隨著智能(neng)手機(ji)、平(ping)板電(dian)(dian)腦和攝像(xiang)機(ji)等便(bian)攜(xie)設備(bei)的(de)不(bu)斷(duan)普及(ji)，人們對電(dian)(dian)源的(de)要(yao)(yao)求以及(ji)對邊充(chong)(chong)電(dian)(dian)邊使用這些設備(bei)的(de)能(neng)力的(de)要(yao)(yao)求與日俱(ju)增。更高的(de)功率要(yao)(yao)求增加了對具有高功率密度和優異充(chong)(chong)電(dian)(dian)能(neng)力的(de)電(dian)(dian)池(chi)的(de)需求。目前，鋰(li)(li)離子（Li-ion）電(dian)(dian)池(chi)和鋰(li)(li)聚合(he)物（Li-po）電(dian)(dian)池(chi)最適合(he)當(dang)前市場對功率密度、充(chong)(chong)電(dian)(dian)能(neng)力和價格的(de)要(yao)(yao)求。但是，有別于鉛酸、鎳氫等其(qi)他(ta)流行的(de)電(dian)(dian)池(chi)技(ji)術(shu)，鋰(li)(li)電(dian)(dian)池(chi)技(ji)術(shu)的(de)性能(neng)也最不(bu)穩定：鋰(li)(li)電(dian)(dian)池(chi)充(chong)(chong)放電(dian)(dian)若管(guan)理不(bu)善，將(jiang)導致充(chong)(chong)電(dian)(dian)時間(jian)長、耗散(san)功率高、效率低(di)(di)和電(dian)(dian)池(chi)壽命比平(ping)均壽命低(di)(di)等問題。圖1顯示了典型鋰(li)(li)離子電(dian)(dian)池(chi)的(de)充(chong)(chong)電(dian)(dian)曲線。

　　傳(chuan)統充電(dian)(dian)器相對簡單，這些充電(dian)(dian)器在(zai)小功率(lv)應用(yong)中(zhong)表(biao)現較好(hao)。然而(er)，它們卻不能有效地適應充電(dian)(dian)曲線的變化，比如，用(yong)戶在(zai)不同電(dian)(dian)源之(zhi)間(jian)(jian)切(qie)換或(huo)者在(zai)充電(dian)(dian)期間(jian)(jian)操作設備。另(ling)外，傳(chuan)統充電(dian)(dian)器在(zai)大功率(lv)和大電(dian)(dian)流應用(yong)中(zhong)，通常效率(lv)較低，耗散功率(lv)較大。

圖1:典型(xing)鋰離子電(dian)池的(de)充電(dian)曲(qu)線。

　　新型線性和開關充電器，比如芯(xin)源(yuan)系(xi)統（MPS）公司的MP2600系(xi)列，采(cai)用電(dian)(dian)源(yuan)路徑(jing)管理(li)技術改變了(le)充電(dian)(dian)曲(qu)線(xian)，從而(er)能(neng)夠以更低的耗散(san)功率(lv)更加(jia)高效地為(wei)電(dian)(dian)池(chi)/系(xi)統供電(dian)(dian)。同時，這些充電(dian)(dian)器也(ye)使系(xi)統的安(an)全性和電(dian)(dian)池(chi)的使用壽(shou)命得(de)到提高。

　　電源管理拓撲種(zhong)類繁多，本(ben)文則重點介紹(shao)以下三種(zhong)：電池饋電、自動選擇和動態電源路徑(jing)。

　　電池饋電拓撲

　　電(dian)(dian)(dian)池饋(kui)電(dian)(dian)(dian)拓(tuo)(tuo)撲是一種實現過程最簡(jian)單、成本最低的拓(tuo)(tuo)撲，這是因為其(qi)電(dian)(dian)(dian)路由充電(dian)(dian)(dian)器、電(dian)(dian)(dian)池和系統組成，如圖2所示。

