隨著智能(neng)手機、平板(ban)電(dian)(dian)(dian)(dian)(dian)腦(nao)和(he)攝像(xiang)機等便(bian)攜(xie)設備的(de)(de)(de)不斷普(pu)及(ji)，人們對(dui)電(dian)(dian)(dian)(dian)(dian)源的(de)(de)(de)要(yao)(yao)求(qiu)以及(ji)對(dui)邊充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)邊使用這些設備的(de)(de)(de)能(neng)力的(de)(de)(de)要(yao)(yao)求(qiu)與日俱增。更高的(de)(de)(de)功率要(yao)(yao)求(qiu)增加了對(dui)具有高功率密度(du)和(he)優異充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)能(neng)力的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)池(chi)的(de)(de)(de)需求(qiu)。目前，鋰(li)離(li)子（Li-ion）電(dian)(dian)(dian)(dian)(dian)池(chi)和(he)鋰(li)聚(ju)合(he)物（Li-po）電(dian)(dian)(dian)(dian)(dian)池(chi)最(zui)適合(he)當(dang)前市(shi)場(chang)對(dui)功率密度(du)、充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)能(neng)力和(he)價格的(de)(de)(de)要(yao)(yao)求(qiu)。但(dan)是，有別(bie)于(yu)鉛酸、鎳氫等其他流行的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)池(chi)技(ji)術(shu)(shu)，鋰(li)電(dian)(dian)(dian)(dian)(dian)池(chi)技(ji)術(shu)(shu)的(de)(de)(de)性(xing)能(neng)也最(zui)不穩(wen)定：鋰(li)電(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)放電(dian)(dian)(dian)(dian)(dian)若(ruo)管理(li)不善，將導致充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)時間長(chang)、耗散(san)功率高、效率低(di)和(he)電(dian)(dian)(dian)(dian)(dian)池(chi)壽命(ming)比平均壽命(ming)低(di)等問題(ti)。圖1顯示了典型鋰(li)離(li)子電(dian)(dian)(dian)(dian)(dian)池(chi)的(de)(de)(de)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)曲線(xian)。

　　傳統(tong)(tong)充電(dian)(dian)器(qi)相對簡單，這些充電(dian)(dian)器(qi)在(zai)小(xiao)功率(lv)(lv)應用(yong)中表(biao)現較(jiao)好。然而，它們(men)卻不能有效地適應充電(dian)(dian)曲線的(de)變化，比(bi)如，用(yong)戶在(zai)不同電(dian)(dian)源之間切換或者在(zai)充電(dian)(dian)期間操作設(she)備。另外，傳統(tong)(tong)充電(dian)(dian)器(qi)在(zai)大(da)功率(lv)(lv)和大(da)電(dian)(dian)流應用(yong)中，通常(chang)效率(lv)(lv)較(jiao)低，耗(hao)散功率(lv)(lv)較(jiao)大(da)。

圖1:典型鋰(li)離(li)子電池的充(chong)電曲線。

　　新型線性和開關充電器，比(bi)如(ru)芯源系統(tong)（MPS）公(gong)司的MP2600系列(lie)，采用電(dian)(dian)源路(lu)徑管(guan)理技術改變了充(chong)電(dian)(dian)曲(qu)線(xian)，從而能(neng)夠(gou)以更低(di)的耗散(san)功率更加高(gao)效地為(wei)電(dian)(dian)池/系統(tong)供電(dian)(dian)。同時，這些充(chong)電(dian)(dian)器也(ye)使(shi)系統(tong)的安(an)全性和(he)電(dian)(dian)池的使(shi)用壽命(ming)得到提高(gao)。

　　電源管理拓(tuo)撲種(zhong)類繁多，本文則重點介紹以(yi)下(xia)三(san)種(zhong)：電池饋電、自動選擇和動態電源路徑。

　　電池饋電拓撲

　　電(dian)池饋(kui)電(dian)拓(tuo)撲(pu)是(shi)一種(zhong)實(shi)現過程最簡單、成本最低(di)的拓(tuo)撲(pu)，這是(shi)因為(wei)其電(dian)路由(you)充(chong)電(dian)器、電(dian)池和(he)系統(tong)組成，如圖2所示。

