• Journal of Communications and Networks
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• 제18권3호
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• pp.327-332
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• 2016

The routing protocol for low-power and lossy networks (RPL) is an internet protocol based routing protocol developed and standardized by IETF in 2012 to support a wide range of applications for low-power and lossy-networks (LLNs). In LLNs consisting of resource-constrained devices, the energy consumption of battery powered sensing devices during network operations can greatly impact network lifetime. In the case of inefficient route selection, the energy depletion from even a few nodes in the network can damage network integrity and reliability by creating holes in the network. In this paper, a composite energy-aware node metric ($RER_{BDI}$) is proposed for RPL; this metric uses both the residual energy ratio (RER) of the nodes and their battery discharge index. This composite metric helps avoid overburdening power depleted network nodes during packet routing from the source towards the destination oriented directed acyclic graph root node. Additionally, an objective function is defined for RPL, which combines the node metric $RER_{BDI}$ and the expected transmission count (ETX) link quality metric; this helps to improve the overall network packet delivery ratio. The COOJA simulator is used to evaluate the performance of the proposed scheme. The simulations show encouraging results for the proposed scheme in terms of network lifetime, packet delivery ratio and energy consumption, when compared to the most popular schemes for RPL like ETX, hop-count and RER.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.193-193
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• 2008

Wearable and ubiquitous micro systems will be greatly growing and their related devices should be self-powered in order to avoid the replacement of finite power sources, for example, by scavenging energy from the environment. With ever reducing power requirements of both analog and digital circuits, power scavenging approaches are becoming increasingly realistic. One approach is to drive an electromechanical converter from ambient motion or vibration. Vibration-driven generators based on electromagnetic, electrostatic and piezoelectric technologies have been demonstrated. Among various generator types proposed so far, piezoelectric generator possesses considerable potential in micro system. To overcome low mechanical-to-electric energy conversion, the piezoelectric device should activate in resonance mode in response to external vibration. Normally, the external vibration excretes at low frequency ranging 0.1 to 200 Hz, whereas the resonant frequencies of the devices are fixed as constant. Therefore, keeping their resonant mode in varying external vibration can be one of important points in enhancing the conversion efficiency. We investigated the possibility of use of multi-bender type piezoelectric devices. To match the external vibration frequency with the device resonant frequency, the various devices with different resonant frequency were chosen.

• 전자통신동향분석
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• 제34권6호
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• pp.133-144
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• 2019

Although deep learning-based visual image recognition technology has evolved rapidly, most of the commonly used methods focus solely on recognition accuracy. However, the demand for low latency and low power consuming image recognition with an acceptable accuracy is rising for practical applications in edge devices. For example, most Internet of Things (IoT) devices have a low computing power requiring more pragmatic use of these technologies; in addition, drones or smartphones have limited battery capacity again requiring practical applications that take this into consideration. Furthermore, some people do not prefer that central servers process their private images, as is required by high performance serverbased recognition technologies. To address these demands, the object and scene recognition technologies for mobile/embedded devices that enable optimized neural networks to operate in mobile and embedded environments are gaining attention. In this report, we briefly summarize the recent trends and issues of object and scene recognition technologies for mobile and embedded devices.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.1213-1214
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• 2015

서지보호장치(Surge Protective Device)가 국내에 본격적으로 설치된 것은 산업화의 발전으로 인해 현장 전력시스템의 복잡성과 다양성 및 급격히 변화하고 있는 우리나의 기후변화 때문일 것이다. 전원계통의 전원용서지보호장치(Poser Systems Surge Protective Devices) 및 통신계통의 통신용서지보호장치(Telecommunication Surge Protective Devices)의 설치는 해마다 증가하고 있다. 이에 따른 제품개발도 급속도로 이루어지고 있으며, 과거 몇년 전만해도 서지보호장치에 대한 표준과 시험설비의 이해와 부족으로 인해 표준에 의한 제품검증이 어려웠으나 2013년 제정된 KS 표준(KS C IEC 61643-11)으로 상당수 제조자가 관련인증을 취득하고 있다. 이 논문에서는 KS표준에서 정의하고 있는 열안전성시험에 대한 방법과 결과판정 및 새로운 기준을 제시하고자 한다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1996년도 창립기념 전력전자학술발표회 논문집
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• pp.117-120
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• 1996

Power conversion system must be increased switching frequency in order to achieve a small size, a light weight and a low noise. However, the switches of converter are subjected to high switching power losses and switching stresses. As a result of those, the power system brings on a low efficiency. In this paper, the authors propose a DC-DC boost converter of high power by partial resonant switch method (PRSM). The switching devices in a proposed circuit are operated with soft switching and the control technique of those is simplified for switch to drive in constant duty cycle. The partial resonant circuit makes use of a inductor using step up and a condenser of loss-less snubber. Also the circuit has a merit which is taken to increase of efficiency, as it makes to a regeneration at input source of accumulated energy in snubber condenser without loss of snubber in conventional circuit. The result is that the switching loss is very low and the efficiency of system is high. The proposed converter is deemed the most suitable for high power applications where the power switching devices are used.