圖2:電池(chi)饋電拓撲(pu)原理圖及(ji)信號圖。

　　這種拓(tuo)撲有(you)三個主要(yao)特性：無論供(gong)電(dian)(dian)(dian)電(dian)(dian)(dian)壓(ya)如何(he)變(bian)化，系(xi)統(tong)電(dian)(dian)(dian)壓(ya)始(shi)終(zhong)等于電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)壓(ya)，電(dian)(dian)(dian)源系(xi)統(tong)始(shi)終(zhong)優先，以(yi)便IBATT ￡ ICHG,并且ICHG最終(zhong)限(xian)制由輸入電(dian)(dian)(dian)源提(ti)供(gong)給系(xi)統(tong)電(dian)(dian)(dian)源總線的最大功率(lv)。當(dang)系(xi)統(tong)與充電(dian)(dian)(dian)器斷開時該拓(tuo)撲還(huan)可以(yi)實現最小的耗散功率(lv)，設置(zhi)ICHG從(cong)根本上(shang)限(xian)定了總輸入電(dian)(dian)(dian)流，這樣，隨著(zhu)系(xi)統(tong)電(dian)(dian)(dian)流（ISYS）的增加，充電(dian)(dian)(dian)電(dian)(dian)(dian)流（IBATT）將等額下降，工作波形如圖2所示。

　　遺憾(han)的(de)是，這種拓(tuo)撲有如下(xia)不足之(zhi)處，從而限(xian)制了(le)它(ta)在更廣應用領域的(de)效(xiao)率和效(xiao)用：

　　在(zai)電(dian)(dian)(dian)池電(dian)(dian)(dian)壓(ya)(ya)太低的情況下，系(xi)統(tong)(tong)無(wu)法工(gong)作(zuo)。電(dian)(dian)(dian)池電(dian)(dian)(dian)壓(ya)(ya)跌至涓流(liu)充(chong)電(dian)(dian)(dian)門限(xian)以下時，充(chong)電(dian)(dian)(dian)器(qi)將把總的輸出(chu)電(dian)(dian)(dian)流(liu)限(xian)制得很低。系(xi)統(tong)(tong)的額外電(dian)(dian)(dian)源(yuan)需求將由電(dian)(dian)(dian)池來(lai)補(bu)充(chong)，從而(er)導致電(dian)(dian)(dian)池能量進一(yi)步(bu)耗盡。由于(yu)系(xi)統(tong)(tong)電(dian)(dian)(dian)壓(ya)(ya)始終等(deng)于(yu)電(dian)(dian)(dian)池電(dian)(dian)(dian)壓(ya)(ya)，一(yi)旦電(dian)(dian)(dian)池電(dian)(dian)(dian)壓(ya)(ya)低到系(xi)統(tong)(tong)最低工(gong)作(zuo)電(dian)(dian)(dian)壓(ya)(ya)以下，系(xi)統(tong)(tong)將停(ting)止工(gong)作(zuo)。

　　雖(sui)然電(dian)池已(yi)具有(you)滿電(dian)量，但(dan)是充(chong)電(dian)器無法進入EOC（結束充(chong)電(dian)）狀態。如果ISYS超過電(dian)池滿電(dian)量門(men)限（IBF），那么ICHG就無法降(jiang)到低于IBF,充(chong)電(dian)狀態始終顯示(shi)正在充(chong)電(dian)，即(ji)使電(dian)池已(yi)經具有(you)滿電(dian)量。

　　電(dian)池(chi)(chi)無法充(chong)(chong)(chong)滿。由于系統優先于電(dian)池(chi)(chi)供電(dian)，因此(ci)電(dian)池(chi)(chi)只能以低(di)電(dian)流進行充(chong)(chong)(chong)電(dian)。此(ci)外，充(chong)(chong)(chong)電(dian)器只能在預期的有效充(chong)(chong)(chong)電(dian)時間(jian)(jian)(jian)內工(gong)作，這樣(yang)可以避(bi)免給壞(huai)電(dian)池(chi)(chi)充(chong)(chong)(chong)電(dian)。如充(chong)(chong)(chong)電(dian)時間(jian)(jian)(jian)超出此(ci)時間(jian)(jian)(jian)段，會導致(zhi)充(chong)(chong)(chong)電(dian)器誤(wu)判壞(huai)電(dian)池(chi)(chi)而停(ting)止充(chong)(chong)(chong)電(dian)。

電源路(lu)徑自(zi)動(dong)選(xuan)擇(ze)拓撲

　　電源(yuan)路徑自動選擇拓(tuo)(tuo)撲(pu)在(zai)電池直接搭載拓(tuo)(tuo)撲(pu)基(ji)礎上外加(jia)了兩(liang)個開關(guan)管，使得(de)系統電源(yuan)可(ke)以根(gen)據輸入電壓(ya)的變(bian)化在(zai)適配器(qi)和電池之間來回切換(huan)。拓(tuo)(tuo)撲(pu)結構及(ji)工(gong)作波形如圖3所示(shi)。

