圖1. USB供電的單節NiMH電池開關模式充電器

       雖然表面上Li+電(dian)池(chi)已經占(zhan)據整個便攜世界，但NiMH電(dian)池(chi)并沒有(you)被完全(quan)遺棄。令人吃驚(jing)的(de)(de)是，盡(jin)管單位重量(liang)(liang)的(de)(de)能(neng)量(liang)(liang)仍然有(you)較(jiao)大(da)差(cha)距，但其單位體積的(de)(de)能(neng)量(liang)(liang)僅比(bi)Li+電(dian)池(chi)低(di)大(da)約15%。NiMH電(dian)池(chi)的(de)(de)最(zui)大(da)缺(que)點是自放電(dian)率較(jiao)高，混合型NiMH電(dian)池(chi)在(zai)(zai)很(hen)大(da)程度解決了(le)這一(yi)問(wen)題，例如(ru)SANYO? Eneloop?電(dian)池(chi)，靜態下一(yi)年之后仍然能(neng)夠保留85%的(de)(de)電(dian)量(liang)(liang)。NiMH電(dian)池(chi)的(de)(de)吸引力在(zai)(zai)于成本低(di)、安全(quan)性高、用戶更(geng)換方便等，至少標準電(dian)池(chi)具備這些優勢。

      圖1所示便攜設備由一節AA型NiMH電池供電，利用USB充電。DS2710充電器開關頻率(lv)大約為150kHz，電(dian)(dian)(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流(liu)為1.1A (典(dian)型(xing)(xing)AA型(xing)(xing)NiMH電(dian)(dian)(dian)(dian)(dian)池在大約0.5°C條件下(xia)(xia))。由(you)于降壓轉換器將(jiang)5V、500mA轉換成電(dian)(dian)(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)(dian)(dian)時的(de)(de)(de)1.5V、1.1A，電(dian)(dian)(dian)(dian)(dian)路(lu)供給電(dian)(dian)(dian)(dian)(dian)池的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)流(liu)(1.1A)大于從USB接口獲得的(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)流(liu)(500mA)。需要(yao)注意(yi)的(de)(de)(de)是，由(you)于在低充(chong)電(dian)(dian)(dian)(dian)(dian)速率(lv)下(xia)(xia)不(bu)能正(zheng)確(que)判斷充(chong)電(dian)(dian)(dian)(dian)(dian)終止，只能采(cai)用500mA或更(geng)大功率(lv)的(de)(de)(de)端(duan)口進(jin)行充(chong)電(dian)(dian)(dian)(dian)(dian)。所以，當枚舉確(que)定只有100mA電(dian)(dian)(dian)(dian)(dian)流(liu)可用時，不(bu)應(ying)激活充(chong)電(dian)(dian)(dian)(dian)(dian)。系(xi)統通(tong)過關閉TMR上的(de)(de)(de)Q2，使定時器電(dian)(dian)(dian)(dian)(dian)阻懸(xuan)空，停(ting)止充(chong)電(dian)(dian)(dian)(dian)(dian)。

     該(gai)充電(dian)器另外一項特別有用的功能是(shi)：通過檢測電(dian)池阻抗(kang)確(que)定接(jie)入的是(shi)否(fou)為堿(jian)(jian)性電(dian)池或故障電(dian)池，檢測到(dao)這(zhe)種狀(zhuang)況時(shi)將禁止充電(dian)。這(zhe)就允許用戶(hu)在緊急情況下插入堿(jian)(jian)性電(dian)池，無需(xu)擔心(xin)意(yi)外充電(dian)。