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、并聯處理，以(yi)滿(man)足不同場合(he)(he)的(de)要求。為了(le)確(que)保(bao)(bao)(bao)鋰離(li)子電(dian)(dian)(dian)池安(an)全可靠的(de)使用(yong)，本文介紹了(le)一種嚴(yan)格、周密的(de)充(chong)(chong)、放電(dian)(dian)(dian)保(bao)(bao)(bao)護(hu)系統(tong)的(de)設(she)計方(fang)案(an)。該方(fang)案(an)采用(yong)充(chong)(chong)電(dian)(dian)(dian)、放電(dian)(dian)(dian)分離(li)的(de)控(kong)制方(fang)式，具有(you)兩(liang)級單(dan)節(jie)過(guo)(guo)充(chong)(chong)電(dian)(dian)(dian)保(bao)(bao)(bao)護(hu)、單(dan)節(jie)過(guo)(guo)放電(dian)(dian)(dian)保(bao)(bao)(bao)護(hu)、兩(liang)級放電(dian)(dian)(dian)過(guo)(guo)電(dian)(dian)(dian)流保(bao)(bao)(bao)護(hu)、放電(dian)(dian)(dian)短路保(bao)(bao)(bao)護(hu)、放電(dian)(dian)(dian)溫(wen)度保(bao)(bao)(bao)護(hu)、充(chong)(chong)電(dian)(dian)(dian)溫(wen)度保(bao)(bao)(bao)護(hu)、充(chong)(chong)電(dian)(dian)(dian)防反接保(bao)(bao)(bao)護(hu)、充(chong)(chong)電(dian)(dian)(dian)時(shi)禁(jin)止放電(dian)(dian)(dian)等(deng)功能，可適用(yong)于各種三／四節(jie)鋰離(li)子可充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)池串聯使用(yong)的(de)場合(he)(he)。

　　1 系統概述

　　該保(bao)(bao)(bao)(bao)護(hu)系(xi)統(tong)采用(yong)精(jing)(jing)工(gong)電(dian)(dian)(dian)(dian)子(zi)(zi)三／四節串聯鋰離(li)子(zi)(zi)可充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)池專(zhuan)用(yong)充、放電(dian)(dian)(dian)(dian)保(bao)(bao)(bao)(bao)護(hu)ICS-8254構建一(yi)級(ji)保(bao)(bao)(bao)(bao)護(hu)。S-8254系(xi)列內(nei)置高精(jing)(jing)度電(dian)(dian)(dian)(dian)壓檢(jian)測(ce)電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)和(he)延(yan)(yan)遲電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)，針對各節電(dian)(dian)(dian)(dian)池進行高精(jing)(jing)度電(dian)(dian)(dian)(dian)壓檢(jian)測(ce)，實(shi)現單節過(guo)(guo)充電(dian)(dian)(dian)(dian)保(bao)(bao)(bao)(bao)護(hu)和(he)單節過(guo)(guo)放電(dian)(dian)(dian)(dian)保(bao)(bao)(bao)(bao)護(hu)，并具備三段過(guo)(guo)電(dian)(dian)(dian)(dian)流(liu)檢(jian)測(ce)功能，通過(guo)(guo)外接電(dian)(dian)(dian)(dian)容可設置過(guo)(guo)充電(dian)(dian)(dian)(dian)檢(jian)測(ce)延(yan)(yan)遲時(shi)間(jian)、過(guo)(guo)放電(dian)(dian)(dian)(dian)檢(jian)測(ce)延(yan)(yan)遲時(shi)間(jian)和(he)過(guo)(guo)電(dian)(dian)(dian)(dian)流(liu)檢(jian)測(ce)延(yan)(yan)遲時(shi)間(jian)1(過(guo)(guo)電(dian)(dian)(dian)(dian)流(liu)檢(jian)測(ce)延(yan)(yan)遲時(shi)間(jian)2和(he)過(guo)(guo)電(dian)(dian)(dian)(dian)流(liu)檢(jian)測(ce)延(yan)(yan)遲時(shi)間(jian)3在芯片內(nei)部被固定)。該系(xi)統(tong)采用(yong)精(jing)(jing)工(gong)電(dian)(dian)(dian)(dian)子(zi)(zi)S-8244系(xi)列內(nei)置高精(jing)(jing)度電(dian)(dian)(dian)(dian)壓檢(jian)測(ce)電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)和(he)延(yan)(yan)遲電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)的鋰離(li)子(zi)(zi)可充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)池二級(ji)保(bao)(bao)(bao)(bao)護(hu)專(zhuan)用(yong)IC實(shi)現電(dian)(dian)(dian)(dian)池的單節二級(ji)充電(dian)(dian)(dian)(dian)保(bao)(bao)(bao)(bao)護(hu)，其保(bao)(bao)(bao)(bao)護(hu)延(yan)(yan)遲時(shi)間(jian)可通過(guo)(guo)外接電(dian)(dian)(dian)(dian)容的容值(zhi)來設置。

