• 한국전자통신학회논문지
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• 제11권2호
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• pp.159-164
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• 2016

무선통신시스템은 한정된 에너지를 갖는 배터리를 사용하기 때문에 저전력 회로로 구현되어야 하며, 이를 위하여 주파수와 상관없이 일정한 전력을 나타내는 전류모드 회로가 연구되어왔다. 본 논문에서는 초저전력 동작이 가능하도록 Dynamic Voltage Scaling 전원을 유도하며, 전류모드 신호처리 중 메모리 동작에서 저장된 에너지가 누설되는 Clock-Feedthrough 문제를 최소화하는 전류메모리 회로를 제안한다. $0.35{\mu}m$ 공정의 BSIM3 모델로 Near-threshold 영역의 전원 전압을 사용한 시뮬레이션을 진행한 결과, 1MHz의 스위칭 동작에서 $2{\mu}m$의 메모리 MOS Width, $0.3{\mu}m$의 스위치 MOS Width, $13{\mu}m$의 Dummy MOS Width로 설계할 때, Clock-Feedthrough의 영향을 최소화시킬 수 있었으며 1.2V의 Near-threshold 전원전압에서 소비전력은 $3.7{\mu}W$가 계산되었다.

• 한국정보통신학회논문지
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• 제13권7호
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• pp.1371-1378
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• 2009

본 논문에서는 로직 공정 기반의 저전력 eFuse OTP 메모리 셀을 제안하였다. eFuse OTP 메모리 셀은 프로그램과 읽기 모드에 최적화되도록 각각의 트랜지스터를 사용하였으며, WL과 BL의 기생적인 커패시턴스를 줄이므로 읽기 모드에서의 동작 전류를 줄였다. 그리고 저전력, 저면적의 eFuse OTP 메모리 IP 설계를 위하여 비동기식 인터페이스, 분리된 I/O, 디지털 센싱 방식의 BL 감지 증폭기 회로를 사용하였다. 모의실험 결과 읽기 모드에서의 동작전류는 VDD, VIO 각각 349.5${\mu}$A, 3.3${\mu}$A로 나왔다. 그리고 동부하이텍 0.18${\mu}$m generic 공정으로 설계된 eFuse OTP 메모 리 IP의 레이아웃 면적은300 ${\times}$557${\mu}m^2$이다.

• Journal of Electrical Engineering and Technology
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• 제10권1호
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• pp.165-175
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• 2015

Energy storage system has been widely applied in power distribution sectors as well as in renewable energy sources to ensure uninterruptible power supply. This paper presents a model predictive algorithm to control a bidirectional AC-DC converter, which is used in an energy storage system for power transferring between the three-phase AC voltage supply and energy storage devices. This model predictive control (MPC) algorithm utilizes the discrete behavior of the converter and predicts the future variables of the system by defining cost functions for all possible switching states. Subsequently, the switching state that corresponds to the minimum cost function is selected for the next sampling period for firing the switches of the AC-DC converter. The proposed model predictive control scheme of the AC-DC converter allows bidirectional power flow with instantaneous mode change capability and fast dynamic response. The performance of the MPC controlled bidirectional AC-DC converter is simulated with MATLAB/Simulink(R) and further verified with 3.0kW experimental prototypes. Both the simulation and experimental results show that, the AC-DC converter is operated with unity power factor, acceptable THD (3.3% during rectifier mode and 3.5% during inverter mode) level of AC current and very low DC voltage ripple. Moreover, an efficiency comparison is performed between the proposed MPC and conventional VOC-based PWM controller of the bidirectional AC-DC converter which ensures the effectiveness of MPC controller.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.219-219
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• 2008

Energy harvesting from the environment has been of great interest as a standalone power source of wireless sensor nodes for ubiquitous sensor networks (USN). There are several power generating methods such as thermal gradients, solar cell, energy produced by human action, mechanical vibration energy, and so on. Most of all, mechanical vibration is easily accessible and has no limitation of weather and environment of outdoor or indoor. In particular, the piezoelectric energy harvesting from ambient vibration sources has attracted attention because it has a relative high power density comparing with other energy scavenging methods. Through recent advances in low power consumption RF transmitters and sensors, it is possible to adopt a micro-power energy harvesting system realized by MEMS technology for the system-on-chip. However, the MEMS energy harvesting system hassome drawbacks such as a high natural frequency over 300 Hz and a small power generation due to a small dimension. To overcome these limitations, we devised a novel power generator with a spiral spring structure. In this case, the energy harvester has a lower natural frequency under 200 Hz than a normal cantilever structure. Moreover, it has higher an energy conversion efficient because shear mode ($d_{15}$) is much larger than 33 mode ($d_{33}$) and the energy conversion efficiency is proportional to the piezoelectric constant (d). We expect the spiral type MEMS power generator would be a good candidate as a standalone power generator for USN.

