LED operating circuit with start-up circuit, LED module with the same, and method for operating an operating circuit

Abstract

Operating circuit for controlling an LED strip (LS), comprising: - a primary-side galvanically isolated clocked converter, in particular a flyback converter, which has a clocked switching element (S1) on its primary side, wherein connections for the LED section (LS) are supplied from the secondary side of the converter, - a start-up circuit (AS) from which the clocked switching element (S1) is controlled for the duration of a start-up phase, and - a control unit (SE) arranged on the secondary side, which is configured to control the clocked switching element (S1), in particular after the start-up phase, and which is further configured to deactivate the start-up circuit (AS) after the start-up phase, wherein in particular a control unit for controlling the clocked switching element (S1) is provided only on the secondary side of the converter, and wherein a threshold value, in particular a variable or programmable value, is stored for the control unit (SE) and is retrievable, and / or wherein the control unit (SE) is configured to detect a supply voltage supplied from the secondary side of the converter, in particular by a first supply circuit (V1), and depending on this, to supply a signal to a driver circuit (DRV).

Description

[0001] The invention relates to an operating circuit for controlling at least one LED path comprising at least one LED, to an LED module or operating device for operating an LED path (LS) comprising such an operating circuit, and to a method for operating an operating circuit for an LED path. In particular, the operating circuit has a clocked converter, in particular a flyback converter (also referred to as an isolated blocking converter), and a start-up circuit. The operating circuit is divided into at least a primary side and a secondary side by an electrically insulating barrier. The clocked converter is designed to transfer electrical energy from the primary side to the secondary side of the operating circuit by inductive coupling. A control unit is arranged on the secondary side of the operating circuit.The operating circuit is therefore divided into two galvanically isolated areas and the clocked converter couples these areas in a potential-separated manner.

[0002] For example, US 2005 / 0 201 123 A1 discloses a converter whose cost and size are reduced by reducing power consumption, without the need for large elements or radiating fins. The converter includes a switching element connected to a DC power source via a transformer primary winding, a control circuit for turning the switching element on and off, a diode and capacitor for rectifying / smoothing the voltage induced in the transformer secondary winding to obtain a DC output, and a start-up circuit for starting the control circuit. The start-up circuit operates as a constant-current circuit during power-up of the control circuit and as a constant-voltage circuit after power-up of the control circuit.

[0003] Furthermore, US 2007 / 0 103 948 A1 discloses a start-up circuit for a power supply. This has an input for connection to a high-voltage source and an output rail for feeding a rectified voltage into the power supply. A first energy storage device is coupled to the output rail to store energy when voltage is first applied to the input, and a second energy storage device is coupled to an output of the power supply to store energy when a voltage appearing at the output of the power supply reaches a substantially steady state. A switching circuit is connected to the first energy storage device and the second energy storage device and is responsive to the first energy storage device having sufficient energy to transfer the energy to the second energy storage device and disconnect the first energy storage device from the output rail.

[0004] Furthermore, WO 2001 / 061832 A2 discloses an output-isolated switching power supply. This includes a transformer with a primary side and two secondary sides, an electronic switch connected in series with the primary side, a first rectifier and filter on the first secondary side to provide a bias voltage during both start-up and operation, and a second rectifier and filter on the second secondary side to provide a regulated output power. A resistor-capacitor network on the primary side provides an initial operating condition, such as a single control pulse, to the electronic switch, causing sufficient energy to be transferred through the first secondary side to provide sufficient start-up energy for operating an integrated current control circuit on the secondary side in a stepped manner.After the initial operating condition, the integrated current control circuit generates a control signal and applies it to the electronic switch via an isolation circuit so that it is switched on and off in a controlled manner to deliver regulated power to the output of the supply.

[0005] The invention is based on the German patent application 10 2012 215 481.7, which was not published at the time of the present application. This application already contains Fig. 3 and Fig. 4 shows an operating circuit with a secondary side control unit.

