引言(yan)

便攜式電子設備設計人(ren)員可以(yi)選(xuan)擇(ze)(ze)各種各樣(yang)的化(hua)學技術、充電器拓(tuo)撲以(yi)及(ji)充電管理解決方(fang)案(an)。選(xuan)擇(ze)(ze)一(yi)款(kuan)最(zui)(zui)為(wei)(wei)合適的解決方(fang)案(an)應該是一(yi)項很簡(jian)單的工(gong)作(zuo)，但(dan)是在(zai)(zai)大多數(shu)情況下這一(yi)過程頗為(wei)(wei)復雜。設計人(ren)員需要在(zai)(zai)性能、成(cheng)本(ben)(ben)、外形尺寸以(yi)及(ji)其(qi)他關(guan)鍵要求方(fang)面找到一(yi)個最(zui)(zui)佳(jia)平(ping)衡點(dian)。本(ben)(ben)文(wen)將(jiang)為(wei)(wei)廣大設計人(ren)員和系(xi)統工(gong)程師提供一(yi)些指導(dao)和幫(bang)助以(yi)使得該選(xuan)擇(ze)(ze)工(gong)作(zuo)變得更為(wei)(wei)輕松。

以 3 “C”開始(shi)實現充電(dian)控制(zhi)

所有(you)使用可充電電池的(de)系統設(she)計人員都(dou)需要清楚一些基礎(chu)設(she)計技術，以確保滿足下面三個(ge)關(guan)鍵的(de)要求：

1、電(dian)(dian)池(chi)(chi)安(an)(an)全(quan)(quan)性: 毋庸(yong)置(zhi)疑，終端(duan)用(yong)戶安(an)(an)全(quan)(quan)是所有系(xi)統設計中最優先考(kao)慮的(de)問(wen)題(ti)。大多(duo)數鋰離(li)子 (Li-Ion) 電(dian)(dian)池(chi)(chi)組和鋰聚(ju)合物(wu) (Li-Pol) 電(dian)(dian)池(chi)(chi)組都含(han)有保護電(dian)(dian)子電(dian)(dian)路。然而(er)，還有一些(xie)系(xi)統設計需要考(kao)慮的(de)關鍵因(yin)素。其中包(bao)括(kuo)但不局(ju)限(xian)于確(que)保在鋰離(li)子電(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)最后階段期間 ?1% 的(de)穩壓容限(xian)、安(an)(an)全(quan)(quan)處(chu)理(li)(li)深度放電(dian)(dian)電(dian)(dian)池(chi)(chi)的(de)預處(chu)理(li)(li)模式(shi)、安(an)(an)全(quan)(quan)計時器以及(ji)電(dian)(dian)池(chi)(chi)溫度監控(kong)。

2、電(dian)(dian)(dian)(dian)(dian)池容量(liang)(liang)：所有(you)的(de)電(dian)(dian)(dian)(dian)(dian)池充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)解決方案都要確保在(zai)每(mei)一次和每(mei)一個(ge)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)周期都能將(jiang)電(dian)(dian)(dian)(dian)(dian)池容量(liang)(liang)充(chong)(chong)至(zhi)充(chong)(chong)滿狀態。過早的(de)終止充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)會導致電(dian)(dian)(dian)(dian)(dian)池運行時(shi)間縮短，這是當今高(gao)功耗的(de)便攜式設備所不希望的(de)。

3、電(dian)(dian)(dian)池(chi)使用壽命(ming)(ming)：遵循(xun)建議的(de)充(chong)電(dian)(dian)(dian)算(suan)法(fa)是(shi)確保(bao)終端用戶實(shi)現每(mei)個電(dian)(dian)(dian)池(chi)組最(zui)多充(chong)電(dian)(dian)(dian)周期的(de)重要一(yi)步(bu)。利用電(dian)(dian)(dian)池(chi)溫度(du)和電(dian)(dian)(dian)壓限定每(mei)一(yi)次充(chong)電(dian)(dian)(dian)、預(yu)處理深度(du)放電(dian)(dian)(dian)電(dian)(dian)(dian)池(chi)并(bing)避免過晚或非(fei)正常充(chong)電(dian)(dian)(dian)終止是(shi)最(zui)大化(hua)電(dian)(dian)(dian)池(chi)使用壽命(ming)(ming)所(suo)必須的(de)一(yi)些(xie)步(bu)驟。

