隨著智能(neng)手機、平板電(dian)(dian)(dian)腦(nao)和(he)(he)攝像(xiang)機等便攜設備(bei)的(de)(de)不斷普及，人們對(dui)電(dian)(dian)(dian)源的(de)(de)要(yao)(yao)求(qiu)(qiu)以及對(dui)邊充(chong)電(dian)(dian)(dian)邊使用這(zhe)些設備(bei)的(de)(de)能(neng)力(li)的(de)(de)要(yao)(yao)求(qiu)(qiu)與日俱增。更高(gao)的(de)(de)功(gong)率(lv)(lv)(lv)(lv)要(yao)(yao)求(qiu)(qiu)增加了對(dui)具有高(gao)功(gong)率(lv)(lv)(lv)(lv)密度(du)和(he)(he)優(you)異充(chong)電(dian)(dian)(dian)能(neng)力(li)的(de)(de)電(dian)(dian)(dian)池(chi)(chi)的(de)(de)需求(qiu)(qiu)。目(mu)前，鋰(li)(li)離(li)子（Li-ion）電(dian)(dian)(dian)池(chi)(chi)和(he)(he)鋰(li)(li)聚合物（Li-po）電(dian)(dian)(dian)池(chi)(chi)最適合當前市(shi)場對(dui)功(gong)率(lv)(lv)(lv)(lv)密度(du)、充(chong)電(dian)(dian)(dian)能(neng)力(li)和(he)(he)價格(ge)的(de)(de)要(yao)(yao)求(qiu)(qiu)。但是，有別于(yu)鉛酸、鎳氫等其(qi)他流行的(de)(de)電(dian)(dian)(dian)池(chi)(chi)技術(shu)，鋰(li)(li)電(dian)(dian)(dian)池(chi)(chi)技術(shu)的(de)(de)性能(neng)也最不穩定：鋰(li)(li)電(dian)(dian)(dian)池(chi)(chi)充(chong)放電(dian)(dian)(dian)若管理不善(shan)，將(jiang)導致充(chong)電(dian)(dian)(dian)時間長、耗散功(gong)率(lv)(lv)(lv)(lv)高(gao)、效(xiao)率(lv)(lv)(lv)(lv)低和(he)(he)電(dian)(dian)(dian)池(chi)(chi)壽命比(bi)平均壽命低等問題。圖1顯示(shi)了典型(xing)鋰(li)(li)離(li)子電(dian)(dian)(dian)池(chi)(chi)的(de)(de)充(chong)電(dian)(dian)(dian)曲線(xian)。

　　傳統充電器相對簡單，這些(xie)充(chong)電(dian)器在(zai)小功率(lv)應(ying)(ying)用中表現較(jiao)(jiao)好(hao)。然而，它們卻(que)不能有效地適(shi)應(ying)(ying)充(chong)電(dian)曲線的變化(hua)，比(bi)如，用戶在(zai)不同電(dian)源之間切(qie)換或(huo)者在(zai)充(chong)電(dian)期間操作設(she)備。另(ling)外(wai)，傳統充(chong)電(dian)器在(zai)大(da)功率(lv)和大(da)電(dian)流(liu)應(ying)(ying)用中，通常效率(lv)較(jiao)(jiao)低，耗散功率(lv)較(jiao)(jiao)大(da)。

圖1:典型鋰離子電池的充電曲線。

　　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(ye)使(shi)系統的(de)安全性和電池的(de)使(shi)用壽命得到提高。

　　電(dian)(dian)源管理拓撲種類繁多，本文則重(zhong)點(dian)介紹以下(xia)三種：電(dian)(dian)池饋電(dian)(dian)、自動(dong)選擇(ze)和動(dong)態電(dian)(dian)源路徑。

　　電池饋電拓撲

　　電(dian)池(chi)饋電(dian)拓撲(pu)是(shi)一種實現過程最簡單(dan)、成本最低(di)的拓撲(pu)，這(zhe)是(shi)因(yin)為其電(dian)路由(you)充(chong)電(dian)器、電(dian)池(chi)和系統組成，如(ru)圖2所示。

圖2:電池饋電拓撲原理圖及信號圖。

　　這種拓撲(pu)有(you)三個主要特性：無論(lun)供(gong)電(dian)電(dian)壓(ya)如(ru)何變化，系統電(dian)壓(ya)始終等于電(dian)池(chi)電(dian)壓(ya)，電(dian)源系統始終優先，以便IBATT ￡ ICHG,并且(qie)ICHG最終限制由輸(shu)入(ru)(ru)電(dian)源提供(gong)給系統電(dian)源總線的(de)最大功(gong)率。當系統與充電(dian)器斷(duan)開時該拓撲(pu)還可以實現(xian)最小(xiao)的(de)耗散(san)功(gong)率，設置(zhi)ICHG從根(gen)本上限定了總輸(shu)入(ru)(ru)電(dian)流(liu)，這樣，隨著(zhu)系統電(dian)流(liu)（ISYS）的(de)增加(jia)，充電(dian)電(dian)流(liu)（IBATT）將等額下降，工作波形如(ru)圖2所示。

