原子(zi)(zi)電(dian)子(zi)(zi)有(you)很多(duo)能級,當(dang)電(dian)子(zi)(zi)從高能級向(xiang)低能級躍遷時,電(dian)子(zi)(zi)的能量(liang)就(jiu)減少(shao)了,而減少(shao)的能量(liang)則轉變(bian)成(cheng)光(guang)子(zi)(zi)發射出(chu)去(qu)。大量(liang)的這些光(guang)子(zi)(zi)就(jiu)是激光(guang)了。
LED發光原理類似。不過(guo)不同的是,LED并不是通(tong)過(guo)原子內部的電子躍(yue)變來(lai)發(fa)光的,而是通(tong)過(guo)將(jiang)電壓加(jia)在LED的PN結兩端,使PN結本身(shen)形成一個(ge)能級(實際上,是一(yi)系列的能級),然后(hou)電子在這個能級上躍變并產生光子來發光的。
二、led手電筒電路圖
強光手電筒電路圖
這個電路(lu)(lu)大致(zhi)可(ke)以分為(wei)三部分:1、整流降(jiang)壓部分;2、電池(chi);3、發光回路(lu)(lu)部分
1、整流(liu)降壓(ya)部分由(you)AC1、AC2、R1、C1、D1-D4、R及交(jiao)流(liu)指(zhi)示燈組(zu)成。220V交(jiao)流(liu)電(dian)源接AC1、AC2。經R1、C1分壓(ya)后(hou)得(de)到(dao)約6V的交(jiao)流(liu)電(dian)壓(ya)。經橋式整流(liu)后(hou)在電(dian)池的負極(ji)(ji)和正極(ji)(ji)之間得(de)到(dao)約4.2V的直(zhi)流(liu)電(dian)壓(ya)。
2、電池部分(fen)工作狀態有3種:充電、放(fang)電、不(bu)充也不(bu)放(fang)。
(1)如果插上交流電(dian)(dian),電(dian)(dian)池(chi)(chi)兩端接(jie)反極性電(dian)(dian)壓且大于電(dian)(dian)池(chi)(chi)放電(dian)(dian)電(dian)(dian)壓,電(dian)(dian)池(chi)(chi)就處于充電(dian)(dian)狀態(不管開關有沒有閉(bi)合都充電(dian)(dian))。
(2)不(bu)插交流電(dian)、閉合開(kai)關,發光(guang)回路接通,燈(deng)亮,電(dian)池放電(dian)。
(3)如果不插交流電,斷開開關,電池不充(chong)電也不放電。
3、發光(guang)(guang)回路由開關、白(bai)光(guang)(guang)發光(guang)(guang)二極管(guan)及其限流(liu)(liu)(liu)電(dian)阻與電(dian)池共同組成(cheng)。只(zhi)要開關閉合燈就亮。插交流(liu)(liu)(liu)電(dian)由交流(liu)(liu)(liu)供(gong)電(dian),否則由電(dian)池供(gong)電(dian)。
這個簡單,C1是(shi)限流(liu)電(dian)(dian)(dian)(dian)容,R1是(shi)C1的(de)泄放電(dian)(dian)(dian)(dian)阻(防(fang)止在(zai)(zai)拔掉插頭后(hou),C1的(de)殘存(cun)電(dian)(dian)(dian)(dian)壓(ya)(ya)通過插頭電(dian)(dian)(dian)(dian)人),D1~D4構成了橋式整(zheng)流(liu),將C1限流(liu)后(hou)的(de)交流(liu)變為(wei)了直流(liu),然后(hou)送給(gei)電(dian)(dian)(dian)(dian)池(chi)充(chong)電(dian)(dian)(dian)(dian),因為(wei)電(dian)(dian)(dian)(dian)池(chi)的(de)存(cun)在(zai)(zai),所以限流(liu)后(hou)的(de)電(dian)(dian)(dian)(dian)壓(ya)(ya)不會低于(yu)電(dian)(dian)(dian)(dian)池(chi)電(dian)(dian)(dian)(dian)壓(ya)(ya)(相當(dang)于(yu)穩(wen)壓(ya)(ya)作(zuo)用),考慮(lv)到二極管的(de)降壓(ya)(ya)作(zuo)用,因此才有(you)了D1那端為(wei)6V電(dian)(dian)(dian)(dian)壓(ya)(ya)的(de)緣故。
LED10及330歐電阻(zu)是充電指示燈(deng)。至于燈(deng)后面的部分,就是5組LED加限流電阻(zu)構成的照(zhao)明電路,沒什么(me)特別(bie)的。
其實,嚴格(ge)地說那個電(dian)(dian)(dian)容不是(shi)降(jiang)(jiang)壓(ya)(ya)電(dian)(dian)(dian)容,而只是(shi)限(xian)流,降(jiang)(jiang)壓(ya)(ya)還(huan)需(xu)要(yao)配合后面的穩(wen)壓(ya)(ya)二極管等。但是(shi),人們通常(chang)喜(xi)歡將(jiang)這個電(dian)(dian)(dian)路叫“電(dian)(dian)(dian)容降(jiang)(jiang)壓(ya)(ya)”電(dian)(dian)(dian)路。
如果(guo)AC2電(dian)(dian)(dian)壓(ya)高(gao)(gao),電(dian)(dian)(dian)流經(jing)D4、電(dian)(dian)(dian)池、D2再(zai)到AC1。如果(guo)AC1電(dian)(dian)(dian)壓(ya)高(gao)(gao),電(dian)(dian)(dian)流經(jing)D1、電(dian)(dian)(dian)池、D3再(zai)到AC2。因此(ci),不管AC幾高(gao)(gao),總是上(shang)邊的電(dian)(dian)(dian)壓(ya)高(gao)(gao),都變成了(le)上(shang)正下負(fu),即實現了(le)整流。
如果沒D2,那么(me)當AC1電(dian)壓高的時候,會(hui)通過(guo)D3直接向AC2短路(lu)。