保(bao)證(zheng)蓄(xu)(xu)電(dian)(dian)池(chi)(chi)既充(chong)足電(dian)(dian)又不(bu)會出現過充(chong)電(dian)(dian)現象， 完(wan)全滿(man)足蓄(xu)(xu)電(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)需要(yao)。

　　UC3906可構成雙電平浮充充電器， 充(chong)電(dian)(dian)(dian)(dian)(dian)過(guo)程(cheng)分為(wei)3個充(chong)電(dian)(dian)(dian)(dian)(dian)狀態， 如圖2所示： 大電(dian)(dian)(dian)(dian)(dian)流恒流充(chong)電(dian)(dian)(dian)(dian)(dian)狀態， 高電(dian)(dian)(dian)(dian)(dian)壓過(guo)充(chong)電(dian)(dian)(dian)(dian)(dian)狀態和低電(dian)(dian)(dian)(dian)(dian)壓恒壓浮充(chong)狀態。

　　

 

　　圖2 雙電平浮充(chong)充(chong)電狀(zhuang)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到較低的(de)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。充電器主電路(lu)由功率(lv)MOSFET ( IRF9503) 、續(xu)流二極(ji)管(guan)( UES2402) 和濾波電感(gan)( 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)流控(kong)制回路(lu)與電(dian)池(chi)充電(dian)邏輯狀態電(dian)路(lu)

 

　　對小容量蓄(xu)電(dian)(dian)(dian)池充(chong)(chong)電(dian)(dian)(dian)器可采用線性串聯調整管來控(kong)(kong)制(zhi)充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)， 而對于開(kai)關型充(chong)(chong)電(dian)(dian)(dian)器， UC3906鉛(qian)酸蓄(xu)電(dian)(dian)(dian)池充(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(he)充(chong)(chong)電(dian)(dian)(dian)邏輯狀態控(kong)(kong)制(zhi)的功(gong)能， 并(bing)能提供充(chong)(chong)電(dian)(dian)(dian)的溫度補(bu)償控(kong)(kong)制(zhi)功(gong)能。

　　蓄電(dian)(dian)(dian)池兩端的分(fen)壓(ya)(ya)電(dian)(dian)(dian)阻(zu)監控蓄電(dian)(dian)(dian)池電(dian)(dian)(dian)壓(ya)(ya)， 分(fen)壓(ya)(ya)電(dian)(dian)(dian)阻(zu)的阻(zu)值確定浮充電(dian)(dian)(dian)壓(ya)(ya)、過充電(dian)(dian)(dian)壓(ya)(ya)和(he)涓流充電(dian)(dian)(dian)門限電(dian)(dian)(dian)壓(ya)(ya)。差(cha)動(dong)電(dian)(dian)(dian)流取樣(yang)比較器(qi)產生過充電(dian)(dian)(dian)狀態的轉換(huan)信號， 電(dian)(dian)(dian)壓(ya)(ya)放(fang)大器(qi)放(fang)大補償電(dian)(dian)(dian)壓(ya)(ya)回路的信號。

　　在溫度為25 ℃， Uref值(zhi)為2.3 V時：

　　過充電壓：

　　

 

　　浮充電壓：

　　

 

　　過充轉換電壓(ya)：U12=0.95Uoc=28.03 V

　　浮充轉換電壓：U13=0.9UF=24.8 V

　　最大充電電流：

　　

 

　　過充終止電流：

　　

 

　　2.2 開(kai)關型(xing)電流源(yuan)控制回(hui)路

　　輸(shu)入電(dian)(dian)(dian)壓(ya)(ya)( 35 /50 V) 經10 kΩ電(dian)(dian)(dian)阻(zu)與1N4744穩壓(ya)(ya)管組成的穩壓(ya)(ya)電(dian)(dian)(dian)路穩壓(ya)(ya)后(hou)， 又經TIP31晶體管射隨器輸(shu)出+14 V電(dian)(dian)(dian)壓(ya)(ya)， 作為控制電(dian)(dian)(dian)路的電(dian)(dian)(dian)源電(dian)(dian)(dian)壓(ya)(ya)。

