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(xie)特(te)性。此外，我們(men)還將探討一個(ge)應用和現有(you)的解決(jue)方案。

　　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)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)周期(qi)，以(yi)實現(xian)安(an)全(quan)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)并(bing)最大(da)化電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)使(shi)用(yong)時(shi)(shi)(shi)間(jian)。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)分兩(liang)個階段(duan)：恒定電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu) （CC） 和恒定電(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)池(chi)(chi)(chi)(chi)位于(yu)(yu)完全(quan)充(chong)(chong)(chong)滿電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)以(yi)下(xia)(xia)時(shi)(shi)(shi)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)經(jing)過穩(wen)(wen)壓(ya)(ya)進入電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)。在CC模(mo)式(shi)(shi)下(xia)(xia)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)經(jing)過穩(wen)(wen)壓(ya)(ya)達到兩(liang)個值之一。如果電(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)壓(ya)(ya)非常(chang)低(di)，則充(chong)(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(jiang)(jiang)低(di)至(zhi)(zhi)預(yu)充(chong)(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(ping)(ping)，以(yi)適(shi)應電(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)池(chi)(chi)(chi)(chi)損壞。該(gai)閾值因電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)化學(xue)屬性而(er)不(bu)同，一般(ban)(ban)取(qu)決(jue)于(yu)(yu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)制造(zao)廠商。一旦(dan)(dan)電(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)壓(ya)(ya)升(sheng)(sheng)至(zhi)(zhi)預(yu)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)閾值以(yi)上，充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)便升(sheng)(sheng)至(zhi)(zhi)快(kuai)速(su)充(chong)(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(ping)(ping)。典(dian)型電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)的(de)(de)最大(da)建議快(kuai)速(su)充(chong)(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)(shi)內耗盡電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)所需的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)），但該(gai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)也取(qu)決(jue)地電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)制造(zao)廠商。典(dian)型充(chong)(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(de)(de)是最大(da)化電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)使(shi)用(yong)時(shi)(shi)(shi)間(jian)。對(dui)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)充(chong)(chong)(chong)電(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)壓(ya)(ya)上升(sheng)(sheng)。一旦(dan)(dan)電(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)壓(ya)(ya)升(sheng)(sheng)至(zhi)(zhi)穩(wen)(wen)壓(ya)(ya)電(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)(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)逐漸減少，同時(shi)(shi)(shi)對(dui)電(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)壓(ya)(ya)進行穩(wen)(wen)壓(ya)(ya)以(yi)防止過充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。在這(zhe)種模(mo)式(shi)(shi)下(xia)(xia)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)充(chong)(chong)(chong)電(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)流(liu)(liu)逐漸減少，同時(shi)(shi)(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)阻抗降(jiang)(jiang)低(di)。如果電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)降(jiang)(jiang)至(zhi)(zhi)預(yu)定電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)(ping)（一般(ban)(ban)為快(kuai)速(su)充(chong)(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(de)(de)10%），則終止充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。我(wo)們一般(ban)(ban)不(bu)對(dui)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)浮充(chong)(chong)(chong)電(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)池(chi)(chi)(chi)(chi)使(shi)用(yong)壽(shou)命。圖1 以(yi)圖形方式(shi)(shi)說明了(le)典(dian)型的(de)(de)充(chong)(chong)(chong)電(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

　　線性解決方(fang)案與開(kai)關模式解決方(fang)案對比

　　將(jiang)適配(pei)器(qi)電(dian)壓(ya)轉降為電(dian)池電(dian)壓(ya)并(bing)控制(zhi)不同充電(dian)階段的(de)拓撲(pu)結構有兩(liang)種：線性穩壓(ya)器(qi)和電(dian)感開關。這(zhe)兩(liang)種拓撲(pu)結構在(zai)體積、效率、解決方案成本和電(dian)磁干擾 （EMI） 輻(fu)射方面(mian)各有優缺點。我(wo)們下面(mian)介紹這(zhe)兩(liang)種拓撲(pu)結構的(de)各種優點和一些折中方法。

