Analysis and design of LLC resonant converter considering rectifier voltage oscillation

The LLC resonant converter employing the center-tap rectifier can suffer from high voltage oscillation across the secondary diodes owing to the transformer secondary leakage inductance. The amplitude of the voltage oscillation is varied according to the operation region, i.e., below resonant region and above resonant region. To reduce the diode voltage stress without snubbers, this paper analyzes the voltage oscillation mechanism and presents the design guideline for small voltage oscillation.