Method and system for optical communication
In various embodiments of the present invention data is transmitted in light emitted by a light source by generating a continuous-time data signal and generating, based thereon, a drive signal that provides power to the light source, thereby causing the light source to emit light; variations in the amplitude of the drive signal represent information in the continuous-time data signal. A change in average power delivered to the light source as a result of the variations in the amplitude of the drive signal is detected and power to the light source is adjusted to compensate.
1. A system comprising:
a data source for generating a data signal;
a light emitting diode (LED) light source;
an electrical filter to remove high frequency edges or signals from the data signal thereby generating a filtered signal;
an amplifier coupled to the electrical filter to convert the filtered signal into a driver current to drive the LED light source;
a power converter to convert an alternating current (AC) wall power into a direct current (DC); and
a control circuit incorporated into the amplifier to regulate the DC received from the power converter into the driver current to drive the LED light source.
2. The system of claim 1 , wherein:
the data source generates a pulse-width-modulation (PWM) signal as the data signal; and
the high frequency edges or signals removed by the electrical filter are a carrier frequency in the PWM signal.
3. The system of claim 2 , wherein:
the electrical filter filters the PWM signal from the data source and generates a continuous time waveform as the filtered signal.
4. The system of claim 1 , wherein the amplifier is a linear converter which linearly converts the filtered signal into the driver current to drive the LED light source.
5. The system of claim 1 , wherein the amplifier is a switching amplifier.
6. The system of claim 5 , wherein:
the power converter converts the AC wall power into constant DC voltage; and
the switching amplifier is a buck or buck derived topology circuit.
7. The system of claim 5 , further comprising:
the power converter converts the AC wall power into constant DC current; and
wherein the switching amplifier is a buck-boost or boost topology circuit.
8. The system of claim 5 , wherein:
the data source generates a pulse-width-modulation (PWM) signal as the data signal to control the switching amplifier; and
the switching amplifier includes one or more switch-control terminals to receive the PWM signal as an input and amplifies the PWM signal.
9. The system of claim 8 , wherein:
the electrical filter includes one or more inductors and capacitors connected to an output of the one or more switch-control terminals of the switching amplifier to remove the high frequency edges or signals from the amplified PWM signal.
10. The system of claim 8 , wherein the PWM signal input of the switching amplifier includes a desired modulation signal and a direct current (DC) operating point for the switching amplifier to provide an average DC to the LED light source that is equivalent to the average DC without modulation.
11. The system of claim 10 , wherein:
the power converter converts the AC wall power into constant DC voltage; and
the DC operating point for the switching amplifier is set using a voltage reference to which the desired modulation signal is added.
12. The system of claim 10 , wherein:
the power converter converts the AC wall power into constant DC current;
the LED light source is part of a string of LEDs having a measured LED string voltage; and
the DC operating point for the switching amplifier is set using a voltage reference such that voltage input to the switching amplifier equals the measured LED string voltage.
13. A system comprising:
a data source for generating a data signal;
a light emitting diode (LED) light source;
a digital-to-analog converter (DAC) to remove high frequency edges or signals from the data signal thereby generating a filtered signal by sampling the data signal at intervals and outputting a voltage or current indicative of level, pulse width, or frequency of the data signal;
an amplifier coupled to the DAC to convert the filtered signal into a driver current to drive the LED light source;
a power converter to convert an alternating current (AC) wall power into a constant direct current (DC);
a control circuit incorporated into the amplifier to regulate the constant DC received from the power converter into the driver current to drive the LED light source; and
wherein the amplifier is a switching amplifier having a buck or buck derived topology circuit.
14. The system of claim 13 , wherein the amplifier is a linear converter which linearly converts the filtered signal into the driver current to drive the LED light source.
15. A system comprising:
a data source for generating a data signal;
a light emitting diode (LED) light source;
a digital-to-analog converter (DAC) to remove high frequency edges or signals from the data signal thereby generating a filtered signal by sampling the data signal at intervals and outputting a voltage or current indicative of level, pulse width, or frequency of the data signal;
an amplifier coupled to the DAC to convert the filtered signal into a driver current to drive the LED light source;
a power converter to convert an alternating current (AC) wall power into a constant direct current (DC);
a control circuit incorporated into the amplifier to regulate the constant DC received from the power converter into the driver current to drive the LED light source; and
wherein the amplifier is a switching amplifier having a buck-boost or boost topology circuit.
16. The system of claim 15 , wherein the amplifier is a linear converter which linearly converts the filtered signal into the driver current to drive the LED light source.
17. A system comprising:
a data source for generating a data signal;
a light emitting diode (LED) light source;
a digital-to-analog converter (DAC) to remove high frequency edges or signals from the data signal thereby generating a filtered signal by sampling the data signal at intervals and outputting a voltage or current indicative of level, pulse width, or frequency of the data signal;
an amplifier coupled to the DAC to convert the filtered signal into a driver current to drive the LED light source;
wherein the data source generates a pulse-width-modulation (PWM) signal as the data signal to control the amplifier; and
the amplifier includes one or more switch-control terminals to receive the PWM signal as an input and amplifies the PWM signal.
18. The system of claim 17 , wherein the DAC includes one or more inductors and capacitors connected to an output of the one or more switch-control terminals of the amplifier to remove the high frequency edges or signals from the amplified PWM signal.
19. The system of claim 17 , wherein the PWM signal input of the amplifier includes a desired modulation signal and a direct current (DC) operating point for the amplifier to provide an average DC to the LED light source that is equivalent to the average DC without modulation.
20. The system of claim 17 , wherein the amplifier is a linear converter which linearly converts the filtered signal into the driver current to drive the LED light source.