小型低成本上網本、超便攜 PC (UMPC) 和移動互聯網設備 (MID) 正變得越來越流行，并得到了用戶的廣泛認可。這些便攜設備中使用的鋰離子 (Li-Ion) 電池充電系統比移動電話中使用的鋰離子電池充電系統要復雜得多。理解其電池充電器的諸多要求成為提高系統安全性的關鍵。本文將討論鋰離子電池充電的許多要求，如：充電系統安全性和充電器與系統之間的性能優化等，還介紹了一個同步開關獨立電池充電器IC控制器設計實例，它擁有動態電源管理功能，用于優化上網本應用的適配器額定功率和對電池快速充電。

　　上網本是小型、輕便和低價筆記本電腦的一種快速衍生品，主要用于一般計算和訪問網絡應用。大多數上網本均使用Intel Atom 微處理器以及2～3塊串聯鋰離子電池組。

　　超便攜(xie)PC (UMPC) 擁有(you)一個功能強(qiang)大的處(chu)理器(qi)(qi)，擁有(you)一個 具有(you)觸摸功能的4～7英寸的顯示屏(ping)，可以運行與(yu)Windows Vista兼容的軟件。超便攜(xie) PC 還(huan)擁有(you)全球定位系統 (GPS) 設(she)備(bei)、指紋識別(bie)器(qi)(qi)、TV 調諧器(qi)(qi)以及存儲卡讀(du)卡器(qi)(qi)等(deng)。它由(you)2～3 塊串聯鋰離子(zi)電池組供(gong)電。

　　移動互聯網(wang)設備 (MID) 是一種具有多媒體功(gong)能的(de)手(shou)持式(shi)電腦，可以提(ti)供無線網(wang)絡訪問(wen)，具有雙向(xiang)通(tong)信(xin)和實時共享功(gong)能，專為(wei)向(xiang)個人（非企業用戶）提(ti)供娛樂(le)、資(zi)訊和定位服(fu)務而設計。MID 的(de)外形(xing)尺寸比智(zhi)能電話大，但比 UMPC 小(xiao)，通(tong)常使用一個鋰離子電池組供電。

　　動態電源管理

　　電池充電電壓和電(dian)流對(dui)電(dian)池使(shi)(shi)用壽(shou)命和電(dian)池容(rong)(rong)量至關重要。電(dian)池充(chong)電(dian)電(dian)壓越高，電(dian)池容(rong)(rong)量也就越高。這(zhe)些便(bian)(bian)攜設備因其(qi)微處理(li)器(qi)功(gong)耗很低(di)(di)，需要的(de)(de)(de)總功(gong)耗低(di)(di)于(yu)(yu)筆記(ji)本(ben)電(dian)腦(nao)，所(suo)用的(de)(de)(de)電(dian)源適(shi)(shi)配(pei)器(qi)功(gong)率(lv)一般在(zai) 40 瓦(wa)以(yi)下(xia)，而(er)筆記(ji)本(ben)電(dian)腦(nao)通常使(shi)(shi)用 60 瓦(wa)和 90 瓦(wa)的(de)(de)(de)適(shi)(shi)配(pei)器(qi)。但是，仍然要求這(zhe)種適(shi)(shi)配(pei)器(qi)在(zai)給電(dian)池充(chong)電(dian)的(de)(de)(de)同時為系(xi)統(tong)供電(dian)，從而(er)最(zui)小化適(shi)(shi)配(pei)器(qi)額定功(gong)率(lv)。由于(yu)(yu)微處理(li)器(qi)的(de)(de)(de)高脈動功(gong)率(lv)特性(xing)，電(dian)池充(chong)電(dian)以(yi)及為微處理(li)器(qi)提供最(zui)大功(gong)率(lv)所(suo)要求的(de)(de)(de)總功(gong)率(lv)輕易便(bian)(bian)超出了適(shi)(shi)配(pei)器(qi)的(de)(de)(de)最(zui)大可(ke)用功(gong)率(lv)。

