單體鋰離子 （Li-Ion） 電池充電器的選項有很多種。隨著手持設備業務的不斷發展，對電池充電器的要求也不斷增加。要為完成這項工作而選擇正確的集成電路 （IC），我們必須權衡幾個因素。在開始設計以前，我們必須考慮諸如解決方案尺寸、USB標準、充電速率和成本等因素。必須將這些因素按照重要程度依次排列，然后選擇相應的充電器IC。本文中，我們將介紹不同的充電拓撲結構，并研究電池充電器IC的(de)一些(xie)特性。此外，我們還將探討一個(ge)應用和現(xian)有的(de)解決方案。

　　鋰離子電池充電周期

　　鋰離子電池要求(qiu)專門的充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)周期，以實(shi)現安(an)全(quan)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)并(bing)最(zui)大(da)化電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)使用(yong)時(shi)(shi)間。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)分(fen)兩(liang)個階段：恒定電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu) （CC） 和(he)恒定電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya) （CV）。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)位于完全(quan)充(chong)(chong)滿電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)以下(xia)(xia)時(shi)(shi)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)經過穩(wen)(wen)壓(ya)(ya)(ya)進入電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)。在CC模式下(xia)(xia)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)經過穩(wen)(wen)壓(ya)(ya)(ya)達到(dao)兩(liang)個值之一(yi)。如果電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)非(fei)常低，則(ze)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)降低至(zhi)預(yu)(yu)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平，以適應(ying)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)并(bing)防(fang)止(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)損(sun)壞。該閾(yu)值因(yin)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)化學屬性(xing)而不(bu)同(tong)，一(yi)般(ban)取決于電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)制造(zao)廠(chang)商。一(yi)旦電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)升(sheng)至(zhi)預(yu)(yu)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)閾(yu)值以上(shang)，充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)便升(sheng)至(zhi)快速(su)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平。典型(xing)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)的最(zui)大(da)建議快速(su)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)為1C（C=1 小時(shi)(shi)內耗(hao)盡電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)所需的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)），但該電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)也取決地電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)制造(zao)廠(chang)商。典型(xing)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)為~0.8C，目的是最(zui)大(da)化電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)使用(yong)時(shi)(shi)間。對(dui)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)時(shi)(shi)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)上(shang)升(sheng)。一(yi)旦電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)升(sheng)至(zhi)穩(wen)(wen)壓(ya)(ya)(ya)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)（一(yi)般(ban)為4.2V），充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)逐漸減(jian)少，同(tong)時(shi)(shi)對(dui)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)進行穩(wen)(wen)壓(ya)(ya)(ya)以防(fang)止(zhi)過充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。在這(zhe)種模式下(xia)(xia)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)時(shi)(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)逐漸減(jian)少，同(tong)時(shi)(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)阻抗降低。如果電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)降至(zhi)預(yu)(yu)定電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平（一(yi)般(ban)為快速(su)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)的10%），則(ze)終止(zhi)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。我們一(yi)般(ban)不(bu)對(dui)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)浮(fu)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，因(yin)為這(zhe)樣會縮短電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)使用(yong)壽(shou)命(ming)。圖1 以圖形方式說明了(le)典型(xing)的充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)周期。

　　圖1典型鋰離子充電周期

　　線性解決方(fang)案與開(kai)關模式解決方(fang)案對(dui)比(bi)

　　將適(shi)配器電(dian)壓轉降(jiang)為電(dian)池電(dian)壓并(bing)控制不(bu)同(tong)充電(dian)階段的(de)拓撲結構(gou)有兩種(zhong)(zhong)：線(xian)性穩壓器和電(dian)感(gan)開關。這(zhe)兩種(zhong)(zhong)拓撲結構(gou)在體積、效率、解決(jue)方案成本和電(dian)磁干(gan)擾 （EMI） 輻射方面(mian)各(ge)有優(you)缺點(dian)。我們下(xia)面(mian)介紹(shao)這(zhe)兩種(zhong)(zhong)拓撲結構(gou)的(de)各(ge)種(zhong)(zhong)優(you)點(dian)和一些(xie)折(zhe)中方法。

