Power line communication system

• US 5,264,823 A
• Filed: 11/02/1992
• Issued: 11/23/1993
• Est. Priority Date: 09/28/1990
• Status: Expired due to Term

• Current Assignee: OSRAM Sylvania Inc. (Ams-Osram AG)
• Original Assignee: Motorola Lighting, Inc. (Ams-Osram AG)
• Inventors: Stevens, Carlile R.
• Primary Examiner(s): Crosland, Donnie L.
• Application Number:
  US07/970,535
• Time in Patent Office: 386 Days
• Field of Search: 340/310 R, 340/310 CP, 340/310 A, 455/3.3, 375/37
• US Class Current: 375/238
• CPC Class Codes: H04B 2203/542 using zero crossing information
• CPC Class Codes: H04B 2203/5458 Monitor sensor; Alarm systems
• CPC Class Codes: H04B 2203/5495 having measurements and testing channel
• CPC Class Codes: H04B 3/542 the information being in digital form
• CPC Class Codes: H05B 47/185 via power line carrier transmission

Abstract

Data is transmitted on a power line as a momentary interruption of the power at or near the zero crossing of the current. The interruption is preferably a small fraction of the period of the frequency of the power line. The data is transmitted only to those devices in series circuit with the transmitter. The transmitter combines 60 Hz and 120 Hz clock signals with data from a shift register to interrupt current in a predetermined pattern, in which an interruption of both the positive going and negative going zero crossings define a logic "1" and the absence of interruptions is a logic "0." A data prefix identifies succeeding bits as data. The receiver produces a pulse width modulated signal in response to the data.

Claims

1. A communication system for transmitting bits of data an AC power lines comprising:

a transmitter having switch means connected in series with at least one of said power lines and control means for rendering said switch means non-conductive for predetermined periods during cycles of said alternating current in accordance with the bits of data;

the control means comprising;

first clock pulse generating means for generating first clock pulses in response to each zero crossing of said alternating current;

second clock pulse generating means for generating second clock pulses in response to alternate zero crossings of said alternating current;

combining means for combining said first and second clock pulses to produce a control signal for rendering said switch means non-conductive;

a receiver connected with said AC power lines downstream of said transmitter, the receiver having detection means for detecting whether current on the AC power lines have been interrupted;

whereby during each of said predetermined period when said switch means is non-conductive an interruption of power occurs which is detected by said receiver.

2. The communication system as set forth in claim 1 wherein a plurality of bits of data are transmitted in consecutive cycles of said alternating current.

3. The communication system as set forth in claim 1 wherein control means renders said switch means non-conductive for predetermined periods twice during a given cycle of said alternating current for encoding a predetermined logic level.

4. The communication system as set forth in claim 1 wherein said receiver means comprises:

means for detecting the duration of the periods when said switch means is non-conducting.

5. The communication system as set forth in claim 1 wherein said second clock pulses are phase shifted relative to the zero crossings of said alternating current.

6. The communication system as set forth in claim 1 wherein said second clock pulses are delayed relative to the zero crossings of said alternating current.

7. A receiver for use in a system for controlling lighting devices powered from AC power lines by transmitting bits of control data on said AC power lines, the receiver comprising:

power interruption detector means for producing a pulse in response to each interruption of said alternating current;

pulse duration detection means coupled to the output of said zero crossing detector means for producing a pulse only when the duration of a pulse from said power interruption detector means exceeds a predetermined time;

shift register means coupled to the output of said pulse duration detection means for storing data, said shift register means having parallel data outputs;

logic means coupled to the outputs of said shift register means for analyzing the content of said data;

data register means coupled to the output of said logic means and said shift register means for selectively storing data under the control of said logic means;

timing means coupled to said data register means for producing a pulse width modulated signal in response to said data; and

switch means for connection to one of said AC power lines and responsive to said pulse width modulated signal for being selectively rendered conductive or non-conductive.

8. In a system for communicating over AC power lines, a transmitter comprising:

zero crossing detector means for producing a pulse in response to each zero crossing of said alternating current;

pulse generating means coupled to said power lines for producing pulses synchronized with and at the same frequency as said alternating current;

shift register means for storing data representative of a predetermined power level;

control means connected to said shift register means for causing said data to be serially read out from said shift register means as a series of pulses;

logic means coupled to said zero crossing detector means, said pulse generating means, and said shift register means for combining the outputs thereof to produce a control signal comprising pulses; and

switch means in series with at least one of said AC power lines and responsive to said control signal for being selectively rendered conductive or non-conductive.

9. The system for communicating over AC power lines as set forth in claim 8 wherein some of the data inputs to said shift register means are kept at a fixed voltage to provide the same data on successive loadings of said shift register means and wherein some of the data inputs to said shift register means are not at a fixed voltage to provide variable data on successive loadings of said shift register means.

10. The system for communicating over AC power lines as set forth in claim 8 wherein said logic means includes timing means for determining the duration of pulses in said control signal.

11. The system for communicating over AC power lines as set forth in claim 10 wherein said logic means further comprises timing means for controlling the interval during which said control signal is applied to said switch means.

12. In a system for communicating over AC power lines, a receiver comprising:

zero crossing detector means for producing a pulse in response to each zero crossing of said alternating current;

pulse duration detection means coupled to the output of said zero crossing detector means for producing a pulse only when the duration of a pulse from said zero crossing detector means exceeds a predetermined time;

shift register means coupled to the output of said pulse duration detection means for storing data, said shift register means having parallel data outputs;

logic means coupled to the outputs of said shift register means for analyzing the content of said data;

data register means coupled to the output of said logic means and said shift register means for selectively storing data under the control of said logic means;

timing means coupled to said data register means for producing a pulse width modulated signal in response to said data; and

switch means connected to one of said AC power lines and responsive to said pulse width modulated signal for being selectively rendered conductive or non-conductive.