EP3603345B1 - Circuit arrangement and method for operating lamps - Google Patents

Circuit arrangement and method for operating lamps Download PDF

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Publication number
EP3603345B1
EP3603345B1 EP18719548.2A EP18719548A EP3603345B1 EP 3603345 B1 EP3603345 B1 EP 3603345B1 EP 18719548 A EP18719548 A EP 18719548A EP 3603345 B1 EP3603345 B1 EP 3603345B1
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EP
European Patent Office
Prior art keywords
transformer
switch
circuit arrangement
control unit
supply voltage
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EP18719548.2A
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German (de)
French (fr)
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EP3603345A1 (en
Inventor
David GAJDOS
Thomas Steffens
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Zumtobel Lighting GmbH Austria
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Zumtobel Lighting GmbH Austria
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/37—Converter circuits
    • H05B45/3725—Switched mode power supply [SMPS]
    • H05B45/382—Switched mode power supply [SMPS] with galvanic isolation between input and output
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/37—Converter circuits
    • H05B45/3725—Switched mode power supply [SMPS]

Definitions

  • the present invention relates to a circuit arrangement which is provided for operating lighting means, the lighting means being in particular LEDs. Furthermore, the invention relates to a method for operating lighting means, wherein a circuit that can be supplied with voltage and is clocked by means of at least one switch is used, via which a transformer for transmitting electrical energy from a primary winding to a secondary winding is fed and in which the lighting means via the Secondary winding of the transformer can be supplied with power.
  • LEDs light sources based on semiconductors, such as LEDs
  • LEDs usually cannot be supplied directly with the voltage made available by the power supply network. Instead, efficient LED operation is only possible if a specified voltage drops across the LED and a current flows through the LED that is within a specified range.
  • AC LED modules some solutions for realizing so-called AC LED modules are known from the prior art, in which the LED module can be connected directly to the general power supply network, these solutions, however, also require a relatively high level of effort.
  • LEDs are operated with the aid of what is known as a converter, which converts the supply voltage made available on the input side into a DC voltage suitable for operating the LEDs.
  • a converter which converts the supply voltage made available on the input side into a DC voltage suitable for operating the LEDs.
  • Figure 1 shows a currently preferred circuit variant.
  • FIG. 1 a circuit arrangement 100 for operating an LED path 110 is shown, which is based on the topology of a so-called flyback converter.
  • the supply voltage U AC made available on the input side is first rectified by a rectifier 101, which is derived from this
  • the resulting voltage which now consists of positive half-waves, is smoothed with the aid of a capacitor 102.
  • an approximately constant voltage U DC arises, which is fed to the primary winding L1 of a transformer or transformer 102.
  • the secondary winding L2 On the secondary side of this transformer 102 is the secondary winding L2, via which the LED path 110 is then supplied.
  • a current flow through the primary winding L1 of the transformer 102 is permitted or interrupted, whereby by selecting a suitable frequency or a suitable duty cycle for the PWM signal for control of the switch 105, a suitable current flow is generated on the secondary side, which current flow is suitable for the operation of the LED path 110.
  • the present invention is therefore based on the object of specifying a novel solution for operating lighting means in which the disadvantages described above are avoided.
  • the solution according to the invention is initially based on the knowledge that the above-mentioned smoothing capacitor, which is viewed as problematic, can also be dispensed with, provided that the alternating control of the switch is carried out in a suitable manner.
  • a transformer with a Primary winding and a secondary winding are used, with a controllable switching element connected in series with the primary winding, with the aid of which a current flow through the primary winding is alternately caused or interrupted, with a rectified but not smoothed AC voltage now as the supply voltage for the transformer is used and depending on the current level of the supply voltage, the steepness of the rising or falling edge of the signal for controlling the switch is adapted.
  • a circuit arrangement for operating lighting means in particular for operating one or more LEDs, is proposed, the circuit arrangement having a circuit that can be supplied with voltage and clocked by means of at least one switch, via which a transformer for transmitting electrical energy from a primary winding to a secondary winding is fed the lighting means can be supplied with power via the secondary winding of the transformer, as well as a control unit for alternating control of the switch, the supply voltage for the transformer being a rectified, non-smoothed alternating voltage and the control unit being designed to be dependent of the supply voltage for the transformer to adapt the following parameters for the control of the switch: the steepness of the rising and / or the falling edge, with the control of the controllable switch via an RC element with an adjustable resistor.
  • the invention proposes a method for operating lighting means, in particular for operating one or more LEDs, in which a circuit that can be supplied with voltage and clocked by means of at least one switch feeds a transformer for transmitting electrical energy from a primary winding to a secondary winding, the lighting means via the secondary winding of the transformer can be supplied with current, the supply voltage being for the transformer is a rectified, unsmoothed AC voltage and the parameters for controlling the switch are adapted depending on the supply voltage for the transformer: the steepness of the rising and / or falling edge, with the controllable switch being controlled via an RC Link is made with an adjustable resistance.
  • the secondary current can also be monitored in order to optimize the control behavior for the switch.
  • appropriate means can be provided for detecting the secondary-side current, an optocoupler preferably being used for this purpose, with the aid of which the signal reproducing the secondary-side current is transmitted to the primary side of the transformer, on which the driver for the switch is also positioned.
  • a constant current source is provided on the secondary side of the transformer, which is arranged in series with the lighting means to be operated.
  • the primary task of this constant current source is initially to avoid excessive current flow through the lighting means.
  • the constant current source is designed to be controllable and that it is also controlled accordingly by the control unit in order to additionally optimize the supply for the lighting means.
  • the power transmission between the primary winding and the secondary winding of the transformer can also be designed flexibly according to a further preferred embodiment in that the winding ratio between the primary winding and the secondary winding can be changed.
  • the primary winding and / or the secondary winding is divided into partial windings, the partial windings then being optionally activated or activated by the control unit can be deactivated so that they are an active part or no part of the transformer. This possibility enables the power to be transmitted to the secondary side with the lighting means in a particularly flexible and efficient manner.
  • the switch is controlled via an RC element, the RC element having an adjustable resistance.
  • the resistance value of the RC element By influencing the resistance value of the RC element, the behavior over time of the control signal for the switch can be influenced. In particular, this makes it possible to influence the steepness of the rising or falling edge of the control signal.
  • the adjustable resistor is formed by internal components of a microcontroller. As will be explained in more detail below, microcontrollers usually have an internal voltage divider for outputting an analog signal, the individual resistors of which can be combined accordingly. According to the particularly preferred embodiment, these components are now used to form the adjustable resistance of the RC element.
  • the RC element has a plurality of capacitances which can optionally be activated or deactivated by the control unit.
  • the form of the control signal for the clocked switch can be influenced even more flexibly via the RC element.
  • Another preferred measure to optimize the control behavior for the switch consists in bridging the capacitor of the RC element with a further controllable switch. This can, if necessary, be switched on in order to deactivate the effect of the RC element and, for example, to end the switching cycle for the controllable switch of the transformer immediately. If necessary, the This second switch is controlled with the aid of an additional RC element. This then makes it possible to specifically influence the falling edge of the control signal for the switch.
  • FIG 2 first shows the basic concept of the circuit arrangement according to the invention or the procedure according to the invention for operating an LED path.
  • the solution shown is supplied with an AC supply voltage U AC on the input side of the circuit arrangement generally provided with the reference numeral 1, this voltage then first being converted into a rectified AC supply voltage U DC by a rectifier 5 - for example a bridge rectifier.
  • the flyback converter shown also consists in that the circuit arrangement 1 has a transformer 10 with a primary winding L1 and a secondary winding L2, the secondary winding L2 then supplying the LED path 110 with current.
  • the secondary circuit of the circuit arrangement 1 is shown in a very simplified manner and the secondary winding L2 is directly connected to the LEDs 110.
  • the secondary circuit could, however, also be designed in a more complex manner and in particular the LED arrangement 110 could not only consist of a single serial LED string, but could have a more complex interconnection of LEDs.
  • a controllable switching element 11 in the form of a transistor is provided in series with the primary winding L1 of the transformer 10, via which a current flow via the primary winding L1 can be allowed or interrupted can be.
  • the control of the switch 11 takes place via a driver or control unit 20.
  • the driver circuit 20 controls the switch 11 in a more flexible manner than in the prior art.
  • the steepness of the control signal u for the switch 11 is adapted to the rising and / or falling edge.
  • a significantly more complex control signal u now results for the switch 11 of the arrangement 1 according to the invention.
  • this has the advantage that the smoothing capacitor can be completely dispensed with.
  • the change in the control signal for the switch 11 must therefore take place flexibly as a function of the current actual value of the supply voltage U DC .
  • a high-frequency control signal u is therefore required, the course of which is continuously adapted. It is possible, for example, to subdivide the range of the supply voltage U DC into different sub-areas and to select a suitable signal course when activating the switch 11 for each sub-area. Activation of the switch that is continuously dependent on the current value of the supply voltage would, however, also be conceivable.
  • FIG. 3 shows first of all a basic version of the circuit arrangement 1 according to the invention, with comparable elements Figure 2 are provided with the reference number. However, it can be seen in Figure 3 For example, that - as mentioned above - the LED arrangement 110 can be designed in the most varied of ways.
  • FIG Figure 2 explains the transformer 10 with the primary winding L1 and the secondary winding L2 as well as the controllable switch 11, which is connected in series with the primary winding L1 of the transformer 10.
  • the activation of the switch 11 by the control unit or the driver 20 should, as mentioned, take place as a function of the supply voltage U for the transformer 10, which is obtained by rectifying the externally supplied AC supply voltage U AC with the aid of the rectifier 5.
  • the control unit 20 In order to be able to actuate the switch 11 accordingly, the control unit 20 must therefore have precise knowledge of the current value of the rectified supply voltage U DC .
  • a corresponding sensor unit 25 is provided for this, which is connected to the output of the rectifier 5 and transmits a corresponding signal to the control unit 20.
  • the evaluation of the supply voltage available for the transformer 10 with regard to the measurement accuracy can optionally be improved by the fact that - as in Figure 3 indicated - a zero crossing detection is additionally carried out with the aid of a further unit 30.
  • This unit is thus directly connected to the external supply voltage U AC or connected to the input of the rectifier 5 and supplies corresponding information regarding the zero crossing either to the unit 25, via which the supply voltage for the transformer 10 is evaluated and / or to the Control unit 20 itself.
  • FIG. 4 A further development of the in Figure 3
  • the basic concept shown is in Figure 4 shown. Again, the same components are provided with the same reference numerals, the unit 30 for zero crossing detection now not only being viewed as optional.
  • Essential addition to the arrangement according to Figure 3 is, however, that in this case information regarding the actual im Secondary circuit current flowing is obtained.
  • an optocoupler 35 is provided, which is connected to the secondary circuit in series with the LED arrangement 110 and transmits corresponding information to the control unit 20. This can then adapt the control for the switch 11 accordingly in the sense of a regulation, in order, if necessary, to produce a desired current flow through the LED arrangement 110 in a targeted manner.
  • a constant current source 36 is provided in the secondary circuit, which is connected in series with the LED arrangement 110.
  • the task of this constant current source 36 is to prevent an excessive current flow in the secondary circuit.
  • Such constant current sources are often used in circuit arrangements for operating LEDs and represent a safety measure which ensures that the LEDs are not damaged due to an excessively high current.
  • the constant current source 36 can also be designed as a controllable constant current source and is then in turn controlled by the control circuit 20.
  • the secondary winding L2 of the transformer 10 is divided into two partial windings L21 and L22, which over Control elements 13 and 14 can optionally be added to the secondary circuit of the circuit arrangement 1.
  • the control elements 13, 14 in this case consist of transistors which are controlled via a potential separation which is implemented with the aid of an optocoupler.
  • the control unit 20 can optionally add or decouple the partial windings of the two windings L1 and L2 of the transformer 10 from the corresponding primary circuit or secondary circuit, so that the winding ratio of the transformer 10 can be adjusted in different steps.
  • the concept of flexible setting of the winding ratio of the transformer 10 can also be applied to the circuit variants of Figures 3 and 4 the use of the in Figure 5 shown constant current source 36 is not absolutely necessary.
  • the form of the signal is to be influenced.
  • the measures now described relate in particular to the question of how the shape of the signal is influenced beyond the state of the art, i.e. in particular in what way the steepness of the rising and falling edges of the signal is modified.
  • a first basic variant is in Figure 7 shown, only the essential components of the circuit arrangement 1 for realizing this variant can be seen.
  • the control unit 20 is shown, which is connected on the output side to the switch 11 in order to control it. It is now provided according to the invention that the signal edges, in particular the rising signal edges, are influenced when the switch 11 is actuated in that the control signal is transmitted via an RC element.
  • control unit 20 is based on a microprocessor and microprocessors often have a DAC output via which an analog output signal is output as a function of a digital setpoint value.
  • the analog output signal is generated with the aid of a voltage divider integrated in the microprocessor, which has several individual resistors.
  • the voltage divider is indicated schematically by a series arrangement of several individual resistors 23, these being optionally combined with one another by a multiplexer - not shown in detail - in order to form a voltage divider which is ultimately responsible for the drop in a desired analog voltage at the DAC output of the control unit 20 cares.
  • the supply voltage Vdd for the control unit 20 is provided by the unit 25 connected to the output of the rectifier for detecting the actual value of the input voltage for the transformer 10.
  • the unit 25 also transmits a signal representing the level of the supply voltage.
  • a variable resistor By appropriately combining the resistors 23 of the integrated voltage divider of the control unit 20, a variable resistor can then be formed which, together with the capacitor C1, forms the RC element via which the switch 11 is controlled. Since the RC element influences the course of the control signal for the switch 11 over time, the change can therefore the integrated resistance of the control unit 20 can influence the signal curve. A very elegant possibility is thus created of influencing in particular the steepness of the rise of the control signal for the switch 11 in a simple manner.
  • FIG. 8 A further development of this idea just explained is in Figure 8 shown.
  • This consists in that a further controllable switch Q0 is provided parallel to the capacitor C1 of the RC element, via which the capacitor C1 of the RC element can optionally be bridged or discharged. This makes it possible, by activating this switch Q0, to abruptly cancel the time-delaying effect of the RC element with regard to the control of the switch 11, so that the signal shape can also be influenced here.
  • the mode of operation of the RC element could of course also be modified by changing the value of the capacitance of the RC element.
  • a corresponding solution to this is in Figure 9 now three - preferably differently dimensioned - capacitors C1, C2 and Cn are provided (the number can, however, be selected as desired), with a controllable switch Q1, Q2 and Qn being provided in series with the corresponding capacitance, via which the Associated capacitors C1, C2 or Cn can optionally be added to the control circuit for controlling the switch 11.
  • the control unit 20 can therefore add any combination of these capacitances to the control circuit for the switch 11, so that in this way - possibly in combination with an adaptation of the voltage at the DAC output - the signal curve can be influenced even more finely.
  • FIG. 2 shows a further development which is used in particular to influence the falling edge of the control signal for switch 11.
  • switch Q0 is not controlled directly via the control unit 20, but again an RC element is interposed.
  • the combination of resistor R0 and capacitance C0 can be used to adapt the signal profile when controlling the discharge switch Q0 and thus the steepness of the falling edge of the control signal can be set.
  • the resistor R0 can again be designed to be variable, in that internal voltage divider components of the control unit 20 are used to implement this resistor.
  • the capacitance value can also be made variable, if necessary, by, as in the exemplary embodiment, from Figure 9 There are several capacitances connected in parallel, which can be optionally added to the corresponding control path by means of controllable switches.
  • the measures allow the switch of the transformer to be controlled in a very specific way. This makes it possible to precisely set the current realized on the output side for supplying the LEDs and thereby enable optimal operation of the illuminants, although the smoothing capacitor provided on the input side, which is usually provided in a flyback converter, can be dispensed with.

