隨著智能(neng)手機(ji)(ji)、平板電(dian)(dian)(dian)(dian)(dian)腦和攝像(xiang)機(ji)(ji)等(deng)便(bian)攜設備的(de)(de)(de)不斷普及(ji)，人(ren)們對(dui)電(dian)(dian)(dian)(dian)(dian)源(yuan)的(de)(de)(de)要(yao)求以及(ji)對(dui)邊充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)邊使(shi)用(yong)這些設備的(de)(de)(de)能(neng)力(li)的(de)(de)(de)要(yao)求與日俱增。更(geng)高(gao)的(de)(de)(de)功(gong)率(lv)(lv)要(yao)求增加(jia)了(le)對(dui)具有(you)高(gao)功(gong)率(lv)(lv)密度和優異充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)能(neng)力(li)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的(de)(de)(de)需(xu)求。目前(qian)(qian)，鋰離(li)子（Li-ion）電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)和鋰聚(ju)合物（Li-po）電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)最適(shi)合當前(qian)(qian)市場對(dui)功(gong)率(lv)(lv)密度、充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)能(neng)力(li)和價格的(de)(de)(de)要(yao)求。但是，有(you)別于鉛酸、鎳氫(qing)等(deng)其他流行的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)技(ji)術(shu)，鋰電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)技(ji)術(shu)的(de)(de)(de)性能(neng)也最不穩定：鋰電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)充(chong)(chong)放電(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、耗散功(gong)率(lv)(lv)高(gao)、效率(lv)(lv)低和電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)壽(shou)命比平均(jun)壽(shou)命低等(deng)問題(ti)。圖(tu)1顯(xian)示了(le)典型鋰離(li)子電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的(de)(de)(de)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)曲線(xian)。

　　傳統(tong)充(chong)電(dian)器(qi)相對簡單，這些(xie)充(chong)電(dian)器(qi)在小功(gong)率(lv)應用中表現較好。然而(er)，它(ta)們卻不(bu)能有(you)效地適應充(chong)電(dian)曲線(xian)的(de)變化(hua)，比如，用戶在不(bu)同電(dian)源之間(jian)切換或者(zhe)在充(chong)電(dian)期(qi)間(jian)操作設備。另外，傳統(tong)充(chong)電(dian)器(qi)在大(da)(da)功(gong)率(lv)和大(da)(da)電(dian)流應用中，通常效率(lv)較低，耗散功(gong)率(lv)較大(da)(da)。

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

　　新型線性和開關充電器，比如芯源系(xi)統（MPS）公司的MP2600系(xi)列，采(cai)用(yong)(yong)電(dian)源路徑管理(li)技術改變了充(chong)電(dian)曲線，從而能夠以更(geng)低的耗散功率更(geng)加高效(xiao)地(di)為電(dian)池/系(xi)統供電(dian)。同(tong)時，這些(xie)充(chong)電(dian)器也使(shi)系(xi)統的安全性和(he)電(dian)池的使(shi)用(yong)(yong)壽(shou)命得到提高。

　　電(dian)源管理拓撲(pu)種類繁多，本文(wen)則重點介紹以(yi)下(xia)三種：電(dian)池饋電(dian)、自(zi)動選擇(ze)和(he)動態電(dian)源路徑。

　　電池饋電拓撲

　　電池(chi)饋(kui)電拓撲是一種實現過程最(zui)簡單、成(cheng)本最(zui)低的拓撲，這是因(yin)為(wei)其電路由充電器、電池(chi)和系統(tong)組成(cheng)，如圖2所示。

