EP2375868A2 - Electronic pre-switching device with interface device - Google Patents

Abstract

The ballast (1) has an interface device (50) comprising a signal path i.e. input port (51), to guide brightness control information, which is assigned to external digital control signals, to an input port (31) of a microcontroller (30). The interface device comprises a Zener diode to detect a control signal structure of the control signals and for opening a signal path, which is assigned to the detected signal structure, and/or to block the signal path, which is not assigned to the detected signal structure. An enhancement-type transistor of the signal paths is controlled by the signals. An independent claim is also included for a method for operating an electronic ballast for driving a lamp.

Description

The invention relates to an electronic ballast for operating a lamp, with an interface device, which has on the input side a connection device for receiving externally supplied brightness control information in the form of external control signals, and with a control device which is connected to the interface device for receiving brightness control information and configured to drive the brightness of the lamp in response to the received brightness control information, and a method of operating such a ballast.

Such electronic ballasts (ECG) are particularly suitable for the operation of gas discharge lamps, high-pressure discharge lamps or light-emitting diodes (LED), where they can be used flexibly due to the provision of the interface device. The fact that they are set up both for receiving external control signals which can be generated by switches or buttons, as well as for receiving external digital control signals, such ECGs both as an independent light control device and as a ballast as a single component of a lighting system for operation one or more lamps are used. In the first application, the brightness control information is usually generated by means of a switch or a button and transmitted to the TOE; In the second application, the ECG can, for example, from a central system control digital control signals, in particular Receive signals according to the DALI (digital addressable lighting interface) standard and control the brightness of the lamp in response to this brightness control information.

Such a known electronic ballast is for example in the German patent application DE 197 57 295 A1 described. In the known electronic ballast, the interface device is designed to supply both control signals generated via a switch or pushbutton and digital control signals as external brightness control information to the same terminals of the control device. However, this increases the requirement on the functionality of the control device of the electronic ballast used, furthermore, despite increased functionality of the control device, it is not ensured in each case that the respective control signal is allocated and processed without error in the control device.

The present invention has for its object to at least partially overcome the existing disadvantages of conventional electronic ballasts.

This object is achieved on the device side already with an electronic ballast having the features of claim 1. The ECG according to the invention is characterized in that the interface device has a first signal path for guiding brightness control information, which is assigned to external digital control signals to a first input signal terminal of the control device and a second, from the first at least partially different signal path for guiding brightness control information, which external control signals designed as switching signals to a second, the first different input signal terminal of the control device, and that the interface device comprises means for detecting the control signal structure the externally supplied control signal and to open the signal path, which is associated with the detected signal structure, and / or blocking a signal path which is not associated with the detected signal structure.

With the described design of the electronic ballast according to the invention it is achieved that, on the one hand, the received external control signal, which is assigned to a brightness control information, i. represents such, is applied to an associated input port of the control device and subsequently with knowledge of the signal structure of the applied control signal, the processing of the associated control information can be performed. Control signals of a specific signal structure are thereby supplied to the associated input port of the control device, so that it no longer has to be designed to differentiate the various control signal structures. In this case, the interface device has means for detecting the different control signal structures of the externally supplied control signal, because in each case a signal structure is assigned to a specific signal path within the interface device. After the signal structure has been detected, the respective control signal can be guided in a targeted manner on the assigned and predetermined signal path and thus supplied to the assigned and predetermined input signal connection of the control device.

It should be noted that the interface device of the electronic ballast according to the invention is not limited to two signal paths for external control signals, which are each assigned to a signal structure. It is also possible to include further such signal paths for differentiating different structures from external control signals, wherein the control device can then have a number of control inputs adapted to the number of signal paths.

The assignment of brightness control information to the respective external control signals can be achieved, for example be realized that this control information is encoded in a predetermined manner in the associated external control signal. Accordingly, the associated brightness control information can be decoded from such a control signal or the control information can be derived from the control signal. Preferably, the brightness control information content of the signal is completely retained when it is carried on the associated, ie associated signal path within the interface device, wherein on this signal path, for example, a conversion or conversion of the signal can take place.

It is particularly expedient if the input-side connection device of the interface device for receiving externally supplied brightness control information, i. for receiving the externally supplied control signals is designed as a two-wire connection, which simplifies the connection to the external control signal provision. It is particularly expedient if both the control signals generated by a switch or a button and the digital control signals via the same input terminals of the terminal device, in particular via said two-wire connection to the ECG can be applied. As a rule, either the control signals generated by a switch or a push button and thus designed as switching signals or the digital control signals are applied to the two-wire connection, depending on whether the inventive ballast used, for example, as an independent light control device or as a component in a lighting system is.