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  • Circuit Arrangement For Electric Light Sources In General (AREA)

Description

Die vorliegende Erfindung betrifft eine Schaltungsanordnung, die zum Betreiben von Leuchtmitteln vorgesehen ist, wobei es sich bei den Leuchtmitteln insbesondere um LEDs handelt. Ferner betrifft die Erfindung ein Verfahren zum Betreiben von Leuchtmitteln, wobei eine mit Spannung versorgbare und mittels wenigstens eines Schalters getaktete Schaltung zum Einsatz kommt, über die ein Übertrager zum Übertragen elektrischer Energie von einer Primärwicklung zu einer Sekundärwicklung gespeist wird und bei der die Leuchtmittel über die Sekundärwicklung des Übertragers mit Strom versorgbar sind.The present invention relates to a circuit arrangement which is provided for operating lighting means, the lighting means being in particular LEDs. Furthermore, the invention relates to a method for operating lighting means, wherein a circuit that can be supplied with voltage and is clocked by means of at least one switch is used, via which a transformer for transmitting electrical energy from a primary winding to a secondary winding is fed and in which the lighting means via the Secondary winding of the transformer can be supplied with power.

Das Betreiben von Leuchtmitteln auf Halbleiterbasis wie bspw. LEDs ist mit einem gewissen Aufwand verbunden, da LEDs im Vergleich zu klassischen Lichtquellen wie Glühbirnen oder dergleichen üblicherweise nicht unmittelbar mit der durch das Stromversorgungsnetz zur Verfügung gestellten Spannung versorgt werden können. Stattdessen ist ein effizienter LED-Betrieb nur dann möglich, wenn über die LED eine vorgegebene Spannung abfällt und durch die LED ein Strom fließt, der innerhalb eines vorgegebenen Bereichs liegt. Zwar sind aus dem Stand der Technik einige Lösungen zur Realisierung sog. AC-LED-Module bekannt, bei denen das LED-Modul unmittelbar mit dem allgemeinen Stromversorgungsnetz verbunden werden kann, auch diese Lösungen erfordern allerdings einen verhältnismäßig hohen Aufwand.The operation of light sources based on semiconductors, such as LEDs, is associated with a certain amount of effort, since, in comparison to classic light sources such as light bulbs or the like, LEDs usually cannot be supplied directly with the voltage made available by the power supply network. Instead, efficient LED operation is only possible if a specified voltage drops across the LED and a current flows through the LED that is within a specified range. Although some solutions for realizing so-called AC LED modules are known from the prior art, in which the LED module can be connected directly to the general power supply network, these solutions, however, also require a relatively high level of effort.

Üblicherweise ist deshalb vorgesehen, LEDs mit Hilfe eines sog. Konverters zu betreiben, der die eingangsseitig zur Verfügung gestellte Versorgungsspannung in eine für den Betrieb der LEDs geeignete Gleichspannung umsetzt. Auch hierfür sind unterschiedliche Lösungsansätze bekannt, wobei Figur 1 eine derzeit bevorzugte Schaltungsvariante zeigt.It is therefore usually provided that LEDs are operated with the aid of what is known as a converter, which converts the supply voltage made available on the input side into a DC voltage suitable for operating the LEDs. Different approaches to a solution are also known for this, with Figure 1 shows a currently preferred circuit variant.

