• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.5
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• pp.949-954
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• 2007

In this work, temperature stable frequency-to-voltage converter is proposed. In FVC circuit input frequency is converted into output voltage signal. A FLL is similar to PLL in the way that it generates an output signal which tracks an input reference signal. A PLL is built on a phase detector, a charge pump, and a low pass filter. However, FLL does not require the use of the phase detector, the charge pump and low pass filter. The FVC is designed by using $0.25{\mu}m$ CMOS process technology. From simulation results, the variation of output voltage is less than ${\pm}2%$ in the temperature range $0^{\circ}C\;to\;75^{\circ}C$ when the input frequency is from 70MHz to 140MHz.

• Journal of Electrical Engineering and Technology
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• v.12 no.4
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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.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.4
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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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• v.11 no.4
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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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• v.7 no.1
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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.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.4
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• pp.891-896
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• 2011

This paper describes the differential voltage-to-frequency converter which is realized current conveyor circuits. The output frequency of the differential voltage-to-frequency converter is proportional to the difference of two input voltages. The designed circuit is simulated by HSPICE. The range of input voltage difference is from several volts to several milli-volts. From the simulation results the error is less than from -1.9% to +1.8% compared to the calculated values.

• Journal of the Korea Institute of Military Science and Technology
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• v.23 no.5
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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.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.2
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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.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.1
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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.

• Proceedings of the KIEE Conference
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• 1998.11c
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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.