• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.713-718
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• 1998

Due to high power ratings and low conduction loss, the IGBT has become more attractive in high power applications. However, its slower characteristics than those of MOSFET cause severe switching losses and switching frequency limitation. This paper proposes the IGBT's soft switching concept with the help of MOSFET, where each of the IGBT and MOSFET plays its role during on-periods and switching instants. Also, the switching losses are analyzed by using the linearized modeling and the modeling and the operations of a converter are investigated to confirm the soft switching of IGBT's.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.364-369
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• 2002

Presently, a high frequency switching technique is used for a converter design to reduce its size and weight. However an increased switching frequency introduces a high switching loss. To the reduce switching loss, soft switching techniques using ZVS and ZCS are applied. It is very important to improve efficiency. However In general to develop new converter circuits, the efficiency and other performance parameters can be determined after design, implementation and experiments. The idea in this paper is to determine and predict efficiency and other operating characteristics without realization and experiments. Thereby a complex design and implementation can be avoided. PSPICE is used as a simulation tool. This is verified by comparing simulation and experiments results of the two different soft switching converters.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.1148-1150
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• 2003

Power conversion system must be increased switching frequency in order to achieve a small size, a light weight and a low noise. However, the switches of converter are subjected to high switching power losses and switching stresses. As a result of those, the power system brings on a low efficiency. To improved these, a large number of soft switching topologies included a resonant circuit has been prosed. But these circuits increase number of switch in circuit and complicate sequence of switching operation. In this paper, the authors propose a high power factor and high efficiency DC-DC converter using single-pulse soft switching by partial resonant switching node. The switching devices in a prosed circuit are operated with soft switching by the partial resonant method, that is, Partial Resonant Switch Mode Power Converter. The partial resonant circuit makes use of a inductor using step up and a condenser of loss-less snubber. The result is that the switching loss is very low and the efficiency of system is high. Also the proposed converter is deemed the most suitable for high power applications where the power switching devices are used. Some simulative results on computer results are included to confirm the validity of the analytical results.

• Journal of Power Electronics
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• v.13 no.2
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• pp.250-255
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• 2013

This paper proposes an optimal current distribution method of dual-rotor brushless DC machines (DR-BLDCMs) which have inner and outer surface-mounted permanent-magnet rotors. The DR-BLDCM has high power density and high torque density compare to the conventional single rotor BLDCM. To drive the DR-BLDCM, dual 3-phase PWM inverters are required to excite the currents of a dual stator of the DR-BLDCM and an optimal current distribution algorithm is also needed to enhance the system efficiency. In this paper, the copper loss and the switching loss of a DR-BLDCM drive system are analyzed according to the motor parameters and the switching frequency. Moreover, the optimal current distribution method is proposed to minimize the total electrical loss. The validity of the proposed method was verified through several experiments.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.675-677
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• 2000

In the paper the eddy current loss in brushless DC motor due to switching frequency supplied by PWM inverter, is analyzed. The compensated conductivity is used in order to analyze the eddy current loss in brushless DC motor which has lamination structure. The eddy current loss is deceased when switching frequency supplied by PWM inverter is gradually increased from 1.2kHz up to 12kHz. The high switching frequency of PWM inverter make the output wave into a similar sine wave and this leads to the decreasing eddy current loss.

• ETRI Journal
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• v.44 no.2
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• pp.274-285
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• 2022

Retransmission in optical burst switching networks is a solution to recover data loss by retransmitting the dropped burst. The ingress node temporarily stores a copy of the complete burst and sends it each time it receives a retransmission request from the core node. Some retransmission schemes have been suggested, but uncontrolled retransmission often increases the network load, consumes more bandwidth, and consequently, increases the probability of contention. Controlled retransmission is therefore essential. This paper proposes a new controlled retransmission scheme for loss recovery, where the available bandwidth of wavelength channels and the burst lifetime are referred to as network conditions to determine whether to transmit a dropped burst. A retrial queue-based analysis model is also constructed to validate the proposed retransmission scheme. The simulation and analysis results show that the controlled retransmission scheme is more efficient than the previously suggested schemes regarding byte loss probability, successful retransmission rate, and network throughput.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.7
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• pp.1349-1355
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• 2009

