圖1. USB供電的單節NiMH電池開關模式充電器

       雖然表(biao)面上Li+電(dian)(dian)池已經占據(ju)整個便(bian)攜世界(jie)，但NiMH電(dian)(dian)池并沒有(you)被(bei)完(wan)全遺棄(qi)。令人(ren)吃驚的(de)是(shi)，盡管單位重量(liang)的(de)能(neng)量(liang)仍(reng)然有(you)較大差(cha)距，但其單位體積的(de)能(neng)量(liang)僅比Li+電(dian)(dian)池低大約15%。NiMH電(dian)(dian)池的(de)最(zui)大缺點是(shi)自放電(dian)(dian)率較高，混合(he)型(xing)NiMH電(dian)(dian)池在很(hen)大程度(du)解決了這(zhe)一問題，例如(ru)SANYO? Eneloop?電(dian)(dian)池，靜(jing)態下(xia)一年(nian)之后仍(reng)然能(neng)夠保留85%的(de)電(dian)(dian)量(liang)。NiMH電(dian)(dian)池的(de)吸引力在于成(cheng)本(ben)低、安全性(xing)高、用戶更換方(fang)便(bian)等(deng)，至少(shao)標準電(dian)(dian)池具(ju)備這(zhe)些優(you)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(guan)頻率大(da)約(yue)為(wei)150kHz，電(dian)(dian)(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流為(wei)1.1A (典(dian)型AA型NiMH電(dian)(dian)(dian)(dian)(dian)池在(zai)(zai)大(da)約(yue)0.5°C條(tiao)件下)。由于降壓轉換(huan)器(qi)將5V、500mA轉換(huan)成電(dian)(dian)(dian)(dian)(dian)池充(chong)電(dian)(dian)(dian)(dian)(dian)時(shi)的1.5V、1.1A，電(dian)(dian)(dian)(dian)(dian)路供給電(dian)(dian)(dian)(dian)(dian)池的電(dian)(dian)(dian)(dian)(dian)流(1.1A)大(da)于從USB接(jie)口(kou)獲得(de)的電(dian)(dian)(dian)(dian)(dian)流(500mA)。需要注意的是，由于在(zai)(zai)低(di)充(chong)電(dian)(dian)(dian)(dian)(dian)速率下不能(neng)正確(que)(que)判斷充(chong)電(dian)(dian)(dian)(dian)(dian)終止，只能(neng)采用500mA或更(geng)大(da)功(gong)率的端(duan)口(kou)進行充(chong)電(dian)(dian)(dian)(dian)(dian)。所(suo)以，當枚(mei)舉確(que)(que)定只有100mA電(dian)(dian)(dian)(dian)(dian)流可用時(shi)，不應激活充(chong)電(dian)(dian)(dian)(dian)(dian)。系統(tong)通過(guo)關(guan)閉TMR上(shang)的Q2，使定時(shi)器(qi)電(dian)(dian)(dian)(dian)(dian)阻(zu)懸空，停(ting)止充(chong)電(dian)(dian)(dian)(dian)(dian)。

     該充(chong)電(dian)器(qi)另外一項特別有用(yong)(yong)的(de)功能是(shi)(shi)：通過檢測電(dian)池阻抗確(que)定接入的(de)是(shi)(shi)否為(wei)堿性電(dian)池或故障電(dian)池，檢測到這(zhe)種狀況(kuang)時將禁止充(chong)電(dian)。這(zhe)就允許(xu)用(yong)(yong)戶(hu)在緊急情況(kuang)下(xia)插入堿性電(dian)池，無需擔心(xin)意外充(chong)電(dian)。