In the fuel-cell electric vehicle system, the low-voltage output of unit fuel-cell demands a number of cells to be stacked in series to produce a DC link voltage which is high enough to drive the vehicle inverter system. However, this increases the complexity of the fuel-cell control system This paper presents a design of high-efficiency boost converter emplying the average current-mode control, which is able to convert a low voltage of a fuel-cell generator with a small number of unit cells to a stable and high DC link voltage for electric vehicle applications.