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(bian)攜PC (UMPC) 擁(yong)有(you)(you)一個功能強(qiang)大(da)的處理器，擁(yong)有(you)(you)一個 具(ju)有(you)(you)觸(chu)摸功能的4～7英寸(cun)的顯示屏(ping)，可以(yi)運行與Windows Vista兼容的軟(ruan)件。超(chao)便(bian)攜 PC 還擁(yong)有(you)(you)全(quan)球定位系統 (GPS) 設備(bei)、指紋識別器、TV 調諧器以(yi)及存儲卡讀卡器等。它由(you)2～3 塊串聯鋰(li)離子電池組供電。

　　移動(dong)互聯網設備(bei) (MID) 是一(yi)(yi)種具有(you)多媒體功能的(de)(de)手持式(shi)電(dian)腦，可以提供(gong)無線網絡訪問，具有(you)雙向(xiang)通信和實時共(gong)享功能，專為向(xiang)個人（非企業用(yong)戶）提供(gong)娛樂、資訊和定位(wei)服務而設計。MID 的(de)(de)外形尺(chi)寸比智能電(dian)話大(da)，但(dan)比 UMPC 小，通常使用(yong)一(yi)(yi)個鋰(li)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)(dian)流對電(dian)(dian)(dian)池使用壽(shou)命和(he)電(dian)(dian)(dian)池容量(liang)至(zhi)關重(zhong)要。電(dian)(dian)(dian)池充電(dian)(dian)(dian)電(dian)(dian)(dian)壓(ya)越(yue)高，電(dian)(dian)(dian)池容量(liang)也就(jiu)越(yue)高。這些便攜設備因其微處理(li)器(qi)(qi)(qi)(qi)功(gong)耗(hao)很低，需要的(de)(de)總(zong)(zong)功(gong)耗(hao)低于筆(bi)記本電(dian)(dian)(dian)腦(nao)，所用的(de)(de)電(dian)(dian)(dian)源適(shi)配(pei)(pei)器(qi)(qi)(qi)(qi)功(gong)率(lv)一(yi)般在(zai) 40 瓦以(yi)下(xia)，而(er)筆(bi)記本電(dian)(dian)(dian)腦(nao)通常使用 60 瓦和(he) 90 瓦的(de)(de)適(shi)配(pei)(pei)器(qi)(qi)(qi)(qi)。但是，仍然要求這種(zhong)適(shi)配(pei)(pei)器(qi)(qi)(qi)(qi)在(zai)給電(dian)(dian)(dian)池充電(dian)(dian)(dian)的(de)(de)同時為(wei)系(xi)統供電(dian)(dian)(dian)，從而(er)最(zui)(zui)(zui)小(xiao)化適(shi)配(pei)(pei)器(qi)(qi)(qi)(qi)額定(ding)功(gong)率(lv)。由于微處理(li)器(qi)(qi)(qi)(qi)的(de)(de)高脈動功(gong)率(lv)特性，電(dian)(dian)(dian)池充電(dian)(dian)(dian)以(yi)及為(wei)微處理(li)器(qi)(qi)(qi)(qi)提(ti)供最(zui)(zui)(zui)大功(gong)率(lv)所要求的(de)(de)總(zong)(zong)功(gong)率(lv)輕易便超出了適(shi)配(pei)(pei)器(qi)(qi)(qi)(qi)的(de)(de)最(zui)(zui)(zui)大可用功(gong)率(lv)。

　　為了優化系統和電池充電器，我(wo)們(men)通過引入(ru)最(zui)大適配器(qi)電(dian)(dian)(dian)(dian)(dian)流(liu)調(diao)節環路(lu)使(shi)用了動態(tai)電(dian)(dian)(dian)(dian)(dian)源(yuan)管(guan)理(li) (DPM) 功(gong)(gong)(gong)能。如果輸(shu)入(ru)適配器(qi)電(dian)(dian)(dian)(dian)(dian)流(liu)達(da)到了調(diao)節閾值(zhi)，則電(dian)(dian)(dian)(dian)(dian)池充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)器(qi)自動降低有效充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)，同(tong)時(shi)優先為系統(tong)供電(dian)(dian)(dian)(dian)(dian)，以使(shi)其不(bu)超出(chu)適配器(qi)的(de)(de)最(zui)大功(gong)(gong)(gong)率(lv)極限。在為系統(tong)供電(dian)(dian)(dian)(dian)(dian)以后，剩余功(gong)(gong)(gong)率(lv)用于對(dui)電(dian)(dian)(dian)(dian)(dian)池充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)。一(yi)旦脈沖功(gong)(gong)(gong)率(lv)終止，充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)器(qi)便(bian)自動恢復最(zui)快充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)模式，以縮短充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)時(shi)間（圖1）。一(yi)種重(zhong)要的(de)(de)規范(fan)是輸(shu)入(ru)電(dian)(dian)(dian)(dian)(dian)流(liu)調(diao)節精(jing)度。輸(shu)入(ru)電(dian)(dian)(dian)(dian)(dian)流(liu)調(diao)節精(jing)度越(yue)高，適配器(qi)提供的(de)(de)功(gong)(gong)(gong)率(lv)越(yue)多，同(tong)時(shi)電(dian)(dian)(dian)(dian)(dian)池充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)的(de)(de)速度也(ye)就越(yue)快。

