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)(chuan)、并聯處理，以滿足不同場合的(de)要(yao)求(qiu)。為了(le)確保鋰(li)離(li)子電(dian)(dian)池安全可靠的(de)使用(yong)，本(ben)文介紹(shao)了(le)一(yi)種(zhong)嚴格、周密的(de)充(chong)(chong)、放(fang)(fang)電(dian)(dian)保護(hu)系(xi)統的(de)設計(ji)方(fang)案。該方(fang)案采(cai)用(yong)充(chong)(chong)電(dian)(dian)、放(fang)(fang)電(dian)(dian)分離(li)的(de)控制方(fang)式(shi)，具有兩級單節過(guo)充(chong)(chong)電(dian)(dian)保護(hu)、單節過(guo)放(fang)(fang)電(dian)(dian)保護(hu)、兩級放(fang)(fang)電(dian)(dian)過(guo)電(dian)(dian)流保護(hu)、放(fang)(fang)電(dian)(dian)短路保護(hu)、放(fang)(fang)電(dian)(dian)溫度保護(hu)、充(chong)(chong)電(dian)(dian)溫度保護(hu)、充(chong)(chong)電(dian)(dian)防反接保護(hu)、充(chong)(chong)電(dian)(dian)時禁止放(fang)(fang)電(dian)(dian)等功能，可適(shi)用(yong)于(yu)各種(zhong)三／四節鋰(li)離(li)子可充(chong)(chong)電(dian)(dian)電(dian)(dian)池串(chuan)(chuan)聯使用(yong)的(de)場合。

　　1 系統概述

　　該保(bao)(bao)護系統(tong)采用(yong)精(jing)(jing)工電(dian)(dian)(dian)(dian)子(zi)三(san)／四節(jie)串聯鋰離(li)子(zi)可(ke)充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)專用(yong)充(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系列(lie)內置高(gao)精(jing)(jing)度電(dian)(dian)(dian)(dian)壓(ya)檢測(ce)電(dian)(dian)(dian)(dian)路(lu)和延(yan)(yan)(yan)遲電(dian)(dian)(dian)(dian)路(lu)，針對(dui)各節(jie)電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)進行高(gao)精(jing)(jing)度電(dian)(dian)(dian)(dian)壓(ya)檢測(ce)，實(shi)現單節(jie)過(guo)(guo)(guo)充(chong)電(dian)(dian)(dian)(dian)保(bao)(bao)護和單節(jie)過(guo)(guo)(guo)放(fang)(fang)電(dian)(dian)(dian)(dian)保(bao)(bao)護，并具備三(san)段過(guo)(guo)(guo)電(dian)(dian)(dian)(dian)流(liu)檢測(ce)功能，通過(guo)(guo)(guo)外接電(dian)(dian)(dian)(dian)容(rong)(rong)可(ke)設置過(guo)(guo)(guo)充(chong)電(dian)(dian)(dian)(dian)檢測(ce)延(yan)(yan)(yan)遲時(shi)(shi)間(jian)、過(guo)(guo)(guo)放(fang)(fang)電(dian)(dian)(dian)(dian)檢測(ce)延(yan)(yan)(yan)遲時(shi)(shi)間(jian)和過(guo)(guo)(guo)電(dian)(dian)(dian)(dian)流(liu)檢測(ce)延(yan)(yan)(yan)遲時(shi)(shi)間(jian)1(過(guo)(guo)(guo)電(dian)(dian)(dian)(dian)流(liu)檢測(ce)延(yan)(yan)(yan)遲時(shi)(shi)間(jian)2和過(guo)(guo)(guo)電(dian)(dian)(dian)(dian)流(liu)檢測(ce)延(yan)(yan)(yan)遲時(shi)(shi)間(jian)3在(zai)芯片內部被固定)。該系統(tong)采用(yong)精(jing)(jing)工電(dian)(dian)(dian)(dian)子(zi)S-8244系列(lie)內置高(gao)精(jing)(jing)度電(dian)(dian)(dian)(dian)壓(ya)檢測(ce)電(dian)(dian)(dian)(dian)路(lu)和延(yan)(yan)(yan)遲電(dian)(dian)(dian)(dian)路(lu)的(de)鋰離(li)子(zi)可(ke)充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)二(er)級(ji)保(bao)(bao)護專用(yong)IC實(shi)現電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)的(de)單節(jie)二(er)級(ji)充(chong)電(dian)(dian)(dian)(dian)保(bao)(bao)護，其(qi)保(bao)(bao)護延(yan)(yan)(yan)遲時(shi)(shi)間(jian)可(ke)通過(guo)(guo)(guo)外接電(dian)(dian)(dian)(dian)容(rong)(rong)的(de)容(rong)(rong)值來設置。

