• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.314-316
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• 2005

Light flicker is a notorious phenomenon influencing light quality. The flicker of the light flux outputs from the light sources perceived by human eyes depends upon the lamp brightness fluctuations for projector display. This paper describes a ballast ignition control system, which makes the lamp strike frequency phase lock the blanking time period to minimize the flicker effect

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.4
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• pp.262-267
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• 2014

This study describes that light flicker of LED lamp is improved by placing an AC-powered LED block in each phase of three-phase AC power. Rectified current is considered as an instantaneous luminous flux because the current flowing through the LED block is proportional to the amount of light emitted by the LED block. Percent flicker is calculated simply by modeling the rectified current flowing through the LED block to a triangular wave current. Percent flicker is 100% in single-phase AC powered LED lamp. Percent flicker of the same level as that in an incandescent lamp (6%~14%) is however, achieved if light emission starts before $40^{\circ}$ in each voltage phase of three-phase AC power.

• Journal of Electrical Engineering and Technology
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• v.10 no.6
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• pp.2334-2342
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• 2015

This paper proposes an LED driving circuit with a digital controller, power factor correct (PFC) function, and low light flicker. The key topology of the proposed circuit is a conventional Flyback combined with a pre-stage. As a result, there will be less light flicker than with other one-stage PFC circuits. A digital controller, implemented using a low-cost microcontroller, dsPIC30F2020, will meet PFC and low light flicker. The experimental results validate the functionality of the proposed circuit.

• Journal of Sensor Science and Technology
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• v.26 no.6
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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.

• Journal of Sensor Science and Technology
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• v.29 no.3
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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.

• Journal of Sensor Science and Technology
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• v.29 no.2
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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.

• Journal of Sensor Science and Technology
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• v.27 no.3
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• pp.143-149
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• 2018

In this paper, we introduce an edge-spike modulation method for visible light communication (VLC). This method is effective in preventing LED flicker and 120 Hz noise interference in base-band VLC. In the VLC transmitter, edge-spikes are generated by passing the digital data through a simple RC-high pass filter (HPF). The LED modulation of the edge-spikes does not change the average power of the LED light; thus it prevents LED flicker. In the VLC receiver, the 120 Hz noise from other lighting lamps is easily eliminated by RC-HPF, while the edge-spike signal is detected normally. In our experiment, the message of an air-quality sensor was successfully transmitted using edge-spike modulation. This structure is useful in constructing, e.g., wireless gas monitoring sensor systems to warn and prevent harmful gas leakage accidents in buildings using LED light.

• Journal of IKEEE
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• v.22 no.2
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• pp.316-323
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• 2018

In this paper, we newly introduce the three-level byte-inversion transmission method for preventing LED flicker in visible light communication (VLC). The VLC transmitter sequentially sends the original signal and the inverted signal in byte units using a three-level LED modulator. The average optical power of the LED is kept constant during data transmission, thus flicker-free. In the VLC receiver, the original data is easily recovered using a simple comparator. This structure is very simple because additional clock or carrier is not required for flicker prevention. The developed flicker prevention scheme could be very useful for constructing the flicker-free indoor VLC system in low cost.

• Journal of Industrial Convergence
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• v.21 no.2
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• pp.125-131
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• 2023

In this paper, research was conducted to solve the problem of reducing the dimming level and flicker that occurs in the visible light communication system. Visible light communication is a convergence technology that provides both communication and lighting, and must satisfy not only communication performance but also lighting performance. However, since the existing data transmission method transmits without considering the transmission data sequence, it reduces the dimming level and causes a flicker phenomenon. To solve this problem, in this paper, the Dimming Improvement and Flicker Reduction Mapping technique was studied. Existing systems simply transmitted data of '0' and '1', but in this system, original data transmission channels and DIFR (Dimming Improvement and Flicker Reduction) transmission channels are assigned to RGB channels. Original data is allocated to the R channel and original data or inverse original data is allocated to the DIFR-G channel, and the DIFR-B channel maintains the maximum dimming level by transmitting through the logical operation of the R channel and the G channel. At the same time, the flicker phenomenon is prevented by preventing continuous occurrence of 'OFF' patterns. Through this, we proposed an adaptive data allocation algorithm that can faithfully play a role as a light as well as a communication function.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.15 no.3
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• pp.146-154
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• 2016

Visible light communication using LED is a technique for transmitting digital data using the light of the LED. Recently, high-speed data rate plays an important role. Therefore, many scholars have researched the MIMO-VLC which is able to increase data rate using a lot of LED transmitters. However, it has problems such as light interference and flicker when transmitting different bit. Many researcher have focused on reduce interference. However it is not considered about flicker problem. Flicker is defined unstable brightness. It occurred the tired of human eyes, lowers eyesight and also decreases concentration. In order to solve this flicker problem in MIMO-VLC, we propose the PFM(Parallel Flicker Mitigation) code. PFM code using combinatorial theory can maintain constant brightness the whole bit duration. Therefore, it is possible to assure the brightness by confirm simulation results.