隨著智能(neng)(neng)(neng)手機(ji)、平板(ban)電(dian)(dian)(dian)(dian)腦和(he)攝像機(ji)等便攜設備(bei)的(de)(de)不(bu)(bu)斷普(pu)及，人們對電(dian)(dian)(dian)(dian)源的(de)(de)要求以及對邊充(chong)電(dian)(dian)(dian)(dian)邊使(shi)用這些(xie)設備(bei)的(de)(de)能(neng)(neng)(neng)力(li)的(de)(de)要求與日俱增。更高(gao)的(de)(de)功率要求增加了對具有(you)高(gao)功率密度(du)和(he)優異充(chong)電(dian)(dian)(dian)(dian)能(neng)(neng)(neng)力(li)的(de)(de)電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的(de)(de)需(xu)求。目前，鋰(li)(li)(li)離(li)子(zi)（Li-ion）電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)和(he)鋰(li)(li)(li)聚合物(wu)（Li-po）電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)最適合當前市(shi)場對功率密度(du)、充(chong)電(dian)(dian)(dian)(dian)能(neng)(neng)(neng)力(li)和(he)價格的(de)(de)要求。但是，有(you)別于鉛酸(suan)、鎳氫等其他(ta)流行的(de)(de)電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)技(ji)術(shu)(shu)，鋰(li)(li)(li)電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)技(ji)術(shu)(shu)的(de)(de)性能(neng)(neng)(neng)也最不(bu)(bu)穩定(ding)：鋰(li)(li)(li)電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)充(chong)放電(dian)(dian)(dian)(dian)若管理不(bu)(bu)善，將(jiang)導(dao)致充(chong)電(dian)(dian)(dian)(dian)時間(jian)長、耗散功率高(gao)、效(xiao)率低和(he)電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)壽命比平均壽命低等問題。圖1顯示了典型(xing)鋰(li)(li)(li)離(li)子(zi)電(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的(de)(de)充(chong)電(dian)(dian)(dian)(dian)曲線。

　　傳統充(chong)電器(qi)相對簡單(dan)，這些充(chong)電器(qi)在(zai)小(xiao)功率(lv)應用中表現較好。然而，它(ta)們卻不能有效(xiao)地適應充(chong)電曲線(xian)的變化，比如，用戶(hu)在(zai)不同電源之間切換或者在(zai)充(chong)電期(qi)間操作設(she)備。另外(wai)，傳統充(chong)電器(qi)在(zai)大功率(lv)和大電流應用中，通常效(xiao)率(lv)較低，耗散(san)功率(lv)較大。

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，比如芯(xin)源系統(tong)（MPS）公(gong)司的(de)(de)MP2600系列(lie)，采用(yong)電(dian)源路(lu)徑管(guan)理技(ji)術改變了充電(dian)曲線，從(cong)而(er)能夠以更(geng)低(di)的(de)(de)耗散功(gong)率更(geng)加高(gao)效地為電(dian)池(chi)/系統(tong)供電(dian)。同時，這些充電(dian)器也使系統(tong)的(de)(de)安全性和電(dian)池(chi)的(de)(de)使用(yong)壽命(ming)得到提高(gao)。

　　電源管理拓撲種類繁多，本文則重點介(jie)紹以下三種：電池饋電、自動選擇和動態電源路徑。

　　電池饋電拓撲

　　電池饋電拓撲是一種(zhong)實現(xian)過程最簡單、成(cheng)本最低的拓撲，這是因為其(qi)電路(lu)由充電器(qi)、電池和系統組成(cheng)，如(ru)圖2所示。