Genau genommen ist in Figur 1 eine Schaltungsanordnung 100 zum Betreiben einer LED-Strecke 110 gezeigt, die auf der Topologie eines sog. Flyback-Konverters beruht. Hierbei wird zunächst die eingangsseitig zur Verfügung gestellte Versorgungsspannung UAC durch einen Gleichrichter 101 gleichgerichtet, die hieraus resultierende Spannung, die nunmehr aus positiven Halbwellen besteht, wird mit Hilfe eines Kondensators 102 geglättet. Es entsteht in diesem Fall dann eine annähernd konstante Spannung UDC, die der Primärwicklung L1 eines Transformators bzw. Übertragers 102 zugeführt wird. Auf der Sekundärseite dieses Übertragers 102 befindet sich die Sekundärwicklung L2, über die dann die Versorgung der LED-Strecke 110 erfolgt. Mit Hilfe eines steuerbaren Schalters 105, der durch eine Treiberschaltung 106 alternierend angesteuert wird, wird hierbei ein Stromfluss durch die Primärwicklung L1 des Übertragers 102 zugelassen bzw. unterbrochen, wobei durch Wahl einer geeigneten Frequenz bzw. eines geeigneten Tastverhältnisses für das PWM-Signal zur Ansteuerung des Schalters 105 sekundärseitig ein geeigneter Stromfluss erzeugt wird, der für den Betrieb der LED-Strecke 110 geeignet ist.Strictly speaking, in Figure 1 a circuit arrangement 100 for operating an LED path 110 is shown, which is based on the topology of a so-called flyback converter. In this case, the supply voltage U AC made available on the input side is first rectified by a rectifier 101, which is derived from this The resulting voltage, which now consists of positive half-waves, is smoothed with the aid of a capacitor 102. In this case, an approximately constant voltage U DC arises, which is fed to the primary winding L1 of a transformer or transformer 102. On the secondary side of this transformer 102 is the secondary winding L2, via which the LED path 110 is then supplied. With the help of a controllable switch 105, which is alternately controlled by a driver circuit 106, a current flow through the primary winding L1 of the transformer 102 is permitted or interrupted, whereby by selecting a suitable frequency or a suitable duty cycle for the PWM signal for control of the switch 105, a suitable current flow is generated on the secondary side, which current flow is suitable for the operation of the LED path 110.

Der in Figur 1 dargestellte Flyback-Konverter hat sich zum Betreiben von LEDs vielfach bewährt und findet in unterschiedlichsten Varianten breite Verwendung. Ein gewisser Nachteil dieser bekannten Lösung besteht allerdings darin, dass der parallel zur Primärwicklung L1 und Schalter 105 erforderliche Glättungskondensator 102 verhältnismäßig groß ausgeführt sein muss und damit die Kosten der Schaltungsanordnung 100 erhöht. Ferner stellt dieser Kondensator 102 das anfälligste Bauteil der Schaltungsanordnung 100 dar und weist eine verhältnismäßig kurze Lebensdauer auf. US 7,511,437 B1 zeigt eine Betriebsschaltung für Leuchtdioden. Ein gleichgerichtetes, jedoch nicht geglättetes Wechselspannungssignal wird einem Konverter zum Betrieb der Leuchtdioden zugeführt. Ein Schalter des Konverters wird basierend auf Parametern der Versorgungsspannung angesteuert. Insbesondere wird dabei eine Schaltfrequenz und eine Taktung des Schalters angepasst.The in Figure 1 The flyback converter shown has proven itself many times over for operating LEDs and is widely used in the most varied of variants. A certain disadvantage of this known solution, however, is that the smoothing capacitor 102 required in parallel with the primary winding L1 and switch 105 has to be made relatively large and thus increases the costs of the circuit arrangement 100. Furthermore, this capacitor 102 represents the most vulnerable component of the circuit arrangement 100 and has a relatively short service life. US 7,511,437 B1 shows an operating circuit for light emitting diodes. A rectified but not smoothed AC voltage signal is fed to a converter for operating the light emitting diodes. A switch of the converter is controlled based on parameters of the supply voltage. In particular, a switching frequency and a timing of the switch are adapted.

Der vorliegenden Erfindung liegt deshalb die Aufgabenstellung zugrunde, eine neuartige Lösung zum Betreiben von Leuchtmitteln anzugeben, bei der die oben beschriebenen Nachteile vermieden werden.The present invention is therefore based on the object of specifying a novel solution for operating lighting means in which the disadvantages described above are avoided.

Die Aufgabe wird durch eine Schaltungsanordnung zum Betreiben von Leuchtmitteln, welche die Merkmale des Anspruchs 1 aufweist, gelöst. Ferner wird die Aufgabenstellung durch ein Verfahren gemäß Anspruch 10 gelöst. Vorteilhafte Weiterbildungen der Erfindung sind Gegenstand der abhängigen Ansprüche.The object is achieved by a circuit arrangement for operating lighting means which has the features of claim 1. Furthermore, the object is achieved by a method according to claim 10. Advantageous further developments of the invention are the subject of the dependent claims.

Die erfindungsgemäße Lösung beruht zunächst auf der Erkenntnis, dass auf den oben erwähnten und als problematisch angesehenen Glättungskondensator auch verzichtet werden kann, sofern das alternierende Ansteuern des Schalters in geeigneter Weise vorgenommen wird. Genau genommen kann wiederum ein Übertrager mit einer Primärwicklung und einer Sekundärwicklung zum Einsatz kommen, wobei in Serie zu der Primärwicklung ein steuerbares Schaltelement geschaltet ist, mit dessen Hilfe alternierend ein Stromfluss durch die Primärwicklung hervorgerufen bzw. unterbrochen wird, wobei nunmehr erfindungsgemäß als Versorgungsspannung für den Übertrager eine gleichgerichtete, allerdings nicht geglättete Wechselspannung verwendet wird und abhängig von der aktuellen Höhe der Versorgungsspannung die Steilheit der ansteigenden oder abfallenden Flanke des Signals zum Ansteuern des Schalters angepasst wird. Es hat sich also gezeigt, dass ein Glätten der gleichgerichteten Wechselspannung nicht zwingend erforderlich ist, sofern das Ansteuerverhalten für den Schalter in geeigneter Weise - insbesondere abhängig vom aktuellen Wert der Versorgungsspannung - beeinflusst wird. Auch in diesem Fall ist es dann möglich, sekundärseitig einen gewünschten Stromfluss zum Versorgen der Leuchtmittel hervorzurufen.The solution according to the invention is initially based on the knowledge that the above-mentioned smoothing capacitor, which is viewed as problematic, can also be dispensed with, provided that the alternating control of the switch is carried out in a suitable manner. Strictly speaking, a transformer with a Primary winding and a secondary winding are used, with a controllable switching element connected in series with the primary winding, with the aid of which a current flow through the primary winding is alternately caused or interrupted, with a rectified but not smoothed AC voltage now as the supply voltage for the transformer is used and depending on the current level of the supply voltage, the steepness of the rising or falling edge of the signal for controlling the switch is adapted. It has thus been shown that smoothing the rectified AC voltage is not absolutely necessary if the control behavior for the switch is influenced in a suitable manner - in particular as a function of the current value of the supply voltage. In this case, too, it is then possible to produce a desired current flow on the secondary side for supplying the lighting means.

Erfindungsgemäß wird also eine Schaltungsanordnung zum Betreiben von Leuchtmitteln, insbesondere zum Betreiben einer oder mehrerer LEDs vorgeschlagen, wobei die Schaltungsanordnung eine mit Spannung versorgbare und mittels wenigstens eines Schalters getaktete Schaltung aufweist, über die ein Übertrager zum Übertragen elektrischer Energie von einer Primärwicklung zu einer Sekundärwicklung gespeist wird, wobei die Leuchtmittel über die Sekundärwicklung des Übertragers mit Strom versorgbar sind, sowie eine Steuereinheit zum alternierenden Ansteuern des Schalters, wobei es sich bei der Versorgungsspannung für den Übertrager um eine gleichgerichtete, nicht geglättete Wechselspannung handelt und wobei die Steuereinheit dazu ausgebildet ist, abhängig von der Versorgungsspannung für den Übertrager den folgenden Parameter für die Ansteuerung des Schalters anzupassen: die Steilheit der ansteigenden und/oder der abfallenden Flanke, wobei die Ansteuerung des steuerbaren Schalters über ein RC-Glied mit einem einstellbaren Widerstand erfolgt.According to the invention, a circuit arrangement for operating lighting means, in particular for operating one or more LEDs, is proposed, the circuit arrangement having a circuit that can be supplied with voltage and clocked by means of at least one switch, via which a transformer for transmitting electrical energy from a primary winding to a secondary winding is fed the lighting means can be supplied with power via the secondary winding of the transformer, as well as a control unit for alternating control of the switch, the supply voltage for the transformer being a rectified, non-smoothed alternating voltage and the control unit being designed to be dependent of the supply voltage for the transformer to adapt the following parameters for the control of the switch: the steepness of the rising and / or the falling edge, with the control of the controllable switch via an RC element with an adjustable resistor.

