在有些應用中，較長(chang)的(de)電(dian)(dian)池(chi)壽命(ming)、較多的(de)充(chong)(chong)電(dian)(dian)次數或(huo)較安全的(de)電(dian)(dian)池(chi)比電(dian)(dian)池(chi)容(rong)量更重要。本文介紹幾種可以(yi)極大延長(chang)電(dian)(dian)池(chi)壽命(ming)的(de)鋰離子電(dian)(dian)池(chi)充(chong)(chong)電(dian)(dian)和放電(dian)(dian)方(fang)法。

  幾乎所有高性能便攜式產品都會使用包括鋰離子聚合物電池在內的可再充電鋰離子電池，這是因為與(yu)其他可再充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)池相(xiang)比(bi)，鋰離子電(dian)(dian)(dian)池有(you)較(jiao)高(gao)的(de)能(neng)量密度(du)、較(jiao)高(gao)的(de)電(dian)(dian)(dian)池電(dian)(dian)(dian)壓(ya)、自(zi)放電(dian)(dian)(dian)少、周期壽命非常長，而(er)且環(huan)保，且充(chong)(chong)電(dian)(dian)(dian)和維護簡單。另外，由于(yu)其具(ju)有(you)相(xiang)對高(gao)的(de)電(dian)(dian)(dian)壓(ya)（2.9V至4.2V），因此很多便攜(xie)式產(chan)品都能(neng)用(yong)單節電(dian)(dian)(dian)池工作，從而(er)簡化(hua)了產(chan)品總(zong)體設(she)計。C速率等于(yu)特定條(tiao)件下的(de)充(chong)(chong)電(dian)(dian)(dian)或放電(dian)(dian)(dian)電(dian)(dian)(dian)流，定義如下：I=M×Cn

  其中：I = 充電(dian)或放電(dian)電(dian)流(liu)，單(dan)位為(wei)A；M = C的倍數(shu)或分數(shu)；C = 額定容量的數(shu)值，單(dan)位為(wei)Ah；N = 小時(shi)數(shu)（對應于C）。

  以(yi)1倍(bei)C速率放(fang)(fang)(fang)(fang)電(dian)(dian)(dian)的(de)電(dian)(dian)(dian)池將在一個(ge)小時內釋(shi)放(fang)(fang)(fang)(fang)標(biao)稱(cheng)的(de)額定(ding)容(rong)量。例如，如果標(biao)稱(cheng)容(rong)量是1000mAhr,那(nei)么1C的(de)放(fang)(fang)(fang)(fang)電(dian)(dian)(dian)速率對應于1000mA的(de)放(fang)(fang)(fang)(fang)電(dian)(dian)(dian)電(dian)(dian)(dian)流，C/10的(de)速率對應100mA的(de)放(fang)(fang)(fang)(fang)電(dian)(dian)(dian)電(dian)(dian)(dian)流。

  通常生產商標定的電池容量都是指n=5時，即5小時放電的容量。例如，上述電池在200mA恒流放電時能夠提供5小時的工作時間。理論上該電池在1000mA恒流放電時能夠提供1小時的工作時間。然而實際上由于大電池放電時效能降低，此時的工作時間將小于1小時。
 

