Matching networks have useful applications in transforming voltages and impedances in resonant inverters and dc-dc converters. Stacking multiple stages of matching networks can, in some cases, increase the efficiency because each stage is responsible for smaller transformation, but it also reduces the available inductor volume for each stage which can increase the loss.

At COMPEL 2017, we presented a paper (link for pdf) on optimization of matching networks with volume constraints to determine the optimum number of stages and other design choices for various transformation ratios, volumes and impedances. Adding the volume constraint to the typical matching network design process helps provide a better perspective on the number of stages that should be used. Simple design rules for designing matching networks, with a constraint on the available volume, are presented for voltage transformation ratios lower than 20.

High-frequency power conversion is useful for miniaturization of power electronics, but requires low loss passive components to achieve high power densities without thermal issues.

At COMPEL 2017, we presented a paper (link for pdf) investigating the lowest achievable ESR and the highest achievable power capability of a resonant tank using an air-core inductor with a single-layer foil winding and commercially available capacitors. A loss model is presented and online catalogs of multilayer ceramic capacitors are searched for components that can provide a low ESR when combined with an optimally designed inductor for various resonance frequencies.

The resulting resonator has a measured sub-mΩ ESR and high efficiency with 250 V dc rating in a 1 cm³ volume. The resonant tank, when used in a resonant switched-capacitor converter, has kilowatt-range power capability. A power converter, using this resonant tank, will be limited by the power density of switches and interconnects rather than by passive components.