• Journal of Biomedical Engineering Research
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• v.26 no.2
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• pp.95-99
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• 2005

We have performed EEG current source imaging on the cortical surface using visual evoked potentials (VEPs) recorded inside a 3.0 T MRI magnet. In order to remove ballistocardiogram (BCG) artifacts in the VEPs, an improved BCG template subtraction technique is devised. Using the cortically constrained current source imaging technique and pattern-reversal visual stimulations, we have obtained current source maps from 10 subjects. To validate the EEG current source imaging inside the magnet, we have compared the current source maps to the ones obtained outside the magnet. The experimental results demonstrate that there is a strong correspondence between the current source maps, proving that current source imaging is feasible with the evoked potentials recorded inside a 3.0 T MRI magnet.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.2
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• pp.60-64
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• 2001

The degradation process of silicone rubber was investigated by leakage current monitoring in Inclined-Plane method. DAS (Data Acquisition System) with 12-bit, 8-channel A/D converter was prepared. Average current, cumulative charge, current waveform and the number of peak pulses were measured on-line. And, FFT (Fast Fourier Transform) analysis was performed with stored current waveform. Besides, maximum erosion depth was measured in order to use as the indicator of the degradation process. So, the results of leakage current components and maximum erosion depth measurements were compared to find one or more components which have trends of changing similarly to that of erosion process. The result suggests that the ratio of peak current to r.m.s. current, harmonic contents and the number of peak pulses are well corresponding with the degradation process.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.699-702
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• 2002

A DC current sensor is disclosed in which two pairs of saturable cores are provided so as enclose a conductor carrying a direct current to be measured. On each of the saturable cores, a bias winding, a feedback winding and an output winding are wound. Circuit for detection of an asymmetry in the magnetization current, generated by a reference alternating voltage, in a signal-conditioner. The reference alternating voltage is fed to the respective series circuits such that no resultant induction current is induced in the modulating current. The voltages over the resistor form input signals for two peak value detectors, the strength of the output signal of which represents the degree of asymmetry of magnetization current. This paper describes the development a DC current sensor and its signal-conditioner.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.6
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• pp.221-226
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• 2006

The current flowing though a power line is measured by a current transformer (CT). Since a CT is a kind of transformer, saturation of magnetic flux in the core may occur when a large primary current flows. This saturation makes the secondary current of a CT distorted and causes problems in the protection point of view. Because of the current distortion, a protection relay cannot collect the correct information showing how the primary power system changed. Consequently, the current distortion may cause the mal-operation or operation time delay of protective relay. In this paper, an algorithm based on AR model and LSQ is proposed to compensate the saturated CT secondary currents. Various test results indicate that the proposed algorithm can accurately compensate a severely distorted secondary current and is not affected by remanence.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1239-1243
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• 2004

A novel voltage-current reference circuit for stable voltage-current applications is Proposed. Circuits for a positive and for a negative voltage-current reference are presented and are designed with commercial CMOS technology. The voltage-current reference that is stable over ambient temperature variations is an important component of most data acquisition systems. These results are verified by the HSPICE simulation $0.8{\mu}m$ parameter. As the result, the temperature dependency of output voltage and output current each is $0.57mV/^{\circ}C$, $0.11{\mu}A/^{\circ}C$ and the power dissipation is 1.8 mV on 5V supply voltage.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.35C no.5
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• pp.33-40
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• 1998

In this paper, a design of current-mode continuous-time filters for low voltage and low frequency applications using complementary bipolar current mirrors is presented. The proposed current-mode filters consist of simple bipolar current mirrors and capacitors and are quite suitable for monolithic integration. Since the design method of the proposed current-mode filters are based on the integrator type of realization, it can be used for a wide range of applications. Since the input impedance of simple bipolar current mirror is small, in this paper, negative feedback amplifier is used to realize is designed by cascade method. The cutoff frequency of the designed filter can be easily tunable by the DC controlling current from 60kHz to 120kHz. The characteristics of the designed current-mode filters are simulated and examined by SPICE using standard bipolar transistor parameters.

• Proceedings of the KIPE Conference
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• 1998.07a
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• pp.154-157
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• 1998

In this paper, the inverter TIG(Tungsten Inert Gas) welding system with high power efficiency by means of pulse current control of welding process is presented. In TIG welding, pulse current control is utilized in order to attain less apatter and high welding performance. The four factors which determine the welding performance of the pulse current are frequency, base current, peak current, and peak current duty current, and peak current duty ratio. In this paper, we analyze these factors should be controlled to achieve minimum power input. To demonstrate the practical significance of our results, we present some experimental results as well as simulation results.

• Journal of Power Electronics
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• v.16 no.2
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• pp.621-630
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• 2016

In this paper, a single current sensor technique (SCST) is proposed for single-phase full-bridge inverters. The proposed SCST measures the currents of multiple branches at the same time, and reconstructs the average inductor, capacitor, and load current in a single switching cycle. Since all of the branches' current in the LC filter and the load are obtained using the SCST, both the inductor and the capacitor current feedback schemes can be selectively applied while taking advantages of each other. This paper also analyzes both of the current feedback schemes from the view point of the closed-loop output impedance. The proposed SCST and the analysis in this paper are verified through experiments on a 3kVA single-phase uninterruptible power supply (UPS).

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.7
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• pp.1254-1259
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• 2008

A new CMOS current-mode integrator for low-voltage analog integrated circuit design is presented. The proposed current-mode integrator is based on cross-coupled gain-boosting topology. When it is compared with that of the typical current-mirror type current-mode integrator, the proposed current-mode integrator achieves high current gain and unity gain frequency with the same transistor size. As a application circuit of the proposed integrator, we designed the 1.8V 200MHz band current-mode lowpass filter. These are verified by Hspice simulation using $0.18{\mu}m$ CMOS technology.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.9
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• pp.464-469
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• 2004

The leakage current of transmission insulators contaminated with salt, clay, and kaolin was examined in the Gochang's Long Periods Testing Center. The Insulators were artificially contaminated and estimated with the method of equivalent salt deposit density(ESDD). The artificially contaminated insulators were installed with the same condition as in the real transmission power line and applied with 154 (kV). The leakage current of the artificially contaminated insulators was measured with environment conditions, such as temperature and humidity by the a automatic leakage current detecting system. The leakage current of heavily contaminated insulator was abruptly increased above 72［%］ of humidity, even though the leakage current was similar between the contaminated and non-contaminated insulators below 72［%］ of humidity. Also, it was found that the humidity was much more important than the temperature in the leakage current of transmission insulators. The leakage current of contaminated insulator was decreased when it was plenty of rainfall, resulting from natural washing.