Evaluation of Semiconductor Losses in Cryogenic DC-DC Converters

A detailed experimental evaluation is reported of DC-DC power electronic converters operating at cryogenic temperatures; the motivation for the study being the eventual integration of a converter with a superconducting electrical machine or energy storage device, SMES, with the benefit of increasing power density. The performance is examined of 120 V and 500 V, 500 W prototypes operating at temperatures down to 20 K; in particular the semiconductor losses are analyzed. Several designs are considered for each voltage level involving different power MOSFET devices, different power diodes, including a silicon carbide Schottky diode, a diode-less synchronous rectifier topology, and a zero voltage resonant transition DC-DC converter. The overall reduction of semiconductor losses at cryogenic temperatures compared with room temperature was up to 85%, depending on the particular circuit