圖 1  動態電源管理的電池充電結構(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(chu)現逆(ni)向適配器電(dian)壓，也(ye)不能開(kai)啟系統。

　　b、電池充電安全性

　　在極低或(huo)極高電(dian)(dian)(dian)(dian)池(chi)(chi)溫(wen)(wen)度條件下對鋰離子電(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)(dian)(dian)是很危險的。當電(dian)(dian)(dian)(dian)池(chi)(chi)在4.3V溫(wen)(wen)度達(da)到 175oC 時，LiCoO2 負極材料的鋰離子電(dian)(dian)(dian)(dian)池(chi)(chi)可(ke)能會爆炸。已發(fa)布的許(xu)多工業電(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)(dian)(dian)器安全規定（例如：日(ri)本(ben)電(dian)(dian)(dian)(dian)子和信息技(ji)術(shu)行業協(xie)會 (JEITA) 等）通(tong)過減(jian)少(shao)低或(huo)高電(dian)(dian)(dian)(dian)池(chi)(chi)溫(wen)(wen)度下的電(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流和電(dian)(dian)(dian)(dian)壓來(lai)達(da)到電(dian)(dian)(dian)(dian)池(chi)(chi)安全充(chong)電(dian)(dian)(dian)(dian)的目的。

　　要開始充(chong)電(dian)(dian)(dian)(dian)過(guo)程，一般電(dian)(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)(dian)溫(wen)度范圍在 0oC ～40oC 之間(jian)。因此，必須通過(guo)電(dian)(dian)(dian)(dian)量監(jian)測(ce)計(ji)或充(chong)電(dian)(dian)(dian)(dian)器來監(jian)測(ce)電(dian)(dian)(dian)(dian)池(chi)溫(wen)度。電(dian)(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)(dian)系統失效時，安全(quan)定時器是另一層保護(hu)。當安全(quan)定時器終(zhong)止(zhi)(zhi)時，電(dian)(dian)(dian)(dian)池(chi)便停(ting)止(zhi)(zhi)充(chong)電(dian)(dian)(dian)(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)來說，最為常用(yong)的(de)鋰離子(zi)電(dian)(dian)(dian)池(chi)是具有 2200-2600mAh 容量的(de) 18650 鋰離子(zi)電(dian)(dian)(dian)池(chi)。12-V 或(huo) 19-V 適配器在(zai) 0.7oC 充(chong)(chong)電(dian)(dian)(dian)率情況下，充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流約為 2-4A。高效充(chong)(chong)電(dian)(dian)(dian)要求(qiu)同步開(kai)關降壓型拓撲(pu)。其還要求(qiu)在(zai)出現(xian)元件故障或(huo)非正常運行狀(zhuang)態(tai)（例如：充(chong)(chong)電(dian)(dian)(dian)器輸出短路(lu)或(huo)電(dian)(dian)(dian)感短路(lu)等(deng)）時有一個無煙(yan)充(chong)(chong)電(dian)(dian)(dian)系統。充(chong)(chong)電(dian)(dian)(dian)器需要有此類保護機制來防止起火或(huo)冒(mao)煙(yan)。

　　上網本、UMPC 和 MID 的電池充電器解決方案

　　根據系(xi)統優化和安全(quan)要求，圖2顯示了一款適用(yong)于(yu)上(shang)網(wang)本(ben)應(ying)用(yong)且(qie)具有動態(tai)電(dian)(dian)(dian)源管理(li)功能的(de)獨立型(xing)高效同步(bu)開關(guan)(guan)鋰離子電(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)器(qi)。這種設計示例使(shi)用(yong)200mA預充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)和2A快速(su)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)以(yi)及 3 小時安全(quan)定時器(qi)來對(dui)2節鋰離子電(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)。通過(guo)監測輸入電(dian)(dian)(dian)流(liu)感應(ying)電(dian)(dian)(dian)阻(zu)R1兩端的(de)壓(ya)降實現DPM功能。同步(bu)開關(guan)(guan)充(chong)電(dian)(dian)(dian)器(qi)以(yi)600kHz 的(de)開關(guan)(guan)頻率工作，以(yi)優化效率和解決方案尺寸。外(wai)部電(dian)(dian)(dian)阻(zu)分(fen)壓(ya)器(qi)R11和R12用(yong)于(yu)設置理(li)想的(de)電(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)壓(ya)。要想獲得最大的(de)電(dian)(dian)(dian)池(chi)容量，請(qing)將外(wai)部電(dian)(dian)(dian)阻(zu)分(fen)壓(ya)器(qi)設置為每節電(dian)(dian)(dian)池(chi) 4.2V 的(de)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)壓(ya)。

　　如欲獲得最(zui)長(chang)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)使用壽命，請將(jiang)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓(ya)設置為每節電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)4.1V。通過(guo)讓外部功(gong)率 MOSFET 適合(he)于許多沒有主控制(zhi)器的不同電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充電(dian)(dian)(dian)(dian)(dian)應用，這種(zhong)情(qing)況可(ke)以將(jiang)1到6節鋰離子串聯電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充至10A。其還擁有其他保(bao)護功(gong)能(neng)，例如：輸入過(guo)壓(ya)、電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充電(dian)(dian)(dian)(dian)(dian)過(guo)壓(ya)、電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)短路、過(guo)充電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流保(bao)護等，并自動監測(ce)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)溫度，以達(da)到安(an)全充電(dian)(dian)(dian)(dian)(dian)的目(mu)的。

圖2 上網本充(chong)電器設計實(shi)例(li)

　　隨著便攜式計(ji)算(suan)設(she)備(bei)的(de)發(fa)展，其擁(yong)有了更多(duo)的(de)特(te)性(xing)，這時電池充電和(he)系統設(she)計(ji)便成為獲得(de)高安(an)全和(he)高性(xing)能(neng)系統最重(zhong)要的(de)設(she)計(ji)因(yin)素。