• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.3
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• pp.397-409
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• 1993

This paper proposed the design methodology of the 8 bit binary parallel adder with carry book-ahead scheme via current-mode CMOS multivalued logic and simulated the proposed adder under $5{\mu}m$ standard IC process technology. The threshold conditions of $G_K$ and $P_K$ which are needed for m-valued parallel adder with CLA are evaluated and adopted for quaternary logic. The design of quaternary CMOS logic circuits, encoder, decoder, mod-4 adder, $G_K$ and $P_K$ detecting circuit and current-voltage converter is proposed and is simulated to prove the operations. These circuits are necessary for binary arithmetic using multivalued logic. By comparing with the conventional binary adder and the CCD-MVL adder, We show that the proposed adder cab be designed one look-ahead carry generator with 1-level structure under standard CMOS technology and confirm the usefulness of the proposed adder.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.6
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• pp.28-36
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• 2008

This paper describes a low-power CMOS analog front-end block for UHF band RFID tag chips. It satisfies ISO/IEC 18000-6C and includes a memory block for test. For reducing power consumption, it operates with an internally generated power supply of 1V. An ASK demodulator using a current-mode schmitt trigger is proposed and designed. The proposed demodulator can more exactly demodulate than conventional demodulator with low current consumption. It is designed using a $0.18{\mu}m$ CMOS technology. Measurement results show that it can operate properly with an input as low as $0.25V_{peak}$ and consumes $2.63{\mu}A$. The chip size is $0.12mm^2$.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2500-2505
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• 2007

The vacuum interrupter (VI) is used for medium-voltage switching circuits due to its abilities and advantages as a compact and environmental friendly circuit breaker. In general, the application of a sufficiently strong axial magnetic field (AMF) permits the arc to be maintained in a diffused mode to a high-current vacuum arc. A full understanding of the vacuum arc physics is very important since it can aid to improve the performance of vacuum interrupter. In order to closely examine the vacuum arc phenomena, it is necessary to predict the magnetohydrodynamic (MHD) characteristics by the multidisciplinary numerical modeling, which is coupled with the electromagnetic and hydrodynamic fields, simultaneously. In this study, we have investigated the electromagnetic behaviors of high-current vacuum arcs for two different types of AMF contacts, which are coil-type and cup-type, using a commercial finite element analysis (FEA) package, ANSYS. The present results are compared with those of MAXWELL 3D, a reliable electromagnetic analysis software, for verification.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.4
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• pp.390-396
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• 2004

Recently, there have been Increasing demands for high power factor and low harmonic distortion in the current drawn from utility. The harmonic limits imposed by international standards. It need the PFC techniques in order to reduce line current harmonics and comply with the standards. The average current control method that is the most proper PFC control method in a switching power supply of middle and high power has been used mostly to PFC control method. However, the switching device of PFC circuit has frequently destructed at power return after instantaneous power interrupt. Therefore, this paper have verified the cause of this problems and proposed the solution through simulation and experiment

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2515-2518
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• 2008

The vacuum interrupter (VI) is widely used in medium-voltage switching circuits due to its abilities and advantages as an environmental friendly circuit breaker. An understanding of the vacuum arc flow phenomena is very important for improving the performance of vacuum interrupter. In order to closely examine the vacuum arc phenomena, it is necessary to predict the magnetohydrodynamic (MHD) characteristics by the multidisciplinary numerical modeling, which is coupled with the electromagnetic and the thermal flow fields, simultaneously. In this study, we have investigated arc plasma constriction phenomena and an effect of AMF on the arc plasma with the high-current vacuum arcs for the cup-type AMF electrode by using a commercial finite element analysis (FEA) package, ANSYS. The simulation results applied with various AMFs and constant Joule heat generation show that strong axial magnetic field (AMF) permits the arc to be maintained in a diffused mode to a high-current vacuum arc. However, further studies are required on the two-way coupling method and radiation model for arc plasma in order to accomplish the advanced analysis method.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.1
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• pp.61-65
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• 2017

