引言

便攜(xie)式電(dian)(dian)子設(she)(she)備設(she)(she)計(ji)人員可(ke)以(yi)選擇(ze)(ze)各種各樣的化學技術、充電(dian)(dian)器拓撲以(yi)及充電(dian)(dian)管(guan)理解(jie)決(jue)方案(an)。選擇(ze)(ze)一款最(zui)為(wei)合適的解(jie)決(jue)方案(an)應(ying)該(gai)是(shi)(shi)一項很簡單(dan)的工作，但是(shi)(shi)在大多數(shu)情況下這一過程(cheng)頗為(wei)復雜。設(she)(she)計(ji)人員需要在性能、成本、外形尺(chi)寸以(yi)及其他(ta)關(guan)鍵要求方面找到一個最(zui)佳平衡點。本文(wen)將為(wei)廣大設(she)(she)計(ji)人員和(he)系統工程(cheng)師(shi)提供(gong)一些指導(dao)和(he)幫助以(yi)使(shi)得該(gai)選擇(ze)(ze)工作變得更為(wei)輕松(song)。

以 3 “C”開始實(shi)現充(chong)電控制

所有使用可(ke)充電(dian)電(dian)池的系統設計人員都需(xu)要清楚一些基(ji)礎(chu)設計技(ji)術，以(yi)確保滿足下面三個關鍵的要求：

1、電(dian)池(chi)安(an)全性: 毋(wu)庸(yong)置疑，終端(duan)用戶安(an)全是所有系統(tong)設(she)計中(zhong)最優先考慮(lv)的(de)問題。大多數(shu)鋰(li)離子(zi) (Li-Ion) 電(dian)池(chi)組(zu)和鋰(li)聚合物 (Li-Pol) 電(dian)池(chi)組(zu)都含有保(bao)護電(dian)子(zi)電(dian)路。然而，還有一(yi)些系統(tong)設(she)計需要考慮(lv)的(de)關鍵因素。其(qi)中(zhong)包括但不局限于確保(bao)在鋰(li)離子(zi)電(dian)池(chi)充(chong)電(dian)最后階段期間(jian) ?1% 的(de)穩壓容限、安(an)全處(chu)(chu)理(li)深度放(fang)電(dian)電(dian)池(chi)的(de)預處(chu)(chu)理(li)模(mo)式、安(an)全計時(shi)器以及電(dian)池(chi)溫度監(jian)控。

2、電(dian)池(chi)(chi)容(rong)量：所有的電(dian)池(chi)(chi)充(chong)電(dian)解決方案都要(yao)確保在每一次(ci)和(he)每一個充(chong)電(dian)周(zhou)期(qi)都能將電(dian)池(chi)(chi)容(rong)量充(chong)至(zhi)充(chong)滿(man)狀態(tai)。過早的終止(zhi)充(chong)電(dian)會導致電(dian)池(chi)(chi)運行時間(jian)縮短，這是(shi)當(dang)今高功耗的便攜式設備所不(bu)希望(wang)的。

3、電(dian)池(chi)使用(yong)壽命：遵循建議的充電(dian)算(suan)法是確保終(zhong)端用(yong)戶實現每個電(dian)池(chi)組(zu)最(zui)多充電(dian)周(zhou)期(qi)的重(zhong)要(yao)一(yi)步。利(li)用(yong)電(dian)池(chi)溫度(du)和電(dian)壓限定(ding)每一(yi)次(ci)充電(dian)、預(yu)處理(li)深度(du)放電(dian)電(dian)池(chi)并避免過(guo)晚或非(fei)正常(chang)充電(dian)終(zhong)止是最(zui)大化(hua)電(dian)池(chi)使用(yong)壽命所(suo)必須的一(yi)些(xie)步驟。

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

精(jing)確的電壓和(he)/或電流調節 ? ?

充電限制

（電壓和溫(wen)度） ? ?

溫度監(jian)控 ? ? ?

預處理 ? ? ?

充電結束終止 ? ? ?

充電計時器 ?

充電(dian)狀態報告 ? ?

電(dian)池插入與去(qu)除探測 ?

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(xuan)擇
現在系統設(she)計(ji)人員(yuan)可以在多種電(dian)池(chi)化(hua)學技術(shu)(shu)中進(jin)(jin)行(xing)選(xuan)擇(ze)。設(she)計(ji) 人員(yuan)通常會(hui)根據下面的一些標準進(jin)(jin)行(xing)電(dian)池(chi)化(hua)學技術(shu)(shu)的選(xuan)擇(ze)，其中包括：

? 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(shou)命

近年來，盡管使用鋰離子電(dian)池(chi)(chi)和鋰聚合物電(dian)池(chi)(chi)的趨勢增強，但是 Ni 電(dian)池(chi)(chi)化學(xue)技術仍然是諸多消費(fei)類應用一個(ge)不錯的選項。

