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(zai)很寬的(de)溫度范圍(wei)內精(jing)確充(chong)電(dian)， 延(yan)長(chang)蓄電(dian)池的(de)使用壽命; 可以消除充(chong)電(dian)過程中的(de)極化現(xian)象， 提高充(chong)電(dian)效(xiao)率(lv)。

　　1 UC3906的結(jie)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)出電(dian)(dian)(dian)壓與電(dian)(dian)(dian)流(liu)。電(dian)(dian)(dian)壓和電(dian)(dian)(dian)流(liu)檢測比較(jiao)器檢測蓄電(dian)(dian)(dian)池的充電(dian)(dian)(dian)狀(zhuang)態， 并控制狀(zhuang)態邏輯電(dian)(dian)(dian)路的輸(shu)入信號。

　　

 

　　圖1 UC3906內部結(jie)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(chong)電(dian)電(dian)流過大而(er)損壞蓄電(dian)池(chi)。

　　蓄(xu)(xu)電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的(de)(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)壓與環(huan)境(jing)溫(wen)(wen)(wen)度(du)有(you)關， 溫(wen)(wen)(wen)度(du)每升高1 ℃， 蓄(xu)(xu)電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)單(dan)格電(dian)(dian)(dian)(dian)壓下降(jiang)4 mV, 也就是說蓄(xu)(xu)電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的(de)(de)(de)(de)(de)(de)浮充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)壓有(you)負的(de)(de)(de)(de)(de)(de)溫(wen)(wen)(wen)度(du)系數- 4 mV/℃。普(pu)通(tong)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)器如果在(zai)25 ℃處于最佳工作(zuo)狀態， 在(zai)環(huan)境(jing)溫(wen)(wen)(wen)度(du)為(wei)0 ℃就會充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)不足， 而(er)在(zai)溫(wen)(wen)(wen)度(du)為(wei)45 ℃時(shi)可能因嚴重過(guo)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)而(er)縮短(duan)蓄(xu)(xu)電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的(de)(de)(de)(de)(de)(de)使(shi)用壽(shou)命。而(er)UC3906的(de)(de)(de)(de)(de)(de)最重要的(de)(de)(de)(de)(de)(de)特性(xing)是具有(you)精確的(de)(de)(de)(de)(de)(de)基準(zhun)電(dian)(dian)(dian)(dian)壓， 其(qi)基準(zhun)電(dian)(dian)(dian)(dian)壓的(de)(de)(de)(de)(de)(de)大小隨環(huan)境(jing)溫(wen)(wen)(wen)度(du)而(er)變化， 且變化規律與鉛酸蓄(xu)(xu)電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的(de)(de)(de)(de)(de)(de)溫(wen)(wen)(wen)度(du)特性(xing)一致。同時(shi)芯片只需(xu)(xu)1.7 mA的(de)(de)(de)(de)(de)(de)輸(shu)入電(dian)(dian)(dian)(dian)流就可工作(zuo)， 這樣可以盡量減(jian)小芯片的(de)(de)(de)(de)(de)(de)功耗， 實(shi)現對(dui)環(huan)境(jing)溫(wen)(wen)(wen)度(du)的(de)(de)(de)(de)(de)(de)準(zhun)確檢測。在(zai)0~70 ℃溫(wen)(wen)(wen)度(du)范圍(wei)內可以保(bao)證(zheng)蓄(xu)(xu)電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)既充(chong)(chong)(chong)(chong)足電(dian)(dian)(dian)(dian)又不會出現過(guo)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)現象(xiang)， 完全滿足蓄(xu)(xu)電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)需(xu)(xu)要。

　　UC3906可構成雙電平浮充充電器， 充電過程分為3個充電狀態(tai)(tai)(tai)， 如圖2所示： 大電流恒流充電狀態(tai)(tai)(tai)， 高電壓(ya)過充電狀態(tai)(tai)(tai)和低電壓(ya)恒壓(ya)浮充狀態(tai)(tai)(tai)。

　　

 

　　圖2 雙電(dian)(dian)平浮充充電(dian)(dian)狀態(tai)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% ,充電器輸出電(dian)壓下降到較低的浮充電(dian)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(gong)率(lv)MOSFET ( IRF9503) 、續(xu)流二極管( UES2402) 和濾波(bo)電感( 130 μH) 等元件組(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(lu)與電(dian)池充(chong)電(dian)邏輯狀(zhuang)態電(dian)路(lu)

 

