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)一些特性。此外，我們還將探討一個應用和現有(you)的(de)解決方案(an)。

　　鋰離子電池充電周期

　　鋰離子電池要求專門的(de)(de)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)周期(qi)，以(yi)實現安全充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)并最大化(hua)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)使用(yong)(yong)時(shi)間(jian)。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)分兩(liang)個階段：恒定電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu) （CC） 和恒定電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya) （CV）。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)位于(yu)完全充(chong)(chong)(chong)(chong)(chong)(chong)滿電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)以(yi)下時(shi)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)經過(guo)穩壓(ya)(ya)進(jin)(jin)入電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)。在CC模式下，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)經過(guo)穩壓(ya)(ya)達(da)到(dao)兩(liang)個值之一(yi)(yi)(yi)(yi)。如果(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)非(fei)常低(di)，則(ze)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(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)(dian)(dian)(dian)流(liu)降低(di)至(zhi)(zhi)預(yu)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(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)(dian)(dian)(dian)平(ping)，以(yi)適應電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)并防止(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)損壞。該閾值因電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)化(hua)學屬性(xing)而不同，一(yi)(yi)(yi)(yi)般(ban)取(qu)決于(yu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)制(zhi)造廠(chang)(chang)商(shang)。一(yi)(yi)(yi)(yi)旦(dan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)升(sheng)至(zhi)(zhi)預(yu)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)閾值以(yi)上，充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)便升(sheng)至(zhi)(zhi)快速(su)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(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)(dian)(dian)(dian)流(liu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)。典型(xing)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的(de)(de)最大建議快速(su)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(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)(dian)(dian)(dian)流(liu)為1C（C=1 小時(shi)內耗盡電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)所需(xu)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)），但該電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)也取(qu)決地電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)制(zhi)造廠(chang)(chang)商(shang)。典型(xing)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(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)(dian)(dian)(dian)流(liu)為~0.8C，目的(de)(de)是最大化(hua)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)使用(yong)(yong)時(shi)間(jian)。對電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)時(shi)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)上升(sheng)。一(yi)(yi)(yi)(yi)旦(dan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)升(sheng)至(zhi)(zhi)穩壓(ya)(ya)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)（一(yi)(yi)(yi)(yi)般(ban)為4.2V），充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(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)(dian)(dian)(dian)流(liu)逐漸減(jian)少，同時(shi)對電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)進(jin)(jin)行穩壓(ya)(ya)以(yi)防止(zhi)過(guo)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。在這(zhe)種模式下，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)時(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)逐漸減(jian)少，同時(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)阻抗(kang)降低(di)。如果(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)降至(zhi)(zhi)預(yu)定電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)（一(yi)(yi)(yi)(yi)般(ban)為快速(su)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(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)(dian)(dian)(dian)流(liu)的(de)(de)10%），則(ze)終止(zhi)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。我們一(yi)(yi)(yi)(yi)般(ban)不對電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)浮充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，因為這(zhe)樣會縮短電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)使用(yong)(yong)壽命。圖1 以(yi)圖形方(fang)式說明了典型(xing)的(de)(de)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)周期(qi)。

　　圖1典型鋰離子充電周期

　　線(xian)性解(jie)(jie)決方案與(yu)開(kai)關模(mo)式(shi)解(jie)(jie)決方案對比

　　將適配器電(dian)壓轉降為電(dian)池電(dian)壓并控(kong)制不同(tong)充電(dian)階段的拓(tuo)(tuo)撲(pu)結構(gou)有兩(liang)種：線性穩壓器和(he)(he)電(dian)感開關。這兩(liang)種拓(tuo)(tuo)撲(pu)結構(gou)在體積、效(xiao)率(lv)、解決方(fang)案成本和(he)(he)電(dian)磁干擾 （EMI） 輻射方(fang)面各有優(you)缺點(dian)。我(wo)們下面介紹這兩(liang)種拓(tuo)(tuo)撲(pu)結構(gou)的各種優(you)點(dian)和(he)(he)一些折中方(fang)法。