Ferner wird erfindungsgemäß ein Verfahren zum Betreiben von Leuchtmitteln, insbesondere zum Betreiben einer oder mehrerer LEDs vorgeschlagen, bei dem eine mit Spannung versorgbare und mittels wenigstens eines Schalters getaktete Schaltung einen Übertrager zum Übertragen elektrischer Energie von einer Primärwicklung zu einer Sekundärwicklung speist, wobei die Leuchtmittel über die Sekundärwicklung des Übertragers mit Strom versorgbar sind, wobei es sich bei der Versorgungsspannung für den Übertrager um eine gleichgerichtete, nicht geglättete Wechselspannung handelt und wobei abhängig von der Versorgungsspannung für den Übertrager der Parameter für die Ansteuerung des Schalters angepasst wird: die Steilheit der ansteigenden und/oder der abfallenden Flanke, wobei die Ansteuerung des steuerbaren Schalters über ein RC-Glied mit einem einstellbaren Widerstand erfolgt.Furthermore, the invention proposes a method for operating lighting means, in particular for operating one or more LEDs, in which a circuit that can be supplied with voltage and clocked by means of at least one switch feeds a transformer for transmitting electrical energy from a primary winding to a secondary winding, the lighting means via the secondary winding of the transformer can be supplied with current, the supply voltage being for the transformer is a rectified, unsmoothed AC voltage and the parameters for controlling the switch are adapted depending on the supply voltage for the transformer: the steepness of the rising and / or falling edge, with the controllable switch being controlled via an RC Link is made with an adjustable resistance.

Die erfindungsgemäße Lösung stellt also eine Weiterentwicklung des klassischen Prinzips des Flyback-Konverters dar, welche es nunmehr allerdings erlaubt, auf den anfälligen und kostenaufwendigen Glättungskondensator zu verzichten. Trotz allem kann bei entsprechend geeigneter Ansteuerung des Schalters in effizienter Weise die Anordnung von Leuchtmitteln mit Strom versorgt und betrieben werden.The solution according to the invention thus represents a further development of the classic principle of the flyback converter, which, however, now allows the susceptible and costly smoothing capacitor to be dispensed with. In spite of everything, if the switch is appropriately controlled, the arrangement of lighting means can be supplied with power and operated in an efficient manner.

Dabei kann neben der erforderlichen Überwachung der Versorgungsspannung auch eine Überwachung des sekundärseitigen Stroms vorgenommen werden, um das Ansteuerverhalten für den Schalter zu optimieren. Hierfür können entsprechende Mittel zum Erfassen des sekundärseitigen Stroms vorgesehen sein, wobei hierzu vorzugsweise ein Optokoppler zum Einsatz kommt, mit dessen Hilfe das den sekundärseitigen Strom wiedergebende Signal auf die Primärseite des Übertragers, auf der auch der Treiber für den Schalter positioniert ist, übertragen wird.In addition to the necessary monitoring of the supply voltage, the secondary current can also be monitored in order to optimize the control behavior for the switch. For this purpose, appropriate means can be provided for detecting the secondary-side current, an optocoupler preferably being used for this purpose, with the aid of which the signal reproducing the secondary-side current is transmitted to the primary side of the transformer, on which the driver for the switch is also positioned.

Weiterhin kann gemäß einer bevorzugten Ausführungsform vorgesehen sein, dass auf der Sekundärseite des Übertragers eine Konstantstromquelle vorgesehen ist, die in Serie zu den zu betreibenden Leuchtmitteln angeordnet ist. Primäraufgabe dieser Konstantstromquelle ist es zunächst, einen zu hohen Stromfluss durch die Leuchtmittel zu vermeiden. Es kann allerdings auch vorgesehen sein, dass die Konstantstromquelle steuerbar ausgeführt ist und auch diese zusätzlich durch die Steuereinheit entsprechend angesteuert wird, um zusätzlich die Versorgung für die Leuchtmittel zu optimieren.Furthermore, according to a preferred embodiment it can be provided that a constant current source is provided on the secondary side of the transformer, which is arranged in series with the lighting means to be operated. The primary task of this constant current source is initially to avoid excessive current flow through the lighting means. However, it can also be provided that the constant current source is designed to be controllable and that it is also controlled accordingly by the control unit in order to additionally optimize the supply for the lighting means.

Die Leistungsübertragung zwischen Primärwicklung und Sekundärwicklung des Übertragers kann ferner gemäß einer weiter bevorzugten Ausführungsform flexibel gestaltet werden, indem das Wicklungsverhältnis zwischen Primärwicklung und Sekundärwicklung veränderbar ist. Hierzu kann vorgesehen sein, dass die Primärwicklung und/oder die Sekundärwicklung in Teilwicklungen unterteilt ist, wobei die Teilwicklungen dann durch die Steuereinheit wahlweise aktiviert oder deaktiviert werden können, sodass sie also aktiver Bestandteil oder kein Bestandteil des Übertragers sind. Durch diese Möglichkeit kann in besonders flexibler und effizienter Weise eine Übertragung der Leistung auf die Sekundärseite mit den Leuchtmitteln vorgenommen werden.The power transmission between the primary winding and the secondary winding of the transformer can also be designed flexibly according to a further preferred embodiment in that the winding ratio between the primary winding and the secondary winding can be changed. For this purpose, it can be provided that the primary winding and / or the secondary winding is divided into partial windings, the partial windings then being optionally activated or activated by the control unit can be deactivated so that they are an active part or no part of the transformer. This possibility enables the power to be transmitted to the secondary side with the lighting means in a particularly flexible and efficient manner.

Andere Weiterbildungen der Erfindung betreffen die Frage, in welcher Weise die erfindungsgemäße Einflussnahme auf das Ansteuersignal für die Ansteuerung des steuerbaren Schalters erfolgt.Other developments of the invention relate to the question of the manner in which the inventive influence on the control signal for the control of the controllable switch takes place.

Dabei ist zunächst vorgesehen, dass die Ansteuerung des Schalters über ein RC-Glied erfolgt, wobei das RC-Glied einen einstellbaren Widerstand aufweist. Indem auf den Widerstandswert des RC-Glieds Einfluss genommen wird, kann das zeitliche Verhalten des Ansteuersignals für den Schalter beeinflusst werden. Insbesondere besteht hierdurch die Möglichkeit, auf die Steilheit der ansteigenden oder abfallenden Flanke des Steuersignals Einfluss zu nehmen. Besonders bevorzugt ist hierbei vorgesehen, dass der einstellbare Widerstand durch interne Komponenten eines Mikrocontrollers gebildet ist. Wie nachfolgend noch näher erläutert wird, weisen Mikrocontroller zur Ausgabe eines analogen Signals in der Regel intern einen Spannungsteiler auf, dessen Einzelwiderstände wahlweise entsprechend kombiniert werden können. Diese Komponenten werden nunmehr gemäß der besonders bevorzugten Ausführungsform dazu genutzt, den einstellbaren Widerstand des RC-Glieds zu bilden.It is initially provided that the switch is controlled via an RC element, the RC element having an adjustable resistance. By influencing the resistance value of the RC element, the behavior over time of the control signal for the switch can be influenced. In particular, this makes it possible to influence the steepness of the rising or falling edge of the control signal. It is particularly preferred here that the adjustable resistor is formed by internal components of a microcontroller. As will be explained in more detail below, microcontrollers usually have an internal voltage divider for outputting an analog signal, the individual resistors of which can be combined accordingly. According to the particularly preferred embodiment, these components are now used to form the adjustable resistance of the RC element.

Alternativ oder ergänzend hierzu kann allerdings auch vorgesehen sein, dass das RC-Glied mehrere Kapazitäten aufweist, welche wahlweise durch die Steuereinheit aktiviert bzw. deaktiviert werden können. In diesem Fall kann also nochmals flexibler über das RC-Glied Einfluss auf die Form des Ansteuersignals für den getakteten Schalter genommen werden.As an alternative or in addition to this, however, it can also be provided that the RC element has a plurality of capacitances which can optionally be activated or deactivated by the control unit. In this case, the form of the control signal for the clocked switch can be influenced even more flexibly via the RC element.

Eine weitere bevorzugte Maßnahme, das Ansteuerverhalten für den Schalter zu optimieren, besteht ferner darin, den Kondensator des RC-Glieds durch einen weiteren steuerbaren Schalter zu überbrücken. Dieser kann ggf. leitend geschaltet werden, um die Wirkung des RC-Glieds zu deaktivieren und bspw. den Schaltzyklus für den steuerbaren Schalter des Übertragers unmittelbar zu beenden. Dabei kann ggf. auch die Ansteuerung dieses zweiten Schalters mit Hilfe eines zusätzlichen RC-Glieds erfolgen. Dieses ermöglicht es dann, gezielt die abfallende Flanke des Ansteuersignals für den Schalter zu beeinflussen.Another preferred measure to optimize the control behavior for the switch consists in bridging the capacitor of the RC element with a further controllable switch. This can, if necessary, be switched on in order to deactivate the effect of the RC element and, for example, to end the switching cycle for the controllable switch of the transformer immediately. If necessary, the This second switch is controlled with the aid of an additional RC element. This then makes it possible to specifically influence the falling edge of the control signal for the switch.

