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的一些特性(xing)。此(ci)外，我們還將探討一個(ge)應(ying)用和現有的解決(jue)方案。

　　鋰離子電池充電周期

　　鋰離子電池要求專門(men)的(de)充(chong)(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)周期，以(yi)(yi)實現(xian)安全(quan)充(chong)(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)并(bing)最(zui)大化電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)使用時(shi)(shi)(shi)間。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)充(chong)(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)分兩(liang)(liang)個(ge)階段：恒(heng)定(ding)(ding)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu) （CC） 和恒(heng)定(ding)(ding)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya) （CV）。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)位(wei)于完全(quan)充(chong)(chong)(chong)(chong)(chong)(chong)(chong)滿(man)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)以(yi)(yi)下時(shi)(shi)(shi)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)經(jing)過(guo)穩(wen)(wen)(wen)壓(ya)進入電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)。在CC模式(shi)下，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)經(jing)過(guo)穩(wen)(wen)(wen)壓(ya)達到(dao)兩(liang)(liang)個(ge)值之一(yi)(yi)(yi)。如(ru)(ru)果電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)非常低，則(ze)充(chong)(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(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)(dian)流(liu)(liu)(liu)降低至(zhi)預(yu)(yu)充(chong)(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(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)(dian)平，以(yi)(yi)適(shi)應電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)并(bing)防止電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)損壞。該閾值因(yin)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)化學屬性(xing)而不同，一(yi)(yi)(yi)般取(qu)決(jue)于電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)制造廠商。一(yi)(yi)(yi)旦(dan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)升至(zhi)預(yu)(yu)充(chong)(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)閾值以(yi)(yi)上，充(chong)(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)便升至(zhi)快速(su)充(chong)(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(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)(dian)流(liu)(liu)(liu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平。典(dian)型電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)的(de)最(zui)大建(jian)議快速(su)充(chong)(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(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)(dian)流(liu)(liu)(liu)為(wei)1C（C=1 小(xiao)時(shi)(shi)(shi)內耗盡電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)所需的(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)），但(dan)該電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)也取(qu)決(jue)地電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)制造廠商。典(dian)型充(chong)(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(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)(dian)流(liu)(liu)(liu)為(wei)~0.8C，目的(de)是最(zui)大化電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)使用時(shi)(shi)(shi)間。對電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)充(chong)(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)時(shi)(shi)(shi)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)上升。一(yi)(yi)(yi)旦(dan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)升至(zhi)穩(wen)(wen)(wen)壓(ya)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)（一(yi)(yi)(yi)般為(wei)4.2V），充(chong)(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(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)(dian)流(liu)(liu)(liu)逐漸減(jian)少，同時(shi)(shi)(shi)對電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)進行穩(wen)(wen)(wen)壓(ya)以(yi)(yi)防止過(guo)充(chong)(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。在這(zhe)種模式(shi)下，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)充(chong)(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)時(shi)(shi)(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)逐漸減(jian)少，同時(shi)(shi)(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)阻抗降低。如(ru)(ru)果電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)降至(zhi)預(yu)(yu)定(ding)(ding)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平（一(yi)(yi)(yi)般為(wei)快速(su)充(chong)(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(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)(dian)流(liu)(liu)(liu)的(de)10%），則(ze)終止充(chong)(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。我們一(yi)(yi)(yi)般不對電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)浮充(chong)(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，因(yin)為(wei)這(zhe)樣會縮短電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)使用壽(shou)命(ming)。圖1 以(yi)(yi)圖形方式(shi)說明了(le)典(dian)型的(de)充(chong)(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(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(jue)方(fang)案(an)與開(kai)關模式解決(jue)方(fang)案(an)對(dui)比

　　將適(shi)配器電(dian)壓轉降為電(dian)池電(dian)壓并控制(zhi)不同充電(dian)階段的拓(tuo)撲結構有兩(liang)種：線(xian)性穩(wen)壓器和(he)電(dian)感(gan)開(kai)關。這兩(liang)種拓(tuo)撲結構在體積(ji)、效率、解決方案(an)成本和(he)電(dian)磁干(gan)擾(rao) （EMI） 輻射方面(mian)各(ge)有優(you)缺點。我們下面(mian)介(jie)紹這兩(liang)種拓(tuo)撲結構的各(ge)種優(you)點和(he)一(yi)些折中方法(fa)。

