EP1233654A1 - Circuit and method for adapting the characteristic curve of an LED - Google Patents

Abstract

The arrangement has at least one series circuit in parallel with the LED arrangement and containing a load resistance and a controllable switch element. The switch element is coupled to an evaluation device that detects the LED arrangement operating voltage and drives the switch element so a load current flows in the load resistance and the sum of the load and LED currents lies on a current-voltage characteristic determined by external elements. <??>The arrangement has at least one series circuit (3) in parallel with the LED arrangement (2) and containing a load resistance (RL) and a controllable switching element (T) whose electrical resistance in the on state can be controlled via a control input. The switch element is coupled to an evaluation device (4) that detects the operating voltage (UB) of the LED arrangement and drives the switch element accordingly so that a load current flows in the load resistance and the sum of the load current and LED current gives a current value on a current-voltage characteristic determined by external elements, especially monitoring devices. Independent claims are also included for the following: a LED signaling lamp, a light signal arrangement and a method of adapting the current flow through a LED signaling lamp to a defined characteristic.

Description

The invention relates to a circuit arrangement for Characteristic curve adaptation of a light-emitting diode arrangement and to a Light-emitting diode arrangement, in particular a light-emitting diode arrangement for a railway signal system.

Light-emitting diodes (hereinafter referred to as LED) meanwhile reached a brightness that their use in Enable traffic signal systems. For example, are known Traffic lights with signaling devices that act as light emitting Elements have light emitting diodes. Furthermore are also already known railway light signal systems in which LEDs are used as light emitters. This is about but it is only a matter of complete systems First installation of signal systems. Here the operating conditions and the peripherals for control and Monitoring optimally to the requirements of LED technology can be set.

These optimal conditions are in existing signal systems, originally with different signal lamps or light sources, such as propane-driven shape signals, are not given. The ones in use electrical circuits in traffic lights are sensitive to the electrical behavior of a conventional signal lamp and not matched to an LED arrangement.

The electrical resistance of these conventional signal lamps increases with increasing operating voltage, in contrast to light emitting diodes that are smaller than the forward voltage has an infinitely high electrical, so to speak Exhibit resistance. This is illustrated in the diagram in FIG. 1, in which the electrical resistance over the operating voltage is plotted and the course of the electrical Resistance of a conventional signal lamp (solid Curve) according to an LED arrangement (dotted curve) Figure 2 is juxtaposed. With the LED arrangement according to the circuit diagram of Figure 2 are a plurality of individual LEDs 20 connected in parallel and each individual LED has one Series resistor 21.

From the diagram of Figure 1 is the difference in electrical Behavior of the LED arrangement to the signal lamp more conventional Kind clearly visible. At low operating voltages the conventional signal lamp has a small electrical one Resistance, which increases as the operating voltage increases elevated. In contrast, the LED arrangement has small ones Operating voltages a very large electrical resistance, which changes with increasing operating voltage reduced.

In the existing signaling systems, the peripheral ones are usually Conditions such as the energy supply parameters fixed and specifically designed for conventional Types of signal lamps. Additional problems arise if the feeding conditions, that is, the conditions of the Supply of electrical energy, on compliance with certain Parameters are monitored and non-compliance the conditions of safety-relevant reactions of the system must be done.

An ice rink light based on LEDs that tries to eliminating this problem is, for example, from the WO 95/12512 known. In this an adjustment of the electrical resistance of the LED signal with a serial LED arrangement on the one in place of the LED arrangement existing signal lamp by means of an electrical Resistance after a previous review of the LED arrangement in the idle state (here is, among other things, a Switch in the parallel strand of the load resistor open) in parallel to the serial LED arrangement, provided that LED arrangement is OK. The load resistor connected in parallel leads to an additional flow of electricity in operation, the then along with the current through the serial LED array causes a total current flow that the power consumption of a simulated kind of signal lamp originally intended. In the signal box of the railway system is this way that the lamp is working properly.

The difficulty arises with this known arrangement on that adapting the LED arrangement to the electrical Behavior of a signal lamp for which the signal system was originally is designed only in a narrow supply voltage range is guaranteed. This leads especially to signal systems to drawbacks in which a night voltage drop is intended to reduce the light intensity at night, to prevent glare and glare.

The fact that the signal in the basic state, i.e. when the signal is not activated and switched off parallel resistance, essential behaves with higher resistance than a conventional signal lamp. The This makes susceptibility to interference signals essential higher and it can lead to dangerous conditions, like resonance phenomena that cause the signal to blink Can cause untimely, or also to increased sensitivity lead to electrostatic charges.

Finally, it is disadvantageous in the known arrangement that in the event of failure of a single LED in the serial arrangement the entire signal fails.

The object of the present invention is a Develop circuitry with the help of signal lamps conventional type to be replaced by LED arrangements and at the same time the remaining components of the underlying Leave the signal system largely unchanged.

This task is accomplished by a circuit arrangement with the Features of claim 1 solved. Preferred further training the circuit arrangement are the subject of the dependent claims 2 to 4. An LED signal lamp with a Circuit arrangement according to the invention is the subject of 5. A particularly preferred light signal arrangement is the subject of claim 6 and a particularly preferred use of the circuit arrangement, the light emitting diode signal lamp or the light signal arrangement is the subject of claim 7. A method according to which the circuit arrangement works is the subject of the claim 8. A preferred further development of the process is the subject of claim 9.

