Power System-on-Chip for Future Airborne Sensor Systems

Abstract

This thesis looks into the requirements on technology to realize a fully integrated GaN power System-on-Chip for a switched mode DC-to-DC converter that could be used in future airborne sensor systems. A fully integrated power stage would save much space and weight, which is beneficial in any application and, especially, for airborne applications. The topologies considered include conventional Buck-type converters, interleaved Buck converters and switched capacitor converters. The target input voltage is 270V and the power stage conversion ratio is 10-to-1. Focusing primarily on optimizing steady state efficiency the necessary integrated passive components are designed and simulated. It is identified that an advanced technology for multi-layered or very thick conductors is a requirement, and based upon these two new inductor topologies are proposed. The multi-layered inductors utilize two coupled layers of 5 μm thick spiral conductors and the very thick inductors use a single conductor layer with a 30 μm conductor. A simple linear model is also presented to describe the most important performance characteristics for commercial GaN devices, the correlation between parasitic drain-source capacitance and the maximum tolerated drain-source voltage and current. Finally, complete power stage design examples are presented alongside approximate on-chip area requirements for the analyzed active and passive components. The performance of the designs are verified with simulations and the multi-layered inductors provide power stages with optimum efficiencies of 46% to 65% at switching frequencies in the 70 to 150MHz range. The very thick inductors reach efficiencies of 61% to 71% operating at 40 to 80MHz.