[0006] Fig. 1, which the Fig. 3 from the above-mentioned German application, already shows in a block diagram an operating circuit supplied with a direct or alternating current on the primary side. The alternating current is rectified by a rectifier if necessary. The LED path LS is supplied on the secondary side via a converter clocked with an actively controlled switching element S1 (flyback converter). The clocked converter has a transformer T1, T11 for potential-isolated energy transmission. It can also be seen that a control unit S, which is Fig. 1 is referred to as “ASIC”, alternatively implemented by an integrated circuit IC or a microcontroller arranged on the secondary side.

[0007] The control unit S also controls the switch of the clocked converter in a potential-isolated manner, in particular by inductive coupling using a second transformer T2. The control by the second transformer T2 is effected in such a way that the clocked switching element S1 of the clocked converter, in particular a gate of a field-effect transistor (e.g., FET or MOSFET), is controlled accordingly. Thus, the control unit S can be arranged on the secondary side and still control the clocked switching element S1 of the clocked converter arranged on the primary side. In this way, the control unit S can control the clock or the T on -Set the time of the clocked converter. The second transformer T2 can also be designed, for example, as a so-called "coreless transformer" (air coil) or as an optocoupler.

[0008] In order to supply the control unit S with electricity even during a start-up phase, it must be ensured that the supply can be provided without a direct electrical supply via the clocked converter. A direct electrical supply for the control unit until the clocked converter is operating properly, ie, at a specific clock rate, can be provided, as described in Fig. 1, via a resistor R startup1Although this breaks the potential separation, the resistor is dimensioned such that safety regulations (e.g. SELV regulations) are complied with (SELV = Safety Extra Low Voltage, i.e. a small electrical voltage which, due to its low level and insulation compared to the higher-voltage circuit on the primary side, offers special protection against electric shock and is so small that electrical body currents are normally without consequences).

[0009] Within the scope of this SELV regulation, a high-resistance, non-isolated connection is permissible. For example, the resistance R startup1 be dimensioned in the megaohm range.

[0010] As soon as the control unit properly clocks the switch of the clocked converter, the control unit is then supplied with voltage via an inductive decoupling, which is Fig. 1 is shown as auxiliary winding T12 of the transformer T1, TL.

[0011] Further in Fig. 2, which the Fig. 4 from the above-mentioned German application, a capacitive start-up control of the control unit S is shown. However, the transmission of the start-up voltage or the start-up energy for the control unit S is carried out capacitively via the capacitors C LNK1 and C LNK2 .

[0012] With the capacitive supply during the start-up phase, a defined change in the input voltage of the capacitor C LNK1by a timing circuit T, which outputs an alternating signal with a predetermined frequency (adjustable by an external RC element, not shown). Typically, the signal output by the timing circuit T varies between the value of the supply voltage and zero. The timing circuit T thus converts a smoothed, rectified supply voltage into a defined, varying voltage, which serves as the supply for the capacitor C LNK1 but also the capacitor C LNK2 serves.

[0013] The frequency of the timing circuit T and the capacitance of the capacitor C LNK1 be selected so that a desired starting current is set at the control unit. The starting current typically has a value in the range of 10-100 µA. The frequency with which the timer T switches the capacitor C is selected accordingly low. LNK1Inductive transfer of the starting current from the primary side to the secondary side is also known. Alternatively, an optocoupler can be used to control (gate control) the clocked switching element S1. This is then supplied with power on its secondary side, for example.

[0014] Based on the prior art outlined above, the invention aims to enable a power supply to the secondary side, and in particular, to provide a supply voltage to the control unit arranged on the secondary side, while reducing circuit costs and switching / power losses. In particular, this should enable an electrical supply to the secondary-side control unit without the need for auxiliary windings or additional transformers. Transformers that comply with SELV regulations, in particular, incur relatively high circuit costs.

[0015] The invention therefore provides a solution to this problem, as claimed in the independent claims. Further developments of the invention are the subject of the dependent claims.

[0016] In a first aspect, the invention provides an operating circuit for controlling an LED track, comprising: - a potential-isolated clocked converter supplied with a supply voltage on the primary side, in particular a flyback converter, which has a clocked switching element on its primary side, wherein connections for the LED path are supplied from the secondary side of the converter, - a primary-side starting circuit from which the clocked switching element is controlled for the duration of a starting phase, and - a control unit arranged on the secondary side, which is configured to control the clocked switching element, in particular after the start-up phase, and which is further configured to deactivate the start-up circuit after the start-up phase. Preferably, no control unit for controlling the clocked switching element is provided on the primary side of the converter, i.e., a control unit for controlling the clocked switching element is then provided only on the secondary side of the converter.

