Power density optimization of resonant tanks using standard capacitors

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. This paper investigates the lowest achievable ESR 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 cm
³
volume. The resonant tank, when used in a resonant switched-capacitor converter, can theoretically handle up to 12 kW assuming a tolerable loss of 2 W, and the power converter itself will be limited by the power density of switches and interconnects rather than by passive components.