• 대한의용생체공학회:의공학회지
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• 제36권5호
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• pp.169-176
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• 2015

Implantable closed-loop epilepsy controllers require ideally both accurate epileptic seizure detection and low power consumption. On-chip oscillators can be used in implantable devices because they consume less power than other oscillators such as crystal oscillators. In this study, we investigated the tolerable error range of a lower power on-chip oscillator without losing the accuracy of seizure detection. We used 24 ictal and 14 interictal intracranial electroencephalographic segments recorded from epilepsy surgery patients. The performance variations with respect to oscillator frequency errors were estimated in terms of specificity, modified sensitivity, and detection timing difference of seizure onset using Generic Osorio Frei Algorithm. The frequency errors of on-chip oscillators were set at ${\pm}10%$ as the worst case. Our results showed that an oscillator error of ${\pm}10%$ affected both specificity and modified sensitivity by less than 3%. In addition, seizure onsets were detected with errors earlier or later than without errors and the average detection timing difference varied within less than 0.5 s range. The results suggest that on-chip oscillators could be useful for low-power implantable devices without error compensation circuitry requiring significant additional power. These findings could help the design of closed-loop systems with a seizure detector and automated stimulators for intractable epilepsy patients.

• 한국정보통신학회논문지
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• 제25권11호
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• pp.1596-1602
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• 2021

사물인터넷 시스템에서 배터리로 동작하는 사물인터넷 장치는 저전력 소모가 필수이다. 일반적으로 사물인터넷 장치들은 주기적으로 수면 상태에 진입하여 전력 소모를 줄인다. 하지만 비동기 사용자 요구 환경에서는 응답시간을 줄이기 위해 듀티 사이클을 줄여야 하므로 전력 소모 절감 효과가 줄어든다. 본 논문에서는 실내 전등 제어와 같은 비동기 제어가 필요한 환경에서도 장치의 전력 소모 절감 효과를 높일 수 있는 새로운 기법을 제안한다. 제안하는 반복 깨우기(repetitive wake-up) 기법은 스마트폰에서 깨우기 신호를 반복적으로 전송하고 사물인터넷 장치는 듀티 사이클을 최소화함으로써 전력 소모를 줄일 수 있다. 스마트폰 앱과 사물인터넷 장치를 구현하고 실험을 통해 제안하는 반복 깨우기 기법이 기존의 동기적 수면/활동 기법보다 최대 5배 이상 전력 소모를 줄일 수 있음을 보였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 전력전자학술대회 논문집(2)
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• pp.677-681
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• 2004

This paper presents the design and implementation of a low-profile power supply developed for AC-PDP application systems. In the proposed power supply, planar magnetics and SMD devices are integrated into advanced power conversion techniques to implement a low-profile power supply applicable to most AC-PDP application systems. Engineering details on the design and fabrication of planar magnetic components are presented. The performance of the prototype power supply is also demonstrated to validate the application potentials of the proposed power supply.

• Journal of Power Electronics
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• 제10권4호
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• pp.335-341
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• 2010

In this paper, an interleaved soft switching boost converter for a Photovoltaic Power Conditioning System (PV-PCS) with high efficiency is proposed. In order to raise the efficiency of the proposed converter, a 2-phase interleaved boost converter integrated with soft switching cells is used. All of the switching devices in the proposed converter achieve zero current switching (ZCS) or zero voltage switching (ZVS). Thus, the proposed circuit has a high efficiency characteristic due to low switching losses. To analyze the power losses of the proposed converter, two experimental sets have been built. One consists of normal devices (MOSFETs, Fast Recovery (FR) diodes) and the other consists of advanced power devices (CoolMOSs, SiC-Schottky Barrier Diodes (SBDs)). To verify the validity of the proposed topology, theoretical analysis and experimental results are presented.

• 대한전자공학회논문지SD
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• 제41권5호
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• pp.15-21
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• 2004

본 논문에서는 저전력 스위치에 사용되는 소자의 포화전압 특성을 개선하기 위해 새로운 구조의 BJT를 제안하고 있다 기존에 사용되던 finger transistor(FT)의 경우 포화전압이 높아 저전력 소자의 특성을 만족하지 않아 multi base island transistor(MBIT)로 구조를 변경함으로써 저전류 영역에서의 포화전압은 충분히 낮아 저전력용 소자의 특성을 만족하지만, 이 역시 고전류 영역에서는 여전히 포화전압이 높아져 저전력용 소자의 특성을 만족하지 못하는 문제가 발생한다. 이에 본 논문에서는 folded back electrode를 이용한 새로운 구조의 BJT(FBET)를 제안하여 그 특성을 조사하였다. 새로운 구조의 트랜지스터를 적용함으로써 MBIT 구조에 비해 에미터 면적은 35 % 증가하고 접촉창의 면적이 92 % 증가하여, 저 전류 영역에서의 포화 전압은 30 % 감소하였고 고 전류 영역에서의 포화 전압은 에미터 면적 증가와 에미터 접촉 창 면적 증가에 의해 각각 30 %와 7 %씩 감소하여 전체적으로는 37 %가 감소하는 특성을 나타내었다.