• Proceedings of the KIEE Conference
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• 1998.11a
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• pp.141-143
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• 1998

A new small-signal model for the controlled on-time boost Power factor correction (PFC) circuit is Presented. The proposed small-signal model is valid up to high frequencies ever 1kHz. IF to remove the low-frequency ripple from the output a 120Hz notch filter is used the proposed model can be used for the control design of the PFC circuit to improve the dynamics of the output voltage. The accuracy of the model is confirmed by comparing the experimental results with the simulational result.

• Journal of the Korean institute of surface engineering
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• v.34 no.4
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• pp.327-336
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• 2001

The skinpassing conditions such as roll type, roll force and roll roughness of the work roll were evaluated to give the surface properties of the galvanized steel sheets that were required for automotive and to get rid of the surface defects that caused with the bad control of galvanized coating process parameters. The surface defects of the galvanized steel sheets such as the ripple mark and the scratch were completely removed as the roll force of SPM work roll was increased and the amount of the transfer of roll surface texture to the strip was also gained a lot. The image clarity of electro discharge textured (EDT) coated steel sheets before and after painting was higher than that of the bright (BRT) and shot blasted (SBT) coated steel sheets because of higher PPI value, lower waviness and uniform surface pattern. Since micro-craters transferred on the surface of the galvanized steel sheets played a role of nucleation sites of chromate reaction, Increase of micro-craters was bring to better corrosion resistance with the increase of the roll force and the use of EDT roll at the skin pass mill.

• Proceedings of the KIPE Conference
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• 2010.11a
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• pp.70-71
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• 2010

태양광 전력조절기에서 임의의 위상을 갖는 모듈통합형 스트링 구조는 출력 커패시터의 리플 크기가 모듈 수만큼 생기게 되어 일정 리플을 위한 커패시턴스를 키워야 하고 이는 크기 및 가격, 효율 면의 입장에서 불리한 요소가 될 수 있다. 본 논문에서는 모듈간의 위상 동기화를 통한 인터리빙 기법을 적용하여 DC-Link 전압의 리플이 저감됨을 분석 및 시뮬레이션을 통해 확인하고 이를 하드웨어 Prototype 제작하여 타당성을 검증하였다.

• Journal of Power Electronics
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• v.19 no.6
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• pp.1449-1457
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• 2019

This paper presents two voltage domain stacking topologies for powering integrated digital loads such as multiprocessors or 3D integrated circuits. Pairs of loads and capacitors are connected in series to form a stack of voltage domains. The voltage is balanced by switching the position of the capacitors in one case and the position of the loads in the other case. This method makes the voltage regulation robust to large differential load power consumption. The first configuration can be named the load stacking topology. The second configuration can be named the capacitor stacking topology. This paper aims at proposing and comparing these two topologies. Models of both topologies and a switching scheme are presented. The behavior, control scheme, losses and overall performance are analyzed and compared theoretically in simulation and experiments. Experimental results show that the capacitor stacking topology has better performance with a 30% voltage ripple reduction.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.406-407
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• 2019

본 논문에서는 유도전동기의 V/F 속도제어 시 특정 구간에 발생하는 전류 리플 저감에 대한 방법을 제안한다. V/F 속도제어 시 특정 구간에 발생하는 전류 리플을 분석하고, 주파수에 따른 극전압 보상량을 결정하여 보상하였다. 극전압 보상을 통해 유도전동기의 전류 리플을 저감시켜 인버터의 효율적인 제어가 가능하게 하였다. 이를 15kW 유도전동기 시스템에 대한 실험을 통해 제안된 방법의 효율성을 검증하였다.

• Proceedings of the KIPE Conference
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• 2018.11a
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• pp.77-79
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• 2018

본 논문에서는 inductive power transfer (IPT) 시스템 2차측 semi-bridgeless 정류기에 pulse density modulation (PDM) 제어를 적용하였을 때 1차측에 나타나는 영향을 최소화하기 위한 공진 네트워크 설계 방안을 제안한다. PDM 제어를 적용하였을 때 2차측 전류 리플이 증가하는 문제를 해결하기 위해 2차측 수신 인덕턴스를 증가시킴으로써 전류 리플을 저감하여 1차측 영향을 최소화한다. 이를 위해 적절한 설계 조건을 구하는 방안에 대하여 제시하고, 방안의 적용에 따른 1차측 영향을 시뮬레이션을 통해 분석한다.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.5
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• pp.402-409
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• 2022

In vector-controlled drive systems, the current measurement offset error causes unwanted torque ripple, resulting in speed and torque control performance degradation. The current measurement offset error is caused by various factors, including thermal drift. This study proposes a simple DC offset error compensation method for a surface permanent magnet motor based on a disturbance observer. The disturbance observer is designed in the stationary reference frame. The proposed method uses only the measured current and machine parameters without additional hardware. The effect of parameter variations is analyzed, and the performance of the current measurement offset error compensation method is validated using simulation and experimental results.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.11
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• pp.1550-1559
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• 2013

Light emitting diode(LED) lighting has been applied various industry fields because of its high efficiency, low power consumption, long life time, and environment friendly characteristics. Generally, LED lighting needs a driver to maintain constant current. Most popular driver is the switching converter. In the converter, there are several electrolytic capacitors. However the lifespan of the electrolytic capacitor is much shorter than LED. Therefore the lifespan of LED lighting with electrolytic capacitor is decreased. Also, LED lighting needs dimming control because of various needs and energy saving. This paper presents the dimmable single-stage PFC DCM flyback converter without electrolytic capacitor and parallel LC resonant filter for reducing 120[Hz] ripple on the output. The type 2 controller is used to maintain constant current and the analog dimming control is used. The proposed converter is verified through simulation and experimental works.

• Journal of Information Technology Services
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• v.15 no.3
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• pp.33-50
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• 2016

In a dynamic IT environment, employees often utilize external IT resources to work more efficiently and flexibly. However, the use of external IT resources beyond its control may cause difficulties in the company. This is known as "Shadow IT." In spite of efficiency gains or cost savings, Shadow IT presents problems for companies such as the outflow of enterprise data. To address these problems, appropriate measures are required to maintain a balance between flexibility and control. Therefore, in this study, we developed a new information security management system called AIIMS (Advanced IT service & Information security Management System) and the Shadow IT Evaluation Model. The proposed model reflects a Shadow IT's attributes such as innovativeness, effectiveness, and ripple effect. AIIMS consists of five fields: current analysis; Shadow IT management plans; management process; education and training; and internal audit. There are additional management items and sub-items within these five fields. Using AIIMS, we expect to not only mitigate the potential risks of Shadow IT but also create successful business outcomes. Now is the time to draw to the Light in the Shadow IT.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.1
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• pp.34-39
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• 2002

Most X-ray generator had been used do rectifier type transformer high tension generator which is supplied in a clinical diagnosis. But it is difficult to miniaturize and become light weight. Also, because the ripple rate of tube voltage is high, X-ray generating efficiency is very low. Therefore, it is supplied gradually from abroad being developed high tension generator for inverter type X-ray generator which use semi-conductor switching element for electric power that have high speed switching ability to solved these problem. But, semi-conductor element of big capacity are used by X-ray tube's big consumption power and diffusion is difficult in the small size hospital because production cost is ascending by doing digital control through DSP and product price becomes expensive. Therefore, in this paper, design and manufactured CR type voltage divider for feedback control of tube voltage of high frequency resonance type inverter and high tension transformer for high frequency to apply economical diffusion type X-ray generator which have wide output voltage and load extent. It is Proved do X-ray generator and stability of X-ray tube's output characteristics through an experiment.