The control signal received by the interface device is examined within the device with respect to its structure and assigned to one of the possible structures. For this purpose, the interface device on the said means for detecting the control signal structure of the externally supplied control signal. This agent is suitable to detect and differentiate in principle any parameter of the signal, for example the frequency response and / or the amplitude of the signal. In this respect, it may be expedient if the means for detecting the control signal structure of the externally supplied control signal and for opening the signal path, which is associated with the detected signal structure, a device for threshold detection with associated switch, a microcontroller device for signal evaluation with associated and controlled by this switch device and / or a crossover, whereby the control signal can be passed via the associated signal path to the corresponding input signal terminal of the control device.

In a particularly cost-effective embodiment, the means for detecting the control signal structure of the externally supplied control signal and for opening the signal path associated with the control signal may comprise a zener diode which changes to the conducting state when a predetermined threshold voltage is present. Such an embodiment is particularly expedient if the control signal structures to be differentiated differ in particular in the voltage amplitude, so that it can be determined by providing a zener diode that the corresponding signal path is opened only when a voltage greater than the threshold voltage of the zener diode is present , A control signal structure which has a lower voltage amplitude, or a control signal with such a signal structure, remains blocked by such a signal path having a Zener diode.

To open the respective signal path assigned to the recognized signal structure, the interface device can have at least one switch which switches the respective signal path to the associated input port of the control device. Such a switch can be self-controlled, as in the described example of the zener diode. It However, it is also possible to use a switch with a control input, which can be controlled in particular via the external control input signal of the interface device or via a signal derived therefrom.

It is particularly expedient if in each case at least one switch is included for both the first and the second signal path, wherein both switches are in a non-conducting state in the idle state, in particular after an operational initialization of the ballast. This ensures that no signal path is opened before the detection of the signal structure of the external control signal, which in turn can ensure that not accidentally an external control signal at the wrong control signal input of the control device comes to rest.

In order to avoid such a misdirection of the external control signal via a signal path not assigned to this signal or its signal structure and thus to an unassigned control signal input of the control device, it can also, in particular in the presence of time-varying control signals, such as a push-button signal with a modulation of For example, 50 Hz, 60 Hz or 100 Hz be advantageous if a switch of a signal path can be controlled via a delay element, wherein expediently applied to the delay element, the external control signal or a signal derived therefrom. As a result, otherwise erroneous guides of the external control signal or the control information associated with this signal can be avoided, which prevents misinterpretations in the control device. In such an embodiment, the delay element may be formed, for example, as an RC element, wherein the capacitor is charged by the applied external control signal or a signal derived therefrom and the voltage on the capacitor is used as a switching voltage for opening a signal path.

To avoid an undesirable state at an input signal terminal of the control device, it may also be useful if the ballast according to the invention is designed so that after opening one of the two signal paths of the other signal path is automatically blocked.

Advantageously, it can be provided that at least one of the signal paths in the interface device has electronic components for transforming the control signal carried on this signal path. For example, it may be provided to provide an optocoupler or a DC / DC converter for galvanic decoupling. In addition, however, it is also possible to use in a signal path signal shaping components, such as an A / D converter or a V / f converter with subsequent digitization, so that, for example, an analogue probe signal, which is received by the interface device and which due Its signal structure one of the two signal paths in the interface device, so that a particular input signal terminal of the interface device is assigned and this is supplied, is converted in the course of its signal transmission by the interface device into a digital signal, which, however, with respect to its control information corresponds to the button signal of the switch. In this way it is possible, for example, for both input signal connections to be set up on the control device for receiving digital control signals, wherein the digitized control signal is applied to the second input signal connection of the control device via the second signal path. By such a transformation, the external control signals can be adapted to the respective control device.

Preferably, the switches used in the invention may be formed as semiconductor switches such as transistors.

In terms of the method, the invention solves the above object with a method for operating an electronic ballast for driving a lamp, with an interface device receiving externally supplied brightness control information on the input side in the form of control signals, and with a control device to which brightness control information is forwarded and which controls the brightness of the lamp in response to the received control information. The inventive method is characterized in that the control device at a first input signal terminal brightness control information, which external digital control signals is assigned via a first signal path of the interface device for processing and further at a second input signal terminal via a second signal path of the interface device brightness control information , which is associated with control signals designed as external switching signals, the signal structure of an external control signal being detected in the interface device and opened depending on the detected signal structure of the signal path associated with this signal structure and / or blocking a signal path which does not block the detected signal structure assigned.

