圖1. USB供電的單節NiMH電池開關模式充電器

       雖(sui)然(ran)表面上Li+電(dian)(dian)(dian)池(chi)已經占據整(zheng)個便攜世(shi)界，但(dan)NiMH電(dian)(dian)(dian)池(chi)并沒有被完全(quan)(quan)遺棄(qi)。令(ling)人吃驚(jing)的(de)是(shi)(shi)，盡(jin)管(guan)單位重量(liang)的(de)能量(liang)仍(reng)然(ran)有較大差距，但(dan)其單位體積的(de)能量(liang)僅比Li+電(dian)(dian)(dian)池(chi)低大約15%。NiMH電(dian)(dian)(dian)池(chi)的(de)最大缺點是(shi)(shi)自(zi)放(fang)電(dian)(dian)(dian)率較高(gao)，混合(he)型NiMH電(dian)(dian)(dian)池(chi)在很大程(cheng)度解決了這一問題，例如SANYO? Eneloop?電(dian)(dian)(dian)池(chi)，靜態下一年之后仍(reng)然(ran)能夠保留85%的(de)電(dian)(dian)(dian)量(liang)。NiMH電(dian)(dian)(dian)池(chi)的(de)吸引力在于成本低、安全(quan)(quan)性高(gao)、用戶更換方便等，至少標準(zhun)電(dian)(dian)(dian)池(chi)具備(bei)這些(xie)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(guan)頻(pin)率(lv)大約為150kHz，電(dian)(dian)(dian)池(chi)充(chong)(chong)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)為1.1A (典型AA型NiMH電(dian)(dian)(dian)池(chi)在(zai)大約0.5°C條件下)。由于(yu)降壓(ya)轉(zhuan)換器(qi)將5V、500mA轉(zhuan)換成電(dian)(dian)(dian)池(chi)充(chong)(chong)電(dian)(dian)(dian)時的(de)1.5V、1.1A，電(dian)(dian)(dian)路供給電(dian)(dian)(dian)池(chi)的(de)電(dian)(dian)(dian)流(liu)(1.1A)大于(yu)從USB接(jie)口獲得(de)的(de)電(dian)(dian)(dian)流(liu)(500mA)。需(xu)要注意的(de)是，由于(yu)在(zai)低充(chong)(chong)電(dian)(dian)(dian)速率(lv)下不(bu)(bu)能正確判斷充(chong)(chong)電(dian)(dian)(dian)終止，只(zhi)能采用500mA或更(geng)大功(gong)率(lv)的(de)端口進行充(chong)(chong)電(dian)(dian)(dian)。所以，當枚舉確定只(zhi)有100mA電(dian)(dian)(dian)流(liu)可用時，不(bu)(bu)應(ying)激(ji)活充(chong)(chong)電(dian)(dian)(dian)。系(xi)統通過關(guan)閉TMR上的(de)Q2，使定時器(qi)電(dian)(dian)(dian)阻(zu)懸(xuan)空，停止充(chong)(chong)電(dian)(dian)(dian)。

     該(gai)充電(dian)(dian)器(qi)另外(wai)(wai)一項特別有用(yong)的(de)功能是(shi)：通過檢測電(dian)(dian)池(chi)阻抗確定接入的(de)是(shi)否為堿性電(dian)(dian)池(chi)或故障電(dian)(dian)池(chi)，檢測到這種狀況(kuang)(kuang)時將(jiang)禁止充電(dian)(dian)。這就允許用(yong)戶在緊急情況(kuang)(kuang)下插入堿性電(dian)(dian)池(chi)，無需(xu)擔(dan)心意外(wai)(wai)充電(dian)(dian)。