　　一(yi)般來說，電(dian)(dian)感(gan)(gan)開關(guan)是獲(huo)得最(zui)(zui)高效(xiao)率(lv)的(de)最(zui)(zui)佳選擇。利用電(dian)(dian)阻(zu)器等檢(jian)測(ce)組件(jian)，在(zai)輸出(chu)(chu)端(duan)檢(jian)測(ce)充電(dian)(dian)電(dian)(dian)流(liu)(liu)。充電(dian)(dian)器在(zai)CC 模式(shi)下時，電(dian)(dian)流(liu)(liu)反(fan)饋(kui)(kui)電(dian)(dian)路(lu)(lu)控制占空(kong)比。電(dian)(dian)池電(dian)(dian)壓檢(jian)測(ce)反(fan)饋(kui)(kui)電(dian)(dian)路(lu)(lu)控制CV 模式(shi)下的(de)占空(kong)比。根據特性(xing)集的(de)不(bu)同，可(ke)能會(hui)出(chu)(chu)現其他一(yi)些(xie)控制環路(lu)(lu)。我(wo)們(men)將在(zai)后面(mian)詳(xiang)細討論(lun)這些(xie)環路(lu)(lu)。電(dian)(dian)感(gan)(gan)開關(guan)電(dian)(dian)路(lu)(lu)要求開關(guan)組件(jian)、整(zheng)流(liu)(liu)器、電(dian)(dian)感(gan)(gan)和輸入(ru)及輸出(chu)(chu)電(dian)(dian)容(rong)器。就許多應用而言，通過選擇一(yi)種將開關(guan)組件(jian)和整(zheng)流(liu)(liu)器都嵌入(ru)到(dao)(dao)IC 中的(de)器件(jian)，可(ke)以(yi)縮小解決方(fang)案的(de)尺(chi)寸。根據不(bu)同的(de)負載，這些(xie)電(dian)(dian)路(lu)(lu)的(de)典(dian)型效(xiao)率(lv)為(wei)80% 到(dao)(dao)96%。開關(guan)轉換(huan)器因其電(dian)(dian)感(gan)(gan)尺(chi)寸一(yi)般會(hui)要求更多的(de)空(kong)間，同時也更加昂貴。開關(guan)轉換(huan)器還會(hui)引(yin)起電(dian)(dian)感(gan)(gan)EMI 輻射，以(yi)及開關(guan)帶來的(de)輸出(chu)(chu)端(duan)噪聲。

　　線性充電器通過降低(di)旁路組(zu)件(jian)的(de)輸(shu)(shu)入(ru)(ru)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)，降低(di)DC 電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)。這樣(yang)做的(de)好處(chu)是解決(jue)(jue)方(fang)(fang)案(an)只要(yao)求三(san)個(ge)組(zu)件(jian)：旁路組(zu)件(jian)和輸(shu)(shu)入(ru)(ru)/輸(shu)(shu)出電(dian)(dian)(dian)(dian)(dian)(dian)容。相比(bi)電(dian)(dian)(dian)(dian)(dian)(dian)感(gan)開關，線性壓(ya)(ya)(ya)降穩(wen)壓(ya)(ya)(ya)器 （LDO） 通常為一款低(di)成(cheng)本的(de)解決(jue)(jue)方(fang)(fang)案(an)，且噪聲更低(di)。通過穩(wen)壓(ya)(ya)(ya)旁路組(zu)件(jian)的(de)電(dian)(dian)(dian)(dian)(dian)(dian)阻來(lai)(lai)限制進入(ru)(ru)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)的(de)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)，從(cong)而對(dui)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)進行控制。電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)反(fan)饋一般來(lai)(lai)自充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器IC 的(de)輸(shu)(shu)入(ru)(ru)。對(dui)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)進行檢測，以提供(gong)CV 反(fan)饋。改變旁路組(zu)件(jian)的(de)電(dian)(dian)(dian)(dian)(dian)(dian)阻，來(lai)(lai)維持進入(ru)(ru)IC 輸(shu)(shu)入(ru)(ru)端(duan)的(de)恒定電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)或者(zhe)恒定電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)。器件(jian)的(de)輸(shu)(shu)入(ru)(ru)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)等于(yu)負載電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)。這就是說解決(jue)(jue)方(fang)(fang)案(an)的(de)效(xiao)率等于(yu)輸(shu)(shu)出電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)與輸(shu)(shu)入(ru)(ru)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)的(de)比(bi)。LDO 解決(jue)(jue)方(fang)(fang)案(an)的(de)缺點是高輸(shu)(shu)入(ru)(ru)輸(shu)(shu)出電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)比(bi)時(shi)（即低(di)電(dian)(dian)(dian)(dian)(dian)(dian)量情況）效(xiao)率較低(di)。所有功(gong)率都(dou)被旁路組(zu)件(jian)消耗，其(qi)意味著LDO 并(bing)非那(nei)些(xie)輸(shu)(shu)入(ru)(ru)輸(shu)(shu)出差(cha)較大的(de)高充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)應用的(de)理想選(xuan)擇。這些(xie)高功(gong)耗應用要(yao)求散熱，從(cong)而增加了解決(jue)(jue)方(fang)(fang)案(an)的(de)尺寸。