圖(tu)2:電(dian)池饋電(dian)拓撲(pu)原(yuan)理圖(tu)及信號圖(tu)。

　　這(zhe)種(zhong)拓撲有三個主要特性：無論(lun)供(gong)電(dian)(dian)電(dian)(dian)壓(ya)如(ru)何變化，系(xi)統(tong)電(dian)(dian)壓(ya)始終(zhong)等于電(dian)(dian)池電(dian)(dian)壓(ya)，電(dian)(dian)源系(xi)統(tong)始終(zhong)優先(xian)，以(yi)便(bian)IBATT ￡ ICHG,并(bing)且(qie)ICHG最終(zhong)限制由輸(shu)入電(dian)(dian)源提(ti)供(gong)給系(xi)統(tong)電(dian)(dian)源總(zong)線(xian)的最大功(gong)率。當(dang)系(xi)統(tong)與充電(dian)(dian)器斷開時該拓撲還可以(yi)實現最小的耗散功(gong)率，設(she)置(zhi)ICHG從根(gen)本上(shang)限定(ding)了總(zong)輸(shu)入電(dian)(dian)流(liu)，這(zhe)樣，隨著系(xi)統(tong)電(dian)(dian)流(liu)（ISYS）的增加(jia)，充電(dian)(dian)電(dian)(dian)流(liu)（IBATT）將等額下降，工作波形如(ru)圖2所(suo)示。

　　遺憾的是，這種拓撲有如下不足(zu)之處，從而限制了它在(zai)更廣應用領域的效(xiao)率(lv)和效(xiao)用：

　　在電(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)壓太低的情(qing)況下，系(xi)統無法工作。電(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)壓跌至涓(juan)流充(chong)電(dian)(dian)(dian)(dian)門(men)限以下時，充(chong)電(dian)(dian)(dian)(dian)器將(jiang)把總的輸出電(dian)(dian)(dian)(dian)流限制得很(hen)低。系(xi)統的額外電(dian)(dian)(dian)(dian)源(yuan)需求將(jiang)由電(dian)(dian)(dian)(dian)池(chi)(chi)來補充(chong)，從而導致電(dian)(dian)(dian)(dian)池(chi)(chi)能量進一步耗盡(jin)。由于(yu)系(xi)統電(dian)(dian)(dian)(dian)壓始(shi)終(zhong)等于(yu)電(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)壓，一旦電(dian)(dian)(dian)(dian)池(chi)(chi)電(dian)(dian)(dian)(dian)壓低到系(xi)統最低工作電(dian)(dian)(dian)(dian)壓以下，系(xi)統將(jiang)停止工作。

　　雖然電(dian)池已(yi)(yi)具有滿(man)(man)電(dian)量(liang)，但是充電(dian)器(qi)無法(fa)進(jin)入EOC（結束充電(dian)）狀態。如果ISYS超過(guo)電(dian)池滿(man)(man)電(dian)量(liang)門限（IBF），那么ICHG就無法(fa)降到低于IBF,充電(dian)狀態始(shi)終顯示正(zheng)在充電(dian)，即使電(dian)池已(yi)(yi)經具有滿(man)(man)電(dian)量(liang)。

　　電(dian)池無(wu)法充(chong)(chong)滿。由于系統(tong)優(you)先于電(dian)池供電(dian)，因此電(dian)池只(zhi)能(neng)以低電(dian)流進行(xing)充(chong)(chong)電(dian)。此外，充(chong)(chong)電(dian)器(qi)只(zhi)能(neng)在預期的有效充(chong)(chong)電(dian)時間(jian)內工作，這樣可(ke)以避(bi)免給壞(huai)電(dian)池充(chong)(chong)電(dian)。如充(chong)(chong)電(dian)時間(jian)超(chao)出此時間(jian)段，會(hui)導致充(chong)(chong)電(dian)器(qi)誤判壞(huai)電(dian)池而停止充(chong)(chong)電(dian)。

