• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.12
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• pp.2685-2692
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• 2009

We propose pulsed magnetic stimulation below 30W by the AC(60Hz) switching control of leakage transformer primary which has some advantage of cost and size compared to a typical pulsed power supply. Pulse repetition rate is adjusted from 5Hz to 60Hz to control magnetic stimulation output. In this magnetic stimulation, a low voltage open loop control for high voltage discharge circuit is employed to avoid the HV sampling or switching and high voltage leakage transformer is used to convert rectified low voltage pulse to high voltage one. A ZCS(Zero Cross Switch)circuit and a DSP & FPGA are used to control gate signal of SCR precisely. The pulse repetition rate is limited by 60Hz due to the frequency of AC line and a high leakage inductance. The maximum magnetic stimulation output was obtained about 33W at pulse repetition rate of 60Hz, total 40, 80, 120, $160^{\circ}$, SCR gate trigger angle $90^{\circ}$ and total output.

• Journal of Power Electronics
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• v.5 no.3
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• pp.233-239
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• 2005

In this paper, a new conceptual circuit configuration of a 3-phase voltage source, soft switching AC-DC-AC converter using an IGBT module, which has one ARCPL circuit and one ARDCL circuit, is presented. In actuality, the ARCPL circuit is applied in the 3-phase voltage source rectifier side, and the ARDCL circuit is in the inverter side. And more, each power semiconductor device has a novel clamp snubber circuit, which can save the power semiconductor device from voltage and current across each power device. The proposed soft switching circuits have only two active power semiconductor devices. These ARCPL and ARDCL circuits consist of fewer parts than the conventional soft switching circuit. Furthermore, the proposed 3-phase voltage source soft switching AC-DC-AC power conversion system needs no additional sensor for complete soft switching as compared with the conventional 3-phase voltage source AC-DC-AC power conversion system. In addition to this, these soft switching circuits operate only once in one sampling term. Therefore, the power conversion efficiency of the proposed AC-DC-AC converter system will get higher than a conventional soft switching converter system because of the reduced ARCPL and ARDCL circuit losses. The operation timing and terms for ARDCL and ARCPL circuits are calculated and controlled by the smoothing DC capacitor voltage and the output AC current. Using this control, the loss of the soft switching circuits are reduced owing to reduced resonant inductor current in ARCPL and ARDCL circuits as compared with the conventional controlled soft switching power conversion system. The operating performances of proposed soft switching AC-DC-AC converter treated here are evaluated on the basis of experimental results in a 50kVA setup in this paper. As a result of experiment on the 50kVA system, it was confirmed that the proposed circuit could reduce conduction noise below 10 MHz and improve the conversion efficiency from 88. 5% to 90.5%, when compared with the hard switching circuit.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.4
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• pp.356-362
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• 2005

In this paper, in order to develop a simple and high efficient ballast without an external ignitor, a half-bridge type ballast with a coupled inductor and a frequency controlled synchronous rectifier is proposed. The Internal LC resonance of the buck converter is used to generate a high voltage pulse for the ignition, and the coupled inductor filter is used for steady state ripple cancellation. Also, a synchronous buck converter is applied for the DC/DC converter stage. In order to improve the efficiency of the ballast, a frequency control method is proposed. This scheme reduces a circulation current and trun off loss of the MOSFET switch on the constant power operation, which results in increase of the efficiency of the ballast system about 4$\%$, compared to a fixed frequency control. It consists a 2-stage version ballast with a PFC circuit. The results are verified nth hardware experiments.

• Journal of KIISE:Information Networking
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• v.29 no.1
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• pp.31-39
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• 2002

The VPN(Virtual Private Network) is a private network constructed logically on a public network infrastructure. There have been numerous studies to support the VPN services by using different technologies such as IP in IP, GRE, L2TP, MPLS and so on. Among these technologies, MPLS has shown many merits in aspects of QoS, security, and management, compared with other technologies. As an enhancement of the VPN that is controlled by MPLS PE(Provider Edge) routers, this paper presents the VPN controlled by MPLS CE(Customer Edge) routers. The functional architecture of the CE based VPN and operations of the CE routers are described along with the performance comparison of CE based MPLS VPN. It has been shown that the CE based VPN has more advantages than PE based VPN with respect to independency, scalability, security, and complexity.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.1
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• pp.42-50
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• 2016

Recently, researches about the communication between LED array and the camera (alias 'Visual-MIMO'), have been actively conducted, and the application to the vehicle and a smart phone is expected to be maximized. Since the bit error may occur if the ISI is severe in a LED array, it is necessary to switch from the multiplexing to the diversity mode. In this paper, according to the use or not of a reference array pattern, a method for determining the transition time to the diversity mode is suggested and verified. When using the reference pattern, it determines the transition time to the diversity mode from the multiplexing using the brightness information of the received image. If the reference array pattern is not used, the size of LED array compared to the entire image according to the distance is used and the size of the LED array at the distance of a severe ISI may be used for the determination of transition time to the diversity. Finally, the proposed method is verified through the simulation and hardware experiments as well as by analyzing the performance in accordance with the ISI level and the distance.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.12
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• pp.639-647
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• 2001

