隨著智能手機(ji)(ji)、平板電(dian)(dian)(dian)(dian)(dian)腦和攝像機(ji)(ji)等便攜設備(bei)的(de)不斷普及(ji)，人(ren)們對電(dian)(dian)(dian)(dian)(dian)源的(de)要求(qiu)以及(ji)對邊充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)邊使用這些設備(bei)的(de)能力的(de)要求(qiu)與日俱(ju)增。更高的(de)功(gong)率(lv)要求(qiu)增加了(le)對具有高功(gong)率(lv)密度和優(you)異充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)能力的(de)電(dian)(dian)(dian)(dian)(dian)池(chi)的(de)需(xu)求(qiu)。目前，鋰(li)(li)離子(zi)（Li-ion）電(dian)(dian)(dian)(dian)(dian)池(chi)和鋰(li)(li)聚(ju)合(he)物（Li-po）電(dian)(dian)(dian)(dian)(dian)池(chi)最適合(he)當前市場對功(gong)率(lv)密度、充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)能力和價格(ge)的(de)要求(qiu)。但是，有別于鉛(qian)酸、鎳(nie)氫(qing)等其他(ta)流行的(de)電(dian)(dian)(dian)(dian)(dian)池(chi)技(ji)術，鋰(li)(li)電(dian)(dian)(dian)(dian)(dian)池(chi)技(ji)術的(de)性(xing)能也最不穩定(ding)：鋰(li)(li)電(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)放(fang)電(dian)(dian)(dian)(dian)(dian)若管理不善，將導致充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)時間長、耗散(san)功(gong)率(lv)高、效率(lv)低和電(dian)(dian)(dian)(dian)(dian)池(chi)壽命比平均(jun)壽命低等問題。圖(tu)1顯(xian)示了(le)典型(xing)鋰(li)(li)離子(zi)電(dian)(dian)(dian)(dian)(dian)池(chi)的(de)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)曲(qu)線(xian)。

　　傳統充電器相對簡(jian)單，這些充(chong)(chong)電(dian)器在(zai)(zai)小(xiao)功率(lv)(lv)(lv)應(ying)(ying)用(yong)中表現較(jiao)好。然(ran)而，它(ta)們(men)卻不能有效(xiao)地適應(ying)(ying)充(chong)(chong)電(dian)曲線的變化，比(bi)如，用(yong)戶在(zai)(zai)不同電(dian)源之間(jian)(jian)切換(huan)或者在(zai)(zai)充(chong)(chong)電(dian)期間(jian)(jian)操作設備。另外，傳統充(chong)(chong)電(dian)器在(zai)(zai)大功率(lv)(lv)(lv)和大電(dian)流應(ying)(ying)用(yong)中，通常效(xiao)率(lv)(lv)(lv)較(jiao)低，耗散功率(lv)(lv)(lv)較(jiao)大。

圖1:典型鋰(li)離子電(dian)(dian)池的(de)充(chong)電(dian)(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，這些充電器也使系統的安全性和電池(chi)的使用(yong)壽命得到提高(gao)。

　　電源管理(li)拓撲種類(lei)繁多，本文則重(zhong)點介紹以下三種：電池饋(kui)電、自動選擇和動態電源路(lu)徑。

　　電池饋電拓撲

　　電(dian)池(chi)饋電(dian)拓撲是(shi)一(yi)種(zhong)實現過(guo)程最(zui)簡單、成本(ben)最(zui)低的(de)拓撲，這是(shi)因為其電(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(tu)2:電(dian)池饋電(dian)拓撲原理(li)圖(tu)及信號圖(tu)。

　　這種拓(tuo)撲有三(san)個主要特性：無論(lun)供電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)壓(ya)如(ru)何(he)變化(hua)，系(xi)統電(dian)(dian)(dian)(dian)(dian)壓(ya)始終等于電(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)壓(ya)，電(dian)(dian)(dian)(dian)(dian)源(yuan)系(xi)統始終優(you)先，以便IBATT ￡ ICHG,并(bing)且ICHG最(zui)終限制由(you)輸(shu)(shu)入電(dian)(dian)(dian)(dian)(dian)源(yuan)提(ti)供給系(xi)統電(dian)(dian)(dian)(dian)(dian)源(yuan)總線的最(zui)大功率。當系(xi)統與(yu)充(chong)電(dian)(dian)(dian)(dian)(dian)器斷(duan)開時該拓(tuo)撲還可以實現(xian)最(zui)小的耗散功率，設置ICHG從(cong)根本上(shang)限定了總輸(shu)(shu)入電(dian)(dian)(dian)(dian)(dian)流(liu)，這樣，隨著系(xi)統電(dian)(dian)(dian)(dian)(dian)流(liu)（ISYS）的增(zeng)加(jia)，充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)（IBATT）將等額下降(jiang)，工作波(bo)形如(ru)圖2所示。

