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。此外(wai)，我(wo)們還將探(tan)討(tao)一個應用(yong)和(he)現有(you)的解決方案(an)。

　　鋰離子電池充電周期

　　鋰離子電池要求(qiu)專(zhuan)門的充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)周期，以實(shi)現安全充(chong)(chong)(chong)(chong)(chong)(chong)電(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)池(chi)(chi)(chi)(chi)(chi)使用(yong)時(shi)間。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)分兩個(ge)階段：恒定電(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)壓(ya) （CV）。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)位于完全充(chong)(chong)(chong)(chong)(chong)(chong)滿電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)以下(xia)時(shi)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)經過(guo)穩壓(ya)進(jin)入電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)。在CC模式下(xia)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)經過(guo)穩壓(ya)達到兩個(ge)值之一。如果(guo)(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)非常低(di)，則充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)降低(di)至預(yu)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)，以適應(ying)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)并防(fang)止電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)損壞。該閾(yu)值因電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)化學屬(shu)性而(er)不(bu)(bu)同(tong)，一般(ban)(ban)取決于電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)制造(zao)(zao)廠商。一旦電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)升至預(yu)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)閾(yu)值以上(shang)，充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)便升至快(kuai)(kuai)速(su)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)。典(dian)型電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)的最(zui)(zui)大(da)建(jian)議快(kuai)(kuai)速(su)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)為(wei)1C（C=1 小時(shi)內耗盡電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)所需的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)），但該電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)也取決地電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)制造(zao)(zao)廠商。典(dian)型充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)為(wei)~0.8C，目的是最(zui)(zui)大(da)化電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)使用(yong)時(shi)間。對電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)時(shi)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)上(shang)升。一旦電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)升至穩壓(ya)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)（一般(ban)(ban)為(wei)4.2V），充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)逐漸(jian)減(jian)(jian)少(shao)，同(tong)時(shi)對電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)進(jin)行穩壓(ya)以防(fang)止過(guo)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。在這(zhe)種模式下(xia)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)時(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)逐漸(jian)減(jian)(jian)少(shao)，同(tong)時(shi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)阻抗(kang)降低(di)。如果(guo)(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)降至預(yu)定電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)平(ping)（一般(ban)(ban)為(wei)快(kuai)(kuai)速(su)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)的10%），則終止充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。我們一般(ban)(ban)不(bu)(bu)對電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)浮充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，因為(wei)這(zhe)樣會縮短電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)(chi)使用(yong)壽命。圖1 以圖形方式說明了典(dian)型的充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)周期。

　　圖1典型鋰離子充電周期

　　線性解決方案(an)(an)與開關(guan)模(mo)式解決方案(an)(an)對比

　　將適配(pei)器電(dian)(dian)壓(ya)(ya)轉降為電(dian)(dian)池(chi)電(dian)(dian)壓(ya)(ya)并控制不同充電(dian)(dian)階段的(de)拓撲(pu)結(jie)構(gou)(gou)有兩(liang)種：線(xian)性穩壓(ya)(ya)器和電(dian)(dian)感開關。這兩(liang)種拓撲(pu)結(jie)構(gou)(gou)在體積、效率、解決方(fang)案成本和電(dian)(dian)磁干擾 （EMI） 輻射(she)方(fang)面各有優(you)(you)缺點(dian)。我(wo)們下面介紹這兩(liang)種拓撲(pu)結(jie)構(gou)(gou)的(de)各種優(you)(you)點(dian)和一些折(zhe)中方(fang)法。

