TNY279設計的LED驅動電源

TNY279PN屬于TinySwitch-III系列TNY279PN是(shi)一(yi)(yi)款(kuan)更具(ju)靈活(huo)性及更大功(gong)率范圍的(de)高(gao)效離線式開關IC。TinySwitch-III功(gong)能(neng)說明TinySwitch-III結合了高(gao)電(dian)(dian)壓功(gong)率MOSFET開關同(tong)在(zai)一(yi)(yi)個(ge)(ge)設備(bei)的(de)電(dian)(dian)源(yuan)控(kong)(kong)制器(qi).不同(tong)于傳(chuan)統的(de)PWM（脈寬調制）控(kong)(kong)制器(qi)，它(ta)用(yong)簡單(dan)ON/OFF控(kong)(kong)制來調節(jie)輸出電(dian)(dian)壓.該(gai)控(kong)(kong)制器(qi)包括(kuo)一(yi)(yi)個(ge)(ge)振蕩器(qi)，使(shi)能(neng)電(dian)(dian)路（檢測及邏輯(ji)），限流(liu)狀態機。由于TinySwitch-III設計的(de)最高(gao)電(dian)(dian)流(liu)限制水(shui)平(ping)和頻(pin)率是(shi)恒定的(de)，輸送到負載的(de)功(gong)率與(yu)變壓器(qi)的(de)初(chu)級電(dian)(dian)感和峰值初(chu)級電(dian)(dian)流(liu)的(de)平(ping)方成(cheng)正比。

下圖為反(fan)激式轉換器(qi)，使(shi)用了TinySwitch-III系列(lie)的(de)(de)一(yi)(yi)個器(qi)件(jian)（U2， TNY279PN）給(gei)(gei)6個高(gao)(gao)亮度流(liu)(liu)(liu)明LED（LXHL系列(lie)）提供高(gao)(gao)達1.8 A 的(de)(de)負(fu)載(zai)電(dian)(dian)(dian)流(liu)(liu)(liu)。輸出電(dian)(dian)(dian)壓(ya)比(bi)LED串(chuan)的(de)(de)正向電(dian)(dian)(dian)壓(ya)降稍低。因此當(dang)LED燈串(chuan)連接到(dao)(dao)(dao)電(dian)(dian)(dian) 源(yuan)時(shi)，電(dian)(dian)(dian)源(yuan)工(gong)作在(zai)(zai)恒流(liu)(liu)(liu)（CC）模(mo)式。如果LED串(chuan)沒接到(dao)(dao)(dao)電(dian)(dian)(dian)源(yuan)，穩(wen) 壓(ya)管VR1提供電(dian)(dian)(dian)壓(ya)反(fan)饋(kui)，將輸出電(dian)(dian)(dian)壓(ya)調(diao)整(zheng)在(zai)(zai)13.5 VDC左右。一(yi)(yi)個 100 mW的(de)(de)電(dian)(dian)(dian)阻（R11）檢(jian)測輸出電(dian)(dian)(dian)流(liu)(liu)(liu)，通(tong)過(guo)一(yi)(yi)個運放（U1）驅(qu)(qu)動(dong)(dong) 光耦給(gei)(gei)U2提供反(fan)饋(kui)。TinySwitch-III系列(lie)器(qi)件(jian)通(tong)過(guo)關斷或(huo)跳過(guo) 圖 1. 帶無源(yuan)PFC的(de)(de)LED燈驅(qu)(qu)動(dong)(dong)電(dian)(dian)(dian)源(yuan)原理圖 MOSFET開關周(zhou)期(qi)進行穩(wen)壓(ya)。當(dang)負(fu)載(zai)電(dian)(dian)(dian)流(liu)(liu)(liu)達到(dao)(dao)(dao)電(dian)(dian)(dian)流(liu)(liu)(liu)設置(zhi)閾(yu)值時(shi)， U1驅(qu)(qu)動(dong)(dong)U3導通(tong)。U3內(nei)的(de)(de)光三極(ji)管從(cong)U2的(de)(de)EN/UV腳拉出電(dian)(dian)(dian)流(liu)(liu)(liu)，使(shi) U2跳過(guo)周(zhou)期(qi)。一(yi)(yi)旦輸出電(dian)(dian)(dian)流(liu)(liu)(liu)降到(dao)(dao)(dao)電(dian)(dian)(dian)流(liu)(liu)(liu)設置(zhi)閾(yu)值以(yi)下，U1停止驅(qu)(qu)動(dong)(dong) U3，U3停止從(cong)U2的(de)(de)EN/UV腳拉出電(dian)(dian)(dian)流(liu)(liu)(liu)，開關周(zhou)期(qi)重新(xin)使(shi)能。 TL431(U4)給(gei)(gei)U1提供一(yi)(yi)個參(can)考電(dian)(dian)(dian)壓(ya)，以(yi)和R11兩(liang)端的(de)(de)電(dian)(dian)(dian)壓(ya)降做比(bi)較。效(xiao)率比(bi)較高(gao)(gao)，在(zai)(zai)滿載(zai)條件(jian)下>70%，符合CEC/能源(yuan)之星2008對帶載(zai)模(mo)式效(xiao)率的(de)(de)要求(qiu)，采用反(fan)激式拓(tuo)撲(pu)結構，集(ji)成度高(gao)(gao).