在有些應(ying)用中(zhong)，較(jiao)(jiao)長的電(dian)池壽命、較(jiao)(jiao)多的充(chong)(chong)電(dian)次數或較(jiao)(jiao)安(an)全(quan)的電(dian)池比電(dian)池容量(liang)更重要。本文介紹幾種可以極大(da)延長電(dian)池壽命的鋰離(li)子電(dian)池充(chong)(chong)電(dian)和(he)放電(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(yin)為與其(qi)他可再充(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)池(chi)相比，鋰離子電(dian)(dian)(dian)(dian)池(chi)有(you)較高的(de)能量(liang)密(mi)度、較高的(de)電(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)壓(ya)、自放電(dian)(dian)(dian)(dian)少(shao)、周期壽命非常長，而且環(huan)保(bao)，且充(chong)(chong)電(dian)(dian)(dian)(dian)和維護簡單。另(ling)外(wai)，由于其(qi)具有(you)相對高的(de)電(dian)(dian)(dian)(dian)壓(ya)（2.9V至4.2V），因(yin)此很多便攜式產(chan)品都能用單節電(dian)(dian)(dian)(dian)池(chi)工(gong)作，從而簡化了產(chan)品總(zong)體設計。C速率等于特定條件下(xia)(xia)的(de)充(chong)(chong)電(dian)(dian)(dian)(dian)或放電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)，定義如下(xia)(xia)：I=M×Cn

  其中：I = 充(chong)電(dian)或放電(dian)電(dian)流，單位(wei)為A；M = C的倍(bei)數或分(fen)數；C = 額定(ding)容量(liang)的數值，單位(wei)為Ah；N = 小時數（對應于C）。

  以1倍C速(su)率(lv)放(fang)電的(de)電池將(jiang)在一個小時內釋(shi)放(fang)標稱(cheng)的(de)額定容量(liang)。例如，如果標稱(cheng)容量(liang)是1000mAhr,那(nei)么1C的(de)放(fang)電速(su)率(lv)對應(ying)于1000mA的(de)放(fang)電電流，C/10的(de)速(su)率(lv)對應(ying)100mA的(de)放(fang)電電流。

