無(wu)論是(shi)做(zuo)什么(me)用途，或(huo)制造商是(shi)誰，手持(chi)(chi)式電(dian)(dian)(dian)子設備(bei)都(dou)有一(yi)(yi)個共同的(de)(de)特性：一(yi)(yi)個可充(chong)電(dian)(dian)(dian)的(de)(de)電(dian)(dian)(dian)池，多數情況下還有一(yi)(yi)個內(nei)建的(de)(de)充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)路(lu)(lu)。當(dang)一(yi)(yi)個AC適(shi)配(pei)器這樣的(de)(de)外(wai)部(bu)電(dian)(dian)(dian)源(yuan)或(huo)一(yi)(yi)個USB端(duan)口(kou)接(jie)到手持(chi)(chi)設備(bei)的(de)(de)輸入端(duan)，充(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)路(lu)(lu)將對電(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)。當(dang)接(jie)到外(wai)部(bu)電(dian)(dian)(dian)源(yuan)時，如果設備(bei)正處在開機狀態，理想的(de)(de)情形是(shi)，設備(bei)應當(dang)從外(wai)部(bu)電(dian)(dian)(dian)源(yuan)汲取(qu)盡可能多的(de)(de)功(gong)率，以節省電(dian)(dian)(dian)池壽命。要(yao)實現(xian)這個功(gong)能則需要(yao)一(yi)(yi)個自動(dong)的(de)(de)電(dian)(dian)(dian)源(yuan)選擇電(dian)(dian)(dian)路(lu)(lu)，這個電(dian)(dian)(dian)路(lu)(lu)通常是(shi)集(ji)成在充(chong)電(dian)(dian)(dian)控(kong)制IC內(nei)。設計者可以從動(dong)態或(huo)靜態電(dian)(dian)(dian)源(yuan)路(lu)(lu)徑管(guan)理當(dang)中選擇其(qi)中的(de)(de)一(yi)(yi)種，進行電(dian)(dian)(dian)源(yuan)管(guan)理。

　　在電(dian)(dian)(dian)(dian)(dian)池(chi)供電(dian)(dian)(dian)(dian)(dian)的手(shou)持設備中，動態電(dian)(dian)(dian)(dian)(dian)源(yuan)路(lu)徑管(guan)理(li)(DPPM)是更流行的機制。DPPM功能框圖(tu)如圖(tu)1所(suo)示(shi)。主通路(lu)元(yuan)(yuan)件(jian)QMAIN是一(yi)(yi)個(ge)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)穩(wen)壓(ya)(ya)器，提(ti)(ti)供一(yi)(yi)個(ge)經過穩(wen)壓(ya)(ya)的輸出電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)VOUT。第二個(ge)通路(lu)元(yuan)(yuan)件(jian)QCharge是充(chong)電(dian)(dian)(dian)(dian)(dian)控制元(yuan)(yuan)件(jian)，由VOUT供電(dian)(dian)(dian)(dian)(dian)，提(ti)(ti)供恒定的電(dian)(dian)(dian)(dian)(dian)流或恒定的電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)對(dui)電(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)(dian)(dian)。在充(chong)電(dian)(dian)(dian)(dian)(dian)期間(jian)，如果輸出電(dian)(dian)(dian)(dian)(dian)流超過電(dian)(dian)(dian)(dian)(dian)源(yuan)的電(dian)(dian)(dian)(dian)(dian)流限值，QCharge就會變成一(yi)(yi)個(ge)開關(guan)，將電(dian)(dian)(dian)(dian)(dian)池(chi)連(lian)到(dao)系統上，提(ti)(ti)供一(yi)(yi)部分(fen)所(suo)需的輸出電(dian)(dian)(dian)(dian)(dian)流。

　　DPPM有(you)(you)幾個好處(chu)。首先，當(dang)(dang)(dang)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)完(wan)全(quan)放電(dian)(dian)(dian)(dian)(dian)時(shi)(shi)(電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)耗盡的(de)(de)(de)情況(kuang))，DPPM能讓外部(bu)電(dian)(dian)(dian)(dian)(dian)源立刻給設(she)(she)備供(gong)電(dian)(dian)(dian)(dian)(dian)。如果沒有(you)(you)電(dian)(dian)(dian)(dian)(dian)源路徑(jing)管理，在電(dian)(dian)(dian)(dian)(dian)量耗盡的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)被(bei)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)到(dao)系(xi)(xi)統(tong)(tong)能夠啟動(dong)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)壓(ya)等級之(zhi)前(qian)(一(yi)般是(shi)(shi)高于3V)，系(xi)(xi)統(tong)(tong)是(shi)(shi)無法上電(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)。這個等待周期(qi)取決于充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)路的(de)(de)(de)涓流(liu)(liu)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)設(she)(she)定，可能是(shi)(shi)幾分(fen)(fen)鐘到(dao)十分(fen)(fen)鐘的(de)(de)(de)時(shi)(shi)間。其次，當(dang)(dang)(dang)用外部(bu)電(dian)(dian)(dian)(dian)(dian)源對電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)時(shi)(shi)，DPPM會把(ba)來(lai)自(zi)外部(bu)電(dian)(dian)(dian)(dian)(dian)源的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)分(fen)(fen)到(dao)兩個路徑(jing)中，一(yi)條路徑(jing)為手持(chi)設(she)(she)備提供(gong)必要(yao)的(de)(de)(de)功率，另一(yi)條路徑(jing)輸(shu)出(chu)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)，來(lai)給電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)。當(dang)(dang)(dang)外部(bu)電(dian)(dian)(dian)(dian)(dian)源的(de)(de)(de)輸(shu)入(ru)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)達到(dao)限值時(shi)(shi)，電(dian)(dian)(dian)(dian)(dian)源路徑(jing)管理會對輸(shu)入(ru)到(dao)手持(chi)系(xi)(xi)統(tong)(tong)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)進(jin)行(xing)優(you)先級分(fen)(fen)類(lei)。這樣如果當(dang)(dang)(dang)系(xi)(xi)統(tong)(tong)工作時(shi)(shi)，電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)正在充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)，電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)可以在最短的(de)(de)(de)時(shi)(shi)間內(nei)充(chong)(chong)(chong)(chong)(chong)滿(man)，因為動(dong)態控制的(de)(de)(de)充(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)是(shi)(shi)為這個目(mu)標而優(you)化的(de)(de)(de)。當(dang)(dang)(dang)外部(bu)電(dian)(dian)(dian)(dian)(dian)源被(bei)移走時(shi)(shi)，QCharge立刻完(wan)全(quan)打開，把(ba)電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)連到(dao)系(xi)(xi)統(tong)(tong)上，向系(xi)(xi)統(tong)(tong)輸(shu)出(chu)所需的(de)(de)(de)全(quan)部(bu)功率。