Letztendlich eröffnen also die oben genannten Maßnahmen die Möglichkeit, eine äußerst präzise Ansteuerung des getakteten Schalters für den Übertrager vorzunehmen, was wiederum die Möglichkeit eröffnet, einen sekundärseitigen Stromfluss sehr genau einzustellen, ohne dass hierfür der Einsatz eines primärseitigen Glättungskondensators erforderlich wäre. Dabei ist darauf hinzuweisen, dass die zur Optimierung des Ansteuerverhaltens oben erwähnten zusätzlichen Kondensatoren deutlich kleiner dimensioniert sind als der im Flyback-Konverter erforderliche Glättungskondensator, sodass hier die im Zusammenhang mit der Flyback-Technologie auftretenden Probleme hinsichtlich des Kondensators zu vernachlässigen sind.Ultimately, the measures mentioned above open up the possibility of extremely precise control of the clocked switch for the transformer, which in turn opens up the possibility of setting a secondary-side current flow very precisely without the use of a primary-side smoothing capacitor being required. It should be pointed out that the additional capacitors mentioned above for optimizing the control behavior are dimensioned significantly smaller than the smoothing capacitor required in the flyback converter, so that the capacitor problems associated with flyback technology can be neglected here.

Nachfolgend soll die Erfindung anhand der beiliegenden Zeichnung näher erläutert werden. Es zeigen:

Figur 1
eine aus dem Stand der Technik bekannte Lösung zur Ansteuerung von LEDs, die auf der Verwendung eines Flyback-Konverters beruht;
Figur 2
eine grundsätzliche Darstellung des erfindungsgemäßen Konzepts zum Ansteuern einer Leuchtmittelgruppe;
Figur 3
ein erstes Ausführungsbeispiel einer erfindungsgemäßen Schaltungsanordnung;
Figuren 4 - 6
verschiedene Weiterentwicklungen der in Figur 3 gezeigten Schaltungsanordnung;
Figur 7
eine erste Maßnahme zur Optimierung der Ansteuerung des steuerbaren Schalters und
Figuren 8 - 10
weitere Varianten zur Optimierung der Ansteuerung des steuerbaren Schalters gemäß der vorliegenden Erfindung.
The invention will be explained in more detail below with reference to the accompanying drawing. Show it:
Figure 1
a solution known from the prior art for controlling LEDs, which is based on the use of a flyback converter;
Figure 2
a basic representation of the inventive concept for controlling a group of illuminants;
Figure 3
a first embodiment of a circuit arrangement according to the invention;
Figures 4 - 6
various further developments of the in Figure 3 circuit arrangement shown;
Figure 7
a first measure to optimize the control of the controllable switch and
Figures 8-10
further variants for optimizing the control of the controllable switch according to the present invention.

Figur 2 zeigt zunächst das grundsätzliche Konzept der erfindungsgemäßen Schaltungsanordnung bzw. der erfindungsgemäßen Vorgehensweise zum Betreiben einer LED-Strecke. Ebenso wie bei der aus dem Stand der Technik bekannten und in Figur 1 dargestellten Lösung wird der allgemein mit dem Bezugszeichen 1 versehenen Schaltungsanordnung eingangsseitig eine Versorgungswechselspannung UAC zugeführt, wobei diese Spannung dann zunächst durch einen Gleichrichter 5 - bspw. einen Brückengleichrichter - in eine gleichgerichtete Versorgungswechselspannung UDC umgesetzt wird. Figure 2 first shows the basic concept of the circuit arrangement according to the invention or the procedure according to the invention for operating an LED path. As with the one known from the prior art and in Figure 1 The solution shown is supplied with an AC supply voltage U AC on the input side of the circuit arrangement generally provided with the reference numeral 1, this voltage then first being converted into a rectified AC supply voltage U DC by a rectifier 5 - for example a bridge rectifier.

Eine weitere Übereinstimmung zu dem in Figur 1 gezeigten Flyback-Konverter besteht ferner darin, dass die Schaltungsanordnung 1 einen Übertrager 10 mit einer Primärwicklung L1 und einer Sekundärwicklung L2 aufweist, wobei die Sekundärwicklung L2 dann die LED-Strecke 110 mit Strom versorgt. Im dargestellten Ausführungsbeispiel ist der Sekundärkreis der Schaltungsanordnung 1 sehr vereinfacht dargestellt und die Sekundärwicklung L2 ist unmittelbar mit den LEDs 110 verbunden. Selbstverständlich könnte der Sekundärkreis allerdings auch komplexer ausgestaltet sein und insbesondere könnte die LED-Anordnung 110 auch nicht lediglich aus einem einzigen seriellen LED-Strang bestehen, sondern eine komplexere Verschaltung von LEDs aufweisen.Another match to the in Figure 1 The flyback converter shown also consists in that the circuit arrangement 1 has a transformer 10 with a primary winding L1 and a secondary winding L2, the secondary winding L2 then supplying the LED path 110 with current. In the exemplary embodiment shown, the secondary circuit of the circuit arrangement 1 is shown in a very simplified manner and the secondary winding L2 is directly connected to the LEDs 110. Of course, the secondary circuit could, however, also be designed in a more complex manner and in particular the LED arrangement 110 could not only consist of a single serial LED string, but could have a more complex interconnection of LEDs.

Schließlich besteht eine weiter Übereinstimmung zu der aus dem Stand der Technik bekannten Lösung darin, dass in Serie zur Primärwicklung L1 des Übertragers 10 ein steuerbares Schaltelement 11 in Form eines Transistors vorgesehen ist, über den also wahlweise ein Stromfluss über die Primärwicklung L1 zugelassen bzw. unterbrochen werden kann. Die Ansteuerung des Schalters llerfolgt hierbei über eine Treiber- bzw. Steuereinheit 20.Finally, a further correspondence with the solution known from the prior art is that a controllable switching element 11 in the form of a transistor is provided in series with the primary winding L1 of the transformer 10, via which a current flow via the primary winding L1 can be allowed or interrupted can be. The control of the switch 11 takes place via a driver or control unit 20.

Der wesentliche Unterschied hinsichtlich des strukturellen Aufbaus besteht darin, dass auf den in Figur 1 dargestellten und im Stand der Technik grundsätzlich erforderlichen Glättungskondensator verzichtet wird. D.h., die von dem Gleichrichter 5 gleichgerichtete eingangsseitige Wechselspannung bildet nunmehr eine Versorgungsspannung UDC für den Übertrager 10, die nicht konstant bzw. zumindest annähernd konstant ist, sondern stattdessen aus positiven Halbwellen, die im Wesentlichen etwa sinusförmig ausgebildet sind, besteht. Trotz allem kann auch mit dieser speziellen Versorgungsspannung U für den Übertrager 10 ein geeigneter LED-Betrieb realisiert werden. D.h., es besteht trotz allem die Möglichkeit, sekundärseitig die LED-Anordnung 110 mit einer für den Betrieb der LEDs geeigneten Spannung und einem geeigneten Strom zu versorgen.The main difference in terms of the structural design is that the in Figure 1 shown and in principle required in the prior art smoothing capacitor is dispensed with. That is, the input-side AC voltage rectified by the rectifier 5 now forms a supply voltage U DC for the transformer 10, which is not constant or at least approximately constant, but instead consists of positive half-waves that are generated in Are essentially approximately sinusoidal, there is. In spite of everything, a suitable LED operation can also be implemented with this special supply voltage U for the transformer 10. That is, despite everything, there is the possibility of supplying the LED arrangement 110 on the secondary side with a voltage and a suitable current that are suitable for operating the LEDs.

Hierzu ist vorgesehen, dass die Treiberschaltung 20 eine im Vergleich zum Stand der Technik flexiblere Ansteuerung des Schalters 11 vornimmt. Insbesondere ist vorgesehen, dass abhängig vom aktuellen Wert der Versorgungsspannung U für den Übertrager 10, also abhängig vom aktuellen Wert der gleichgerichteten Versorgungswechselspannung das Steuersignal u für den Schalter 11 hinsichtlich seiner Steilheit der ansteigenden und/oder abfallenden Flanke angepasst wird. Im Vergleich zu einem rein rechteckförmigen PWM-Signal, wie es bei der Ansteuerung des Schalters des Flyback-Konverters in Figur 1 vorgesehen ist, ergibt sich nun also ein deutlich komplexeres Ansteuersignal u für den Schalter 11 der erfindungsgemäßen Anordnung 1. Hierdurch wird allerdings der Vorteil erzielt, dass auf den Glättungskondensator vollständig verzichtet werden kann.For this purpose, it is provided that the driver circuit 20 controls the switch 11 in a more flexible manner than in the prior art. In particular, it is provided that depending on the current value of the supply voltage U for the transformer 10, i.e. depending on the current value of the rectified AC supply voltage, the steepness of the control signal u for the switch 11 is adapted to the rising and / or falling edge. Compared to a purely square-wave PWM signal, as is the case when the flyback converter switch is activated in Figure 1 is provided, a significantly more complex control signal u now results for the switch 11 of the arrangement 1 according to the invention. However, this has the advantage that the smoothing capacitor can be completely dispensed with.

Die Änderung des Ansteuersignals für den Schalter 11 muss also flexibel abhängig vom aktuellen Istwert der Versorgungsspannung UDC erfolgen. Es ist also ein hochfrequentes Ansteuersignal u erforderlich, dessen Verlauf ständig angepasst wird. Dabei besteht beispielsweise die Möglichkeit, den Bereich der Versorgungsspannung UDC in verschiedene Teilbereiche zu unterteilen und für jeden Teilbereich einen jeweils geeigneten Signalverlauf bei der Ansteuerung des Schalters 11 auszuwählen. Auch eine kontinuierlich vom aktuellen Wert der Versorgungsspannung abhängige Ansteuerung des Schalters wäre allerdings denkbar.The change in the control signal for the switch 11 must therefore take place flexibly as a function of the current actual value of the supply voltage U DC . A high-frequency control signal u is therefore required, the course of which is continuously adapted. It is possible, for example, to subdivide the range of the supply voltage U DC into different sub-areas and to select a suitable signal course when activating the switch 11 for each sub-area. Activation of the switch that is continuously dependent on the current value of the supply voltage would, however, also be conceivable.

