• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.1857-1859
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• 1998

This paper proposes a circuit technique that reduces losses cauased by reverse-recovery characteristics of the diode in converters. In high voltage, high power, Reverse recovery characteristics of the diode gives large stresses to switching devices. To solve the problem, we propose a circuit with active snubber between diode and switch. By controling di/dt rate of thr diode, the proposed technique reduces the losses and the stresses of switching devices.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.6
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• pp.396-405
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• 2019

Single-phase full-bridge inverters have shoot-through problems. Dead time is an essential way of solving these issues, but it distorts the output voltage and current. Dual-buck inverters are designed to eliminate the abovementioned problems. However, these inverters result in switching power loss and electromagnetic interference due to the diode reverse-recovery problem. Previous studies have suggested reducing the switching power loss from diode reverse-recovery, but their proposed methods have complex circuit configurations and high system costs. To alleviate the switching power loss from diode reverse-recovery, the current work proposes a dual-buck inverter with a coupled inductor. In the structure of the proposed inverter, the current flowing into the original diode is divided into a new diode. Therefore, the switching power loss is reduced, and the efficiency of the proposed inverter is improved. Simulation waveforms and experimental results for a 1.0 kW prototype inverter are discussed to verify the performance of the proposed inverter.

• Journal of IKEEE
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• v.24 no.2
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• pp.586-591
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• 2020

An interleaved current-fed high step-up DC-DC converter is proposed. Besides high voltage gain, a low ripple input current is achieved by adopting interleaving operation. Moreover, soft-switching characteristic of the proposed converter reduces switching losses of active power switches and raise the conversion efficiency. The reverse-recovery problem of output rectifiers is also alleviated by controlling the current changing rates of diodes by utilizing the leakage inductances of transformers. Experimental results obtained on a 200W prototype are discussed.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.746-748
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• 1993

To overcome the problem of the diode reverse recovery in high switching frequency inverter, a new gate drive scheme is proposed for IGBT in this paper. Using this circuit, the reverse recovery current can be controlled and faster switching time can be achieved for hard switching inverter. The over-current protection method, which is suitable for the proposed gate driver, is also presented. The operation of the proposed circuit is investigated and its usefulness is verified through the experimental results.

• Archives of Reconstructive Microsurgery
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• v.20 no.1
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• pp.64-67
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• 2011

Reconstruction of the distal portion of the great toe has always represented a difficult problem to surgeons. There are many methods of flap reconstruction described for foot defects, but none for tip of the great toe. We report a case of reconstruction of the great toe using a homodigital reverse pedicle island flap method. A 25-year-old man had a crushing injury at the distal phalanx of the left great toe. A homodigital reverse pedicle island flap was raised from the dorso-medial aspect of the proximal phalanx of the great toe based on the distal dorsal arcade. The flap covered the exposed distal phalanx and stump was closed without shortening. He made an uncomplicated recovery and when seen 6 months later he had a good cosmetic and functional result. A homodigital reverse pedicle island flap is described for the reconstruction of the distal part of the great toe. It involves only a single stage procedure with minimal donor site morbidity and provides a good cosmetic results.

• Journal of Korean Institute of Industrial Engineers
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• v.34 no.4
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• pp.398-407
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• 2008

We consider a product recovery system that a single product is stocked in order to meet a demand from customers who may return products after usage. This paper addresses a problem of when to release a procurement process to replenish serviceable inventory and how many new products to procure. The structure of the optimal procurement policy is examined and numerically identified as a monotonic threshold curve. A numerical procedure is presented to jointly find the optimal procurement order size, optimal procurement policy, and optimal discounted profit. Sensitivity analysis also indicates that these optimal performance measurements have monotonic properties with respect to system parameters.

• Industrial Engineering and Management Systems
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• v.13 no.4
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• pp.383-397
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• 2014

Reverse logistics network design issues have been popularly discussed in recent years. However, few papers in the past literature have been dedicated to incentive effect on return quantity of used products. The purpose of this study is to formulate a dynamic nonlinear programming model of reverse logistics network design with the aim of managing the used products allocation by coordinating the collection centers and recovery facilities to warrant economic efficiency. In the optimization model, a fuzzy approach is applied to interpret the relationship between the rate of return and the suggested incentives. Due to funding constraints in setting up the collection centers, this work considers these centers as multi-capacity levels, which can be opened or closed at different periods. In view of the fact that the problem is known as NP-hard, we propose a heuristic method based on tabu search procedure to solve the presented model. Finally, several dominance properties of optimal solutions are demonstrated in comparison with the results of a state-of-the-art commercial solver.

• Journal of Power Electronics
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• v.9 no.6
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• pp.823-834
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• 2009

This paper proposes a high-efficiency single-stage ac/dc converter. The proposed converter features low voltage stresses and reduced switching losses. It operates at the boundary of discontinuous- and continuous-conduction modes by employing variable switching frequency control. The turn-on switching loss of the switch can be reduced by turning it on when the voltage across it is at a minimum. The voltage across the bulk capacitor is independent of the output loads and maintained within the practical range for the universal line input, so the problem of high voltage stress across the bulk capacitor is alleviated. Moreover, the voltage stress of the output diodes is clamped to the output voltage, and the output diodes are turned off at zero-current. Thus, the reverse-recovery related losses of the output diodes are eliminated. The operational principles and circuit analysis are presented. A prototype circuit was built and tested for a 150 W (50V/3A) output power. The experimental results verify the performance of the proposed converter.

• Bulletin of the Korea Photovoltaic Society
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• v.3 no.2
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• pp.42-47
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• 2017

The potential induced degradation (PID) phenomenon shows severe power loss within several years from the initial installation of solar power system. The accumulated power loss by PID is inevitable because the PID is suspected only if the power loss exceeds several percent. In this paper, we analyzed the cases of PID diagnosis and recovery by visiting the suspected PID site about 17 months after the installation of the 100kW PV system. The power difference of the two 50kW inverters was more than 20kWh, and the PR difference was more than 8%. From the beginning of the installation, the difference in power gradually increased. The recovery was observed for about 7 months by applying 1000V in the reverse bias at night. As a result, the power difference of the two inverters was recovered to within 2kWh. In the case of a power station suffering from PID in the field, it will be helpful for stable development operation by quick diagnosis and problem solving.

• Journal of the Korea Society of Computer and Information
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• v.14 no.7
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• pp.161-168
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• 2009

In this paper, we studied about an consolidated transportation model to transport EOL (end-of-life) electronic household appliances for recycling in South Korea. The objective is to minimize the total traveling distance of the vehicles transporting EOL electronic household appliances collected by local authorities and major manufacturers' distribution centers to assigned R/C(recycling center) in South Korea. Current reverse logistics for recycling EOL electronic household appliances is operated by local authorities and major manufacturers individually, and it is inefficient for the following reasons: excessive traveling distance, transportation cost, low truck capacity utilization, and so on. The presented model is developed to solve this problem. We apply a integer programming to solve this problem and present computational results using actual field data.