Passive power line communication device and method

Abstract

The present invention relates to the field of transferring information over the power line to and/or from the device or devices powered by said power line. Devices that may be powered by either alternating current (AC) or direct current (DC) their operation may be controlled by which type of power they are receiving, AC, +DC or −DC. Data may also transmitted by alternating the polarity of each half cycle of the power line, on a one half by one half cycle basis, in a controlled manner such that the powered device may receive such data to control its mode of operation. A method of reducing the heat in the switching devices and a system of encoding the data such that each powered device may have a different address and therefore may return data when requested is also disclosed.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application of U.S. Patent Application Ser. No. 10/839,224 filed May 6, 2004, which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to the field of transferring information to and/or from a device or devices over the same power line from which the device or devices are receiving their power.

BACKGROUND OF THE INVENTION

There are many varied public domain circuits involving transmitting information data on a power line while that line is also supplying power to devices connected to it. This is normally referred to as PLC or Power Line Carrier. The electric power utility companies have been using it for years. There are also proprietary methods of accomplishing such data transmission. My Pat. No. 5,264,823 discloses one such method. All of the current methods have one or more draw backs that prevent them from being used in all applications. These draw backs include loading of the data signal placed on the power line by the devices being powered by that line, electrical noise picked up by the line or created by the loads on the line being interpreted as valid data and cross talk between other data sources. Some prior art circuits such as my patent referenced above involve changing the shape of the sine wave present on the power line and, as a result introducing harmonic distortion back to the utility supplying the power this and other prior art circuits involve connecting an electronic switching device in series with the line supplying the power. Since all electronic switching devices have some forward voltage drop across them which, when multiplied by the current flowing through them, produces undesirable heat which must be dissipated in some manner.

SUMMARY OF THE INVENTION

Accordingly, the above problems and difficulties are addressed by the present invention which incorporates a method of changing how the power is supplied by the power line to the connected load. When supplying power to devices that use a bridge rectifier, which converts the incoming AC voltage to DC voltage, the input power may be AC, +DC or −DC with no adverse effect on the operation of the powered device. In its simplest form the disclosed invention may cause the powered device or devices to operate in two separate states in response to whether AC or DC voltage is applied to its input. The next level of operation would be to cause the powered device to operate in three different on states depending on whether AC, +DC or −DC is applied to its input. In the concepts more complex form, the three different types of drive can be alternated from one to the other as a means of transmitting data from the power source to the devices being powered without creating any harmonic distortion.

Because only the devices down stream from the source of power receive the information there is no possibility of cross talk with devices powered on separate legs of the same power source. Additionally, because it is normally a fairly direct run for the switch panel to the powered devices it is very easy to send higher frequency AC on a DC power line specially if the higher frequency is transmitted from the powered devices at or near the zero crossing point of the AC power line. Thus, a powered device may be addressed in the manner discussed above and then it may respond to the power source by sending AC frequency back to the power source during a following DC interval. A typical application of the inventive concept disclosed herein would be to drive one or more controllable output fluorescent ballasts where the data supplied to the powered ballast may determine the light level output as well as monitor the operation of the ballast.

The problem of heat generated by the inserted electronic switching device is greatly reduced by the addition of a relay that has no significant forward voltage drop and therefore no generated heat while the relay contacts are closed. In applications where data is transmitted over the power line by switching the polarity of the line voltage these data transmissions are of a relatively short duration. Including a relay that effectively shorts out the switching device when it is not transmitting data can almost completely eliminate the heat generation problem.