　　為了優化系統和電池充電器，我們通過引入最(zui)大(da)適(shi)配器電(dian)流(liu)調節(jie)(jie)環路使用了(le)動態(tai)電(dian)源管(guan)理 (DPM) 功能。如果輸(shu)(shu)入適(shi)配器電(dian)流(liu)達到(dao)了(le)調節(jie)(jie)閾值，則電(dian)池充(chong)電(dian)器自動降低有效充(chong)電(dian)電(dian)流(liu)，同(tong)時優先為系統(tong)供(gong)(gong)電(dian)，以使其不超(chao)出(chu)適(shi)配器的(de)最(zui)大(da)功率(lv)極限。在為系統(tong)供(gong)(gong)電(dian)以后(hou)，剩余功率(lv)用于(yu)對電(dian)池充(chong)電(dian)。一旦脈沖功率(lv)終止，充(chong)電(dian)器便自動恢復最(zui)快充(chong)電(dian)模(mo)式，以縮短充(chong)電(dian)時間（圖1）。一種(zhong)重要的(de)規范是輸(shu)(shu)入電(dian)流(liu)調節(jie)(jie)精度。輸(shu)(shu)入電(dian)流(liu)調節(jie)(jie)精度越(yue)高，適(shi)配器提供(gong)(gong)的(de)功率(lv)越(yue)多，同(tong)時電(dian)池充(chong)電(dian)的(de)速度也就越(yue)快。

圖(tu) 1  動態電源(yuan)管(guan)理(li)的電池充電結構圖(tu)

　　計算系統和電池充電器安全性

　　a、適配器輸入和電池過壓保護 (OVP)

　　就筆記本電腦而言，一般使用19-V和16-V的適配器，而5-V 適配器則普遍用于智能電話。上網本、UMPC和MID通常使用這些適配器來節省開發成本，但其往往不要求19V 適配器對1到3節串聯電池組充電。此外，IEEE P1725 要求系統包括輸入適配器和電池 OVP。如果這些便攜式設備遇到過輸入電壓，則其會阻止您開啟系統。如果電池過充，則立即關閉電池充電器。如果出現逆(ni)向適配器電壓，也不能開啟(qi)系統。

　　b、電池充電安全性

　　在極低(di)或極高電(dian)池(chi)(chi)溫(wen)度條件下對鋰離子電(dian)池(chi)(chi)充電(dian)是很危險的(de)。當電(dian)池(chi)(chi)在4.3V溫(wen)度達到(dao) 175oC 時，LiCoO2 負極材料(liao)的(de)鋰離子電(dian)池(chi)(chi)可能會爆(bao)炸。已發(fa)布的(de)許多(duo)工(gong)業電(dian)池(chi)(chi)充電(dian)器安(an)全規(gui)定(ding)（例如：日本電(dian)子和(he)信息(xi)技(ji)術行業協(xie)會 (JEITA) 等）通過減少低(di)或高電(dian)池(chi)(chi)溫(wen)度下的(de)電(dian)池(chi)(chi)充電(dian)電(dian)流和(he)電(dian)壓(ya)來(lai)達到(dao)電(dian)池(chi)(chi)安(an)全充電(dian)的(de)目的(de)。

　　要(yao)開始充(chong)(chong)電(dian)過程，一般電(dian)池充(chong)(chong)電(dian)溫度范圍在 0oC ～40oC 之間。因此，必(bi)須通過電(dian)量監(jian)測(ce)(ce)計或充(chong)(chong)電(dian)器(qi)來監(jian)測(ce)(ce)電(dian)池溫度。電(dian)池充(chong)(chong)電(dian)系統失(shi)效時(shi)(shi)，安(an)全定時(shi)(shi)器(qi)是另(ling)一層保(bao)護。當(dang)安(an)全定時(shi)(shi)器(qi)終止時(shi)(shi)，電(dian)池便(bian)停止充(chong)(chong)電(dian)。