圖(tu)2:電池(chi)饋電拓撲原理圖(tu)及信號圖(tu)。

　　這種(zhong)拓撲有(you)三(san)個(ge)主要特(te)性(xing)：無論供電(dian)(dian)(dian)電(dian)(dian)(dian)壓如何變(bian)化，系(xi)(xi)統電(dian)(dian)(dian)壓始終(zhong)等于電(dian)(dian)(dian)池電(dian)(dian)(dian)壓，電(dian)(dian)(dian)源系(xi)(xi)統始終(zhong)優先，以便IBATT ￡ ICHG,并(bing)且ICHG最終(zhong)限(xian)制由輸入電(dian)(dian)(dian)源提供給系(xi)(xi)統電(dian)(dian)(dian)源總線的最大功(gong)率(lv)。當(dang)系(xi)(xi)統與充(chong)電(dian)(dian)(dian)器斷開(kai)時該(gai)拓撲還可以實現最小的耗(hao)散功(gong)率(lv)，設(she)置ICHG從根本上限(xian)定了(le)總輸入電(dian)(dian)(dian)流，這樣，隨著(zhu)系(xi)(xi)統電(dian)(dian)(dian)流（ISYS）的增加(jia)，充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流（IBATT）將(jiang)等額下降，工作波形如圖2所(suo)示。

　　遺憾的是，這種拓撲(pu)有如下不足之(zhi)處，從而限(xian)制了它在更廣應用領(ling)域的效率(lv)和效用：

　　在電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)壓(ya)太低(di)(di)的情(qing)況(kuang)下，系(xi)(xi)(xi)統無(wu)法工(gong)作(zuo)(zuo)。電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)壓(ya)跌至涓流充電(dian)(dian)(dian)門限以下時，充電(dian)(dian)(dian)器將把(ba)總(zong)的輸出電(dian)(dian)(dian)流限制得很(hen)低(di)(di)。系(xi)(xi)(xi)統的額外電(dian)(dian)(dian)源需求將由電(dian)(dian)(dian)池(chi)來補(bu)充，從而導致電(dian)(dian)(dian)池(chi)能量進一(yi)步耗盡。由于(yu)系(xi)(xi)(xi)統電(dian)(dian)(dian)壓(ya)始終等于(yu)電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)壓(ya)，一(yi)旦電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)壓(ya)低(di)(di)到系(xi)(xi)(xi)統最(zui)低(di)(di)工(gong)作(zuo)(zuo)電(dian)(dian)(dian)壓(ya)以下，系(xi)(xi)(xi)統將停止工(gong)作(zuo)(zuo)。

　　雖然電(dian)(dian)池已(yi)具有滿(man)電(dian)(dian)量，但是充電(dian)(dian)器無法進入EOC（結束充電(dian)(dian)）狀態。如果ISYS超過電(dian)(dian)池滿(man)電(dian)(dian)量門限（IBF），那么ICHG就無法降到低于IBF,充電(dian)(dian)狀態始(shi)終顯示(shi)正在充電(dian)(dian)，即使(shi)電(dian)(dian)池已(yi)經具有滿(man)電(dian)(dian)量。

　　電(dian)(dian)(dian)(dian)池(chi)無法充(chong)(chong)(chong)(chong)滿(man)。由于系統優先于電(dian)(dian)(dian)(dian)池(chi)供電(dian)(dian)(dian)(dian)，因此電(dian)(dian)(dian)(dian)池(chi)只(zhi)能以低電(dian)(dian)(dian)(dian)流進行充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)。此外(wai)，充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)器只(zhi)能在預期(qi)的有(you)效充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)時(shi)間(jian)內(nei)工作，這樣可以避免(mian)給壞電(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)。如充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)時(shi)間(jian)超出此時(shi)間(jian)段，會導(dao)致(zhi)充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)器誤判壞電(dian)(dian)(dian)(dian)池(chi)而停止充(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)。

電源(yuan)路徑自動(dong)選擇(ze)拓撲

　　電(dian)(dian)源路徑自動選擇拓撲在電(dian)(dian)池直接搭載拓撲基礎上外加(jia)了兩個開關管，使得系統(tong)電(dian)(dian)源可以根據輸(shu)入(ru)電(dian)(dian)壓的(de)變化在適配(pei)器和電(dian)(dian)池之間來回切換。拓撲結構(gou)及(ji)工作波形(xing)如圖3所示(shi)。

