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(chuan)、并聯處理，以滿(man)足不(bu)同(tong)場(chang)合(he)的(de)要(yao)求(qiu)。為了確(que)保(bao)(bao)(bao)(bao)(bao)鋰離子電(dian)(dian)(dian)池安全(quan)可靠(kao)的(de)使(shi)用，本文介(jie)紹了一種嚴格、周密(mi)的(de)充(chong)、放(fang)電(dian)(dian)(dian)保(bao)(bao)(bao)(bao)(bao)護(hu)系統的(de)設計方案。該方案采(cai)用充(chong)電(dian)(dian)(dian)、放(fang)電(dian)(dian)(dian)分離的(de)控制方式，具有兩(liang)級單(dan)節(jie)過(guo)充(chong)電(dian)(dian)(dian)保(bao)(bao)(bao)(bao)(bao)護(hu)、單(dan)節(jie)過(guo)放(fang)電(dian)(dian)(dian)保(bao)(bao)(bao)(bao)(bao)護(hu)、兩(liang)級放(fang)電(dian)(dian)(dian)過(guo)電(dian)(dian)(dian)流保(bao)(bao)(bao)(bao)(bao)護(hu)、放(fang)電(dian)(dian)(dian)短(duan)路(lu)保(bao)(bao)(bao)(bao)(bao)護(hu)、放(fang)電(dian)(dian)(dian)溫度(du)保(bao)(bao)(bao)(bao)(bao)護(hu)、充(chong)電(dian)(dian)(dian)溫度(du)保(bao)(bao)(bao)(bao)(bao)護(hu)、充(chong)電(dian)(dian)(dian)防反接(jie)保(bao)(bao)(bao)(bao)(bao)護(hu)、充(chong)電(dian)(dian)(dian)時(shi)禁止(zhi)放(fang)電(dian)(dian)(dian)等功(gong)能(neng)，可適用于(yu)各種三／四(si)節(jie)鋰離子可充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)池串(chuan)聯使(shi)用的(de)場(chang)合(he)。

　　1 系統概述

　　該保(bao)(bao)護系(xi)統采(cai)用精工電(dian)(dian)(dian)(dian)子(zi)三(san)／四節(jie)(jie)(jie)串聯鋰(li)離(li)子(zi)可(ke)充(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)池(chi)專用充(chong)(chong)、放(fang)(fang)電(dian)(dian)(dian)(dian)保(bao)(bao)護ICS-8254構建一級(ji)保(bao)(bao)護。S-8254系(xi)列內置高(gao)精度(du)電(dian)(dian)(dian)(dian)壓檢(jian)測電(dian)(dian)(dian)(dian)路(lu)(lu)和(he)(he)(he)延遲(chi)電(dian)(dian)(dian)(dian)路(lu)(lu)，針對各(ge)節(jie)(jie)(jie)電(dian)(dian)(dian)(dian)池(chi)進行高(gao)精度(du)電(dian)(dian)(dian)(dian)壓檢(jian)測，實(shi)現(xian)單節(jie)(jie)(jie)過(guo)(guo)充(chong)(chong)電(dian)(dian)(dian)(dian)保(bao)(bao)護和(he)(he)(he)單節(jie)(jie)(jie)過(guo)(guo)放(fang)(fang)電(dian)(dian)(dian)(dian)保(bao)(bao)護，并具(ju)備三(san)段過(guo)(guo)電(dian)(dian)(dian)(dian)流檢(jian)測功能，通過(guo)(guo)外接電(dian)(dian)(dian)(dian)容可(ke)設(she)置過(guo)(guo)充(chong)(chong)電(dian)(dian)(dian)(dian)檢(jian)測延遲(chi)時間、過(guo)(guo)放(fang)(fang)電(dian)(dian)(dian)(dian)檢(jian)測延遲(chi)時間和(he)(he)(he)過(guo)(guo)電(dian)(dian)(dian)(dian)流檢(jian)測延遲(chi)時間1(過(guo)(guo)電(dian)(dian)(dian)(dian)流檢(jian)測延遲(chi)時間2和(he)(he)(he)過(guo)(guo)電(dian)(dian)(dian)(dian)流檢(jian)測延遲(chi)時間3在芯片內部被固定)。該系(xi)統采(cai)用精工電(dian)(dian)(dian)(dian)子(zi)S-8244系(xi)列內置高(gao)精度(du)電(dian)(dian)(dian)(dian)壓檢(jian)測電(dian)(dian)(dian)(dian)路(lu)(lu)和(he)(he)(he)延遲(chi)電(dian)(dian)(dian)(dian)路(lu)(lu)的(de)鋰(li)離(li)子(zi)可(ke)充(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)池(chi)二級(ji)保(bao)(bao)護專用IC實(shi)現(xian)電(dian)(dian)(dian)(dian)池(chi)的(de)單節(jie)(jie)(jie)二級(ji)充(chong)(chong)電(dian)(dian)(dian)(dian)保(bao)(bao)護，其(qi)保(bao)(bao)護延遲(chi)時間可(ke)通過(guo)(guo)外接電(dian)(dian)(dian)(dian)容的(de)容值來設(she)置。

