MS student Derek Chou with advisor R. Pilawa-Podgurski

Figure 17: Outer dimensions of a PCB 250 W prototype

Wide-bandgap semiconductor devices such as gallium nitride and silicon carbide have found use in power electronics as high-performance switches, allowing for higher frequency switching with minimal losses; this in turn reduces the required physical size of many of the passive components required in such designs, mainly the capacitors and inductors employed in switched-mode power supplies. The flying-capacitor multilevel converter topology makes it possible to reduce the size of the components so much that the printed circuit board material and footprint becomes a limiting factor in pushing power densities to higher levels. A flexible power circuit board (PCB) prototype has been constructed to explore this potential. With the ability to bend and yield to its surroundings, a flexible PCB substrate can withstand temperature cycles and conform to non-flat surfaces, such as on the outer surfaces of electric machines.

Figure 18: PCB board thickness

Additionally, the substrate is extremely lightweight. Figure 17 shows the outer dimensions of a 250 W prototype, and Figure 18 the thickness of the board, not including connectors. The prototype achieves a specific power density of greater than 14 kW/ kg and a volumetric power density of greater 109 W/in³. This research is supported by the Center for the Power Optimization of Electro-Thermal Systems (POETS).