DC-DC converter for battery charging circuit

A converting circuit for an on-board charging device, the converting circuit comprising:

• a first resonant converter including at least two first switching elements and configured to output a first output voltage under constant voltage control to follow a predetermined ratio of a minimum voltage of a battery connected to an output terminal according to a first control signal that is input to the at least two first switching elements;
• a second resonant converter including at least two second switching elements and configured to output a second output voltage under constant voltage control to follow the predetermined ratio of the minimum voltage of the battery according to a second control signal that is input to the at least two second switching elements;
• a phase shift full-bridge converter configured to transmit, to the output terminal, at least a portion of a direct current (DC) voltage that is transmitted from an input terminal due to a phase shift between the first control signal and the second control signal generated according to an operating mode of the battery;
• and
• a controller configured to generate a first control signal and a second control signal for determining a switching frequency to follow the predetermined ratio of the minimum voltage of the battery, and to generate a pulse of generating a phase shift between the first control signal and the second control signal for constant current control that follows a reference current value set to correspond to a charging or discharging section of the battery or for constant voltage control that follows a difference value between a maximum voltage and the minimum voltage of the battery.