　　c、電池充電器輸出短路和過充電流保護

　　對(dui)于一些計算應用(yong)來(lai)說，最為常用(yong)的鋰離子(zi)電(dian)池是具(ju)有(you) 2200-2600mAh 容量的 18650 鋰離子(zi)電(dian)池。12-V 或(huo)(huo) 19-V 適配器(qi)在 0.7oC 充電(dian)率情況下，充電(dian)電(dian)流(liu)約(yue)為 2-4A。高效充電(dian)要求(qiu)同(tong)步(bu)開(kai)關降壓型拓(tuo)撲。其還要求(qiu)在出現元件(jian)故障或(huo)(huo)非正常運行狀態（例(li)如：充電(dian)器(qi)輸出短(duan)路(lu)或(huo)(huo)電(dian)感短(duan)路(lu)等）時(shi)有(you)一個(ge)無煙充電(dian)系統。充電(dian)器(qi)需要有(you)此類(lei)保護(hu)機制來(lai)防(fang)止起火或(huo)(huo)冒煙。

　　上網本、UMPC 和 MID 的電池充電器解決方案

　　根據系統(tong)優化和安(an)全(quan)要求，圖2顯示了一款適用(yong)于(yu)上網本應用(yong)且具有動態電(dian)(dian)(dian)(dian)(dian)源(yuan)管理功能(neng)的(de)獨立型(xing)高效同步(bu)開(kai)關(guan)鋰離子電(dian)(dian)(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)(dian)(dian)器。這種(zhong)設計示例使用(yong)200mA預充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流和2A快速(su)充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流以及 3 小時(shi)(shi)安(an)全(quan)定時(shi)(shi)器來(lai)對2節鋰離子電(dian)(dian)(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)(dian)(dian)。通過監(jian)測輸入電(dian)(dian)(dian)(dian)(dian)流感應電(dian)(dian)(dian)(dian)(dian)阻R1兩端的(de)壓(ya)降實(shi)現DPM功能(neng)。同步(bu)開(kai)關(guan)充(chong)電(dian)(dian)(dian)(dian)(dian)器以600kHz 的(de)開(kai)關(guan)頻(pin)率工作，以優化效率和解決方案尺寸。外部電(dian)(dian)(dian)(dian)(dian)阻分壓(ya)器R11和R12用(yong)于(yu)設置(zhi)理想的(de)電(dian)(dian)(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓(ya)。要想獲得最大(da)的(de)電(dian)(dian)(dian)(dian)(dian)池容量，請將外部電(dian)(dian)(dian)(dian)(dian)阻分壓(ya)器設置(zhi)為每節電(dian)(dian)(dian)(dian)(dian)池 4.2V 的(de)充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓(ya)。

　　如欲獲(huo)得最長電(dian)(dian)(dian)(dian)池(chi)(chi)使用壽命(ming)，請將電(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)壓(ya)設置(zhi)為每節電(dian)(dian)(dian)(dian)池(chi)(chi)4.1V。通過(guo)(guo)讓外(wai)部(bu)功率(lv) MOSFET 適合于許多(duo)沒有(you)主控(kong)制器的(de)不同電(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)(dian)(dian)應用，這(zhe)種情況可以將1到6節鋰離子串聯電(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)至10A。其(qi)還擁有(you)其(qi)他(ta)保(bao)護功能(neng)，例如：輸入(ru)過(guo)(guo)壓(ya)、電(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)(dian)(dian)過(guo)(guo)壓(ya)、電(dian)(dian)(dian)(dian)池(chi)(chi)短(duan)路(lu)、過(guo)(guo)充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)保(bao)護等，并自動監(jian)測電(dian)(dian)(dian)(dian)池(chi)(chi)溫度，以達到安全充(chong)電(dian)(dian)(dian)(dian)的(de)目的(de)。

圖2 上網本充電(dian)器設計實例

　　隨著便(bian)攜(xie)式計(ji)(ji)(ji)算(suan)設備(bei)的發展，其擁有了更(geng)多的特(te)性(xing)，這時電(dian)池(chi)充電(dian)和(he)系(xi)(xi)統(tong)設計(ji)(ji)(ji)便(bian)成(cheng)為獲得高安全和(he)高性(xing)能系(xi)(xi)統(tong)最重(zhong)要的設計(ji)(ji)(ji)因素(su)。