  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(li)離子電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)推薦方(fang)(fang)(fang)法(fa)(fa)是，向電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)提(ti)供一(yi)(yi)(yi)個±1%限(xian)壓(ya)的(de)(de)恒定(ding)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)，直到電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)(chong)(chong)(chong)滿電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，然后停止充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。用(yong)來(lai)決定(ding)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)何時(shi)充(chong)(chong)(chong)(chong)(chong)滿電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)方(fang)(fang)(fang)法(fa)(fa)包(bao)括：給總的(de)(de)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)時(shi)間定(ding)時(shi)、監(jian)視充(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)或兼用(yong)這(zhe)兩種(zhong)方(fang)(fang)(fang)法(fa)(fa)。第(di)一(yi)(yi)(yi)種(zhong)方(fang)(fang)(fang)法(fa)(fa)采用(yong)限(xian)壓(ya)恒定(ding)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)，變化范圍從C/2到1C,持續(xu)2.5至(zhi)(zhi)(zhi)3小時(shi)，使電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)達到100%充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。也可以使用(yong)較低的(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)，但是將(jiang)需要(yao)(yao)更長(chang)時(shi)間。第(di)二種(zhong)方(fang)(fang)(fang)法(fa)(fa)與第(di)一(yi)(yi)(yi)種(zhong)方(fang)(fang)(fang)法(fa)(fa)類似，只是需要(yao)(yao)監(jian)視充(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)。隨著電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)的(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)上(shang)升(sheng)，這(zhe)與采用(yong)第(di)一(yi)(yi)(yi)種(zhong)方(fang)(fang)(fang)法(fa)(fa)時(shi)完全相(xiang)同。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)達到編程限(xian)壓(ya)值（也稱為浮動(dong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)）時(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)開始下(xia)降(jiang)。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)一(yi)(yi)(yi)開始下(xia)降(jiang)時(shi)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)約(yue)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)至(zhi)(zhi)(zhi)容(rong)量(liang)的(de)(de)50%至(zhi)(zhi)(zhi)60%.浮動(dong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)繼續(xu)提(ti)供，直到充(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)降(jiang)至(zhi)(zhi)(zhi)足夠低的(de)(de)水平（C/10至(zhi)(zhi)(zhi)C/20），這(zhe)時(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)約(yue)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)至(zhi)(zhi)(zhi)容(rong)量(liang)的(de)(de)92%至(zhi)(zhi)(zhi)99%,充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)周期(qi)終止。目前，要(yao)(yao)為標準鋰(li)離子電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)快速充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)（不到1小時(shi)）至(zhi)(zhi)(zhi)容(rong)量(liang)的(de)(de)100%,還(huan)沒有(you)一(yi)(yi)(yi)種(zhong)安全的(de)(de)方(fang)(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)電(dian)(dian)(dian)(dian)(dian)曲(qu)線，圖中顯示了(le)充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)、電(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)壓和電(dian)(dian)(dian)(dian)(dian)池(chi)容量隨時間的(de)變化。那么(me)怎樣(yang)才能正確地為(wei)鋰離子電(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)(dian)(dian)呢(ni)？鋰離子電(dian)(dian)(dian)(dian)(dian)池(chi)最(zui)適合(he)的(de)充(chong)電(dian)(dian)(dian)(dian)(dian)過程(cheng)可以分為(wei)四個(ge)階段：涓流(liu)充(chong)電(dian)(dian)(dian)(dian)(dian)、恒流(liu)充(chong)電(dian)(dian)(dian)(dian)(dian)、恒壓充(chong)電(dian)(dian)(dian)(dian)(dian)以及充(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續(xu)(xu)涓(juan)流(liu)充電。連續(xu)(xu)涓(juan)流(liu)充電會導致金屬鋰出現極板電鍍效(xiao)應。這(zhe)會使電池不穩定，并且(qie)有可能導致突(tu)然的自動快速解(jie)體(ti)。

  有兩種典型的(de)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)終止方(fang)法：采用(yong)最小(xiao)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)判斷或(huo)采用(yong)定時(shi)器（或(huo)者兩者的(de)結(jie)合）。最小(xiao)電(dian)(dian)(dian)(dian)流(liu)法監視恒壓充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)階段(duan)(duan)的(de)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)，并在充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)減小(xiao)到0.02C至(zhi)0.07C范圍時(shi)終止充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)。第二種方(fang)法從(cong)恒壓充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)階段(duan)(duan)開始(shi)時(shi)計時(shi)，持續充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)兩個小(xiao)時(shi)后終止充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)過程。

  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)用了更多(duo)安(an)全措(cuo)施。例如如果電(dian)(dian)池溫度超出指定(ding)窗(chuang)口（通(tong)常為0℃至(zhi)45℃），那么充電(dian)(dian)會暫停。

  1 決定(ding)鋰(li)離(li)子電池周期壽命(ming)(ming)或服務壽命(ming)(ming)的因素

  不存在(zai)任(ren)何延(yan)長或縮(suo)短電(dian)池壽(shou)(shou)命的單一因(yin)素，而常常是幾種因(yin)素合起來發揮作用。就延(yan)長周(zhou)期壽(shou)(shou)命而言有以下方法可以延(yan)長電(dian)池壽(shou)(shou)命：

