鋰離子可充電電池是20世紀開發成功的新型高能電池，相對于傳統的鎳鎘電池和鎳氫電池而言，具有容量大、工作電壓高、工作溫度范圍寬、循環壽命長、自放電率低、無記憶效應、無污染等優點，自問世以來已廣泛應用于軍事和民用小型電器中，如移動電話、便攜式計算機、攝像機、照相機等，部分代替了傳統電池。單節鋰離子電池的電壓約為3．6V，容量也不可能無限大，因此，常將單節鋰離子電池進行串、并聯(lian)處理，以滿足不(bu)同場(chang)合的(de)要求。為了確保(bao)(bao)(bao)(bao)(bao)鋰(li)離子(zi)電(dian)(dian)池安全可靠的(de)使(shi)用(yong)，本文介紹了一種嚴格、周密(mi)的(de)充(chong)、放電(dian)(dian)保(bao)(bao)(bao)(bao)(bao)護(hu)系統的(de)設計方(fang)案。該方(fang)案采用(yong)充(chong)電(dian)(dian)、放電(dian)(dian)分離的(de)控制方(fang)式，具有兩(liang)級(ji)單節過(guo)充(chong)電(dian)(dian)保(bao)(bao)(bao)(bao)(bao)護(hu)、單節過(guo)放電(dian)(dian)保(bao)(bao)(bao)(bao)(bao)護(hu)、兩(liang)級(ji)放電(dian)(dian)過(guo)電(dian)(dian)流保(bao)(bao)(bao)(bao)(bao)護(hu)、放電(dian)(dian)短路保(bao)(bao)(bao)(bao)(bao)護(hu)、放電(dian)(dian)溫度保(bao)(bao)(bao)(bao)(bao)護(hu)、充(chong)電(dian)(dian)溫度保(bao)(bao)(bao)(bao)(bao)護(hu)、充(chong)電(dian)(dian)防(fang)反接保(bao)(bao)(bao)(bao)(bao)護(hu)、充(chong)電(dian)(dian)時禁止放電(dian)(dian)等功能，可適用(yong)于各(ge)種三／四節鋰(li)離子(zi)可充(chong)電(dian)(dian)電(dian)(dian)池串聯(lian)使(shi)用(yong)的(de)場(chang)合。

