Power supply device and communication system for lighting systems comprising the same, as well as method for supplying voltage to an electrical load

Abstract

Power supply device (40) for a communication system (30) for lighting systems (10), comprising: an input with a voltage terminal (44) and a ground terminal (46) for connection to a first power supply source (42) which has an input voltage (U e ) between these terminals (44, 46), and an output with corresponding terminals (48, 49) for connection to at least one interface (50, 81, 91) of a control and / or operating device, a current control device (401) having an input node (410) and an output node (411), wherein the current control device (401) is designed to control a current (I e ) to a predetermined maximum value (I max ) to limit characterized by, a circuit which is designed to provide an output voltage (U a ) which is present between the voltage terminal (48) and the ground terminal (49) of the output, and depending on the detected output voltage (U a ) the input node of the current control device (401) with a voltage (U red ) which is higher than the input voltage (U e ) is reduced.

Description

Technical area

[0001] The present invention relates to a power supply device and a method for supplying power to a communication system for lighting systems. The invention further relates to a communication system comprising the device and a corresponding lighting system. State of the art

[0002] As building automation advances, digital bus systems are increasingly being used, allowing, for example, centrally or decentrally controlling lighting systems comprising a large number of luminaires. One such standard is provided by the DALI protocol (DALI: "Digital Addressable Lighting Interface"). This communication standard, defined in the IEC 62386 and IEC 60929 family of standards, Annex E, is based on the earlier DSI (Digital Signal Interface) standard and closes the gap between conventional, analog 1-10 V interfaces and complex digital bus systems such as KNX / EIB (European Installation Bus) or LON (Local Operating Network), etc., which also include the networking and control of other household appliances beyond lighting.

[0003] With the DALI communication standard (currently available; further developments and extensions are currently being discussed), up to 64 lighting control devices in buildings can be connected to the bus via interfaces, which are controlled or monitored by one or more control units. A larger number of control devices is possible by setting up DALI gateways. The lighting control devices can be electronic ballasts, transformers, actuators, sensors, or dimmers, etc. The interfaces can have a controller and a memory in which parameters such as up to 16 programmed scene values ​​or up to 16 group addresses (under which groups of control devices are grouped) are stored. Each interface is individually addressable.The bus has a two-wire cable through which all operating and control devices receive the same signal in bidirectional data exchange. In individual cases, only the operating device addressed in the signal is addressed, except when the system is operating in so-called broadcast mode. All bus topologies (star, line, tree) can be used, although ring topologies should be avoided.

[0004] The DALI communication standard stipulates that the bus is supplied with approximately 16 volts DC. The bus thus acts both as a signal line and, albeit to a lesser extent, as a power supply. Signals are generated by a transmitting interface through pulsed short circuits between the two wires. The respective sequence of voltage drops from 16 volts to 0 volts is detected and evaluated by the other devices or interfaces. The standard allows certain tolerance ranges to be maintained for both the transmitter and the receiver. The "HIGH level" may be between +11.5 and +20.5 volts (i.e., 16.0 ± 4.5 volts) for the transmitter and between +9.5 and +22.5 volts (i.e., 16.0 ± 6.5 volts) for the receiver. A voltage change of just 2 volts across the line is tolerated, which in practice limits the maximum length between any two devices or interfaces to approximately 300 meters.The “LOW level” may accordingly be between -4.5 and +4.5 volts (ie, 0.0 ± 4.5 volts) for the transmitter and between -6.5 and +6.5 volts (ie, 0.0 ± 6.5 volts) for the receiver.

[0005] The transmitted signals can be used, for example, to set individual luminaires with corresponding ECGs connected via interfaces and controllers to desired brightness, color, or color temperature values, or these settings can also be made in groups. Furthermore, the transmitted signals can also be used to recall the (lighting) scenes stored in the aforementioned memories. Status feedback such as lamp errors, operating times, temperatures (from connected sensors), or the current or last used dimming setting as a start value can be sent from the interfaces. The mains voltage switch of the operating devices can also be individually controlled via the bus. According to the standard, signals can be transmitted at a transmission rate of up to 1,200 bits per second.

[0006] This simple yet highly efficient design continuously supplies a DC voltage of approximately 16 volts during operation. To limit the total power consumption, each operating device is allowed a maximum of 2 milliamperes (mA), so that with 64 connected devices, a total of 128 mA can be used to supply power. For control devices such as sensors, however, no explicit restrictions are specified; however, the current flows on the DALI bus can usually be entirely sufficient in these cases, so that at least in these cases, an alternative power supply can be dispensed with, saving costs. Furthermore, the DALI communication standard specifies a maximum current limit of 250 mA on the bus.

[0007] A known power supply device for such a communication system for lighting systems therefore regularly comprises a current control device designed to limit a current provided by a power supply source (e.g., 16 volts) at its input node and output from it via its output node to an output of the device on the bus to a predetermined maximum value. In practice, the maximum values ​​are 30 to 250 mA. Singular current peaks that may briefly exceed 250 mA (i.e., for periods small compared to the pulse width of the signal) are tolerated. The power supply source includes a switching power supply that generates a galvanically isolated voltage of, for example, 16 volts by means of an electronic ballast or switching converter.

[0008] As described, the usual current consumption by the interfaces involved is generally below this maximum value. Therefore, regulated current limitation usually only occurs when one or the other interface periodically short-circuits the signal and ground lines (or wires) of the bus in a bit-by-bit pulse during signal transmission. In this state, which corresponds to communication through signal generation or an error, the entire power loss is lost at the current control device, which in the case of DALI communication amounts to P = 16 V × 0.25 A = 4 W and is converted into heat in the device (usually at a transistor). However, if the Manchester code is used for signal transmission in accordance with the protocol, the bus is short-circuited for a maximum of 50% of the time, i.e. an average maximum power loss of 2 W during signal transmission.With current technology, devices with four or more outputs are often developed for independent bus systems. However, in the event of a fault with a permanent short circuit, the power loss can be as high as 16 watts. Overheating and device failure are possible. Furthermore, considerable cooling expenditure is required, which should generally be avoided.

