JP5008145B2 - Digital control of electronic ballast using AC power line as communication medium - Google Patents

Description

  There are various ways of communicating via power lines known in the prior art. These prior art efforts to communicate over the power line range from simply applying the disturbance to the power line once per power cycle to communicating with the high frequency carrier of the power line. Many of these communication configurations are functional, but have been subject to many technical and economic disadvantages that make them unsuitable in practice. For example, US Pat. No. 4,348,582 proposes a power line communication system described in the circuit of FIG. In order to generate the notch 2 in the power signal 4 of the AC line 10, the silicon controlled rectifier (thyristor) 6 (SCR) controlled by a set of control circuits 8 is before the AC voltage zero crosses from positive to negative. For a short time, approximately 1 millisecond. While the SCR 6 is in a conducting state, the voltage applied to the load 12 is near zero. This causes a notch in the AC power supply signal 4 as shown in FIG. The receiver circuit of the load 12 detects the presence or absence of a notch and interprets it as digital data.

  The above solution has several drawbacks. First, the transmission rate is simply 60 bits / second because the notch is only introduced in the half cycle from positive to negative. The SCR cannot be blocked by the gate signal. If the SCR conducts immediately after the zero crossing, the power line is shorted through the SCR for half a cycle of the power signal that releases the fuse and immediately destroys the functional capability of the circuit.

  Therefore, there is a need for a new and improved method of using an AC power line as a communication medium.

  Electronic ballasts are typically low cost products that are manufactured and purchased in relatively large numbers. Therefore, it is important that no power line communication system for use with electronic ballasts (ballasts) dramatically increase the cost of individual ballasts.

  Embodiments of the present invention are directed to a system for providing communication between a central controller and at least one electronic ballast using an AC power line as a communication medium. The system includes a bridge rectifier for rectifying the AC power line signal propagating to the AC power line to generate a rectified power line signal. When activated, the shorting member generates a short circuit condition in the AC power line. The control circuit includes a phase detection circuit for monitoring the output of the bridge rectifier and determining when to activate the shorting member based on the output. The short-circuit means is preferably a MOSFET. The electronic ballast receiver detects a short circuit. The dimming function of the electronic ballast is controlled based on a number of short circuit conditions detected by the receiver. The short circuit condition is preferably generated only when the AC power line signal has a voltage potential that is not more than 10% of the maximum voltage potential of the power line signal and is just before the zero crossing by the AC power line signal.

  Another embodiment of the present invention is an apparatus for enabling communication between an electronic ballast controller and at least one electronic ballast through an AC power line having an AC power signal supplying power to the at least one electronic ballast. Directed. The apparatus includes a controller configured to selectively short the AC power line approximately when the AC power signal changes from negative to positive or from positive to negative to produce a stretched zero cross. Yes. Preferably, the MOSFET is used to selectively short the AC power line and generate an extended zero cross. The controller includes a bridge rectifier for rectifying the AC power signal and a phase detection circuit for monitoring the output of the bridge rectifier to determine when to short the AC power line. The AC power line is preferably shorted just before the polarity change of the AC power signal. A receiver positioned in at least one ballast is configured to detect the presence or absence of a stretched zero cross when the power line signal changes polarity. The presence or absence of an extended zero cross is used by the ballast to control the dimming function of the ballast.

  Yet another embodiment of the invention is directed to a method of enabling communication between a controller and at least one electronic ballast over an AC power line that supplies power to the at least one electronic ballast. In accordance with this method, the controller is used to selectively stretch the zero crossing that occurs when the AC power line power signal transitions from positive to negative polarity or from negative to positive polarity. The power signal is rectified and the rectified power signal is used to control the occurrence of zero cross stretching. Zero cross extension is generated by selectively shorting the AC power line. The selective short circuit occurs just before the polarity change of the AC power signal. The AC power line is preferably shorted with a MOSFET. The presence or absence of zero cross extension when the power line signal changes polarity is detected by at least one electronic ballast. The presence or absence of the zero cross extension is interpreted according to a predetermined code to enable communication between the controller and at least one electronic ballast. Preferably, the zero cross extension is used to transmit the desired dimming amount to at least one electronic ballast. In such an embodiment, the ratio between the stretched zero cross and the unstretched zero cross is used to transmit information from the controller to at least one electronic ballast.

