• 전력전자학회논문지
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• 제19권4호
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• pp.327-331
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• 2014

LED(Light Emitting Diode) is a semiconductor device utilizing electroluminescent effect is a phenomenon in which a type of P-N junction diode, the light of short wavelength which a voltage is applied in the forward direction is released. LED is advantageous in reducing the energy as environmentally materials that can greatly reduce the carbon emissions, recent it has attracted attention IT(Information Technology) and GT(Green Technology) industry. In addition, there are advantages long life, high efficiency, and excellent response speed, LED have come into the spotlight as the illumination means to replace the existing fluorescent light and incandescent light bulb. When connecting to MR16 electronic transformer for existing LED driver circuit, due to malfunction of the dimmer and the electronic transformer, flicker occurs and linear dimming is not possible. Therefore, in this paper, we suggest an LED drive circuit there is no flicker with the corresponding dimming MR16 electronic transformer. Further, we explain the principles of the LED current control technique and the principle of the drive circuit of the LED, in order to validate the proposed circuit through prototyping and simulation.

• 센서학회지
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• 제29권2호
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• pp.75-81
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• 2020

We introduce a new visible light communication (VLC) method in which three-level return-to-zero (RZ) modulation is used for flicker-free transmission. In the VLC transmitter, the three-level RZ modulation ensures that the average optical power is constant; thus, a flicker-free light-emitting diode (LED) light is achieved. In the VLC receiver, a resistor-capacitor high-pass filter is used for generating spike signals, which are used for data recovery while eliminating the 120 Hz optical noise from adjacent lighting lamps. In transmission experiments, we applied this method for wireless transmission of an air quality sensor message using the visible light of an LED array. This configuration is useful for the construction of indoor wireless sensor networks for air pollution monitoring using LED lights.

• 센서학회지
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• 제26권6호
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• pp.408-413
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• 2017

In this paper, we newly developed a byte-inverted transmission method for flicker-free visible light communication (VLC). The VLC transmitter sends original data in the former half period of the clock, and inverted data and in the latter half period of the clock. The VLC receiver receives the original data in the in the former half period of the clock. In this system, we used 480Hz clock that was generated from the 60Hz power line. The average optical power of the LED array in the transmitter is constant, thus flicker-free, in the observation time longer than the period of the clock that is about 2ms. This period is shorter than the maximum flickering time period (MFTP) of 5ms that is generally considered to be safe. This configuration is very useful in constructing indoor wireless sensor networks using LED light because it is flicker-free and does not require additional transmission channel for clock transmission.

• 한국생산제조학회지
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• 제26권3호
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• pp.328-336
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• 2017

The exit surface of a lens is designed using a three-dimensional free-form expression in order to easily modify a curved surface. This enables the design of numerical values and mathematical things using three-dimensional free-form expression, and enhances precision because it can be fine-tuned via numerical control. The standard of "Classification of Luminaire Light Distribution" for outdoor lighting fixtures by IESNA is adopted in order to examine the correlation between three-dimensional free-form surface expression and lighting performance. The variation of light distribution type and range is analyzed using the values of maximum light intensity and 50% light intensity. The actual tolerance occurs owing to parameters such as the thickness of the lens, the distance between LEDs, and the movement of the center of the incident surface; the effects of changes in these parameters on the performance are compared and analyzed.

• 마이크로전자및패키징학회지
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• 제23권4호
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• pp.35-41
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• 2016

고출력 LED 조명용 패키지를 제조함에 있어서 발열은 LED의 광출력과 수명에 매우 중요한 영향을 주는 인자로 알려져 있다. 본 연구에서는 가로등용 고출력 LED 패키지를 개발함에 있어서 효과적인 방열을 하기 위하여 방열효과가 상대적으로 우수한 구조인 chip-on-a-heat sink 구조를 가지는 세라믹-메탈 기반의 패키지를 제조하였다. 열확산 기능을 하는 heat sink 기판소재는 알루미늄 합금을, LED 어레이 회로를 형성하는 절연막으로는 저온동시소성용 glass-ceramics을 사용하였다. 특히 열처리 시 가장 이슈가 되는 세라믹-금속 하이브리드 패키지 기판의 휨을 억제하기 위한 수단으로서, glass-ceramic 절연막을 부분 코팅함으로써 휨현상을 용이하게 줄일 수 있게 되었다. 또한, LED 패키지의 방열특성의 향상 즉 열저항도 기존의 MCPCB 패키지나 전면 코팅형 절연막 패키지에 비해 훨씬 낮아지는 효과를 얻었을 뿐 아니라, 세라믹 코팅소재의 절감효과도 볼 수 있게 되었다.