電源路(lu)徑(jing)自動選擇拓撲

　　電(dian)源路徑自(zi)動選(xuan)擇(ze)拓(tuo)撲(pu)(pu)在(zai)電(dian)池直(zhi)接搭載拓(tuo)撲(pu)(pu)基礎上外加了兩個開(kai)關管，使得(de)系統(tong)電(dian)源可以根據(ju)輸入電(dian)壓(ya)的變化在(zai)適配器(qi)和電(dian)池之間來回切換。拓(tuo)撲(pu)(pu)結構及工作波形如圖3所示。

圖3:電(dian)源路徑自動選擇拓撲及工作波形。

　　與電(dian)(dian)(dian)池(chi)饋(kui)電(dian)(dian)(dian)拓撲結構相比(bi)(bi)，此拓撲有(you)實質性的(de)改進。它將系(xi)(xi)統直接(jie)跟交流適配(pei)(pei)器相連(lian)，與充(chong)電(dian)(dian)(dian)器獨立開來，因而能夠提供(gong)更大的(de)系(xi)(xi)統電(dian)(dian)(dian)流、更高(gao)的(de)效率(lv)并且允(yun)許系(xi)(xi)統在低電(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)壓下工(gong)作。此外，其(qi)價格(ge)也(ye)比(bi)(bi)較(jiao)(jiao)低廉。然而，當適配(pei)(pei)器輸出電(dian)(dian)(dian)壓變(bian)化(hua)較(jiao)(jiao)大的(de)時候，系(xi)(xi)統電(dian)(dian)(dian)壓也(ye)會隨之變(bian)化(hua)，所以此拓撲要(yao)(yao)求(qiu)系(xi)(xi)統能夠接(jie)受(shou)比(bi)(bi)較(jiao)(jiao)寬的(de)輸入電(dian)(dian)(dian)壓變(bian)化(hua)范圍。此外，也(ye)要(yao)(yao)求(qiu)適配(pei)(pei)器具有(you)更高(gao)的(de)額定功(gong)率(lv)，以滿(man)足系(xi)(xi)統和充(chong)電(dian)(dian)(dian)器的(de)最(zui)大總功(gong)率(lv)需求(qiu)，以及系(xi)(xi)統負載(zai)突變(bian)時的(de)功(gong)率(lv)變(bian)化(hua)要(yao)(yao)求(qiu)。

　　圖(tu)4是采(cai)用MPS公司(si)的MP2611構成的電(dian)(dian)源路徑自動選擇拓(tuo)撲(pu)的原理圖(tu)。為了防止(zhi)出現不穩(wen)定情況，當VBATT接近(jin)VIN時，MP2611會(hui)(hui)斷開系(xi)統與(yu)(yu)電(dian)(dian)池的連接。此外，它(ta)還會(hui)(hui)在S1 （M1及M2）與(yu)(yu)S2（M3）之間插入一個消(xiao)隱期(qi)，以(yi)防出現電(dian)(dian)流貫通，從而損壞系(xi)統和電(dian)(dian)池。

圖4:采用MP2611構成(cheng)的電(dian)源路徑自動選(xuan)擇拓撲。

　　動態電源(yuan)路徑管理拓(tuo)撲（DPPM）

　　動態(tai)電源路(lu)徑管理（DPPM）技(ji)術采用(yong)了一(yi)套附加的(de)檢(jian)測模塊，測量系統(tong)電壓(ya)或(huo)者(zhe)輸入電流，實時(shi)監測總功率需求(qiu)。一(yi)旦功率需求(qiu)超過(guo)預設(she)值(zhi)，通(tong)過(guo)充電器降低充電電流來保證適配器輸出功率恒定(ding)而(er)不(bu)過(guo)載。