　　S-8254通(tong)過(guo)SEL端子可以實(shi)現電(dian)池三(san)節串聯(lian)用或四節串聯(lian)用的(de)切換；S-8244則通(tong)過(guo)電(dian)阻R22短路第(di)四節電(dian)池電(dian)壓檢測端子VCC3和VSS即可用作三(san)節電(dian)池串聯(lian)使(shi)用時的(de)二級保護。

　　2 各保(bao)護功能的實(shi)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(bao)護系統(tong)原理圖(tu)。

　　2．1 過放電保護

　　通(tong)常狀態(tai)下，S-8254放(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)控制(zhi)用端(duan)(duan)子(zi)DOP為(wei)VSS(電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)4的(de)負電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya))電(dian)(dian)(dian)(dian)(dian)(dian)位，放(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)MOS管(guan)QDISl，QDIS2處于導通(tong)狀態(tai)，系統可正(zheng)常進行放(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)工作(zuo)。當檢測到某節電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)低于2．7V(VDLn)，且這(zhe)種狀態(tai)保持在TDL(TDL時(shi)間由過放(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)檢測延遲端(duan)(duan)子(zi)CDT外接電(dian)(dian)(dian)(dian)(dian)(dian)容CS決定)以(yi)上時(shi)，DOP端(duan)(duan)子(zi)的(de)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)變為(wei)VDD(電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)1的(de)正(zheng)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya))電(dian)(dian)(dian)(dian)(dian)(dian)位，放(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)MOS管(guan)關閉(bi)，停止放(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)，這(zhe)種狀態(tai)稱為(wei)過放(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)狀態(tai)。進入(ru)過放(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)狀態(tai)后，VMP端(duan)(duan)子(zi)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)經(jing)(jing)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)R3由負載下拉至VDD／2以(yi)下，S-8254轉為(wei)休(xiu)眠(mian)狀態(tai)；斷開負載后，VMP端(duan)(duan)子(zi)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)經(jing)(jing)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)R9、充電(dian)(dian)(dian)(dian)(dian)(dian)MOS管(guan)QCHRl和QCHR2由VDD上拉至VDD／2以(yi)上且低于VDD，S-8254退出休(xiu)眠(mian)狀態(tai)。當所有電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)都在3．0V(VDUn)以(yi)上時(shi)，過放(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)狀態(tai)被解除，系統恢復正(zheng)常放(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)工作(zuo)。