　　對小容量蓄(xu)電(dian)(dian)池(chi)充(chong)電(dian)(dian)器可采用線性串(chuan)聯調整管來控(kong)制(zhi)充(chong)電(dian)(dian)電(dian)(dian)流， 而對于開關(guan)型充(chong)電(dian)(dian)器， UC3906鉛酸蓄(xu)電(dian)(dian)池(chi)充(chong)電(dian)(dian)控(kong)制(zhi)集成電(dian)(dian)路具有充(chong)電(dian)(dian)電(dian)(dian)壓控(kong)制(zhi)和(he)充(chong)電(dian)(dian)邏輯狀態控(kong)制(zhi)的功(gong)能(neng)， 并能(neng)提供充(chong)電(dian)(dian)的溫(wen)度補償控(kong)制(zhi)功(gong)能(neng)。

　　蓄電(dian)(dian)(dian)(dian)(dian)(dian)池兩端的分壓(ya)(ya)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)監(jian)控蓄電(dian)(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)， 分壓(ya)(ya)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)的阻(zu)值(zhi)確定(ding)浮充電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)、過充電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)和涓流充電(dian)(dian)(dian)(dian)(dian)(dian)門限電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)。差(cha)動(dong)電(dian)(dian)(dian)(dian)(dian)(dian)流取樣比較器產生過充電(dian)(dian)(dian)(dian)(dian)(dian)狀態的轉換信號， 電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)放大(da)器放大(da)補償電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)回路的信號。

　　在溫度為25 ℃， Uref值為2.3 V時：

　　過充電壓：

　　

 

　　浮充電壓：

　　

 

　　過(guo)充轉換電壓：U12=0.95Uoc=28.03 V

　　浮充轉換電(dian)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)流源控制(zhi)回(hui)路(lu)

　　輸入電壓(ya)(ya)(ya)(ya)( 35 /50 V) 經10 kΩ電阻(zu)與1N4744穩壓(ya)(ya)(ya)(ya)管組成的(de)穩壓(ya)(ya)(ya)(ya)電路穩壓(ya)(ya)(ya)(ya)后， 又(you)經TIP31晶體(ti)管射隨(sui)器輸出+14 V電壓(ya)(ya)(ya)(ya)， 作為控制電路的(de)電源電壓(ya)(ya)(ya)(ya)。

　　PWM頻率設定為(wei)100 kHz, 以(yi)減小輸出濾波器的體積， 蓄電(dian)(dian)池充(chong)電(dian)(dian)電(dian)(dian)流從0.1 Ω/5 W電(dian)(dian)阻(zu)上取樣， 差動放大增益為(wei)5。

　　開關型(xing)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)源控(kong)(kong)制(zhi)回路的(de)(de)(de)(de)性能對充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)狀(zhuang)(zhuang)態(tai)控(kong)(kong)制(zhi)轉(zhuan)換有很大(da)(da)的(de)(de)(de)(de)影響， 在(zai)大(da)(da)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)快(kuai)速充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)狀(zhuang)(zhuang)態(tai)下， 充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器(qi)要(yao)能提供最大(da)(da)的(de)(de)(de)(de)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu); 在(zai)浮充(chong)(chong)狀(zhuang)(zhuang)態(tai)下， 充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器(qi)輸(shu)出電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)很小(xiao)(xiao)。因此， 充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器(qi)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)控(kong)(kong)制(zhi)回路的(de)(de)(de)(de)增益變化范(fan)圍應大(da)(da)于60 db, 采(cai)用普通(tong)的(de)(de)(de)(de)峰值(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)反(fan)(fan)饋很難(nan)滿足要(yao)求(qiu)， 24 V20 Ah鉛酸蓄電(dian)(dian)(dian)(dian)(dian)(dian)池開關型(xing)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器(qi)采(cai)用平均電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)反(fan)(fan)饋回路見圖4.它比(bi)峰值(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)反(fan)(fan)饋控(kong)(kong)制(zhi)相對復雜(za)， 利(li)用平均電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)反(fan)(fan)饋控(kong)(kong)制(zhi)回路可以(yi)使(shi)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器(qi)電(dian)(dian)(dian)(dian)(dian)(dian)路在(zai)以(yi)下幾方面有所改(gai)進： ①由于誤差放大(da)(da)在(zai)較低工作(zuo)頻率范(fan)圍內的(de)(de)(de)(de)高增益， 從(cong)而使(shi)閉環電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)的(de)(de)(de)(de)控(kong)(kong)制(zhi)精度得到了提高; ②在(zai)大(da)(da)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)的(de)(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)不連(lian)續時， 可以(yi)改(gai)善大(da)(da)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)輸(shu)出級的(de)(de)(de)(de)非線(xian)性; ③可以(yi)提高充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器(qi)電(dian)(dian)(dian)(dian)(dian)(dian)路在(zai)很小(xiao)(xiao)的(de)(de)(de)(de)脈沖占空(kong)比(bi)工作(zuo)條(tiao)件下的(de)(de)(de)(de)抗(kang)開關峰值(zhi)噪聲的(de)(de)(de)(de)能力。