　　一(yi)般來說，電(dian)(dian)(dian)(dian)感(gan)開(kai)(kai)(kai)(kai)關是獲得最(zui)高(gao)效率的(de)(de)最(zui)佳選(xuan)擇。利用(yong)電(dian)(dian)(dian)(dian)阻器(qi)等檢測(ce)組(zu)(zu)件，在輸出(chu)(chu)(chu)端(duan)(duan)檢測(ce)充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)。充電(dian)(dian)(dian)(dian)器(qi)在CC 模式下時，電(dian)(dian)(dian)(dian)流(liu)(liu)反饋電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)控制占(zhan)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)(lu)(lu)控制CV 模式下的(de)(de)占(zhan)空(kong)比。根據特(te)性集的(de)(de)不(bu)同，可能(neng)會(hui)出(chu)(chu)(chu)現其他一(yi)些控制環路(lu)(lu)(lu)。我們將在后面詳細討論這(zhe)些環路(lu)(lu)(lu)。電(dian)(dian)(dian)(dian)感(gan)開(kai)(kai)(kai)(kai)關電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)要求開(kai)(kai)(kai)(kai)關組(zu)(zu)件、整流(liu)(liu)器(qi)、電(dian)(dian)(dian)(dian)感(gan)和(he)輸入及(ji)輸出(chu)(chu)(chu)電(dian)(dian)(dian)(dian)容器(qi)。就許多(duo)應用(yong)而言，通(tong)過選(xuan)擇一(yi)種將開(kai)(kai)(kai)(kai)關組(zu)(zu)件和(he)整流(liu)(liu)器(qi)都嵌入到IC 中(zhong)的(de)(de)器(qi)件，可以(yi)縮(suo)小解決(jue)方案的(de)(de)尺寸。根據不(bu)同的(de)(de)負載，這(zhe)些電(dian)(dian)(dian)(dian)路(lu)(lu)(lu)的(de)(de)典型效率為(wei)80% 到96%。開(kai)(kai)(kai)(kai)關轉換器(qi)因其電(dian)(dian)(dian)(dian)感(gan)尺寸一(yi)般會(hui)要求更多(duo)的(de)(de)空(kong)間，同時也更加昂貴。開(kai)(kai)(kai)(kai)關轉換器(qi)還會(hui)引(yin)起電(dian)(dian)(dian)(dian)感(gan)EMI 輻射，以(yi)及(ji)開(kai)(kai)(kai)(kai)關帶來的(de)(de)輸出(chu)(chu)(chu)端(duan)(duan)噪聲。