　　一(yi)般來說，電(dian)(dian)(dian)(dian)感(gan)(gan)(gan)開(kai)(kai)關是獲得最高效率(lv)的(de)(de)最佳選擇。利用電(dian)(dian)(dian)(dian)阻器(qi)(qi)等檢測(ce)組(zu)件(jian)，在(zai)(zai)輸(shu)(shu)出(chu)(chu)端(duan)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(zai)(zai)CC 模式下時，電(dian)(dian)(dian)(dian)流(liu)反(fan)饋(kui)電(dian)(dian)(dian)(dian)路(lu)控(kong)制占空比。電(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)壓檢測(ce)反(fan)饋(kui)電(dian)(dian)(dian)(dian)路(lu)控(kong)制CV 模式下的(de)(de)占空比。根據(ju)特性(xing)集的(de)(de)不同(tong)，可能會出(chu)(chu)現其(qi)他一(yi)些控(kong)制環(huan)路(lu)。我們將在(zai)(zai)后面詳(xiang)細討(tao)論(lun)這(zhe)些環(huan)路(lu)。電(dian)(dian)(dian)(dian)感(gan)(gan)(gan)開(kai)(kai)關電(dian)(dian)(dian)(dian)路(lu)要(yao)求(qiu)開(kai)(kai)關組(zu)件(jian)、整流(liu)器(qi)(qi)、電(dian)(dian)(dian)(dian)感(gan)(gan)(gan)和輸(shu)(shu)入(ru)及輸(shu)(shu)出(chu)(chu)電(dian)(dian)(dian)(dian)容器(qi)(qi)。就(jiu)許多應(ying)用而言，通過選擇一(yi)種將開(kai)(kai)關組(zu)件(jian)和整流(liu)器(qi)(qi)都嵌入(ru)到IC 中的(de)(de)器(qi)(qi)件(jian)，可以縮小解決方案的(de)(de)尺寸。根據(ju)不同(tong)的(de)(de)負載，這(zhe)些電(dian)(dian)(dian)(dian)路(lu)的(de)(de)典型效率(lv)為80% 到96%。開(kai)(kai)關轉換器(qi)(qi)因(yin)其(qi)電(dian)(dian)(dian)(dian)感(gan)(gan)(gan)尺寸一(yi)般會要(yao)求(qiu)更(geng)多的(de)(de)空間，同(tong)時也更(geng)加昂貴(gui)。開(kai)(kai)關轉換器(qi)(qi)還會引起電(dian)(dian)(dian)(dian)感(gan)(gan)(gan)EMI 輻射(she)，以及開(kai)(kai)關帶來的(de)(de)輸(shu)(shu)出(chu)(chu)端(duan)噪(zao)聲。

　　線性充電器通過(guo)降低(di)旁(pang)(pang)路組(zu)(zu)(zu)(zu)件的(de)(de)(de)(de)(de)輸(shu)(shu)(shu)入(ru)(ru)(ru)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)，降低(di)DC 電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)。這(zhe)樣做的(de)(de)(de)(de)(de)好(hao)處(chu)是解(jie)決(jue)(jue)方案只要(yao)求三個組(zu)(zu)(zu)(zu)件：旁(pang)(pang)路組(zu)(zu)(zu)(zu)件和輸(shu)(shu)(shu)入(ru)(ru)(ru)/輸(shu)(shu)(shu)出電(dian)(dian)(dian)(dian)(dian)容。相比電(dian)(dian)(dian)(dian)(dian)感開關，線性壓(ya)(ya)降穩壓(ya)(ya)器(qi) （LDO） 通常為一(yi)款低(di)成本的(de)(de)(de)(de)(de)解(jie)決(jue)(jue)方案，且噪聲(sheng)更低(di)。通過(guo)穩壓(ya)(ya)旁(pang)(pang)路組(zu)(zu)(zu)(zu)件的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)阻來(lai)限制進(jin)入(ru)(ru)(ru)電(dian)(dian)(dian)(dian)(dian)池的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)，從而對充電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)進(jin)行控制。電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)反(fan)饋一(yi)般來(lai)自充電(dian)(dian)(dian)(dian)(dian)器(qi)IC 的(de)(de)(de)(de)(de)輸(shu)(shu)(shu)入(ru)(ru)(ru)。對電(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)進(jin)行檢測(ce)，以提供CV 反(fan)饋。改(gai)變旁(pang)(pang)路組(zu)(zu)(zu)(zu)件的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)阻，來(lai)維持進(jin)入(ru)(ru)(ru)IC 輸(shu)(shu)(shu)入(ru)(ru)(ru)端(duan)的(de)(de)(de)(de)(de)恒(heng)定(ding)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)或者恒(heng)定(ding)電(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)。器(qi)件的(de)(de)(de)(de)(de)輸(shu)(shu)(shu)入(ru)(ru)(ru)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)等(deng)于負載電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)。這(zhe)就(jiu)是說解(jie)決(jue)(jue)方案的(de)(de)(de)(de)(de)效率(lv)等(deng)于輸(shu)(shu)(shu)出電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)與輸(shu)(shu)(shu)入(ru)(ru)(ru)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)的(de)(de)(de)(de)(de)比。LDO 解(jie)決(jue)(jue)方案的(de)(de)(de)(de)(de)缺點是高(gao)輸(shu)(shu)(shu)入(ru)(ru)(ru)輸(shu)(shu)(shu)出電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)比時（即低(di)電(dian)(dian)(dian)(dian)(dian)量(liang)情況）效率(lv)較(jiao)低(di)。所有功(gong)率(lv)都被旁(pang)(pang)路組(zu)(zu)(zu)(zu)件消耗，其意(yi)味著LDO 并非(fei)那(nei)些輸(shu)(shu)(shu)入(ru)(ru)(ru)輸(shu)(shu)(shu)出差(cha)較(jiao)大的(de)(de)(de)(de)(de)高(gao)充電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)應用(yong)的(de)(de)(de)(de)(de)理想(xiang)選擇。這(zhe)些高(gao)功(gong)耗應用(yong)要(yao)求散熱，從而增(zeng)加了(le)解(jie)決(jue)(jue)方案的(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。

