• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2014년도 추계학술대회
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• pp.278-281
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• 2014

본 논문에서는 진동에너지 하베스팅을 위한 세 가지 종류의 전파 정류기를 비교 분석 하였다. 첫번째 정류기는 두 개의 능동 다이오드(active diode)와 두 개의 MOSFET로 구성된 전파 정류기로 능동 다이오드의 비교기는 정류기의 출력으로부터 전력을 공급받는다. 두 번째는 네 개의 MOSFET로 구성된 정류기와 하나의 능동 다이오드로 구성된 2단 정류기이며, 마찬가지로 비교기는 정류기의 출력으로부터 전력을 공급받는다. 세 번째는 두 번째 정류기와 동일한 구조이나 비교기의 전력을 정류기의 입력으로부터 공급받는 input-powered 정류기이다. 이 정류기들을 0.35um CMOS 공정으로 설계하고 모의실험을 통해 성능을 비교, 분석하였다. 부하가 큰 경우에는 첫 번째 정류기를 이용하는 것이, 부하가 작은 경우에는 두 번째 정류기를 이용하는 것이 효율적인 측면에서 유리하다. 또한 효율보다는 진동에너지의 유무에 따른 전력 소모가 중요하다면 세 번째 정류기가 유리하다.

• Journal of Power Electronics
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• 제15권4호
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• pp.1131-1138
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• 2015

This study presents an input-powered high-efficiency interface circuit for energy harvesting systems, and introduces a zero standby power design to reduce power consumption significantly while removing the external power supply. This interface circuit is composed of two stages. The first stage voltage doubler uses a positive feedback control loop to improve considerably the conversion speed and efficiency, and boost the output voltage. The second stage active diode adopts a common-grid operational amplifier (op-amp) to remove the influence of offset voltage in the traditional comparator, which eliminates leakage current and broadens bandwidth with low power consumption. The system supplies itself with the harvested energy, which enables it to enter the zero standby mode near the zero crossing points of the input current. Thereafter, high system efficiency and stability are achieved, which saves power consumption. The validity and feasibility of this design is verified by the simulation results based on the 65 nm CMOS process. The minimum input voltage is down to 0.3 V, the maximum voltage efficiency is 99.6% with a DC output current of 75.6 μA, the maximum power efficiency is 98.2% with a DC output current of 40.4 μA, and the maximum output power is 60.48 μW. The power loss of the entire interface circuit is only 18.65 μW, among which, the op-amp consumes only 2.65 μW.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권4호
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• pp.1889-1910
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• 2017

This paper investigates a protocol so-called Adaptive Harvest Then Transmit (AHTT) for wireless powered communication networks (WPCNs) in multiple-input single-output (MISO) downlink systems, which assists in transmitting signals from a multi-antenna transmitter to a single-antenna receiver. Particularly, the power constrained relay is supplied with power by utilizing radio frequency (RF) signals from the source. In order to take advantage of multiple antennas, two different linear processing schemes, including Maximum Ratio Combining (MRC) and Selection Combination (SC) are studied. The system outage capacity and ergodic capacity are evaluated for performance analysis. Furthermore, the optimal power allocation is also considered. Our numerical and simulation results prove that the implementation of multiple antennas helps boost the energy harvesting capability. Therefore, this paper puts forward a new way to the energy efficiency (EE) enhancement, which contributes to better system performance.

• Water Engineering Research
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• 제4권1호
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• pp.1-17
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• 2003

A mathematical model was developed to simulate the performance of a prototype wind-powered reverse osmosis desalination system. The model consists of two sub-models operated in a series. The first sub-model is the wind-energy conversion sub-model, which has wind energy and feed water as its input and pressurized feed water as its output. The second sub-model is a reverse osmosis (RO) process sub-model, with pressurized feed water as its input and the flow and salinity of the product water or permeate as its output. Model coefficients were determined based on field experiments of a prototype wind powered RO desalination system of the University of Hawaii, from June to December 2001. The mathematical model developed by this study predicts the performance of wind-powered RO desalination systems under different design conditions. The system optimization is achieved using a linear programming approach. Based on the results of system optimization, a design guide is prepared, which can be used by both manufacturer and end-user of the wind-driven reverse osmosis system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
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• pp.6-8
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• 2004

