隨著(zhu)智能(neng)(neng)(neng)手機(ji)、平板電(dian)(dian)(dian)(dian)(dian)(dian)腦和(he)(he)攝像(xiang)機(ji)等便攜設(she)(she)備(bei)的(de)(de)不斷普及，人們(men)對電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)的(de)(de)要求(qiu)以及對邊充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)邊使用這些設(she)(she)備(bei)的(de)(de)能(neng)(neng)(neng)力的(de)(de)要求(qiu)與日(ri)俱增。更高的(de)(de)功(gong)(gong)率(lv)(lv)要求(qiu)增加了(le)對具有高功(gong)(gong)率(lv)(lv)密(mi)度和(he)(he)優異充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)能(neng)(neng)(neng)力的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的(de)(de)需(xu)求(qiu)。目前(qian)，鋰(li)(li)離(li)(li)子(zi)（Li-ion）電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)和(he)(he)鋰(li)(li)聚合物（Li-po）電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)最(zui)(zui)適合當前(qian)市場(chang)對功(gong)(gong)率(lv)(lv)密(mi)度、充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)能(neng)(neng)(neng)力和(he)(he)價(jia)格的(de)(de)要求(qiu)。但是，有別于鉛酸、鎳氫(qing)等其他流行的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)技(ji)術，鋰(li)(li)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)技(ji)術的(de)(de)性能(neng)(neng)(neng)也最(zui)(zui)不穩定：鋰(li)(li)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)充(chong)放電(dian)(dian)(dian)(dian)(dian)(dian)若(ruo)管理不善，將導致充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)時間長、耗(hao)散(san)功(gong)(gong)率(lv)(lv)高、效率(lv)(lv)低(di)(di)和(he)(he)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)壽(shou)命比(bi)平均(jun)壽(shou)命低(di)(di)等問題。圖1顯示(shi)了(le)典型鋰(li)(li)離(li)(li)子(zi)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的(de)(de)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)曲線。

　　傳統充電器相對簡單，這些充電(dian)器在小功率(lv)(lv)應用中表(biao)現較(jiao)好。然而，它(ta)們卻不能有(you)效(xiao)地適應充電(dian)曲線的變化，比如，用戶在不同電(dian)源之間切(qie)換或者在充電(dian)期(qi)間操作設備。另外(wai)，傳統(tong)充電(dian)器在大功率(lv)(lv)和大電(dian)流應用中，通常(chang)效(xiao)率(lv)(lv)較(jiao)低，耗散功率(lv)(lv)較(jiao)大。

圖1:典型(xing)鋰離子電池的(de)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，這些充電器也使系(xi)統的安全性和電池的使用壽命得到(dao)提高。

　　電源管理拓撲種(zhong)(zhong)類繁(fan)多，本文則重點介紹以下三(san)種(zhong)(zhong)：電池饋電、自(zi)動選擇和動態電源路徑(jing)。

　　電池饋電拓撲

　　電(dian)池饋電(dian)拓撲是(shi)一種實現(xian)過(guo)程最簡單(dan)、成本最低的拓撲，這是(shi)因為其電(dian)路由充電(dian)器、電(dian)池和系(xi)統組成，如圖2所示(shi)。

圖2:電(dian)池饋電(dian)拓撲(pu)原理圖及信號圖。

　　這種(zhong)拓撲有三(san)個主要特性：無論供電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)壓(ya)如(ru)何變化，系(xi)統電(dian)(dian)(dian)(dian)壓(ya)始(shi)終等于(yu)電(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)壓(ya)，電(dian)(dian)(dian)(dian)源(yuan)系(xi)統始(shi)終優先，以便IBATT ￡ ICHG,并且ICHG最(zui)終限(xian)制由輸入電(dian)(dian)(dian)(dian)源(yuan)提供給系(xi)統電(dian)(dian)(dian)(dian)源(yuan)總線(xian)的最(zui)大功率。當(dang)系(xi)統與充電(dian)(dian)(dian)(dian)器斷開時該拓撲還可以實(shi)現最(zui)小(xiao)的耗散功率，設置ICHG從根本上限(xian)定了總輸入電(dian)(dian)(dian)(dian)流，這樣，隨著系(xi)統電(dian)(dian)(dian)(dian)流（ISYS）的增(zeng)加，充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)流（IBATT）將等額下降，工作(zuo)波形(xing)如(ru)圖(tu)2所示。

　　遺憾的是(shi)，這種拓撲有(you)如下不足之處(chu)，從而限(xian)制了(le)它在(zai)更(geng)廣(guang)應用領域的效率和效用：

　　在電(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)壓(ya)(ya)太低的(de)情況(kuang)下(xia)，系(xi)(xi)統(tong)無法(fa)工(gong)(gong)作。電(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)壓(ya)(ya)跌至涓流(liu)充電(dian)(dian)(dian)(dian)門限(xian)以下(xia)時，充電(dian)(dian)(dian)(dian)器將(jiang)把總的(de)輸出電(dian)(dian)(dian)(dian)流(liu)限(xian)制得很(hen)低。系(xi)(xi)統(tong)的(de)額外電(dian)(dian)(dian)(dian)源(yuan)需求將(jiang)由電(dian)(dian)(dian)(dian)池(chi)(chi)來補充，從而導致(zhi)電(dian)(dian)(dian)(dian)池(chi)(chi)能量進(jin)一步耗盡(jin)。由于(yu)系(xi)(xi)統(tong)電(dian)(dian)(dian)(dian)壓(ya)(ya)始終等于(yu)電(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)壓(ya)(ya)，一旦電(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)壓(ya)(ya)低到系(xi)(xi)統(tong)最(zui)低工(gong)(gong)作電(dian)(dian)(dian)(dian)壓(ya)(ya)以下(xia)，系(xi)(xi)統(tong)將(jiang)停止工(gong)(gong)作。