[0009] The document US 2015 / 0349752 A1 discloses a power supply device for lighting systems in which the output voltage is detected and, depending thereon, the input voltage of the current control device is reduced.

[0010] The document DE 10 2005 012 662 A1 shows a power supply device for a lighting device, wherein the output voltage and input voltage are detected and then a multiplication factor for the voltage converter is set so that the power loss is minimized.

[0011] The document US 2015 / 0351183 A1 shows a lighting system with a communication device in which the auxiliary modules or loads are controlled by a reduction of the input voltage by a master module.

[0012] The Italian publication IT TO 00 2013 0788 A, which originates from the present applicant, describes a communication system with a power supply device and associated interface for a control or operating device, in which unwanted power losses in the current control device are reduced. The output voltage at the output of the power supply device, to which the signal and ground lines of the bus are connected, is monitored. If this voltage drops during data signal transmission or in the event of a fault, the current control device is regulated to a significantly reduced maximum value for current limitation.

[0013] In an example described in IT TO 00 2013 0788 A, the current regulation device comprises a measuring or shunt resistor through which the current supplied to the bus flows and across which a certain value of the voltage applied to the measuring resistor drops, depending on the output voltage. If the voltage across the measuring resistor exceeds a threshold, a transistor of the current regulation device is increasingly switched off. The maximum current limit is reduced by making the measuring or shunt resistor variable. In the example, the measuring or shunt resistor is split into two partial resistors, one of which can be bridged by another transistor. This is controlled by a comparator or Schmitt trigger, which detects the output voltage at the device's output and compares it with a reference.If the output voltage drops to less than half of the input voltage, which in DALI would correspond to leaving the "HIGH level", then one partial resistor is bridged, which is dimensioned in comparison to the remaining partial resistance of the shunt resistor in such a way that the output current in this state is regulated to only 25 mA, i.e. one tenth of the originally intended current limit.

[0014] On the side of the interfaces acting as load in this case, a sufficient supply of power in this state is ensured by installing a storage capacitor with a series-connected diode in the circuit in question, from which the load (e.g. a sensor, etc.) is temporarily supplied with power, but which is charged with an average of 16 V.

[0015] However, the proposed communication system interferes with the interface design due to the significantly reduced output current. Furthermore, it remains unclear how to handle the case of a prolonged short circuit on the bus that can no longer be attributed to data signal transmission and may represent a fault. Description of the invention

[0016] It is therefore an object of the invention to provide a power supply device and a corresponding communication system which offer a reduction in power loss in the case of data transmissions while at the same time offering a cost-saving structure.

[0017] The object is achieved by a power supply device for a communication system for lighting systems having the features of claim 1 and by a corresponding communication system having the features of claim 15 and by a method according to claim 17.

[0018] The starting point is a device for supplying power to a communication system for lighting systems, which device comprises an input for connection to a first power supply source and an output for connection to interfaces of control and / or operating devices of the communication system. A current control device with an input and an output node is provided therein and is designed to limit a current provided by the first power supply source at the input node and output by it (i.e., the current control device) via the output node to the output, to a predetermined maximum value. This maximum value can be 250 mA or less, as provided for in the DALI communication standard IEC 62386. However, the invention is not limited to specific communication standards, and other values, as well as standard-compliant or standard-free designs, are also possible.The precise design of the current control device is of secondary importance in the proposed scope, because, as will be explained below, the proposal made here does not necessarily provide feedback from the detected output voltage into the current control device itself, but rather on its input node.

[0019] The input of the device has a voltage terminal and a ground terminal, which can be connected to the first power supply source. This can then provide an input voltage between these terminals. In the DALI case, the input voltage can be, for example, 16.0 ± 4.5 volts; however, the first power supply source is not part of the device proposed here. The first power supply source can comprise a primary switch-mode power supply to ensure the galvanic isolation of the control line (bus) from the mains voltage, as required, for example, by the DALI communication standard. This can be a flyback or forward converter, etc., without limiting the invention.Optionally, a secondary switched-mode power supply, such as a step-down converter, can also be provided, which converts a direct voltage supplied by the primary switched-mode power supply, purely for example 24 volts, to the specified input voltage, e.g. 16.0 ± 4.5 volts.

[0020] The device's output is equipped with corresponding terminals (voltage connection and ground connection). Due to the galvanic isolation from the mains, the interconnected ground connections at the input and output are "floating" and, in practical installation, are not connected to PE (physical ground). These two connections correspond, for example, to the 2-wire DALI bus.

[0021] The invention now provides a circuit which is designed to detect an output voltage which is present between the voltage terminal and the ground terminal of the output and, depending on the detected output voltage, to supply the input node of the current control device with a voltage which is reduced compared to the input voltage present between the terminals of the input when the device is connected to the first power supply source.

[0022] As described, feedback is provided from the device's output voltage to the input node of the current control device. More precisely, the voltage supplied to the input node by the circuit is reduced compared to the input voltage. This can be achieved by obtaining the reduced voltage from the input voltage through measures within the circuit itself, i.e., by having reduced, i.e., comparatively lower, values, or by obtaining a corresponding reduced voltage from an independent source. For this purpose, the input voltage at the device's input must be separated from the input node and replaced with the reduced voltage from another source.