無(wu)論選擇何種(zhong)電(dian)(dian)(dian)池(chi)化(hua)學(xue)技(ji)術(shu)，遵循每(mei)一(yi)種(zhong)電(dian)(dian)(dian)池(chi)化(hua)學(xue)技(ji)術(shu)的正(zheng)確充(chong)(chong)電(dian)(dian)(dian)管(guan)理技(ji)術(shu)都(dou)是至關(guan)重要的。這些技(ji)術(shu)將(jiang)確保電(dian)(dian)(dian)池(chi)在每(mei)一(yi)次(ci)和每(mei)個充(chong)(chong)電(dian)(dian)(dian)周期都(dou)能被充(chong)(chong)至最大容量，而不(bu)會降低安全(quan)性或縮短(duan)電(dian)(dian)(dian)池(chi)使用壽(shou)命(ming)。

NiCd / NIMH

在一個充(chong)電(dian)(dian)(dian)(dian)周(zhou)期開始之(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(dui)鎳(nie)鎘 (NiCd) 電(dian)(dian)(dian)(dian)池和(he)(he)鎳(nie)氫 (NiMH) 電(dian)(dian)(dian)(dian)池必須(xu)要進(jin)行(xing)檢驗和(he)(he)調節。如(ru)果(guo)電(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)壓或(huo)溫(wen)(wen)度(du)超(chao)出了允許(xu)的(de)極限是不允許(xu)進(jin)行(xing)快速充(chong)電(dian)(dian)(dian)(dian)的(de)。出于安(an)全考慮，對(dui)所有(you)“熱”電(dian)(dian)(dian)(dian)池（一般高(gao)于 45?C）的(de)充(chong)電(dian)(dian)(dian)(dian)工作都(dou)會暫時終止，直到(dao)電(dian)(dian)(dian)(dian)池冷卻到(dao)正常工作溫(wen)(wen)度(du)范圍內才會再次運(yun)轉。要想(xiang)處理一個“冷”電(dian)(dian)(dian)(dian)池（一般低于 10?C）或(huo)過(guo)度(du)放電(dian)(dian)(dian)(dian)的(de)電(dian)(dian)(dian)(dian)池（每節電(dian)(dian)(dian)(dian)池通常低于 1V），需要施加一個溫(wen)(wen)和(he)(he)的(de)點(dian)滴式電(dian)(dian)(dian)(dian)流。

當電(dian)(dian)(dian)(dian)(dian)(dian)池溫(wen)度(du)和電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)正(zheng)確時快速充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)開(kai)始。通常用 1C 或(huo)更低的(de)(de)恒(heng)定電(dian)(dian)(dian)(dian)(dian)(dian)流對 NiMH 電(dian)(dian)(dian)(dian)(dian)(dian)池進行充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)。一些(xie) NiCd 電(dian)(dian)(dian)(dian)(dian)(dian)池可以用高(gao)達 4C 的(de)(de)速率(lv)進行充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)。采用適當的(de)(de)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)終(zhong)止(zhi)來避(bi)免有害(hai)的(de)(de)過充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)。就鎳基可充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)池而言，快速充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)終(zhong)止(zhi)基于電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)或(huo)溫(wen)度(du)。如圖 1 所示，典型的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)終(zhong)止(zhi)方(fang)法是(shi)峰(feng)值電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)探測(ce)，在峰(feng)值時即每(mei)個電(dian)(dian)(dian)(dian)(dian)(dian)池的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)在 0～-4mV 范圍(wei)內，快速充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)被終(zhong)止(zhi)。基于溫(wen)度(du)的(de)(de)快速充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)終(zhong)止(zhi)方(fang)法是(shi)觀察電(dian)(dian)(dian)(dian)(dian)(dian)池溫(wen)度(du)上升(sheng)率(lv) ?T/?t 來探測(ce)完全充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)。典型的(de)(de) ?T/?t 率(lv)為 1?C/每(mei)分鐘(zhong)。

鋰離子/鋰聚合物電池(chi)
與 NiCd 電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)和 NiMh 電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)相類似(si)，在快速充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)之前盡可能檢驗(yan)并調(diao)節鋰(li)離子電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)。驗(yan)證和處理方法與上(shang)述使用的(de)方法相類似(si)。 驗(yan)證和預處理之后，先(xian)用一個 1C 或更(geng)低的(de)電(dian)(dian)(dian)(dian)(dian)流對(dui)(dui)鋰(li)離子電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)進行充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)，直到電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)達(da)(da)到其(qi)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓(ya)極(ji)限(xian)為止。該充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)階段通常會補(bu)充(chong)(chong)(chong)(chong)高達(da)(da) 70% 的(de)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)容量。然后用一個通常為 4.2V 的(de)恒(heng)定電(dian)(dian)(dian)(dian)(dian)壓(ya)對(dui)(dui)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)進行充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)。為將(jiang)安全性(xing)和電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)容量，必須(xu)要(yao)將(jiang)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)壓(ya)穩定在至少 ?1%。在此(ci)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)期間，電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)汲(ji)取的(de)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流逐漸下降(jiang)。就 1C 充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)率而言，一旦電(dian)(dian)(dian)(dian)(dian)流電(dian)(dian)(dian)(dian)(dian)平下降(jiang)到初始充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流的(de) 10-15% 以下充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)通常就會終(zhong)止.

