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PC (UMPC) 擁(yong)有一個功能強(qiang)大(da)的(de)(de)處理(li)器(qi)，擁(yong)有一個 具有觸(chu)摸功能的(de)(de)4～7英寸的(de)(de)顯示屏，可以運行與Windows Vista兼容的(de)(de)軟件。超便攜 PC 還(huan)擁(yong)有全球定位系統 (GPS) 設備、指紋識別器(qi)、TV 調(diao)諧器(qi)以及存(cun)儲卡讀卡器(qi)等。它由2～3 塊串聯鋰離子(zi)電池組供(gong)電。

　　移(yi)動互聯網設(she)備 (MID) 是一(yi)種具有多(duo)媒體功(gong)能的(de)手(shou)持式(shi)電腦(nao)，可以提(ti)供無線網絡訪問(wen)，具有雙向通信和實時共享功(gong)能，專為向個人（非企業用戶）提(ti)供娛(yu)樂、資(zi)訊和定位服務(wu)而(er)設(she)計。MID 的(de)外(wai)形尺(chi)寸比(bi)智能電話大，但比(bi) UMPC 小，通常使用一(yi)個鋰(li)離子電池組供電。

　　動態電源管理

　　電池充電電壓和電(dian)(dian)流對電(dian)(dian)池使用壽(shou)命和電(dian)(dian)池容(rong)量至關(guan)重要。電(dian)(dian)池充(chong)(chong)電(dian)(dian)電(dian)(dian)壓(ya)越(yue)高(gao)，電(dian)(dian)池容(rong)量也就越(yue)高(gao)。這些(xie)便攜(xie)設備因其微(wei)處理器(qi)(qi)功(gong)(gong)(gong)(gong)耗很低，需(xu)要的(de)(de)(de)總功(gong)(gong)(gong)(gong)耗低于筆(bi)(bi)記(ji)本電(dian)(dian)腦，所(suo)用的(de)(de)(de)電(dian)(dian)源(yuan)適配器(qi)(qi)功(gong)(gong)(gong)(gong)率一般在 40 瓦以下，而筆(bi)(bi)記(ji)本電(dian)(dian)腦通常使用 60 瓦和 90 瓦的(de)(de)(de)適配器(qi)(qi)。但(dan)是，仍然要求這種(zhong)適配器(qi)(qi)在給電(dian)(dian)池充(chong)(chong)電(dian)(dian)的(de)(de)(de)同(tong)時為(wei)系統供電(dian)(dian)，從(cong)而最(zui)小(xiao)化適配器(qi)(qi)額定功(gong)(gong)(gong)(gong)率。由于微(wei)處理器(qi)(qi)的(de)(de)(de)高(gao)脈動功(gong)(gong)(gong)(gong)率特性，電(dian)(dian)池充(chong)(chong)電(dian)(dian)以及為(wei)微(wei)處理器(qi)(qi)提供最(zui)大(da)功(gong)(gong)(gong)(gong)率所(suo)要求的(de)(de)(de)總功(gong)(gong)(gong)(gong)率輕易便超(chao)出了適配器(qi)(qi)的(de)(de)(de)最(zui)大(da)可(ke)用功(gong)(gong)(gong)(gong)率。

　　為了優化系統和電池充電器，我們通過引入(ru)最(zui)大適(shi)配器電(dian)(dian)流(liu)(liu)調(diao)(diao)節(jie)(jie)環(huan)路使用了動(dong)態電(dian)(dian)源(yuan)管(guan)理 (DPM) 功(gong)能。如果輸(shu)入(ru)適(shi)配器電(dian)(dian)流(liu)(liu)達到了調(diao)(diao)節(jie)(jie)閾(yu)值(zhi)，則電(dian)(dian)池充(chong)(chong)(chong)電(dian)(dian)器自動(dong)降(jiang)低(di)有效充(chong)(chong)(chong)電(dian)(dian)電(dian)(dian)流(liu)(liu)，同時優先為系統(tong)供電(dian)(dian)，以使其不(bu)超出適(shi)配器的(de)最(zui)大功(gong)率(lv)(lv)極限。在為系統(tong)供電(dian)(dian)以后，剩余功(gong)率(lv)(lv)用于對電(dian)(dian)池充(chong)(chong)(chong)電(dian)(dian)。一旦(dan)脈沖功(gong)率(lv)(lv)終止，充(chong)(chong)(chong)電(dian)(dian)器便自動(dong)恢復最(zui)快充(chong)(chong)(chong)電(dian)(dian)模式(shi)，以縮短充(chong)(chong)(chong)電(dian)(dian)時間(jian)（圖1）。一種重(zhong)要的(de)規范是輸(shu)入(ru)電(dian)(dian)流(liu)(liu)調(diao)(diao)節(jie)(jie)精度(du)(du)。輸(shu)入(ru)電(dian)(dian)流(liu)(liu)調(diao)(diao)節(jie)(jie)精度(du)(du)越(yue)高，適(shi)配器提供的(de)功(gong)率(lv)(lv)越(yue)多，同時電(dian)(dian)池充(chong)(chong)(chong)電(dian)(dian)的(de)速度(du)(du)也就(jiu)越(yue)快。