　　圖1，動態(tai)電(dian)源路徑(jing)管(guan)理框圖

　　但DPPM機制有一些限制。第一種情況是，當系統電流發生快速瞬變時，電壓會下降。這種情況如果發生在電池充電期間，如果系統電流處在突發方式下，輸出端的負載電流會周期性地迅速從接近零升高到2A以上。由于這個電流超過了輸入電源的最大容量，充電FET不得不將電流反向，提供一部分的突發電流。由于電流反向需要一定的時間，在這段時間內，輸出電壓會降低，導致電流產生畸變，如圖2所示。第二各限制條件是IC設計的成本和復雜度，因為由兩個通路元件需要調節。一個元件調節到系統的輸出電壓，另一個調節對電池充電的電壓或電流。

　　圖(tu)2，靜態(tai)電(dian)源(yuan)路徑管理的(de)瞬(shun)態(tai)電(dian)流響應

　　靜態電源路徑管路

　　靜態電源路徑管理(SPPM)是一個(ge)簡化的(de)解決(jue)辦(ban)法，能達到上面提(ti)到的(de)第一個(ge)目標，不會(hui)出現(xian)電(dian)壓下(xia)降的(de)情況(kuang)。然而，它(ta)沒法解決(jue)第二個(ge)問題(ti)，即區(qu)分系統和充電(dian)電(dian)流的(de)優先級(ji)。

　　SPPM機(ji)制(zhi)的(de)概(gai)念(nian)如圖(tu)(tu)3所示(shi)。主FET QMAIN是充電(dian)控(kong)制(zhi)器(qi)元件(jian)。開(kai)(kai)關(guan)(guan)SW1連接(jie)電(dian)池(chi)(chi)和(he)(he)系(xi)(xi)統。當電(dian)池(chi)(chi)電(dian)壓(ya)(ya)高(gao)于VPPM閾值(系(xi)(xi)統的(de)最小(xiao)工作電(dian)壓(ya)(ya)，一般是3.2V)，開(kai)(kai)關(guan)(guan)導通(tong)，無(wu)論外(wai)部(bu)電(dian)源(yuan)存在與否，電(dian)池(chi)(chi)都會連到系(xi)(xi)統。這樣，當系(xi)(xi)統突然汲(ji)取電(dian)流時，由于開(kai)(kai)關(guan)(guan)已(yi)經處在導通(tong)狀態，電(dian)池(chi)(chi)能(neng)夠隨時提(ti)供(gong)系(xi)(xi)統所需的(de)電(dian)流。這樣就解決了電(dian)壓(ya)(ya)降和(he)(he)電(dian)流畸變(bian)問(wen)題(ti)，如圖(tu)(tu)5所示(shi)。由于在設(she)(she)計中僅需要一個調整元件(jian)對電(dian)池(chi)(chi)的(de)充電(dian)電(dian)壓(ya)(ya)或電(dian)流進(jin)行(xing)調節，IC設(she)(she)計成本和(he)(he)復雜度也降低(di)了。如果(guo)需要極低(di)阻(zu)抗(kang)的(de)開(kai)(kai)關(guan)(guan)，圖(tu)(tu)3中的(de)開(kai)(kai)關(guan)(guan)SW1可以放到IC外(wai)面來(lai)實現，進(jin)一步降低(di)成本。

　　如果電(dian)池(chi)電(dian)壓(ya)低于(yu)VPPM的(de)(de)閾值(zhi)，SW1就(jiu)(jiu)開啟，VOUT將(jiang)變(bian)成4.2V的(de)(de)恒(heng)(heng)壓(ya)源(yuan)(yuan)，向系統(tong)供(gong)電(dian)。與此同時，50mA的(de)(de)恒(heng)(heng)流源(yuan)(yuan)ITRKL被(bei)激活，在涓流模式下對(dui)電(dian)池(chi)充電(dian)，直到電(dian)壓(ya)達到VPPM閾值(zhi)(有一定滯后(hou))，然后(hou)SW1會關閉，電(dian)池(chi)就(jiu)(jiu)連到系統(tong)上。這樣就(jiu)(jiu)解決了沒電(dian)電(dian)池(chi)的(de)(de)啟動問題。

　　由于SPPM解決在電池沒電情況下的系統啟動問題，對于手持式應用來說，這是一種很有吸引力的電池充電器解決方案。

　　圖3，靜態電源路徑管理框圖

　　圖4，靜態(tai)電源路(lu)徑管(guan)理控(kong)制流(liu)程

　　圖5，靜態(tai)電(dian)源路徑管(guan)理的瞬態(tai)電(dian)流響應