[0023] In any case, the reduced voltage at the input node, with otherwise unchanged current regulation, means that, for example, in the data signal transmission state in the communication system, a required current (e.g., 250 mA for DALI) can be maintained, while the power loss can be reduced. For example, if the reduced voltage supplied to the input node of the current regulation device is set at a quarter of the input voltage, the power loss, which is mainly converted into heat in the current regulation device, is reduced to P=4V × 0.25A = 1W in the short-circuited bus state, i.e., also to a quarter (with signal transmission and use of the Manchester code: maximum 0.50 W, see above). This makes it possible to save costs for useless power consumption and for the effort required for increased cooling capacity, as well as for interventions in the connected interfaces.

[0024] According to a further development, the circuit is designed to supply the current control device with the reduced voltage when the output voltage falls below a predetermined threshold, and to supply the current control device with the input voltage when the output voltage exceeds the predetermined threshold. It is important, of course, that the reduced voltage at the input node and the threshold of the output voltage are aligned, because otherwise the feedback cannot return from the reduced voltage supply state to the original state, in which the output voltage essentially corresponds to the input voltage.

[0025] According to a further development, the circuit comprises a threshold switch which is connected to the output node of the current control device and which outputs a signal depending on whether the output voltage falls below or exceeds the predetermined threshold value. The threshold switch can be implemented as an operational amplifier, comparator, Schmitt trigger, or similar. However, this aspect is not limited to this. A simple implementation as an electronic switch and / or as a transistor of any type is also possible. Detecting the output voltage using a threshold switch represents a particularly efficient and simple way of implementing the desired feedback. "Detecting" here does not mean that precise values ​​of the output voltage are determined. This already includes the (binary) differentiation between a value above or below the threshold value or the like.

[0026] According to a further development, the circuit comprises a first electronic switch, the first terminal of which is connected to the voltage terminal of the input and the second terminal of which is connected to the input node of the current control device, wherein the first electronic switch is designed to open or close depending on the signal output by the threshold switch in order to prevent or allow the input voltage to be applied to the input node. The first electronic switch can be designed as a transistor, in particular as a bipolar or field-effect transistor, etc. Its control electrode or base or gate can be connected to an output of the threshold switch, e.g. the comparator. The implementation of the feedback to the input node of the current control device via the first electronic switch results in a particularly simple and efficient design.

[0027] According to a further development, the circuit comprises a second power supply source that provides the reduced voltage and is connected to an input node of the current control device and to the second terminal of the first electronic switch, and is designed to supply the current control device with the reduced voltage. In combination with the first electronic switch, a particular advantage arises in that, with a simple structure, switching can be performed back and forth between the input voltage due to the first power supply source and the reduced voltage due to the second power supply source, depending on the output voltage at the input node.

[0028] The second power supply source can be a power supply independent of the first power supply source or can be connected to it by another circuit part. For example, it can comprise a voltage regulator that regulates the input voltage provided by the first power supply source to the reduced voltage and then outputs this voltage at its output terminal. The voltage regulator can be a linear or a switching regulator. Also included is the case in which the first power supply source - as described above - has a primary switch-mode power supply (for a voltage of, for example, 24 V) and a secondary switch-mode power supply connected to it, namely one that then supplies the input voltage at the terminals of the input (e.g., a voltage of 16 or 17 V), and another that supplies the reduced voltage at the input node of the current regulation device (e.g.,a reduced voltage of 4 V).

[0029] When the first electronic switch is closed, the competition between the two voltages can be resolved by connecting the output terminal of the voltage regulator to an anode terminal of a rectifier diode, whose cathode terminal is connected to the input node of the current regulation device and to the second terminal of the electronic switch. The rectifier diode ensures that the reduced voltage only becomes active when the first electronic switch opens.

[0030] According to a specific embodiment, the threshold switch comprises a comparator whose inverting input is connected to the output voltage at the device's output, and whose non-inverting input is connected to a reference voltage, wherein the signal is output at the comparator's output depending on a comparison result of the two voltages. Alternatively, the threshold switch can comprise a second electronic switch whose control terminal is connected to the output voltage at the voltage terminal of the device's output, whose working electrode is connected via an ohmic resistor to a control terminal of the first electronic switch, and whose reference electrode is connected to the ground terminal. Other implementations are also possible. However, both variants realize a particularly simple, yet efficient and reliable structure for detecting the output voltage level.

[0031] According to an advantageous development, the current control device has an input terminal with a first node, which is connected via a shunt resistor to a working electrode of a third electronic switch, the reference electrode of which is connected to an output terminal of the current control device. For this purpose, a voltage source is provided for providing a predetermined voltage difference, the positive terminal of which is connected to the node and the negative terminal of which is connected to a control electrode of the third electronic switch. In principle, other structures are also known for implementing a current control device. The comparison of the voltage difference across the shunt resistor, which is a direct consequence of the applied output voltage, i.e., is dependent on it, with a voltage difference predetermined by a voltage source, i.e., a fixed voltage difference, has proven to be particularly advantageous, reliable (e.g.temperature) and compatible with the feedback proposed here with a reduction of the voltage at the input node.

[0032] The following aspects refer, but are not expressly limited, to the DALI communication standard, meaning that the device may be DALI compliant: According to one embodiment, the device comprises the first power supply source, wherein the first power supply source is configured to provide the input voltage with a value of 16.0 ± 4.5 volts. The second power supply source is then configured to provide a reduced voltage with a value of 9.5 volts or less, preferably 7 volts or less, more preferably 5 volts or less, at the input of the current regulation device. A particularly suitable value is around 4 volts. The lower the reduced voltage, the lower the power loss. As described above, the first power supply source can be or comprise a primary switch-mode power supply and optionally additionally a secondary switch-mode power supply.

[0033] The predetermined maximum value for limiting the current delivered to the output via the output node can be 250 milliamperes or less (e.g., 200 mA). Higher values ​​are also possible according to extensions or modifications to the standard.

