Design and Fabrication of SiC based Stepper Motor Driver for Higherature Environments

This paper describes the manufacturing procedure, testing and application of a high temperature (HT) and radiation tolerant silicon carbide (SiC) semiconductor device technology used to fabricate a stepper motor driver circuit for HT spacecraft applications. The proposed circuit employs 4H-SiC MOSFET technology and diodes designed to operate at high ambient temperatures (>400°C). The discrete FET portion of test dies is comprised of various widths and lengths of n-and p-channel discrete FETs for device optimization and compact model development, which is achieved by engineering doping profiles in conjunction with innovative device designs. The fabricated circuit consists of a logic synthesizer sub-system consisting of various HT logic gate modules and ring oscillators along with a specialized HT gate driver circuit. The proposed system is used to drive a 12V stepper motor at varying speeds in both clockwise and counterclockwise directions. Control schemes for a digital logic gate based unidirectional control and closed loop bidirectional control are also implemented with a customizable directional and stall control capabilities. The proposed topology uses all low side power devices and high side diodes to gain the advantage of single shared gate driver circuit for cost effectiveness and reliability enhancement. Results at 600°C environment report a conversion efficiency of 98%, with a Mean Time to Failure (MTTF) of 450 k-hours, which validates the proposed technology to be suitable for HT power conversion.