The wireless power transfer (WPT) method for electric vehicles (EVs) is becoming more popular, and to ensure the interoperability of WPT systems, the Society of Automotive Engineers (SAE) established the J2954 recommended practice (RP). It includes powering frequency, electrical parameters, specifications, testing procedures, and other contents for EV WPT. Specifically, it describes the ranges of self-inductances of the transmitting coil, the receiving coil, and coupling coefficient (k), as well as the impedance matching values of the WPT system. Following the electrical parameters listed in SAE J2954 RP is crucial to ensure the EV wireless charging system is interoperable. This paper introduces a method for adjusting the effective permeability of the ferrite blocks in the standard model, to tune the self-inductance of the coils as well as the coupling coefficient. To guarantee the given values of the self-inductance of the coil and coupling coefficient matched those in the standard, we slightly modified the air-gap between the ferrite tiles in a specific region. Based on this method, it was possible to successfully tune the self-inductance of the transmitting coil and receiving coil as well as the coupling coefficient. The proposed method was verified by simulation and experimental measurements.

Silicon carbide (SiC) devices can significantly increase power efficiency, temperature reliability, power capacity, and power density because of their outstanding characteristics. Nevertheless, in the bridge-leg configuration of a power converter, the high-speed switching capability of SiC mosfets is often restricted by the coupling noise between high-side mosfet and low-side mosfet. The coupling noise caused by high ${dv/dt}$ and ${di/dt}$ in switching transient will increase the switching loss and the risk of mosfet breakdown. In order to completely take advantage of the superior feature of SiC mosfets, a novel multilevel gate driver is proposed in this article to mitigate the coupling noise effectively. Compared to the conventional gate drivers, the proposed gate driver adds a capacitor, an auxiliary mosfet, a Zener diode, and two resistors to regulate the turn-off voltage bias felicitously. In this article, the operation principle of the proposed gate driver is first introduced, to the best of our knowledge. Moreover, to obtain the circuit parameters accurately, a series of formulas have also been derived by equivalent circuit models. A 230-V/4.6-A synchronous buck converter based on SiC mosfets is successfully experimented to verify this proposed gate driver.

Wireless power transfer (WPT) is an emerging technology deployed for a wide range of applications. Various design challenges need to be addressed at both circuit and system levels. However, the conventional modeling methods either require impractical assumptions or only focus on the coil-to-coil part. This article presents a system-level model for WPT applications, including all the critical interior blocks, such as power amplifier, transmitter coil, receiver coil, matching networks, and rectifier. An accurate characterization method is proposed to obtain the rectifier impedance as a realistic load condition. Then, through frequency harmonic analysis, the power capabilities along the power flow path are analytically derived for both the fundamental and higher order harmonic components. The system efficiency and the power loss at each block can be accurately estimated. As a result, this model can not only optimize the system performance, but also help improve the thermal design for WPT products. With the assistance of this improved model, a practical design methodology is introduced to optimize the system parameters. An experimental prototype is built to validate the proposed model and the design methodology. Good correlations are observed between the calculations and experiments in both the time-domain and frequency-domain results.

As an essential component in power applications, magnetic cores and their design play an important role in achieving high efficiency and high power density. Accurate measurement of the core loss is important for inductor and power converter optimization. Loss measurement depends on exactly determining the phase angle between the voltage and the current. However, measurement errors can be introduced due to the discrepancies in propagation delays in the voltage and current sensors. In addition, the propagation delay is frequency-dependent but has a large influence in the MHz range and above. Previously, several methods have been proposed to compensate for this discrepancy, but they are time-consuming and can result in large measurement errors. In this article, a characterization method for core loss based on a vector network analyzer (VNA) and an impedance converter is proposed to accurately measure the phase discrepancies between voltage and current sensors. The proposed method is experimentally verified up to 15 MHz with a three-coil test setup.

With the increasing switching frequencies and power densities in modern power converters, magnetic core losses are becoming more essential for efficiency and thermal optimization. Traditionally, the two-winding method suffers from sensitivity to phase error in practical measurements; this is mainly created by the unknown phase shift of a current-sensing resistor. Several methods have been developed to characterize the phase shift of a current shunt resistor; however, the load effects of oscilloscopes are ignored. As a result, the corresponding phase shift can be significantly underestimated. This article proposes an improved method for phase shift extraction of a current shunt to solve the problem. The effectiveness of the shunt characterization method is experimentally verified up to 50 MHz. Benefits from the proposed method, the time-consuming component tuning process is not required for core loss measurement. A measurement verification at 10 MHz shows its validity. Finally, a current shunt implemented with a coaxial resistor array is designed with a phase shift of 0.05 $^\circ$ at 10 MHz and a parasitic inductance as low as 42 pH.

An intermodulation (IM) generator based on substrate integrated waveguide (SIW) is demonstrated. This generator has maximal 80 dB dynamic range with a size that is smaller than 65 mm × 40 mm × 1.5 mm. A biased Schottky diode is mounted onto the slotted plane of SIW and it consists of a nonlinear dipole to radiate nonlinear signal to the carrier domain and serve as reference signal. A polarized slot helps focus the linear carrier wave onto the diode and construct a bias-controlled IM distortion. The experiment proves that this device can generate the IM3 reference ranges from −112 to −32 dBm at 2 × 43 dBm, while its minimum step can reach lesser than 0.5 dB. This proposed device can serve as tunable IM standards in PIM test and calibrate the commercial PIM tester.