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(wen)度范圍內(nei)精確充(chong)電， 延長(chang)蓄電池(chi)的使用壽命; 可以消除充(chong)電過(guo)程中(zhong)的極(ji)化現象， 提高充(chong)電效率。

　　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(de)輸出電壓(ya)與(yu)電流。電壓(ya)和(he)電流檢測比較器檢測蓄(xu)電池的(de)充(chong)電狀態， 并(bing)控制狀態邏輯(ji)電路的(de)輸入信(xin)號。

　　

 

　　圖(tu)1 UC3906內部結構框圖(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)免了因充電(dian)電(dian)流過大而損壞蓄電(dian)池。

　　蓄(xu)電(dian)(dian)(dian)(dian)池(chi)(chi)的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)壓(ya)(ya)與(yu)(yu)環(huan)境溫(wen)(wen)(wen)度有(you)關， 溫(wen)(wen)(wen)度每升(sheng)高1 ℃， 蓄(xu)電(dian)(dian)(dian)(dian)池(chi)(chi)單格(ge)電(dian)(dian)(dian)(dian)壓(ya)(ya)下降(jiang)4 mV, 也就(jiu)是說蓄(xu)電(dian)(dian)(dian)(dian)池(chi)(chi)的(de)(de)(de)(de)(de)(de)浮充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)壓(ya)(ya)有(you)負的(de)(de)(de)(de)(de)(de)溫(wen)(wen)(wen)度系(xi)數- 4 mV/℃。普通充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)器如果在(zai)25 ℃處于(yu)最佳工作狀態， 在(zai)環(huan)境溫(wen)(wen)(wen)度為(wei)0 ℃就(jiu)會充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)不足(zu)(zu)(zu)， 而(er)(er)在(zai)溫(wen)(wen)(wen)度為(wei)45 ℃時可能因嚴(yan)重過充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)而(er)(er)縮(suo)短蓄(xu)電(dian)(dian)(dian)(dian)池(chi)(chi)的(de)(de)(de)(de)(de)(de)使(shi)用(yong)壽(shou)命。而(er)(er)UC3906的(de)(de)(de)(de)(de)(de)最重要(yao)的(de)(de)(de)(de)(de)(de)特(te)性是具有(you)精確的(de)(de)(de)(de)(de)(de)基(ji)準(zhun)電(dian)(dian)(dian)(dian)壓(ya)(ya)， 其(qi)基(ji)準(zhun)電(dian)(dian)(dian)(dian)壓(ya)(ya)的(de)(de)(de)(de)(de)(de)大小(xiao)隨環(huan)境溫(wen)(wen)(wen)度而(er)(er)變(bian)化， 且變(bian)化規律與(yu)(yu)鉛酸蓄(xu)電(dian)(dian)(dian)(dian)池(chi)(chi)的(de)(de)(de)(de)(de)(de)溫(wen)(wen)(wen)度特(te)性一致。同(tong)時芯(xin)片(pian)只需(xu)1.7 mA的(de)(de)(de)(de)(de)(de)輸入電(dian)(dian)(dian)(dian)流就(jiu)可工作， 這樣可以盡量減小(xiao)芯(xin)片(pian)的(de)(de)(de)(de)(de)(de)功耗， 實現(xian)對環(huan)境溫(wen)(wen)(wen)度的(de)(de)(de)(de)(de)(de)準(zhun)確檢(jian)測。在(zai)0~70 ℃溫(wen)(wen)(wen)度范圍內可以保證蓄(xu)電(dian)(dian)(dian)(dian)池(chi)(chi)既充(chong)(chong)(chong)足(zu)(zu)(zu)電(dian)(dian)(dian)(dian)又不會出現(xian)過充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)現(xian)象， 完全滿足(zu)(zu)(zu)蓄(xu)電(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)需(xu)要(yao)。

　　UC3906可構成雙電平浮充充電器， 充(chong)(chong)電(dian)過程分(fen)為3個充(chong)(chong)電(dian)狀(zhuang)(zhuang)態(tai)(tai)， 如圖2所(suo)示： 大電(dian)流(liu)恒(heng)流(liu)充(chong)(chong)電(dian)狀(zhuang)(zhuang)態(tai)(tai)， 高電(dian)壓過充(chong)(chong)電(dian)狀(zhuang)(zhuang)態(tai)(tai)和(he)低(di)電(dian)壓恒(heng)壓浮充(chong)(chong)狀(zhuang)(zhuang)態(tai)(tai)。

　　

 

