An Efficiency Optimized Analysis Method for a Family of Phase-Shift-Modulated Synchronous Rectification Resonant Converters

Aiming to the issue of low efficiency caused by zero-voltage switching (ZVS) missing of phase-shift modulation (PSM) under light load condition, an efficiency optimized analysis method (EOAM) for synchronous rectification resonant converters is proposed. EOAM is realized by adjusting the synchronous rectifier (SR) advance conduction time <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T_R</i>. So, the mathematical model of the controlled variable <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T_R</i> and loss is established. And a trade-off between the reduced loss and the increased loss is emerged during the adjustment process. And the optimal SR advance conduction time (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T_R</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">_op</sub>) corresponding to the optimal efficiency (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">η</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">op</sub>) under different working conditions is discussed in detail. Furthermore, the optimization methods under different working conditions are put forward and refined. To verify the effectiveness of the theoretical analysis, a 500-W experimental prototype of inductor-capacitor-inductor-capacitor (LCLC) converter is built. Compared with the traditional method of without EOAM, the proposed EOAM can improve efficiency of light load (10% load) by more than 2.6% (92.44%<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">–</i>95.077%). And the highest efficiency after efficiency improvement with EOAM is appeared at <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</i> = 100 W (20% load), reaching to 95.821%.