Operating device for a lighting means

Abstract

The invention relates to an operating device (10) for a lighting means, comprising: a connection (17) for connecting a load (11); and an electronic circuit (12) which is designed to provide an output voltage or intermediate voltage for supplying the connected load (11), wherein the circuit (12) has a smoothing capacitor (13), in particular an electrolytic capacitor, which is designed to stabilise the output voltage or intermediate voltage. The operating device (10) also comprises a control unit (15) which is designed to detect a voltage value of the stabilised output voltage or intermediate voltage and to compare the detected voltage value with a minimum threshold value (VBus_min), wherein the control unit (15) is also designed to adapt the output voltage or intermediate voltage and / or an output power of the operating device (10) if the voltage value reaches or falls below the minimum threshold value (VBus_min).

Description

[0001] CONTROL UNIT FOR A LIGHT SOURCE

[0002] Description:

[0003] 1. Field of the invention

[0004] The present invention relates to an operating device for a light source, in particular an LED driver, and a method for operating such an operating device.

[0005] 2. Background

[0006] The maximum lifespan of an LED driver is limited by the lifespan of its internal components. Two-stage LED drivers often include an electrolytic capacitor to stabilize an intermediate voltage. The electrolytic capacitor is primarily intended to reduce periodic fluctuations in the intermediate voltage. This smoothing process typically leaves behind a residual ripple in the intermediate voltage, also known as voltage ripple. However, the electrical properties of the electrolytic capacitor, such as its capacitance or ESR (Equivalent Series Resistance), degrade over time. Consequently, the voltage ripple increases over time.

[0007] The increasing voltage ripple can cause the intermediate voltage to fall below a defined minimum voltage due to the growing fluctuations. Falling below this minimum voltage often triggers a shutdown of the driver. After this shutdown, the driver is frequently replaced in practice, even though it could often still deliver some of its original performance. Thus, the degradation of the electrolytic capacitor limits the driver's lifespan.

[0008] It is therefore an object of the present invention to increase the service life of a control device for light sources, in particular an LED driver.

[0009] These and other problems, which will be mentioned in the following description or which may be recognized by a person skilled in the art, are solved by the subject matter of the independent claims. The dependent claims further develop the central idea of ​​the present invention in a particularly advantageous manner.

[0010] 3. Detailed description of the invention

[0011] According to a first aspect of the present invention, a control gear for a light source is provided. The control gear comprises: a connection for connecting a load; an electronic circuit configured to provide an output or intermediate voltage for supplying the connected load; wherein the circuit includes a smoothing capacitor, in particular an electrolytic capacitor, configured to stabilize the output or intermediate voltage. The control gear further comprises a control unit configured to detect a voltage value of the stabilized output or intermediate voltage and to compare the detected voltage value with a minimum threshold; wherein the control unit is further configured to adjust the output or intermediate voltage and / or an output power of the control gear when the voltage value reaches or falls below the minimum threshold.

[0012] This achieves the advantage that an increase in voltage ripple, i.e., a periodic fluctuation of the stabilized output or intermediate voltage, is efficiently detected, and countermeasures can be initiated. This can increase the service life of the operating device. For example, the minimum threshold is chosen to be just above the operating device's shutdown threshold, i.e., above a minimum voltage value below which the driver is switched off.

[0013] The control gear can be a driver, especially an LED driver, or a ballast for light sources. The control gear can be single-stage or multi-stage, e.g., a two-stage, control gear.

[0014] The output voltage is, for example, a bus voltage provided at an output of the control device to supply the load. The intermediate voltage can be a voltage provided by a first stage of the control device, which is then converted into an output voltage by a second stage of the control device.

[0015] The load supplied with the output voltage is typically a light source, such as an LED light source or an LED module. The electronic circuit can be a driver circuit. The electronic circuit can include a PFC or an AC / DC converter circuit.

[0016] The control unit can be an ASIC, a microcontroller, or another logic circuit.

