• Journal of IKEEE
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• v.16 no.4
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• pp.335-342
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• 2012

This paper is studied on a new DCM-ZVS step up-down AC-DC converter of high performance, that is, high system efficiency and power factor correction (PFC). The switching devices in the proposed converter are operated by soft switching technique using a new quasi-resonant circuit, and are driven with discontinuous conduction mode (DCM) according to pulse width modulation (PWM). The quasi-resonant circuit uses a step up-down inductor and a loss-less snubber capacitor. The proposed converter with DCM also simplifies the requirement of control circuits and reduces the number of control components. The input AC current waveform in the proposed converter becomes a quasi-sinusoidal waveform proportional to the magnitude of input AC voltage under constant switching frequency. As a result, the proposed converter obtains low switching power loss and high efficiency, and its input power factor is nearly in unity. The validity of the analytical findings is confirmed by some computer simulation results and experimental results.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.15 no.1
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• pp.51-58
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• 2001

Recently, DC-DC converters significantly increase the total losses as rising switching frequency. Trnditional soft switching technique for reducing switching losses even increase voltage/Clment stress of switch In this paper, Resonant circuit for soft switching is connected in parallel with power stage and only operates just before tum-on of the main sWItch. Therefore, ills doesn't affect the total circuit QI'||'&'||'pound;ration. The object of tIns paper is to make the linearized equivalent loss mxleIs. and to analyze the total losses by experiment. ZVT-PWlvI converter designed with 170-260[V] input, 400[V] 5[A] output, and 100[kHz] switching frequency is tested respectively with 500[W], 1[kW], 1.5[kW], and 2[kW] loads. The total losses in input 220[V], 2[kW] load are analyzed by usirm the linearized equivalent loss models.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.4
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• pp.505-508
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• 2012

A permanent magnet flux switching (PMFS) machine has a simple rotor, whilst both magnets and coils are set in the stator, resulting in easy removal of heat due to both copper loss and eddy current loss in magnets. However, the volume of magnets used in PMFS machines is usually larger than in conventional PM machines, and leakage flux does exist at the non-airgap side. To make full use of the magnets and gain higher power density, a novel 3-dimensional (3D) field PMFS machine is developed. It combines merits of the tubular linear machine, external-rotor rotary machine and axial-flux rotary machine, hence, offers high power density and peak torque capability, as well as efficient utility of magnets owing to the unique configuration of triple airgap fields.

• Proceedings of the KIEE Conference
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• 2003.04a
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• pp.262-265
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• 2003

In this paper, a new active snubber circuit that overcomes most of the drawbacks of the normal "zero voltage transition pulse width modulation" (ZVT-PWM) converter is proposed to contrive a new family of ZVT- PWM converter. A converter with the proposed snubber circuit can also operate at light load conditions. A design procedure of the proposed active snubber circuit is also presented. Additionally, at full output power in the proposed soft switching converter, the main switch loss is about 27[%] and the total circuit loss is about 36[%] of that in its counterpart hard switching converter, and so the overall efficiency, which is about 91[%] in the hard switching case, increases to about 97[%].

• ETRI Journal
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• v.31 no.1
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• pp.31-41
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• 2009

Optical burst switching is a promising switching paradigm for the next IP-over-optical network backbones. However, its burst loss performance is greatly affected by burst contention. Several methods have been proposed to address this problem, some of them requiring the network to be flooded by frequent state dissemination signaling messages. In this work, we present a traffic engineering approach for path selection with the objective of minimizing contention using only topological information. The main idea is to balance the traffic across the network to reduce congestion without incurring link state dissemination protocol penalties. We propose and evaluate two path selection strategies that clearly outperform shortest path routing. The proposed path selection strategies can be used in combination with other contention resolution methods to achieve higher levels of performance and support the network reaching stability when it is pushed under stringent working conditions. Results show that the network connectivity is an important parameter to consider.

• Proceedings of the KIEE Conference
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• 2002.04a
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• pp.186-189
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• 2002

This paper presents an improved ZVT(Zero Voltage Transition) DC/DC Boost Converter using Active Snubber. The Conventional ZVT PWM Boost Converter is improved to minimize the switching loss of auxiliary switch using the minimum number of the components. In this thesis, advantage and disadvantages of Conventional ZVT Converter using a auxiliary resonant circuit is discussed. Then Improved ZVT soft switching converter will be discussed. In comparison a previous ZVT converter, The proposed converter reduces turn-off switching loss of the auxiliary switch Therefore, the proposed converter has a high efficiency by active snubber. The prototype of 100kHz, 2kW system was implemented to show the improved performance.

• Proceedings of the KIEE Conference
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• 2001.07a
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• pp.279-281
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• 2001

This paper presents a chaotic neural networks to solve the distribution feeder reconfiguration problem for loss reduction. Feeder reconfiguration problem is the determination of switching option that minimizes the power losses for a particular set of loads in distribution systems. A chaotic neural networks is used to determine the switching combinations, select the status of the switches, and find the best combination of switches for minimum loss. The proposed method has been tested on 32 bus system, and the results indicate that it is able to determine the appropriate switching options for optimal configuration.

• Journal of Electrical Engineering and Technology
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• v.13 no.2
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• pp.699-703
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• 2018

Flux-switching permanent magnet machines (FSPMM) have doubly-salient and simple structures making it cost effective and suitable for mass production. In addition, it is possible to increase the rotor rotating speed and concentrate the flux of the permanent magnet on the air-gap. Due to these merits, the FSPMM can be applied to the various industry applications. To improve the performance, various design variables need to be studied in terms of design techniques. In this paper, we especially concentrate on the distribution of iron losses using a two-dimensional finite-element method (2D FEM). As a result, we can get an information for high efficiency FSPMM design.

• Journal of Power Electronics
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• v.16 no.3
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• pp.894-904
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• 2016

This study examines the zero-voltage switching (ZVS) operation of an active-clamped forward converter (ACFC) with a current-doubler rectifier (CDR). The ZVS condition can be obtained with a much smaller leakage inductance compared to that of a conventional ACFC. Due to the significantly reduced leakage inductance, the design is optimized and the circulating loss is reduced. The operation of the ACFC with a CDR is analyzed, and a detailed ZVS analysis is conducted on the basis of a steady-state analysis. From the results, a design consideration for ZVS improvement is presented. Loss analyses of the converters shows that enhanced soft-switching contributes to an efficiency improvement under light-load condition. Experimental results from a 100-W (5-V/20-A) prototype verify that the ACFC with a CDR can attain ZVS across an extended load range of loads and achieve a higher efficiency than conventional ACFCs.

• Proceedings of the KIEE Conference
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• 1998.07g
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• pp.2464-2466
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• 1998

A switch is a component with two or more ports that selectively transmits, redirects, or blocks optical power in a fiber transmission line. Our switch uses rotation mechanism using stepping motor, hence the common optical fiber can scan and allign to one of the arrayed N optical fibers to provide optical path by electronic precise control. The developed switch is consisted of switching module and its control module. The performance parameters of a switching loss and a repeatability are considered very important. We performed the study to reduce the switching loss and improve the repeatability of switch. The switch can be widely used as a test instrument of optical device and of optical cable in factory, also of optical cable monitoring systems.