準諧振返馳式LED調光器之數位式初級側控制

Abstract

本論文發展準諧振返馳式轉換器(quasi-resonant flyback converter)之數位式初級側感測(primary-side sensing, PSS)技術，應用於TRIAC調光LED驅動器。傳統返馳式轉換器屬於硬切模式，會造成很高的切換損失，而本論文利用DSP讓返馳式轉換器操作於準諧振模式，初級側感測技術利用輔助線圈獲得輸出電壓資訊，亦可用來偵測開關汲-源極電壓波谷，使返馳式轉換器達到波谷切換(valley-switching)，切換損失將會降低，提升整體效率。使用初級側感測技術必須利用初級側能獲得的訊號估測LED電流，現金的作法只有估測次級側二極體的平均電流，本論文的方法，則是將輸出電容和負載加入估測式子，這樣可以使電流估測精確度提高。調光方面則是利用TRIAC改變導通角當做電流命令達到LED調光效果。本文利用數位訊號處理晶片TMS320F2812結合外部偵測波谷機制使返馳式轉換器運作於準諧振模式，並且應用於TRIAC 調光LED驅動器，藉由實驗結果驗證其可行性。

In this paper proposes a digital primary side sensing (PSS) control technique for the quasi-resonant flyback converter in applications to TRIAC dimmable LED drivers. Conventional flyback converter is a hard-cut mode, will cause high switching losses, and this paper use DSP for flyback converter operating in quasi-resonant mode, primary side sensing technology uses information about auxiliary winding to obtain the output voltage is also can be used to detect the switch drain - source voltage of the valley, so that flyback converter switch to valley, switching losses will be reduced, improving overall efficiency. Using primary side sensing technology can be obtained using the primary-side LED current signal estimate, the cash side of the approach only to estimate the secondary diode average current, the method of this paper, the output capacitor and load by adding estimate equation, which can improve the accuracy of current estimates. Dimming side is to use the TRIAC conduction angle as a change order to achieve LED current dimming. In this paper, TMS320F2812 digital signal processing chip with external detection mechanism that valley a flyback converter operates in quasi-resonant mode, and used TRIAC dimmable LED driver by experimental results verify its feasibility.