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(chao)便攜(xie)(xie)PC (UMPC) 擁(yong)有(you)一(yi)個功(gong)(gong)能強大的處理器(qi)(qi)，擁(yong)有(you)一(yi)個 具有(you)觸摸功(gong)(gong)能的4～7英寸(cun)的顯示屏，可以(yi)運行與Windows Vista兼容(rong)的軟件(jian)。超(chao)便攜(xie)(xie) PC 還擁(yong)有(you)全球定位系(xi)統 (GPS) 設(she)備、指(zhi)紋識別(bie)器(qi)(qi)、TV 調諧器(qi)(qi)以(yi)及存儲卡讀(du)卡器(qi)(qi)等(deng)。它由2～3 塊串聯鋰離子電(dian)池組供電(dian)。

　　移動互(hu)聯網(wang)設備 (MID) 是一種具有多媒體功(gong)能的手持式電(dian)腦，可以提供(gong)無線網(wang)絡訪問，具有雙向通信(xin)和(he)實時(shi)共享功(gong)能，專為(wei)向個(ge)人（非企(qi)業(ye)用戶）提供(gong)娛樂、資訊和(he)定位服務(wu)而設計。MID 的外形尺寸(cun)比智能電(dian)話大，但比 UMPC 小，通常(chang)使用一個(ge)鋰離子電(dian)池組供(gong)電(dian)。

　　動態電源管理

　　電池充電電壓和(he)電(dian)(dian)流對(dui)電(dian)(dian)池(chi)(chi)使用(yong)壽命和(he)電(dian)(dian)池(chi)(chi)容量(liang)至關(guan)重要。電(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)電(dian)(dian)壓越(yue)高(gao)，電(dian)(dian)池(chi)(chi)容量(liang)也就(jiu)越(yue)高(gao)。這些便攜(xie)設(she)備因(yin)其(qi)微(wei)處理器(qi)功(gong)(gong)耗很(hen)低(di)，需(xu)要的(de)(de)總功(gong)(gong)耗低(di)于(yu)筆記(ji)本(ben)電(dian)(dian)腦，所用(yong)的(de)(de)電(dian)(dian)源適(shi)配器(qi)功(gong)(gong)率(lv)一(yi)般在(zai) 40 瓦以(yi)(yi)下，而筆記(ji)本(ben)電(dian)(dian)腦通常(chang)使用(yong) 60 瓦和(he) 90 瓦的(de)(de)適(shi)配器(qi)。但(dan)是，仍(reng)然要求(qiu)這種適(shi)配器(qi)在(zai)給電(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)的(de)(de)同(tong)時為系(xi)統供電(dian)(dian)，從而最小化(hua)適(shi)配器(qi)額(e)定(ding)功(gong)(gong)率(lv)。由于(yu)微(wei)處理器(qi)的(de)(de)高(gao)脈(mo)動功(gong)(gong)率(lv)特(te)性，電(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)以(yi)(yi)及為微(wei)處理器(qi)提供最大(da)功(gong)(gong)率(lv)所要求(qiu)的(de)(de)總功(gong)(gong)率(lv)輕易便超出了適(shi)配器(qi)的(de)(de)最大(da)可用(yong)功(gong)(gong)率(lv)。

