EP4646035A1

EP4646035A1 - Control bus power supply with dynamic maximum bus supply current

Info

Publication number: EP4646035A1
Application number: EP24173308.8A
Authority: EP
Inventors: Harald Netzer; Clemens KUCERA
Original assignee: Tridonic GmbH and Co KG
Current assignee: Tridonic GmbH and Co KG
Priority date: 2024-04-30
Filing date: 2024-04-30
Publication date: 2025-11-05

Abstract

A power supply device for a control bus comprises a power supply circuit configured to output an adjustable current to the control bus, and a short-switching circuit configured to selectively apply a short circuit to the control bus. The power supply device further comprises a measurement circuit configured to measure a current on the control bus when the short circuit is applied to the control bus. A control circuit of the power supply device is configured to control the short-switching circuit and the power supply circuit, and the control circuit is configured to determine the adjustable current based on the measured current on the control bus. The invention also includes a method for controlling the power supply device and a driver device including the power supply device for the control bus.

Description

The invention is in the field of lighting systems and of control busses for lighting systems. In particular, the invention concerns a power supply device for a control bus of an infrastructure system, and a driver device for the infrastructure system.
Current building infrastructure systems arrange a plurality of infrastructure devices over a building and connect the individual infrastructure devices with a control bus for communicating messages between the devices for controlling the infrastructure system.
A typical example for such an infrastructure system is a lighting system that uses a control bus for controlling the individual devices of the lighting system, which include luminaires, sensors, push-button devices, dimming devices, lighting servers, for example. The control bus of the lighting system may operate according to a standard from the series of technical standards known as Digital Addressable Lighting Interface (DALI^RTM) standardized in IEC 62386, and known as DALI, DALI-2, and D4i.
A DALI control bus comprises at least one application controller and bus power supply, often arranged within another device, e.g. light driver device, at least one input device, e.g. sensor(s), push-button device(s), and further devices, e.g. electrical ballasts (light driver devices, in particular LED driver devices) each equipped with DALI interfaces. The application controller may configure, query, and control each device on the control bus via a bi-directional data exchange. Multiple application controllers may coexist on the same control bus. Typical DALI bus power supplies deliver up to 250 mA supply current for the DALI bus.
Technical standards governing a control bus typically define a maximum supply current for all power supplies connected to the control bus. For the example of the DALI bus, the sum of maximum supply currents of all bus power supplies connected to and active at the DALI bus is never to exceed 250 mA.
Problems can arise when maintenance of the infrastructure system, e.g. updating the firmware of connected driver devices via the control bus, requires connecting an additional power supply device to the control bus. Normally, one or plural bus power supplies arranged within driver devices power the control bus. Connecting the additional bus power supply to the control bus may result in currents flowing on the bus lines of the control bus that violate the limit for the total current set in the applicable control bus standard.
In the example of the DALI bus, the result of connecting the additional bus power supply in addition to the bus power supplies already present at the DALI bus may have the effect of a total current exceeding 250 mA flowing on the DALI bus when short circuiting the DALI bus during communication. However, currents exceeding of 250 mA may harm and destroy parts of the DALI interfaces of the devices connected to the DALI bus.
It is an object of the invention to improve the processes requiring additional bus power supplies at a control bus of infrastructure systems after installation in the field, and the equipment linked with the control bus with regard to availability and simplicity of application.
The power supply device for a control bus according to independent claim 1, the driver device, and the method for controlling a power supply for a control bus of an infrastructure system according to the corresponding independent claims provide advantageous solutions to the aforementioned problem.
The dependent claims define further advantageous embodiments.
According to a first aspect, the power supply device for a control bus comprises a power supply circuit configured to output an adjustable current to the control bus and a short-switching circuit configured to apply selectively a short circuit to the control bus. The power supply device further comprises a measurement circuit configured to measure a current on the control bus when the short circuit is applied to the control bus. The control circuit is configured to control the short-switching circuit and the power supply circuit, wherein the control circuit is configured to determine the adjustable current based on the measured current on the control bus.
The power supply is a bus power supply device (bus power supply). The power supply device may be an application controller and bus power supply of a lighting network, e.g. a DALI-standard based lighting network.
The power supply circuit (adjustable power supply circuit) is configured to output an adjustable current to the control bus. The adjustable current in particular is an adjustable maximum current (maximum supply current), which is set by a respective current control signal and which the current the power supply circuit outputs during operation not exceeds. The power supply circuit obtains the current control signal from externally, in particular from the control circuit.
By measuring the actual current on the short circuited control bus, while the power supply circuit is not yet outputting the adjustable current to the control bus, and determining the adjustable current based on the measured actual current, and outputting the determined adjustable current to the control bus, the power supply device is able to automatically adapt to an existing system and ensure that the regulations of the applicable bus standard for the control bus are not violated by the additional current in form of the adjustable current output by the power supply device to the control bus, that will increase the total current on the control bus that is currently present.