[0017] According to one embodiment, the smoothing capacitor is designed to stabilize the output or intermediate voltage by reducing a periodic fluctuation of the output or intermediate voltage.

[0018] According to one embodiment, the control unit is configured to reduce the output power of the operating device when the voltage reaches or falls below the minimum threshold. This has the advantage of reducing the magnitude of the voltage ripple (and thus the periodic drop in the output / intermediate voltage due to the ripple). This measure allows the margin between the output or intermediate voltage and the operating device's shutdown threshold to be increased.

[0019] According to one embodiment, the control unit is configured to reduce the output power of the operating device in such a way that a constant distance is maintained between the output or intermediate voltage and the minimum threshold. This achieves the advantage that, after the minimum threshold is first reached, a fixed "safety margin" is maintained between this margin and the potential shutdown threshold of the operating device. The minimum distance between the output or intermediate voltage and the minimum threshold refers in particular to the distance between the minima of the periodically fluctuating (stabilized) output or intermediate voltage and the minimum threshold.

[0020] According to one embodiment, the control unit is configured to increase the output or intermediate voltage of the operating device when the voltage value reaches or falls below the minimum threshold. This achieves the advantage of increasing the minimum voltage value to which the output or intermediate voltage periodically drops due to voltage fluctuations. This increases the margin between the output or intermediate voltage and the shutdown threshold of the operating device.

[0021] For example, the control unit is configured to increase a nominal or average value of the output or intermediate voltage when the voltage value reaches or falls below the minimum threshold. The control unit can also perform both actions (reducing the output power and increasing the output or intermediate voltage) in combination when it detects that the voltage value has fallen below the minimum threshold.

[0022] According to one embodiment, the control unit is configured to compare the detected voltage value with an overvoltage threshold; wherein the control unit is further configured to deactivate the operating device when the voltage value reaches or exceeds the overvoltage threshold.

[0023] According to one embodiment, the control unit is designed to raise the overvoltage threshold when the output or intermediate voltage of the operating device is increased as a result of reaching or falling below the minimum threshold.

[0024] According to one embodiment, the control unit is designed to continuously or periodically detect the voltage value of the stabilized output or intermediate voltage, particularly during the supply of the connected load.

[0025] According to one embodiment, the operating device further comprises a display unit, wherein the control unit is configured to drive the display unit to output a warning signal when the voltage value reaches or falls below the minimum threshold.

[0026] According to a second aspect of the present invention, a method for operating a control gear for a light source, in particular a control gear according to the first aspect of the invention, is provided. The method comprises the following steps: providing an output or intermediate voltage to supply a load connected to the control gear; stabilizing the output or intermediate voltage by means of a smoothing capacitor, in particular an electrolytic capacitor; detecting a voltage value of the stabilized output or intermediate voltage; comparing the voltage value with a minimum threshold; and adjusting the output or intermediate voltage and / or an output power of the control gear when the voltage value reaches or falls below the minimum threshold.

[0027] According to one embodiment, stabilizing the output or intermediate voltage includes reducing periodic fluctuations in the output or intermediate voltage. According to one embodiment, the output power of the operating device is reduced when the voltage value reaches or falls below the minimum threshold.

[0028] For example, the output power of the operating device is reduced in such a way that a minimum difference between the output or intermediate voltage and the minimum threshold is kept constant.

[0029] According to one embodiment, the output or intermediate voltage of the operating device is increased when the voltage value reaches or falls below the minimum threshold. For example, a nominal value or an average value of the output or intermediate voltage is increased.

[0030] The two measures (reducing the output power and increasing the output or intermediate voltage) can also be implemented in combination if the voltage value detects that the minimum threshold has been breached. This way, the service life of the operating device can be extended while its performance is maintained in the best possible manner.

[0031] According to one embodiment, the voltage value of the stabilized output or intermediate voltage is continuously or periodically recorded, particularly during the supply of the connected load.

[0032] According to one embodiment, the method further comprises comparing the detected voltage value with an overvoltage threshold; and deactivating the operating device when the voltage value reaches or exceeds the overvoltage threshold.