　　一般(ban)來說，電(dian)(dian)(dian)(dian)(dian)(dian)感(gan)開(kai)(kai)關(guan)(guan)(guan)是獲得最(zui)高效(xiao)率(lv)的(de)(de)(de)(de)最(zui)佳(jia)選(xuan)擇。利用電(dian)(dian)(dian)(dian)(dian)(dian)阻器(qi)(qi)等檢測(ce)組(zu)件(jian)，在輸出端檢測(ce)充電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)流。充電(dian)(dian)(dian)(dian)(dian)(dian)器(qi)(qi)在CC 模(mo)式下時，電(dian)(dian)(dian)(dian)(dian)(dian)流反(fan)饋電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)控制(zhi)占空比。電(dian)(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)(dian)壓檢測(ce)反(fan)饋電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)控制(zhi)CV 模(mo)式下的(de)(de)(de)(de)占空比。根據特(te)性(xing)集的(de)(de)(de)(de)不同，可能(neng)會出現其(qi)(qi)他一些(xie)控制(zhi)環(huan)路(lu)。我們將在后面詳細討論這(zhe)(zhe)些(xie)環(huan)路(lu)。電(dian)(dian)(dian)(dian)(dian)(dian)感(gan)開(kai)(kai)關(guan)(guan)(guan)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)要求開(kai)(kai)關(guan)(guan)(guan)組(zu)件(jian)、整流器(qi)(qi)、電(dian)(dian)(dian)(dian)(dian)(dian)感(gan)和輸入(ru)及輸出電(dian)(dian)(dian)(dian)(dian)(dian)容器(qi)(qi)。就許多應用而言(yan)，通(tong)過選(xuan)擇一種(zhong)將開(kai)(kai)關(guan)(guan)(guan)組(zu)件(jian)和整流器(qi)(qi)都嵌入(ru)到(dao)IC 中的(de)(de)(de)(de)器(qi)(qi)件(jian)，可以縮小解決方案的(de)(de)(de)(de)尺寸。根據不同的(de)(de)(de)(de)負載，這(zhe)(zhe)些(xie)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)的(de)(de)(de)(de)典型效(xiao)率(lv)為80% 到(dao)96%。開(kai)(kai)關(guan)(guan)(guan)轉(zhuan)換器(qi)(qi)因其(qi)(qi)電(dian)(dian)(dian)(dian)(dian)(dian)感(gan)尺寸一般(ban)會要求更多的(de)(de)(de)(de)空間(jian)，同時也更加昂貴。開(kai)(kai)關(guan)(guan)(guan)轉(zhuan)換器(qi)(qi)還會引起電(dian)(dian)(dian)(dian)(dian)(dian)感(gan)EMI 輻射，以及開(kai)(kai)關(guan)(guan)(guan)帶來的(de)(de)(de)(de)輸出端噪聲。

　　線性充電器通(tong)過降(jiang)低(di)(di)(di)旁(pang)路組件的(de)(de)(de)輸(shu)(shu)入(ru)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)，降(jiang)低(di)(di)(di)DC 電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)。這樣做的(de)(de)(de)好(hao)處是(shi)解決方案(an)只要求三個(ge)組件：旁(pang)路組件和輸(shu)(shu)入(ru)/輸(shu)(shu)出(chu)(chu)電(dian)(dian)(dian)(dian)(dian)容。相比電(dian)(dian)(dian)(dian)(dian)感開關(guan)，線(xian)性壓(ya)(ya)(ya)降(jiang)穩壓(ya)(ya)(ya)器 （LDO） 通(tong)常為一款低(di)(di)(di)成(cheng)本的(de)(de)(de)解決方案(an)，且噪(zao)聲更低(di)(di)(di)。通(tong)過穩壓(ya)(ya)(ya)旁(pang)路組件的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)阻(zu)來限(xian)制(zhi)進(jin)(jin)入(ru)電(dian)(dian)(dian)(dian)(dian)池的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)，從(cong)而對充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)進(jin)(jin)行控(kong)制(zhi)。電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)反饋(kui)一般來自充(chong)電(dian)(dian)(dian)(dian)(dian)器IC 的(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)(jin)行檢測，以提(ti)供CV 反饋(kui)。改變旁(pang)路組件的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)阻(zu)，來維持進(jin)(jin)入(ru)IC 輸(shu)(shu)入(ru)端的(de)(de)(de)恒(heng)定電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)或(huo)者恒(heng)定電(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)。器件的(de)(de)(de)輸(shu)(shu)入(ru)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)等于(yu)負載電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)。這就是(shi)說解決方案(an)的(de)(de)(de)效率(lv)(lv)等于(yu)輸(shu)(shu)出(chu)(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)比。LDO 解決方案(an)的(de)(de)(de)缺點是(shi)高(gao)輸(shu)(shu)入(ru)輸(shu)(shu)出(chu)(chu)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)比時（即低(di)(di)(di)電(dian)(dian)(dian)(dian)(dian)量情況）效率(lv)(lv)較(jiao)低(di)(di)(di)。所有(you)功(gong)率(lv)(lv)都被旁(pang)路組件消耗(hao)(hao)，其意味著LDO 并非那(nei)些輸(shu)(shu)入(ru)輸(shu)(shu)出(chu)(chu)差較(jiao)大的(de)(de)(de)高(gao)充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)應(ying)用的(de)(de)(de)理想選擇。這些高(gao)功(gong)耗(hao)(hao)應(ying)用要求散熱，從(cong)而增加(jia)了解決方案(an)的(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(ying)該使用什么樣的拓撲？

