넓은 load 범위에서 높은 효율을 가지는 Active Clamp Forward-Flyback converter에 관한 연구

Abstract

This thesis proposes a structure of a dc-dc active clamp forward-flyback converter for high efficiency in wide output power range. To achieve the zero-voltage-switching of power switches for the wide output power range, a leakage inductor (Llk), which is a parasitic inductor in the transformer primary side, is not used; instead, a small forward inductor (Lf), which also acts as an output filter inductor, is located between two secondary diodes in the transformer secondary side. Also, to solve the problem of ringing in the voltage of the secondary diodes caused by Llk, two capacitors are inserted to the transformer secondary side, which helps the voltage across secondary diodes to be clamped at the voltage stored in the capacitors. The experimental results which are tested at an output power range of 20 W ~ 100 W and a switching frequency of 100 kHz show the efficiency measured as 94.1 % at an output power of 20 W, and 94.8 % at an output power of 100 W, so the efficiency variation was measured as 0.7% along a wide output power range of 20 W ~ 100 W.