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(yi)些特性。此外，我們還將探討一(yi)個應用和現有的(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)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)周期(qi)，以(yi)實(shi)現(xian)安全(quan)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)并最(zui)(zui)大(da)化電(dian)(dian)(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)(shi)間。電(dian)(dian)(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)(dian)(dian)分兩個(ge)階段：恒(heng)定(ding)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu) （CC） 和恒(heng)定(ding)電(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)池(chi)(chi)(chi)(chi)(chi)(chi)位于(yu)完全(quan)充(chong)(chong)滿(man)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)以(yi)下時(shi)(shi)(shi)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)經過穩(wen)壓(ya)(ya)進(jin)入電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)。在(zai)CC模式(shi)下，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)經過穩(wen)壓(ya)(ya)達到兩個(ge)值(zhi)之一。如果電(dian)(dian)(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)(dian)(dian)壓(ya)(ya)非常低(di)，則(ze)充(chong)(chong)電(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)流(liu)(liu)(liu)(liu)降低(di)至(zhi)預充(chong)(chong)電(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)平(ping)，以(yi)適應(ying)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)并防(fang)(fang)止電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)損壞。該(gai)閾值(zhi)因(yin)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)化學屬(shu)性而不同，一般(ban)(ban)取(qu)決(jue)(jue)于(yu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)制(zhi)造廠商。一旦(dan)電(dian)(dian)(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)(dian)(dian)壓(ya)(ya)升(sheng)至(zhi)預充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)閾值(zhi)以(yi)上(shang)，充(chong)(chong)電(dian)(dian)(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)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)。典型電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)的(de)最(zui)(zui)大(da)建(jian)議快速(su)充(chong)(chong)電(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)流(liu)(liu)(liu)(liu)為1C（C=1 小時(shi)(shi)(shi)內耗(hao)盡電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)所需的(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)），但該(gai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)也取(qu)決(jue)(jue)地電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)制(zhi)造廠商。典型充(chong)(chong)電(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)流(liu)(liu)(liu)(liu)為~0.8C，目的(de)是最(zui)(zui)大(da)化電(dian)(dian)(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)(shi)間。對電(dian)(dian)(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)(dian)(dian)時(shi)(shi)(shi)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)上(shang)升(sheng)。一旦(dan)電(dian)(dian)(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)(dian)(dian)壓(ya)(ya)升(sheng)至(zhi)穩(wen)壓(ya)(ya)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)（一般(ban)(ban)為4.2V），充(chong)(chong)電(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)流(liu)(liu)(liu)(liu)逐漸減(jian)少(shao)，同時(shi)(shi)(shi)對電(dian)(dian)(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)(dian)(dian)壓(ya)(ya)進(jin)行穩(wen)壓(ya)(ya)以(yi)防(fang)(fang)止過充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。在(zai)這種模式(shi)下，電(dian)(dian)(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)(dian)(dian)時(shi)(shi)(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)逐漸減(jian)少(shao)，同時(shi)(shi)(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)阻抗降低(di)。如果電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)(liu)降至(zhi)預定(ding)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)（一般(ban)(ban)為快速(su)充(chong)(chong)電(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)流(liu)(liu)(liu)(liu)的(de)10%），則(ze)終止充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。我(wo)們一般(ban)(ban)不對電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)浮充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，因(yin)為這樣會縮(suo)短電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)(chi)使用(yong)壽命。圖1 以(yi)圖形方式(shi)說明了典型的(de)充(chong)(chong)電(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

　　線性解決(jue)方案與開(kai)關模(mo)式(shi)解決(jue)方案對比

　　將適配器電(dian)(dian)壓(ya)轉降(jiang)為電(dian)(dian)池電(dian)(dian)壓(ya)并控(kong)制(zhi)不同(tong)充電(dian)(dian)階(jie)段的(de)拓(tuo)撲(pu)(pu)結構有(you)兩種(zhong)：線(xian)性穩壓(ya)器和電(dian)(dian)感開(kai)關。這(zhe)兩種(zhong)拓(tuo)撲(pu)(pu)結構在體(ti)積、效率、解決方(fang)案成本和電(dian)(dian)磁干擾 （EMI） 輻射方(fang)面(mian)(mian)各有(you)優缺(que)點。我(wo)們下(xia)面(mian)(mian)介紹這(zhe)兩種(zhong)拓(tuo)撲(pu)(pu)結構的(de)各種(zhong)優點和一些(xie)折中方(fang)法。