　　1 系統概述

　　該保(bao)護(hu)(hu)(hu)(hu)(hu)系(xi)統采(cai)(cai)用精(jing)(jing)工電(dian)(dian)(dian)子三／四節(jie)(jie)串聯鋰離(li)子可充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)池(chi)(chi)專用充(chong)(chong)、放(fang)電(dian)(dian)(dian)保(bao)護(hu)(hu)(hu)(hu)(hu)ICS-8254構(gou)建一(yi)級保(bao)護(hu)(hu)(hu)(hu)(hu)。S-8254系(xi)列(lie)內置高精(jing)(jing)度電(dian)(dian)(dian)壓檢測(ce)(ce)電(dian)(dian)(dian)路和(he)延(yan)遲(chi)(chi)電(dian)(dian)(dian)路，針對(dui)各節(jie)(jie)電(dian)(dian)(dian)池(chi)(chi)進行(xing)高精(jing)(jing)度電(dian)(dian)(dian)壓檢測(ce)(ce)，實現單節(jie)(jie)過(guo)(guo)(guo)充(chong)(chong)電(dian)(dian)(dian)保(bao)護(hu)(hu)(hu)(hu)(hu)和(he)單節(jie)(jie)過(guo)(guo)(guo)放(fang)電(dian)(dian)(dian)保(bao)護(hu)(hu)(hu)(hu)(hu)，并具(ju)備三段過(guo)(guo)(guo)電(dian)(dian)(dian)流(liu)檢測(ce)(ce)功能(neng)，通過(guo)(guo)(guo)外接(jie)電(dian)(dian)(dian)容(rong)可設(she)(she)置過(guo)(guo)(guo)充(chong)(chong)電(dian)(dian)(dian)檢測(ce)(ce)延(yan)遲(chi)(chi)時(shi)(shi)間、過(guo)(guo)(guo)放(fang)電(dian)(dian)(dian)檢測(ce)(ce)延(yan)遲(chi)(chi)時(shi)(shi)間和(he)過(guo)(guo)(guo)電(dian)(dian)(dian)流(liu)檢測(ce)(ce)延(yan)遲(chi)(chi)時(shi)(shi)間1(過(guo)(guo)(guo)電(dian)(dian)(dian)流(liu)檢測(ce)(ce)延(yan)遲(chi)(chi)時(shi)(shi)間2和(he)過(guo)(guo)(guo)電(dian)(dian)(dian)流(liu)檢測(ce)(ce)延(yan)遲(chi)(chi)時(shi)(shi)間3在芯片內部(bu)被固定)。該系(xi)統采(cai)(cai)用精(jing)(jing)工電(dian)(dian)(dian)子S-8244系(xi)列(lie)內置高精(jing)(jing)度電(dian)(dian)(dian)壓檢測(ce)(ce)電(dian)(dian)(dian)路和(he)延(yan)遲(chi)(chi)電(dian)(dian)(dian)路的(de)鋰離(li)子可充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)池(chi)(chi)二級保(bao)護(hu)(hu)(hu)(hu)(hu)專用IC實現電(dian)(dian)(dian)池(chi)(chi)的(de)單節(jie)(jie)二級充(chong)(chong)電(dian)(dian)(dian)保(bao)護(hu)(hu)(hu)(hu)(hu)，其保(bao)護(hu)(hu)(hu)(hu)(hu)延(yan)遲(chi)(chi)時(shi)(shi)間可通過(guo)(guo)(guo)外接(jie)電(dian)(dian)(dian)容(rong)的(de)容(rong)值來設(she)(she)置。

　　S-8254通過SEL端子(zi)可(ke)以實現電池(chi)三節串聯(lian)用或(huo)四節串聯(lian)用的切(qie)換；S-8244則通過電阻R22短(duan)路第(di)四節電池(chi)電壓檢測端子(zi)VCC3和(he)VSS即(ji)可(ke)用作三節電池(chi)串聯(lian)使(shi)用時的二級保(bao)護(hu)。

　　2 各保(bao)護功(gong)能的(de)實現

S-8254系列充、放電保護電壓和過電流檢測電壓以50mV為進階單位，S-8244系列過充電檢測電壓以5mV為進階單位，系統根據不同場合的使用需求，可以選擇相應適合的型號。現以圖1保護系統為例，采用S-8254AAVFT和S-8244AAPFN作為保護IC，具體說明各保護功能的實現過程。
 

　　圖1為四節(jie)電池串聯使用時(shi)的保護系統原理(li)圖。

　　2．1 過放電保護(hu)

　　通常(chang)狀(zhuang)(zhuang)態(tai)(tai)(tai)下，S-8254放(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)控制用端(duan)子(zi)(zi)DOP為(wei)VSS(電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)4的負(fu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya))電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位，放(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)MOS管(guan)QDISl，QDIS2處(chu)于(yu)導通狀(zhuang)(zhuang)態(tai)(tai)(tai)，系(xi)(xi)統(tong)可正常(chang)進行(xing)放(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)工作。當檢測到某節(jie)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)低于(yu)2．7V(VDLn)，且這種(zhong)(zhong)狀(zhuang)(zhuang)態(tai)(tai)(tai)保持在(zai)TDL(TDL時(shi)(shi)間由過放(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)檢測延遲端(duan)子(zi)(zi)CDT外接電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)容CS決定)以(yi)上時(shi)(shi)，DOP端(duan)子(zi)(zi)的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)變(bian)為(wei)VDD(電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)1的正電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya))電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)位，放(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)MOS管(guan)關(guan)閉，停止(zhi)放(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，這種(zhong)(zhong)狀(zhuang)(zhuang)態(tai)(tai)(tai)稱為(wei)過放(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)狀(zhuang)(zhuang)態(tai)(tai)(tai)。進入過放(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)狀(zhuang)(zhuang)態(tai)(tai)(tai)后，VMP端(duan)子(zi)(zi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)經(jing)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)R3由負(fu)載(zai)下拉(la)至(zhi)VDD／2以(yi)下，S-8254轉為(wei)休(xiu)眠狀(zhuang)(zhuang)態(tai)(tai)(tai)；斷(duan)開負(fu)載(zai)后，VMP端(duan)子(zi)(zi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)經(jing)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)R9、充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)MOS管(guan)QCHRl和QCHR2由VDD上拉(la)至(zhi)VDD／2以(yi)上且低于(yu)VDD，S-8254退出休(xiu)眠狀(zhuang)(zhuang)態(tai)(tai)(tai)。當所有電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)都在(zai)3．0V(VDUn)以(yi)上時(shi)(shi)，過放(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)狀(zhuang)(zhuang)態(tai)(tai)(tai)被(bei)解除，系(xi)(xi)統(tong)恢復正常(chang)放(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)工作。