　　S-8254通過SEL端子(zi)可以實現(xian)電(dian)(dian)池三節(jie)(jie)串(chuan)聯用(yong)(yong)或四節(jie)(jie)串(chuan)聯用(yong)(yong)的切(qie)換；S-8244則通過電(dian)(dian)阻R22短路第四節(jie)(jie)電(dian)(dian)池電(dian)(dian)壓(ya)檢測端子(zi)VCC3和VSS即可用(yong)(yong)作(zuo)三節(jie)(jie)電(dian)(dian)池串(chuan)聯使用(yong)(yong)時的二(er)級保護。

　　2 各保護功能的實(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1為四節電(dian)池串聯使用時的保護(hu)系統(tong)原理圖。

　　2．1 過放電保(bao)護

　　通常(chang)狀(zhuang)態(tai)下(xia)，S-8254放(fang)電(dian)(dian)(dian)(dian)(dian)控制用(yong)端子(zi)(zi)(zi)DOP為(wei)(wei)VSS(電(dian)(dian)(dian)(dian)(dian)池4的(de)負電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya))電(dian)(dian)(dian)(dian)(dian)位，放(fang)電(dian)(dian)(dian)(dian)(dian)MOS管QDISl，QDIS2處于導通狀(zhuang)態(tai)，系(xi)統可正(zheng)常(chang)進行放(fang)電(dian)(dian)(dian)(dian)(dian)工(gong)作。當(dang)檢測到某節電(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)低(di)于2．7V(VDLn)，且這(zhe)種狀(zhuang)態(tai)保持在(zai)TDL(TDL時間由過(guo)放(fang)電(dian)(dian)(dian)(dian)(dian)檢測延遲端子(zi)(zi)(zi)CDT外接電(dian)(dian)(dian)(dian)(dian)容CS決定(ding))以(yi)上(shang)時，DOP端子(zi)(zi)(zi)的(de)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)變為(wei)(wei)VDD(電(dian)(dian)(dian)(dian)(dian)池1的(de)正(zheng)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya))電(dian)(dian)(dian)(dian)(dian)位，放(fang)電(dian)(dian)(dian)(dian)(dian)MOS管關(guan)閉，停止放(fang)電(dian)(dian)(dian)(dian)(dian)，這(zhe)種狀(zhuang)態(tai)稱(cheng)為(wei)(wei)過(guo)放(fang)電(dian)(dian)(dian)(dian)(dian)狀(zhuang)態(tai)。進入過(guo)放(fang)電(dian)(dian)(dian)(dian)(dian)狀(zhuang)態(tai)后，VMP端子(zi)(zi)(zi)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)經電(dian)(dian)(dian)(dian)(dian)阻R3由負載下(xia)拉(la)至VDD／2以(yi)下(xia)，S-8254轉為(wei)(wei)休眠(mian)狀(zhuang)態(tai)；斷(duan)開負載后，VMP端子(zi)(zi)(zi)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)經電(dian)(dian)(dian)(dian)(dian)阻R9、充電(dian)(dian)(dian)(dian)(dian)MOS管QCHRl和QCHR2由VDD上(shang)拉(la)至VDD／2以(yi)上(shang)且低(di)于VDD，S-8254退出休眠(mian)狀(zhuang)態(tai)。當(dang)所(suo)有電(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)都在(zai)3．0V(VDUn)以(yi)上(shang)時，過(guo)放(fang)電(dian)(dian)(dian)(dian)(dian)狀(zhuang)態(tai)被解除，系(xi)統恢復正(zheng)常(chang)放(fang)電(dian)(dian)(dian)(dian)(dian)工(gong)作。

　　2．2 過電(dian)流、短路保護(hu)