  給鋰離子電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)推薦方(fang)法(fa)(fa)(fa)是，向電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)提(ti)供一(yi)個±1%限(xian)(xian)壓(ya)(ya)(ya)的(de)(de)(de)恒定(ding)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)，直到(dao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)充(chong)(chong)(chong)(chong)(chong)滿(man)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，然后(hou)停止(zhi)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。用來決定(ding)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)何(he)時(shi)(shi)充(chong)(chong)(chong)(chong)(chong)滿(man)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)方(fang)法(fa)(fa)(fa)包括(kuo)：給總的(de)(de)(de)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)時(shi)(shi)間定(ding)時(shi)(shi)、監視(shi)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)或兼用這(zhe)兩種(zhong)方(fang)法(fa)(fa)(fa)。第(di)一(yi)種(zhong)方(fang)法(fa)(fa)(fa)采用限(xian)(xian)壓(ya)(ya)(ya)恒定(ding)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)，變(bian)化范圍從(cong)C/2到(dao)1C,持續2.5至(zhi)(zhi)3小時(shi)(shi)，使(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)達(da)到(dao)100%充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。也可以使(shi)用較低(di)的(de)(de)(de)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)，但是將需要(yao)更(geng)長時(shi)(shi)間。第(di)二種(zhong)方(fang)法(fa)(fa)(fa)與第(di)一(yi)種(zhong)方(fang)法(fa)(fa)(fa)類似，只(zhi)是需要(yao)監視(shi)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)。隨著(zhu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的(de)(de)(de)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)上升(sheng)，這(zhe)與采用第(di)一(yi)種(zhong)方(fang)法(fa)(fa)(fa)時(shi)(shi)完(wan)全(quan)相同(tong)。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)達(da)到(dao)編(bian)程限(xian)(xian)壓(ya)(ya)(ya)值（也稱為浮(fu)動(dong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)）時(shi)(shi)，充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)開始下(xia)降。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)一(yi)開始下(xia)降時(shi)(shi)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)約充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)至(zhi)(zhi)容(rong)(rong)量的(de)(de)(de)50%至(zhi)(zhi)60%.浮(fu)動(dong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)繼續提(ti)供，直到(dao)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)降至(zhi)(zhi)足夠低(di)的(de)(de)(de)水平（C/10至(zhi)(zhi)C/20），這(zhe)時(shi)(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)約充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)至(zhi)(zhi)容(rong)(rong)量的(de)(de)(de)92%至(zhi)(zhi)99%,充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)周(zhou)期終(zhong)止(zhi)。目前，要(yao)為標準鋰離子電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)快速(su)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)（不到(dao)1小時(shi)(shi)）至(zhi)(zhi)容(rong)(rong)量的(de)(de)(de)100%,還沒(mei)有一(yi)種(zhong)安(an)全(quan)的(de)(de)(de)方(fang)法(fa)(fa)(fa)。

  有些鋰離子電池充電器允許使用熱敏電阻監視電池溫度。這么做的主要目的是，如果電池溫度超出推薦的0℃至40℃窗口范圍，就禁止充電。與鎳鎘或鎳氫金屬電池不同，鋰離子電池在充電時溫度上升非常少。圖1是一個典型的鋰離子電池充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)曲線(xian)，圖中顯示了充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)、電(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)壓(ya)和電(dian)(dian)(dian)(dian)(dian)池容量隨時(shi)間(jian)的變化。那么怎樣才能正確地為(wei)鋰(li)(li)離(li)(li)子電(dian)(dian)(dian)(dian)(dian)池充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)呢？鋰(li)(li)離(li)(li)子電(dian)(dian)(dian)(dian)(dian)池最(zui)適合的充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)過(guo)程(cheng)可以(yi)分(fen)為(wei)四(si)個階(jie)段：涓流(liu)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)、恒流(liu)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)、恒壓(ya)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)以(yi)及充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)終止。參考圖1.

  階段1:涓流充電--涓流充電用來先對完全放電的電池單元進行預充（恢復性充電）。在電池電壓低于3V左右時，先采用最大0.1C的恒定電流對電池進行充電。
  階段2:恒流充電--當電池電壓上升到涓流充電閾值以上時，提高充電電流進行恒流充電。恒流充電的電流在0.2C至 1.0C之間。恒流充電時的電流并不要求十分精確，準恒定電流也可以。在線性充電器設計中，電流經常隨著電池電壓的上升而上升，以盡量減輕傳輸晶體管上的 散熱問題。大于1C的恒流充電并不會縮短整個充電周期時間，因此這種做法不可取。當以更高電流充電時，由于電極反應的過壓以及電池內部阻抗上的電壓上升，電池電壓會更快速地上升。恒流充電階段會變短，但由于下面恒壓充電階段的時間會相應增加，因此總的充電周期時間并不會縮短。
  階段3:恒壓充電-- 當電池電壓上升到4.2V時，恒流充電結束，開始恒壓充電階段。為使性能達到最佳，穩壓容差應當優于+1%.
階段4:充電終止--與鎳電池不同，并不建議對鋰離子電池連(lian)續涓流充電(dian)。連(lian)續涓流充電(dian)會導致金屬鋰出現極(ji)板電(dian)鍍效應。這會使電(dian)池(chi)不穩定，并且有可能(neng)導致突然的自動快速(su)解體。

