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A.J. Zhang

Bio: A.J. Zhang is an academic researcher. The author has contributed to research in topics: Ćuk converter & Flyback converter. The author has an hindex of 1, co-authored 1 publications receiving 882 citations.

Papers
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Proceedings ArticleDOI
07 Aug 2002
TL;DR: In this article, a LLC resonant converter is proposed for front end DC/DC conversion in a distributed power system, which utilizes leakage and magnetizing inductance of a transformer.
Abstract: A new LLC resonant converter is proposed for front end DC/DC conversion in a distributed power system. Three advantages are achieved with this resonant converter. First, ZVS turn on and low turn off current of MOSFETs are achieved. The switching loss is reduced so we can operate the converter at higher switching frequency. The second advantage is that with this topology, we can optimize the converter at high input voltage. Finally, with this topology, we can eliminate the secondary filter inductor, so the voltage stress on the secondary rectifier will be limited to two times the output voltage, better rectifier diodes can be used and secondary conduction loss can be reduced. The converter utilizes leakage and magnetizing inductance of a transformer. With magnetic integration concept, all the magnetic components can be built in one magnetic core. The operation and characteristic of this converter is introduced and efficiency comparison between this converter and a conventional PWM converter is given which shows a great improvement by using this topology.

941 citations

Proceedings ArticleDOI
04 Nov 2022
TL;DR: In this paper , a proportional current sampling method is proposed for smaller current-transformer (CT) design and more compact integration of the CT with the main transformer, and a prototype of high constrictive integrated magnetics is developed for a 2700W server power converter.
Abstract: As one kind of the key passive components in converter, magnetics is playing more and more important role for higher efficiency and higher power density design. To achieve these goals, a proportional current sampling method is proposed, which is an interesting study targeted for smaller current-transformer (CT) design and more compact integration of the CT with main transformer. In this paper, the author firstly studied main transformer winding structure to ensure proportional current sharing from designated wire, then proposed the integration of CT with main transformer having the innovative predefined winding structure, finally a prototype of high constrictive integrated magnetics has been developed for a 2700W server power converter and the test results match well with theoretical analysis.

Cited by
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Proceedings ArticleDOI
19 Mar 2006
TL;DR: In this paper, the relationship between converter efficiency and operation range with different circuit parameters has been revealed and an optimal design methodology has been developed based on the revealed relationship, and a 1MHz, 1kW LLC converter is designed to verify the proposed method.
Abstract: Although LLC resonant converter can achieve wide operation range with high efficiency, lack of design methodology makes it difficult to be implemented. In this paper, based on the theoretical analysis on the operation principles during normal condition and holdup time, the relationship between converter efficiency and operation range with different circuit parameters has be revealed. An optimal design methodology has been developed based on the revealed relationship. A 1MHz, 1kW LLC converter is designed to verify the proposed method.

638 citations

Book
15 Sep 2014
TL;DR: In this article, the authors present a practical guide for understanding basic GaN transistor construction, characteristics, and applications, as well as specific application examples demonstrating design techniques when employing GaN devices.
Abstract: This timely second edition has been substantially expanded to keep students and practicing power conversion engineers ahead of the learning curve in GaN technology advancements. Acknowledging that GaN transistors are not one-to-one replacements for the current MOSFET technology, this book serves as a practical guide for understanding basic GaN transistor construction, characteristics, and applications. Included are discussions on the fundamental physics of these power semiconductors, layout and other circuit design considerations, as well as specific application examples demonstrating design techniques when employing GaN devices.

506 citations

Journal ArticleDOI
TL;DR: In this paper, a multiresonant dc-dc converter in a two-stage smart battery charger for neighborhood electric vehicle applications is presented, which eliminates both low and high-frequency current ripple on the battery, thus maximizing battery life without penalizing the volume of the charger.
Abstract: In this paper, resonant tank design procedure and practical design considerations are presented for a high performance LLC multiresonant dc-dc converter in a two-stage smart battery charger for neighborhood electric vehicle applications. The multiresonant converter has been analyzed and its performance characteristics are presented. It eliminates both low- and high-frequency current ripple on the battery, thus maximizing battery life without penalizing the volume of the charger. Simulation and experimental results are presented for a prototype unit converting 390 V from the input dc link to an output voltage range of 48-72 V dc at 650 W. The prototype achieves a peak efficiency of 96%.

390 citations

Patent
01 Oct 2002
TL;DR: In this article, a Factorized Power Architecture (FPA) method and apparatus includes a front end power regulator (PRM) which provides one or more controlled DC bus voltages which are distributed through the system and converted to the desired load voltages using voltage transformation modules (VTMs) at the point of load.
Abstract: A Factorized Power Architecture (“FPA”) method and apparatus includes a front end power regulator (“PRM) which provides one or more controlled DC bus voltages which are distributed through the system and converted to the desired load voltages using one or more DC voltage transformation modules (“VTMs”) at the point of load. VTMs convert the DC bus voltage to the DC voltage required by the load using a fixed transformation ratio K=V out /V in and with a low output resistance. VTMs exhibit high power density, efficiency and, owing to their inherent simplicity and component utilization, reliability. VTMs may be paralleled and share power without dedicated protocol and control interfaces, supporting scalability and fault tolerance. Feedback may be provided from a feedback controller at the point of load to the front end or to upstream, on-board power regulator modules (“PRMs”) to achieve precise regulation.

389 citations

Journal ArticleDOI
TL;DR: Possessing the very optimal ZVS +ZCS soft-switching feature, this proposed converter will have a minimized switching loss if all of the main switches are implemented with metal-oxide-semiconductor field-effect transistors, and thereby, the proposed converter is fully soft switched and totally snubberless.
Abstract: A bidirectional DC-DC converter (BDC) with a new CLLC-type resonant tank, which features zero-voltage switching (ZVS) for the input inverting choppers and zero-current switching (ZCS) for the output rectifier switches, regardless of the direction of the power flow, is proposed in this paper. Possessing the very optimal ZVS +ZCS soft-switching feature, this proposed converter will have a minimized switching loss if all of the main switches are implemented with metal-oxide-semiconductor field-effect transistors, and thereby, the proposed converter is fully soft switched and totally snubberless. The detail operation principles, as well as the design considerations, are presented. The methodologies to develop a unidirectional ZVS+ZCS dc-dc converter for the corresponding pulsewidth modulation and frequency modulation converters are proposed. The approach on how to construct a fully soft-switched BDC has also been proposed and analyzed. Finally, a topology extension is made, and another fully soft-switched BDC is derived. A prototype, which interfaces the 400-48-V dc buses for the uninterrupted power supply system with a power rating of 500 VA, was developed to verify the validity and applicability of this proposed converter. The highest applicable conversion efficiencies for the bidirectional operational modes are exceeding 96%.

383 citations