A Multi-Kilowatt Low-Profile GaN Inverter for Light Electric Vehicles and High-Power Tools

An ultra-compact three-phase inverter with 8 de-vices per switch is presented for a combined output power of 7.3 kW at 48 V. Due to the use of Gallium-Nitride (GaN) transistors the design can operate at a frequency of 50 kHz and above without significant loss penalty. Parallel switching of the GaN device is enabled by symmetrical a layout with a “butterfly” structure. The high switching frequency enables to shrink the size of the DC-link capacitor to an overall size of 72 by 132 mm with a height of as low as 4 mm depending on the chosen cooling solution resulting in an overall volume of 0.1 liter. The measured peak efficiency of over 99.3% enables small heatsink size and high output power with minimal airflow. Under free convection and device temperature limited to 100°C the inverter reached an output power of 4 kW with efficiency above 99% across the operation range. Using active cooling the capable of delivering 7.3kW while keeping device temperatures around 60°C.