　　功耗及溫升計算

　　其中，η為充電器的效率，而POUT = VOUT × IOUT。利用熱阻，可以計算得到功耗帶來的溫升。每種應用的熱阻都不同，其取決于電路板布局、氣流和封裝等具體參數。我們應該針對終端應用電路板對熱阻建模。請記住，產品說明書中定義的ΘJA 并非這種應用中熱阻的恰當表示方法。

   應該(gai)使(shi)用什么樣的拓(tuo)撲？

　　您需要研究的第一個參數是充電電流。對于一些小型應用來說，例如：充電電流介于25Ma 到150mA 之間的藍牙TM耳機等，最佳解決方案幾乎都是線性充電器。這些應用一般都具有非常小的體積，無法為開關的更多組件提供額外空間。另外，由于其非常低的功耗要求，功耗帶來的溫升可以忽略不計。對于手機應用來說，充電電流一般在350-700mA 范圍以內。在這種范圍中，很多時候線性解決方案仍然非常有效。由于它們通常都為低成本手機，其成本壓力更大，因此線性充電器便成為一種理想的解決方案。智能手機應用的電池體積較大，且充電電流需求大于1.5A，這時使用開關解決方案則更加合理。1.5A 電流條件下，溫升會非常大。例如，使用一個線性充電器通過5V 適配器對一塊3.6V 電池充電時(shi)，效(xiao)(xiao)率為(wei)72%。首先，這(zhe)(zhe)(zhe)個(ge)(ge)效(xiao)(xiao)率聽起來(lai)(lai)(lai)似(si)乎不(bu)太壞。如果(guo)您從功(gong)耗(hao)的(de)(de)角度(du)(du)來(lai)(lai)(lai)看(kan)它，這(zhe)(zhe)(zhe)種應用(yong)要消(xiao)耗(hao)約2W。在一個(ge)(ge)熱(re)阻(zu) （ΘJA） 為(wei)40°C/W 的(de)(de)應用(yong)中，芯片溫(wen)度(du)(du)上(shang)升(sheng)80°C。在40°C 環(huan)境(jing)溫(wen)度(du)(du)下，電路板溫(wen)度(du)(du)會(hui)上(shang)升(sheng)至120°C，其對手(shou)持設備(bei)來(lai)(lai)(lai)說是(shi)不(bu)可(ke)接受(shou)的(de)(de)。在極(ji)低(di)(di)電池電壓（即3 V）下，這(zhe)(zhe)(zhe)一問(wen)題甚至會(hui)變得極(ji)端嚴重。相同(tong)3V 條件下，溫(wen)度(du)(du)升(sheng)至120°C。讓我們來(lai)(lai)(lai)看(kan)相同(tong)條件下的(de)(de)開(kai)(kai)關(guan)(guan)解(jie)決方案，使用(yong)一個(ge)(ge)單體電池IC 充電器時(shi)，效(xiao)(xiao)率上(shang)升(sheng)至約85%。使用(yong)一塊3.6V 電池時(shi)，功(gong)耗(hao)低(di)(di)于1W，從而帶來(lai)(lai)(lai)40°C 的(de)(de)溫(wen)升(sheng)。3V 時(shi)這(zhe)(zhe)(zhe)種改善更加(jia)明顯。假設3V 輸出時(shi)的(de)(de)效(xiao)(xiao)率為(wei)80%，則功(gong)耗(hao)低(di)(di)于800 mW，因此溫(wen)升(sheng)會(hui)更低(di)(di)（約32°C）。這(zhe)(zhe)(zhe)些智能手(shou)機的(de)(de)體積(ji)一般(ban)可(ke)以(yi)容許(xu)稍(shao)大一點的(de)(de)解(jie)決方案，并且能夠承受(shou)開(kai)(kai)關(guan)(guan)模式解(jie)決方案相關(guan)(guan)的(de)(de)稍(shao)許(xu)成本增(zeng)加(jia)。

