• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.908-911
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• 2004

In this paper, we describe a robust image processing algorithm to recognize the road lane in real-time. For the real-time processing, a detection area is decided by a lane segment of a previous frame and edges are detected on the basis of the lane width. For the robust driving, the global threshold with the Otsu algorithm is used to get a binary image in a frame. Therefore, reliable edges are obtained from the algorithms suggested in this paper in a short time. Lastly, the lane segment is found by hough transform. We made a RC(Radio Control) car equipped with a vision system and verified these algorithms using the RC Car.

• Proceedings of the KIEE Conference
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• 2006.10d
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• pp.139-142
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• 2006

This paper describes a new method using random modulated strategies for switched reluctance machines. The proposed method is combined random turn-on, turn-off angle technique and random pulse width modulation technique. The purpose of this proposed method is to decrease harmonic spectrum, and thus reduce the emitted acoustical noise. A random generator is generated by linear congruential generator (LCG) using random pulse position (RPP) scheme. Simulation results show that the harmonic intensity of proposed method is better than that of conventional method.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.7
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• pp.674-678
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• 2008

Low level laser therapy has various therapy effects. This paper performed the basic study for fabricating the low level laser therapy apparatus, and one of the goals of this paper was to make this apparatus used handily. The apparatus has been fabricated using the laser diode and microprocessor unit. The apparatus used a 635 nm laser diode for laser medical therapy and was designed for a pulse width modulation type to increase stimulation effects. In this study, the designed device was used to find out how 635 nm laser diode affected the skin injury of SD-Rat(Sprague-Dawley Rat). We divided the participants into two groups; irradiation group which was irradiated 10 minutes a day for 9 consecutive days, and none irradiation group. The results showed that the study group had lower incidence of inflammation and faster recovery, compared with the control group.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2009.10a
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• pp.189-191
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• 2009

기존의 형광 램프용 전자식 안정기는 램프와 안정기의 수명 연장을 가져다주었다. 형광 램프용 전자식 안정기는 기존의 60Hz로 형광등을 점등하는 자기식 안정기에 비해 향상된 점등과 에너지를 절약 측면에서 큰 장점을 보이고 있다. 형광 램프의 조광방식으로 크게 3가지 방식으로 나뉘는데 위상제어를 이용한 방식, PWM(Pulse Width Modulation)방식, 저전압 제어방식이 있다. 본 논문은 기존의 사용 방법과는 달리 안정기 내부의 인버터 공진 특성을 이용하여 주파수를 변환시켜 형광 램프를 디밍하였다.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.309-312
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• 2000

Single-phase multi-level AC-DC converter is proposed that is composed of diode bridge and switch. The number of the supply current level is depending on the individual current level of the converter. A converter circuit the number of the level is equal to $\textrm{2}^{M+1}$-1 The proposed circuit has converter with 31 current levels. When the number of current level is increased smoother sinusoidal waveform can be obtained directly and it is possible to control the supply current almost continuously from zero to maximum without step changes of generating high voltage as pulse width modulation switching loss is decreased it has an advantage in large capacity. it is illustrated technique are confirmed the validity and effectiveness through the simulation & experiments

• Proceedings of the KIEE Conference
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• 2003.04a
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• pp.262-265
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• 2003

In this paper, a new active snubber circuit that overcomes most of the drawbacks of the normal "zero voltage transition pulse width modulation" (ZVT-PWM) converter is proposed to contrive a new family of ZVT- PWM converter. A converter with the proposed snubber circuit can also operate at light load conditions. A design procedure of the proposed active snubber circuit is also presented. Additionally, at full output power in the proposed soft switching converter, the main switch loss is about 27[%] and the total circuit loss is about 36[%] of that in its counterpart hard switching converter, and so the overall efficiency, which is about 91[%] in the hard switching case, increases to about 97[%].

• Journal of Power Electronics
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• v.9 no.6
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• pp.866-873
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• 2009

In general, the output voltage level of a PV array varies widely at various irradiances and temperatures. The MPP (Maximum Power Point) range of a medium- or high-power PV PCS is normally 450~830Vdc or 300~600Vdc. This means the PV PCS should operate in a wide range of modulation indexes. The PV PCS should satisfy the harmonic current requirement that the TDD (Total demand distortion) shall not exceed 5%. This paper proposes a new PWM control method for a medium- or high-power PV PCS which increases the efficiency of power conversion in all operation ranges with acceptable harmonic ripple currents. This paper compares and analyzes appropriate PWM schemes for the PV PCS in the view points of conversion efficiency and current harmonics.

• Proceedings of the KIPE Conference
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• 2009.11a
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• pp.143-145
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• 2009

The method for the current equalization of the rectifier diodes in LLC resonant converter is proposed. The method decreases the current difference between the rectifier diodes using the auxiliary winding of the transformer and asymmetrical pulse width modulation (APWM). The analytical reason of the current unbalance is investigated and the operation principle of the proposed method and APWM control loop are explained. The performance of the proposed method was verified on a 480-W, 400-V/24-V dc/dc converter.

• Proceedings of the KIPE Conference
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• 2009.11a
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• pp.268-270
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• 2009

This paper proposes a simple starting method to arrange the rotor position of the blushless DC motor (BLDC) without additional sensors and any information of motor parameters. Both the stator current and time period for arranging the rotor position can be easily adjusted by modulating a pulse width of switching devices. Using the proposed method, it is demonstrated experimentally that the BLDC starts up very smoothly.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.2
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• pp.167-174
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• 2015

This study describes how digital time delay deteriorates control performance in zero voltage switching (ZVS) phase-shifted full bridge (PSFB) converter. The small-signal model of the ZVS PSFB converter is derived from the buck-converter small-signal model. Digital time delay effects have been considered according to the digital sampling methods. The analysis verifies that digital time delays reduce the stability margin of the converter, and the double sampling technique exhibits better performance than the single sampling technique. Both simulation and experimental results based on 250 W ZVS PSFB confirm the validity of the analyses performed in the study.