[0033] According to one embodiment, the method further includes raising the overvoltage threshold if the output or intermediate voltage of the operating device is increased as a result of reaching or falling below the minimum threshold.

[0034] 4. Brief description of the characters

[0035] Exemplary embodiments of the invention are shown in the drawings and are described in more detail below. They show: TP1312E-W0

[0036] Fig. 1 shows a schematic representation of a control gear for a light source according to one embodiment;

[0037] Fig. 2 shows a circuit diagram of an electronic circuit of a control gear for a light source according to one embodiment;

[0038] Fig. 3A-B Voltage waveforms of an output or intermediate voltage of an operating device according to one embodiment;

[0039] Fig. 4A-B Voltage waveforms of an output or intermediate voltage of an operating device according to one embodiment; and

[0040] Fig. 5 shows a flowchart of a method for operating a control device for a light source according to one embodiment.

[0041] 5. Detailed description

[0042] Fig. 1 shows a schematic representation of a control gear 10 for a light source according to one embodiment. The control gear 10 is, for example, an LED driver.

[0043] The operating device 10 comprises a terminal 17 for connecting a load 11; and an electronic circuit 12 configured to provide an output or intermediate voltage for supplying the connected load 11; wherein the circuit 12 includes a smoothing capacitor 13 configured to stabilize the output or intermediate voltage. The operating device 10 further comprises a control unit 15 configured to detect a voltage value of the stabilized output or intermediate voltage and to compare the detected voltage value with a minimum threshold; wherein the control unit 15 is configured to adjust the output or intermediate voltage and / or an output power of the operating device when the voltage value reaches or falls below the minimum threshold.

[0044] The smoothing capacitor 13 is in particular an electrolytic capacitor (electrolytic capacitor).

[0045] The smoothing capacitor 13 is designed, for example, to stabilize and smooth out periodic fluctuations in the output or intermediate voltage. For instance, the smoothing capacitor 13 can reduce periodic voltage fluctuations caused by rectification or a high-frequency switch. This voltage ripple of the stabilized output or intermediate voltage increases with the increasing degradation of the smoothing capacitor 13.

[0046] The voltage value of the stabilized output or intermediate voltage refers in particular to a current level of this voltage, which fluctuates constantly due to residual ripple. This fluctuating voltage value can be monitored by the control unit 15.

[0047] By monitoring the stabilized output or intermediate voltage, and in particular by comparing this voltage with the minimum threshold, the control unit 15 can detect whether and when the voltage ripple has reached a certain magnitude despite the stabilization provided by the capacitor 13. In response, the control unit 15 can initiate countermeasures that either reduce the ripple or increase the minimum value to which the output or intermediate voltage drops due to the ripple.

[0048] For example, the minimum threshold is chosen so that it is just above the shutdown threshold of the operating device, i.e., above a minimum voltage value below which the driver is switched off or deactivated. Thus, the control unit 15 can react to the increase in ripple before the operating device is switched off and, if necessary, replaced.

[0049] As a first countermeasure, the control unit 15 can reduce the output power of the operating device 10 when the voltage value reaches or falls below the minimum threshold. In this way, the magnitude of the voltage ripple (and thus the periodic drop in the output / intermediate voltage due to the ripple) can be reduced.

[0050] As a second countermeasure, the control unit 15 can increase the output or intermediate voltage of the operating device when the voltage value reaches or falls below the minimum threshold. In this way, the minimum voltage value to which the output or intermediate voltage periodically drops due to voltage ripple can be raised. Both countermeasures increase the margin between the output or intermediate voltage and a potential shutdown threshold of the operating device. This will be explained further with reference to Figures 3A-B and 4A-B.

[0051] The control unit 15 can also perform both countermeasures (reducing the output power and increasing the output or intermediate voltage) in combination when it detects that the voltage value has fallen below the minimum threshold.

