無論是(shi)做什(shen)么用途，或(huo)制(zhi)造商(shang)是(shi)誰，手(shou)持式(shi)電(dian)(dian)(dian)(dian)(dian)(dian)子設(she)備都有一(yi)個共同的(de)特性：一(yi)個可(ke)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)的(de)電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)，多數情況下還有一(yi)個內建(jian)的(de)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)。當一(yi)個AC適配器這(zhe)樣(yang)的(de)外(wai)部(bu)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)或(huo)一(yi)個USB端口接(jie)到(dao)手(shou)持設(she)備的(de)輸入端，充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)將對電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)。當接(jie)到(dao)外(wai)部(bu)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)時(shi)，如果設(she)備正處在開機狀(zhuang)態(tai)，理想的(de)情形是(shi)，設(she)備應當從(cong)外(wai)部(bu)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)汲(ji)取盡可(ke)能多的(de)功率(lv)，以(yi)節(jie)省電(dian)(dian)(dian)(dian)(dian)(dian)池(chi)壽命。要(yao)實現這(zhe)個功能則需要(yao)一(yi)個自(zi)動(dong)(dong)的(de)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)選(xuan)擇(ze)電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)，這(zhe)個電(dian)(dian)(dian)(dian)(dian)(dian)路(lu)通常是(shi)集成在充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)控制(zhi)IC內。設(she)計者可(ke)以(yi)從(cong)動(dong)(dong)態(tai)或(huo)靜態(tai)電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)路(lu)徑管(guan)理當中選(xuan)擇(ze)其(qi)中的(de)一(yi)種(zhong)，進行電(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)管(guan)理。

　　在電(dian)(dian)(dian)(dian)(dian)池供(gong)電(dian)(dian)(dian)(dian)(dian)的(de)手持設備中，動(dong)態電(dian)(dian)(dian)(dian)(dian)源路(lu)徑管理(li)(DPPM)是(shi)更(geng)流(liu)行的(de)機制。DPPM功能框圖(tu)(tu)如(ru)圖(tu)(tu)1所示(shi)。主通路(lu)元(yuan)件(jian)QMAIN是(shi)一(yi)(yi)個(ge)電(dian)(dian)(dian)(dian)(dian)壓穩壓器，提(ti)供(gong)一(yi)(yi)個(ge)經過(guo)穩壓的(de)輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)壓VOUT。第二個(ge)通路(lu)元(yuan)件(jian)QCharge是(shi)充(chong)電(dian)(dian)(dian)(dian)(dian)控制元(yuan)件(jian)，由(you)VOUT供(gong)電(dian)(dian)(dian)(dian)(dian)，提(ti)供(gong)恒定(ding)的(de)電(dian)(dian)(dian)(dian)(dian)流(liu)或恒定(ding)的(de)電(dian)(dian)(dian)(dian)(dian)壓對電(dian)(dian)(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)(dian)(dian)。在充(chong)電(dian)(dian)(dian)(dian)(dian)期間，如(ru)果輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)流(liu)超過(guo)電(dian)(dian)(dian)(dian)(dian)源的(de)電(dian)(dian)(dian)(dian)(dian)流(liu)限值(zhi)，QCharge就會變成一(yi)(yi)個(ge)開關(guan)，將(jiang)電(dian)(dian)(dian)(dian)(dian)池連(lian)到(dao)系(xi)統上(shang)，提(ti)供(gong)一(yi)(yi)部分(fen)所需的(de)輸(shu)(shu)出(chu)電(dian)(dian)(dian)(dian)(dian)流(liu)。

