引言

便(bian)攜式電(dian)子設(she)備設(she)計人員可以(yi)選(xuan)擇各種各樣的(de)化學(xue)技術、充電(dian)器(qi)拓撲以(yi)及充電(dian)管(guan)理解決方案(an)。選(xuan)擇一(yi)(yi)(yi)(yi)款最為(wei)合適的(de)解決方案(an)應(ying)該是一(yi)(yi)(yi)(yi)項很簡單的(de)工作，但是在(zai)大(da)多數情況下這一(yi)(yi)(yi)(yi)過程(cheng)頗為(wei)復雜。設(she)計人員需(xu)要(yao)在(zai)性能、成本、外形(xing)尺(chi)寸(cun)以(yi)及其(qi)他關鍵要(yao)求方面(mian)找到一(yi)(yi)(yi)(yi)個最佳平(ping)衡點。本文(wen)將為(wei)廣(guang)大(da)設(she)計人員和系(xi)統工程(cheng)師(shi)提供一(yi)(yi)(yi)(yi)些指導(dao)和幫助以(yi)使得該選(xuan)擇工作變得更(geng)為(wei)輕松(song)。

以(yi) 3 “C”開始實現充電控制

所有(you)使(shi)用可充電電池(chi)的(de)系(xi)統(tong)設(she)計人員(yuan)都需要清楚一些(xie)基礎設(she)計技術，以確保滿足下面三個關鍵的(de)要求：

1、電(dian)(dian)(dian)(dian)(dian)池安(an)全性: 毋庸置疑，終端(duan)用戶(hu)安(an)全是所(suo)有(you)(you)系統設(she)計(ji)(ji)中最(zui)優先考(kao)慮的(de)問(wen)題。大多數鋰離子 (Li-Ion) 電(dian)(dian)(dian)(dian)(dian)池組(zu)和(he)鋰聚合物 (Li-Pol) 電(dian)(dian)(dian)(dian)(dian)池組(zu)都(dou)含有(you)(you)保(bao)護(hu)電(dian)(dian)(dian)(dian)(dian)子電(dian)(dian)(dian)(dian)(dian)路。然而，還有(you)(you)一些(xie)系統設(she)計(ji)(ji)需要(yao)考(kao)慮的(de)關鍵(jian)因素。其中包括(kuo)但不局限于確保(bao)在鋰離子電(dian)(dian)(dian)(dian)(dian)池充電(dian)(dian)(dian)(dian)(dian)最(zui)后階段(duan)期間 ?1% 的(de)穩壓(ya)容限、安(an)全處理深(shen)度放電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)池的(de)預處理模式(shi)、安(an)全計(ji)(ji)時(shi)器以及(ji)電(dian)(dian)(dian)(dian)(dian)池溫度監控。

2、電(dian)(dian)池(chi)容(rong)量：所有的電(dian)(dian)池(chi)充(chong)電(dian)(dian)解決(jue)方案都(dou)要確保(bao)在(zai)每(mei)一(yi)(yi)次和每(mei)一(yi)(yi)個充(chong)電(dian)(dian)周期都(dou)能將電(dian)(dian)池(chi)容(rong)量充(chong)至充(chong)滿狀態。過(guo)早的終止充(chong)電(dian)(dian)會導致電(dian)(dian)池(chi)運行時(shi)間縮短，這是(shi)當今高功耗的便(bian)攜式設備所不希望的。

3、電(dian)(dian)(dian)池(chi)使(shi)用(yong)壽命：遵循(xun)建議的(de)(de)充電(dian)(dian)(dian)算法是確保終端用(yong)戶(hu)實現每個電(dian)(dian)(dian)池(chi)組最(zui)(zui)多充電(dian)(dian)(dian)周期的(de)(de)重(zhong)要一(yi)步。利用(yong)電(dian)(dian)(dian)池(chi)溫度和電(dian)(dian)(dian)壓限定每一(yi)次充電(dian)(dian)(dian)、預處(chu)理(li)深度放電(dian)(dian)(dian)電(dian)(dian)(dian)池(chi)并避免過晚或非(fei)正(zheng)常充電(dian)(dian)(dian)終止是最(zui)(zui)大化電(dian)(dian)(dian)池(chi)使(shi)用(yong)壽命所必(bi)須(xu)的(de)(de)一(yi)些步驟。

充電特(te)性(xing) 電池(chi)安(an)全性(xing) 電池(chi)容量 電池(chi)使用壽(shou)命

精確(que)的電壓(ya)和/或電流調節 ? ?