　　遺憾的是(shi)，這種拓撲有如下不足之處，從而(er)限制了(le)它在更廣應用領(ling)域(yu)的效率(lv)和效用：

　　在電(dian)(dian)池(chi)電(dian)(dian)壓(ya)太低(di)(di)(di)的(de)情況下(xia)，系(xi)統(tong)(tong)無法工(gong)作(zuo)。電(dian)(dian)池(chi)電(dian)(dian)壓(ya)跌(die)至(zhi)涓流(liu)充(chong)電(dian)(dian)門限(xian)(xian)以下(xia)時(shi)，充(chong)電(dian)(dian)器將(jiang)把總(zong)的(de)輸出(chu)電(dian)(dian)流(liu)限(xian)(xian)制得很低(di)(di)(di)。系(xi)統(tong)(tong)的(de)額外電(dian)(dian)源需求將(jiang)由電(dian)(dian)池(chi)來補充(chong)，從而導致電(dian)(dian)池(chi)能(neng)量進一步耗盡(jin)。由于(yu)系(xi)統(tong)(tong)電(dian)(dian)壓(ya)始終等于(yu)電(dian)(dian)池(chi)電(dian)(dian)壓(ya)，一旦電(dian)(dian)池(chi)電(dian)(dian)壓(ya)低(di)(di)(di)到系(xi)統(tong)(tong)最(zui)低(di)(di)(di)工(gong)作(zuo)電(dian)(dian)壓(ya)以下(xia)，系(xi)統(tong)(tong)將(jiang)停止工(gong)作(zuo)。

　　雖然電(dian)池已具有滿電(dian)量，但是充(chong)電(dian)器(qi)無(wu)法進入EOC（結束充(chong)電(dian)）狀態。如果ISYS超過電(dian)池滿電(dian)量門限（IBF），那么(me)ICHG就無(wu)法降(jiang)到低于IBF,充(chong)電(dian)狀態始終顯示正在充(chong)電(dian)，即使電(dian)池已經(jing)具有滿電(dian)量。

　　電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池無法充滿。由于系統優先于電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池供電(dian)(dian)(dian)(dian)(dian)(dian)(dian)，因此電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池只能以(yi)低電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流進行充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)。此外，充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)器只能在(zai)預期的有效充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)時(shi)間內(nei)工作，這(zhe)樣可以(yi)避免給壞電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)。如充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)時(shi)間超(chao)出此時(shi)間段(duan)，會導(dao)致充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)器誤判壞電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池而停止充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)。

電源路(lu)徑自(zi)動選擇(ze)拓撲

　　電源路徑自(zi)動選擇拓撲(pu)在(zai)電池直(zhi)接搭載拓撲(pu)基礎上外加了兩個開關管，使得系統(tong)電源可以根據輸(shu)入電壓的變(bian)化在(zai)適配器和電池之間來回切換。拓撲(pu)結構(gou)及工作波形如圖3所示(shi)。

圖3:電源路(lu)徑(jing)自動選擇拓撲及工作(zuo)波形。

　　與電(dian)池饋電(dian)拓(tuo)(tuo)撲結構(gou)相(xiang)比(bi)(bi)，此拓(tuo)(tuo)撲有實質性的(de)(de)改進。它將系(xi)(xi)統(tong)(tong)直(zhi)接跟交流適(shi)配(pei)器相(xiang)連(lian)，與充電(dian)器獨立開來，因而能夠提供(gong)更大的(de)(de)系(xi)(xi)統(tong)(tong)電(dian)流、更高(gao)的(de)(de)效率并且允許系(xi)(xi)統(tong)(tong)在(zai)低(di)電(dian)池電(dian)壓(ya)(ya)(ya)下工作。此外，其價格也比(bi)(bi)較低(di)廉(lian)。然而，當適(shi)配(pei)器輸出(chu)電(dian)壓(ya)(ya)(ya)變(bian)化(hua)較大的(de)(de)時候，系(xi)(xi)統(tong)(tong)電(dian)壓(ya)(ya)(ya)也會隨之(zhi)變(bian)化(hua)，所以此拓(tuo)(tuo)撲要求(qiu)系(xi)(xi)統(tong)(tong)能夠接受(shou)比(bi)(bi)較寬的(de)(de)輸入電(dian)壓(ya)(ya)(ya)變(bian)化(hua)范圍。此外，也要求(qiu)適(shi)配(pei)器具有更高(gao)的(de)(de)額定功率，以滿足系(xi)(xi)統(tong)(tong)和充電(dian)器的(de)(de)最大總功率需(xu)求(qiu)，以及系(xi)(xi)統(tong)(tong)負載突變(bian)時的(de)(de)功率變(bian)化(hua)要求(qiu)。