　　S-8254通(tong)(tong)過(guo)SEL端(duan)子可(ke)以實現電池(chi)三(san)節(jie)(jie)串聯(lian)用(yong)或(huo)四節(jie)(jie)串聯(lian)用(yong)的(de)切換；S-8244則(ze)通(tong)(tong)過(guo)電阻(zu)R22短路第四節(jie)(jie)電池(chi)電壓檢(jian)測(ce)端(duan)子VCC3和VSS即(ji)可(ke)用(yong)作三(san)節(jie)(jie)電池(chi)串聯(lian)使(shi)用(yong)時的(de)二(er)級保護。

　　2 各(ge)保護功(gong)能的實現

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為四節電池串聯使(shi)用時的(de)保護系統原理(li)圖(tu)。

　　2．1 過(guo)放電保護(hu)

　　通常(chang)狀(zhuang)(zhuang)態(tai)(tai)(tai)(tai)(tai)下，S-8254放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)控制用(yong)端(duan)子(zi)DOP為VSS(電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)4的(de)負(fu)(fu)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya))電(dian)(dian)(dian)(dian)(dian)(dian)位(wei)，放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)MOS管QDISl，QDIS2處于(yu)導通狀(zhuang)(zhuang)態(tai)(tai)(tai)(tai)(tai)，系統可(ke)正(zheng)常(chang)進行放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)工(gong)作。當(dang)檢測(ce)到某節電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)低于(yu)2．7V(VDLn)，且這(zhe)種狀(zhuang)(zhuang)態(tai)(tai)(tai)(tai)(tai)保持在TDL(TDL時間由過(guo)放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)檢測(ce)延遲端(duan)子(zi)CDT外接(jie)電(dian)(dian)(dian)(dian)(dian)(dian)容CS決定)以上(shang)時，DOP端(duan)子(zi)的(de)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)變為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))電(dian)(dian)(dian)(dian)(dian)(dian)位(wei)，放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)MOS管關閉，停止放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)，這(zhe)種狀(zhuang)(zhuang)態(tai)(tai)(tai)(tai)(tai)稱為過(guo)放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)狀(zhuang)(zhuang)態(tai)(tai)(tai)(tai)(tai)。進入過(guo)放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)狀(zhuang)(zhuang)態(tai)(tai)(tai)(tai)(tai)后，VMP端(duan)子(zi)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)經(jing)(jing)電(dian)(dian)(dian)(dian)(dian)(dian)阻R3由負(fu)(fu)載下拉(la)至VDD／2以下，S-8254轉(zhuan)為休(xiu)眠狀(zhuang)(zhuang)態(tai)(tai)(tai)(tai)(tai)；斷開負(fu)(fu)載后，VMP端(duan)子(zi)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)經(jing)(jing)電(dian)(dian)(dian)(dian)(dian)(dian)阻R9、充電(dian)(dian)(dian)(dian)(dian)(dian)MOS管QCHRl和QCHR2由VDD上(shang)拉(la)至VDD／2以上(shang)且低于(yu)VDD，S-8254退出休(xiu)眠狀(zhuang)(zhuang)態(tai)(tai)(tai)(tai)(tai)。當(dang)所有電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)都(dou)在3．0V(VDUn)以上(shang)時，過(guo)放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)狀(zhuang)(zhuang)態(tai)(tai)(tai)(tai)(tai)被(bei)解除(chu)，系統恢復正(zheng)常(chang)放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)工(gong)作。

