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(xing)串、并聯(lian)處理，以滿足不(bu)同場合(he)的(de)要求。為(wei)了確保(bao)鋰離(li)(li)(li)子電(dian)(dian)(dian)池安全(quan)可靠的(de)使(shi)用，本文介紹了一(yi)種嚴格、周密的(de)充(chong)(chong)、放(fang)電(dian)(dian)(dian)保(bao)護(hu)系統的(de)設計方案(an)。該(gai)方案(an)采用充(chong)(chong)電(dian)(dian)(dian)、放(fang)電(dian)(dian)(dian)分(fen)離(li)(li)(li)的(de)控制方式(shi)，具有兩級單(dan)節(jie)過(guo)充(chong)(chong)電(dian)(dian)(dian)保(bao)護(hu)、單(dan)節(jie)過(guo)放(fang)電(dian)(dian)(dian)保(bao)護(hu)、兩級放(fang)電(dian)(dian)(dian)過(guo)電(dian)(dian)(dian)流保(bao)護(hu)、放(fang)電(dian)(dian)(dian)短路保(bao)護(hu)、放(fang)電(dian)(dian)(dian)溫度(du)保(bao)護(hu)、充(chong)(chong)電(dian)(dian)(dian)溫度(du)保(bao)護(hu)、充(chong)(chong)電(dian)(dian)(dian)防反接保(bao)護(hu)、充(chong)(chong)電(dian)(dian)(dian)時(shi)禁(jin)止放(fang)電(dian)(dian)(dian)等功(gong)能(neng)，可適用于各種三／四節(jie)鋰離(li)(li)(li)子可充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)池串聯(lian)使(shi)用的(de)場合(he)。

　　1 系統概述

　　該(gai)(gai)保(bao)護(hu)(hu)系(xi)(xi)(xi)統采用(yong)精工電(dian)(dian)(dian)(dian)子三／四(si)節串聯鋰離(li)子可充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)池專(zhuan)用(yong)充(chong)、放電(dian)(dian)(dian)(dian)保(bao)護(hu)(hu)ICS-8254構建一級(ji)保(bao)護(hu)(hu)。S-8254系(xi)(xi)(xi)列內(nei)置高精度(du)電(dian)(dian)(dian)(dian)壓檢(jian)測(ce)電(dian)(dian)(dian)(dian)路(lu)和延(yan)(yan)遲(chi)(chi)(chi)電(dian)(dian)(dian)(dian)路(lu)，針(zhen)對各節電(dian)(dian)(dian)(dian)池進行高精度(du)電(dian)(dian)(dian)(dian)壓檢(jian)測(ce)，實(shi)現(xian)單(dan)節過(guo)(guo)(guo)充(chong)電(dian)(dian)(dian)(dian)保(bao)護(hu)(hu)和單(dan)節過(guo)(guo)(guo)放電(dian)(dian)(dian)(dian)保(bao)護(hu)(hu)，并具(ju)備三段(duan)過(guo)(guo)(guo)電(dian)(dian)(dian)(dian)流(liu)檢(jian)測(ce)功能(neng)，通(tong)過(guo)(guo)(guo)外接(jie)電(dian)(dian)(dian)(dian)容(rong)可設(she)置過(guo)(guo)(guo)充(chong)電(dian)(dian)(dian)(dian)檢(jian)測(ce)延(yan)(yan)遲(chi)(chi)(chi)時(shi)(shi)間(jian)(jian)、過(guo)(guo)(guo)放電(dian)(dian)(dian)(dian)檢(jian)測(ce)延(yan)(yan)遲(chi)(chi)(chi)時(shi)(shi)間(jian)(jian)和過(guo)(guo)(guo)電(dian)(dian)(dian)(dian)流(liu)檢(jian)測(ce)延(yan)(yan)遲(chi)(chi)(chi)時(shi)(shi)間(jian)(jian)1(過(guo)(guo)(guo)電(dian)(dian)(dian)(dian)流(liu)檢(jian)測(ce)延(yan)(yan)遲(chi)(chi)(chi)時(shi)(shi)間(jian)(jian)2和過(guo)(guo)(guo)電(dian)(dian)(dian)(dian)流(liu)檢(jian)測(ce)延(yan)(yan)遲(chi)(chi)(chi)時(shi)(shi)間(jian)(jian)3在芯(xin)片內(nei)部(bu)被固(gu)定)。該(gai)(gai)系(xi)(xi)(xi)統采用(yong)精工電(dian)(dian)(dian)(dian)子S-8244系(xi)(xi)(xi)列內(nei)置高精度(du)電(dian)(dian)(dian)(dian)壓檢(jian)測(ce)電(dian)(dian)(dian)(dian)路(lu)和延(yan)(yan)遲(chi)(chi)(chi)電(dian)(dian)(dian)(dian)路(lu)的(de)鋰離(li)子可充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)池二級(ji)保(bao)護(hu)(hu)專(zhuan)用(yong)IC實(shi)現(xian)電(dian)(dian)(dian)(dian)池的(de)單(dan)節二級(ji)充(chong)電(dian)(dian)(dian)(dian)保(bao)護(hu)(hu)，其保(bao)護(hu)(hu)延(yan)(yan)遲(chi)(chi)(chi)時(shi)(shi)間(jian)(jian)可通(tong)過(guo)(guo)(guo)外接(jie)電(dian)(dian)(dian)(dian)容(rong)的(de)容(rong)值來設(she)置。