In summation of this section of the of disclosure, the invention is a simple means of controlling powered devices by altering the type the power supplied to said devices. One aspect of the invention to vary or modulate the type of power supplied in order to send data to an individually addressed powered device as well as to allow that addressed powered device to respond as to its condition of operation. All the switching of the type of power supplied to the device or devices is done at the time the voltage is passing though zero and only complete half cycles are used thus invention operates without introducing any harmonic or other form of distortion on the source of AC power or to powered devices. Another aspect of the invention is that the is data sent to the powered devices in such a manner that it is not possible for powered devices to a different unit of the disclosed invention but connected to the same power source to receive data intended for powered devices connected . The invention may optionally include a low impedance device, such as a relay, to minimize any heat generated when the invention is not switching the type of power to the powered device or devices.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation, together with further objects and advantages thereof, may best be understood with reference to the following description, taken in connection with the accompanying drawings in which:

FIG. 1 is a block diagram of a typical application of the disclosed invention being used to control a series of fluorescent lighting fixtures.

FIG. 2 is a schematic representation of one aspect of the disclosed concept in its simplest form;

FIG. 3 is a schematic representation of a more complex three level control using the disclosed concept;

FIG. 4 is a schematic representation of the preferred embodiment of the disclosed invention where the type of power is alternated in such a manner as to send data to the powered devices;

FIG. 5 depicts a graphic representation of one method of coding the switching of the types of power to send data to the powered devices; and

FIG. 6 shows how the data of FIG. 5 is organized into a word with each of the multiple words associated with one or more of the powered devices connected to its output.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 1, the disclosed invention is contained in block 1, the Power Switching Module. AC line power enters at terminals 2 and 3 and is supplied to the powered devices, in this case fluorescent fixtures 4, by wires 5 and 6. Power Switching Module 1 may contain the circuits depicted in FIGS. 2, 3 or 4 or any other circuit that is capable of supplying AC, +DC or −DC in response to local or remote selection.

FIG. 2 depicts the simplest form of the preferred embodiment. The output at terminals 10 and 11 is either the same AC power that is input to the device or +DC power depending upon the position of switch S2. Switch S1 is an optional off/on switch. With switch S1 in the shown position, power flows on wire 7 to one set of contacts on switch S2, through the switch to wire 5 which is connected to output terminal 10 and on wire 8 to the other set of contacts on switch S2, through the switch to wire 6 connected to output terminal 11. Wires 7 and 8 also connect to pins 1 and 3, which are the AC inputs to bridge diode D1. The output of bridge diode D1, Pins 2 and 4, is connected to the other set of contacts of switch S2. When the position switch S2 is as shown the output at 10 and 11 is the same as the input at 2 and 3. When S2 is set to its other position the outputs 10 and 11 are connected to diode bridge D1 and the output will be +DC. The fluorescent fixtures 4 of FIG. 1 would, in this case, sense this change from AC to DC and change the light level to some predetermined amount.

FIG. 3 is the same as FIG. 2 except that a second switch S2 has been added. In this case, switch S2 still shifts the output at 10 and 11 from AC to DC but when switch S2 is in the DC output position switch S3 switches the output to and from +DC or −DC. When the circuit of FIG. 3 is incorporated in block 1 of FIG. 1 then the powered devices, in this case fluorescent fixtures, can be switched to three states of operation or light levels, as would be the case with fluorescent fixtures.

Referring now to FIG. 4, AC input voltage enters at points 2 and 3 connected to bridge rectifier DB1 by lines 31 and 32 after passing through optional inductor L1. The AC input is also connected by the same lines 31 and 32 to the contacts of relay 36 that are normally closed when the relay is not energized, thus when the relay is not energized, the AC voltage provided at input 2 and 3 is connected to outputs 10 and 11 directly. The plus and minus connections of bridge rectifier DB1 are connected by a series of switching devices S4, S5, S6 and S7 to the contacts on relay 36 that are connected when the relay is energized, this is done by lines 37 and 38.

