Unidirectional fast switching non-isolated 100 kW fuel cell boost converter

This paper describes the power stage of a non-isolated unidirectional 400 V 100 kW DC-DC converter for fuel cell vehicles that reaches a switching frequency of 150 kHz with industry power modules. The power modules are equipped with custom made DCB-substrate assembled with a combination of fast 600 V superjunction Si-MOSFETs and SiC-Schottky diodes. For all other components like drivers, current sensors and the auxiliary supply converter standard products have been used to facilitate an automotive specification, and a cost efficient production. The inductors are custom-made to reduce choke losses and volume. The converter reaches an efficiency of 98 % at full load (166->400 V, 590 A lowside current). Furthermore a simple and reliable DC-link discharge unit is described that discharges with constant power and is far smaller and faster than a conventional resistor solution. Based on a constant current discharge device using a Power MOSFET in linear operation, it is extended with a small analog circuit to a roughly constant power discharge device.