A worldwide awareness of the environment is accelerating fuel cell vehicle development. With respect to power electronics, special requirement is on the development of high efficiency, high voltage ratio bi-directional DC/DC converter for fuel cell energy system management. In this paper, two bi-directional DC/DC converters, which are developed for Ford Motor Company’s fuel cell vehicle, are compared from different aspects. Comparison is concentrated on the circuit topology and EMI performance. Emphasis is placed on soft-switch, hard-switch, synchronized rectification, auxiliary start-up winding and their effect on EMI performance in this kind of isolated bi-directional converter. Comparison includes circuits analysis and test result. The EMI test setup is described. EMI measurements are given and explained. EMI solutions for bi-directional DC/DC converter are discussed. An EMI filter is designed and final test result is given. / Master of Science