在有些應用中，較長(chang)的(de)(de)電(dian)(dian)池(chi)壽命、較多的(de)(de)充電(dian)(dian)次數或較安全的(de)(de)電(dian)(dian)池(chi)比電(dian)(dian)池(chi)容量更重要。本文介紹幾種可以(yi)極大(da)延長(chang)電(dian)(dian)池(chi)壽命的(de)(de)鋰離(li)子電(dian)(dian)池(chi)充電(dian)(dian)和放電(dian)(dian)方(fang)法(fa)。

  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(yin)為(wei)與其他(ta)可(ke)再充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)池(chi)相(xiang)比，鋰離子電(dian)(dian)(dian)池(chi)有較(jiao)高的能量密度、較(jiao)高的電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)壓、自放電(dian)(dian)(dian)少、周期(qi)壽命非常長，而(er)且環保，且充(chong)電(dian)(dian)(dian)和維護簡單(dan)。另外，由(you)于(yu)其具(ju)有相(xiang)對(dui)高的電(dian)(dian)(dian)壓（2.9V至4.2V），因(yin)此(ci)很(hen)多便攜式產(chan)品都(dou)能用(yong)單(dan)節電(dian)(dian)(dian)池(chi)工作，從而(er)簡化(hua)了產(chan)品總(zong)體設計。C速率等(deng)于(yu)特定(ding)條件下的充(chong)電(dian)(dian)(dian)或放電(dian)(dian)(dian)電(dian)(dian)(dian)流，定(ding)義如下：I=M×Cn

  其中：I = 充(chong)電或放電電流，單位為A；M = C的倍數(shu)或分(fen)數(shu)；C = 額(e)定容量的數(shu)值，單位為Ah；N = 小(xiao)時數(shu)（對應于(yu)C）。

  以1倍C速(su)率放電(dian)的(de)(de)電(dian)池將在一個小時內釋放標稱(cheng)的(de)(de)額定容(rong)量。例如，如果標稱(cheng)容(rong)量是1000mAhr,那么(me)1C的(de)(de)放電(dian)速(su)率對應(ying)于1000mA的(de)(de)放電(dian)電(dian)流，C/10的(de)(de)速(su)率對應(ying)100mA的(de)(de)放電(dian)電(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(li)子電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)(de)推(tui)薦方(fang)(fang)法(fa)(fa)是，向電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)提供一個±1%限壓(ya)(ya)的(de)(de)(de)(de)恒(heng)定(ding)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流，直到(dao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)(chong)滿電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，然后停止充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。用(yong)(yong)來決(jue)定(ding)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)何時(shi)(shi)(shi)充(chong)(chong)(chong)滿電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)(de)方(fang)(fang)法(fa)(fa)包括(kuo)：給總(zong)的(de)(de)(de)(de)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)時(shi)(shi)(shi)間定(ding)時(shi)(shi)(shi)、監視充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流或(huo)兼用(yong)(yong)這(zhe)兩(liang)種(zhong)(zhong)方(fang)(fang)法(fa)(fa)。第(di)(di)(di)一種(zhong)(zhong)方(fang)(fang)法(fa)(fa)采(cai)(cai)用(yong)(yong)限壓(ya)(ya)恒(heng)定(ding)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流，變化(hua)范(fan)圍從C/2到(dao)1C,持續(xu)2.5至(zhi)(zhi)(zhi)3小時(shi)(shi)(shi)，使電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)達到(dao)100%充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。也可以(yi)使用(yong)(yong)較低(di)的(de)(de)(de)(de)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流，但是將需(xu)要(yao)更長時(shi)(shi)(shi)間。第(di)(di)(di)二種(zhong)(zhong)方(fang)(fang)法(fa)(fa)與第(di)(di)(di)一種(zhong)(zhong)方(fang)(fang)法(fa)(fa)類(lei)似，只是需(xu)要(yao)監視充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流。隨著電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)的(de)(de)(de)(de)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)上升，這(zhe)與采(cai)(cai)用(yong)(yong)第(di)(di)(di)一種(zhong)(zhong)方(fang)(fang)法(fa)(fa)時(shi)(shi)(shi)完全(quan)相同。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)達到(dao)編程限壓(ya)(ya)值（也稱(cheng)為(wei)浮動(dong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)）時(shi)(shi)(shi)，充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流開(kai)始下降。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流一開(kai)始下降時(shi)(shi)(shi)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)約(yue)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)至(zhi)(zhi)(zhi)容量的(de)(de)(de)(de)50%至(zhi)(zhi)(zhi)60%.浮動(dong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)繼續(xu)提供，直到(dao)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流降至(zhi)(zhi)(zhi)足夠(gou)低(di)的(de)(de)(de)(de)水(shui)平(ping)（C/10至(zhi)(zhi)(zhi)C/20），這(zhe)時(shi)(shi)(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)約(yue)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)至(zhi)(zhi)(zhi)容量的(de)(de)(de)(de)92%至(zhi)(zhi)(zhi)99%,充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)周期(qi)終止。目(mu)前(qian)，要(yao)為(wei)標準鋰離(li)子電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)快速充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)（不(bu)到(dao)1小時(shi)(shi)(shi)）至(zhi)(zhi)(zhi)容量的(de)(de)(de)(de)100%,還沒(mei)有一種(zhong)(zhong)安(an)全(quan)的(de)(de)(de)(de)方(fang)(fang)法(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)(chong)電(dian)曲線(xian)，圖中顯示了充(chong)(chong)(chong)(chong)電(dian)電(dian)流(liu)、電(dian)池(chi)(chi)電(dian)壓和電(dian)池(chi)(chi)容(rong)量隨時(shi)間(jian)的(de)變(bian)化。那(nei)么(me)怎樣才能正確地為(wei)鋰離子(zi)電(dian)池(chi)(chi)充(chong)(chong)(chong)(chong)電(dian)呢？鋰離子(zi)電(dian)池(chi)(chi)最適(shi)合(he)的(de)充(chong)(chong)(chong)(chong)電(dian)過程(cheng)可以分(fen)為(wei)四個階段(duan)：涓流(liu)充(chong)(chong)(chong)(chong)電(dian)、恒流(liu)充(chong)(chong)(chong)(chong)電(dian)、恒壓充(chong)(chong)(chong)(chong)電(dian)以及充(chong)(chong)(chong)(chong)電(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續涓(juan)流充(chong)電。連續涓(juan)流充(chong)電會導(dao)致金(jin)屬(shu)鋰(li)出現(xian)極板電鍍效應。這會使電池不(bu)穩定，并且有可能導(dao)致突然的自(zi)動快速解(jie)體。