　　DPPM有幾(ji)個(ge)好處。首先(xian)(xian)，當(dang)電(dian)(dian)(dian)(dian)(dian)池(chi)完全放電(dian)(dian)(dian)(dian)(dian)時(shi)(電(dian)(dian)(dian)(dian)(dian)池(chi)耗(hao)(hao)盡的(de)情況)，DPPM能(neng)讓外部(bu)(bu)(bu)(bu)(bu)電(dian)(dian)(dian)(dian)(dian)源立刻給(gei)設(she)備(bei)供(gong)電(dian)(dian)(dian)(dian)(dian)。如(ru)果(guo)(guo)沒有電(dian)(dian)(dian)(dian)(dian)源路徑管理(li)，在(zai)(zai)(zai)電(dian)(dian)(dian)(dian)(dian)量耗(hao)(hao)盡的(de)電(dian)(dian)(dian)(dian)(dian)池(chi)被(bei)(bei)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)到(dao)(dao)系(xi)統(tong)能(neng)夠啟動的(de)電(dian)(dian)(dian)(dian)(dian)壓等級之前(qian)(一般是高于(yu)(yu)3V)，系(xi)統(tong)是無法上(shang)電(dian)(dian)(dian)(dian)(dian)的(de)。這(zhe)(zhe)個(ge)等待周期取決(jue)于(yu)(yu)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)路的(de)涓(juan)流(liu)(liu)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)設(she)定，可(ke)能(neng)是幾(ji)分鐘到(dao)(dao)十分鐘的(de)時(shi)間(jian)。其(qi)次，當(dang)用(yong)外部(bu)(bu)(bu)(bu)(bu)電(dian)(dian)(dian)(dian)(dian)源對電(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)時(shi)，DPPM會把(ba)來(lai)自(zi)外部(bu)(bu)(bu)(bu)(bu)電(dian)(dian)(dian)(dian)(dian)源的(de)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)分到(dao)(dao)兩個(ge)路徑中(zhong)，一條(tiao)路徑為(wei)手(shou)(shou)持(chi)(chi)設(she)備(bei)提供(gong)必要的(de)功(gong)率，另一條(tiao)路徑輸出(chu)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)，來(lai)給(gei)電(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)。當(dang)外部(bu)(bu)(bu)(bu)(bu)電(dian)(dian)(dian)(dian)(dian)源的(de)輸入(ru)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)達到(dao)(dao)限值(zhi)時(shi)，電(dian)(dian)(dian)(dian)(dian)源路徑管理(li)會對輸入(ru)到(dao)(dao)手(shou)(shou)持(chi)(chi)系(xi)統(tong)的(de)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)進行優先(xian)(xian)級分類。這(zhe)(zhe)樣如(ru)果(guo)(guo)當(dang)系(xi)統(tong)工(gong)作(zuo)時(shi)，電(dian)(dian)(dian)(dian)(dian)池(chi)正(zheng)在(zai)(zai)(zai)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)，電(dian)(dian)(dian)(dian)(dian)池(chi)可(ke)以在(zai)(zai)(zai)最短(duan)的(de)時(shi)間(jian)內充(chong)(chong)(chong)滿，因(yin)為(wei)動態控制的(de)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)(liu)是為(wei)這(zhe)(zhe)個(ge)目標(biao)而優化的(de)。當(dang)外部(bu)(bu)(bu)(bu)(bu)電(dian)(dian)(dian)(dian)(dian)源被(bei)(bei)移(yi)走(zou)時(shi)，QCharge立刻完全打開，把(ba)電(dian)(dian)(dian)(dian)(dian)池(chi)連到(dao)(dao)系(xi)統(tong)上(shang)，向系(xi)統(tong)輸出(chu)所需的(de)全部(bu)(bu)(bu)(bu)(bu)功(gong)率。

　　圖1，動態電源路徑(jing)管理框圖

　　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2，靜(jing)態電源路徑(jing)管理的瞬態電流響應

　　靜態電源路徑管路

　　靜態電源路徑管理(SPPM)是一(yi)個(ge)簡化的(de)解決辦法(fa)，能達到上面提(ti)到的(de)第一(yi)個(ge)目(mu)標，不會出現電壓下降的(de)情況。然而，它沒法(fa)解決第二個(ge)問(wen)題，即區分(fen)系統(tong)和充(chong)電電流的(de)優(you)先級。

　　SPPM機制的概(gai)念(nian)如(ru)圖(tu)3所示。主(zhu)FET QMAIN是充電(dian)(dian)(dian)(dian)控制器元件。開(kai)(kai)關SW1連(lian)接電(dian)(dian)(dian)(dian)池和系(xi)統(tong)(tong)。當電(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)壓高于VPPM閾值(zhi)(系(xi)統(tong)(tong)的最小工(gong)作(zuo)電(dian)(dian)(dian)(dian)壓，一般是3.2V)，開(kai)(kai)關導通，無論外部(bu)電(dian)(dian)(dian)(dian)源存在與否，電(dian)(dian)(dian)(dian)池都會(hui)連(lian)到系(xi)統(tong)(tong)。這樣，當系(xi)統(tong)(tong)突然汲取電(dian)(dian)(dian)(dian)流時，由于開(kai)(kai)關已經處在導通狀態，電(dian)(dian)(dian)(dian)池能(neng)夠隨時提供系(xi)統(tong)(tong)所需的電(dian)(dian)(dian)(dian)流。這樣就解決了(le)電(dian)(dian)(dian)(dian)壓降和電(dian)(dian)(dian)(dian)流畸(ji)變問(wen)題，如(ru)圖(tu)5所示。由于在設計中僅需要一個調整元件對電(dian)(dian)(dian)(dian)池的充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)壓或電(dian)(dian)(dian)(dian)流進(jin)行調節，IC設計成本和復雜度也(ye)降低了(le)。如(ru)果需要極低阻抗的開(kai)(kai)關，圖(tu)3中的開(kai)(kai)關SW1可以放到IC外面來實現，進(jin)一步降低成本。

　　如果(guo)電(dian)(dian)池電(dian)(dian)壓(ya)低于VPPM的(de)(de)(de)閾(yu)值，SW1就開啟(qi)，VOUT將(jiang)變成4.2V的(de)(de)(de)恒壓(ya)源，向系統供電(dian)(dian)。與此同時(shi)，50mA的(de)(de)(de)恒流源ITRKL被激活，在涓流模式下對(dui)電(dian)(dian)池充電(dian)(dian)，直(zhi)到電(dian)(dian)壓(ya)達(da)到VPPM閾(yu)值(有一(yi)定滯后)，然后SW1會關閉，電(dian)(dian)池就連到系統上(shang)。這樣就解決了沒(mei)電(dian)(dian)電(dian)(dian)池的(de)(de)(de)啟(qi)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(tu)3，靜態電源路徑管理(li)框圖(tu)

　　圖4，靜(jing)態電源路徑(jing)管理控制流程(cheng)

　　圖5，靜態(tai)電源路徑管理的瞬態(tai)電流響應