　　該系(xi)統(tong)采用2個(ge)并聯(lian)的(de)(de)20mΩ功率(lv)電(dian)(dian)(dian)(dian)阻(zu)RS1，RS2用于(yu)(yu)過(guo)(guo)電(dian)(dian)(dian)(dian)流(liu)檢測(ce)(ce)(ce)。當(dang)放(fang)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)大(da)于(yu)(yu)20A時，過(guo)(guo)電(dian)(dian)(dian)(dian)流(liu)1，2檢測(ce)(ce)(ce)端(duan)子VINI和VSS之間(jian)的(de)(de)電(dian)(dian)(dian)(dian)壓(ya)差大(da)于(yu)(yu)過(guo)(guo)電(dian)(dian)(dian)(dian)流(liu)檢測(ce)(ce)(ce)電(dian)(dian)(dian)(dian)位1VI0V1(O．2V)，且(qie)這種(zhong)狀(zhuang)(zhuang)(zhuang)態保持(chi)在(zai)TIOVl(TIOVl時間(jian)由過(guo)(guo)電(dian)(dian)(dian)(dian)流(liu)1檢測(ce)(ce)(ce)延遲端(duan)子CDT外接電(dian)(dian)(dian)(dian)容C3決定)以上(shang)時，DOP端(duan)子的(de)(de)電(dian)(dian)(dian)(dian)壓(ya)變為(wei)(wei)VDD電(dian)(dian)(dian)(dian)位，放(fang)電(dian)(dian)(dian)(dian)MOS管關(guan)閉，停止放(fang)電(dian)(dian)(dian)(dian)，進入(ru)過(guo)(guo)電(dian)(dian)(dian)(dian)流(liu)1保護狀(zhuang)(zhuang)(zhuang)態。在(zai)過(guo)(guo)電(dian)(dian)(dian)(dian)流(liu)狀(zhuang)(zhuang)(zhuang)態下(xia)，VMP端(duan)子電(dian)(dian)(dian)(dian)壓(ya)經(jing)電(dian)(dian)(dian)(dian)阻(zu)R3由負(fu)(fu)載(zai)下(xia)拉(la)至VSS；斷開負(fu)(fu)載(zai)后，VMP端(duan)子電(dian)(dian)(dian)(dian)壓(ya)經(jing)IC內部(bu)RVMD電(dian)(dian)(dian)(dian)阻(zu)被(bei)上(shang)拉(la)至過(guo)(guo)電(dian)(dian)(dian)(dian)流(liu)檢測(ce)(ce)(ce)電(dian)(dian)(dian)(dian)位3VIOV3(電(dian)(dian)(dian)(dian)池1的(de)(de)正(zheng)電(dian)(dian)(dian)(dian)壓(ya)VC1～1．2V)以上(shang)，過(guo)(guo)電(dian)(dian)(dian)(dian)流(liu)狀(zhuang)(zhuang)(zhuang)態解除，系(xi)統(tong)恢復(fu)正(zheng)常放(fang)電(dian)(dian)(dian)(dian)。當(dang)放(fang)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)大(da)于(yu)(yu)50A時，VINI和VSS之間(jian)的(de)(de)電(dian)(dian)(dian)(dian)壓(ya)差大(da)于(yu)(yu)過(guo)(guo)電(dian)(dian)(dian)(dian)流(liu)檢測(ce)(ce)(ce)電(dian)(dian)(dian)(dian)位2VIOV2(0．5V)，且(qie)這種(zhong)狀(zhuang)(zhuang)(zhuang)態保持(chi)在(zai)TIOV2(1ms)以上(shang)時，進入(ru)過(guo)(guo)電(dian)(dian)(dian)(dian)流(liu)2保護狀(zhuang)(zhuang)(zhuang)態。當(dang)負(fu)(fu)載(zai)出現短路時，過(guo)(guo)電(dian)(dian)(dian)(dian)流(liu)3檢測(ce)(ce)(ce)端(duan)子VMP的(de)(de)電(dian)(dian)(dian)(dian)壓(ya)被(bei)瞬間(jian)拉(la)至VIOV3以下(xia)(檢測(ce)(ce)(ce)延遲時間(jian)TI0V3為(wei)(wei)300μs)，系(xi)統(tong)進入(ru)短路保護(過(guo)(guo)電(dian)(dian)(dian)(dian)流(liu)3保護)狀(zhuang)(zhuang)(zhuang)態。

