Design of a High Performance Flying Capacitor Multilevel Inverter for Electric Vehicles With Stacked Printed Circuit Boards

Drivetrain efficiency and weight represent significant barriers toward the development of future electric aircraft. Multilevel inverter designs have achieved impressive performance in these applications, with the flying capacitor multilevel (FCML) topology demonstrating particular promise. FCML converters contain many active devices along with associated gate drive circuitry. In order to achieve simultaneous goals of high density, high efficiency, and good signal integrity, the printed-circuit-board (PCB) layout and physical design of the converter is of utmost importance. In this work, a stacked PCB design is presented, which shields the low-voltage gate signals from interference, while also enabling an uninterrupted power path, low commutation loop inductance, and compact volume. A 400 V, 6.25 kW, 8-level FCML prototype is fabricated, which achieves 89 kW/kg specific power, 214 kW/L power density and 98.64<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> peak efficiency, with a THD of 0.72<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\%$</tex-math></inline-formula>.