   應該使用什么(me)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)(xiao)率(lv)為(wei)72%。首先，這(zhe)個(ge)效(xiao)(xiao)率(lv)聽起(qi)來(lai)(lai)似乎不太(tai)壞。如(ru)果(guo)您從功耗的(de)(de)角度(du)來(lai)(lai)看它，這(zhe)種應用要消耗約2W。在一個(ge)熱阻 （ΘJA） 為(wei)40°C/W 的(de)(de)應用中，芯片溫度(du)上升80°C。在40°C 環境溫度(du)下(xia)，電(dian)路(lu)板(ban)溫度(du)會(hui)上升至(zhi)120°C，其(qi)對手(shou)持設(she)(she)備(bei)來(lai)(lai)說(shuo)是(shi)不可接受的(de)(de)。在極低電(dian)池(chi)(chi)電(dian)壓（即(ji)3 V）下(xia)，這(zhe)一問(wen)題(ti)甚(shen)至(zhi)會(hui)變(bian)得(de)極端嚴重。相(xiang)同(tong)3V 條件下(xia)，溫度(du)升至(zhi)120°C。讓我們來(lai)(lai)看相(xiang)同(tong)條件下(xia)的(de)(de)開關(guan)解(jie)(jie)決(jue)(jue)方案(an)，使用一個(ge)單體(ti)電(dian)池(chi)(chi)IC 充電(dian)器時，效(xiao)(xiao)率(lv)上升至(zhi)約85%。使用一塊3.6V 電(dian)池(chi)(chi)時，功耗低于1W，從而帶來(lai)(lai)40°C 的(de)(de)溫升。3V 時這(zhe)種改善更(geng)加明顯。假設(she)(she)3V 輸出時的(de)(de)效(xiao)(xiao)率(lv)為(wei)80%，則功耗低于800 mW，因此溫升會(hui)更(geng)低（約32°C）。這(zhe)些智能(neng)手(shou)機的(de)(de)體(ti)積一般可以容許(xu)稍大一點的(de)(de)解(jie)(jie)決(jue)(jue)方案(an)，并(bing)且能(neng)夠承受開關(guan)模式解(jie)(jie)決(jue)(jue)方案(an)相(xiang)關(guan)的(de)(de)稍許(xu)成(cheng)本增加。

　　為任務選擇正確的IC

　　在您已經完成(cheng)您的(de)初(chu)步熱(re)分析(xi)并且選(xuan)好充(chong)電(dian)器(qi)拓撲以(yi)后，您便可以(yi)轉到選(xuan)擇應用(yong)的(de)最佳IC 上來。新型的(de)電(dian)池(chi)充(chong)電(dian)器(qi)解決(jue)方案集成(cheng)了許(xu)多(duo)(duo)特性(xing)，可以(yi)利用(yong)它(ta)們改(gai)善系統的(de)性(xing)能。諸如(ru)輸入(ru)過壓(ya)保護、電(dian)源路(lu)徑管理 （PPM）、VIN_DPM、散熱(re)穩壓(ya)、負(fu)溫度系數熱(re)敏電(dian)阻 （NTC） 監測和USB 充(chong)電(dian)等(deng)特性(xing)，都被集成(cheng)到許(xu)多(duo)(duo)電(dian)池(chi)充(chong)電(dian)器(qi)IC 中(zhong)。大多(duo)(duo)數單體電(dian)池(chi)充(chong)電(dian)器(qi)解決(jue)方案都已將要求FET 集成(cheng)到了器(qi)件中(zhong)，旨在節省(sheng)電(dian)路(lu)板面積。

