隨著智能手(shou)機、平板電(dian)(dian)腦和攝像機等便攜設備的(de)不(bu)斷普及，人們對(dui)(dui)電(dian)(dian)源的(de)要(yao)求(qiu)(qiu)以及對(dui)(dui)邊充(chong)電(dian)(dian)邊使用這(zhe)些設備的(de)能力(li)的(de)要(yao)求(qiu)(qiu)與日俱(ju)增。更高的(de)功率(lv)(lv)要(yao)求(qiu)(qiu)增加了對(dui)(dui)具有高功率(lv)(lv)密度和優異(yi)充(chong)電(dian)(dian)能力(li)的(de)電(dian)(dian)池(chi)的(de)需求(qiu)(qiu)。目(mu)前(qian)，鋰(li)離(li)子（Li-ion）電(dian)(dian)池(chi)和鋰(li)聚合(he)物（Li-po）電(dian)(dian)池(chi)最(zui)適合(he)當前(qian)市場(chang)對(dui)(dui)功率(lv)(lv)密度、充(chong)電(dian)(dian)能力(li)和價格的(de)要(yao)求(qiu)(qiu)。但(dan)是，有別于鉛酸、鎳氫(qing)等其他流行的(de)電(dian)(dian)池(chi)技術(shu)，鋰(li)電(dian)(dian)池(chi)技術(shu)的(de)性能也最(zui)不(bu)穩定：鋰(li)電(dian)(dian)池(chi)充(chong)放電(dian)(dian)若管理不(bu)善(shan)，將導致充(chong)電(dian)(dian)時間長、耗(hao)散(san)功率(lv)(lv)高、效率(lv)(lv)低和電(dian)(dian)池(chi)壽命比平均壽命低等問題。圖1顯(xian)示了典型(xing)鋰(li)離(li)子電(dian)(dian)池(chi)的(de)充(chong)電(dian)(dian)曲線。

　　傳統充電(dian)器相對簡單，這(zhe)些(xie)充電(dian)器在(zai)小(xiao)功率(lv)(lv)應(ying)用(yong)中表現較(jiao)(jiao)好。然而(er)，它們(men)卻不能(neng)有(you)效地適應(ying)充電(dian)曲線的變(bian)化，比(bi)如(ru)，用(yong)戶在(zai)不同(tong)電(dian)源(yuan)之間(jian)(jian)切換或者在(zai)充電(dian)期間(jian)(jian)操作設備(bei)。另外，傳統充電(dian)器在(zai)大功率(lv)(lv)和(he)大電(dian)流(liu)應(ying)用(yong)中，通(tong)常效率(lv)(lv)較(jiao)(jiao)低(di)，耗散功率(lv)(lv)較(jiao)(jiao)大。

圖1:典(dian)型鋰離子電池的充電曲線。

　　新型線性和開關充電器，比(bi)如芯源系(xi)統(tong)（MPS）公(gong)司的(de)MP2600系(xi)列，采用電源路徑管理技術改變了充電曲(qu)線，從而能(neng)夠(gou)以更低的(de)耗散(san)功率(lv)更加(jia)高效地為電池(chi)/系(xi)統(tong)供電。同時，這些充電器也使系(xi)統(tong)的(de)安全性和電池(chi)的(de)使用壽命得到提高。

　　電(dian)源管理拓撲種類繁多，本文則重點介紹以(yi)下三種：電(dian)池饋電(dian)、自動選擇和動態(tai)電(dian)源路徑(jing)。

　　電池饋電拓撲

　　電(dian)池饋電(dian)拓(tuo)(tuo)撲是一種(zhong)實現過程最(zui)簡單、成(cheng)(cheng)本最(zui)低(di)的拓(tuo)(tuo)撲，這是因為其電(dian)路由充電(dian)器、電(dian)池和系統組成(cheng)(cheng)，如圖2所示。

