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Fuel cell technology is continuously gaining ground in E-mobility applications. Fuel cells require a constant supply of pressurized air, for which high-speed turbo compressors with air bearings are an optimal choice to reduce size, guarantee oil-free operation required for the lifetime of the fuel cell, and increase efficiency. However, the inverter driving the electric motor of the turbo compressor does not scale down with increasing speed; therefore, other technology advances are required to achieve an overall compressor system with low weight. New power electronic topologies (double-bridge voltage sources inverter), cutting edge power semiconductor technology (gallium nitride), and multiobjective optimization techniques allow reducing the inverter size, increasing inverter efficiency, and improving the output current quality and in return lowering the losses in the electric motor. This enables the electrical, mechanical, and thermal integration of the inverter into the compressor housing of very high-speed and compact turbo compressors, thereby reducing the size and weight of the overall compressor system by a factor of two. Furthermore, a turbo compressor with an integrated inverter reduces complexity and cost for operators with savings in casing, cables, coolant piping, and connectors and reduces EMI noise by shielding the high-frequency motor currents with one housing. Beside its main application for fuel cell air supply, the advantages gained by an integrated inverter can also be used in other boosting and air handling applications such as advanced air and exhaust handling in combustion engines. The proposed integration concept is verified with a 280,000 rpm, 1 kW turbo compressor, targeted for the Balance of Plant (BoP) of a 5–15 kW fuel cell. The experimental results show that the temperature limits on the power electronics parts can be kept below the limit of 90 °C up to a coolant temperature of 55 °C, and beside the advantage of lower cabling effort, the efficiency of the compressor system (turbo compressor and integrated inverter) is increased by 5.5% compared to a turbo compressor without an integrated inverter.

This paper discusses the impact of the back-gate bias on the ON-state drain breakdown voltage of high-voltage silicon-on-insulator (SOI) MOSFETs. This is mandatory in order to understand the physical mechanisms behind the limitations of the safe operation area (SOA) of SOI power devices. The back-gate electrode of the SOI material will add an additional dimension to the SOA, thereby causing further reliability constraints on the circuit design. For small and negative back-gate bias, the SOA is limited by the ON-state breakdown whereas the OFF-state breakdown sets the limit for positive back-gate bias. For the first time, an analytical model of the breakdown voltage covering the reasonable back-gate voltage range is presented providing a first step toward a closed form circuit simulation of this effect. It is shown that the back-gate potential impacts on the breakdown behavior by modulating the carrier distribution in the drift region, the base transport factor of the parasitic bipolar transistor, and the drift region resistance. Moreover, it is shown that avalanche multiplication is the limiting breakdown mechanism for lateral SOI power devices.Index Terms-Device breakdown, high-voltage, ON-state breakdown, RESURF, silicon-on-insulator (SOI), Smart Power.

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