Integrated Coupled Inductors With Functionality of Current Balancing Transformer for Two-Phase Synchronous DC-DC Converters

With the emerging technology of wide-band-gap power semiconductors and modern ferrite materials, the switching frequency of dc-dc converters can be pushed to mega-hertz range to achieve higher power density. In order to deal with a high conduction current, multiphase converters are adopted to distribute the current for both power devices and windings. However, the current unbalance among phases may cause unexpected power loss to the converters. In this letter, the current unbalance issue is addressed by an integrated current balancing transformer for a two-phase dc-dc converter. The current of two phases in the converter can be automatically compensated to be identical by the proposed structure, which also reduces the complexity of the control system. A 1-MHz GaN-based two-phase buck converter is built to verify the proposed structure and its efficiency achieves 97.5% at 4 V/6 A output with the ZVS turn-on of the switches.