無(wu)論是(shi)(shi)做什么用(yong)途，或(huo)制造商是(shi)(shi)誰，手(shou)持式電(dian)(dian)(dian)(dian)(dian)子(zi)設(she)(she)備(bei)都有(you)一(yi)(yi)個(ge)共同的特性：一(yi)(yi)個(ge)可充(chong)電(dian)(dian)(dian)(dian)(dian)的電(dian)(dian)(dian)(dian)(dian)池，多數情(qing)況下(xia)還有(you)一(yi)(yi)個(ge)內建(jian)的充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)路(lu)。當一(yi)(yi)個(ge)AC適配器這樣的外部電(dian)(dian)(dian)(dian)(dian)源或(huo)一(yi)(yi)個(ge)USB端(duan)(duan)口接(jie)(jie)到手(shou)持設(she)(she)備(bei)的輸入端(duan)(duan)，充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)路(lu)將對(dui)電(dian)(dian)(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)(dian)(dian)。當接(jie)(jie)到外部電(dian)(dian)(dian)(dian)(dian)源時，如(ru)果設(she)(she)備(bei)正處在(zai)開機狀態，理想的情(qing)形是(shi)(shi)，設(she)(she)備(bei)應當從(cong)外部電(dian)(dian)(dian)(dian)(dian)源汲取盡可能多的功率，以(yi)節省電(dian)(dian)(dian)(dian)(dian)池壽命(ming)。要實(shi)現這個(ge)功能則(ze)需要一(yi)(yi)個(ge)自動的電(dian)(dian)(dian)(dian)(dian)源選擇電(dian)(dian)(dian)(dian)(dian)路(lu)，這個(ge)電(dian)(dian)(dian)(dian)(dian)路(lu)通常(chang)是(shi)(shi)集成在(zai)充(chong)電(dian)(dian)(dian)(dian)(dian)控制IC內。設(she)(she)計者可以(yi)從(cong)動態或(huo)靜態電(dian)(dian)(dian)(dian)(dian)源路(lu)徑管理當中選擇其中的一(yi)(yi)種，進行電(dian)(dian)(dian)(dian)(dian)源管理。

　　在(zai)(zai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)供電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)手持設備中(zhong)，動態(tai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)路(lu)(lu)徑管理(DPPM)是(shi)更流(liu)(liu)行(xing)的(de)機制(zhi)。DPPM功能框圖如圖1所(suo)示(shi)。主通(tong)路(lu)(lu)元(yuan)(yuan)件QMAIN是(shi)一個(ge)(ge)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓穩(wen)壓器(qi)，提(ti)供一個(ge)(ge)經過(guo)穩(wen)壓的(de)輸出(chu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓VOUT。第(di)二個(ge)(ge)通(tong)路(lu)(lu)元(yuan)(yuan)件QCharge是(shi)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)控(kong)制(zhi)元(yuan)(yuan)件，由VOUT供電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，提(ti)供恒(heng)定的(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)或(huo)恒(heng)定的(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓對電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。在(zai)(zai)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)期(qi)間，如果輸出(chu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)超過(guo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)的(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)限值，QCharge就會變成一個(ge)(ge)開關，將電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)連到系統(tong)上，提(ti)供一部分(fen)所(suo)需(xu)的(de)輸出(chu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)。

　　DPPM有幾(ji)個(ge)好處(chu)。首先，當(dang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)完全(quan)放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)時(電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)耗盡的(de)(de)(de)(de)情(qing)況(kuang))，DPPM能讓外部(bu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)立刻(ke)給(gei)設備供(gong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。如果沒有電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)路(lu)(lu)(lu)徑(jing)管(guan)理，在電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)量耗盡的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)被(bei)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)到(dao)(dao)(dao)系(xi)統(tong)能夠啟動(dong)的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓等級之前(一(yi)(yi)般是(shi)(shi)高于3V)，系(xi)統(tong)是(shi)(shi)無(wu)法上電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)(de)。這個(ge)等待(dai)周(zhou)期取決于充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)的(de)(de)(de)(de)涓流(liu)(liu)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)設定，可(ke)能是(shi)(shi)幾(ji)分(fen)鐘(zhong)(zhong)到(dao)(dao)(dao)十(shi)分(fen)鐘(zhong)(zhong)的(de)(de)(de)(de)時間(jian)。其次，當(dang)用外部(bu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)對電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)時，DPPM會把(ba)來自外部(bu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)分(fen)到(dao)(dao)(dao)兩個(ge)路(lu)(lu)(lu)徑(jing)中(zhong)，一(yi)(yi)條(tiao)路(lu)(lu)(lu)徑(jing)為(wei)手持(chi)設備提供(gong)必要的(de)(de)(de)(de)功(gong)率，另(ling)一(yi)(yi)條(tiao)路(lu)(lu)(lu)徑(jing)輸出充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)，來給(gei)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。當(dang)外部(bu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)的(de)(de)(de)(de)輸入電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)達到(dao)(dao)(dao)限值時，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)路(lu)(lu)(lu)徑(jing)管(guan)理會對輸入到(dao)(dao)(dao)手持(chi)系(xi)統(tong)的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)進行優(you)先級分(fen)類。這樣如果當(dang)系(xi)統(tong)工作時，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)正(zheng)在充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)可(ke)以在最短的(de)(de)(de)(de)時間(jian)內充(chong)(chong)滿，因為(wei)動(dong)態控制的(de)(de)(de)(de)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)是(shi)(shi)為(wei)這個(ge)目標而優(you)化(hua)的(de)(de)(de)(de)。當(dang)外部(bu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)被(bei)移走(zou)時，QCharge立刻(ke)完全(quan)打開，把(ba)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)連到(dao)(dao)(dao)系(xi)統(tong)上，向(xiang)系(xi)統(tong)輸出所(suo)需的(de)(de)(de)(de)全(quan)部(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，靜態(tai)電(dian)源路(lu)徑(jing)管(guan)理的瞬(shun)態(tai)電(dian)流(liu)響應(ying)

