Cryogenic MOSFET power conversion

Possible applications of low-temperature electronics in the field of cryogenic power conversion are examined. Full-bridge amplifiers were built and tested at liquid-nitrogen temperature. Transistor conduction and switching losses are analyzed and compared for 300 K and 77 K. The effect of low-temperature operation on overall power conversion efficiency is explored. It is concluded that commercially available MOSFETs in plastic or metal packages work very well if immersed in a bath of liquid nitrogen despite the fact that they were not designed for such a cold application. They can be operated at much higher current levels, and high-efficiency switchmode circuits can be designed. Heatsinks other than the liquid nitrogen are not required. This permits the design of extremely small, lightweight, and low-cost power conversion circuits