隨著智能(neng)手機、平板電(dian)(dian)(dian)(dian)(dian)腦和(he)攝像機等便攜設備的不斷普(pu)及(ji)，人們對電(dian)(dian)(dian)(dian)(dian)源的要求以及(ji)對邊充(chong)電(dian)(dian)(dian)(dian)(dian)邊使(shi)用這些設備的能(neng)力的要求與日俱增。更高的功率(lv)要求增加(jia)了對具有高功率(lv)密度和(he)優異充(chong)電(dian)(dian)(dian)(dian)(dian)能(neng)力的電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)的需(xu)求。目前，鋰(li)(li)離子（Li-ion）電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)和(he)鋰(li)(li)聚合物（Li-po）電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)最(zui)(zui)適合當前市(shi)場對功率(lv)密度、充(chong)電(dian)(dian)(dian)(dian)(dian)能(neng)力和(he)價(jia)格(ge)的要求。但是(shi)，有別于鉛酸、鎳氫等其(qi)他(ta)流(liu)行的電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)技(ji)(ji)術(shu)，鋰(li)(li)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)技(ji)(ji)術(shu)的性(xing)能(neng)也最(zui)(zui)不穩定：鋰(li)(li)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)充(chong)放(fang)電(dian)(dian)(dian)(dian)(dian)若管(guan)理不善，將(jiang)導致(zhi)充(chong)電(dian)(dian)(dian)(dian)(dian)時間長、耗散功率(lv)高、效(xiao)率(lv)低(di)和(he)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)壽(shou)命比平均壽(shou)命低(di)等問題。圖1顯示了典(dian)型鋰(li)(li)離子電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)的充(chong)電(dian)(dian)(dian)(dian)(dian)曲線。

　　傳統(tong)充(chong)(chong)電器(qi)相(xiang)對簡單，這些充(chong)(chong)電器(qi)在(zai)小功(gong)率應用中表現較(jiao)好。然而，它們卻不能有(you)效地適應充(chong)(chong)電曲線(xian)的變化，比如，用戶在(zai)不同電源之間(jian)切換或者(zhe)在(zai)充(chong)(chong)電期(qi)間(jian)操作(zuo)設備。另外，傳統(tong)充(chong)(chong)電器(qi)在(zai)大功(gong)率和大電流應用中，通常效率較(jiao)低，耗散(san)功(gong)率較(jiao)大。

圖(tu)1:典型(xing)鋰離子電池(chi)的充電曲線。

　　新型線性和開關充電器，比如芯源系(xi)(xi)統(tong)（MPS）公司的(de)(de)MP2600系(xi)(xi)列，采(cai)用電源路徑管(guan)理(li)技術(shu)改(gai)變了(le)充電曲線，從而能夠(gou)以(yi)更低的(de)(de)耗(hao)散功率(lv)更加(jia)高效(xiao)地為(wei)電池(chi)(chi)/系(xi)(xi)統(tong)供(gong)電。同時，這些(xie)充電器也使(shi)系(xi)(xi)統(tong)的(de)(de)安(an)全性和電池(chi)(chi)的(de)(de)使(shi)用壽命得(de)到(dao)提高。

　　電(dian)(dian)源(yuan)管理拓撲種(zhong)(zhong)類繁多，本文則重點介紹以下三(san)種(zhong)(zhong)：電(dian)(dian)池(chi)饋電(dian)(dian)、自動選擇和(he)動態電(dian)(dian)源(yuan)路徑。

　　電池饋電拓撲

　　電池饋電拓(tuo)(tuo)撲是一種實現過程最簡單(dan)、成本最低的(de)拓(tuo)(tuo)撲，這是因(yin)為其電路由充(chong)電器、電池和(he)系統組(zu)成，如圖(tu)2所示。

