Fuel cell is one of the promising renewable and sustainable power sources because of its high power density and very low emission. It can be utilized as a clean power source for various applications such as portable electronic appliances, transportation and residential building. In order to design a highly efficient fuel cell power system, a suitable DC DC converter is required. Among the various topologies of DC DC converters, interleaved boost converter (IBC) has been proposed as a suitable interface for fuel cells to convert low voltage high current input into a high voltage low current output. The advantages of interleaved boost converter compared to the classical boost converter are low input current ripple, high efficiency, faster transient response, reduced electromagnetic emission and improved reliability. In the proposed interleaved converter, the front end inductors are magnetically coupled to improve the electrical performance and reduce the weight and size. This paper focuses on a three-phase directly coupled IBC using CoolMOS transistor and Silicon carbide (SiC) diode instead of the classical two-phase reported in the literature based on the tradeoff between the ripple content, cost and complexity. Mathematical analysis of overall current ripple, design equations and switching loss studies for IBC have been presented. Simulation of IBC interfaced with fuel cells have been performed using MATLAB/SIMULINK. Hardware prototypes have been built to validate the results. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.