引言

便攜式電(dian)子設備設計人(ren)員可(ke)以(yi)(yi)選擇各(ge)種各(ge)樣(yang)的化學(xue)技術、充電(dian)器拓撲以(yi)(yi)及充電(dian)管理(li)解決方(fang)案。選擇一(yi)(yi)款最(zui)為合適的解決方(fang)案應(ying)該(gai)是一(yi)(yi)項很簡單的工(gong)作，但是在大(da)多數情況(kuang)下這(zhe)一(yi)(yi)過程(cheng)頗為復雜(za)。設計人(ren)員需要(yao)在性能、成本、外形尺寸以(yi)(yi)及其(qi)他關(guan)鍵要(yao)求方(fang)面找到(dao)一(yi)(yi)個最(zui)佳平衡(heng)點。本文將為廣大(da)設計人(ren)員和(he)系統工(gong)程(cheng)師提供一(yi)(yi)些指導和(he)幫助以(yi)(yi)使(shi)得該(gai)選擇工(gong)作變得更為輕松。

以(yi) 3 “C”開(kai)始(shi)實現充電控制(zhi)

所有使用可(ke)充電(dian)電(dian)池的系統設計人員都(dou)需要清(qing)楚一些基礎設計技術，以確保(bao)滿足下面三(san)個關鍵(jian)的要求：

1、電(dian)(dian)池(chi)(chi)安(an)(an)全性: 毋庸置疑(yi)，終端用戶安(an)(an)全是(shi)所有(you)系(xi)(xi)統設計中最(zui)優先考(kao)慮的問題。大多數鋰離(li)子 (Li-Ion) 電(dian)(dian)池(chi)(chi)組(zu)和鋰聚(ju)合物 (Li-Pol) 電(dian)(dian)池(chi)(chi)組(zu)都含有(you)保護電(dian)(dian)子電(dian)(dian)路。然而，還有(you)一些系(xi)(xi)統設計需要考(kao)慮的關鍵(jian)因素(su)。其中包括(kuo)但不局限于確(que)保在鋰離(li)子電(dian)(dian)池(chi)(chi)充(chong)電(dian)(dian)最(zui)后(hou)階段期間 ?1% 的穩壓容限、安(an)(an)全處理深度放電(dian)(dian)電(dian)(dian)池(chi)(chi)的預(yu)處理模式、安(an)(an)全計時器以(yi)及(ji)電(dian)(dian)池(chi)(chi)溫度監控。

2、電(dian)(dian)(dian)池(chi)容(rong)量(liang)：所(suo)有的電(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)解決方案都(dou)要(yao)確(que)保在每一(yi)次和每一(yi)個充(chong)電(dian)(dian)(dian)周期都(dou)能將電(dian)(dian)(dian)池(chi)容(rong)量(liang)充(chong)至充(chong)滿狀態。過早的終止充(chong)電(dian)(dian)(dian)會導(dao)致電(dian)(dian)(dian)池(chi)運行時間縮短，這是當今高功耗的便攜(xie)式設備所(suo)不希望的。

3、電(dian)(dian)(dian)池(chi)使用(yong)壽命：遵循建議的(de)(de)充電(dian)(dian)(dian)算法是確(que)保終端用(yong)戶實現每個電(dian)(dian)(dian)池(chi)組(zu)最多充電(dian)(dian)(dian)周期的(de)(de)重要(yao)一步。利(li)用(yong)電(dian)(dian)(dian)池(chi)溫度和電(dian)(dian)(dian)壓限定每一次充電(dian)(dian)(dian)、預處理深度放電(dian)(dian)(dian)電(dian)(dian)(dian)池(chi)并避免過晚或非正常充電(dian)(dian)(dian)終止是最大化電(dian)(dian)(dian)池(chi)使用(yong)壽命所(suo)必須的(de)(de)一些步驟。

充電(dian)特性(xing)(xing) 電(dian)池安全性(xing)(xing) 電(dian)池容量 電(dian)池使用壽命

精確的電(dian)壓和(he)/或電(dian)流(liu)調節 ? ?

充電限制

（電壓和(he)溫度） ? ?

溫度監控(kong) ? ? ?

預處理 ? ? ?

充電結束終(zhong)止 ? ? ?

充電計時器 ?

充電狀態報告 ? ?

電池(chi)插入與(yu)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(shu)的選擇(ze)
現(xian)在系統(tong)設(she)計人員可(ke)以在多(duo)種電池化學技(ji)(ji)術中(zhong)進行(xing)選擇。設(she)計 人員通常會根據下面的一些標準進行(xing)電池化學技(ji)(ji)術的選擇，其中(zhong)包(bao)括(kuo)：

? 能量密度

? 規格和外形尺寸

? 成本

? 使用模(mo)式(shi)和使用壽命

近年來，盡管使用鋰離子電池(chi)和鋰聚合(he)物電池(chi)的(de)趨勢增強，但是 Ni 電池(chi)化學(xue)技術仍(reng)然是諸多消費類應用一個(ge)不錯的(de)選項。

