This paper presents a design for a high-frequency DC-DC converter with the coupled inductor and integrated current balancing transformer. The converter can deliver 32 W from 12 V intput to the 4 V output. A high efficiency and high power density are achieved by ZVS turn-on and the magnetic integrated. In order to deliver a 6 A rated output current, a two-phase QSW Buck converter operating at the synchronous mode is seleted as the topology to reduce the conduction loss both for the switches and the windings. The current unbalancing issue is solved by an integrated magnetic device with a customized core. The semiconductors selection and the core design are also discussed in the paper. A 1 MHz prototype is built to verify the design process. The prototype achieves 97.45% efficiency at 4 V/ 6 A output and the ZVS turn-on capability is also verified experimentally.