  有兩種典型的充(chong)電(dian)終止方法：采(cai)用最小(xiao)充(chong)電(dian)電(dian)流(liu)判(pan)斷或采(cai)用定時(shi)(shi)器（或者兩者的結(jie)合）。最小(xiao)電(dian)流(liu)法監視恒(heng)壓充(chong)電(dian)階段的充(chong)電(dian)電(dian)流(liu)，并在充(chong)電(dian)電(dian)流(liu)減小(xiao)到0.02C至(zhi)0.07C范(fan)圍時(shi)(shi)終止充(chong)電(dian)。第二種方法從恒(heng)壓充(chong)電(dian)階段開始時(shi)(shi)計時(shi)(shi)，持(chi)續充(chong)電(dian)兩個小(xiao)時(shi)(shi)后終止充(chong)電(dian)過程(cheng)。

  上述四階段的充電法完成對完全放電電池的充電約需要2.5至3小時。高級充電器還采用了更多(duo)安全(quan)措施(shi)。例如如果電池溫度超出指(zhi)定窗口（通(tong)常為0℃至45℃），那么充電會暫停(ting)。

  1 決定鋰離子電池周期壽命或服務壽命的(de)因素

  不(bu)存(cun)在任(ren)何延長或縮短電(dian)池壽命(ming)的單一因素，而(er)常(chang)常(chang)是幾種因素合起來發揮作用(yong)。就延長周期(qi)壽命(ming)而(er)言有以下(xia)方法可以延長電(dian)池壽命(ming)：

1).采用部(bu)分(fen)放(fang)電(dian)的做法。在再充電(dian)前僅使用20%或30%的電(dian)池(chi)容(rong)量(liang)會極(ji)大延(yan)長(chang)周期壽命。作為(wei)一個一般性的規則，5至(zhi)10個淺放(fang)電(dian)周期等于(yu)1個滿放(fang)電(dian)周期。盡管部(bu)分(fen)放(fang)電(dian)周期可能(neng)達到數千次，但是(shi)保持電(dian)池(chi)處于(yu)滿充電(dian)狀態也縮(suo)短電(dian)池(chi)壽命。如(ru)果可能(neng)，應(ying)該(gai)避免滿放(fang)電(dian)周期（降至(zhi)2.5V或3V,取決于(yu)化學(xue)材料）。

2).避免充電(dian)(dian)至(zhi)(zhi)容量(liang)的100%.選(xuan)擇一(yi)個較低(di)的浮動(dong)電(dian)(dian)壓可以(yi)做到這一(yi)點(dian)。降低(di)浮動(dong)電(dian)(dian)壓將提高周期(qi)壽(shou)命和(he)服務壽(shou)命，代(dai)價是(shi)降低(di)電(dian)(dian)池容量(liang)。浮動(dong)電(dian)(dian)壓降低(di)100mV至(zhi)(zhi)300mV可以(yi)將周期(qi)壽(shou)命延長2至(zhi)(zhi)5倍或更長。與其他(ta)化學材料相比，鋰(li)離子(zi)鈷化學材料對較高浮動(dong)電(dian)(dian)壓更敏感。磷酸鋰(li)離子(zi)電(dian)(dian)池一(yi)般(ban)比更常見的鋰(li)離子(zi)電(dian)(dian)池的浮動(dong)電(dian)(dian)壓低(di)。

3). 選擇合適的充電終止方法。選擇一個采用最小充電電流終止（C/10或C/x）的充電器，通過不(bu)充(chong)電(dian)(dian)到(dao)容(rong)量(liang)的100%,也(ye)可以延長電(dian)(dian)池(chi)壽命(ming)。例(li)如，電(dian)(dian)流降(jiang)至(zhi)C/5時結束(shu)充(chong)電(dian)(dian)周(zhou)期與將浮動電(dian)(dian)壓降(jiang)至(zhi)4.1V的效(xiao)果類似(si)。在這(zhe)兩種情況下(xia)，電(dian)(dian)池(chi)都(dou)只充(chong)電(dian)(dian)至(zhi)約為容(rong)量(liang)的85%,這(zhe)是決(jue)定電(dian)(dian)池(chi)壽命(ming)的一個重要(yao)因素。

