The dual-active-bridge (DAB) converters inherit favorite features including zero-voltage switching (ZVS) capability, wide voltage range, and natural bidirectional power flow. Facing different applications and high market requirements, conventional DAB topologies with various modulations are gradually inadequate, so topological modifications are emerged in the literature to deal with these situations. Based on their characteristics of these modified DAB topologies, in this article, we provide a comprehensive review and classification, and the methodology to modify DAB topologies is proposed. First, basic cells including input/output types, active bridges, transformers, and auxiliary high-frequency networks are introduced. Next, by combining these cells flexibly, modified DAB converters are derived, and they are classified in terms of structural characteristics and discussed in detail. Finally, the characteristics, merits, and demerits of the modified DAB converters are concluded. Evolvement history, future trends, and the derivation of new topologies are also analyzed. This article aims to present a clear picture of the general law and framework of the modified DAB topologies and give the inspiration to derive new DAB topologies to address specific requirements.

Dual active bridge (DAB) converters are widely studied for applications requiring isolation, bidirectional power flow and high efficiency. To solve the problem of limited zero voltage switching (ZVS) range and achieve seamless transition for extended-phase-shift (EPS) control, the magnetizing current is utilized and an optimized control law is proposed in this article. With the injection of magnetizing current, the two ZVS regions under EPS control will be creatively intersected with a large region, instead of disconnected or just intersected at a particular point as in previous studies. The ZVS model considering switch junction capacitors, ZVS region analysis with magnetizing current injection and power transfer characteristics are analyzed. Based on these analyses, the optimized EPS control is proposed to achieve full load range ZVS, low root-mean-square current and maximum transmission power capability. A 250 kHz, 500 W GaN-based DAB prototype is built to verify the effectiveness of the proposed solution.

It is a challenge for dual-active-bridge (DAB) converters to take a good balance between full-load-range zero-voltage switching (ZVS) and control complexity with a wide voltage range. Dual-phase-shift (DPS) control can extend the ZVS range greatly compared with single-phase-shift (SPS) control, and it has fewer control variables with reduced operation modes compared with triple-phase-shift (TPS) control. However, with conventional DPS control, at least a pair of switches will be operated under hard switching within a large power range, which severely reduces the efficiency, especially at the high switching frequency. To solve this problem, based on the Lagrange multiplier method (LMM), an optimized DPS control utilizing magnetizing current is proposed. In this article, the magnetizing inductance is designed to create the possibility of full-load-range ZVS achievement for all power switches. Based on ZVS analysis considering switch junction capacitors and power characteristics analysis, a power control law premised on full-load-range ZVS achievement is proposed to achieve low current stress. Finally, the effectiveness of the proposed solution is verified by experimental results obtained with a 500-W, 250-kHz gallium–nitride (GaN)-based prototype.

A decoupled extended phase shift control is proposed to decrease the control complexity and achieve full load range zero voltage switching (ZVS) for dual active bridge (DAB) dc–dc converters. In the proposed solution, full load range ZVS is achieved by adding an extra small fixed duty cycle and utilizing the magnetizing current. In addition, the two control variables are decoupled, since the control of the duty cycle is only determined by the voltage conversion ratio and is independent of the phase shift angle, which avoids the detection of operation mode and switching of control laws. The ZVS model considering junction capacitors and magnetizing inductance, ZVS region under full load range, and derivation of control law are analyzed in detail. Finally, the effectiveness of the proposed solution is experimentally verified on a 500-W, 250kHz GaN-based prototype.

In this letter, a switch-multiplexed quasi-two-stage buck-dual-active-bridge (DAB) (SMBDAB) and its modulation strategy are proposed. Under the quasi-two-stage buck-DAB architecture, one bridge of the primary side of the proposed converter is multiplexed as both the bridge of the buck circuit and the DAB circuit to reduce the power switches. In addition, with the voltage-matching modulation, multiplexing still ensures that the voltages on both sides of the leakage inductor of the DAB circuit are always matched when the voltage gain of the converter changes, and thus, the zero-voltage switching (ZVS) of all the switches can be achieved. Furthermore, the partial power transfer characteristics of the buck circuit still maintains, which could reduce the power rating of the inductor for the buck circuit. The working principle, power transfer characteristics, and full range ZVS design are analyzed. Finally, the effectiveness of the SMBDAB converter is verified through experimental results from a 1kW prototype.

An integrated Buck-LC converter for a wide voltage range is proposed in this paper based on a quasi-two-stage structure. In the integrated quasi-two-stage Buck-LC (IQBLC) converter, the LC resonant stage is under DCX mode and the Buck stage can achieve voltage regulation. The buck stage is integrated into the DCX stage, which can reduce the number of switches. The inductor of the buck stage only transfers a part of the output power which benefits the efficiency improvement and ZVS achievement. Different working modes and modulation strategies are presented for the IQBLC converter to further extend the voltage gain. The soft switching of all switches can be realized under different modes and loads. Besides, a duty cycle control trajectory is proposed to realize continuous voltage gain adjustment under multimode operation. The voltage gain characteristics, partial power characteristics, ZVS conditions, and discontinuous mode constraints of the LC stage are analyzed in detail in the paper. Experimental results are obtained from a 1kW prototype to validate the effectiveness of the proposed converter.