　　2．2 過(guo)電流、短路保護

　　該系統采用2個并聯的(de)20mΩ功率電(dian)(dian)(dian)(dian)(dian)阻RS1，RS2用于(yu)過(guo)(guo)(guo)(guo)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)檢(jian)(jian)(jian)(jian)測(ce)。當(dang)放(fang)(fang)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)大于(yu)20A時(shi)，過(guo)(guo)(guo)(guo)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)1，2檢(jian)(jian)(jian)(jian)測(ce)端(duan)(duan)子(zi)(zi)VINI和(he)VSS之(zhi)間的(de)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)差大于(yu)過(guo)(guo)(guo)(guo)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)檢(jian)(jian)(jian)(jian)測(ce)電(dian)(dian)(dian)(dian)(dian)位(wei)1VI0V1(O．2V)，且這種(zhong)狀態(tai)保(bao)(bao)(bao)(bao)持在(zai)TIOVl(TIOVl時(shi)間由過(guo)(guo)(guo)(guo)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)1檢(jian)(jian)(jian)(jian)測(ce)延遲端(duan)(duan)子(zi)(zi)CDT外接電(dian)(dian)(dian)(dian)(dian)容C3決定)以(yi)上時(shi)，DOP端(duan)(duan)子(zi)(zi)的(de)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)變(bian)為VDD電(dian)(dian)(dian)(dian)(dian)位(wei)，放(fang)(fang)電(dian)(dian)(dian)(dian)(dian)MOS管關閉，停止放(fang)(fang)電(dian)(dian)(dian)(dian)(dian)，進(jin)入(ru)過(guo)(guo)(guo)(guo)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)1保(bao)(bao)(bao)(bao)護(hu)(hu)狀態(tai)。在(zai)過(guo)(guo)(guo)(guo)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)狀態(tai)下(xia)(xia)(xia)，VMP端(duan)(duan)子(zi)(zi)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)經電(dian)(dian)(dian)(dian)(dian)阻R3由負載(zai)下(xia)(xia)(xia)拉(la)(la)至(zhi)(zhi)VSS；斷開(kai)負載(zai)后，VMP端(duan)(duan)子(zi)(zi)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)經IC內部RVMD電(dian)(dian)(dian)(dian)(dian)阻被上拉(la)(la)至(zhi)(zhi)過(guo)(guo)(guo)(guo)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)檢(jian)(jian)(jian)(jian)測(ce)電(dian)(dian)(dian)(dian)(dian)位(wei)3VIOV3(電(dian)(dian)(dian)(dian)(dian)池1的(de)正(zheng)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)VC1～1．2V)以(yi)上，過(guo)(guo)(guo)(guo)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)狀態(tai)解除，系統恢復正(zheng)常放(fang)(fang)電(dian)(dian)(dian)(dian)(dian)。當(dang)放(fang)(fang)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)大于(yu)50A時(shi)，VINI和(he)VSS之(zhi)間的(de)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)差大于(yu)過(guo)(guo)(guo)(guo)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)檢(jian)(jian)(jian)(jian)測(ce)電(dian)(dian)(dian)(dian)(dian)位(wei)2VIOV2(0．5V)，且這種(zhong)狀態(tai)保(bao)(bao)(bao)(bao)持在(zai)TIOV2(1ms)以(yi)上時(shi)，進(jin)入(ru)過(guo)(guo)(guo)(guo)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)2保(bao)(bao)(bao)(bao)護(hu)(hu)狀態(tai)。當(dang)負載(zai)出現短路(lu)時(shi)，過(guo)(guo)(guo)(guo)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)3檢(jian)(jian)(jian)(jian)測(ce)端(duan)(duan)子(zi)(zi)VMP的(de)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)被瞬(shun)間拉(la)(la)至(zhi)(zhi)VIOV3以(yi)下(xia)(xia)(xia)(檢(jian)(jian)(jian)(jian)測(ce)延遲時(shi)間TI0V3為300μs)，系統進(jin)入(ru)短路(lu)保(bao)(bao)(bao)(bao)護(hu)(hu)(過(guo)(guo)(guo)(guo)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)3保(bao)(bao)(bao)(bao)護(hu)(hu))狀態(tai)。