圖(tu)3:電源路徑自(zi)動選擇拓撲及工作波形。

　　與電池饋電拓(tuo)撲結構相(xiang)比(bi)，此(ci)拓(tuo)撲有實質(zhi)性的(de)改(gai)進。它(ta)將(jiang)系(xi)統(tong)(tong)(tong)直接跟交流(liu)適配(pei)器(qi)相(xiang)連，與充電器(qi)獨(du)立開(kai)來，因(yin)而(er)能夠提供(gong)更大(da)的(de)系(xi)統(tong)(tong)(tong)電流(liu)、更高的(de)效率(lv)(lv)并(bing)且允許(xu)系(xi)統(tong)(tong)(tong)在低電池電壓(ya)下(xia)工作。此(ci)外，其價(jia)格也(ye)比(bi)較(jiao)(jiao)低廉(lian)。然而(er)，當適配(pei)器(qi)輸出電壓(ya)變(bian)化較(jiao)(jiao)大(da)的(de)時候，系(xi)統(tong)(tong)(tong)電壓(ya)也(ye)會隨之變(bian)化，所以(yi)此(ci)拓(tuo)撲要求(qiu)系(xi)統(tong)(tong)(tong)能夠接受比(bi)較(jiao)(jiao)寬的(de)輸入電壓(ya)變(bian)化范圍。此(ci)外，也(ye)要求(qiu)適配(pei)器(qi)具(ju)有更高的(de)額定功(gong)率(lv)(lv)，以(yi)滿足系(xi)統(tong)(tong)(tong)和充電器(qi)的(de)最大(da)總(zong)功(gong)率(lv)(lv)需求(qiu)，以(yi)及系(xi)統(tong)(tong)(tong)負載突變(bian)時的(de)功(gong)率(lv)(lv)變(bian)化要求(qiu)。

　　圖4是(shi)采用MPS公司的(de)MP2611構成的(de)電(dian)源路徑(jing)自動選(xuan)擇拓撲的(de)原(yuan)理圖。為了防止(zhi)出現(xian)不穩定情(qing)況，當VBATT接近VIN時(shi)，MP2611會(hui)斷(duan)開系統與電(dian)池的(de)連(lian)接。此外，它還會(hui)在S1 （M1及M2）與S2（M3）之間插入一個消隱期(qi)，以防出現(xian)電(dian)流貫通，從(cong)而損壞(huai)系統和電(dian)池。

圖4:采用MP2611構成(cheng)的(de)電源(yuan)路徑(jing)自動選擇拓撲。

　　動態電源(yuan)路(lu)徑(jing)管理拓(tuo)撲（DPPM）

　　動態電(dian)(dian)源路徑管(guan)理（DPPM）技術(shu)采(cai)用了一套附加的檢測(ce)模塊，測(ce)量系(xi)統電(dian)(dian)壓(ya)或者(zhe)輸入電(dian)(dian)流(liu)，實時監測(ce)總功率需(xu)求。一旦功率需(xu)求超過(guo)預設值，通過(guo)充電(dian)(dian)器降低充電(dian)(dian)電(dian)(dian)流(liu)來保證適配器輸出功率恒定(ding)而不過(guo)載。