充電特性 電池(chi)安全性 電池(chi)容量 電池(chi)使用(yong)壽命

精確的電壓和/或(huo)電流調節(jie) ? ?

充電限制

（電壓和溫(wen)度） ? ?

溫(wen)度監控(kong) ? ? ?

預處理 ? ? ?

充電結束終止 ? ? ?

充電計時器 ?

充電狀態報告 ? ?

電池插入與(yu)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(xue)技術的選擇
現在(zai)(zai)系(xi)統設計(ji)(ji)人(ren)員可以在(zai)(zai)多種(zhong)電池化學技(ji)術(shu)中進行選擇(ze)。設計(ji)(ji) 人(ren)員通常會根(gen)據下面的一些標準進行電池化學技(ji)術(shu)的選擇(ze)，其中包括：

? 能量密度

? 規格和外形尺寸

? 成本

? 使(shi)用模式和使(shi)用壽命(ming)

近年來，盡管使用鋰(li)(li)離子電池(chi)和鋰(li)(li)聚合(he)物電池(chi)的趨勢增強，但(dan)是 Ni 電池(chi)化學技(ji)術仍然(ran)是諸多消費(fei)類應(ying)用一個不錯的選項。

無論(lun)選擇何(he)種電(dian)池(chi)(chi)化學技術，遵(zun)循每(mei)一種電(dian)池(chi)(chi)化學技術的(de)正(zheng)確充(chong)電(dian)管理技術都是至(zhi)關重要(yao)的(de)。這些技術將(jiang)確保(bao)電(dian)池(chi)(chi)在每(mei)一次和每(mei)個充(chong)電(dian)周期都能被充(chong)至(zhi)最大容量，而不會降低(di)安全(quan)性或縮短電(dian)池(chi)(chi)使用壽命。

NiCd / NIMH

在一(yi)個充電(dian)(dian)周期開始之前，并且盡可能在開始快(kuai)速(su)充電(dian)(dian)之前對(dui)鎳(nie)鎘(ge) (NiCd) 電(dian)(dian)池(chi)和(he)鎳(nie)氫 (NiMH) 電(dian)(dian)池(chi)必須(xu)要進行檢驗和(he)調節。如果電(dian)(dian)池(chi)電(dian)(dian)壓或(huo)溫(wen)(wen)(wen)度(du)超出(chu)(chu)了允許的(de)(de)極(ji)限是不允許進行快(kuai)速(su)充電(dian)(dian)的(de)(de)。出(chu)(chu)于安全考慮，對(dui)所有“熱(re)”電(dian)(dian)池(chi)（一(yi)般(ban)(ban)高(gao)于 45?C）的(de)(de)充電(dian)(dian)工作都會(hui)暫時終止，直到電(dian)(dian)池(chi)冷(leng)卻(que)到正常工作溫(wen)(wen)(wen)度(du)范圍(wei)內(nei)才會(hui)再(zai)次運轉。要想處理一(yi)個“冷(leng)”電(dian)(dian)池(chi)（一(yi)般(ban)(ban)低于 10?C）或(huo)過度(du)放電(dian)(dian)的(de)(de)電(dian)(dian)池(chi)（每節電(dian)(dian)池(chi)通常低于 1V），需要施加一(yi)個溫(wen)(wen)(wen)和(he)的(de)(de)點滴式電(dian)(dian)流。