• 대한전자공학회논문지SD
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• 제48권12호
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• pp.91-96
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• 2011

본 논문에서는 전류 모드 동작에 기반한 IEEE 802.15.4 규격을 만족하는 2.4GHz 저전력 직접 변환 송신기를 제안하고 $0.13{\mu}m$ CMOS 공정을 이용하여 구현하였다. 제안된 송신기는 디지털-아날로그 변환기, 저역통과 필터, 가변 이득 I/Q 상향 혼합기, 구동 증폭기 및 LO 버퍼를 포함하는 주파수 나누기 2회로로 구성되어 있다. 디지털-아날로그 변환기와 저역통과 필터(LPF), 가변이득 I/Q 상향 혼합기의 트랜스컨덕터 단을 하나의 전류 미러 회로로 합친 간단한 구조를 제안하여 전력 소모를 줄이면서 선형성을 향상할 수 있도록 하였다. 구동 증폭기는 캐스코드 타입의 증폭기로 제어 신호를 이용하여 이득을 조절할 수 있게 하였고, 외부 4.8GHz 신호를 받아 주파수 나누기 2 전류 모드 로직 (CML) 회로를 사용하여 2.4GHz I/Q 차동 LO 신호를 생성하도록 설계하였다. 구현한 송신기는 30dB의 이득 조정 범위를 가지면서 0dBm의 최대 출력 신호에서 33dBc의 LO 누설 성분, 40dBc의 3차 하모닉 성분의 특성을 보이며, 구현한 칩의 면적은 $1.76mm{\times}1.26mm$으로 전력소모는 1.2V 단일 전원 전압으로부터 10.2mW이다.

• 한국전자통신학회논문지
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• 제7권5호
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• pp.983-989
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• 2012

IEEE 802.3az LPI 메커니즘은 전송할 데이터가 없을 경우 취침 모드로 천이하여 다수의 컴포넌트들을 저전력 상태를 유지하게 함으로써 에너지 효율성을 향상시킨다. LPI는 소량의 데이터가 주기적으로 전송되는 상황에서는 잦은 전송 모드 변환에 따른 오버헤드 때문에 에너지 효율이 크게 개선되지 못하는 문제점이 있다. 본 논문에서는 전송계층 트래픽 특성 및 네트워크 상태에 따라 LPI 모드 상태 천이를 적응적으로 수행하는 개선된 LPI 메커니즘을 제안한다. 시뮬레이션 방법에 의한 성능 분석을 통해 제안한 메커니즘이 다양한 트래픽 부하에 대해서 기존 방법보다 에너지 효율성을 향상시키는 것으로 나타났다.

• 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.

• 대한전기학회논문지:전력기술부문A
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• 제54권3호
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• pp.122-132
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• 2005

This paper presents a novel approach based on Prony method to analysis of small signal stability in power system. Prony method is a valuable tool in identifying transfer function and estimating the modal parameter of power system oscillation from measured or computed discrete time signal. This paper define the relative residue of time signal and propose the condition to select low frequency oscillation in each generator. This paper describes the application results of proposed algorithm with respect to KEPCO systems. Simulation results show that the proposed algorithm can be used as another tools of power systems analysis.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(2)
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• pp.89-92
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• 2001

In this paper, a simple low-power CMOS current reference circuit is proposed. The reference circuit includes parasitic pnp BJTs and resistors. Temperature compensation is made by adding a current component proportional to a thermal voltage to a current component proportional to a base-to-emitter voltage. The designed circuit has been simulated using a 0.25${\mu}{\textrm}{m}$ n-well CMOS process parameters. The simulation results show that the reference current is 34.96$mutextrm{A}$$\pm$0.04$mutextrm{A}$ in the temperature range of -2$0^{\circ}C$ to 12$0^{\circ}C$ The reference current varies less than 0.6% when the power supply voltage changes from 2.5V to 3.5V For $V_{DD=5V}$ and T=3$0^{\circ}C$ the power consumption is 520㎼ during normal operation but reduces to 0.l㎻ during power-down mode.

• 반도체디스플레이기술학회지
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• 제9권2호
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• pp.7-10
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• 2010

In this paper, we design a modem SoC (System on Chip) for low power consumption and high speed wireless communications. Among various schemes of high speed communications, an MB-OFDM (Multi Band-Orthogonal Frequency Division Multiplexing) UWB (Ultra-Wide-Band) chip is designed. The MB-OFDM uses wide-band frequency to provide high speed data rate. Additionally, the system imposes no interference to other services. The 90nm CMOS (Complementary Metal-Oxide Semiconductor) technology is used for the SoC design. Especially, power management mode is implemented to reduce the power consumption.