該充電器設計具有電池極性(xing)自(zi)動(dong)識(shi)別(bie)電路，免去了以往需(xu)要人工轉換極性(xing)的操作，使用起來更加方便

一、電路原理

　　電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)如附圖所示：Q1及(ji)外圍元件構成(cheng)(cheng)自激振蕩器．經變壓器B降壓、D5整流后在C4上(shang)得到(dao)9.4v的(de)直流電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓。通(tong)過R6限(xian)流．Q10(TL431)穩(wen)壓后．在Q3發(fa)射極輸出4.2v電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓供(gong)鋰(li)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)。其(qi)極性自動(dong)識別電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)由Q5～Q8、R12～R15組成(cheng)(cheng)。當(dang)A點(dian)接(jie)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)正(zheng)極，B點(dian)接(jie)負(fu)極時，Q8因為有R12提(ti)供(gong)正(zheng)偏電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓而導(dao)通(tong)，Q5由R14提(ti)供(gong)偏壓導(dao)通(tong)。充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流由Q5→A點(dian)→電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)E→B點(dian)→Q8的(de)C極形(xing)成(cheng)(cheng)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)回路(lu)(lu)。當(dang)A點(dian)接(jie)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)負(fu)極，而B接(jie)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)正(zheng)極時充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流則由Q7→B點(dian)→電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)E→A點(dian)→Q6的(de)C極形(xing)成(cheng)(cheng)充(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)回路(lu)(lu)．從(cong)而完成(cheng)(cheng)自動(dong)識別電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)極性的(de)功能。

　　當有充電電流流過(guo)R6時，Q4導通(tong)，LED1閃爍發光(guang)(LED1為(wei)(wei)(wei)自帶振蕩器的三色發光(guang)二極管，能夠隨機(ji)變幻出(chu)多彩的閃光(guang))。充電完成后Q4因為(wei)(wei)(wei)沒有足夠的導通(tong)電壓(ya)而截(jie)止(zhi)，LED1熄(xi)滅。LED2為(wei)(wei)(wei)電源指示燈。

 電路原理圖

 　二、常見故障排(pai)除

　　故障(zhang)一(yi)：電源指示(shi)燈不亮。

　　檢(jian)修：測Q1管正常(chang),但b極無偏置電壓；再測R2為開(kai)路,更換R2后故障排(pai)除(chu)。

　　故障(zhang)二：電源指示燈不亮。檢修：測Q1已經擊穿,再測R1及R3均已開(kai)路。測其他元件正常，更換上述元件后故障(zhang)排除(chu)。