4).限(xian)(xian)制(zhi)電(dian)(dian)(dian)池(chi)溫度(du)(du)。限(xian)(xian)制(zhi)電(dian)(dian)(dian)池(chi)的極限(xian)(xian)溫度(du)(du)可以延(yan)長電(dian)(dian)(dian)池(chi)壽(shou)命，尤其是禁止在(zai)0℃以下充電(dian)(dian)(dian)。在(zai)0℃以下充電(dian)(dian)(dian)促(cu)進金屬在(zai)電(dian)(dian)(dian)池(chi)陽極上的鍍敷，這可能造成內部短(duan)路，產生熱量(liang)并使電(dian)(dian)(dian)池(chi)不穩定(ding)和不安全。很(hen)多(duo)電(dian)(dian)(dian)池(chi)充電(dian)(dian)(dian)器都有測量(liang)電(dian)(dian)(dian)池(chi)溫度(du)(du)的裝(zhuang)置，以確保不會(hui)在(zai)極限(xian)(xian)溫度(du)(du)時充電(dian)(dian)(dian)。

5).避免大的充電(dian)(dian)和放電(dian)(dian)電(dian)(dian)流，因為這會縮短周期壽命。有些(xie)化學材料更適合較大電(dian)(dian)流，如(ru)鋰離子(zi)錳和磷酸(suan)鋰離子(zi)電(dian)(dian)池(chi)。大電(dian)(dian)流給電(dian)(dian)池(chi)施(shi)加了過大的壓(ya)力。

6).避(bi)免低(di)于2V或(huo)2.5V的深(shen)度放電(dian)(dian)(dian)(dian)，因(yin)為這會迅速(su)永久性損壞鋰離子電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)。可(ke)能發生內部金屬鍍敷，這會引起短路，使電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)不(bu)可(ke)用或(huo)不(bu)安全。大多數鋰離子電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)在(zai)電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)組內部都有(you)電(dian)(dian)(dian)(dian)子電(dian)(dian)(dian)(dian)路，如(ru)果充電(dian)(dian)(dian)(dian)或(huo)放電(dian)(dian)(dian)(dian)時電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)電(dian)(dian)(dian)(dian)壓低(di)于2.5V、超(chao)過4.3V或(huo)如(ru)果電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)電(dian)(dian)(dian)(dian)流超(chao)過預定門限值(zhi)，該電(dian)(dian)(dian)(dian)子電(dian)(dian)(dian)(dian)路就(jiu)會斷開電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)連(lian)接。

  2 鋰離子充(chong)電--系統注(zhu)意事項

  要快(kuai)速(su)可靠地完(wan)成充(chong)電過程需要一(yi)個高性(xing)能(neng)的(de)充(chong)電系統。為實(shi)現(xian)可靠且經濟高效的(de)解決(jue)方(fang)案，設計時應(ying)當考慮到以下系統參(can)數：

2.1 輸入源
  許多應用都采用極廉價(jia)的墻(qiang)式(shi)適配器作為輸(shu)入(ru)電(dian)(dian)源。其輸(shu)出電(dian)(dian)壓(ya)主要依(yi)賴于交流輸(shu)入(ru)電(dian)(dian)壓(ya)和從(cong)墻(qiang)式(shi)適配器流出的負載(zai)電(dian)(dian)流。

  在美國標準的墻面插座上交流母線輸入電壓的變化范圍一般為90VRMS至132VRMS.假設額定輸入電壓為120VRMS,容差為+10%, ?25%.充電器必須為電池提供適當的穩壓措施，從而不受輸入電壓的影響。充電器的輸入電壓與交流母線電壓和充電電流成比例：
 
VO=2VIN×a-1O（REQ+RPTC）-2×VFD
  REQ是(shi)次級繞(rao)(rao)組的(de)電(dian)阻(zu)與初級繞(rao)(rao)組反射電(dian)阻(zu)的(de)和。RPTC是(shi)PTC的(de)電(dian)阻(zu)，VFD是(shi)橋式整流器的(de)前向壓(ya)(ya)降(jiang)(jiang)。此外變壓(ya)(ya)器磁芯損失也會使輸出電(dian)壓(ya)(ya)略有降(jiang)(jiang)低(di)。

  利用汽車適配(pei)器充電的(de)(de)應(ying)用也(ye)會遇(yu)到類似的(de)(de)問題(ti)。汽車適配(pei)器的(de)(de)輸出電壓典(dian)型范圍為9V至(zhi)18V.