　　2．3 過(guo)充電保護(hu)

為了確保電池的安全性，該系統對于過充電狀態采取了兩級保護措施。首先，當檢測到某節電池電壓高于4．05V(VCU2n)，且這種狀態保持在TCU2(TCU2時間由S-8244過充電檢測延遲端子ICT外接電容C16決定)以上時，S-8244充電控制用端子CO輸出動態“H”，二級充電MOS管QCHR2關閉，停止充電，這種狀態稱為過充電狀態；進入過充電狀態后，當所有電池電壓都在3．80V(VCL2n)以下時，過充電狀態解除。若因某種原因導致S-8244保護失效，則S-8254過充電保護生效，當檢測到某節電池電壓高于4．25V(VCUln)，且這種狀態保持在TCUl(TCUl時間由S-8254過充電檢測延遲端子CCT外接電容C2決定)以上時，S-8254充電控制用端子COP變為高阻抗，一級充電MOS管QCHRl的G極被外接電阻R2拉高，QCHRl關閉，進入過充電狀態；當所有電池電壓都在4．15V(VCLln)以下時，過充電狀態解除。
2．4 充(chong)電溫度(du)保護(hu)

　　為了確保充(chong)(chong)(chong)電(dian)(dian)時(shi)(shi)(shi)的(de)(de)(de)安全(quan)性(xing)和(he)延(yan)長電(dian)(dian)池的(de)(de)(de)使(shi)用壽命，電(dian)(dian)池的(de)(de)(de)充(chong)(chong)(chong)電(dian)(dian)溫(wen)度應(ying)控(kong)制(zhi)在O～45℃之(zhi)間(jian)為宜。該系統采(cai)用一(yi)個負溫(wen)度系數的(de)(de)(de)NTC溫(wen)度傳感器RES和(he)一(yi)個2路比較器LM393來實現充(chong)(chong)(chong)電(dian)(dian)溫(wen)度保護(hu)，其原理圖如(ru)圖2所示(shi)：當(dang)充(chong)(chong)(chong)電(dian)(dian)溫(wen)度位于(yu)O～45℃之(zhi)間(jian)時(shi)(shi)(shi)，LM393的(de)(de)(de)兩路比較器輸出均為高阻態，PNP型三極(ji)管Q1關斷，對充(chong)(chong)(chong)電(dian)(dian)電(dian)(dian)路不產生影(ying)響；隨(sui)著(zhu)溫(wen)度的(de)(de)(de)升(sheng)高，RES阻值逐漸(jian)變(bian)小，當(dang)溫(wen)度大(da)于(yu)45℃時(shi)(shi)(shi)，LM393下面一(yi)路比較器反轉，輸出低電(dian)(dian)平，通(tong)過二極(ji)管D6將Q1的(de)(de)(de)B極(ji)拉低，Q1導(dao)通(tong)，充(chong)(chong)(chong)電(dian)(dian)MOS管QCHRl的(de)(de)(de)G極(ji)C_QCHR被強制(zhi)拉高，QCHRl關閉，停止充(chong)(chong)(chong)電(dian)(dian)；同樣，隨(sui)著(zhu)溫(wen)度的(de)(de)(de)降(jiang)低，RES阻值逐漸(jian)變(bian)大(da)，當(dang)溫(wen)度小于(yu)O℃時(shi)(shi)(shi)，LM393上面一(yi)路比較器輸出低電(dian)(dian)平，通(tong)過二極(ji)管D5將Q1導(dao)通(tong)，從(cong)而關閉QCHRl，停止充(chong)(chong)(chong)電(dian)(dian)。