  有兩種(zhong)典型的充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)終(zhong)(zhong)止方法：采用最小(xiao)(xiao)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)判斷或采用定(ding)時(shi)器（或者(zhe)兩者(zhe)的結合）。最小(xiao)(xiao)電(dian)(dian)(dian)(dian)(dian)流(liu)法監視恒(heng)壓(ya)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)階段的充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)，并在充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)減小(xiao)(xiao)到0.02C至(zhi)0.07C范圍(wei)時(shi)終(zhong)(zhong)止充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)。第二種(zhong)方法從恒(heng)壓(ya)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)階段開始(shi)時(shi)計時(shi)，持續充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)兩個小(xiao)(xiao)時(shi)后(hou)終(zhong)(zhong)止充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)過(guo)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(cai)用了(le)更多安全(quan)措施(shi)。例如如果(guo)電池(chi)溫(wen)度超出指定窗口(kou)（通(tong)常為(wei)0℃至45℃），那么充電會(hui)暫停。

  1 決定鋰離(li)子電池周期壽(shou)命(ming)(ming)或服務壽(shou)命(ming)(ming)的因素

  不存在任何(he)延(yan)長(chang)或縮短電池壽(shou)命(ming)的單一因素(su)(su)，而(er)常常是幾(ji)種因素(su)(su)合起來發揮作用。就延(yan)長(chang)周期壽(shou)命(ming)而(er)言有(you)以下方法可以延(yan)長(chang)電池壽(shou)命(ming)：

1).采用(yong)(yong)部分(fen)(fen)放(fang)電(dian)(dian)(dian)的(de)做法(fa)。在再充電(dian)(dian)(dian)前僅(jin)使用(yong)(yong)20%或30%的(de)電(dian)(dian)(dian)池容量會(hui)極(ji)大延(yan)長周期(qi)壽(shou)命。作為一(yi)個(ge)一(yi)般性的(de)規(gui)則，5至10個(ge)淺(qian)放(fang)電(dian)(dian)(dian)周期(qi)等(deng)于1個(ge)滿(man)放(fang)電(dian)(dian)(dian)周期(qi)。盡管(guan)部分(fen)(fen)放(fang)電(dian)(dian)(dian)周期(qi)可能達到數(shu)千(qian)次，但是保持電(dian)(dian)(dian)池處于滿(man)充電(dian)(dian)(dian)狀態(tai)也(ye)縮短電(dian)(dian)(dian)池壽(shou)命。如果可能，應該避免滿(man)放(fang)電(dian)(dian)(dian)周期(qi)（降至2.5V或3V,取(qu)決于化學材(cai)料）。

