Metacapacitors: Printed thin film, flexible capacitors for power conversion applications

The Metacapacitors project aims to improve efficiency, functionality and form factor of offline power converters suitable for LED solid-state lighting, with a view to developing an attractive technology platform for load management and power conversion across a broad range of applications. Based on integrated switched-capacitor (SC) topologies, the project adopts an integrated approach from materials to devices to circuits. We designed capacitors based on high- $\kappa$ dielectric nanocrystals, that can be prepared using high-throughput microfabrication/nanotechnology techniques, ink deposition and multilayering. The capacitor dielectric, a nanocomposite composed of (Ba, Sr)TiO $_{3}$ nanocrystals in polyfurfuryl alcohol (BST/PFA, $\kappa$ $ > 20$ , $100 \text{Hz}$ – $1\ \text{MHz}$ , loss $ , $20\ \text{kHz}$ ), targets a high volumetric capacitance density and ripple current capability. The Dielectric is demonstrated to function in a finished capacitor $ > \! 1000\ \text{h}$ at $125 ^\circ \text{C}$ . The capacitors were board integrated with a custom hybrid-switched-capacitor-resonant dc–dc converter IC. The converter integrates a balanced SC front-end with a series resonant tank, enabling nearly lossless current regulation and tranformerless galvanic isolation. The converter IC can be stacked in the voltage domain to interface a range of inputs. The tested driver delivers about $ 15\;\text{W}$ at $ 470\;\text{mA}$ to a string of $ 12$ LEDs with $ 90\%$ peak efficiency.