1).采用部分放(fang)電(dian)(dian)的做法(fa)。在再(zai)充(chong)電(dian)(dian)前僅使用20%或(huo)30%的電(dian)(dian)池(chi)容量會極大延長周(zhou)期(qi)壽命。作為一個一般性的規(gui)則，5至10個淺放(fang)電(dian)(dian)周(zhou)期(qi)等(deng)于(yu)1個滿放(fang)電(dian)(dian)周(zhou)期(qi)。盡管部分放(fang)電(dian)(dian)周(zhou)期(qi)可(ke)能(neng)達(da)到數千(qian)次，但是保(bao)持電(dian)(dian)池(chi)處于(yu)滿充(chong)電(dian)(dian)狀態也(ye)縮短(duan)電(dian)(dian)池(chi)壽命。如果可(ke)能(neng)，應該避免滿放(fang)電(dian)(dian)周(zhou)期(qi)（降至2.5V或(huo)3V,取決于(yu)化(hua)學材料）。

2).避免(mian)充電(dian)(dian)至容(rong)量(liang)的(de)100%.選擇一個(ge)較低(di)的(de)浮(fu)動電(dian)(dian)壓(ya)(ya)可以做到(dao)這一點。降低(di)浮(fu)動電(dian)(dian)壓(ya)(ya)將提高周期(qi)壽(shou)命和服務壽(shou)命，代價是降低(di)電(dian)(dian)池(chi)容(rong)量(liang)。浮(fu)動電(dian)(dian)壓(ya)(ya)降低(di)100mV至300mV可以將周期(qi)壽(shou)命延(yan)長2至5倍或(huo)更長。與其他化學材(cai)料(liao)相比，鋰(li)(li)離(li)子(zi)鈷化學材(cai)料(liao)對較高浮(fu)動電(dian)(dian)壓(ya)(ya)更敏感。磷酸鋰(li)(li)離(li)子(zi)電(dian)(dian)池(chi)一般比更常見的(de)鋰(li)(li)離(li)子(zi)電(dian)(dian)池(chi)的(de)浮(fu)動電(dian)(dian)壓(ya)(ya)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，通過不充(chong)電(dian)到容量(liang)的100%,也可以延長電(dian)池(chi)壽命。例如，電(dian)流降至C/5時結束充(chong)電(dian)周期與將浮(fu)動電(dian)壓降至4.1V的效果類似。在這(zhe)兩種(zhong)情況下，電(dian)池(chi)都(dou)只(zhi)充(chong)電(dian)至約為容量(liang)的85%,這(zhe)是決(jue)定電(dian)池(chi)壽命的一個重要因(yin)素。

4).限制電(dian)(dian)(dian)池(chi)溫(wen)(wen)度(du)。限制電(dian)(dian)(dian)池(chi)的(de)極限溫(wen)(wen)度(du)可(ke)以延長電(dian)(dian)(dian)池(chi)壽命，尤其(qi)是禁止在(zai)0℃以下充電(dian)(dian)(dian)。在(zai)0℃以下充電(dian)(dian)(dian)促進金屬在(zai)電(dian)(dian)(dian)池(chi)陽極上的(de)鍍敷，這可(ke)能造成內部短路(lu)，產生(sheng)熱量(liang)并使電(dian)(dian)(dian)池(chi)不穩定和不安全。很多電(dian)(dian)(dian)池(chi)充電(dian)(dian)(dian)器都(dou)有測量(liang)電(dian)(dian)(dian)池(chi)溫(wen)(wen)度(du)的(de)裝置(zhi)，以確(que)保不會在(zai)極限溫(wen)(wen)度(du)時充電(dian)(dian)(dian)。

5).避免大的(de)充(chong)電(dian)和(he)放電(dian)電(dian)流(liu)(liu)，因(yin)為(wei)這會縮短周(zhou)期壽命(ming)。有些化學(xue)材(cai)料更適(shi)合較(jiao)大電(dian)流(liu)(liu)，如鋰離子(zi)錳和(he)磷酸鋰離子(zi)電(dian)池。大電(dian)流(liu)(liu)給電(dian)池施加(jia)了過大的(de)壓力。