圖2:電(dian)池饋電(dian)拓撲原理圖及信號圖。

　　這種拓(tuo)撲(pu)有三個主要特性：無論供(gong)電(dian)(dian)(dian)電(dian)(dian)(dian)壓(ya)如何(he)變(bian)化(hua)，系統電(dian)(dian)(dian)壓(ya)始終(zhong)等于電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)壓(ya)，電(dian)(dian)(dian)源(yuan)系統始終(zhong)優(you)先，以便IBATT ￡ ICHG,并且ICHG最(zui)終(zhong)限(xian)制由輸(shu)入(ru)電(dian)(dian)(dian)源(yuan)提供(gong)給(gei)系統電(dian)(dian)(dian)源(yuan)總(zong)線的最(zui)大功率。當系統與充電(dian)(dian)(dian)器(qi)斷開時該拓(tuo)撲(pu)還可以實現最(zui)小的耗散功率，設置ICHG從根本上(shang)限(xian)定了總(zong)輸(shu)入(ru)電(dian)(dian)(dian)流(liu)，這樣(yang)，隨著系統電(dian)(dian)(dian)流(liu)（ISYS）的增加，充電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)（IBATT）將等額(e)下降，工(gong)作波形如圖2所(suo)示。

　　遺憾的是，這種拓撲有如下不(bu)足之(zhi)處，從而限制了它在更廣應用領域(yu)的效(xiao)率和效(xiao)用：

　　在電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)壓(ya)太低(di)(di)的(de)情況下，系(xi)統(tong)無法工(gong)作(zuo)(zuo)。電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)壓(ya)跌至(zhi)涓流(liu)充(chong)電(dian)(dian)(dian)門限(xian)(xian)以(yi)下時，充(chong)電(dian)(dian)(dian)器將(jiang)(jiang)把總(zong)的(de)輸(shu)出電(dian)(dian)(dian)流(liu)限(xian)(xian)制得很低(di)(di)。系(xi)統(tong)的(de)額外電(dian)(dian)(dian)源需求將(jiang)(jiang)由(you)電(dian)(dian)(dian)池(chi)來補充(chong)，從而導致電(dian)(dian)(dian)池(chi)能(neng)量(liang)進一步(bu)耗盡。由(you)于(yu)系(xi)統(tong)電(dian)(dian)(dian)壓(ya)始(shi)終(zhong)等于(yu)電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)壓(ya)，一旦電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)壓(ya)低(di)(di)到系(xi)統(tong)最低(di)(di)工(gong)作(zuo)(zuo)電(dian)(dian)(dian)壓(ya)以(yi)下，系(xi)統(tong)將(jiang)(jiang)停止工(gong)作(zuo)(zuo)。

　　雖然電(dian)池已具有滿(man)電(dian)量，但是充電(dian)器無法進入EOC（結(jie)束(shu)充電(dian)）狀(zhuang)態(tai)。如果(guo)ISYS超過電(dian)池滿(man)電(dian)量門限(xian)（IBF），那(nei)么ICHG就無法降到低于IBF,充電(dian)狀(zhuang)態(tai)始終顯示正在(zai)充電(dian)，即使電(dian)池已經具有滿(man)電(dian)量。

　　電(dian)(dian)(dian)池(chi)無(wu)法(fa)充(chong)滿。由于系統(tong)優先于電(dian)(dian)(dian)池(chi)供電(dian)(dian)(dian)，因此電(dian)(dian)(dian)池(chi)只(zhi)能(neng)以低電(dian)(dian)(dian)流進行充(chong)電(dian)(dian)(dian)。此外，充(chong)電(dian)(dian)(dian)器(qi)只(zhi)能(neng)在預期的有效(xiao)充(chong)電(dian)(dian)(dian)時(shi)間內(nei)工作，這樣可以避免給壞電(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)。如充(chong)電(dian)(dian)(dian)時(shi)間超出此時(shi)間段，會導(dao)致充(chong)電(dian)(dian)(dian)器(qi)誤判壞電(dian)(dian)(dian)池(chi)而停止(zhi)充(chong)電(dian)(dian)(dian)。

電(dian)源路徑自動選擇拓撲

　　電源路徑(jing)自動選擇(ze)拓(tuo)撲在電池直接搭載拓(tuo)撲基礎上外加了兩個開關管，使得(de)系統電源可以根據輸(shu)入電壓的變化在適(shi)配器(qi)和(he)電池之間來回切(qie)換(huan)。拓(tuo)撲結構及工作波形如圖3所(suo)示。