　　S-8254通(tong)過SEL端子(zi)可以實現(xian)電(dian)(dian)池三(san)節(jie)串聯用(yong)或四節(jie)串聯用(yong)的(de)切換(huan)；S-8244則通(tong)過電(dian)(dian)阻(zu)R22短路第四節(jie)電(dian)(dian)池電(dian)(dian)壓檢(jian)測(ce)端子(zi)VCC3和VSS即可用(yong)作(zuo)三(san)節(jie)電(dian)(dian)池串聯使用(yong)時的(de)二級保(bao)護。

　　2 各(ge)保護功(gong)能(neng)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(tu)1為四節電池串聯(lian)使用時的保護系統原理圖(tu)。

　　2．1 過放(fang)電保護(hu)

　　通(tong)常狀(zhuang)(zhuang)態(tai)(tai)(tai)下，S-8254放(fang)電(dian)(dian)控制用端(duan)子DOP為VSS(電(dian)(dian)池(chi)4的負(fu)電(dian)(dian)壓)電(dian)(dian)位(wei)，放(fang)電(dian)(dian)MOS管(guan)QDISl，QDIS2處于導通(tong)狀(zhuang)(zhuang)態(tai)(tai)(tai)，系統可正常進(jin)行放(fang)電(dian)(dian)工作。當檢測到某(mou)節(jie)電(dian)(dian)池(chi)電(dian)(dian)壓低(di)于2．7V(VDLn)，且(qie)這(zhe)種狀(zhuang)(zhuang)態(tai)(tai)(tai)保持在(zai)(zai)TDL(TDL時間由(you)過(guo)放(fang)電(dian)(dian)檢測延遲端(duan)子CDT外接電(dian)(dian)容CS決(jue)定)以(yi)上時，DOP端(duan)子的電(dian)(dian)壓變為VDD(電(dian)(dian)池(chi)1的正電(dian)(dian)壓)電(dian)(dian)位(wei)，放(fang)電(dian)(dian)MOS管(guan)關閉(bi)，停止放(fang)電(dian)(dian)，這(zhe)種狀(zhuang)(zhuang)態(tai)(tai)(tai)稱為過(guo)放(fang)電(dian)(dian)狀(zhuang)(zhuang)態(tai)(tai)(tai)。進(jin)入過(guo)放(fang)電(dian)(dian)狀(zhuang)(zhuang)態(tai)(tai)(tai)后，VMP端(duan)子電(dian)(dian)壓經電(dian)(dian)阻R3由(you)負(fu)載下拉至VDD／2以(yi)下，S-8254轉為休(xiu)眠(mian)狀(zhuang)(zhuang)態(tai)(tai)(tai)；斷開負(fu)載后，VMP端(duan)子電(dian)(dian)壓經電(dian)(dian)阻R9、充(chong)電(dian)(dian)MOS管(guan)QCHRl和QCHR2由(you)VDD上拉至VDD／2以(yi)上且(qie)低(di)于VDD，S-8254退(tui)出休(xiu)眠(mian)狀(zhuang)(zhuang)態(tai)(tai)(tai)。當所(suo)有電(dian)(dian)池(chi)電(dian)(dian)壓都在(zai)(zai)3．0V(VDUn)以(yi)上時，過(guo)放(fang)電(dian)(dian)狀(zhuang)(zhuang)態(tai)(tai)(tai)被解除(chu)，系統恢復(fu)正常放(fang)電(dian)(dian)工作。

　　2．2 過電流、短路(lu)保護(hu)