　　為了優化系統和電池充電器，我們通過(guo)引入最(zui)大適配(pei)(pei)器(qi)電(dian)(dian)(dian)(dian)(dian)流(liu)調(diao)(diao)節(jie)(jie)環(huan)路使用了(le)動(dong)態(tai)電(dian)(dian)(dian)(dian)(dian)源(yuan)管理 (DPM) 功(gong)能(neng)。如果輸(shu)入適配(pei)(pei)器(qi)電(dian)(dian)(dian)(dian)(dian)流(liu)達(da)到了(le)調(diao)(diao)節(jie)(jie)閾值，則(ze)電(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)(dian)(dian)器(qi)自動(dong)降低有效充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)，同時優(you)先(xian)為(wei)系統供電(dian)(dian)(dian)(dian)(dian)，以(yi)(yi)使其(qi)不(bu)超出(chu)適配(pei)(pei)器(qi)的(de)(de)最(zui)大功(gong)率(lv)極(ji)限。在為(wei)系統供電(dian)(dian)(dian)(dian)(dian)以(yi)(yi)后(hou)，剩余功(gong)率(lv)用于對電(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)(dian)(dian)。一旦脈沖功(gong)率(lv)終止，充(chong)電(dian)(dian)(dian)(dian)(dian)器(qi)便自動(dong)恢復最(zui)快充(chong)電(dian)(dian)(dian)(dian)(dian)模式，以(yi)(yi)縮短充(chong)電(dian)(dian)(dian)(dian)(dian)時間（圖1）。一種(zhong)重(zhong)要(yao)的(de)(de)規(gui)范是輸(shu)入電(dian)(dian)(dian)(dian)(dian)流(liu)調(diao)(diao)節(jie)(jie)精度。輸(shu)入電(dian)(dian)(dian)(dian)(dian)流(liu)調(diao)(diao)節(jie)(jie)精度越高，適配(pei)(pei)器(qi)提供的(de)(de)功(gong)率(lv)越多(duo)，同時電(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)(dian)(dian)的(de)(de)速度也就越快。

圖(tu)(tu) 1  動態電源管理的電池充電結構圖(tu)(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。如果出現逆向適配(pei)器電壓，也(ye)不能開啟系統。

　　b、電池充電安全性

　　在極(ji)低或極(ji)高電(dian)(dian)(dian)池(chi)溫(wen)度(du)條件下對鋰離(li)子電(dian)(dian)(dian)池(chi)充(chong)(chong)電(dian)(dian)(dian)是很危險(xian)的(de)(de)(de)。當(dang)電(dian)(dian)(dian)池(chi)在4.3V溫(wen)度(du)達到 175oC 時，LiCoO2 負極(ji)材料的(de)(de)(de)鋰離(li)子電(dian)(dian)(dian)池(chi)可能會爆炸。已(yi)發布的(de)(de)(de)許(xu)多工(gong)業電(dian)(dian)(dian)池(chi)充(chong)(chong)電(dian)(dian)(dian)器安全規(gui)定（例如：日(ri)本(ben)電(dian)(dian)(dian)子和信(xin)息技術行業協會 (JEITA) 等(deng)）通過減少低或高電(dian)(dian)(dian)池(chi)溫(wen)度(du)下的(de)(de)(de)電(dian)(dian)(dian)池(chi)充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)和電(dian)(dian)(dian)壓來達到電(dian)(dian)(dian)池(chi)安全充(chong)(chong)電(dian)(dian)(dian)的(de)(de)(de)目的(de)(de)(de)。

　　要開始(shi)充(chong)電(dian)(dian)過(guo)程，一般電(dian)(dian)池(chi)充(chong)電(dian)(dian)溫(wen)度范圍在 0oC ～40oC 之間。因此，必須通過(guo)電(dian)(dian)量監(jian)測計(ji)或充(chong)電(dian)(dian)器來監(jian)測電(dian)(dian)池(chi)溫(wen)度。電(dian)(dian)池(chi)充(chong)電(dian)(dian)系統(tong)失效時，安全定(ding)時器是(shi)另(ling)一層保護。當安全定(ding)時器終(zhong)止(zhi)時，電(dian)(dian)池(chi)便停止(zhi)充(chong)電(dian)(dian)。