　　遺憾的是(shi)，這(zhe)種拓撲(pu)有如下不(bu)足之處，從(cong)而限制了它在(zai)更廣應用領域的效率和(he)效用：

　　在電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)壓太低(di)的(de)(de)情況下，系統無(wu)法(fa)工(gong)作。電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)壓跌至(zhi)涓流(liu)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)門限以下時(shi)，充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)器將把總的(de)(de)輸出電(dian)(dian)(dian)(dian)(dian)(dian)流(liu)限制得(de)很低(di)。系統的(de)(de)額外電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)需求將由(you)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)來補充(chong)，從而導致電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)能量進一步耗盡。由(you)于(yu)系統電(dian)(dian)(dian)(dian)(dian)(dian)壓始終等于(yu)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)壓，一旦電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)(dian)(dian)壓低(di)到系統最低(di)工(gong)作電(dian)(dian)(dian)(dian)(dian)(dian)壓以下，系統將停止(zhi)工(gong)作。

　　雖然電(dian)(dian)池已(yi)具有滿(man)電(dian)(dian)量，但是充電(dian)(dian)器(qi)無(wu)法(fa)進(jin)入(ru)EOC（結(jie)束充電(dian)(dian)）狀態(tai)。如果(guo)ISYS超過(guo)電(dian)(dian)池滿(man)電(dian)(dian)量門限（IBF），那(nei)么ICHG就(jiu)無(wu)法(fa)降到低于IBF,充電(dian)(dian)狀態(tai)始(shi)終顯示(shi)正在充電(dian)(dian)，即使電(dian)(dian)池已(yi)經具有滿(man)電(dian)(dian)量。

　　電(dian)池無法充(chong)(chong)滿。由(you)于系統優先(xian)于電(dian)池供電(dian)，因此(ci)電(dian)池只(zhi)能以低電(dian)流進行充(chong)(chong)電(dian)。此(ci)外，充(chong)(chong)電(dian)器只(zhi)能在預期的(de)有效充(chong)(chong)電(dian)時間內工作(zuo)，這樣可(ke)以避(bi)免給(gei)壞電(dian)池充(chong)(chong)電(dian)。如充(chong)(chong)電(dian)時間超出此(ci)時間段(duan)，會導致充(chong)(chong)電(dian)器誤判(pan)壞電(dian)池而停止充(chong)(chong)電(dian)。

電(dian)源路徑自動選擇拓撲

　　電(dian)源路徑自動選擇拓(tuo)(tuo)撲(pu)在(zai)電(dian)池(chi)直接搭載拓(tuo)(tuo)撲(pu)基礎上外加了兩個開關管(guan)，使得(de)系統電(dian)源可以根(gen)據輸入電(dian)壓(ya)的變化在(zai)適配器和電(dian)池(chi)之間來回切換。拓(tuo)(tuo)撲(pu)結構及工作波(bo)形(xing)如(ru)圖3所示(shi)。

圖3:電(dian)源路徑自動(dong)選擇拓撲及工作波形。

　　與電(dian)池(chi)饋電(dian)拓(tuo)撲結構相比(bi)，此拓(tuo)撲有實(shi)質性的(de)改進。它將系統(tong)直接跟交流(liu)適配器(qi)相連，與充(chong)電(dian)器(qi)獨立開來，因(yin)而能夠(gou)提供更(geng)大(da)的(de)系統(tong)電(dian)流(liu)、更(geng)高的(de)效率(lv)并(bing)且允(yun)許系統(tong)在低電(dian)池(chi)電(dian)壓(ya)下工作。此外(wai)，其(qi)價格也(ye)比(bi)較(jiao)低廉(lian)。然(ran)而，當適配器(qi)輸出電(dian)壓(ya)變化(hua)較(jiao)大(da)的(de)時候(hou)，系統(tong)電(dian)壓(ya)也(ye)會隨之(zhi)變化(hua)，所以(yi)此拓(tuo)撲要(yao)求系統(tong)能夠(gou)接受比(bi)較(jiao)寬的(de)輸入電(dian)壓(ya)變化(hua)范圍(wei)。此外(wai)，也(ye)要(yao)求適配器(qi)具有更(geng)高的(de)額定功(gong)(gong)率(lv)，以(yi)滿足系統(tong)和(he)充(chong)電(dian)器(qi)的(de)最大(da)總功(gong)(gong)率(lv)需求，以(yi)及系統(tong)負載突變時的(de)功(gong)(gong)率(lv)變化(hua)要(yao)求。

　　圖4是采用MPS公司的MP2611構成的電(dian)(dian)源(yuan)路(lu)徑(jing)自動選擇拓撲的原理(li)圖。為了防(fang)止出現不穩定(ding)情況(kuang)，當(dang)VBATT接(jie)近VIN時，MP2611會斷開系統(tong)與電(dian)(dian)池的連接(jie)。此外，它還會在S1 （M1及M2）與S2（M3）之間(jian)插入一個消隱期，以防(fang)出現電(dian)(dian)流貫通，從(cong)而損壞系統(tong)和(he)電(dian)(dian)池。

