• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.30-31
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• 2011

현재의 고출력 LED (Light Emitting Diode)는 긴 수명시간, 적은 유지보수 비용, 그리고 고효율의 특징으로 차세대 조명 소자로 각광받고 있다. 본 논문에서는 Two-stage LED 구동 회로에서 온도 변화에 따른 정전류 제어가 가능한 LED 구동 드라이브의 효율을 개선하기 위해 입력 전압을 기본 전압으로 하고 LED 출력전류를 통한 전압 변동분 만을 전력변환하여 보상 할 수 있는 LED 구동 드라이브 회로를 연구 하였다. 제안된 비절연 전압 변동분 보상회로는 기존 DC/DC 컨버터를 이용한 LED 구동 드라이브에 비해 효율이 개선 되었음을 실험을 통해 알 수 있었다.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.3
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• pp.116-123
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• 1999

SMPS는 수위칭 소자를 이용하여 효과적으로 전력을 변환시킨다. 여기에서 가장 중요한 파라미터가 스위칭 주파수이다. 스위칭 주파수를 증가시킴에 따라 전원장치의 소형경량화가 가능하다. 그러나 기존 PWM 컨버터에서는 치명적인 단점으로 스위칭 주파수를 증가시킴에 따라 스위칭 손실 및 EMI 문제를 야기한다. 특히 SMPS의 동작은 상당히 큰 di/dt와 dv/dt에 기인한 EMI 전도성 잡음을 발생시킨다. EMI를 감소시키는 방법들로는 고전적이고 고가인 입력필터 혹은 주 전력단에 능동필터를 첨가하는 방법 등이 있어 왔다. 본 논문에서는 DC/DC 포워드 컨버터에 대해 EMI 잡음 발생원 및 잡음 경로를 분석하였다. SMPS에서 방출되는 전도성 잡음은 스위칭 주파수와 그 고주파 주파수에 집중되어 있다. 따라서 본 연구에서는 일정 출력전압에는 큰 영향 없이 스위칭 주파수를 약간씩 변조하게 되는 RPWM 제어를 통하여 전도성 잡음의 주파수 대역을 측면대역으로 분사시키어 전체 첨두치를 저감시키고, 고조파 스펙트럼을 개선할 수 있다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.8
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• pp.1544-1550
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• 2009

In this paper, a new single phase voltage sag/swell compensator using direct power conversion is proposed. A new compensator consists of input/output filter, series transformer and direct ac-ac converter, which is a single-phase back-to-back PWM converter without dc-link capacitors. Advantages of the proposed compensator include: simple power circuit by eliminating dc link electrolytic capacitors and thereby, improved reliability and increased life time of the entire compensator; simple PWM strategy or compensating voltage sag/swell at the same time and reduced switching losses in the ac-ac converter. Further, the proposed scheme is able to adopt simple switch commutation method without requiring complex four-step commutation method that is commonly employed in the direct power conversion. Simulation and experimental results are shown to demonstrate the advantages of the new compensator and PWM strategy. A 220V, 3kVA single-phase compensator based on the digital signal processor controller is built and tested.

• Journal of the Korean Institute of Telematics and Electronics
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• v.8 no.1
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• pp.1-8
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• 1971

A survey meter which is used a G-M counter sensitive to beta and gamma radiation is studied. This device is completely transistorized, operated with battery, and can be read directly the 3 full-scale meter range: 2.5, 25 and 250 MR/HR respectively. The collector-coupled monostabel multivibrator consisting of a counting-rate meter circuit, and the astable blocking oscillator consisting of a dc-de converter for power supply are analyzed and derived the design dquations. To improve the resolving time of the G-M counter the device is designed to be triggered by low pulse in the order of 0.5v.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.2
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• pp.90-94
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• 2011

In this paper, the energy transfer is associated with high frequency band and try to analysis the rectifier circuit structure and characteristics and find ways to maximum efficiency. Input signal at 13.56MHz is converted output DC signal with the experiments and measurements. Rectifier cirsuits can be divided into the half-wave, full-wave, bridge rectifier circuit. Research to the present with the passive components are carried out with a focus on efficiency improvements. Factors affecting the efficiency of rectification is dependent on the characteristics of the device. In this experiment, about 70% efficiency can be measured. By using an improved device for high efficiency could be obtained higher efficiency.