The additional circuitry required in the power supply device for implementing the proposed intelligent bus power supply is limited, as functions executed by elements such as the measurement circuit and the control circuit either may be implemented by circuit components already present in known power supply devices or by using components requiring only limited additional cost. Shunt resistors and switchable short circuits have only limited complexity and cost, and the control circuit may use resources such as microcontrollers already present in many devices including bus power supplies and bus interfaces, e.g., light driver devices.
According to an embodiment of the bus power supply device, the control circuit is configured to determine whether the power supply device is connected to the control bus. In case of control circuit determining that the power supply device has been connected to the control bus, the control circuit is configured to control the short-switching circuit to selectively apply the short circuit to the control bus for a predetermined amount of time.
This ensures an autonomously executed process of powering up the power supply device on the control bus, which avoids human faults, and also ensures that bus standards are not violated. Information on the bus standard can be stored in the power supply or read out from the bus, when connecting the power supply to the bus.
Any harm to other devices connected to the bus, their bus interfaces and the circuit components thereof is avoided.
In an embodiment, the measurement circuit of the power supply device is further configured to measure a bus voltage on the control bus for determining whether the power supply device is connected to the control bus.
Monitoring the bus voltage is already implemented in some devices with control bus interfaces, or requires only limited additional resources. Thus, the implementation cost for an implementation, e.g. using an analogue-to-digital converter (AD converter) included in a microcontroller also providing the functions of the control circuit are only small.
The predetermined amount of time is 10 ms in a preferred embodiment of the power supply device.
The short time duration is sufficient for measuring the total current on the control bus.
According to an embodiment of the power supply device, the measurement circuit includes a shunt resistor arranged in series in the short circuit and an AD converter circuit configured to measure a voltage over the shunt resistor for determining the current when the short circuit is switched to the control bus.
The implementation cost for the measurement circuit are therefore low, in particular since the AD converter may be already present in a microcontroller integrated circuit (IC), simultaneously providing functions of the control circuit.
The control circuit of an embodiment of the power supply device is configured to determine the adjustable current as a maximum current output by the power supply circuit.
This ensures that during operation of the power supply circuit, the total current on the control bus never exceeds the maximum current set for the power supply circuit, and therefore applicable current limits of the control bus.
According to an embodiment of the power supply circuit, the control circuit is configured to determine the adjustable current output by the power supply circuit based on the measured current and further based on a specified maximum bus current of the control bus.
This ensures that during operation of the power supply circuit, the total current on the control bus never exceeds the applicable current limits as specified for the control bus in the applicable bus standards.
The power supply device according to an embodiment includes the control circuit configured to calculate a difference between the specified maximum bus current of the control bus and the measured current for determining the adjustable current output by the power supply circuit.
Therefore, the total current on the control bus during operation never exceeds the applicable current limits as specified for the control bus in the applicable bus standards. The adjustable current output by the power supply circuit is determined by a computationally efficient difference operation that involves as a pre-stored value the specified maximum bus current of the control bus, and the measured total current value without the additional current provided by the power supply device.
The specified maximum bus current of the control bus bases on a maximum current specified in a lighting control standard, in particular in a DALI series standard in an embodiment of the power supply device.
The DALI series standards specify a maximum current on the control bus, which may be violated resulting in potential harm to circuit components of DALI interfaces designed taking the maximum current according to the DALI series standards into account.
The power supply device according to an embodiment comprises a bus interface circuit configured to connect the power supply device to the control bus including a lighting control bus, in particular a DALI series lighting control bus.
The driver device according to the second aspect includes a power supply device for a control bus according to one of the preceding embodiments of the power supply device of the first aspect.
Driver devices include often control bus interfaces that have a bus power supply. The advantageous effects of the power supply device according the first aspect may be realized in the driver device that already has control circuitry in the form of microcontrollers or application specific circuits (ASICs). The microcontrollers or ASICs may also take over the functions of the control circuit for the intelligent bus power supply provided by the power supply device according to the first aspect, thereby ensuring a cost efficient implementation in the driver device.
The driver device according to an embodiment is a light driver device, in particular a LED driver device, and comprises a control bus interface that includes the power supply device.
The method for controlling a power supply device for a control bus of an infrastructure system according to the third aspect includes steps of: applying, by a short-switching circuit, a short circuit to the control bus for a predetermined amount of time; measuring, by a measurement circuit, a current on the control bus while the short circuit is applied to the control bus; determining, by a control circuit, an adjustable current based on the measured current on the control bus; and controlling, by the control circuit, a power supply circuit to output the determined adjustable current to the control bus.
The method for controlling a power supply device for a control bus of an infrastructure system according to the third aspect achieve corresponding advantageous effects as discussed with reference to power supply device of the first aspect.
The following description of embodiments refers to the figures, in which

