Journal of information and communication convergence engineering

The Korea Institute of Information and Commucation Engineering (한국정보통신학회)
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Dimming Control of LED Light Using Pulse Frequency Modulation in Visible Light Communication

  • Lee, Seong-Ho (Department of Electronics and IT Media Engineering, Seoul National University of Science and Technology)
  • Received : 2021.09.23
  • Accepted : 2021.11.06
  • Published : 2021.12.31
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Abstract

Light-emitting diodes (LEDs) are modulated using a square wave pulse sequence for flicker prevention and dimming control in visible light communication (VLC). In a VLC transmitter, the high and low bits of the non-return-to-zero (NRZ) data are converted to two square waves of different frequencies, which continue for a finite time defined by the fill ratio in an NRZ bit time. As the average optical power was kept constant and independent of data transmission, the LED was flicker-free. Dimming control is carried out by changing the fill ratio of the square wave in the NRZ bit time. In the experiments, the illumination of the LED light was controlled in the range of approximately 19.2% to 96.2% of the continuous square wave modulated LED light. In the VLC receiver, a high-pass filter combined with a latch circuit was used to recover the transmitted signal while preventing noise interference from adjacent lighting lamps.

Keywords

Acknowledgement

This study was supported by the Research Program funded by the SeoulTech (Seoul National University of Science and Technology).

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