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)(de)溫(wen)度范圍(wei)內精確(que)充電(dian)， 延長蓄電(dian)池的(de)(de)使用壽命; 可以消除(chu)充電(dian)過(guo)程中的(de)(de)極(ji)化(hua)現象(xiang)， 提高充電(dian)效(xiao)率。

　　1 UC3906的結(jie)構及工(gong)作(zuo)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(de)輸出(chu)電壓與(yu)電流。電壓和電流檢測比較器(qi)檢測蓄電池的(de)充電狀(zhuang)態， 并控制(zhi)狀(zhuang)態邏輯電路的(de)輸入信號。

　　

 

　　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，避免(mian)了因充電(dian)電(dian)流過大而損(sun)壞蓄電(dian)池(chi)。

　　蓄(xu)(xu)(xu)(xu)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的(de)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)與環(huan)境(jing)(jing)溫(wen)(wen)(wen)度有(you)關， 溫(wen)(wen)(wen)度每(mei)升高1 ℃， 蓄(xu)(xu)(xu)(xu)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)單格(ge)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)下(xia)降4 mV, 也(ye)就(jiu)是(shi)說蓄(xu)(xu)(xu)(xu)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的(de)浮(fu)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)有(you)負的(de)溫(wen)(wen)(wen)度系數- 4 mV/℃。普通(tong)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器如果在25 ℃處(chu)于最(zui)佳工(gong)作(zuo)狀態， 在環(huan)境(jing)(jing)溫(wen)(wen)(wen)度為0 ℃就(jiu)會充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)不(bu)足(zu)(zu)， 而(er)在溫(wen)(wen)(wen)度為45 ℃時(shi)可能因嚴重過(guo)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)而(er)縮(suo)短(duan)蓄(xu)(xu)(xu)(xu)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的(de)使用壽命。而(er)UC3906的(de)最(zui)重要的(de)特(te)性是(shi)具有(you)精確的(de)基(ji)準電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)， 其基(ji)準電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)的(de)大小(xiao)隨環(huan)境(jing)(jing)溫(wen)(wen)(wen)度而(er)變(bian)化(hua)， 且變(bian)化(hua)規律與鉛酸蓄(xu)(xu)(xu)(xu)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的(de)溫(wen)(wen)(wen)度特(te)性一致。同時(shi)芯(xin)(xin)片(pian)只需1.7 mA的(de)輸入電(dian)(dian)(dian)(dian)(dian)(dian)流就(jiu)可工(gong)作(zuo)， 這樣可以(yi)盡量(liang)減小(xiao)芯(xin)(xin)片(pian)的(de)功耗， 實現(xian)對(dui)環(huan)境(jing)(jing)溫(wen)(wen)(wen)度的(de)準確檢測。在0~70 ℃溫(wen)(wen)(wen)度范圍內可以(yi)保證(zheng)蓄(xu)(xu)(xu)(xu)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)既充(chong)(chong)(chong)足(zu)(zu)電(dian)(dian)(dian)(dian)(dian)(dian)又(you)不(bu)會出(chu)現(xian)過(guo)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)現(xian)象(xiang)， 完全滿足(zu)(zu)蓄(xu)(xu)(xu)(xu)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)需要。

　　UC3906可構成雙電平浮充充電器， 充(chong)電(dian)(dian)過程(cheng)分為3個(ge)充(chong)電(dian)(dian)狀(zhuang)態(tai)， 如圖2所示： 大電(dian)(dian)流(liu)恒(heng)流(liu)充(chong)電(dian)(dian)狀(zhuang)態(tai)， 高電(dian)(dian)壓過充(chong)電(dian)(dian)狀(zhuang)態(tai)和低電(dian)(dian)壓恒(heng)壓浮充(chong)狀(zhuang)態(tai)。

　　

 

　　圖2 雙電(dian)平浮充充電(dian)狀態曲(qu)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(shu)出電壓(ya)下降(jiang)到較低的浮充電壓(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(zhu)電(dian)路由功率MOSFET ( IRF9503) 、續流二極管( UES2402) 和濾波電(dian)感( 130 μH) 等元件組成。

　　

 

　　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)(dian)壓電(dian)(dian)流控制回路與(yu)電(dian)(dian)池充電(dian)(dian)邏輯(ji)狀態電(dian)(dian)路

 