6).避(bi)免低(di)于(yu)2V或2.5V的深度放(fang)(fang)電(dian)(dian)(dian)，因為這(zhe)(zhe)會(hui)(hui)迅速永久性損壞(huai)鋰(li)離(li)子(zi)(zi)電(dian)(dian)(dian)池(chi)。可能發生內部(bu)金屬鍍敷，這(zhe)(zhe)會(hui)(hui)引(yin)起短路(lu)，使電(dian)(dian)(dian)池(chi)不(bu)可用或不(bu)安全。大多(duo)數鋰(li)離(li)子(zi)(zi)電(dian)(dian)(dian)池(chi)在電(dian)(dian)(dian)池(chi)組內部(bu)都有電(dian)(dian)(dian)子(zi)(zi)電(dian)(dian)(dian)路(lu)，如(ru)果(guo)(guo)充電(dian)(dian)(dian)或放(fang)(fang)電(dian)(dian)(dian)時(shi)電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)壓(ya)低(di)于(yu)2.5V、超(chao)過4.3V或如(ru)果(guo)(guo)電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)流(liu)超(chao)過預定門限(xian)值，該電(dian)(dian)(dian)子(zi)(zi)電(dian)(dian)(dian)路(lu)就會(hui)(hui)斷(duan)開電(dian)(dian)(dian)池(chi)連(lian)接。

  2 鋰離子充(chong)電--系統注意事項

  要(yao)快速可靠(kao)地完成充(chong)電過程需要(yao)一個(ge)高性能的充(chong)電系統(tong)(tong)。為實現可靠(kao)且經濟高效的解決方案(an)，設計時(shi)應(ying)當考慮到以下系統(tong)(tong)參數：

2.1 輸入源
  許(xu)多應用(yong)都采用(yong)極廉價的墻式適配器作(zuo)為(wei)輸(shu)(shu)入電(dian)(dian)源。其(qi)輸(shu)(shu)出電(dian)(dian)壓(ya)主要依賴于交流(liu)輸(shu)(shu)入電(dian)(dian)壓(ya)和(he)從墻式適配器流(liu)出的負載(zai)電(dian)(dian)流(liu)。

  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(ji)(ji)繞(rao)組的(de)電(dian)阻(zu)與初級(ji)(ji)繞(rao)組反射電(dian)阻(zu)的(de)和。RPTC是PTC的(de)電(dian)阻(zu)，VFD是橋式整流器(qi)的(de)前向壓降。此外變壓器(qi)磁(ci)芯損失(shi)也會使(shi)輸出(chu)電(dian)壓略有降低。

  利(li)用汽車適配器充電的(de)應(ying)用也會(hui)遇到(dao)類(lei)似的(de)問題。汽車適配器的(de)輸出電壓典型范圍為(wei)9V至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(le)盡可能地充分利用電池容(rong)(rong)量，輸(shu)(shu)出(chu)(chu)電壓穩壓精(jing)(jing)度非(fei)常(chang)關(guan)鍵。輸(shu)(shu)出(chu)(chu)電壓精(jing)(jing)度的(de)小幅(fu)度下降也會導致電池容(rong)(rong)量的(de)大(da)幅(fu)減少。然而出(chu)(chu)于安全(quan)和(he)可靠性方(fang)面的(de)考慮，輸(shu)(shu)出(chu)(chu)電壓也不能隨意設置得過高。圖(tu)2顯示出(chu)(chu)了(le)輸(shu)(shu)出(chu)(chu)電壓穩定精(jing)(jing)度的(de)重要性。

3 充電終止方法

  毋庸(yong)置疑，過(guo)充(chong)始終是鋰離(li)子(zi)電(dian)池(chi)充(chong)電(dian)的心頭大(da)患。準確的充(chong)電(dian)終止方(fang)法對于安全可(ke)靠的充(chong)電(dian)系統來說非常關鍵。

