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(bian)攜PC (UMPC) 擁(yong)(yong)(yong)有(you)一個(ge)功(gong)能強大的(de)(de)處理器，擁(yong)(yong)(yong)有(you)一個(ge) 具有(you)觸摸功(gong)能的(de)(de)4～7英(ying)寸(cun)的(de)(de)顯示屏(ping)，可以運行(xing)與(yu)Windows Vista兼容的(de)(de)軟件。超便(bian)攜 PC 還擁(yong)(yong)(yong)有(you)全球定(ding)位系(xi)統 (GPS) 設備(bei)、指紋(wen)識別器、TV 調諧器以及存儲卡(ka)讀卡(ka)器等。它(ta)由(you)2～3 塊串聯(lian)鋰離子(zi)電池組供電。

　　移動互(hu)聯(lian)網設(she)備 (MID) 是(shi)一種(zhong)具(ju)有多媒體功(gong)能的(de)手持式電(dian)(dian)腦，可以提供無線網絡訪問，具(ju)有雙向(xiang)通信和實時共享功(gong)能，專為(wei)向(xiang)個人(ren)（非企業(ye)用戶）提供娛樂、資訊和定位服務而設(she)計。MID 的(de)外形尺(chi)寸比智能電(dian)(dian)話大(da)，但比 UMPC 小，通常使用一個鋰(li)離子(zi)電(dian)(dian)池組供電(dian)(dian)。

　　動態電源管理

　　電池充電電壓和電(dian)(dian)(dian)流對電(dian)(dian)(dian)池使用(yong)壽命和電(dian)(dian)(dian)池容量至關重(zhong)要(yao)。電(dian)(dian)(dian)池充電(dian)(dian)(dian)電(dian)(dian)(dian)壓(ya)越高(gao)，電(dian)(dian)(dian)池容量也就越高(gao)。這(zhe)些(xie)便攜(xie)設備因其微處理器(qi)(qi)(qi)功(gong)(gong)(gong)耗(hao)很低(di)，需要(yao)的(de)(de)總(zong)功(gong)(gong)(gong)耗(hao)低(di)于筆(bi)(bi)記本電(dian)(dian)(dian)腦，所(suo)用(yong)的(de)(de)電(dian)(dian)(dian)源(yuan)適(shi)(shi)(shi)(shi)配(pei)器(qi)(qi)(qi)功(gong)(gong)(gong)率(lv)一般在(zai) 40 瓦以下，而(er)筆(bi)(bi)記本電(dian)(dian)(dian)腦通常(chang)使用(yong) 60 瓦和 90 瓦的(de)(de)適(shi)(shi)(shi)(shi)配(pei)器(qi)(qi)(qi)。但是，仍(reng)然要(yao)求(qiu)這(zhe)種適(shi)(shi)(shi)(shi)配(pei)器(qi)(qi)(qi)在(zai)給電(dian)(dian)(dian)池充電(dian)(dian)(dian)的(de)(de)同時(shi)為系統供電(dian)(dian)(dian)，從而(er)最(zui)小化適(shi)(shi)(shi)(shi)配(pei)器(qi)(qi)(qi)額定(ding)功(gong)(gong)(gong)率(lv)。由于微處理器(qi)(qi)(qi)的(de)(de)高(gao)脈(mo)動功(gong)(gong)(gong)率(lv)特性(xing)，電(dian)(dian)(dian)池充電(dian)(dian)(dian)以及為微處理器(qi)(qi)(qi)提(ti)供最(zui)大(da)功(gong)(gong)(gong)率(lv)所(suo)要(yao)求(qiu)的(de)(de)總(zong)功(gong)(gong)(gong)率(lv)輕易便超出了(le)適(shi)(shi)(shi)(shi)配(pei)器(qi)(qi)(qi)的(de)(de)最(zui)大(da)可用(yong)功(gong)(gong)(gong)率(lv)。