As used in this application, the term "control signal over a first signal path" means not only the original external digital control signal received from the interface device but also any derived, derived or converted signal from that external digital control signal. Such a conversion can be carried out, for example, via an A / D converter, a D / A converter, a DC / DC converter and / or via an optocoupler. In the same way, the term "control signal via a second signal path" not only describes that at the interface device On the input side received, designed as a switching signal control signal, but also in the course of leadership on the second signal path, possibly derived therefrom control signal, which is guided over the second signal path to the associated second input signal terminal of the control device. In addition, it should be noted that the terms used in this context, such as "first" and "second", respectively, are for the purpose of differentiation only, but are not intended to limit the order or the like.

Fig. 1a

in einer Prinzipskizze ein erfindungsgemäß ausgebildetes elektronische Vorschaltgerät,

Fig. 1b

in einer Prinzipdarstellung zwei unterschiedliche externe Steuersignale symbolisiert,

Fig. 2

in einer Detailansicht eine Schnittstellenvorrichtung sowie den daran angeschlossenen Mikrocontroller einer Ausführungsform eines erfindungsgemäßen elektronischen Vorschaltgerätes und

Fig. 3

in einer Detailansicht eine Schnittstellenvorrichtung sowie den daran angeschlossenen Mikrocontroller einer weiteren Ausführungsform eines erfindungsgemäßes elektronischen Vorschaltgerätes,

zeigt.The invention will be explained in the following by describing a plurality of embodiments and further characteristics essential to the invention with reference to the accompanying drawings, in which:

Fig. 1a

in a schematic diagram of an inventively designed electronic ballast,

Fig. 1b

symbolizes two different external control signals in a schematic representation,

Fig. 2

in a detailed view of an interface device and the connected microcontroller of an embodiment of an electronic ballast according to the invention and

Fig. 3

in a detailed view of an interface device and the microcontroller connected thereto of a further embodiment of an inventive electronic ballast,

shows.

Fig. 1a shows an inventively designed electronic ballast 1 in a schematic diagram. In this it has a mains-powered rectifier 10, which the mains voltage in a rectified DC link voltage converts and outputs to an inverter 20. The inverter 20 may be formed, for example, as a half-bridge with two switches connected in series between a positive supply voltage and ground, which are controlled via the control device designed as a microcontroller 30 alternately for closing and opening via the control line S. The load circuit connected to the inverter 20 has a discharge lamp 40 through which a lamp current i _L flows after the ignition process. To simplify the presentation, other components such as an ignition device or a preheater may not be shown in the schematic diagram under certain circumstances, since they are well known to the person skilled in the art, so that it need not be discussed further here. The same applies in particular to any existing additional measuring devices, for example for detecting the lamp current and / or the lamp voltage whose signals are used by the microcontroller 30 to operate the lamp.

Essential to the present invention is the supply of external brightness control information to the microcontroller 30 via an interface device 50. For this purpose, the interface device 50 has an input port 51, which in the described embodiment is designed as a two-wire connection to the connections 51a, 51b. In an embodiment not shown, an input port may be provided with more than two ports. According to the invention, the interface device 50 is designed such that brightness control information can be applied to the input port 51 both in the form of control signals which are generated by means of a switch or a pushbutton and in the form of external digital control signals.

Fig. 1b shows in a schematic diagram symbolizes two examples of the provision of such external control signals that can be applied to the port 51.

In the left example, by means of a switch 60 connected to mains voltage N, L, external control signals are generated, i. for the duration of the closing of the switch 60, a sinusoidal mains current is emitted. In another embodiment, instead of a switch, a push-button may be used, and the push-button or switch may also switch another voltage such as a constant voltage. The external control signal generated in this way is generally used in the electronic ballast according to the invention in those cases in which the electronic ballast is used as an independent light control device. The supplied external control signals are interpreted by the microcontroller 30 as brightness control information, for example for switching on or off or for dimming the lamp.

In Fig. 1b , Right side, the application of an external digital control signal in the form of a DALI (digitally addressable lighting interface) signal indicated symbolized, via which the microcontroller 30 in such applications receives control information, for example, from a central light control device when the ECG as a single component in a lighting system is integrated. These DALI signals may include, for example, the information for switching on or dimming the lamp or lamps connected to the ECG.