　　PWM頻率設定為100 kHz, 以(yi)減(jian)小輸出(chu)濾波器(qi)的體積， 蓄電池充電電流從(cong)0.1 Ω/5 W電阻上取樣， 差(cha)動放(fang)大增益為5。

　　開(kai)關型(xing)電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)源控(kong)制(zhi)回(hui)路(lu)的(de)(de)(de)性能(neng)對(dui)充電(dian)(dian)(dian)狀態控(kong)制(zhi)轉(zhuan)換有很大(da)(da)的(de)(de)(de)影(ying)響， 在(zai)大(da)(da)電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)快速充電(dian)(dian)(dian)狀態下(xia)， 充電(dian)(dian)(dian)器(qi)(qi)(qi)要(yao)能(neng)提(ti)供最(zui)大(da)(da)的(de)(de)(de)充電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)(liu)(liu); 在(zai)浮充狀態下(xia)， 充電(dian)(dian)(dian)器(qi)(qi)(qi)輸(shu)出(chu)電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)很小。因此(ci)， 充電(dian)(dian)(dian)器(qi)(qi)(qi)電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)控(kong)制(zhi)回(hui)路(lu)的(de)(de)(de)增益變化范(fan)圍應大(da)(da)于60 db, 采(cai)用(yong)普通的(de)(de)(de)峰值(zhi)電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)反(fan)(fan)(fan)饋(kui)(kui)很難滿足要(yao)求， 24 V20 Ah鉛酸蓄電(dian)(dian)(dian)池開(kai)關型(xing)充電(dian)(dian)(dian)器(qi)(qi)(qi)采(cai)用(yong)平(ping)均電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)反(fan)(fan)(fan)饋(kui)(kui)回(hui)路(lu)見圖4.它(ta)比(bi)峰值(zhi)電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)反(fan)(fan)(fan)饋(kui)(kui)控(kong)制(zhi)相(xiang)對(dui)復雜， 利用(yong)平(ping)均電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)反(fan)(fan)(fan)饋(kui)(kui)控(kong)制(zhi)回(hui)路(lu)可(ke)以(yi)(yi)使(shi)充電(dian)(dian)(dian)器(qi)(qi)(qi)電(dian)(dian)(dian)路(lu)在(zai)以(yi)(yi)下(xia)幾方(fang)面有所改進： ①由于誤差放大(da)(da)在(zai)較低工作頻率范(fan)圍內的(de)(de)(de)高(gao)(gao)增益， 從(cong)而使(shi)閉環電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)的(de)(de)(de)控(kong)制(zhi)精(jing)度得到了提(ti)高(gao)(gao); ②在(zai)大(da)(da)電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)充電(dian)(dian)(dian)的(de)(de)(de)工作狀態下(xia)， 當電(dian)(dian)(dian)感電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)不(bu)連續時(shi)， 可(ke)以(yi)(yi)改善大(da)(da)電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)輸(shu)出(chu)級的(de)(de)(de)非線性; ③可(ke)以(yi)(yi)提(ti)高(gao)(gao)充電(dian)(dian)(dian)器(qi)(qi)(qi)電(dian)(dian)(dian)路(lu)在(zai)很小的(de)(de)(de)脈沖占空比(bi)工作條件(jian)下(xia)的(de)(de)(de)抗開(kai)關峰值(zhi)噪聲的(de)(de)(de)能(neng)力。

　　

 