　　2．3 過充電保護

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(chong)電(dian)溫度保護

　　為(wei)了確保(bao)充(chong)電時的安全性和延長電池(chi)的使(shi)用壽命，電池(chi)的充(chong)電溫(wen)(wen)度(du)應(ying)控制在O～45℃之間(jian)為(wei)宜(yi)。該(gai)系(xi)統采用一(yi)(yi)個(ge)負溫(wen)(wen)度(du)系(xi)數的NTC溫(wen)(wen)度(du)傳感器(qi)RES和一(yi)(yi)個(ge)2路(lu)比(bi)較(jiao)器(qi)LM393來實現(xian)充(chong)電溫(wen)(wen)度(du)保(bao)護，其原理圖(tu)(tu)如圖(tu)(tu)2所(suo)示：當(dang)充(chong)電溫(wen)(wen)度(du)位于O～45℃之間(jian)時，LM393的兩(liang)路(lu)比(bi)較(jiao)器(qi)輸(shu)(shu)出(chu)(chu)均為(wei)高(gao)阻態(tai)，PNP型三(san)極管Q1關斷，對充(chong)電電路(lu)不產生影(ying)響；隨著(zhu)溫(wen)(wen)度(du)的升(sheng)高(gao)，RES阻值逐(zhu)漸變小，當(dang)溫(wen)(wen)度(du)大于45℃時，LM393下(xia)面一(yi)(yi)路(lu)比(bi)較(jiao)器(qi)反轉，輸(shu)(shu)出(chu)(chu)低(di)電平(ping)，通(tong)過(guo)二極管D6將Q1的B極拉低(di)，Q1導通(tong)，充(chong)電MOS管QCHRl的G極C_QCHR被強(qiang)制拉高(gao)，QCHRl關閉(bi)(bi)，停止充(chong)電；同樣(yang)，隨著(zhu)溫(wen)(wen)度(du)的降低(di)，RES阻值逐(zhu)漸變大，當(dang)溫(wen)(wen)度(du)小于O℃時，LM393上面一(yi)(yi)路(lu)比(bi)較(jiao)器(qi)輸(shu)(shu)出(chu)(chu)低(di)電平(ping)，通(tong)過(guo)二極管D5將Q1導通(tong)，從而關閉(bi)(bi)QCHRl，停止充(chong)電。

　　2．5 其他(ta)保護功能

　　該系(xi)統(tong)通過一些簡單有(you)效的電(dian)路設(she)計，巧妙地(di)實現了所需(xu)的某些保護功能。

　　2．5．1 放電(dian)溫度保(bao)護

　　為了確保(bao)電池的(de)使用安全性，需對電池的(de)放電溫(wen)度(du)(du)進行限制。該系統在放電MOS管QDISl，QDIS2的(de)G極C_QDIS和VDD之間連接了一個常開型(xing)可恢復(fu)溫(wen)度(du)(du)保(bao)險(xian)絲F1。通常狀態下F1保(bao)持開路。不(bu)影響(xiang)正常放電；當電池溫(wen)度(du)(du)高(gao)于(yu)75℃時，F1閉(bi)合，C_QDIS與VDD導通．放電MOS管關閉(bi)，停止放電，從而(er)實現放電溫(wen)度(du)(du)保(bao)護功能。

　　2．5．2 充電防反接保護

　　若誤將充電器的(de)(de)正、負極(ji)反(fan)接(jie)入系統中(zhong)，則會由(you)充電(dian)器和電(dian)池(chi)共(gong)同形成一個大電(dian)流(liu)回路(lu)，導致元器件損壞，甚(shen)至(zhi)帶來更大的(de)(de)安全危害。該系統在(zai)充電(dian)回路(lu)中(zhong)串接(jie)進一個防反(fan)接(jie)二(er)極(ji)管D1，這樣即使充電(dian)器反(fan)接(jie)，因此時CHRl的(de)(de)電(dian)位將(jiang)高于(yu)(yu)CHR+，由(you)于(yu)(yu)二(er)極(ji)管D1的(de)(de)存在(zai)，系統將(jiang)構(gou)不(bu)成回路(lu)，從而對其起到了保護作(zuo)用。

　　2．5．3 充電時禁止放電

　　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(shi)，CHR+懸空(kong)，對放(fang)電(dian)工作(zuo)不產生影響；當(dang)連接(jie)充電(dian)器進行充電(dian)時(shi)，C_QDIS通過D4被CHR+強制拉高(gao)，QDISl，QDIS2關閉，禁止放(fang)電(dian)。

　　鋰(li)離子可充電電池以(yi)其(qi)特有的(de)(de)性能優勢已經在多個領域中得到(dao)(dao)了普(pu)遍應(ying)用，可以(yi)預計其(qi)必(bi)將(jiang)成為21世紀的(de)(de)主要動力(li)電源(yuan)之一(yi)。隨著鋰(li)離子可充電電池工業的(de)(de)發展，保(bao)護(hu)系統作為其(qi)不可分割的(de)(de)一(yi)部分必(bi)將(jiang)起到(dao)(dao)越來越重(zhong)要的(de)(de)作用。