　　該(gai)系統采用2個并聯的20mΩ功率電(dian)(dian)(dian)阻RS1，RS2用于(yu)過(guo)(guo)(guo)(guo)電(dian)(dian)(dian)流(liu)檢(jian)測。當放(fang)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)大(da)于(yu)20A時(shi)，過(guo)(guo)(guo)(guo)電(dian)(dian)(dian)流(liu)1，2檢(jian)測端子VINI和VSS之間(jian)的電(dian)(dian)(dian)壓(ya)差(cha)大(da)于(yu)過(guo)(guo)(guo)(guo)電(dian)(dian)(dian)流(liu)檢(jian)測電(dian)(dian)(dian)位(wei)1VI0V1(O．2V)，且這種狀態(tai)保(bao)持(chi)在(zai)TIOVl(TIOVl時(shi)間(jian)由過(guo)(guo)(guo)(guo)電(dian)(dian)(dian)流(liu)1檢(jian)測延(yan)遲端子CDT外接電(dian)(dian)(dian)容C3決定)以上(shang)(shang)時(shi)，DOP端子的電(dian)(dian)(dian)壓(ya)變為(wei)VDD電(dian)(dian)(dian)位(wei)，放(fang)電(dian)(dian)(dian)MOS管關閉，停(ting)止(zhi)放(fang)電(dian)(dian)(dian)，進(jin)入(ru)過(guo)(guo)(guo)(guo)電(dian)(dian)(dian)流(liu)1保(bao)護狀態(tai)。在(zai)過(guo)(guo)(guo)(guo)電(dian)(dian)(dian)流(liu)狀態(tai)下，VMP端子電(dian)(dian)(dian)壓(ya)經(jing)電(dian)(dian)(dian)阻R3由負(fu)載(zai)(zai)下拉(la)至VSS；斷開(kai)負(fu)載(zai)(zai)后，VMP端子電(dian)(dian)(dian)壓(ya)經(jing)IC內部RVMD電(dian)(dian)(dian)阻被上(shang)(shang)拉(la)至過(guo)(guo)(guo)(guo)電(dian)(dian)(dian)流(liu)檢(jian)測電(dian)(dian)(dian)位(wei)3VIOV3(電(dian)(dian)(dian)池1的正電(dian)(dian)(dian)壓(ya)VC1～1．2V)以上(shang)(shang)，過(guo)(guo)(guo)(guo)電(dian)(dian)(dian)流(liu)狀態(tai)解除(chu)，系統恢復正常放(fang)電(dian)(dian)(dian)。當放(fang)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)大(da)于(yu)50A時(shi)，VINI和VSS之間(jian)的電(dian)(dian)(dian)壓(ya)差(cha)大(da)于(yu)過(guo)(guo)(guo)(guo)電(dian)(dian)(dian)流(liu)檢(jian)測電(dian)(dian)(dian)位(wei)2VIOV2(0．5V)，且這種狀態(tai)保(bao)持(chi)在(zai)TIOV2(1ms)以上(shang)(shang)時(shi)，進(jin)入(ru)過(guo)(guo)(guo)(guo)電(dian)(dian)(dian)流(liu)2保(bao)護狀態(tai)。當負(fu)載(zai)(zai)出現短(duan)路時(shi)，過(guo)(guo)(guo)(guo)電(dian)(dian)(dian)流(liu)3檢(jian)測端子VMP的電(dian)(dian)(dian)壓(ya)被瞬間(jian)拉(la)至VIOV3以下(檢(jian)測延(yan)遲時(shi)間(jian)TI0V3為(wei)300μs)，系統進(jin)入(ru)短(duan)路保(bao)護(過(guo)(guo)(guo)(guo)電(dian)(dian)(dian)流(liu)3保(bao)護)狀態(tai)。

　　2．3 過(guo)充電保護

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 充電(dian)溫度保護

　　為了確保充(chong)(chong)(chong)電(dian)(dian)(dian)時的(de)(de)安全(quan)性和延長(chang)電(dian)(dian)(dian)池的(de)(de)使用壽命，電(dian)(dian)(dian)池的(de)(de)充(chong)(chong)(chong)電(dian)(dian)(dian)溫(wen)(wen)度(du)(du)(du)(du)應控制(zhi)在O～45℃之間為宜(yi)。該系統(tong)采(cai)用一(yi)個負溫(wen)(wen)度(du)(du)(du)(du)系數的(de)(de)NTC溫(wen)(wen)度(du)(du)(du)(du)傳感器(qi)(qi)RES和一(yi)個2路(lu)比(bi)(bi)較器(qi)(qi)LM393來實現充(chong)(chong)(chong)電(dian)(dian)(dian)溫(wen)(wen)度(du)(du)(du)(du)保護，其原理圖如圖2所(suo)示：當(dang)充(chong)(chong)(chong)電(dian)(dian)(dian)溫(wen)(wen)度(du)(du)(du)(du)位于(yu)O～45℃之間時，LM393的(de)(de)兩路(lu)比(bi)(bi)較器(qi)(qi)輸出(chu)均(jun)為高(gao)(gao)阻(zu)(zu)態，PNP型三極(ji)管(guan)Q1關斷，對充(chong)(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)路(lu)不產生影響；隨(sui)著溫(wen)(wen)度(du)(du)(du)(du)的(de)(de)升高(gao)(gao)，RES阻(zu)(zu)值(zhi)逐漸(jian)(jian)變小，當(dang)溫(wen)(wen)度(du)(du)(du)(du)大(da)于(yu)45℃時，LM393下面一(yi)路(lu)比(bi)(bi)較器(qi)(qi)反(fan)轉(zhuan)，輸出(chu)低(di)(di)電(dian)(dian)(dian)平，通(tong)(tong)過(guo)二(er)極(ji)管(guan)D6將Q1的(de)(de)B極(ji)拉低(di)(di)，Q1導(dao)通(tong)(tong)，充(chong)(chong)(chong)電(dian)(dian)(dian)MOS管(guan)QCHRl的(de)(de)G極(ji)C_QCHR被強制(zhi)拉高(gao)(gao)，QCHRl關閉，停(ting)止充(chong)(chong)(chong)電(dian)(dian)(dian)；同樣，隨(sui)著溫(wen)(wen)度(du)(du)(du)(du)的(de)(de)降低(di)(di)，RES阻(zu)(zu)值(zhi)逐漸(jian)(jian)變大(da)，當(dang)溫(wen)(wen)度(du)(du)(du)(du)小于(yu)O℃時，LM393上面一(yi)路(lu)比(bi)(bi)較器(qi)(qi)輸出(chu)低(di)(di)電(dian)(dian)(dian)平，通(tong)(tong)過(guo)二(er)極(ji)管(guan)D5將Q1導(dao)通(tong)(tong)，從而關閉QCHRl，停(ting)止充(chong)(chong)(chong)電(dian)(dian)(dian)。