　　c、電池充電器輸出短路和過充電流保護

　　對于一(yi)些計(ji)算應用(yong)來(lai)說，最為常用(yong)的鋰離(li)子電(dian)(dian)(dian)池是具有 2200-2600mAh 容量(liang)的 18650 鋰離(li)子電(dian)(dian)(dian)池。12-V 或(huo)(huo)(huo) 19-V 適配器在 0.7oC 充(chong)電(dian)(dian)(dian)率情況下，充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)約為 2-4A。高(gao)效充(chong)電(dian)(dian)(dian)要求同(tong)步開關(guan)降壓型拓撲。其還要求在出(chu)現元件故障或(huo)(huo)(huo)非正常運行狀態（例(li)如：充(chong)電(dian)(dian)(dian)器輸出(chu)短路(lu)或(huo)(huo)(huo)電(dian)(dian)(dian)感短路(lu)等）時有一(yi)個無煙(yan)充(chong)電(dian)(dian)(dian)系統。充(chong)電(dian)(dian)(dian)器需要有此類(lei)保護機制來(lai)防止起火或(huo)(huo)(huo)冒煙(yan)。

　　上網本、UMPC 和 MID 的電池充電器解決方案

　　根(gen)據系統優化和安全要求，圖2顯示了一款適用于上網本應(ying)用且(qie)具有(you)動態(tai)電(dian)(dian)(dian)(dian)(dian)源管理功能的獨立型高(gao)效同步開(kai)關鋰離子(zi)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充電(dian)(dian)(dian)(dian)(dian)器(qi)(qi)。這(zhe)種設計(ji)示例使用200mA預充電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流和2A快速(su)充電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流以(yi)及 3 小時安全定時器(qi)(qi)來對2節鋰離子(zi)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充電(dian)(dian)(dian)(dian)(dian)。通(tong)過監測輸入電(dian)(dian)(dian)(dian)(dian)流感應(ying)電(dian)(dian)(dian)(dian)(dian)阻R1兩端的壓降實現(xian)DPM功能。同步開(kai)關充電(dian)(dian)(dian)(dian)(dian)器(qi)(qi)以(yi)600kHz 的開(kai)關頻率工作，以(yi)優化效率和解決方案(an)尺寸。外(wai)部電(dian)(dian)(dian)(dian)(dian)阻分(fen)壓器(qi)(qi)R11和R12用于設置理想(xiang)(xiang)的電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓。要想(xiang)(xiang)獲(huo)得最大的電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)容(rong)量，請將外(wai)部電(dian)(dian)(dian)(dian)(dian)阻分(fen)壓器(qi)(qi)設置為(wei)每節電(dian)(dian)(dian)(dian)(dian)池(chi)(chi) 4.2V 的充電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓。

　　如欲獲得最長電(dian)池(chi)使用壽命，請將電(dian)池(chi)充(chong)(chong)電(dian)電(dian)壓(ya)設(she)置(zhi)為每節電(dian)池(chi)4.1V。通(tong)過(guo)(guo)讓外部功率 MOSFET 適合于許多沒(mei)有主控制(zhi)器(qi)的(de)不同電(dian)池(chi)充(chong)(chong)電(dian)應用，這種情(qing)況可以將1到6節鋰(li)離子串聯電(dian)池(chi)充(chong)(chong)至10A。其(qi)還擁有其(qi)他保護(hu)(hu)功能，例如：輸入過(guo)(guo)壓(ya)、電(dian)池(chi)充(chong)(chong)電(dian)過(guo)(guo)壓(ya)、電(dian)池(chi)短路、過(guo)(guo)充(chong)(chong)電(dian)電(dian)流保護(hu)(hu)等，并自動監測電(dian)池(chi)溫度(du)，以達到安全(quan)充(chong)(chong)電(dian)的(de)目的(de)。

圖2 上(shang)網(wang)本(ben)充電器設計實例

　　隨著便攜式(shi)計(ji)算設備的發展，其擁有了(le)更(geng)多的特性(xing)，這(zhe)時電(dian)池充電(dian)和(he)系統設計(ji)便成為獲得高(gao)安全和(he)高(gao)性(xing)能系統最(zui)重要的設計(ji)因素。