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(te)性。此外，我(wo)們還將探討一個(ge)應用和現有的(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)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)周(zhou)期(qi)，以(yi)實現(xian)安全(quan)充(chong)(chong)(chong)(chong)(chong)電(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)池(chi)(chi)(chi)(chi)使(shi)用(yong)時(shi)間(jian)。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)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)分(fen)兩個(ge)階段：恒定(ding)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu) （CC） 和恒定(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)位于完全(quan)充(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)下(xia)(xia)時(shi)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)經過穩(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模式下(xia)(xia)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)經過穩(wen)壓(ya)達到(dao)兩個(ge)值之一(yi)(yi)。如果(guo)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(chang)低，則(ze)充(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(jiang)低至預充(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(ping)，以(yi)適應電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)并防止(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)損壞。該閾值因電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)化(hua)學屬性(xing)而(er)不同，一(yi)(yi)般(ban)取決于電(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)旦電(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)升至預充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)閾值以(yi)上(shang)，充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)便升至快速(su)充(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(ping)。典(dian)型(xing)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)的最大建議快速(su)充(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 小時(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)也取決地電(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(xing)充(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，目的是最大化(hua)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)使(shi)用(yong)時(shi)間(jian)。對(dui)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)電(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)壓(ya)上(shang)升。一(yi)(yi)旦電(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)升至穩(wen)壓(ya)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)（一(yi)(yi)般(ban)為(wei)4.2V），充(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(zhu)漸(jian)減(jian)(jian)少，同時(shi)對(dui)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(xing)穩(wen)壓(ya)以(yi)防止(zhi)過充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。在這種模式下(xia)(xia)，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)電(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)流(liu)(liu)(liu)逐(zhu)漸(jian)減(jian)(jian)少，同時(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)阻抗降(jiang)低。如果(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)降(jiang)至預定(ding)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)（一(yi)(yi)般(ban)為(wei)快速(su)充(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10%），則(ze)終止(zhi)充(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)般(ban)不對(dui)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)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，因為(wei)這樣會縮短電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)使(shi)用(yong)壽命(ming)。圖(tu)1 以(yi)圖(tu)形方(fang)式說明了典(dian)型(xing)的充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)周(zhou)期(qi)。

　　圖1典型鋰離子充電周期

　　線(xian)性(xing)解決方案與開(kai)關模式(shi)解決方案對比

　　將(jiang)適配(pei)器(qi)電(dian)(dian)(dian)(dian)壓(ya)轉降為電(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)壓(ya)并控制(zhi)不同(tong)充電(dian)(dian)(dian)(dian)階段的拓(tuo)撲結構(gou)有兩(liang)種：線性穩(wen)壓(ya)器(qi)和(he)(he)(he)電(dian)(dian)(dian)(dian)感開關(guan)。這兩(liang)種拓(tuo)撲結構(gou)在體(ti)積(ji)、效率、解(jie)決方(fang)案成本和(he)(he)(he)電(dian)(dian)(dian)(dian)磁干(gan)擾 （EMI） 輻(fu)射方(fang)面各有優(you)缺點。我們下面介紹這兩(liang)種拓(tuo)撲結構(gou)的各種優(you)點和(he)(he)(he)一些折(zhe)中(zhong)方(fang)法(fa)。