• 한국전자통신학회논문지
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• 제9권1호
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• pp.111-122
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• 2014

중소기업은 창조경제의 중추적 역할을 담당하는 핵심 성장 동력원으로서 중요한 위치를 차지함에도 불구하고 중소기업의 현실은 희망이 없다. 중소기업의 혁신을 통한 중장기적 성장전략을 제시하고자 유망자유기술 탐색방법을 제안하고, 2006년부터 2010년까지 PCT 출원되어 공개된 특허를 조사하여 기술동향을 정량 분석한 다음, LED품목을 사례로 들어 PCT 및 국내 특허정보를 분석하고, 미래 유망 자유기술을 탐색하였다. 제시된 자유기술탐색 방법은 중소기업의 국제시장 진출 방향 설정 및 국가산업 전략의 수립에도 활용이 가능할 것이다.

• 센서학회지
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• 제27권3호
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• pp.175-181
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• 2018

In this paper, we introduce a new dimming control method in a visible light communication (VLC) system wherein byteinversion is adopted for flicker-free transmission. In the VLC transmitter, the original and the inverted data were sent sequentially and the remnant time in one period was used for the dimming control of the LED light. In the VLC receiver, only the original data was recovered using the gating signal whose width was the same as the length of the original data. In our experiments, the dimming control ranges were measured to be 22%-53%, 11%-76%, and 5%-88% of the CW LED light when the data rates were 9.6, 19.2, and 38.4 kbps, respectively. In this system, we used a 240-Hz sync pulse whose period was 4.16 ms, which was shorter than the maximum flickering time period of 5 ms that is generally considered to be safe. This configuration is very simple and useful in constructing indoor wireless sensor networks using the flicker-free LED lamps with dimming control capability.

• 센서학회지
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• 제29권3호
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• pp.180-186
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• 2020

In this study, we applied edge-pulse modulation to prevent the flicker of light-emitting diode (LED) light in a visible light identification system. In the visible light transmitter, positive pulses were transmitted at the edges of the low-to-high transition points, and negative pulses were transmitted at the edges of the high-to-low transition points of the non-return-to-zero (NRZ) data waveforms. In the visible light receiver, the NRZ waveforms were regenerated by making low-to-high and high-to-low transitions at the point of the positive and negative pulses, respectively. This method has two advantages. First, it ensures that the LED light is flicker-free because the average optical power of the LED was kept constant during data transmission in the transmitter. Second, the 120 Hz optical noise from the adjacent lighting lamps was easily cut off using a simple RC-high pass filter in the receiver.

• 센서학회지
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• 제29권3호
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• pp.149-155
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• 2020

In this study, we employed Manchester code for illumination control and flicker prevention of the light-emitting diode (LED) used in a visible light communication (VLC) system. In the VLC transmitter, the duty factor of the Manchester code was utilized for illumination control; in the VLC receiver, the spike signal from an RC-high pass filter was utilized to recover the transmitted signal whilst suppressing the 120-Hz noise arising from adjacent lighting lamps. Instead of the clock being transmitted in a separate channel, a syncmark signal was transmitted in front of each data byte and used as the reference time for transforming the Manchester code to non-return-to-zero (NRZ) data in the receiver. In experiments, the LED illumination was controlled in the range of approximately 12-84% of the constant wave (CW) light via changing of the duty factor from 10% to 90%. This scheme is useful for constructing indoor wireless sensor networks using LED light that is flicker-free and presents capability for illumination control.

• 전기전자학회논문지
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• 제23권2호
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• pp.571-579
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• 2019

가시광통신은 조명과 통신을 동시에 수행하므로, 데이터 전송과정에서 광전력의 변동으로 인하여 발생하는 플리커를 방지함과 동시에 조명제어 기능을 갖추는 것이 중요하다. 본 논문에서는 플리커를 방지하고 조명제어를 위하여 맨체스터코드를 사용하였다. 송신부에서는 맨체스터코드의 듀티율을 사용하여 LED의 조명을 제어하였고, 수신부에서는 RC-고역통과필터의 가장자리 스파이크 신호를 사용하여 인접된 잡음광을 차단하고 맨체스터코드를 복구하였다. 실험에서 LED 빛은 플리커가 없는 상태를 유지하였고, 맨체스터코드의 듀티율을 변경함으로써 평균 광전력을 CW LED 광의 약 8~68 % 의 범위에서 제어하였다.