　　一(yi)(yi)般來(lai)說，電(dian)感(gan)開(kai)關(guan)(guan)是獲得(de)最(zui)高效(xiao)率(lv)的(de)(de)(de)最(zui)佳選擇(ze)。利用電(dian)阻器等檢(jian)測組件，在(zai)(zai)(zai)輸(shu)(shu)(shu)出(chu)端檢(jian)測充(chong)電(dian)電(dian)流(liu)(liu)(liu)。充(chong)電(dian)器在(zai)(zai)(zai)CC 模式下(xia)時(shi)，電(dian)流(liu)(liu)(liu)反(fan)饋電(dian)路控制占空(kong)比。電(dian)池電(dian)壓(ya)檢(jian)測反(fan)饋電(dian)路控制CV 模式下(xia)的(de)(de)(de)占空(kong)比。根據特(te)性集的(de)(de)(de)不同(tong)，可(ke)能會出(chu)現其他一(yi)(yi)些控制環路。我們將在(zai)(zai)(zai)后面詳(xiang)細討論這些環路。電(dian)感(gan)開(kai)關(guan)(guan)電(dian)路要求(qiu)開(kai)關(guan)(guan)組件、整流(liu)(liu)(liu)器、電(dian)感(gan)和輸(shu)(shu)(shu)入(ru)及(ji)輸(shu)(shu)(shu)出(chu)電(dian)容器。就許(xu)多(duo)應用而言，通過選擇(ze)一(yi)(yi)種將開(kai)關(guan)(guan)組件和整流(liu)(liu)(liu)器都(dou)嵌入(ru)到(dao)IC 中的(de)(de)(de)器件，可(ke)以縮小(xiao)解(jie)決方案的(de)(de)(de)尺寸(cun)。根據不同(tong)的(de)(de)(de)負(fu)載，這些電(dian)路的(de)(de)(de)典型效(xiao)率(lv)為80% 到(dao)96%。開(kai)關(guan)(guan)轉(zhuan)換(huan)器因其電(dian)感(gan)尺寸(cun)一(yi)(yi)般會要求(qiu)更(geng)多(duo)的(de)(de)(de)空(kong)間，同(tong)時(shi)也更(geng)加昂貴。開(kai)關(guan)(guan)轉(zhuan)換(huan)器還會引起(qi)電(dian)感(gan)EMI 輻(fu)射，以及(ji)開(kai)關(guan)(guan)帶來(lai)的(de)(de)(de)輸(shu)(shu)(shu)出(chu)端噪聲。