　　一般來說(shuo)，電(dian)(dian)(dian)(dian)感開(kai)關是獲(huo)得最(zui)高效(xiao)率(lv)的(de)(de)(de)最(zui)佳選擇。利用電(dian)(dian)(dian)(dian)阻器(qi)(qi)等檢測(ce)組件(jian)，在輸(shu)出端檢測(ce)充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)。充電(dian)(dian)(dian)(dian)器(qi)(qi)在CC 模式下時(shi)，電(dian)(dian)(dian)(dian)流(liu)反饋電(dian)(dian)(dian)(dian)路(lu)控制(zhi)占空(kong)比。電(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)壓檢測(ce)反饋電(dian)(dian)(dian)(dian)路(lu)控制(zhi)CV 模式下的(de)(de)(de)占空(kong)比。根(gen)據特性集的(de)(de)(de)不同，可(ke)能會(hui)出現其他(ta)一些(xie)控制(zhi)環路(lu)。我們將在后(hou)面詳(xiang)細討論這(zhe)些(xie)環路(lu)。電(dian)(dian)(dian)(dian)感開(kai)關電(dian)(dian)(dian)(dian)路(lu)要(yao)求開(kai)關組件(jian)、整(zheng)流(liu)器(qi)(qi)、電(dian)(dian)(dian)(dian)感和輸(shu)入及輸(shu)出電(dian)(dian)(dian)(dian)容器(qi)(qi)。就(jiu)許多應用而言，通過選擇一種將開(kai)關組件(jian)和整(zheng)流(liu)器(qi)(qi)都嵌入到IC 中的(de)(de)(de)器(qi)(qi)件(jian)，可(ke)以(yi)縮小解決方案的(de)(de)(de)尺寸。根(gen)據不同的(de)(de)(de)負載，這(zhe)些(xie)電(dian)(dian)(dian)(dian)路(lu)的(de)(de)(de)典型效(xiao)率(lv)為80% 到96%。開(kai)關轉換器(qi)(qi)因(yin)其電(dian)(dian)(dian)(dian)感尺寸一般會(hui)要(yao)求更多的(de)(de)(de)空(kong)間，同時(shi)也更加昂貴。開(kai)關轉換器(qi)(qi)還(huan)會(hui)引(yin)起電(dian)(dian)(dian)(dian)感EMI 輻射，以(yi)及開(kai)關帶來的(de)(de)(de)輸(shu)出端噪聲。