　　

 

　　圖4 平(ping)均電(dian)流反(fan)饋電(dian)路圖

　　電流(liu)控制(zhi)回路選(xuan)用(yong)UC3823PWM控制(zhi)器， 因為(wei)它在非常(chang)小的(de)(de)(de)(de)脈(mo)沖占空(kong)比(bi)到(dao)100%的(de)(de)(de)(de)脈(mo)沖占空(kong)比(bi)的(de)(de)(de)(de)變化范圍(wei)內能夠線性工作(zuo)(zuo); UC3823PWM控制(zhi)器的(de)(de)(de)(de)帶寬和電路結構完全滿(man)足平均電流(liu)控制(zhi)回路的(de)(de)(de)(de)要求; UC3823PWM控制(zhi)器輸出驅動(dong)級(ji)與開關(guan)電流(liu)源輸出功率(lv)級(ji)連接簡單。運放當(dang)作(zuo)(zuo)差(cha)動(dong)放大(da)器使用(yong)，用(yong)以檢測開關(guan)電流(liu)源的(de)(de)(de)(de)輸出電流(liu)， 并(bing)把該電流(liu)信號變換為(wei)適當(dang)的(de)(de)(de)(de)電壓信號。

　　2.3 功率輸出級

　　功率輸出級采用(yong)降壓(ya)(ya)式(shi)開(kai)關電(dian)(dian)(dian)(dian)流(liu)源(yuan)。為了(le)簡化UC3823的(de)高端(duan)驅(qu)動電(dian)(dian)(dian)(dian)路， 輸出開(kai)關管(guan)(guan)采用(yong)直接耦(ou)合P溝道(dao)MOSFET.流(liu)入(ru)(ru)MOSFET的(de)開(kai)關電(dian)(dian)(dian)(dian)流(liu)提(ti)供柵(zha)極電(dian)(dian)(dian)(dian)荷， 使MOSFET導通， 接在(zai)(zai)(zai)柵(zha)極與源(yuan)極的(de)穩壓(ya)(ya)管(guan)(guan)將柵(zha)極電(dian)(dian)(dian)(dian)壓(ya)(ya)限(xian)制(zhi)在(zai)(zai)(zai)12 V.PNP管(guan)(guan)的(de)作用(yong)是釋放(fang)柵(zha)極電(dian)(dian)(dian)(dian)荷， 從而使MOSFET加速關斷。在(zai)(zai)(zai)續流(liu)二(er)極管(guan)(guan)兩端(duan)加入(ru)(ru)RC緩沖器(qi)， 可(ke)以抑(yi)制(zhi)電(dian)(dian)(dian)(dian)路寄(ji)生參數引(yin)起的(de)高頻(pin)自激振蕩。在(zai)(zai)(zai)輸出電(dian)(dian)(dian)(dian)路中加入(ru)(ru)整流(liu)管(guan)(guan)， 可(ke)以避免在(zai)(zai)(zai)電(dian)(dian)(dian)(dian)源(yuan)中斷后蓄電(dian)(dian)(dian)(dian)池(chi)組對充電(dian)(dian)(dian)(dian)器(qi)放(fang)電(dian)(dian)(dian)(dian)。

　　1) UC3906內(nei)部基(ji)準(zhun)電(dian)(dian)(dian)壓的(de)(de)溫度(du)(du)系數與鉛酸蓄電(dian)(dian)(dian)池(chi)的(de)(de)溫度(du)(du)系數相同， 從而保證了蓄電(dian)(dian)(dian)池(chi)在較寬的(de)(de)溫度(du)(du)范圍(wei)內(nei)實現蓄電(dian)(dian)(dian)池(chi)的(de)(de)精(jing)確快速充電(dian)(dian)(dian)， 且不會過充影響(xiang)蓄電(dian)(dian)(dian)池(chi)壽(shou)命。

　　2) UC3823PWM控制器在非常小的脈沖(chong)占空比到100%的脈沖(chong)占空比的變化范圍(wei)內能夠線性工(gong)作;UC3823PWM控制器的帶寬和電路(lu)結(jie)構完全滿足(zu)平均(jun)電流控制回路(lu)的要(yao)求。