Experimental investigation of a soft-switching three-phase, three-voltage bus DC/DC converter for fuel cell vehicle applications

A soft-switching three-phase, three-voltage (14 V/42 V/high voltage) bus dc/dc converter is presented for power management in fuel cell vehicle applications. It features reduced ripple currents, smaller capacitances, high efficiency and a larger power handling capability. The mathematic model is derived and used in the determination of the soft-switching criteria with and without the 14 V bus load current. The topology was verified experimentally with a 6 kW prototype that occupies a small foot print of 19.8 cm times 27.9 cm. The efficiency of the converter is above 96% in most load conditions with a maximum efficiency of 96.99%. An efficiency of 95.2% was achieved at the maximum output power of 6.4 kW in the boost mode. Dynamic response test results in the buck and boost modes are also shown.