　　2．2 過電(dian)流、短路保護

　　該系(xi)統采用(yong)2個并聯的(de)(de)(de)20mΩ功率電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)RS1，RS2用(yong)于(yu)(yu)(yu)過(guo)(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)檢(jian)測(ce)(ce)(ce)。當(dang)放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)大(da)(da)于(yu)(yu)(yu)20A時(shi)(shi)，過(guo)(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)1，2檢(jian)測(ce)(ce)(ce)端(duan)子(zi)VINI和(he)(he)VSS之間(jian)(jian)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)差大(da)(da)于(yu)(yu)(yu)過(guo)(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)檢(jian)測(ce)(ce)(ce)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)1VI0V1(O．2V)，且這種狀(zhuang)態(tai)(tai)保持在(zai)(zai)TIOVl(TIOVl時(shi)(shi)間(jian)(jian)由(you)過(guo)(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)1檢(jian)測(ce)(ce)(ce)延遲端(duan)子(zi)CDT外(wai)接電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容C3決定)以上(shang)時(shi)(shi)，DOP端(duan)子(zi)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)變為VDD電(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)，放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)MOS管(guan)關(guan)閉，停止(zhi)放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)，進入過(guo)(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)1保護狀(zhuang)態(tai)(tai)。在(zai)(zai)過(guo)(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)狀(zhuang)態(tai)(tai)下(xia)，VMP端(duan)子(zi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)經電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)R3由(you)負載(zai)下(xia)拉至(zhi)VSS；斷開負載(zai)后，VMP端(duan)子(zi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)經IC內部(bu)RVMD電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)被上(shang)拉至(zhi)過(guo)(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)檢(jian)測(ce)(ce)(ce)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)3VIOV3(電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池1的(de)(de)(de)正(zheng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)VC1～1．2V)以上(shang)，過(guo)(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)狀(zhuang)態(tai)(tai)解(jie)除，系(xi)統恢(hui)復正(zheng)常放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)。當(dang)放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)大(da)(da)于(yu)(yu)(yu)50A時(shi)(shi)，VINI和(he)(he)VSS之間(jian)(jian)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)差大(da)(da)于(yu)(yu)(yu)過(guo)(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)檢(jian)測(ce)(ce)(ce)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)2VIOV2(0．5V)，且這種狀(zhuang)態(tai)(tai)保持在(zai)(zai)TIOV2(1ms)以上(shang)時(shi)(shi)，進入過(guo)(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)2保護狀(zhuang)態(tai)(tai)。當(dang)負載(zai)出現(xian)短(duan)路(lu)時(shi)(shi)，過(guo)(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)3檢(jian)測(ce)(ce)(ce)端(duan)子(zi)VMP的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)被瞬間(jian)(jian)拉至(zhi)VIOV3以下(xia)(檢(jian)測(ce)(ce)(ce)延遲時(shi)(shi)間(jian)(jian)TI0V3為300μs)，系(xi)統進入短(duan)路(lu)保護(過(guo)(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)3保護)狀(zhuang)態(tai)(tai)。

　　2．3 過充電(dian)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(wen)度保護

　　為(wei)了確(que)保充電(dian)(dian)(dian)時的(de)(de)安(an)全性(xing)和延長電(dian)(dian)(dian)池的(de)(de)使用壽(shou)命，電(dian)(dian)(dian)池的(de)(de)充電(dian)(dian)(dian)溫度(du)(du)應(ying)控制在O～45℃之(zhi)間為(wei)宜。該系統采用一(yi)個負(fu)溫度(du)(du)系數(shu)的(de)(de)NTC溫度(du)(du)傳感(gan)器(qi)(qi)(qi)(qi)RES和一(yi)個2路(lu)比較器(qi)(qi)(qi)(qi)LM393來實現充電(dian)(dian)(dian)溫度(du)(du)保護，其原理圖如圖2所(suo)示：當充電(dian)(dian)(dian)溫度(du)(du)位于O～45℃之(zhi)間時，LM393的(de)(de)兩路(lu)比較器(qi)(qi)(qi)(qi)輸出均(jun)為(wei)高(gao)(gao)阻態，PNP型三極(ji)管Q1關(guan)斷(duan)，對充電(dian)(dian)(dian)電(dian)(dian)(dian)路(lu)不(bu)產(chan)生影響；隨(sui)著(zhu)溫度(du)(du)的(de)(de)升高(gao)(gao)，RES阻值逐(zhu)漸(jian)變小，當溫度(du)(du)大(da)于45℃時，LM393下(xia)面一(yi)路(lu)比較器(qi)(qi)(qi)(qi)反(fan)轉，輸出低電(dian)(dian)(dian)平，通(tong)(tong)過二(er)極(ji)管D6將Q1的(de)(de)B極(ji)拉(la)(la)低，Q1導通(tong)(tong)，充電(dian)(dian)(dian)MOS管QCHRl的(de)(de)G極(ji)C_QCHR被(bei)強制拉(la)(la)高(gao)(gao)，QCHRl關(guan)閉，停(ting)止(zhi)充電(dian)(dian)(dian)；同樣(yang)，隨(sui)著(zhu)溫度(du)(du)的(de)(de)降低，RES阻值逐(zhu)漸(jian)變大(da)，當溫度(du)(du)小于O℃時，LM393上面一(yi)路(lu)比較器(qi)(qi)(qi)(qi)輸出低電(dian)(dian)(dian)平，通(tong)(tong)過二(er)極(ji)管D5將Q1導通(tong)(tong)，從而關(guan)閉QCHRl，停(ting)止(zhi)充電(dian)(dian)(dian)。

