便攜式電源的應用范圍很廣，也很多樣化。產品包括消耗 uW 級平均功率的無線傳感器節點以及可用小車推著的、電池組耗電數百瓦-時的醫療或數據采集系統。不過，盡管應用種類很多，仍然出現了幾個趨勢，設計師日益需要給產品提供更大的功率，以支持不斷增多的功能，同時也在考慮怎樣用任何可用電源給電池充電。要滿足第一種需求，就要提高電池容量。不幸的是，用戶大多比較心急，容量提高以后，還必須在一個合理的時間內充滿電，這就導致要增大充電電流。要滿足第二種需求，就要求電池充電解決方案提供極大的靈活性。本文將更詳細地討論這些問題。
更大的功率
   考(kao)慮(lv)一下新(xin)式(shi)手持式(shi)設(she)(she)備(bei)(bei)，面(mian)向(xiang)消費者的(de)(de)(de)設(she)(she)備(bei)(bei)和(he)工業設(she)(she)備(bei)(bei)都可能包括蜂窩(wo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)話(hua)調制解(jie)調器(qi)、Wi-Fi 模(mo)塊、藍牙模(mo)塊、大(da)尺(chi)寸背光照明顯(xian)示屏… 等等。很(hen)多(duo)手持式(shi)設(she)(she)備(bei)(bei)的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源架構都與蜂窩(wo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)話(hua)的(de)(de)(de)非常相(xiang)似。一般(ban)情況下，用一個 3.7V 的(de)(de)(de)鋰(li)離(li)(li)子電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)作為主(zhu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源，因為鋰(li)離(li)(li)子電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)按重量和(he)按體積的(de)(de)(de)能量密(mi)度(du)都很(hen)高 (單位分別為 Wh/kg 和(he) Wh/m3)。過去，很(hen)多(duo)大(da)功(gong)率設(she)(she)備(bei)(bei)都采用 7.4V 鋰(li)離(li)(li)子電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)，以(yi)降低(di)(di)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)要求，不(bu)過低(di)(di)價 5V 電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)源管理 IC 的(de)(de)(de)上(shang)市已經促(cu)使越來越多(duo)的(de)(de)(de)手持式(shi)設(she)(she)備(bei)(bei)采用了(le)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓更低(di)(di)的(de)(de)(de)架構。平板電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)腦很(hen)好地說明了(le)這(zhe)一點(dian)：一個典型的(de)(de)(de)平板電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)腦有極多(duo)的(de)(de)(de)功(gong)能以(yi)及非常大(da)的(de)(de)(de)顯(xian)示屏 (就便攜式(shi)設(she)(she)備(bei)(bei)而(er)言(yan))。用 3.7V 電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)供電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)時，其容量必須以(yi)數(shu)千(qian)毫(hao)安(an)-小時計算。為了(le)在幾個小時內(nei)給(gei)這(zhe)樣(yang)一個電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)充滿(man)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，需要數(shu)千(qian) mA 的(de)(de)(de)充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)。      

   然而，如果沒有大電流交流適配器，盡管充電電流這么高，也不能防止消費者用 USB 端口給大功率設備充電的想法。為了滿足這種需求，當交流適配器可用時，電池充電器必須能以大電流 (>2A) 充電，而在沒有交流適配器可用時，電池充電器必(bi)須仍能(neng)高效(xiao)地(di)利用 USB 端口提供 2.5W 至(zhi) 4.5W 功(gong)率。此外，器(qi)件必(bi)須保護敏感的(de)下游(you)低壓組件免受可能(neng)出現過壓情況所導致的(de)損壞，同時必(bi)須無縫(feng)地(di)將大電(dian)(dian)流從 USB 輸入、交流適(shi)配器(qi)或(huo)電(dian)(dian)池(chi)傳送(song)到負載，并最大限(xian)度地(di)降低功(gong)耗(hao)。另外，該 IC 還必(bi)須安全地(di)管理電(dian)(dian)池(chi)充電(dian)(dian)算法(fa)，并監(jian)視關(guan)鍵的(de)系統參數。