　　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)，效率(lv)為(wei)(wei)72%。首先，這(zhe)個(ge)效率(lv)聽起來似(si)乎不太壞。如果您(nin)從功(gong)耗(hao)的(de)(de)(de)角度來看它，這(zhe)種應用要消耗(hao)約(yue)2W。在一(yi)個(ge)熱阻 （ΘJA） 為(wei)(wei)40°C/W 的(de)(de)(de)應用中，芯(xin)片溫(wen)(wen)度上升80°C。在40°C 環(huan)境溫(wen)(wen)度下，電路板溫(wen)(wen)度會上升至120°C，其對(dui)手(shou)持(chi)設(she)備來說(shuo)是不可(ke)接受(shou)的(de)(de)(de)。在極低電池電壓（即3 V）下，這(zhe)一(yi)問(wen)題(ti)甚(shen)至會變得極端嚴重。相同(tong)3V 條件下，溫(wen)(wen)度升至120°C。讓我們(men)來看相同(tong)條件下的(de)(de)(de)開關解(jie)決方案(an)，使用一(yi)個(ge)單體(ti)電池IC 充電器時(shi)，效率(lv)上升至約(yue)85%。使用一(yi)塊3.6V 電池時(shi)，功(gong)耗(hao)低于1W，從而帶(dai)來40°C 的(de)(de)(de)溫(wen)(wen)升。3V 時(shi)這(zhe)種改善更加(jia)明(ming)顯(xian)。假設(she)3V 輸出時(shi)的(de)(de)(de)效率(lv)為(wei)(wei)80%，則功(gong)耗(hao)低于800 mW，因此溫(wen)(wen)升會更低（約(yue)32°C）。這(zhe)些(xie)智(zhi)能手(shou)機的(de)(de)(de)體(ti)積一(yi)般可(ke)以容許稍(shao)大一(yi)點的(de)(de)(de)解(jie)決方案(an)，并且能夠承受(shou)開關模式解(jie)決方案(an)相關的(de)(de)(de)稍(shao)許成本增加(jia)。

　　為任務選擇(ze)正(zheng)確的(de)IC

　　在(zai)您(nin)已經完成(cheng)您(nin)的(de)初步熱分析并且(qie)選(xuan)好充(chong)電(dian)(dian)(dian)(dian)器拓撲以后，您(nin)便可(ke)以轉到(dao)選(xuan)擇應用的(de)最佳IC 上來。新型的(de)電(dian)(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)(dian)器解決方案集成(cheng)了許(xu)多特(te)性，可(ke)以利(li)用它們改善(shan)系統的(de)性能。諸如輸(shu)入(ru)過壓保(bao)護(hu)、電(dian)(dian)(dian)(dian)源路徑(jing)管(guan)理 （PPM）、VIN_DPM、散熱穩(wen)壓、負溫度系數熱敏電(dian)(dian)(dian)(dian)阻 （NTC） 監測(ce)和USB 充(chong)電(dian)(dian)(dian)(dian)等特(te)性，都被集成(cheng)到(dao)許(xu)多電(dian)(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)(dian)器IC 中(zhong)。大多數單體電(dian)(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)(dian)器解決方案都已將要求FET 集成(cheng)到(dao)了器件中(zhong)，旨在(zai)節省電(dian)(dian)(dian)(dian)路板(ban)面積。