The interface device 50 of the electronic ballast 10 according to the invention is embodied such that the control information associated with the external digital control signals is fed to an input port 31 with corresponding input signal terminals 31a, b and the control information associated with the external switching signals is sent to another input port with other input signal terminals 32a, b of the control device 30 be guided. For this purpose, the interface device 50 has a first signal path for guiding the control information associated with the external digital control signals from the input port 51 to a first output port 52 having output ports 52a, b and further a second signal path for guiding the control information associated with the external switching signals from the input port 51 to a second output port 53 having output ports 53a, b. Each of these output ports 52, 53 is connected to an associated input port or input port 31, 32 of the microcontroller 30. This ensures that at one input port 31, the control information is present for further processing, which corresponds to the external digital control signals and at the other input signal port 32 of the microcontroller 30, the control information is applied, which is associated with the external switching signals, ie corresponding thereto.

In order to provide a separation of the different control signals within the interface device 50, this has in the illustrated embodiment, a means for detecting the control signal structure of the externally supplied control signal and for opening one of the two signal paths, which is associated with the detected control signal structure. Embodiments thereof will now be described with reference to FIGS Figures 2 and 3 explains which for clarity of illustration the ECG according to the invention in excerpt, with only the microcontroller 30 and the interface device 50, 50 'are shown.

It is assumed that at the input port 51 of the interface device 50 with respect to Fig. 1b described external control signals may be present, which represent a brightness control information for the microcontroller 30. First, with reference to the embodiment according to Fig. 2 Assuming that the electronic ballast is integrated into a lighting system and insofar as at the input port 51 with the input terminals 51a, 51b, a digital DALI signal is applied. This signal passes through the bridge rectifier 70, which serves the polarity reversal and via the self-conducting MOSFET transistor 71, the photodiode of the opto-coupler 72, the Zener diode 73 and the resistor 74. The signal associated with the external DALI signal passes through the phototransistor of the opto-coupler 72 after passing through a signal matching, which by the two resistors 75, 76, the transistor 77 and the diode 78 is realized, on the associated input port 31 of the microcontroller 30. The signal waveform described corresponds to the signal path within the interface device 50 on which the control signal is passed, which is the external digital control signal, which is applied to the input port 51 , corresponds. The zener diode 80 is designed so that its threshold voltage is greater than the maximum voltage amplitude of the digital signal applied to the input port 51, so that the diode blocks the other signal path for control signals. In the example described, the threshold voltage of the Zener diode is 24V.

However, at input port 51, the above is with reference to FIG Fig. 1b described switch signal with a sequence of 50 Hz mains oscillations, this signal is rectified via the component 70 and can open the second signal path on reaching the threshold voltage at the Zener diode 80, the further via the resistor 81, the photodiode of the optocoupler 82 and the resistor 74 runs. The signal associated with the external control signal passes via the phototransistor of the optocoupler 82 to the input port 32 of the microcontroller 30. The control information which is assigned to the external control signal and applied to the input port 51 of the interface device 50 is thus fed to the assigned input port 32 of the controller.

In order to avoid that the applied external switching signal leads to a signal at the input port 31 of the microcontroller 30, with the opening of the second signal path, the transistor 79 is turned on, whereby the transistor 71 blocks, so that the first-described signal path is interrupted is. If the external control signal has a sequence of rectangular voltage pulses with an amplitude which is greater than the threshold voltage of the zener diode 80, it is ensured at any time that only one of the two described signal paths to the input port 32 or to the input port 31 is opened.

In order to ensure a simultaneous opening of both signal paths even in cases in which the external control signal is formed as a switching signal with a sequence of sinusoidal voltage pulses in particular, the in Fig. 3 illustrated embodiment of an electronic ballast according to the invention are used, wherein also in FIG. 3 For clarity of illustration only the components microcontroller 30 and the interface device 50 'are shown. Regarding Fig. 2 same components are in Fig. 3 provided with the same reference numerals.