2.2 恒流充電的速率和精度
   特定應用的拓撲結構選擇可能要由充電電流來決定。出于尺寸和成本方面的考慮，低檔和中檔的快速充電應用則傾向于采用線性解決方案，然 而線性解決方案會以熱的形式損失更多能耗。對于線性充電系統來說，恒流充電的容差變得極為重要。如果穩壓容差太大，傳輸晶體管和其他元器件都需要更大體 積，從而增加尺寸和成本。此外，如果恒流充電電流過小，整個充電周期將會延長。
2.3 輸出電壓的穩定精度
   為了盡可(ke)能地充分利用電(dian)(dian)池容量，輸(shu)出(chu)(chu)(chu)電(dian)(dian)壓(ya)(ya)(ya)穩壓(ya)(ya)(ya)精度非常關鍵。輸(shu)出(chu)(chu)(chu)電(dian)(dian)壓(ya)(ya)(ya)精度的小幅度下降也會導(dao)致電(dian)(dian)池容量的大幅減少。然而出(chu)(chu)(chu)于安全和可(ke)靠性方(fang)面的考(kao)慮，輸(shu)出(chu)(chu)(chu)電(dian)(dian)壓(ya)(ya)(ya)也不能隨意(yi)設置得過(guo)高。圖2顯(xian)示出(chu)(chu)(chu)了輸(shu)出(chu)(chu)(chu)電(dian)(dian)壓(ya)(ya)(ya)穩定精度的重要(yao)性。

3 充電終止方法

  毋庸置疑，過充(chong)(chong)始終是鋰離子電池充(chong)(chong)電的心頭大患。準確的充(chong)(chong)電終止(zhi)方法對(dui)于安(an)全可靠的充(chong)(chong)電系統來說(shuo)非(fei)常關鍵。

3 .1 電池溫度監控
  一(yi)般情況下，鋰(li)離子(zi)電(dian)池(chi)充(chong)(chong)電(dian)時(shi)的(de)溫(wen)度(du)(du)范圍(wei)應(ying)當在(zai)0℃至45℃。在(zai)此溫(wen)度(du)(du)范圍(wei)之外對電(dian)池(chi)充(chong)(chong)電(dian)會導致(zhi)電(dian)池(chi)過熱。在(zai)充(chong)(chong)電(dian)周期(qi)(qi)中(zhong)，電(dian)池(chi)內的(de)壓力(li)上升還會 導致(zhi)電(dian)池(chi)膨脹。隨(sui)著溫(wen)度(du)(du)上升，壓力(li)也會過大，這可(ke)能(neng)(neng)會導致(zhi)電(dian)池(chi)內部的(de)機械破(po)裂或材料泄漏，嚴重時(shi)還有(you)可(ke)能(neng)(neng)導致(zhi)爆炸。在(zai)此溫(wen)度(du)(du)范圍(wei)之外 對電(dian)池(chi)充(chong)(chong)電(dian)還會損害電(dian)池(chi)的(de)性能(neng)(neng)，或縮短電(dian)池(chi)的(de)預期(qi)(qi)壽命。

  通常(chang)鋰離子電池包內(nei)都(dou)采用了(le)熱(re)敏電阻來準確測量電池溫(wen)度(du)。充電器檢測熱(re)敏電阻的阻值，當阻值超出規定(ding)工作范(fan)(fan)圍，即溫(wen)度(du)超過規定(ding)范(fan)(fan)圍時，充電被禁止。

3.2 電池放電電流或反向泄漏電流
  在許(xu)多應用中(zhong)，即使輸(shu)入電(dian)(dian)(dian)源不(bu)存(cun)在，充電(dian)(dian)(dian)系統仍(reng)然(ran)與電(dian)(dian)(dian)池(chi)相連。充電(dian)(dian)(dian)系統必須保(bao)證(zheng)輸(shu)入電(dian)(dian)(dian)源不(bu)存(cun)在時(shi)，從電(dian)(dian)(dian)池(chi)汲(ji)取(qu)的電(dian)(dian)(dian)流(liu)(liu)極小。最大泄漏電(dian)(dian)(dian)流(liu)(liu)應當小于(yu)(yu)幾個微(wei)安(an)(an)，通常應小于(yu)(yu)一個微(wei)安(an)(an)。

4 鋰離子(zi)充電--應用實例

  將以上幾(ji)點系統(tong)注意事(shi)項事(shi)先充分考(kao)慮，就(jiu)能開(kai)發出適合的充電(dian)管理(li)系統(tong)。

