Actively Cooled Minority-Carrier Devices for Power Conditioning

New power semiconductor device performance is limited by cooling because high heat-flux cooling systems have not matched their increased power density. Therefore, real designs rarely achieve device ratings. American Superconductor (ASC) demonstrated CryoPower+, which cools a variety of power MOSFET topologies by direct immersion in coolants from 77-300K, with boiling where appropriate. CryoPower (TM) optimizes system cost, size, efficiency and pulse handling capability for only MOSFET applications ASC proposes a new innovation, to extend CryoPower(TM) to IGBT/MTO minority-carrier devices. This innovation first requires Phase I characterization of conduction and switching losses, and of the safe operating area (SOA) across an economical temperature range. Characterization concentrates on four-layer devices such as the new high-voltage, insulated-gate, bipolar transistors (HVIGBT) and MOS-controlled, turn-off thyristors (MTO). High device switching losses depend on minority carrier lifetimes, which decrease considerably with temperature. We expect an economic and reliable active cooling system to allow increased switching frequencies. Device SOA should also increase with active cooling, dependent on nonlinear mechanisms inherent in the chosen device. Phase I Characterization data and Phase II hardware demonstration data will help realize the full economic benefit of this innovation by allowing device performance and cooling system optirnization. The Phase I and II programs will enable industry to reap the synergetic benefits of both CryoPower(TM) and IGBT/MTO technologies. Multi-megawatt, high voltage applications using new power semiconductor devices are found in numerous Military and Commercial systems. These range from pulse power circuits for radar and sonar systems, to large industrial process controllers, where small percentile increases in system efficiency and reliability can translate into large operating cost reductions and profit increases.