　　為了優化系統和電池充電器，我(wo)們通過(guo)引入(ru)最(zui)大適(shi)配器(qi)電(dian)(dian)(dian)(dian)流(liu)調(diao)節(jie)環路使(shi)用了動(dong)態電(dian)(dian)(dian)(dian)源管理(li) (DPM) 功(gong)(gong)能(neng)。如果輸入(ru)適(shi)配器(qi)電(dian)(dian)(dian)(dian)流(liu)達到了調(diao)節(jie)閾值，則電(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)器(qi)自動(dong)降低有效充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)，同時(shi)優先(xian)為系(xi)統(tong)(tong)供(gong)電(dian)(dian)(dian)(dian)，以(yi)(yi)使(shi)其不超(chao)出適(shi)配器(qi)的(de)最(zui)大功(gong)(gong)率(lv)極(ji)限(xian)。在為系(xi)統(tong)(tong)供(gong)電(dian)(dian)(dian)(dian)以(yi)(yi)后，剩余功(gong)(gong)率(lv)用于對電(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)。一旦脈沖功(gong)(gong)率(lv)終止，充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)器(qi)便自動(dong)恢(hui)復(fu)最(zui)快(kuai)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)模式，以(yi)(yi)縮短充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)時(shi)間（圖1）。一種重要的(de)規范是輸入(ru)電(dian)(dian)(dian)(dian)流(liu)調(diao)節(jie)精(jing)度。輸入(ru)電(dian)(dian)(dian)(dian)流(liu)調(diao)節(jie)精(jing)度越高，適(shi)配器(qi)提供(gong)的(de)功(gong)(gong)率(lv)越多，同時(shi)電(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)的(de)速度也就(jiu)越快(kuai)。

圖 1  動態電源管理的電池充(chong)電結(jie)構(gou)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。如果出現逆向(xiang)適配器電(dian)壓，也不能開啟系(xi)統。

　　b、電池充電安全性

　　在極(ji)低或極(ji)高(gao)電(dian)池(chi)(chi)(chi)溫(wen)度條件下對(dui)鋰離子電(dian)池(chi)(chi)(chi)充(chong)電(dian)是很危險的(de)。當電(dian)池(chi)(chi)(chi)在4.3V溫(wen)度達(da)到(dao) 175oC 時，LiCoO2 負極(ji)材料的(de)鋰離子電(dian)池(chi)(chi)(chi)可能會(hui)爆炸。已發布的(de)許多工業電(dian)池(chi)(chi)(chi)充(chong)電(dian)器安全規定（例如：日本(ben)電(dian)子和(he)信(xin)息(xi)技術(shu)行業協(xie)會(hui) (JEITA) 等(deng)）通過(guo)減少(shao)低或高(gao)電(dian)池(chi)(chi)(chi)溫(wen)度下的(de)電(dian)池(chi)(chi)(chi)充(chong)電(dian)電(dian)流和(he)電(dian)壓來達(da)到(dao)電(dian)池(chi)(chi)(chi)安全充(chong)電(dian)的(de)目的(de)。

　　要(yao)開始充(chong)(chong)電過(guo)程，一般電池(chi)(chi)充(chong)(chong)電溫(wen)(wen)度范(fan)圍在 0oC ～40oC 之間(jian)。因此，必須通(tong)過(guo)電量監(jian)(jian)測計或充(chong)(chong)電器(qi)來(lai)監(jian)(jian)測電池(chi)(chi)溫(wen)(wen)度。電池(chi)(chi)充(chong)(chong)電系統失效時(shi)，安全定(ding)時(shi)器(qi)是(shi)另一層保護。當安全定(ding)時(shi)器(qi)終止(zhi)時(shi)，電池(chi)(chi)便停(ting)止(zhi)充(chong)(chong)電。

