• Proceedings of the KIEE Conference
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• 1994.11a
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• pp.48-50
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• 1994

In this paper, the optimal fuzzy controller of exciter and governor in synchronous generator improve the stability of power system with varying loads and disturbances in power system. Parameters of the proposed fuzzy controller were optimally self-tuned by the steepest descent method and were applied to power system stabilization. The related simulation results show that the proposed control technique are more powerful than the conventional ones for reductions of undershoot and for minimization of settling time.

• Journal of Power Electronics
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• v.18 no.6
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• pp.1627-1633
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• 2018

A constant voltage AC-DC converter based on digital assistant technology is proposed in this paper, which has rapid dynamic response capability. The converter operates in the PFM (Pulse Frequency Modulation) mode. According to the load state, the compensation current produced by the digital compensation module was injected into the CS pin to adjust the switching pulse width dynamically and improve the dynamic response. The control chip is implemented based on NEC $1{\mu}m$ 5V/40V HVCMOS process. A 5V/1.2A prototype has been built to verify the proposed control method. When the load jumps from idle to heavy, the undershoot time is only 7.4ms.

• Proceedings of the KIPE Conference
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• 2020.08a
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• pp.160-162
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• 2020

A control technique for the auxiliary buck/boost converter is proposed herein to improve the load transient response of the buck converter. The proposed technique improves the system efficiency by enabling the soft switching operation of the auxiliary converter. The design guidelines for achieving capacitor charge balance for the output capacitor during the transient are also presented herein. The experimental results revealed that the output voltage undershoot and settling time during the load step-up transient were 40 mV and 14 ㎲, respectively, and the output voltage overshoot and settling time during the load step-down transient were 35 mV and 21 ㎲, respectively. The performance and effectiveness of the proposed technique were experimentally verified using a prototype buck converter with a 15-V input, 3.3-V output, and 200-kHz switching frequency.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.1
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• pp.148-156
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• 2013

This paper suggests a multi-level and multi-output SMPS based on a shared digital logic controller through independently operating in each dedicated time periods. Although the shared architecture can be devised with small area and high efficiency, it has critical drawbacks that real-time control of each DPWM generators are impossible and its output voltage can be unstable. To solve these problems, a real-time current compensation scheme is proposed as a solution. A current consumption of the core block and entire block with four driver buffers was simulated about 4.9mA and 30mA at 10MHz switching frequency and 100MHz core operating frequency. Output voltage ripple was 11 mV at 3.3V output voltage. Over/undershoot voltage was 10mV/19.6mV at 3.3V output voltage. The noise performance was simulated at 800mA and 100KHz load regulation. Core circuit can be implemented small size in $700{\mu}m{\times}800{\mu}m$ area. For the verification of proposed circuit, the simulations were carried out with Dong-bu Hitek BCD $0.35{\mu}m$ technology.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.49 no.1
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• pp.15-24
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• 2012

In this paper, we suggest the dynamic-response-free SMPS using a new high-resolution DPWM generator based on switched-capacitor delay technique. In the proposed system, duty ratio of DPWM is controlled by voltage slope of an internal capacitor using switched-capacitor delay technique. In the proposed circuit, it is possible to track output voltage by controlling current of the internal capacitor of the DPWM generator through comparison between the feedback voltage and the reference voltage. Therefore the proposed circuit is not restricted by the dynamic-response characteristic which is a problem in the existing SMPS using the closed-loop control method. In addition, it has great advantage that ringing phenomenon due to overshoot/undershoot does not appear on output voltage. The proposed circuit can operate at switching frequencies of 1MHz~10MHz using internal operating frequency of 100 MHz. The maximum current of the core circuit is 2.7 mA and the total current of the entire circuit including output buffer is 15 mA at the switching frequency of 10 MHz. The proposed circuit has DPWM duty ratio resolution of 0.125 %. It can accommodate load current up to 1 A. The maximum ripple of output voltage is 8 mV. To verify operation of the proposed circuit, we carried out simulation with Dongbu Hitek BCD $0.35{\mu}m$ technology parameter.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.12 s.354
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• pp.89-101
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• 2006

Frequency-variant transmission line parameters are determined. Then the signal transient characterizations of frequency-dependent multi-coupled lines are investigated. With the proposed method, an accurate signal integrity degradation such as signal ringing (overshoot, undershoot) and crosstalk noises relevant to the switching patterns of signals, rising / falling time(tr, tf) and line lengths is investigated. It is shown that there may be approximately 26% discrepancy of signal transients and 260% difference of crosstalk noises between the constant RLC model and frequency-variant RLC model in on-chip global interconnects while those of package lines are 11% and 70%, respectively.

