• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.86-88
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• 1996

A method is presented for the development of the PC-based measurement system on the 6 cathodes-single anode type multi-functional oxygen electrodes for detecting various components of the solution by measuring the dissolved oxygen(DO) concentration. The system is consisted with the 6 channel sensor signal modyfing circuits for the sensor and the PC interface circuits using the single chip microprocessor 80c196kc. Typical polarograms for the DO probes under test using this sensor circuits are presented. This system covers wide range of measuring time from 300sec to over 16 hour in one measurement step by programming the 9 monitor disply mode.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.1724-1728
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• 2008

Track circuit is transmitted throughout the rails. In order to insure safe and reliable operation of track circuits, the track and the environment should respect mandatory electrical characteristics. In addition, for cab signalling through track Circuit as per TVM 430, these electrical characteristics should insure the transmission to the train. Track circuits have several operation and safety functions. They can detect the train position and broken rails. When track circuits are used as track to train transmission, they also have to be powered enough to be captured by the train sensors.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.12
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• pp.8-14
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• 2015

An effective way to ensure that LEDs produce wanted light output is to use a current driving topology, because the brightness of LEDs is directly related to their current. However, this topology may lead to the lifetime shortening of a illumination system because over-currents may flow through non-damaged LEDs in case some LEDs are damaged. This paper presents an adaptive current control circuits for LEDs, which protect LEDs in a good state by limiting the driving currents according to the number of damaged ones. The proposed control circuits consist of a simple constant-current driver and a micro-controller which monitors the voltage of LED array without any auxiliary current sensors for fault diagnosis. And the driving current is automatically controlled into 6-levels according to the number of failures.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.2
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• pp.359-362
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• 2010

In this study, inverter logic circuits on a plastic substrate are built with two top-gate FETs in series on a single ZnO nanowire. The voltage transfer characteristics of the ZnO nanowire-based inverter logic circuit exhibit a clear inverting operation. The logic swing, gain and transition width of the inverter logic circuit is about 90 %, 1.03 and 1.2 V, respectively. The result of mechanical bending cycles of the inverter logic circuit on a plastic substrate shows that the stable performance is maintained even after many hundreds of bending cycles.

• Journal of Power Electronics
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• v.9 no.4
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• pp.567-574
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• 2009

A linear transfer function for the output current control of frequency-controlled resonant inverters is proposed in this paper. The circuit of resonant inverters can be transformed into two coupled circuits through the complex phasor transform. The circuits consist of cross-coupled power sources and passive elements. The circuits are used to induce the state space equation, which is transformed into the $4^{th}$ order cross-coupled transfer function. The $4^{th}$ order cross-coupled transfer function is modeled into a $2^{nd}$ order linear transfer function based on a behavior analysis of the pole and zero locations that facilitate a simple and intuitive linear transfer function. The feasibility and validity of the proposed linear transfer function were verified by simulation and experiment.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.8
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• pp.517-524
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• 2004

In this paper, a novel zero-voltage-switching(ZVS) resonant DC-DC converter is proposed. It is composed of two symmetrical active-clamped circuits, the converter can be achieve ZVS in each switches. Also, active clamp capacitor ratios($\alpha$) of proposed circuit can be reduce a peak stress of switching voltage for each main switch. Simulation results using Pspice 9.2 ver and $C^{++}$ characteristic analysis show a provement for the validity of theoretical analysis. The analysis of the proposed Current-Fed Push Pull type DC-DC converter is generally described by using normalized parameter, and achieved an evaluated characteristic values which is needed to design a circuit. We confirm a rightfulness theoretical analysis by comparing a theoretical values and experimental values obtained from experiment using MOSFET as switching devices.

• Journal of Power Electronics
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• v.4 no.4
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• pp.197-204
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• 2004

Two-stage Power-Factor-Correction (PFC) converters are the most common circuits for drawing sinusoidal and in phase current waveforms from an ac source with a good regulated output voltage. The first stage is a boost PFC converter with average-current-mode control for achieving the near-unity power factor and the second stage is a forward converter with voltage-mode control to regulate the output voltage. Stability analysis and design methods of two-stage PFC converters have previously been discussed using linear models. Recently, new nonlinear phenomena have been detected in pre-regulator boost PFC circuits and a new nonlinear model has been proposed for pre-regulated PFC converters. Therefore, investigation of two-stage PFC converters from the nonlinear viewpoint becomes important because the second stage DC/DC converter adds more complexity to the circuit. So, this paper introduces a study of the stability of two-stage PFC converters. A novel nonlinear model of two-stage PFC converters is proposed. Then, a stability analysis is made based upon this nonlinear model. The high correspondence between the simulated and experimental results confirms our analysis.

• Transactions on Electrical and Electronic Materials
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• v.12 no.1
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• pp.7-10
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• 2011

High voltage (HV) integrated circuits are viable alternatives to discrete circuits in a wide variety of applications. A HV device generally used in these circuits is a lateral double diffused metal oxide semiconductor (LDMOS) transistor. Attempts to model LDMOS devices are complicated by the existence of the lightly doped drain and by the extension of the poly-silicon and the gate oxide. Several physically based investigations of the bias-dependent drift resistance of HV devices have been conducted, but a complete physical model has not been reported. We propose a new technique to model HV devices using both the BSIM3 SPICE model and a bias dependent resistor model (sub-circuit macro model).

• Journal of Power Electronics
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• v.6 no.2
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• pp.114-120
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• 2006

This paper compares two types of direct torque controllers for permanent magnet synchronous motors(PMSMs). These controllers both use a single-chip FPGA(Field Programmable Gate Array) but have differing hardware configurations. One of the controllers was constructed by programming a soft-core CPU and hardware logic circuits written in VHDL(Very high speed IC Hardware Description Language), while the other was constructed of only hardware logic circuits. The characteristics of these two controllers were compared in this paper. The results show the controller constructed of only hardware logic circuits was able to shorten the control period and it was able to suppress the low torque ripple.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2003.11a
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• pp.311-314
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• 2003

In this paper, proposed circuit proposes that Active-Clamp-Circuits basis of a current-fed inverter linked type high frequency resonant dc-dc converter of conventional. and the paper the most of characteristics of the reduced high voltage stress main switches with active clamp circuits and output current constant with the resonant part consists of L, C resonant tank circuit. Also, the capacitor (C$_1$, C$_2$) connected in switches are a common using by resonance capacitor and ZVS capacitor. and circuit analysis used state equation of each part modes. Also we conform a rightfulness theoretical analysis by comparing a parameters values and simulation values obtained from simulation using Power MOS-FET as switching devices.