A Mechanically Ultra-thin Flying Capacitor Multilevel Converter with Embedded Passive Components

This work explores the design and fabrication of ultra-thin power converters, which utilize the advantageous form factor and inductor size reduction of flying capacitor multilevel (FCML) converters. For the high voltage (i.e. 400 V) applications considered here, careful attention is paid to meeting stringent creepage and clearance requirements. A hardware prototype is developed and tested to evaluate a novel low inductance commutation loop design, which utilizes Printed Circuit Board (PCB) embedded local capacitors. The vertically embedded capacitors yield small parasitic inductance, while simultaneously allowing excellent creepage/clearance through physical separation of high voltage terminals on opposite sides of the PCB. An ultra-low profile form factor is achieved through additional recessing of the remaining passive components, yielding a 4.72 mm total board height (including PCB thickness), in a 6-level, 400 V, 1.8 kW hardware prototype, with a power density above 3 kW/in(3), and a peak efficiency of 98.7%.