圖3:電源路徑(jing)自動選擇拓撲及工作(zuo)波形(xing)。

　　與電(dian)池饋電(dian)拓(tuo)撲結構相比，此(ci)(ci)拓(tuo)撲有(you)實質性的(de)改進。它(ta)將系(xi)(xi)(xi)統(tong)(tong)(tong)直接跟(gen)交(jiao)流(liu)適配(pei)(pei)器相連，與充電(dian)器獨立開來(lai)，因(yin)而能(neng)夠(gou)提(ti)供更大的(de)系(xi)(xi)(xi)統(tong)(tong)(tong)電(dian)流(liu)、更高的(de)效率(lv)(lv)并且允(yun)許系(xi)(xi)(xi)統(tong)(tong)(tong)在(zai)低(di)電(dian)池電(dian)壓下(xia)工作。此(ci)(ci)外，其價格(ge)也(ye)比較(jiao)低(di)廉。然而，當適配(pei)(pei)器輸(shu)出電(dian)壓變化較(jiao)大的(de)時候，系(xi)(xi)(xi)統(tong)(tong)(tong)電(dian)壓也(ye)會隨之變化，所以此(ci)(ci)拓(tuo)撲要(yao)(yao)求系(xi)(xi)(xi)統(tong)(tong)(tong)能(neng)夠(gou)接受(shou)比較(jiao)寬的(de)輸(shu)入(ru)電(dian)壓變化范圍。此(ci)(ci)外，也(ye)要(yao)(yao)求適配(pei)(pei)器具有(you)更高的(de)額定功(gong)率(lv)(lv)，以滿足系(xi)(xi)(xi)統(tong)(tong)(tong)和(he)充電(dian)器的(de)最大總功(gong)率(lv)(lv)需求，以及系(xi)(xi)(xi)統(tong)(tong)(tong)負載(zai)突變時的(de)功(gong)率(lv)(lv)變化要(yao)(yao)求。

　　圖4是采用MPS公(gong)司的(de)MP2611構成(cheng)的(de)電(dian)(dian)源路徑自動選擇(ze)拓撲的(de)原理(li)圖。為了防(fang)(fang)止出現不穩定情況，當VBATT接近VIN時，MP2611會斷開系(xi)(xi)統(tong)與電(dian)(dian)池(chi)的(de)連接。此外，它還會在S1 （M1及M2）與S2（M3）之間插入一個消隱期，以(yi)防(fang)(fang)出現電(dian)(dian)流貫通，從而損(sun)壞系(xi)(xi)統(tong)和電(dian)(dian)池(chi)。

圖(tu)4:采用MP2611構成的電源路徑自動選擇拓(tuo)撲。

　　動態(tai)電源(yuan)路(lu)徑管理(li)拓撲（DPPM）

　　動態電(dian)源路徑管理(li)（DPPM）技術采用了一套附(fu)加的檢測模(mo)塊，測量系統電(dian)壓或者輸(shu)入電(dian)流，實(shi)時監測總功率需求。一旦功率需求超過(guo)預設值，通過(guo)充電(dian)器(qi)降低充電(dian)電(dian)流來保證適配器(qi)輸(shu)出功率恒定(ding)而(er)不過(guo)載。