　　為任務選擇正確的IC

　　在(zai)您已經完成您的初步熱分析并(bing)且(qie)選(xuan)好充(chong)電(dian)(dian)器(qi)(qi)拓撲以(yi)后(hou)，您便(bian)可以(yi)轉到(dao)(dao)選(xuan)擇應用的最佳IC 上來(lai)。新型的電(dian)(dian)池充(chong)電(dian)(dian)器(qi)(qi)解決方案集(ji)成了許多特性，可以(yi)利用它(ta)們改(gai)善系統(tong)的性能。諸如輸(shu)入過(guo)壓保(bao)護、電(dian)(dian)源路徑管(guan)理(li) （PPM）、VIN_DPM、散熱穩壓、負(fu)溫度系數熱敏電(dian)(dian)阻 （NTC） 監測(ce)和USB 充(chong)電(dian)(dian)等特性，都被集(ji)成到(dao)(dao)許多電(dian)(dian)池充(chong)電(dian)(dian)器(qi)(qi)IC 中(zhong)。大多數單體(ti)電(dian)(dian)池充(chong)電(dian)(dian)器(qi)(qi)解決方案都已將要(yao)求(qiu)FET 集(ji)成到(dao)(dao)了器(qi)(qi)件中(zhong)，旨(zhi)在(zai)節(jie)省電(dian)(dian)路板面積。

　　輸入(ru)過壓保(bao)護(hu)（單輸入(ru)與雙輸入(ru)對比）

　　在當今的(de)(de)市場(chang)(chang)(chang)上，USB 電(dian)(dian)(dian)源(yuan)已(yi)(yi)經(jing)成為最為常見的(de)(de)電(dian)(dian)(dian)源(yuan)，因此通過(guo)(guo)USB 電(dian)(dian)(dian)源(yuan)充電(dian)(dian)(dian)已(yi)(yi)經(jing)成為一(yi)(yi)種(zhong)(zhong)必然(ran)性。市場(chang)(chang)(chang)已(yi)(yi)經(jing)從(cong)使(shi)用(yong)專門AC 適(shi)配器和單(dan)(dan)獨USB 接(jie)(jie)口(kou)的(de)(de)初始雙輸(shu)(shu)入(ru)(ru)(ru)(ru)轉變為將一(yi)(yi)個USB 接(jie)(jie)口(kou)既作為墻上電(dian)(dian)(dian)源(yuan)適(shi)合器接(jie)(jie)口(kou)使(shi)用(yong)，也作為使(shi)用(yong)相同線纜的(de)(de)USB 數據輸(shu)(shu)入(ru)(ru)(ru)(ru)接(jie)(jie)口(kou)的(de)(de)單(dan)(dan)輸(shu)(shu)入(ru)(ru)(ru)(ru)解(jie)決方(fang)案(an)。這(zhe)樣便導(dao)致一(yi)(yi)種(zhong)(zhong)從(cong)雙輸(shu)(shu)入(ru)(ru)(ru)(ru)解(jie)決方(fang)案(an)向單(dan)(dan)輸(shu)(shu)入(ru)(ru)(ru)(ru)解(jie)決方(fang)案(an)的(de)(de)轉移(yi)。單(dan)(dan)輸(shu)(shu)入(ru)(ru)(ru)(ru)在接(jie)(jie)口(kou)方(fang)面存(cun)在許多(duo)挑戰。由于存(cun)在如此多(duo)的(de)(de)配件(jian)市場(chang)(chang)(chang)適(shi)配器解(jie)決方(fang)案(an)和一(yi)(yi)種(zhong)(zhong)通用(yong)接(jie)(jie)口(kou)，輸(shu)(shu)入(ru)(ru)(ru)(ru)端必須要能夠在無(wu)損(sun)壞的(de)(de)情況下(xia)承受(shou)更(geng)高(gao)的(de)(de)電(dian)(dian)(dian)壓(ya)(ya)。由于電(dian)(dian)(dian)池(chi)充電(dian)(dian)(dian)器始終(zhong)連接(jie)(jie)到(dao)輸(shu)(shu)入(ru)(ru)(ru)(ru)端，因此充電(dian)(dian)(dian)器對(dui)所有下(xia)游(you)電(dian)(dian)(dian)路實施過(guo)(guo)電(dian)(dian)(dian)壓(ya)(ya)狀態保護(hu)是有道理的(de)(de)。為了(le)實施這(zhe)一(yi)(yi)功能，市場(chang)(chang)(chang)上出現了(le)許多(duo)能夠承受(shou)20V 甚至30V 電(dian)(dian)(dian)壓(ya)(ya)的(de)(de)解(jie)決方(fang)案(an)。另外，這(zhe)些器件(jian)都具(ju)有過(guo)(guo)電(dian)(dian)(dian)壓(ya)(ya)保護(hu) （OVP） 電(dian)(dian)(dian)路，其在輸(shu)(shu)入(ru)(ru)(ru)(ru)超出OVP 閾值(zhi)時阻止器件(jian)運行。這(zhe)樣便進(jin)一(yi)(yi)步(bu)保護(hu)了(le)下(xia)游(you)電(dian)(dian)(dian)路，使(shi)其免受(shou)潛(qian)在的(de)(de)瞬態過(guo)(guo)電(dian)(dian)(dian)壓(ya)(ya)狀態損(sun)壞。

