MAINSTREAM ENGINEERING CORP — Department of Defense SBIR Phase I: A15-084

Description

Current military vehicles use battery-isolating diodes to transfer current between two sets of battery banks, which are heavy, inefficient, and only allow current flow from the higher charged (higher voltage) battery to the other. This proposal details efforts to develop a bi-directional dc-dc converter for military vehicles to allow for smart control of current transfer between battery banks, as well as increased efficiency compared to the legacy system. Mainstream proposes a 500 A, 4-quadrant, interleaved, bi-directional, dc-dc converter that is built using high-current GaN devices. The proposed modular GaN based battery isolator unit (BIU) is developed on a multiple GaN device PCB with two interleaved (parallel) modules, has a zero-percent de-rating when bucking and boosting, and is cooled using only natural convection with an aluminum heat spreader. The BIU also incorporates a novel common mode (CM) EMI filter topology, using low-loss nanocrystalline magnetic material for the CM choke, to further reduce overall system volume and weight. This approach results in a 4-quadrant dc-dc converter with an efficiency of 94.7% and power density of 18.5 W/in3 (including thermal management system). At the completion of the Phase I, Mainstreams BIU will be a Technology Readiness Level (TRL) 4.