　　圖2 雙電平浮充充電狀態曲線

　　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(ya)下(xia)降到(dao)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(zhu)電路由功率(lv)MOSFET ( IRF9503) 、續流二極管( UES2402) 和濾波電感( 130 μH) 等元(yuan)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)壓(ya)電(dian)流控制(zhi)回路與電(dian)池(chi)充(chong)電(dian)邏輯(ji)狀態電(dian)路

 

　　對(dui)小容量蓄(xu)電(dian)池(chi)充(chong)電(dian)器可(ke)采用線性串聯調整管(guan)來(lai)控制充(chong)電(dian)電(dian)流(liu)， 而對(dui)于開關型充(chong)電(dian)器， UC3906鉛(qian)酸蓄(xu)電(dian)池(chi)充(chong)電(dian)控制集成電(dian)路具有充(chong)電(dian)電(dian)壓控制和(he)充(chong)電(dian)邏輯(ji)狀態控制的(de)功(gong)能(neng)， 并能(neng)提供充(chong)電(dian)的(de)溫度補償控制功(gong)能(neng)。

　　蓄(xu)電(dian)(dian)(dian)池(chi)兩端的(de)分(fen)壓(ya)電(dian)(dian)(dian)阻(zu)(zu)監(jian)控蓄(xu)電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)壓(ya)， 分(fen)壓(ya)電(dian)(dian)(dian)阻(zu)(zu)的(de)阻(zu)(zu)值(zhi)確定浮充(chong)電(dian)(dian)(dian)壓(ya)、過(guo)(guo)充(chong)電(dian)(dian)(dian)壓(ya)和涓(juan)流充(chong)電(dian)(dian)(dian)門限電(dian)(dian)(dian)壓(ya)。差動電(dian)(dian)(dian)流取樣比較器產生過(guo)(guo)充(chong)電(dian)(dian)(dian)狀(zhuang)態(tai)的(de)轉換信號， 電(dian)(dian)(dian)壓(ya)放大器放大補(bu)償電(dian)(dian)(dian)壓(ya)回路的(de)信號。

　　在(zai)溫(wen)度為25 ℃， Uref值為2.3 V時：

　　過充電壓：

　　

 

　　浮充電壓：

　　

 

　　過充(chong)轉換電壓(ya)：U12=0.95Uoc=28.03 V

　　浮充轉(zhuan)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(dian)流(liu)源控制回路

　　輸入電(dian)(dian)壓( 35 /50 V) 經10 kΩ電(dian)(dian)阻與1N4744穩(wen)壓管(guan)組成的(de)穩(wen)壓電(dian)(dian)路穩(wen)壓后， 又經TIP31晶體管(guan)射隨器輸出(chu)+14 V電(dian)(dian)壓， 作為控(kong)制(zhi)電(dian)(dian)路的(de)電(dian)(dian)源電(dian)(dian)壓。

　　PWM頻率設定為100 kHz, 以(yi)減小輸出濾波器的體積， 蓄電池充電電流從(cong)0.1 Ω/5 W電阻(zu)上取(qu)樣(yang)， 差動放(fang)大增(zeng)益為5。

　　開(kai)(kai)關型電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)源控(kong)制回(hui)路(lu)的(de)性能(neng)對(dui)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)狀(zhuang)態(tai)(tai)控(kong)制轉換(huan)有很大(da)(da)(da)的(de)影響(xiang)， 在大(da)(da)(da)電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)快速充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)狀(zhuang)態(tai)(tai)下， 充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)器(qi)(qi)要能(neng)提供最(zui)大(da)(da)(da)的(de)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)(liu)(liu); 在浮(fu)充(chong)(chong)(chong)(chong)狀(zhuang)態(tai)(tai)下， 充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)器(qi)(qi)輸出電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)很小。因此， 充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)器(qi)(qi)電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)控(kong)制回(hui)路(lu)的(de)增(zeng)益(yi)(yi)變化(hua)范圍(wei)應(ying)大(da)(da)(da)于(yu)60 db, 采用普通的(de)峰值電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)反饋(kui)很難滿(man)足要求， 24 V20 Ah鉛酸(suan)蓄電(dian)(dian)(dian)池開(kai)(kai)關型充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)器(qi)(qi)采用平(ping)均電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)反饋(kui)回(hui)路(lu)見圖(tu)4.它比峰值電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)反饋(kui)控(kong)制相對(dui)復雜， 利用平(ping)均電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)反饋(kui)控(kong)制回(hui)路(lu)可以(yi)使充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)器(qi)(qi)電(dian)(dian)(dian)路(lu)在以(yi)下幾方面(mian)有所改(gai)進： ①由于(yu)誤差放大(da)(da)(da)在較低(di)工(gong)作頻率(lv)范圍(wei)內的(de)高(gao)增(zeng)益(yi)(yi)， 從而使閉環電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)的(de)控(kong)制精度(du)得到(dao)了提高(gao); ②在大(da)(da)(da)電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)的(de)工(gong)作狀(zhuang)態(tai)(tai)下， 當電(dian)(dian)(dian)感(gan)電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)不連續時， 可以(yi)改(gai)善大(da)(da)(da)電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)輸出級(ji)的(de)非線性; ③可以(yi)提高(gao)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)器(qi)(qi)電(dian)(dian)(dian)路(lu)在很小的(de)脈沖占空(kong)比工(gong)作條件下的(de)抗開(kai)(kai)關峰值噪(zao)聲(sheng)的(de)能(neng)力。