圖 1  動態(tai)電(dian)(dian)源管理的電(dian)(dian)池充電(dian)(dian)結構圖

　　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(guo)出現逆向適配器電(dian)壓，也不能開啟系統。

　　b、電池充電安全性

　　在極(ji)低(di)或(huo)極(ji)高(gao)電(dian)(dian)(dian)池溫(wen)度條件下(xia)(xia)對(dui)鋰(li)(li)離子電(dian)(dian)(dian)池充電(dian)(dian)(dian)是很危(wei)險的(de)(de)。當電(dian)(dian)(dian)池在4.3V溫(wen)度達到 175oC 時，LiCoO2 負極(ji)材料的(de)(de)鋰(li)(li)離子電(dian)(dian)(dian)池可能(neng)會(hui)爆炸。已(yi)發布的(de)(de)許多工業電(dian)(dian)(dian)池充電(dian)(dian)(dian)器安(an)全規定（例如：日(ri)本電(dian)(dian)(dian)子和信息技術行業協會(hui) (JEITA) 等）通過減(jian)少低(di)或(huo)高(gao)電(dian)(dian)(dian)池溫(wen)度下(xia)(xia)的(de)(de)電(dian)(dian)(dian)池充電(dian)(dian)(dian)電(dian)(dian)(dian)流和電(dian)(dian)(dian)壓來(lai)達到電(dian)(dian)(dian)池安(an)全充電(dian)(dian)(dian)的(de)(de)目的(de)(de)。

　　要開始充(chong)電(dian)(dian)(dian)過(guo)程(cheng)，一(yi)般電(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)溫度范圍(wei)在 0oC ～40oC 之(zhi)間。因(yin)此，必須通(tong)過(guo)電(dian)(dian)(dian)量(liang)監測計或充(chong)電(dian)(dian)(dian)器來監測電(dian)(dian)(dian)池溫度。電(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)系統失效(xiao)時(shi)，安(an)全定(ding)時(shi)器是另一(yi)層保護。當安(an)全定(ding)時(shi)器終止時(shi)，電(dian)(dian)(dian)池便停止充(chong)電(dian)(dian)(dian)。

　　c、電池充電器輸出短路和過充電流保護

　　對于(yu)一(yi)(yi)些計算應用(yong)來(lai)說，最為(wei)常用(yong)的鋰(li)(li)離(li)子電(dian)(dian)池(chi)是具有(you)(you) 2200-2600mAh 容量(liang)的 18650 鋰(li)(li)離(li)子電(dian)(dian)池(chi)。12-V 或(huo) 19-V 適配器在 0.7oC 充(chong)電(dian)(dian)率情況下(xia)，充(chong)電(dian)(dian)電(dian)(dian)流約(yue)為(wei) 2-4A。高效充(chong)電(dian)(dian)要(yao)求同步開(kai)關(guan)降壓型拓撲。其還要(yao)求在出(chu)(chu)現元件故障或(huo)非(fei)正常運(yun)行狀態（例如：充(chong)電(dian)(dian)器輸(shu)出(chu)(chu)短(duan)路(lu)或(huo)電(dian)(dian)感短(duan)路(lu)等）時(shi)有(you)(you)一(yi)(yi)個(ge)無煙充(chong)電(dian)(dian)系統(tong)。充(chong)電(dian)(dian)器需要(yao)有(you)(you)此類(lei)保護機(ji)制來(lai)防止起火或(huo)冒煙。

　　上網本、UMPC 和 MID 的電池充電器解決方案

　　根據系統優化和(he)安(an)全要求，圖2顯示了一款適用(yong)(yong)(yong)于上網(wang)本應(ying)(ying)用(yong)(yong)(yong)且具有動態電(dian)源管理(li)功能的(de)獨立型(xing)高(gao)效(xiao)同步開(kai)關鋰(li)離(li)子(zi)電(dian)池(chi)充(chong)(chong)(chong)電(dian)器。這種設計示例使用(yong)(yong)(yong)200mA預充(chong)(chong)(chong)電(dian)電(dian)流和(he)2A快速充(chong)(chong)(chong)電(dian)電(dian)流以(yi)及 3 小時(shi)安(an)全定時(shi)器來對2節鋰(li)離(li)子(zi)電(dian)池(chi)充(chong)(chong)(chong)電(dian)。通過監測輸入電(dian)流感應(ying)(ying)電(dian)阻R1兩端(duan)的(de)壓(ya)(ya)降實現DPM功能。同步開(kai)關充(chong)(chong)(chong)電(dian)器以(yi)600kHz 的(de)開(kai)關頻率工作，以(yi)優化效(xiao)率和(he)解決(jue)方案尺寸。外部電(dian)阻分壓(ya)(ya)器R11和(he)R12用(yong)(yong)(yong)于設置理(li)想(xiang)的(de)電(dian)池(chi)充(chong)(chong)(chong)電(dian)電(dian)壓(ya)(ya)。要想(xiang)獲得(de)最大的(de)電(dian)池(chi)容量，請將外部電(dian)阻分壓(ya)(ya)器設置為每(mei)節電(dian)池(chi) 4.2V 的(de)充(chong)(chong)(chong)電(dian)電(dian)壓(ya)(ya)。

　　如欲獲得(de)最長電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)使用壽命，請將電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓設(she)置為每節(jie)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)4.1V。通過(guo)讓外(wai)部(bu)功(gong)率(lv) MOSFET 適合(he)于許多(duo)沒有主控(kong)制器的不同電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)應用，這(zhe)種情況可以將1到6節(jie)鋰離子串聯電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)至10A。其(qi)還擁有其(qi)他保護功(gong)能，例如：輸入過(guo)壓、電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)過(guo)壓、電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)短路(lu)、過(guo)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)保護等，并自動監測電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)溫度(du)，以達到安(an)全充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)的目的。

圖2 上(shang)網本(ben)充(chong)電器設(she)計實例

　　隨著便攜式計(ji)(ji)算設(she)備的(de)(de)發展(zhan)，其擁有(you)了更(geng)多的(de)(de)特性，這時電(dian)池充電(dian)和(he)系統(tong)設(she)計(ji)(ji)便成為獲得高(gao)安全和(he)高(gao)性能系統(tong)最重要的(de)(de)設(she)計(ji)(ji)因素(su)。