　　一(yi)般來說(shuo)，電(dian)(dian)感(gan)(gan)(gan)開關(guan)(guan)是獲得最高效率的(de)(de)(de)最佳選擇。利用電(dian)(dian)阻器(qi)(qi)等檢測(ce)組(zu)件(jian)(jian)，在輸出(chu)(chu)端檢測(ce)充電(dian)(dian)電(dian)(dian)流(liu)。充電(dian)(dian)器(qi)(qi)在CC 模式(shi)下時，電(dian)(dian)流(liu)反饋電(dian)(dian)路(lu)(lu)控制占(zhan)空(kong)比(bi)(bi)。電(dian)(dian)池(chi)電(dian)(dian)壓檢測(ce)反饋電(dian)(dian)路(lu)(lu)控制CV 模式(shi)下的(de)(de)(de)占(zhan)空(kong)比(bi)(bi)。根據特性集的(de)(de)(de)不同(tong)，可能會出(chu)(chu)現其(qi)他一(yi)些(xie)(xie)控制環(huan)路(lu)(lu)。我們將在后面(mian)詳(xiang)細討論這(zhe)些(xie)(xie)環(huan)路(lu)(lu)。電(dian)(dian)感(gan)(gan)(gan)開關(guan)(guan)電(dian)(dian)路(lu)(lu)要求(qiu)開關(guan)(guan)組(zu)件(jian)(jian)、整(zheng)流(liu)器(qi)(qi)、電(dian)(dian)感(gan)(gan)(gan)和輸入及(ji)輸出(chu)(chu)電(dian)(dian)容器(qi)(qi)。就許多應用而(er)言，通過選擇一(yi)種(zhong)將開關(guan)(guan)組(zu)件(jian)(jian)和整(zheng)流(liu)器(qi)(qi)都嵌(qian)入到IC 中的(de)(de)(de)器(qi)(qi)件(jian)(jian)，可以縮小(xiao)解決方案的(de)(de)(de)尺寸。根據不同(tong)的(de)(de)(de)負載，這(zhe)些(xie)(xie)電(dian)(dian)路(lu)(lu)的(de)(de)(de)典型效率為(wei)80% 到96%。開關(guan)(guan)轉(zhuan)換器(qi)(qi)因(yin)其(qi)電(dian)(dian)感(gan)(gan)(gan)尺寸一(yi)般會要求(qiu)更多的(de)(de)(de)空(kong)間，同(tong)時也更加昂貴。開關(guan)(guan)轉(zhuan)換器(qi)(qi)還會引起(qi)電(dian)(dian)感(gan)(gan)(gan)EMI 輻射，以及(ji)開關(guan)(guan)帶來的(de)(de)(de)輸出(chu)(chu)端噪聲。

　　線性充電器通(tong)過(guo)降低(di)旁路(lu)(lu)組(zu)件的(de)(de)(de)(de)輸(shu)(shu)入(ru)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)，降低(di)DC 電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)。這(zhe)樣做的(de)(de)(de)(de)好(hao)處是解(jie)決(jue)方(fang)案(an)只要求(qiu)三個(ge)組(zu)件：旁路(lu)(lu)組(zu)件和(he)輸(shu)(shu)入(ru)/輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)容。相(xiang)比(bi)電(dian)(dian)(dian)(dian)(dian)感開關，線性壓(ya)(ya)(ya)降穩壓(ya)(ya)(ya)器(qi) （LDO） 通(tong)常為(wei)一(yi)款低(di)成本的(de)(de)(de)(de)解(jie)決(jue)方(fang)案(an)，且噪聲更(geng)低(di)。通(tong)過(guo)穩壓(ya)(ya)(ya)旁路(lu)(lu)組(zu)件的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)阻來限制(zhi)進(jin)入(ru)電(dian)(dian)(dian)(dian)(dian)池的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)流(liu)，從(cong)而對充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)進(jin)行控制(zhi)。電(dian)(dian)(dian)(dian)(dian)流(liu)反饋一(yi)般來自(zi)充(chong)電(dian)(dian)(dian)(dian)(dian)器(qi)IC 的(de)(de)(de)(de)輸(shu)(shu)入(ru)。對電(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)進(jin)行檢(jian)測(ce)，以提(ti)供CV 反饋。改變旁路(lu)(lu)組(zu)件的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)阻，來維持進(jin)入(ru)IC 輸(shu)(shu)入(ru)端的(de)(de)(de)(de)恒(heng)定電(dian)(dian)(dian)(dian)(dian)流(liu)或者恒(heng)定電(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)。器(qi)件的(de)(de)(de)(de)輸(shu)(shu)入(ru)電(dian)(dian)(dian)(dian)(dian)流(liu)等于負載電(dian)(dian)(dian)(dian)(dian)流(liu)。這(zhe)就是說(shuo)解(jie)決(jue)方(fang)案(an)的(de)(de)(de)(de)效率(lv)等于輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)與輸(shu)(shu)入(ru)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)的(de)(de)(de)(de)比(bi)。LDO 解(jie)決(jue)方(fang)案(an)的(de)(de)(de)(de)缺(que)點是高(gao)輸(shu)(shu)入(ru)輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)比(bi)時（即低(di)電(dian)(dian)(dian)(dian)(dian)量情況(kuang)）效率(lv)較低(di)。所有功率(lv)都被旁路(lu)(lu)組(zu)件消耗(hao)，其意味著LDO 并非那些(xie)輸(shu)(shu)入(ru)輸(shu)(shu)出(chu)差較大(da)的(de)(de)(de)(de)高(gao)充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)應用(yong)的(de)(de)(de)(de)理(li)想選擇。這(zhe)些(xie)高(gao)功耗(hao)應用(yong)要求(qiu)散熱，從(cong)而增加(jia)了解(jie)決(jue)方(fang)案(an)的(de)(de)(de)(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。

