Cryogenic Four-switch Buck-Boost Converter Design for All Electric Aircraft

To improve the electric aircraft system efficiency performance, the efficient cryogenically-cooled superconducting cables and motors are adopted. The overall system performance can be further improved if the power electronics converters can work under cryogenic temperatures. The gallium nitride (GaN) high electron mobility transistor (HEMT), which has the best overall performance under cryogenic temperatures among various types of semicoductors, are adopted to design the power converter. Due to the current limitation of individual GaN HEMT, a half-bridge power module with three GaN HEMTs in parallel for each switching position is designed. The circuit layout considerations are discussed to ensure identic circuit parasitics and balanced current sharing operation. Based on the converter power loss and size models, the genetic algorithm based optimal design for the four-switch buck-boost converter is discussed. The theoretical efficiency performances under different operating conditions are presented. The double pulse test (DPT) is performed to valiadte the function of the designed half-bridge power module. The thermal test of the power module is conducted to validate the symmetric layout design for the paralleled devices.