Anhand der Figuren 3-6 sollen nunmehr zunächst verschiedene Varianten der erfindungsgemäßen Schaltungsanordnung erläutert werden. Diese Varianten betreffen insbesondere die Frage, inwiefern das grundsätzliche Schaltungskonzept strukturell erweitert werden kann, um die Ansteuerung zu optimieren. Anhand der später näher erläuterten Figuren 7-10 wird dann beschrieben, in welcher Weise speziell das Ansteuersignal für den Schalter in erfindungsgemäßer Weise beeinflusst werden kann. Figur 3 zeigt hierbei zunächst eine Grundversion der erfindungsgemäßen Schaltungsanordnung 1, wobei vergleichbare Elemente zu Figur 2 mit dem Bezugszeichen versehen sind. Erkennbar ist allerdings in Figur 3 bspw., dass - wie oben erwähnt - die LED-Anordnung 110 in unterschiedlichster Weise gestaltet sein kann.Based on Figures 3-6 different variants of the circuit arrangement according to the invention will now be explained first. These variants relate in particular to the question of the extent to which the basic circuit concept can be structurally expanded in order to optimize the control. Based on the later explained in more detail Figures 7-10 it is then described in which way the control signal for the switch can be influenced in the manner according to the invention. Figure 3 shows first of all a basic version of the circuit arrangement 1 according to the invention, with comparable elements Figure 2 are provided with the reference number. However, it can be seen in Figure 3 For example, that - as mentioned above - the LED arrangement 110 can be designed in the most varied of ways.

Wesentliche Elemente der erfindungsgemäßen Schaltungsanordnung 1 sind also wie anhand von Figur 2 erläutert der Übertrager 10 mit der Primärwicklung L1 und der Sekundärwicklung L2 sowie der steuerbare Schalter 11, der in Serie zur Primärwicklung L1 des Übertragers 10 geschaltet wird. Die Ansteuerung des Schalters 11 durch die Steuereinheit bzw. den Treiber 20 soll wie erwähnt in Abhängigkeit von der Versorgungsspannung U für den Übertrager 10 erfolgen, die durch das Gleichrichten der extern zugeführten Versorgungswechselspannung UAC mit Hilfe des Gleichrichters 5 erhalten wird. Um eine entsprechende Ansteuerung des Schalters 11 vornehmen zu können, muss also die Steuereinheit 20 genaue Kenntnis hinsichtlich des aktuellen Werts der gleichgerichteten Versorgungsspannung UDC haben. Hierfür ist eine entsprechende Sensoreinheit 25 vorgesehen, welche mit dem Ausgang des Gleichrichters 5 verbunden ist und ein entsprechendes Signal an die Steuereinheit 20 übermittelt. Die Bewertung der für den Übertrager 10 zur Verfügung stehenden Versorgungsspannung hinsichtlich der Messgenauigkeit kann dabei optional dadurch verbessert werden, dass - wie in Figur 3 angedeutet - zusätzlich mit Hilfe einer weiteren Einheit 30 eine Nulldurchgangserkennung vorgenommen wird. Diese Einheit ist also unmittelbar mit der externen Versorgungsspannung UAC verbunden bzw. mit dem Eingang des Gleichrichters 5 verbunden und liefert eine entsprechende Information hinsichtlich des Nulldurchgangs entweder an die Einheit 25, über welche die Versorgungsspannung für den Übertrager 10 bewertet wird und/oder an die Steuereinheit 20 selbst.Essential elements of the circuit arrangement 1 according to the invention are therefore as shown in FIG Figure 2 explains the transformer 10 with the primary winding L1 and the secondary winding L2 as well as the controllable switch 11, which is connected in series with the primary winding L1 of the transformer 10. The activation of the switch 11 by the control unit or the driver 20 should, as mentioned, take place as a function of the supply voltage U for the transformer 10, which is obtained by rectifying the externally supplied AC supply voltage U AC with the aid of the rectifier 5. In order to be able to actuate the switch 11 accordingly, the control unit 20 must therefore have precise knowledge of the current value of the rectified supply voltage U DC . A corresponding sensor unit 25 is provided for this, which is connected to the output of the rectifier 5 and transmits a corresponding signal to the control unit 20. The evaluation of the supply voltage available for the transformer 10 with regard to the measurement accuracy can optionally be improved by the fact that - as in Figure 3 indicated - a zero crossing detection is additionally carried out with the aid of a further unit 30. This unit is thus directly connected to the external supply voltage U AC or connected to the input of the rectifier 5 and supplies corresponding information regarding the zero crossing either to the unit 25, via which the supply voltage for the transformer 10 is evaluated and / or to the Control unit 20 itself.

Eine Weiterentwicklung des in Figur 3 gezeigten Basiskonzepts ist in Figur 4 gezeigt. Wiederum sind gleiche Komponenten mit den gleichen Bezugszeichen versehen, wobei nunmehr die Einheit 30 zur Nulldurchgangserkennung nicht nur als optional betrachtet wird. Wesentliche Ergänzung zu der Anordnung gemäß Figur 3 ist allerdings, dass in diesem Fall auch eine Information hinsichtlich des tatsächlich im Sekundärkreis fließenden Stroms erhalten wird. Hierfür ist ein Optokoppler 35 vorgesehen, der mit dem Sekundärkreis in Serie zur LED-Anordnung 110 verbunden ist und eine entsprechende Information an die Steuereinheit 20 übermittelt. Diese kann dann im Sinne einer Regelung die Ansteuerung für den Schalter 11 entsprechend anpassen, um ggf. gezielt einen gewünschten Stromfluss durch die LED-Anordnung 110 hervorzurufen.A further development of the in Figure 3 The basic concept shown is in Figure 4 shown. Again, the same components are provided with the same reference numerals, the unit 30 for zero crossing detection now not only being viewed as optional. Essential addition to the arrangement according to Figure 3 is, however, that in this case information regarding the actual im Secondary circuit current flowing is obtained. For this purpose, an optocoupler 35 is provided, which is connected to the secondary circuit in series with the LED arrangement 110 and transmits corresponding information to the control unit 20. This can then adapt the control for the switch 11 accordingly in the sense of a regulation, in order, if necessary, to produce a desired current flow through the LED arrangement 110 in a targeted manner.

Die zuvor anhand von Figur 4 erläuterte Rückkopplung mit Hilfe des Optokopplers 35 zur Regelung des sekundärseitigen Stroms kann weiterhin durch eine Figur 5 gezeigte Maßnahme zusätzlich verbessert werden. Hier ist eine Konstantstromquelle 36 im Sekundärkreis vorgesehen, die in Serie zur LED-Anordnung 110 geschaltet ist. Die Aufgabe dieser Kontantstromquelle 36 besteht darin, einen zu hohen Stromfluss im Sekundärkreis zu verhindern. Derartige Konstantstromquellen kommen häufig bei Schaltungsanordnungen zum Betreiben von LEDs zum Einsatz und stellen eine Sicherheitsmaßnahme dar, durch die gewährleistet ist, dass die LEDs nicht aufgrund eines zu hohen Stroms beschädigt werden. Gemeinsam mit der durch den Optokoppler 35 erzielten Rückkopplung, durch die eine Regelung des sekundärseitigen Stroms erzielt wird, kann also eine besonders effiziente aber sichere Ansteuerung der LEDs vorgenommen werden. Die Konstantstromquelle 36 kann hierbei auch als steuerbare Konstantstromquelle ausgeführt sein und wird dann wiederum durch die Steuerschaltung 20 angesteuert.The previously based on Figure 4 explained feedback with the help of the optocoupler 35 for regulating the secondary-side current can continue by a Figure 5 The measure shown can also be improved. Here, a constant current source 36 is provided in the secondary circuit, which is connected in series with the LED arrangement 110. The task of this constant current source 36 is to prevent an excessive current flow in the secondary circuit. Such constant current sources are often used in circuit arrangements for operating LEDs and represent a safety measure which ensures that the LEDs are not damaged due to an excessively high current. Together with the feedback achieved by the optocoupler 35, by means of which regulation of the secondary-side current is achieved, a particularly efficient but reliable control of the LEDs can thus be carried out. The constant current source 36 can also be designed as a controllable constant current source and is then in turn controlled by the control circuit 20.