   應該使用什(shen)么(me)樣的拓(tuo)撲(pu)？

　　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，效(xiao)(xiao)率(lv)(lv)為(wei)72%。首先，這(zhe)個(ge)效(xiao)(xiao)率(lv)(lv)聽起來(lai)(lai)(lai)似乎不太壞。如(ru)果您從(cong)功耗(hao)(hao)(hao)的(de)(de)(de)角度(du)(du)來(lai)(lai)(lai)看(kan)它，這(zhe)種應用(yong)要消耗(hao)(hao)(hao)約(yue)2W。在一個(ge)熱阻 （ΘJA） 為(wei)40°C/W 的(de)(de)(de)應用(yong)中，芯片溫(wen)度(du)(du)上升(sheng)(sheng)(sheng)(sheng)80°C。在40°C 環(huan)境溫(wen)度(du)(du)下，電(dian)(dian)(dian)路板溫(wen)度(du)(du)會上升(sheng)(sheng)(sheng)(sheng)至120°C，其對手(shou)(shou)持(chi)設(she)備來(lai)(lai)(lai)說是不可接(jie)受的(de)(de)(de)。在極低(di)電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)壓（即3 V）下，這(zhe)一問題甚(shen)至會變得極端嚴重(zhong)。相同3V 條(tiao)件(jian)下，溫(wen)度(du)(du)升(sheng)(sheng)(sheng)(sheng)至120°C。讓我們來(lai)(lai)(lai)看(kan)相同條(tiao)件(jian)下的(de)(de)(de)開(kai)(kai)關解決(jue)方案(an)，使用(yong)一個(ge)單體(ti)電(dian)(dian)(dian)池(chi)IC 充電(dian)(dian)(dian)器(qi)時，效(xiao)(xiao)率(lv)(lv)上升(sheng)(sheng)(sheng)(sheng)至約(yue)85%。使用(yong)一塊(kuai)3.6V 電(dian)(dian)(dian)池(chi)時，功耗(hao)(hao)(hao)低(di)于(yu)1W，從(cong)而(er)帶來(lai)(lai)(lai)40°C 的(de)(de)(de)溫(wen)升(sheng)(sheng)(sheng)(sheng)。3V 時這(zhe)種改善更加(jia)明(ming)顯。假設(she)3V 輸(shu)出時的(de)(de)(de)效(xiao)(xiao)率(lv)(lv)為(wei)80%，則功耗(hao)(hao)(hao)低(di)于(yu)800 mW，因此溫(wen)升(sheng)(sheng)(sheng)(sheng)會更低(di)（約(yue)32°C）。這(zhe)些智能手(shou)(shou)機的(de)(de)(de)體(ti)積一般可以容許稍大一點的(de)(de)(de)解決(jue)方案(an)，并且能夠(gou)承受開(kai)(kai)關模式解決(jue)方案(an)相關的(de)(de)(de)稍許成(cheng)本(ben)增加(jia)。