圖(tu)(tu)2:電池饋電拓(tuo)撲原理圖(tu)(tu)及信號圖(tu)(tu)。

　　這種(zhong)拓(tuo)撲(pu)有三個主要(yao)特性(xing)：無論(lun)供電(dian)(dian)電(dian)(dian)壓(ya)如何變化，系(xi)(xi)統(tong)(tong)電(dian)(dian)壓(ya)始終(zhong)(zhong)等于電(dian)(dian)池電(dian)(dian)壓(ya)，電(dian)(dian)源系(xi)(xi)統(tong)(tong)始終(zhong)(zhong)優先，以(yi)便(bian)IBATT ￡ ICHG,并且ICHG最(zui)終(zhong)(zhong)限制(zhi)由輸入電(dian)(dian)源提供給系(xi)(xi)統(tong)(tong)電(dian)(dian)源總線的最(zui)大功率。當(dang)系(xi)(xi)統(tong)(tong)與充(chong)電(dian)(dian)器斷(duan)開時該(gai)拓(tuo)撲(pu)還(huan)可以(yi)實現(xian)最(zui)小的耗(hao)散功率，設(she)置ICHG從根本上限定了總輸入電(dian)(dian)流(liu)，這樣，隨著系(xi)(xi)統(tong)(tong)電(dian)(dian)流(liu)（ISYS）的增加，充(chong)電(dian)(dian)電(dian)(dian)流(liu)（IBATT）將(jiang)等額下降，工作波形如圖2所示。

　　遺憾的(de)是，這種拓撲有如下不足之處，從(cong)而(er)限制了(le)它在更廣(guang)應用領域的(de)效率和效用：

　　在電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)(dian)壓(ya)太低的(de)情況下(xia)，系(xi)(xi)統(tong)無法(fa)工作(zuo)。電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)(dian)壓(ya)跌至涓流(liu)充(chong)電(dian)(dian)(dian)(dian)(dian)門限(xian)以下(xia)時，充(chong)電(dian)(dian)(dian)(dian)(dian)器(qi)將(jiang)把總(zong)的(de)輸(shu)出電(dian)(dian)(dian)(dian)(dian)流(liu)限(xian)制得很低。系(xi)(xi)統(tong)的(de)額外電(dian)(dian)(dian)(dian)(dian)源需求(qiu)將(jiang)由(you)(you)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)來補充(chong)，從而導致電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)能(neng)量(liang)進一(yi)步耗盡。由(you)(you)于系(xi)(xi)統(tong)電(dian)(dian)(dian)(dian)(dian)壓(ya)始(shi)終等于電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)(dian)壓(ya)，一(yi)旦電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)(dian)壓(ya)低到系(xi)(xi)統(tong)最低工作(zuo)電(dian)(dian)(dian)(dian)(dian)壓(ya)以下(xia)，系(xi)(xi)統(tong)將(jiang)停止工作(zuo)。

　　雖然電(dian)(dian)池已具有(you)滿電(dian)(dian)量，但是充(chong)電(dian)(dian)器無(wu)法(fa)進入EOC（結束充(chong)電(dian)(dian)）狀(zhuang)態。如果ISYS超(chao)過電(dian)(dian)池滿電(dian)(dian)量門限（IBF），那么ICHG就無(wu)法(fa)降到低于(yu)IBF,充(chong)電(dian)(dian)狀(zhuang)態始終顯示正在充(chong)電(dian)(dian)，即使電(dian)(dian)池已經具有(you)滿電(dian)(dian)量。

　　電(dian)(dian)(dian)池無法充(chong)(chong)(chong)滿。由(you)于(yu)系統優先(xian)于(yu)電(dian)(dian)(dian)池供電(dian)(dian)(dian)，因此電(dian)(dian)(dian)池只(zhi)(zhi)能以低電(dian)(dian)(dian)流進(jin)行充(chong)(chong)(chong)電(dian)(dian)(dian)。此外(wai)，充(chong)(chong)(chong)電(dian)(dian)(dian)器(qi)只(zhi)(zhi)能在預期的有效充(chong)(chong)(chong)電(dian)(dian)(dian)時(shi)間內(nei)工作，這樣(yang)可以避免給壞電(dian)(dian)(dian)池充(chong)(chong)(chong)電(dian)(dian)(dian)。如充(chong)(chong)(chong)電(dian)(dian)(dian)時(shi)間超出此時(shi)間段，會導致充(chong)(chong)(chong)電(dian)(dian)(dian)器(qi)誤判壞電(dian)(dian)(dian)池而停止充(chong)(chong)(chong)電(dian)(dian)(dian)。