當電(dian)(dian)(dian)池(chi)溫(wen)度和電(dian)(dian)(dian)壓(ya)正確時快速(su)充(chong)電(dian)(dian)(dian)開始。通常用(yong) 1C 或(huo)更(geng)低的(de)(de)恒定電(dian)(dian)(dian)流對 NiMH 電(dian)(dian)(dian)池(chi)進(jin)行(xing)充(chong)電(dian)(dian)(dian)。一(yi)些 NiCd 電(dian)(dian)(dian)池(chi)可以用(yong)高達(da) 4C 的(de)(de)速(su)率進(jin)行(xing)充(chong)電(dian)(dian)(dian)。采用(yong)適當的(de)(de)充(chong)電(dian)(dian)(dian)終(zhong)止來避免有害的(de)(de)過充(chong)電(dian)(dian)(dian)。就鎳基可充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)池(chi)而言，快速(su)充(chong)電(dian)(dian)(dian)終(zhong)止基于電(dian)(dian)(dian)壓(ya)或(huo)溫(wen)度。如(ru)圖 1 所示，典型的(de)(de)電(dian)(dian)(dian)壓(ya)終(zhong)止方法是(shi)峰值電(dian)(dian)(dian)壓(ya)探(tan)(tan)測，在峰值時即每(mei)個(ge)電(dian)(dian)(dian)池(chi)的(de)(de)電(dian)(dian)(dian)壓(ya)在 0～-4mV 范(fan)圍內，快速(su)充(chong)電(dian)(dian)(dian)被(bei)終(zhong)止。基于溫(wen)度的(de)(de)快速(su)充(chong)電(dian)(dian)(dian)終(zhong)止方法是(shi)觀察電(dian)(dian)(dian)池(chi)溫(wen)度上(shang)升率 ?T/?t 來探(tan)(tan)測完全(quan)充(chong)電(dian)(dian)(dian)。典型的(de)(de) ?T/?t 率為 1?C/每(mei)分鐘。

鋰離子/鋰聚合物(wu)電池(chi)
與(yu)(yu) NiCd 電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)和 NiMh 電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)相(xiang)類似，在(zai)快(kuai)速充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)之(zhi)前(qian)盡可能(neng)檢驗并調節鋰離子電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)。驗證和處(chu)理(li)(li)方法與(yu)(yu)上(shang)述使用(yong)(yong)的(de)方法相(xiang)類似。 驗證和預處(chu)理(li)(li)之(zhi)后(hou)，先用(yong)(yong)一個 1C 或更低的(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)對鋰離子電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)進行(xing)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，直到電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)達到其充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓極限為止。該充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)階(jie)段通(tong)(tong)常會補充(chong)高達 70% 的(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)容量。然后(hou)用(yong)(yong)一個通(tong)(tong)常為 4.2V 的(de)恒(heng)定(ding)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓對電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)進行(xing)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。為將安(an)全(quan)性和電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)容量，必須(xu)要將充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓穩定(ding)在(zai)至少 ?1%。在(zai)此充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)期間，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)汲取的(de)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)逐漸下降(jiang)。就 1C 充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)率(lv)而(er)言，一旦電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平下降(jiang)到初始充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)的(de) 10-15% 以下充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)通(tong)(tong)常就會終止.

開關模式(shi)與(yu)線性充電(dian)拓(tuo)撲(pu)的(de)對(dui)比

傳統上來說，手持設(she)備(bei)都(dou)使用線(xian)(xian)性(xing)充電(dian)拓(tuo)撲。該方法(fa)具有(you)諸(zhu)多(duo)優勢：低實施(shi)成本、設(she)計簡捷以及無高頻開關(guan)的(de)(de)無噪聲運(yun)行。但是，線(xian)(xian)性(xing)拓(tuo)撲會增加系統功(gong)耗，尤其是當電(dian)池容量更高引起(qi)的(de)(de)充電(dian)率(lv)增加的(de)(de)時候。如(ru)果(guo)設(she)計人員無法(fa)管理設(she)計的(de)(de)散熱(re)問題，這就會成為一個主要(yao)缺點(dian)。