3 .1 電池溫度監控
  一般情況下，鋰(li)離子(zi)電(dian)(dian)(dian)池(chi)(chi)(chi)充(chong)電(dian)(dian)(dian)時的溫度(du)范圍(wei)應當在(zai)0℃至45℃。在(zai)此溫度(du)范圍(wei)之外對(dui)電(dian)(dian)(dian)池(chi)(chi)(chi)充(chong)電(dian)(dian)(dian)會導(dao)致(zhi)電(dian)(dian)(dian)池(chi)(chi)(chi)過熱。在(zai)充(chong)電(dian)(dian)(dian)周期中，電(dian)(dian)(dian)池(chi)(chi)(chi)內的壓(ya)力上(shang)升還(huan)會 導(dao)致(zhi)電(dian)(dian)(dian)池(chi)(chi)(chi)膨脹。隨著溫度(du)上(shang)升，壓(ya)力也會過大(da)，這可能會導(dao)致(zhi)電(dian)(dian)(dian)池(chi)(chi)(chi)內部的機(ji)械破裂或(huo)材料泄漏，嚴重時還(huan)有(you)可能導(dao)致(zhi)爆炸。在(zai)此溫度(du)范圍(wei)之外 對(dui)電(dian)(dian)(dian)池(chi)(chi)(chi)充(chong)電(dian)(dian)(dian)還(huan)會損(sun)害電(dian)(dian)(dian)池(chi)(chi)(chi)的性能，或(huo)縮短電(dian)(dian)(dian)池(chi)(chi)(chi)的預期壽命。

  通常鋰(li)離(li)子電(dian)池(chi)(chi)包內都采用了熱敏(min)電(dian)阻(zu)來準確測(ce)量電(dian)池(chi)(chi)溫(wen)度(du)。充電(dian)器檢測(ce)熱敏(min)電(dian)阻(zu)的阻(zu)值(zhi)，當阻(zu)值(zhi)超(chao)出規定工作(zuo)范(fan)圍(wei)，即(ji)溫(wen)度(du)超(chao)過(guo)規定范(fan)圍(wei)時(shi)，充電(dian)被禁止。

3.2 電池放電電流或反向泄漏電流
  在許多應(ying)用中，即使輸入(ru)電(dian)(dian)(dian)(dian)(dian)源不存在，充電(dian)(dian)(dian)(dian)(dian)系統仍然與電(dian)(dian)(dian)(dian)(dian)池相連。充電(dian)(dian)(dian)(dian)(dian)系統必須保證輸入(ru)電(dian)(dian)(dian)(dian)(dian)源不存在時，從電(dian)(dian)(dian)(dian)(dian)池汲(ji)取的電(dian)(dian)(dian)(dian)(dian)流極(ji)小(xiao)。最大泄漏電(dian)(dian)(dian)(dian)(dian)流應(ying)當(dang)小(xiao)于幾個微安，通(tong)常(chang)應(ying)小(xiao)于一個微安。

4 鋰(li)離子(zi)充電--應(ying)用實例

  將(jiang)以(yi)上幾(ji)點系(xi)統(tong)注意事(shi)項事(shi)先充(chong)分考慮，就(jiu)能開發出適合的充(chong)電管(guan)理系(xi)統(tong)。

4.1 線性解決方案
  當存在穩壓良好(hao)的輸入電(dian)(dian)源時(shi)，通常采用(yong)線(xian)(xian)性充(chong)(chong)電(dian)(dian)解決(jue)方案(an)。在此類應用(yong)中(zhong)，線(xian)(xian)性解決(jue)方案(an)的優點(dian)包括易用(yong)、尺寸小(xiao)以及(ji)成本(ben)低。由(you)于(yu)線(xian)(xian)性充(chong)(chong)電(dian)(dian)解決(jue)方案(an) 效(xiao)率低因此影響(xiang)設(she)計的最重(zhong)要因素就是(shi)散熱(re)設(she)計。最糟(zao)的情況是(shi)器(qi)件從涓流充(chong)(chong)電(dian)(dian)階段向 恒流充(chong)(chong)電(dian)(dian)階段轉換時(shi)，在此情況下(xia)，傳輸晶體管必(bi)須散發最大(da)的熱(re)能，必(bi)須在充(chong)(chong)電(dian)(dian)電(dian)(dian)流、系統尺寸、成本(ben)和(he)散熱(re)要求之間進行權衡。