電源路徑(jing)自動選擇拓撲

　　電(dian)源(yuan)路徑自動選擇拓(tuo)撲(pu)在電(dian)池(chi)直接搭載(zai)拓(tuo)撲(pu)基礎(chu)上外加了兩個開關(guan)管，使得系(xi)統(tong)電(dian)源(yuan)可以(yi)根據輸(shu)入電(dian)壓的變化在適配器和(he)電(dian)池(chi)之間來(lai)回切(qie)換(huan)。拓(tuo)撲(pu)結構及工作(zuo)波形如圖3所(suo)示。

圖3:電源路(lu)徑(jing)自動選擇拓撲及工作波(bo)形。

　　與(yu)電(dian)(dian)(dian)池饋電(dian)(dian)(dian)拓撲(pu)結(jie)構(gou)相比，此拓撲(pu)有(you)實質性的改進(jin)。它將(jiang)系統直(zhi)接(jie)跟交(jiao)流適配器(qi)相連，與(yu)充(chong)電(dian)(dian)(dian)器(qi)獨立開來，因而(er)能(neng)夠提(ti)供(gong)更(geng)大(da)的系統電(dian)(dian)(dian)流、更(geng)高的效率并且(qie)允許(xu)系統在(zai)低電(dian)(dian)(dian)池電(dian)(dian)(dian)壓(ya)(ya)下工作。此外，其價格也(ye)比較(jiao)低廉。然(ran)而(er)，當適配器(qi)輸出電(dian)(dian)(dian)壓(ya)(ya)變(bian)(bian)化較(jiao)大(da)的時候(hou)，系統電(dian)(dian)(dian)壓(ya)(ya)也(ye)會(hui)隨之變(bian)(bian)化，所以此拓撲(pu)要(yao)求(qiu)(qiu)系統能(neng)夠接(jie)受比較(jiao)寬(kuan)的輸入(ru)電(dian)(dian)(dian)壓(ya)(ya)變(bian)(bian)化范圍。此外，也(ye)要(yao)求(qiu)(qiu)適配器(qi)具有(you)更(geng)高的額(e)定功率，以滿(man)足系統和充(chong)電(dian)(dian)(dian)器(qi)的最大(da)總功率需求(qiu)(qiu)，以及系統負載突(tu)變(bian)(bian)時的功率變(bian)(bian)化要(yao)求(qiu)(qiu)。

　　圖4是采用MPS公司(si)的MP2611構成(cheng)的電源路徑自動選擇拓撲的原(yuan)理圖。為了(le)防止出(chu)現不穩定情況，當VBATT接(jie)近VIN時，MP2611會斷(duan)開(kai)系統與電池的連(lian)接(jie)。此外，它還會在S1 （M1及M2）與S2（M3）之間插入一個消(xiao)隱期(qi)，以(yi)防出(chu)現電流貫通，從而損壞系統和電池。

圖4:采用(yong)MP2611構成的電(dian)源(yuan)路徑自(zi)動選擇(ze)拓撲。

　　動(dong)態電源(yuan)路(lu)徑(jing)管(guan)理拓撲（DPPM）

　　動(dong)態電(dian)源路徑管理(li)（DPPM）技術采用了(le)一(yi)套(tao)附加的檢測(ce)模塊，測(ce)量(liang)系統電(dian)壓或者輸(shu)入電(dian)流(liu)，實時監測(ce)總功(gong)率需(xu)求(qiu)。一(yi)旦功(gong)率需(xu)求(qiu)超過預設值，通過充電(dian)器(qi)降低(di)充電(dian)電(dian)流(liu)來保(bao)證(zheng)適配器(qi)輸(shu)出功(gong)率恒定而不過載。

