• 대한임베디드공학회논문지
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• 제13권3호
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• pp.117-124
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• 2018

Wearable devices have become widespread. Fitness band is one of common wearable devices, providing useful functions. It helps users to monitor and collect their status such as heart rate and travel distance. Wearable devices, including fitness bands, are designed in small size and it ends up having small battery capacity. In that regard, it is necessary to expand the lifetime of wearable devices. Conventional power management scheme of wearable devices is based on DVFS Ondemand Governor and peripheral control by timeout event, such as turning off the LCD. In this paper, we propose a hybrid governor applying hardware supporting low power mode such as sleep mode to exploit the periodicity of fitness band task. In addition, we show hybrid governor outperforms in power consumption than conventional power management scheme of wearable devices based on Ondemand Governor through experiments.

• IEIE Transactions on Smart Processing and Computing
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• 제3권4호
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• pp.221-225
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• 2014

Low power RF devices, such as RFID and Zigbee, are important for ubiquitous sensing. These devices, however, are powered by portable energy sources, such as batteries, which limits their use. To mitigate this problem, this study developed RF energy harvesting with W-CDMA for a low power RF device. Diodes are required with a low turn on voltage because the diode threshold is larger than the received peak voltage of the rectifying antenna (rectenna). Therefore, a Schottky diode HSMS-286 was used. A prototype of RF energy harvesting device showed the maximum gain of 5.8dBi for the W-CDMA signal. The 16 patch antennas were manufactured with a 10 dielectric constant PTFT board. In low power RF devices, the transmitter requires a step-up voltage of 2.5~5V with up to 35 mA. To meet this requirement, the Texas Instruments TPS61220 was used as a low input voltage step-up converter. From the evaluated result, the achievable incident power of the rectenna at 926mV to operate Zigbee can be obtained within a distance of 12m.

• KIEE International Transactions on Electrophysics and Applications
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• 제3C권3호
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• pp.91-98
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• 2003

The importance of improving the quality of electric power is being strongly raised, owing to an increasing use of sensitive and small-sized electronic devices and systems. The transient over-voltages on low-voltage power distribution systems are induced by direct or indirect lightning return strokes. These can cause damage and/or malfunction of the utility systems for home automation, office automation, factory automation, medical automation, etc. The behaviors of lightning overvoltages transferred through the transformer to the low-voltage distribution systems using a Marx generator were experimentally investigated. Furthermore, the coupling mechanisms of lightning overvoltages transferred to the low-voltage systems were clearly illustrated through a theoretical simulation using a Pspice program. The overvoltages in low-voltage ac power systems are rarely limited by the application of the surge arrester to the primary side of the distribution transformer. A superior surge protection scheme is to install surge protection devices at the service entrance switchboard and/or at the load devices in TN power systems.

• 대한임베디드공학회논문지
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• 제10권2호
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• pp.91-99
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• 2015

The electric power consumed by the embedded devices has become a critical issue because the reduction of power consumption is an important factor to prolong the battery-operated devices' lifetime. Many researches and techniques to reduce the power consumption have been proposed and developed but any power method cannot guarantee optimal power consumption of an embedded device - it would be faced with numerous situation - in all ways. Specifically, power researches for embedded devices deployed in the industry field have hardly been done. In this paper, low power service is proposed to minimize power reduction with the several usage status of embedded devices in the industry field. The usage status is basically classified according to the distance between the device and the user which is obtained by the ultrasonic and PIR sensor. The performance evaluation shows that the proposed scheme can reduce the power consumption by up to 45.3% compared to the device with no power reduction scheme. It also shows that the power consumption of the proposed scheme is 5.2% ~ 16.8% lower than that of the timeout scheme.

• 한국전기전자재료학회논문지
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• 제26권3호
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• pp.190-193
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• 2013

Power MOSFET and Power IGBT is develop in power savings, high efficiency, small size, high reliability, fast switching, low noise. Power MOSFET can be used high-speed switching transistors devices. Power MOSFET is devices the voltage-driven approach switching devices are design to handle on large power, power supplies, converters. In this paper, design the 80V MOSFET Planar Gate type, and design the Trench Gate type for realization of low on-resistance. For both structures, by comparing and analyzing the results of the simulation and characterization.

