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The loss and volume of the synchronous buck converter are influenced by various circuit parameters such as switching frequency, inductor, and dead time. However, their impact on the loss and volume has not been comprehensively analyzed and evaluated. To investigate and assess the loss and volume of synchronous buck converter over a wide load range, an automatic digital optimization design method is proposed in this article. First, the process established a complete circuit analytical model based on various operating conditions. Then, with the developed analytical model, the methodology is developed to comprehensively evaluate the loss and volume of the converter and investigate the impacts of the above-mentioned factors. Experimental results demonstrate that the proposed method can accurately predict the effects of switching frequency and inductor on the converter's efficiency and power density. Moreover, the method is effective in optimizing dead time. The proposed analysis and method provide guidance and a foundation for the parameter optimization and design of the synchronous buck converter.

With the wide application of the CLLC converters in bidirectional electric vehicle chargers, it becomes more important to improve their performance through proper parameter design. Compared with the frequency domain model, the time-domain model can significantly improve the accuracy of converter design. However, the currently generalized operation mode analysis method requires complicated operating mode judgment and solving systems of transcendental equations, which limits its practicality. To address this issue, a discrete event-driven piecewise analytic model (DEPAM) of CLLC converter is proposed in this article. DEPAM obtains the transient and steady-state waveforms without the need for operating mode judgment and solving transcendental equations. Relying on DEPAM, a design methodology of the CLLC converter is introduced in this article, which applies the lookup table method to the normalized parameters and achieves a complete traversal of all possible parameter combinations of the CLLC converter. This traversal considers gain range, soft-switching, capacitor voltage stress, and rms current simultaneously. Finally, the design methodology is demonstrated through a 1 kW prototype with 98.8% peak efficiency.

Bond wire fault is one of the most prominent degradation types for silicon carbide (SiC) mosfets, which could be detected and monitored through appropriate precursors. In this article, an online bond wire fault monitoring method for SiC mosfets with Kelvin package is proposed. It is based on the fact that the bond wires parasitic inductances are affected by bond wire fault over time. The variations of parasitic inductances can be converted into the variations of the voltage ringing between the Kelvin source and power source (vKS-S) during the turn-on event. To eliminate the affecting factors, the voltage ringing of the circuit parasitic inductance (vCIR) is introduced, and the division of the peak values of the two voltages ringing is used as the new bond wire fault precursor. The study results indicate that the proposed precursor has high sensitivity and high resolution to monitor each bond wire fault. Besides, the monitoring results are not affected by factors such as junction temperature, load current, and bus voltage. Therefore, the proposed fault monitoring method can be implemented online without knowing the factor information. The confirmatory experiment is carried out to verify the correctness of the proposed method.

In this article, a time-division multiplexing (TDM) modulation technology is proposed to enhance the efficiency of modular multiactive bridge (MMAB) converters in multiport power electronic transformers over a wide operating range. The TDM modulation retains the simplicity of single phase-shift (SPS) modulation while achieving efficiency improvement by adopting different structures (i.e., half-bridge and full-bridge) under different operating conditions with dc bias capacitors. However, determining the optimal structure under the same operating condition poses a significant challenge due to the strong coupling among MMAB ports. To address this issue, this article analyzes a dual-active bridge converter to investigate the steady-state characteristics of different structures, including the root-mean-square current and zero-voltage switching. By decomposing the MMAB converter into different transmission branches, the optimal combination structure of half-bridge and full-bridge are selected based on the branch powers, forming a simple and efficient TDM modulation technology. Finally, an experimental prototype of a four-port MMAB converter is established and tested. The results demonstrate that the proposed TDM can increase efficiency up to 19.09% compared to SPS, validating the correctness and effectiveness of the theoretical analysis.

This article presents a modeling method to build a complete and accurate multitime-scale analytical model for low-voltage eGaN HEMTs-based zero-voltage switching buck converter with consideration of parasitic inductors, nonlinear junction capacitors, and nonlinear transconductance. The switching steady-state modes and switching transient modes are discussed in detail based on their corresponding equivalent circuits. The state equations of each mode are solved by MATLAB software to obtain the key operating waveforms throughout one switching cycle. Moreover, the established switching steady-state model and switching transient model are numerically merged together through continuous state variables, and then the multitime-scale model for stable operation is formed based on the iterative method. The waveforms and switching energy losses predicted by the model within one switching cycle are compared with the experimental results, respectively, to verify the accuracy of the model. In the end, the dead time is optimized based on the proposed model, and the optimization result is verified to be effective in reducing the switching energy loss through the experiment.