　　為任務選擇(ze)正確的IC

　　在您(nin)已經(jing)完成(cheng)您(nin)的初步熱(re)分析并(bing)且選(xuan)好充(chong)電(dian)(dian)器(qi)拓撲以(yi)后，您(nin)便可(ke)以(yi)轉到選(xuan)擇應用的最佳(jia)IC 上來(lai)。新型(xing)的電(dian)(dian)池充(chong)電(dian)(dian)器(qi)解(jie)決方(fang)案集(ji)(ji)(ji)成(cheng)了許多(duo)特性(xing)，可(ke)以(yi)利用它們改善系統的性(xing)能。諸如輸入過壓(ya)保護(hu)、電(dian)(dian)源(yuan)路(lu)徑管理 （PPM）、VIN_DPM、散(san)熱(re)穩壓(ya)、負溫度系數(shu)熱(re)敏電(dian)(dian)阻(zu) （NTC） 監測(ce)和USB 充(chong)電(dian)(dian)等特性(xing)，都(dou)被集(ji)(ji)(ji)成(cheng)到許多(duo)電(dian)(dian)池充(chong)電(dian)(dian)器(qi)IC 中。大(da)多(duo)數(shu)單體(ti)電(dian)(dian)池充(chong)電(dian)(dian)器(qi)解(jie)決方(fang)案都(dou)已將要求FET 集(ji)(ji)(ji)成(cheng)到了器(qi)件中，旨(zhi)在節省(sheng)電(dian)(dian)路(lu)板面積。

　　輸入過(guo)壓保護（單輸入與(yu)雙輸入對比）

　　在(zai)(zai)(zai)當今的市(shi)場(chang)(chang)(chang)上，USB 電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)已經(jing)成為(wei)最為(wei)常見的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)，因(yin)(yin)此通過(guo)(guo)(guo)USB 電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)已經(jing)成為(wei)一(yi)種(zhong)(zhong)必(bi)(bi)然性。市(shi)場(chang)(chang)(chang)已經(jing)從(cong)使(shi)(shi)用(yong)專(zhuan)門AC 適(shi)配(pei)器(qi)和單獨(du)USB 接(jie)口(kou)(kou)的初始(shi)雙(shuang)輸(shu)(shu)入(ru)轉變為(wei)將一(yi)個USB 接(jie)口(kou)(kou)既作為(wei)墻上電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)適(shi)合(he)器(qi)接(jie)口(kou)(kou)使(shi)(shi)用(yong)，也作為(wei)使(shi)(shi)用(yong)相(xiang)同線纜的USB 數據(ju)輸(shu)(shu)入(ru)接(jie)口(kou)(kou)的單輸(shu)(shu)入(ru)解(jie)(jie)決(jue)(jue)(jue)(jue)方(fang)案(an)。這樣便導致一(yi)種(zhong)(zhong)從(cong)雙(shuang)輸(shu)(shu)入(ru)解(jie)(jie)決(jue)(jue)(jue)(jue)方(fang)案(an)向(xiang)單輸(shu)(shu)入(ru)解(jie)(jie)決(jue)(jue)(jue)(jue)方(fang)案(an)的轉移。單輸(shu)(shu)入(ru)在(zai)(zai)(zai)接(jie)口(kou)(kou)方(fang)面存(cun)在(zai)(zai)(zai)許多挑戰。由于(yu)存(cun)在(zai)(zai)(zai)如此多的配(pei)件市(shi)場(chang)(chang)(chang)適(shi)配(pei)器(qi)解(jie)(jie)決(jue)(jue)(jue)(jue)方(fang)案(an)和一(yi)種(zhong)(zhong)通用(yong)接(jie)口(kou)(kou)，輸(shu)(shu)入(ru)端必(bi)(bi)須要能夠在(zai)(zai)(zai)無損壞的情(qing)況下承受(shou)更高的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)。由于(yu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)始(shi)終連接(jie)到輸(shu)(shu)入(ru)端，因(yin)(yin)此充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器(qi)對所有(you)(you)下游(you)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)實施(shi)過(guo)(guo)(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)狀態保(bao)護(hu)是有(you)(you)道(dao)理的。為(wei)了(le)(le)實施(shi)這一(yi)功(gong)能，市(shi)場(chang)(chang)(chang)上出(chu)現了(le)(le)許多能夠承受(shou)20V 甚至30V 電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)的解(jie)(jie)決(jue)(jue)(jue)(jue)方(fang)案(an)。另外，這些器(qi)件都具有(you)(you)過(guo)(guo)(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)保(bao)護(hu) （OVP） 電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)，其(qi)在(zai)(zai)(zai)輸(shu)(shu)入(ru)超出(chu)OVP 閾值時阻止(zhi)器(qi)件運行(xing)。這樣便進一(yi)步保(bao)護(hu)了(le)(le)下游(you)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)，使(shi)(shi)其(qi)免受(shou)潛在(zai)(zai)(zai)的瞬(shun)態過(guo)(guo)(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)狀態損壞。