Schließlich zeigt Figur 6 eine zusätzliche Weiterbildung, die berücksichtigt, dass die Höhe der Versorgungsspannung UDC für den Übertrager 10 - im Vergleich zu einem klassischen Flyback-Konverter - stark schwankt. Um sekundärseitig eine für den LED-Betrieb optimale Spannung erzielen zu können, wäre es also von Vorteil, dass Wicklungsverhältnis des Übertragers 10 variabler gestalten zu können. Dies wird mit der in Figur 6 dargestellten Weiterbildung erreicht, indem hier sowohl die Primärwicklung L1 als auch die Sekundärwicklung L2 in Teilwicklungen unterteilt sind. Genau genommen besteht die Primärwicklung L1 nunmehr aus zwei Teilwicklungen L11 und L12, die in Serie miteinander verbunden sind, wobei allerdings durch einen zusätzlichen Schalter 12 die zweite Teilwicklung L12 überbrückt werden kann. In vergleichbarer Weise ist auch die Sekundärwicklung L2 des Übertragers 10 in zwei Teilwicklungen L21 und L22 unterteilt, die über Steuerelemente 13 und 14 wahlweise dem Sekundärkreis der Schaltungsanordnung 1 hinzugefügt werden können. Die Steuerelemente 13, 14 bestehen hierbei aus Transistoren, die über eine Potentialtrennung, die jeweils mit Hilfe eines Optokopplers realisiert wird, angesteuert werden.Finally shows Figure 6 an additional development that takes into account that the level of the supply voltage U DC for the transformer 10 - compared to a classic flyback converter - fluctuates greatly. In order to be able to achieve an optimal voltage for the LED operation on the secondary side, it would be advantageous to be able to make the winding ratio of the transformer 10 more variable. This is done with the in Figure 6 Achieved development shown in that both the primary winding L1 and the secondary winding L2 are divided into partial windings here. Strictly speaking, the primary winding L1 now consists of two partial windings L11 and L12, which are connected to one another in series, although the second partial winding L12 can be bridged by an additional switch 12. In a comparable way, the secondary winding L2 of the transformer 10 is divided into two partial windings L21 and L22, which over Control elements 13 and 14 can optionally be added to the secondary circuit of the circuit arrangement 1. The control elements 13, 14 in this case consist of transistors which are controlled via a potential separation which is implemented with the aid of an optocoupler.

Abhängig von der Höhe der Versorgungsspannung UDC kann also die Steuereinheit 20 wahlweise die Teilwicklungen der beiden Wicklungen L1 bzw. L2 des Übertragers 10 dem entsprechenden Primärkreis bzw. Sekundärkreis hinzufügen oder davon entkoppeln, sodass in verschiedenen Schritten das Wicklungsverhältnis des Übertragers 10 angepasst werden kann. Hierdurch wird eine nochmals bessere Möglichkeit zur Ansteuerung der LED-Anordnung 110 geschaffen, da trotz starker Veränderung der Versorgungsspannung UDC immer ein Wicklungsverhältnis für den Übertrager 10 eingestellt werden kann, welches das Erzielen einer geeigneten Spannung im Sekundärkreis für den LED-Betrieb ermöglicht. Dabei kann das Konzept des flexiblen Einstellens des Wicklungsverhältnisses des Übertragers 10 auch auf die Schaltungsvarianten der Figuren 3 und 4 übertragen werden, die Verwendung der in Figur 5 gezeigten Konstantstromquelle 36 ist nicht zwingend erforderlich.Depending on the level of the supply voltage U DC , the control unit 20 can optionally add or decouple the partial windings of the two windings L1 and L2 of the transformer 10 from the corresponding primary circuit or secondary circuit, so that the winding ratio of the transformer 10 can be adjusted in different steps. This creates an even better option for controlling the LED arrangement 110, since despite a strong change in the supply voltage U DC , a winding ratio can always be set for the transformer 10 which enables a suitable voltage to be achieved in the secondary circuit for LED operation. The concept of flexible setting of the winding ratio of the transformer 10 can also be applied to the circuit variants of Figures 3 and 4 the use of the in Figure 5 shown constant current source 36 is not absolutely necessary.

Anhand der Figuren 7-10 sollen nunmehr verschiedene Maßnahmen beschrieben werden, über die gezielt Einfluss auf das Ansteuersignal für den steuerbaren Schalter 11 genommen werden kann. In gleicher Weise kann dann selbstverständlich auch eine Ansteuerung des Schalters 12 vorgenommen werden, sofern eine Unterteilung der Wicklungen des Übertragers 10 vorgenommen wird und lediglich die in Figur 6 gezeigte erste Teilwicklung L11 betrieben werden soll. Die nachfolgenden Erläuterungen beziehen sich allerdings auf die Variante mit einer einteiligen Ausgestaltung der Primärwicklung L1 sowie der Sekundärwicklung L2, wie sie in den Figuren 3 bis 5 gezeigt ist.Based on Figures 7-10 Various measures are now to be described by means of which the control signal for the controllable switch 11 can be influenced in a targeted manner. In the same way, the switch 12 can of course also be controlled if the windings of the transformer 10 are subdivided and only those shown in FIG Figure 6 shown first partial winding L11 is to be operated. However, the following explanations relate to the variant with a one-piece design of the primary winding L1 and the secondary winding L2, as shown in FIG Figures 3 to 5 is shown.

Wie bereits erwähnt, soll beim Ansteuern des Schalters 11 Einfluss auf die Form des Signals genommen werden. Die nunmehr beschriebenen Maßnahmen betreffen dabei insbesondere die Frage, wie über den Stand der Technik hinausgehend die Form des Signals beeinflusst wird, also insbesondere in welcher Weise die Steilheit der ansteigenden sowie der abfallenden Flanke des Signals modifiziert wird.As already mentioned, when the switch 11 is activated, the form of the signal is to be influenced. The measures now described relate in particular to the question of how the shape of the signal is influenced beyond the state of the art, i.e. in particular in what way the steepness of the rising and falling edges of the signal is modified.

Dabei ist eine erste grundsätzliche Variante in Figur 7 gezeigt, wobei nur die zur Realisierung dieser Variante wesentlichen Bestandteile der Schaltungsanordnung 1 erkennbar sind. Gezeigt ist insbesondere die Steuereinheit 20, welche ausgangsseitig mit dem Schalter 11 verbunden ist, um diesen anzusteuern. Dabei ist erfindungsgemäßen nunmehr vorgesehen, dass eine Beeinflussung der Signalflanken, insbesondere der ansteigenden Signalflanken beim Ansteuern des Schalters 11 dadurch vorgenommen wird, dass die Übermittlung des Steuersignals über ein RC-Glied erfolgt.A first basic variant is in Figure 7 shown, only the essential components of the circuit arrangement 1 for realizing this variant can be seen. In particular, the control unit 20 is shown, which is connected on the output side to the switch 11 in order to control it. It is now provided according to the invention that the signal edges, in particular the rising signal edges, are influenced when the switch 11 is actuated in that the control signal is transmitted via an RC element.

Erkennbar ist hierzu in Figur 7 der Kondensator C1 des RC-Glieds, nicht jedoch der zugehörige Widerstand. Dieser wird in besonders vorteilhafter Weise durch interne Widerstandskomponenten der Steuereinheit 20 erzielt. Dabei wird der Umstand genutzt, dass die Steuereinheit 20 auf einem Mikroprozessor basiert und Mikroprozessoren oftmals einen DAC-Ausgang aufweisen, über den abhängig von einem digitalen Sollwert ein analoges Ausgangssignal ausgegeben wird. Die Erzeugung des analogen Ausgangssignals wird dabei mit Hilfe eines in den Mikroprozessor integrierten Spannungsteilers vorgenommen, der mehrere Einzelwiderstände aufweist. In Figur 8 ist der Spannungsteiler schematisch durch eine serielle Anordnung mehrerer Einzelwiderstände 23 angedeutet, wobei diese durch einen - nicht näher dargestellten - Multiplexer wahlweise miteinander kombiniert werden, um einen Spannungsteiler zu bilden, der letztendlich für den Abfall einer gewünschten analogen Spannung am DAC-Ausgang der Steuereinheit 20 sorgt. Die Versorgungsspannung Vdd für die Steuereinheit 20 wird hierbei durch die mit dem Ausgang des Gleichrichters verbundene Einheit 25 zum Erfassen des Istwerts der Eingangsspannung für den Übertrager 10 bereitgestellt. Zusätzlich übermittelt die Einheit 25 allerdings wie bereits erwähnt auch ein die Höhe der Versorgungsspannung repräsentierendes Signal.This can be seen in Figure 7 the capacitor C1 of the RC element, but not the associated resistor. This is achieved in a particularly advantageous manner by internal resistance components of the control unit 20. This makes use of the fact that the control unit 20 is based on a microprocessor and microprocessors often have a DAC output via which an analog output signal is output as a function of a digital setpoint value. The analog output signal is generated with the aid of a voltage divider integrated in the microprocessor, which has several individual resistors. In Figure 8 the voltage divider is indicated schematically by a series arrangement of several individual resistors 23, these being optionally combined with one another by a multiplexer - not shown in detail - in order to form a voltage divider which is ultimately responsible for the drop in a desired analog voltage at the DAC output of the control unit 20 cares. The supply voltage Vdd for the control unit 20 is provided by the unit 25 connected to the output of the rectifier for detecting the actual value of the input voltage for the transformer 10. In addition, however, as already mentioned, the unit 25 also transmits a signal representing the level of the supply voltage.

Durch entsprechendes Kombinieren der Widerstände 23 des integrierten Spannungsteilers der Steuereinheit 20 kann dann also ein variabler Widerstand gebildet werden, der gemeinsam mit dem Kondensator C1 das RC-Glied bildet, über den die Ansteuerung des Schalters 11 erfolgt. Da das RC-Glied den zeitlichen Verlauf des Ansteuersignals für den Schalter 11 beeinflusst, kann also durch die Veränderung des integrierten Widerstands der Steuereinheit 20 Einfluss auf den Signalverlauf genommen werden. Es wird also eine sehr elegante Möglichkeit geschaffen, in einfacher Weise insbesondere die Steilheit des Anstiegs des Steuersignals für den Schalter 11 zu beeinflussen.By appropriately combining the resistors 23 of the integrated voltage divider of the control unit 20, a variable resistor can then be formed which, together with the capacitor C1, forms the RC element via which the switch 11 is controlled. Since the RC element influences the course of the control signal for the switch 11 over time, the change can therefore the integrated resistance of the control unit 20 can influence the signal curve. A very elegant possibility is thus created of influencing in particular the steepness of the rise of the control signal for the switch 11 in a simple manner.