　　2．5 其(qi)他保(bao)護功能

　　該(gai)系統通(tong)過一些簡單有效(xiao)的電(dian)路設(she)計，巧妙地實現了所(suo)需的某些保(bao)護(hu)功能。

　　2．5．1 放電溫度(du)保護

　　為了確保電(dian)池(chi)(chi)的(de)使用安全性，需對電(dian)池(chi)(chi)的(de)放電(dian)溫(wen)度進行(xing)限制。該系統在放電(dian)MOS管(guan)QDISl，QDIS2的(de)G極C_QDIS和VDD之間連接了一個(ge)常開型可恢復溫(wen)度保險絲F1。通常狀態下F1保持開路(lu)。不(bu)影響正常放電(dian)；當電(dian)池(chi)(chi)溫(wen)度高于75℃時，F1閉合，C_QDIS與VDD導通．放電(dian)MOS管(guan)關閉，停止放電(dian)，從而實現放電(dian)溫(wen)度保護(hu)功能。

　　2．5．2 充(chong)電(dian)防反(fan)接保護(hu)

　　若誤將充電器的正、負極反(fan)接(jie)(jie)入系(xi)統(tong)中(zhong)，則(ze)會由(you)充電(dian)器(qi)和電(dian)池共同形成(cheng)(cheng)一個(ge)大電(dian)流回(hui)路，導致元器(qi)件損壞，甚至帶來(lai)更大的安全危害。該系(xi)統(tong)在充電(dian)回(hui)路中(zhong)串接(jie)(jie)進一個(ge)防(fang)反(fan)接(jie)(jie)二(er)極管(guan)D1，這樣即(ji)使(shi)充電(dian)器(qi)反(fan)接(jie)(jie)，因此時CHRl的電(dian)位將高(gao)于(yu)(yu)CHR+，由(you)于(yu)(yu)二(er)極管(guan)D1的存在，系(xi)統(tong)將構不(bu)成(cheng)(cheng)回(hui)路，從(cong)而(er)對其起到(dao)了保(bao)護(hu)作用。

　　2．5．3 充電時禁(jin)止放電

　　系統在連接充電器進行充電的過程中若允許其進行放電工作，可能會帶來不必要的安全隱患，因此該系統在充電器的正極輸入端CHR+和C_QDIS之間接入了一個二極管D4。在未連接充電器時(shi)，CHR+懸(xuan)空，對放電工作不產生影響；當連(lian)接充(chong)電器進行充(chong)電時(shi)，C_QDIS通過D4被CHR+強制拉(la)高，QDISl，QDIS2關閉，禁止放電。

　　鋰離子可(ke)充(chong)電電池(chi)(chi)以(yi)其(qi)特(te)有的(de)(de)性能優勢(shi)已(yi)經在多個領域中得到(dao)了普(pu)遍應用(yong)，可(ke)以(yi)預計其(qi)必將成為21世(shi)紀(ji)的(de)(de)主要(yao)動(dong)力電源之一。隨(sui)著(zhu)鋰離子可(ke)充(chong)電電池(chi)(chi)工業的(de)(de)發展，保護系(xi)統作為其(qi)不可(ke)分(fen)割(ge)的(de)(de)一部分(fen)必將起到(dao)越(yue)來(lai)越(yue)重(zhong)要(yao)的(de)(de)作用(yong)。