　　例如，基(ji)于輸(shu)入(ru)(ru)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)的DPPM（圖5）通(tong)(tong)過比較(jiao)輸(shu)入(ru)(ru)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)與預(yu)設(she)(she)參(can)考電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)來(lai)判斷(duan)輸(shu)入(ru)(ru)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)是否達(da)到適(shi)配器的輸(shu)出電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)限(xian)制(zhi)。若適(shi)配器電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)已經(jing)達(da)到該限(xian)制(zhi)，適(shi)配器電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)將降(jiang)至(zhi)預(yu)設(she)(she)參(can)考電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)，然(ran)后充(chong)電(dian)(dian)(dian)(dian)(dian)器通(tong)(tong)過動態降(jiang)低充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)來(lai)防止系統電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)繼續下(xia)(xia)降(jiang)。只要輸(shu)入(ru)(ru)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)保(bao)持在該限(xian)制(zhi)的水平或者低于該限(xian)制(zhi)，就仍(reng)然(ran)有電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)向(xiang)電(dian)(dian)(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)(dian)(dian)。然(ran)而，由系統電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)下(xia)(xia)降(jiang)引起的不穩定(ding)或噪(zao)聲使得這種(zhong)基(ji)于電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)的DPPM結構(gou)不適(shi)合應用在某些對噪(zao)聲敏感的場合，比如音頻(pin)設(she)(she)備。

圖(tu)5:基于輸(shu)入電(dian)(dian)壓的動態(tai)電(dian)(dian)源(yuan)路徑管理。

基于輸(shu)入(ru)電流(liu)(liu)的(de)(de)(de)DPPM（圖6）采用檢測電阻(zu)來(lai)評估輸(shu)入(ru)電流(liu)(liu)，當輸(shu)入(ru)電流(liu)(liu)達到(dao)預設電流(liu)(liu)門(men)限時，通過動態降(jiang)低(di)電池(chi)電流(liu)(liu)來(lai)防止適配(pei)器(qi)過載(zai)或系統電壓(ya)下(xia)降(jiang)。這樣(yang)就保證了系統電壓(ya)的(de)(de)(de)穩定，降(jiang)低(di)了適配(pei)器(qi)的(de)(de)(de)額外功率(lv)要求(qiu)。同時，該拓撲(pu)還具備電池(chi)反向補充供電的(de)(de)(de)能(neng)力。

圖6:基于輸入(ru)電(dian)流的(de)動態電(dian)源路徑管理。

　　有(you)些充(chong)電(dian)(dian)(dian)(dian)器(qi)（例(li)如(ru)MPS公司的(de)MP2607）可以根據(ju)不同電(dian)(dian)(dian)(dian)源(yuan)要求，優化選擇不同的(de)動態(tai)電(dian)(dian)(dian)(dian)源(yuan)路徑管理方案。MP2607根據(ju)不同的(de)適(shi)(shi)(shi)配(pei)器(qi)類(lei)型，在(zai)基于(yu)(yu)輸入(ru)電(dian)(dian)(dian)(dian)壓(ya)和(he)基于(yu)(yu)輸入(ru)電(dian)(dian)(dian)(dian)流的(de)DPPM兩(liang)種(zhong)拓(tuo)撲之間進(jin)行智能選擇。若輸入(ru)是交(jiao)流適(shi)(shi)(shi)配(pei)器(qi)，MP2607采(cai)用(yong)基于(yu)(yu)輸入(ru)電(dian)(dian)(dian)(dian)壓(ya)的(de)DPPM技術，控制適(shi)(shi)(shi)配(pei)器(qi)交(jiao)流電(dian)(dian)(dian)(dian)壓(ya)，使(shi)得交(jiao)流適(shi)(shi)(shi)配(pei)器(qi)可以同時為(wei)系統供(gong)電(dian)(dian)(dian)(dian)和(he)為(wei)電(dian)(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)(dian)，工(gong)作波形如(ru)圖7所示。

圖(tu)7:MP2607在(zai)交(jiao)流適配器輸(shu)入時的動態電源(yuan)路徑管(guan)理。

　　在USB輸入(ru)模(mo)式下(xia)(xia)，MP2607采用基(ji)于(yu)輸入(ru)電流(liu)的DPPM.如圖(tu)8所示，考慮到USB提供電流(liu)能力有限，設置充電電流(liu)在USB限制電流(liu)以下(xia)(xia)。若(ruo)系統負載電流(liu)大于(yu)USB限流(liu)值(zhi)，電池(chi)將反(fan)向補充供電。

圖(tu)8:MP2607在USB輸(shu)入時的動態(tai)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(fang)案(an)，從而(er)給用(yong)戶(hu)帶(dai)來(lai)前所未有的便利(li)、性(xing)能和效率(lv)。