The main difference between the interface devices 50 according to FIG Fig. 2 and 50 'according to Fig. 3 is that instead of a normally-on transistor 71, a normally-off transistor 90 is arranged in the current path which carries the signal associated with the external digital control signal. This transistor 90 is switched by a delay element, which is arranged parallel to the input port 51 and the resistor 92, the diode 93 and the integrator capacitor 94 includes, which can transfer the self-locking transistor 90 in the conductive state after a corresponding charge. If, at the input port 51 of the interface device 50 'at its terminals 51a, b, a digital control signal with a voltage amplitude which is smaller than the threshold voltage of the Zener diode 80, both signal paths of the interface device 50 are initially locked. In this case, the signal path for the signal which is assigned to a switching signal, in turn via the components 70, 80, 81, 82 and 74,79 or from the optocoupler 82 to the associated second Input signal port 32 of the microcontroller 30. The latter designates the signal path relevant here to the microcontroller for the brightness control information which is assigned to the external switching signals. In the microcontroller, the input signal received at the port 32 is guided via corresponding components to the reference ground. The signal path for the signal, which is assigned to an external digital control signal, passes via the components 70, 90, 72, 73 and 74 or from the phototransistor of the opto-coupler 72 via the level adaptation formed by the components 75-78 to the first input port 31 of FIG Mikrocontrollers 30. The latter denotes the signal path relevant here to the microcontroller for the brightness control information, which is assigned to the external digital control signals. Here, too, the signal received at the first input port 31 is internally guided via corresponding components to the reference ground within the controller.

If an external digital control signal, for example a DALI signal, is now applied to the input port 51 of the interface device 50 ', both are initially blocked with the above explanations regarding the two signal paths. Since the input voltage is lower than the threshold voltage, the zener diode 80 blocks the non-normally-off switch 90 because the capacitor C1 initially has no voltage. Regardless of whether the applied external digital control signal is monopolar or bipolar, the bridge rectifier 70 outputs an average positive voltage at which the capacitor C1 is charged. After the voltage across the capacitor has been reached in order to drive the transistor 90 for conduction, the signal path for the digital signal is enabled, ie opened, and thus lies against the input port 31 of the microcontroller 30. The amount of time necessary to turn on the normally-off transistor 90 depends on the time constant of the RC element and the structure of the digital signal itself. Also at the in Fig. 3 illustrated embodiment is as with reference to Fig. 2 explains, the threshold of the zener diode 80 is set so that it can not be reached when applying an external digital signal at the input port 51, so that the signal path associated with a switching signal is not open.

If, however, the ECG is used independently, the control signals input to the ECG at the input port 51 are switching signals. Will these switching signals as related to Fig. 1b described by switching mains voltage generated, thus is a network pulse train with a frequency of 50 Hz at the input port 51 at. This pulse sequence is rectified by means of the bridge 70. As long as the voltage at the Zener diode 80 is lower than the threshold voltage of 24 V, the associated signal path is blocked. During this time, the capacitor 94 is charged via the resistor 92 and the diode 93. In order to avoid that the capacitor 94 is charged in the presence of brightness control information in the form of an external switching signal at the port 51 for turning on the self-locking switch 90, the time constant of the delay element is set accordingly. It is determined by the resistor 92 and the capacitor 94, and adjusted so that the switch 90 can not go into the conductive state before the threshold voltage of the zener diode 80 is reached and thus the signal path for the external switching signals associated signal is open. Due to the current flow through the resistor 74, the transistor 79 is turned on and thus discharges the capacitor 94, so that the transistor 90 can not go into the conductive state. In the manner described it is ensured that the switch 90 remains locked in any case when the described external switching signal is present at the input port 51. Thus it can be achieved that at no time a signal at the input port
31 of the microcontroller 30 is applied, so that undetermined states can be avoided in the controller.

In non-specified embodiments, other signal transformations can be provided in the two signal paths. By way of example, an AD converter can also be provided in the signal path which includes the optocoupler 82, so that the input port 32 of the microcontroller 30 in this case is designed to process digital signals.

LIST OF REFERENCE NUMBERS

1

electronic ballast electronic ballast

10

rectifier

20

inverter

30

microcontroller

31

first input port of the microcontroller / input port

31a, 31b

Input signal terminals of the first input port

32

second input port of the microcontroller / input port

32a, 32b

Input port / input signal port of the second input port

40

Discharge lamp / lamp

50

Interface device

50 '

Interface device

51

Input port of the interface device

51a, 51b

Input signal terminals of the interface device

52

first exit port

52a

output port

52b

output port

53

second output port

53a

output port

53b

output port

60

switch

70

Bridge rectifier

71

self-conducting transistor

72

optocoupler

73

Zener diode

74

resistance

75

resistance

76

resistance

77

transistor

78

Zener diode

79

transistor

80

Zener diode

81

resistance

82

optocoupler

90

self-locking transistor

91

resistance

92

resistance

93

diode

94

capacitor

i _L

lamp current

(N, L)

mains voltage

S

control line

Claims (16)