Fig. 1 shows a flowchart illustrating a control method for controlling a power supply device implementing an intelligent power supply according to an embodiment;
Fig. 2 provides an overview over the architecture of a lighting system;
Fig. 3 displays a simplified block diagram of a power supply device of an embodiment.

In the figures, corresponding elements have the same reference signs. The discussion of the figures avoids discussion of same reference signs in different figures wherever considered possible without adversely affecting comprehensibility and avoiding unnecessary repetitions for sake of conciseness.
Fig. 1 shows a flowchart illustrating a control method for controlling a power supply device 6 according to an embodiment.
The power supply device 6 includes a short-switching circuit 14, a measurement circuit 15, an adjustable power supply circuit 12 for outputting a supply current to the control bus 8, and a control circuit 13. The structural elements of the power supply device 6 are discussed in more detail, in particular concerning specific implementations with reference to fig. 3 below.
The method executes a sequence of steps for controlling the power supply device 6 for a control bus 8. In particular, the sequence of steps controls the process of connecting to and putting into operation the power supply device 6 at the control bus 8 already installed and operational in a building infrastructure system, e.g. a lighting system 1.
The lighting system 1 is discussed in more detail with reference to fig. 2. The method steps of fig. 1 illustrate the process of connecting the power supply device 6, e.g. an intelligent DALI bus power supply to the control bus 8, which has the form of a DALI bus.
By default, the bus power supply 6, in particular the adjustable power supply circuit 12, is set to output a current I_SUPPLY = 0 mA at its bus interface circuit 17 in step S1.
In step S2, the power supply device 6 is connected with the control bus 8. Connecting the power supply device 6 with the control bus 8 includes connecting physically (mechanically) and electrically the connectors of the bus interface circuit 17 with corresponding connectors, e.g. including wires (bus lines) of the bus wiring of the control bus 8.
The power supply device 6 of an embodiment determines whether the power supply device 6 is connected with the control bus 8 automatically, e.g. by measuring a bus voltage between the connectors of the bus interface circuit 17.
Once the power supply device 6 has determined that the power supply device 6 is connected with the control bus 8, the method proceeds to step S3.
In step S3, the power supply device 6 applies a short circuit to the control bus 8 for a predetermined amount of time. In particular, the short-switching circuit 14 applies a short circuit to the control bus 8 until a predetermined amount of time has elapsed.
A short circuit corresponds to a direct electrical connection with no or only small resistance value of the electrical connection between the bus lines of the control bus 8.
The predetermined amount of time may have a duration of some milliseconds, e.g. 10 ms.
The control circuit 13 may include a timer that controls the short-switching circuit 14 to switch the short circuit between the bus lines of the control bus 8 for the predetermined amount of time (predetermined time).
The method now proceeds to step S4, in which the power supply device 6 measures an electric current (current) flowing via the short circuit on the control bus 8 while the short circuit is applied to the control bus 8. In particular, in step S4, the measurement circuit 15 measures the current on the control bus while the short circuit is applied to the control bus 8.
The measured current I_SUPPLY corresponds to the sum of the maximum bus supply currents of all the bus power supplies currently connected to the control bus 8.
The measurement circuit 15 provides the measured current I_SUPPLY to the control circuit 13. In a specific embodiment, at least parts of the measurement circuit 15 are implemented using an AD converter circuit forming part of the control circuit 13. In this embodiment, the AD converter circuit provides the measured current I_SUPPLY to evaluation circuitry of the control circuit 13.
The method proceeds to step S5, in which the power supply device 6 releases the short circuit from the control bus 8. In particular, in step S5, the control circuit 13 controls the short-switching circuit 14 to open the short circuit between the bus lines of the control bus 8 after the predetermined amount of time has elapsed.
The method proceeds to step S6. In step S6, the power supply device 6 compares the measured current I_SUPPLY with a specified maximum bus current of the control bus 8. In particular, the control circuit 13 compares the measured current I_SUPPLY with the specified maximum bus current of the control bus 8.
