隨著智能(neng)(neng)手機、平(ping)板電(dian)(dian)腦(nao)和(he)攝像(xiang)機等(deng)便攜(xie)設(she)備(bei)的(de)(de)(de)不(bu)斷普(pu)及(ji)，人們對電(dian)(dian)源的(de)(de)(de)要求(qiu)以及(ji)對邊充(chong)(chong)電(dian)(dian)邊使(shi)用這些設(she)備(bei)的(de)(de)(de)能(neng)(neng)力的(de)(de)(de)要求(qiu)與日俱增。更(geng)高的(de)(de)(de)功(gong)率(lv)(lv)要求(qiu)增加了對具有(you)高功(gong)率(lv)(lv)密度(du)和(he)優異充(chong)(chong)電(dian)(dian)能(neng)(neng)力的(de)(de)(de)電(dian)(dian)池(chi)的(de)(de)(de)需求(qiu)。目(mu)前，鋰離子(zi)（Li-ion）電(dian)(dian)池(chi)和(he)鋰聚合(he)(he)物（Li-po）電(dian)(dian)池(chi)最適合(he)(he)當前市場對功(gong)率(lv)(lv)密度(du)、充(chong)(chong)電(dian)(dian)能(neng)(neng)力和(he)價格(ge)的(de)(de)(de)要求(qiu)。但(dan)是(shi)，有(you)別于鉛酸、鎳氫等(deng)其他流(liu)行的(de)(de)(de)電(dian)(dian)池(chi)技術(shu)，鋰電(dian)(dian)池(chi)技術(shu)的(de)(de)(de)性能(neng)(neng)也最不(bu)穩定：鋰電(dian)(dian)池(chi)充(chong)(chong)放電(dian)(dian)若管理不(bu)善，將(jiang)導致充(chong)(chong)電(dian)(dian)時(shi)間長(chang)、耗散功(gong)率(lv)(lv)高、效率(lv)(lv)低和(he)電(dian)(dian)池(chi)壽命(ming)比(bi)平(ping)均壽命(ming)低等(deng)問題(ti)。圖1顯(xian)示(shi)了典(dian)型鋰離子(zi)電(dian)(dian)池(chi)的(de)(de)(de)充(chong)(chong)電(dian)(dian)曲線(xian)。

　　傳統充電器相對簡單，這些充(chong)電器在(zai)(zai)(zai)(zai)小功率(lv)應(ying)用(yong)中(zhong)表現較(jiao)好。然而，它們卻不能有(you)效地適(shi)應(ying)充(chong)電曲線的(de)變化，比如，用(yong)戶在(zai)(zai)(zai)(zai)不同電源之間切換或者在(zai)(zai)(zai)(zai)充(chong)電期間操作設(she)備。另外，傳統充(chong)電器在(zai)(zai)(zai)(zai)大功率(lv)和大電流應(ying)用(yong)中(zhong)，通常效率(lv)較(jiao)低，耗散功率(lv)較(jiao)大。

圖1:典型鋰離子電池的(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，這些充電器也使系統的安全性和電池的使用壽命(ming)得(de)到提高。

　　電源管理拓撲種類繁多，本文(wen)則重點介紹(shao)以(yi)下三種：電池饋電、自動(dong)(dong)選擇(ze)和(he)動(dong)(dong)態電源路徑(jing)。

　　電池饋電拓撲

　　電(dian)(dian)池饋電(dian)(dian)拓(tuo)撲(pu)是一(yi)種實現(xian)過程最簡單、成(cheng)本最低的拓(tuo)撲(pu)，這是因為其電(dian)(dian)路(lu)由充電(dian)(dian)器、電(dian)(dian)池和系統組(zu)成(cheng)，如圖2所示。