2).避免充電(dian)(dian)(dian)至容(rong)量的(de)100%.選擇一(yi)個較(jiao)低(di)(di)的(de)浮動電(dian)(dian)(dian)壓(ya)可以(yi)做到這一(yi)點(dian)。降(jiang)(jiang)低(di)(di)浮動電(dian)(dian)(dian)壓(ya)將(jiang)提高周期壽命和服務壽命，代價是降(jiang)(jiang)低(di)(di)電(dian)(dian)(dian)池容(rong)量。浮動電(dian)(dian)(dian)壓(ya)降(jiang)(jiang)低(di)(di)100mV至300mV可以(yi)將(jiang)周期壽命延(yan)長2至5倍(bei)或(huo)更(geng)長。與其他化學材料(liao)相(xiang)比(bi)，鋰(li)離子(zi)鈷化學材料(liao)對較(jiao)高浮動電(dian)(dian)(dian)壓(ya)更(geng)敏感(gan)。磷酸鋰(li)離子(zi)電(dian)(dian)(dian)池一(yi)般比(bi)更(geng)常見的(de)鋰(li)離子(zi)電(dian)(dian)(dian)池的(de)浮動電(dian)(dian)(dian)壓(ya)低(di)(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)到容量的100%,也可以延長(chang)電(dian)(dian)池壽命(ming)。例如，電(dian)(dian)流降(jiang)至C/5時(shi)結束充(chong)電(dian)(dian)周期(qi)與將浮動電(dian)(dian)壓降(jiang)至4.1V的效果類(lei)似。在這(zhe)兩種情況下，電(dian)(dian)池都(dou)只充(chong)電(dian)(dian)至約為容量的85%,這(zhe)是決定(ding)電(dian)(dian)池壽命(ming)的一個重要(yao)因素。

4).限(xian)制電(dian)(dian)池(chi)溫(wen)度。限(xian)制電(dian)(dian)池(chi)的(de)極限(xian)溫(wen)度可以(yi)延(yan)長電(dian)(dian)池(chi)壽命，尤其是禁止在(zai)(zai)0℃以(yi)下充電(dian)(dian)。在(zai)(zai)0℃以(yi)下充電(dian)(dian)促進金屬(shu)在(zai)(zai)電(dian)(dian)池(chi)陽極上的(de)鍍敷，這(zhe)可能造成內部短路，產生熱量并使(shi)電(dian)(dian)池(chi)不(bu)穩定和不(bu)安全(quan)。很(hen)多電(dian)(dian)池(chi)充電(dian)(dian)器都有測量電(dian)(dian)池(chi)溫(wen)度的(de)裝置，以(yi)確保不(bu)會在(zai)(zai)極限(xian)溫(wen)度時充電(dian)(dian)。

5).避免大(da)的充電(dian)(dian)(dian)和放電(dian)(dian)(dian)電(dian)(dian)(dian)流，因(yin)為這(zhe)會縮短周期壽命。有(you)些化學材料更適合較大(da)電(dian)(dian)(dian)流，如鋰離子錳(meng)和磷(lin)酸鋰離子電(dian)(dian)(dian)池。大(da)電(dian)(dian)(dian)流給電(dian)(dian)(dian)池施加了過大(da)的壓力(li)。

6).避免低于2V或(huo)(huo)2.5V的(de)深度放電(dian)(dian)(dian)，因(yin)為這(zhe)(zhe)會迅(xun)速永久性損壞鋰離(li)(li)子電(dian)(dian)(dian)池(chi)。可能(neng)發生內(nei)部(bu)金屬鍍(du)敷，這(zhe)(zhe)會引起短(duan)路，使電(dian)(dian)(dian)池(chi)不(bu)可用或(huo)(huo)不(bu)安(an)全。大(da)多數鋰離(li)(li)子電(dian)(dian)(dian)池(chi)在電(dian)(dian)(dian)池(chi)組內(nei)部(bu)都有電(dian)(dian)(dian)子電(dian)(dian)(dian)路，如果充電(dian)(dian)(dian)或(huo)(huo)放電(dian)(dian)(dian)時電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)壓低于2.5V、超過4.3V或(huo)(huo)如果電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)流(liu)超過預(yu)定門限(xian)值，該電(dian)(dian)(dian)子電(dian)(dian)(dian)路就會斷開(kai)電(dian)(dian)(dian)池(chi)連接(jie)。