　　2．2 過電流、短路保護

　　該(gai)系(xi)統采(cai)用2個并聯的(de)(de)20mΩ功(gong)率電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻RS1，RS2用于(yu)過(guo)(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)檢(jian)測(ce)(ce)。當放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)大(da)于(yu)20A時，過(guo)(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)1，2檢(jian)測(ce)(ce)端(duan)子(zi)(zi)VINI和(he)VSS之間(jian)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)差(cha)大(da)于(yu)過(guo)(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)檢(jian)測(ce)(ce)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)1VI0V1(O．2V)，且這(zhe)種(zhong)狀態(tai)保(bao)持在(zai)(zai)TIOVl(TIOVl時間(jian)由過(guo)(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)1檢(jian)測(ce)(ce)延遲(chi)端(duan)子(zi)(zi)CDT外接電(dian)(dian)(dian)(dian)(dian)(dian)(dian)容(rong)C3決定)以(yi)(yi)(yi)上時，DOP端(duan)子(zi)(zi)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)變為VDD電(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)，放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)MOS管關閉，停止放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)，進(jin)入過(guo)(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)1保(bao)護(hu)狀態(tai)。在(zai)(zai)過(guo)(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)狀態(tai)下(xia)，VMP端(duan)子(zi)(zi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)經電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻R3由負(fu)載(zai)下(xia)拉(la)(la)至(zhi)(zhi)VSS；斷開負(fu)載(zai)后，VMP端(duan)子(zi)(zi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)經IC內部RVMD電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻被上拉(la)(la)至(zhi)(zhi)過(guo)(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)檢(jian)測(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)正電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)VC1～1．2V)以(yi)(yi)(yi)上，過(guo)(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)狀態(tai)解除，系(xi)統恢復正常放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)。當放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)大(da)于(yu)50A時，VINI和(he)VSS之間(jian)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)差(cha)大(da)于(yu)過(guo)(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)檢(jian)測(ce)(ce)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)位(wei)2VIOV2(0．5V)，且這(zhe)種(zhong)狀態(tai)保(bao)持在(zai)(zai)TIOV2(1ms)以(yi)(yi)(yi)上時，進(jin)入過(guo)(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)2保(bao)護(hu)狀態(tai)。當負(fu)載(zai)出現短路(lu)時，過(guo)(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)3檢(jian)測(ce)(ce)端(duan)子(zi)(zi)VMP的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)被瞬間(jian)拉(la)(la)至(zhi)(zhi)VIOV3以(yi)(yi)(yi)下(xia)(檢(jian)測(ce)(ce)延遲(chi)時間(jian)TI0V3為300μs)，系(xi)統進(jin)入短路(lu)保(bao)護(hu)(過(guo)(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)3保(bao)護(hu))狀態(tai)。

　　2．3 過充(chong)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 充電溫度保護(hu)