[0052] For example, the control unit 15 can adjust the output power and / or the output or intermediate voltage by selectively controlling one or more components of the electronic circuit 12, such as by controlling a switch of the electronic circuit 12. The adjustment of the output power and / or the output or intermediate voltage refers in particular to changing these parameters.

[0053] To determine the voltage value, the control unit can first divide the output or intermediate voltage and then feed it into an input of the control unit. A voltage divider is used for this purpose, for example. Based on this signal, the control unit can compare it to the minimum threshold value, e.g., using a comparator. The actual voltage value at the input of the control unit can therefore be a value representative of the output or intermediate voltage (e.g., a divided value of the output or intermediate voltage).

[0054] The control gear 10 can be an LED driver or a comparable ballast. The control gear 10 can be a single-stage or multi-stage control gear, e.g., a two-stage control gear.

[0055] The output voltage is, for example, a bus voltage that the operating device 10 provides at terminal 17 to supply the load 11. The intermediate voltage can be a voltage provided by a first stage of the operating device, which is then converted into an output voltage by a second stage of the operating device.

[0056] In a two-stage control gear 10, the first stage comprises, for example, a rectifier and / or filter, and the second stage a PFC circuit, a DC / DC converter, or a switching regulator. A corresponding smoothing capacitor 13 can be arranged before the output of the first stage to stabilize the intermediate voltage, and / or before the output of the second stage to stabilize the output voltage. The connected load 11 is, in particular, the light source, for example, an LED light source or LED module, for whose operation the control gear 10 is designed. The load 11, e.g., the light source, can be supplied with electrical energy by the control gear 10. The output power refers in particular to the electrical power that the control gear 10 provides to supply the load 11.

[0057] The electronic circuit 12 can be, or include, a PFC circuit or an (AC / DC or DC / DC) converter circuit.

[0058] The control unit 15 can be an ASIC, a microcontroller, or another logic circuit. The control unit 15 can be a component of the electronic circuit or be electrically connected to it.

[0059] The operating device 10 may also have an input for receiving a supply voltage (not shown in Fig. 1).

[0060] Terminal 17 can be connected to an output of the circuit 12 or the operating device 10. Terminal 17 can include a suitable plug connector and / or socket (e.g., a DC socket) for connecting the load 11. The load 11 can be supplied with electrical energy via terminal 17, e.g., in the form of a constant current or constant voltage signal.

[0061] The control unit 15 can be configured to continuously or periodically detect the voltage value of the stabilized intermediate or output voltage.

[0062] For example, the control unit 15 is designed to compare the detected voltage value with the minimum threshold only a certain time after the connected load has been supplied with power. This prevents the minimum reference value from triggering a corresponding adjustment when the operating device is activated or immediately after the load is connected.

[0063] The operating device 10 may include an optional display unit 16. The control unit 15 may be configured to drive the display unit 16 to output a warning signal when the voltage value reaches or falls below the minimum threshold. For example, the display unit 16 is an optical element, e.g., a signal LED, or an acoustic element, and the warning signal is a corresponding optical or acoustic signal.

[0064] The control unit 15 can further be configured to compare the detected voltage value with an overvoltage threshold and to deactivate the operating device 10 if the voltage value reaches or exceeds the overvoltage threshold. This comparison serves in particular to protect the operating device 10 from overvoltage.

[0065] Alternatively or additionally, the control unit 15 can issue a further warning signal when the overvoltage threshold is reached / exceeded, e.g. via the display element 16.

[0066] For example, the control unit 15 can raise the overvoltage threshold if the output or intermediate voltage of the operating device increases as a result of reaching or falling below the minimum threshold. This prevents the increased output or intermediate voltage from triggering a shutdown of the operating device 10 if the increased output or intermediate voltage would otherwise reach the original overvoltage threshold. Advantageously, the output or intermediate voltage should not be increased arbitrarily, as an excessive increase could damage components of the operating device 10. For example, an increase up to a certain threshold is possible. This limitation is primarily due to the electrolytic capacitor 13 and any subsequent components or stages.