　　雖然電(dian)(dian)池(chi)已具(ju)有滿電(dian)(dian)量，但是充電(dian)(dian)器無法(fa)進入EOC（結束充電(dian)(dian)）狀態(tai)。如果(guo)ISYS超過電(dian)(dian)池(chi)滿電(dian)(dian)量門限（IBF），那么(me)ICHG就無法(fa)降到(dao)低(di)于IBF,充電(dian)(dian)狀態(tai)始終顯(xian)示正在充電(dian)(dian)，即(ji)使電(dian)(dian)池(chi)已經具(ju)有滿電(dian)(dian)量。

　　電(dian)池(chi)(chi)無法(fa)充滿。由于系統優先于電(dian)池(chi)(chi)供(gong)電(dian)，因此(ci)電(dian)池(chi)(chi)只(zhi)能(neng)以低電(dian)流進行充電(dian)。此(ci)外，充電(dian)器(qi)只(zhi)能(neng)在(zai)預期(qi)的(de)有(you)效充電(dian)時間(jian)內工作，這樣可以避(bi)免(mian)給壞電(dian)池(chi)(chi)充電(dian)。如充電(dian)時間(jian)超出(chu)此(ci)時間(jian)段，會導致充電(dian)器(qi)誤判壞電(dian)池(chi)(chi)而停止(zhi)充電(dian)。

電源路徑自動選擇拓撲

　　電源路徑(jing)自動選擇拓(tuo)撲在電池直接(jie)搭載拓(tuo)撲基礎上外加了兩個開關管，使得系統電源可以根據輸(shu)入(ru)電壓(ya)的變(bian)化在適配器和電池之間來(lai)回切換(huan)。拓(tuo)撲結(jie)構(gou)及工作波形如圖3所示。

圖3:電源路徑(jing)自動(dong)選擇拓(tuo)撲(pu)及工作波形。

　　與電(dian)(dian)(dian)(dian)池饋電(dian)(dian)(dian)(dian)拓撲(pu)結構相比，此拓撲(pu)有實質(zhi)性的(de)改進。它將系(xi)(xi)(xi)統直接(jie)跟交(jiao)流適配器(qi)相連，與充(chong)電(dian)(dian)(dian)(dian)器(qi)獨立開來，因而能夠提(ti)供更大(da)(da)的(de)系(xi)(xi)(xi)統電(dian)(dian)(dian)(dian)流、更高的(de)效(xiao)率(lv)(lv)并(bing)且允許系(xi)(xi)(xi)統在低(di)電(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)壓(ya)下工作。此外，其(qi)價格也(ye)(ye)(ye)比較低(di)廉(lian)。然(ran)而，當適配器(qi)輸(shu)出電(dian)(dian)(dian)(dian)壓(ya)變(bian)化(hua)較大(da)(da)的(de)時候，系(xi)(xi)(xi)統電(dian)(dian)(dian)(dian)壓(ya)也(ye)(ye)(ye)會(hui)隨之變(bian)化(hua)，所以此拓撲(pu)要(yao)求(qiu)系(xi)(xi)(xi)統能夠接(jie)受比較寬的(de)輸(shu)入電(dian)(dian)(dian)(dian)壓(ya)變(bian)化(hua)范(fan)圍。此外，也(ye)(ye)(ye)要(yao)求(qiu)適配器(qi)具有更高的(de)額定功率(lv)(lv)，以滿(man)足系(xi)(xi)(xi)統和充(chong)電(dian)(dian)(dian)(dian)器(qi)的(de)最大(da)(da)總(zong)功率(lv)(lv)需(xu)求(qiu)，以及系(xi)(xi)(xi)統負載突變(bian)時的(de)功率(lv)(lv)變(bian)化(hua)要(yao)求(qiu)。

　　圖(tu)4是采用MPS公司的(de)MP2611構成的(de)電(dian)源路徑自動選(xuan)擇(ze)拓撲的(de)原(yuan)理圖(tu)。為了防止出現(xian)不穩(wen)定(ding)情(qing)況，當VBATT接近VIN時(shi)，MP2611會斷開系統(tong)與電(dian)池的(de)連接。此外，它還(huan)會在S1 （M1及M2）與S2（M3）之間插入一(yi)個(ge)消隱期，以防出現(xian)電(dian)流(liu)貫通，從(cong)而損(sun)壞系統(tong)和電(dian)池。