  例(li)如(ru)，應用(yong)中需要利用(yong)一(yi)個5V ±5%的(de)(de)輸入電(dian)(dian)源以(yi)0.5C或1C的(de)(de)恒(heng)定(ding)電(dian)(dian)流對一(yi)個1000mAh的(de)(de)單(dan)節(jie)鋰離(li)子電(dian)(dian)池充(chong)(chong)電(dian)(dian)。圖3顯示了如(ru)何利用(yong)Microchip的(de)(de) MCP73843構成(cheng)一(yi)個低(di)成(cheng)本的(de)(de)獨立解(jie)決方案，只需要極少量的(de)(de)外部(bu)元器件，就可以(yi)實現所需要的(de)(de)充(chong)(chong)電(dian)(dian)算(suan)法。MCP73843完美(mei)地結合了高精度恒(heng)流充(chong)(chong)電(dian)(dian)、 恒(heng)壓(ya)(ya)穩壓(ya)(ya)以(yi)及自動充(chong)(chong)電(dian)(dian)終止(zhi)等(deng)功能。

  為進一步減(jian)小線性解決方案(an)的尺寸、降低其成(cheng)本和復雜性，許(xu)多外(wai)部元器(qi)(qi)件都可以集成(cheng)到充(chong)電(dian)管(guan)(guan)理(li)控制器(qi)(qi)中。先進的封裝可以提供更高的集成(cheng)度，當然(ran)也會犧牲一定的靈活性。此外(wai)此類充(chong)電(dian)管(guan)(guan)理(li)控制器(qi)(qi) 還(huan)會實現一定的熱調節(jie)功(gong)能(neng)。熱調節(jie)功(gong)能(neng)可根據器(qi)(qi)件管(guan)(guan)芯溫度來限制充(chong)電(dian)電(dian)流，從而(er)可在保證器(qi)(qi)件可靠性的情況下優化充(chong)電(dian)周(zhou)期時(shi)間，熱調節(jie)功(gong)能(neng)大大降低了(le)散熱設 計(ji)的工作量。

  基于(yu)Microchip MCP73861的(de)全集成線性解決方案如圖4所示。MCP73861包含了MCP73843的(de)所有(you)功能，另外還包括(kuo)電流檢測(ce)、傳輸(shu)晶體管、反(fan)向放電保護以及(ji)電池溫(wen)度監(jian)測(ce)。

4.2 充電周期波形
  利用(yong)MCP73843在(zai)1C和0.5C恒流(liu)充(chong)電(dian)速率(lv)(lv)下的整個(ge)充(chong)電(dian)周(zhou)期如圖5.以0.5C而不是(shi)1C速率(lv)(lv)充(chong)電(dian)時(shi)(shi)，充(chong)電(dian)結(jie)束的時(shi)(shi)間(jian)(jian)大約晚了(le)一個(ge)小時(shi)(shi)。充(chong)電(dian)終止電(dian)流(liu)從0.07C降到(dao)0.035C,使得(de)最終電(dian)池容(rong)量從~98%增長到(dao)~100%.系(xi)統設計師必須在(zai)充(chong)電(dian)時(shi)(shi)間(jian)(jian)、功率(lv)(lv)損耗(hao)和可用(yong)電(dian)池容(rong)量之間(jian)(jian)進行權(quan)衡。

