• Journal of Power Electronics
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• v.18 no.1
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• pp.171-184
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• 2018

Unbalanced and distorted grid voltages cause the grid side current of a current source PWM rectifier to be heavily distorted. They can also cause the DC-link current to fluctuate with a huge amplitude. In order to enhance the performance of a current-source PWM rectifier under unbalanced and harmonic grid voltage conditions, a mathematical model of a current-source PWM rectifier is established and a flexible multi-objective control strategy is proposed to control the DC-link current and grid-current. The fundamental positive/negative sequence, $5^{th}$ and $7^{th}$ order harmonic components of the grid voltage are first separated with the proposed control strategy. The grid current reference are optimized based on three objectives: 1) sinusoidal and symmetrical grid current, 2) sinusoidal grid current and elimination of the DC-current $2^{nd}$ order fluctuations, and 3) elimination of the DC-current $2^{nd}$ and $6^{th}$ order fluctuations. To avoid separation of the grid current components, a multi-frequency proportional-resonant controller is applied to control the fundamental positive/negative sequence, $5^{th}$ and $7^{th}$ order harmonic current. Finally, experimental results verify the effectiveness of proposed control strategy.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.6
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• pp.23-29
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• 1995

In this study, Active noise controlis implemented with single channel and multi-channel adaptive algorithm in 3 dimensional reverberant enclosure sound. field, which occurrs in complicated acoustic mode. First, for the one case excited with the resonant frequency of an enclosure, a target of control and the other cases excited with band-pass filtered random noise(100~400Hz), it is implemented to control reducing interior noise of enclosure with single channel and realtime multi-channel adaptive algorithm for global noise reduction in enclosure.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.289-290
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• 2019

2차측 Multi-winding구조의 LLC공진형 컨버터는 교차조절(Cross-regulation) 특성에 의해 각 출력의 부하의 변화에 따라 출력전압의 불균형 문제가 있다. 본 논문에서는 2차측 Multi-winding 구조의 LLC공진형 컨버터에서 나타나는 교차조절 특성을 이론적으로 분석하고 240W급 LLC공진형 컨버터를 이용하여 실험을 진행한다. 실험 결과를 통해 출력 채널 수의 증가에 따른 교차조절 특성에 대해 고찰한다.

• Journal of the Semiconductor & Display Technology
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• v.20 no.3
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• pp.157-160
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• 2021

In this paper, a 20W class multi-output QR flyback converter for auxiliary power supply was designed to stabilize 4 output voltages, and the efficiency and load characteristics were compared and analyzed. It was checked if each output affects other output characteristics through experiment. As a result, the experimental circuit reached a high efficiency of 82.5% or more at a load power of over 20W, and the maximum power loss was 2.6W. Consequently, it was confirmed that all of 4 output voltages of the multi-output QR flyback converter constructed in this paper were stabilized within 0.5% in full-load range, and each output was independently controlled in an electrically isolated state.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.6
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• pp.453-460
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• 2008

This paper proposes a new multi-output LLC resonant converter by using single control IC, which has the tight-regulated dual output voltage without additional power devices and controller. The proposed converter has master and slave outputs, of which regulations are achieved by the PWM(pulse width modulation) and PFM(pulse frequency modulation), respectively. Different from the conventional dual-output LLC resonant converter, the proposed converter has no additional post-regulators like a boost converter. Therefore, it features a low cost, small size, and high efficiency. To confirm the validity and prove the superiority of proposed converter, simulated and experimental results on a 50" FHD PDP power set prototype are presented.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.261-261
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• 2007

Wearable and ubiquitous micro systems will be greatly growing and their related devices should be self-powered in order to avoid the replacement of finite power sources, for example, by scavenging energy from the environment. With ever reducing power requirements of both analog and digital circuits, power scavenging approaches are becoming increasingly realistic. One approach is to drive an electromechanical converter from ambient motion or vibration. Vibration-driven generators based on electromagnetic, electrostatic and piezoelectric technologies have been demonstrated. Among various generator types proposed so far, piezoelectric generator possesses considerable potential in micro system. To overcome low mechanical-to- electric energy conversion, the piezoelectric device should activate in resonance mode in response to external vibration. Normally, the external vibration excretes at low frequency ranging 0.1 to 200 Hz, whereas the resonant frequencies of the devices are fixed as constant. Therefore, keeping their resonant mode in varying external vibration can be one of important points in enhancing the conversion efficiency. We investigated the possibility of use of multi-bender type piezoelectric devices. To match the external vibration frequency with the device resonant frequency, the various devices with different resonant frequency were chosen. Under an external vibration acceleration of 0.1G at 120 Hz, the device exhibited a peak-to-peak voltage of 2.8 V and a power of 0.5 mw in resonance mode.