  2 鋰離(li)子(zi)充電(dian)--系統注意事項

  要快速可靠(kao)地完成充電過(guo)程需要一個高性(xing)能的(de)充電系統。為實(shi)現可靠(kao)且經濟高效的(de)解(jie)決方案，設計(ji)時應當考慮到以下系統參數：

2.1 輸入源
  許多應用(yong)都采用(yong)極廉價的墻式適配器作為輸入電源。其(qi)輸出(chu)電壓(ya)主要(yao)依賴于交流輸入電壓(ya)和(he)從墻式適配器流出(chu)的負載(zai)電流。

  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是次級繞(rao)組(zu)的(de)(de)電(dian)阻(zu)與初(chu)級繞(rao)組(zu)反射電(dian)阻(zu)的(de)(de)和。RPTC是PTC的(de)(de)電(dian)阻(zu)，VFD是橋(qiao)式整流(liu)器(qi)的(de)(de)前向(xiang)壓(ya)(ya)降。此外變壓(ya)(ya)器(qi)磁芯損(sun)失也會使(shi)輸出電(dian)壓(ya)(ya)略有降低(di)。

  利用(yong)汽車適配器充電的(de)應用(yong)也會遇到類似的(de)問(wen)題。汽車適配器的(de)輸出電壓典型范圍為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(neng)地充分(fen)利用電池容量，輸(shu)出(chu)(chu)電壓(ya)穩(wen)(wen)壓(ya)精度(du)(du)非常(chang)關鍵。輸(shu)出(chu)(chu)電壓(ya)精度(du)(du)的小幅度(du)(du)下降也會(hui)導致電池容量的大(da)幅減少。然而出(chu)(chu)于安全(quan)和(he)可(ke)靠性(xing)方面的考慮，輸(shu)出(chu)(chu)電壓(ya)也不能(neng)隨(sui)意設(she)置得過高。圖(tu)2顯(xian)示出(chu)(chu)了輸(shu)出(chu)(chu)電壓(ya)穩(wen)(wen)定(ding)精度(du)(du)的重要(yao)性(xing)。

3 充電終止方法

  毋庸置疑，過(guo)充始終是鋰(li)離子電池(chi)充電的(de)心頭大患。準確的(de)充電終止方(fang)法(fa)對于安全可(ke)靠(kao)的(de)充電系統來(lai)說非常關(guan)鍵。

3 .1 電池溫度監控
  一(yi)般情況(kuang)下(xia)，鋰離子電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充電(dian)(dian)(dian)(dian)(dian)(dian)時(shi)的溫度范圍(wei)應當在(zai)(zai)0℃至45℃。在(zai)(zai)此溫度范圍(wei)之外(wai)對電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充電(dian)(dian)(dian)(dian)(dian)(dian)會(hui)(hui)(hui)導致電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)過(guo)熱。在(zai)(zai)充電(dian)(dian)(dian)(dian)(dian)(dian)周期中(zhong)，電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)內的壓(ya)力上(shang)升(sheng)還(huan)(huan)會(hui)(hui)(hui) 導致電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)膨(peng)脹。隨著溫度上(shang)升(sheng)，壓(ya)力也會(hui)(hui)(hui)過(guo)大，這可(ke)能會(hui)(hui)(hui)導致電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)內部的機(ji)械破裂(lie)或(huo)(huo)材料泄漏，嚴重時(shi)還(huan)(huan)有可(ke)能導致爆炸。在(zai)(zai)此溫度范圍(wei)之外(wai) 對電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充電(dian)(dian)(dian)(dian)(dian)(dian)還(huan)(huan)會(hui)(hui)(hui)損(sun)害電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)的性能，或(huo)(huo)縮短電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)的預(yu)期壽(shou)命。

  通常鋰離子電(dian)池包內都采用了熱(re)敏電(dian)阻來(lai)準確測(ce)(ce)量電(dian)池溫度(du)。充電(dian)器檢測(ce)(ce)熱(re)敏電(dian)阻的阻值，當阻值超(chao)出規定(ding)工作范圍(wei)，即溫度(du)超(chao)過規定(ding)范圍(wei)時，充電(dian)被禁止(zhi)。

