System and method for data transmission over a power line of a switch mode power supply by frequency modulating the switch frequency thereof

Abstract

A method of transmitting data over a power line of a switch mode power supply system comprises the steps of: encoding a switch frequency of the switch mode power supply with the data; generating a ripple voltage at the encoded switch frequency by the switch mode power supply; conducting the generated ripple voltage over the power line of the system; coupling the ripple voltage from the power line; and decoding the data from the encoded switch frequency of the coupled ripple voltage.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram schematic of a SMPS system suitable for embodying at least one aspect of the present invention.

FIG. 2 is a block diagram schematic of an embodiment for FM encoding a switch frequency of the ripple voltage of an SMPS by modulating the charging current of the saw tooth wave form which produces the switching frequency thereof.

FIG. 3 is an illustration of the variation in the saw tooth wave form caused by the modulation of charging current.

FIG. 4 is a circuit schematic of an exemplary circuit for producing the modulating current according to data content.

FIG. 5 is a block diagram schematic of an exemplary FM decoder unit.

FIG. 6 is a circuit schematic of an exemplary FM decoder unit.

Claims

1. Method of transmitting data over a power line of a switch mode power supply system, said method comprising: encoding a switch frequency of the switch mode power supply with said data;generating a ripple voltage at said encoded switch frequency by the switch mode power supply;conducting said generated ripple voltage over the power line of said system;coupling said ripple voltage from the power line; anddecoding said data from the encoded switch frequency of said coupled ripple voltage.

2. The method of claim 1 wherein the step of encoding includes frequency modulating the switch frequency of the ripple voltage with the data; and wherein the step of decoding includes frequency demodulating the data from the modulated switch frequency of the coupled ripple voltage.

3. The method of claim 2 including producing the switch frequency of the switch mode power supply by a timing waveform governed by a current.

4. The method of claim 3 wherein the step of frequency modulating the switch frequency includes modulating the governing current of the timing waveform.

5. The method of claim 3 wherein the timing waveform is produced by charging a capacitor with a charging current; and wherein the step of frequency modulating the switch frequency includes mixing a modulation current with the governing current to form a composite charging current of the timing waveform.

6. The method of claim 1 wherein the step of encoding includes modulating the switch frequency of the ripple voltage about a rest frequency.

7. The method of claim 2 wherein the step of frequency demodulating includes detecting slopes of the coupled ripple voltage and generating first signals indicative thereof.

8. The method of claim 7 wherein the step of frequency demodulating includes detecting peaks of the first signals and generating second signals indicative thereof.

9. The method of claim 8 wherein the step of frequency demodulating includes filtering the second signals to produce the decoded data.

10. The method of claim 1 wherein the step of decoding includes amplifying the coupled ripple voltage with an auto gain control amplifier.

11. System for transmitting data over a power line comprising: a switch mode power supply operative at a switch frequency for generating a ripple voltage over the power line at the switch frequency;first circuit for encoding the switch frequency of the ripple voltage with said data; andsecond circuit for coupling said ripple voltage from the power line and for decoding said data from the encoded switch frequency of said coupled ripple voltage.

12. The system of claim 11 wherein the first circuit includes a circuit for frequency modulating the switch frequency of the ripple voltage with the data; and wherein the second circuit includes a circuit for frequency demodulating the data from the modulated switch frequency of the coupled ripple voltage.

13. The system of claim 12 wherein the switch mode power supply generates a timing waveform governed by a current for producing the switch frequency thereof; and wherein the circuit for frequency modulating the switch frequency includes a circuit for modulating the governing current of the timing circuit.

14. The system of claim 13 wherein the timing waveform is produced by charging a capacitor with the governing current; and wherein the circuit for frequency modulating the switch frequency includes a circuit for mixing a modulation current with the governing current to form a composite charging current of the timing waveform.

15. The system of claim 11 wherein the first circuit includes a circuit for modulating the switch frequency of the ripple voltage about a rest frequency.

16. The system of claim 12 wherein the circuit for frequency demodulating includes a circuit for detecting slopes of the coupled ripple voltage and generating first signals indicative thereof.

17. The system of claim 16 wherein the circuit for frequency demodulating includes a circuit for detecting peaks of the first signals and generating second signals indicative thereof.

18. The system of claim 17 wherein the circuit for frequency demodulating includes a circuit for filtering the second signals to produce the decoded data.

19. The system of claim 11 wherein the second circuit includes an amplifier circuit for amplifying the coupled ripple voltage with an auto gain control.

20. A vision system for a commercial vehicle comprising: at least one camera for viewing scenes surrounding said vehicle;a switch mode power supply for providing power at a regulated voltage potential over a power line to said at least one camera, said switch mode power supply operative at a switch frequency for generating a ripple voltage over the power line at the switch frequency thereof;first circuit for encoding the switch frequency of the switch mode power supply with data for controlling said at least one camera; andsecond circuit, coupled to said power line and at least one camera, for coupling said ripple voltage from the power line and for decoding said data from the encoded switch frequency of said coupled ripple voltage to control said at least one camera therewith.