• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.1879-1881
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• 1998

The conducted differential mode (DM) EMI in a flyback converter are analyzed. Circuit modeling of passive components and PCB pattern for the EMI simulation are presented. Using the model, high frequency noise path is analyzed. The analyses are verified with simulations by identifying the peakings of the EMI pattern.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.4
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• pp.277-284
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• 2017

For passive power factor correction, the valley fill circuit approach is attractive for low power applications because of low cost, high efficiency, and simple circuit design. However, to vouch for the product quality, two dc-link capacitors in the valley fill circuit should be selected to withstand the peak rectified ac input voltage. The common mode (CM) and differential mode (DM) choke should be used to suppress the electromagnetic interference (EMI) noise, thereby resulting in large size volume product. This paper presents the practical design and implementation of a valley fill flyback converter with reduced dc link capacitors and EMI magnetic volumes. By using the proposed over voltage protection circuit, dc-link capacitors in the valley fill circuit can be selected to withstand half the peak rectified ac input voltage, and the proposed CM/DM choke can be successfully adopted. The proposed circuit effectiveness is shown by simulation and experimentally verified by a 78W prototype.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.1 s.92
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• pp.56-65
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• 2005

We proposed the Power-line EMI filter for vehicle-shelter which have attenuation performance of 100 dB from 10kHz to 1 GHz. The inductor and capacitor for EMI filter design was charactenzed using circuit simulator and then, we experimentally verified 100 dB attenuation for the conducted emission noise through power line. This results will be used for the application systems of protection weapons against EMI attacks as well as vehicle-shelter.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.12
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• pp.963-968
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• 2018

In this paper, a compact common mode filter using passive elements is designed and fabricated. To design a common mode filter with required frequency response, the equivalent circuits of the common mode filter in differential mode and common mode were analyzed. Compared with the former filter using a ${\lambda}/4$ resonator, the size of the proposed structure was reduced by 60 %. The fabricated common mode filter has a maximum differential mode insertion loss of 1.2 dB and a minimum common mode absorption efficiency of 78.2% in the CMA - bandwidth of 27.5 %.

• Journal of Power Electronics
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• v.19 no.2
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• pp.403-412
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• 2019

Aiming at the problems of large dv/dt and di/dt in traditional single-ended converters and high electromagnetic interference (EMI) noise levels, a single-ended isolated converter using the secondary resonance technique is proposed in this paper. In the proposed converter, the voltage stress of the main power switch can be reduced and the voltage across the output diode is clamped to the output voltage when compared to the conventional flyback converter. In addition, the peak current stress through the main power switch can be decreased and zero current switching (ZCS) of the output diode can be achieved through the resonance technique. Moreover, the EMI noise coupling path and an equivalent model of the proposed converter topology are presented through the operational principle of the proposed converter. Analysis results indicate that the common mode (CM) EMI noise and the differential mode (DM) EMI noise of such a converter are deduced since the frequency spectra of the equivalent controlled voltage sources and controlled current source are decreased when compared with the traditional flyback converter. Furthermore, appropriate parameter selection of the resonant circuit network can increase the equivalent impedance in the EMI coupling path in the low frequency range, which further reduces the common mode interference. Finally, a simulation model and a 60W experimental prototype of the proposed converter are built and tested. Experimental results verify the theoretical analysis.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.3
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• pp.260-266
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• 2004

Because the EMI filter is mainly designed by trial and error method, it takes many times to reduce the conducted EMI noise in a power converter. Thus, a newly analytical design procedure is proposed to overcome the problem in this paper. High frequency models of each component are built, md, using the modeling circuits, the filter design is carried out applicable to each mode. Based on the accumulated database for practical components, and the measurement data of EUT with a standard filter, the filler design algorithm is presented. Finally, the validity of the Proposed models and design method is verified through the measurement results.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03a
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• pp.65-84
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• 2000