• Korean Journal of Optics and Photonics
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• v.1 no.1
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• pp.7-11
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• 1990

Resonant multi photon ionization (RMPD of Hg atoms is studied by focusing a high-power laser into the ionization cell. The intermediate resonant state is taken as $6d^1D_2$ with the 4-photon resonance wavelength of 560.7 nm. The ionization signal is measured as Hg vapor pressure (0.1-3.0 Torr), laser intensity $(10-120GW/\textrm{cm}^2)$, and laser wavelength (559-569 nm) vary. AC Stark shift and line broadening of the resonant state $(6d^1D_2)$ are observed and the shift factor is measured to be $-0.6(cm^{-1}/GW/\textrm{cm}^2$. It is also observed that the ionization signal increases as the Hg vapor pressure increases up to a certain value of pressure, however, if the pressure further increases, the signal decreases. The order of non-linearity, which discribes the laser intensity dependence of ionization rate, is measured to be 3 at the resonance, and compared with the theoretical results.esults.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.9
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• pp.715-721
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• 2013

Minimization techniques are adaptations of Helical structure, Meta material, multi-layer structure etc. But, Helical structure is not suited to minimization technique of RF circuit having single resonant frequency. Because it generate resonant frequency following as rotation of circumference. Meta material and multi layer structure have weakness of expenditure and complex structure. In addition, conventional three dimensional M$\ddot{o}$bius Strip and planar M$\ddot{o}$bius Strip are not two dimensional planar M$\ddot{o}$bius Strip that has weakness of electrical coupling effect. Therefore, in this paper, we proposed miniaturized and reduced electrical coupling effect antenna by adaptation of Quasi M$\ddot{o}$bius Strip that topology is same as three dimensional M$\ddot{o}$bius Strip with Via-Hole structure. According to the simulation result, physical circumferential length is 1/3 minimized compared with conventional ring antenna under the same resonant frequency. In addition, coupling effect is not nearly generates near to the resonant frequency, 2.4GHz.

• Advances in nano research
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• v.3 no.1
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• pp.29-37
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• 2015

In the current study, the nonlinear vibration properties of an embedded zigzag single-walled carbon nanotube (SWCNT) are investigated. Winkler-type model is used to simulate the interaction of the zigzag SWCNTs with a surrounding elastic medium. The relation between deflection amplitudes and resonant frequencies of the SWCNT is derived through harmonic balance method. The equivalent Young's modulus and shear modulus for zigzag SWCNT are derived using an energy-equivalent model. The amplitude - frequency curves for large-amplitude vibrations are graphically illustrated. The simulation results show that the chirality of zigzag carbon nanolube as well as surrounding elastic medium play more important roles in the nonlinear vibration of the single-walled carbon nanotubes.

• Journal of the Korea Society of Computer and Information
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• v.15 no.8
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• pp.59-66
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• 2010

In this paper, the internal antenna for mobile communication handset which is able to control both coupling coefficient and resonant frequency without any major modification of radiator and ground plane of antenna. Novel internal antenna with its controllable resonant frequency is presented for triple-band or over mobile handsets. The operating range can include GSM(880~960 MHz), GPS($1,575{\pm}10MHz$), DCS(1,710~1,880MHz), US-PCS(1,850~1,990 MHz), and W-CDMA(1,920~2,170 MHz). The proposed antenna is realized by combination of a half wavelength loaded line antenna and PIFA(Planner Inverted F Antenna). A single shorting and feeding points are used and they are common to both antenna structures. One of two inductors which is placed at each shorting post, one inductor is for adjusts amount of coupling, and the other controlling the resonant frequency in DCS/US-PCS/WCDMA bands. The inductance range for control of input impedance is between 0nH and 6.8nH, and each of gain variation in GSM, GPS and DCS/US-PCS/WCDMA band is under 0.15dBi, 0.73dBi and 0.29dBi. The inductance range for control of the resonant frequency is between 1640MHz and 2500MHz, and each of gain variation in GSM, GPS and DCS/US-PCS/WCDMA band is under 0.46dBi, 0.53dBi and 0.8dBi.