　　目前，隨著(zhu)綠色(se)輸入(ru)（即太陽能電池）或無線充電的出現，應用(yong)又再(zai)一次向雙輸入(ru)要求(qiu)轉移。根據(ju)具體的應用(yong)要求(qiu)，兩種配置結(jie)構(gou)都可以使用(yong)。

　　電(dian)源路(lu)徑(jing)管理/最小系統電(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監測，消(xiao)除了(le)這些(xie)問(wen)題［2］。

　　圖 2 傳統(tong)拓(tuo)撲結構舉例

　　圖 3 電源路徑拓撲結構舉例(li)

　　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(yu)系(xi)統(tong)(tong)電(dian)(dian)(dian)流(liu)(liu)和(he)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)是單獨編程的(de)，因此可(ke)以(yi)(yi)使(shi)用(yong)適配器的(de)滿功率，其與(yu)電(dian)(dian)(dian)池(chi)(chi)的(de)容(rong)量和(he)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)的(de)大小均無關。傳(chuan)統(tong)(tong)拓撲結(jie)構中(zhong)，充(chong)電(dian)(dian)(dian)器的(de)輸出電(dian)(dian)(dian)流(liu)(liu)必須設定為(wei)最(zui)大充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)，以(yi)(yi)應對沒有(you)系(xi)統(tong)(tong)負(fu)載的(de)情況。當系(xi)統(tong)(tong)中(zhong)有(you)負(fu)載時，由于(yu)系(xi)統(tong)(tong)吸收可(ke)用(yong)電(dian)(dian)(dian)流(liu)(liu)，有(you)效充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)降低。例如，一(yi)個使(shi)用(yong)900 mA 適配器和(he)500 mAhr 電(dian)(dian)(dian)池(chi)(chi)的(de)系(xi)統(tong)(tong)，使(shi)用(yong)傳(chuan)統(tong)(tong)方法可(ke)以(yi)(yi)編程500 mA 的(de)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)。如果系(xi)統(tong)(tong)負(fu)載為(wei)200 mA，有(you)效充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)僅為(wei)300 mA，充(chong)電(dian)(dian)(dian)時間幾(ji)乎翻(fan)了(le)一(yi)翻(fan)。如果使(shi)用(yong)PPM 來研究這一(yi)相(xiang)同案例，輸入電(dian)(dian)(dian)流(liu)(liu)限制設定為(wei)900 mA。這樣便允許(xu)全部500 mA充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)，且擁有(you)多達400 mA 的(de)額外系(xi)統(tong)(tong)電(dian)(dian)(dian)流(liu)(liu)。

　　終止和早期計時(shi)器超時(shi)

　　在對(dui)總電(dian)(dian)(dian)流進行(xing)穩壓(ya)的傳(chuan)統系(xi)(xi)統中，電(dian)(dian)(dian)流在電(dian)(dian)(dian)池(chi)和負載之間共用。如果系(xi)(xi)統負載足夠大(da)到從電(dian)(dian)(dian)池(chi)拉取充電(dian)(dian)(dian)電(dian)(dian)(dian)流，且在計(ji)時(shi)(shi)器(qi)超時(shi)(shi)以前電(dian)(dian)(dian)池(chi)不充電(dian)(dian)(dian)，則(ze)計(ji)時(shi)(shi)器(qi)會(hui)出現偽超時(shi)(shi)。另外，如果系(xi)(xi)統電(dian)(dian)(dian)流絕(jue)對(dui)不會(hui)降至設定(ding)終(zhong)(zhong)(zhong)止(zhi)(zhi)電(dian)(dian)(dian)流以下，則(ze)永遠不會(hui)終(zhong)(zhong)(zhong)止(zhi)(zhi)。電(dian)(dian)(dian)源路(lu)徑管理通(tong)過(guo)單獨監(jian)測(ce)充電(dian)(dian)(dian)電(dian)(dian)(dian)流，并(bing)動態地使(shi)用可穩壓(ya)計(ji)時(shi)(shi)器(qi)（通(tong)過(guo)減少充電(dian)(dian)(dian)電(dian)(dian)(dian)流進行(xing)穩壓(ya)），防止(zhi)(zhi)這些條(tiao)件出現。就終(zhong)(zhong)(zhong)止(zhi)(zhi)問題而(er)言，單獨對(dui)充電(dian)(dian)(dian)電(dian)(dian)(dian)流進行(xing)監(jian)測(ce)，可讓終(zhong)(zhong)(zhong)止(zhi)(zhi)條(tiao)件測(ce)定(ding)變得容易。