The objective of this paper is to develop a powered wheelchair controller based on EMG for users with high-level spinal cord injury using a proportional control scheme. An advantage of EMG is relative convenience of acquisition by a surface electrode to users. Direction information can be easily extracted from two EMG channels and force information can be acquired by proportional relationship between the amplitude of EMG and user's power, respectively. Pattern classification algorithm is a threshold method with a supervised learning process. Furthermore, the emergency situation can be avoided using an interrupt function. We evaluated the performance of powered wheelchair controller by navigating a pre-defined path with three non-handicapped people. The results show the feasibility of EMG as an input interface for powered wheelchair and other devices for the seriously disabled.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.84.5-84
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• 2001

The objective of this paper is to develop a powered wheelchair controller based on EMG for users with high-level spinal cord injury. EMG is very naturally measured when the user Indicating a certain direction, and the force information which will be used for the speed of wheelchair is easily extracted from EMG. Furthermore, the emergency situation based on EMG will be checked relatively ease. We classified the pre-defined motions such as rest case, forward movement, left movement, and right movement by Fuzzy Min-Max Neural Networks (FMMNN). This classification results shows the feasibility of EMG as an input interface for powered wheelchair. To make the system low cost and small size, we developed EMG AMP and its controller ...

• Journal of Electrical Engineering and Technology
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• 제13권6호
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• pp.2553-2560
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• 2018

In Korea, there are no instances where a hydrogen fuel cell power generation system has been used in a railway vehicle. Only the basic topology has been studied. In the previous study, conventional converters using a single switch were applied to the fuel cell power generation system. Therefore, current stress on the switch at converter on-off transitions would be large when controlling a large-capacity railway vehicle. In addition, since the input side ripple is also large, there is a problem with a shortening of the lifetime of both the fuel cell power generation system and the inductor. In this paper, a soft-switching transformer inductor boost converter for fuel cell powered railway vehicles was proposed. A technique to reduce both the switching current stress generated during on-off transitions, and the input ripple current flowing in the inductor were studied. The soft-switching TIB converter uses a transformer-type inductor to configure the entire circuit in an interleaved method, and reduces both input current ripple and the current ripple of the inductor and switch.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1999년도 전력전자학술대회 논문집
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• pp.646-649
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• 1999

A new isolated boost dc to dc convertor suitable for a low input voltage application is proposed. The proposed convertor features the low switch current stresses, the wide input voltage range operation, and the inherent inrush current protection characteristics, essential to design a low to high voltage conversion circuit. A comparative analysis and experimental results are presented to show the validity of the proposed convertor.

• 전자공학회논문지
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• 제52권3호
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• pp.19-24
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• 2015

본 논문에서는 massive multiple-input multiple-output (MIMO) 기반의 wireless powered communication network (WPCN)에서 에너지 효율을 향상시키기 위한 기지국 안테나 수 최적화 기법을 제안한다. 제안하는 기법은 massive MIMO 시스템의 채널 hardening 특성을 이용하여 채널 이득을 안테나 수에 대한 식으로 근사한다. 그리고 근사화 된 최적화 문제에 편미분을 적용한 후 Lambert-W 함수를 이용하여 최적해를 closed form으로 찾는다. 모의실험을 통해 제안하는 기법의 근사 과정과 최적화 문제를 해결하는 방법이 적절함을 보이고, closed form 해가 exhaustive search 방법으로 찾은 해와 오차가 크지 않음을 확인한다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제16권3호
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• pp.255-260
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• 2016

In this paper, a full-wave rectifier (FWR) with a simple vibration detector suitable for use with vibrational energy harvesting systems is presented. Conventional active FWRs where active diodes are used to reduce the diode voltage drop and increase the system efficiency are usually powered from the output. Output-powered FWRs exhibit relatively high efficiencies because the comparators used in active diodes are powered from the stable output voltage. Nevertheless, a major drawback is that these FWRs consume power from the output storage capacitor even when the system is not harvesting any energy. To overcome the problem, a technique using a simple vibration detector consisting of a peak detector and a level converter is proposed. The vibration detector detects whether vibrational energy exists or not in the input terminal and disables the comparators when there is no vibrational energy. The proposed FWR with the vibration detector is designed using a $0.35-{\mu}m$ CMOS process. Simulation results have verified the effectiveness of the proposed scheme. By using the proposed vibration detector, a decrease in leakage current by approximately 67,000 times can be achieved after the vibration disappears.