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
   考慮一(yi)下(xia)新式(shi)手(shou)持式(shi)設(she)備(bei)，面(mian)向(xiang)消費者的(de)(de)設(she)備(bei)和工業設(she)備(bei)都可能(neng)包括蜂窩電(dian)(dian)(dian)(dian)(dian)話(hua)調(diao)制解(jie)調(diao)器、Wi-Fi 模塊、藍牙模塊、大(da)尺寸(cun)背光照明顯示屏… 等等。很(hen)(hen)多(duo)手(shou)持式(shi)設(she)備(bei)的(de)(de)電(dian)(dian)(dian)(dian)(dian)源(yuan)架(jia)構(gou)都與蜂窩電(dian)(dian)(dian)(dian)(dian)話(hua)的(de)(de)非常(chang)相似(si)。一(yi)般情況下(xia)，用(yong)一(yi)個(ge) 3.7V 的(de)(de)鋰(li)離(li)(li)子(zi)電(dian)(dian)(dian)(dian)(dian)池(chi)作為(wei)主(zhu)電(dian)(dian)(dian)(dian)(dian)源(yuan)，因為(wei)鋰(li)離(li)(li)子(zi)電(dian)(dian)(dian)(dian)(dian)池(chi)按重量和按體積的(de)(de)能(neng)量密度都很(hen)(hen)高(gao) (單位分別為(wei) Wh/kg 和 Wh/m3)。過(guo)去，很(hen)(hen)多(duo)大(da)功率設(she)備(bei)都采用(yong) 7.4V 鋰(li)離(li)(li)子(zi)電(dian)(dian)(dian)(dian)(dian)池(chi)，以(yi)降低(di)電(dian)(dian)(dian)(dian)(dian)流要求，不過(guo)低(di)價 5V 電(dian)(dian)(dian)(dian)(dian)源(yuan)管理(li) IC 的(de)(de)上市已經促使(shi)越來越多(duo)的(de)(de)手(shou)持式(shi)設(she)備(bei)采用(yong)了電(dian)(dian)(dian)(dian)(dian)壓更(geng)低(di)的(de)(de)架(jia)構(gou)。平(ping)板電(dian)(dian)(dian)(dian)(dian)腦(nao)(nao)很(hen)(hen)好地說明了這(zhe)一(yi)點：一(yi)個(ge)典型(xing)的(de)(de)平(ping)板電(dian)(dian)(dian)(dian)(dian)腦(nao)(nao)有(you)極多(duo)的(de)(de)功能(neng)以(yi)及非常(chang)大(da)的(de)(de)顯示屏 (就便攜式(shi)設(she)備(bei)而(er)言)。用(yong) 3.7V 電(dian)(dian)(dian)(dian)(dian)池(chi)供電(dian)(dian)(dian)(dian)(dian)時(shi)，其容(rong)量必須以(yi)數千(qian)毫安-小時(shi)計(ji)算。為(wei)了在幾個(ge)小時(shi)內給這(zhe)樣一(yi)個(ge)電(dian)(dian)(dian)(dian)(dian)池(chi)充(chong)滿電(dian)(dian)(dian)(dian)(dian)，需要數千(qian) mA 的(de)(de)充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流。      

   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(gao)效地(di)(di)(di)利用 USB 端口(kou)提供 2.5W 至 4.5W 功率。此(ci)外，器(qi)件(jian)(jian)必(bi)須保(bao)護敏感的(de)下游低壓組件(jian)(jian)免受可能(neng)出現過(guo)壓情況所(suo)導(dao)致的(de)損壞，同(tong)時(shi)必(bi)須無縫地(di)(di)(di)將大電(dian)(dian)流(liu)從 USB 輸入、交流(liu)適配器(qi)或(huo)電(dian)(dian)池(chi)(chi)傳送(song)到負載，并最大限(xian)度(du)地(di)(di)(di)降低功耗(hao)。另外，該 IC 還必(bi)須安全地(di)(di)(di)管理電(dian)(dian)池(chi)(chi)充電(dian)(dian)算法，并監視關(guan)鍵的(de)系統參數。