　　目前，隨著綠色(se)輸入（即太陽能(neng)電池）或(huo)無線充電的出(chu)現，應用(yong)又(you)再一次向(xiang)雙輸入要求(qiu)轉移。根據具體(ti)的應用(yong)要求(qiu)，兩(liang)種配置結構都可以(yi)使用(yong)。

　　電(dian)源路徑管理/最小系統(tong)電(dian)壓

　　電池充電器的一般方法是將系統直接連接到電池，讓充電器同時為電池和系統供電。然后，對系統的總電流進行穩壓，這樣做存在幾個問題。特別是低電池電量啟動、終止干擾和早期計時器超時等問題。電源路徑管理通過對電池電流和系統電流進行分別(bie)監測，消除(chu)了這(zhe)些問題［2］。

　　圖 2 傳統拓撲結構舉例

　　圖 3 電源(yuan)路徑拓撲結構舉(ju)例

　　最低系統電壓

　　使用傳統方法時，系統電壓始終與電池相同。因此，電池深度放電時，在電池充電到某個可用電平以前系統都不會啟動。利用PPM，可對系統電壓單獨穩壓，將其與電池電壓區分開來。這就意味著可以實現最低系統電壓，其與電池電壓無關。對用戶而言，這就意味著連接適配器的同時他們便可以使用設備，假設條件是其具有足夠的功率來驅動系統。如bq25060 等器件就具有這種功能。

   更短的充電時間

　　由于系(xi)統(tong)(tong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)和(he)(he)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)是單獨編程的，因此可以使(shi)(shi)用(yong)(yong)適配器(qi)的滿功(gong)率，其與電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池的容量和(he)(he)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)的大小(xiao)均無關(guan)。傳統(tong)(tong)拓撲結構中，充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)的輸出(chu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)必須設定為(wei)最大充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)，以應對沒有系(xi)統(tong)(tong)負(fu)載(zai)的情況。當系(xi)統(tong)(tong)中有負(fu)載(zai)時，由于系(xi)統(tong)(tong)吸收(shou)可用(yong)(yong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)，有效充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)降低(di)。例如(ru)，一(yi)個(ge)使(shi)(shi)用(yong)(yong)900 mA 適配器(qi)和(he)(he)500 mAhr 電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池的系(xi)統(tong)(tong)，使(shi)(shi)用(yong)(yong)傳統(tong)(tong)方法可以編程500 mA 的充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)。如(ru)果(guo)系(xi)統(tong)(tong)負(fu)載(zai)為(wei)200 mA，有效充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)僅(jin)為(wei)300 mA，充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)時間幾(ji)乎翻了一(yi)翻。如(ru)果(guo)使(shi)(shi)用(yong)(yong)PPM 來(lai)研究(jiu)這一(yi)相同案(an)例，輸入電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)限制(zhi)設定為(wei)900 mA。這樣便(bian)允許全部500 mA充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)，且(qie)擁有多達400 mA 的額外(wai)系(xi)統(tong)(tong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)。