　　例(li)如，基于輸入電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)的DPPM（圖(tu)5）通(tong)過比(bi)(bi)較(jiao)輸入電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)與預(yu)設參考(kao)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)來判(pan)斷輸入電(dian)(dian)(dian)(dian)流是否達到適(shi)(shi)配器的輸出電(dian)(dian)(dian)(dian)流限(xian)(xian)制。若適(shi)(shi)配器電(dian)(dian)(dian)(dian)流已經達到該限(xian)(xian)制，適(shi)(shi)配器電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)將降(jiang)至(zhi)預(yu)設參考(kao)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)，然(ran)后充(chong)電(dian)(dian)(dian)(dian)器通(tong)過動(dong)態(tai)降(jiang)低充(chong)電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流來防(fang)止系統(tong)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)繼續下降(jiang)。只要輸入電(dian)(dian)(dian)(dian)流保持在該限(xian)(xian)制的水平或者低于該限(xian)(xian)制，就仍然(ran)有電(dian)(dian)(dian)(dian)流向電(dian)(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)(dian)。然(ran)而(er)，由系統(tong)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)下降(jiang)引(yin)起的不穩定或噪(zao)聲使(shi)得(de)這種(zhong)基于電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)的DPPM結構不適(shi)(shi)合(he)應用在某些對噪(zao)聲敏感的場合(he)，比(bi)(bi)如音頻設備。

圖5:基于(yu)輸入(ru)電(dian)壓的動態電(dian)源路徑管理。

基于輸入(ru)電(dian)(dian)(dian)流(liu)的(de)DPPM（圖6）采用檢測電(dian)(dian)(dian)阻(zu)來評(ping)估輸入(ru)電(dian)(dian)(dian)流(liu)，當(dang)輸入(ru)電(dian)(dian)(dian)流(liu)達到預設電(dian)(dian)(dian)流(liu)門限時，通過(guo)動態降(jiang)低(di)電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)流(liu)來防止適(shi)配器過(guo)載或(huo)系統電(dian)(dian)(dian)壓下(xia)降(jiang)。這樣就(jiu)保證了系統電(dian)(dian)(dian)壓的(de)穩定，降(jiang)低(di)了適(shi)配器的(de)額外功(gong)率要求(qiu)。同(tong)時，該拓撲(pu)還(huan)具備(bei)電(dian)(dian)(dian)池(chi)反向補充供電(dian)(dian)(dian)的(de)能力。

圖(tu)6:基于輸入(ru)電流的動態電源路徑管理。

　　有(you)些(xie)充電(dian)(dian)(dian)器（例如MPS公司的(de)(de)MP2607）可以根據(ju)不(bu)同電(dian)(dian)(dian)源要求，優化選(xuan)擇不(bu)同的(de)(de)動態電(dian)(dian)(dian)源路徑管理方(fang)案。MP2607根據(ju)不(bu)同的(de)(de)適配(pei)器類型，在(zai)基于(yu)(yu)輸入(ru)電(dian)(dian)(dian)壓(ya)和基于(yu)(yu)輸入(ru)電(dian)(dian)(dian)流(liu)的(de)(de)DPPM兩種(zhong)拓撲之間(jian)進行(xing)智(zhi)能(neng)選(xuan)擇。若輸入(ru)是(shi)交(jiao)流(liu)適配(pei)器，MP2607采用基于(yu)(yu)輸入(ru)電(dian)(dian)(dian)壓(ya)的(de)(de)DPPM技(ji)術，控(kong)制適配(pei)器交(jiao)流(liu)電(dian)(dian)(dian)壓(ya)，使得(de)交(jiao)流(liu)適配(pei)器可以同時為系(xi)統供電(dian)(dian)(dian)和為電(dian)(dian)(dian)池充電(dian)(dian)(dian)，工(gong)作波形如圖7所示。

圖7:MP2607在交流適(shi)配器輸入時的動態電源路徑管(guan)理。

　　在USB輸(shu)入模式(shi)下，MP2607采用基(ji)于輸(shu)入電(dian)流的DPPM.如圖(tu)8所(suo)示，考慮到USB提(ti)供電(dian)流能力有(you)限(xian)，設置充電(dian)電(dian)流在USB限(xian)制(zhi)電(dian)流以下。若系統(tong)負載電(dian)流大于USB限(xian)流值，電(dian)池(chi)將反向補充供電(dian)。

圖8:MP2607在(zai)USB輸入時的動態電(dian)源路徑(jing)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(fang)案(an)，從而給用戶帶(dai)來前所未有的便利、性能和效率(lv)。