在有些應用中，較長的電(dian)池(chi)壽命、較多的充(chong)電(dian)次(ci)數或較安(an)全的電(dian)池(chi)比(bi)電(dian)池(chi)容量更重要。本文介紹幾(ji)種可以極大延(yan)長電(dian)池(chi)壽命的鋰離子電(dian)池(chi)充(chong)電(dian)和放電(dian)方法。

  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)(yin)為與(yu)其他可再(zai)充(chong)電(dian)(dian)電(dian)(dian)池(chi)相(xiang)比，鋰(li)離子電(dian)(dian)池(chi)有較(jiao)高的(de)能量密(mi)度、較(jiao)高的(de)電(dian)(dian)池(chi)電(dian)(dian)壓(ya)、自(zi)放電(dian)(dian)少、周期壽(shou)命非常長，而且環保，且充(chong)電(dian)(dian)和維(wei)護簡單(dan)。另外，由于其具有相(xiang)對高的(de)電(dian)(dian)壓(ya)（2.9V至4.2V），因(yin)(yin)此很多(duo)便攜式產品都能用單(dan)節電(dian)(dian)池(chi)工(gong)作，從而簡化了產品總(zong)體設計。C速率等于特定條件(jian)下(xia)的(de)充(chong)電(dian)(dian)或放電(dian)(dian)電(dian)(dian)流，定義如下(xia)：I=M×Cn

  其中：I = 充電(dian)或放(fang)電(dian)電(dian)流，單(dan)位(wei)為(wei)A；M = C的(de)倍數(shu)或分數(shu)；C = 額定容(rong)量(liang)的(de)數(shu)值，單(dan)位(wei)為(wei)Ah；N = 小時數(shu)（對應于(yu)C）。

  以1倍C速(su)率放(fang)(fang)電(dian)的(de)電(dian)池將(jiang)在一個小時內(nei)釋放(fang)(fang)標稱(cheng)的(de)額定(ding)容量。例(li)如(ru)(ru)，如(ru)(ru)果(guo)標稱(cheng)容量是1000mAhr,那么1C的(de)放(fang)(fang)電(dian)速(su)率對(dui)應于1000mA的(de)放(fang)(fang)電(dian)電(dian)流(liu)，C/10的(de)速(su)率對(dui)應100mA的(de)放(fang)(fang)電(dian)電(dian)流(liu)。

  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)池(chi)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)推(tui)薦方(fang)法(fa)(fa)是，向電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)提供一(yi)個±1%限壓的(de)(de)恒定電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)，直(zhi)到(dao)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)(chong)(chong)(chong)(chong)滿(man)電(dian)(dian)(dian)(dian)(dian)(dian)，然后停(ting)止充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)。用(yong)來決定電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)何(he)時(shi)(shi)(shi)充(chong)(chong)(chong)(chong)(chong)(chong)滿(man)電(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)方(fang)法(fa)(fa)包(bao)括(kuo)：給總的(de)(de)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)時(shi)(shi)(shi)間(jian)定時(shi)(shi)(shi)、監視(shi)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)或兼用(yong)這兩種(zhong)(zhong)方(fang)法(fa)(fa)。第(di)一(yi)種(zhong)(zhong)方(fang)法(fa)(fa)采(cai)用(yong)限壓恒定電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)，變化范圍從C/2到(dao)1C,持續(xu)(xu)2.5至3小(xiao)時(shi)(shi)(shi)，使電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)達(da)到(dao)100%充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)。也可以使用(yong)較低的(de)(de)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)，但是將(jiang)需要更長時(shi)(shi)(shi)間(jian)。第(di)二種(zhong)(zhong)方(fang)法(fa)(fa)與第(di)一(yi)種(zhong)(zhong)方(fang)法(fa)(fa)類似，只是需要監視(shi)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)。隨(sui)著電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)的(de)(de)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)，電(dian)(dian)(dian)(dian)(dian)(dian)壓上升(sheng)，這與采(cai)用(yong)第(di)一(yi)種(zhong)(zhong)方(fang)法(fa)(fa)時(shi)(shi)(shi)完全(quan)相同。電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)壓達(da)到(dao)編程限壓值（也稱為浮(fu)動電(dian)(dian)(dian)(dian)(dian)(dian)壓）時(shi)(shi)(shi)，充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)開始下降。電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)一(yi)開始下降時(shi)(shi)(shi)，電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)約充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)至容(rong)量(liang)(liang)的(de)(de)50%至60%.浮(fu)動電(dian)(dian)(dian)(dian)(dian)(dian)壓繼(ji)續(xu)(xu)提供，直(zhi)到(dao)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)降至足夠低的(de)(de)水平(ping)（C/10至C/20），這時(shi)(shi)(shi)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)約充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)至容(rong)量(liang)(liang)的(de)(de)92%至99%,充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)周期終止。目前，要為標(biao)準鋰離子電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)快速充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)（不到(dao)1小(xiao)時(shi)(shi)(shi)）至容(rong)量(liang)(liang)的(de)(de)100%,還沒有一(yi)種(zhong)(zhong)安全(quan)的(de)(de)方(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)曲線(xian)，圖中顯示了充(chong)電(dian)電(dian)流(liu)(liu)、電(dian)池電(dian)壓(ya)(ya)和電(dian)池容量隨時(shi)間的變化。那么怎樣才(cai)能正(zheng)確地為(wei)鋰離(li)子電(dian)池充(chong)電(dian)呢？鋰離(li)子電(dian)池最(zui)適(shi)合的充(chong)電(dian)過程可以分為(wei)四個階段：涓流(liu)(liu)充(chong)電(dian)、恒流(liu)(liu)充(chong)電(dian)、恒壓(ya)(ya)充(chong)電(dian)以及充(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流充電(dian)。連續涓流充電(dian)會(hui)導(dao)致(zhi)金屬鋰(li)出(chu)現極板電(dian)鍍效應。這會(hui)使(shi)電(dian)池不(bu)穩定，并且有(you)可(ke)能(neng)導(dao)致(zhi)突然的自動快速(su)解體(ti)。

