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(yong)有(you)(you)一(yi)個(ge)功能強大的處理器，擁(yong)有(you)(you)一(yi)個(ge) 具有(you)(you)觸摸功能的4～7英寸的顯示屏，可以(yi)運行與Windows Vista兼(jian)容的軟件。超便攜(xie) PC 還(huan)擁(yong)有(you)(you)全球(qiu)定(ding)位(wei)系統 (GPS) 設備、指紋識別器、TV 調諧器以(yi)及存儲卡(ka)讀卡(ka)器等。它由2～3 塊串聯鋰離子(zi)電(dian)(dian)池組供電(dian)(dian)。

　　移動互聯網設備(bei) (MID) 是(shi)一種具有(you)多(duo)媒體功能的(de)手持式(shi)電(dian)腦(nao)，可以提供(gong)無線(xian)網絡訪問，具有(you)雙向通(tong)信和實(shi)時(shi)共(gong)享功能，專為向個人（非企業用戶）提供(gong)娛(yu)樂、資訊和定位服務而設計。MID 的(de)外形(xing)尺寸比(bi)(bi)智能電(dian)話大(da)，但比(bi)(bi) UMPC 小，通(tong)常使用一個鋰離子電(dian)池組供(gong)電(dian)。

　　動態電源管理

　　電池充電電壓和電(dian)(dian)(dian)流(liu)對(dui)電(dian)(dian)(dian)池(chi)(chi)(chi)使用(yong)壽(shou)命(ming)和電(dian)(dian)(dian)池(chi)(chi)(chi)容量(liang)至關重(zhong)要(yao)。電(dian)(dian)(dian)池(chi)(chi)(chi)充電(dian)(dian)(dian)電(dian)(dian)(dian)壓越高(gao)(gao)，電(dian)(dian)(dian)池(chi)(chi)(chi)容量(liang)也(ye)就(jiu)越高(gao)(gao)。這些(xie)便攜設備(bei)因其微處理器功(gong)耗(hao)很低，需要(yao)的(de)總功(gong)耗(hao)低于筆(bi)記本(ben)電(dian)(dian)(dian)腦，所用(yong)的(de)電(dian)(dian)(dian)源適(shi)(shi)配(pei)器功(gong)率一(yi)般在 40 瓦以下，而筆(bi)記本(ben)電(dian)(dian)(dian)腦通常使用(yong) 60 瓦和 90 瓦的(de)適(shi)(shi)配(pei)器。但是，仍(reng)然(ran)要(yao)求(qiu)這種(zhong)適(shi)(shi)配(pei)器在給電(dian)(dian)(dian)池(chi)(chi)(chi)充電(dian)(dian)(dian)的(de)同(tong)時為(wei)系統供電(dian)(dian)(dian)，從而最小化適(shi)(shi)配(pei)器額(e)定功(gong)率。由于微處理器的(de)高(gao)(gao)脈動功(gong)率特(te)性，電(dian)(dian)(dian)池(chi)(chi)(chi)充電(dian)(dian)(dian)以及為(wei)微處理器提(ti)供最大(da)功(gong)率所要(yao)求(qiu)的(de)總功(gong)率輕(qing)易(yi)便超出了適(shi)(shi)配(pei)器的(de)最大(da)可用(yong)功(gong)率。