充電限制

（電壓和溫度(du)） ? ?

溫度(du)監控 ? ? ?

預處理 ? ? ?

充電結束終止 ? ? ?

充電計時器 ?

充電狀態報告 ? ?

電池插(cha)入與去除探(tan)測 ?

最小電池泄漏 ?

短路電流限制 ?

自動再充電 ?

電池化學(xue)技術的選擇(ze)
現在(zai)系統設(she)計人(ren)員可(ke)以在(zai)多種電池化學技(ji)術(shu)中(zhong)進行選擇(ze)。設(she)計 人(ren)員通常會根據下面(mian)的一(yi)些標(biao)準進行電池化學技(ji)術(shu)的選擇(ze)，其中(zhong)包括：

? 能量密度

? 規格和外形尺寸

? 成本

? 使用模(mo)式(shi)和使用壽(shou)命

近年來(lai)，盡管使用鋰(li)離子電(dian)池(chi)(chi)和鋰(li)聚合物電(dian)池(chi)(chi)的趨勢增強，但是 Ni 電(dian)池(chi)(chi)化(hua)學技(ji)術仍然是諸多消費(fei)類應(ying)用一個不錯的選項。

無論選擇何種電(dian)池(chi)化學技術，遵循每(mei)一種電(dian)池(chi)化學技術的正確充(chong)(chong)(chong)電(dian)管理技術都是至關重(zhong)要的。這些技術將確保(bao)電(dian)池(chi)在(zai)每(mei)一次(ci)和每(mei)個充(chong)(chong)(chong)電(dian)周期(qi)都能被(bei)充(chong)(chong)(chong)至最(zui)大容量(liang)，而不會降低(di)安全性或縮短電(dian)池(chi)使用壽命(ming)。

NiCd / NIMH

在一個充(chong)電(dian)(dian)(dian)(dian)周期開始之(zhi)前，并且盡可能在開始快速充(chong)電(dian)(dian)(dian)(dian)之(zhi)前對鎳(nie)鎘 (NiCd) 電(dian)(dian)(dian)(dian)池(chi)(chi)和(he)鎳(nie)氫 (NiMH) 電(dian)(dian)(dian)(dian)池(chi)(chi)必須(xu)要進(jin)行檢驗和(he)調(diao)節。如(ru)果電(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)壓或(huo)溫度(du)超出(chu)了允(yun)許(xu)的(de)極限是不允(yun)許(xu)進(jin)行快速充(chong)電(dian)(dian)(dian)(dian)的(de)。出(chu)于(yu)安全考慮，對所有“熱”電(dian)(dian)(dian)(dian)池(chi)(chi)（一般高于(yu) 45?C）的(de)充(chong)電(dian)(dian)(dian)(dian)工作都(dou)會(hui)(hui)暫時終止，直到(dao)電(dian)(dian)(dian)(dian)池(chi)(chi)冷卻到(dao)正常(chang)工作溫度(du)范(fan)圍(wei)內才會(hui)(hui)再次運(yun)轉(zhuan)。要想(xiang)處(chu)理一個“冷”電(dian)(dian)(dian)(dian)池(chi)(chi)（一般低于(yu) 10?C）或(huo)過度(du)放電(dian)(dian)(dian)(dian)的(de)電(dian)(dian)(dian)(dian)池(chi)(chi)（每節電(dian)(dian)(dian)(dian)池(chi)(chi)通(tong)常(chang)低于(yu) 1V），需要施加一個溫和(he)的(de)點滴式電(dian)(dian)(dian)(dian)流。