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

　　這(zhe)種拓撲有三個主要(yao)特(te)性(xing)：無論供(gong)電(dian)(dian)(dian)電(dian)(dian)(dian)壓(ya)如何變化(hua)，系統電(dian)(dian)(dian)壓(ya)始終等(deng)于電(dian)(dian)(dian)池電(dian)(dian)(dian)壓(ya)，電(dian)(dian)(dian)源系統始終優先(xian)，以便(bian)IBATT ￡ ICHG,并且ICHG最終限制由輸(shu)入(ru)電(dian)(dian)(dian)源提供(gong)給系統電(dian)(dian)(dian)源總線的(de)(de)最大(da)功率(lv)。當系統與充(chong)電(dian)(dian)(dian)器斷開時(shi)該(gai)拓撲還可以實(shi)現最小的(de)(de)耗散(san)功率(lv)，設置ICHG從根(gen)本上(shang)限定了總輸(shu)入(ru)電(dian)(dian)(dian)流，這(zhe)樣，隨著系統電(dian)(dian)(dian)流（ISYS）的(de)(de)增(zeng)加，充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流（IBATT）將等(deng)額(e)下(xia)降，工作波形如圖2所示。

　　遺憾的(de)是，這種拓撲有如下不(bu)足之處，從而限制了它(ta)在更廣應(ying)用領域的(de)效率和效用：

　　在電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)壓(ya)太低(di)的情況(kuang)下(xia)，系(xi)(xi)統(tong)無法(fa)工作(zuo)。電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)壓(ya)跌至涓流充電(dian)(dian)(dian)門(men)限以(yi)下(xia)時，充電(dian)(dian)(dian)器將(jiang)(jiang)把總的輸(shu)出(chu)電(dian)(dian)(dian)流限制得很(hen)低(di)。系(xi)(xi)統(tong)的額外電(dian)(dian)(dian)源需求將(jiang)(jiang)由(you)電(dian)(dian)(dian)池(chi)來補充，從而導致電(dian)(dian)(dian)池(chi)能量進一步耗盡。由(you)于系(xi)(xi)統(tong)電(dian)(dian)(dian)壓(ya)始終等于電(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)到系(xi)(xi)統(tong)最低(di)工作(zuo)電(dian)(dian)(dian)壓(ya)以(yi)下(xia)，系(xi)(xi)統(tong)將(jiang)(jiang)停止工作(zuo)。

　　雖然電池(chi)已具有滿電量，但是(shi)充電器無法進入EOC（結束充電）狀態。如果ISYS超過電池(chi)滿電量門限（IBF），那么ICHG就無法降到低于(yu)IBF,充電狀態始終(zhong)顯示(shi)正(zheng)在充電，即使(shi)電池(chi)已經具有滿電量。

　　電(dian)(dian)(dian)(dian)池(chi)無法充(chong)(chong)(chong)滿。由于(yu)系統優先于(yu)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(yi)低電(dian)(dian)(dian)(dian)流進行(xing)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)。此外，充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)器只(zhi)能在預期的有效充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)時間(jian)內(nei)工(gong)作，這樣可以(yi)避免給壞(huai)電(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)。如充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)時間(jian)超出此時間(jian)段，會(hui)導致充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)器誤判壞(huai)電(dian)(dian)(dian)(dian)池(chi)而停止充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)。

電(dian)源路徑(jing)自動(dong)選擇拓(tuo)撲

　　電(dian)源路徑自動選擇(ze)拓撲在電(dian)池直接搭(da)載拓撲基礎上(shang)外加了兩(liang)個(ge)開關(guan)管(guan)，使得(de)系統電(dian)源可以根據輸入電(dian)壓的(de)變化(hua)在適配器和(he)電(dian)池之間來(lai)回切換。拓撲結構及(ji)工(gong)作波形如(ru)圖3所示。

