引(yin)言

便攜式電子設(she)(she)(she)備設(she)(she)(she)計人員可以選擇各(ge)種各(ge)樣(yang)的化(hua)學(xue)技術、充電器拓撲(pu)以及(ji)充電管理解決方案。選擇一(yi)款最為(wei)合適(shi)的解決方案應該是(shi)一(yi)項(xiang)很簡單的工作，但是(shi)在大(da)多數(shu)情況下這(zhe)一(yi)過程(cheng)頗為(wei)復(fu)雜。設(she)(she)(she)計人員需要在性能、成本(ben)、外形尺寸(cun)以及(ji)其(qi)他關鍵要求方面找到一(yi)個最佳(jia)平(ping)衡點。本(ben)文將為(wei)廣大(da)設(she)(she)(she)計人員和(he)系統工程(cheng)師提(ti)供一(yi)些指導和(he)幫助以使得(de)該選擇工作變得(de)更為(wei)輕松。

以 3 “C”開(kai)始實現(xian)充電控制

所有使用(yong)可充電電池的系(xi)統設計人員都(dou)需要清楚一些(xie)基礎設計技術(shu)，以確保滿足下面(mian)三個關鍵(jian)的要求：

1、電(dian)(dian)(dian)(dian)池(chi)(chi)安全性: 毋庸(yong)置疑(yi)，終端用戶(hu)安全是所有(you)系(xi)統(tong)設計(ji)中最優先(xian)考慮的(de)問題。大多數鋰離子(zi) (Li-Ion) 電(dian)(dian)(dian)(dian)池(chi)(chi)組和(he)鋰聚合物 (Li-Pol) 電(dian)(dian)(dian)(dian)池(chi)(chi)組都含(han)有(you)保護電(dian)(dian)(dian)(dian)子(zi)電(dian)(dian)(dian)(dian)路。然而，還有(you)一些系(xi)統(tong)設計(ji)需要考慮的(de)關鍵(jian)因素(su)。其中包(bao)括但不局限于確保在鋰離子(zi)電(dian)(dian)(dian)(dian)池(chi)(chi)充電(dian)(dian)(dian)(dian)最后階段期(qi)間 ?1% 的(de)穩壓容限、安全處理(li)深度放電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)池(chi)(chi)的(de)預處理(li)模式、安全計(ji)時器以及電(dian)(dian)(dian)(dian)池(chi)(chi)溫度監(jian)控。

2、電(dian)池(chi)容量(liang)：所有的(de)電(dian)池(chi)充(chong)(chong)(chong)電(dian)解決方案都要確保在每一次(ci)和(he)每一個充(chong)(chong)(chong)電(dian)周期都能將(jiang)電(dian)池(chi)容量(liang)充(chong)(chong)(chong)至充(chong)(chong)(chong)滿狀(zhuang)態。過早的(de)終(zhong)止充(chong)(chong)(chong)電(dian)會導致電(dian)池(chi)運行時間縮短，這(zhe)是當(dang)今高功耗(hao)的(de)便攜(xie)式設備所不希望的(de)。

3、電(dian)(dian)(dian)(dian)池使用(yong)壽命：遵(zun)循(xun)建議的(de)充(chong)電(dian)(dian)(dian)(dian)算法是確保(bao)終端用(yong)戶實(shi)現每個電(dian)(dian)(dian)(dian)池組最多充(chong)電(dian)(dian)(dian)(dian)周期的(de)重要(yao)一步。利用(yong)電(dian)(dian)(dian)(dian)池溫(wen)度(du)(du)和電(dian)(dian)(dian)(dian)壓限定每一次充(chong)電(dian)(dian)(dian)(dian)、預處(chu)理深度(du)(du)放(fang)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)池并避(bi)免過晚或非正常充(chong)電(dian)(dian)(dian)(dian)終止是最大化電(dian)(dian)(dian)(dian)池使用(yong)壽命所(suo)必(bi)須的(de)一些步驟。

充電特性(xing) 電池安全性(xing) 電池容量 電池使用壽命(ming)

精確的電(dian)(dian)壓(ya)和/或電(dian)(dian)流調節(jie) ? ?