圖(tu)4:采用MP2611構成(cheng)的電源(yuan)路(lu)徑(jing)自動選擇(ze)拓撲。

　　動態電源路徑管理(li)拓(tuo)撲（DPPM）

　　動態電源路徑管理（DPPM）技術(shu)采用(yong)了一(yi)套附加的檢測模塊，測量系統電壓或者輸入電流(liu)，實時監測總功(gong)率(lv)需求。一(yi)旦功(gong)率(lv)需求超(chao)過預設值，通過充電器降低充電電流(liu)來保證適配器輸出(chu)功(gong)率(lv)恒定而不過載。

　　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(tong)過(guo)動態降(jiang)低(di)充(chong)電(dian)(dian)電(dian)(dian)流(liu)來(lai)防止系統(tong)電(dian)(dian)壓(ya)繼續(xu)下(xia)降(jiang)。只要輸(shu)入電(dian)(dian)流(liu)保持在該限制(zhi)的水平或者低(di)于(yu)(yu)該限制(zhi)，就仍然有電(dian)(dian)流(liu)向電(dian)(dian)池充(chong)電(dian)(dian)。然而，由系統(tong)電(dian)(dian)壓(ya)下(xia)降(jiang)引起的不(bu)穩定或噪聲使得(de)這種基于(yu)(yu)電(dian)(dian)壓(ya)的DPPM結構不(bu)適合(he)應(ying)用(yong)在某些對噪聲敏(min)感(gan)的場合(he)，比如音頻設備。

圖5:基于輸入電壓的動態電源路徑管(guan)理。

基于輸(shu)入電(dian)(dian)流(liu)的(de)DPPM（圖6）采(cai)用檢測電(dian)(dian)阻來評估輸(shu)入電(dian)(dian)流(liu)，當輸(shu)入電(dian)(dian)流(liu)達到預設電(dian)(dian)流(liu)門(men)限時(shi)，通過動態(tai)降(jiang)低(di)電(dian)(dian)池電(dian)(dian)流(liu)來防止適(shi)配器過載或系統(tong)電(dian)(dian)壓(ya)下降(jiang)。這樣就保證了系統(tong)電(dian)(dian)壓(ya)的(de)穩定，降(jiang)低(di)了適(shi)配器的(de)額(e)外功率要求。同時(shi)，該拓(tuo)撲(pu)還具備電(dian)(dian)池反(fan)向補充供電(dian)(dian)的(de)能力(li)。

圖6:基于輸入電(dian)流的(de)動(dong)態電(dian)源路(lu)徑(jing)管理。

　　有(you)些充電(dian)(dian)(dian)器(qi)（例如(ru)MPS公司的(de)MP2607）可(ke)以(yi)根據不(bu)(bu)同(tong)電(dian)(dian)(dian)源要求，優化選(xuan)(xuan)擇(ze)不(bu)(bu)同(tong)的(de)動(dong)態電(dian)(dian)(dian)源路徑管理方案。MP2607根據不(bu)(bu)同(tong)的(de)適(shi)配器(qi)類型，在基(ji)于(yu)輸入電(dian)(dian)(dian)壓和基(ji)于(yu)輸入電(dian)(dian)(dian)流的(de)DPPM兩種拓(tuo)撲之間進(jin)行智能選(xuan)(xuan)擇(ze)。若(ruo)輸入是(shi)交流適(shi)配器(qi)，MP2607采用基(ji)于(yu)輸入電(dian)(dian)(dian)壓的(de)DPPM技(ji)術，控制適(shi)配器(qi)交流電(dian)(dian)(dian)壓，使得交流適(shi)配器(qi)可(ke)以(yi)同(tong)時(shi)為(wei)系統供電(dian)(dian)(dian)和為(wei)電(dian)(dian)(dian)池充電(dian)(dian)(dian)，工作波形如(ru)圖(tu)7所(suo)示(shi)。

圖7:MP2607在交流適配器輸入時的動態電(dian)源路徑管理。

　　在(zai)USB輸(shu)入模式下(xia)，MP2607采用基于輸(shu)入電(dian)(dian)(dian)流(liu)(liu)(liu)的DPPM.如(ru)圖8所示(shi)，考慮到(dao)USB提供電(dian)(dian)(dian)流(liu)(liu)(liu)能(neng)力有限(xian)(xian)，設置(zhi)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)(liu)在(zai)USB限(xian)(xian)制電(dian)(dian)(dian)流(liu)(liu)(liu)以(yi)下(xia)。若系統負載(zai)電(dian)(dian)(dian)流(liu)(liu)(liu)大(da)于USB限(xian)(xian)流(liu)(liu)(liu)值(zhi)，電(dian)(dian)(dian)池將反向補充(chong)供電(dian)(dian)(dian)。

圖8:MP2607在USB輸入時(shi)的動(dong)態電源路徑管(guan)理(li)。

　　總之，具有動態電源路徑管理的充電器（尤(you)其是那(nei)些能(neng)在不同(tong)管理模式之(zhi)間切換的充電(dian)器）可以為(wei)移動(dong)電(dian)子設(she)備提(ti)供更(geng)加精妙的電(dian)源(yuan)解決方案，從而(er)給用戶帶(dai)來前(qian)所未有的便利、性(xing)能(neng)和效率。