[0034] Furthermore, the value of the reference voltage with which the output voltage is compared can preferably be between 0.1 volts and 9.0 volts, but less than the reduced voltage. The distance between the reference voltage and the reduced voltage should be clear and include tolerances, e.g. 3.0 up to 4.5 volts, to allow a safe return (switching) to the original input voltage when, for example, a short circuit for data signal transmission is ended. Since the upper limit for the reduced voltage is preferably 9.5 volts (lower tolerance limit according to the DALI communication standard), and a reference voltage should in any case be greater than 0 volts, a limited margin in the range 3.0 - 6.0 volts for the reduced voltage represents the preferred target range. The reduced voltage can lie in a fixed interval with tolerance limits, but can also be variable.

[0035] The invention also provides a communication system for lighting systems, comprising a power supply device as described above. Furthermore, it comprises at least one, preferably several interfaces corresponding to one or more control and / or operating devices for connection to the output terminals of the device. The interface is configured to periodically short-circuit the voltage present between the voltage terminal and the ground terminal at the output of the device in order to transmit a digital data signal. The connection is established via a corresponding bus, e.g., a 2-wire DALI bus. Within this, the device and the interface comply with a standard of the IEC 62386 family called "Digital Addressable Interface for Lighting" (DALI).

[0036] The communication system, for example, comprises the interface of an operating device with an LED module, signal bus connections, and an associated power supply device. Strictly speaking, such a minimal configuration of a communication system is a communication device. The scope of protection here refers to the interface with an integrated power supply. However, the communication system can also refer to individual interfaces of control devices (sensors / actuators or central control units, for example, with a connected PC as described in the exemplary embodiments) with an integrated power supply, or even to the entire bus including all connected interfaces.

[0037] A method for powering a communication system for lighting systems comprises the following steps: - Providing an input voltage between a voltage terminal and a ground terminal of an input of a power supply device, - Providing a current control device having an input and an output node, wherein the current control device is designed to limit a current provided by the first power supply source at the input node and output by it via the output node to an output of the device having a voltage and a ground connection, to a predetermined maximum value, - Detecting an output voltage that is present between the voltage terminal and the ground terminal of the output, - Comparing the output voltage with a given reference voltage, - Reducing the voltage applied to the input node of the current control device to a predetermined value depending on the comparison result.

[0038] Further advantages, features, and details of the invention will become apparent from the claims, the following description of preferred embodiments, and the drawings. In the figures, like reference numerals designate like features and functions. Short description of the drawing(s)

[0039] They show: Fig. 1 shows a schematic block diagram of a lighting system compatible with embodiments of the invention, including a communication system; Fig. 2 shows a comparative example of a device for supplying power to a communication system; Fig. 3 shows a schematic block diagram of a first embodiment of a power supply device for supplying a communication system with power; Fig. 4 shows a more detailed block diagram of a second embodiment of a power supply device for supplying a communication system with power; Fig. 5 shows a schematic representation of an example of a communication system with interfaces on a DALI bus, which are provided by the power supply device according to Fig. 4 or Fig. 8 are supplied with power; Fig. 6 a diagram with a time course of different voltages which in the embodiment of the Fig. 4 were determined during a data signal pulse at different positions of the circuit shown: Input voltage U e , reduced voltage U red , signal voltage U sig , output voltage U a ; Fig. 7 according to the scenario in Fig. 7 a diagram with a time course of the current I e, which is controlled by the current control device; Fig. 8 in a more detailed block diagram to Fig. 4 alternative third embodiment of a power supply device for supplying a communication system with power. Preferred embodiments of the invention

[0040] In the figures, identical or similar components or components with identical or similar effects are provided with the same reference symbols.

[0041] Fig. 1 shows a schematic block diagram of a lighting system 10 compatible with embodiments of the invention. The lighting system comprises a number of luminaires 110, for example, LED modules or fluorescent lamps, etc., having one or more LEDs (light-emitting diodes), each (or together) supplied by an electronic ballast (EB) 100 with suitably conditioned power from a mains power line M (with, for example, 230 volts alternating current (AC)) to which they are connected. The electronic ballast 100 can comprise EMC filters, rectifiers, power factor correction, and, depending on the luminaire type, other electronic components that are known in detail to those skilled in the art.

[0042] The electronic ballasts 100 and luminaires 110 are each controlled or monitored by operating devices 80, which have a microcontroller 82 with memory and an interface 81 for connection to a signal bus 70, which in this exemplary embodiment is designed as a DALI communication bus (standard of the IEC 62386 family) and has a 2-wire cable. The DALI communication bus 70 connects the interfaces 81 of the operating devices 80 to an interface 50 of a communication system 30, which functions as a control device. For this purpose, the communication system also has a microcontroller 60 with memory. Furthermore, the communication system 30 has a power supply device 40 for supplying the communication system 30 with power. For this purpose, the power supply device 40 has, for example, its own connection to the mains power line (e.g., 230 V AC).On the output side, it is connected to the signal bus 70 and feeds in a DC voltage of e.g. 16-17 V.

[0043] In addition to the power supply device 40 and the interfaces 50, 81 of the control and operating devices, interfaces 91 of sensors 90 or actuators (not shown) are also connected to the DALI communication bus 70. These also have a microcontroller 92 with memory, but do not require a mains connection, for example, since the power supplied via the DALI communication bus 70 can be entirely sufficient.

