• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.6
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• pp.569-575
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• 2003

This paper present a new fully-automated PC-based instrumental system that could quickly measure and analyze the efficiency of switching power supplies for the entire operating range. In the proposed system, we applied an Indirect method for high-voltage low-current measurements and a direct method for low-voltage high-current measurements, in order to obtain a high accuracy with minimum equipment requirement. Compared to the conventional methods, the newly proposed system offers more accurate and much faster real-time assessment of the efficiency with minimum measurement error. The performance and accuracy of the proposed system are verified using a 50 W switching power supply intended for telecommunication applications.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.4
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• pp.630-638
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• 2001

This paper has been proposed a structure composed of FIRs and IIR filters as digital decimation filter to compensate the drooping inband on the high precision AU chips. The area of chip has been reduced compared with the conventional structure because the RAM and MAC is reduced. The passband ripple$(\leq\; 0.4535 \times fs)$, passband attenuation(at $\; 0.4535 \times fs$ and stopband attenuation$(\geq\; 0.59\times fs)$ of the 6th-order $\Delta\Sigma$ modulator and digital decimation filter had $\pm0.0007[dB]$, -0.0013[dB] and -110[dB] respectively. Also the inband group delay, which was almost same compared with the conventional digital decimation filter structure, was 30.07/fs[s] band the error of group delay was 0.1672%.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.136-139
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• 2004

This thesis is realization of embedded system that of MPEG-2 down conversion using IDCT. A method for down conversion of MPEG compressed video is to perform low-pass filtering and sub-sampling after full decompression. However, this method is need large memory and high computational complexity. Recent research has been focussed on the down conversion in the DCT domain. But DCT method is reduced image qualify. The embedded system is require low complexity, and high speed algorithm. When applied to embedded system that down conversion method, DCT method is played average 29 frame per second, and better 25% than spatial-domain down conversion.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.2
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• pp.299-306
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• 2011

In this paper, a blind adaptive equalization algorithm based on PDF-distance minimization and a set of Delta functions is introduced and its superior robustness against impulsive noise and multipath characteristics of underwater communication channels is proved. The conventional CMA based on MSE has shown to be incapable of coping with impulsive noise, and correntropy blind algorithm has also revealed to yield not satisfying performance for the mission. On the other hand, the blind adaptive equalization algorithm based on PDF-distance minimization and a set of Delta functions has been proved to solve effectively the problem of impulsive noise and multipath characteristics of underwater communication channels through theoretical and simulation analysis.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.4
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• pp.324-331
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• 2007

This paper studies new estimation method for state of charge (SOC) of the hybrid electric vehicle lithium battery using sliding mode observer. A simple R-C Lithium battery modeling technique is established and the errors caused by simple modeling was compensated by the sliding mode observer. The structure of the sliding mode observer is simple, but it shows robust control property against modeling errors and uncertainties. The performance of the system has been verified by the UUDS test. The test results of the proposed observer system shows robust tracking performance under real driving environments.

• Journal of Sensor Science and Technology
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• v.28 no.3
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• pp.177-181
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• 2019

Pressure sensors are used in various industries such as automobiles, airplanes, medical equipment, and coolers. Even if the ambient temperature changes, the measurement is reliable and stable. In this study a diaphragm-type pressure sensor was used to derive a temperature-compensated pressure estimation equation for accurate pressure measurement at $100^{\circ}C$ and $-40^{\circ}C$. To understand the characteristics of the pressure sensor diaphragm with respect to temperature and pressure, experiments were conducted in temperature-variable chamber using FEM analysis to confirm that the influence of temperature effect was nonlinear. Based on the experimental results, a nonlinear method for calculating the pressure by compensating for the error due to temperature was derived. The calculated pressure value is lower than 0.5 % at low and high temperatures, and lower than 0.4 % at $22^{\circ}C$, thereby eliminating the effect of temperature.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.1
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• pp.9-15
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• 2019

Sensorless electric superchargers have recently been actively developed to provide a large amount of oxygen to engines in order assist the combustion process for miniaturizing the engines and improving fuel efficiency. The model-based sensorless method for surface-mounted permanent magnet synchronous motors has a disadvantage in that the system may become unstable due to parameter variations in low-speed operation and the rapid-acceleration section. An electric supercharger requires fast response to improve the engine response delay, such as the turbocharger turbo-rack. Therefore, the responsiveness must be improved to use the model-based sensorless system. The position compensation algorithm designed in this study is controlled by converting the position error into the beta, which is the angle formed by the d-axis and the stator current during sudden speed change. In this study, we improved the response of the model-based sensorless system through the algorithm and verified the algorithm validity by applying the algorithm to an actual dual-motor supercharger.

• Journal of IKEEE
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• v.25 no.1
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• pp.101-108
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• 2021

This paper proposes a parallel control method of a modular DC/DC converter for electric vehicle (EV) chargers. The EV chargers have been increasing the power capacity using modular converters. There are output current imbalances between the modules, which are caused by the difference of the impedance, delay of the gate driver, and error of the sensors. The conventional strategies for the equal distribution of the output current cause the voltage drop or the high volume and cost of the converters. Therefore, the proposed parallel control strategy effectively balances the output current of modules using a current compensation method. The proposed strategy is verified by simulations. Additional experimental results will be added under various conditions.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.68 no.3
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• pp.430-438
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• 2019

For a pump or a compressor motor, a high periodic load torque variation is induced by the mechanical works, and it causes system vibration and noise. To minimize these problems, load torque compensation method, injecting periodic torque current, could be utilized. However, with the sensorless control method, which is usually utilized in the pump and compressor for low cost, the periodic torque current degrades the accuracy of the rotor position estimation owing to the inductance variation. This paper analyzes the rotor position and speed estimation error of sensorless control method with constant motor parameters under period loading. Assuming the constant speed by the accurate load torque compensation, the speed error equation is derived in frequency domain with inductance depending on the stator current. Further, it is also shown that the rotor position error could be minimized by compensating the inductance variation. The simulation and experimental results verify that the derived speed error model and the validity of the inductance compensation method.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.6
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• pp.481-488
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• 2022

This study proposes compensation methods for the initial position error and torque ripple in vector control of two-phase hybrid stepping motors. Stepping motors have an asymmetrical structure due to misalignment, such as the eccentricity generated by the manufacturing and assembly process. When vector control is applied using the position information measured by an incremental encoder attached to the rotor shaft of such stepping motors, the following problems occur. First, an initial position error occurs during the forced excitation process for the initial rotor position alignment. Second, torque ripple corresponding to the mechanical rotation frequency is generated. In this study, these non-ideal phenomena that occur in vector control of the stepping motor are analyzed, and compensation methods are proposed to eliminate them. The validity of the proposed initial position error and torque ripple compensation methods is verified through experiments on a two-phase hybrid stepping motor drive system.