A Magnetic Design Method Considering DC- Biased Magnetization for Integrated Magnetic Components Used in Multi-Phase Boost Converters

High-power-density and high-efficiency in DC/DC converters are required in various applications such as the automotive application. Interleaved multi-phase circuits with integrated magnetic components can fulfill these requirements because passive components occupying significant space in power converters can be downsized without high-switching frequency driving of power devices. However, DC-biased magnetization is a drawback of integrated magnetic components because of unbalanced inductor average currents. This imbalance arises from the tolerance between the phase components. To overcome this problem, inductor average current control is implemented in interleaved multi-phase DC/DC converters. Nevertheless, the imbalance cannot be completely eliminated because the current sensors inserted into each phase have gain errors. The purpose of this paper is to present a magnetic design method to improve the immunity to unbalanced currents. A comprehensive analysis is carried out with two main objectives: 1) to prevent magnetic saturation, which may arise due to the current unbalance and 2) to downsize the magnetic components by selecting the optimal coupling coefficient taking into consideration the maximum permissible percentage of unbalanced currents. Simulation case studies are presented to support the analysis. Finally, a 1 kW prototype of the interleaved boost converter is built to validate the accuracy of the design method.