[0044] A control or monitoring device 20, such as a PC, a server, etc., is connected to the communication system 30 and allows interaction by the user of the lighting system 10. The control device 20 can initiate the transmission of transmission signals to the operating devices 80 or the sensors 90, etc., as well as receive and evaluate signals sent by them and received via the interface 50. The signals transmitted by the sensors 90 can contain, for example, environmental information such as time, temperature, humidity, pressure, voltage, or other mechanical or electrical variables, etc.The signals initiated by control device 20 can contain control information, such as the retrieval of status information such as dimming position (current brightness value), operating time, lamp faults, the activation of a mains voltage switch in control device 80, changed dimming values ​​or the activation of stored scenes, new group assignment (configuration), etc. The signals are transmitted on the 2-wire line by targeted pulsed short-circuiting of the two lines while otherwise maintaining a constant voltage of around 16 V. The DALI communication standard uses Manchester code for data encoding, i.e., the edges of the pulses are evaluated instead of the "HIGH" or "LOW" pulses themselves. The DALI communication standard offers a polarity-protected connection to the 2-wire line. In the following, the two wires are subjectively referred to as the control line and the ground line.Reverse polarity protection is ensured, for example, by bridge rectifiers.

[0045] The power supply device 40 is examined in more detail below. The DA-LI communication standard requires galvanic isolation of the system from the mains connection, which is why primary switch-mode power supplies (not shown, e.g., flyback converters) are provided to provide the required voltage of 16.0 V ± 4.5 volts. Alternatively, secondary switch-mode power supplies (not shown, e.g., buck converters) can be provided downstream to stabilize an intermediate voltage of, for example, approximately 24 V provided by the primary switch-mode power supply to the required voltage of 16.0 V ± 4.5 volts.

[0046] In the examples shown below, a power supply device 40 has an input with a voltage terminal 44 and a ground terminal 46, to which a voltage of 16.0 V ± 4.5 volts is applied. In the examples, the input voltage is approximately 17 volts. The voltage and the state-dependent current supplied are supplied by a power supply source 42, which represents, for example, the switching power supply(s) mentioned above. The power supply source 42 may be part of the device 40, but does not have to be.

[0047] Fig. Figure 2 shows a comparative example of a power supply device 40. It comprises the input with terminals 44, 46, between which the input voltage Ue is applied, a current control device 401, and an output with terminals 48, 49 for connecting to the control and ground lines of the signal bus 70 (DALI communication bus). A resistor R22 and a capacitor C1 serve to stabilize the output voltage Ua output between terminals 48, 49.

[0048] Current control device 401 is designed to limit the current supplied to the signal bus 70 (DALI communication bus) at the output terminals 48, 49 to a maximum value of 250 mA (or less). For this purpose, the input voltage terminal 44 is connected via a measuring resistor R23 to the emitter of a PNP bipolar transistor Q4. Its collector, in turn, is directly connected to the output voltage terminal 48.

[0049] At the same time, the emitter of another PNP bipolar transistor Q9 is connected to the input voltage terminal 44. Its collector is connected to ground GND (or to the input and output ground terminals 46 and 49, respectively) via a resistor R20. Furthermore, the base of bipolar transistor Q4 is also connected to the collector of another bipolar transistor Q9, and the base of this other bipolar transistor Q9 is connected to the emitter of bipolar transistor Q4 via a resistor R21.

[0050] During operation, under normal conditions (16 or 17 V, no short circuit), only a very low voltage drop is dropped across the resistor R23. The bipolar transistor Q4 is activated, and a current flows towards the load, to the output terminal 48. If the terminals 48, 49 of the output are now short-circuited in order to transmit a DALI signal pulse on the connected signal bus 70 (the short circuit can be caused, for example, by the interface of the control unit / communication system 30 when the data transmission is initiated by the control device 20), a stronger current flows, and the voltage between the terminals of the resistor R23 rises, exceeding the threshold voltage of the further bipolar transistor Q9, which now becomes increasingly conductive, so that the bipolar transistor Q4 increasingly blocks. A current flows through the resistor R20. The components are dimensioned such that a current flows through the partially deactivated orA regulated current of maximum 250 mA can flow through the partially blocked bipolar transistor Q4.

[0051] The aforementioned document IT TO 00 2013 0788 A proposes feedback from an output node directly to the ohmic resistor R23 in the current control device by varying this resistance as a function of the output voltage. In one example, the measuring resistor is varied such that the maximum current limiting value in the event of a short circuit (output voltage equal to zero) is only 25 mA. The power loss, converted predominantly into heat in the transistor Q4 when the bus is short-circuited, is therefore only P = 16 V × 0.025 A = 0.4 W. As described, however, one of the problems is that the current flow available in this state may not be sufficient to supply the connected devices.

[0052] Embodiments of the present invention now provide for leaving the current control device untouched and instead providing feedback to the input node of the current control device, whereby the current control itself is less influenced but the voltage supplied to it is reduced.

[0053] Fig. Figure 3 shows a first embodiment of the invention using a schematic block diagram, which clearly illustrates the basic principle. The power supply source 42, the input terminals 44, 26, the current control device 401, and the output terminals 48, 49 are provided unchanged. The current control device 401 can, for example, be the one shown in Fig. 2. However, an additional circuit is provided, which includes a threshold switch 402, a first electronic switch 403, and a second power supply source 404. The threshold switch 402 detects the output voltage U present between the output terminals 48, 49. a and determines whether it exceeds a threshold value or not. If the output voltage U a the threshold value (e.g. because the output terminals are short-circuited, ie, U a = 0 V), the threshold switch sends a signal to the first electronic switch 403, causing it to open. As a result, the input voltage U applied to terminals 44, 46 of the input is efrom an input node 410 of the current control device 401. Instead, the current control device 401 is now supplied with power from the second power supply source 404, specifically with a voltage U e (17 V) reduced voltage U red , which here is, for example, 4 V. As shown, the second power supply source 404 itself is also connected to the terminals 44, 46 of the input, thus drawing its own power from that of the first power supply source 42. The second power supply source 404 can be designed as a simple voltage regulator, but with regard to reducing power loss, implementing a separate switching power supply for the second power supply source 404 may be more advantageous.