[0017] The control unit can be electrically supplied from the secondary side of the converter.

[0018] A threshold value, in particular a variable or programmable one, is stored for retrieval by the control unit. Additionally or alternatively, the control unit detects a supply voltage originating from the secondary side of the converter, in particular supplied by a first supply circuit, and delivers a signal to a driver circuit based on this value.

[0019] The driver circuit can be connected to the starting circuit and in particular to a second supply circuit supplying the starting circuit.

[0020] The driver circuit can activate / deactivate a first switching element and preferably alternatively or additionally a second switching element.

[0021] The first switching element can deactivate the second supply circuit when activated / deactivated, in particular by outputting a signal to a third switching element.

[0022] The second switching element can deactivate the start-up circuit when activated / deactivated and, in particular, connect a reset input of the start-up circuit to ground.

[0023] For activating / deactivating the first switching element and / or the second switching element, the driver circuit can output an output signal whose amplitude is in particular above a breakdown voltage of a Zener diode.

[0024] The driver circuit can output the output signal when it receives an input signal from the control unit.

[0025] The Zener diode can be connected to a gate terminal of the first switching element and / or the second switching element. Preferably, the first switching element and / or the second switching element can be activated / deactivated upon output of the output signal.

[0026] When the first switching element is activated / deactivated, the third switching element can be deactivated / activated.

[0027] The driver circuit can receive the input signal from a control unit and transmit it from a secondary side to a primary side of the operating circuit by means of a transmission element, e.g. an optocoupler, an inductive coupling, a capacitive coupling, and / or a resistor, and optionally filter and / or amplify it.

[0028] The start-up circuit can supply the control unit with electrical power for the duration of the start-up phase.

[0029] The control unit can clock the switching element.

[0030] The start-up circuit can be connected to the control unit by means of a coupling element, e.g. an optocoupler, an inductive coupling, a capacitive coupling and / or a resistor, across an electrically insulating barrier.

[0031] A third supply circuit may be provided between the connecting element and the control unit, which may filter, amplify, rectify and / or smooth a signal output by the starting circuit.

[0032] The coupling element and / or the transmission element can be a high-ohm resistor, e.g. greater than 1 MΩ.

[0033] After the start-up phase, the operating circuit can only supply the secondary control unit from the secondary side of the converter.

[0034] During the start-up phase, the secondary control unit can only be supplied by the start-up circuit.

[0035] The driver circuit, in particular a passive one, can be provided for controlling the switching element. When controlled by the control unit, the driver circuit can operate the clocked switching element, in particular the gate of a transistor, at a clock rate determined by the control unit.

[0036] The converter can bridge the electrically insulating barrier of the operating circuit. The electrically insulating barrier can be a galvanically insulating barrier or a SELV barrier.

[0037] The control unit can deactivate the start-up circuit if the supply voltage supplied to the control unit exceeds the threshold value.

[0038] The start-up circuit can be a clock generator, a timer, a timer / pulser, a timing circuit and / or an oscillator.

[0039] In a further aspect, the invention provides an LED module or operating device for operating an LED track, comprising an operating circuit as described above and an LED track supplied thereby.

[0040] In yet another aspect, the invention provides a method for operating an operating circuit for LED paths, wherein a potential-isolated clocked converter, in particular a flyback converter, which has a clocked switching element on its primary side and is supplied with a supply voltage on the primary side, wherein connections for the LED path are supplied from the secondary side of the converter, the clocked switching element is controlled from a start-up circuit for the duration of a start-up phase, and wherein a control unit arranged on the secondary side controls the clocked switching element, in particular after the start-up phase, and deactivates the start-up circuit after the start-up phase. In particular, no control unit for controlling the clocked switching element is provided on the primary side of the converter.

