• 한국정보통신학회논문지
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• 제11권5호
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• pp.949-954
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• 2007

본 논문에서는 CMOS 공정을 이용하여 동작온도에 무관한 FVC(Frequency-to-Voltage Convener) 회로를 제안한다. FVC는 FLL(Frequency Locked Loop)의 핵심 회로로서 주파수 신호를 전압신호로 변환하는 회로이다. FLL 회로는 PLL(Phase-Locked Loop) 회로 같이 고정된 주파수 신호를 생성하는 회로지만, PLL과는 달리 위상비교기, charge pump, 저역 필터 등이 필요치 않아 간단히 회로를 구성할 수 있다. FVC 회로의 설계는 $0.25{\mu}m$ CMOS 공정을 이용하였다. 설계되어진 회로의 입력 주파수는 70MHz에서 140MHz를 사용하였다. 회로의 시뮬레이션 결과 동작 온도가 $0^{\circ}C$에서 $75^{\circ}C$까지 변화할 때 변환된 출력 전압의 변화는 상온에 비하여 ${\pm}2%$이내였다.

• Journal of Electrical Engineering and Technology
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• 제12권4호
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• pp.1376-1385
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• 2017

This paper proposes a method for estimating the expected frequency of voltage swells caused by asymmetrical faults in a power system. Although voltage swell is less common than voltage sag, repeated swells can have severe destructive impact on sensitive equipment. It is essential to understand system performance related to voltage swells for finding optimal countermeasures. An expected swell frequency at a sensitive load terminal can be estimated based on the concept of an area of vulnerability (AOV) and long-term system fault data. This paper describes an effective method for calculating an AOV to voltage swells. Interval estimation for an expected swell frequency is also presented for effective understanding of system performance. The proposed method provides long-term performance evaluation of the frequency and degree of voltage swell occurrences.

• 조명전기설비학회논문지
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• 제27권4호
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• pp.16-22
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• 2013

This paper presents a method to analyze the voltage sag data obtained from monitoring systems. In order to establish effective countermeasures against voltage sag problems, an assessment of the system performance with respect to voltage sags is needed. Generally, the average annual sag frequency can be estimated by using the recorded voltage sag events for several years. However, the simple average value can not give the information about the errors of estimation. Such an average estimation is not useful for establishing effective solutions for voltage sag problems. Therefore, this paper proposes an effective method based on the Interval Estimation method. The estimation of voltage sag frequency is performed by using the average frequency and Poisson probability model. The proposed method can give the expected annual sag frequency and upper one-sided bound frequency.

• Journal of Electrical Engineering and Technology
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• 제11권4호
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• pp.921-930
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• 2016

This paper proposes a design and control method for a high-voltage direction current modular multilevel converter (HVDC-MMC) considering the capacitor voltage ripple of the submodule (SM). The capacitor voltage ripple consists of the line frequency and double-line-frequency components. The double line- frequency component does not fluctuate according to the active power, whereas the line-frequency component is highly influenced by the grid-side voltage and current. If the grid voltage drops, a conventional converter increases the current to maintain the active power. A grid voltage drops, current increment, or both occur with a capacitor voltage ripple higher than the limit value. In order to reliably control an MMC within a limit value, the SM capacitor should be designed on the basis of the capacitor voltage ripple. In this paper, the capacitor voltage ripple according to the grid voltage and current are analyzed, and the proposed control method includes a current limitation method considering the capacitor voltage ripple. The proposed design and control method are verified through simulation using PSCAD/EMTDC.

• Journal of Information Processing Systems
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• 제7권1호
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• pp.93-102
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• 2011

In deeply scaled CMOS technologies, two major non-ideal factors are threatening the survival of the CMOS; i) PVT (process, voltage, and temperature) variations and ii) leakage power consumption. In this paper, we propose a novel post-silicon tuning methodology to scale optimum voltage and frequency "dynamically". The proposed design technique will use our PVT sensor circuits to monitor the variations and based on the monitored variation data, voltage and frequency will be compensated "automatically". During the compensation process, supply voltage is dynamically adjusted to guarantee the minimum total power consumption without violating the frequency requirement. The simulation results show that the proposed technique can reduce the total power by 85% and the static power by 53% on average for the selected ISCAS'85 benchmark circuits with 45 nm CMOS technology compared to the results of the traditional PVT compensation method.

