無(wu)論是(shi)做(zuo)什么用途，或(huo)制造(zao)商是(shi)誰，手持(chi)式電(dian)(dian)(dian)(dian)子設備(bei)(bei)都有一(yi)(yi)個(ge)共同的(de)特性：一(yi)(yi)個(ge)可(ke)充電(dian)(dian)(dian)(dian)的(de)電(dian)(dian)(dian)(dian)池，多數情(qing)(qing)況下還有一(yi)(yi)個(ge)內建的(de)充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)路。當一(yi)(yi)個(ge)AC適配器這樣的(de)外(wai)部電(dian)(dian)(dian)(dian)源或(huo)一(yi)(yi)個(ge)USB端口接到手持(chi)設備(bei)(bei)的(de)輸入端，充電(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)路將對電(dian)(dian)(dian)(dian)池充電(dian)(dian)(dian)(dian)。當接到外(wai)部電(dian)(dian)(dian)(dian)源時，如果設備(bei)(bei)正處在開機狀態，理(li)想(xiang)的(de)情(qing)(qing)形(xing)是(shi)，設備(bei)(bei)應當從外(wai)部電(dian)(dian)(dian)(dian)源汲(ji)取盡可(ke)能多的(de)功率，以(yi)節省電(dian)(dian)(dian)(dian)池壽命(ming)。要實(shi)現這個(ge)功能則需要一(yi)(yi)個(ge)自動的(de)電(dian)(dian)(dian)(dian)源選(xuan)擇電(dian)(dian)(dian)(dian)路，這個(ge)電(dian)(dian)(dian)(dian)路通常是(shi)集成在充電(dian)(dian)(dian)(dian)控制IC內。設計者可(ke)以(yi)從動態或(huo)靜(jing)態電(dian)(dian)(dian)(dian)源路徑管(guan)理(li)當中選(xuan)擇其中的(de)一(yi)(yi)種，進(jin)行(xing)電(dian)(dian)(dian)(dian)源管(guan)理(li)。

　　在(zai)電(dian)(dian)(dian)(dian)(dian)池(chi)供(gong)電(dian)(dian)(dian)(dian)(dian)的(de)手持(chi)設(she)備(bei)中，動態電(dian)(dian)(dian)(dian)(dian)源(yuan)路(lu)徑管理(DPPM)是更流(liu)行的(de)機制。DPPM功能(neng)框圖(tu)如圖(tu)1所示。主通(tong)路(lu)元件QMAIN是一個(ge)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)穩壓(ya)(ya)器，提供(gong)一個(ge)經過穩壓(ya)(ya)的(de)輸出(chu)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)VOUT。第二個(ge)通(tong)路(lu)元件QCharge是充電(dian)(dian)(dian)(dian)(dian)控制元件，由(you)VOUT供(gong)電(dian)(dian)(dian)(dian)(dian)，提供(gong)恒定的(de)電(dian)(dian)(dian)(dian)(dian)流(liu)或(huo)恒定的(de)電(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)對電(dian)(dian)(dian)(dian)(dian)池(chi)充電(dian)(dian)(dian)(dian)(dian)。在(zai)充電(dian)(dian)(dian)(dian)(dian)期(qi)間(jian)，如果輸出(chu)電(dian)(dian)(dian)(dian)(dian)流(liu)超過電(dian)(dian)(dian)(dian)(dian)源(yuan)的(de)電(dian)(dian)(dian)(dian)(dian)流(liu)限值，QCharge就(jiu)會變成一個(ge)開關，將電(dian)(dian)(dian)(dian)(dian)池(chi)連(lian)到系統上，提供(gong)一部分(fen)所需的(de)輸出(chu)電(dian)(dian)(dian)(dian)(dian)流(liu)。

