引(yin)言

便攜式(shi)電(dian)子(zi)設備設計(ji)人(ren)員(yuan)(yuan)可以(yi)(yi)選擇(ze)各種各樣的(de)化學技(ji)術、充(chong)電(dian)器(qi)拓撲以(yi)(yi)及充(chong)電(dian)管理解決方案。選擇(ze)一(yi)(yi)(yi)(yi)(yi)款最(zui)為合(he)適的(de)解決方案應(ying)該是一(yi)(yi)(yi)(yi)(yi)項(xiang)很(hen)簡單的(de)工(gong)作，但是在(zai)大多數(shu)情況下這一(yi)(yi)(yi)(yi)(yi)過程頗為復雜(za)。設計(ji)人(ren)員(yuan)(yuan)需要(yao)在(zai)性能、成(cheng)本(ben)、外形尺寸以(yi)(yi)及其(qi)他關鍵要(yao)求(qiu)方面(mian)找到一(yi)(yi)(yi)(yi)(yi)個(ge)最(zui)佳(jia)平衡點。本(ben)文將為廣大設計(ji)人(ren)員(yuan)(yuan)和(he)系統工(gong)程師提供一(yi)(yi)(yi)(yi)(yi)些指導和(he)幫助以(yi)(yi)使得(de)(de)該選擇(ze)工(gong)作變(bian)得(de)(de)更(geng)為輕松。

以(yi) 3 “C”開始實現(xian)充電控制

所有使用(yong)可(ke)充(chong)電電池的系統設(she)計人員都需要清(qing)楚一(yi)些基礎設(she)計技術，以(yi)確保滿足下面(mian)三個關鍵(jian)的要求：

1、電(dian)池(chi)安全(quan)性(xing): 毋庸置疑，終端用(yong)戶安全(quan)是所有(you)系統設(she)(she)計(ji)中(zhong)最(zui)優先(xian)考(kao)慮的問題。大多數鋰(li)離(li)子 (Li-Ion) 電(dian)池(chi)組和鋰(li)聚合物 (Li-Pol) 電(dian)池(chi)組都含(han)有(you)保護電(dian)子電(dian)路(lu)。然而，還有(you)一(yi)些系統設(she)(she)計(ji)需要考(kao)慮的關鍵因素。其中(zhong)包括但不局限于確(que)保在鋰(li)離(li)子電(dian)池(chi)充電(dian)最(zui)后階段期間 ?1% 的穩壓(ya)容限、安全(quan)處(chu)理深度(du)放電(dian)電(dian)池(chi)的預處(chu)理模(mo)式、安全(quan)計(ji)時器以(yi)及電(dian)池(chi)溫(wen)度(du)監(jian)控。

2、電(dian)(dian)池(chi)容量：所有的(de)電(dian)(dian)池(chi)充(chong)(chong)電(dian)(dian)解決方案都要確保(bao)在每(mei)一次和(he)每(mei)一個充(chong)(chong)電(dian)(dian)周期(qi)都能將電(dian)(dian)池(chi)容量充(chong)(chong)至充(chong)(chong)滿(man)狀態。過早的(de)終止(zhi)充(chong)(chong)電(dian)(dian)會導致(zhi)電(dian)(dian)池(chi)運行時間縮短，這是當今高功耗的(de)便攜(xie)式(shi)設(she)備所不希望的(de)。

3、電(dian)(dian)池使(shi)用(yong)(yong)壽命：遵循建(jian)議的(de)充(chong)(chong)電(dian)(dian)算法是確(que)保(bao)終(zhong)端(duan)用(yong)(yong)戶實(shi)現每(mei)個(ge)電(dian)(dian)池組最多充(chong)(chong)電(dian)(dian)周(zhou)期(qi)的(de)重要一步。利(li)用(yong)(yong)電(dian)(dian)池溫度(du)和(he)電(dian)(dian)壓限定每(mei)一次(ci)充(chong)(chong)電(dian)(dian)、預處(chu)理深度(du)放電(dian)(dian)電(dian)(dian)池并避(bi)免過晚(wan)或非正常充(chong)(chong)電(dian)(dian)終(zhong)止是最大(da)化電(dian)(dian)池使(shi)用(yong)(yong)壽命所(suo)必(bi)須的(de)一些步驟。