　　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(ji)算應(ying)用來說，最為(wei)常(chang)用的(de)鋰離(li)子電(dian)(dian)池(chi)是具有(you) 2200-2600mAh 容量(liang)的(de) 18650 鋰離(li)子電(dian)(dian)池(chi)。12-V 或(huo) 19-V 適(shi)配器在(zai) 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(gao)效充(chong)電(dian)(dian)要求(qiu)同步開(kai)關降壓型(xing)拓(tuo)撲。其還要求(qiu)在(zai)出現元件故(gu)障或(huo)非正常(chang)運行狀(zhuang)態（例如(ru)：充(chong)電(dian)(dian)器輸出短(duan)路(lu)或(huo)電(dian)(dian)感短(duan)路(lu)等(deng)）時有(you)一(yi)(yi)個無煙充(chong)電(dian)(dian)系統。充(chong)電(dian)(dian)器需要有(you)此類保(bao)護機制(zhi)來防(fang)止起火(huo)或(huo)冒(mao)煙。

　　上網本、UMPC 和 MID 的電池充電器解決方案

　　根據系統優化和安全要(yao)求，圖2顯示了一款適用于(yu)上網本(ben)應用且(qie)具有動態電(dian)(dian)(dian)(dian)(dian)源管理功(gong)能(neng)的(de)(de)獨(du)立(li)型高效(xiao)同步(bu)開(kai)關(guan)鋰離子電(dian)(dian)(dian)(dian)(dian)池充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)器(qi)。這種設(she)計示例使用200mA預充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)和2A快速(su)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)以及 3 小時安全定時器(qi)來對2節鋰離子電(dian)(dian)(dian)(dian)(dian)池充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)。通過監(jian)測(ce)輸入電(dian)(dian)(dian)(dian)(dian)流(liu)感應電(dian)(dian)(dian)(dian)(dian)阻(zu)R1兩(liang)端的(de)(de)壓(ya)降實現DPM功(gong)能(neng)。同步(bu)開(kai)關(guan)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)器(qi)以600kHz 的(de)(de)開(kai)關(guan)頻率(lv)工(gong)作，以優化效(xiao)率(lv)和解決方案尺寸。外部(bu)電(dian)(dian)(dian)(dian)(dian)阻(zu)分(fen)壓(ya)器(qi)R11和R12用于(yu)設(she)置理想的(de)(de)電(dian)(dian)(dian)(dian)(dian)池充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓(ya)。要(yao)想獲得最大的(de)(de)電(dian)(dian)(dian)(dian)(dian)池容量，請將(jiang)外部(bu)電(dian)(dian)(dian)(dian)(dian)阻(zu)分(fen)壓(ya)器(qi)設(she)置為每節電(dian)(dian)(dian)(dian)(dian)池 4.2V 的(de)(de)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓(ya)。

　　如(ru)欲獲(huo)得最長電(dian)(dian)(dian)池(chi)(chi)使用(yong)壽命，請將電(dian)(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)壓設置為每節(jie)電(dian)(dian)(dian)池(chi)(chi)4.1V。通過讓外部功率 MOSFET 適合于(yu)許多沒有主控制(zhi)器的不(bu)同電(dian)(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)(dian)應用(yong)，這種情況(kuang)可(ke)以將1到6節(jie)鋰離子(zi)串(chuan)聯(lian)電(dian)(dian)(dian)池(chi)(chi)充(chong)至(zhi)10A。其(qi)還擁有其(qi)他保(bao)護功能，例如(ru)：輸入過壓、電(dian)(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)(dian)過壓、電(dian)(dian)(dian)池(chi)(chi)短路、過充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流保(bao)護等(deng)，并自(zi)動監(jian)測電(dian)(dian)(dian)池(chi)(chi)溫度(du)，以達到安全(quan)充(chong)電(dian)(dian)(dian)的目(mu)的。

圖2 上網本充電(dian)器設(she)計實(shi)例

　　隨著便攜式計算設備的(de)(de)發展，其擁(yong)有了更多的(de)(de)特(te)性，這時電(dian)池充電(dian)和系統設計便成為獲得(de)高安(an)全(quan)和高性能系統最重(zhong)要的(de)(de)設計因素。