  有(you)兩(liang)種典型的(de)充電(dian)(dian)(dian)(dian)(dian)終止方法：采(cai)用(yong)(yong)最小充電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)判斷或(huo)采(cai)用(yong)(yong)定(ding)時(shi)(shi)器（或(huo)者兩(liang)者的(de)結(jie)合(he)）。最小電(dian)(dian)(dian)(dian)(dian)流(liu)法監視恒壓充電(dian)(dian)(dian)(dian)(dian)階段的(de)充電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)，并在充電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)減小到(dao)0.02C至(zhi)0.07C范圍時(shi)(shi)終止充電(dian)(dian)(dian)(dian)(dian)。第二種方法從恒壓充電(dian)(dian)(dian)(dian)(dian)階段開始時(shi)(shi)計時(shi)(shi)，持續充電(dian)(dian)(dian)(dian)(dian)兩(liang)個(ge)小時(shi)(shi)后終止充電(dian)(dian)(dian)(dian)(dian)過(guo)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)安全(quan)措施。例如(ru)如(ru)果電(dian)池溫度超出指定窗口（通常為0℃至45℃），那么充(chong)電(dian)會(hui)暫停。

  1 決定(ding)鋰(li)離子電池周期壽(shou)命或服務壽(shou)命的因素

  不存在(zai)任何延(yan)長(chang)或(huo)縮短電池壽(shou)命(ming)(ming)的單一因素，而常常是(shi)幾種因素合起來發揮作用。就(jiu)延(yan)長(chang)周期壽(shou)命(ming)(ming)而言有(you)以下方法(fa)可以延(yan)長(chang)電池壽(shou)命(ming)(ming)：

1).采(cai)用部分(fen)放電(dian)(dian)的做(zuo)法。在再充電(dian)(dian)前(qian)僅使(shi)用20%或30%的電(dian)(dian)池(chi)容量會極大延(yan)長周(zhou)(zhou)期(qi)(qi)壽(shou)命。作為一(yi)個(ge)一(yi)般性(xing)的規則，5至10個(ge)淺(qian)放電(dian)(dian)周(zhou)(zhou)期(qi)(qi)等于1個(ge)滿(man)(man)放電(dian)(dian)周(zhou)(zhou)期(qi)(qi)。盡管(guan)部分(fen)放電(dian)(dian)周(zhou)(zhou)期(qi)(qi)可(ke)能達到數千次，但是保持電(dian)(dian)池(chi)處于滿(man)(man)充電(dian)(dian)狀態也縮(suo)短電(dian)(dian)池(chi)壽(shou)命。如果可(ke)能，應該避免滿(man)(man)放電(dian)(dian)周(zhou)(zhou)期(qi)(qi)（降(jiang)至2.5V或3V,取決于化學材料）。