　　線性充電器通過(guo)降低(di)旁路(lu)組(zu)件(jian)(jian)(jian)的(de)輸(shu)(shu)(shu)入(ru)(ru)(ru)電(dian)(dian)(dian)壓(ya)(ya)(ya)，降低(di)DC 電(dian)(dian)(dian)壓(ya)(ya)(ya)。這(zhe)樣(yang)做的(de)好處是(shi)解(jie)決方(fang)案只要(yao)求(qiu)三個組(zu)件(jian)(jian)(jian)：旁路(lu)組(zu)件(jian)(jian)(jian)和輸(shu)(shu)(shu)入(ru)(ru)(ru)/輸(shu)(shu)(shu)出(chu)電(dian)(dian)(dian)容。相比電(dian)(dian)(dian)感(gan)開關，線性(xing)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(jie)決方(fang)案，且噪聲更低(di)。通過(guo)穩(wen)壓(ya)(ya)(ya)旁路(lu)組(zu)件(jian)(jian)(jian)的(de)電(dian)(dian)(dian)阻(zu)來限制進(jin)入(ru)(ru)(ru)電(dian)(dian)(dian)池的(de)電(dian)(dian)(dian)流(liu)(liu)，從(cong)而對(dui)(dui)充電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)進(jin)行控制。電(dian)(dian)(dian)流(liu)(liu)反饋(kui)一般來自充電(dian)(dian)(dian)器IC 的(de)輸(shu)(shu)(shu)入(ru)(ru)(ru)。對(dui)(dui)電(dian)(dian)(dian)池電(dian)(dian)(dian)壓(ya)(ya)(ya)進(jin)行檢測，以提供CV 反饋(kui)。改變旁路(lu)組(zu)件(jian)(jian)(jian)的(de)電(dian)(dian)(dian)阻(zu)，來維持進(jin)入(ru)(ru)(ru)IC 輸(shu)(shu)(shu)入(ru)(ru)(ru)端的(de)恒定電(dian)(dian)(dian)流(liu)(liu)或者恒定電(dian)(dian)(dian)池電(dian)(dian)(dian)壓(ya)(ya)(ya)。器件(jian)(jian)(jian)的(de)輸(shu)(shu)(shu)入(ru)(ru)(ru)電(dian)(dian)(dian)流(liu)(liu)等(deng)于負載電(dian)(dian)(dian)流(liu)(liu)。這(zhe)就是(shi)說解(jie)決方(fang)案的(de)效(xiao)率等(deng)于輸(shu)(shu)(shu)出(chu)電(dian)(dian)(dian)壓(ya)(ya)(ya)與輸(shu)(shu)(shu)入(ru)(ru)(ru)電(dian)(dian)(dian)壓(ya)(ya)(ya)的(de)比。LDO 解(jie)決方(fang)案的(de)缺點是(shi)高輸(shu)(shu)(shu)入(ru)(ru)(ru)輸(shu)(shu)(shu)出(chu)電(dian)(dian)(dian)壓(ya)(ya)(ya)比時（即低(di)電(dian)(dian)(dian)量情況(kuang)）效(xiao)率較低(di)。所(suo)有功率都被旁路(lu)組(zu)件(jian)(jian)(jian)消耗，其(qi)意味著LDO 并非那些輸(shu)(shu)(shu)入(ru)(ru)(ru)輸(shu)(shu)(shu)出(chu)差(cha)較大(da)的(de)高充電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)應用(yong)的(de)理想選擇(ze)。這(zhe)些高功耗應用(yong)要(yao)求(qiu)散熱，從(cong)而增加了解(jie)決方(fang)案的(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(ying)該使用什么樣的拓(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(shi)(shi)，效(xiao)率為72%。首先，這個(ge)效(xiao)率聽起來似乎(hu)不太(tai)壞。如果您從功耗(hao)(hao)的角(jiao)度(du)(du)來看它，這種應用(yong)要消耗(hao)(hao)約(yue)2W。在(zai)(zai)一個(ge)熱(re)阻 （ΘJA） 為40°C/W 的應用(yong)中，芯片溫度(du)(du)上升80°C。在(zai)(zai)40°C 環境(jing)溫度(du)(du)下，電(dian)(dian)路(lu)板(ban)溫度(du)(du)會上升至120°C，其(qi)對手持設(she)備(bei)來說是不可(ke)接受的。在(zai)(zai)極低電(dian)(dian)池(chi)電(dian)(dian)壓（即3 V）下，這一問(wen)題甚至會變得(de)極端嚴重。相同3V 條(tiao)件(jian)下，溫度(du)(du)升至120°C。讓我們來看相同條(tiao)件(jian)下的開關解(jie)決方(fang)案，使用(yong)一個(ge)單(dan)體(ti)電(dian)(dian)池(chi)IC 充電(dian)(dian)器時(shi)(shi)，效(xiao)率上升至約(yue)85%。使用(yong)一塊3.6V 電(dian)(dian)池(chi)時(shi)(shi)，功耗(hao)(hao)低于(yu)1W，從而帶來40°C 的溫升。3V 時(shi)(shi)這種改善更(geng)加(jia)明顯(xian)。假設(she)3V 輸出時(shi)(shi)的效(xiao)率為80%，則功耗(hao)(hao)低于(yu)800 mW，因此(ci)溫升會更(geng)低（約(yue)32°C）。這些智能手機的體(ti)積(ji)一般可(ke)以容許稍大一點(dian)的解(jie)決方(fang)案，并(bing)且能夠承受開關模式解(jie)決方(fang)案相關的稍許成(cheng)本增加(jia)。