圖3:電源路徑自(zi)動選擇拓撲及工作波形(xing)。

　　與(yu)電(dian)(dian)池饋電(dian)(dian)拓(tuo)(tuo)撲結(jie)構相比，此拓(tuo)(tuo)撲有實質(zhi)性的(de)改進(jin)。它將系(xi)統(tong)(tong)直接(jie)跟(gen)交流(liu)適配器(qi)(qi)(qi)相連，與(yu)充(chong)電(dian)(dian)器(qi)(qi)(qi)獨立開來，因而(er)能夠提供更(geng)(geng)大的(de)系(xi)統(tong)(tong)電(dian)(dian)流(liu)、更(geng)(geng)高的(de)效率(lv)(lv)并且允許系(xi)統(tong)(tong)在低電(dian)(dian)池電(dian)(dian)壓下工作。此外，其(qi)價格也(ye)比較低廉。然而(er)，當適配器(qi)(qi)(qi)輸出電(dian)(dian)壓變(bian)化(hua)較大的(de)時(shi)候，系(xi)統(tong)(tong)電(dian)(dian)壓也(ye)會隨之(zhi)變(bian)化(hua)，所以(yi)(yi)此拓(tuo)(tuo)撲要求(qiu)系(xi)統(tong)(tong)能夠接(jie)受比較寬的(de)輸入電(dian)(dian)壓變(bian)化(hua)范圍。此外，也(ye)要求(qiu)適配器(qi)(qi)(qi)具有更(geng)(geng)高的(de)額定功(gong)(gong)率(lv)(lv)，以(yi)(yi)滿足系(xi)統(tong)(tong)和充(chong)電(dian)(dian)器(qi)(qi)(qi)的(de)最大總功(gong)(gong)率(lv)(lv)需求(qiu)，以(yi)(yi)及(ji)系(xi)統(tong)(tong)負載(zai)突變(bian)時(shi)的(de)功(gong)(gong)率(lv)(lv)變(bian)化(hua)要求(qiu)。

　　圖4是采用MPS公司(si)的(de)(de)MP2611構成的(de)(de)電(dian)源路徑自動(dong)選(xuan)擇拓撲的(de)(de)原理(li)圖。為(wei)了防(fang)止出(chu)現(xian)不穩(wen)定情況，當VBATT接近(jin)VIN時，MP2611會斷(duan)開系統(tong)與電(dian)池的(de)(de)連接。此(ci)外，它還會在S1 （M1及M2）與S2（M3）之間(jian)插(cha)入一個消隱期，以防(fang)出(chu)現(xian)電(dian)流貫通，從(cong)而(er)損壞系統(tong)和電(dian)池。

圖4:采用MP2611構成的電源(yuan)路徑(jing)自動選(xuan)擇拓撲。

　　動態電源路徑(jing)管(guan)理拓撲（DPPM）

　　動態電(dian)(dian)(dian)(dian)源路(lu)徑管理（DPPM）技術(shu)采用(yong)了一套附(fu)加的(de)檢(jian)測(ce)模(mo)塊(kuai)，測(ce)量系統電(dian)(dian)(dian)(dian)壓或者輸入電(dian)(dian)(dian)(dian)流，實時監測(ce)總(zong)功率(lv)(lv)需(xu)求(qiu)。一旦功率(lv)(lv)需(xu)求(qiu)超過預(yu)設值，通過充電(dian)(dian)(dian)(dian)器(qi)降低(di)充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流來保證適配(pei)器(qi)輸出(chu)功率(lv)(lv)恒定(ding)而不過載。