[0067] Fig. 2 shows a circuit diagram of the electronic circuit 12 of the control device 10 according to one embodiment. For example, the control device 10 shown in Fig. 1 has such an electronic circuit 12.

[0068] In the example shown in Fig. 2, the electronic circuit 12 is configured as a power factor correction (PFC) circuit. However, this is only one example, and the circuit 12 could also have a different topology. For example, the circuit could also be a converter circuit or a boost or buck-boost circuit. The circuit 12 in Fig. 2 has an input stage 24, which is connected to a mains connection to receive a mains voltage. The input stage 24 includes, for example, an EMI filter and a bridge rectifier.

[0069] The exemplary PFC circuit 12 further comprises a switch 21, an inductor 22, and a diode 23. The switch 21 can be alternately opened and closed by the control unit 15 to charge the inductor 22 and subsequently discharge it via the diode 23. For this purpose, an output of the control unit 15 can be connected to a control electrode of the switch 21. A shunt resistor can be provided to detect the current through the closed switch at an input of the control unit 15 as a control variable.

[0070] The smoothing capacitor 13, referred to in Fig. 2 as buffer capacitor (Engi.: Buffer Capacitor), can be arranged behind the diode 23 and can smooth the output voltage VBus, which is output to the load 11.

[0071] An input of the control unit 15 can be connected via a voltage divider 14 to a signal path between the smoothing capacitor 13 and the connected load 11. In Fig.

[0072] 2. The voltage divider is formed, for example, by the resistors Rhigh and Rlow. The voltage divider 14 can divide the detected output voltage down to generate a measurement signal VBus_sns, which is fed to the input of the control unit 15. The control unit 15 can compare this signal with a reference value representing the minimum threshold (e.g., using a comparator). In this way, the control unit 15 can compare a voltage value of the output voltage VBus with the minimum threshold and detect whether it has been reached or fallen below.

[0073] Figures 3A and 3B show voltage waveforms of the output voltage VBus of the control gear 10 for lamps according to one embodiment. The example shown in Figures 3A and 3B corresponds to the embodiment in which the output power of the control gear 10 is reduced when the voltage value reaches or falls below the minimum threshold value VBus_min (Variant 1).

[0074] Fig. 3A shows the change in a ripple of the stabilized output voltage VBus over the lifetime of the operating device 10, e.g. an LED driver.

[0075] As can be seen in this figure, the stabilized output voltage VBus of a new operating device 10 is subject to a certain voltage ripple. Due to this ripple, the voltage value of the bus voltage VBus fluctuates around a nominal value 31, which can be set by the control unit 13. The nominal value 31 can be an average value of the voltage around which the output voltage VBus fluctuates.

[0076] The voltage ripple of a new operating device 10 is usually still relatively low, so that VBus remains significantly above the minimum threshold value VBus_min despite the fluctuation. The smallest difference between VBus_min and VBus is shown in Fig. 3A as Vmargin.

[0077] As the smoothing capacitor ages, its capacitance decreases. This leads to an increase in voltage ripple and thus to a greater fluctuation around the nominal voltage value 31. At a certain point 32, the output voltage VBus reaches the minimum threshold value VBus_min.

[0078] In response, the control unit 15 can reduce the output power of the operating device 10, thereby decreasing the voltage ripple, i.e., the fluctuation around the nominal voltage level 31. Consequently, the minimum distance 33 between VBus_min and VBus (i.e., the distance between the periodic minima of VBus and VBus_min) increases again. In this way, a "safety margin" between VBus and VBus_min can be restored. Maintaining this "safety margin" ensures that VBus does not fall below VBus_min and, in particular, does not fall below a shutdown threshold of the operating device 10. For example, the output power of the operating device 10 is continuously reduced further during operation to keep the distance 33 constant.

[0079] Figure 3B shows the change in output power (top diagram) and the changes in the ratios of Vmargin to VBus_min and VBus_peak to Peak_Ripple (bottom diagram). VBus_peak refers to an upper threshold of the bus voltage, for example, an overvoltage threshold, and Peak_Ripple refers to a current maximum of the voltage ripple.