開(kai)關模式與線性充電拓撲的對比(bi)

傳統(tong)上來說，手持設(she)備都使(shi)用線性充電(dian)拓撲(pu)。該方法具有諸多優勢(shi)：低實施成本、設(she)計(ji)簡(jian)捷以及無高(gao)頻(pin)開關的(de)無噪聲運行(xing)。但是，線性拓撲(pu)會增加(jia)系統(tong)功耗(hao)，尤其是當電(dian)池容量更高(gao)引起的(de)充電(dian)率增加(jia)的(de)時候。如果設(she)計(ji)人員(yuan)無法管理(li)設(she)計(ji)的(de)散熱問題，這就會成為一個主要缺點(dian)。

當 PC USB 端(duan)口(kou)作為電(dian)(dian)源時，則會(hui)出現其他一些(xie)缺(que)點。當今在許多便(bian)攜式設計上(shang)都(dou)具有 USB 充(chong)電(dian)(dian)選(xuan)項，并且(qie)都(dou)可提(ti)供高達 500mA 的(de)充(chong)電(dian)(dian)率。就(jiu)線性解決方案而(er)言(yan)，由(you)于其效率較低(di)(di)，可以從 PC USB 傳(chuan)輸的(de)“電(dian)(dian)能”量就(jiu)被大大降(jiang)低(di)(di)，從而(er)導致了充(chong)電(dian)(dian)時間(jian)過長。

這(zhe)就是開(kai)(kai)(kai)關(guan)模式拓(tuo)撲有用武之(zhi)地的(de)(de)(de)原因。開(kai)(kai)(kai)關(guan)模式拓(tuo)撲的(de)(de)(de)主(zhu)要優勢在于(yu)效率(lv)的(de)(de)(de)提高。與線(xian)性穩壓器(qi)不(bu)同，電源(yuan)開(kai)(kai)(kai)關(guan)（或多個開(kai)(kai)(kai)關(guan)）在飽(bao)和的(de)(de)(de)區域內運行(xing)，其大大降(jiang)低了總體損(sun)耗(hao)(hao)。降(jiang)壓轉換器(qi)中(zhong)功率(lv)損(sun)耗(hao)(hao)的(de)(de)(de)主(zhu)要包括開(kai)(kai)(kai)關(guan)損(sun)耗(hao)(hao)（在電源(yuan)開(kai)(kai)(kai)關(guan)中(zhong)）以(yi)及濾(lv)波電感中(zhong)的(de)(de)(de) DC 損(sun)耗(hao)(hao)。根據設計參數(shu)的(de)(de)(de)不(bu)同，在這(zhe)些(xie)應用中(zhong)出現效率(lv)大大高于(yu) 95% 的(de)(de)(de)情(qing)況就不(bu)足為(wei)奇了。

當人(ren)們聽到(dao)開(kai)關模(mo)式(shi)這(zhe)個(ge)術語時大(da)(da)多數人(ren)都會想到(dao)大(da)(da)型 IC、大(da)(da) PowerFET 以及超大(da)(da)型電感(gan)(gan)! 事實上(shang)，雖然對于(yu)處理數十(shi)安(an)培電流的(de)應用(yong)而(er)言(yan)確實是(shi)這(zhe)樣(yang)，但是(shi)對于(yu)手持設(she)備(bei)的(de)新一(yi)代(dai)(dai)解決方案(an)而(er)言(yan)情況就(jiu)不(bu)一(yi)樣(yang)了(le)。新一(yi)代(dai)(dai)單體鋰離子開(kai)關模(mo)式(shi)充電器采用(yong)了(le)最高(gao)級(ji)別的(de)芯片集成，高(gao)于(yu) 1MHz 的(de)使用(yong)頻率以最小化電感(gan)(gan)尺寸。圖(tu) 1 說明了(le)當今市(shi)場上(shang)已(yi)開(kai)始(shi)銷售的(de)此類(lei)解決方案(an)。該硅芯片的(de)尺寸不(bu)到(dao) 4 mm2，其(qi)集成了(le)高(gao)側和低(di)側 PowerFET。由(you)于(yu)采用(yong)了(le) 3MHz 開(kai)關頻率，該解決方案(an)要求(qiu)一(yi)個(ge)小型 1uH 電感(gan)(gan)， 其(qi)外形(xing)尺寸僅為：2mm x 2.5mm x 1.2mm (WxLxH)。

充電器的選擇

電(dian)池(chi)充(chong)電(dian)器工具使(shi)得設(she)計人員(yuan)選擇正確的充(chong)電(dian)器的過程更輕松。