隨著(zhu)智能(neng)(neng)手機、平板電(dian)(dian)(dian)腦和(he)攝(she)像(xiang)機等(deng)便攜設備(bei)(bei)的(de)(de)(de)(de)(de)不(bu)(bu)斷普及，人們對電(dian)(dian)(dian)源(yuan)的(de)(de)(de)(de)(de)要(yao)求(qiu)(qiu)以及對邊充(chong)電(dian)(dian)(dian)邊使用這(zhe)些設備(bei)(bei)的(de)(de)(de)(de)(de)能(neng)(neng)力的(de)(de)(de)(de)(de)要(yao)求(qiu)(qiu)與日俱增。更高的(de)(de)(de)(de)(de)功率要(yao)求(qiu)(qiu)增加了對具有高功率密度(du)和(he)優異充(chong)電(dian)(dian)(dian)能(neng)(neng)力的(de)(de)(de)(de)(de)電(dian)(dian)(dian)池(chi)(chi)的(de)(de)(de)(de)(de)需(xu)求(qiu)(qiu)。目前，鋰離子（Li-ion）電(dian)(dian)(dian)池(chi)(chi)和(he)鋰聚合物（Li-po）電(dian)(dian)(dian)池(chi)(chi)最適合當前市(shi)場對功率密度(du)、充(chong)電(dian)(dian)(dian)能(neng)(neng)力和(he)價格的(de)(de)(de)(de)(de)要(yao)求(qiu)(qiu)。但(dan)是(shi)，有別于鉛(qian)酸、鎳氫等(deng)其他流行的(de)(de)(de)(de)(de)電(dian)(dian)(dian)池(chi)(chi)技術(shu)，鋰電(dian)(dian)(dian)池(chi)(chi)技術(shu)的(de)(de)(de)(de)(de)性能(neng)(neng)也最不(bu)(bu)穩定：鋰電(dian)(dian)(dian)池(chi)(chi)充(chong)放電(dian)(dian)(dian)若管理(li)不(bu)(bu)善(shan)，將導致充(chong)電(dian)(dian)(dian)時間長、耗散功率高、效率低和(he)電(dian)(dian)(dian)池(chi)(chi)壽命比(bi)平均壽命低等(deng)問題。圖1顯示了典(dian)型鋰離子電(dian)(dian)(dian)池(chi)(chi)的(de)(de)(de)(de)(de)充(chong)電(dian)(dian)(dian)曲線(xian)。

　　傳統充電器相(xiang)對簡單，這些充(chong)電器在(zai)小(xiao)功(gong)率應用中表現(xian)較(jiao)好。然而，它們卻不能有效地適應充(chong)電曲線的變化，比(bi)如，用戶(hu)在(zai)不同電源(yuan)之間(jian)切換或者在(zai)充(chong)電期間(jian)操作設(she)備。另外，傳統充(chong)電器在(zai)大功(gong)率和大電流應用中，通常效率較(jiao)低，耗散功(gong)率較(jiao)大。

圖1:典型鋰離子電(dian)池的充(chong)電(dian)曲線。

　　新型線性和開關充電器，比如芯源系統（MPS）公司的MP2600系列，采用電源路徑管理技術改變了充電曲線，從而能夠以更低的耗散功率更加高效地為電池/系統供電。同時，這些充電器也使(shi)系統的安全(quan)性和電(dian)池的使(shi)用壽命得到提高。

　　電源(yuan)管理拓撲種(zhong)類繁(fan)多，本文則重(zhong)點(dian)介紹以下三種(zhong)：電池饋電、自動(dong)選(xuan)擇和動(dong)態電源(yuan)路徑。

　　電池饋電拓撲

　　電(dian)池饋(kui)電(dian)拓撲是一種實現過程最簡單(dan)、成(cheng)本最低的拓撲，這(zhe)是因為(wei)其電(dian)路(lu)由充電(dian)器(qi)、電(dian)池和系統組(zu)成(cheng)，如圖(tu)2所示。