　　輸(shu)(shu)入(ru)(ru)過壓保護（單輸(shu)(shu)入(ru)(ru)與(yu)雙(shuang)輸(shu)(shu)入(ru)(ru)對比）

　　在(zai)當今(jin)的(de)(de)(de)市(shi)場(chang)上(shang)(shang)，USB 電(dian)(dian)(dian)(dian)(dian)源已(yi)經(jing)(jing)成為(wei)最為(wei)常見的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)源，因此通過(guo)(guo)USB 電(dian)(dian)(dian)(dian)(dian)源充(chong)電(dian)(dian)(dian)(dian)(dian)已(yi)經(jing)(jing)成為(wei)一(yi)(yi)(yi)種必(bi)然性。市(shi)場(chang)已(yi)經(jing)(jing)從使用(yong)(yong)專門AC 適(shi)(shi)(shi)配器(qi)和(he)單(dan)(dan)獨USB 接(jie)(jie)口(kou)的(de)(de)(de)初(chu)始雙輸(shu)(shu)(shu)入(ru)(ru)轉(zhuan)變(bian)為(wei)將一(yi)(yi)(yi)個USB 接(jie)(jie)口(kou)既(ji)作為(wei)墻上(shang)(shang)電(dian)(dian)(dian)(dian)(dian)源適(shi)(shi)(shi)合器(qi)接(jie)(jie)口(kou)使用(yong)(yong)，也作為(wei)使用(yong)(yong)相同線(xian)纜的(de)(de)(de)USB 數據輸(shu)(shu)(shu)入(ru)(ru)接(jie)(jie)口(kou)的(de)(de)(de)單(dan)(dan)輸(shu)(shu)(shu)入(ru)(ru)解決(jue)方案(an)。這(zhe)(zhe)樣(yang)便導致一(yi)(yi)(yi)種從雙輸(shu)(shu)(shu)入(ru)(ru)解決(jue)方案(an)向單(dan)(dan)輸(shu)(shu)(shu)入(ru)(ru)解決(jue)方案(an)的(de)(de)(de)轉(zhuan)移。單(dan)(dan)輸(shu)(shu)(shu)入(ru)(ru)在(zai)接(jie)(jie)口(kou)方面存在(zai)許多挑戰(zhan)。由(you)于存在(zai)如此多的(de)(de)(de)配件市(shi)場(chang)適(shi)(shi)(shi)配器(qi)解決(jue)方案(an)和(he)一(yi)(yi)(yi)種通用(yong)(yong)接(jie)(jie)口(kou)，輸(shu)(shu)(shu)入(ru)(ru)端(duan)(duan)必(bi)須要(yao)能夠(gou)(gou)在(zai)無(wu)損壞的(de)(de)(de)情況下承受(shou)更高(gao)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)。由(you)于電(dian)(dian)(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)(dian)(dian)器(qi)始終連接(jie)(jie)到輸(shu)(shu)(shu)入(ru)(ru)端(duan)(duan)，因此充(chong)電(dian)(dian)(dian)(dian)(dian)器(qi)對(dui)所有(you)(you)下游電(dian)(dian)(dian)(dian)(dian)路實(shi)施(shi)過(guo)(guo)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)狀(zhuang)態(tai)保護(hu)是有(you)(you)道(dao)理(li)的(de)(de)(de)。為(wei)了(le)實(shi)施(shi)這(zhe)(zhe)一(yi)(yi)(yi)功(gong)能，市(shi)場(chang)上(shang)(shang)出現(xian)了(le)許多能夠(gou)(gou)承受(shou)20V 甚至30V 電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)的(de)(de)(de)解決(jue)方案(an)。另(ling)外，這(zhe)(zhe)些器(qi)件都具有(you)(you)過(guo)(guo)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)保護(hu) （OVP） 電(dian)(dian)(dian)(dian)(dian)路，其(qi)在(zai)輸(shu)(shu)(shu)入(ru)(ru)超出OVP 閾值時阻(zu)止器(qi)件運行。這(zhe)(zhe)樣(yang)便進一(yi)(yi)(yi)步保護(hu)了(le)下游電(dian)(dian)(dian)(dian)(dian)路，使其(qi)免受(shou)潛(qian)在(zai)的(de)(de)(de)瞬態(tai)過(guo)(guo)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)狀(zhuang)態(tai)損壞。