充電(dian)特(te)性(xing) 電(dian)池(chi)安(an)全性(xing) 電(dian)池(chi)容量(liang) 電(dian)池(chi)使用壽命(ming)

精確的電(dian)壓和(he)/或電(dian)流調(diao)節(jie) ? ?

充電限制

（電(dian)壓和溫度） ? ?

溫度監控 ? ? ?

預處理 ? ? ?

充電結束終止 ? ? ?

充電計時器 ?

充電(dian)狀態報(bao)告(gao) ? ?

電池(chi)插入與去(qu)除探測(ce) ?

最小電池泄漏 ?

短路電流限制 ?

自動再充電 ?

電池化學技術的選擇
現在系統設(she)計人(ren)員(yuan)可以在多種電池化學技術(shu)中(zhong)進行選擇(ze)。設(she)計 人(ren)員(yuan)通常會根(gen)據下面的一些標準進行電池化學技術(shu)的選擇(ze)，其中(zhong)包括：

? 能量密度

? 規格和外形尺寸

? 成本

? 使(shi)用(yong)模式和使(shi)用(yong)壽命

近年來，盡(jin)管(guan)使用(yong)鋰離子電池(chi)(chi)和鋰聚合(he)物(wu)電池(chi)(chi)的趨勢增(zeng)強，但是(shi) Ni 電池(chi)(chi)化(hua)學(xue)技(ji)術(shu)仍然(ran)是(shi)諸多(duo)消費類(lei)應用(yong)一個不錯(cuo)的選項。

無論選(xuan)擇(ze)何(he)種電(dian)池化學技(ji)術(shu)，遵循每一種電(dian)池化學技(ji)術(shu)的正確(que)充電(dian)管理技(ji)術(shu)都是至關重要的。這些技(ji)術(shu)將確(que)保(bao)電(dian)池在每一次和每個充電(dian)周期都能被(bei)充至最大容量，而不會降低安全性或(huo)縮短電(dian)池使用壽命。

NiCd / NIMH

在一(yi)(yi)個(ge)充(chong)電(dian)(dian)(dian)(dian)周期(qi)開(kai)(kai)始(shi)之前，并且盡(jin)可能在開(kai)(kai)始(shi)快速(su)充(chong)電(dian)(dian)(dian)(dian)之前對鎳(nie)鎘 (NiCd) 電(dian)(dian)(dian)(dian)池(chi)(chi)和鎳(nie)氫(qing) (NiMH) 電(dian)(dian)(dian)(dian)池(chi)(chi)必(bi)須要進行檢驗和調節。如果電(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)壓或(huo)溫度超出(chu)了允許的極(ji)限是不允許進行快速(su)充(chong)電(dian)(dian)(dian)(dian)的。出(chu)于(yu)(yu)安全考(kao)慮(lv)，對所有“熱”電(dian)(dian)(dian)(dian)池(chi)(chi)（一(yi)(yi)般高于(yu)(yu) 45?C）的充(chong)電(dian)(dian)(dian)(dian)工作都會(hui)暫時終止(zhi)，直(zhi)到電(dian)(dian)(dian)(dian)池(chi)(chi)冷卻(que)到正常工作溫度范(fan)圍內(nei)才會(hui)再(zai)次(ci)運轉(zhuan)。要想處(chu)理(li)一(yi)(yi)個(ge)“冷”電(dian)(dian)(dian)(dian)池(chi)(chi)（一(yi)(yi)般低(di)(di)于(yu)(yu) 10?C）或(huo)過(guo)度放電(dian)(dian)(dian)(dian)的電(dian)(dian)(dian)(dian)池(chi)(chi)（每節電(dian)(dian)(dian)(dian)池(chi)(chi)通(tong)常低(di)(di)于(yu)(yu) 1V），需要施加(jia)一(yi)(yi)個(ge)溫和的點(dian)滴(di)式電(dian)(dian)(dian)(dian)流。