圖3:電源路徑自動選擇拓(tuo)撲及工作波形。

　　與電(dian)池(chi)饋(kui)電(dian)拓(tuo)(tuo)撲(pu)結構相比(bi)，此拓(tuo)(tuo)撲(pu)有(you)實質(zhi)性的(de)(de)改進(jin)。它將系(xi)(xi)(xi)統(tong)(tong)直接跟交流(liu)適配(pei)器(qi)相連(lian)，與充(chong)電(dian)器(qi)獨立開來，因(yin)而能夠提供更大的(de)(de)系(xi)(xi)(xi)統(tong)(tong)電(dian)流(liu)、更高的(de)(de)效率(lv)(lv)并且(qie)允許系(xi)(xi)(xi)統(tong)(tong)在低電(dian)池(chi)電(dian)壓(ya)下(xia)工(gong)作(zuo)。此外，其價格也比(bi)較(jiao)低廉。然而，當(dang)適配(pei)器(qi)輸出電(dian)壓(ya)變化較(jiao)大的(de)(de)時(shi)候(hou)，系(xi)(xi)(xi)統(tong)(tong)電(dian)壓(ya)也會隨之變化，所以此拓(tuo)(tuo)撲(pu)要(yao)求系(xi)(xi)(xi)統(tong)(tong)能夠接受比(bi)較(jiao)寬(kuan)的(de)(de)輸入電(dian)壓(ya)變化范圍。此外，也要(yao)求適配(pei)器(qi)具有(you)更高的(de)(de)額定功率(lv)(lv)，以滿足系(xi)(xi)(xi)統(tong)(tong)和充(chong)電(dian)器(qi)的(de)(de)最大總功率(lv)(lv)需(xu)求，以及系(xi)(xi)(xi)統(tong)(tong)負載突變時(shi)的(de)(de)功率(lv)(lv)變化要(yao)求。

　　圖(tu)4是采用(yong)MPS公(gong)司的(de)(de)MP2611構成的(de)(de)電源路徑自動選擇拓撲的(de)(de)原理圖(tu)。為了(le)防止出現不(bu)穩定情(qing)況(kuang)，當VBATT接近(jin)VIN時，MP2611會斷開(kai)系(xi)統(tong)與電池的(de)(de)連(lian)接。此(ci)外(wai)，它還會在(zai)S1 （M1及M2）與S2（M3）之(zhi)間(jian)插入(ru)一個消隱期，以防出現電流(liu)貫(guan)通(tong)，從而損壞系(xi)統(tong)和(he)電池。

圖4:采(cai)用MP2611構成的電源(yuan)路徑自動選擇拓撲。

　　動(dong)態電源路徑管理拓撲（DPPM）

　　動態電(dian)源路徑管理(li)（DPPM）技術采(cai)用了一(yi)套附加的檢測(ce)(ce)模(mo)塊，測(ce)(ce)量(liang)系(xi)統電(dian)壓或(huo)者輸(shu)入電(dian)流，實時監測(ce)(ce)總功(gong)率(lv)需求(qiu)。一(yi)旦功(gong)率(lv)需求(qiu)超過預(yu)設(she)值，通過充電(dian)器降低(di)充電(dian)電(dian)流來保證適(shi)配器輸(shu)出功(gong)率(lv)恒定而不過載。

　　例(li)如，基于(yu)(yu)(yu)輸(shu)入(ru)(ru)電(dian)(dian)壓(ya)(ya)(ya)的(de)DPPM（圖(tu)5）通過(guo)比較(jiao)輸(shu)入(ru)(ru)電(dian)(dian)壓(ya)(ya)(ya)與(yu)預設(she)參(can)考電(dian)(dian)壓(ya)(ya)(ya)來判斷輸(shu)入(ru)(ru)電(dian)(dian)流是否達(da)到(dao)適配器的(de)輸(shu)出電(dian)(dian)流限制(zhi)。若適配器電(dian)(dian)流已(yi)經達(da)到(dao)該(gai)限制(zhi)，適配器電(dian)(dian)壓(ya)(ya)(ya)將降(jiang)(jiang)(jiang)至預設(she)參(can)考電(dian)(dian)壓(ya)(ya)(ya)，然后充電(dian)(dian)器通過(guo)動態降(jiang)(jiang)(jiang)低(di)充電(dian)(dian)電(dian)(dian)流來防止系統電(dian)(dian)壓(ya)(ya)(ya)繼續下(xia)降(jiang)(jiang)(jiang)。只要輸(shu)入(ru)(ru)電(dian)(dian)流保持(chi)在該(gai)限制(zhi)的(de)水(shui)平或者低(di)于(yu)(yu)(yu)該(gai)限制(zhi)，就仍(reng)然有電(dian)(dian)流向電(dian)(dian)池充電(dian)(dian)。然而，由系統電(dian)(dian)壓(ya)(ya)(ya)下(xia)降(jiang)(jiang)(jiang)引起的(de)不穩定或噪(zao)聲(sheng)使得這(zhe)種基于(yu)(yu)(yu)電(dian)(dian)壓(ya)(ya)(ya)的(de)DPPM結構不適合(he)應用在某(mou)些對噪(zao)聲(sheng)敏感的(de)場合(he)，比如音(yin)頻設(she)備(bei)。