　　2．5 其他保護功能(neng)

　　該系(xi)統通過一些簡單有效的電(dian)路設計，巧妙(miao)地實現了所需的某些保護功能。

　　2．5．1 放電溫(wen)度(du)保(bao)護(hu)

　　為(wei)了確(que)保電(dian)(dian)池(chi)的使用安全性，需對電(dian)(dian)池(chi)的放(fang)(fang)電(dian)(dian)溫(wen)度(du)進行限制。該系統在放(fang)(fang)電(dian)(dian)MOS管QDISl，QDIS2的G極C_QDIS和(he)VDD之間連接了一個常(chang)開型可恢復溫(wen)度(du)保險絲F1。通常(chang)狀態下F1保持開路。不影響正常(chang)放(fang)(fang)電(dian)(dian)；當電(dian)(dian)池(chi)溫(wen)度(du)高于75℃時，F1閉合，C_QDIS與VDD導通．放(fang)(fang)電(dian)(dian)MOS管關閉，停(ting)止放(fang)(fang)電(dian)(dian)，從而實(shi)現放(fang)(fang)電(dian)(dian)溫(wen)度(du)保護功能。

　　2．5．2 充電防(fang)反接保(bao)護

　　若誤將充電器的(de)正、負極(ji)(ji)反接(jie)入系(xi)(xi)統(tong)(tong)(tong)中(zhong)，則會由充電(dian)器和(he)電(dian)池共同形成一個大(da)電(dian)流回路，導致元(yuan)器件損壞(huai)，甚至帶來(lai)更大(da)的(de)安全(quan)危害。該系(xi)(xi)統(tong)(tong)(tong)在(zai)充電(dian)回路中(zhong)串接(jie)進一個防(fang)反接(jie)二(er)極(ji)(ji)管(guan)D1，這樣(yang)即使充電(dian)器反接(jie)，因(yin)此時CHRl的(de)電(dian)位將高于(yu)CHR+，由于(yu)二(er)極(ji)(ji)管(guan)D1的(de)存(cun)在(zai)，系(xi)(xi)統(tong)(tong)(tong)將構不成回路，從而對其起到了保護作(zuo)用。

　　2．5．3 充電時(shi)禁止放電

　　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，CHR+懸空，對放電(dian)(dian)工作不產(chan)生影(ying)響；當(dang)連接充(chong)電(dian)(dian)器進行充(chong)電(dian)(dian)時，C_QDIS通過D4被(bei)CHR+強制拉高(gao)，QDISl，QDIS2關閉，禁止放電(dian)(dian)。

　　鋰(li)離子(zi)可充電(dian)電(dian)池以其特有的(de)(de)性(xing)能優勢已經(jing)在(zai)多個(ge)領(ling)域中(zhong)得到(dao)了普遍應用，可以預計其必將成為(wei)21世紀的(de)(de)主要(yao)動力電(dian)源(yuan)之一。隨著鋰(li)離子(zi)可充電(dian)電(dian)池工業的(de)(de)發(fa)展，保(bao)護系(xi)統作(zuo)為(wei)其不(bu)可分(fen)割的(de)(de)一部(bu)分(fen)必將起到(dao)越(yue)來越(yue)重要(yao)的(de)(de)作(zuo)用。