[0080] The upper diagram in Fig. 3B shows a decrease in output power from time 34 onwards, when VBus reaches the threshold value VBus_min. In particular, the output power is reduced such that the (minimal) difference between VBus and VBus_min (corresponding to Vmargin) is kept constant. The ratio of VBus_peak to Peak_Ripple can also be kept constant by reducing the output power. Figs. 4A and 4B show voltage waveforms of the output voltage VBus of the control gear 10 for lamps according to one embodiment. The example shown in Figs. 4A and 4B corresponds to the embodiment in which the output voltage is increased when the voltage value reaches or falls below the minimum threshold value VBus_min (variant 2).

[0081] Fig. 4A again shows the change in ripple on the output voltage VBus over the lifetime of the operating device 10.

[0082] In response to the minimum threshold value VBus_min being reached by the output voltage VBus, the control unit 15 can increase the nominal value 31 of the output voltage. In this way, the "safety margin" 33 between VBus and VBus_min can be restored.

[0083] Fig. 4B shows the change in output power (top diagram) as well as the changes in the ratios of Vmargin to VBus_min and of VBus_peak to Peak_Ripple (bottom diagram) for variant 2.

[0084] The output power can be reduced again such that the (minimal) difference between VBus and VBus_min (corresponding to Vmargin) is kept constant, thus the ratio Vmargin to VBus_min also remains constant from time 34 onwards. Unlike variant 1 (reducing the output power), however, the ratio of VBus_peak to Peak_Ripple increases from time 34 onwards.

[0085] Figures 3A-3B and 4A-4B show an example of the output voltage VBus. However, comparable voltage waveforms would also apply to the stabilized intermediate voltage if it were measured and adjusted accordingly.

[0086] By adjusting the output or intermediate voltage or output power, it is possible to prevent the output or intermediate voltage from falling below the shutdown threshold of the control gear. In conventional control gear, falling below this threshold often leads to immediate deactivation, as this is considered a worst-case scenario. The deactivated control gear is then usually replaced immediately. The adjustment described above (of output power, output / intermediate voltage) thus increases the reliability of the control gear and reduces the potential replacement cycle, thereby lowering the overall annual installation costs. Furthermore, because the control gear can continue operating with reduced power and / or increased output / intermediate voltage, the user has more time to eventually replace the control gear if necessary.

[0087] Fig. 5 shows a flowchart of a method 50 for operating a control gear 10 for a light source, in particular an LED driver, according to one embodiment. For example, the method 50 can be carried out by the control gear 10 shown in Fig. 1.

[0088] The procedure 10 comprises the following steps: providing 51 an output or intermediate voltage to supply the load 11 connected to the operating device 10; stabilizing 52 the output or intermediate voltage by means of the smoothing capacitor 13, in particular an electrolytic capacitor; detecting 53 the voltage value of the stabilized output or intermediate voltage; comparing 54 the voltage value with the minimum threshold VBus_min; and adjusting 55 the output or intermediate voltage and / or the output power of the operating device 10 when the voltage value reaches or falls below the minimum threshold (VBus_min).

[0089] The step of stabilizing the output or intermediate voltage 52 includes in particular a reduction of a periodic fluctuation of the output or intermediate voltage.

[0090] For example, adjusting the output power 55 involves reducing the output power when the voltage value reaches or falls below the minimum threshold VBus_min.

[0091] The output power can be reduced such that the minimum margin Vmargin between the stabilized output or intermediate voltage and the minimum threshold VBus_min is kept constant. The minimum margin Vmargin refers in particular to the distance between the periodically occurring minima of the stabilized output or intermediate voltage (due to the ripple remaining after stabilization).

[0092] Adjusting the output or intermediate voltage of the operating device 10 can include increasing the output or intermediate voltage when the voltage value reaches or falls below the minimum threshold VBus_min. In particular, a nominal value or an average value of the output or intermediate voltage is increased.