無論選擇何種電(dian)池(chi)化學(xue)技術(shu)，遵循(xun)每一種電(dian)池(chi)化學(xue)技術(shu)的正確充(chong)電(dian)管理技術(shu)都(dou)是至(zhi)關(guan)重要的。這些技術(shu)將確保電(dian)池(chi)在每一次和每個充(chong)電(dian)周期(qi)都(dou)能被充(chong)至(zhi)最大容量(liang)，而不會降(jiang)低安全性(xing)或縮短電(dian)池(chi)使用壽命。

NiCd / NIMH

在一個充(chong)(chong)電(dian)周期開(kai)(kai)始之(zhi)前(qian)(qian)，并且盡可能在開(kai)(kai)始快(kuai)速(su)充(chong)(chong)電(dian)之(zhi)前(qian)(qian)對(dui)鎳鎘 (NiCd) 電(dian)池和(he)鎳氫 (NiMH) 電(dian)池必須(xu)要進行檢驗和(he)調節(jie)。如果電(dian)池電(dian)壓或溫度超出(chu)了(le)允許(xu)的(de)(de)極限是不允許(xu)進行快(kuai)速(su)充(chong)(chong)電(dian)的(de)(de)。出(chu)于(yu)安全考慮，對(dui)所有“熱”電(dian)池（一般高于(yu) 45?C）的(de)(de)充(chong)(chong)電(dian)工作都會暫時終(zhong)止，直到(dao)電(dian)池冷(leng)卻到(dao)正常工作溫度范圍內才會再(zai)次運轉(zhuan)。要想處理一個“冷(leng)”電(dian)池（一般低于(yu) 10?C）或過度放電(dian)的(de)(de)電(dian)池（每(mei)節(jie)電(dian)池通(tong)常低于(yu) 1V），需要施加(jia)一個溫和(he)的(de)(de)點滴式電(dian)流(liu)。

當電(dian)(dian)(dian)(dian)池溫度(du)和電(dian)(dian)(dian)(dian)壓(ya)正確(que)時快(kuai)速(su)(su)充(chong)(chong)電(dian)(dian)(dian)(dian)開始。通常用(yong) 1C 或更低的(de)(de)恒定電(dian)(dian)(dian)(dian)流(liu)對 NiMH 電(dian)(dian)(dian)(dian)池進行(xing)充(chong)(chong)電(dian)(dian)(dian)(dian)。一(yi)些 NiCd 電(dian)(dian)(dian)(dian)池可以用(yong)高達 4C 的(de)(de)速(su)(su)率(lv)(lv)(lv)進行(xing)充(chong)(chong)電(dian)(dian)(dian)(dian)。采用(yong)適當的(de)(de)充(chong)(chong)電(dian)(dian)(dian)(dian)終止來(lai)避免(mian)有(you)害的(de)(de)過充(chong)(chong)電(dian)(dian)(dian)(dian)。就鎳基(ji)可充(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)池而言，快(kuai)速(su)(su)充(chong)(chong)電(dian)(dian)(dian)(dian)終止基(ji)于電(dian)(dian)(dian)(dian)壓(ya)或溫度(du)。如圖(tu) 1 所示，典型的(de)(de)電(dian)(dian)(dian)(dian)壓(ya)終止方(fang)法(fa)是峰值電(dian)(dian)(dian)(dian)壓(ya)探(tan)測，在(zai)峰值時即每(mei)個(ge)電(dian)(dian)(dian)(dian)池的(de)(de)電(dian)(dian)(dian)(dian)壓(ya)在(zai) 0～-4mV 范圍內，快(kuai)速(su)(su)充(chong)(chong)電(dian)(dian)(dian)(dian)被終止。基(ji)于溫度(du)的(de)(de)快(kuai)速(su)(su)充(chong)(chong)電(dian)(dian)(dian)(dian)終止方(fang)法(fa)是觀察(cha)電(dian)(dian)(dian)(dian)池溫度(du)上升率(lv)(lv)(lv) ?T/?t 來(lai)探(tan)測完全充(chong)(chong)電(dian)(dian)(dian)(dian)。典型的(de)(de) ?T/?t 率(lv)(lv)(lv)為 1?C/每(mei)分(fen)鐘。

鋰(li)離子/鋰(li)聚合物電池
與 NiCd 電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池和(he) NiMh 電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池相類似，在(zai)快(kuai)速充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)之(zhi)前(qian)盡可能檢驗(yan)(yan)并(bing)調節鋰離子(zi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池。驗(yan)(yan)證和(he)處(chu)理方(fang)(fang)法與上述使(shi)用(yong)的(de)方(fang)(fang)法相類似。 驗(yan)(yan)證和(he)預(yu)處(chu)理之(zhi)后(hou)，先用(yong)一個 1C 或更低的(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)對鋰離子(zi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池進(jin)行(xing)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，直到(dao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池達到(dao)其充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)極(ji)限為止。該充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)階段通(tong)常會補充(chong)(chong)(chong)(chong)(chong)高達 70% 的(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池容(rong)量(liang)。然后(hou)用(yong)一個通(tong)常為 4.2V 的(de)恒定電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)對電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池進(jin)行(xing)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。為將(jiang)安(an)全性(xing)和(he)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池容(rong)量(liang)，必須要將(jiang)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)穩(wen)定在(zai)至少 ?1%。在(zai)此充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)期間，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池汲取(qu)的(de)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)逐漸下降。就 1C 充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)率而言，一旦電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平下降到(dao)初(chu)始充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)的(de) 10-15% 以下充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)通(tong)常就會終止.