2).避免充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)至容量(liang)的(de)(de)100%.選擇一個較低的(de)(de)浮(fu)(fu)動電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)可(ke)以做到(dao)這一點(dian)。降低浮(fu)(fu)動電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)將提高周期壽命和(he)服(fu)務壽命，代價是降低電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)容量(liang)。浮(fu)(fu)動電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)降低100mV至300mV可(ke)以將周期壽命延長2至5倍或更(geng)長。與(yu)其他(ta)化學(xue)材(cai)料相(xiang)比，鋰(li)離子(zi)鈷化學(xue)材(cai)料對較高浮(fu)(fu)動電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)更(geng)敏感。磷酸鋰(li)離子(zi)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)一般比更(geng)常見的(de)(de)鋰(li)離子(zi)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)的(de)(de)浮(fu)(fu)動電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)低。

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(guo)不充(chong)電(dian)到容量的(de)100%,也可以延長電(dian)池(chi)壽(shou)命(ming)。例(li)如，電(dian)流(liu)降至(zhi)C/5時(shi)結(jie)束充(chong)電(dian)周期與將(jiang)浮動電(dian)壓降至(zhi)4.1V的(de)效(xiao)果類似。在(zai)這兩種情況下，電(dian)池(chi)都(dou)只充(chong)電(dian)至(zhi)約為容量的(de)85%,這是(shi)決(jue)定電(dian)池(chi)壽(shou)命(ming)的(de)一個重要因素。

4).限(xian)(xian)制(zhi)電(dian)池(chi)溫度。限(xian)(xian)制(zhi)電(dian)池(chi)的極限(xian)(xian)溫度可以(yi)延長(chang)電(dian)池(chi)壽(shou)命(ming)，尤其(qi)是禁止在(zai)0℃以(yi)下(xia)充(chong)電(dian)。在(zai)0℃以(yi)下(xia)充(chong)電(dian)促進金(jin)屬在(zai)電(dian)池(chi)陽極上的鍍(du)敷，這可能造成內部短路，產(chan)生熱量并使電(dian)池(chi)不穩定(ding)和(he)不安全(quan)。很多(duo)電(dian)池(chi)充(chong)電(dian)器都有測量電(dian)池(chi)溫度的裝置，以(yi)確保不會在(zai)極限(xian)(xian)溫度時充(chong)電(dian)。

5).避(bi)免大的充(chong)電(dian)(dian)和(he)放電(dian)(dian)電(dian)(dian)流，因(yin)為這會(hui)縮短(duan)周期壽命。有些化學材料更適合較大電(dian)(dian)流，如鋰離(li)子錳和(he)磷酸(suan)鋰離(li)子電(dian)(dian)池。大電(dian)(dian)流給(gei)電(dian)(dian)池施加了過大的壓力。

6).避免低于(yu)2V或2.5V的深(shen)度放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)，因為這(zhe)會迅速永久性損壞鋰(li)離子(zi)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)。可(ke)能(neng)發生內部(bu)金屬鍍(du)敷，這(zhe)會引(yin)起短路(lu)，使電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)不(bu)可(ke)用或不(bu)安全。大(da)多數鋰(li)離子(zi)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)在電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)組內部(bu)都(dou)有電(dian)(dian)(dian)(dian)(dian)(dian)子(zi)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)，如果充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)或放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)時電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)壓低于(yu)2.5V、超(chao)過4.3V或如果電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)流超(chao)過預(yu)定門限值，該電(dian)(dian)(dian)(dian)(dian)(dian)子(zi)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)就(jiu)會斷開(kai)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)連接。

  2 鋰離子充電--系統注意事項

  要快(kuai)速可(ke)靠地完成充電過程需要一(yi)個高性能的充電系統。為(wei)實現可(ke)靠且經(jing)濟(ji)高效的解決(jue)方案，設計時應當考慮到以下系統參數(shu)：

