Experimental Investigations of State-of-the-Art 650-V Class Power MOSFETs for Cryogenic Power Conversion at 77K

With consideration of both the operating properties from cryogenic MOSFETs and refrigerating costs from cryogenic refrigerators, this paper attempts to carry out the experimental tests and performance evaluations of state-of-the-art 650-V class MOSFETs, and thus to explore a possible design guideline for cryogenic power conversions at liquid nitrogen temperature. Three cryogenic operating behaviors of on-state resistances and breakdown voltages of five types of commercial power MOSFETs and on-state voltage across their built-in reverse diodes are tested from 300 K to 77 K. The measured on-state resistances obtained in low-current tests show almost double-exponential functional relations with the operating temperatures, while the other two cryogenic parameters are directly or inversely proportional to the operating temperatures. Moreover, cryogenic on-state resistance behaviors in high-current tests from 20 A to 90 A are also found to have double-exponential functional relations with the operating currents. Based on the experimental results and their fitted temperature-dependent and current-dependent functions, integrated evaluation of overall energy efficiency involved with refrigerating cost is presented to form a feasible design guideline for cryogenic power conversions. Finally, two 40-kW and 4-MW boost choppers are conceptually designed and discussed to verify the proposed design guideline for the use in various MOSFET-based cryogenic power conversions.