圖5:基(ji)于輸入電(dian)壓的動態電(dian)源路徑管理。

基于輸入(ru)電(dian)(dian)(dian)(dian)流(liu)的(de)DPPM（圖6）采(cai)用檢測電(dian)(dian)(dian)(dian)阻來評(ping)估輸入(ru)電(dian)(dian)(dian)(dian)流(liu)，當輸入(ru)電(dian)(dian)(dian)(dian)流(liu)達到預設(she)電(dian)(dian)(dian)(dian)流(liu)門限(xian)時，通過(guo)動態(tai)降低電(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)流(liu)來防止適(shi)配器過(guo)載或系統電(dian)(dian)(dian)(dian)壓下(xia)降。這樣就保證了系統電(dian)(dian)(dian)(dian)壓的(de)穩定，降低了適(shi)配器的(de)額外功(gong)率(lv)要求。同時，該拓(tuo)撲還具備電(dian)(dian)(dian)(dian)池反(fan)向補充供電(dian)(dian)(dian)(dian)的(de)能力。

圖6:基于輸入電流(liu)的動態電源路徑管理(li)。

　　有些(xie)充電(dian)(dian)(dian)器(qi)（例如MPS公司(si)的MP2607）可以根據不(bu)同(tong)電(dian)(dian)(dian)源要求，優化選擇(ze)不(bu)同(tong)的動(dong)態(tai)電(dian)(dian)(dian)源路徑管(guan)理(li)方(fang)案。MP2607根據不(bu)同(tong)的適(shi)(shi)配(pei)器(qi)類(lei)型，在基(ji)(ji)于(yu)(yu)輸(shu)入電(dian)(dian)(dian)壓(ya)和(he)基(ji)(ji)于(yu)(yu)輸(shu)入電(dian)(dian)(dian)流(liu)的DPPM兩種拓撲之間進行智(zhi)能選擇(ze)。若輸(shu)入是交流(liu)適(shi)(shi)配(pei)器(qi)，MP2607采用基(ji)(ji)于(yu)(yu)輸(shu)入電(dian)(dian)(dian)壓(ya)的DPPM技術，控制適(shi)(shi)配(pei)器(qi)交流(liu)電(dian)(dian)(dian)壓(ya)，使得交流(liu)適(shi)(shi)配(pei)器(qi)可以同(tong)時為(wei)系統供電(dian)(dian)(dian)和(he)為(wei)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(shi)配器(qi)輸入時(shi)的(de)動態電源路(lu)徑管理。

　　在USB輸(shu)入模式下，MP2607采(cai)用基于輸(shu)入電流(liu)(liu)(liu)(liu)的DPPM.如圖(tu)8所示，考慮到USB提供(gong)電流(liu)(liu)(liu)(liu)能(neng)力(li)有(you)限(xian)，設置充(chong)電電流(liu)(liu)(liu)(liu)在USB限(xian)制電流(liu)(liu)(liu)(liu)以下。若系(xi)統負載(zai)電流(liu)(liu)(liu)(liu)大于USB限(xian)流(liu)(liu)(liu)(liu)值，電池將反向(xiang)補充(chong)供(gong)電。

圖8:MP2607在USB輸入時的動態電(dian)源路徑管理。

　　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(fang)案(an)，從而給(gei)用(yong)戶帶來前所未有的便利、性能和效率(lv)。