• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.504-506
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• 2005

This paper proposes a new neutral current reduction method using PQR instantaneous power theory on the active power filter, unbalanced nonlinear load condition in three-phase four-wire systems. For reduction of neutral line current, the single phase active power filter is used and its performance is same with the three-phase four-wire active power filter. For fully-digital implementation, ramp comparison PWM method was adopted. Simulation results verify good performance of the proposed current control strategy on the shunt APFs.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.522-524
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• 2018

A New Direct AC LED Driver has been proposed for wide output power range and precise constant current regulation using an advanced auto commutation topology. The conventional shunt regulation method provides a stepped input current shape by fixed regulation references in the linear regulator of the each channel, which results in poor current regulation and high THD. The conventional method needs to assign a linear regulator in each LED channel so that the number of linear regulator increases when extending the number of channels especially at high power application. The proposed regulation method can drive multiple switches to regulate each LED channel current by a single amplifier with sinusoidal reference so that large number of LED channel can be simply extended with less BOM cost and low THD is obtained with the accurate current regulation thanks to the sinusoidal input current control in the closed loop control. To confirm the validity of the proposed circuit, theoretical analysis and experimental results from a 20-W LED driver prototype are presented.

• Journal of electromagnetic engineering and science
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• v.10 no.1
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• pp.6-12
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• 2010

In this paper, highly efficient class-F power amplifiers(PAs) with harmonic-controlling transmission lines(TLs) were built for cellular and WLAN applications at 840 MHz and 2.4 GHz each. Also, based on these single-band PAs, a dualband class-F PA was designed after a careful investigation into the harmonics of the two frequencies. The harmonic-controlling TL was designed for the class-F operation at dualband by switching the length of the shunt $\lambda$/4 TL part, while the series $\lambda$/4 TL is optimized for both frequencies. To verify the performance, two class-F PAs optimized at each frequency and a dualband class-F PA at the corresponding frequencies were built with the secondand the third-harmonic control circuits at each frequencies. As a result, the PA#1 at 840 MHz has a peak drain efficiency of 81.2 % with an output power of 24.4 dBm, while the PA#2 at 2.35 GHz shows a drain efficiency of 94.5 % with an output of 22.8 dBm. Finally, the dualband class-F PA#3 showed 60.5 % and 50.9 % drain efficiencies at 840 MHz and 2.4 GHz, with powers of 23.8 dBm and 19.62 dBm, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.4C
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• pp.371-379
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• 2002

In this paper, the MMIC SPST switches operating from DC to 3GHz were designed and implemented. Prior to the design of switches, the small and large-signal switch models were needed to predict switch performance accurately. The newly proposed small-signal switch model parameters were extracted from measured S-parameters using optimization technique with estimated initial values and boundary limits. In the extraction of large-signal switch model parameters, the current source was modeled by fitting empirical equations to measured DC data and the charge model was derived from extracted channel capacitances from measured S-parameters varying the drain-source voltage. To design basic series-shunt SPST switches and isolation-improved SPST switches, we applied this model to commercial microwave circuit simulator. The improved SPST switches exhibited 0.302dB insertion loss, 35.762dB isolation, 1.249 input VSWR, 1.254 output VSWR, and about 15.7dBm PldB with 0/-3V control voltages at 3GHz.

• Journal of the Korean Society of Marine Environment & Safety
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• v.15 no.3
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• pp.257-262
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• 2009

The unified power flow controller(UPFC) is one of the most effective devices in the FACTS family. This paper concerns about a filtering technique for reducing the computer calculation to determine the optimal location of UPFC in a power system. The sensitivities of the power generation cost for UPFC control parameters are evaluated. This technique requires that only one optimal power flow is run to get UPFC sensitivities for all possible transmission lines. To find out a optimal locating of a single UPFC in power system, an ideal transformer model which consists of a complex turns ratio and a variable shunt admittance was used. In this model, the UPFC control variables do not depend on UPFC input and output currents and voltages. The sensitivity method was tested on a 5-bus system derived from the IEEE 14-bus system and IEEE 14-bus system to establish its effectiveness.

• Journal of Veterinary Clinics
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• v.26 no.2
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• pp.123-129
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• 2009

Patent ductus arteriosus(PDA) is an abnormal shunt between the descending aorta and pulmonary artery through the incompletely closed ductus arteriosus and is the most common congenital heart defect in dogs. Recent human genetic studies found that a the gene mutation in transcription factor AP-2 beta(TFAP2B) was responsible for syndromic cases of PDA. Mutations in the TFAP2B gene are associated with certain congenital cardiac defects in humans that include PDA. In this study, we isolated the entire coding exons of canine TFAP2B gene for genetic screening in dogs with PDA. Analysis of the deduced amino acid sequence suggested that the canine TFAP2B are phylogenetically closer to the human TFAP2B(100% identity in amino acid sequence) than mouse and rat. In cTFAP2B gene screening, one single c.936+203G>A base change was found in affected Maltese dogs with PDA. However, further screening found the same base change in one unaffected control dog, suggesting this base change might be polymorphism. No other base changes were found in other dog breeds enrolled in this study. Because the base change was located in the intronic region and found in an unaffected control dog, TFAP2B might not be responsible for familial PDA in Malteses and sporadic cases of other dog breeds, although the gene promoter region should be investigated before reaching to this conclusion. A future study that may take this study further would be to collect more samples and to screen TFAP2B in various breeds of dogs with PDA and other various congenital heart defects.