　　為任務選擇正確的IC

　　在您(nin)已經完成(cheng)(cheng)您(nin)的(de)初步熱分析并且選好充(chong)(chong)電(dian)(dian)(dian)器拓(tuo)撲以后，您(nin)便可以轉到(dao)(dao)選擇應用的(de)最佳IC 上來。新型的(de)電(dian)(dian)(dian)池(chi)充(chong)(chong)電(dian)(dian)(dian)器解決方案(an)集成(cheng)(cheng)了(le)許多特性，可以利用它們改善系(xi)統(tong)的(de)性能。諸如輸入過壓保護、電(dian)(dian)(dian)源路(lu)徑管理 （PPM）、VIN_DPM、散(san)熱穩壓、負溫度系(xi)數熱敏(min)電(dian)(dian)(dian)阻(zu) （NTC） 監測(ce)和(he)USB 充(chong)(chong)電(dian)(dian)(dian)等特性，都被集成(cheng)(cheng)到(dao)(dao)許多電(dian)(dian)(dian)池(chi)充(chong)(chong)電(dian)(dian)(dian)器IC 中(zhong)。大多數單體電(dian)(dian)(dian)池(chi)充(chong)(chong)電(dian)(dian)(dian)器解決方案(an)都已將要求FET 集成(cheng)(cheng)到(dao)(dao)了(le)器件中(zhong)，旨在節省電(dian)(dian)(dian)路(lu)板面積。

　　輸入過壓保護（單(dan)輸入與雙(shuang)輸入對比）

　　在(zai)(zai)當今的(de)(de)(de)市(shi)場(chang)上(shang)，USB 電(dian)(dian)(dian)源已(yi)(yi)經(jing)成為(wei)(wei)最(zui)為(wei)(wei)常見的(de)(de)(de)電(dian)(dian)(dian)源，因此通(tong)過USB 電(dian)(dian)(dian)源充電(dian)(dian)(dian)已(yi)(yi)經(jing)成為(wei)(wei)一種必然性。市(shi)場(chang)已(yi)(yi)經(jing)從使用專門AC 適(shi)配器(qi)和單獨USB 接(jie)口(kou)(kou)的(de)(de)(de)初始雙輸(shu)(shu)入(ru)轉變為(wei)(wei)將一個USB 接(jie)口(kou)(kou)既作為(wei)(wei)墻上(shang)電(dian)(dian)(dian)源適(shi)合器(qi)接(jie)口(kou)(kou)使用，也(ye)作為(wei)(wei)使用相同線纜的(de)(de)(de)USB 數據輸(shu)(shu)入(ru)接(jie)口(kou)(kou)的(de)(de)(de)單輸(shu)(shu)入(ru)解(jie)決(jue)方(fang)(fang)(fang)案(an)。這(zhe)樣便(bian)導致一種從雙輸(shu)(shu)入(ru)解(jie)決(jue)方(fang)(fang)(fang)案(an)向單輸(shu)(shu)入(ru)解(jie)決(jue)方(fang)(fang)(fang)案(an)的(de)(de)(de)轉移(yi)。單輸(shu)(shu)入(ru)在(zai)(zai)接(jie)口(kou)(kou)方(fang)(fang)(fang)面(mian)存(cun)在(zai)(zai)許(xu)多(duo)挑戰。由(you)于存(cun)在(zai)(zai)如此多(duo)的(de)(de)(de)配件市(shi)場(chang)適(shi)配器(qi)解(jie)決(jue)方(fang)(fang)(fang)案(an)和一種通(tong)用接(jie)口(kou)(kou)，輸(shu)(shu)入(ru)端必須要能(neng)夠(gou)(gou)在(zai)(zai)無損(sun)(sun)壞的(de)(de)(de)情況下(xia)承受更高的(de)(de)(de)電(dian)(dian)(dian)壓(ya)。由(you)于電(dian)(dian)(dian)池充電(dian)(dian)(dian)器(qi)始終連(lian)接(jie)到輸(shu)(shu)入(ru)端，因此充電(dian)(dian)(dian)器(qi)對所有下(xia)游電(dian)(dian)(dian)路實施過電(dian)(dian)(dian)壓(ya)狀態(tai)(tai)保護(hu)是有道理的(de)(de)(de)。為(wei)(wei)了實施這(zhe)一功(gong)能(neng)，市(shi)場(chang)上(shang)出(chu)(chu)現了許(xu)多(duo)能(neng)夠(gou)(gou)承受20V 甚(shen)至30V 電(dian)(dian)(dian)壓(ya)的(de)(de)(de)解(jie)決(jue)方(fang)(fang)(fang)案(an)。另外，這(zhe)些器(qi)件都具有過電(dian)(dian)(dian)壓(ya)保護(hu) （OVP） 電(dian)(dian)(dian)路，其在(zai)(zai)輸(shu)(shu)入(ru)超出(chu)(chu)OVP 閾(yu)值時阻止器(qi)件運行。這(zhe)樣便(bian)進一步保護(hu)了下(xia)游電(dian)(dian)(dian)路，使其免受潛在(zai)(zai)的(de)(de)(de)瞬態(tai)(tai)過電(dian)(dian)(dian)壓(ya)狀態(tai)(tai)損(sun)(sun)壞。