Eine Weiterbildung dieses soeben erläuterten Gedankens ist in Figur 8 gezeigt. Diese besteht darin, dass parallel zu dem Kondensator C1 des RC-Glieds ein weiterer steuerbarer Schalter Q0 vorgesehen ist, über den der Kondensator C1 des RC-Glieds wahlweise überbrückt bzw. entladen werden kann. Hierdurch besteht die Möglichkeit, durch Aktivieren dieses Schalters Q0 die zeitverzögernde Wirkung des RC-Glieds bzgl. der Ansteuerung des Schalters 11 abrupt aufzuheben, sodass also die Signalform hier zusätzlich beeinflusst werden kann.A further development of this idea just explained is in Figure 8 shown. This consists in that a further controllable switch Q0 is provided parallel to the capacitor C1 of the RC element, via which the capacitor C1 of the RC element can optionally be bridged or discharged. This makes it possible, by activating this switch Q0, to abruptly cancel the time-delaying effect of the RC element with regard to the control of the switch 11, so that the signal shape can also be influenced here.

Ein Modifizieren der Wirkungsweise des RC-Glieds könnte selbstverständlich auch dadurch vorgenommen werden, dass der Wert der Kapazität des RC-Glieds verändert wird. Eine entsprechende Lösung hierzu ist in Figur 9 gezeigt, wobei nunmehr drei - vorzugsweise unterschiedlich dimensionierte - Kondensatoren C1, C2 und Cn vorgesehen sind (die Anzahl kann allerdings beliebig gewählt werden), wobei jeweils in Serie zu der entsprechenden Kapazität ein steuerbarer Schalter Q1, Q2 und Qn vorgesehen ist, über den der zugehörige Kondensatoren C1, C2 bzw. Cn wahlweise dem Ansteuerkreis zum Ansteuern des Schalters 11 hinzugefügt werden kann. Die Steuereinheit 20 kann also eine beliebige Kombination dieser Kapazitäten dem Ansteuerkreis für den Schalter 11 hinzufügen, sodass hierdurch - ggf. in Kombination mit einer Anpassung der Spannung am DAC Ausgang - nochmals feiner abgestimmt der Signalverlauf beeinflusst werden kann.The mode of operation of the RC element could of course also be modified by changing the value of the capacitance of the RC element. A corresponding solution to this is in Figure 9 now three - preferably differently dimensioned - capacitors C1, C2 and Cn are provided (the number can, however, be selected as desired), with a controllable switch Q1, Q2 and Qn being provided in series with the corresponding capacitance, via which the Associated capacitors C1, C2 or Cn can optionally be added to the control circuit for controlling the switch 11. The control unit 20 can therefore add any combination of these capacitances to the control circuit for the switch 11, so that in this way - possibly in combination with an adaptation of the voltage at the DAC output - the signal curve can be influenced even more finely.

Figur 10 zeigt schließlich eine Weiterbildung, welche insbesondere einer Beeinflussung der abfallenden Flanke des Ansteuersignals für den Schalter 11 dient. Hier ist vorgesehen, dass der bereits bei den Varianten der Figuren 8 und 9 vorgesehene Schalter Q0 nicht direkt über die Steuereinheit 20 angesteuert wird, sondern wiederum ein RC-Glied zwischengeschaltet ist. Auch für dieses RC-Glied gilt das gleiche wie für die Realisierung und Wirkung des RC-Glieds zum Ansteuern des Schalters 11. D.h., durch die Kombination aus Widerstand R0 und Kapazität C0 kann der Signalverlauf bei der Ansteuerung des Entladeschalters Q0 angepasst und damit die Steilheit der abfallenden Flanke des Steuersignals eingestellt werden. Dabei kann wiederum der Widerstand R0 variabel gestaltet werden, indem interne Spannungsteilerkomponenten der Steuereinheit 20 zur Realisierung dieses Widerstands genutzt werden. Auch kann der Kapazitätswert ggf. variabel gestaltet werden, indem ebenso wie bei dem Ausführungsbeispiel der Figur 9 mehrere parallel geschaltete Kapazitäten vorhanden sind, die mittels steuerbarer Schalter wahlweise dem entsprechenden Ansteuerpfad hinzugefügt werden. Figure 10 Finally, FIG. 2 shows a further development which is used in particular to influence the falling edge of the control signal for switch 11. Here it is provided that the already with the variants of the Figures 8 and 9 provided switch Q0 is not controlled directly via the control unit 20, but again an RC element is interposed. The same applies to this RC element as to the implementation and effect of the RC element for controlling the switch 11. In other words, the combination of resistor R0 and capacitance C0 can be used to adapt the signal profile when controlling the discharge switch Q0 and thus the steepness of the falling edge of the control signal can be set. In this case, the resistor R0 can again be designed to be variable, in that internal voltage divider components of the control unit 20 are used to implement this resistor. The capacitance value can also be made variable, if necessary, by, as in the exemplary embodiment, from Figure 9 There are several capacitances connected in parallel, which can be optionally added to the corresponding control path by means of controllable switches.

Letztendlich erlauben also die Maßnahmen in sehr spezifischer Weise den Schalter des Übertragers anzusteuern. Hierdurch besteht die Möglichkeit, den ausgangsseitig realisierten Strom zum Versorgen der LEDs genau einzustellen und hierdurch einen optimalen Betrieb der Leuchtmittel zu ermöglichen, wobei trotz allem auf den eingangsseitig vorgesehenen Glättungskondensator, der üblicherweise bei einem Flyback-Konverter vorgesehen ist, verzichtet werden kann.Ultimately, the measures allow the switch of the transformer to be controlled in a very specific way. This makes it possible to precisely set the current realized on the output side for supplying the LEDs and thereby enable optimal operation of the illuminants, although the smoothing capacitor provided on the input side, which is usually provided in a flyback converter, can be dispensed with.

Claims (12)

  1. A circuit arrangement (1) for operating lamps (110), in particular for operating one or more LEDs, having:
    • a circuit which can be supplied with voltage and is clocked by means of at least one switch (11), and by means of which circuit a transformer (10) for transmitting electrical energy is fed from a primary winding (L1) to a secondary winding (L2), wherein the lamps (110) can be supplied with current via the secondary winding (L2) of the transformer (10), and
    • a control unit (20) for alternatingly activating the switch (11),
    wherein the supply voltage (UDC) for the transformer (10) is a rectified, non-smoothed alternating voltage,
    characterized in that
    the control unit (20) is designed to adapt the following parameter for controlling the switch (11), depending on the supply voltage (UDC) for the transformer (10):
    the slope of the rising and/or falling edge, wherein the control of the controllable switch (11) takes place via an RC element with an adjustable resistance.
  2. The circuit arrangement according to claim 1,
    characterized in that
    the supply voltage (UDC) for the transformer (10) consists essentially of sinusoidal half-waves.
  3. The circuit arrangement according to claim 1 or 2,
    characterized in that
    said circuit arrangement has means for detecting a signal representing the secondary-side current, which signal is supplied to the control unit (20), wherein the means for detecting the signal preferably comprise an optocoupler (35).
  4. The circuit arrangement according to one of the preceding claims,
    characterized in that
    said circuit arrangement has a constant current source (36), which is arranged in series with the lamps (110) to be operated, wherein the constant current source (36) can preferably be activated by the control unit (20).
  5. The circuit arrangement according to one of the preceding claims,
    characterized in that
    the primary winding (L1) and/or the secondary winding (L2) of the transformer (10) are subdivided into partial windings (L11, L12, L21, L22), wherein the partial windings (L11, L12, L21, L22) can be selectively activated or deactivated by the control unit (20).
  6. The circuit arrangement according to claim 5,
    characterized in that
    the adjustable resistance of the RC element is formed by internal components of the control unit (20).
  7. The circuit arrangement according to claim 1 or 6,
    characterized in that
    the RC element has at least two capacitors (C1, C2, Cn), which can be selectively activated or deactivated by the control unit (20).
  8. The circuit arrangement according to one of claims 1, 6 or 7,
    characterized in that
    the capacitance or capacitances of the RC element can be bridged by a controllable switch (Q0).
  9. The circuit arrangement according to claim 8,
    characterized in that
    the controllable switch (Q0) for bridging the RC element is controlled by means of a further RC element, wherein the resistance and/or the capacitance of the further RC element are preferably variable.
  10. A method for operating lamps (110), in particular for operating one or more LEDs, in which a circuit which can be supplied with voltage and is clocked by means of at least one switch (11) supplies a transformer (10) for transmitting electrical energy from a primary winding (L1) to a secondary winding (L2),
    wherein the lamps (110) can be supplied with current via the secondary winding (L2) of the transformer (10), and
    wherein the supply voltage (UDC) for the transformer (10) is a rectified, non-smoothed alternating voltage,
    characterized in that
    the following parameter for controlling the switch (11) is adapted depending on the supply voltage (UDC) for the transformer (10):
    the slope of the rising and/or falling edge, wherein the controllable switch (11) is controlled via an RC element with an adjustable resistance.
  11. The method according to claim 10,
    characterized in that
    the supply voltage (UDC) for the transformer (10) consists essentially of sinusoidal half-waves.
  12. The method according to claim 10 or 11,
    characterized in that
    the primary winding (L1) and/or the secondary winding (L2) of the transformer (10) are subdivided into partial windings (L11, L12, L21, L22), wherein the partial windings (L11, L12, L21, L22) are selectively activated or deactivated.
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