We present an integrated optical microswitch, composed of silicon waveguides, gold-coaled silicon micromirrors, and electrostatic contact actuators, for applications to the optical signal transceivers. For a low switching voltage, we modify the conventional curled electrode microactuator into a electrostatic microactuator with touch-down beams. We fabricate the silicon waveguides and the electrostatically actuated micromirrors using the ICP etching process of SOI wafers. We observe the single mode wave propagation through the silicon waveguide with the measured micromirror loss of $4.18\pm0.25dB$. We analyze major source of the micromirror loss, thereby presenting guidelines for low-loss micromirror designs. From the fabricated microswitch, we measure the switching voltage of 31.74V at the resonant frequency of 6.89kHz. Compared to the conventional microactuator, the present contact microactuator achieves 77.4% reduction of the switching voltage. We also discuss a feasible method to reduce the switching voltage to 10V level by using the electrode insulation layers having the residual stress less than 30MPa.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.10
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• pp.1256-1262
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• 2016

As the population of camping is increased in campsites and auto camp sites, the electrical equipment can safely supply electricity to users in a variety of electricity bill policy is required in the campsite. In this paper, we develop the vending machine for electricity that can control the outdoor electrical outlet from the management server using the Z-Wave WPAN and android mobile application. The developed vending machine for electricity consists of the management server, the controller, the outdoor outlet box, and the mobile application. The management server provides reservation and electricity bill payment to users. The management server controls the electrical outlet box through the controller to safely supply electricity to users. The controller that is a relay device between the management server and the switch controls switches based on Z-Wave mesh network. Outdoor electrical outlet box has 2 meter switches. We receive the relevant authorization to provide commercial electricity services using the outdoor electrical outlet box in the campsite.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.3B no.3
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• pp.147-154
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• 2003

This paper presents a high-frequency boost type ZVS-PWM chopper-fed DC-DC power converter with a single active auxiliary edge-resonant snubber at the load stage which can be designed for power conditioners such as solar photovoltaic generation, fuel cell generation, battery and super capacitor energy storages. Its principle operation in steady-state is described in addition to a prototype setup. The experimental results of boost type ZVS-PWM chopper proposed here, are evaluated and verified with a practical design model in terms of its switching voltage and current waveforms, the switching v-i trajectory and the temperature performance of IGBT module, the actual power conversion efficiency, and the EMI of radiated and conducted emissions, and then discussed and compared with the hard switching scheme from an experimental point of view. Finally, this paper proposes a practical method to suppress parasitic oscillation due to the active auxiliary resonant switch at ZCS turn-off mode transition with the aid of an additional lossless clamping diode loop, and can be reduced the EMI conducted emission.

• Journal of Power Electronics
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• v.15 no.1
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• pp.146-159
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• 2015

Since the power capacity needed for the propulsion of large ships is very large, a multiphase AC induction propulsion mode is generally adopted to meet the higher requirements of reliability, redundancy and maintainability. This paper gives a detailed description of the development of a 20MW fifteen-phase PWM driver for advanced fifteen-phase propulsion induction motors with a special third-harmonic injection in terms of the main circuit hardware, control system design, experiments, etc. The adoption of the modular design method for the main circuit hardware design can make the enclosed mechanical structure simple and maintainable. It can also avoid the larger switch stresses caused by the multiple turn on of the IGBTs in conventional large-capacity converter systems. The use of the distributed controller design method based on a high-speed fiber-optic ring net for the control system can overcome such disadvantages as the poor reliability and long maintenance times arising from the conventional centralized controller which is designed according to point-to-point communication. Finally, the performance of the 20MW PWM driver is verified by experimentation on a new fifteen-phase induction propulsion motor.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.4
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• pp.358-365
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• 2011

Recently, the LED(Light Emitting Diode) replacing incandescent light bulbs and fluorescent light has great attentions as a most promising candidate for the next generation lighting source due to its environment-friendly characteristics, long life and excellent efficiency. Moreover, since it is a semiconductor device which can convert the electric energy to visible light at a very high speed, it can also used as a communication device. Therefore, the VLC(Visible Light Communication) using the LED can perform the near field communication and lighting function at the same time without additional expenses. However, since the switching device of the conventional LED driver for VLC is operated in the linear region, there exist several drawbacks such as a poor power conversion efficiency and serious heat generation. On the other hand, since the proposed driver is operated in the on/off switching region, it features a higher efficiency and more improved heat generation. To verify the validity of the proposed LED driver, experimental results from a prototype of 20W rated LED driver applied to 3MHz bps broadcasting audio system are given.