• 한국정보통신학회논문지
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• 제15권4호
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• pp.891-896
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• 2011

이 논문에서는 전류 컨베이어 회로를 이용하여 입력 전압의 차에 비례하는 주파수 신호를 생성하는 회로를 설계하였다. 설계된 회로는 HSPICE를 이용하여 회로의 동작을 분석하였으며, 입력 전압 차는 수V에서 수mV 단위까지 변화시키면서 출력 주파수를 시뮬레이션하였다. 회로의 시뮬레이션 결과 이론적인 계산값과 비교하였을 때 에러는 -1.9%에서 +1.8% 이내였다.

• 한국군사과학기술학회지
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• 제23권5호
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• pp.516-522
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• 2020

In this paper, the frequency detector which detects the clock frequency of the embedded system is proposed and analyzed. The proposed frequency detector is consisted of filter and peak voltage detector. The clock signal is converted from square wave to triangular wave by the filter. The peak voltage of the triangular wave is determined according to the frequency response of filter. The peak voltage detector detects and holds the peak voltage of the signal. Moreover, the proposed clock frequency detector can detect the frequency within 1ms and it gives guarantee of real-time operation.

• 전력전자학회논문지
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• 제21권2호
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• pp.102-110
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• 2016

In this paper, a high-frequency dual mode control LLC resonant converter with wide input voltage range is proposed through zero voltage switching (ZVS) under the universal line input voltage and every load conditions. Conventional small power adapter driving should be satisfied with universal line input voltage because it has no power factor correction circuit regulation. The conventional LLC resonant converter for an adapter can reduce the size of transformer in terms of high-frequency driving and ZVS. However, this converter has a disadvantage in terms of design of resonant tank under various input voltages because the frequency modulation range is very wide to satisfy voltage conversion gain. Compared with the conventional one, the proposed LLC converter can be adapted to universal line input voltage and high-frequency driving because it is controlled by pulse width modulation and pulse frequency modulation with control voltage. The validity of the proposed LLC converter is proved through the 60 W prototype.

• 한국전기전자재료학회논문지
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• 제32권1호
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• pp.40-46
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• 2019

To study the frequency response characteristics of alternating-current-driven organic light-emitting diodes (OLEDs), we fabricated blue-fluorescent OLEDs and analyzed their electroluminescent characteristics according to the alternating current voltage and frequency. The luminance-frequency characteristics of alternating-current-driven OLED was similar to that of a low-pass filter, and the luminance of high-voltage OLED decreased at higher frequency than low-voltage OLED. The luminance characteristics of the OLED according to the frequency is due to the capacitive reactance in the OLED, generated during the alternating current driving. The frequency response characteristics of the OLED according to the voltage is due to the decrease in internal resistance of the organic layer. In addition, the negative voltage component of the alternating current did not affect the frequency response of the OLED. Therefore, the electroluminescent characteristics of OLED with an alternating current power of 60 Hz are not influenced by the frequency.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부 C
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• pp.959-961
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• 1998

In this paper, we present design rule of high-voltage rectangular generator working in wide band frequency domain. Though power electronics now have voltage ratings up to several kV, it is difficult to design and fabricate high-voltage systems with the power electronic devices alone. So we have combined IGBT with technically designed transformer to get the high-voltage rectangular waveforms. In this work, next two things are the main factors. The first one is design of transformer working low-frequency domain of less than 10Hz. And the second one is adding offset voltage part. As a result, we can get variable frequency high-voltage rectangular waveform and this can be used as a voltage source of sandpaper manufacturing process.