　　線性充電器通過(guo)降(jiang)低(di)旁(pang)(pang)路組(zu)件(jian)的(de)(de)(de)(de)輸(shu)入(ru)(ru)(ru)電(dian)(dian)壓(ya)(ya)(ya)，降(jiang)低(di)DC 電(dian)(dian)壓(ya)(ya)(ya)。這樣做的(de)(de)(de)(de)好處是解(jie)決(jue)(jue)方案(an)只要求三個(ge)組(zu)件(jian)：旁(pang)(pang)路組(zu)件(jian)和輸(shu)入(ru)(ru)(ru)/輸(shu)出電(dian)(dian)容。相比電(dian)(dian)感開關，線性(xing)壓(ya)(ya)(ya)降(jiang)穩壓(ya)(ya)(ya)器 （LDO） 通常為一(yi)款低(di)成(cheng)本的(de)(de)(de)(de)解(jie)決(jue)(jue)方案(an)，且噪聲更低(di)。通過(guo)穩壓(ya)(ya)(ya)旁(pang)(pang)路組(zu)件(jian)的(de)(de)(de)(de)電(dian)(dian)阻(zu)來(lai)限制進入(ru)(ru)(ru)電(dian)(dian)池(chi)的(de)(de)(de)(de)電(dian)(dian)流(liu)，從(cong)而對(dui)(dui)充(chong)電(dian)(dian)電(dian)(dian)流(liu)進行控制。電(dian)(dian)流(liu)反饋一(yi)般來(lai)自(zi)充(chong)電(dian)(dian)器IC 的(de)(de)(de)(de)輸(shu)入(ru)(ru)(ru)。對(dui)(dui)電(dian)(dian)池(chi)電(dian)(dian)壓(ya)(ya)(ya)進行檢測，以提供(gong)CV 反饋。改變(bian)旁(pang)(pang)路組(zu)件(jian)的(de)(de)(de)(de)電(dian)(dian)阻(zu)，來(lai)維持進入(ru)(ru)(ru)IC 輸(shu)入(ru)(ru)(ru)端的(de)(de)(de)(de)恒定(ding)(ding)電(dian)(dian)流(liu)或者恒定(ding)(ding)電(dian)(dian)池(chi)電(dian)(dian)壓(ya)(ya)(ya)。器件(jian)的(de)(de)(de)(de)輸(shu)入(ru)(ru)(ru)電(dian)(dian)流(liu)等(deng)于負載電(dian)(dian)流(liu)。這就是說解(jie)決(jue)(jue)方案(an)的(de)(de)(de)(de)效率等(deng)于輸(shu)出電(dian)(dian)壓(ya)(ya)(ya)與輸(shu)入(ru)(ru)(ru)電(dian)(dian)壓(ya)(ya)(ya)的(de)(de)(de)(de)比。LDO 解(jie)決(jue)(jue)方案(an)的(de)(de)(de)(de)缺點(dian)是高(gao)(gao)輸(shu)入(ru)(ru)(ru)輸(shu)出電(dian)(dian)壓(ya)(ya)(ya)比時（即低(di)電(dian)(dian)量(liang)情況(kuang)）效率較(jiao)低(di)。所有(you)功(gong)率都被旁(pang)(pang)路組(zu)件(jian)消耗(hao)，其意味著LDO 并非那些輸(shu)入(ru)(ru)(ru)輸(shu)出差較(jiao)大的(de)(de)(de)(de)高(gao)(gao)充(chong)電(dian)(dian)電(dian)(dian)流(liu)應(ying)(ying)用(yong)的(de)(de)(de)(de)理(li)想選擇。這些高(gao)(gao)功(gong)耗(hao)應(ying)(ying)用(yong)要求散(san)熱，從(cong)而增加了解(jie)決(jue)(jue)方案(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(ying)該使用什么樣(yang)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，效(xiao)率(lv)(lv)(lv)為(wei)72%。首先，這(zhe)(zhe)個(ge)效(xiao)率(lv)(lv)(lv)聽起來似(si)乎不太壞。如果您從功(gong)(gong)耗(hao)(hao)的(de)(de)角度(du)來看它，這(zhe)(zhe)種應用(yong)要消耗(hao)(hao)約(yue)2W。在(zai)(zai)一(yi)個(ge)熱阻(zu) （ΘJA） 為(wei)40°C/W 的(de)(de)應用(yong)中，芯片溫度(du)上升80°C。在(zai)(zai)40°C 環境(jing)溫度(du)下(xia)，電(dian)路板溫度(du)會(hui)上升至120°C，其對手持設(she)備來說是不可(ke)接(jie)受(shou)的(de)(de)。在(zai)(zai)極(ji)低(di)電(dian)池電(dian)壓（即3 V）下(xia)，這(zhe)(zhe)一(yi)問題甚至會(hui)變得極(ji)端嚴重。相同3V 條(tiao)件下(xia)，溫度(du)升至120°C。讓我(wo)們(men)來看相同條(tiao)件下(xia)的(de)(de)開(kai)(kai)關(guan)解決(jue)方案，使用(yong)一(yi)個(ge)單體(ti)電(dian)池IC 充電(dian)器時，效(xiao)率(lv)(lv)(lv)上升至約(yue)85%。使用(yong)一(yi)塊(kuai)3.6V 電(dian)池時，功(gong)(gong)耗(hao)(hao)低(di)于1W，從而帶來40°C 的(de)(de)溫升。3V 時這(zhe)(zhe)種改(gai)善(shan)更加(jia)明顯。假設(she)3V 輸出時的(de)(de)效(xiao)率(lv)(lv)(lv)為(wei)80%，則功(gong)(gong)耗(hao)(hao)低(di)于800 mW，因此溫升會(hui)更低(di)（約(yue)32°C）。這(zhe)(zhe)些智能手機的(de)(de)體(ti)積一(yi)般(ban)可(ke)以容許稍(shao)大一(yi)點的(de)(de)解決(jue)方案，并且能夠(gou)承受(shou)開(kai)(kai)關(guan)模式解決(jue)方案相關(guan)的(de)(de)稍(shao)許成本增加(jia)。

　　為任務選擇正確的IC

　　在(zai)您已經完成(cheng)您的初步熱(re)分析并(bing)且選好充電器(qi)拓撲以(yi)后，您便可以(yi)轉到選擇應用的最佳(jia)IC 上來。新型的電池充電器(qi)解(jie)決方案集成(cheng)了(le)許多(duo)(duo)特性，可以(yi)利用它們(men)改(gai)善系統(tong)的性能。諸(zhu)如輸(shu)入過壓保護、電源路徑管理 （PPM）、VIN_DPM、散熱(re)穩(wen)壓、負溫度系數熱(re)敏電阻 （NTC） 監測和USB 充電等(deng)特性，都(dou)被集成(cheng)到許多(duo)(duo)電池充電器(qi)IC 中(zhong)。大(da)多(duo)(duo)數單體電池充電器(qi)解(jie)決方案都(dou)已將要求FET 集成(cheng)到了(le)器(qi)件中(zhong)，旨在(zai)節省(sheng)電路板面積(ji)。