　　DPPM有幾(ji)個好處。首先(xian)，當電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)完全(quan)(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)(chi)(chi)耗盡(jin)的(de)(de)情況)，DPPM能(neng)(neng)讓外(wai)(wai)部(bu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)立刻給(gei)(gei)設備供電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。如果(guo)沒有電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)路(lu)徑(jing)(jing)管理(li)，在電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)量耗盡(jin)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)被充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)到(dao)(dao)系統(tong)能(neng)(neng)夠(gou)啟(qi)動的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓等(deng)級之前(一(yi)(yi)般是高于(yu)3V)，系統(tong)是無法上(shang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)。這(zhe)個等(deng)待周(zhou)期取(qu)決于(yu)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)的(de)(de)涓流(liu)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)設定，可能(neng)(neng)是幾(ji)分鐘到(dao)(dao)十分鐘的(de)(de)時間。其次，當用外(wai)(wai)部(bu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)對電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)時，DPPM會把(ba)來自外(wai)(wai)部(bu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)分到(dao)(dao)兩(liang)個路(lu)徑(jing)(jing)中，一(yi)(yi)條(tiao)(tiao)路(lu)徑(jing)(jing)為(wei)手持設備提(ti)供必要的(de)(de)功率，另一(yi)(yi)條(tiao)(tiao)路(lu)徑(jing)(jing)輸(shu)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)，來給(gei)(gei)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)充(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。當外(wai)(wai)部(bu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)的(de)(de)輸(shu)入(ru)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)達(da)到(dao)(dao)限值時，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)路(lu)徑(jing)(jing)管理(li)會對輸(shu)入(ru)到(dao)(dao)手持系統(tong)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)進行優(you)先(xian)級分類。這(zhe)樣如果(guo)當系統(tong)工作(zuo)時，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)正在充(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)(chi)(chi)可以在最短的(de)(de)時間內(nei)充(chong)(chong)滿，因為(wei)動態控制的(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)是為(wei)這(zhe)個目標而優(you)化的(de)(de)。當外(wai)(wai)部(bu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源(yuan)(yuan)(yuan)(yuan)被移走時，QCharge立刻完全(quan)(quan)打開(kai)，把(ba)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)連到(dao)(dao)系統(tong)上(shang)，向系統(tong)輸(shu)出所需的(de)(de)全(quan)(quan)部(bu)功率。

　　圖1，動態(tai)電源路徑管理框圖

　　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)電源路徑管理的(de)瞬態(tai)電流響應

　　靜態電源路徑管路

　　靜態電源路徑管理(SPPM)是一個簡化的解決辦法，能達(da)到上面(mian)提到的第一個目(mu)標，不會(hui)出現電(dian)壓下降的情況。然而，它(ta)沒法解決第二個問(wen)題，即區分(fen)系統和(he)充電(dian)電(dian)流的優先級。

　　SPPM機制的(de)(de)概念如(ru)圖(tu)3所示。主FET QMAIN是(shi)充電(dian)(dian)(dian)控制器(qi)元(yuan)件。開關(guan)SW1連(lian)接(jie)電(dian)(dian)(dian)池(chi)(chi)(chi)和(he)系(xi)統(tong)。當電(dian)(dian)(dian)池(chi)(chi)(chi)電(dian)(dian)(dian)壓(ya)高于(yu)VPPM閾值(系(xi)統(tong)的(de)(de)最小工(gong)作電(dian)(dian)(dian)壓(ya)，一般是(shi)3.2V)，開關(guan)導通(tong)，無論(lun)外部電(dian)(dian)(dian)源存在與否(fou)，電(dian)(dian)(dian)池(chi)(chi)(chi)都會(hui)連(lian)到(dao)系(xi)統(tong)。這樣，當系(xi)統(tong)突(tu)然汲(ji)取(qu)電(dian)(dian)(dian)流時，由(you)于(yu)開關(guan)已經處在導通(tong)狀態，電(dian)(dian)(dian)池(chi)(chi)(chi)能夠隨時提供系(xi)統(tong)所需的(de)(de)電(dian)(dian)(dian)流。這樣就解決了(le)電(dian)(dian)(dian)壓(ya)降和(he)電(dian)(dian)(dian)流畸變問題，如(ru)圖(tu)5所示。由(you)于(yu)在設計中僅需要一個調(diao)整元(yuan)件對電(dian)(dian)(dian)池(chi)(chi)(chi)的(de)(de)充電(dian)(dian)(dian)電(dian)(dian)(dian)壓(ya)或電(dian)(dian)(dian)流進(jin)行(xing)調(diao)節，IC設計成(cheng)本和(he)復雜(za)度(du)也降低(di)了(le)。如(ru)果(guo)需要極低(di)阻抗的(de)(de)開關(guan)，圖(tu)3中的(de)(de)開關(guan)SW1可以放到(dao)IC外面來實現，進(jin)一步降低(di)成(cheng)本。

　　如(ru)果電(dian)池電(dian)壓(ya)(ya)低(di)于VPPM的閾值，SW1就(jiu)開啟，VOUT將變成4.2V的恒壓(ya)(ya)源，向系統(tong)供電(dian)。與此同(tong)時，50mA的恒流(liu)源ITRKL被激活(huo)，在(zai)涓流(liu)模式下對電(dian)池充(chong)電(dian)，直到(dao)電(dian)壓(ya)(ya)達到(dao)VPPM閾值(有(you)一定(ding)滯后)，然后SW1會(hui)關閉(bi)，電(dian)池就(jiu)連到(dao)系統(tong)上。這樣就(jiu)解決了沒電(dian)電(dian)池的啟動問題。

　　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(tu)3，靜態電(dian)源路徑(jing)管理框圖(tu)

　　圖4，靜態電源路徑(jing)管理控制(zhi)流程(cheng)

　　圖(tu)5，靜態電源路(lu)徑管理的瞬(shun)態電流響應