2.1 輸入源
  許多應用都采用極(ji)廉價的(de)(de)墻式(shi)適配器作(zuo)為輸(shu)入電源。其輸(shu)出電壓(ya)主要(yao)依賴于交流(liu)輸(shu)入電壓(ya)和從墻式(shi)適配器流(liu)出的(de)(de)負載電流(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(shi)次級繞組的電(dian)(dian)阻與初級繞組反射電(dian)(dian)阻的和。RPTC是(shi)PTC的電(dian)(dian)阻，VFD是(shi)橋式整流器的前向壓(ya)(ya)降。此外變壓(ya)(ya)器磁芯損失也會使輸(shu)出(chu)電(dian)(dian)壓(ya)(ya)略有降低。

  利用汽車適配(pei)(pei)器(qi)充電(dian)的(de)應用也會(hui)遇(yu)到類似(si)的(de)問題。汽車適配(pei)(pei)器(qi)的(de)輸出電(dian)壓(ya)典型(xing)范圍為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(wei)了(le)盡可能(neng)地充分利用電(dian)(dian)池(chi)容(rong)量(liang)，輸(shu)出(chu)電(dian)(dian)壓(ya)穩壓(ya)精度非(fei)常關鍵。輸(shu)出(chu)電(dian)(dian)壓(ya)精度的(de)小幅度下降(jiang)也會導致電(dian)(dian)池(chi)容(rong)量(liang)的(de)大幅減少。然而出(chu)于安全和可靠性方面的(de)考慮，輸(shu)出(chu)電(dian)(dian)壓(ya)也不(bu)能(neng)隨意設(she)置得過高。圖2顯示出(chu)了(le)輸(shu)出(chu)電(dian)(dian)壓(ya)穩定精度的(de)重(zhong)要性。

3 充電終止方法

  毋庸(yong)置疑，過充(chong)始終(zhong)是鋰離子電(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)的心頭(tou)大患(huan)。準確(que)的充(chong)電(dian)(dian)(dian)終(zhong)止方法(fa)對于安(an)全(quan)可靠(kao)的充(chong)電(dian)(dian)(dian)系統來說非(fei)常關鍵(jian)。

3 .1 電池溫度監控
  一(yi)般情況(kuang)下，鋰(li)離子電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)時(shi)的(de)(de)溫度范(fan)圍(wei)應當在(zai)(zai)0℃至45℃。在(zai)(zai)此溫度范(fan)圍(wei)之外對電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)會(hui)(hui)導致(zhi)(zhi)(zhi)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)過熱。在(zai)(zai)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)周期中(zhong)，電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)內(nei)的(de)(de)壓力(li)上(shang)升(sheng)還會(hui)(hui) 導致(zhi)(zhi)(zhi)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)膨脹。隨(sui)著溫度上(shang)升(sheng)，壓力(li)也會(hui)(hui)過大，這可能會(hui)(hui)導致(zhi)(zhi)(zhi)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)內(nei)部的(de)(de)機械(xie)破裂或材料泄漏(lou)，嚴重時(shi)還有(you)可能導致(zhi)(zhi)(zhi)爆炸。在(zai)(zai)此溫度范(fan)圍(wei)之外 對電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)還會(hui)(hui)損害電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)的(de)(de)性(xing)能，或縮短電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)的(de)(de)預期壽(shou)命(ming)。

  通常鋰離子電(dian)(dian)(dian)池(chi)包內都采(cai)用了熱敏電(dian)(dian)(dian)阻(zu)來準確測(ce)量電(dian)(dian)(dian)池(chi)溫度。充電(dian)(dian)(dian)器檢測(ce)熱敏電(dian)(dian)(dian)阻(zu)的阻(zu)值，當阻(zu)值超出規定工作范圍，即溫度超過規定范圍時(shi)，充電(dian)(dian)(dian)被禁(jin)止。

3.2 電池放電電流或反向泄漏電流
  在許多(duo)應用中，即使輸入(ru)電(dian)(dian)源(yuan)不存(cun)在，充電(dian)(dian)系(xi)統仍(reng)然與電(dian)(dian)池相連。充電(dian)(dian)系(xi)統必須保證輸入(ru)電(dian)(dian)源(yuan)不存(cun)在時(shi)，從(cong)電(dian)(dian)池汲(ji)取的電(dian)(dian)流極小。最大泄漏電(dian)(dian)流應當小于(yu)幾個(ge)微安，通常應小于(yu)一個(ge)微安。

4 鋰離子(zi)充電--應用實例

  將以上幾點系統注意(yi)事(shi)(shi)項(xiang)事(shi)(shi)先充(chong)分(fen)考慮，就能開發出適合的(de)充(chong)電管理系統。