　　例(li)如(ru)(ru)，基于(yu)輸(shu)入(ru)(ru)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓的(de)DPPM（圖5）通過(guo)比(bi)較輸(shu)入(ru)(ru)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓與(yu)預設(she)參(can)考(kao)(kao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓來判斷輸(shu)入(ru)(ru)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流是否(fou)達到適配(pei)(pei)器的(de)輸(shu)出電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流限(xian)(xian)制(zhi)。若適配(pei)(pei)器電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流已經達到該限(xian)(xian)制(zhi)，適配(pei)(pei)器電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓將(jiang)降(jiang)至預設(she)參(can)考(kao)(kao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓，然后充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)器通過(guo)動態降(jiang)低充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流來防止系統電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓繼續下降(jiang)。只要輸(shu)入(ru)(ru)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流保(bao)持在該限(xian)(xian)制(zhi)的(de)水平或(huo)者低于(yu)該限(xian)(xian)制(zhi)，就仍然有電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流向電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)。然而(er)，由系統電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓下降(jiang)引起的(de)不(bu)穩定(ding)或(huo)噪聲(sheng)使得這種(zhong)基于(yu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓的(de)DPPM結構不(bu)適合應用在某些對噪聲(sheng)敏感的(de)場合，比(bi)如(ru)(ru)音頻設(she)備。

圖(tu)5:基于輸入電(dian)壓(ya)的動(dong)態(tai)電(dian)源路徑管理(li)。

基于輸入(ru)電(dian)(dian)流(liu)(liu)(liu)的(de)DPPM（圖6）采用檢測電(dian)(dian)阻來(lai)評(ping)估輸入(ru)電(dian)(dian)流(liu)(liu)(liu)，當輸入(ru)電(dian)(dian)流(liu)(liu)(liu)達到預(yu)設電(dian)(dian)流(liu)(liu)(liu)門(men)限(xian)時，通過動態(tai)降低(di)(di)電(dian)(dian)池(chi)電(dian)(dian)流(liu)(liu)(liu)來(lai)防止適(shi)(shi)配器(qi)過載或系統電(dian)(dian)壓下降。這樣就保證了(le)系統電(dian)(dian)壓的(de)穩定，降低(di)(di)了(le)適(shi)(shi)配器(qi)的(de)額(e)外(wai)功率要求(qiu)。同時，該拓撲還具備電(dian)(dian)池(chi)反向補充供電(dian)(dian)的(de)能力。

圖6:基于(yu)輸入電(dian)流的動態電(dian)源(yuan)路徑管(guan)理。

　　有(you)些充電(dian)(dian)(dian)(dian)(dian)器（例如(ru)(ru)MPS公司的MP2607）可以(yi)根據不(bu)同(tong)電(dian)(dian)(dian)(dian)(dian)源要求，優化選(xuan)擇不(bu)同(tong)的動態電(dian)(dian)(dian)(dian)(dian)源路徑管理(li)方案。MP2607根據不(bu)同(tong)的適配器類型，在基于輸(shu)入(ru)電(dian)(dian)(dian)(dian)(dian)壓和(he)基于輸(shu)入(ru)電(dian)(dian)(dian)(dian)(dian)流的DPPM兩種拓撲(pu)之間進行智能(neng)選(xuan)擇。若輸(shu)入(ru)是交(jiao)流適配器，MP2607采用基于輸(shu)入(ru)電(dian)(dian)(dian)(dian)(dian)壓的DPPM技術，控(kong)制適配器交(jiao)流電(dian)(dian)(dian)(dian)(dian)壓，使得交(jiao)流適配器可以(yi)同(tong)時(shi)為系(xi)統供電(dian)(dian)(dian)(dian)(dian)和(he)為電(dian)(dian)(dian)(dian)(dian)池充電(dian)(dian)(dian)(dian)(dian)，工作波(bo)形如(ru)(ru)圖(tu)7所示。

圖7:MP2607在交(jiao)流適配器(qi)輸入時的動態(tai)電源路(lu)徑(jing)管理。

　　在(zai)USB輸入模式下(xia)，MP2607采用基于輸入電(dian)(dian)流的DPPM.如(ru)圖(tu)8所示，考慮到USB提(ti)供電(dian)(dian)流能力(li)有(you)限，設(she)置(zhi)充電(dian)(dian)電(dian)(dian)流在(zai)USB限制電(dian)(dian)流以下(xia)。若(ruo)系統負載電(dian)(dian)流大(da)于USB限流值(zhi)，電(dian)(dian)池將(jiang)反向補(bu)充供電(dian)(dian)。

圖8:MP2607在USB輸(shu)入(ru)時的動(dong)態電源(yuan)路徑管理(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(jie)決方案，從(cong)而給用(yong)戶帶(dai)來(lai)前所未有(you)的便利、性能和效率。