　　為了優化系統和電池充電器，我們通過引入(ru)最大適(shi)配(pei)(pei)器(qi)電(dian)(dian)流(liu)(liu)調(diao)(diao)節(jie)環(huan)路(lu)使用(yong)了(le)動態電(dian)(dian)源管(guan)理 (DPM) 功能。如果輸入(ru)適(shi)配(pei)(pei)器(qi)電(dian)(dian)流(liu)(liu)達到了(le)調(diao)(diao)節(jie)閾值(zhi)，則電(dian)(dian)池充(chong)(chong)(chong)電(dian)(dian)器(qi)自(zi)(zi)動降低(di)有(you)效充(chong)(chong)(chong)電(dian)(dian)電(dian)(dian)流(liu)(liu)，同時(shi)優先(xian)為(wei)系統(tong)供電(dian)(dian)，以使其不(bu)超出適(shi)配(pei)(pei)器(qi)的(de)最大功率(lv)極限。在為(wei)系統(tong)供電(dian)(dian)以后，剩余功率(lv)用(yong)于對電(dian)(dian)池充(chong)(chong)(chong)電(dian)(dian)。一(yi)旦脈沖功率(lv)終(zhong)止，充(chong)(chong)(chong)電(dian)(dian)器(qi)便自(zi)(zi)動恢復(fu)最快(kuai)充(chong)(chong)(chong)電(dian)(dian)模式(shi)，以縮短充(chong)(chong)(chong)電(dian)(dian)時(shi)間（圖1）。一(yi)種重(zhong)要的(de)規范(fan)是輸入(ru)電(dian)(dian)流(liu)(liu)調(diao)(diao)節(jie)精(jing)度。輸入(ru)電(dian)(dian)流(liu)(liu)調(diao)(diao)節(jie)精(jing)度越(yue)高，適(shi)配(pei)(pei)器(qi)提供的(de)功率(lv)越(yue)多，同時(shi)電(dian)(dian)池充(chong)(chong)(chong)電(dian)(dian)的(de)速度也就(jiu)越(yue)快(kuai)。

圖(tu) 1  動態電源管理的(de)電池(chi)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(guo)出現逆向適配器(qi)電壓，也不能開啟系統(tong)。

　　b、電池充電安全性

　　在極低(di)或極高電(dian)(dian)(dian)池(chi)溫度條(tiao)件下(xia)對鋰(li)離子(zi)(zi)電(dian)(dian)(dian)池(chi)充電(dian)(dian)(dian)是很危險的(de)(de)。當電(dian)(dian)(dian)池(chi)在4.3V溫度達(da)到(dao) 175oC 時，LiCoO2 負極材(cai)料(liao)的(de)(de)鋰(li)離子(zi)(zi)電(dian)(dian)(dian)池(chi)可(ke)能會爆(bao)炸。已發布的(de)(de)許多工業電(dian)(dian)(dian)池(chi)充電(dian)(dian)(dian)器安(an)全規定（例(li)如：日本電(dian)(dian)(dian)子(zi)(zi)和信息(xi)技(ji)術行(xing)業協會 (JEITA) 等）通過減少低(di)或高電(dian)(dian)(dian)池(chi)溫度下(xia)的(de)(de)電(dian)(dian)(dian)池(chi)充電(dian)(dian)(dian)電(dian)(dian)(dian)流和電(dian)(dian)(dian)壓(ya)來(lai)達(da)到(dao)電(dian)(dian)(dian)池(chi)安(an)全充電(dian)(dian)(dian)的(de)(de)目的(de)(de)。

　　要開(kai)始充(chong)(chong)電(dian)過(guo)程，一般電(dian)池(chi)充(chong)(chong)電(dian)溫(wen)(wen)度范圍在 0oC ～40oC 之間。因此，必須通(tong)過(guo)電(dian)量監測(ce)計或充(chong)(chong)電(dian)器來監測(ce)電(dian)池(chi)溫(wen)(wen)度。電(dian)池(chi)充(chong)(chong)電(dian)系(xi)統(tong)失效(xiao)時，安全定時器是另一層(ceng)保(bao)護。當安全定時器終止時，電(dian)池(chi)便停止充(chong)(chong)電(dian)。

