Current Dip Analysis and Efficiency Optimization in DCZVS Flyback Converters Via State Trajectory Approximation

Double-clamp zero-voltage-switching (DCZVS) flyback converter can achieve high-frequency soft switching and high power-density, which have great potential for industrial applications. However, previous soft-switching analysis for DCZVS flyback converter have neglected the resonant current dip phenomenon during the dead-time or lack quantitative insights due to the complexity of time-domain modeling. This paper proposes a state trajectory approximation method to analyze the current dip, enabling precise soft-switching guarantees and partial lossless absorption of leakage inductance energy, thereby improving efficiency. Experimental validation on a high power-density prototype with <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$160-420 \mathrm{V}$</tex> input and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$28 \mathrm{V} / 600 \mathrm{W}$</tex> output demonstrates a peak efficiency of 94.37 % with an increase of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{0. 6 8 \%}$</tex>.