4.1 線性解決方案
  當存在(zai)(zai)穩壓良(liang)好的(de)輸(shu)(shu)入電(dian)(dian)(dian)源時，通(tong)常采用(yong)線(xian)性(xing)充電(dian)(dian)(dian)解(jie)(jie)決(jue)方案(an)。在(zai)(zai)此類應用(yong)中，線(xian)性(xing)解(jie)(jie)決(jue)方案(an)的(de)優點包括(kuo)易用(yong)、尺寸小以及成本(ben)低(di)。由于線(xian)性(xing)充電(dian)(dian)(dian)解(jie)(jie)決(jue)方案(an) 效率低(di)因(yin)此影響設計(ji)的(de)最重要(yao)因(yin)素就是(shi)散(san)熱設計(ji)。最糟的(de)情況是(shi)器件從涓流充電(dian)(dian)(dian)階段向 恒(heng)流充電(dian)(dian)(dian)階段轉換時，在(zai)(zai)此情況下(xia)，傳輸(shu)(shu)晶體(ti)管(guan)必須散(san)發最大的(de)熱能，必須在(zai)(zai)充電(dian)(dian)(dian)電(dian)(dian)(dian)流、系統尺寸、成本(ben)和(he)散(san)熱要(yao)求之(zhi)間進行權(quan)衡。

  例(li)如(ru)，應用(yong)(yong)(yong)中需(xu)(xu)要利用(yong)(yong)(yong)一個(ge)5V ±5%的(de)(de)輸入電(dian)源以0.5C或(huo)1C的(de)(de)恒(heng)定電(dian)流(liu)對一個(ge)1000mAh的(de)(de)單節鋰離子電(dian)池充(chong)電(dian)。圖(tu)3顯示了如(ru)何利用(yong)(yong)(yong)Microchip的(de)(de) MCP73843構成(cheng)一個(ge)低成(cheng)本的(de)(de)獨立解決方案，只需(xu)(xu)要極少量的(de)(de)外部元器件，就可以實(shi)現所需(xu)(xu)要的(de)(de)充(chong)電(dian)算法(fa)。MCP73843完美地結合了高(gao)精(jing)度恒(heng)流(liu)充(chong)電(dian)、 恒(heng)壓穩(wen)壓以及自動(dong)充(chong)電(dian)終止等功能。

  為(wei)進一步減小(xiao)線性解(jie)決方案的(de)(de)尺寸、降低其成本(ben)和復雜性，許多外(wai)部元器(qi)(qi)件都可(ke)(ke)以集成到充(chong)電管理控(kong)制器(qi)(qi)中。先進的(de)(de)封(feng)裝可(ke)(ke)以提供更(geng)高的(de)(de)集成度(du)，當(dang)然也會犧牲一定的(de)(de)靈(ling)活性。此外(wai)此類充(chong)電管理控(kong)制器(qi)(qi) 還會實(shi)現一定的(de)(de)熱(re)(re)(re)調(diao)節(jie)功(gong)能。熱(re)(re)(re)調(diao)節(jie)功(gong)能可(ke)(ke)根據器(qi)(qi)件管芯溫(wen)度(du)來限制充(chong)電電流，從而可(ke)(ke)在保證器(qi)(qi)件可(ke)(ke)靠性的(de)(de)情況(kuang)下優化充(chong)電周期(qi)時間(jian)，熱(re)(re)(re)調(diao)節(jie)功(gong)能大大降低了散熱(re)(re)(re)設(she) 計的(de)(de)工作量。

  基于(yu)Microchip MCP73861的全(quan)集成線性解(jie)決方案如圖4所示。MCP73861包含了MCP73843的所有功(gong)能，另外(wai)還包括電流檢測、傳輸晶體管、反(fan)向放電保護以及電池溫度監測。

4.2 充電周期波形
  利用(yong)MCP73843在1C和(he)0.5C恒(heng)流充電(dian)(dian)(dian)(dian)(dian)速(su)率下(xia)的整個(ge)充電(dian)(dian)(dian)(dian)(dian)周期(qi)如圖5.以0.5C而不是(shi)1C速(su)率充電(dian)(dian)(dian)(dian)(dian)時，充電(dian)(dian)(dian)(dian)(dian)結(jie)束(shu)的時間大約晚了一個(ge)小時。充電(dian)(dian)(dian)(dian)(dian)終止電(dian)(dian)(dian)(dian)(dian)流從0.07C降(jiang)到0.035C,使得最終電(dian)(dian)(dian)(dian)(dian)池容量(liang)從~98%增長到~100%.系統設計師必(bi)須在充電(dian)(dian)(dian)(dian)(dian)時間、功率損耗和(he)可用(yong)電(dian)(dian)(dian)(dian)(dian)池容量(liang)之間進行權衡。