Europe and US which have more restrictive regulations than Korea about the noise and vibration during construction are using Auger-cast Pile to reduce the problem relating with noise and vibration. However Auger-cast Pile has problems like difficult quality control and low bearing capacity. In Europe, Displacement in-situ concrete Pile has been used to sove that problems since 1990s, and Korea has performed the test construction in 1997 and it has been used as the real structural foundation since 1998. Test and real construction results verified that the allowable capacity of the pile(diameter = 410mm) is between 70 and 100ton. Though De Beer & Van Imps design method utilizing CPT result is used to calculate the bearing capacity of the Displacement in-situ Pile, Korea is dependant upon the SPT as the sounding test, so design method utilizing SPT result is necessary to promote the application of the pile. To find out reasonable design method using SPT result, rearing capacity of the pile constructed in sand and clay in Korea was calculated using Meyerhof, SPT-CPT translation method, Nordlund, Douglas and DM-7 method, and the calculation results were compared to the load test result. Analysis result shows that SPT-CPT translation method is more reliable than others and economical design can be possible because it considers efficiently the friction capacity of Displacement in-situ Pile.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.2
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• pp.143-148
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• 2022

For the purpose of treating health checkups and recovery of patients in a super-aged society, hospitals use devices designed with a reduction circuit of electromagnetic waves associated with the specific absorption rate of electromagnetic waves absorbed by the human body. In this paper, we proposed a filter improvement design method capable of reducing electromagnetic waves. As a result of confirming the validity of the proposed technique through simulation and experimental results, the following result values were obtained. Applying the common-mode (CM) inductor 4 mH to a calibration circuit, noise decreased in a multiband spectrum. Using the differential mode(DM) inductor 40 µH element in the primary calibration circuit, the noise decreased by 15 dB or more in the 3 MHz band spectrum. Also, applying the Admittance Capacitance (Y-Cap) 10 nF element in the secondary calibration circuit resulted in the decrease by more than 30 dB in the band spectrum before 2 MHz. After using a common-mode inductor 4 mH element in the tertiary calibration circuit, it decreased by more than 15 dB in the band spectrum after 2 MHz.

• Proceedings of the Korean Information Science Society Conference
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• 2006.10d
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• pp.502-505
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• 2006

본 논문은 고해상도의 영상을 처리하는 이동기기 등에 사용되는 SoC(System On a Chip)에 구현이 용이한 효과적인 화질 향상 (잡음감소와 윤곽강조) 을 위한 방법과 구조에 대한 것이다. 최근 이동기기의 발전과 진화에 따라 여러 형태의 이동기기가 개발되고 있는데 그 중 최근 인기를 끌고 있는 포터블 미디어 플레이어 (PMP)나 HD(Hight Definition)급 camcorder 등이 고해상도의 영상을 처리하는 이동기기로 분류될 수 있다. 이러한 이동기기에서 고해상도 영상에 대한 화질 향상을 기존의 복잡한 방법을 사용해 처리한다면 메모리 대역폭이나 하드웨어 크기 등의 증가로 이동기기에서 구현하는데 어려움이 따른다. 이에 본 논문에서는 이러한 이동기기에서의 고해상도의 화질 향상을 입력영상의 종류에 따라 선택적으로 메모리 대역폭 사용 없이 하드웨어 크기를 최소화하여 FPGA (field programmable gate array)나 ASIC (application specific integrated circuit)으로 구현이 용이하도록 하는 방법과 구조에 대해 설명하고 실제 영상을 가지고 실험한 결과로 주관적 화질 향상 효과를 가져 온 것을 확인할 수 있었다.

• Smart Media Journal
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• v.4 no.2
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• pp.62-67
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• 2015

During several decades, hard disk drive(HDD) has been used in most computer systems as secondary storage and, however, the performance enhancement of HDD is limited by its mechanical properties. On the other hand, although the flash memory based solid state drive (SSD) has more advantages over HDD such as high performance and low noise, SSD is still too expensive for common usage and expected to take several years to replace HDD completely. Therefore, SSD caching mechanism using the SSD as a cache of high capacity HDD has been highlighted lately. The representatives of SSD caching mechanisms are typically bcache, dm-cache, Flashcache, and EnhanceIO. Each of them has its own internal mechanism and implementation, and this makes them to show their own pros. and cons. In this paper, we analyze the characteristics of each SSD caching mechanisms and compare the performance of them under various workloads. We expect that our contribution will be useful to enhance the performance of SSD caching mechanisms.