• Journal of Korean Society for Geospatial Information Science
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• v.9 no.1 s.17
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• pp.27-38
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• 2001

The GIS construction project using the Digital Map has been progressed actively since the enforcement of NGIS project in 1995. But, the Digital Map actually can't use directly in building GIS because of many defects of the digital map such as geometric features errors(the overshoot/undershoot of line or the opening of polygon), non-topology etc. Many advanced countries in GIS has provided users Framework Data which is generated topology defined spatial relationships and used as a basic data of national geospatial information. In this study, we proposed the definition and the scope of Framework Data as a basemap of the Nation Geospatial Information and studied for the management and construction of the Transportation/Road Framework Data which is a core and basic data among them.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.07a
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• pp.74-76
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• 2010

Digital images or videos are used in modern digital devices. The resolution of HDTV in digital broadcasting system is higher than that of previous analog systems. Also, mobile phone with 3G can provide images as well as video streaming services in realtime. In these circumstances, the visual quality of images has become an important factor. We can make image clear by transient improvement process that reduces transient in edges. In this paper, we present an transient improvement algorithm. The proposed algorithm improves edges by making smooth edge to steep edge. Before performing transient improvement algorithm, edge detection algorithm should be operated. Laplacian operator is used in edge detection, and the absolute value of it is used to calculate gain value. Then, local maximum and minimum values are computed to discriminate current pixel value to raise up or pull down. Compensating value that gain value multiplies with the difference between maximum (or minimum) value and current pixel value adds (or subtracts) to current pixel value. That is, improved signal is generated by making the narrow transient of edge. The advantage of proposed algorithm is that it doesn't produce shooting problem like overshoot or undershoot.

• Economic and Environmental Geology
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• v.23 no.1
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• pp.73-79
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• 1990

Controlled source audio-frequency magnetotelluric (CSAMT) has the great advantage of efficient mapping resistivity distribution and relatively deep depth of investigation. Moreover, CSAMT may be regarded more attractive than audio-frequency magnetotelluric in the sense of the strong and controllable signal. However, it has the problem such as undershoot and/or near-field effect that is hard to be interpreted if the interpretation method of MT is directly applied. The problem arises from the existance of controlled source which makes CSAMT attractive. So the characteristics of CSAMT response should be thoroughly understood prior to interpretation stage. In this study, numerical modeling program for horizontally layered earth was developped for the interpretation of CSAMT field data. CSAMT field survey was run as a follow-up to resistivity dipole-dipole study over the same survey line at Bongmyung coal mine. The survey used a grounded dipole source 2 Km in length and located 7.5Km south in this study. A good agreement between field CSAMT data and calculated data was demonstrated even in geologically complex earth situations.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.23 no.2
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• pp.1-6
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• 2015

The RSA is intended to prevent the following five types of events from becoming an accident: landing overruns, landing undershoots, landing veer-offs, takeoff overruns and takeoff veer-offs. The improved models are based on evidence from worldwide accidents and incidents that occurred during the past 27 years. The analysis utilizes historical data from the specific airport and allows the user to take into consideration specific operational conditions to which movements are subject, as well as the actual or planned RSA conditions in terms of dimensions, configuration, type of terrain, and boundaries defined by existing obstacles. This paper shows how to apply the improved models for Risk Assessment of Runway Safety Areas (Airport cooperative research program(ACRP) Report 50) into an airport and the outcome differences between the old models based on ACRP report 3-Analysis of aircraft overrun and undershoots for runway safety areas and the new models from ACRP report 50 in the specific airport.