　　例如，基于輸入電(dian)壓(ya)的(de)DPPM（圖5）通(tong)過比較輸入電(dian)壓(ya)與預設(she)(she)參考電(dian)壓(ya)來判斷輸入電(dian)流是否達到適配(pei)器(qi)的(de)輸出電(dian)流限(xian)(xian)制(zhi)。若適配(pei)器(qi)電(dian)流已(yi)經(jing)達到該(gai)(gai)限(xian)(xian)制(zhi)，適配(pei)器(qi)電(dian)壓(ya)將(jiang)降(jiang)至(zhi)預設(she)(she)參考電(dian)壓(ya)，然后(hou)充(chong)電(dian)器(qi)通(tong)過動態降(jiang)低充(chong)電(dian)電(dian)流來防止系統電(dian)壓(ya)繼續下降(jiang)。只要輸入電(dian)流保持在該(gai)(gai)限(xian)(xian)制(zhi)的(de)水平或者低于該(gai)(gai)限(xian)(xian)制(zhi)，就仍然有電(dian)流向電(dian)池充(chong)電(dian)。然而，由系統電(dian)壓(ya)下降(jiang)引起的(de)不穩定或噪聲(sheng)(sheng)使得這種基于電(dian)壓(ya)的(de)DPPM結構不適合(he)應用在某些對噪聲(sheng)(sheng)敏(min)感的(de)場合(he)，比如音頻設(she)(she)備。

圖5:基于輸入(ru)電(dian)壓的動(dong)態電(dian)源路徑管理(li)。

基(ji)于輸入電(dian)(dian)(dian)流(liu)(liu)(liu)的DPPM（圖6）采用(yong)檢測(ce)電(dian)(dian)(dian)阻來評估輸入電(dian)(dian)(dian)流(liu)(liu)(liu)，當(dang)輸入電(dian)(dian)(dian)流(liu)(liu)(liu)達到預(yu)設電(dian)(dian)(dian)流(liu)(liu)(liu)門限時(shi)，通過動態降低電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)流(liu)(liu)(liu)來防止適(shi)配器過載或系統(tong)電(dian)(dian)(dian)壓下降。這(zhe)樣就(jiu)保證(zheng)了(le)(le)系統(tong)電(dian)(dian)(dian)壓的穩(wen)定(ding)，降低了(le)(le)適(shi)配器的額外(wai)功率要(yao)求。同時(shi)，該拓撲還具備電(dian)(dian)(dian)池(chi)反向補充供電(dian)(dian)(dian)的能力。

圖6:基于輸入電(dian)流的動態電(dian)源路徑管(guan)理。

　　有些充電(dian)器（例如MPS公司的MP2607）可以根據不同電(dian)源(yuan)要(yao)求，優化選(xuan)擇不同的動(dong)態電(dian)源(yuan)路徑管理(li)方案。MP2607根據不同的適配器類(lei)型，在基于(yu)輸入電(dian)壓(ya)和基于(yu)輸入電(dian)流的DPPM兩種拓撲之間進行(xing)智能選(xuan)擇。若(ruo)輸入是(shi)交流適配器，MP2607采用基于(yu)輸入電(dian)壓(ya)的DPPM技術，控制適配器交流電(dian)壓(ya)，使得交流適配器可以同時為系統供電(dian)和為電(dian)池充電(dian)，工作波形如圖7所示。

圖7:MP2607在(zai)交(jiao)流適配(pei)器輸入時(shi)的動(dong)態電源路徑(jing)管理(li)。

　　在(zai)USB輸入模式下，MP2607采用基于(yu)輸入電(dian)流(liu)的(de)DPPM.如圖8所(suo)示，考慮到(dao)USB提(ti)供(gong)電(dian)流(liu)能力有限(xian)(xian)，設置充電(dian)電(dian)流(liu)在(zai)USB限(xian)(xian)制(zhi)電(dian)流(liu)以下。若系統負(fu)載電(dian)流(liu)大于(yu)USB限(xian)(xian)流(liu)值，電(dian)池將反向(xiang)補充供(gong)電(dian)。

圖8:MP2607在USB輸入時的動(dong)態電源(yuan)路徑管理。

　　總之，具有動態電源路徑管理的充電器（尤其是那些能在不同管理模式之間切換的充電器）可以為移動電子設備提供更加精妙的電源解決方案(an)，從而給用戶帶來前所未有的(de)便利、性能和(he)效率。