當(dang)電(dian)(dian)(dian)(dian)池溫(wen)度(du)(du)和(he)電(dian)(dian)(dian)(dian)壓正(zheng)確時快(kuai)速(su)(su)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)開始。通常用(yong) 1C 或(huo)更低的恒(heng)定(ding)電(dian)(dian)(dian)(dian)流(liu)對 NiMH 電(dian)(dian)(dian)(dian)池進行(xing)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)。一些 NiCd 電(dian)(dian)(dian)(dian)池可(ke)以用(yong)高達 4C 的速(su)(su)率(lv)進行(xing)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)。采用(yong)適當(dang)的充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)終(zhong)(zhong)止(zhi)來避免有害的過充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)。就鎳(nie)基可(ke)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)池而言(yan)，快(kuai)速(su)(su)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)終(zhong)(zhong)止(zhi)基于電(dian)(dian)(dian)(dian)壓或(huo)溫(wen)度(du)(du)。如(ru)圖 1 所示，典型(xing)的電(dian)(dian)(dian)(dian)壓終(zhong)(zhong)止(zhi)方法是峰值電(dian)(dian)(dian)(dian)壓探測，在(zai)峰值時即(ji)每(mei)個電(dian)(dian)(dian)(dian)池的電(dian)(dian)(dian)(dian)壓在(zai) 0～-4mV 范圍內，快(kuai)速(su)(su)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)被終(zhong)(zhong)止(zhi)。基于溫(wen)度(du)(du)的快(kuai)速(su)(su)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)終(zhong)(zhong)止(zhi)方法是觀察電(dian)(dian)(dian)(dian)池溫(wen)度(du)(du)上升率(lv) ?T/?t 來探測完全充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)。典型(xing)的 ?T/?t 率(lv)為 1?C/每(mei)分(fen)鐘(zhong)。

鋰(li)離子/鋰(li)聚(ju)合物(wu)電池
與 NiCd 電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)和 NiMh 電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)相(xiang)類(lei)似，在快速充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)之(zhi)前盡可能檢(jian)驗(yan)并(bing)調節(jie)鋰(li)離(li)子電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)。驗(yan)證和處理方法(fa)與上(shang)述使用的(de)方法(fa)相(xiang)類(lei)似。 驗(yan)證和預處理之(zhi)后，先用一個(ge) 1C 或更低的(de)電(dian)(dian)(dian)(dian)(dian)流對鋰(li)離(li)子電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)進(jin)行(xing)(xing)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)，直到電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)達(da)到其充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓(ya)極限為止(zhi)。該充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)階段(duan)通常會補充(chong)(chong)(chong)高達(da) 70% 的(de)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)容量。然后用一個(ge)通常為 4.2V 的(de)恒定電(dian)(dian)(dian)(dian)(dian)壓(ya)對電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)進(jin)行(xing)(xing)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)。為將(jiang)安(an)全性(xing)和電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)容量，必須要(yao)將(jiang)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)壓(ya)穩定在至少 ?1%。在此充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)期間，電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)汲取的(de)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流逐漸下(xia)(xia)(xia)降。就 1C 充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)率而言，一旦(dan)電(dian)(dian)(dian)(dian)(dian)流電(dian)(dian)(dian)(dian)(dian)平下(xia)(xia)(xia)降到初始(shi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流的(de) 10-15% 以(yi)下(xia)(xia)(xia)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)通常就會終止(zhi).

