• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.4
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• pp.321-328
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• 2008

In this paper, variable gain amplifier(VGA) with a gain slope controller has been proposed and verified by circuit simulations and measurements. The proposed VGA has a gain control, gain slope switch and variable gain range. The input source coupled pair with diode connected load is used for VGA gain stage. The gain slope controller with switch can control VGA gain slope. The proposed VGA is fabricated in $0.18{\mu}m$ CMOS process for multi -standard wireless receiver. The proposed two stage VGA consumes min. 2.0 mW to max. 2.6 mW in gain control range and gives input IP3 of -3.77 dBm and NF of 28.7 dB at 1.8 V power supply under -25 dBm, 1 MHz input. The proposed VGA has 37 dB(-16 dB $\sim$ 21 dB) variable gain range, and 8 dB gain range control per 0.3 V control voltage, and can provide variable gain, positive and negative gain slope control, and gain range control. This VGA characteristics provide design flexibility in multi-standard wireless receiver.

• Journal of Power Electronics
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• v.11 no.6
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• pp.914-921
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• 2011

Commencing with incandescent light bulbs, every load today creates harmonics. Unfortunately, these loads vary with respect to their amount of harmonic content and their response to problems caused by harmonics. The prevalent difficulties with harmonics are voltage and current waveform distortions. In addition, Electronic equipment like computers, battery chargers, electronic ballasts, variable frequency drives, and switching mode power supplies generate perilous amounts of harmonics. Issues related to harmonics are of a greater concern to engineers and building designers because they do more than just distort voltage waveforms, they can overheat the building wiring, cause nuisance tripping, overheat transformer units, and cause random end-user equipment failures. Thus power quality is becoming more and more serious with each passing day. As a result, active power filters (APFs) have gained a lot of attention due to their excellent harmonic compensation. However, the performance of the active filters seems to have contradictions with different control techniques. The main objective of this paper is to analyze shunt active filters with fuzzy and pi controllers. To carry out this analysis, active and reactive current methods ($i_d-i_q$) are considered. Extensive simulations were carried out. The simulations were performed under balance, unbalanced and non sinusoidal conditions. The results validate the dynamic behavior of fuzzy logic controllers over PI controllers.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.220-221
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• 2006

This paper presents a single-phase parallel active power filter with an analog control circuit to eliminate for harmonic source currents generated by nonlinear loads. The proposed system removes the harmonic source currents by injecting a compensation current that is 180' out of phase with the load harmonic current. The detection of the load harmonics is realized by a simple new structure, referred to the Notch Filter with GIC (Generalized Impedance Converter), which has higher Q than existing harmonic detecters and a simpler structure. The compensation current is obtained using the proposed harmonic detection circuit, DC-Link voltage, and output current of the full-bridge inverter controlled current mode PWM controller. The operation of the proposed system is verified experimentally.

• Journal of Electrical Engineering and Technology
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• v.8 no.6
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• pp.1389-1399
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• 2013

A discrete controller is designed for low power dc-dc switched mode power supplies. The approach is based on time domain and the control loop continuously and concurrently tunes the compensator parameters to meet the converter specifications. A digital state feedback control combined with the load estimator provides a complete compensation, which further improves the dynamic performance of the closed loop system. Simulation of digitally controlled Buck converter is performed with MATLAB/Simulink. Experimental results are given to demonstrate the effectiveness of the controller using LabVIEW with a data acquisition card (model DAQ Pad - 6009).

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.5
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• pp.817-824
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• 2021

The SDN(Software Defined Networking) technology, which appeared to overcome the limitations of the existing network system, resolves the rigidity of the existing system through the separation of HW and SW in network equipment. These characteristics of SDN provide wide scalability beyond hardware-oriented network equipment, and provide flexible load balancing policies in data centers of various sizes. In the meantime, many studies have been conducted to apply the advantages of SDN to data centers and have shown their effectiveness. The method mainly used in previous studies was to periodically check the server load and perform load balancing based on this. In this method, the more the number of servers and the shorter the server load check cycle, the more traffic increases. In this paper, we propose a new load balancing technique that can eliminate unnecessary traffic and manage server resources more efficiently by reporting to the controller when a specific level of load occurs in the server to solve this limitation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.7
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• pp.943-949
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• 2013

