• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.6
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• pp.504-510
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• 2002

Recently, thin film capacitors of high dielectric constant and low leakage current are applied to integrated devices. In this study, (Ba, Sr)$TiO_3$ (BST) thin films for low cost were prepared by Sol-Gel method. BST solution was spin-coated on Pt/$SiO_2$/Si substrate at 4,000 rpm for 10 seconds. Coating process was repeated 3 times and then sintered at $700^{\circ}C$ for 30 minutes. Structural and electrical characteristics of each specimen were analyzed by TG-DTA, SEM, fractal phenomenon, voltage-current and dielectric factor. Thickness of BST ceramics thin films are about 2,600~2,800 ${\AA}$ at depositing 3 times. Dielectric constant of thin films was decreased in 1 kHz~1 MHz. Dielectric constant and loss to frequency were 250 and 0.02 in $(Ba_{0.7}Sr_{0.3})TiO_3$ (BST3). Leakage current of BST3 was $10^{-9}\sim10^{-11}$/ A under 3 V.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.1039-1041
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• 2000

To obtain a high performance in a vector controlled induction machine, it is essential to know the instantaneous position of the rotor flux which depends on the rotor time constant. But the rotor time constant mainly varies due to the temperature rise in the motor winding, so real time compensating algorithm is necessary. This paper proposes that it uses short duration pulses added to the constant flux command current and then resultant torque command current produced by speed controller is utilized for the rotor resistance estimation. This method has advantages with a low computational requirement and does not require voltage sensors. The proposed method is proved by simulations.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.5
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• pp.183-189
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• 2015

In this paper, we propose an efficient implementation method that current-voltage sourcing and measuring for LED using (+) single power. this method has the advantage of reducing the error of the circuit and calibration of system, and also improving the complexity of hardware than the method of using a (+)(-) current or voltage sourcing and measuring.

• Journal of Environmental Science International
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• v.7 no.6
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• pp.793-801
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• 1998

In this study, the Dilution Method is used to measure river discharge through the hydraulic model test. the dilution method is divided into Constant-Rate-Infection Method and Slug-Injection Method in the river discharge measurement techniques. When the dilution method is applied in the hydraulic model flume, it is analyzed that the estimated error of constant-rate-injection method is less than that of the slug-in-jection method, and the result shows that floodflow analysis is more efficient than lowflow analysis as compared observed discharge with calculated discharge. The result of statistical error analysis shows that the constant-rate-injection method is appropriate technique for the measurement of the river discharge. Therefore, the dilution method among the river discharge measurement techniques can be applied for the river basin which can't be measured with current meter or unsteady-flow regime in the urban-small drainage or hydraulic structure equipment area and can be obtained more exact results than any other discharge measurement techniques.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.56 no.2
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• pp.65-73
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• 2007

In this study, the pulse charger and voltage regulator are proposed that can reuse the waste lead acid battery. The first we develop the voltage regulator that can reuse the waste lead battery. And the pulse current is applied to the terminal of the waste lead acid battery. The voltage regulator is available principle of the pulse current which can reduce the sulfate to incipient material such as Pb and PbO2. Therefore the internal resistance of the lead acid battery is decreased, the performance of the lead acid battery is improved and the durability is prolonged. The second we develop the pulse charger using the voltage regulator. The pulse charger uses the switch mode of the forward convert method. The pulse charger maintain the constant voltage in state removing the lead acid battery and when it connected the pulse charger, it is converted the charge mode of the constant current immediately. It continues the rapid charge until the full state of the lead acid battery. After that the pulse charger is converted to the charge mode of constant voltage automatically, and then it continues the normal charge. The experiment results show that the effectiveness of the voltage regulator and pulse charger such as the good performance and the prolonged durability in lead acid battery of the small and large capacity.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.12
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• pp.101-107
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• 1995

To improve the leakage current, we developed two step sputtering method where PZT thin film in first deposited at room temperature followed by 600.deg. C deposition. The method used an amorphous PZT layer deposited at room temperature to keep a stable interface during sputtering at high temperature. PZT thin films were deposited on Pt/Ti/SiO$_{2}$/Si substrate at room temperature and 600.deg. C sequentially. The effect of the layer deposited at room temperature was investigated with regard to I-V characteristics and P-E hysteresis loop. In the case of the sample with the layer deposited at room temperature, both leakage current and dielectric constant were decreased. The thicker the layer deposited at room temperature was, the lower dielectric constant was. However, leakage current was indepenent of the variation of the thickness ratio. The sample with 200$\AA$ of the layer deposited at room temperature showed the most promising results in both dielectric constant and leakage current.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.203-206
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• 2004

To analysis the electrokinetic phenomena in the ground dependent on the way of applied electric power, such as constant current and constant voltage, the governing equations are derived considering advection, diffusion, ionmigration, and then they were formulated using by finite difference method. The developed program is verified by comparing the tested and predicted results reported in present papers. The results indicate that the slightly small electrical potential is predicted for constant current and for constant voltage pH near to the cathode was small than the test results. But the other predictions including the final suction, pH of electrolyte and cumulative flow are similar to the test results and predictions.

• Journal of Power Electronics
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• v.16 no.3
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• pp.840-848
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• 2016

A primary-side regulation AC-DC converter operating in the PFM (Pulse Frequency Modulation) mode with a high precision output current is designed, which applies a novel inductance compensation technique to improve the precision of the output current, which reduces the bad impact of the large tolerance of the transformer primary side inductance in the same batch. In this paper, the output current is regulated by the OSC charging current, which is controlled by a CC (constant current) controller. Meanwhile, for different primary inductors, the inductance compensation module adjusts the OSC charging current finely to improve the accuracy of the output current. The operation principle and design of the CC controller and the inductance compensation module are analyzed and illustrated herein. The control chip is implemented based on a TSMC 0.35μm 5V/40V BCD process, and a 12V/1.1A prototype has been built to verify the proposed control method. The deviation of the output current is within ±3% and the variation of the output current is less than 1% when the inductances of the primary windings vary by 10%.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.6
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• pp.262-270
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• 2003

In this paper, the characteristics of single-phase line-start permanent magnet synchronous motor driven by constant voltage are analyzed on d-q axis vector diagram and compared with that of current controlled motor. The coupled method of symmetrical coordinates and d-q axis voltage equation are applied to the analysis method like the analysis of single-phase induction motor. From the result of the analysis, it is seen that motors driven by constant voltage source have effects on not only the amplitude of current and torque but also current and current phase angle, so overall characteristics such as power factor and load angle are affected by circuit parameters. For precise analysis and design of single-phase line-start synchronous motor, its characteristics should be analyzed on d-q axis vector plan in consideration of the variation of circuit parameters.

• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.910-915
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• 2003

This paper describes the design of a 2-phase stepping motor driver using CPLD(Complex Programmable Logic Device). The driver IC such as L297 (SGS-Thomson Microelectronics), which is mostly used has some problems in PWM control because of the switching noise of power MOSFETs. It causes current ripple and acoustic noise. To improve theses characteristics, we proposed a new current control method that the output PWM frequency is almost constant using a digital filter. Also we proposed constant current method for 1-2 phase(half step) excitation. The proposed method is implemented with CPLD(Xilinx, XC9572-PC44). Experimental results show the effectiveness of the proposed method.