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The application of conventional spread spectrum techniques for conducted electromagnetic emission (EME) reduction in inductive-resonant wireless power transfer (WPT) systems may not reduce conducted EME enough due to specific frequency characteristics of the resonant systems and it can lead to some "adverse effects", mainly in terms of decreased efficiency. Therefore, in this paper, an improved spread spectrum approach, multi-switching frequency and multi-duty cycle (MFMD) technique, is proposed. The proposed approach can give a considerably better conducted EME reduction along with a better efficiency than the conventional spread spectrum techniques based on a multi-switching frequency scheme. In the proposed approach, the inductive-resonant WPT system can operate at multiple switching frequencies (e.g., three different frequencies) and for a part of a control signal with a specific switching frequency, there is a specific duty cycle. The technique can be implemented in a simple way using an inexpensive 8-bit microcontroller. The effect of the MFMD scheme on the conducted EME and efficiency of the WPT system is studied in detail. The WPT system conducted EME and the efficiency are studied experimentally with a designed laboratory prototype. The performance characteristics of the WPT system with the MFMD scheme are compared to those with the multi-switching frequency scheme and without the spread spectrum. The WPT system with the proposed spread spectrum technique has a better performance than that with the conventional spread spectrum technique. [ABSTRACT FROM AUTHOR]

Inductive-resonant wireless power transfer systems are often used for wireless transfer of electric power. However, they are significant sources of radiated electromagnetic emissions. The effect of spread-spectrum approach based on classical switching frequency modulation of inductive-resonant wireless power transfer system inverter operating frequency and multi-frequency technique on the radiated emissions and efficiency is studied experimentally in detail. The influence of the classical frequency modulation and multi-frequency technique parameters on the peak radiated emission levels and the efficiency of the inductive-resonant wireless power transfer system are investigated more comprehensively. It is shown in the paper that the spread-spectrum approaches can lead to an appreciable radiated emissions reduction with small or large impact on the system's efficiency. Some useful recommendations on how to choose parameters of the periodic switching frequency modulation or the multi-frequency technique considering a trade-off between the radiated emissions reduction and the efficiency are also proposed. [ABSTRACT FROM AUTHOR]

A promising solution for inductive power transfer and wireless charging is presented on the basis of a single-phase three-level T-type Neutral Point Clamped GaN-based inverter with two coupled transmitting coils. The article focuses on the feasibility study of GaN transistor application in the wireless power transfer system based on the T-type inverter on the primary side. An analysis of power losses in the main components of the system is performed: semiconductors and magnetic elements. System modeling was performed using Power Electronics Simulation Software (PSIM). It is shown that the main losses of the system are static losses in the filter inductor and rectifier diodes on the secondary side, while GaN transistors can be successfully used for the wireless power transfer system. The main features of the Printed Circuit Board (PCB) design of GaN transistors are considered in advance. [ABSTRACT FROM AUTHOR]