3.2 電池放電電流或反向泄漏電流
  在許多應用(yong)中，即使輸(shu)入電(dian)(dian)源(yuan)不(bu)存(cun)在，充(chong)電(dian)(dian)系(xi)統仍然與(yu)電(dian)(dian)池相連。充(chong)電(dian)(dian)系(xi)統必須保證輸(shu)入電(dian)(dian)源(yuan)不(bu)存(cun)在時，從電(dian)(dian)池汲取(qu)的電(dian)(dian)流極小。最大泄漏電(dian)(dian)流應當小于幾個微安(an)，通(tong)常應小于一個微安(an)。

4 鋰離子充電--應(ying)用實例

  將以(yi)上幾點系(xi)統注意事項事先(xian)充分考(kao)慮，就能(neng)開發出適合的充電(dian)管理系(xi)統。

4.1 線性解決方案
  當(dang)存在(zai)穩(wen)壓良好的輸(shu)入電(dian)(dian)源時，通(tong)常采用線性(xing)充(chong)(chong)電(dian)(dian)解決(jue)方(fang)案。在(zai)此類(lei)應用中，線性(xing)解決(jue)方(fang)案的優點包(bao)括易用、尺寸小以及(ji)成本(ben)低。由(you)于線性(xing)充(chong)(chong)電(dian)(dian)解決(jue)方(fang)案 效率(lv)低因(yin)此影響(xiang)設(she)(she)計的最重要因(yin)素就是(shi)散(san)熱設(she)(she)計。最糟(zao)的情(qing)況(kuang)是(shi)器件從涓(juan)流(liu)充(chong)(chong)電(dian)(dian)階(jie)段(duan)向(xiang) 恒流(liu)充(chong)(chong)電(dian)(dian)階(jie)段(duan)轉換時，在(zai)此情(qing)況(kuang)下，傳輸(shu)晶體管(guan)必(bi)須散(san)發最大的熱能，必(bi)須在(zai)充(chong)(chong)電(dian)(dian)電(dian)(dian)流(liu)、系統尺寸、成本(ben)和散(san)熱要求(qiu)之間進行(xing)權衡。

  例(li)如，應用中需要(yao)利用一個(ge)5V ±5%的輸入電(dian)(dian)(dian)源(yuan)以(yi)(yi)0.5C或1C的恒定(ding)電(dian)(dian)(dian)流(liu)對(dui)一個(ge)1000mAh的單節(jie)鋰離(li)子(zi)電(dian)(dian)(dian)池充電(dian)(dian)(dian)。圖3顯(xian)示了如何利用Microchip的 MCP73843構(gou)成(cheng)一個(ge)低成(cheng)本的獨立解決方案，只需要(yao)極少量(liang)的外部元器件(jian)，就可以(yi)(yi)實現所需要(yao)的充電(dian)(dian)(dian)算法。MCP73843完美地結合(he)了高精度恒流(liu)充電(dian)(dian)(dian)、 恒壓穩(wen)壓以(yi)(yi)及自動充電(dian)(dian)(dian)終止(zhi)等功(gong)能。

  為進(jin)一步減小線性(xing)(xing)解決方案的(de)(de)(de)尺寸(cun)、降低其成本和復雜性(xing)(xing)，許多(duo)外部元器(qi)件(jian)(jian)都(dou)可(ke)(ke)以集成到充電(dian)(dian)管(guan)理控制(zhi)器(qi)中。先進(jin)的(de)(de)(de)封裝可(ke)(ke)以提供更高的(de)(de)(de)集成度，當(dang)然也會犧牲一定的(de)(de)(de)靈活性(xing)(xing)。此(ci)外此(ci)類(lei)充電(dian)(dian)管(guan)理控制(zhi)器(qi) 還會實(shi)現一定的(de)(de)(de)熱(re)調(diao)節(jie)功(gong)能。熱(re)調(diao)節(jie)功(gong)能可(ke)(ke)根(gen)據器(qi)件(jian)(jian)管(guan)芯(xin)溫度來限制(zhi)充電(dian)(dian)電(dian)(dian)流，從而可(ke)(ke)在(zai)保證器(qi)件(jian)(jian)可(ke)(ke)靠性(xing)(xing)的(de)(de)(de)情況下優化充電(dian)(dian)周期(qi)時(shi)間，熱(re)調(diao)節(jie)功(gong)能大(da)(da)大(da)(da)降低了散熱(re)設 計(ji)的(de)(de)(de)工作量(liang)。