　　輸(shu)(shu)入過壓保(bao)護（單輸(shu)(shu)入與(yu)雙輸(shu)(shu)入對(dui)比）

　　在當(dang)今(jin)的(de)市(shi)(shi)場(chang)上，USB 電(dian)(dian)(dian)源已經成為(wei)最為(wei)常見的(de)電(dian)(dian)(dian)源，因此通過(guo)(guo)(guo)USB 電(dian)(dian)(dian)源充電(dian)(dian)(dian)已經成為(wei)一(yi)(yi)種必然性。市(shi)(shi)場(chang)已經從使用(yong)(yong)專門AC 適(shi)配器(qi)和單獨USB 接(jie)(jie)(jie)(jie)口(kou)(kou)(kou)的(de)初始雙輸入(ru)(ru)(ru)轉變(bian)為(wei)將(jiang)一(yi)(yi)個(ge)USB 接(jie)(jie)(jie)(jie)口(kou)(kou)(kou)既作為(wei)墻上電(dian)(dian)(dian)源適(shi)合器(qi)接(jie)(jie)(jie)(jie)口(kou)(kou)(kou)使用(yong)(yong)，也作為(wei)使用(yong)(yong)相(xiang)同線(xian)纜的(de)USB 數據輸入(ru)(ru)(ru)接(jie)(jie)(jie)(jie)口(kou)(kou)(kou)的(de)單輸入(ru)(ru)(ru)解(jie)(jie)決(jue)方(fang)(fang)案(an)。這樣(yang)便(bian)導致一(yi)(yi)種從雙輸入(ru)(ru)(ru)解(jie)(jie)決(jue)方(fang)(fang)案(an)向(xiang)單輸入(ru)(ru)(ru)解(jie)(jie)決(jue)方(fang)(fang)案(an)的(de)轉移(yi)。單輸入(ru)(ru)(ru)在接(jie)(jie)(jie)(jie)口(kou)(kou)(kou)方(fang)(fang)面存在許多挑戰。由于存在如此多的(de)配件市(shi)(shi)場(chang)適(shi)配器(qi)解(jie)(jie)決(jue)方(fang)(fang)案(an)和一(yi)(yi)種通用(yong)(yong)接(jie)(jie)(jie)(jie)口(kou)(kou)(kou)，輸入(ru)(ru)(ru)端必須要能夠在無損壞的(de)情(qing)況下(xia)承受(shou)更(geng)高的(de)電(dian)(dian)(dian)壓。由于電(dian)(dian)(dian)池充電(dian)(dian)(dian)器(qi)始終連接(jie)(jie)(jie)(jie)到輸入(ru)(ru)(ru)端，因此充電(dian)(dian)(dian)器(qi)對所有(you)下(xia)游電(dian)(dian)(dian)路實(shi)施(shi)過(guo)(guo)(guo)電(dian)(dian)(dian)壓狀態保(bao)(bao)護是有(you)道理的(de)。為(wei)了(le)實(shi)施(shi)這一(yi)(yi)功能，市(shi)(shi)場(chang)上出現(xian)了(le)許多能夠承受(shou)20V 甚至(zhi)30V 電(dian)(dian)(dian)壓的(de)解(jie)(jie)決(jue)方(fang)(fang)案(an)。另外(wai)，這些器(qi)件都具有(you)過(guo)(guo)(guo)電(dian)(dian)(dian)壓保(bao)(bao)護 （OVP） 電(dian)(dian)(dian)路，其(qi)在輸入(ru)(ru)(ru)超出OVP 閾值(zhi)時阻(zu)止器(qi)件運行。這樣(yang)便(bian)進一(yi)(yi)步保(bao)(bao)護了(le)下(xia)游電(dian)(dian)(dian)路，使其(qi)免(mian)受(shou)潛(qian)在的(de)瞬態過(guo)(guo)(guo)電(dian)(dian)(dian)壓狀態損壞。

