• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.4
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• pp.1376-1384
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• 1996

Measuring the velocity of fluid flow, semiconductor flow sensors are widely used in the various fields of engineering and science such as the semiconductor manufacturing processes and electronic control engines for automobiles. In the near future, this type of sensors will replace present hot wire type sensors or other type flow sensor due to its low price, easy handling and small size. To develop the advanced semiconductor flow sensor, it is necessary to obtain characteristics of the flow and the heat transfer around the sensor in advance. In the present study, the theoretical analysis including mathematical modeling and numerical calculation to predict the characteristics of heat transfer and flow field around the sensor was carried out. The main parameters for optimum design of the flow sensor are the free stream velocity, the heat generation rate of silicon arm and the distance between arms. Effects of these parameters on flow and heat transfer around the sensor and the temperature difference between arms are examined.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1214-1217
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• 2004

현재 전기용량의 국가표준은 1 kHz, 1592 Hz에서만 유지 및 보급이 되고 있다. 그러나 전기용량 및 임피던스를 측정하는 브리지와 LCR meter들은 비교적 넓은 주파수 범위에서 측정이 가능하도록 생산이 되고 있다. 따라서 이러한 기기들의 교정은 실제적으로 사용되고 있는 주파수 전 영역이 아닌 1 kHz 만 되고 있어서 완전한 교정이라고 할 수 없다. 본 논문에서는 이를 해결하기위하여 임피던스 analyzer의 one-port 측정기술을 사용하여 4-terminal-pair(이하 4TP) 전기용량 표준기 각각의 terminal에서 임피던스를 필요 주파수에서 측정하고, 측정된 임피던스 matrix를 이용하여 4TP의 transfer 어드미턴스와 출력임피던스를 계산 하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.2
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• pp.333-338
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• 2008

In this paper, a new NMOS current-mirror type bridge rectifier for driving RFID chips, whose minimum input voltage required to obtain the effective DC output voltage is low enough and whose power dissipation can be reduced than that of conventional one, is proposed. The designed rectifier is able to supply high enough and well-rectified DC voltages to drive RFID transponder chips for the frequency range of 13.56 MHz HF(for ISO 18000-3), 915 MHz UHF(fur ISO 18000-6), and 2.45 GHz microwave(for ISO 18000-4). Output characteristics of the proposed rectifier are analyzed with the high frequency equivalent circuit. And the circuitry method for effective reducing of the gate leakage current due to the increasing of operating frequency is also proposed theoretically. Using this method, the power consumption of $100\;{\mu}W$ and the DC output voltage of 2.13V for 3V peak-to-peak input voltage and $45\;K{\Omega}$ load resistance are obtained. Compared to conventional one, the proposed rectifier operates in more stable and shows superior characteristics in UHF and microwave frequencies.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.4
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• pp.307-314
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• 2009

In this paper, we proposes a multilevel inverter which can synthesize multi output voltage levels by adding DC voltage sources and switch components. In the proposed circuit topology, full-bride inverter determines the output polarity and the number of output voltage levels are defined by the operation of the additional switches. It can reduce the number of switch devices compared with the conventional approaches when they generate the same number of output voltage levels. To verify the validity of the proposed multilevel inverter, we present simulation and experimental results using a prototype.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.45 no.4
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• pp.60-67
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• 2008

This paper presents a new full-bridge soft switching PWM DC-DC converter circuit topology that adding two switcher, two lossless snubber quasi-resonance capacity, two diode to power source for general welding machine. This half bridge soft switching Is low voltage hight current output that first coil current is smaller than second coil current in high frequency transformer can be obtained with decreasing path loss in conventional DC bus line switcher. As it operate ZCS/ZVS in full range, high frequency, high efficiency and high output are implemented at low voltage and high DC current switching power supplies. All of this items are got from simulation and the result of experiment. If make up for the weak points of this proposed circuit, it will be used more easily for next generation TIG, MIG and MAG type of arc-welding machine.

• Journal of Sensor Science and Technology
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• v.5 no.3
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• pp.17-24
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• 1996

In order to reduce the offset and its temperature drift by the different properties of the piezoresistors and the residual stress of the piezoresistive pressure sensor, a double Wheatstone-bridge pressure sensor was studied. Because the compensation bridge was arranged near by the pressure sensitive bridge, which have the similar offset component, reduction of the offset and its temperature drift was realized by the mathematical subtraction of the output of two bridges. It was configured the compensation of the offset and its temperature drift. By this compensation method, the offset and its temperature drift were reduced approximately 95% respectively. The sensitivity of the fabricated pressure sensor was $11.7\;mV/Vkg/cm^{-2}$ for $0.9\;kgfcm^{-2}$ full-scale pressure range.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.5
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• pp.181-186
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• 2017

IEC 61850 is a standard for power utility automation. Using IEC 61850 that uses ethernet may consume more costs for the automation than its value in small distribution substations. Thus, less expense and installation cost are required for the automation of small distribution substations. This study used inexpensive and easy-to-install IEEE 802.15.4 and implemented a bridge between IEC 61850 and IEEE 802.15.4, using Raspberry Pi to connect the existing IEC 61850. Using IEEE 1588, IEC 61850 traffic performances were evaluated, such as SV, GOOSE and MMS. Analyzing IEC 61850 requirements and performance evaluation results, the scope of application of IEEE 802.15.4 was decided.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.4
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• pp.541-557
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• 1986

본 연구에서는 캐패시턴스 성분을 고려한 브리지(bridge) 모델을 적용하여 지 금까지 설명할 수 없었던 문제를 설명함으로서 이 모델의 정당성을 확인하고자 하며, 더욱 나아가 다른 여러가지 변수에 대한 응답특성의 예측을 가능하게 하고자 한다.

• Proceedings of the KIPE Conference
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• 2020.08a
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• pp.73-75
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• 2020

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.4
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• pp.81-94
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• 2010

This paper presents a high efficiency resonant asymmetrical half-bridge flyback converter. The primary half-bridge circuit of the converter operates by a soft-switching type using the asymmetrical pulse-width modulation (PWM) method with the resonant capacitance and transformer leakage inductance. The secondary flyback circuit of the proposed converter utilizes a synchronous rectifier, which operates by a new voltage-driven method with a simple drive circuit. Thus the proposed converter improves the total efficiency. This paper explains the operational principle of the proposed converter by each mode and shows the converter design consideration and a design example for the prototype converter, respectively. After that, the proposed simple driving technique of the synchronous rectifier by a voltage-driven method is explained, briefly. The designed prototype converter has wide input voltage (AC $V_{in,rms}$=75~265[V]), 5[V] DC output voltage, and 100[W] output power. To verify the excellent performance of the proposed converter, the designed prototype is implemented and experimented. The good performance of the proposed converter is shown through the experimental results.