  The present invention is directed to a power line communication system for providing communication capability between a control module and at least one electronic ballast. In particular, the preferred embodiment of the present invention is directed to a process that enables communication between a central controller and a set of electronic dimming ballasts operated according to an energy management system. These communications are enabled by a power line communication controller that transmits digital data via the AC power line of the lighting branch circuit and an electronic ballast that filters data from the AC power signal. Since the ratio of ballast to power line communication system controller is preferably in the range of 20/1 up to 60/1 and cost is a major factor in the marketability of such systems, this preferred system is relatively It includes disturbances in the power line that are easily detected by inexpensive circuits. Embodiments of the present invention also include an effective communication protocol that converts transmission data into dimming data for ballast.

  Referring to FIG. 3, a power line communication circuit according to the present invention is shown. The circuit comprises a bridge rectifier 16 connected to an AC line input 18 that provides a load 20. A MOSFET 22 controlled by a set of control circuits 24 is used to generate notches in the power signal. In particular, a notch for a power communication system is induced in the power line in the following manner. The control circuit 24 includes a phase detection circuit that monitors the output voltage 26 of the bridge rectifier 16 as shown in FIG. When the rectified voltage 26 approaches the zero voltage cross, the MOSFET 22 becomes conductive. MOSFET 22 remains on until the penetrating current returns to zero. During the conduction of the MOSFET 22, the supply voltage to the load 20 is maintained near zero. This creates a desired stretched zero cross, i.e., a notch that is used to digitally transmit information on the power line. The circuit of FIG. 3 allows transmission of 1 bit of information every half cycle of the AC waveform. In this way, a 60 Hz standard power signal can be used to transmit 120 bits / second of data.

  An isolation inductor 28 is preferably positioned between the AC line input 18 and the notch generation circuits 16, 22 and 24. The isolation inductor 28 prevents notches generated in the power signal supplied to the load 20 from propagating the power line to the AC line input 18 and thereby causing a failure in unintended branches of the power supply network. To prevent. The inductor 28 makes it possible to build several different communication systems that are independent of each other and isolated from each other.

  The bottom waveform 32 of FIG. 5 is an output voltage waveform of a detection circuit constructed in accordance with an embodiment of the present invention showing notch disturbances at the rising end 38 and the falling end 40 of the AC power line voltage 42. By using the MOSFET, it is possible to control the on / off of the notch generation circuit. The receiver detection circuit interprets the notch as a series of pulses 32 that determine whether the pulse width indicates a notch 34 or a non-notch 36. Preferably, the wider pulse 34 corresponds to the presence of a notch and the narrower pulse 36 corresponds to the absence of a notch.

  In an embodiment of the invention directed to an electronic dimming ballast system, each ballast has a detection circuit that monitors the AC power signal for the presence or absence of a power line communication system induced notch. The microcontroller in the ballast measures the pulse width and determines the presence or absence of a notch. One skilled in the art will appreciate that there are a myriad of ways in which a series of pulses can be decoded and converted to digital data. In a particularly preferred embodiment of the invention, the ratio of notch to non-notch corresponds to the desired brightness level of the electronic dimming ballast. For example, if a non-notch is transmitted, each of the branch circuit ballasts receiving communications based on the notch is set to full brightness. When the notch is induced every half cycle, each ballast is set to full dimness. If the other half cycle has a notch, the ballast is set to 50% brightness.

  The embodiments of the present invention described above provide several improvements over the prior art. First, the use of a bridge rectifier allows notches to be generated every half cycle, allowing 120 bits / second data transmission, ie twice that of the prior art circuit. Second, the use of a MOSFET as a short circuit semiconductor device in a power line communication circuit provides the ability to control the on / off operation of the short circuit device, thereby preventing the potential for failure of the short circuit condition. Third, the use of separate inductors allows the use of a power line communication circuit in each branch of the circuit without the induced notch interrupting the supply voltage supplied to the other branches.