圖2:電(dian)(dian)池饋(kui)電(dian)(dian)拓撲原(yuan)理圖及信號圖。

　　這(zhe)種拓撲(pu)有三(san)個主要特性：無論供電(dian)(dian)(dian)電(dian)(dian)(dian)壓(ya)如(ru)(ru)何(he)變化，系(xi)統(tong)(tong)電(dian)(dian)(dian)壓(ya)始終(zhong)等于電(dian)(dian)(dian)池電(dian)(dian)(dian)壓(ya)，電(dian)(dian)(dian)源(yuan)系(xi)統(tong)(tong)始終(zhong)優先(xian)，以便IBATT ￡ ICHG,并且ICHG最(zui)(zui)終(zhong)限制由輸入電(dian)(dian)(dian)源(yuan)提供給(gei)系(xi)統(tong)(tong)電(dian)(dian)(dian)源(yuan)總線的最(zui)(zui)大功(gong)率。當系(xi)統(tong)(tong)與充電(dian)(dian)(dian)器斷開時該拓撲(pu)還可以實現(xian)最(zui)(zui)小的耗(hao)散功(gong)率，設置(zhi)ICHG從(cong)根本上限定了總輸入電(dian)(dian)(dian)流(liu)，這(zhe)樣，隨(sui)著(zhu)系(xi)統(tong)(tong)電(dian)(dian)(dian)流(liu)（ISYS）的增(zeng)加，充電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)（IBATT）將等額下降，工作波形如(ru)(ru)圖(tu)2所(suo)示。

　　遺憾的是，這(zhe)種拓撲有如(ru)下不足之處(chu)，從(cong)而限(xian)制了它在更廣應用領域的效率和效用：

　　在電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)壓(ya)太低(di)(di)的情況下(xia)，系(xi)統(tong)無法工作。電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)壓(ya)跌(die)至涓(juan)流(liu)充(chong)(chong)(chong)電(dian)(dian)(dian)門限以(yi)下(xia)時(shi)，充(chong)(chong)(chong)電(dian)(dian)(dian)器(qi)將(jiang)把總的輸出電(dian)(dian)(dian)流(liu)限制得很低(di)(di)。系(xi)統(tong)的額外電(dian)(dian)(dian)源需求將(jiang)由電(dian)(dian)(dian)池(chi)來補(bu)充(chong)(chong)(chong)，從而導(dao)致電(dian)(dian)(dian)池(chi)能量進一(yi)步耗(hao)盡。由于系(xi)統(tong)電(dian)(dian)(dian)壓(ya)始(shi)終(zhong)等(deng)于電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)壓(ya)，一(yi)旦電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)壓(ya)低(di)(di)到系(xi)統(tong)最低(di)(di)工作電(dian)(dian)(dian)壓(ya)以(yi)下(xia)，系(xi)統(tong)將(jiang)停止工作。

　　雖(sui)然(ran)電(dian)(dian)(dian)池已具有(you)(you)滿電(dian)(dian)(dian)量，但是充電(dian)(dian)(dian)器(qi)無法進入EOC（結束充電(dian)(dian)(dian)）狀態。如果ISYS超過電(dian)(dian)(dian)池滿電(dian)(dian)(dian)量門限（IBF），那(nei)么ICHG就(jiu)無法降到低于IBF,充電(dian)(dian)(dian)狀態始終顯示正在(zai)充電(dian)(dian)(dian)，即使電(dian)(dian)(dian)池已經具有(you)(you)滿電(dian)(dian)(dian)量。

　　電(dian)(dian)(dian)(dian)(dian)池(chi)無法充(chong)滿。由于系統(tong)優先于電(dian)(dian)(dian)(dian)(dian)池(chi)供電(dian)(dian)(dian)(dian)(dian)，因(yin)此(ci)電(dian)(dian)(dian)(dian)(dian)池(chi)只(zhi)能(neng)以(yi)低電(dian)(dian)(dian)(dian)(dian)流進行充(chong)電(dian)(dian)(dian)(dian)(dian)。此(ci)外，充(chong)電(dian)(dian)(dian)(dian)(dian)器只(zhi)能(neng)在預(yu)期的有效充(chong)電(dian)(dian)(dian)(dian)(dian)時(shi)(shi)間(jian)內(nei)工作，這(zhe)樣可以(yi)避免給壞電(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)(dian)(dian)。如充(chong)電(dian)(dian)(dian)(dian)(dian)時(shi)(shi)間(jian)超出此(ci)時(shi)(shi)間(jian)段(duan)，會導致充(chong)電(dian)(dian)(dian)(dian)(dian)器誤判(pan)壞電(dian)(dian)(dian)(dian)(dian)池(chi)而停止充(chong)電(dian)(dian)(dian)(dian)(dian)。

