Power line communication transmitter with amplifier circuit

1. A transmitter circuit configured and arranged to communicate over power distribution lines that carry power using alternating current (AC) that operates at a power-line frequency, the transmitter circuit comprising:

an amplifier circuit configured and arranged to:

receive a first data signal in the form of a carrier wave that is modulated to represent data bits; and

convert the first data signal to a pulse density modulation (PDM) encoded signal using high frequency pulses that introduce high frequency components;

a low-pass filter configured and arranged to filter the high frequency components of the PDM encoded signal to produce a second data signal, such that the second data signal is an amplification of the first data signal; and

a coupling circuit configured and arranged to communicatively couple the second data signal from the low-pass filter to the power distribution lines and to filter the power-line frequency.

2. The transmitter of claim 1 , wherein:

the second data signal is a differential signal having a first differential component and a second differential component;

the amplifier circuit is configured to convert the first signal into a first PDM encoded signal and a second PDM encoded signal; and

the low-pass filter is configured and arranged to filter high frequency components of the first and second PDM encoded signals to produce the respective first and second differential components of the second data signal.

3. The transmitter circuit of claim 1 , wherein the second data signal has a frequency and a phase that are the same as a frequency and phase of the first data signal, and has a greater amplitude than the first data signal.

4. The transmitter circuit of claim 1 , wherein the PDM encoded signal is encoded using a pulse rate frequency that is greater than a frequency of the first data signal.

5. The transmitter circuit of claim 4 , wherein:

the pulse rate frequency is greater than or equal to 300 KHz; and

the first data signal has a frequency less than or equal to 20 KHz.

6. The transmitter circuit of claim 5 , wherein the first data signal has a frequency greater than 2 KHz.

7. The transmitter circuit of claim 1 , wherein the amplifier circuit is a Class D amplifier.

8. The transmitter circuit of claim 1 , wherein the coupling circuit includes:

a transformer;

a first series capacitor coupled to a primary winding of the transformer; and

a second series capacitor coupled to a secondary winding of the transformer.

9. The transmitter circuit of claim 1 , wherein the first data signal is a phase-shift encoded data signal.

10. The transmitter circuit of claim 1 , wherein the PDM encoded signal is encoded using pulse width modulation.

11. The transmitter circuit of claim 1 , further including:

a data signal generation circuit configured and adapted to:

select one of a plurality of carrier frequencies; and

modulate a carrier signal, having the selected one of the plurality of carrier frequencies, to encode data bits to produce the first data signal;

a current sensing circuit configured and arranged to sense current provided to the power distribution lines by the coupling circuit; and

a feedback circuit configured and arranged to:

adjust a gain of the amplifier circuit as a function of the sensed current and the selected one of the plurality of carrier frequencies.

12. The transmitter of claim 11 , wherein the feedback circuit is configured and arranged to adjust the gain of the amplifier circuit by performing the steps including:

setting the gain of the amplifier circuit to a lowest gain setting of the amplifier circuit; and

in response to the sensed current being less than a reference current, increasing the gain of the amplifier circuit.

13. The transmitter of claim 11 , wherein the feedback circuit is configured and arranged to adjust the gain of the amplifier circuit in response to changes in load impedance, after setting the gain of the amplifier circuit.

14. A method for communicating data over power distribution lines that carry power using alternating current (AC) that operates at a power-line frequency, the method comprising:

using a processing circuit configured and arranged to amplify a first data signal by performing operations including:

converting the first data signal to a pulse density modulation (PDM) encoded signal; and

filtering high frequency components of the PDM encoded signal to produce a second data signal, the second data signal being an amplification of the first data signal;

communicating the second data signal from the processing circuit to the power distribution lines;

filtering the power-line frequency between the power distribution lines and the processing circuit;

selecting one of a plurality of carrier frequencies;

modulating a carrier signal, having the selected one of the plurality of carrier frequencies, to encode data bits to produce the first data signal;

sensing current provided to the power distribution lines by the second data signal; and

adjusting a gain of the amplification of the first data signal as a function of the sensed current and the selected one of the plurality of carrier frequencies.

15. A method for communicating data over power distribution lines that carry power using alternating current (AC) that operates at a power-line frequency, the method comprising:

using a processing circuit configured and arranged to amplify a first data signal by performing operations including:

converting the first data signal to a pulse density modulation (PDM) encoded signal; and

filtering high frequency components of the PDM encoded signal to produce a second data signal, the second data signal being an amplification of the first data signal;

communicating the second data signal from the processing circuit to the power distribution lines; and

filtering the power-line frequency between the power distribution lines and the processing circuit, wherein:

the second data signal is a differential signal having a first differential component and a second differential component; and

the processing circuit is configured to:

convert the first signal into a first PDM encoded signal and a second PDM encoded signal; and

filter high frequency components of the first and second PDM encoded signals to produce the respective first and second differential components of the second data signal.

16. The method of claim 14 , wherein the PDM encoded signal is encoded using a pulse rate frequency that is greater than a frequency of the first data signal.

17. The method of claim 16 , wherein:

the pulse rate frequency is greater than or equal to 200 KHz; and

the first data signal has a frequency less than or equal to 20 KHz.

18. The method of claim 17 , wherein the first data signal has a frequency greater than 2 KHz.

19. The method of claim 14 , wherein the converting the first data signal to the PDM encoded signal includes processing the first data signal with a Class D amplifier.

20. An apparatus including:

the transmitter circuit of claim 1 , and

a collector circuit connected to a command center of a power line communication network, and configured and arranged to receive the second data signal from the transmitter circuit over the power distribution lines.

21. The apparatus of claim 20 , wherein the first data signal is associated with power meter information.

22. The apparatus of claim 20 , further including a command center of a power line communication network.