  基于Microchip MCP73861的全集成線性解決方案如圖(tu)4所示。MCP73861包含(han)了MCP73843的所有功能，另外還包括電流(liu)檢測、傳(chuan)輸晶體(ti)管、反(fan)向放電保(bao)護以及電池溫度監測。

4.2 充電周期波形
  利(li)用(yong)MCP73843在(zai)1C和0.5C恒流充(chong)電(dian)速率(lv)下的(de)整(zheng)個充(chong)電(dian)周期(qi)如圖5.以(yi)0.5C而不是(shi)1C速率(lv)充(chong)電(dian)時(shi)(shi)，充(chong)電(dian)結束的(de)時(shi)(shi)間大(da)約晚了一個小時(shi)(shi)。充(chong)電(dian)終止電(dian)流從0.07C降到0.035C,使得最(zui)終電(dian)池(chi)容量(liang)從~98%增長到~100%.系(xi)統設計師(shi)必須(xu)在(zai)充(chong)電(dian)時(shi)(shi)間、功率(lv)損(sun)耗和可(ke)用(yong)電(dian)池(chi)容量(liang)之間進行(xing)權衡。

4.3 開關式充電解決方案
  輸(shu)入(ru)電(dian)(dian)壓波動范圍寬或輸(shu)入(ru)輸(shu)出電(dian)(dian)壓差大的(de)應用(yong)(yong)通(tong)常(chang)采(cai)用(yong)(yong)開關式充電(dian)(dian)解決(jue)方案。例(li)如應用(yong)(yong)中需要(yao)利(li)用(yong)(yong)汽車適配器(qi)以0.5C或1C的(de)恒定電(dian)(dian)流(liu)(liu)對一(yi)個2200mAh的(de)單(dan)節(jie)(jie)鋰離子(zi)電(dian)(dian)池充電(dian)(dian)，由于散(san)熱等問(wen)題，利(li)用(yong)(yong)線性(xing)(xing)解決(jue)方案實現極為困難，當然也可以采(cai)用(yong)(yong)支持熱調節(jie)(jie)的(de)線性(xing)(xing)解決(jue)方案，但(dan)降低充電(dian)(dian)電(dian)(dian)流(liu)(liu)造成的(de)充電(dian)(dian)周期延(yan)長是無法接受(shou)的(de)。

  成功設計開關式(shi)充電(dian)解決(jue)方案的第一(yi)步是選擇設計結構：降(jiang)壓(ya)式(shi)、升(sheng)壓(ya)式(shi)、升(sheng)/降(jiang)壓(ya)式(shi)、反激(ji)式(shi)、單端(duan)初級電(dian)感(gan)(gan)式(shi)或(huo)者其他形式(shi)。SEPIC拓撲結構的優(you)點是低端(duan)柵極驅動(dong)和(he)電(dian)流(liu)檢(jian)測(ce)、持續(xu)輸(shu)(shu) 入電(dian)流(liu)以及輸(shu)(shu)入和(he)輸(shu)(shu)出間的直(zhi)流(liu)隔離，其主要(yao)缺點是需(xu)要(yao)兩(liang)個電(dian)感(gan)(gan)和(he)一(yi)個能量傳輸(shu)(shu)電(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(yong)的電(dian)源結(jie)構是SEPIC.單(dan)片機提供了(le)極大(da)的設計靈(ling)活 性。此外單(dan)片機還可以(yi)與電(dian)池包內的電(dian)池監控器通信，從(cong)而大(da)大(da)縮(suo)短充電(dian)周期時(shi)間(jian)。

  利用開(kai)關式充電(dian)解決方案的整個充電(dian)周(zhou)(zhou)期如圖6所示(shi)。通過在充電(dian)系統中采用電(dian)池監(jian)控器，可以大大縮短充電(dian)周(zhou)(zhou)期，使用電(dian)池監(jian)控器就不必再檢測電(dian)池包保護電(dian)路兩端的電(dian)壓以及充電(dian)電(dian)流的接觸電(dian)阻。

5 結論

  在目前的(de)便攜式產品(pin)中，要正確(que)地實現電(dian)池充電(dian)需要仔細(xi)地設計考慮。本(ben)文討論了鋰離子電(dian)池的(de)線性和開關式充電(dian)解決方案，本(ben)文所(suo)探討的(de)指導(dao)原(yuan)則和設計考慮要素，實際上(shang)也是(shi)所(suo)有電(dian)池充電(dian)系統設計都需要考慮的(de)。