圖(tu)(tu)2:電池饋電拓撲原理圖(tu)(tu)及信號圖(tu)(tu)。

　　這種拓(tuo)撲有三個(ge)主要特性：無論供(gong)電(dian)(dian)(dian)電(dian)(dian)(dian)壓如何(he)變化(hua)，系(xi)統(tong)電(dian)(dian)(dian)壓始(shi)終等(deng)于電(dian)(dian)(dian)池電(dian)(dian)(dian)壓，電(dian)(dian)(dian)源(yuan)系(xi)統(tong)始(shi)終優先，以便IBATT ￡ ICHG,并(bing)且ICHG最終限(xian)制由輸入電(dian)(dian)(dian)源(yuan)提供(gong)給系(xi)統(tong)電(dian)(dian)(dian)源(yuan)總線的(de)最大功率。當系(xi)統(tong)與充電(dian)(dian)(dian)器斷開(kai)時該拓(tuo)撲還可(ke)以實現最小的(de)耗散功率，設置(zhi)ICHG從(cong)根本(ben)上限(xian)定了總輸入電(dian)(dian)(dian)流，這樣，隨著(zhu)系(xi)統(tong)電(dian)(dian)(dian)流（ISYS）的(de)增(zeng)加，充電(dian)(dian)(dian)電(dian)(dian)(dian)流（IBATT）將(jiang)等(deng)額下降，工作波形如圖2所示。

　　遺憾的(de)是，這(zhe)種拓撲(pu)有(you)如下不足之(zhi)處，從而限制(zhi)了(le)它(ta)在(zai)更廣應(ying)用(yong)領域(yu)的(de)效率(lv)和效用(yong)：

　　在(zai)電(dian)(dian)池(chi)電(dian)(dian)壓太低(di)的(de)情(qing)況下，系(xi)統(tong)無法工(gong)作。電(dian)(dian)池(chi)電(dian)(dian)壓跌至涓流充(chong)電(dian)(dian)門(men)限(xian)以(yi)下時，充(chong)電(dian)(dian)器將把總的(de)輸出電(dian)(dian)流限(xian)制(zhi)得(de)很(hen)低(di)。系(xi)統(tong)的(de)額外電(dian)(dian)源需求將由電(dian)(dian)池(chi)來補充(chong)，從而導致電(dian)(dian)池(chi)能(neng)量(liang)進(jin)一步耗(hao)盡。由于系(xi)統(tong)電(dian)(dian)壓始終等于電(dian)(dian)池(chi)電(dian)(dian)壓，一旦電(dian)(dian)池(chi)電(dian)(dian)壓低(di)到系(xi)統(tong)最(zui)低(di)工(gong)作電(dian)(dian)壓以(yi)下，系(xi)統(tong)將停止工(gong)作。

　　雖然電(dian)池已具(ju)有滿(man)電(dian)量，但是充(chong)電(dian)器無法進入EOC（結束(shu)充(chong)電(dian)）狀(zhuang)態。如果ISYS超過電(dian)池滿(man)電(dian)量門限（IBF），那么ICHG就無法降到低于IBF,充(chong)電(dian)狀(zhuang)態始終顯示正在充(chong)電(dian)，即使電(dian)池已經具(ju)有滿(man)電(dian)量。

　　電(dian)池(chi)無法(fa)充(chong)(chong)(chong)(chong)滿(man)。由于系統優先于電(dian)池(chi)供電(dian)，因此(ci)(ci)電(dian)池(chi)只(zhi)能以低(di)電(dian)流進行充(chong)(chong)(chong)(chong)電(dian)。此(ci)(ci)外，充(chong)(chong)(chong)(chong)電(dian)器(qi)只(zhi)能在預期的(de)有效充(chong)(chong)(chong)(chong)電(dian)時間內工作，這樣可以避免(mian)給壞(huai)電(dian)池(chi)充(chong)(chong)(chong)(chong)電(dian)。如充(chong)(chong)(chong)(chong)電(dian)時間超出(chu)此(ci)(ci)時間段，會導致充(chong)(chong)(chong)(chong)電(dian)器(qi)誤判壞(huai)電(dian)池(chi)而停(ting)止充(chong)(chong)(chong)(chong)電(dian)。