• The Journal of Korean Association of Computer Education
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• v.9 no.2
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• pp.101-109
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• 2006

We propose an adaptive digital watermarking algorithm using HVS(human visual system) and SOM(Self-Organizing Map) among neural networks. This method adjusts adaptively the strength of the watermark which is embedded in different blocks according to block classification in DCT(Discrete Cosine Transform) domain. All blocks in 3 classes out of 4 are selected to embed a watermark. Watermark sequences are embedded in 6 lowest frequency coefficients of each block except the DC component. The experimental results are excellent.

• Journal of the Korean Society for Railway
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• v.19 no.5
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• pp.617-628
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• 2016

This paper proposes the structure of a smart transformer to improve the performance of the 60Hz main power transformer for rolling stock. The proposed smart transformer is a kind of solid state transformer that consists of semiconductor switching devices and high frequency transformers. This smart transformer would have smaller size than the conventional 60Hz main transformer for rolling stock, making it possible to operate AC electrified track efficiently by power factor control. The proposed structure employs a cascade H-Bridge converter to interface with the high voltage AC single phase grid as the rectifier part. Each H-Bridge converter in the rectifier part is connected by a Dual-Active-Bridge (DAB) converter to generate an isolated low voltage DC output source of the system. Because the AC voltage in the train system is a kind of medium voltage, the number of the modules would be several tens. To control the entire smart transformer, the inner DC voltage of the modules, the AC input current, and the output DC voltage must be controlled instantaneously. In this paper, a control algorithm to operate the proposed structure is suggested and confirmed through computer simulation.

• Journal of IKEEE
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• v.28 no.1
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• pp.78-89
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• 2024

PMIC chips based on a BCD process used in automotive semiconductors require multi-time programmable (MTP) intellectual property (IP) that does not require additional masks to trim analog circuits. In this paper, MTP cell size was reduced by about 18.4% by using MTP cells using PMOS capacitors (PCAPs) instead of NMOS capacitors (NCAPs) in MTP cells, which are single poly EEPROM cells with two transistors and one MOS capacitor for small-area MTP IP design. In addition, from the perspective of MTP IP circuit design, the two-stage voltage shifter circuit is applied to the CG drive circuit and TG drive circuit of MTP IP design, and in order to reduce the area of the DC-DC converter circuit, the VPP (=7.75V), VNN (=-7.75V) and VNNL (=-2.5V) charge pump circuits using the charge pumping method are placed separately for each charge pump.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.39 no.4
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• pp.408-417
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• 2002

Gabor cosine and sine functions have widely been used to describe the human visual filters. This paper presents a new method to locally represent image frequency components using these functions. The parameters of basis functions are determined based on dc ripple and the sidelobe strength of step response. The resultant transform consisting of Gabor cosine and sine functions is compared with existing transforms by computing the joint effective width and by applying to the image reconstruction with the limited number of transformed coefficients. The experimental results show that the proposed transform has better performance than DGT and DCT.

• Korean Journal of Optics and Photonics
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• v.15 no.2
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• pp.183-189
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• 2004

As high quality digital cameras become readily available, digital cameras are being used not only for simple picture recording but also as information storing media in various fields. However, due to the fact that the spectral responses of the camera sensors are different from color matching functions of the CIE standard observer, the color can not be measured using these cameras. This study shows a method for converting camera image to sRGB image, in which color information is preserved. The transfer matrix between camera output signals and CIE stimulus values was determined using a multiple regression method with Macbeth ColorChecker as target colors. The CIE stimulus values for camera output signals can be mapped with a transfer matrix, and these values are converted to sRGB signals. As the result of testing a Kodak DC220 digital camera, the average color difference of Macbeth ColorChecker between true and displayed colors was 2.1 $\Delta$ $E_{ab}$ $^{*}$.$^{*}$.