圖4:采用MP2611構(gou)成的(de)電源路徑自動(dong)選(xuan)擇拓(tuo)撲。

　　動態電(dian)源(yuan)路徑管理(li)拓(tuo)撲（DPPM）

　　動(dong)態電(dian)源路徑管理（DPPM）技術采(cai)用了(le)一套附加的檢測(ce)模塊，測(ce)量(liang)系統(tong)電(dian)壓(ya)或者輸入電(dian)流，實(shi)時(shi)監測(ce)總功(gong)率需求。一旦功(gong)率需求超(chao)過預設值，通過充電(dian)器降低(di)充電(dian)電(dian)流來保證適配器輸出功(gong)率恒(heng)定而不過載。

　　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)態降低充電(dian)電(dian)流(liu)來防止系統(tong)電(dian)壓(ya)繼續(xu)下降。只(zhi)要輸入電(dian)流(liu)保持在該(gai)限(xian)制的水平或者低于(yu)該(gai)限(xian)制，就仍然有電(dian)流(liu)向(xiang)電(dian)池充電(dian)。然而，由系統(tong)電(dian)壓(ya)下降引起的不穩定或噪(zao)(zao)聲使得(de)這種基于(yu)電(dian)壓(ya)的DPPM結(jie)構不適合應用在某些對(dui)噪(zao)(zao)聲敏感的場合，比如音頻設備(bei)。

圖5:基于(yu)輸入電壓的動態電源路徑管理(li)。

基于輸入(ru)電(dian)(dian)(dian)(dian)(dian)流的(de)(de)(de)DPPM（圖6）采(cai)用(yong)檢測電(dian)(dian)(dian)(dian)(dian)阻來評估(gu)輸入(ru)電(dian)(dian)(dian)(dian)(dian)流，當輸入(ru)電(dian)(dian)(dian)(dian)(dian)流達(da)到預(yu)設電(dian)(dian)(dian)(dian)(dian)流門限(xian)時，通(tong)過(guo)動態降(jiang)低(di)電(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)流來防止適配器(qi)過(guo)載(zai)或系統(tong)電(dian)(dian)(dian)(dian)(dian)壓下(xia)降(jiang)。這樣就保(bao)證(zheng)了(le)系統(tong)電(dian)(dian)(dian)(dian)(dian)壓的(de)(de)(de)穩定，降(jiang)低(di)了(le)適配器(qi)的(de)(de)(de)額外功率(lv)要求。同時，該拓撲還具(ju)備電(dian)(dian)(dian)(dian)(dian)池反向補充供電(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)能(neng)力。

圖6:基于輸入電流的動態(tai)電源(yuan)路徑管理。

　　有些充電(dian)(dian)(dian)器（例如MPS公司的(de)MP2607）可以根(gen)據不(bu)同電(dian)(dian)(dian)源要求(qiu)，優化選(xuan)(xuan)擇(ze)(ze)不(bu)同的(de)動態(tai)電(dian)(dian)(dian)源路徑(jing)管(guan)理方案。MP2607根(gen)據不(bu)同的(de)適(shi)配(pei)器類型(xing)，在基于輸(shu)入(ru)(ru)(ru)電(dian)(dian)(dian)壓(ya)和基于輸(shu)入(ru)(ru)(ru)電(dian)(dian)(dian)流的(de)DPPM兩種拓撲之間進(jin)行智(zhi)能選(xuan)(xuan)擇(ze)(ze)。若(ruo)輸(shu)入(ru)(ru)(ru)是(shi)交(jiao)(jiao)流適(shi)配(pei)器，MP2607采用基于輸(shu)入(ru)(ru)(ru)電(dian)(dian)(dian)壓(ya)的(de)DPPM技術(shu)，控制適(shi)配(pei)器交(jiao)(jiao)流電(dian)(dian)(dian)壓(ya)，使得交(jiao)(jiao)流適(shi)配(pei)器可以同時為(wei)(wei)系統(tong)供電(dian)(dian)(dian)和為(wei)(wei)電(dian)(dian)(dian)池(chi)充電(dian)(dian)(dian)，工作波(bo)形(xing)如圖7所示。

圖7:MP2607在交流適配器輸入時(shi)的動態(tai)電源路徑(jing)管理。

　　在USB輸入模式下，MP2607采用基于輸入電(dian)(dian)流的DPPM.如圖(tu)8所示，考(kao)慮到(dao)USB提供(gong)電(dian)(dian)流能力(li)有限，設(she)置(zhi)充電(dian)(dian)電(dian)(dian)流在USB限制電(dian)(dian)流以下。若(ruo)系統負載電(dian)(dian)流大于USB限流值，電(dian)(dian)池將反向(xiang)補充供(gong)電(dian)(dian)。

圖8:MP2607在USB輸(shu)入時的動態電源路徑管理。

　　總之，具有動態電源路徑管理的充電器（尤其是(shi)那些能在不同管理模式之(zhi)間切換的充電(dian)器）可以為(wei)移動電(dian)子設備(bei)提供(gong)更加精妙的電(dian)源(yuan)解決方案，從(cong)而給用(yong)戶帶(dai)來前(qian)所未有的便利、性(xing)能和效(xiao)率。