Which one of the switching devices S4 through S7 is closed at any one time is controlled by the controller 35. Switch S4 is controlled by a line 18 connected to the drive output DR-S4. Switch S5 is connected and controlled through line 15 to drive output DR-S3. Switch S6 is connected by line 12 to drive output DR-S2 and switch S7 is controlled by a line 9 connected to output DR-S1 of controller 35. Switching devices S4 through S7 may be either field effect transistors, bipolar transistors, silicon controlled rectifiers, triacs, or gate turnoff thyristors. They may also any other switching device that can switch fast enough to turn on and off for a controlling a half cycle of the typical AC power line. If the output at 10 and 11 is to be (+) DC on 10 relative to 11, then, the controlling device closes switch S4 such that the plus voltage from the bridge rectifier DB1 is connected to the output 10 and closes switch S7 for the return path from output 11 back to the minus side of bridge rectifier DB1 by other relay contact. If a (−) DC output is desired, with minus on pin 10 relative to pin 11, then, switch 6 is closed, supplying that minus to pin 10 by top set of relay contacts, and the return path from output 11 is supplied back to the plus side of the bridge rectifier by switch 5 through the other relay contact.

The controller detects the zero crossing point of the AC line voltage through sensing resistors R1 and R2 connected to each side of the AC line input. The controller may activate the switches S4 through S7 in any sequence such as to provide any variation in half cycle outputs, either positive or negative, at pins 10 or 11. This will be discussed more below in terms of how to transmit data to the units connected as shown on FIG. 1. Such an arrangement of positive and negative pulses is depicted FIG. 5 and will be explained in the discussion of that figure. Using this method it is possible for each of the devices connected down line from the unit at outputs 10 and 11 to be addressed and supplied with data to affect and monitor their operation.

The common reference point, the controller, at VSS is line 19, which is connected to the negative side of bridge rectifier DB1, such that one outside of the output is common to the controlling device. This allows a sensor connected at resistor R4 connected to line 13, 10 output, by line 43 to the feedback input of the controller. This will be discussed in more detail shortly.

A separate isolated logic power supply, 42, supplies the plus and minus DC for the controller and is tied to the common 19. AC input to the logic power supplies, supplied lines 31 and 32, which are connected on the AC side of the device. In the event feedback of information from the control devices is feedback on the power line and detected on line 13 by a resistor or 4 and line 43 to the feedback input of the controller. Thus when the particular combination of half cycles is detected by the control device, thus that feedback is requested the control device sends a burst of higher frequency at the zero crossing point which can then be detected by the controller and interpreted. This again will be discussed in more detail shortly. This particular embodiment, shown in FIG. 4, is different from the embodiment shown in the FIG. 4 of my previous patent in that the bridge rectifier is composed of triacs, optically triggered. The significant difference between the two designs is that when triacs are used in a bridge configuration they tend to have a two volt forward drop and in in a bridge configuration there is a total of a 4 volt forward drop. If the particular line feeding the control devices needs typically 15 amps, 15 amps times the 4-volt drop produces a wattage loss of the 15 times 4, or 60 watts of heat. This heat must be dissipated in some manner. In the current FIG. 4, the bridge rectifier would have approximately a 2-volt drop, which would only amount to 30 watts of heat, and the switches may be selected to be devices that have very low forward voltage drops, as example a bipolar transistor or an appropriately selected field affect transistor, such that in a 15-volt circuit, at least 15 to 20 watts of heat may be eliminated. Of course if data is only transmitted approximately one percent of the time, and during the rest of the time the relay is de-energized, allowing a current to flow directly from the line to the power devices, no heat will be generated during 99 percent of the time and thus, 60 watts translates to 6 tenths of a watt on an average basis, which is quite acceptable in most situations. Since the relay is an electromechanical device, it is selected to one that opens and closes rapidly enough that no great amount of current is being conducted during the opening and closing time as the controller synchronizes this time with the zero crossing of the AC line voltage. In the currently pending patent application No. 10/839,224, which is incorporated herein by a reference including all its figures, the triac bridge can handle the load during the time the relay is opening and closing, which is a slight advantage over the embodiment depicted in the current FIG. 4. This advantage has to be weighed against the amount of heat generated and how often data needs to be transmitted.