　　線性充電器通過降(jiang)低(di)旁路(lu)組件(jian)(jian)的(de)(de)(de)(de)(de)(de)輸(shu)入(ru)(ru)電(dian)(dian)壓(ya)，降(jiang)低(di)DC 電(dian)(dian)壓(ya)。這樣做的(de)(de)(de)(de)(de)(de)好處是解決(jue)(jue)(jue)方(fang)(fang)案(an)只(zhi)要求三個組件(jian)(jian)：旁路(lu)組件(jian)(jian)和輸(shu)入(ru)(ru)/輸(shu)出(chu)(chu)電(dian)(dian)容。相比(bi)(bi)電(dian)(dian)感開關，線性壓(ya)降(jiang)穩壓(ya)器(qi)(qi) （LDO） 通常為一款低(di)成本的(de)(de)(de)(de)(de)(de)解決(jue)(jue)(jue)方(fang)(fang)案(an)，且噪聲更(geng)低(di)。通過穩壓(ya)旁路(lu)組件(jian)(jian)的(de)(de)(de)(de)(de)(de)電(dian)(dian)阻來限制進入(ru)(ru)電(dian)(dian)池(chi)的(de)(de)(de)(de)(de)(de)電(dian)(dian)流(liu)(liu)(liu)，從而對(dui)充(chong)(chong)電(dian)(dian)電(dian)(dian)流(liu)(liu)(liu)進行控(kong)制。電(dian)(dian)流(liu)(liu)(liu)反饋(kui)一般來自充(chong)(chong)電(dian)(dian)器(qi)(qi)IC 的(de)(de)(de)(de)(de)(de)輸(shu)入(ru)(ru)。對(dui)電(dian)(dian)池(chi)電(dian)(dian)壓(ya)進行檢(jian)測，以提(ti)供CV 反饋(kui)。改(gai)變旁路(lu)組件(jian)(jian)的(de)(de)(de)(de)(de)(de)電(dian)(dian)阻，來維持(chi)進入(ru)(ru)IC 輸(shu)入(ru)(ru)端的(de)(de)(de)(de)(de)(de)恒定電(dian)(dian)流(liu)(liu)(liu)或(huo)者恒定電(dian)(dian)池(chi)電(dian)(dian)壓(ya)。器(qi)(qi)件(jian)(jian)的(de)(de)(de)(de)(de)(de)輸(shu)入(ru)(ru)電(dian)(dian)流(liu)(liu)(liu)等于負載(zai)電(dian)(dian)流(liu)(liu)(liu)。這就是說解決(jue)(jue)(jue)方(fang)(fang)案(an)的(de)(de)(de)(de)(de)(de)效率(lv)等于輸(shu)出(chu)(chu)電(dian)(dian)壓(ya)與輸(shu)入(ru)(ru)電(dian)(dian)壓(ya)的(de)(de)(de)(de)(de)(de)比(bi)(bi)。LDO 解決(jue)(jue)(jue)方(fang)(fang)案(an)的(de)(de)(de)(de)(de)(de)缺(que)點是高輸(shu)入(ru)(ru)輸(shu)出(chu)(chu)電(dian)(dian)壓(ya)比(bi)(bi)時(shi)（即(ji)低(di)電(dian)(dian)量(liang)情況）效率(lv)較(jiao)低(di)。所有功率(lv)都被旁路(lu)組件(jian)(jian)消耗(hao)，其意味著LDO 并非那些輸(shu)入(ru)(ru)輸(shu)出(chu)(chu)差較(jiao)大的(de)(de)(de)(de)(de)(de)高充(chong)(chong)電(dian)(dian)電(dian)(dian)流(liu)(liu)(liu)應用的(de)(de)(de)(de)(de)(de)理想選(xuan)擇。這些高功耗(hao)應用要求散熱，從而增加(jia)了(le)解決(jue)(jue)(jue)方(fang)(fang)案(an)的(de)(de)(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(shi)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，效率(lv)為72%。首先，這(zhe)個效率(lv)聽起來似(si)乎(hu)不太壞。如果您從功耗(hao)(hao)的(de)(de)角度(du)(du)來看(kan)(kan)它(ta)，這(zhe)種應用(yong)(yong)(yong)要(yao)消耗(hao)(hao)約2W。在一(yi)個熱阻 （ΘJA） 為40°C/W 的(de)(de)應用(yong)(yong)(yong)中，芯片(pian)溫度(du)(du)上(shang)(shang)升80°C。在40°C 環(huan)境溫度(du)(du)下(xia)，電(dian)路板溫度(du)(du)會上(shang)(shang)升至120°C，其對手持設(she)備(bei)來說是(shi)不可(ke)接受的(de)(de)。在極低(di)(di)電(dian)池電(dian)壓（即3 V）下(xia)，這(zhe)一(yi)問題甚(shen)至會變得極端(duan)嚴重。相同(tong)3V 條件下(xia)，溫度(du)(du)升至120°C。讓我們(men)來看(kan)(kan)相同(tong)條件下(xia)的(de)(de)開關(guan)解(jie)決方(fang)(fang)案，使用(yong)(yong)(yong)一(yi)個單(dan)體電(dian)池IC 充電(dian)器時，效率(lv)上(shang)(shang)升至約85%。使用(yong)(yong)(yong)一(yi)塊(kuai)3.6V 電(dian)池時，功耗(hao)(hao)低(di)(di)于1W，從而帶來40°C 的(de)(de)溫升。3V 時這(zhe)種改善更加明顯。假設(she)3V 輸出時的(de)(de)效率(lv)為80%，則(ze)功耗(hao)(hao)低(di)(di)于800 mW，因此(ci)溫升會更低(di)(di)（約32°C）。這(zhe)些智能手機(ji)的(de)(de)體積一(yi)般可(ke)以容許稍大(da)一(yi)點的(de)(de)解(jie)決方(fang)(fang)案，并且能夠(gou)承受開關(guan)模式(shi)解(jie)決方(fang)(fang)案相關(guan)的(de)(de)稍許成本增加。

