Characterization of a Si and GaN converter at cryogenic temperatures

The efficiency improvement of a Si-MOSFET and GaN-HEMT synchronous buck converter at low temperatures is demonstrated and discussed in detail. By carefully selecting suitable components for cryogenic temperatures and characterizing them from room temperature to low temperatures, the functionality of each component is demonstrated before cryogenic operation of the entire converter and the impact of the component properties on the total losses are considered. Overall, a power loss reduction of up to 60% could be achieved with both converters at 87 K compared to losses at room temperature. Thereby, the conduction losses of the transistors as well as the DC winding losses of the inductor have the greatest impact on loss reduction at low temperatures.