A 21.6 kW/L Two-Phase Immersion-Cooled Isolated DC-DC Converter

This paper introduces a sealed, passive two-phase immersion cooling concept using Novec 7000 dielectric fluid for transformer-isolated DC-DC converters with high power density. The concept relies on liquid-to-vapour phase change heat transfer from the surfaces of all converter components, supporting heat fluxes up to 40 W/cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>. Experimental results are presented demonstrating the improvements in maximum winding current density and magnetic core flux density achieved by immersion in Novec 7000. This illustrates the potential for volume-minimisation of magnetic components. A novel transformer design is presented which maximises fluid contact with the core and windings while maintaining good electrical isolation between primary and secondary side. An 800 V, 18 kW CLLC resonant converter prototype with total volume of 0.81 L is designed and built. Preliminary testing demonstrates a power density of 21.6 kW/L at an input voltage of 620 V and a switching frequency of 860 kHz.