電源路徑自動(dong)選(xuan)擇拓撲(pu)

　　電(dian)源(yuan)路徑自動選擇拓(tuo)撲(pu)(pu)在(zai)電(dian)池直(zhi)接(jie)搭載(zai)拓(tuo)撲(pu)(pu)基(ji)礎(chu)上外(wai)加了兩(liang)個開(kai)關管，使得系統電(dian)源(yuan)可(ke)以根據輸入電(dian)壓的變化(hua)在(zai)適配器(qi)和電(dian)池之間來回切(qie)換。拓(tuo)撲(pu)(pu)結構及工作波(bo)形如(ru)圖3所示。

圖3:電源路(lu)徑自動選(xuan)擇(ze)拓撲及工(gong)作波形。

　　與(yu)(yu)電(dian)(dian)(dian)池饋電(dian)(dian)(dian)拓(tuo)撲(pu)結構(gou)相比(bi)，此(ci)拓(tuo)撲(pu)有(you)實質性的改進。它將系(xi)統(tong)直接跟交流適(shi)配(pei)器(qi)相連，與(yu)(yu)充電(dian)(dian)(dian)器(qi)獨立(li)開(kai)來，因(yin)而能(neng)夠(gou)(gou)提(ti)供更(geng)大(da)的系(xi)統(tong)電(dian)(dian)(dian)流、更(geng)高(gao)的效(xiao)率(lv)并且允許系(xi)統(tong)在低電(dian)(dian)(dian)池電(dian)(dian)(dian)壓(ya)(ya)下工作(zuo)。此(ci)外，其價格也比(bi)較低廉。然而，當適(shi)配(pei)器(qi)輸出電(dian)(dian)(dian)壓(ya)(ya)變化(hua)(hua)較大(da)的時候，系(xi)統(tong)電(dian)(dian)(dian)壓(ya)(ya)也會隨(sui)之變化(hua)(hua)，所(suo)以(yi)此(ci)拓(tuo)撲(pu)要(yao)求(qiu)系(xi)統(tong)能(neng)夠(gou)(gou)接受比(bi)較寬的輸入電(dian)(dian)(dian)壓(ya)(ya)變化(hua)(hua)范圍。此(ci)外，也要(yao)求(qiu)適(shi)配(pei)器(qi)具(ju)有(you)更(geng)高(gao)的額定功率(lv)，以(yi)滿足系(xi)統(tong)和充電(dian)(dian)(dian)器(qi)的最大(da)總功率(lv)需求(qiu)，以(yi)及系(xi)統(tong)負載(zai)突變時的功率(lv)變化(hua)(hua)要(yao)求(qiu)。

　　圖4是采用(yong)MPS公司(si)的(de)(de)MP2611構成的(de)(de)電源路徑自動選擇拓(tuo)撲的(de)(de)原理圖。為(wei)了防(fang)止出現不(bu)穩(wen)定情況(kuang)，當VBATT接近VIN時，MP2611會斷開系(xi)(xi)統與(yu)電池的(de)(de)連(lian)接。此外，它(ta)還會在S1 （M1及M2）與(yu)S2（M3）之間插入一個(ge)消(xiao)隱期，以(yi)防(fang)出現電流貫通，從而損壞(huai)系(xi)(xi)統和電池。

