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Author

Shin Nakagawa

Bio: Shin Nakagawa is an academic researcher. The author has contributed to research in topics: Ćuk converter & Buck–boost converter. The author has an hindex of 3, co-authored 5 publications receiving 17 citations.

Papers
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Proceedings ArticleDOI
01 Aug 2006
TL;DR: Based on the conventional forward converter, the transformer's magnetizing inductance is made small, and a reset winding of the transformer is moved to the secondary side, and furthermore, the anode terminal of the freewheeling diode is connected at a different point.
Abstract: Based on the conventional forward converter, the transformer's magnetizing inductance is made small, and a reset winding of the transformer is moved to the secondary side, and furthermore, the anode terminal of the freewheeling diode is connected at a different point. Then a novel topology of DC-DC converter is proposed, and its power efficiency is predicted to be improved. This converter has both operations of forward and flyback manners, and both of two diodes in the output side are maintained to be ON for a portion of the switching period. This operation results in the zero ripple of the output inductor current. This novel converter is confirmed to have some prominent features of withstand-voltage reduction for the main switch and ripper reduction of the output inductor current. As a result, this converter obtains a higher efficiency over the conventional forward converter. This paper describes its basic operation, and analyzes the steady-state characteristics by means of the extended state-space averaging method. The analytical results are confirmed experimentally, and an experimental result of a high efficiency of 94% was obtained for the input voltage of 140V and the output load of 18V and 4A.

6 citations

Proceedings ArticleDOI
07 May 2007
TL;DR: In this paper, the authors proposed a forward-flyback-mixed converter (FFB converter), where both the forward and the flyback actions are mixed, which has some prominent features of the voltage reduction for the main switch, the current-ripple reduction of output inductor, size reduction, and power loss reduction.
Abstract: This paper proposes a novel DC-DC converter where both the forward and the flyback actions are mixed. This novel converter has some prominent features of the voltage reduction for the main switch, the current-ripple reduction of output inductor, the size reduction, and the power loss reduction. This converter is named "Forward-Flyback-Mixed converter" and is abbreviated as "FFB converter." This paper presents the detailed analyses of static and dynamic characteristics for the continuous-conduction and the discontinuous-conduction modes. Comparing the analysis, simulation, and experiment, all the results agree well, and the analytical models were verified. Furthermore, comparing the proposed FFB converter with the conventional forward converter, it is clarified that the efficiency improvement is achieved and the FFB converter has a higher efficiency of 94% for output load of 18V/4A, and that its highly stable operation is performed.

6 citations

Proceedings ArticleDOI
18 Jun 2006
TL;DR: A novel topology of DC-DC converter is proposed, and its power efficiency is predicted to be improved, and the steady-state characteristics by means of the extended state-space averaging method are analyzed.
Abstract: Based on the conventional forward converter, the transformer's magnetizing inductance is made small, and a reset winding of the transformer is moved to the secondary side, and furthermore, the anode terminal of the freewheeling diode is connected to a different point. Then a novel topology of DC-DC converter is proposed, and its power efficiency is predicted to be improved. This converter has both operations of forward and flyback manners, and both of two diodes in the output side are maintained to be ON for a portion of the switching period. This operation results in the reduction of current ripple in the output inductor. Furthermore this novel converter is confirmed to have a prominent feature such as the reduction of withstand voltage for the main switch. As a result, this converter obtains a higher efficiency over the conventional forward converter. This paper describes its basic operation, and analyzes the steady-state characteristics by means of the extended state-space averaging method. The analytical results are confirmed experimentally, and a high efficiency of 94% was obtained for the input voltage of 140V and the output load of 18V and 4A.

3 citations

Journal ArticleDOI
TL;DR: An improved type of the Hybrid-Parallel Power-Factor-Correction (HP-PFC) converter is proposed that has the advantage of a higher efficiency and improved input current waveform and complies with the severe regulation of IEC61000-3-2 Class D.
Abstract: This paper proposes an improved type of the Hybrid-Parallel Power-Factor-Correction (HP-PFC) converter. It has the advantage of a higher efficiency and improved input current waveform. This advantage achieved through changing new charging path of the bulk capacitor and balancing the power flow from the two transformers to the output. This new circuit has been analyzed using MATLAB/Simulink and confirmed with experiment. As a conclusion, it is confirmed that this improved HP-PFC converter complies with the severe regulation of IEC61000-3-2 Class D. Moreover, a high efficiency of 90% is achieved for 15 V/6 A output power under the worldwide line voltage conditions.