　　輸入過壓保護（單輸入與雙輸入對比）

　　在(zai)(zai)當今的(de)(de)(de)市場(chang)上(shang)，USB 電(dian)(dian)(dian)源(yuan)(yuan)已(yi)經成為(wei)最為(wei)常見的(de)(de)(de)電(dian)(dian)(dian)源(yuan)(yuan)，因此通過(guo)USB 電(dian)(dian)(dian)源(yuan)(yuan)充電(dian)(dian)(dian)已(yi)經成為(wei)一(yi)種(zhong)必然性。市場(chang)已(yi)經從使用專門AC 適(shi)(shi)配器(qi)和單獨(du)USB 接(jie)口的(de)(de)(de)初始雙(shuang)輸(shu)(shu)入轉變為(wei)將一(yi)個USB 接(jie)口既作為(wei)墻上(shang)電(dian)(dian)(dian)源(yuan)(yuan)適(shi)(shi)合器(qi)接(jie)口使用，也作為(wei)使用相同(tong)線纜(lan)的(de)(de)(de)USB 數據輸(shu)(shu)入接(jie)口的(de)(de)(de)單輸(shu)(shu)入解(jie)決方(fang)案(an)。這(zhe)(zhe)樣(yang)便導致(zhi)一(yi)種(zhong)從雙(shuang)輸(shu)(shu)入解(jie)決方(fang)案(an)向(xiang)單輸(shu)(shu)入解(jie)決方(fang)案(an)的(de)(de)(de)轉移。單輸(shu)(shu)入在(zai)(zai)接(jie)口方(fang)面(mian)存(cun)在(zai)(zai)許多挑戰。由(you)于存(cun)在(zai)(zai)如此多的(de)(de)(de)配件市場(chang)適(shi)(shi)配器(qi)解(jie)決方(fang)案(an)和一(yi)種(zhong)通用接(jie)口，輸(shu)(shu)入端(duan)必須要能(neng)夠在(zai)(zai)無損(sun)壞(huai)的(de)(de)(de)情(qing)況(kuang)下承受更高的(de)(de)(de)電(dian)(dian)(dian)壓。由(you)于電(dian)(dian)(dian)池充電(dian)(dian)(dian)器(qi)始終(zhong)連接(jie)到輸(shu)(shu)入端(duan)，因此充電(dian)(dian)(dian)器(qi)對所有下游(you)電(dian)(dian)(dian)路實(shi)(shi)施過(guo)電(dian)(dian)(dian)壓狀(zhuang)態保(bao)護是有道理的(de)(de)(de)。為(wei)了實(shi)(shi)施這(zhe)(zhe)一(yi)功能(neng)，市場(chang)上(shang)出現了許多能(neng)夠承受20V 甚至30V 電(dian)(dian)(dian)壓的(de)(de)(de)解(jie)決方(fang)案(an)。另(ling)外，這(zhe)(zhe)些器(qi)件都具有過(guo)電(dian)(dian)(dian)壓保(bao)護 （OVP） 電(dian)(dian)(dian)路，其在(zai)(zai)輸(shu)(shu)入超出OVP 閾值(zhi)時阻止器(qi)件運(yun)行。這(zhe)(zhe)樣(yang)便進一(yi)步保(bao)護了下游(you)電(dian)(dian)(dian)路，使其免受潛在(zai)(zai)的(de)(de)(de)瞬(shun)態過(guo)電(dian)(dian)(dian)壓狀(zhuang)態損(sun)壞(huai)。