[0041] The invention will now be described with reference to the figures, which show: Fig. 1 shows a first circuit arrangement according to the prior art. Fig. 2 shows a second circuit arrangement according to the prior art. Fig. 3 shows schematically a first embodiment of a circuit arrangement according to the invention. Fig. 4 shows schematically a control according to the first embodiment of Fig. 1. Fig. 5a and Fig. 5b show an example of a concrete design of circuit parts as they can be used in the circuit arrangement according to the invention. Fig. 6a and Fig. 6b schematically show a second embodiment of a circuit arrangement according to the invention and a corresponding control.

[0042] Fig. Figure 3 shows an exemplary first embodiment of the invention. A switching element S1, which can of course be designed as a switch or transistor, is the clocked element of a clocked converter (flyback converter) with a transformer TR.

[0043] The invention now makes use of the fact that in this topology of a clocked converter, the energy path of the clocked converter (transformer TR, switching element S1, output diode D out and output capacitor C out) for transferring energy from the primary side of the operating circuit to the secondary side. On the primary side of the operating circuit, a start-up circuit AS (timer or pulse generator) is provided, which controls the switching element S1 and in particular a gate of the switching element S1. This control causes the switching element S1 to switch on and off in a clocked manner. Energy is transferred from the primary side to the secondary side of the operating circuit. On the secondary side, a supply circuit V1 is provided, which supplies the control unit SE and which, in particular, controls the output diode D out is connected downstream.

[0044] If the control unit SE is sufficiently supplied, i.e., in particular if its supply voltage exceeds a predetermined threshold, the control unit SE takes over the control of the switching element S1 on the primary side.

[0045] For this, as in Fig. As shown in Figure 4, a driver circuit DRV is provided, which receives control signals from the control unit SE on the secondary side and transmits them to the primary side, for example, by means of inductive or capacitive coupling. Preferably, the driver circuit DRV also ensures that the transmitted signals are processed on the primary side. For example, a so-called E-driver circuit (E-Drive) or a so-called C-driver circuit (C-Drive) can be used as the driver circuit DRV.

[0046] However, the transmission of the control signals for controlling the switching element S1 on the primary side can lead to the control of the switching element S1 by means of the starting circuit AS coming into conflict with the control by the control unit SE.

[0047] To avoid this, the driver circuit DRV transmits a shutdown signal to the start-up circuit AS and to a second supply circuit V2 that supplies the start-up circuit AS. This is shown schematically in Fig. 4. The control unit SE transmits a control signal DRV IN on the secondary side to the driver circuit DRV, exemplified as a sequence of voltage pulses. The driver circuit DRV generates at least one output signal DRV on the primary side. OUT . The at least one output signal DRV OUT can then be fed to the second supply circuit V2 (1) to deactivate / activate it. At the same time, the at least one output signal DRV OUT to activate / deactivate the start-up circuit AS (2) and to clock the switching element S1 (3).

[0048] A low-cost integrated circuit (IC, ASIC, etc.), known, for example, as a 555 timer, can be used as the start-up circuit AS. A Zener diode with a series resistor, for example, can be used as the second supply circuit V2. To deactivate or disconnect the supply to the start-up circuit AS, the connection between the Zener diode and the series resistor must be broken.

[0049] A schematic and yet more detailed primary-side arrangement of the starting circuit AS and the second supply circuit V2 is shown in the Fig. 5a and Fig. 5b. It should be noted that although the inventive solution dispenses with the provision of an additional supply to the secondary-side control unit SE from the primary side, two supply circuits are used.

[0050] However, this is still advantageous because a very inexpensive and potentially inefficient supply circuit V2 can be used on the primary side. As explained later, this supply circuit V2 is only used during the start-up phase of the operating circuit. However, this is offset by the high costs of a voltage supply on the primary side and the transmission across the galvanically isolating barrier (SELV barrier) to supply the secondary side, since such a transmission requires at least an expensive transformer compliant with the SELV standard.

[0051] The functionality of the Fig. 5A, Fig. The circuit parts shown in Figure 5B are as follows: The circuit components are supplied with power from a rectified AC voltage. When the driver circuit DRV receives a signal DRV OUToutputs, ie, if on the secondary side a corresponding control by the control unit SE with an input signal DRV IN exceeding the breakdown voltage of a Zener diode D5 (in Fig. 5b as a pulsed voltage signal with amplitude 9V), the voltage at the transistor Q1 increases (in Fig. 5b shown as a voltage increase to e.g. 2.1V at the gate of transistor Q1).