[0054] Fig. Figure 4 shows a second embodiment of the invention in more detail. The basic structure with the power supply source 42, the input terminals 44, 46, the current control device 401, the feedback circuit consisting of the threshold switch 402, the first electronic switch 403, and the second power supply source 404, and the output terminals 48, 49 is also present here.

[0055] The current control device 401 comprises an input node 410, which is connected via a resistor R6 to the emitter of a PNP bipolar transistor Q4 (“third” electronic switch). The resistor R6 is designed here as a measuring or shunt resistor, and its resistance is, for example, 4-5 Ω. The collector of the PNP bipolar transistor is connected to an output node 411 of the current control device 401 and the voltage terminal 48 of the device 40. The third electronic switch is designed as a Darlington transistor and comprises a correspondingly connected further PNP bipolar transistor Q3. The input node 410 is further connected to a positive terminal of a voltage source 45. The voltage source 45 can, without limiting the scope of protection, be, for example, a battery, or an electronic component such as a linear series regulator (e.g., LM317) or a precision shunt regulator (e.g.,TL431) etc. In this case, the voltage source 45 provides a constant voltage reference U. ref1 of approximately 1.25 V. The negative terminal of voltage source 45 is connected to the anode of a diode D1, whose cathode is connected to the anode of another diode D3. The cathode of the other diode D3 is connected via a resistor R7 to ground potential and also to the base of the Darlington transistor or PNP bipolar transistor Q3, i.e., the control electrode of the third electronic switch. The resistance of the resistor R7 is, for example, 5-10 kΩ. The two diodes D1 and D3 serve as compensation diodes with respect to the base-emitter junctions of the bipolar transistors Q3 and Q4. The voltage reference supplied by voltage source 45 serves for the actual current limitation.

[0056] As long as there is no short circuit on the signal bus 70 for signal transmission, the voltage drop across the shunt resistor R6 is lower than the voltage reference of the voltage source 45. The base current for the PNP bipolar transistors Q3 and Q4 flows through the ohmic resistor R7 and controls the two transistors Q3, Q4 of the Darlington circuit. If the load is too high or in the event of a short circuit, the voltage drop across the shunt resistor R6 increases and exceeds the voltage reference. As a result, the base current stagnates and the third electronic switch (Q3, Q4) increasingly blocks. The voltage at the output node 411 or between the terminals 48, 49 (output voltage U a ) decreases accordingly.

[0057] The threshold switch 402 detects this output voltage U a, wherein a comparator U3 is set up, the inverting input of which is connected to the output node 411 of the current control device 401 or to the voltage terminal 48 of the output. The non-inverting input of the comparator U3 is connected to a reference voltage U ref2 This is obtained from a voltage divider formed by a resistor connected between the voltage terminal 44 and the ground terminal 46 of the input (ie, the input voltage U e is present) is formed by a series-connected resistor R12 and two diodes D2 and D4. The resistance of the resistor R12 is, for example, 50 kΩ. Due to the two diodes D2 and D4 arranged from the tapping point of the voltage divider to ground, the reference voltage U ref2 approximately 1.4 V. In this and other embodiments, the threshold or reference voltage can also be chosen higher and realized by additional or other components.

[0058] At the usually high output voltage U a is determined by the comparator U3 based on the comparison with the lower reference voltage U ref2 A low-level signal is output at its output, which is fed to the first electronic switch 403, more precisely, to the base of a PNP bipolar transistor Q2 representing this switch via a base series resistor R1 (e.g., 5 kΩ). A detector of the PNP bipolar transistor Q2 is connected to the voltage terminal 44 of the input. The first electronic switch is closed in this state. If the load is too high or the output voltage is short-circuited, the reference voltage U ref2The voltage drops below the reference voltage, and comparator U3 outputs a high-level signal from voltage terminal 44, corresponding to its voltage supply. PNP bipolar transistor Q2 now blocks, and the first electronic switch 403 is open. Input node 410 is thus disconnected from the direct input voltage supply.

[0059] The second power supply source 404 is constructed from an actual voltage source 43 and a diode D5, with the anode connected to the positive terminal of the voltage source 43. The cathode of the diode D5 is connected to the collector of the PNP bipolar transistor Q2 and to the input node 410 of the current regulation device 401. The voltage source 43 can include a voltage regulator. The voltage source 43 can be supplied with power from the first power supply source 42, from its switching power supplies, or from a separate source. The voltage source 43 supplies a substantially constant voltage U red , which is compared to the input voltage U e reduced and in the exemplary embodiment is 4 volts. As soon as the first electronic switch 403 or the PNP bipolar transistor Q2 is opened, the reduced voltage U red impressed on the input node 410 via the diode D5.

[0060] This has only minor consequences for the current control device 401, because the comparison between the resistance dropping across the shunt resistor R6 and the voltage reference U ref1 changes only slightly. The bipolar current regulator implemented here is quite stable with respect to input voltage fluctuations. The current limit is still active at a maximum value of 250 mA. The power loss with a short-circuited output is only P = 4 V × 0.25 A = 1 W (or 0.5 W with signal transmission using Manchester code), without any loss of current flow. This means that there is no interference with the control or operating devices or the sensors or actuators. A particular advantage is that the device for supplying power to the communication system can be reduced in terms of installation space, because any cooling surfaces can be designed smaller or even entire heat sinks can be omitted.

[0061] Fig. Figure 5 shows a schematic circuit diagram for the signal bus 70 (DALI communication bus) connected to the output of the device 40 (voltage connection 48 to the control line and ground connection 49 to the ground line). The interface 50 of the control unit or the communication system 30 is shown here only with regard to the transmission functions, i.e., functional units for reception are omitted. A voltage source contains the microcontroller 60, which applies a pulsed voltage via an ohmic resistor R4 (base series resistor) to the base of the NPN bipolar transistor Q1 in order to selectively open and close it. Closing the NPN bipolar transistor Q1 causes a short circuit between the connections 48, 49 or the control and ground lines of the signal bus 70. The capacitor C4 and the ohmic resistor R5 also serve for stabilization. Schematically shown in Fig. 5 also shows individual consumers such as operating devices 80 or control devices (sensors 90).