　　基于(yu)輸(shu)入電壓的動態電源管理 （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。這種開(kai)/關脈沖發生并不是我們想(xiang)要的。

　　圖 4 無 VIN-DPM 情況下(xia)的輸入崩潰

　　VIN-DPM 通(tong)過限制(zhi)(zhi)輸入(ru)(ru)電流(liu)阻止(zhi)脈沖發生(sheng)(sheng)，從(cong)而(er)防止(zhi)輸入(ru)(ru)源崩(beng)潰。圖5 顯示了超負載USB 端(duan)口的(de)結果。VIN-DPM 功能(neng)開始生(sheng)(sheng)效，降低輸入(ru)(ru)電流(liu)限制(zhi)(zhi)，從(cong)而(er)防止(zhi)輸入(ru)(ru)源崩(beng)潰。

　　圖 5 使用VIN-DPM的輸入超負載(zai)保護

　　NTC 監(jian)測（包括JEITA）

　　通過(guo)充電(dian)期間的(de)監(jian)測防(fang)止電(dian)池(chi)組損壞甚至是爆炸時，電(dian)池(chi)溫(wen)(wen)(wen)度極(ji)為(wei)重要。一般(ban)來(lai)說，通過(guo)對集(ji)成到電(dian)池(chi)組中或(huo)者(zhe)靠近系統板上電(dian)池(chi)組安裝(zhuang)的(de)NTC 熱敏電(dian)阻進行監(jian)測，來(lai)完(wan)成這項工作。許多充電(dian)器(qi)都具(ju)有集(ji)成到IC 中的(de)NTC 監(jian)測功能。如(ru)果電(dian)池(chi)溫(wen)(wen)(wen)度處在某(mou)些非安全溫(wen)(wen)(wen)度下(xia)時，這些IC 便對溫(wen)(wen)(wen)度和禁用充電(dian)電(dian)流進行監(jian)測。

　　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(zhong)無需主機關聯的(de)(de)獨立解決(jue)方(fang)案。對于NTC 受主機監測的(de)(de)系統來說，許(xu)多IC 都提供了非(fei)常(chang)簡單的(de)(de)實施(shi)。I2C 接(jie)(jie)口(kou)(kou)允許(xu)用戶動(dong)(dong)態地改變充(chong)電(dian)(dian)電(dian)(dian)壓和充(chong)電(dian)(dian)電(dian)(dian)流，使用具有(you)這種(zhong)接(jie)(jie)口(kou)(kou)的(de)(de)充(chong)電(dian)(dian)器時，主機根(gen)據電(dian)(dian)池(chi)溫度來修改充(chong)電(dian)(dian)參數。這種(zhong)方(fang)法在(zai)沒有(you)硬件改動(dong)(dong)的(de)(de)情(qing)況下，在(zai)為不同(tong)平臺和電(dian)(dian)池(chi)設置要(yao)求(qiu)的(de)(de)溫度閾(yu)值(zhi)方(fang)面擁(yong)有(you)一定的(de)(de)靈活(huo)性。

　　USB 充電標(biao)準

　　USB 充電時，可以使用許多充電器IC，它們都(dou)結(jie)合了USB100和USB500 電(dian)(dian)流(liu)限(xian)制。通過USB 充電(dian)(dian)器(qi)輸出運(yun)行(xing)所有下游(you)電(dian)(dian)路(lu)，讓(rang)廣大設計(ji)人員能夠確保(bao)不超出USB 電(dian)(dian)流(liu)限(xian)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(cheng)了一(yi)(yi)個(ge)連接(jie)電(dian)源(yuan)(yuan)并通過(guo)(guo)電(dian)源(yuan)(yuan)供電(dian)的(de)5V LDO。每當連接(jie)一(yi)(yi)個(ge)有效(xiao)電(dian)源(yuan)(yuan)時(shi)，這種輸出(chu)便有效(xiao)。5V LDO 穩(wen)(wen)壓電(dian)壓保(bao)護USB 電(dian)路(lu)免受未穩(wen)(wen)壓適配器和其他過(guo)(guo)電(dian)壓狀態的(de)損(sun)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(ying)該就會變得簡單(dan)了。