4.1 線性解決方案
  當存在(zai)(zai)穩壓(ya)良好的(de)(de)輸(shu)入電(dian)(dian)源時，通(tong)常采用線性充(chong)電(dian)(dian)解(jie)決方案。在(zai)(zai)此(ci)類應用中，線性解(jie)決方案的(de)(de)優(you)點包括易(yi)用、尺(chi)寸小以(yi)及(ji)成(cheng)本低。由于線性充(chong)電(dian)(dian)解(jie)決方案 效率低因此(ci)影響設(she)計的(de)(de)最(zui)重要因素就是散熱設(she)計。最(zui)糟的(de)(de)情況(kuang)是器件(jian)從涓流(liu)充(chong)電(dian)(dian)階段向 恒流(liu)充(chong)電(dian)(dian)階段轉(zhuan)換時，在(zai)(zai)此(ci)情況(kuang)下，傳輸(shu)晶體管必須散發最(zui)大的(de)(de)熱能，必須在(zai)(zai)充(chong)電(dian)(dian)電(dian)(dian)流(liu)、系統尺(chi)寸、成(cheng)本和散熱要求(qiu)之間進行(xing)權衡(heng)。

  例如(ru)，應用(yong)中需(xu)(xu)要(yao)利用(yong)一(yi)個(ge)5V ±5%的(de)(de)(de)輸入電(dian)(dian)源(yuan)以(yi)0.5C或(huo)1C的(de)(de)(de)恒(heng)定電(dian)(dian)流(liu)對一(yi)個(ge)1000mAh的(de)(de)(de)單節鋰離子電(dian)(dian)池充電(dian)(dian)。圖3顯示了(le)(le)如(ru)何利用(yong)Microchip的(de)(de)(de) MCP73843構成一(yi)個(ge)低成本的(de)(de)(de)獨立(li)解決方案，只(zhi)需(xu)(xu)要(yao)極(ji)少(shao)量的(de)(de)(de)外部元器件，就(jiu)可以(yi)實現所需(xu)(xu)要(yao)的(de)(de)(de)充電(dian)(dian)算法(fa)。MCP73843完美(mei)地結(jie)合了(le)(le)高(gao)精度恒(heng)流(liu)充電(dian)(dian)、 恒(heng)壓穩(wen)壓以(yi)及自動充電(dian)(dian)終止等功能。

  為進一(yi)步減小(xiao)線性解決方(fang)案的(de)尺寸(cun)、降(jiang)低其成本和復雜(za)性，許多(duo)外部元器件都可(ke)以集成到充(chong)電管(guan)理控制器中。先進的(de)封裝可(ke)以提(ti)供更高的(de)集成度，當然(ran)也會犧(xi)牲一(yi)定的(de)靈活(huo)性。此外此類充(chong)電管(guan)理控制器 還(huan)會實現一(yi)定的(de)熱(re)調(diao)節(jie)功(gong)能(neng)。熱(re)調(diao)節(jie)功(gong)能(neng)可(ke)根據(ju)器件管(guan)芯溫度來限制充(chong)電電流，從而可(ke)在保(bao)證器件可(ke)靠(kao)性的(de)情(qing)況下優化充(chong)電周期(qi)時間，熱(re)調(diao)節(jie)功(gong)能(neng)大大降(jiang)低了散熱(re)設 計的(de)工作量。

  基于(yu)Microchip MCP73861的全集成線(xian)性解決方案如圖4所示。MCP73861包含了MCP73843的所有(you)功能，另外還包括電(dian)流檢測(ce)、傳輸晶體管、反向放電(dian)保護以及電(dian)池溫度監測(ce)。

4.2 充電周期波形
  利用MCP73843在(zai)1C和0.5C恒流充(chong)(chong)電(dian)速(su)率下(xia)的整個(ge)(ge)充(chong)(chong)電(dian)周期(qi)如圖5.以(yi)0.5C而(er)不是1C速(su)率充(chong)(chong)電(dian)時，充(chong)(chong)電(dian)結束的時間(jian)大約晚了一個(ge)(ge)小時。充(chong)(chong)電(dian)終(zhong)止電(dian)流從0.07C降到(dao)0.035C,使(shi)得最終(zhong)電(dian)池(chi)容(rong)量(liang)從~98%增長到(dao)~100%.系統設(she)計師必須在(zai)充(chong)(chong)電(dian)時間(jian)、功率損(sun)耗和可用電(dian)池(chi)容(rong)量(liang)之間(jian)進行(xing)權衡。

