Research

Research Overview

We aim to push power electronics toward higher frequency, higher power density, and higher efficiency. By combining circuit design, device characterization, electromagnetic modeling, and hardware validation, we build practical power conversion systems for future energy, transportation, and computing applications.

Wide-Bandgap Device Characterization

We investigate the dynamic switching behavior of SiC and GaN power devices under high-frequency and high-slew-rate operating conditions. As part of this effort, we develop MHz-range double-pulse test platforms for switches to study parasitic-induced ringing, waveform distortion, and switching loss mechanisms. Through hardware measurements, waveform analysis, and parasitic-aware modeling, we evaluate device performance beyond datasheet specifications and support the reliable design of high-frequency power converters.

Multi-Frequency Multi-Receiver MHz Wireless Power Transfer using Class-Φ2 Inverter

This project develops a MHz wireless power transfer system that can power multiple receivers at the same time using a single inverter and transmitter coil. Conventional multi-receiver systems often require separate power electronics or time-sharing between receivers, which increases complexity and limits transmitter utilization. In this project, the Class-Φ2 inverter is intentionally designed to strengthen its third-harmonic output, allowing both the fundamental and third-harmonic frequencies to serve as simultaneous power-delivery channels.

The project also optimizes a multi-frequency resonating compensation network so the transmitter sees an efficient, near-resistive load at both frequencies. This reduces unnecessary reactive power flow and improves power conversion. A prototype demonstrated 353 W of combined output power with 76% peak DC-to-load efficiency across a 15 mm coil-to-coil distance. The results show that inverter harmonics can be actively used for controlled multi-load wireless power transfer, enabling simpler and more scalable wireless charging systems.

Modeling and Optimization of Self-Resonant Planar Coil

This project introduces a comprehensive mathematical framework and a gradient-based optimization method to design high-frequency, self-resonant planar coils for wireless power transfer (WPT) applications. Operating at 13.56 MHz, these coils utilize internal capacitance formed by two closely spaced copper windings to eliminate the need for discrete external capacitors, which are often prone to high-voltage stress in high-power systems. The study derives closed-form expressions for inductance, capacitance, and series resistance based on Archimedean spiral geometry.

By implementing a Sequential Least Squares Programming (SLSQP) algorithm in Python, the research identifies the optimal geometric parameters, such as turn count, trace width, and dielectric thickness, that maximize the coil's quality factor (Q) while maintaining resonance. Experimental validation was conducted using a fabricated copper-sheet prototype driven by a single-switch class Phi-2 resonant inverter, selected for its reliability and soft-switching capabilities at MHz frequencies. The optimized coil achieved a measured quality factor exceeding 700. In hardware tests, the system successfully transferred 640 W of power across a 13 cm gap with a coil-to-coil efficiency of 95%.

High-Power and High-Frequency Class-Φ2 Inverter for UAV WPT Applications

This project aims to develop kW-level inverters operating at 13.56 MHz, achieving high efficiency and accommodating load variations. For single-switch topologies such as the Class-Φ2 inverter, switching-device losses and the resulting thermal bottleneck limit the inverter's continuous power conversion capability. It is therefore crucial to investigate the factors contributing to switching device losses and determine the maximum power a single inverter can handle. Then, it will be feasible to utilize power combining circuits at the inverter outputs to achieve kW-level power delivery.

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