  A novel and useful specific example of “digital control of electronic ballast using an AC power line as a communication medium” has been described, but such references are not included in the claims, except as defined in the claims. It is not intended to be construed as limiting the scope of the invention.

FIG. 1 is a prior art circuit for generating a notch in an AC power signal. FIG. 2 is a prior art power line communication signal having a notch in the positive to negative transition of the AC power signal. FIG. 3 is a circuit diagram showing an embodiment of the present invention. FIG. 4 is a graph of the output of a bridge rectifier of a power line communication circuit configured in accordance with an embodiment of the present invention. FIG. 5 is a graph of voltage waveforms generated by a power line communication circuit configured in accordance with an embodiment of the present invention.

Explanation of symbols

2, 34 Notch 4 Power signal 6 Thyristor 8, 24 Control circuit 10 AC line 12, 20 Load 16 Bridge rectifier 22 MOSFET
26 Output voltage 28 Separating inductor 32 Pulse

Claims (16)

A system for generating a notch in an AC power signal propagated on an AC power line to communicate via an AC power line connected to an AC line input,
A rectifier for rectifying the AC power line signal to the power line to generate a rectified power line signal;
A switch device connected to the AC power line, the switch device activating the switch device to short-circuit the AC power line;
A control circuit connected to the rectifier that activates the switch device to generate a notch in the AC power line signal when the rectified power line signal reaches a reference signal;
A separation inductor is connected between the AC line input and the rectifier .   The system of claim 1, further comprising at least one electronic ballast connected to the AC power line, wherein the dimming function of the electronic ballast is controlled by a notch in the AC power line signal.   The system of claim 1, further comprising a phase detection circuit for monitoring the rectified signal to determine when the rectified signal reaches the reference voltage.   4. The system of claim 3, further comprising a rectifier connected to the phase detection circuit so that the phase detection circuit can determine a change in polarity of the power signal. An AC input terminal for receiving the AC power line signal;
A load output terminal for transmitting the AC line signal to the load;
A first circuit path connected to the AC input terminal and having the rectifier, the switch and the control circuit;
A second circuit path connected to the AC input terminal and the load output terminal;
The system of claim 1, further comprising:   The system of claim 1, further comprising a receiver for detecting a notch in the AC power signal.   The system of claim 1, wherein the switch device is a MOSFET.   The system of claim 1, wherein the reference voltage is 10% or less of a maximum voltage potential of the power line signal.   The system of claim 1, wherein the rectified signal reaches a reference voltage just prior to zero crossing by the power line signal. A method for enabling communication between the at least one electronic ballast and a controller on an AC power line connected to an AC line input , supplying power to the at least one electronic ballast, comprising:
Generating a rectified power line signal by rectifying an AC power signal of the AC power line;
Sending the rectified power line signal to the controller capable of activating a switch that shorts the AC power line;
In case of stretching a zero crossing that occurs when the AC signal of the AC power line the rectifying power line signal has reached the zero-crossing of the rectified power line signal changes from negative to polarity or negative from positive to positive polarity Using the controller to activate the switch ;
When the polarity in the AC power line signal changes, the at least one electronic ballast detects the presence / absence of a zero-cross stretcher, interprets the presence / absence of the zero-cross stretcher according to a predetermined code, and the controller and the at least Enabling communication between one electronic circuit; and
Connecting a separation inductor between the AC line input and the rectifier to prevent notches generated in the AC power line signal from propagating to the AC line input by activating the switch;
A method comprising the steps of:   The method of claim 10, further comprising using the rectified power signal to rectify the power signal and control the generation of the zero-cross stretcher.   The method of claim 10, wherein the zero-cross extension is generated by selectively shorting the AC line.   The method of claim 12, wherein the selective short circuit occurs immediately prior to a change in polarity of the AC power signal.   The method of claim 10, further comprising using the zero cross stretching to communicate a desired dimming amount to the at least one electronic ballast.   The method of claim 10, wherein selectively extending the zero cross further comprises shorting the AC power line with the MOSFET.   The method of claim 10, further comprising using a ratio between a stretched zero cross and a non-stretched zero cross to communicate information from the controller to the at least one electronic circuit.

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