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LED電源的幾種常見保護電路設計

  • 時間：2012-11-20 15:50:57

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      一款好的LED開關電源除了需要穩定、高效、可靠外，電路的各種保護措施也必須精心設計，避免在復雜環境條件下能夠迅速的對開關電源電路和負載進行有效保護，本文介紹LED開關電源的幾種常見保護電路。　　
1、過電流保護電路　　
      在直流LED開關電源電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)中，為了保護(hu)調(diao)(diao)整(zheng)管(guan)在電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)短路(lu)(lu)(lu)、電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)增大時(shi)不被(bei)燒毀。其基(ji)本方法是，當(dang)輸出電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)超過某一值時(shi)，調(diao)(diao)整(zheng)管(guan)處于(yu)反(fan)向偏置狀(zhuang)態(tai)，從(cong)而截(jie)止(zhi)(zhi)，自動切斷電(dian)(dian)(dian)(dian)(dian)(dian)(dian) 路(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)。過電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)保護(hu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)由三極(ji)(ji)管(guan)BG2 和(he)分壓(ya)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻R4、R5組成。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)正常工作時(shi)，通(tong)過R4與R5的(de)壓(ya)作用(yong)，使(shi)得(de)BG2 的(de)基(ji)極(ji)(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)位比發(fa)射(she)極(ji)(ji)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)位高，發(fa)射(she)結承受(shou)反(fan)向電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)。于(yu)是BG2 處于(yu)截(jie)止(zhi)(zhi)狀(zhuang)態(tai)（相當(dang)于(yu)開(kai)路(lu)(lu)(lu)），對穩壓(ya)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)沒有(you)影響(xiang)。當(dang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)短路(lu)(lu)(lu)時(shi)，輸出電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)為零，BG2 的(de)發(fa)射(she)極(ji)(ji)相當(dang)于(yu)接地，則BG2 處于(yu)飽和(he)導通(tong)狀(zhuang)態(tai)（相當(dang)于(yu)短路(lu)(lu)(lu)），從(cong)而使(shi)調(diao)(diao)整(zheng)管(guan)BG1    基(ji)極(ji)(ji)和(he)發(fa)射(she)極(ji)(ji)近于(yu)短路(lu)(lu)(lu)，而處于(yu)截(jie)止(zhi)(zhi)狀(zhuang)態(tai)，切斷電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路(lu)(lu)(lu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)，從(cong)而達(da)到保護(hu)目的(de)。