電(dian)源路徑自動選(xuan)擇拓撲

　　電(dian)(dian)源(yuan)路(lu)徑(jing)自動選擇拓(tuo)撲(pu)(pu)(pu)在電(dian)(dian)池直接搭載拓(tuo)撲(pu)(pu)(pu)基(ji)礎上(shang)外加了(le)兩個開關(guan)管，使得系統電(dian)(dian)源(yuan)可(ke)以根據輸入電(dian)(dian)壓的變(bian)化在適(shi)配器和電(dian)(dian)池之間(jian)來回切(qie)換(huan)。拓(tuo)撲(pu)(pu)(pu)結構及工作波形如圖3所(suo)示。

圖3:電源路徑自動(dong)選擇(ze)拓撲及(ji)工作波(bo)形。

　　與電(dian)(dian)池饋電(dian)(dian)拓撲(pu)(pu)結構相比(bi)，此(ci)(ci)拓撲(pu)(pu)有實質(zhi)性的(de)改進。它將系(xi)統(tong)(tong)直接跟交流適(shi)配(pei)器(qi)相連，與充電(dian)(dian)器(qi)獨立開來，因而能夠提供更大(da)的(de)系(xi)統(tong)(tong)電(dian)(dian)流、更高的(de)效率(lv)(lv)并且允(yun)許系(xi)統(tong)(tong)在(zai)低電(dian)(dian)池電(dian)(dian)壓下工作。此(ci)(ci)外(wai)，其價格也(ye)比(bi)較(jiao)低廉。然而，當適(shi)配(pei)器(qi)輸出電(dian)(dian)壓變化(hua)較(jiao)大(da)的(de)時候，系(xi)統(tong)(tong)電(dian)(dian)壓也(ye)會隨之變化(hua)，所以(yi)(yi)此(ci)(ci)拓撲(pu)(pu)要求系(xi)統(tong)(tong)能夠接受比(bi)較(jiao)寬(kuan)的(de)輸入電(dian)(dian)壓變化(hua)范圍。此(ci)(ci)外(wai)，也(ye)要求適(shi)配(pei)器(qi)具(ju)有更高的(de)額定功(gong)(gong)率(lv)(lv)，以(yi)(yi)滿足系(xi)統(tong)(tong)和充電(dian)(dian)器(qi)的(de)最大(da)總(zong)功(gong)(gong)率(lv)(lv)需求，以(yi)(yi)及系(xi)統(tong)(tong)負載突變時的(de)功(gong)(gong)率(lv)(lv)變化(hua)要求。

　　圖(tu)(tu)4是(shi)采用MPS公司的MP2611構成的電源路徑(jing)自動選擇拓撲的原理圖(tu)(tu)。為了防止(zhi)出(chu)現(xian)不穩定情況，當VBATT接近VIN時，MP2611會斷開系統(tong)與電池的連接。此外，它(ta)還會在S1 （M1及M2）與S2（M3）之間插入一個消隱期，以防出(chu)現(xian)電流貫通(tong)，從而損(sun)壞系統(tong)和(he)電池。

圖4:采用MP2611構成的電源(yuan)路(lu)徑自動(dong)選擇拓(tuo)撲。

　　動態電(dian)源路徑(jing)管(guan)理拓撲（DPPM）

　　動態電(dian)(dian)源路徑管(guan)理(li)（DPPM）技術采用了一(yi)套附(fu)加的(de)檢測(ce)模塊，測(ce)量系統(tong)電(dian)(dian)壓或(huo)者輸入電(dian)(dian)流，實時(shi)監測(ce)總功(gong)率(lv)需(xu)求。一(yi)旦功(gong)率(lv)需(xu)求超過預設值，通過充電(dian)(dian)器降低充電(dian)(dian)電(dian)(dian)流來保證適配器輸出功(gong)率(lv)恒定而(er)不過載。