　　目(mu)前，隨(sui)著綠色(se)輸入（即太陽(yang)能電池）或無線充電的(de)出現(xian)，應(ying)用(yong)又再一次(ci)向雙輸入要求轉移。根據具體(ti)的(de)應(ying)用(yong)要求，兩種配置結構都可以使用(yong)。

　　電(dian)源路徑管理/最(zui)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(he)系統電流進行分別監測，消(xiao)除了(le)這些問題［2］。

　　圖(tu) 2 傳統拓撲結構舉例

　　圖 3 電源路徑(jing)拓撲結構舉例

　　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)統電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)和(he)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)是單獨編程的(de)(de)(de)(de)，因此(ci)可以使(shi)(shi)用(yong)適配器(qi)的(de)(de)(de)(de)滿功率(lv)，其與(yu)電(dian)(dian)(dian)(dian)池(chi)(chi)的(de)(de)(de)(de)容量和(he)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)的(de)(de)(de)(de)大小均無關。傳(chuan)統拓撲結(jie)構中(zhong)，充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)器(qi)的(de)(de)(de)(de)輸出電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)必須設(she)定(ding)為最(zui)大充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)，以應對沒有(you)(you)系(xi)統負(fu)載的(de)(de)(de)(de)情況。當系(xi)統中(zhong)有(you)(you)負(fu)載時，由于(yu)系(xi)統吸(xi)收可用(yong)電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)，有(you)(you)效充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)降低。例如，一個使(shi)(shi)用(yong)900 mA 適配器(qi)和(he)500 mAhr 電(dian)(dian)(dian)(dian)池(chi)(chi)的(de)(de)(de)(de)系(xi)統，使(shi)(shi)用(yong)傳(chuan)統方法可以編程500 mA 的(de)(de)(de)(de)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)。如果系(xi)統負(fu)載為200 mA，有(you)(you)效充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)僅(jin)為300 mA，充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)時間(jian)幾乎翻了一翻。如果使(shi)(shi)用(yong)PPM 來研(yan)究這(zhe)(zhe)一相同(tong)案(an)例，輸入電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)限制設(she)定(ding)為900 mA。這(zhe)(zhe)樣(yang)便允許全部500 mA充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)，且(qie)擁有(you)(you)多達400 mA 的(de)(de)(de)(de)額外系(xi)統電(dian)(dian)(dian)(dian)流(liu)(liu)(liu)。

　　終止和早(zao)期計時器(qi)超時

　　在(zai)對總(zong)電(dian)(dian)(dian)(dian)流進行(xing)穩(wen)壓(ya)的傳統(tong)系(xi)統(tong)中，電(dian)(dian)(dian)(dian)流在(zai)電(dian)(dian)(dian)(dian)池和負載之間共用(yong)(yong)。如(ru)果系(xi)統(tong)負載足夠(gou)大到從電(dian)(dian)(dian)(dian)池拉取充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流，且在(zai)計時(shi)(shi)器超時(shi)(shi)以(yi)前電(dian)(dian)(dian)(dian)池不(bu)(bu)充電(dian)(dian)(dian)(dian)，則計時(shi)(shi)器會出現偽超時(shi)(shi)。另外，如(ru)果系(xi)統(tong)電(dian)(dian)(dian)(dian)流絕對不(bu)(bu)會降至設定終止(zhi)(zhi)電(dian)(dian)(dian)(dian)流以(yi)下，則永遠不(bu)(bu)會終止(zhi)(zhi)。電(dian)(dian)(dian)(dian)源路徑管理通(tong)過單(dan)獨監測充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流，并動態地使用(yong)(yong)可(ke)穩(wen)壓(ya)計時(shi)(shi)器（通(tong)過減少充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流進行(xing)穩(wen)壓(ya)），防止(zhi)(zhi)這些(xie)條件出現。就終止(zhi)(zhi)問(wen)題而言(yan)，單(dan)獨對充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流進行(xing)監測，可(ke)讓(rang)終止(zhi)(zhi)條件測定變得容易。