圖4:采用(yong)MP2611構成的(de)電源路徑自動選擇(ze)拓撲。

　　動態(tai)電源路徑管理(li)拓撲(pu)（DPPM）

　　動態電(dian)(dian)源路徑管理（DPPM）技術采用了一(yi)套附(fu)加的檢測(ce)(ce)(ce)模(mo)塊(kuai)，測(ce)(ce)(ce)量系統電(dian)(dian)壓或者(zhe)輸入(ru)電(dian)(dian)流，實時(shi)監(jian)測(ce)(ce)(ce)總功率(lv)需求。一(yi)旦功率(lv)需求超(chao)過(guo)預設值，通過(guo)充(chong)電(dian)(dian)器降低充(chong)電(dian)(dian)電(dian)(dian)流來保證適配器輸出功率(lv)恒(heng)定而(er)不過(guo)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，然后充電器通過動態降低充電(dian)(dian)電(dian)(dian)流來防(fang)止系(xi)統電(dian)(dian)壓繼續下降。只要輸入電(dian)(dian)流保持在(zai)該(gai)限(xian)制的(de)水平或者低于(yu)該(gai)限(xian)制，就仍(reng)然(ran)有電(dian)(dian)流向電(dian)(dian)池充電(dian)(dian)。然(ran)而，由系(xi)統電(dian)(dian)壓下降引起的(de)不穩定或噪聲使得這種基于(yu)電(dian)(dian)壓的(de)DPPM結構不適(shi)合(he)應用(yong)在(zai)某些對噪聲敏(min)感的(de)場合(he)，比(bi)如音(yin)頻設備。

圖5:基于輸入電壓的動態(tai)電源路徑管理。

基于輸(shu)入電(dian)流的DPPM（圖6）采用檢測電(dian)阻來評估輸(shu)入電(dian)流，當(dang)輸(shu)入電(dian)流達到預設(she)電(dian)流門限時，通過動態降(jiang)低電(dian)池電(dian)流來防止適配器(qi)過載(zai)或系統電(dian)壓(ya)下(xia)降(jiang)。這樣就保證了系統電(dian)壓(ya)的穩定，降(jiang)低了適配器(qi)的額外功率要求。同時，該(gai)拓撲還(huan)具備電(dian)池反(fan)向補充供電(dian)的能(neng)力。

圖(tu)6:基于輸入電流的動態電源路(lu)徑管理。

　　有些充電(dian)(dian)(dian)(dian)器(qi)（例如MPS公司的MP2607）可以根據不(bu)同電(dian)(dian)(dian)(dian)源要求，優化選擇(ze)不(bu)同的動態電(dian)(dian)(dian)(dian)源路徑管理方(fang)案(an)。MP2607根據不(bu)同的適配(pei)器(qi)類型，在基于(yu)輸入(ru)電(dian)(dian)(dian)(dian)壓和基于(yu)輸入(ru)電(dian)(dian)(dian)(dian)流的DPPM兩(liang)種(zhong)拓撲之間進行智(zhi)能選擇(ze)。若(ruo)輸入(ru)是(shi)交(jiao)流適配(pei)器(qi)，MP2607采用(yong)基于(yu)輸入(ru)電(dian)(dian)(dian)(dian)壓的DPPM技術(shu)，控制適配(pei)器(qi)交(jiao)流電(dian)(dian)(dian)(dian)壓，使得交(jiao)流適配(pei)器(qi)可以同時為系統(tong)供電(dian)(dian)(dian)(dian)和為電(dian)(dian)(dian)(dian)池(chi)充電(dian)(dian)(dian)(dian)，工作波形如圖(tu)7所示。

圖7:MP2607在(zai)交流適配器輸入時的動態電源路徑管理。

　　在USB輸入模式下(xia)，MP2607采用基于(yu)輸入電(dian)(dian)流的DPPM.如圖(tu)8所示，考慮(lv)到USB提(ti)供電(dian)(dian)流能(neng)力有(you)限，設置充(chong)電(dian)(dian)電(dian)(dian)流在USB限制電(dian)(dian)流以(yi)下(xia)。若系統負(fu)載(zai)電(dian)(dian)流大于(yu)USB限流值，電(dian)(dian)池將反向補(bu)充(chong)供電(dian)(dian)。

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

　　總之，具有動態電源路徑管理的充電器（尤(you)其(qi)是那些能在不同(tong)管(guan)理模式(shi)之(zhi)間切換的充電(dian)器）可(ke)以(yi)為(wei)移動(dong)電(dian)子(zi)設備提供更(geng)加精妙的電(dian)源解決方案，從而給用戶帶來前所未有的便利、性能和效率(lv)。