A Resonant Tank Design for LLC Resonant Converter Considering Leakage Inductance of Current Doubler Rectifier

LLC resonant converters are widely used in various applications because of their relatively simple structure and high efficiency. However, the problem is a decrease in efficiency due to an increase in the current on the secondary side of the transformer when the difference between input and output voltage is large. As the solution, there is a technique of adapting a current doubler rectifier with an inverse-coupled inductor. However, the leakage inductance of the inverse-coupled inductor in the current doubler rectifier affects the resonant tank, and although other studies have been designed to eliminate this effect, the leakage inductance is never completely zero, and the impact on the resonant-tank cannot be ignored. Therefore, this paper proposes a design in which leakage inductance, which cannot be ignored, is actively utilized. New resonant characteristics are presented based on FHA analysis, and actual measurement on a 60V/10A output prototype shows a 1.36% improvement in efficiency compared to convention-al LLC.