4.3 開關式充電解決方案
  輸入電(dian)(dian)(dian)壓(ya)波(bo)動范圍寬(kuan)或(huo)輸入輸出電(dian)(dian)(dian)壓(ya)差大的(de)(de)應(ying)(ying)用(yong)通常采(cai)用(yong)開關式充(chong)電(dian)(dian)(dian)解決方案(an)。例如應(ying)(ying)用(yong)中需要利用(yong)汽車適配器以0.5C或(huo)1C的(de)(de)恒定電(dian)(dian)(dian)流對一個2200mAh的(de)(de)單節(jie)鋰離子電(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)，由于散熱(re)等問題(ti)，利用(yong)線性解決方案(an)實現極(ji)為困難，當然(ran)也可以采(cai)用(yong)支持熱(re)調節(jie)的(de)(de)線性解決方案(an)，但(dan)降(jiang)低充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流造成的(de)(de)充(chong)電(dian)(dian)(dian)周期延(yan)長是無法接受的(de)(de)。

  成功(gong)設計開關式(shi)(shi)充電(dian)(dian)解決(jue)方(fang)案(an)的(de)第一(yi)步是(shi)選(xuan)擇設計結(jie)構(gou)：降壓(ya)式(shi)(shi)、升壓(ya)式(shi)(shi)、升/降壓(ya)式(shi)(shi)、反激式(shi)(shi)、單端初級電(dian)(dian)感式(shi)(shi)或者其他形(xing)式(shi)(shi)。SEPIC拓撲結(jie)構(gou)的(de)優點是(shi)低端柵極驅動和電(dian)(dian)流檢(jian)測、持續輸(shu) 入(ru)電(dian)(dian)流以(yi)及輸(shu)入(ru)和輸(shu)出間的(de)直(zhi)流隔(ge)離，其主要缺點是(shi)需要兩個電(dian)(dian)感和一(yi)個能量傳輸(shu)電(dian)(dian)容。

  MCP1630是一款可配合單片機使用的高速脈寬調制器，配合單片機，MCP1630可控制電源系統占空比，提供輸出電壓或電流穩定 功能。PIC16F684單片機可用于輸出穩壓或穩流，以及開關頻率和最大占空比的調整。MCP1630產生占空比，并可根據不同外部輸入提供快速過流保 護。充電器采用的(de)電源結構是SEPIC.單片機提供了極大(da)(da)的(de)設計靈活 性。此外單片機還可(ke)以與電池包內(nei)的(de)電池監(jian)控器通信，從而大(da)(da)大(da)(da)縮短充(chong)電周期時間。

  利(li)用開(kai)關式(shi)充(chong)電(dian)(dian)(dian)(dian)解決方案的(de)整個充(chong)電(dian)(dian)(dian)(dian)周(zhou)期(qi)如圖6所示。通過在充(chong)電(dian)(dian)(dian)(dian)系統中(zhong)采用電(dian)(dian)(dian)(dian)池(chi)(chi)監(jian)控(kong)器，可以(yi)大大縮短充(chong)電(dian)(dian)(dian)(dian)周(zhou)期(qi)，使用電(dian)(dian)(dian)(dian)池(chi)(chi)監(jian)控(kong)器就(jiu)不必再(zai)檢(jian)測電(dian)(dian)(dian)(dian)池(chi)(chi)包保護電(dian)(dian)(dian)(dian)路兩端的(de)電(dian)(dian)(dian)(dian)壓以(yi)及充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)的(de)接觸電(dian)(dian)(dian)(dian)阻。

5 結論

  在目前(qian)的(de)(de)便攜式產品(pin)中，要正確地(di)實(shi)現電池充(chong)電需(xu)要仔細地(di)設(she)(she)計(ji)考(kao)慮(lv)。本(ben)文討論(lun)了鋰離子電池的(de)(de)線性和開(kai)關式充(chong)電解(jie)決方案，本(ben)文所探討的(de)(de)指導原則和設(she)(she)計(ji)考(kao)慮(lv)要素，實(shi)際(ji)上(shang)也是所有電池充(chong)電系統設(she)(she)計(ji)都需(xu)要考(kao)慮(lv)的(de)(de)。