Abstract:
A lighting control system includes a master unit and a plurality of slave units. The slave units are respectively designed to consume power by operating lighting means, are supplied by a common power supply unit, can be provided with commands from the master unit, and are respectively provided with a control unit which modulates the power consumption of the associated slave unit according to a defined protocol. The master unit is designed to measure the power consumed by all slave units.

Description:
INCORPORATION BY REFERENCE 
     The present application claims benefit of European Patent Application No. 14161501.3, filed Mar. 25, 2014, the entire contents of which are incorporated by reference herein as if fully set forth. 
     FIELD OF THE INVENTION 
     The present invention relates to a lighting system and to a method for operating a lighting system, in which a power consumption is used as a communication channel. 
     BACKGROUND 
     In lighting systems, usually a master unit controls the operation of attached slave units, for example lamps. A connection between the master unit and the slave units usually uses a directed wired connection, or a bus connection, for example DALI, or even a wireless connection. Implementing a full bidirectional communication between the master unit and the individual slave units requires a receiver and a transmitter on both ends. This results in a complex hardware of the individual components and thereby a high manufacturing cost. A solution to this problem is to reduce the communication to a unidirectional communication from the master unit to the slave units. In this case though, a feedback from the slave units to the master unit is not possible. The master unit has no way of knowing if a command has reached its destination and was implemented. 
     The German patent application DE 10 2004 002 027 A1 shows a lighting system, in which a master unit provides power to a number of slave units using a DC output circuit. The state of the DC output circuit is monitored. The slave units are able to deliberately change the state of the DC output circuit in order to transmit feedback information to the master unit. 
     The system shown there though is disadvantages, since the slave units require a communication unit able to affect the state changes of the DC output circuit. In comparison to a full bidirectional communication between the master unit and the slave units, this solution does not significantly reduce the hardware complexity. 
     SUMMARY 
     Accordingly, the object of the invention is to provide a lighting system and a method for operating a lighting system, which allow for a transmission of commands to the slave units and a feedback from the slave units without requiring a complex hardware setup. 
     The object is solved by the features of claim  1  for the system and claim  10  for the method. The dependent claims contain further developments. 
     An inventive lighting control system comprises a master unit and a plurality of slave units. The slave units are respectively designed to consume power by operating lighting means, are supplied by a common power supply unit, can be provided with commands from the master unit, and are respectively provided with a control unit which modulates the power consumption of the associated slave unit according to a defined protocol. The master unit is designed to measure the power consumed by all slave units. It is thereby possible to achieve an information feedback from the slave units to the master unit without requiring any additional communication hardware. 
     Advantageously, the slave units are adapted to transmit a signal to the master unit by modulating the power consumption. The master unit is then adapted to recreate the signal from the measured power consumption of all slave units. It is therefore possible to create an information flow from the slave unit to the master unit. 
     Advantageously, the master unit and the slave unit comprise a communication unit. The communication unit of the master unit is then adapted to unidirectionally transmit commands to the communication unit of the slave unit. The control unit of the slave unit is then adapted to unidirectionally receive commands from the communication unit of the master unit using the communication unit of the slave unit. It is thereby possible to transmit the commands from the master unit to the slave unit. 
     Also advantageously, the communication unit of the master unit is connected to the control unit of the slave unit using a direct wired connection and/or a bus connection and/or a wireless connection. The control unit of the master unit is then adapted to transmit the commands to the control unit of the slave unit using the direct wired connection and/or the bus connection and/or the wireless connection. A high flexibility in setting up the communication system is thereby achieved. 
     The control unit of the master unit is advantageously adapted to query the control unit of the slave unit using the communication unit of the master unit and the communication unit of the slave unit. In this case, the control unit of the slave unit is adapted to answer queries of the control unit of the master by modulating the power consumption. A two-way communication is thereby possible. 
     Advantageously, the system comprises an address assigning unit adapted to assign addresses to all slave units connected to the master unit. The control unit of the master unit is then adapted to transmit commands to the control unit of the slave unit and to the control unit of the further slave unit using addresses assigned to the slave unit and the further slave unit. The communication units of the slave units are adapted to detect commands targeted at their respective slave unit. The control units of the slave units are adapted to only process commands targeted at their respective slave unit. It is thereby possible to achieve a communication from the master unit only to select slave units. 
     Advantageously, the control unit of the master unit is adapted to transmit a command to all connected slave units using the communication unit of the master unit instructing all connected slave units to increase or decrease the respective power consumption by a defined amount. The control units of all connected slave units are then adapted to increase or decrease the power consumption of their respective slave unit as instructed. The control unit of the master unit is in this case adapted to determine a number of connected slave units from a resulting change in total power consumption of all connected slave units. Thereby, it is very easily possible to determine the number of connected slave units. 
     The control units of the slave units are advantageously adapted to modulate the power consumption using an amplitude-shift keying, especially an on-off keying or a phase-shift keying or a frequency-shift keying, and/or using a modulation frequency below 10 Hz, preferably below 5 Hz, most preferably below 1 Hz. Thereby a greater flexibility in performing the modulation is achieved. 