　　為任務選擇正(zheng)確的IC

　　在(zai)您已經完成(cheng)您的初步熱(re)分析并且選(xuan)好充(chong)電(dian)(dian)(dian)(dian)器(qi)拓(tuo)撲以后，您便可以轉(zhuan)到(dao)選(xuan)擇應用(yong)的最佳IC 上來。新型的電(dian)(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)(dian)器(qi)解(jie)決(jue)方(fang)案(an)集(ji)成(cheng)了許(xu)多特性，可以利用(yong)它們改善系(xi)統(tong)的性能(neng)。諸如輸(shu)入過壓保(bao)護、電(dian)(dian)(dian)(dian)源路徑管(guan)理 （PPM）、VIN_DPM、散熱(re)穩(wen)壓、負溫度(du)系(xi)數(shu)熱(re)敏電(dian)(dian)(dian)(dian)阻 （NTC） 監測和USB 充(chong)電(dian)(dian)(dian)(dian)等特性，都被集(ji)成(cheng)到(dao)許(xu)多電(dian)(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)(dian)器(qi)IC 中(zhong)。大多數(shu)單體電(dian)(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)(dian)器(qi)解(jie)決(jue)方(fang)案(an)都已將要求FET 集(ji)成(cheng)到(dao)了器(qi)件中(zhong)，旨(zhi)在(zai)節省電(dian)(dian)(dian)(dian)路板面積。

　　輸入(ru)過壓保護（單輸入(ru)與雙(shuang)輸入(ru)對(dui)比(bi)）

　　在(zai)(zai)當今的(de)(de)(de)(de)市場(chang)上，USB 電(dian)(dian)源已(yi)經成(cheng)為(wei)最為(wei)常見的(de)(de)(de)(de)電(dian)(dian)源，因此通(tong)過(guo)(guo)USB 電(dian)(dian)源充(chong)電(dian)(dian)已(yi)經成(cheng)為(wei)一(yi)(yi)(yi)種必然性。市場(chang)已(yi)經從(cong)使用(yong)專門AC 適配(pei)器(qi)和(he)單(dan)獨(du)USB 接(jie)口的(de)(de)(de)(de)初(chu)始(shi)雙輸(shu)入(ru)(ru)(ru)轉(zhuan)變為(wei)將一(yi)(yi)(yi)個(ge)USB 接(jie)口既作(zuo)為(wei)墻上電(dian)(dian)源適合器(qi)接(jie)口使用(yong)，也作(zuo)為(wei)使用(yong)相同線纜(lan)的(de)(de)(de)(de)USB 數據輸(shu)入(ru)(ru)(ru)接(jie)口的(de)(de)(de)(de)單(dan)輸(shu)入(ru)(ru)(ru)解(jie)決(jue)(jue)方(fang)(fang)案(an)(an)。這(zhe)(zhe)樣(yang)便(bian)導(dao)致一(yi)(yi)(yi)種從(cong)雙輸(shu)入(ru)(ru)(ru)解(jie)決(jue)(jue)方(fang)(fang)案(an)(an)向單(dan)輸(shu)入(ru)(ru)(ru)解(jie)決(jue)(jue)方(fang)(fang)案(an)(an)的(de)(de)(de)(de)轉(zhuan)移。單(dan)輸(shu)入(ru)(ru)(ru)在(zai)(zai)接(jie)口方(fang)(fang)面存(cun)在(zai)(zai)許多挑戰。由于存(cun)在(zai)(zai)如此多的(de)(de)(de)(de)配(pei)件市場(chang)適配(pei)器(qi)解(jie)決(jue)(jue)方(fang)(fang)案(an)(an)和(he)一(yi)(yi)(yi)種通(tong)用(yong)接(jie)口，輸(shu)入(ru)(ru)(ru)端(duan)必須要(yao)能夠(gou)在(zai)(zai)無損(sun)壞的(de)(de)(de)(de)情況下(xia)承受(shou)更高的(de)(de)(de)(de)電(dian)(dian)壓(ya)。由于電(dian)(dian)池充(chong)電(dian)(dian)器(qi)始(shi)終連接(jie)到輸(shu)入(ru)(ru)(ru)端(duan)，因此充(chong)電(dian)(dian)器(qi)對所有下(xia)游電(dian)(dian)路實施(shi)過(guo)(guo)電(dian)(dian)壓(ya)狀態(tai)保(bao)護(hu)(hu)是有道理的(de)(de)(de)(de)。為(wei)了實施(shi)這(zhe)(zhe)一(yi)(yi)(yi)功能，市場(chang)上出現了許多能夠(gou)承受(shou)20V 甚至(zhi)30V 電(dian)(dian)壓(ya)的(de)(de)(de)(de)解(jie)決(jue)(jue)方(fang)(fang)案(an)(an)。另外，這(zhe)(zhe)些器(qi)件都具有過(guo)(guo)電(dian)(dian)壓(ya)保(bao)護(hu)(hu) （OVP） 電(dian)(dian)路，其(qi)在(zai)(zai)輸(shu)入(ru)(ru)(ru)超出OVP 閾值(zhi)時阻止(zhi)器(qi)件運(yun)行。這(zhe)(zhe)樣(yang)便(bian)進(jin)一(yi)(yi)(yi)步保(bao)護(hu)(hu)了下(xia)游電(dian)(dian)路，使其(qi)免受(shou)潛在(zai)(zai)的(de)(de)(de)(de)瞬態(tai)過(guo)(guo)電(dian)(dian)壓(ya)狀態(tai)損(sun)壞。