　　終止和早期計時器超時

　　在(zai)對總電(dian)(dian)(dian)(dian)流(liu)(liu)進(jin)行(xing)穩(wen)壓的傳(chuan)統(tong)系(xi)統(tong)中，電(dian)(dian)(dian)(dian)流(liu)(liu)在(zai)電(dian)(dian)(dian)(dian)池和負(fu)載(zai)(zai)之間共用。如果(guo)系(xi)統(tong)負(fu)載(zai)(zai)足夠大到從電(dian)(dian)(dian)(dian)池拉取充(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)，且在(zai)計(ji)(ji)時(shi)(shi)(shi)器(qi)(qi)超(chao)時(shi)(shi)(shi)以(yi)前電(dian)(dian)(dian)(dian)池不充(chong)(chong)電(dian)(dian)(dian)(dian)，則計(ji)(ji)時(shi)(shi)(shi)器(qi)(qi)會出現(xian)偽超(chao)時(shi)(shi)(shi)。另外，如果(guo)系(xi)統(tong)電(dian)(dian)(dian)(dian)流(liu)(liu)絕對不會降至設(she)定(ding)終(zhong)止(zhi)(zhi)(zhi)電(dian)(dian)(dian)(dian)流(liu)(liu)以(yi)下，則永(yong)遠不會終(zhong)止(zhi)(zhi)(zhi)。電(dian)(dian)(dian)(dian)源路徑(jing)管(guan)理(li)通(tong)過(guo)單獨監測(ce)充(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)，并動態(tai)地使用可穩(wen)壓計(ji)(ji)時(shi)(shi)(shi)器(qi)(qi)（通(tong)過(guo)減少充(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)進(jin)行(xing)穩(wen)壓），防止(zhi)(zhi)(zhi)這些條件出現(xian)。就(jiu)終(zhong)止(zhi)(zhi)(zhi)問(wen)題而言，單獨對充(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)進(jin)行(xing)監測(ce)，可讓(rang)終(zhong)止(zhi)(zhi)(zhi)條件測(ce)定(ding)變得容易(yi)。

　　基于(yu)輸(shu)入電壓的動態電源(yuan)管理 （VIN-DPM）

　　為了防止出現輸入源超負載的欠壓狀態，一些器件實施了基于輸入電壓的動態電源管理 （VIN-DPM）。這種環路降低輸入電流限制來防止輸入崩潰。VIN-DPM 環路對輸入電壓進行有效的穩壓，來最大化電源的電流。圖4 顯示了在無VIN-DPM 保護的情況下USB 端口的超負載結果。請注意，輸入電壓降至電源狀態良好閾值以下時，充電器關閉。這樣便關閉了電源負載，并允許輸入電壓恢復，從而開啟充電器。這(zhe)種(zhong)開/關脈沖(chong)發生并不是我們(men)想(xiang)要的(de)。

　　圖 4 無 VIN-DPM 情況下的輸(shu)入崩潰

　　VIN-DPM 通過限制(zhi)輸(shu)入(ru)電(dian)流阻止(zhi)脈沖發生，從而防(fang)止(zhi)輸(shu)入(ru)源(yuan)崩(beng)潰。圖5 顯(xian)示了超(chao)負(fu)載USB 端(duan)口的結果。VIN-DPM 功能開始生效，降低輸(shu)入(ru)電(dian)流限制(zhi)，從而防(fang)止(zhi)輸(shu)入(ru)源(yuan)崩(beng)潰。