　　靜態電源路徑管路

　　靜態電源路徑管理(SPPM)是(shi)一個簡(jian)化的(de)(de)(de)解決辦法，能達到(dao)上(shang)面提到(dao)的(de)(de)(de)第(di)一個目(mu)標(biao)，不(bu)會出現電壓下降的(de)(de)(de)情況。然(ran)而，它沒法解決第(di)二個問題，即區分系統和充(chong)電電流(liu)的(de)(de)(de)優先級。

　　SPPM機(ji)制的(de)(de)概(gai)念如圖3所示。主FET QMAIN是充電(dian)(dian)控(kong)制器元件(jian)。開(kai)關(guan)(guan)SW1連(lian)接電(dian)(dian)池(chi)和(he)系(xi)統。當(dang)電(dian)(dian)池(chi)電(dian)(dian)壓(ya)高于(yu)VPPM閾值(系(xi)統的(de)(de)最小工作電(dian)(dian)壓(ya)，一(yi)般是3.2V)，開(kai)關(guan)(guan)導(dao)通，無論外部(bu)電(dian)(dian)源存在(zai)與否，電(dian)(dian)池(chi)都會連(lian)到(dao)系(xi)統。這樣，當(dang)系(xi)統突然汲(ji)取電(dian)(dian)流(liu)(liu)時(shi)，由于(yu)開(kai)關(guan)(guan)已經處在(zai)導(dao)通狀態，電(dian)(dian)池(chi)能(neng)夠隨時(shi)提供系(xi)統所需的(de)(de)電(dian)(dian)流(liu)(liu)。這樣就解決了電(dian)(dian)壓(ya)降和(he)電(dian)(dian)流(liu)(liu)畸變問題，如圖5所示。由于(yu)在(zai)設(she)計中(zhong)僅需要一(yi)個調整元件(jian)對(dui)電(dian)(dian)池(chi)的(de)(de)充電(dian)(dian)電(dian)(dian)壓(ya)或電(dian)(dian)流(liu)(liu)進行(xing)調節，IC設(she)計成本和(he)復雜度也降低了。如果(guo)需要極低阻抗的(de)(de)開(kai)關(guan)(guan)，圖3中(zhong)的(de)(de)開(kai)關(guan)(guan)SW1可以放(fang)到(dao)IC外面來(lai)實現(xian)，進一(yi)步降低成本。

　　如果電(dian)(dian)(dian)(dian)(dian)池電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)低于VPPM的(de)閾值，SW1就開(kai)啟，VOUT將變(bian)成4.2V的(de)恒(heng)(heng)壓(ya)(ya)源，向(xiang)系(xi)統(tong)(tong)供(gong)電(dian)(dian)(dian)(dian)(dian)。與此同時，50mA的(de)恒(heng)(heng)流源ITRKL被激活(huo)，在涓流模式下對電(dian)(dian)(dian)(dian)(dian)池充電(dian)(dian)(dian)(dian)(dian)，直到(dao)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)達到(dao)VPPM閾值(有一定滯后)，然后SW1會關閉，電(dian)(dian)(dian)(dian)(dian)池就連到(dao)系(xi)統(tong)(tong)上。這樣就解(jie)決了沒電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)池的(de)啟動問題(ti)。

　　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(lu)徑(jing)管(guan)理框圖

　　圖(tu)4，靜態電(dian)源路徑管理控制流程

　　圖5，靜態電源路徑管(guan)理的瞬態電流響(xiang)應