開關模式與線性充電拓撲的(de)對比(bi)

傳統上來說，手持設(she)備都使用線性充電拓撲。該方法(fa)具有諸(zhu)多(duo)優勢：低(di)實(shi)施成本、設(she)計(ji)(ji)簡捷以及無(wu)高頻開關的(de)無(wu)噪聲運行。但是(shi)，線性拓撲會增加系統功(gong)耗，尤其(qi)是(shi)當電池容量更高引起(qi)的(de)充電率增加的(de)時候(hou)。如果設(she)計(ji)(ji)人員無(wu)法(fa)管(guan)理設(she)計(ji)(ji)的(de)散熱問題(ti)，這就會成為一個主要缺點。

當 PC USB 端口作(zuo)為電(dian)源時，則(ze)會(hui)出(chu)現其他一些缺(que)點。當今(jin)在許多便(bian)攜式設計上(shang)都具有 USB 充(chong)電(dian)選項，并且(qie)都可提供高(gao)達 500mA 的(de)充(chong)電(dian)率。就線性解決(jue)方案而(er)言，由于其效率較低(di)，可以從 PC USB 傳輸(shu)的(de)“電(dian)能”量(liang)就被大大降低(di)，從而(er)導致了充(chong)電(dian)時間過(guo)長。

這(zhe)就是開(kai)(kai)(kai)關模式(shi)拓(tuo)撲有用(yong)武之地的(de)原因。開(kai)(kai)(kai)關模式(shi)拓(tuo)撲的(de)主要(yao)優勢在(zai)于(yu)效率(lv)的(de)提高。與(yu)線性穩壓器(qi)不同(tong)，電源開(kai)(kai)(kai)關（或(huo)多個開(kai)(kai)(kai)關）在(zai)飽和(he)的(de)區域內運行，其大大降(jiang)低了總體(ti)損耗(hao)。降(jiang)壓轉換器(qi)中(zhong)(zhong)功率(lv)損耗(hao)的(de)主要(yao)包括開(kai)(kai)(kai)關損耗(hao)（在(zai)電源開(kai)(kai)(kai)關中(zhong)(zhong)）以(yi)及濾波電感中(zhong)(zhong)的(de) DC 損耗(hao)。根據設計參數的(de)不同(tong)，在(zai)這(zhe)些應用(yong)中(zhong)(zhong)出現效率(lv)大大高于(yu) 95% 的(de)情況(kuang)就不足(zu)為奇了。

當人們聽(ting)到開(kai)(kai)關(guan)(guan)模式這(zhe)個(ge)術語時大(da)多數人都會(hui)想到大(da)型 IC、大(da) PowerFET 以(yi)及(ji)超大(da)型電(dian)感! 事實上(shang)，雖然對(dui)(dui)于(yu)(yu)處理數十安培電(dian)流的應用而言確實是(shi)這(zhe)樣(yang)，但是(shi)對(dui)(dui)于(yu)(yu)手持(chi)設備的新一(yi)(yi)代解決方案(an)而言情況就不一(yi)(yi)樣(yang)了。新一(yi)(yi)代單體鋰離(li)子開(kai)(kai)關(guan)(guan)模式充電(dian)器采用了最(zui)高(gao)級別的芯(xin)片(pian)集成，高(gao)于(yu)(yu) 1MHz 的使(shi)用頻(pin)率以(yi)最(zui)小化電(dian)感尺(chi)寸(cun)。圖 1 說明了當今(jin)市場上(shang)已開(kai)(kai)始銷售的此類解決方案(an)。該硅芯(xin)片(pian)的尺(chi)寸(cun)不到 4 mm2，其(qi)集成了高(gao)側(ce)和低側(ce) PowerFET。由于(yu)(yu)采用了 3MHz 開(kai)(kai)關(guan)(guan)頻(pin)率，該解決方案(an)要(yao)求一(yi)(yi)個(ge)小型 1uH 電(dian)感， 其(qi)外形尺(chi)寸(cun)僅為：2mm x 2.5mm x 1.2mm (WxLxH)。

充(chong)電器的選擇(ze)

電(dian)池充電(dian)器工具使得設計人員(yuan)選擇正確的(de)充電(dian)器的(de)過程更(geng)輕松。