• Journal of Power Electronics
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• v.2 no.3
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• pp.189-198
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• 2002

New concept of energy recovery for plasma display panel (PDP) Is proposed. Different from conventional LC resonant sustaining drivers, the current built up before inverting the polarity of the panel electrodes is utilized to change the panel Polarity together with energy Previously charged in Panel capacitance. This operation Provides zero -voltage-switching of switches and reduction of EMI by rejecting the surge current when the sustain switches are turned on. The build-up current helps to reduce transition time of panel polarity and may produce more stable light waveforms. This method shows a desirable characteristic that the circuit loss is similar to that of series resonant type energy recovery circuit which is very effective method.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.378-381
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• 2002

This paper describes a novel multilevel ad/dc power converter suitable for the protection of frequent output short-circuit. The output dc power of the proposed converter can be disconnected from the load within several hundred microseconds at the instant of short-circuit fault. The rising time of the dc load voltage is as small as several hundred microseconds, and there is no overshoot of the do voltage because the dc output capacitors keep undischarged state. Analysis and simulations are carried out to investigate the operation and usefulness of the proposed scheme.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.551-554
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• 2002

This paper describes a new interactive inverter between a photovoltaic(PV) array and single-phase utility that avoid the bulky input (60Hz) transformer on the AC side. The interface employs a pwm boost converter on the DC side followed by a pwm current-forced single-phase rectifier for injecting the power from the PV array into the mains. The current waveform at the AC side remains sinusoidal and exactly in phase at all time. The circuit also has the advantage of requiring fewer switching device than high-frequency link system. This paper describes modeling of PV array and new system topology. Simulation results on the performance of the connection are also presented.

• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.544-547
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• 2003

The purpose of this paper is to develop the straightforward design guidelines of PD/PID speed controller for Industry servo drives with plug and play concept. The controller gains are uniquely determined from the current control loop dynamics, speed loop delay, and mechanical parameters. In order to eliminate the mechanical friction uncertainties, an automatic PD/PI control mode switching algorithm Is introduced using online spectrum analysis of motor torque command. The dynamic performance of the proposed scheme assures a fast tracking response curve with minimal oscillation and settling time over the whole operating conditions. For comprehensive comparison of conventional PI control scheme, extensive test is carried out on actual servo system.

• Journal of Power Electronics
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• v.16 no.2
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• pp.621-630
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• 2016

In this paper, a single current sensor technique (SCST) is proposed for single-phase full-bridge inverters. The proposed SCST measures the currents of multiple branches at the same time, and reconstructs the average inductor, capacitor, and load current in a single switching cycle. Since all of the branches' current in the LC filter and the load are obtained using the SCST, both the inductor and the capacitor current feedback schemes can be selectively applied while taking advantages of each other. This paper also analyzes both of the current feedback schemes from the view point of the closed-loop output impedance. The proposed SCST and the analysis in this paper are verified through experiments on a 3kVA single-phase uninterruptible power supply (UPS).

• Journal of Electrical Engineering and Technology
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• v.5 no.3
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• pp.484-492
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• 2010

Magnetic switch is a kind of saturable inductor, which utilizes nonlinearity of the magnetization curve of ferromagnetic materials. The right understanding of the saturation phenomena, magnetic properties, voltage-time product, and switching characteristics of the magnetic switch is essential in designing the magnetic pulse compressor (MPC). In this paper, the historical background of research on the MPC, fundamental physical properties of the magnetic switches, and application fields of the MPC are presented. Further, an in-depth analysis of pulse compression in series and parallel MPCs is incorporated. As practical application examples, a series MPC used for water treatments and a parallel MPC used for pulsed electric field (PEF) inactivation of bacteria are cited.

• Journal of Power Electronics
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• v.11 no.4
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• pp.599-605
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• 2011

This paper proposes a gain scheduling method that improves the stability of grid-connected systems employing an LCL-filter. The method adjusts the current controller gain through an estimation of the grid impedance in order to reduce the resonance that occurs when using an LCL-filter to reduce switching harmonics. An LCL-filter typically has a frequency spectrum with a resonance peak. A change of the grid-impedance results in a change to the resonant frequency. Therefore an LCL-filter needs a damping method that is applicable when changing the grid impedance for stable system control. The proposed method instantaneously estimates the grid impedance and observes the resonant frequency at the same time. Consequently, the proposed method adjusts the current controller gain using a gain scheduling method in order to guarantee current controller stability when a change in the resonant frequency occurs. The effectiveness of the proposed method has been verified by simulations and experimental results.

• The Transactions of the Korea Information Processing Society
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• v.7 no.4
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• pp.1073-1081
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• 2000

This paper proposes a new fault-tolerant technique for bitonic sorting networks which can be used for designing ATM switches based on Batcher-Banyan network. The main goal in this paper is to design a cost-effective fault-tolerant bitonic sorting network. In order to recover a fault, additional comparison elements and additional links are used. A Dynamic Redundant Bitonic Sorting (DRBS) network is based on the Dynamic Redundant network and can be constructed with several different variations. The proposed fault-tolerant sorting network offers high fault-tolerance; low time delays; maintenance of cell sequence; simple routing; and regularity and modularity.

• Proceedings of the KIEE Conference
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• 2002.11b
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• pp.94-97
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• 2002

A new small signal stability analysis method for eigenvalue analysis is presented. The method is based on the computation of the transition matrix over a specified time interval that corresponds to one cycle operation of the system The method is applicable to any system with or without nonlinear elements. An applicable example of RCF method is presented and the eigenvalues are compared with those of the conventional state space method to show the exactness of the computed eigenvalues of the new method. Also, the variations of oscillation modes which were caused by the switching operation can be analyzed exactly using RCF method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.16-17
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• 2005

Local lifetime control by ion implantation has become an useful tool for production of modern power devices. In this work, punch-through diodes were irradiated with protons for the high speed power diode fabrication. Proton irradiation was executed at the various energy and dose conditions. Characterization of the device was performed by I-V, C-V and Trr measurement. We obtained enhanced reverse recovery time characteristics which was about 45% of original device and about 73% of electron irradiated device. The measurement results showed that proton irradiation was able to effectively reduce minority carrier lifetime.