The control circuit 13 may read the specified maximum bus current of the control bus 8 from a memory of the power supply device 6, in particular, an internal memory of the control circuit 13. Alternatively, an external memory connected with the control circuit 13, e.g. an external memory of the power supply device 6, of a bus interface 11, or a light driver device 3, 4, 5 may store the specified maximum bus current of the control bus 8.
The specified maximum bus current of the control bus 8 corresponds to a maximum current specified in a lighting control standard, e.g., a DALI series standard.
The specified maximum bus current of the control bus 8 may be 250 mA for the DALI series standard applicable for the control bus 8.
In case the comparison of step S6 provides the result that the measured current I_SUPPLY is equal to or even exceeds the specified maximum bus current of the control bus 8, the method proceeds to step S7 (NO).
In step S7, the power supply device 6 maintains the supply current I_SUPPLY output by the power supply device at o mA as set in step S1. In particular, the control circuit 13 maintains the adjustable power supply circuit 12 to output the current I_SUPPLY = o mA via the bus interface circuit 17 to the control bus 8.
The processing in the branch including step S6-NO-S7 ensures that the total current on the control bus 8 is not increased further by adding an additional current I_SUPPLY by the power supply device 6.
In case the comparison of step S6 provides the result that the measured current I_SUPPLY is smaller than the specified maximum bus current of the control bus 8, the method proceeds to step S8 (YES).
In step S8, the power supply device 6 determines an adjustable current based on the measured current I_SUPPLY on the control bus 8.
In particular, the control circuit 13 determines an adjustable current based on the measured current I_SUPPLY during the predetermined amount of time on the control bus 8, measured in step S4.
In particular, the control circuit 13 determines the adjustable current as a maximum current (maximum current limit) for the current to be output by the power supply circuit 12 during operation.
The control circuit 13 determines the adjustable current output by the power supply circuit 12 based on the measured current and further based on a specified maximum bus current of the control bus 8. In particular, the control circuit 13 calculates in step S8 a difference between the specified maximum bus current of the control bus 8 and the measured current I_SUPPLY and determines the adjustable current output by the power supply circuit 12 as the calculated difference.
The method proceeds then to step S9. In step S9, the power supply device 6 sets the adjustable current output by the power supply device 6 based on the measured current I_SUPPLY on the control bus 8, particular as the maximum current I_SUPPLY, MAX for the current to be output by the power supply circuit 12.
In particular, in step S9, the control circuit 13 controls the adjustable power supply circuit 12 to provide the determined adjustable current with a set maximum current I_SUPPLY, MAX to the control bus 8 via the bus interface circuit 17.
In step S10, the control circuit 13 enables the adjustable power supply circuit 12 to provide the determined adjustable current with the set maximum current I_SUPPLY, MAX to the control bus 8 via the bus interface circuit 17.
The processing of the control method for controlling the power supply device 6 then terminates. The control method for controlling the process of connecting and powering up the power supply device 6 to the control bus 8 in steps S3 to S10 in particular provides an intelligent bus power supply for the control bus 8 of an infrastructures system.
The power supply device 6 calculates the output current limit for the power supply device 6 using a measured value for the current I_SUPPLY on the control bus 8, and the applicable maximum current limit of specified by the control bus standard and pre-set in the power supply device 6.
In an example, the difference current I_SUPPLY, DIFF between a measured current I_SUPPLY of 100 mA and the specified maximum bus current of the control bus 8 of 250 mA might be calculated as 150 mA. The intelligent bus power supply device 6 then sets its output current limitation I_SUPPLY, MAX to 150mA in step S9 and then enables its output via the bus interface circuit 17 to the control bus 8. This ensures that the actual current on the control bus 8 will never exceed the specified maximum bus current of the control bus 8 of 250 mA.
Fig. 2 provides an overview over the architecture of a lighting system 1.
The lighting system 1 is a specific example for an infrastructure system. The lighting system 1 comprises a control bus according to the DALI standard for connecting the individual devices of the lighting system 1 using their respective DALI interfaces 9.