Logic power to operate the microprocessor, the optotriacs and the relay is supplied by Logic Power Supply 16 which may be any form of the many power supplies on the market today that converts the AC line power, shown supplied at pins 1 and 3, with an output of, in this case, +5V shown at pin 2 and the common reference at Pin 4. The +5V is distributed on wire 17 to each optotriac, the relay RL1 and the microprocessor U1 at the Vdd pin 14. The +5V is also output on line 19 for operation of the Photocell or other external control devices, as discussed below. The 0 V reference from the power supply on line 17 is also output for external control devices for convenience even though it is common to one side of the AC power line.

The software in the microprocessor U1 may develop any number of code sequences that the powered devices connected to the Power Switching Module's output are programmed to receive and decode. To demonstrate how data may be transmitted, FIGS. 5 and 6 depict one coding sequence to accomplish the required date transfer. Refer now to FIG. 5 which depicts the internal coding of a word of data. The start and end of each data word is ‘marked’ by a marker of two AC line cycles 24. In between the start and end markers there is a series ‘1’ and ‘0’ digital data bits. A ‘1’ bit is represented by two positive AC line half cycles 25 while a ‘0’ bit is represented by two negative AC line half cycles 26. Since each data bit, either ‘1’ 25 or ‘0’ 26, consist of two half cycles of the same polarity they are easily distinguished from markers 24 in which each half cycle changes polarity. Such a system increases the reliability of the data transmission.

FIG. 6 depicts a complete data word as it may be broken down. Each data word contains as series of bits comprising an address 27, following the start marker, that identifies the connected powered device for which the data is intended. More than one device may have the same address if the devices with the same addresses are to have the same performance. The number of address bits depends on the number of connected devices. As an example, a four bit address would allow the addressing of sixteen different powered devices. Following the address, a number of bits 28 are allocated for data to be transmitted to the addressed device. Again as an example, if a fluorescent fixture were being addressed, six bits of data could be used to request sixty-four different light levels one of which could be off. Optionally, a portion or the word 30 may be set aside for return data from the addressed device. In this case, during the time that the return data is expected the voltage to the devices may be −DC during which time the powered device places relative high frequency positive bursts on the power line. These high frequency bursts would be sensed by the microprocessor, in this case via DC blocking capacitor C3 connected between power wire 9 and microprocessor at pin 2. In the case that data return is desired, it may be necessary to add the optional inductor L1 to prevent the high frequency, generated by the power devices during data return, from getting on the power line and effecting other systems connected to the same power line. Also if the data return feature is utilized each powered device must have its own address.

One of the advantages of the disclosed concept is that only devices connected down line from the Power Switching Module are effected by data transfer out and therefore there can be no cross talk between other devices connected to the same power source. The only possibility of cross talk would be when powered devices are sending information back using high frequency bursts as discussed above. In this event the problem is resolved by adding the optional inductor L1 to block the high frequency bursts from the input power source.

Referring back to FIG. 4, it can be seen that there may be three different methods of determining what data needs to be sent down line to the powered devices. In the case of the example depicted in FIG. 1 the light output of the fluorescent fixtures connected to the output of the Power Switching Module may be controlled in three different ways. A photocell input 22, which monitors the amount of light on the surface illuminated by the fluorescent fixtures, can tell the microprocessor to transmit code to tell the fluorescent fixtures to adjust the amount of light output to maintain a constant amount of light on the illuminated surface. The amount of light desired may be set, with or without the photocell feedback, by the setting of the local control potentiometer R4. Serial Clock 18, Serial Data Out 20 and Serial Data In 21 connected at pins 10, 8 and 7 respectively of microprocessor U1 represent an RS232 serial type data port. This port would allow a remote computer to program the devices powered by the disclosed invention utilizing the programming method discussed above. Such a remote computer control system could also be a DALI control protocol.