In this paper a prototype of high frequency heating power supply system based on the high frequency heating principle is designed to take the place of acupuncture, moxibustion, warm dressing treatment and some other traditional physical therapy methods. Which possess the advantages of low cost, convenient, easy operation and good effect. The high frequency heating power supply can generate a pulse voltage of more than 1KV with 300KHz switching frequency to heat the patient's skin. The skin temperature can reach to $41{\sim}42^{\circ}C$. The peak current control method is used to maintain the skin temperature in the designed range. The design of the main circuit is based on the flyback converter topology. An easier and practical design method is proposed in this paper. The power supply system prototype is verified to be stable and reliable by both the simulation and experimental results.

• Journal of Sensor Science and Technology
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• v.31 no.4
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• pp.271-277
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• 2022

We analyzed the effects of the interface trap on the output characteristics of an inversion mode n-channel GaN Schottky barrier (SB)-MOSFET based on the N_it distribution using TCAD simulation. As interface trap number density (N_it) increased, the threshold voltage increased while the drain current density decreased. Under N_it=5.0×10¹⁰ cm^-2 condition, the threshold voltage was 3.2 V for V_DS=1 V, and the drain current density reduced to 2.4 mA/mm relative to the non-trap condition. Regardless of the N_it distribution type, there was an increase in the subthreshold swing (SS) following an increase in N_it. Under U-shaped N_it distribution, it was confirmed that the SS varied depending on the gate voltage. The interface fixed charge (Q_f) caused an shift in the threshold voltage and increased the off-state current collectively with the surface trap. In summary, GaN SB-MOSFET can be a building block for high power UV optoelectronic circuit provided the surface state is significantly reduced.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.14 no.6
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• pp.129-135
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• 2015

This paper shows significant methods that improve the lifespan of LED modules as well as efficiently using an aluminum heat-sink for LED module in high power. It proposes a method that raises stability and lifespan to protect LED modules and the power unit when the LED module has been used for a long hours at high temperatures. During the research, we applied a method of pulse-width modulation (PWM) in order to prevent the phenomenon that the entire power of a system is turned off and the lifespan is reduced when the LED nodule reacts to the high temperatures. To protect the LED module and SMPS based on high efficiency, a temperature sensor is attached underneath the circuit board and the sensor measures the temperature of circuit board when the LED module is powered on. The electrical power connected to SMPS is controlled by PWM when the temperature of the LED module reaches a particular temperature.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.3
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• pp.302-311
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• 2005

We propose an improved active forward converter by adding a non-dissipative snubber circuit to the secondary of the conventional active clamp forward converter in this paper. The snubber circuit is composed of a tapped inductor, a snubber capacitor, and two diodes. Comparing with the conventional one, the proposed one makes it possible ZVS to operate in a smaller magnetizing current condition. The operational principles and the equivalent mode analysis of an improved active forward converter are mentioned in this paper. In conclusion, we constructed the prototype of the modified active forward converter with 300W output capacity and verified higher efficiency compared to the conventional one.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.454-457
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• 1997

The purpose of this study is to develop an optimal model, using existing models, that is able to estimate the amount of spatter utilizing artificial neural network in the short circuit transfer mode of gas metal arc (GMA) welding. The amount of spatter generated during welding can become a barometer which represents the process stability of metal transfer in GMA welding, and it depends on some factors which constitute a periodic waveforms of welding current and arc voltage in short circuit GMA welding. So, the 12 factors, which could express the characteristics for the waveforms, and the amount of spatter are used as input and output variables of the neural network, respectively. Two neural network models to estimate the amount of spatter are proposed: A neural network model, where arc extinction is not considered, and a combined neural network model where it is considered. In order to reduce the calculation time it take to produce an output, the input vector and hidden layers for each model are optimized using the correlation coefficients between each factor and the amount of spattcr. The est~mation performance of each optimized model to the amount of spatter IS assessed and compared to the est~mation performance of the model proposed by Kang. Also, through the evaluation for the estimation performance of each optimized model, it is shown that the combined neural network model can almost perfectly predict the amount of spatter.