　　

 

　　圖4 平均電流反饋電路(lu)圖

　　電(dian)流(liu)(liu)(liu)控制(zhi)回路選用(yong)UC3823PWM控制(zhi)器(qi)(qi)(qi)， 因為它在非常小的(de)脈沖占(zhan)空比(bi)(bi)到100%的(de)脈沖占(zhan)空比(bi)(bi)的(de)變化(hua)范圍(wei)內能夠線性(xing)工作; UC3823PWM控制(zhi)器(qi)(qi)(qi)的(de)帶寬和(he)電(dian)路結構完全滿(man)足平(ping)均電(dian)流(liu)(liu)(liu)控制(zhi)回路的(de)要求; UC3823PWM控制(zhi)器(qi)(qi)(qi)輸(shu)出(chu)驅動(dong)級(ji)與開關(guan)電(dian)流(liu)(liu)(liu)源輸(shu)出(chu)功率級(ji)連接簡單。運放(fang)當(dang)(dang)作差動(dong)放(fang)大(da)器(qi)(qi)(qi)使用(yong)，用(yong)以檢(jian)測開關(guan)電(dian)流(liu)(liu)(liu)源的(de)輸(shu)出(chu)電(dian)流(liu)(liu)(liu)， 并把該電(dian)流(liu)(liu)(liu)信號變換為適當(dang)(dang)的(de)電(dian)壓信號。

　　2.3 功率輸(shu)出級(ji)

　　功率(lv)輸(shu)出(chu)級采用(yong)降(jiang)壓(ya)式開(kai)關(guan)電(dian)流源(yuan)。為了(le)簡化UC3823的(de)(de)(de)高端驅動電(dian)路， 輸(shu)出(chu)開(kai)關(guan)管采用(yong)直接(jie)耦合P溝(gou)道(dao)MOSFET.流入MOSFET的(de)(de)(de)開(kai)關(guan)電(dian)流提供柵(zha)極(ji)(ji)電(dian)荷， 使(shi)MOSFET導通(tong)， 接(jie)在(zai)柵(zha)極(ji)(ji)與源(yuan)極(ji)(ji)的(de)(de)(de)穩壓(ya)管將柵(zha)極(ji)(ji)電(dian)壓(ya)限(xian)制在(zai)12 V.PNP管的(de)(de)(de)作用(yong)是釋放柵(zha)極(ji)(ji)電(dian)荷， 從而使(shi)MOSFET加(jia)速關(guan)斷(duan)。在(zai)續流二(er)極(ji)(ji)管兩端加(jia)入RC緩沖(chong)器(qi)， 可(ke)以(yi)抑(yi)制電(dian)路寄生參(can)數引起的(de)(de)(de)高頻自(zi)激(ji)振蕩。在(zai)輸(shu)出(chu)電(dian)路中加(jia)入整(zheng)流管， 可(ke)以(yi)避免在(zai)電(dian)源(yuan)中斷(duan)后(hou)蓄(xu)電(dian)池(chi)組(zu)對充電(dian)器(qi)放電(dian)。

　　1) UC3906內(nei)部基準電(dian)(dian)(dian)壓的溫度系數與鉛酸蓄(xu)電(dian)(dian)(dian)池的溫度系數相同， 從而保證了蓄(xu)電(dian)(dian)(dian)池在(zai)較(jiao)寬(kuan)的溫度范圍內(nei)實(shi)現蓄(xu)電(dian)(dian)(dian)池的精確快速充電(dian)(dian)(dian)， 且不會過充影響蓄(xu)電(dian)(dian)(dian)池壽命。

　　2) UC3823PWM控制(zhi)器在非(fei)常小(xiao)的脈沖占(zhan)空(kong)比到100%的脈沖占(zhan)空(kong)比的變化范圍(wei)內能夠線性工作;UC3823PWM控制(zhi)器的帶寬和電路結構完全滿足平均電流控制(zhi)回路的要求。