4.3 開關式充電解決方案
  輸(shu)入電(dian)壓波動(dong)范圍寬(kuan)或輸(shu)入輸(shu)出電(dian)壓差(cha)大(da)的(de)應用(yong)通(tong)常采(cai)用(yong)開關(guan)式充(chong)電(dian)解(jie)(jie)決方(fang)案(an)。例(li)如應用(yong)中需(xu)要利用(yong)汽車(che)適配(pei)器以0.5C或1C的(de)恒定電(dian)流(liu)對一(yi)個2200mAh的(de)單節(jie)鋰(li)離子(zi)電(dian)池充(chong)電(dian)，由于(yu)散熱等(deng)問題，利用(yong)線(xian)性解(jie)(jie)決方(fang)案(an)實現極為困難，當然也可(ke)以采(cai)用(yong)支持熱調節(jie)的(de)線(xian)性解(jie)(jie)決方(fang)案(an)，但降(jiang)低充(chong)電(dian)電(dian)流(liu)造成的(de)充(chong)電(dian)周期延長(chang)是無法接(jie)受的(de)。

  成功(gong)設(she)(she)計開(kai)關式(shi)(shi)充(chong)電(dian)(dian)(dian)解決方案的(de)(de)第一步是(shi)選擇設(she)(she)計結構：降壓(ya)(ya)式(shi)(shi)、升壓(ya)(ya)式(shi)(shi)、升/降壓(ya)(ya)式(shi)(shi)、反激式(shi)(shi)、單端(duan)初級電(dian)(dian)(dian)感式(shi)(shi)或者其他(ta)形式(shi)(shi)。SEPIC拓撲結構的(de)(de)優(you)點(dian)是(shi)低端(duan)柵極驅(qu)動(dong)和電(dian)(dian)(dian)流檢測、持(chi)續輸(shu)(shu) 入電(dian)(dian)(dian)流以及輸(shu)(shu)入和輸(shu)(shu)出間的(de)(de)直(zhi)流隔離，其主要缺點(dian)是(shi)需要兩(liang)個電(dian)(dian)(dian)感和一個能量傳(chuan)輸(shu)(shu)電(dian)(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。充電器采用的電(dian)(dian)源結(jie)構是(shi)SEPIC.單(dan)(dan)片機提(ti)供了極大的設(she)計靈活 性。此外(wai)單(dan)(dan)片機還可(ke)以與(yu)電(dian)(dian)池(chi)包內的電(dian)(dian)池(chi)監(jian)控(kong)器(qi)通信，從而大大縮(suo)短充電(dian)(dian)周期時間(jian)。

  利(li)用開關式充(chong)(chong)(chong)電(dian)(dian)解決方案的整個充(chong)(chong)(chong)電(dian)(dian)周(zhou)期(qi)(qi)如圖6所示。通過在充(chong)(chong)(chong)電(dian)(dian)系統中采(cai)用電(dian)(dian)池監控器，可(ke)以大大縮短充(chong)(chong)(chong)電(dian)(dian)周(zhou)期(qi)(qi)，使用電(dian)(dian)池監控器就不必再檢(jian)測(ce)電(dian)(dian)池包保護電(dian)(dian)路兩端(duan)的電(dian)(dian)壓以及充(chong)(chong)(chong)電(dian)(dian)電(dian)(dian)流的接觸(chu)電(dian)(dian)阻(zu)。

5 結論

  在(zai)目前的(de)便攜(xie)式產(chan)品中(zhong)，要正確地實現電(dian)(dian)池(chi)充(chong)電(dian)(dian)需(xu)要仔(zi)細地設(she)(she)計考慮。本文討(tao)論了鋰(li)離子電(dian)(dian)池(chi)的(de)線性和(he)開關式充(chong)電(dian)(dian)解決方案，本文所探討(tao)的(de)指導原則和(he)設(she)(she)計考慮要素，實際上也(ye)是所有電(dian)(dian)池(chi)充(chong)電(dian)(dian)系統(tong)設(she)(she)計都(dou)需(xu)要考慮的(de)。