　　圖 5 使用VIN-DPM的(de)輸入超(chao)負載(zai)保護

　　NTC 監測（包(bao)括JEITA）

　　通過充(chong)電(dian)(dian)期間(jian)的監(jian)(jian)測(ce)(ce)防止電(dian)(dian)池(chi)組損(sun)壞甚至是爆炸時(shi)，電(dian)(dian)池(chi)溫度極(ji)為重要。一般來說，通過對集(ji)成(cheng)到(dao)電(dian)(dian)池(chi)組中或者靠近系(xi)統板上電(dian)(dian)池(chi)組安裝的NTC 熱敏電(dian)(dian)阻進行監(jian)(jian)測(ce)(ce)，來完成(cheng)這項工作。許多充(chong)電(dian)(dian)器都具有集(ji)成(cheng)到(dao)IC 中的NTC 監(jian)(jian)測(ce)(ce)功(gong)能。如果電(dian)(dian)池(chi)溫度處在某些非安全溫度下時(shi)，這些IC 便對溫度和禁(jin)用(yong)充(chong)電(dian)(dian)電(dian)(dian)流進行監(jian)(jian)測(ce)(ce)。

　　一種新興的電池充電標準是日本電池溫度標準 （JEITA）。這種標準規定了一些需降低充電電壓或者電流以提供更安全運行的中間溫度。該JEITA標準在許多充電器IC 中也很容易實施。例如，單輸入單體鋰離子電池充電器集成了一種無需主(zhu)機(ji)關聯的(de)獨(du)立(li)解決方(fang)(fang)案。對(dui)于NTC 受主(zhu)機(ji)監測的(de)系統來(lai)說，許(xu)(xu)多IC 都提(ti)供了非常簡單的(de)實(shi)施。I2C 接口(kou)允(yun)許(xu)(xu)用(yong)戶動(dong)(dong)態地改變充(chong)電(dian)電(dian)壓(ya)和充(chong)電(dian)電(dian)流，使用(yong)具有(you)(you)這(zhe)種接口(kou)的(de)充(chong)電(dian)器(qi)時(shi)，主(zhu)機(ji)根據電(dian)池溫度來(lai)修改充(chong)電(dian)參數(shu)。這(zhe)種方(fang)(fang)法在(zai)沒有(you)(you)硬件改動(dong)(dong)的(de)情況(kuang)下(xia)，在(zai)為不同平臺(tai)和電(dian)池設置要求的(de)溫度閾值方(fang)(fang)面擁有(you)(you)一定(ding)的(de)靈活性。

　　USB 充電標準(zhun)

　　USB 充電時，可以使用許多充電器IC，它們都結合了(le)USB100和USB500 電(dian)流(liu)限制。通過(guo)USB 充電(dian)器(qi)輸出(chu)運行所有下(xia)游電(dian)路，讓廣大設計人員能夠確保不(bu)超(chao)出(chu)USB 電(dian)流(liu)限制。

　　額外功率輸出

　　隨著USB 充電的流行，許多應用都要求一個USB PHY 或者USB 收發器與主機枚舉。因此，這些器件通常直接連接到VBUS 電源，從而要求過電壓保護。因此，許多充電器IC 都集成了(le)一個連接電(dian)(dian)源(yuan)(yuan)并通過電(dian)(dian)源(yuan)(yuan)供(gong)電(dian)(dian)的(de)5V LDO。每當連接一個有效(xiao)電(dian)(dian)源(yuan)(yuan)時(shi)，這種輸出便有效(xiao)。5V LDO 穩壓(ya)(ya)電(dian)(dian)壓(ya)(ya)保護(hu)USB 電(dian)(dian)路免受未穩壓(ya)(ya)適配(pei)器和其他過電(dian)(dian)壓(ya)(ya)狀態的(de)損害。

　　　為單體鋰離子電池充電有很多種方法。我們必須對諸如充電電流、可用空間、USB 標準、成本和特性集等要求進行研究，以選擇最佳的解決方案。首先按照重要程度把這些要求排列出來，然后選擇最適合這些要求的拓撲結構。請一定要考慮散熱因素，最后為每種輸出選擇最具成本效益的解決方案。在這些簡單步驟之后，您的電池充電器設(she)計(ji)應該就會變得簡單了。