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(yi)經占據整個便攜世界，但NiMH電(dian)池(chi)并沒有被(bei)完全(quan)遺棄。令人吃(chi)驚的(de)(de)(de)是，盡管(guan)單位(wei)重量的(de)(de)(de)能(neng)量仍然有較大(da)(da)(da)(da)差距(ju)，但其單位(wei)體積的(de)(de)(de)能(neng)量僅比Li+電(dian)池(chi)低大(da)(da)(da)(da)約15%。NiMH電(dian)池(chi)的(de)(de)(de)最大(da)(da)(da)(da)缺點是自放電(dian)率較高(gao)，混合型NiMH電(dian)池(chi)在很大(da)(da)(da)(da)程度解(jie)決了(le)這(zhe)(zhe)一問題，例如SANYO? Eneloop?電(dian)池(chi)，靜態(tai)下一年之(zhi)后仍然能(neng)夠保留(liu)85%的(de)(de)(de)電(dian)量。NiMH電(dian)池(chi)的(de)(de)(de)吸引(yin)力在于成本低、安全(quan)性高(gao)、用(yong)戶更(geng)換方便等，至少標準電(dian)池(chi)具備這(zhe)(zhe)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(da)約為150kHz，電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)充(chong)電(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)流為1.1A (典型(xing)AA型(xing)NiMH電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)在(zai)(zai)大(da)約0.5°C條件下(xia))。由于(yu)降壓轉換(huan)器將(jiang)5V、500mA轉換(huan)成電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)充(chong)電(dian)(dian)(dian)(dian)(dian)時的1.5V、1.1A，電(dian)(dian)(dian)(dian)(dian)路(lu)供給電(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的電(dian)(dian)(dian)(dian)(dian)流(1.1A)大(da)于(yu)從USB接口(kou)獲得的電(dian)(dian)(dian)(dian)(dian)流(500mA)。需(xu)要注(zhu)意的是，由于(yu)在(zai)(zai)低充(chong)電(dian)(dian)(dian)(dian)(dian)速率(lv)下(xia)不能正確判斷充(chong)電(dian)(dian)(dian)(dian)(dian)終(zhong)止(zhi)，只(zhi)(zhi)能采用500mA或更大(da)功率(lv)的端口(kou)進行(xing)充(chong)電(dian)(dian)(dian)(dian)(dian)。所以，當枚舉確定(ding)只(zhi)(zhi)有100mA電(dian)(dian)(dian)(dian)(dian)流可(ke)用時，不應激(ji)活充(chong)電(dian)(dian)(dian)(dian)(dian)。系統通過(guo)關閉TMR上的Q2，使(shi)定(ding)時器電(dian)(dian)(dian)(dian)(dian)阻(zu)懸空，停止(zhi)充(chong)電(dian)(dian)(dian)(dian)(dian)。

     該充(chong)電(dian)器另(ling)外一項特別有用的功(gong)能是：通(tong)過檢(jian)(jian)測電(dian)池(chi)(chi)阻抗確(que)定接入的是否為堿(jian)性(xing)電(dian)池(chi)(chi)或(huo)故(gu)障(zhang)電(dian)池(chi)(chi)，檢(jian)(jian)測到這種(zhong)狀況時將禁止(zhi)充(chong)電(dian)。這就允(yun)許用戶(hu)在(zai)緊急情況下插入堿(jian)性(xing)電(dian)池(chi)(chi)，無需擔心意(yi)外充(chong)電(dian)。