　　c、電池充電器輸出短路和過充電流保護

　　對于一些計算應用(yong)來(lai)說，最為常(chang)用(yong)的鋰(li)離子電(dian)(dian)池是具有(you) 2200-2600mAh 容量的 18650 鋰(li)離子電(dian)(dian)池。12-V 或(huo) 19-V 適(shi)配器(qi)在 0.7oC 充(chong)電(dian)(dian)率情況下，充(chong)電(dian)(dian)電(dian)(dian)流約(yue)為 2-4A。高(gao)效充(chong)電(dian)(dian)要(yao)求(qiu)同步開(kai)關降壓型拓撲。其還要(yao)求(qiu)在出現元件故障(zhang)或(huo)非正常(chang)運(yun)行狀態（例如：充(chong)電(dian)(dian)器(qi)輸出短(duan)路(lu)或(huo)電(dian)(dian)感短(duan)路(lu)等）時有(you)一個無煙(yan)充(chong)電(dian)(dian)系統。充(chong)電(dian)(dian)器(qi)需要(yao)有(you)此類保護機制來(lai)防止起火或(huo)冒煙(yan)。

　　上網本、UMPC 和 MID 的電池充電器解決方案

　　根據系統優(you)化(hua)(hua)和(he)安全(quan)要求，圖2顯示了一款適(shi)用于(yu)上(shang)網本應(ying)用且具有動態電(dian)(dian)(dian)(dian)(dian)源(yuan)管(guan)理功能的(de)(de)(de)獨立型高效同步開關鋰(li)離(li)子(zi)電(dian)(dian)(dian)(dian)(dian)池充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)器(qi)。這種設計(ji)示例使用200mA預充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流和(he)2A快(kuai)速充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流以(yi)及(ji) 3 小時安全(quan)定時器(qi)來(lai)對2節(jie)鋰(li)離(li)子(zi)電(dian)(dian)(dian)(dian)(dian)池充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)。通(tong)過監測(ce)輸入電(dian)(dian)(dian)(dian)(dian)流感應(ying)電(dian)(dian)(dian)(dian)(dian)阻R1兩(liang)端的(de)(de)(de)壓(ya)降實現DPM功能。同步開關充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)器(qi)以(yi)600kHz 的(de)(de)(de)開關頻率(lv)工作(zuo)，以(yi)優(you)化(hua)(hua)效率(lv)和(he)解決方案尺寸。外部電(dian)(dian)(dian)(dian)(dian)阻分壓(ya)器(qi)R11和(he)R12用于(yu)設置理想的(de)(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)。要想獲得最大的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)池容量，請將(jiang)外部電(dian)(dian)(dian)(dian)(dian)阻分壓(ya)器(qi)設置為每(mei)節(jie)電(dian)(dian)(dian)(dian)(dian)池 4.2V 的(de)(de)(de)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓(ya)。

　　如欲獲得最長(chang)電(dian)(dian)(dian)(dian)池(chi)使用壽(shou)命(ming)，請(qing)將(jiang)電(dian)(dian)(dian)(dian)池(chi)充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)壓設(she)置為每節電(dian)(dian)(dian)(dian)池(chi)4.1V。通過(guo)讓外部功率(lv) MOSFET 適合于許多沒有(you)主(zhu)控制器(qi)的(de)不同(tong)電(dian)(dian)(dian)(dian)池(chi)充電(dian)(dian)(dian)(dian)應用，這種情況(kuang)可以(yi)將(jiang)1到6節鋰離子串聯電(dian)(dian)(dian)(dian)池(chi)充至10A。其還擁有(you)其他保護(hu)功能，例如：輸(shu)入過(guo)壓、電(dian)(dian)(dian)(dian)池(chi)充電(dian)(dian)(dian)(dian)過(guo)壓、電(dian)(dian)(dian)(dian)池(chi)短路、過(guo)充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)保護(hu)等，并自動監(jian)測電(dian)(dian)(dian)(dian)池(chi)溫度，以(yi)達(da)到安全充電(dian)(dian)(dian)(dian)的(de)目的(de)。

圖2 上網本充(chong)電器(qi)設計實例(li)

　　隨著便攜(xie)式計(ji)算(suan)設(she)備的發展，其擁有了更多的特性，這時電池充電和系(xi)統(tong)設(she)計(ji)便成(cheng)為獲得高(gao)安全和高(gao)性能系(xi)統(tong)最(zui)重(zhong)要的設(she)計(ji)因素。