• Journal of Information Processing Systems
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• 제9권1호
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• pp.41-52
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• 2013

One of the obstacles preventing the Zigbee protocol from being widely used is the excessive power consumption of Zigbee devices in low bandwidth and low power requirement applications. This paper proposes a protocol that resolves the power efficiency problem. The proposed protocol reduces the power consumption of Zigbee devices in beacon-enabled networks without increasing the time taken by Zigbee peripherals to communicate with their coordinator. The proposed protocol utilizes a beacon control mechanism called a "sleep pattern," which is updated based on the previous event statistics. It determines exactly when Zigbee peripherals wake up or sleep. A simulation of the proposed protocol using realistic parameters and an experiment using commercial products yielded similar results, demonstrating that the protocol may be a solution to reduce the power consumption of Zigbee devices.

• 대한임베디드공학회논문지
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• 제13권3호
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• pp.133-141
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• 2018

There are increasing interests on smart home systems. However, most of the existing works focus on the functionality itself. In this paper, we propose an extensible smart home system based on low power networking such as CoAP, 6LoWPAN, and Zigbee. The proposed home IoT system consists of Home APP, Home Server, Home Broker, and Power Devices. Each component of the system is connected by the low-power network technologies aforementioned. As the end device, Power Device senses the current consumption of the attached appliance and controls the power to it. Power Device reports the sensing data to Home Server via Home Broker. The Home Broker enhances the scalability of the system. Home Broker extends the service area and the user's services, and it manages the connection of the underlying devices and processes, and transmits data to Home Server from Power Devices. Through the experimental evaluation, we show that the proposed system achieves the design goals such as extensibility and low power networking.

• 대한전기학회논문지:전력기술부문A
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• 제52권3호
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• pp.165-172
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• 2003

This paper presents an operation scheme to enhance the power system security by applying FACTS on Power systems. Three main generic types of FACTS devices are suggested an illustrated. Flow congestions over lines have been solved by controlling active power of series-compensated FACTS devices and low voltages at buses have been solved by controlling reactive power of shunt-compensated FACTS devices. Especially, Especially, UPFC has been applied in both line congestion and low voltages. Two kinds of indices which indicate the power system security level related to line flow and bus voltage are utilized in this paper. They have been minimized to enhance the power system security level through the iterative method and the sensitivity vector of security index is derived to determine the direction to minimum. The proposed algorithm has been tested on the IEEE 57-bus system with FACTS devices in a normal condition and a line-faulted contingency.

• 한국산업정보학회논문지
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• 제12권3호
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• pp.95-103
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• 2007

데이터, 비디오, 오디오 등에 대한 디지털 컨버전스 추세와 함께, 최근 휴대용 멀티미디어 재생기(PMP)가 점차 대중화되고 있다. PMP는 DSP, 보다 큰 LCD 스크린, 하드디스크 등이 장착되는 이유로 다른 휴대형 장치들에 비해서 효과적인 전력관리에 대한 필요성이 강조되고 있다. 본 논문에서는 데이터수집 장치를 기반으로 한 하드웨어/소프트웨어기반 전력 측정 시스템 구축에 대해서 설명하고, PMP에서 발생하는 부팅, 동영상 재생, 다양한 비디오 코딩 방식 적용과 같은 다양한 사건 실행시의 전력소모 패턴을 측정하고 분석한다. 분석 결과는 저전력 PMP 장치를 설계하기 위한 유용한 정보를 제공한다.

• 조명전기설비학회논문지
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• 제16권2호
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• pp.90-97
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• 2002

본 논문에서는 철도 시스템에서 사용하는 저압 전원용 서지보호장치(surge protective devices) 규칙의 성능평가 항목 및 성능개선 방안에 대하여 고찰하였다. 먼저 철도시스템 환경과 관련된 전자기장해(electromagnetic interference) 현상을 검토하였다. 그리고 국제규격인 IEC 및 IEEE와 평가항목 및 펑가방법 등을 비교 검토하였다. 검토 결과 국내 철도관련 규격은 국제규격과 비교하여 비교하여 발견하였다. 개선방안으로 서지 보호소자 단위의 시험은 삭제하고, 규격 종류는 전원용과 신호용으로 분리하며, 서지 파형은 국제적으로 인정된 것을 사용하도록 제안하였다. 철도용 저압 서지보호장치에 대해 서지제한전압 측정 및 서지 수명시험을 국제규격에 따라 시험한 결과 만족스러운 결과를 얻었다.