The invention discloses a visible light audio
transmission system based on a phase-locked loop. The existing visible light audio
transmission system has high running cost and maintenance cost and poor anti-interference performance. A
microphone receives the outside sound, the sound is input into an analog-to-
digital conversion module to convert the analog quantity to the digital quantity, and then after a modulation module modulates the digital quantity, a modulated
signal is loaded to LED (
Light Emitting Diode) light to be transmitted through a transmitting circuit module; a
silicon photocell receives a modulated
light signal and converts the modulated
light signal to an
electric signal through a receiving circuit module, a
demodulation module demodulates the electric signals and then inputs the
electric signal to a
waveform shaping module, the digital quantity of the transmitting part is restored, the
signal is converted to an analog
audio signal through a digital-to-analog conversion module, and lastly, the analog
audio signal is amplified through a power
amplifier and drives a
loudspeaker; and the modulation module and the
demodulation module both adopt CD4046 phase-locked loops. According to the
system,
frequency modulation and
demodulation is carried out conveniently and easily by employing the CD4046 phase-locked loops, and
signal transmission is performed by employing the LED light, so that the
confidentiality is good.