　　目前，隨著綠色輸(shu)入（即(ji)太陽能電(dian)池）或無線(xian)充(chong)電(dian)的(de)出現，應用又再(zai)一次(ci)向雙輸(shu)入要求(qiu)轉移。根據(ju)具體(ti)的(de)應用要求(qiu)，兩種配置結構都(dou)可以使用。

　　電(dian)源路徑管理/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(jin)行分(fen)別監測，消除(chu)了(le)這些問(wen)題［2］。

　　圖 2 傳統拓(tuo)撲結構(gou)舉(ju)例

　　圖(tu) 3 電源(yuan)路徑拓撲結(jie)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

　　由于系(xi)統(tong)電(dian)(dian)(dian)(dian)流(liu)(liu)和充(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)是單獨編程的，因(yin)此(ci)可(ke)以使用(yong)(yong)適(shi)配(pei)器的滿功率，其(qi)與電(dian)(dian)(dian)(dian)池的容量和充(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)的大(da)小均無關。傳統(tong)拓撲結構中，充(chong)(chong)電(dian)(dian)(dian)(dian)器的輸出(chu)電(dian)(dian)(dian)(dian)流(liu)(liu)必須設(she)定為(wei)最大(da)充(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)，以應對沒有(you)(you)系(xi)統(tong)負載的情況。當系(xi)統(tong)中有(you)(you)負載時(shi)，由于系(xi)統(tong)吸收可(ke)用(yong)(yong)電(dian)(dian)(dian)(dian)流(liu)(liu)，有(you)(you)效充(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)降低(di)。例(li)如，一個使用(yong)(yong)900 mA 適(shi)配(pei)器和500 mAhr 電(dian)(dian)(dian)(dian)池的系(xi)統(tong)，使用(yong)(yong)傳統(tong)方法可(ke)以編程500 mA 的充(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)。如果系(xi)統(tong)負載為(wei)200 mA，有(you)(you)效充(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)僅為(wei)300 mA，充(chong)(chong)電(dian)(dian)(dian)(dian)時(shi)間幾乎翻(fan)了一翻(fan)。如果使用(yong)(yong)PPM 來研究(jiu)這(zhe)一相同案例(li)，輸入(ru)電(dian)(dian)(dian)(dian)流(liu)(liu)限(xian)制設(she)定為(wei)900 mA。這(zhe)樣便允許全部500 mA充(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)，且擁有(you)(you)多達400 mA 的額外系(xi)統(tong)電(dian)(dian)(dian)(dian)流(liu)(liu)。

　　終止和早期(qi)計時(shi)器超時(shi)

