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  Overview of Wireless Power Transfer

Wireless power transfer (WPT) technology, also known as wireless charging or wireless energy transfer, is a revolutionary approach that enables the transmission of electrical energy from a power source to a receiving device without the need for physical cables or direct electrical contact.

Wireless power transfer technology offers several advantages. It eliminates the need for physical connectors and cables, reducing clutter and simplifying charging processes. Users can simply place their devices on a charging pad or within a designated charging area, and power transfer occurs automatically. This convenience and ease of use make wireless charging an attractive solution for a wide range of applications.

However, wireless power transfer also presents challenges that researchers strive to address. These challenges include optimizing power transfer efficiency, extending the range of wireless charging, ensuring safety, and minimizing electromagnetic interference. Ongoing research and development efforts aim to overcome these obstacles and further enhance the capabilities and adoption of wireless power transfer technology.

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  Wireless Power Transfer System Design for Diverse Application

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  Wireless Power Transfer System Design Optimization

Our laboratory is engaged in research on system design methods that ensure high efficiency across a range of charging environments. One of our primary focuses is the design of a wireless charging pad consisting of multiple transmitting coils, which offers versatility in accommodating receiving coils with varying specifications.

In addition, we are conducting research on developing algorithms that enable optimal operations for these charging pads. By utilizing the methodologies of our laboratory, it becomes possible to achieve maximum efficiency by precisely optimizing the operations based on the size and location of each receiving coil in relation to its corresponding transmitting coil. These advancements pave the way for enhanced performance and seamless wireless charging experiences in diverse charging scenarios. In addition to the design of wireless charging pads, our research also focuses on compensation circuit design. We recognize the importance of minimizing switch loss, as it directly affects the overall efficiency and performance of wireless power transfer systems. Through meticulous analysis and experimentation, we strive to develop circuit designs that effectively mitigate switch loss, ensuring that energy is efficiently transferred from the power source to the receiving device.

Furthermore, our laboratory is dedicated to advancing the field of wireless power transfer through the development of a coupling coefficient extraction method between coils. The coupling coefficient is a critical parameter that determines the efficiency of energy transfer between the transmitting and receiving coils. Our team is actively researching and refining techniques to accurately measure and extract this coefficient, enabling us to optimize the design and configuration of wireless charging systems. By understanding and controlling the coupling coefficient, we can achieve higher power transfer efficiency and improve the overall performance of wireless charging technology.

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  EMF/EMI Reduction using Reactive Shiedling Coil in Wireless Power Transfer System

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  EMF/EMI Reduction through Controlling Power Electronics Circuit

In our laboratory, we are dealing with wireless charging EMC related issues. The wireless charging system is a technology that transfers energy through a magnetic field and has excellent convenience and safety features, but a leakage magnetic field around the system is inevitably generated. There is a possibility that this leakage magnetic field may cause electromagnetic field (EMF) problems related to human body effects or electromagnetic interference (EMI) problems related to interference of electronic devices. In order to provide a safe radio wave environment for wireless charging users, a lot of research has been conducted on solving EMF/EMI problems.

First, research on reactive shielding was conducted. Reactive shielding method doesn’t require additional materials or additional power sources. By using the leakage magnetic field itself as a power source, it is a method of shielding by adjusting the magnitude and phase of the current flowing through the coil through a combination of the shielding coil and the capacitor. It is attracting a lot of attention as a shielding method that has the advantage of not being complex and having excellent shielding performance.

In addition, research on shielding methods through current phase difference adjustment between transmit/receive coils was conducted. Passive, active, and reactive shielding methods have limitations in that they require additional materials. Therefore, there is a need for a way to reduce the stray magnetic field by simply adjusting the transmit/receive capacitors without additional materials. While previous studies have suggested resonance methods that maximize wireless charging efficiency or capacity, this study is differentiated in that it proposes a resonance method that minimizes leakage magnetic fields.

Finally, a study was conducted on how to reduce EMF/EMI through power circuit control. Wireless charging systems usually include power circuits such as PFCs, converters, and inverters. In particular, a DC-DC converter is essential for voltage regulation of the receiver, and the fundamental and harmonic components of the current change depending on the converter duty. In this study, a method for minimizing EMF/EMI was presented through duty control of the DC-DC converter in the receiver.

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  Object Detection using WPT System

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  Train Position Tracking System using WPT System

Wireless power transfer (WPT) is a technology that transmits energy to a load in the form of electromagnetic waves without a transmission line, providing various conveniences and safety. However, A foreign object in the charging area during power transfer causes system malfunction and efficiency reduction. In addition, since the impact on the system varies depending on the type of foreign substances, Foreign object detection (FOD) that distinguishes and detects foreign substances is required. A symmetrical coil with a pressure sensor designed to distinguish and detect substances in the charging area during wireless power transfer is proposed and designed.

WPT is being developed to supply electric power to electric trains, using a source coil in/on the railway track and a pick-up coil on the train. A number of benefits can be obtained by eliminating the catenary and pantograph currently used for railway electric power supply. However, the WPT employs coils, and the electromagnetic field generated by the WPT can interfere with conventional train detection methods, such as track circuits and RFID installed on the tracks. Train position information is critical for railway operation, especially for high-speed trains. Ferrite position identification (FPID), which provides train position information is proposed and designed.