DC Voltage Ripple Oriented Multisteps Frequency Range Design for Resonant DC/DC Converters

The dc voltage ripple must be suppressed within certain range to improve the efficiency as well as guarantee the power quality of resonant dc/dc converters. However, the nonsinusoidal input voltage of resonant network creates big challenge on the analytical methodology. To address this concern, the instantaneous power theory is introduced to make the established model of the dc voltage ripple suitable for any cases. It is derived that the dc voltage ripple largely depends on the switching frequency for the given parameters. Therefore, a multisteps frequency range design approach is presented to ensure allowable voltage ripple in entire power range. To ensure the accuracy of the proposed approach, three possible operating conditions of resonant converters (i.e., at, around, and far away from resonant frequency) are taken into account. Experimental validations further demonstrate the effectiveness of the established model of ripple voltage and the proposed frequency range design using a lab-scale prototype.