The infrastructure system may include other infrastructure systems than the lighting system 1 depicted in fig. 2. The infrastructure system may, e.g. include at least one of a HVAC system, a route guidance system, an emergency guidance system, and a fire alarm system in order to name some further examples.
The driver devices 3, 4, 5 and the control device 2 each include a communication interface in form of the DALI interface 9. The communication interface enables transmitting and receiving communication signals via the control bus 8 in a wired communication network. The wired communication network may operate based on at least one of a DALI network standard, DALI 2 network standard, DALI+ network standard, DiiA network standard, D4i network standard, KNX network standard, ProfiNet network standard, ProfiBus network standard or corresponding standards in the technical fields of building infrastructure systems, lighting systems, communication systems, and smart home systems.
Hence, the control bus 8 may include a communication bus based on another standard than a DALI series standard as the DALI bus 8 illustrated in fig. 2. The control bus 8 benefits from the power supply device 6 in cases in which a maximum current rating for the current on the control bus is specified.
In the exemplary DALI installation of the lighting system 1 of fig. 2, three driver devices 3, 4, 5 may each have an enabled internal DALI bus power supply in their DALI interface 9. The enabled internal bus power supply of the three driver devices 3, 4, 5 each may provide a bus supply current of 60mA. In total, the maximum bus supply current provided to the DALI bus 8 amounts to 180mA.
In fig. 2, an external DALI bus power supply 10 is connected to the DALI bus 8, wherein the external DALI bus power supply 10 has a maximum rated bus supply current of 200mA. In consequence, the regulations of the DALI standard concerning the maximum bus supply current of 250 mA could be violated, as in this case the total possible supply current would amount to 380mA, thereby significantly exceeding the admissible 250 mA of the DALI standard.
The bus power supply device 6 according to an embodiment as illustrated in fig. 3 is configured to automatically adjust its maximum output current I_SUPPLY, MAX based on the other DALI bus power supplies connected to the control bus 8. In particular, when connecting to the DALI bus 8, the power supply device 6 applies a short circuit to the bus lines DA+ and DA- for the predetermined amount of time. The predetermined amount of time may extend to about 10 ms. While applying the short circuit to the bus lines DA+ and DA- of the DALI bus 8, the bus power supply 6 measures the bus current I_SUPPLY that is flowing via the applied short circuit on the control bus 8.
If, for example the measured bus supply current I_SUPPLY is 100 mA, the power supply device 6 determines that the one or more other power supplies connected to the control bus 8 together are able to provide a maximum current of 100mA to the control bus 8.
The power supply device 6 set its own maximum bus supply current limit to, e.g., 150mA in order to ensure that the DALI standard is not violated under any circumstances. Hence, the sum of currents that can be delivered by all bus power supplies included in the DALI interfaces 9 of the driver devices 3, 4, 5 and the DALI interface 11 that comprises the power supply device 6 of the additional device 10 will be 250mA.
Accordingly, the control bus 8 complies with the regulation concerning the current on the bus according to the DALI standard even in case of connecting the additional device 10 to the control bus 8. The electrical specifications of the DALI standard for lighting control defines two-wire bus with a maximum current of 250 mA, a maximum voltage of 22.5 V_DC, and typical signal of 16 V_DC.
The driver devices 3, 4, 5 of fig. 2 each have a mains interface not explicitly shown in fig. 2 for connecting the driver devices 3, 4, 5 with the mains grid 7 (AC mains grid 7). The mains grid 7 supplies not only the driver devices 3, 4, 5 with a mains supply current I_MAINS at a mains supply voltage V_MAINS, but also other electric devices including, but not limited to the control device 2, e.g. a push-button device, and other electronic devices. The other electronic devices may include, e.g., sensors, dimming devices, lighting servers, that are supplied via the mains grid 7 with electric power.
The driver devices 3, 4, 5 of fig. 2 each generate and output a load current, in particular, a LED current I_LED to at least one lighting module not illustrated in fig. 2. The LED current I_LED is a DC current supplying at least one, usually even a plurality of LEDs of the lighting module, which may be arranged in series, in parallel, or in a combination of series and parallel circuit configuration.