當 PC USB 端口作為電(dian)(dian)源時，則(ze)會出現(xian)其他一些缺點。當今在(zai)許多便攜式設計上都(dou)具有(you) USB 充電(dian)(dian)選項，并且(qie)都(dou)可提(ti)供高(gao)達 500mA 的(de)充電(dian)(dian)率(lv)。就(jiu)線(xian)性(xing)解決方案而言，由于其效率(lv)較低，可以從(cong) PC USB 傳輸的(de)“電(dian)(dian)能”量就(jiu)被(bei)大大降低，從(cong)而導致了充電(dian)(dian)時間(jian)過長(chang)。

這(zhe)就是開(kai)(kai)(kai)關(guan)(guan)(guan)模(mo)式拓撲有用武之地的(de)(de)原因。開(kai)(kai)(kai)關(guan)(guan)(guan)模(mo)式拓撲的(de)(de)主(zhu)(zhu)要(yao)(yao)優勢在(zai)(zai)于效(xiao)(xiao)率(lv)的(de)(de)提高(gao)。與(yu)線性(xing)穩壓器不(bu)同，電源開(kai)(kai)(kai)關(guan)(guan)(guan)（或多(duo)個開(kai)(kai)(kai)關(guan)(guan)(guan)）在(zai)(zai)飽和的(de)(de)區域內運行(xing)，其大大降低(di)了總體損(sun)耗(hao)。降壓轉換器中(zhong)功率(lv)損(sun)耗(hao)的(de)(de)主(zhu)(zhu)要(yao)(yao)包括開(kai)(kai)(kai)關(guan)(guan)(guan)損(sun)耗(hao)（在(zai)(zai)電源開(kai)(kai)(kai)關(guan)(guan)(guan)中(zhong)）以及(ji)濾(lv)波(bo)電感中(zhong)的(de)(de) DC 損(sun)耗(hao)。根據設計(ji)參數的(de)(de)不(bu)同，在(zai)(zai)這(zhe)些(xie)應用中(zhong)出現效(xiao)(xiao)率(lv)大大高(gao)于 95% 的(de)(de)情況就不(bu)足為奇了。

當人們聽(ting)到開關模(mo)(mo)式這個術(shu)語時大(da)多數人都會想到大(da)型 IC、大(da) PowerFET 以(yi)(yi)及(ji)超(chao)大(da)型電(dian)感! 事實(shi)上，雖然對于處理數十安培電(dian)流的(de)應用(yong)(yong)而言確(que)實(shi)是這樣，但是對于手持設(she)備(bei)的(de)新(xin)一(yi)代解決(jue)(jue)(jue)方(fang)(fang)案而言情況(kuang)就不一(yi)樣了(le)。新(xin)一(yi)代單體鋰(li)離子開關模(mo)(mo)式充(chong)電(dian)器采(cai)用(yong)(yong)了(le)最高(gao)級(ji)別的(de)芯片集成，高(gao)于 1MHz 的(de)使用(yong)(yong)頻(pin)率以(yi)(yi)最小(xiao)化電(dian)感尺寸。圖 1 說明了(le)當今(jin)市場上已開始銷售的(de)此類解決(jue)(jue)(jue)方(fang)(fang)案。該(gai)硅芯片的(de)尺寸不到 4 mm2，其集成了(le)高(gao)側和低側 PowerFET。由于采(cai)用(yong)(yong)了(le) 3MHz 開關頻(pin)率，該(gai)解決(jue)(jue)(jue)方(fang)(fang)案要(yao)求一(yi)個小(xiao)型 1uH 電(dian)感， 其外(wai)形尺寸僅為(wei)：2mm x 2.5mm x 1.2mm (WxLxH)。

充(chong)電(dian)器的選擇

電(dian)池充電(dian)器工具使得設計(ji)人員(yuan)選擇(ze)正確的(de)充電(dian)器的(de)過程(cheng)更輕(qing)松。