Claims

Claims:

1. Control gear (10) for a light source, comprising: a connection (17) for connecting a load (11); an electronic circuit (12) configured to provide an output or intermediate voltage for supplying the connected load (11); wherein the circuit (12) includes a smoothing capacitor (13), in particular an electrolytic capacitor, which is configured to stabilize the output or intermediate voltage; a control unit (15) which is configured to detect a voltage value of the stabilized output or intermediate voltage and to compare the detected voltage value with a minimum threshold (VBus_min); wherein the control unit (15) is further configured to adjust the output or intermediate voltage and / or output power of the operating device (10) when the voltage value reaches or falls below the minimum threshold (VBus_min).

2. Operating device (10) according to claim 1, wherein the smoothing capacitor (13) is designed to stabilize the output or intermediate voltage by reducing a periodic fluctuation of the output or intermediate voltage.

3. Operating device (10) according to claim 1 or 2, wherein the control unit (15) is configured to reduce the output power of the operating device (10) when the voltage value reaches or falls below the minimum threshold (VBus_min).

4. Operating device (10) according to claim 3, wherein the control unit (15) is configured to reduce the output power of the operating device (10) such that a minimum distance (Vmargin) between the output or intermediate voltage and the minimum threshold (VBus_min) is kept constant. 5- Operating device (10) according to one of the preceding claims, wherein the control unit (15) is configured to increase the output or intermediate voltage of the operating device (10) when the voltage value reaches or falls below the minimum threshold (VBus_min).

6. Operating device (10) according to claim 5, wherein the control unit (15) is configured to increase a nominal value or an average value of the output or intermediate voltage when the voltage value reaches or falls below the minimum threshold (VBus_min).

7. Operating device (10) according to any one of the preceding claims, wherein the control unit (15) is configured to compare the detected voltage value with an overvoltage threshold; wherein the control unit is further configured to deactivate the operating device (10) when the voltage value reaches or exceeds the overvoltage threshold.

8. Operating device (10) according to one of claims 5 or 6 and according to claim 7, wherein the control unit (15) is configured to raise the overvoltage threshold when the output or intermediate voltage of the operating device (10) is increased as a result of reaching or falling below the minimum threshold (VBus_min).

9. Operating device (10) according to any one of the preceding claims, wherein the control unit (15) is configured to continuously or periodically detect the voltage value of the stabilized intermediate or output voltage.

10. Operating device (10) according to any one of the preceding claims, further comprising: a display unit (16); wherein the control unit (15) is configured to control the display unit (16) to output a warning signal when the voltage value reaches or falls below the minimum threshold (VBus_min).

11. Method (50) for operating a control device (10) for a light source, in particular a control device (10) according to one of the preceding claims, comprising: Providing (51) an output or intermediate voltage to supply a load (11) connected to the operating device (10); stabilizing (52) the output or intermediate voltage by means of a smoothing capacitor (13), in particular an electrolytic capacitor; Detect (53) a voltage value of the stabilized output or intermediate voltage; compare (54) the voltage value with a minimum threshold (VBus_min); and adjust (55) the output or intermediate voltage and / or an output power of the operating device (10) when the voltage value reaches or falls below the minimum threshold (VBus_min).

12. Method according to claim 11, wherein stabilizing (52) the output or intermediate voltage includes reducing a periodic fluctuation of the output or intermediate voltage.

13. Method according to claim 11 or 12, wherein an output power of the operating device (10) is reduced when the voltage value reaches or falls below the minimum threshold (VBus_min).

14. Method according to claim 13, wherein the output power of the operating device (10) is reduced such that a minimum distance (Vmargin) between the output or intermediate voltage and the minimum threshold (VBus_min) is kept constant.

15. Method according to any one of claims 11 to 14, wherein the output or intermediate voltage of the operating device (10) is increased when the voltage value reaches or falls below the minimum threshold (VBus_min).

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