When the conventional space vector phase-shifted modulation is applied to the dual active bridge (DAB)-based three-phase single-stage (DAB-3P1S) AC-DC converter, the AC side current error in a switching period is caused because of the coupling of high-frequency transformer currents in the adjacent switching periods and the imprecise dwell times of the active current vectors. By analogizing the DAB-3P1S AC-DC converter into the DAB based DC-DC converter, a dual-period-decoupled space vector phase-shifted modulation (DPD-SVPSM) based on triple phase shifts is proposed to decouple the transformer currents, thus eliminating the AC side current distortion. Moreover, taking the minimization of the RMS value of the transformer current per switching period as the constraint, the exact relationship between the desired AC side current and the three phase shifts is derived to realize the precise control of instantaneous AC side current and the efficiency improvement. Detailed experimental results validate the correctness of the theoretical analysis and the feasibility of the proposed modulation strategy.

Aiming at the high-input-voltage multiple-output low-power applications, an input-series two-transistor flyback auxiliary power supply scheme is proposed and investigated. In this converter, an integrated-transformer is adopted instead of the single-transformer in each series-module, all of the series-modules are operating synchronously, and the input voltage sharing (IVS) can be achieved automatically. The active IVS mechanism of this converter is analyzed, furthermore, through the influence analysis when the series-modules are operating asynchronously and the tolerance features of the key parameters are considered, the related design consideration of the input filter capacitor in each series-module is discussed. Finally, after the simulation verifications, a 60-W laboratory-made prototype of this auxiliary power supply composed of three series-modules is built, by which the feasibility of the presented scheme and the validity of the theoretical analysis are verified.

The maximum phase current (the maximum transfer power) of the dual-active-bridge based three-phase single-stage (DAB-3P1S) ac-dc converter with the present dual-period-decoupled space vector phase-shifted modulation (DPD-SVPSM) is analyzed for the first time in this article. It shows the equal switching period assignment way of the present DPD-SVPSM reduces the utilization of the control period, thus limiting the maximum transfer power of DAB-3P1S ac-dc converter. To enhance the maximum transfer power, a variable switching period based dual-period-decoupled space vector phase-shifted modulation (VDPD-SVPSM) is proposed. Besides, the current stress of DPD-SVPSM and VDPD-SVPSM are analyzed and compared. And it indicates that by properly designing the transformer leakage inductor, VDPD-SVPSM improves the maximum phase current (maximum transfer power) without increasing the current stress of the device, thereby improving the utilization of the system hardware rated capacity then increasing the power density. Detailed experimental results validate the correctness of the theoretical analysis and the feasibility of the proposed VDPD-SVPSM.

In this paper, an input-series two-transistor forward converter is proposed and investigated, which is aimed at high-input voltage multiple-output applications. In this converter, all of the switches are operating synchronously, and the input voltage sharing (IVS) of each series-module is achieved automatically by the coupling of primary windings of the common forward integrated transformer. The active IVS processes are analyzed based on the model of the forward integrated transformer. Through the influence analysis when the mismatches in various series-modules are considered, design principles of the key parameters in each series-module are discussed to suppress the input voltage difference. Finally, a 96-W laboratory-made prototype composed of two forward series-modules is built, and the feasibility of the proposed method and the theoretical analysis are verified by the experimental results.

In this paper, an input-series flyback converter with the coupled-inductor-based passive snubber is proposed, where the input-series converter is based on transformer-integration, and the passive snubber is composed of inductors, capacitors and diodes. The inductors of the snubber in various series-modules are made on a common magnetic core, and the coupled-inductor scheme is adopted. With the help of the coupled-inductor, active input voltage sharing (IVS) of the input-series converter can also be achieved after the switches are turned off, and voltage sharing of the switch in each series-module can be ensured, which overcome the shortcomings of the existing input-series flyback converter. Active voltage sharing processes caused by the coupled-inductor are analyzed in detail. Furthermore, design guideline of the passive snubber is discussed. Finally, experimental study has been done on a 1500Vdc/60W laboratory-made prototype composed of three flyback series-modules, and the feasibility of the proposed method and the theoretical analysis are verified by the experimental results.

In this study, two novel improved passive snubbers suitable for isolated full‐bridge boost topology are proposed. The snubbers are composed of two capacitors, two inductors and four diodes. The voltage spike across the primary side of transformer is absorbed by one capacitor of the snubbers during a charging period, and by the other capacitor in the following charging period. The energy of capacitors can be transferred to the output side of the power factor correction (PFC) converter during one charging period by the resonance of the inductors and capacitors. Taking one improved snubber, for example the operational process of the original and the improved snubbers are analysed in a single‐phase isolated full‐bridge boost PFC converter. Furthermore, between the original and the improved snubbers, comparative analysis about the voltage and current stress, parameters limitation and the reliability are given. Finally, experimental study has been done on a laboratory‐made single‐phase PFC prototype, and the feasibility of the proposed method and the validity of the theoretical analysis are verified by the experimental results.