　　目前，隨著綠(lv)色輸入（即太陽(yang)能電池）或(huo)無線充電的出現，應(ying)用又再(zai)一(yi)次(ci)向雙輸入要求(qiu)轉移。根據(ju)具體的應(ying)用要求(qiu)，兩種配置結構都可以(yi)使用。

　　電源路(lu)徑管理/最小系統電壓

　　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)除了這些問題［2］。

　　圖 2 傳統(tong)拓撲結構舉(ju)例

　　圖 3 電源路徑拓(tuo)撲結構舉例

　　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(yu)系(xi)(xi)(xi)統(tong)(tong)(tong)(tong)電(dian)(dian)(dian)流和(he)(he)(he)充(chong)(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流是(shi)單獨編程(cheng)的(de)(de)，因此(ci)可(ke)以(yi)使(shi)用(yong)適配器的(de)(de)滿功率，其與電(dian)(dian)(dian)池(chi)的(de)(de)容量和(he)(he)(he)充(chong)(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流的(de)(de)大小均無(wu)關。傳統(tong)(tong)(tong)(tong)拓(tuo)撲(pu)結(jie)構中，充(chong)(chong)(chong)電(dian)(dian)(dian)器的(de)(de)輸出(chu)電(dian)(dian)(dian)流必須設定(ding)(ding)為(wei)最大充(chong)(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流，以(yi)應(ying)對沒有系(xi)(xi)(xi)統(tong)(tong)(tong)(tong)負載(zai)的(de)(de)情況。當系(xi)(xi)(xi)統(tong)(tong)(tong)(tong)中有負載(zai)時，由于(yu)系(xi)(xi)(xi)統(tong)(tong)(tong)(tong)吸(xi)收可(ke)用(yong)電(dian)(dian)(dian)流，有效充(chong)(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流降(jiang)低(di)。例(li)如(ru)，一個使(shi)用(yong)900 mA 適配器和(he)(he)(he)500 mAhr 電(dian)(dian)(dian)池(chi)的(de)(de)系(xi)(xi)(xi)統(tong)(tong)(tong)(tong)，使(shi)用(yong)傳統(tong)(tong)(tong)(tong)方法可(ke)以(yi)編程(cheng)500 mA 的(de)(de)充(chong)(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流。如(ru)果系(xi)(xi)(xi)統(tong)(tong)(tong)(tong)負載(zai)為(wei)200 mA，有效充(chong)(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流僅為(wei)300 mA，充(chong)(chong)(chong)電(dian)(dian)(dian)時間幾乎翻了一翻。如(ru)果使(shi)用(yong)PPM 來研(yan)究(jiu)這(zhe)一相同案例(li)，輸入電(dian)(dian)(dian)流限制設定(ding)(ding)為(wei)900 mA。這(zhe)樣便允(yun)許全(quan)部500 mA充(chong)(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流，且擁有多達400 mA 的(de)(de)額(e)外系(xi)(xi)(xi)統(tong)(tong)(tong)(tong)電(dian)(dian)(dian)流。

　　終(zhong)止和早期計(ji)時(shi)器超時(shi)

　　在對(dui)總電(dian)(dian)(dian)流(liu)進(jin)行(xing)穩壓(ya)的傳統(tong)系統(tong)中，電(dian)(dian)(dian)流(liu)在電(dian)(dian)(dian)池和負載之間共用(yong)(yong)。如果(guo)系統(tong)負載足夠大到從電(dian)(dian)(dian)池拉取(qu)充(chong)(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)，且在計時(shi)器(qi)超時(shi)以(yi)前(qian)電(dian)(dian)(dian)池不充(chong)(chong)(chong)電(dian)(dian)(dian)，則(ze)計時(shi)器(qi)會(hui)出現(xian)偽(wei)超時(shi)。另外，如果(guo)系統(tong)電(dian)(dian)(dian)流(liu)絕對(dui)不會(hui)降至設(she)定(ding)終止電(dian)(dian)(dian)流(liu)以(yi)下，則(ze)永遠不會(hui)終止。電(dian)(dian)(dian)源路徑(jing)管理通(tong)過單獨(du)(du)監測充(chong)(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)，并動態地使用(yong)(yong)可穩壓(ya)計時(shi)器(qi)（通(tong)過減少充(chong)(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)進(jin)行(xing)穩壓(ya)），防止這些條件(jian)出現(xian)。就終止問題(ti)而言，單獨(du)(du)對(dui)充(chong)(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)進(jin)行(xing)監測，可讓終止條件(jian)測定(ding)變(bian)得容(rong)易。