The driver devices 3, 4, 5 each include a control circuit, which may in turn comprise at least one of a microcontroller and an ASIC. The control circuit of the driver devices 3, 4, 5 includes also a memory providing data storage capacity for storing information. The memory may form part of the microcontroller or be separate from the microcontroller. The control circuit of the driver devices 3, 4, 5 may perform at least some of the functions of the control circuit 13 of the power supply device 6, thereby reducing the complexity and the respective cost for implementing the intelligent bus power supply by the power supply device 6.
Fig. 3 displays a simplified block diagram of a power supply device 6 (bus power supply device 6) arranged in a bus interface 11 according to an embodiment.
The power supply device 6 includes a bus interface circuit 17 that provides connections for electrically connecting the power supply device 6 to the control bus 8.
The power supply device 6 for the control bus 8 comprises a power supply circuit 12, a control circuit 13, a short-switching circuit 14, and a measurement circuit 15.
The power supply circuit 12 (adjustable power supply circuit 12) is configured to dynamically adjust the output current limit provided to the control bus 8, e.g. the DALI bus of fig. 3.
The short-switching circuit 14 is configured to selectively apply a short circuit to the control bus 8, e.g. the DALI bus of fig. 3.
The short-switching circuit 14 may include at least one switching component, e.g., including at least one field effect transistor (FET) controlled by switching control signals provided by the control circuit 13.
The measurement circuit 15 is configured to measure a current I_SUPPLY on the control bus 8 when the short circuit is switched to the control bus 8.
The measurement circuit 15 may be configured to measure the current flowing when the short circuit is applied to the control bus 8 using, e.g. a shunt resistor arranged as part of the short-switching circuit 14 and an analogue-to-digital converter (ADC) forming part of the control circuit 13.
The control circuit 13 is configured to control the short-switching circuit 14 and to control the power supply circuit 12. In particular, the control circuit 13 is configured to adjust the adjustable current, e.g. the maximum bus current output by the power supply circuit 12 to the control bus 8 based on the measured current on the control bus 8. In particular, the control circuit 13 is configured to adjust the adjustable current, e.g. the maximum bus current output by the power supply circuit 12 to the control bus 8 based the determined maximum bus current determined as the difference between the maximum bus current rating of the electrical specification of the applicable bus standard and the measured current on the control bus 8 when the short circuit is switched to the control bus 8.
The control circuit 13 may include at least one of a microcontroller and an ASIC. The control circuit 13 may include at least one AD converter circuit configured to convert a value of an analogue voltage input via an input to the control circuit 13 into a corresponding digital value of the analogue voltage.
The bus interface 6 further comprises a power supply interface 16 for connecting the power supply device 6 with a DC power supply 18. The DC power supply 18 may form part of the low voltage power supply of a driver device, e.g. a light driver device 3, 4, 5 that includes the bus interface 11.
Not shown in fig. 3 is a low voltage power supply circuit that generates supply voltages for supplying the electric circuits of the power supply device 6, in particular the adjustable power supply circuit 12, the control circuit 13, and the short-switching circuit 14 with required supply voltages.
The low voltage power supply circuit may form part of the power supply device 6. Alternatively or additionally, the low voltage power supply circuit is part of the bus interface 11 or the driver device.
All steps which are performed by the various entities described in the present disclosure as well as the functionalities described to be performed by the various entities are intended to mean that the respective entity is adapted to or configured to perform the respective steps and functionalities.
In the claims as well as in the description the word "comprising" does not exclude the presence of other elements or steps.
The indefinite article "a" or "an" does not exclude a plurality.
A single element or other unit may fulfill the functions of several entities or items recited in the claims. The mere fact that different dependent claims recite certain measures and features of the control circuit does not exclude that a combination of these measures and features cannot combined in an advantageous implementation.
The features described in the discussion of specific embodiments and depicted in the figures may be combined with each other for the invention defined in the attached claims.

