• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1594-1596
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• 1996

The NDT(nondestructive test) using pulse echo method with piezoelectric transducers and the system for NDT including image processing were studoed. The system consisted of pulse generator and receiver, two step motors for X-Y scanner, PC-Scope for data aquisition and PC-Lab for trigger and motor driving. We tested and estimated at one point under the following conditions : 1) just water, 2) Aluminum without any crack and 3) Aluminum with hole. The estimated NDT result of whole area (point : $35{\times}20$) is compared with real samples.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2189-2191
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• 1999

To improve the reliability of the klystron-modulator systems, the stable operations of the thyratron an important factor of the system are required. The thyratron always has a possibility of self-fire according to the conditions of the applied high voltage and this induces the system fault. Therefore a command charging method was introduced to reduce the applied tim8 of the high voltage into the thyratron. The high voltage switch used in the command charging method is the SCR (1.6 kV, 50A) and consists of 10 SCRs in series to discharge 10 kV. A pulse transformer was used to apply the trigger pulse. The objectives of this research are the fabrication of the semiconductor switch and the study of the experimental result of the operation characteristics of the high voltage semiconductor switch.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.10a
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• pp.35-38
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• 2018

This paper describes a low-power MPPT interface for DC-type energy harvesting sources. The proposed circuit consists of an MPPT controller, a bias generator, and a voltage detector. The MPPT controller consists of an MPG (MPPT Pulse Generator) with a schmitt trigger, a logic gate operating according to energy type (light, heat), and a sample/hold circuit. The bias generator is designed by employing a beta multiplier structure, and the voltage detector is implemented using a bulk-driven comparator and a two-stage buffer. The proposed circuit is designed with $0.35{\mu}m$ CMOS process. The simulation results show that the designed circuit consumes less than 100nA of current at an input voltage of less than 3V and the maximum power efficiency is 99.7%. The chip area of the designed circuit is $1151{\mu}m{\times}940{\mu}m$.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.05a
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• pp.869-871
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• 2012

In this paper, we make silicon photodiodes for the detection of pulsed radiation that affects electronics devices and study the output characteristics of photodiodes using circuit design. We conducted the simulation for pulse sensing circuit and experimented the photodiode output characteristics using a high luminance light emitting diode. The results can be used for the design of the input sensor that is trigger of additional module for protecting a electoronics circuit from high energy pulse radiation.

• Journal of Biomedical Engineering Research
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• v.28 no.1
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• pp.132-138
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• 2007

MR(magnetic resonance) image of moving organ such as heart shows serious distortion of MR image due to motion itself. To eliminate motion artifacts, MRI(magnetic resonance imaging) scan sequences requires a trigger pulse like ECG(electro-cardiography) R-wave. ECG-gating using cardiac cycle synchronizes the MRI sequence acquisition to the R-wave in order to eliminate image motion artifacts. In this paper, we designed ECG/PPG(photo-plethysmography) gating system which is for eliminating motion artifacts due to moving organ. This system uses nonmagnetic carbon electrodes, lead wire and shield case for minimizing RF(radio-frequency) pulse and gradient effect. Also, we developed a ECG circuit for preventing saturation by magnetic field and a finger plethysmography sensor using optic fiber. And then, gating pulse is generated by adaptive filtering based on NLMS(normalized least mean square) algorithm. To evaluate the developed system, we measured and compared MR imaging of heart and neck with and without ECG/PPG gating system. As a result, we could get a clean image to be used in clinically. In conclusion, the designed ECG/PPG gating system could be useful method when we get MR imaging of moving organ like a heart.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1603-1605
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• 2001

Eight 300kJ modularized capacitor-banks have been constructed. These modules have been installed and assembled to make a 2.4MJ pulse power system (PPS). This 2.4MJ PPS was developed to be used as a driver of an electrothermal-chemical (ETC) gun. Each capacitor bank has six 22kV, 50kJ capacitors connected in parallel. A triggered vacuum switch (TVS-43) was adopted as a main pulse power-closing switch in each module. The module also contains a crowbar circuit made of three high-voltage diode-stacks, a multi-tap inductor and an energy-dumping resistor. Various current shapes have been formed by a sequential firing of multiple capacitor banks. Resistive dummy load has been used and various combinations of experimental parameters, such as charging voltage, trigger time and inductance, were tested to make flexible current shapes.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.12 no.1
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• pp.45-50
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• 1998

In recent year, inverters and cycloconverters system are widely used for fed induction motor drives. Motor drives by cycloconverter is possible to frequency have been directly changed without AC/DC converter, so that circuits is simpler than inverter. A aims of this paper is the control strategy and hardware design for vector control system by cycloconverter fed induction motor drives. In this paper, Algorithm of vector control is derivlid from the model of controlled current source-fed induction motor. Vector control system is implemented using these algorithm and a pulse width controled cycloconverter using a SCR. Cycloconverter of vector control system is controlled by pulse width of SCR's trigger signal. pulse width is controlled primary command current $li_1l$ and frequency TEX>$\omega_1$..

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.38 no.3
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• pp.249-255
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• 2002

This paper describes on the extraction of ship's real-time movement information using a combination full-function ARPA radar and ECS system that displays radar images and an electronic chart together on a single PC screen. The radar target extractor(RTX) board, developed by Marine Electronics Corporation of Korea, receives radar video, trigger, antenna bearing pulse and heading pulse signals from a radar unit and processes these signals to extract target information. The target data extracted from each pulse repetition interval in DSPs of RTX that installed in 16 bit ISA slot of a IBM PC compatible computer is formatted into a series of radar target messages. These messages are then transmitted to the host PC and displayed on a single screen. The position data of target in range and azimuth direction are stored and used for determining the center of the distributed target by arithmetic averaging after the detection of the target end. In this system, the electronic chart or radar screens can be displayed separately or simulaneously and in radar mode all information of radar targets can be recorded and replayed In spite of a PC based radar system, all essential information required for safe and efficient navigation of ship can be provided.

• Journal of Sensor Science and Technology
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• v.6 no.3
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• pp.194-199
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• 1997

When voltage or current gets out of the magnetic sensor as it is, we have often faced the problems such as introduction of noise and loss of voltage. In order to reduce these problems, a 2 drain MAGFET operating in the saturation region and fabricated by CMOS process, the system of I/V converter, VCO with operational amplifier, and V/F conversion circuits with Schmitt Trigger are designed and fabricated in one package. The absolute sensitivity of magnetic sensor shows 1.9 V/T and the product sensitivity is $3.2{\times}10^{4}\;V/A{\cdot}T$. The characteristic of V/F conversion is very stabilized and has the value of 190 kHz/T.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.12
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• pp.584-590
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• 2002

Crowbar system is usually applied to a pulsed power system in which a capacitor bank is discharged into a load. This provides a free wheeling path for the load current and prevents the capacitor from recharging due to a reverse voltage. Usually diodes have been used as a crowbar switch, but it is not a practical system because the cost of the diodes goes up enormously with increasing the system voltage and current. This paper presents a novel protection scheme of a charging and discharging system of a 300 kJ capacitor bank using a low-cost crowbar system which consists of a crowbar switch and resistors. Triggered vacuum switch(TVS) was used for a crowbar switch, and Rogowski coil was used to determine a trigger time of TVS. When this crowbar system is applied to our pulsed power system which consists of capacitor bank($123muF$), inductor() for forming a pulse, load resistor$(100 m\Omega)$, and a closing switch, instantaneous reversal voltage of capacitor bank could be limited less than 1.8 ㎸ until capacitor bank was charred to 17 ㎸.