[0052] Transistor Q1 is activated, i.e., switched on, when the breakdown voltage of the Zener diode is reached or exceeded. After transistor Q1 is activated, the current flowing through resistors R1 and R2 is diverted directly to ground, so that no more current flows through a resistor R8, which is connected in series with resistors R1 and R2. The series circuit of resistors R1, R2, and R8 is connected to the output of a rectifier on one side and to ground on the other.

[0053] Activating transistor Q1 reduces the voltage at the gate of a second transistor Q2, deactivating the second transistor Q2, i.e., making it non-conductive. This deactivates the second supply circuit V2, which is formed, for example, by a series connection of resistors R3-R6 with the second transistor Q2 and a Zener diode D2, and is connected in parallel to the series connection of resistors R1, R2, and R8. Deactivating transistor Q2 therefore switches off the second supply circuit V2. As a result, the supply voltage Vcc of the start-up circuit AS slowly decreases, depending on the dimensioning of a buffer capacitor C2, which switches off the start-up circuit AS. Otherwise, the buffer capacitor C2 is fed by the second supply circuit V2 when transistor Q2 is active.

[0054] In order to achieve a rapid shutdown of the start-up circuit AS, when the breakdown voltage of the Zener diode D5 is reached, not only the transistor Q1 is activated, i.e. switched on, but also a third transistor Q3, whereby the voltage at a RESET input of the start-up circuit AS suddenly drops, whereby the start-up circuit AS is immediately deactivated.

[0055] It should be noted here that diode D6 is advantageous because, when the start-up circuit AS is deactivated, the output OUT of the start-up circuit AS is not in a so-called tri-state. If diode D6 were missing, signals output by the driver circuit DRV could be diverted via the ground of the start-up circuit AS instead of being delivered to the clocked switching element S1 of the clocked converter.

[0056] In the Fig. 6A and Fig. 6B shows an alternative embodiment of the invention.

[0057] As in Fig. As illustrated in Figure 6A, the starting circuit AS is provided on the primary side of the operating circuit. Starting from the starting circuit AS, a supply voltage can be transmitted to the secondary side by means of a coupling element KE, for example, by means of an inductive or capacitive coupling or transmission via a suitable resistor. This means that, in particular, the signal generated by the starting circuit AS is transmitted via the SELV barrier or the electrically insulating barrier. Transmission via a resistor can, as shown for the prior art, again break the galvanic isolation, while still complying with the corresponding regulations, for example, the SELV regulations.

[0058] On the secondary side, a further supply circuit V3 is provided, which in particular rectifies the signal transmitted by the coupling element KE, in particular a pulsed voltage / current. This further supply circuit V3 generates a supply voltage for the control unit SE.

[0059] If a sufficiently high voltage, for example a voltage that is above a certain threshold value, is applied to the control unit SE, i.e. sufficient electrical power is generated by the starting circuit AS and transmitted by the coupling element KE, the control unit SE will drive the driver circuit DRV by means of the signal DRV IN to control the primary-side switching element S1. The clocked converter then begins to operate, and its output voltage rises.

[0060] As in Fig. As shown in Figure 6b by way of example, the starting circuit AS generates a pulsed signal, whereby a voltage is output on the secondary side of the coupling element KE.

[0061] The additional supply circuit V3 supplies a correspondingly adjusted, e.g., rectified voltage to the control unit SE. When the control unit SE is sufficiently supplied, e.g., when a threshold value is reached by the supplied voltage, the control unit SE outputs a signal DRV. IN to the driver circuit DRV. The driver circuit DRV generates at least one output signal DRV on the primary side. OUT . The at least one output signal DRV OUT can then be fed to the second supply circuit V2 (1) to deactivate / activate it. At the same time, the at least one output signal DRV OUTto activate / deactivate the start-up circuit AS (2) and to clock the switching element S1 (3). After the start-up circuit AS clocks the switching element S1, the power transmitted by the clocked converter on the secondary side of the circuit arrangement increases, and accordingly, the voltage supplied by the supply circuit V1 to the control unit SE also increases, which then serves to supply the control unit SE.