　　例如，基于輸入電壓的DPPM（圖5）通過比較輸入電壓與預設參考電壓來判斷輸入電流是否達到適配器的輸出電流限制。若適配器電流已經達到該限制，適配器電壓將降至預設參考電壓，然后充電器通過動態降(jiang)低(di)充電電流來(lai)防(fang)止系統(tong)電壓繼續下(xia)降(jiang)。只要(yao)輸(shu)入電流保(bao)持在該限制的水平或者低(di)于該限制，就仍(reng)然有電流向電池充電。然而，由系統(tong)電壓下(xia)降(jiang)引起的不穩定或噪聲使得這種基于電壓的DPPM結構不適(shi)合(he)應用在某些對噪聲敏感(gan)的場合(he)，比如音頻設備。

圖(tu)5:基(ji)于輸入電壓的動態電源路徑(jing)管理(li)。

基于(yu)輸入(ru)電(dian)(dian)(dian)流的(de)DPPM（圖6）采(cai)用檢測電(dian)(dian)(dian)阻來(lai)評估輸入(ru)電(dian)(dian)(dian)流，當輸入(ru)電(dian)(dian)(dian)流達到(dao)預設(she)電(dian)(dian)(dian)流門限(xian)時，通過動態降低電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)流來(lai)防(fang)止適配器過載(zai)或系統電(dian)(dian)(dian)壓下降。這樣就保證了系統電(dian)(dian)(dian)壓的(de)穩定，降低了適配器的(de)額外功率要求。同時，該拓撲還具備(bei)電(dian)(dian)(dian)池(chi)反(fan)向補充供電(dian)(dian)(dian)的(de)能力。

圖6:基于輸入電流的動態(tai)電源路(lu)徑管理。

　　有(you)些充電(dian)(dian)(dian)器(qi)（例如MPS公司的(de)MP2607）可以根(gen)據不同(tong)電(dian)(dian)(dian)源要求，優化選擇(ze)不同(tong)的(de)動(dong)態(tai)電(dian)(dian)(dian)源路徑管理方案。MP2607根(gen)據不同(tong)的(de)適(shi)配器(qi)類型(xing)，在基于輸(shu)入(ru)電(dian)(dian)(dian)壓和基于輸(shu)入(ru)電(dian)(dian)(dian)流(liu)(liu)的(de)DPPM兩種拓撲(pu)之間進(jin)行智能(neng)選擇(ze)。若輸(shu)入(ru)是(shi)交(jiao)流(liu)(liu)適(shi)配器(qi)，MP2607采用基于輸(shu)入(ru)電(dian)(dian)(dian)壓的(de)DPPM技術，控制適(shi)配器(qi)交(jiao)流(liu)(liu)電(dian)(dian)(dian)壓，使得交(jiao)流(liu)(liu)適(shi)配器(qi)可以同(tong)時為系統供電(dian)(dian)(dian)和為電(dian)(dian)(dian)池充電(dian)(dian)(dian)，工作波形如圖7所示。

圖7:MP2607在交流適配器輸(shu)入時的動態電(dian)源路徑管(guan)理。

　　在USB輸(shu)入(ru)模式下，MP2607采(cai)用(yong)基于輸(shu)入(ru)電(dian)(dian)(dian)流的DPPM.如圖8所示，考慮到(dao)USB提供(gong)電(dian)(dian)(dian)流能力有限(xian)，設(she)置(zhi)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流在USB限(xian)制電(dian)(dian)(dian)流以下。若系統負載電(dian)(dian)(dian)流大于USB限(xian)流值，電(dian)(dian)(dian)池將反向補充(chong)供(gong)電(dian)(dian)(dian)。

圖8:MP2607在USB輸入時的動態(tai)電(dian)源路(lu)徑管理。

　　總之，具有動態電源路徑管理的充電器（尤其是那(nei)些能在(zai)不(bu)同管理模式之間切換的充(chong)電(dian)器）可以為移動電(dian)子設備(bei)提供更(geng)加精(jing)妙的電(dian)源解決方(fang)案，從而給用(yong)戶(hu)帶(dai)來(lai)前所未(wei)有(you)的便利、性能和效率(lv)。