當(dang)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)溫度和電(dian)(dian)(dian)(dian)(dian)壓正確(que)時(shi)快速充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)開始。通常(chang)用(yong) 1C 或(huo)更低的(de)恒(heng)定電(dian)(dian)(dian)(dian)(dian)流對 NiMH 電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)進行充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)。一些 NiCd 電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)可以用(yong)高(gao)達 4C 的(de)速率(lv)(lv)進行充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)。采用(yong)適當(dang)的(de)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)終(zhong)(zhong)止來避免有害的(de)過充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)。就鎳基可充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)而(er)言(yan)，快速充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)終(zhong)(zhong)止基于電(dian)(dian)(dian)(dian)(dian)壓或(huo)溫度。如圖(tu) 1 所示，典型的(de)電(dian)(dian)(dian)(dian)(dian)壓終(zhong)(zhong)止方法是峰(feng)值(zhi)電(dian)(dian)(dian)(dian)(dian)壓探測(ce)，在峰(feng)值(zhi)時(shi)即每個(ge)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)的(de)電(dian)(dian)(dian)(dian)(dian)壓在 0～-4mV 范(fan)圍內，快速充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)被終(zhong)(zhong)止。基于溫度的(de)快速充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)終(zhong)(zhong)止方法是觀察電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)溫度上升(sheng)率(lv)(lv) ?T/?t 來探測(ce)完全充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)。典型的(de) ?T/?t 率(lv)(lv)為 1?C/每分鐘。

鋰離子/鋰聚(ju)合物電池
與 NiCd 電(dian)(dian)(dian)池(chi)和 NiMh 電(dian)(dian)(dian)池(chi)相(xiang)類似，在快速充(chong)(chong)電(dian)(dian)(dian)之(zhi)前(qian)盡可能檢驗并調節鋰(li)離(li)子電(dian)(dian)(dian)池(chi)。驗證和處理方(fang)法與上述使用的(de)(de)方(fang)法相(xiang)類似。 驗證和預處理之(zhi)后，先用一(yi)(yi)個 1C 或更低的(de)(de)電(dian)(dian)(dian)流(liu)(liu)對鋰(li)離(li)子電(dian)(dian)(dian)池(chi)進行(xing)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)極限為止。該充(chong)(chong)電(dian)(dian)(dian)階段通常會補充(chong)(chong)高達 70% 的(de)(de)電(dian)(dian)(dian)池(chi)容(rong)量。然后用一(yi)(yi)個通常為 4.2V 的(de)(de)恒定(ding)電(dian)(dian)(dian)壓(ya)對電(dian)(dian)(dian)池(chi)進行(xing)充(chong)(chong)電(dian)(dian)(dian)。為將(jiang)安全(quan)性和電(dian)(dian)(dian)池(chi)容(rong)量，必須要(yao)將(jiang)充(chong)(chong)電(dian)(dian)(dian)壓(ya)穩定(ding)在至少 ?1%。在此(ci)充(chong)(chong)電(dian)(dian)(dian)期間，電(dian)(dian)(dian)池(chi)汲取的(de)(de)充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)逐漸下降。就(jiu) 1C 充(chong)(chong)電(dian)(dian)(dian)率(lv)而言，一(yi)(yi)旦電(dian)(dian)(dian)流(liu)(liu)電(dian)(dian)(dian)平(ping)下降到(dao)初始充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)的(de)(de) 10-15% 以下充(chong)(chong)電(dian)(dian)(dian)通常就(jiu)會終(zhong)止.

