Wide Operating Voltage Range Fuel Cell Battery Charger

DC-DC converters for fuel cell applications require wide voltage range operation due to the unique fuel cell characteristic curve. Primary parallel isolated boost converter (PPIBC) is a boost derived topology for low voltage high current applications reaching an efficiency figure up to 98.2 %. This paper proposes a new operation mode for extending the input and output voltage range in PPIBC. The proposed solution does not modify PPIBC power stage; the converter gain is modified by short-circuiting one of the parallel connected primary windings in the topology. The change in operation mode divides by two the converter input-to-output voltage gain. This allows covering the conditions when the fuel cell stack operates in the activation region (maximum output voltage) and increases the degrees of freedom for converter optimization. The transition between operating modes is studied because represents a change in the converter steadystate conditions. A solution is proposed based on precalculation of the duty cycle prior to the transition.