開關(guan)模式與線(xian)性充(chong)電拓撲的對比(bi)

傳統上來說，手持設備都(dou)使用線(xian)性(xing)充電拓撲。該方法具有諸多優勢：低實施(shi)成(cheng)本、設計簡捷以及無(wu)高頻開關的(de)無(wu)噪聲運行。但(dan)是，線(xian)性(xing)拓撲會(hui)增(zeng)(zeng)加系(xi)統功耗，尤其是當電池容量(liang)更(geng)高引起的(de)充電率增(zeng)(zeng)加的(de)時候(hou)。如果設計人員無(wu)法管理設計的(de)散(san)熱問題，這就會(hui)成(cheng)為一個主(zhu)要缺(que)點。

當(dang) PC USB 端(duan)口作(zuo)為電源(yuan)時(shi)，則會出現其他一些缺點。當(dang)今在許(xu)多便攜(xie)式設計上都具(ju)有(you) USB 充電選項(xiang)，并且都可提供高達 500mA 的(de)充電率。就(jiu)(jiu)線性解決方案而(er)言，由于(yu)其效率較低，可以從(cong) PC USB 傳輸的(de)“電能”量就(jiu)(jiu)被大大降低，從(cong)而(er)導致了充電時(shi)間過長。

這就是開(kai)(kai)(kai)關(guan)(guan)(guan)(guan)模(mo)式拓(tuo)撲有用武(wu)之地的(de)(de)(de)原因。開(kai)(kai)(kai)關(guan)(guan)(guan)(guan)模(mo)式拓(tuo)撲的(de)(de)(de)主要(yao)優勢在(zai)于效(xiao)率(lv)的(de)(de)(de)提(ti)高。與線性穩壓器不同，電(dian)源開(kai)(kai)(kai)關(guan)(guan)(guan)(guan)（或多個開(kai)(kai)(kai)關(guan)(guan)(guan)(guan)）在(zai)飽和的(de)(de)(de)區域(yu)內運行(xing)，其大(da)大(da)降低(di)了總體(ti)損耗。降壓轉換器中功(gong)率(lv)損耗的(de)(de)(de)主要(yao)包括開(kai)(kai)(kai)關(guan)(guan)(guan)(guan)損耗（在(zai)電(dian)源開(kai)(kai)(kai)關(guan)(guan)(guan)(guan)中）以及濾波電(dian)感中的(de)(de)(de) DC 損耗。根據設計參(can)數的(de)(de)(de)不同，在(zai)這些應用中出現效(xiao)率(lv)大(da)大(da)高于 95% 的(de)(de)(de)情況就不足(zu)為奇了。

當(dang)人(ren)們聽到開(kai)(kai)關(guan)模式這個(ge)術(shu)語時大(da)多數人(ren)都會想(xiang)到大(da)型(xing) IC、大(da) PowerFET 以(yi)及超大(da)型(xing)電(dian)感(gan)! 事(shi)實上(shang)，雖然(ran)對于處理數十安(an)培電(dian)流的(de)(de)應用(yong)而言確(que)實是這樣(yang)，但是對于手(shou)持設備(bei)的(de)(de)新(xin)一(yi)代解(jie)(jie)決(jue)方案而言情況就(jiu)不(bu)一(yi)樣(yang)了(le)(le)。新(xin)一(yi)代單體鋰離(li)子(zi)開(kai)(kai)關(guan)模式充電(dian)器采(cai)用(yong)了(le)(le)最(zui)高(gao)級(ji)別的(de)(de)芯(xin)(xin)片集成，高(gao)于 1MHz 的(de)(de)使用(yong)頻率以(yi)最(zui)小化電(dian)感(gan)尺寸(cun)。圖(tu) 1 說明了(le)(le)當(dang)今市場上(shang)已開(kai)(kai)始銷售的(de)(de)此類解(jie)(jie)決(jue)方案。該(gai)硅芯(xin)(xin)片的(de)(de)尺寸(cun)不(bu)到 4 mm2，其集成了(le)(le)高(gao)側(ce)和低側(ce) PowerFET。由于采(cai)用(yong)了(le)(le) 3MHz 開(kai)(kai)關(guan)頻率，該(gai)解(jie)(jie)決(jue)方案要求一(yi)個(ge)小型(xing) 1uH 電(dian)感(gan)， 其外形尺寸(cun)僅為：2mm x 2.5mm x 1.2mm (WxLxH)。

充電(dian)器的選擇

電(dian)池充電(dian)器工具使得設計(ji)人(ren)員選擇(ze)正確(que)的充電(dian)器的過(guo)程更輕(qing)松。