• Journal of Electrical Engineering and Technology
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• 제13권1호
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• pp.220-225
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• 2018

A class E power oscillator is demonstrated for 6.78-MHz wireless power transfer system. The oscillator is designed with a class E power amplifier to use an LC feedback network with a high-Q inductor between the input and the output. Multiple capacitors are used to minimize the variation of the oscillation frequency by capacitance tolerance. The gate and drain bias voltages with opposite characteristics to make the frequency shift of the oscillator are connected in a resistance distribution circuit located at the output of the low drop-out regulator and supplied bias voltages for class E operation. The measured output of the class E power oscillator, realized using the co-simulation, shows 9.2 W transmitted power, 6.98 MHz frequency and 86.5% transmission efficiency at the condition with 20 V $V_{DS}$ and 2.4 V $V_{GS}$.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.273-277
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• 1999

A cold cathode flourescent lamp for the backlight in the notebook computer requires high input voltage about 1300(V) when it turns on. But once a discharge starts, the input voltage can be dropped by about one-third for continued output. The equivalent impedance also varies from open to several dozens of kilo-ohms. The piezoelectric transformer converts electrical energy into mechanical energy and then converts it back to electrical energy at a high voltage. Its high output voltage, high efficiency and small size are suitable for driving the LCD backlight in the notebook computer. The piezoelectric transformer operates near the resonance frequency and the output waveform is close to sine wave with very little noise. This paper suggests an inverter for LCD backlight of notebook computer using piezoelectric transformer that includes voltage to frequency converter for gate signal which is useful for tracking of variable resonance frequency depending on load impedance.

• 신재생에너지
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• 제20권2호
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• pp.55-64
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• 2024

To ensure the frequency stability of wind power generation, we analyzedd the existing technology and proposedd a method for changing the gain value with respect to to the rotor speed by adding the MPPT reference value and output reference value that reflect the system frequency. The MPPT control and output were compared and calculated for performance verification. Subsequently, the application of the proposed algorithm led to an increased output when compared with that of the existing control method.

• Journal of information and communication convergence engineering
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• 제7권1호
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• pp.62-65
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• 2009

In this paper, the temperature characteristics of full CMOS FLL(frequency locked loop) re analyzed. The FLL circuit is used to generate an output signal that tracks an input efference signal. The locking time of FLL is short compared to PLL(phase locked loop) circuit because the output signal of FLL is synchronized only in frequency. Also the FLL s designed to allow the circuit to be fully integrated. The FLL circuit is composed two VCs, two buffers, a VCO and two frequency dividers. The temperature variation of frequency divider, FVC and buffer cancelled because the circuit structure. is the same and he temperature effect is cancelled by the comparator. Simulation results are shown to illustrate the performance of the designed FLL circuit with temperature.

• Smart Structures and Systems
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• 제19권5호
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• pp.567-576
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• 2017

Design of piezoelectric energy harvester for a wide operating frequency range is a challenging problem and is currently being investigated by many researchers. Widening the operating frequency is required, as the energy is harvested from ambient source of vibration which consists of spectrum of frequency. This paper presents a new technique to increase the operating frequency range which is achieved by designing a harvester featured by a propped cantilever beam with variable over hang length. The proposed piezoelectric energy harvester is modeled analytically using Euler Bernoulli beam theory and the effectiveness of the harvester is demonstrated through experimentation. The results from analytical model and from experimentation reveal that the proposed energy harvester generates an open circuit output voltage ranging from 36.43 V to 11.94 V for the frequency range of 27.24 Hz to 48.47 Hz. The proposed harvester produces continuously varying output voltage and power in the broadened operating frequency range.

• 한국조명전기설비학회지:조명전기설비
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• 제11권4호
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• pp.59-65
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• 1997

이 논문에서는 형광램프용 가변출력형의 전자식 안정기의 설계방법 및 제어방법을 제안하였다. 마이크로 컨트롤러를 이용한 인버터회로의 주파수제어의 의하여 여러 가지 출력의 형광램프를 점등시킬 수 있는 시제품을 제작하였다. 이 가변출력형 전자식 안정기는 정류회로, 인버터회로, 그리고 여러 가지 출력의 램프에 이용되는 최적의 주파수를 결정하는 주파수 제어회로로 구성되어 있다. 제안된 설계방법의 적합성을 증명하기 의해 11[W], 15[W] 콤팩트 형광램프와 20[W] 형광램프에 적용하여 가변출력형 전자식 안정기의 시제품을 제작하였다. 램프의 전압과 전류를 관찰한 결과, PSpice 시뮬레이션 결과와 거의 일치하였다. 또한 발광효율은 다른 전자식 안정기와 거의 동일하였다. 그러므로 제안된 가변출력형 전자식 안정기의 설계 및 제어방법이 타당함을 입증하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1989년도 하계종합학술대회 논문집
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• pp.527-530
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• 1989

In order to reduce harmonic contents in the inverter output, various PWM ( pulse with modulation ) techniques have been utilized. This paper suggests a single phase inverter with 4-level output and its PWM control scheme. The proposed 4-level output inverter shows better performence than the 3-level output one in respects of the current error and the switching frequency.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 B
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• pp.1292-1294
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• 1996

The general output circuit for PWM output is pushpull using a complimentary MOSFET. The gate driver coupled directly at gate can switch easy upto a high frequency. However, a high reverse recovery current and parastic components make a oscillation output. This paper analyses this phenomenon and proposes a novel output circuit preventing the oscillation.

• 한국정보통신학회논문지
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• 제16권7호
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• pp.1364-1369
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• 2012

TV 주파수 대역(TVWS : TV White Space) 내에서 인접채널 간 다른 통신 시스템이 공존할 수 있는 방안을 구하기 위해 최대허용송신출력 레벨을 분석하였다. 적용된 두 시스템은 WLAN과 WiBro 이며 각 간섭 송신기의 다양한 밀도와 전송출력에 따른 실험 결과를 근거로 전체 성능이 분석되었다. 두 시스템의 간섭밀도와 허용 최대 송신출력의 관계를 알기 위해 간섭 송신기가 WLAN이고 WiBro가 희생 수신기인 경우를 고려하였다. 자유공간 채널모델을 이용한 각 실험 결과는SEAMCAT을 이용하여 구해졌다. 실험을 통해 얻어진 상호 공존 결과는 향후 인접 주파수뿐만 아니라 동일 주파수 환경에서 다양한 통신 프로토콜을 이용하는 무선기기에 대한 상호 공존 조건을 마련하는 기술개발에 활용될 수 있을 것이다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
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• pp.672-674
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• 2004

Many nonlinear controllers for the power system are based on nonlinear models involving the power angle as an element of the state, and therefore the reference value for the power angle is needed. As this reference value is not generally available, it is difficult to apply such nonlinear control methods in practice. To deal with this problem, we present an input-output feedback linearizing control scheme by selecting the output as a combination of the squared voltage and the relative frequency. It is shown that the internal dynamics are locally stable with controllable damping, and that the frequency remains bounded for all time. Simulations illustrate the effectiveness of the proposed method.