開(kai)關模式(shi)與線性充電拓(tuo)撲的對(dui)比

傳統上來說，手持(chi)設備都使用線性充(chong)(chong)電(dian)(dian)拓(tuo)(tuo)撲(pu)。該方法具有諸多優勢：低實施(shi)成本、設計(ji)簡捷以及無(wu)高頻開關的(de)(de)無(wu)噪聲運行。但是(shi)，線性拓(tuo)(tuo)撲(pu)會增(zeng)加系統功耗，尤其是(shi)當電(dian)(dian)池容量(liang)更高引起的(de)(de)充(chong)(chong)電(dian)(dian)率增(zeng)加的(de)(de)時候。如果設計(ji)人員無(wu)法管理設計(ji)的(de)(de)散熱問題(ti)，這(zhe)就會成為一個主要缺點。

當(dang) PC USB 端口作為(wei)電(dian)源時(shi)，則會(hui)出(chu)現其(qi)他一些缺點。當(dang)今(jin)在許多便攜式設(she)計上(shang)都(dou)具有 USB 充電(dian)選項，并且都(dou)可提供高達 500mA 的(de)(de)充電(dian)率。就(jiu)線性(xing)解決方案而言，由于其(qi)效率較低，可以從 PC USB 傳輸(shu)的(de)(de)“電(dian)能”量就(jiu)被大大降(jiang)低，從而導致了(le)充電(dian)時(shi)間過(guo)長。

這就(jiu)是(shi)開(kai)(kai)關(guan)(guan)(guan)模(mo)式拓撲(pu)有用(yong)武之地(di)的(de)原因。開(kai)(kai)關(guan)(guan)(guan)模(mo)式拓撲(pu)的(de)主要(yao)優(you)勢在于(yu)效(xiao)率的(de)提(ti)高。與(yu)線性穩壓器(qi)不(bu)同，電源開(kai)(kai)關(guan)(guan)(guan)（或多(duo)個開(kai)(kai)關(guan)(guan)(guan)）在飽和的(de)區域內(nei)運行(xing)，其大大降低了總體損(sun)(sun)耗。降壓轉換器(qi)中功率損(sun)(sun)耗的(de)主要(yao)包括(kuo)開(kai)(kai)關(guan)(guan)(guan)損(sun)(sun)耗（在電源開(kai)(kai)關(guan)(guan)(guan)中）以及濾(lv)波電感(gan)中的(de) DC 損(sun)(sun)耗。根據(ju)設計參數的(de)不(bu)同，在這些(xie)應(ying)用(yong)中出現效(xiao)率大大高于(yu) 95% 的(de)情(qing)況就(jiu)不(bu)足(zu)為奇了。

當人們聽到(dao)開(kai)關模(mo)式(shi)這(zhe)個(ge)術(shu)語時大(da)(da)多數(shu)人都會想到(dao)大(da)(da)型(xing) IC、大(da)(da) PowerFET 以及超(chao)大(da)(da)型(xing)電(dian)(dian)(dian)感! 事實上，雖然(ran)對于處理數(shu)十安培電(dian)(dian)(dian)流的(de)應用(yong)而(er)言確實是這(zhe)樣，但是對于手持(chi)設備的(de)新一(yi)代(dai)解(jie)決(jue)方(fang)案(an)而(er)言情(qing)況就(jiu)不一(yi)樣了(le)(le)(le)。新一(yi)代(dai)單體鋰離子開(kai)關模(mo)式(shi)充電(dian)(dian)(dian)器采用(yong)了(le)(le)(le)最高級別的(de)芯片集成，高于 1MHz 的(de)使用(yong)頻率(lv)以最小化電(dian)(dian)(dian)感尺(chi)(chi)寸。圖 1 說明(ming)了(le)(le)(le)當今市場上已開(kai)始(shi)銷售(shou)的(de)此類解(jie)決(jue)方(fang)案(an)。該(gai)硅芯片的(de)尺(chi)(chi)寸不到(dao) 4 mm2，其(qi)集成了(le)(le)(le)高側和低側 PowerFET。由于采用(yong)了(le)(le)(le) 3MHz 開(kai)關頻率(lv)，該(gai)解(jie)決(jue)方(fang)案(an)要求一(yi)個(ge)小型(xing) 1uH 電(dian)(dian)(dian)感， 其(qi)外形尺(chi)(chi)寸僅為：2mm x 2.5mm x 1.2mm (WxLxH)。

充(chong)電器的選擇

電(dian)池充電(dian)器工具使得設計(ji)人(ren)員(yuan)選擇正(zheng)確的充電(dian)器的過(guo)程(cheng)更輕(qing)松。