Dual-active-bridge (DAB) circuit is an excellent candidate for high-efficiency, high-power-density and bidirectional electric vehicle chargers. Unlike resonant circuits employing auxiliary inductors and capacitors, DAB minimizes usage of passive components. The challenge, however, lies in the difficulty of securing zero voltage switching (ZVS), particularly at light-to-medium load when using the conventional single-phase-shift (SPS) control. This is of utmost importance not only for the sake of the efficiency but also for minimizing the switch-bridge crosstalk caused by hard switching-on, thereby enhancing the system reliability. Although dual-phase-shift (DPS) and triple-phase-shift (TPS) can be the answer, they do introduce side effects such as larger switching-off current. This paper systematically integrates SPS, DPS and TPS to maximize full-power ZVS range for both steady-state and transient operations in EV chargers. This paper plots ZVS boundaries over the full power range, categorizes all operations into nine states and proposes a smooth transition method among all operation modes. Dead band is also incorporated in the ZVS boundary setting. Experimental results on a SiC-based charger validates the effectiveness of this method of widening ZVS range for output voltage of 200~450VDC and power of 0~20kW, achieving smooth transitions among various modes, and suppressing switch crosstalk, thereby securing high charger reliability.

Zero-Voltage-Switching (ZVS) has been widely applied in wide band gap (WBG) devices based high-switching-frequency converters, for instance, dual-active-bridge (DAB) isolated DC-DC converter, which consists of two H-bridges. To secure ZVS for all eight switches, previous literature mostly focuses on half bridge to analyze switching transitions, which, however, is rather incomplete due to ignoring impact of modulations strategies and cannot fulfill all circumstances. In this letter, the whole H-bridge is used as a unit to analyze ZVS transient process, addressing the ZVS setting in different modulation strategies. The minimal initial inductor energy to complete ZVS process is also pointed out and categorized, which in return can reduce the transformer current thereby enhancing the efficiency. Furthermore, the derivation of accurate ZVS transition time is discussed considering the non-linearity of switch output capacitance, which can be referenced to set up dead-band time. An H-bridge prototype with SiC devices is built up to verify the theory proposed in this letter.

The expansion of electric vehicles made the expansion of charging infrastructure rudimentary to keep up with this developing technology that helps people in a myriad of ways. The main drawback in electric vehicle charging, however, is the time consumed to charge a vehicle. The fast charging of electric vehicles solves this problem thus making it a lucrative technology for consumers. However, the fast charging technology is not without its limitations. In this paper we have identified the technology gaps in EV fast charging stations mostly focused on the extremely fast charging topology. It will help pave a path for researchers to direct their effort in a consolidated manner to contribute to the fast charging infrastructure. A thorough review of all aspects and limitations of existing extremely fast charging (XFC) stations have been identified and supporting data are provided. The importance of DC power network based on free fuel energy sources and silicon carbide-based power electronics are proposed to provide ultra-low cost and ultra-high speed XFC stations.

To further improve the system integration and convenience of the battery charging system for electric vehicles, this letter proposed a multipurpose magnetic coupler-based charging solution that integrates bidirectional on-board charger (OBC), wireless power transfer (WPT), and an auxiliary power module (APM). The proposed solution presents multiple highlights: 1) the first exhibited solution to integrate OBC, WPT, and APM in one unit; 2) magnetic integration that uses a multiwinding WPT pad to eliminate the main transformer of OBC and APM; and 3) topological integration that saves multiple active and passive devices. This letter includes a description of the system topology, operation principles of individual charging modes, a novel magnetic coupler, and the design methodology. Finally, a prototype was constructed and different charging modes were tested to validate the proposed design.

An auxiliary power module (APM) in electric vehicles is a DC/DC converter bridging the high voltage propulsion battery with a low voltage auxiliary system. With the era of connected and autonomous vehicles coming, the power rating of such DC/DC is expected to surge, say from 2.5kW to 6kW. No mention its challenge of wide operating voltage range, e.g., 250~450V input provided by the high voltage propulsion battery and 10~16V at the low voltage auxiliary battery. To meet such voltage and power challenges, this paper proposed a two-stage bidirectional design, i.e., interleaved buck + DC transformer (DCX) offering full voltage range coverage, 3.5kW rated power and peak power of >6kW. Experimental results indicated >96% efficiency, thanks to the zero-switching loss of DCX. In addition, the pre-charge mode to charge the input DC bus capacitor with the low-voltage battery is also achieved using the inner phase shift control at the DCX stage. To save DC-bias blocking capacitors at the low-voltage side, a novel and simple DC bias detection circuit is proposed to sample the DC-current offset of the transformer. Both simulation and test results verified that the proposed method can effectively detect and eliminate the DC bias current.

While the employment of wide bandgap (WBG) devices in high-frequency and high-voltage applications brings benefits such as reduced system size and improved efficiency, it aggravates the electromagnetic interference (EMI) issue due to fast switching. High-frequency EMI noise suppression relies mainly on the filter design, where the filter's performance is strongly affected by parasitics. Through analyzing the common-mode (CM) equivalent circuit of a half-bridge power module, this letter identifies the key parasitics that dominate the performance of a common-mode filter (CMF) at high frequencies. To minimize the parasitics, the concept of integrating the CMF inside the WBG power module package is developed to improve the noise attenuation. A π-type CMF is integrated with a half-bridge GaN-based power module as a prototype to validate the concept. Experiments are conducted by measuring the CM noise spectrum received by the line impedance stabilization networks (LISNs) from the hard switching of the designed power module under 70 V and 80 kHz. Comparing the measured results of the integrated CMF to the externally-added CMF, up to 50 dBμV more attenuation is achieved by the integrated CMF in the frequency range of 10 MHz to 100 MHz, verifying the theoretical analysis and the established CM equivalent circuit.