During the time that data in not being sent or received, which would normally be 99% of the time, the relay RL1 is in the relaxed position and the output of the Power Switching Module is connected to its input. When data is to be transferred the appropriate optotriacs are switched on to carry the load before the relay is activated. This is done synchronized with the power line voltage to minimize any wear on the relay contacts. When all the data has been transferred the optotriacs are kept operational until the relay RL1 has switched to carry the AC current. Resister R1 and capacitor C1 are connected as a snubber across one set of the relay contacts to carry the load for the very short time the relay contacts are moving. Resistor R2 and capacitor C2 provide the same snubbing action for the other set of relay contacts.

Although the present invention has been described in connection with preferred embodiments thereof, many variations and modifications will now become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited, not by the specific disclosure herein, but only by the appended claims.

Claims

1. A device for connection to a power line that communication system for connection to a source of alternating current and voltage operable to supply power to and communicate with one or more powered devices comprising:

means for converting for selecting source of alternating current and voltage for converting said source of alternating current and voltage to direct current and voltage;

circuitry for selecting the polarity, either positive or negative, of the output of said assemblage of components consisting of four diodes connected in a bridge configuration the output of which is connected to of four switching devices interconnected in the manner of a full bridge with the first and second switching device connected in series across the output of the four diode bridge configuration, the third and forth switching devices connected also in series across said four diode bridge configuration with the output of said full bridge configuration being between the junction of said first and second switching device as one terminal and the junction of said third and forth switching devices as the second terminal; and

a controlling means connected to each of the four switching devices comprising said full bridge configuration said controlling means synchronized with the source of alternating current and voltage is such a manner as to cause said switching devices to switch on and off at or near the zero crossing point of the source of alternating current and voltage such as to supply individual half cycles, either positive or negative as required, at twice the frequency of the source of alternating current and voltage to said one or more powered devices.

2. The power source and data communication system of claim 1 wherein said switching devices are bi polar transistors.

3. The power source and data communication system of claim 1 wherein said switching devices are field effect transistors.

4. The power source and data communication system of claim 1 wherein said switching devices are silicone controlled rectifiers.

5. The power source and data communication system of claim 1 wherein said switching devices are gate turn off controlled rectifiers.

6. The power source and data communication system of claim 1 wherein an extremely low impedance switching device is connected across said assemblage of components connected to said source of alternating current and voltage for converting said source of alternating current and voltage to direct current and voltage, said extremely low impedance switching device connected to said controlling means which causes it to conduct when conventional alternating current and voltage power is to be supplied to said one or more powered devices and to be non conductive when half cycles of direct current are supplied to said powered devices to relieve said means for converting said source of alternating current and voltage to direct current and voltage from conducting any current during said period.

7. A power source and data communication system for connection to a source of alternating current and voltage operable to supply power to and communicate with one or more powered devices comprising:

a assemblage of components connected to said source of alternating current and voltage for converting said source of alternating current and voltage to half cycle sinusoidal pulses of either polarity as a source of power for said one or more powered devices;

a means for communicating with said one or more powered devices where individual half cycles of the power line frequency represent digital data bits with one polarity of half cycle pulse representing a zero bit and the opposite polarity representing a one bit.

8. A power source and data communication system of claim 7 wherein a digital data bit is recognized as valid only when two or more half cycle pulses of the same polarity occur one immediately after the other.

9. A power source and data communication system of claim 8 wherein two complete cycles of the AC line power represent the beginning or start of a code sequence.

10. A power source and data communication system of claim 7 wherein the zero and one bits are assembled into a series of bits comprising a code sequence with each code sequence having a grouping of bits indicating the address of one of the said powered devices with the balance of the bits in said code sequence comprising instructions to the powered device whose address is contained in the grouping of bits indicating the which power device is being addressed.

11. A power source and data communication system of claim 9 wherein the code sequence contains a designated space within its sequence of data bits within said code sequence where the addressed powered device can place a signal of a frequency sufficiently higher then the power line frequency as a means of communicating data feedback from said addressed powered device to the assemblage of components connected to said source of alternating current and voltage.

12. A power source and data communication system of claim 9 wherein certain of the data bits within the code sequence are recognized by all the powered devices whether or not that powered device has been addressed to provide for commands universal to all power devices.