     Advantageously, the control unit of the master unit is furthermore adapted to detect when the slave units are not in operation and to activate at least one slave unit, after it was detected that the respective slave unit is not in operation. It is then furthermore adapted to instruct the respective slave unit to modulate the power consumption after the slave unit has been activated and to deactivate the slave unit after the power consumption has been modulated. It is thereby possible to transmit the information from the slave unit to the master unit during times at which the slave unit is not used. For example, the lights in an office building can be switched on and off at night in order to generate the feedback signal. This does not hinder usual office processes, since the office is not occupied during these times. 
     An inventive method serves the purpose of operating a lighting system comprising a master unit and a plurality of slave units. The slave units consume power by operating lighting means, are supplied by a common power supply unit, can be provided with commands from the master unit, and modulate the power consumption of the associated slave unit according to a defined protocol. The master unit measures the power consumed by all slave units. It is thereby possible to achieve a communication path from the slave unit to the control unit without requiring a complex communication infrastructure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An exemplary embodiment of the invention is now further explained with respect to the drawings, in which 
         FIG. 1  shows a first exemplary embodiment of the inventive lighting system; 
         FIG. 2  shows a second exemplary embodiment of the inventive lighting system; 
         FIG. 3  shows a third exemplary embodiment of the inventive lighting system; and 
         FIG. 4  shows an exemplary embodiment of the inventive method. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First we demonstrate the general construction and function of an embodiment of the inventive lighting system along  FIG. 1 . After that, different alternatives of construction are described along  FIG. 2  and  FIG. 3 . Lastly, the function of an embodiment of the inventive method is described regarding  FIG. 4 . Similar entities and reference numbers in different figures have been partially omitted. 
     In  FIG. 1 , a lighting system  1  is depicted. The lighting system  1  comprises a master unit  10 , which comprises a communication unit  11  connected to a control unit  12 , which is furthermore connected to a power supply unit  13  and an address assigning unit  14 . Moreover, the lighting system  1  comprises a slave unit  15 , which comprises a communication unit  16 , a control unit  17 , a power supply unit  18  and a lamp  19 . The control unit  17  is connected to the communication unit  16  and to the power supply unit  18 . The lamp  19  is connected to the power supply unit  18 . The communication unit  11  of the master unit  10  is connected to the communication unit  16  of the slave unit  15 . The power supply unit  13  of the master unit  10  is connected to the power supply unit  18  of the slave unit  15 . The power supply unit  13  of the master unit  10  furthermore comprises a mains connection. 
     The power supply unit  13  of the master unit  10  is supplied with power through its mains connections. The power supply unit  13  processes the mains power, for example performs a transformation to a lower voltage level and a rectification and supplies the remaining components of the master unit  10  with power. Also, the power supply unit  13  supplies power to the power supply unit  18  of the slave unit  15 . The arrow connecting the power supply unit  13  and the power supply unit  18  merely indicates the direction of information flow and not the direction of power flow. 
     The control unit  12  of the master unit  10  is adapted to control the function of the communication unit  11 , the power supply unit  13  and the address assigning unit  14  of the master unit  10 . Especially, the control unit  12  is set up for generating commands, which are transmitted to the slave unit  15  by use of the communication unit  11  of the master unit  10  and the communication unit  16  of the slave unit  15 . These commands are received by the control unit  17  of the slave unit  15  from the communication unit  16  of the slave unit  15 . The commands are processed by the control unit  17 . For example in reaction to such a command, the lamp  19 , which is a power consuming unit is activated or deactivated or dimmed. Also, the control unit  17  is adapted to generate a signal for transmitting information to the master unit  10 . The signal is handed on to the power supply unit  18 , which modulates the power consumption of the slave unit  15  according to the signal. In this example, this can for example be achieved by the power supply unit  18  increasing or decreasing the brightness setting of the lamp  19  or switching the lamp  19  on and off in order to increase or decrease the power consumption of the slave unit  15 . 
     The modulation is performed according a protocol. Due to the use of this protocol, it is possible to achieve a communication using this channel. The protocol can be a standard communication protocol or a proprietary protocol. 
     Especially, the modulation of the power consumption can be an amplitude-shift keying, especially an off-on keying or a phase-shift keying or a frequency-shift keying. Since the power consumption of the slave unit  15  is modulated by the power supply unit  18 , which is a conventional power supply unit and not set up for performing high speed modulation, the modulation frequency is advantageously below 10 Hz, preferably below 5 Hz, most preferably below 1 Hz. This results in a very low data rate of the signal, which can be transmitted from the slave unit  15  to the master unit  10 . On the other hand, this allows for a signal transmission without any additional complex hardware. 
     It is important to note the difference of the modulation of the power consumption according to the present invention to a power line communication. In conventional power line communication systems, a high frequency signal is superimposed onto the power supplying lines. The signal can then be received by all slave units connected to these power supplying lines. The modulated power consumption according to the present invention can only be measured by the master unit  10 , which supplies the power to the slave unit  15 . Also an important difference is that a regular power line communication system does not modulate the power consumption in a low frequency manner as the present invention, but modulates a superimposed voltage with a very high modulation frequency. A power line communication system does not change the power consumption of the respective slave unit at all. 