　　目前，隨著(zhu)綠色輸(shu)入（即太(tai)陽能電池）或無線充(chong)電的(de)出(chu)現，應(ying)用又再一次(ci)向雙輸(shu)入要求(qiu)轉移(yi)。根據具體的(de)應(ying)用要求(qiu)，兩(liang)種配置結構(gou)都(dou)可以使用。

　　電源路徑管理(li)/最(zui)小(xiao)系統(tong)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，消除了這些問題［2］。

　　圖 2 傳統拓撲結構(gou)舉例

　　圖 3 電源路徑拓(tuo)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

　　由于系統(tong)(tong)電(dian)(dian)(dian)流(liu)(liu)(liu)和充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)(liu)是單獨編程(cheng)的，因此可(ke)以使(shi)用(yong)(yong)適配器的滿功率，其與電(dian)(dian)(dian)池的容量和充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)(liu)的大(da)小均無關。傳統(tong)(tong)拓(tuo)撲結構(gou)中，充(chong)(chong)電(dian)(dian)(dian)器的輸出電(dian)(dian)(dian)流(liu)(liu)(liu)必須(xu)設定為(wei)(wei)最(zui)大(da)充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)(liu)，以應對沒有(you)系統(tong)(tong)負載(zai)的情況。當系統(tong)(tong)中有(you)負載(zai)時，由于系統(tong)(tong)吸收可(ke)用(yong)(yong)電(dian)(dian)(dian)流(liu)(liu)(liu)，有(you)效充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)(liu)降低。例(li)如(ru)，一個使(shi)用(yong)(yong)900 mA 適配器和500 mAhr 電(dian)(dian)(dian)池的系統(tong)(tong)，使(shi)用(yong)(yong)傳統(tong)(tong)方法可(ke)以編程(cheng)500 mA 的充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)(liu)。如(ru)果系統(tong)(tong)負載(zai)為(wei)(wei)200 mA，有(you)效充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)(liu)僅為(wei)(wei)300 mA，充(chong)(chong)電(dian)(dian)(dian)時間幾乎(hu)翻了(le)一翻。如(ru)果使(shi)用(yong)(yong)PPM 來研究這(zhe)一相同(tong)案例(li)，輸入電(dian)(dian)(dian)流(liu)(liu)(liu)限制設定為(wei)(wei)900 mA。這(zhe)樣便允(yun)許全部500 mA充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)(liu)，且擁有(you)多達400 mA 的額外(wai)系統(tong)(tong)電(dian)(dian)(dian)流(liu)(liu)(liu)。

　　終止和早(zao)期計時器超時

　　在對(dui)總電(dian)(dian)(dian)流(liu)(liu)(liu)進(jin)行穩壓(ya)的傳統系統中，電(dian)(dian)(dian)流(liu)(liu)(liu)在電(dian)(dian)(dian)池(chi)和(he)負(fu)載之(zhi)間共用。如果(guo)系統負(fu)載足夠(gou)大到從電(dian)(dian)(dian)池(chi)拉取充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)(liu)，且在計(ji)時(shi)器超時(shi)以前電(dian)(dian)(dian)池(chi)不充(chong)(chong)電(dian)(dian)(dian)，則計(ji)時(shi)器會(hui)出現偽超時(shi)。另外，如果(guo)系統電(dian)(dian)(dian)流(liu)(liu)(liu)絕對(dui)不會(hui)降至設定(ding)終止(zhi)(zhi)(zhi)(zhi)電(dian)(dian)(dian)流(liu)(liu)(liu)以下，則永遠(yuan)不會(hui)終止(zhi)(zhi)(zhi)(zhi)。電(dian)(dian)(dian)源(yuan)路徑(jing)管理通過單獨監測(ce)(ce)充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)(liu)，并動態地使用可穩壓(ya)計(ji)時(shi)器（通過減少充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)(liu)進(jin)行穩壓(ya)），防止(zhi)(zhi)(zhi)(zhi)這些條件出現。就終止(zhi)(zhi)(zhi)(zhi)問題而言(yan)，單獨對(dui)充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)(liu)進(jin)行監測(ce)(ce)，可讓終止(zhi)(zhi)(zhi)(zhi)條件測(ce)(ce)定(ding)變得容(rong)易(yi)。