Claims

Power supply device for a control bus (8), wherein the power supply device comprises
a power supply circuit (12) configured to output an adjustable current to the control bus (8);

a short-switching circuit (14) configured to selectively apply a short circuit to the control bus (8);

a measurement circuit (15) configured to measure a current on the control bus (8) when the short circuit is applied to the control bus (8);

a control circuit (13) configured to control the short-switching circuit (14) and the power supply circuit (12), wherein the control circuit (13) is configured to determine the adjustable current based on the measured current on the control bus (8).
Power supply device according to claim 1, wherein
the control circuit (13) is configured to determine whether the power supply device is connected to the control bus (8), and,

the control circuit (13) is configured to control the short-switching circuit (14) to selectively apply the short circuit to the control bus (8) for a predetermined amount of time, in case of determining that the power supply device has been connected to the control bus (8).
Power supply device according to claim 2, wherein
the measurement circuit (15) is further configured to measure a bus voltage on the control bus (8) for determining whether the power supply device is connected to the control bus (8).
Power supply device according to claim 2 or 3, wherein
the predetermined amount of time is 10 ms.
Power supply device according to one of the preceding claims, wherein
the measurement circuit (15) includes a shunt resistor arranged in series in the short circuit and an AD converter circuit configured to measure a voltage over the shunt resistor for determining the current when the short circuit is switched to short circuit the control bus (8).
Power supply device according to one of the preceding claims, wherein
the control circuit (13) is configured to determine the adjustable current as a maximum current output by the power supply circuit (12).
Power supply device according to one of the preceding claims, wherein
the control circuit (13) is configured to determine the adjustable current output by the power supply circuit (12) based on the measured current and further based on a specified maximum bus current of the control bus (8).
Power supply device according to claim 7, wherein
the control circuit (13) is configured to calculate a difference between the specified maximum bus current of the control bus (8) and the measured current for determining the adjustable current output by the power supply circuit (12).
Power supply device according to claim 7 or 8, wherein
the specified maximum bus current of the control bus (8) bases on a maximum current specified in a lighting control standard, in particular a DALI^RTM series standard.
Power supply device according to one of the preceding claims, wherein the power supply device comprises
a bus interface circuit (17) configured to connect the power supply device to the control bus (8) that includes a lighting control bus, in particular a DALI^RTM standard lighting control bus.
Driver device including a power supply device (6) for a control bus (8) according to one of the preceding claims.
Driver device according to claim 11, wherein driver device is a light driver device, in particular a LED driver device comprising a control bus interface (11) that includes the power supply device (6).
Method for controlling a power supply device (6) for a control bus (8), the method including steps of:
applying (S3), by a short-switching circuit (14), a short circuit to the control bus (8) for a predetermined amount of time;

measuring (S4), by a measurement circuit (15), a current on the control bus (8) while the short circuit is applied to the control bus (8);

determining (S8), by a control circuit (13), an adjustable current based on the measured current on the control bus (8); and

controlling (S9, S10), by the control circuit (13), a power supply circuit (12) to output the determined adjustable current to the control bus (8).