Optimization of Cryogenic Power Switching Devices

The innovative approach of operating power electronics in a crvogenic environment depends criticallv on the availabilitx of controllable semiconductor switches capable of high efficiency operation in the temperature range from about 20 K to 150 K. Thc motivation for developing this type of pouer electronics is to realize highly efficient and compact svstems with significantl! improved power/mass ratios and substantially reduced volumes over those attainable at ambient temperatures or above. Further considerations are the enhanced reliability resulting from the reduced thermal cvcling and deterioration due to aging being largely eliminated. Recognizing that switching devices optimized for operation in the crvogenic rangc are the critical engineering issue, this project has as its overall objective the design, fabrication and demonstration of optimized cryogenic switches capable of meeting BMDO requirements in both terrestrial and space applications. Phase I will be devoted to the selection of a candidate switch type and the development of a design basis for Phase II activities. Candidate switch types include, but are not limited to MOSFETs, IGBTs and HBTs. The characteristics of these will be investigated experimentally at cryogenic temperatures using currently available ambient temperature devices Existing device models will be upgraded and used to analyse the physical behavior with verification by the experimental results obtained. Device requirements from a system viewpoint will be established to enable the basis for Phase II to be established. Crvogenic power electronics offers performance and cost improvements over ambient technology, particularly where a cryogenic environment is required or available for the overall system. Commercial applications include, but are by no means limited to, cryogenic capacitive energy storage, superconducting magnetic energy storage, magnetic refrigerators and maglev trains. Development and marketing a range of power handling switching devices will, for the first time, enable the potential of cryogenic power electronics to be fully exploited.