• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.983-984
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• 2006

Multi-band VCO with fast response adaptive frequency calibration (AFC) technique is designed in 1.8V $0.18{\mu}m$ CMOS process. The possible operation is verified for 5.8GHz band, 5.2GHz band, and 2.4GHz band using the switchable L-C resonators for 802.11a/b/g WLAN applications. To linearize its frequency-voltage gain, optimized multiple MOS varactor biasing technique is used. In order to operate in each band frequency range with reduced VCO gain, 4-bit digitally controlled switched-capacitor bank is used and a wide-range digital logic quadricorrelator is implemented for fast frequency detector.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.3
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• pp.352-358
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• 2016

A 5-phase phase-locked loop (PLL) for USB2.0 applications was implemented by using an all-synthesis technique. The length of the time-to-digital converter for the fine phase detector was halved by the operation of a coarse phase detector that uses 5-phase clocks. The maximum time difference between the rising edges of two adjacent-phase clocks was 6 ps at 480 MHz. The PLL chip in a 65-nm process occupies $0.038mm^2$, consumes 4.8 mW at 1.2 V. The measured rms and peak-to-peak output jitters are 8.6 ps and 45 ps, respectively.

• Journal of the Korean Chemical Society
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• v.25 no.2
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• pp.103-109
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• 1981

An inexpensive, yet convenient analog storage device was constructed. Sequentially MOSFET-switched 20 sample and holds equipped with a high input impedance preamplifier were parallelly matched to the digitally controlled shift register system in variable speeds up to 3 kHz. To verify its usefulness, square wave train, sinusiodal wave and some electrochemical data, such as fast-scan voltammogram and transient current-time curves of differential pulse polarography were tested.

• Proceedings of the KIPE Conference
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• 2013.07a
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• pp.157-158
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• 2013

본 논문은 넓은 범위에서 변화하는 입력 전압과 출력 전류 조건에서 동작하는 디지털 제어 방식 공진형 DC-DC 컨버터의 동특성 개선에 대해 기술한다. LLC 직렬 공진형 컨버터의 아날로그 전력 변환단 동특성을 기반으로 150W 디지털 공진형 컨버터 실험보드에 적용하여 아날로그 제어 방식과 디지털 제어방식의 폐루프 성능을 비교한다. 디지털 제어기는 Emulation 방식을 이용하여 설계한다. 제어기 설계의 이론 검증 및 분석은 PSIM Simulation과 실험 측정으로 비교 검증한다.

• Proceedings of the KSR Conference
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• 2005.11a
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• pp.211-216
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• 2005

Resonance of railroad bridge can be broken out when natural frequency of the bridge coincides with exciting frequency of moving forces. In order to avoid aforementioned unpleasant response of the structure, exact determination of dynamic structural properties is important to understand dynamic behavior of the structure under moving train loads. In the present paper, a 25 meters long full scale IPC girder and 15m Precom girder models were fabricated as a test specimen and modal testing was carried out to evaluate modal parameters including natural frequencies and modal damping ratios. In the modal testing, a digitally controlled vibration exciter as well as an impact hammer is applied to obtain frequency response functions more exactly and the modal parameters are evaluated varying with structural status.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.538-544
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• 2006

This paper is to investigate the dynamic characteristics of prestressed concrete (PSC) girder that has been spliced with precast box segments. A 20 m long full-scale spliced precast concrete box railway girder was fabricated and tested to identify its dynamic properties against a monolithic girder. The monolithic girder has the same geometric and material properties with respect to the spliced girder. Dynamic parameters including natural frequency, mode shape, and damping ratio were identified using the a digitally controlled exciter. Modal analyses were performed based on three-dimensional finite element models, and the calculated modal parameters were compared with test results. Finally, the characteristic decrease of natural frequency due to damage for each girder has been examined after the load test.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.331-333
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• 1995

A high performance motor drive system must have a good speed command tracking, a insensitivity to a parameter variation and sampling time. In this paper, a robust speed controller for an induction motor is proposed. The speed controller is fuzzy-sliding adaptive controller and its system continuously is varied. That is, only P gain act in dynamic state, I gain in steady-state. Because this system is a sort of adaptive control system, global stability analysis is used to Lyapunov function. Consequently, in this paper application of fuzzy sliding adaptive controller to induction motor controlled by vecter control is presented and the control system is digitally implemented within DSP.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.209-211
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• 1995

This paper is concerned with High Frequency, High Voltage Generator for X-ray using zero-voltage soft-switching PWM DC-DC high-power converter by Resonant method, which makes the most of the parastic LC parameters of high-voltage transformer link, for diagnostic X-ray power generator. The converter circuit basically utilizes phase-shift pulse width modulated series Resonant full-bridge PWM DC-DC high-power converter operating at a constant frequency;25kHz. The converter output regulation is digitally controlled using DSP (Digital Signal Processor) for obtaining a fast rising time and adjust output voltage within a wide load range.

• Proceedings of the KIPE Conference
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• 2010.11a
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• pp.74-75
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• 2010

As global warming due to burning fossil fuels and natural resource depletion issues have emerged, the development of renewable energy sources such as photovoltaics (PV) has been brought to recent interest. Amongst the vast efforts to harvest and convert solar energy into electricity, the module integrated converters (MIC) has become a worthy topic of research for grid-connected photovoltaic systems. Due to the required high-boosting qualities, only a restricted amount of DC/DC converter topologies can be applied to MICs. This paper investigates the possibility of a tapped-inductor boost converter as a candidate for PV MICs. A dual-inductor interleaving scheme operating slightly above the boundary of the two conduction modes (BCM) is suggested for reduction of input current ripple and minimization of component stress. A digital controller is used for implementation, assuring maximum power tracking and transfer while providing sufficient computational space for other grid connectivity applications, etc. For verification, a 200W converter is designed and simulated via computer software including component losses. High efficiency over a wide power range proves the feasibility of the proposed PV MIC system.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.6
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• pp.381-388
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• 2018

A novel and simple algorithm for accurate calculation of RMS voltage is proposed in a digitally controlled grid-tie inverter system. Given that the actual frequency of grid voltage is continuously changing, the constant sampling frequency cannot be a multiple number of the fundamental frequency. Therefore, the RMS of grid voltage contains periodic oscillations due to the differences in the phase angle of sampled data during calculation. The proposed algorithm precisely calculates and updates the initial phase angle of the first sampled voltage in a half-cycle period using phase-locked loop, which is commonly utilized for phase angle detection in grid-tie inverter systems. The accuracy and dynamic performance of the proposed algorithm are compared with those of other algorithms through various simulations and experiments.