Electronic ballast (1) for operating a lamp (40), with an interface device (50, 50 ') having on the input side a connection device (51) for receiving externally supplied brightness control information in the form of external control signals, and with a control device ( 30) connected to the interface device (50, 50 ') for receiving brightness control information and adapted to drive the brightness of the lamp (40) in response to the received brightness control information, characterized in that the interface device (50, 50 ') has a first signal path (51, 70, 71, 72, 75, 52; 51, 70, 90, 72, 75, 52) for guiding brightness control information, which is assigned to external digital control signals, to a first input signal terminal (12). 31) of the control device (30) and a second, from the first at least partially different signal path (51, 70, 80, 81, 82, 53) for guiding brightness control information associated with external control signals configured as switching signals to a second, different first input signal terminal (32) of the controller (30), and the interface device (50, 50 ') comprises means (80) for detecting the control signal structure of an externally supplied control signal and for opening the signal path, which is associated with the detected signal structure, and / or blocking a signal path which is not associated with the detected signal structure. Electronic ballast (1) according to claim 1, characterized in that the input-side connection means of the interface device (50, 50 ') for receiving externally supplied brightness control information is designed as a two-wire connection (51). Electronic ballast (1) according to claim 1 or 2, characterized in that the means for detecting the control signal structure of the externally supplied control signal and for opening or blocking a signal path means for threshold detection with associated switch (80, 90), a microcontroller means for signal evaluation associated and controlled by this switch device and / or a crossover comprises. Electronic ballast (1) according to claim 3, characterized in that the means for detecting the control signal structure of the externally supplied control signal and for opening the signal associated with the control signal path comprises a Zener diode (80), which passes in the presence of a threshold voltage in the conductive state. Electronic ballast (1) according to claim 1, 2, 3 or 4, characterized in that the interface device (50, 50 ') at least one switch (80; 71, 90), which the respective signal path to the associated input terminal (32; 31) of the control device switches. Electronic ballast (1) according to one of Claims 1 to 5, characterized in that a switch (71, 80, 90) of a signal path is controlled via the external control signal of the interface device (50, 50 '). Electronic ballast (1) according to any one of claims 5 or 6, characterized in that for the first and the second signal path in each case at least one switch (80, 90) is included, both switches after a Betriebsinitialisierung the ballast (1) in non-conductive State are. Electronic ballast (1) according to one of claims 5, 6 or 7, characterized in that a switch via a delay element (92, 93, 94) can be controlled, to which the external control signal is applied. Electronic ballast (1) according to one of claims 4 to 7, characterized in that after opening one of the two signal paths of the other of the two signal paths can be blocked. Electronic ballast (1) according to one of claims 1 to 9, characterized in that at least one of the signal paths of electronic components (70, 72, 82) is designed for forming the external control signal. Method for operating an electronic ballast (1) for driving a lamp, with an interface device (50, 50 ') receiving externally supplied brightness control information on the input side in the form of external control signals, and with a control device to which brightness control information is forwarded and which controls the brightness of the lamp in dependence on the received control information, characterized in that the Control means (30) at a first input signal terminal (31) the brightness control information, which is associated with external digital control signals, via a first signal path (51, 70, 71, 72, 75, 52; 51, 70, 90, 72, 75, 52) of the interface device (50, 50 ') for processing and further receives at a second input signal terminal (32) via a second signal path (51, 70, 80, 81, 82, 53) of the interface device (50, 50') brightness control information , which is assigned as switching signals formed external control signals, receives for processing, wherein in the interface device (50, 50 ') detects the signal structure of the applied external control signal and depending on the detected signal structure of this signal structure associated signal path is opened and / or blocks a signal path which of the detected signal structure is not assigned. A method according to claim 11, characterized in that both signal paths are blocked before the detection of the signal structure of the external control signals. Method according to one of claims 11 or 12, characterized in that the detection of the control signal structure of the externally supplied control signal by a threshold detection, a signal evaluation in a microcontroller device and / or a frequency separation is performed. Method according to one of claims 11, 12 or 13, characterized in that a signal path is opened by driving a switch (80), wherein the switch is closed by the external control signal self-controlled. Method according to one of claims 11 to 14, characterized characterized in that after opening a signal path of the other of the two signal paths is automatically blocked. Method according to one of claims 11 to 15, characterized in that one of the two signal paths is opened with a time delay.

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