Demonstration of a Compact Hard-Switched 3.5 kW DC/DC Converter utilizing Planar Magnetics optimized for low Capacitive Loss

It is necessary to accurately determine the power losses in a converter to obtain a high efficient design. This paper presents an in-depth analysis of all the power losses in a converter. The capacitive loss of the transformer and switches is investigated. A highly efficient 7:1 planar transformer is presented and the design is carefully interleaved to provide a small differential-mode capacitance and AC-resistance. Very accurate finite element simulations of the transformer equivalent circuit parameters are performed using Ansys Maxwell. A compact 3.5kW hard-switched isolated full-bridge forward converter is constructed with a power density of 9.9kW/L when the heatsink is excluded and 6.4kW/L when the heatsink is included. The calculated and measured peak efficiency of the converter is in close agreement with 98.0% and 97.7% respectively, thereby proving the accuracy of the power loss calculations.