     The connection between the communication unit  11  of the master unit  10  and the communication unit  16  of the slave unit  15  can be a direct wired connection or a bus connection, for example a DALI bus or a wireless connection. The connection between the power supply unit  13  of the master unit  10  and the power supply unit  18  of the slave unit  15  is a wired connection. 
     The control unit  12  of the master unit  10  can furthermore be set up for determining times at which the slave unit  15  is usually not in operation. Alternatively, the control unit  17  of the slave unit  15  could inform the control unit  12  of the master unit  10 , when the slave unit  15  is presently not used. These times are ideal for performing the transmission from the slave unit  15  to the control unit  10 , since for modulating the power consumption of the slave unit  15 , it might be necessary to compromise the regular function of the slave unit  15 , in this case, the function of the lamp  19 . 
     In  FIG. 2 , a second embodiment of the inventive lighting system  2  is shown. The lighting system  2  comprises a master unit  20 , a first slave unit  25 , a second slave unit  26  and a third slave unit  27 . The master unit  20  is connected to the slave units  25 - 27  through individual wired connections,  28 ,  29 ,  30 . These connections are used for connecting the communication unit of the master unit  20  to the communication units of the slave units  25 - 27 . Moreover, the master unit  20  is connected to the slave units  25 - 27  through a wired connection connecting the power supply unit of the master unit to the power supply units of the slave units  25 - 27 . 
     In  FIG. 3 , a third exemplary embodiment of the inventive lighting system  3  is shown. A wireless connection  48  connects a master unit  40  to slave units  45 ,  46  and  47 . The wireless connection  48  is used for connecting the communication units of the central controlled unit  40  and the slave units  45 - 47 . Also here, the master unit  40  is connected to the slave units  45 - 47  through a wired connection, connecting the power supply units of the master unit and the slave units  45 - 47 . 
     In case of more than one slave unit, as depicted in  FIG. 2  and  FIG. 3 , the master unit  20 ,  40  can broadcast commands to all slave units  25 - 27 ,  45 - 47 . The signals broadcast by the central units  20 ,  40  are received by the slave units  25 ,  27 ,  45 - 47 . The slave units  25 - 27 ,  45 - 47  can then each modulate the respective power consumption in order to generate a signal for transmission to the respective control unit  20 ,  40 . 
     If the lighting system comprises and address assigning unit  14 , as depicted in  FIG. 1 , the master unit  10  can individually target commands at slave units. In this case, the command comprises the respective address. Only the targeted slave unit processes the respective command and reacts thereupon. 
     The address assigning unit  14  of  FIG. 1  is, furthermore, adapted to assign addresses to individual slave units. For example, the master unit  10  transmits an address assigning request to all connected slave units. Through a user input or an automatic process, an individual slave unit is selected and supplied with an address by the address assigning unit  14 . This process is repeated for all connected slave units until each slave unit has been assigned an address. 
     To prepare the address assigning, the master unit  10  of  FIG. 1  can, furthermore, determine how many slave units are connected by broadcasting a command to all slave units instructing the slave units to increase or decrease the respective power consumption by a finite amount. From the resulting change in power consumption, the master unit can determine the number of connected slave units. 
     In  FIG. 4  an embodiment of the inventive method is shown. In a first step  100 , a master unit of a lighting system creates and transmits a command to a slave unit of the lighting system. In a second step  101 , the slave unit receives the command. In a third step, the slave unit generates a response signal by modulating the power consumed by the slave unit. In a fourth step, this modulated power consumption is detected by the master unit. The signal is recreated therefrom by the master unit. 
     The lighting system  2  shown in  FIG. 2  can also be extended. As already described above it is possible that master unit  20  can measure the combined power consumption of slave unit  25 , slave unit  26  and slave unit  27 . 
     In another embodiment of the invention it can be also be possible for slave unit  25  to measure the power consumption of slave unit  26  and slave unit  27  which are connected to the slave unit  25 . This means that a device can measure the power of devices connected “behind” such device (seen from the view of the master unit  20 ). For example slave unit  26  would be able to measure the power consumption of slave unit  27 . With such arrangement it would be possible to send messages from slave unit  27  to slave unit  26  and slave unit  25  and to send messages from slave unit  26  to slave unit  25 . 
     One of the advantages of such system is that the network topology of slave units depends on the physical location of the slave unit itself. Such system could offer an automatic address assignment that is based on physical location of the slave units within the lighting system  2 . 
     The slave unit  25  and slave unit  26  could comprise a measurement unit to measure the power consumption of slave units connected to those slave units. 
     The invention is not limited to the examples shown above. Especially, the invention can be used for communication between a master unit and a great number of different slave units. The slave units can be, for example, lamps, sensors, actors, etc. The characteristics of the exemplary embodiments can be used in any advantageous combination.