[0062] The Fig. 6 and Fig. 7 shows the result of a simulation for a single short-circuit pulse (here purely as an example from about 0.4 ms to about 0.85 ms) the time courses at different points in the circuit diagram of the Fig. 4 tapped voltages or the resulting current flow.

[0063] In Fig. 6 shows the input voltage U e between terminals 44, 46 of the input, which is constant at about 17 V (dashed line), the output voltage between terminals 48, 49 of the output, the voltage U comp of the signal output by comparator U3, as well as the possibly reduced voltage at the input node 410 of the current control device 401.

[0064] In Fig. 7 shows how, purely for testing purposes, before the NPN bipolar transistor Q1 is closed (short circuit of the signal bus for data transmission), the three Fig. 5 can be activated as a load, which is indicated by the three steps between 0.2 ms and 0.4 ms. In these cases, the load is still below the maximum value I max of 250 mA for current limiting. The maximum value is determined by the dimensioning of the components in the current control device 401. In Fig. 6 it can be seen that the output voltage U a due to the load, which however does not affect the voltages U acting in the additional circuit comp and U red exercises.

[0065] At the moment of short-circuiting (from about 0.4 ms) a short-term overshoot in the current waveform ( Fig. 7), which quickly returned to the maximum value I maxof 250 mA. At the same time, the output voltage U a ( Fig. 6) as expected to 0 V. The voltage U comp of the signal output by the comparator to the first electronic switch 403 was previously at ground potential (0 V), since the output voltage U a the reference voltage U ref2 During the short circuit this is no longer the case (the output voltage U a falls below the reference voltage U at 0 V ref2 of 1.4 V), so that the comparator outputs the signal at its supply voltage (17 V). As a result, the first electronic switch 403 opens (the PNP bipolar transistor Q2 turns off), and the voltage U present at the input node 410 red is reduced to the voltage of 4 V output by the voltage source 43 via the diode D5.

[0066] As soon as the NPN bipolar transistor Q1 is switched on again by the voltage source or the microcontroller 60 of the interface 50 of the control unit, the output voltage U a back to its previous value (about 15 V), so that the threshold switch 402 also responds by switching back to the low level signal (U comp = 0 V) ​​to the first electronic switch 403. This closes again and the input node 410 is again supplied with the input voltage (U red = U e ) supplied.

[0067] An alternative embodiment (third embodiment) is shown in Fig.8. The third embodiment differs from the second embodiment only with regard to the threshold switch 402'. Instead of a comparator U3, a simple NPN bipolar transistor Q5 is used here, the base of which is connected to the output (voltage terminal 48) of the device 40 via a base series resistor R2 and a diode D4. The emitter of the NPN bipolar transistor Q5 is connected to ground potential, and the collector is connected to the base of the PNP bipolar transistor Q2 via the base series resistor R1. A signal level change of the threshold switch 402' occurs when the output voltage Ua falls below the reference voltage Uref2 of the threshold switch, which in this case is the threshold voltage of the NPN bipolar transistor Q5. The mode of operation is otherwise identical to that of the second embodiment.It should be noted that the diode D5 of the second embodiment is also replaced by a Schottky diode D5.

[0068] Further modifications or alternatives to the above-described embodiments will be readily recognized by those skilled in the art as belonging to the invention, insofar as they fall within the scope of protection defined by the appended claims. Thus, instead of the described bipolar transistors, transistors of opposite conductivity types or even other transistor types, such as MOSFETs, etc., can be used. Those skilled in the art will routinely make appropriate adaptations to the circuits.

[0069] Furthermore, the invention has been described primarily in connection with the DALI communication system. Nevertheless, the invention is also applicable to other bus systems based on other protocols and, in particular, other voltage systems, especially if both signals and power supply are to be carried on the same bus lines. LIST OF REFERENCE SYMBOLS: 10 Lighting system 20 Control device (server, PC) 30 Communication system 40 Power supply device 42 First power supply source 43 Second power supply source 44 Voltage connection (input) 45 Voltage source 46 Ground connection (input) 48 Voltage connection (output) 49 Ground connection (output) 50 Interface (control unit: central control unit) 60 microcontrollers with memory 70 Signal bus, DALI communication bus, 2-wire cable 80 Operating device 81 Interface (operating device) 82 microcontrollers with memory 90 Sensor, Actuator 91 Interface (control unit: sensor, actuator) 92 microcontrollers with memory 100 electronic ballasts 110 light 401 Current control device 402 threshold switch 403 First electronic switch 404 Second power supply source C1 capacitor C4 capacitor D1 diode D2 diode D3 diode D4 diode D5 diode D6 Schottky diode M mains power line Q1 NPN transistor Q2 PNP transistor (first electronic switch) Q3 PNP transistor (third electronic switch in Darlington) Q4 PNP transistor (third electronic switch in Darlington) Q5 PNP transistor (second electronic switch Q9 PNP transistor R1 Ohmic resistance R2 Ohmic resistance R4 Ohmic resistance R5 Ohmic resistance R6 Ohmic resistance R7 Ohmic resistance R12 Ohmic resistor R21 Ohmic resistance R22 Ohmic resistance R23 Ohmic resistance U3 Comparator U a Output voltage U comp voltage output from the comparator to the electronic switch U e Input voltage U red Reduced voltage at the input of the current regulator U ref1 Voltage reference in the current regulator U ref2 Threshold or reference voltage at the threshold switch

