Design of resonant converters for high frequency wireless power transfer applications
File(s)
Author(s)
Nikiforidis, Ioannis
Type
Thesis
Abstract
High frequency inductive wireless power transfer is a promising solution that can enable the true potential of many technological applications. The Class EF and Class Φ inverters have
properties that make them ideal candidates for primary coil drivers, but designing such circuits with accuracy is difficult using traditional first order methods due to their complexity.
A generalised design method is proposed in this work, that can be applied to any Class E type inverter, and includes non-linear and parasitic effects that become prevalent at high frequency
operation. A 13.56MHz 50W Class EF2 inverter is developed using this method with 97% efficiency, and no additional manual re-tuning, whilst maintaining all of the other design
requirements. In addition, several circuit configurations are introduced to enable high power operation using GaN technology, including a single common choke push-pull Class DE topology.
A demonstration of a 3.39MHz 3kW DC/DC inductive power system with 95% efficiency, using a parallel push-pull Class E inverter, is shown to confirm the theoretical findings. Furthermore, the typical one-to-one wireless link design is generalised to a one-to-many resonant system through a custom iterative method, which expands the application space of inductive power transfer systems. Then, an implicit method for characterising links at high frequency where measurement instruments fail to produce accurate results is proposed and demonstrated through experiments, by using resonant converters. The limitations of Class E type inverter operation at fixed loads are investigated and overcome by introducing various potential active ontrol schemes, which can even absorb the negative effects of reactive reflections to the primary while maintaining output regulation. Finally, an analytic design method for Class Φ resonant gate drivers is presented and a detailed performance comparison with an equivalent half-bridge driver is conducted, where the resonant gate driver despite the slightly lower efficiency displays better switching characteristics.
properties that make them ideal candidates for primary coil drivers, but designing such circuits with accuracy is difficult using traditional first order methods due to their complexity.
A generalised design method is proposed in this work, that can be applied to any Class E type inverter, and includes non-linear and parasitic effects that become prevalent at high frequency
operation. A 13.56MHz 50W Class EF2 inverter is developed using this method with 97% efficiency, and no additional manual re-tuning, whilst maintaining all of the other design
requirements. In addition, several circuit configurations are introduced to enable high power operation using GaN technology, including a single common choke push-pull Class DE topology.
A demonstration of a 3.39MHz 3kW DC/DC inductive power system with 95% efficiency, using a parallel push-pull Class E inverter, is shown to confirm the theoretical findings. Furthermore, the typical one-to-one wireless link design is generalised to a one-to-many resonant system through a custom iterative method, which expands the application space of inductive power transfer systems. Then, an implicit method for characterising links at high frequency where measurement instruments fail to produce accurate results is proposed and demonstrated through experiments, by using resonant converters. The limitations of Class E type inverter operation at fixed loads are investigated and overcome by introducing various potential active ontrol schemes, which can even absorb the negative effects of reactive reflections to the primary while maintaining output regulation. Finally, an analytic design method for Class Φ resonant gate drivers is presented and a detailed performance comparison with an equivalent half-bridge driver is conducted, where the resonant gate driver despite the slightly lower efficiency displays better switching characteristics.
Version
Open Access
Date Issued
2022-12-31
Date Awarded
01/08/2023
License URL
Advisor
Mitcheson, Paul
Sponsor
European Union’s Horizon 2020 R
Engineering and Physical Sciences Research Council
Bumblebee Power Ltd (Firm)
Innovate UK
Grant Number
722496
EP/R029504/1
MHZIPT 10006065
Publisher Department
Electrical and Electronic Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)