充電限制

（電壓和溫(wen)度） ? ?

溫度監控 ? ? ?

預處理 ? ? ?

充電結(jie)束終止 ? ? ?

充電計時器 ?

充電狀態(tai)報告(gao) ? ?

電池插入與去除探測 ?

最小電池泄漏 ?

短路電流限制 ?

自動再充電 ?

電池化(hua)學技術的選(xuan)擇(ze)
現在(zai)系統設計人員可以(yi)在(zai)多種電(dian)池(chi)化學技術(shu)中進行選(xuan)擇(ze)。設計 人員通常會根據下(xia)面的一些標(biao)準進行電(dian)池(chi)化學技術(shu)的選(xuan)擇(ze)，其(qi)中包括：

? 能量密度

? 規格和外形尺寸

? 成本

? 使用模(mo)式和使用壽命

近年來，盡管使用鋰離子電(dian)池和鋰聚合(he)物電(dian)池的趨(qu)勢增強，但是 Ni 電(dian)池化學技術仍然(ran)是諸多消費類(lei)應用一個不錯的選項。

無論選擇何(he)種電(dian)池化(hua)學(xue)技(ji)術，遵循每一(yi)種電(dian)池化(hua)學(xue)技(ji)術的正確充電(dian)管理技(ji)術都是至關重要的。這些(xie)技(ji)術將確保電(dian)池在每一(yi)次和每個充電(dian)周期(qi)都能被充至最大容量(liang)，而不會(hui)降低(di)安(an)全性或(huo)縮短(duan)電(dian)池使用(yong)壽(shou)命。

NiCd / NIMH

在一(yi)個充(chong)電(dian)(dian)(dian)(dian)周期(qi)開始之(zhi)前(qian)，并且盡可能在開始快速充(chong)電(dian)(dian)(dian)(dian)之(zhi)前(qian)對鎳(nie)鎘 (NiCd) 電(dian)(dian)(dian)(dian)池(chi)和鎳(nie)氫 (NiMH) 電(dian)(dian)(dian)(dian)池(chi)必(bi)須要(yao)進(jin)行檢驗和調節。如果電(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)壓或(huo)溫(wen)(wen)度(du)超出了允許的極限是不允許進(jin)行快速充(chong)電(dian)(dian)(dian)(dian)的。出于(yu)安全考(kao)慮，對所有(you)“熱”電(dian)(dian)(dian)(dian)池(chi)（一(yi)般(ban)高于(yu) 45?C）的充(chong)電(dian)(dian)(dian)(dian)工作都會(hui)暫時終(zhong)止，直到(dao)電(dian)(dian)(dian)(dian)池(chi)冷卻到(dao)正常工作溫(wen)(wen)度(du)范圍內才會(hui)再(zai)次運轉。要(yao)想處理一(yi)個“冷”電(dian)(dian)(dian)(dian)池(chi)（一(yi)般(ban)低(di)于(yu) 10?C）或(huo)過度(du)放電(dian)(dian)(dian)(dian)的電(dian)(dian)(dian)(dian)池(chi)（每(mei)節電(dian)(dian)(dian)(dian)池(chi)通常低(di)于(yu) 1V），需要(yao)施加一(yi)個溫(wen)(wen)和的點滴式電(dian)(dian)(dian)(dian)流。