Claims

[1] Power supply device (40) for a communication system (30) for lighting systems (10), comprising: an input with a voltage terminal (44) and a ground terminal (46) for connection to a first power supply source (42) which has an input voltage (U e ) between these terminals (44, 46), and an output with corresponding terminals (48, 49) for connection to at least one interface (50, 81, 91) of a control and / or operating device, a current control device (401) having an input node (410) and an output node (411), wherein the current control device (401) is designed to control a current (I e ) to a predetermined maximum value (I max ) to limit characterized by , a circuit which is designed to provide an output voltage (U a ) which is present between the voltage terminal (48) and the ground terminal (49) of the output, and depending on the detected output voltage (U a ) the input node of the current control device (401) with a voltage (U red ) which is higher than the input voltage (U e ) is reduced. [2] Power supply device (40) according to claim 1, wherein the circuit is designed to supply the current control device (401) with the reduced voltage (U red ) when the output voltage (U a ) a predetermined threshold value (U ref2 ), and the current control device (401) is connected to the input voltage (U e ) when the output voltage (U a ) the predetermined threshold value (U ref2 ) exceeds. [3] Power supply device (40) according to claim 2, wherein the circuit comprises a threshold switch (402) which is connected to the output node (411) and which, depending on the predetermined threshold value (U ref2 ) by the output voltage (U a ) a signal (U comp ) outputs. [4] Power supply device (40) according to claim 3, wherein the circuit comprises a first electronic switch (403) whose first terminal is connected to the voltage terminal (44) of the input and whose second terminal is connected to the input node (410) of the current control device (401), wherein the first electronic switch (403) is designed to switch depending on the signal (U comp ) to open or close in order to apply the input voltage (U e ) at the input node (410). [5] Power supply device (40) according to claim 4, wherein the circuit comprises a second power supply source (404) which supplies the reduced voltage (U red ), and which is connected to the input node (410) of the current control device (401) and to the second terminal of the first electronic switch (403) and is designed to supply the current control device (401) with the reduced voltage (U red ) to supply. [6] Power supply device (40) according to claim 5, wherein the second power supply source (404) comprises a voltage regulator which controls the input voltage (U e ) to the reduced voltage (U red ) and then outputs it at its output terminal. [7] Power supply device (40) according to claim 6, wherein the voltage regulator is a linear or a switching regulator. [8] Power supply device (40) according to one of claims 6 to 7, wherein the output terminal of the voltage regulator is connected to an anode terminal of a rectifier diode (D5) whose cathode terminal is connected to the input node (410) of the current regulation device and to the second terminal of the electronic switch (403). [9] Power supply device (40) according to one of claims 5 to 8, wherein the threshold switch (402) comprises a comparator (U3) whose inverting input is connected to the output voltage (U a ) at the output of the device, and whose non-inverting input is connected to a reference voltage (U ref2 ), whereby the signal (U comp ) depending on a comparison result of the two voltages at the output of the comparator (U3). [10] Power supply device (40) according to one of claims 5 to 8, wherein the threshold switch (402) comprises a second electronic switch (Q5) whose control terminal is connected to the output voltage (U a ) is connected to the voltage terminal (48) of the output of the power supply device, and whose working electrode is connected via an ohmic resistor (R1) to a control terminal of the first electronic switch (403), and whose reference electrode is connected to the ground terminal (46). [11] Power supply device (40) according to one of claims 5 to 10, wherein the current control device (401) has an input terminal with a first node (410) which is connected via a shunt resistor (R6) to a working electrode of a third electronic switch (Q3, Q4), the reference electrode of which is connected to an output node (411) of the current control device (401), wherein a voltage source (45) is provided for providing a predetermined voltage difference, the positive terminal of which is connected to the node and the negative terminal of which is connected to a control electrode of the third electronic switch (Q3, Q4) directly or indirectly via one or more diodes (D1, D3). [12] Power supply device (40) according to one of claims 5 to 11, further comprising: the first power supply source (42), wherein the first power supply source is designed to supply the input voltage (U e ) having a value of 16 volts, and wherein the second power supply source (43) is designed to provide a reduced voltage (U red ) having a value of 8 volts or less, preferably 6 volts or less, more preferably 4 volts or less. [13] Power supply device (40) according to one of claims 5 to 12, wherein the predetermined maximum value (Imax ) for limiting the current delivered to the output via the output node (411) is 250 milliamperes or less. [14] Power supply device (40) according to one of claims 9 or 10 to 13, as far as related to claim 9, wherein the value of the reference voltage (U ref2 ) is between 0.1 volts and 9.5 volts. [15] Communication system (30) for lighting systems, comprising the power supply device (40) according to one of the preceding claims, a signal bus (70) for connecting to the terminals (48, 49) at the output of the power supply device (40), and at least one interface (50, 81, 91) of an operating and / or control device for connection to the signal bus (70), wherein the interface (50, 81, 91) is designed to transmit a digital signal on the signal bus (70) to the voltage (U a ) periodically short-circuit. [16] Communication system (30) according to claim 15, wherein the power supply device (40), the signal bus (70) and the interface (50, 81, 91) comply with a standard of the IEC 62386 family called "Digital Addressable Interface for Lighting" (DALI). [17] A method for supplying power to a communication system (30) for lighting systems (10), comprising: - Providing an input voltage (U e) between a voltage terminal (48) and a ground terminal (49) of an input of a power supply device (40) for the communication system (30), - Providing a current control device (401) having an input node (401) and an output node (411), wherein the current control device (401) is designed to limit a current provided at the input node and output therefrom via the output node to an output of the power supply device (40) having a voltage connection (48) and a ground connection (49) to a predetermined maximum value (I max ) to limit - Detecting an output voltage (U a ), which is applied between the voltage terminal (48) and the ground terminal (49) of the output, - Compare the output voltage (U a ) with a given reference voltage (U ref2 ), - reducing the voltage (U red ) depending on the comparison result to a predetermined value.

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