　　基于輸入電(dian)壓(ya)的動(dong)態(tai)電(dian)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(guan)脈沖發生并不是我們想(xiang)要的。

　　圖 4 無(wu) VIN-DPM 情況下的輸入崩潰

　　VIN-DPM 通過限制輸(shu)入電流阻止脈沖發(fa)生，從而防(fang)(fang)止輸(shu)入源崩(beng)潰。圖5 顯示了超負載USB 端(duan)口的結果。VIN-DPM 功能開始生效，降低(di)輸(shu)入電流限制，從而防(fang)(fang)止輸(shu)入源崩(beng)潰。

　　圖 5 使用(yong)VIN-DPM的輸入超(chao)負載保(bao)護

　　NTC 監測（包括JEITA）

　　通過充(chong)電(dian)(dian)期間(jian)的監(jian)測防止電(dian)(dian)池(chi)組損壞(huai)甚至是爆(bao)炸時，電(dian)(dian)池(chi)溫(wen)度(du)極為重要。一般(ban)來說(shuo)，通過對(dui)集(ji)成(cheng)到(dao)電(dian)(dian)池(chi)組中(zhong)(zhong)或者靠近系統板上電(dian)(dian)池(chi)組安裝的NTC 熱敏電(dian)(dian)阻(zu)進行監(jian)測，來完成(cheng)這項工作(zuo)。許(xu)多充(chong)電(dian)(dian)器(qi)都具有集(ji)成(cheng)到(dao)IC 中(zhong)(zhong)的NTC 監(jian)測功(gong)能(neng)。如(ru)果電(dian)(dian)池(chi)溫(wen)度(du)處在某些(xie)非安全溫(wen)度(du)下時，這些(xie)IC 便對(dui)溫(wen)度(du)和禁用充(chong)電(dian)(dian)電(dian)(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(yi)種(zhong)(zhong)無需主(zhu)機關聯的(de)(de)(de)獨(du)立解決方(fang)案(an)。對(dui)于NTC 受(shou)主(zhu)機監測的(de)(de)(de)系(xi)統來說(shuo)，許多IC 都(dou)提供了非常(chang)簡單的(de)(de)(de)實(shi)施。I2C 接口允許用戶動(dong)態地改變充電(dian)電(dian)壓和(he)充電(dian)電(dian)流(liu)，使(shi)用具有這(zhe)種(zhong)(zhong)接口的(de)(de)(de)充電(dian)器時，主(zhu)機根據電(dian)池溫度(du)來修改充電(dian)參數。這(zhe)種(zhong)(zhong)方(fang)法(fa)在沒(mei)有硬件改動(dong)的(de)(de)(de)情況(kuang)下(xia)，在為(wei)不(bu)同平臺和(he)電(dian)池設置要求(qiu)的(de)(de)(de)溫度(du)閾值方(fang)面擁有一(yi)定(ding)的(de)(de)(de)靈活性。

　　USB 充電標準

　　USB 充電時，可以使用許多充電器IC，它們(men)都結合了USB100和USB500 電流限制。通過USB 充電器輸(shu)出(chu)(chu)運行所(suo)有下游電路，讓廣大設(she)計人員能夠確保(bao)不(bu)超出(chu)(chu)USB 電流限制。

　　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(cheng)了一(yi)(yi)個連接(jie)電(dian)(dian)源并通過電(dian)(dian)源供電(dian)(dian)的(de)5V LDO。每(mei)當連接(jie)一(yi)(yi)個有效電(dian)(dian)源時，這種輸出便有效。5V LDO 穩壓(ya)電(dian)(dian)壓(ya)保護(hu)USB 電(dian)(dian)路免受未穩壓(ya)適配器和其他過電(dian)(dian)壓(ya)狀態(tai)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，您的電池充電器設計應該就會變得簡單了。