　　對小容量蓄電(dian)(dian)池充電(dian)(dian)器(qi)可采用(yong)線性串聯調整管(guan)來控(kong)制(zhi)充電(dian)(dian)電(dian)(dian)流(liu)， 而對于(yu)開關型充電(dian)(dian)器(qi)， UC3906鉛酸蓄電(dian)(dian)池充電(dian)(dian)控(kong)制(zhi)集成(cheng)電(dian)(dian)路具有充電(dian)(dian)電(dian)(dian)壓控(kong)制(zhi)和(he)充電(dian)(dian)邏輯狀態控(kong)制(zhi)的(de)功能， 并能提供(gong)充電(dian)(dian)的(de)溫度補償控(kong)制(zhi)功能。

　　蓄電(dian)(dian)池兩端(duan)的(de)(de)分壓電(dian)(dian)阻(zu)監控蓄電(dian)(dian)池電(dian)(dian)壓， 分壓電(dian)(dian)阻(zu)的(de)(de)阻(zu)值確(que)定浮充(chong)電(dian)(dian)壓、過(guo)充(chong)電(dian)(dian)壓和涓(juan)流充(chong)電(dian)(dian)門限電(dian)(dian)壓。差(cha)動電(dian)(dian)流取樣比(bi)較(jiao)器(qi)(qi)產生(sheng)過(guo)充(chong)電(dian)(dian)狀(zhuang)態的(de)(de)轉換(huan)信號， 電(dian)(dian)壓放大(da)器(qi)(qi)放大(da)補償電(dian)(dian)壓回路的(de)(de)信號。

　　在溫(wen)度為(wei)25 ℃， Uref值為(wei)2.3 V時：

　　過充電壓：

　　

 

　　浮充電壓：

　　

 

　　過充轉換電壓：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 開關型電流源控制回路

　　輸入電(dian)(dian)壓( 35 /50 V) 經10 kΩ電(dian)(dian)阻與1N4744穩壓管組成(cheng)的穩壓電(dian)(dian)路穩壓后， 又經TIP31晶體(ti)管射隨器(qi)輸出(chu)+14 V電(dian)(dian)壓， 作為控(kong)制電(dian)(dian)路的電(dian)(dian)源(yuan)電(dian)(dian)壓。

　　PWM頻率設定為(wei)100 kHz, 以減小輸出(chu)濾波器(qi)的(de)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(cha)動(dong)放(fang)大增益為(wei)5。

　　開關(guan)型電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)源控(kong)(kong)(kong)制(zhi)回路(lu)的(de)(de)(de)性能(neng)對充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)狀(zhuang)(zhuang)態(tai)控(kong)(kong)(kong)制(zhi)轉換(huan)有很大(da)的(de)(de)(de)影(ying)響， 在(zai)(zai)(zai)大(da)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)快速充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)狀(zhuang)(zhuang)態(tai)下， 充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器要能(neng)提(ti)供最大(da)的(de)(de)(de)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu); 在(zai)(zai)(zai)浮(fu)充(chong)狀(zhuang)(zhuang)態(tai)下， 充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器輸出電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)很小。因此， 充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)控(kong)(kong)(kong)制(zhi)回路(lu)的(de)(de)(de)增(zeng)益變(bian)化范圍(wei)應大(da)于60 db, 采用普通的(de)(de)(de)峰(feng)值電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)反(fan)饋(kui)很難(nan)滿(man)足(zu)要求， 24 V20 Ah鉛酸蓄電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)開關(guan)型充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器采用平(ping)均電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)反(fan)饋(kui)回路(lu)見圖4.它比(bi)峰(feng)值電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)反(fan)饋(kui)控(kong)(kong)(kong)制(zhi)相對復(fu)雜， 利用平(ping)均電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)反(fan)饋(kui)控(kong)(kong)(kong)制(zhi)回路(lu)可以使充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)在(zai)(zai)(zai)以下幾方(fang)面有所改進： ①由于誤差放(fang)大(da)在(zai)(zai)(zai)較(jiao)低工作(zuo)頻(pin)率范圍(wei)內的(de)(de)(de)高增(zeng)益， 從而使閉(bi)環(huan)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)的(de)(de)(de)控(kong)(kong)(kong)制(zhi)精度得到了提(ti)高; ②在(zai)(zai)(zai)大(da)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)工作(zuo)狀(zhuang)(zhuang)態(tai)下， 當電(dian)(dian)(dian)(dian)(dian)(dian)感電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)不連續時， 可以改善大(da)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)輸出級(ji)的(de)(de)(de)非線性; ③可以提(ti)高充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)在(zai)(zai)(zai)很小的(de)(de)(de)脈沖(chong)占(zhan)空(kong)比(bi)工作(zuo)條(tiao)件(jian)下的(de)(de)(de)抗開關(guan)峰(feng)值噪(zao)聲的(de)(de)(de)能(neng)力(li)。

