At 13.56 MHz, the circuit parasitic elements strongly affect the stability, performance, and efficiency of the inverter. In this paper, the effect of parasitic elements in the 13.56 MHz half-bridge inverter is analyzed in detail based on the point of view of the high-frequency ringing in the circuit. A proposed inverter design which aims to attenuate the influence of the parasitic elements is presented, including optimized PCB design and ringing damping design. The simulation and experiment results show that the proposed PCB design not only reduces the parasitic inductance in the ringing loop but also improves the stability of the inverter by avoiding the sub-resonant at low frequency and reducing the radiation EMI noise. This work also points out that the ringing current exists in the circuit even with the proposed optimized PCB design lead to the instability of the inverter at high voltage operating condition. The proposed damping circuit significantly suppresses the ringing in the circuit and improves the stability as well as the efficiency of the inverter. The experiment results confirm that by using the proposed design, the half-bridge inverter module using Silicon MOSFET is stable at 13.56 MHz switching frequency and its efficiency obtains 93:1% at 1.2 kW output power.

This paper proposes and demonstrates a wireless power transfer system design for electric vehicle dynamic charging applications. The dynamic wireless charging (DWC) lane is designed for modularly. Each module has three shorttrack transmitter coils that are placed closely together and connected to a single inverter to reduce the number of inverters. The magnetic coupler design is analyzed and optimized by finite element analysis (FEA) to reduce the output power variation during dynamic charging. The LCC compensation circuit is designed according to the optimal load value to obtain maximum efficiency. The SIC devices are used to improve the efficiency of the high-frequency resonant inverter. A 1.5 kW dynamic charging system prototype is constructed. Experimental results show that the output power variation of 9.5% and the average efficiency of 89.5% are obtained in the moving condition.

This paper presents the proposed design of high power and high efficiency inverter for wireless power transfer systems operating at 13.56 MHz using multiphase resonant inverter and GaN HEMT devices. The high efficiency and the stable of inverter are the main targets of the design. The module design, the power loss analysis and the drive circuit design have been addressed. In experiment, a 3 kW inverter with the efficiency of 96.1% is achieved that significantly improves the efficiency of 13.56 MHz inverter. In near future, a 10 kW inverter with the efficiency of over 95% can be realizable by following this design concept.

This paper presents the ringing suppressing method in class D resonant inverter operating at 13.56MHz for wireless power transfer systems. The ringing loop in half-bridge topology inverter at 13.56MHz strongly effect to the stable, performance and efficiency of the inverter. Typically, this ringing can be damped by using a snubber circuit which is placed parallel to the MOSFETs or using a damping circuit which is place inside the ringing loop. But in the resonant inverter with high power and high frequency, the snubber circuit or general damping circuit may reduce performance and efficiency of inverter. A new damping circuit combining with drive circuit design solution is proposed in this paper. The simulation and experiment results showed that the proposed design significantly suppresses the ringing current and ringing voltage in the circuit. The power loss on the MOSFETs is reduced while the efficiency of inverter increases 2% to obtain 93.1% at 1.2kW output power. The inverter becomes more stable and compact.