4.3 開關式充電解決方案
  輸入電(dian)(dian)(dian)壓(ya)波動范圍寬或輸入輸出電(dian)(dian)(dian)壓(ya)差(cha)大的(de)應(ying)用(yong)(yong)(yong)通常采用(yong)(yong)(yong)開關式充(chong)電(dian)(dian)(dian)解(jie)決(jue)方案。例如應(ying)用(yong)(yong)(yong)中需要(yao)利用(yong)(yong)(yong)汽車適(shi)配器以0.5C或1C的(de)恒定(ding)電(dian)(dian)(dian)流對一個2200mAh的(de)單節鋰(li)離子電(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)，由于散熱等問題(ti)，利用(yong)(yong)(yong)線(xian)性(xing)解(jie)決(jue)方案實現極(ji)為困難，當(dang)然也可以采用(yong)(yong)(yong)支持熱調節的(de)線(xian)性(xing)解(jie)決(jue)方案，但(dan)降低充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流造成的(de)充(chong)電(dian)(dian)(dian)周期延長是無法(fa)接受的(de)。

  成功設計開(kai)關(guan)式(shi)(shi)(shi)(shi)充電(dian)(dian)解(jie)決方案(an)的第一步是(shi)選擇設計結(jie)(jie)構：降(jiang)壓(ya)式(shi)(shi)(shi)(shi)、升壓(ya)式(shi)(shi)(shi)(shi)、升/降(jiang)壓(ya)式(shi)(shi)(shi)(shi)、反激式(shi)(shi)(shi)(shi)、單(dan)端(duan)初級電(dian)(dian)感式(shi)(shi)(shi)(shi)或者其他(ta)形式(shi)(shi)(shi)(shi)。SEPIC拓(tuo)撲(pu)結(jie)(jie)構的優(you)點(dian)是(shi)低(di)端(duan)柵極(ji)驅動和電(dian)(dian)流(liu)檢(jian)測、持續輸(shu)(shu)(shu) 入電(dian)(dian)流(liu)以及輸(shu)(shu)(shu)入和輸(shu)(shu)(shu)出(chu)間(jian)的直流(liu)隔離，其主要(yao)缺(que)點(dian)是(shi)需要(yao)兩個電(dian)(dian)感和一個能量(liang)傳輸(shu)(shu)(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。充電器采用的電(dian)(dian)(dian)源結構是(shi)SEPIC.單(dan)片機提(ti)供了極大(da)的設(she)計靈活 性。此外單(dan)片機還可(ke)以與電(dian)(dian)(dian)池包內的電(dian)(dian)(dian)池監控(kong)器通信(xin)，從而大(da)大(da)縮短充電(dian)(dian)(dian)周期時(shi)間。

  利用開關式充(chong)電(dian)(dian)(dian)(dian)解決方案的整個充(chong)電(dian)(dian)(dian)(dian)周期如圖(tu)6所示。通過在充(chong)電(dian)(dian)(dian)(dian)系(xi)統中采用電(dian)(dian)(dian)(dian)池(chi)監(jian)控器，可以大大縮短充(chong)電(dian)(dian)(dian)(dian)周期，使用電(dian)(dian)(dian)(dian)池(chi)監(jian)控器就不必(bi)再(zai)檢測電(dian)(dian)(dian)(dian)池(chi)包保護電(dian)(dian)(dian)(dian)路兩(liang)端的電(dian)(dian)(dian)(dian)壓以及充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流的接觸電(dian)(dian)(dian)(dian)阻。

5 結論

  在目前的(de)便攜式產品中，要(yao)正確地實(shi)現電(dian)(dian)池充電(dian)(dian)需(xu)要(yao)仔細(xi)地設(she)計(ji)考(kao)慮(lv)(lv)。本文討論了鋰離子電(dian)(dian)池的(de)線(xian)性(xing)和開(kai)關式充電(dian)(dian)解(jie)決方案，本文所探討的(de)指導原則和設(she)計(ji)考(kao)慮(lv)(lv)要(yao)素，實(shi)際上也是所有電(dian)(dian)池充電(dian)(dian)系統(tong)設(she)計(ji)都需(xu)要(yao)考(kao)慮(lv)(lv)的(de)。