2 citations

Proceedings ArticleDOI
01 Jan 2000
TL;DR: In this article, a parallel-structure converter was proposed, where only a single switch is used to reduce both the line harmonics and the output voltage ripple, and the experimental results have confirmed that this converter meets the IEC regulation of lane harmonic distortion, and that it obtains the suppression of output-voltage ripple and high efficiency.
Abstract: This paper proposes a novel parallel-structure converter, where only a single switch is used to reduce both the line harmonics and the output-voltage ripple. The experimental results have confirmed that this converter meets the IEC regulation of lane harmonic distortion, and that it obtains the suppression of output-voltage ripple and a high efficiency.

1 citations


Cited by
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Journal ArticleDOI
TL;DR: The proposed converter has no startup problem and no high voltage spikes on the switches, which otherwise are inherent for current- and voltage-fed-type bidirectional converters, and is easy to achieve soft switching by proper control and design.
Abstract: This paper presents a novel topology named forward-flyback bidirectional DC-DC converter (BDC), which is a hybrid of forward and flyback converters The windings of forward and flyback transformers are connected in series on the primary side and in parallel on the secondary side The proposed converter has no startup problem and no high voltage spikes on the switches, which otherwise are inherent for current- and voltage-fed-type bidirectional converters It is easy to achieve soft switching by proper control and design The built-in flyback transformer acts as a filter inductor, so the current ripple is smaller than flyback BDCs In this paper, the operation principles and characteristics of the proposed topology are analyzed in detail The advantages aforementioned are verified with experimental results of a 300-W prototype

162 citations

Proceedings ArticleDOI
01 Oct 2007
TL;DR: In this article, a DC-DC converter where both forward and flyback actions are mixed is presented, where the turns ratio of the second and third windings of the transformer is set to be a certain value.
Abstract: This paper presents a novel DC-DC converter where both forward and Flyback actions are mixed. Previously, we proposed this converter that has prominent features of reducing the voltage of main switch and the current ripple of output inductor, and as a result, the high efficiency and the size reduction were obtained as reported in the previous paper. And, this paper presents that this converter has four operation modes when the turns ratio of the second and the third windings of the transformer is set to be a certain value. Furthermore, these operation modes are analyzed through the extended state-space averaging method, and are confirmed by simulation. These characteristics are shown by means of a three-dimensional graphics method. This paper presents the detailed analyses of static characteristics for the four operation mode used three-dimensional expression of load characteristics with another winding turns ratio by the extended state-space averaging method.

10 citations

Proceedings ArticleDOI
01 Nov 2013
TL;DR: A high efficiency and high power factor single-stage balanced forward-flyback converter merging a foward and flyback converter topologies is proposed, and theoretical analysis and experimental results from a prototype of 24W LED driver are presented.
Abstract: In this paper, a high efficiency and high power factor single-stage balanced forward-flyback converter merging a foward and flyback converter topologies is proposed. The conventional AC/DC flyback converter can achieve a good power factor but it has a high offset current through the transformer magnetizing inductor, which results in a large core loss and low power conversion efficiency. And, the conventional forward converter can achieve the good power conversion efficiency with the aid of the low core loss but the input current dead zone near zero cross AC input voltage deteriorates the power factor. On the other hand, since the proposed converter can operate as the forward and flyback converters during switch on and off periods, respectively, it cannot only perform the power transfer during an entire switching period but also achieve the high power factor due to the flyback operation. Moreover, since the current balanced capacitor can minimize the offset current through the transformer magnetizing inductor regardless of the AC input voltage, the core loss and volume of the transformer can be minimized. Therefore, the proposed converter features a high efficiency and high power factor. To confirm the validity of the proposed converter, theoretical analysis and experimental results from a prototype of 24W LED driver are presented.

10 citations

Proceedings ArticleDOI
28 Oct 2013
TL;DR: In this article, a center-tapped forward-flyback dc/dc converter with higher efficiency and fewer elements is proposed, where a center tapped transformer is used to remove a conventional freewheeling diode of the forward flyback converter and peak voltage stress and turn-off switching loss are reduced.
Abstract: This paper proposes a center-tapped forward-flyback dc/dc converter with higher efficiency and fewer elements. In the converter, a center-tapped transformer is used to remove a conventional freewheeling diode of forward-flyback converter. Operation principle is changed by this modification and peak voltage stress and turn-off switching loss are reduced. The circuit configuration and principles of operation are analyzed in detail and design consideration is also presented. To verify advantages of the proposed converter, 13 W hardware prototype was built.

8 citations