　　基(ji)于輸入電壓的動態電源管(guan)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(zhong)開/關脈(mo)沖發生(sheng)并不(bu)是我們想(xiang)要的。

　　圖 4 無 VIN-DPM 情況下(xia)的輸入崩(beng)潰

　　VIN-DPM 通過限制(zhi)輸(shu)(shu)(shu)入(ru)(ru)電(dian)流阻止脈沖發生(sheng)，從而(er)防(fang)止輸(shu)(shu)(shu)入(ru)(ru)源崩潰。圖5 顯示了(le)超負(fu)載USB 端口的結果。VIN-DPM 功能開始(shi)生(sheng)效(xiao)，降低輸(shu)(shu)(shu)入(ru)(ru)電(dian)流限制(zhi)，從而(er)防(fang)止輸(shu)(shu)(shu)入(ru)(ru)源崩潰。

　　圖 5 使用VIN-DPM的輸入超負載保護

　　NTC 監(jian)測(ce)（包(bao)括JEITA）

　　通過(guo)(guo)充(chong)電(dian)期間的監(jian)(jian)(jian)測防(fang)止電(dian)池(chi)組(zu)(zu)損壞甚至是(shi)爆炸時(shi)，電(dian)池(chi)溫度(du)極為重要。一(yi)般(ban)來說，通過(guo)(guo)對集成(cheng)到電(dian)池(chi)組(zu)(zu)中(zhong)或(huo)者靠(kao)近系(xi)統板(ban)上電(dian)池(chi)組(zu)(zu)安裝(zhuang)的NTC 熱敏電(dian)阻(zu)進行監(jian)(jian)(jian)測，來完成(cheng)這(zhe)項工作。許多充(chong)電(dian)器都具有(you)集成(cheng)到IC 中(zhong)的NTC 監(jian)(jian)(jian)測功能。如果電(dian)池(chi)溫度(du)處在某些(xie)非安全溫度(du)下時(shi)，這(zhe)些(xie)IC 便對溫度(du)和(he)禁用充(chong)電(dian)電(dian)流進行監(jian)(jian)(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無需(xu)主(zhu)機(ji)(ji)關聯的(de)獨立解決方案(an)。對于NTC 受主(zhu)機(ji)(ji)監測(ce)的(de)系(xi)統來說，許多IC 都(dou)提(ti)供(gong)了非常簡單的(de)實施。I2C 接(jie)口允許用戶動(dong)態(tai)地改(gai)變充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)壓和充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流，使用具有(you)(you)這種接(jie)口的(de)充(chong)電(dian)(dian)(dian)器(qi)時，主(zhu)機(ji)(ji)根據電(dian)(dian)(dian)池溫度來修改(gai)充(chong)電(dian)(dian)(dian)參(can)數。這種方法在(zai)沒有(you)(you)硬件改(gai)動(dong)的(de)情況下，在(zai)為不同平臺和電(dian)(dian)(dian)池設置要求的(de)溫度閾值方面擁有(you)(you)一定的(de)靈活性。

　　USB 充(chong)電(dian)標(biao)準(zhun)

　　USB 充電時，可以使用許多充電器IC，它們(men)都結合了USB100和(he)USB500 電(dian)流(liu)限制。通過USB 充(chong)電(dian)器輸(shu)出運行(xing)所有下游電(dian)路，讓廣(guang)大設計人員能夠確保不超出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(ji)成了(le)一個連(lian)接電(dian)源(yuan)并通過電(dian)源(yuan)供(gong)電(dian)的(de)5V LDO。每當連(lian)接一個有效電(dian)源(yuan)時，這種輸出便(bian)有效。5V LDO 穩壓電(dian)壓保護USB 電(dian)路免(mian)受未穩壓適配器和其(qi)他過電(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，您的電池充電器設計應該就(jiu)會(hui)變得簡(jian)單了。