　　為了確(que)保充(chong)電時(shi)的安全性(xing)和延長電池的使(shi)用(yong)(yong)壽(shou)命，電池的充(chong)電溫(wen)度應控制在O～45℃之間為宜。該系統(tong)采用(yong)(yong)一(yi)個(ge)負溫(wen)度系數的NTC溫(wen)度傳(chuan)感器(qi)(qi)RES和一(yi)個(ge)2路(lu)(lu)(lu)比(bi)(bi)較器(qi)(qi)LM393來實現充(chong)電溫(wen)度保護，其(qi)原理(li)圖如圖2所(suo)示：當(dang)充(chong)電溫(wen)度位于O～45℃之間時(shi)，LM393的兩路(lu)(lu)(lu)比(bi)(bi)較器(qi)(qi)輸出(chu)均為高(gao)阻(zu)態，PNP型三極管Q1關斷(duan)，對充(chong)電電路(lu)(lu)(lu)不產生影響；隨(sui)著溫(wen)度的升高(gao)，RES阻(zu)值逐(zhu)漸(jian)變小(xiao)(xiao)，當(dang)溫(wen)度大于45℃時(shi)，LM393下(xia)面一(yi)路(lu)(lu)(lu)比(bi)(bi)較器(qi)(qi)反轉，輸出(chu)低電平，通(tong)(tong)過二極管D6將Q1的B極拉低，Q1導通(tong)(tong)，充(chong)電MOS管QCHRl的G極C_QCHR被強制拉高(gao)，QCHRl關閉，停(ting)止充(chong)電；同(tong)樣，隨(sui)著溫(wen)度的降(jiang)低，RES阻(zu)值逐(zhu)漸(jian)變大，當(dang)溫(wen)度小(xiao)(xiao)于O℃時(shi)，LM393上面一(yi)路(lu)(lu)(lu)比(bi)(bi)較器(qi)(qi)輸出(chu)低電平，通(tong)(tong)過二極管D5將Q1導通(tong)(tong)，從(cong)而關閉QCHRl，停(ting)止充(chong)電。

　　2．5 其他保護功(gong)能

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

　　2．5．1 放電溫度保護

　　為了確保電(dian)池(chi)的使(shi)用安全性(xing)，需對電(dian)池(chi)的放(fang)電(dian)溫度(du)(du)(du)進(jin)行限制。該(gai)系(xi)統在放(fang)電(dian)MOS管QDISl，QDIS2的G極C_QDIS和(he)VDD之間連接了一個常開型(xing)可恢復溫度(du)(du)(du)保險絲F1。通常狀態下(xia)F1保持開路。不影響正(zheng)常放(fang)電(dian)；當電(dian)池(chi)溫度(du)(du)(du)高于75℃時(shi)，F1閉(bi)合，C_QDIS與(yu)VDD導(dao)通．放(fang)電(dian)MOS管關閉(bi)，停止放(fang)電(dian)，從而(er)實現放(fang)電(dian)溫度(du)(du)(du)保護功(gong)能(neng)。

　　2．5．2 充電防(fang)反接保護

　　若誤將充電器的(de)(de)正、負極(ji)(ji)反(fan)接(jie)入系統中，則會由充(chong)電(dian)器(qi)(qi)和電(dian)池共同形成一個(ge)(ge)大(da)電(dian)流回(hui)(hui)路，導致元器(qi)(qi)件損壞，甚至(zhi)帶來更大(da)的(de)(de)安全(quan)危害。該系統在充(chong)電(dian)回(hui)(hui)路中串接(jie)進一個(ge)(ge)防反(fan)接(jie)二極(ji)(ji)管(guan)(guan)D1，這樣即使充(chong)電(dian)器(qi)(qi)反(fan)接(jie)，因此時CHRl的(de)(de)電(dian)位將高于CHR+，由于二極(ji)(ji)管(guan)(guan)D1的(de)(de)存在，系統將構不成回(hui)(hui)路，從而(er)對其起到了保護作用。

　　2．5．3 充(chong)電(dian)(dian)時(shi)禁止放電(dian)(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+懸空，對放電(dian)(dian)工作不產生(sheng)影響；當連接充電(dian)(dian)器進行充電(dian)(dian)時(shi)，C_QDIS通過D4被CHR+強制拉高，QDISl，QDIS2關閉，禁止放電(dian)(dian)。

　　鋰(li)離子可(ke)充電電池以(yi)其特有(you)的(de)(de)性能優勢已經在多(duo)個領域中得到了(le)普遍應用(yong)，可(ke)以(yi)預計(ji)其必將成(cheng)為21世(shi)紀的(de)(de)主要(yao)動力電源之一。隨著(zhu)鋰(li)離子可(ke)充電電池工業的(de)(de)發展，保護系統作為其不可(ke)分割的(de)(de)一部分必將起到越來(lai)越重要(yao)的(de)(de)作用(yong)。