　　目前，隨(sui)著綠(lv)色(se)輸(shu)入(ru)（即太陽能電(dian)池）或(huo)無(wu)線(xian)充電(dian)的出現，應(ying)用又(you)再一(yi)次向雙輸(shu)入(ru)要求轉移。根據具體的應(ying)用要求，兩(liang)種配置結構都可(ke)以使用。

　　電源路(lu)徑管理/最小系(xi)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(ce)，消(xiao)除(chu)了這些問題［2］。

　　圖(tu) 2 傳統拓(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(you)于系(xi)統(tong)(tong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)和充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)是(shi)單獨編程的，因此可以使(shi)用(yong)適(shi)配器的滿功(gong)率，其與電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池的容量和充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)的大(da)小均無關(guan)。傳(chuan)統(tong)(tong)拓(tuo)撲結構中(zhong)，充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)器的輸出(chu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)必(bi)須設定(ding)為(wei)最(zui)大(da)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)，以應對沒(mei)有系(xi)統(tong)(tong)負(fu)載(zai)的情況。當(dang)系(xi)統(tong)(tong)中(zhong)有負(fu)載(zai)時，由(you)于系(xi)統(tong)(tong)吸收可用(yong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)，有效充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)降低。例如，一個使(shi)用(yong)900 mA 適(shi)配器和500 mAhr 電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池的系(xi)統(tong)(tong)，使(shi)用(yong)傳(chuan)統(tong)(tong)方法可以編程500 mA 的充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)。如果(guo)系(xi)統(tong)(tong)負(fu)載(zai)為(wei)200 mA，有效充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)僅為(wei)300 mA，充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)時間幾(ji)乎翻了一翻。如果(guo)使(shi)用(yong)PPM 來研(yan)究(jiu)這(zhe)(zhe)一相同案例，輸入電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)限制設定(ding)為(wei)900 mA。這(zhe)(zhe)樣便(bian)允許全(quan)部500 mA充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)，且擁(yong)有多達400 mA 的額(e)外系(xi)統(tong)(tong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(liu)。

　　終止(zhi)和早期計時器超時

　　在(zai)對總電(dian)(dian)流(liu)進(jin)行(xing)穩(wen)壓的傳統(tong)系統(tong)中，電(dian)(dian)流(liu)在(zai)電(dian)(dian)池和負(fu)載(zai)之間共用。如果(guo)系統(tong)負(fu)載(zai)足夠大到從電(dian)(dian)池拉取充(chong)(chong)電(dian)(dian)電(dian)(dian)流(liu)，且在(zai)計(ji)時器超時以前電(dian)(dian)池不(bu)充(chong)(chong)電(dian)(dian)，則(ze)計(ji)時器會出現(xian)偽超時。另外，如果(guo)系統(tong)電(dian)(dian)流(liu)絕對不(bu)會降至設定終(zhong)(zhong)止電(dian)(dian)流(liu)以下，則(ze)永遠不(bu)會終(zhong)(zhong)止。電(dian)(dian)源路徑管理通過(guo)單獨監(jian)測充(chong)(chong)電(dian)(dian)電(dian)(dian)流(liu)，并動態地使用可(ke)穩(wen)壓計(ji)時器（通過(guo)減少充(chong)(chong)電(dian)(dian)電(dian)(dian)流(liu)進(jin)行(xing)穩(wen)壓），防止這些條(tiao)件(jian)出現(xian)。就終(zhong)(zhong)止問題而言(yan)，單獨對充(chong)(chong)電(dian)(dian)電(dian)(dian)流(liu)進(jin)行(xing)監(jian)測，可(ke)讓(rang)終(zhong)(zhong)止條(tiao)件(jian)測定變得容易。