　　在對(dui)(dui)總電(dian)(dian)(dian)流進(jin)(jin)(jin)行(xing)穩(wen)壓的傳統系(xi)統中，電(dian)(dian)(dian)流在電(dian)(dian)(dian)池和負(fu)載(zai)之(zhi)間共用(yong)。如果系(xi)統負(fu)載(zai)足夠大到(dao)從電(dian)(dian)(dian)池拉取充電(dian)(dian)(dian)電(dian)(dian)(dian)流，且在計時器(qi)(qi)超時以(yi)前電(dian)(dian)(dian)池不(bu)充電(dian)(dian)(dian)，則計時器(qi)(qi)會(hui)(hui)出(chu)現(xian)偽超時。另外，如果系(xi)統電(dian)(dian)(dian)流絕對(dui)(dui)不(bu)會(hui)(hui)降至設定終止(zhi)(zhi)電(dian)(dian)(dian)流以(yi)下，則永遠不(bu)會(hui)(hui)終止(zhi)(zhi)。電(dian)(dian)(dian)源路徑管(guan)理通過單獨監測(ce)充電(dian)(dian)(dian)電(dian)(dian)(dian)流，并動態地使用(yong)可穩(wen)壓計時器(qi)(qi)（通過減少充電(dian)(dian)(dian)電(dian)(dian)(dian)流進(jin)(jin)(jin)行(xing)穩(wen)壓），防止(zhi)(zhi)這些條件(jian)出(chu)現(xian)。就終止(zhi)(zhi)問題(ti)而言，單獨對(dui)(dui)充電(dian)(dian)(dian)電(dian)(dian)(dian)流進(jin)(jin)(jin)行(xing)監測(ce)，可讓終止(zhi)(zhi)條件(jian)測(ce)定變得容易(yi)。

　　基于輸入電(dian)壓(ya)的(de)動態電(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(zhe)種開/關脈沖發生并不是我們(men)想要(yao)的。

　　圖 4 無(wu) VIN-DPM 情(qing)況下的輸入崩潰

　　VIN-DPM 通(tong)過限制輸(shu)(shu)入(ru)電(dian)流阻(zu)止(zhi)脈沖發生，從而防止(zhi)輸(shu)(shu)入(ru)源崩(beng)潰(kui)。圖5 顯示(shi)了超負載USB 端口的結果。VIN-DPM 功能開始生效，降低輸(shu)(shu)入(ru)電(dian)流限制，從而防止(zhi)輸(shu)(shu)入(ru)源崩(beng)潰(kui)。

　　圖 5 使用VIN-DPM的輸入超負載保(bao)護

　　NTC 監(jian)測（包(bao)括JEITA）

　　通過充(chong)電(dian)期間的監測(ce)防止電(dian)池(chi)組(zu)(zu)損壞甚至是爆炸時(shi)，電(dian)池(chi)溫度極為重要。一般來(lai)說，通過對(dui)集成到(dao)電(dian)池(chi)組(zu)(zu)中或(huo)者靠(kao)近系統板上電(dian)池(chi)組(zu)(zu)安(an)裝(zhuang)的NTC 熱(re)敏電(dian)阻進(jin)行監測(ce)，來(lai)完成這項工作。許多充(chong)電(dian)器(qi)都具有集成到(dao)IC 中的NTC 監測(ce)功能(neng)。如果(guo)電(dian)池(chi)溫度處(chu)在某些非安(an)全(quan)溫度下時(shi)，這些IC 便對(dui)溫度和禁用(yong)充(chong)電(dian)電(dian)流進(jin)行監測(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(ji)成了一種無需主(zhu)機關聯的(de)獨立解決方(fang)案。對于NTC 受(shou)主(zhu)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(jie)口(kou)允(yun)許用戶動態地改(gai)變充電(dian)電(dian)壓和充電(dian)電(dian)流，使用具有(you)這(zhe)種接(jie)口(kou)的(de)充電(dian)器時，主(zhu)機根據電(dian)池溫度(du)來(lai)修改(gai)充電(dian)參數。這(zhe)種方(fang)法(fa)在沒有(you)硬(ying)件改(gai)動的(de)情況下，在為(wei)不同平臺和電(dian)池設置要(yao)求的(de)溫度(du)閾(yu)值方(fang)面擁有(you)一定的(de)靈(ling)活性。

　　USB 充電(dian)標準

　　USB 充電時，可以使用許多充電器IC，它們(men)都(dou)結合了USB100和USB500 電流(liu)限制。通過(guo)USB 充電器(qi)輸出(chu)運行所有下游電路，讓廣(guang)大(da)設(she)計(ji)人員能夠確保不超出(chu)USB 電流(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 都集成了一個連(lian)接電(dian)(dian)源并通過電(dian)(dian)源供電(dian)(dian)的5V LDO。每當連(lian)接一個有效電(dian)(dian)源時，這種(zhong)輸出便(bian)有效。5V LDO 穩壓電(dian)(dian)壓保(bao)護USB 電(dian)(dian)路免受未(wei)穩壓適配器(qi)和其(qi)他過電(dian)(dian)壓狀態(tai)的損害。

　　　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(ying)該就會(hui)變(bian)得簡單了(le)。