Recently, an electric vehicle (EV) has been become a huge issue in the automotive industry. The EV has many electrical units: electric motors, batteries, converters, etc. The DC distribution power system (DPS) is essential for the EV. The DC DPS offers many advantages. However, multiple loads in the DC DPS may affect the severe instability on the DC bus voltage. Therefore, a voltage bus conditioner (VBC) may use the DC DPS. The VBC is used to mitigate the voltage transient on the bus. Thus, a suitable control technique should be selected for the VBC. In this research, Current controller with fixed switching frequency is designed and applied for the VBC. The DC DPS consist of both a resistor load and a boost converter load. The load variations cause the instability of the DC DPS. This instability is mitigated by the VBC. The simulation results by Matlab simulink and experimental results are presented for validating the proposed VBC and designed control technique.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.50 no.5
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• pp.238-245
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• 2001

During an AC motor's start-up accelerating period, a large amount of current is required to reach to the rating speed. This is called in-rush current. This peak in-rush current can be more than about several times the operating or steady-state current in the full load rating of the motor. In-rush current is present in both and electronic ballasts. The main area of concern is the tripping of circuit breaker and fuses which can affect electrical system components From this, we can see that the electrical power controllers will be rather concerned, since they have to supply the actual current necessary to start the motor. This paper presents a new method to reducing in-rush current and energy saving of the single-phase induction motor used in air-conditioner. It can be obtained that proposed system is low cost and small size as compared with other controller. Experiments are focused on a capacitor starting single-phase induction motor. The optimal power saving and in-rush current limiting by phase angle control are verified by experimental results. Also, auxiliary winding was controlled by electronic starting switch.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.353-356
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• 1997

Vehicle steering system determines the direction of a vehicle. A manual steering system consists of mechanical connections between the steering wheel and tires. Recent power steering system adds an actuator to help a driver to steer easily at low speed. However, at front collision, the driver can be injured by steering shaft and the power steering pump decreases the engine power. To solve these problems, electronic power steering system which connects the steering wheel and tires with electronic connection is proposed, that has advantages such as decrease of engine load and increase of driver safety reactive. Since the ratio between driver's steering torque and steering torque of tires can be controlled freely, the torque which is delivered from the road to the driver through tires and steering wheel can be reshaped to make the driver feel comfortable. In this paper, the ratio of delivering steering torque and the magnitude of force to be delivered from road to driver has been controlled using fuzzy controller, and it's effectiveness has been shown through simulation results.

• Journal of the Semiconductor & Display Technology
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• v.19 no.3
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• pp.43-48
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• 2020

The demand for stable plasma has been on the rise because of the increased delivery power amount in the chamber for improving productivity, and fast and accurate plasma impedance matching become a crucial performance measure for radio frequency (RF) power system in semiconductor manufacturing equipment. In this paper, the overall impedance matching was understood, and voltage and current values were extracted with voltage - current (VI) probe to measure plasma impedance in real-time. Actual matching data were analyzed to derive calibration coefficient for V and I measurements to understand the characteristics of VI probe, and we demonstrated the tendency of RF impedance matching according to changes in load impedance. This preliminary empirical research can contribute to fast RF matching as well as advanced equipment control for the next level of detailed investigation on embedded system based-RF matching controller.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.5
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• pp.396-403
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• 2016

Usually, large-sized buses and trucks have a very high load. In addition, frequent braking during downhill or long-distance driving, causes the conventional method using the brake friction to have a problem in safety because of brake fade and brake burst phenomenon. Auxiliary brakes dividing the braking load is essential. Hence, environment-friendly auxiliary brakes, such as contactless brake rather than the engine auxiliary brake system are needed. A study aimed at improving the energy efficiency by recharging electric energy with changing mechanical to electrical energy that occurs when braking is actively in progress. In this paper, the voltage control method is utilized to recover the electric energy generated in the electromagnetic retarder instead of the eddy current. To regenerate the braking energy into the electrical energy, the resonant L-C circuit is configured in the retarder. The voltage generated in the retarder is simply modeled as a transformer. However, retarder voltage control in this paper is simulated by modeling the induction generator because this induction generator modeling is more practical than transformer modeling. The changes in the voltage of the resonance circuit, which depends on the switch pulse duration of the control device, were analyzed. A PI controller algorithm to control this voltage is proposed. The feasibility of modeling retarder and voltage controller are shown by using MATLAB Simulink in this paper.