　　圖4 平均(jun)電(dian)流反饋電(dian)路圖

　　電(dian)(dian)(dian)流(liu)(liu)控(kong)(kong)制(zhi)回路(lu)(lu)選用(yong)UC3823PWM控(kong)(kong)制(zhi)器(qi)， 因為它在非常小的(de)脈沖(chong)占空比到100%的(de)脈沖(chong)占空比的(de)變化范圍內能夠(gou)線性(xing)工作; UC3823PWM控(kong)(kong)制(zhi)器(qi)的(de)帶寬和電(dian)(dian)(dian)路(lu)(lu)結構完全滿(man)足平均電(dian)(dian)(dian)流(liu)(liu)控(kong)(kong)制(zhi)回路(lu)(lu)的(de)要求; UC3823PWM控(kong)(kong)制(zhi)器(qi)輸(shu)出驅動(dong)級與開關電(dian)(dian)(dian)流(liu)(liu)源(yuan)輸(shu)出功率級連接(jie)簡單。運(yun)放(fang)當作差動(dong)放(fang)大器(qi)使用(yong)，用(yong)以檢(jian)測開關電(dian)(dian)(dian)流(liu)(liu)源(yuan)的(de)輸(shu)出電(dian)(dian)(dian)流(liu)(liu)， 并把該電(dian)(dian)(dian)流(liu)(liu)信號(hao)(hao)變換為適當的(de)電(dian)(dian)(dian)壓(ya)信號(hao)(hao)。

　　2.3 功率輸出級

　　功率輸出級采(cai)用(yong)(yong)降壓(ya)(ya)式開關(guan)(guan)電(dian)(dian)流(liu)源(yuan)。為了簡化(hua)UC3823的高(gao)端(duan)(duan)驅動電(dian)(dian)路(lu)， 輸出開關(guan)(guan)管(guan)采(cai)用(yong)(yong)直(zhi)接(jie)耦合P溝道MOSFET.流(liu)入(ru)(ru)MOSFET的開關(guan)(guan)電(dian)(dian)流(liu)提(ti)供柵(zha)極(ji)電(dian)(dian)荷， 使MOSFET導通， 接(jie)在(zai)柵(zha)極(ji)與源(yuan)極(ji)的穩壓(ya)(ya)管(guan)將(jiang)柵(zha)極(ji)電(dian)(dian)壓(ya)(ya)限制在(zai)12 V.PNP管(guan)的作用(yong)(yong)是釋(shi)放(fang)柵(zha)極(ji)電(dian)(dian)荷， 從而使MOSFET加(jia)速關(guan)(guan)斷(duan)(duan)。在(zai)續(xu)流(liu)二極(ji)管(guan)兩端(duan)(duan)加(jia)入(ru)(ru)RC緩沖器(qi)， 可以抑制電(dian)(dian)路(lu)寄生參數引起的高(gao)頻自激振蕩。在(zai)輸出電(dian)(dian)路(lu)中(zhong)加(jia)入(ru)(ru)整流(liu)管(guan)， 可以避免在(zai)電(dian)(dian)源(yuan)中(zhong)斷(duan)(duan)后蓄電(dian)(dian)池組對充電(dian)(dian)器(qi)放(fang)電(dian)(dian)。

　　1) UC3906內部基(ji)準電(dian)(dian)(dian)壓(ya)的(de)(de)溫(wen)度系數與鉛酸蓄(xu)電(dian)(dian)(dian)池(chi)的(de)(de)溫(wen)度系數相同， 從而保證(zheng)了蓄(xu)電(dian)(dian)(dian)池(chi)在較寬的(de)(de)溫(wen)度范圍內實現蓄(xu)電(dian)(dian)(dian)池(chi)的(de)(de)精確快速充電(dian)(dian)(dian)， 且(qie)不會過充影響蓄(xu)電(dian)(dian)(dian)池(chi)壽命。

　　2) UC3823PWM控制(zhi)器在非常小的(de)脈沖(chong)占空比到(dao)100%的(de)脈沖(chong)占空比的(de)變化(hua)范圍(wei)內能夠線性工作;UC3823PWM控制(zhi)器的(de)帶寬和(he)電路結構完(wan)全滿(man)足平(ping)均(jun)電流控制(zhi)回路的(de)要求。