This paper is studied on a novel power factor correction (PFC) AC-DC converter of high efficiency by soft switching technique. The input current waveform in the proposed converter is got to be a sinusoidal form composed of many a discontinuous pulse in proportion to the magnitude of a ac input voltage under the constant switching frequency. Therefore, the input power factor is nearly unity and the control method is simple. The proposed converter adding an electric isolation operates with a discontinuous current mode (DCM) of the reactor in order to obtain some merits of simpler control, such as fixed switching frequency, without synchronization control circuit used in continuous current mode (CCM). To achieve the soft switching (ZCS or ZVS) of control devices, the converter is constructed with a new loss-less snubber for a partial resonant circuit. It is that the switching losses are very low and the efficiency of the converter is high, Particularly, the stored energy in a loss-less snubber capacitor recovers into input side and increases input current from a resonant operation. The result is that the input power factor of the proposed converter is higher than that of a conventional PFC converter. This paper deals mainly with the circuit operations, theoretical, simulated and experimental results of the proposed PFC AC-DC converter in comparison with a conventional PFC AC-DC converter.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.64 no.3
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• pp.146-152
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• 2015

In this paper, we propose a boost DC-DC converter using a modification of the passive auxiliary resonant snubber circuit with a DC-DC converter in a typical active auxiliary resonant snubber-bridge inverter. The proposed boost DC-DC converter is small compared to the DC-DC converter according to the soft-switching scheme that requires a general auxiliary switch by realizing the soft switching operation as a DC-DC converter which does not require an auxiliary switch. It is light-weight, switch the turn-on and turn-off switching loss at the time of the superposition of the voltage and current is extremely small, so small. And the reduction of the surge voltage and current of the switch. In addition, the proposed boost DC-DC converter has a high efficiency over a wide load characteristics change area than conventional hard switching PWM boost converter using an RC snubber loss.

• Korean Journal of Human Ecology
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• v.21 no.6
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• pp.1173-1184
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• 2012

This study estimates a structural model to examine the causal relationships among web browsing, switching cost, and site retention in the context of apparel shopping website. A total of 499 usable questionnaires were obtained from consumers aged from 20 to 49 years. For data analysis, exploratory factor analysis, confirmatory factor analysis and structural model were used. The result showed that consumer's perceived switching costs consisted of three factors: relationship cost, search cost and benefit loss cost. In estimated structural model, the relationship cost was influenced by leisure browsing; the search cost was influenced by informational browsing and leisure browsing; the benefit loss cost was influenced by leisure browsing. Especially, the leisure browsing was the most highly related to the benefit loss cost, and followed by relationship cost and search cost. However, hedonic browsing was not significantly related the factors of switching costs. The search costs significantly affected customer's intentions for site retention. A managerial implication was discussed for e-retailers in order to develop strategic switching costs in building long-term relationships with web browsers on the apparel shopping websites.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.12B no.1
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• pp.37-43
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• 2002

This paper proposes a new zero-current switching (ZCS) pulse-width modulation (PWM) switch cell that has no additional conduction loss of the main switch. In this cell, the main switch and the auxiliary switch turn on and turn off under zero current condition. The diodes commutate softly and the reverse recovery problems are alleviated. The conduction loss and the current stress of the main switch are minimized, since the resonating current for the soft switching does not flow through the main switch. Based on the proposed ZCS PWM switch cell, a new family of dc to dc PWM converters is derived. The new family of ZCS PWM converters is suitable for the high power applications employing IGBTs. Among the new family of dc to dc PWM converters, a boost converter was taken as an example and has been analyzed. Design guidelines with a design example are described and verified by experimental results from the 2.5㎾ prototype boost converter operating at 40KHz.