　　2．5 其他保護(hu)功能

　　該系統通過(guo)一些簡單有效的(de)電(dian)路設計，巧妙地實(shi)現(xian)了所需的(de)某些保護(hu)功能。

　　2．5．1 放電溫度保護

　　為了確(que)保(bao)電(dian)(dian)池的(de)使用(yong)安全性，需(xu)對(dui)電(dian)(dian)池的(de)放(fang)(fang)電(dian)(dian)溫(wen)度(du)進行限(xian)制。該系統在放(fang)(fang)電(dian)(dian)MOS管(guan)QDISl，QDIS2的(de)G極C_QDIS和VDD之(zhi)間連接了一個常開型可恢復溫(wen)度(du)保(bao)險絲F1。通常狀(zhuang)態下F1保(bao)持開路。不(bu)影響正常放(fang)(fang)電(dian)(dian)；當電(dian)(dian)池溫(wen)度(du)高于75℃時，F1閉合(he)，C_QDIS與(yu)VDD導通．放(fang)(fang)電(dian)(dian)MOS管(guan)關閉，停止放(fang)(fang)電(dian)(dian)，從而實現放(fang)(fang)電(dian)(dian)溫(wen)度(du)保(bao)護功能。

　　2．5．2 充電防反接保護

　　若誤將充電器的(de)正(zheng)、負極(ji)反(fan)接(jie)(jie)入系統中(zhong)，則會(hui)由(you)充電(dian)器(qi)和電(dian)池共同形(xing)成(cheng)一(yi)個大(da)電(dian)流(liu)回(hui)(hui)路，導致元器(qi)件損壞，甚至(zhi)帶來更大(da)的(de)安全危害。該系統在充電(dian)回(hui)(hui)路中(zhong)串接(jie)(jie)進一(yi)個防(fang)反(fan)接(jie)(jie)二(er)極(ji)管D1，這樣(yang)即使充電(dian)器(qi)反(fan)接(jie)(jie)，因(yin)此時CHRl的(de)電(dian)位將(jiang)高于(yu)CHR+，由(you)于(yu)二(er)極(ji)管D1的(de)存在，系統將(jiang)構不成(cheng)回(hui)(hui)路，從而對(dui)其起到了保(bao)護作用(yong)。

　　2．5．3 充電(dian)時(shi)禁止(zhi)放電(dian)

　　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(fang)電(dian)工作不產生影響；當連接充電(dian)器進(jin)行充電(dian)時(shi)，C_QDIS通過D4被(bei)CHR+強(qiang)制拉高，QDISl，QDIS2關閉(bi)，禁止放(fang)電(dian)。

　　鋰離子可(ke)充電(dian)(dian)電(dian)(dian)池(chi)以其(qi)特有(you)的(de)性能優(you)勢已經(jing)在多個領域中得到了(le)普遍應用(yong)，可(ke)以預計其(qi)必(bi)將成為(wei)21世紀的(de)主要(yao)動力電(dian)(dian)源之一。隨(sui)著鋰離子可(ke)充電(dian)(dian)電(dian)(dian)池(chi)工業的(de)發展，保護(hu)系統作為(wei)其(qi)不可(ke)分割的(de)一部(bu)分必(bi)將起到越(yue)來(lai)越(yue)重要(yao)的(de)作用(yong)。