[0062] The supply voltage applied to the control unit SE is therefore provided during a start-up phase by the primary-side start-up circuit AS. As shown in the figures, the supply circuit V1 can be connected after an output diode D out of the clocked converter to provide a supply voltage for the control unit SE.

[0063] The primary-side starting circuit AS and the second supply circuit V2 supplying it can then, as already described for the Fig. 5A and Fig. 5B. In particular, as soon as the breakdown voltage of the Zener diode D5 is reached, the start-up circuit AS can be switched off by means of transistors Q1 and Q2. A rapid switch-off is achieved if the corresponding timer circuit, e.g., is designed as a 555 timer, again via the third transistor Q3 and the resistor R RESET .

[0064] Consequently, according to the invention, during a start-up phase, the clocked switching element S1 of the clocked converter is operated from the start-up circuit AS. If there is a sufficient voltage on the secondary side, provided by the clocked converter, which exceeds a certain threshold value, the control unit SE takes over the clocking of the switching element S1. In one embodiment, during the start-up phase, i.e. until the threshold value is reached, the secondary-side control unit can be supplied with power via the start-up circuit AS (for example a pulse generator, an oscillator, etc.). As soon as the corresponding threshold value is then reached or exceeded, the secondary-side control unit SE takes over the clocking of the primary-side converter switch S1. For this purpose, the secondary-side circuit transmits a signal indicating the clock to the primary side of the operating circuit.This signal then also deactivates the primary-side start-up circuit AS and, if applicable, a supply circuit supplying it.

[0065] The threshold value can also refer to the charge state of an energy storage device, e.g. a capacitor, through which sufficient energy can be stored on the secondary side to supply the control unit SE after being supplied by the means until the switching element S1 is clocked by the control unit SE as intended.