　　

 

　　圖4 平均電流反饋電路圖

　　電流(liu)(liu)(liu)控制(zhi)回路選用UC3823PWM控制(zhi)器， 因為(wei)它在非常小(xiao)的脈(mo)沖(chong)占(zhan)空(kong)比到(dao)100%的脈(mo)沖(chong)占(zhan)空(kong)比的變化范圍內(nei)能(neng)夠線性(xing)工作(zuo); UC3823PWM控制(zhi)器的帶寬和電路結構完全滿足平(ping)均電流(liu)(liu)(liu)控制(zhi)回路的要求; UC3823PWM控制(zhi)器輸出驅(qu)動級(ji)與開關電流(liu)(liu)(liu)源輸出功率(lv)級(ji)連接(jie)簡(jian)單。運放當作(zuo)差動放大器使用，用以(yi)檢測開關電流(liu)(liu)(liu)源的輸出電流(liu)(liu)(liu)， 并(bing)把該(gai)電流(liu)(liu)(liu)信號(hao)變換為(wei)適當的電壓(ya)信號(hao)。

　　2.3 功率輸出級

　　功率(lv)輸(shu)出(chu)級采(cai)(cai)用(yong)(yong)降壓(ya)(ya)(ya)式開關(guan)(guan)電(dian)(dian)流(liu)(liu)源(yuan)(yuan)。為了簡化UC3823的(de)高端驅動電(dian)(dian)路(lu)(lu)， 輸(shu)出(chu)開關(guan)(guan)管采(cai)(cai)用(yong)(yong)直接耦合P溝道MOSFET.流(liu)(liu)入(ru)(ru)MOSFET的(de)開關(guan)(guan)電(dian)(dian)流(liu)(liu)提供柵極(ji)電(dian)(dian)荷， 使(shi)MOSFET導(dao)通， 接在(zai)(zai)柵極(ji)與源(yuan)(yuan)極(ji)的(de)穩壓(ya)(ya)(ya)管將(jiang)柵極(ji)電(dian)(dian)壓(ya)(ya)(ya)限(xian)制(zhi)在(zai)(zai)12 V.PNP管的(de)作用(yong)(yong)是釋(shi)放柵極(ji)電(dian)(dian)荷， 從而使(shi)MOSFET加(jia)速關(guan)(guan)斷。在(zai)(zai)續流(liu)(liu)二極(ji)管兩(liang)端加(jia)入(ru)(ru)RC緩沖器， 可以抑制(zhi)電(dian)(dian)路(lu)(lu)寄生參(can)數(shu)引起的(de)高頻自(zi)激(ji)振蕩。在(zai)(zai)輸(shu)出(chu)電(dian)(dian)路(lu)(lu)中(zhong)加(jia)入(ru)(ru)整(zheng)流(liu)(liu)管， 可以避免在(zai)(zai)電(dian)(dian)源(yuan)(yuan)中(zhong)斷后蓄電(dian)(dian)池(chi)組對(dui)充電(dian)(dian)器放電(dian)(dian)。

　　1) UC3906內部基準電(dian)壓的溫度系(xi)數(shu)與鉛酸蓄電(dian)池(chi)的溫度系(xi)數(shu)相同， 從而保證(zheng)了蓄電(dian)池(chi)在較寬的溫度范圍內實(shi)現蓄電(dian)池(chi)的精確(que)快速充電(dian)， 且不會過充影響蓄電(dian)池(chi)壽(shou)命。

　　2) UC3823PWM控(kong)制(zhi)(zhi)器(qi)在(zai)非(fei)常(chang)小(xiao)的(de)脈沖占(zhan)空(kong)比(bi)到100%的(de)脈沖占(zhan)空(kong)比(bi)的(de)變化范圍(wei)內能夠(gou)線性工作(zuo);UC3823PWM控(kong)制(zhi)(zhi)器(qi)的(de)帶寬和(he)電路(lu)結構(gou)完全滿足平(ping)均(jun)電流控(kong)制(zhi)(zhi)回路(lu)的(de)要求。