　　圖4是采用MPS公司的(de)(de)MP2611構成(cheng)的(de)(de)電(dian)源路徑自動選擇(ze)拓撲的(de)(de)原理圖。為(wei)了防止出現不(bu)穩定情(qing)況，當VBATT接近VIN時，MP2611會(hui)斷開系統(tong)與電(dian)池的(de)(de)連接。此外，它還會(hui)在S1 （M1及M2）與S2（M3）之間插入一個消(xiao)隱期(qi)，以(yi)防出現電(dian)流貫通，從(cong)而損壞系統(tong)和電(dian)池。

圖4:采用MP2611構(gou)成的電源路徑自動(dong)選擇拓(tuo)撲(pu)。

　　動態電源路徑(jing)管理拓撲（DPPM）

　　動態電(dian)源路徑管理（DPPM）技術采用了一(yi)套附加的檢測(ce)模塊，測(ce)量系統電(dian)壓或者輸入(ru)電(dian)流，實時監(jian)測(ce)總功率需求(qiu)。一(yi)旦功率需求(qiu)超過預設值，通過充(chong)電(dian)器降低充(chong)電(dian)電(dian)流來保證(zheng)適配器輸出功率恒定而(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(dong)態(tai)降(jiang)(jiang)低充(chong)電(dian)電(dian)流來防(fang)止系統(tong)電(dian)壓(ya)繼續下降(jiang)(jiang)。只要輸入電(dian)流保持在該(gai)限制的(de)(de)(de)水平或者低于(yu)該(gai)限制，就仍然有(you)電(dian)流向電(dian)池(chi)充(chong)電(dian)。然而，由系統(tong)電(dian)壓(ya)下降(jiang)(jiang)引起的(de)(de)(de)不穩定(ding)或噪(zao)(zao)聲(sheng)(sheng)使得這(zhe)種(zhong)基于(yu)電(dian)壓(ya)的(de)(de)(de)DPPM結構(gou)不適合應(ying)用在某些對噪(zao)(zao)聲(sheng)(sheng)敏感的(de)(de)(de)場合，比如音頻設備。

圖5:基于輸入電壓的動態(tai)電源路徑管理(li)。

基于輸(shu)入電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)的(de)DPPM（圖6）采用檢測電(dian)(dian)(dian)阻(zu)來(lai)評估輸(shu)入電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)，當輸(shu)入電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)達(da)到預設電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)門限時，通(tong)過動態降(jiang)低電(dian)(dian)(dian)池電(dian)(dian)(dian)流(liu)(liu)(liu)(liu)來(lai)防(fang)止適(shi)配器過載或系統(tong)電(dian)(dian)(dian)壓下降(jiang)。這樣就保證了系統(tong)電(dian)(dian)(dian)壓的(de)穩定，降(jiang)低了適(shi)配器的(de)額(e)外功率要求。同(tong)時，該(gai)拓撲(pu)還具備電(dian)(dian)(dian)池反向補充供電(dian)(dian)(dian)的(de)能(neng)力。

圖6:基于輸(shu)入電流的動態電源路(lu)徑管(guan)理。

　　有些充電(dian)(dian)(dian)器（例如(ru)MPS公司的(de)MP2607）可(ke)以根據(ju)不同(tong)電(dian)(dian)(dian)源要求(qiu)，優化選擇(ze)不同(tong)的(de)動態(tai)電(dian)(dian)(dian)源路徑管理方案。MP2607根據(ju)不同(tong)的(de)適(shi)配(pei)器類型，在基(ji)(ji)于輸(shu)入(ru)(ru)電(dian)(dian)(dian)壓(ya)和(he)基(ji)(ji)于輸(shu)入(ru)(ru)電(dian)(dian)(dian)流的(de)DPPM兩種拓(tuo)撲(pu)之間進行智(zhi)能選擇(ze)。若輸(shu)入(ru)(ru)是交流適(shi)配(pei)器，MP2607采用基(ji)(ji)于輸(shu)入(ru)(ru)電(dian)(dian)(dian)壓(ya)的(de)DPPM技術，控(kong)制適(shi)配(pei)器交流電(dian)(dian)(dian)壓(ya)，使得交流適(shi)配(pei)器可(ke)以同(tong)時為系統(tong)供電(dian)(dian)(dian)和(he)為電(dian)(dian)(dian)池(chi)充電(dian)(dian)(dian)，工作波形(xing)如(ru)圖7所示。

圖(tu)7:MP2607在(zai)交流適配(pei)器輸入時的動態電源路徑管理。

　　在USB輸入模(mo)式下，MP2607采(cai)用基于輸入電流的DPPM.如圖8所(suo)示，考慮到(dao)USB提供電流能力有限(xian)，設(she)置充(chong)(chong)電電流在USB限(xian)制(zhi)電流以(yi)下。若系統負載電流大于USB限(xian)流值，電池將反(fan)向補充(chong)(chong)供電。

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

　　總之，具有動態電源路徑管理的充電器（尤(you)其是(shi)那些(xie)能(neng)在不同管理模式之間(jian)切(qie)換的充電(dian)器(qi)）可(ke)以為移動電(dian)子設備提供(gong)更加精妙的電(dian)源解決方(fang)案，從而(er)給用戶帶來前(qian)所未有的便利、性(xing)能(neng)和效(xiao)率。