Claims

[1] Operating circuit for controlling an LED line (LS), comprising: - a potential-isolated clocked converter, in particular a flyback converter, which is supplied with a supply voltage on the primary side and has a clocked switching element (S1) on its primary side, wherein connections for the LED path (LS) are supplied from the secondary side of the converter, - a start-up circuit (AS), from which the clocked switching element (S1) is controlled for the duration of a start-up phase, and - a control unit (SE) arranged on the secondary side, which is designed to control the clocked switching element (S1), in particular after the start-up phase, and which is further designed to deactivate the start-up circuit (AS) after the start-up phase, wherein in particular a control unit for controlling the clocked switching element (S1) is provided only on the secondary side of the converter, and wherein a threshold value, in particular a variable or programmable value, is stored for the control unit (SE) in a retrievable manner, and / or wherein the control unit (SE) is designed to detect a supply voltage supplied from the secondary side of the converter, in particular by a first supply circuit (V1), and to supply a signal to a driver circuit (DRV) as a function thereof. [2] Operating circuit according to claim 1, wherein the control unit (SE) is electrically supplied from the secondary side of the converter. [3] Operating circuit according to one of the preceding claims, wherein the driver circuit (DRV) is connected to the starting circuit (AS) and in particular to a second supply circuit (V2) supplying the starting circuit (AS). [4] Operating circuit according to one of the preceding claims, wherein the driver circuit (DRV) activates / deactivates a first switching element (Q1) and preferably alternatively or additionally a second switching element (Q2). [5] Operating circuit according to one of the preceding claims, wherein the first switching element (Q1) deactivates the second supply circuit (V2) upon its activation / deactivation, in particular by outputting a signal to a third switching element (Q3). [6] Operating circuit according to one of the preceding claims, wherein the second switching element (Q2) deactivates the start-up circuit (AS) upon its activation / deactivation and in particular connects a reset input (RESET) of the start-up circuit (AS) to ground. [7] Operating circuit according to one of the preceding claims, wherein the driver circuit (DRV) for activating / deactivating the first switching element (Q1) and / or the second switching element (Q2) generates an output signal (DRV OUT ) whose amplitude is in particular above a breakdown voltage of a Zener diode (D5). [8] Operating circuit according to one of the preceding claims, wherein the driver circuit (DRV) generates the output signal (DRV OUT ) when it receives an input signal (DRV IN ) is supplied. [9] Operating circuit according to one of the preceding claims, wherein the Zener diode (D5) is connected to a gate terminal of the first switching element (Q1) and / or the second switching element (Q2), and wherein preferably the first switching element (Q1) and / or the second switching element (Q2) upon output of the output signal (DRV OUT ) can be activated / deactivated. [10] Operating circuit according to one of the preceding claims, wherein upon activation / deactivation of the first switching element (Q1), the third switching element (Q3) is deactivated / activated. [11] Operating circuit according to one of the preceding claims, wherein the driver circuit (DRV) receives the input signal (DRV IN) from a control unit (SE) and transmits it by means of a transmission element, e.g. an optocoupler, an inductive coupling, a capacitive coupling, and / or a resistor, from the secondary side to a primary side of the operating circuit and, if necessary, filters and / or amplifies it. [12] Operating circuit according to one of the preceding claims, wherein the start-up circuit (AS) supplies the control unit (SE) with electrical power for the duration of the start-up phase. [13] Operating circuit according to one of the preceding claims, wherein the control unit (SE) clocks the switching element (S1). [14] Operating circuit according to one of the preceding claims, wherein the start-up circuit (AS) is connected to the control unit (SE) by means of a coupling element (KE), e.g. an optocoupler, an inductive coupling, a capacitive coupling and / or a resistor, across an electrically insulating barrier. [15] Operating circuit according to one of the preceding claims, wherein a third supply circuit (V3) is provided between the connecting element (KE) and the control unit (SE), which third supply circuit (V3) optionally filters, amplifies, rectifies and / or smoothes a signal output by the start-up circuit (AS). [16] Operating circuit according to one of the preceding claims, wherein the transmission element and / or the coupling element (KE) is a high-ohmic resistor, e.g. greater than 1 MΩ. [17] Operating circuit according to one of the preceding claims, wherein the operating circuit is designed such that the secondary-side control unit (SE) is supplied only from the secondary side of the converter after the start-up phase. [18] Operating circuit according to one of the preceding claims, wherein in the start-up phase the secondary control unit (SE) is supplied exclusively by the start-up circuit (AS). [19] Operating circuit according to one of the preceding claims, wherein the in particular passive driver circuit (DRV) is provided for controlling the switching element (S1) and wherein the driver circuit (DRV) is designed to operate the clocked switching element (S1), in particular the gate of a transistor, with a clock determined by the control unit (SE) when controlled by the control unit (SE). [20] Operating circuit according to one of the preceding claims, wherein the converter bridges the electrically insulating barrier of the operating circuit, and wherein the electrically insulating barrier is a galvanically insulating barrier or a SELV barrier. [21] Operating circuit according to one of the preceding claims, wherein the control unit (SE) deactivates the start-up circuit (AS) when the supply voltage supplied to the control unit (SE) exceeds the threshold value. [22] Operating circuit according to one of the preceding claims, wherein the start-up circuit (AS) is a clock generator, timer, pulse generator and / or oscillator. [23] LED module or operating device for operating an LED line (LS), comprising an operating circuit according to one of the preceding claims and an LED line (LS) supplied therewith. [24] Method for operating an operating circuit for an LED line (LS), wherein: - a potential-isolated clocked converter, in particular a flyback converter, which has a clocked switching element (S1) on its primary side and which is supplied with a supply voltage on the primary side, supplies connections for the LED path (LS) from the secondary side of the converter, wherein the clocked switching element (S1) is controlled from a primary-side start-up circuit (AS) for the duration of a start-up phase, and wherein - a control unit (SE) arranged on the secondary side controls the clocked switching element (S1), in particular after the start-up phase, and deactivates the start-up circuit (AS) after the start-up phase, wherein a control unit for controlling the clocked switching element (S1) is provided, in particular, only on the secondary side of the converter, wherein a threshold value, in particular variable or is stored programmably, and / or wherein the control unit (SE) is configured to detect a supply voltage supplied from the secondary side of the converter, in particular by a first supply circuit (V1), and to supply a signal to a driver circuit (DRV) as a function thereof.

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