當(dang)電(dian)(dian)(dian)(dian)(dian)(dian)池溫(wen)(wen)度(du)和電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)正確時快速(su)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)開始。通常用(yong) 1C 或更低的(de)(de)(de)(de)恒(heng)定電(dian)(dian)(dian)(dian)(dian)(dian)流對(dui) NiMH 電(dian)(dian)(dian)(dian)(dian)(dian)池進(jin)行充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)。一些 NiCd 電(dian)(dian)(dian)(dian)(dian)(dian)池可(ke)以(yi)用(yong)高(gao)達 4C 的(de)(de)(de)(de)速(su)率進(jin)行充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)。采用(yong)適當(dang)的(de)(de)(de)(de)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)終(zhong)(zhong)(zhong)止(zhi)來避免有害的(de)(de)(de)(de)過(guo)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)。就鎳基(ji)(ji)可(ke)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)池而(er)言，快速(su)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)終(zhong)(zhong)(zhong)止(zhi)基(ji)(ji)于電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)或溫(wen)(wen)度(du)。如(ru)圖 1 所示，典型(xing)的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)終(zhong)(zhong)(zhong)止(zhi)方(fang)法是峰值電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)探(tan)測(ce)，在(zai)峰值時即每(mei)個電(dian)(dian)(dian)(dian)(dian)(dian)池的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)在(zai) 0～-4mV 范圍(wei)內，快速(su)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)被(bei)終(zhong)(zhong)(zhong)止(zhi)。基(ji)(ji)于溫(wen)(wen)度(du)的(de)(de)(de)(de)快速(su)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)終(zhong)(zhong)(zhong)止(zhi)方(fang)法是觀察電(dian)(dian)(dian)(dian)(dian)(dian)池溫(wen)(wen)度(du)上升率 ?T/?t 來探(tan)測(ce)完全(quan)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)。典型(xing)的(de)(de)(de)(de) ?T/?t 率為 1?C/每(mei)分鐘。

鋰離子/鋰聚合(he)物電(dian)池(chi)
與(yu)(yu) NiCd 電(dian)(dian)(dian)池(chi)和 NiMh 電(dian)(dian)(dian)池(chi)相類(lei)(lei)似，在快速充(chong)(chong)電(dian)(dian)(dian)之前(qian)盡可能檢(jian)驗(yan)并調節(jie)鋰離子電(dian)(dian)(dian)池(chi)。驗(yan)證和處理方(fang)法(fa)與(yu)(yu)上(shang)述使用(yong)的(de)方(fang)法(fa)相類(lei)(lei)似。 驗(yan)證和預處理之后，先用(yong)一個 1C 或(huo)更(geng)低的(de)電(dian)(dian)(dian)流(liu)對鋰離子電(dian)(dian)(dian)池(chi)進(jin)行充(chong)(chong)電(dian)(dian)(dian)，直到(dao)電(dian)(dian)(dian)池(chi)達到(dao)其充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)壓(ya)極限為(wei)止。該充(chong)(chong)電(dian)(dian)(dian)階段通(tong)常(chang)(chang)會補(bu)充(chong)(chong)高達 70% 的(de)電(dian)(dian)(dian)池(chi)容(rong)量。然后用(yong)一個通(tong)常(chang)(chang)為(wei) 4.2V 的(de)恒定電(dian)(dian)(dian)壓(ya)對電(dian)(dian)(dian)池(chi)進(jin)行充(chong)(chong)電(dian)(dian)(dian)。為(wei)將安全性和電(dian)(dian)(dian)池(chi)容(rong)量，必須要(yao)將充(chong)(chong)電(dian)(dian)(dian)壓(ya)穩定在至少 ?1%。在此充(chong)(chong)電(dian)(dian)(dian)期間，電(dian)(dian)(dian)池(chi)汲(ji)取的(de)充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)逐(zhu)漸下降(jiang)。就 1C 充(chong)(chong)電(dian)(dian)(dian)率而言，一旦電(dian)(dian)(dian)流(liu)電(dian)(dian)(dian)平下降(jiang)到(dao)初始充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)的(de) 10-15% 以下充(chong)(chong)電(dian)(dian)(dian)通(tong)常(chang)(chang)就會終止.