　　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(zhe)種開/關脈(mo)沖發(fa)生并不是我們(men)想要(yao)的。

　　圖 4 無(wu) VIN-DPM 情況下的輸入崩潰

　　VIN-DPM 通(tong)過限(xian)制(zhi)輸(shu)(shu)入(ru)(ru)電流阻止(zhi)(zhi)脈沖(chong)發生(sheng)，從(cong)而防(fang)止(zhi)(zhi)輸(shu)(shu)入(ru)(ru)源崩(beng)潰。圖(tu)5 顯(xian)示了超負載USB 端口的結果。VIN-DPM 功能開始(shi)生(sheng)效，降(jiang)低輸(shu)(shu)入(ru)(ru)電流限(xian)制(zhi)，從(cong)而防(fang)止(zhi)(zhi)輸(shu)(shu)入(ru)(ru)源崩(beng)潰。

　　圖(tu) 5 使用(yong)VIN-DPM的輸入超負載保護

　　NTC 監(jian)測（包括(kuo)JEITA）

　　通過充電(dian)(dian)期間(jian)的監測防止(zhi)電(dian)(dian)池(chi)(chi)組損壞甚至是爆炸時(shi)，電(dian)(dian)池(chi)(chi)溫(wen)度(du)極為重(zhong)要(yao)。一般來說，通過對集成(cheng)(cheng)到電(dian)(dian)池(chi)(chi)組中(zhong)或者靠近系統板(ban)上電(dian)(dian)池(chi)(chi)組安裝(zhuang)的NTC 熱敏電(dian)(dian)阻(zu)進行(xing)監測，來完成(cheng)(cheng)這(zhe)項工作。許(xu)多充電(dian)(dian)器都具有(you)集成(cheng)(cheng)到IC 中(zhong)的NTC 監測功能。如果電(dian)(dian)池(chi)(chi)溫(wen)度(du)處在某些非安全溫(wen)度(du)下時(shi)，這(zhe)些IC 便對溫(wen)度(du)和禁用充電(dian)(dian)電(dian)(dian)流進行(xing)監測。

　　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(le)一種(zhong)無需主(zhu)機關聯的獨立解決方案。對于(yu)NTC 受主(zhu)機監測的系統來(lai)說，許多IC 都提供了(le)非常簡(jian)單的實施。I2C 接口允許用戶動態地改變充(chong)(chong)電(dian)電(dian)壓和(he)充(chong)(chong)電(dian)電(dian)流，使用具有(you)這種(zhong)接口的充(chong)(chong)電(dian)器(qi)時，主(zhu)機根據電(dian)池溫度(du)來(lai)修改充(chong)(chong)電(dian)參數。這種(zhong)方法(fa)在沒(mei)有(you)硬件改動的情(qing)況下，在為不同平臺和(he)電(dian)池設置要(yao)求的溫度(du)閾值方面擁有(you)一定的靈(ling)活(huo)性(xing)。

　　USB 充電(dian)標準(zhun)

　　USB 充電時，可以使用許多充電器IC，它們(men)都結合了(le)USB100和USB500 電(dian)流限(xian)制。通(tong)過USB 充(chong)電(dian)器輸(shu)出運(yun)行所有(you)下游電(dian)路，讓(rang)廣(guang)大設(she)計人員能(neng)夠確保不超出USB 電(dian)流限(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(dou)集成了一個連(lian)接電源(yuan)(yuan)并通過電源(yuan)(yuan)供電的5V LDO。每當連(lian)接一個有(you)效(xiao)電源(yuan)(yuan)時(shi)，這種(zhong)輸出(chu)便(bian)有(you)效(xiao)。5V LDO 穩(wen)壓(ya)電壓(ya)保(bao)護USB 電路(lu)免(mian)受未穩(wen)壓(ya)適配器和其他過電壓(ya)狀態的損害。

　　　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該就會(hui)變得簡(jian)單了。