　　例如，基于(yu)輸(shu)(shu)入電(dian)(dian)(dian)壓(ya)的(de)(de)(de)(de)(de)DPPM（圖5）通過比較輸(shu)(shu)入電(dian)(dian)(dian)壓(ya)與(yu)預(yu)(yu)設(she)參考(kao)電(dian)(dian)(dian)壓(ya)來判(pan)斷(duan)輸(shu)(shu)入電(dian)(dian)(dian)流(liu)(liu)(liu)是(shi)否達到適配器的(de)(de)(de)(de)(de)輸(shu)(shu)出(chu)電(dian)(dian)(dian)流(liu)(liu)(liu)限(xian)(xian)制。若適配器電(dian)(dian)(dian)流(liu)(liu)(liu)已經達到該限(xian)(xian)制，適配器電(dian)(dian)(dian)壓(ya)將降至預(yu)(yu)設(she)參考(kao)電(dian)(dian)(dian)壓(ya)，然(ran)(ran)后(hou)充電(dian)(dian)(dian)器通過動態(tai)降低(di)(di)充電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)(liu)(liu)來防止系統(tong)電(dian)(dian)(dian)壓(ya)繼續下(xia)降。只要輸(shu)(shu)入電(dian)(dian)(dian)流(liu)(liu)(liu)保持在該限(xian)(xian)制的(de)(de)(de)(de)(de)水平或(huo)者低(di)(di)于(yu)該限(xian)(xian)制，就仍然(ran)(ran)有(you)電(dian)(dian)(dian)流(liu)(liu)(liu)向(xiang)電(dian)(dian)(dian)池充電(dian)(dian)(dian)。然(ran)(ran)而，由系統(tong)電(dian)(dian)(dian)壓(ya)下(xia)降引(yin)起的(de)(de)(de)(de)(de)不穩定或(huo)噪(zao)聲(sheng)使得這(zhe)種基于(yu)電(dian)(dian)(dian)壓(ya)的(de)(de)(de)(de)(de)DPPM結(jie)構不適合(he)應用在某些對(dui)噪(zao)聲(sheng)敏感的(de)(de)(de)(de)(de)場合(he)，比如音頻設(she)備。

圖5:基于輸入電(dian)(dian)壓的(de)動態電(dian)(dian)源路徑管理。

基于輸入電(dian)(dian)(dian)流(liu)的DPPM（圖6）采用檢測電(dian)(dian)(dian)阻來(lai)評估輸入電(dian)(dian)(dian)流(liu)，當輸入電(dian)(dian)(dian)流(liu)達到預設電(dian)(dian)(dian)流(liu)門限時(shi)(shi)，通過(guo)動態降低電(dian)(dian)(dian)池電(dian)(dian)(dian)流(liu)來(lai)防止適(shi)配器過(guo)載或系(xi)統電(dian)(dian)(dian)壓下降。這樣就保證(zheng)了系(xi)統電(dian)(dian)(dian)壓的穩定，降低了適(shi)配器的額外功率要(yao)求。同(tong)時(shi)(shi)，該(gai)拓撲還具備電(dian)(dian)(dian)池反向補充供電(dian)(dian)(dian)的能力。

圖6:基于輸入電流的(de)動態電源路徑管理。

　　有些充電(dian)(dian)器（例(li)如MPS公(gong)司的(de)MP2607）可以根(gen)據不(bu)同(tong)電(dian)(dian)源要(yao)求，優(you)化選擇不(bu)同(tong)的(de)動態電(dian)(dian)源路(lu)徑管理(li)方案。MP2607根(gen)據不(bu)同(tong)的(de)適(shi)(shi)配(pei)(pei)器類型，在基于輸(shu)入電(dian)(dian)壓(ya)(ya)和(he)基于輸(shu)入電(dian)(dian)流(liu)(liu)的(de)DPPM兩種拓撲之(zhi)間進行智能(neng)選擇。若輸(shu)入是交流(liu)(liu)適(shi)(shi)配(pei)(pei)器，MP2607采(cai)用基于輸(shu)入電(dian)(dian)壓(ya)(ya)的(de)DPPM技術，控制適(shi)(shi)配(pei)(pei)器交流(liu)(liu)電(dian)(dian)壓(ya)(ya)，使(shi)得交流(liu)(liu)適(shi)(shi)配(pei)(pei)器可以同(tong)時為(wei)系統供電(dian)(dian)和(he)為(wei)電(dian)(dian)池充電(dian)(dian)，工作波形如圖7所(suo)示。

圖7:MP2607在交(jiao)流適(shi)配器(qi)輸入時的動態(tai)電源路徑(jing)管(guan)理。

　　在USB輸入模式下，MP2607采用基于輸入電(dian)流的DPPM.如(ru)圖8所示，考慮到USB提供(gong)電(dian)流能力有限(xian)，設置充(chong)電(dian)電(dian)流在USB限(xian)制電(dian)流以(yi)下。若系統負載電(dian)流大(da)于USB限(xian)流值，電(dian)池(chi)將反向補充(chong)供(gong)電(dian)。

圖(tu)8:MP2607在USB輸入(ru)時(shi)的動態電源路(lu)徑管理(li)。

　　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案，從而(er)給用戶帶來前所未有的(de)便利(li)、性能和效率。