開關模式與線(xian)性充電拓(tuo)撲的對比(bi)

傳統(tong)上來說，手(shou)持設(she)備都(dou)使用線(xian)性充電(dian)拓(tuo)(tuo)撲(pu)。該方法具有(you)諸多優勢：低實(shi)施成本、設(she)計(ji)(ji)簡捷以及(ji)無(wu)高頻開關的無(wu)噪聲(sheng)運行。但(dan)是，線(xian)性拓(tuo)(tuo)撲(pu)會(hui)增加系統(tong)功耗，尤其是當電(dian)池容量更高引起的充電(dian)率增加的時候。如(ru)果設(she)計(ji)(ji)人員無(wu)法管(guan)理設(she)計(ji)(ji)的散熱問(wen)題，這就會(hui)成為(wei)一(yi)個主要缺(que)點。

當(dang) PC USB 端口作為電(dian)(dian)源時，則會出現其他一些缺點。當(dang)今(jin)在許多(duo)便攜式設計(ji)上都具有 USB 充電(dian)(dian)選項，并(bing)且都可提供高達 500mA 的充電(dian)(dian)率(lv)。就(jiu)線(xian)性解決(jue)方(fang)案而言，由(you)于其效率(lv)較低(di)，可以從 PC USB 傳輸(shu)的“電(dian)(dian)能”量(liang)就(jiu)被大大降低(di)，從而導(dao)致(zhi)了充電(dian)(dian)時間過長。

這(zhe)就(jiu)是開(kai)(kai)關(guan)模式(shi)拓(tuo)撲有用武之(zhi)地的(de)原因。開(kai)(kai)關(guan)模式(shi)拓(tuo)撲的(de)主(zhu)(zhu)要優(you)勢在(zai)于效率(lv)(lv)的(de)提高。與線(xian)性穩壓器(qi)不同(tong)，電源開(kai)(kai)關(guan)（或多個開(kai)(kai)關(guan)）在(zai)飽(bao)和的(de)區域(yu)內運行，其大大降(jiang)低了(le)總體損耗(hao)。降(jiang)壓轉換器(qi)中功率(lv)(lv)損耗(hao)的(de)主(zhu)(zhu)要包括開(kai)(kai)關(guan)損耗(hao)（在(zai)電源開(kai)(kai)關(guan)中）以及濾(lv)波(bo)電感中的(de) DC 損耗(hao)。根(gen)據(ju)設計參(can)數的(de)不同(tong)，在(zai)這(zhe)些應用中出現效率(lv)(lv)大大高于 95% 的(de)情況就(jiu)不足為奇了(le)。

當人(ren)們聽到(dao)開(kai)關(guan)(guan)模式這個(ge)(ge)術語時大(da)多數人(ren)都會想到(dao)大(da)型 IC、大(da) PowerFET 以及超大(da)型電感(gan)! 事(shi)實上，雖(sui)然(ran)對(dui)于處理數十安培電流的應用(yong)而言確(que)實是這樣，但是對(dui)于手持設備的新(xin)一代(dai)解決(jue)方(fang)案(an)(an)而言情況就不(bu)一樣了。新(xin)一代(dai)單體(ti)鋰離子開(kai)關(guan)(guan)模式充(chong)電器采用(yong)了最高級(ji)別的芯片集成，高于 1MHz 的使用(yong)頻率以最小化電感(gan)尺(chi)(chi)寸(cun)。圖 1 說明(ming)了當今市場(chang)上已開(kai)始(shi)銷售的此類解決(jue)方(fang)案(an)(an)。該硅芯片的尺(chi)(chi)寸(cun)不(bu)到(dao) 4 mm2，其(qi)集成了高側和低側 PowerFET。由(you)于采用(yong)了 3MHz 開(kai)關(guan)(guan)頻率，該解決(jue)方(fang)案(an)(an)要(yao)求一個(ge)(ge)小型 1uH 電感(gan)， 其(qi)外形尺(chi)(chi)寸(cun)僅為：2mm x 2.5mm x 1.2mm (WxLxH)。

充電器的選擇

電池充電器工(gong)具(ju)使得設計人員選擇正確的充電器的過(guo)程更輕松。