　　基于(yu)輸入電(dian)(dian)壓的動態電(dian)(dian)源管理(li) （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/關(guan)脈沖發生并不(bu)是我們想要的(de)。

　　圖 4 無(wu) VIN-DPM 情況(kuang)下的輸入崩潰

　　VIN-DPM 通過(guo)限制輸入電(dian)流阻止脈沖發生(sheng)，從而(er)防止輸入源崩潰。圖5 顯(xian)示了超負載USB 端口的結(jie)果。VIN-DPM 功能開始生(sheng)效，降(jiang)低輸入電(dian)流限制，從而(er)防止輸入源崩潰。

　　圖 5 使用(yong)VIN-DPM的輸入超(chao)負載保護

　　NTC 監測(ce)（包括(kuo)JEITA）

　　通過(guo)充(chong)電(dian)期間的(de)監(jian)測防止電(dian)池(chi)組損壞甚至是爆(bao)炸時，電(dian)池(chi)溫(wen)度(du)極為重要(yao)。一(yi)般來說，通過(guo)對(dui)集成到電(dian)池(chi)組中(zhong)或者靠近系統(tong)板上電(dian)池(chi)組安裝的(de)NTC 熱敏電(dian)阻進行監(jian)測，來完成這(zhe)項(xiang)工作。許多充(chong)電(dian)器都具有集成到IC 中(zhong)的(de)NTC 監(jian)測功能。如果電(dian)池(chi)溫(wen)度(du)處在某(mou)些(xie)非安全溫(wen)度(du)下時，這(zhe)些(xie)IC 便對(dui)溫(wen)度(du)和(he)禁(jin)用充(chong)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(yi)種無(wu)需主機關聯的(de)獨立解決方(fang)案。對于NTC 受主機監測的(de)系統來(lai)說，許多(duo)IC 都提供(gong)了非常簡單的(de)實施。I2C 接口允(yun)許用(yong)戶動態地改(gai)變(bian)充(chong)(chong)電(dian)電(dian)壓(ya)和(he)充(chong)(chong)電(dian)電(dian)流，使用(yong)具有這種接口的(de)充(chong)(chong)電(dian)器(qi)時，主機根據電(dian)池溫度來(lai)修(xiu)改(gai)充(chong)(chong)電(dian)參數。這種方(fang)法在(zai)沒有硬件改(gai)動的(de)情況下，在(zai)為(wei)不(bu)同平臺和(he)電(dian)池設置(zhi)要求的(de)溫度閾值方(fang)面(mian)擁有一(yi)定(ding)的(de)靈活性(xing)。

　　USB 充電標準

　　USB 充電時，可以使用許多充電器IC，它們都結合(he)了USB100和USB500 電(dian)流(liu)限(xian)制。通(tong)過USB 充電(dian)器輸出(chu)運(yun)行所(suo)有下游電(dian)路，讓廣大設計人員能夠確保不超出(chu)USB 電(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(ji)成(cheng)了一(yi)個連(lian)接(jie)(jie)電(dian)源并通過電(dian)源供(gong)電(dian)的5V LDO。每當(dang)連(lian)接(jie)(jie)一(yi)個有(you)效電(dian)源時，這(zhe)種(zhong)輸出便有(you)效。5V LDO 穩壓(ya)電(dian)壓(ya)保(bao)護USB 電(dian)路免受未穩壓(ya)適配器和其(qi)他過電(dian)壓(ya)狀態(tai)的損(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(gai)就會(hui)變得簡單了。