In the circuit arrangement according to the invention is parallel to the arrangement of light emitting diodes from at least one a switching element and a load resistor. The Switching element, that is, its current path, has in the on State a variable electrical resistance, the resistance value of which is regulated by a control signal becomes. The switching element is for this purpose to an evaluation device coupled, the operating voltage of the LED arrangement detected. The evaluation device controls on the basis of the detected input signal of the operating voltage Switching element depending on the detected operating voltage such that a load current over the load resistance flows. The sum of the load current and the LED current results a current value assigned to the operating voltage on a through external elements, especially monitoring devices, given current-voltage characteristic.

In a preferred development, the switching element is a Transistor whose current path is in series with the load resistor is switched and its control path to an operational amplifier is coupled. The operational amplifier transmits during operation a control signal to the control connection, the type from the operating voltage signal at the corresponding input of the Operational amplifier depends. Controls with the control signal the operational amplifier the conductivity of the current path of the transistor depending on the level of the operating voltage.

Is particularly preferred in the last embodiment the circuit arrangement a voltage divider circuit connected in parallel to the LED arrangement. The center tap the circuit arrangement is on one non-inverting input of the operational amplifier and to an inverting input of the operational amplifier a reference voltage source is coupled.

These special embodiments of the invention Circuit arrangement advantageously allow an exchange conventional signal lamps by means of LED arrangements without too much technical effort and without the periphery to the signal lamp with regard to its electrical energy supply and adapt the monitoring measures to have to.

The circuit arrangement is particularly suitable for light signal arrangements, which at night to reduce the Luminous intensity of the signal with the lowest possible operating voltage (Night dining conditions) are operated and the on Day with the greatest possible operating voltage. The Switching element is maximum for this at night dining conditions permeable and more resistive in day-to-day conditions.

The circuit arrangement, the light-emitting diode arrangement, is particularly preferred or the light signal arrangement in a railway light signal system used where a conventional Signal lamp to be replaced by an LED arrangement.

The light-emitting diode arrangement connected in parallel to the circuit arrangement a parallel connection is particularly preferred from a variety of individual LED components or from a variety of LED series connections from several LEDs.

The circuit arrangement enables a safe signal Adaptation of the electrical characteristic of an LED signal lamp to the characteristic of a conventional signal lamp. "Technically signal safe "in this case means the arrangement even in the event of a fault (component failure, etc.) in advance definable limits responded.

The circuit arrangement consumes in the faultless state at the lowest operating voltage (for example under night dining conditions) the greatest current. With the greatest operating voltage (for example, in the case of daily dining conditions) is the Power consumption of the circuit arrangement reduced.

An LED signal lamp equipped with this circuit arrangement (LED arrangement including circuit arrangement for Characteristic curve adaptation) is about in railway beacon systems a wide voltage range can be used, the electrical Characteristic values of this LED signal lamp in a faultless state almost identical to the electrical characteristics of a conventional one Signal lamp are. Leave in faulty condition advantageously specify limit conditions which apply to Proof of the signal-safe function are required.

The particular advantage of the circuit arrangement according to the invention, in particular compared to that described in WO 95/12512 Arrangement, therefore, is that the amount of total resistance of load resistance and switching element of the Amount of operating voltage depends and not just a single one has a fixed value. The ratio of current through the LED arrangement to the current through the The parallel branch with the load resistance thus varies depending on the level of the operating voltage. When arranging according to WO 95/12512, on the other hand, after a checking step the LED arrangement in the idle state when open Switches and thus open parallel line of switches closed, provided the LED array is in the review step is found to be okay.

In contrast, in the circuit arrangement according to the invention at low operating voltages, for example at Night dining conditions with lower than day dining conditions Operating voltage, the parallel string from load resistance and switching element with low resistance and at high operating voltages, like for example in daytime dining conditions are present, high impedance.

The parallel connection of a variety of LED components or LED component rows has the special advantage not that if a single LED component fails immediately the entire signal fails, but that the rest error-free LED components maintain functionality enable the signal. A monitoring effort like him in the arrangement known from WO95 / 12512, can therefore be omitted in the present case.

The circuit arrangement fulfills the basic functionality according to the invention, after which to adjust the current flow by an LED signal lamp to an external energy supply and monitoring devices predetermined characteristic by means of a switch connected in parallel to the LED arrangement adjustable load circuit on the level of the operating voltage for the LED arrangement dependent load current is generated. This additional load current, results in total with the LED current through the LED arrangement one of the at the LED arrangement assigned operating voltage Current value on the specified characteristic.

Further advantages and preferred further developments and embodiments result from the following in connection with the figures 3 to 7 embodiment explained.

The circuit arrangement, light emitting diode signal lamp or Light signal arrangement according to the invention is quite suitable particularly preferred for use in a signaling system, in which the light emitting diode arrangement from a far from this arranged energy supply and control device, which is located in a control center, for example, is supplied. This is particularly the case in light signal systems of rail traffic, road traffic light systems and light signal systems for air traffic.

Brief Description:

Figur 1

(oben bereits näher erläutert), ein Diagramm, in dem die Widerstands-Spannungskennlinien einer herkömmlichen Signallampe und einer LED-Anordnung gemäß Figur 2 schematisch dargestellt sind;

Figur 2

(oben bereits näher erläutert), ein Schaltdiagramm einer LED-Anordnung zum Einsatz in einer Leuchtsignalanlage an Stelle einer herkömmliche Signallampe;

Figur 3,

ein Strom-Spannungsdiagramm, in dem schematisch die Strom-Spannungskennlinien einer herkömmlichen Signallampe und einer LED-Anordnung nach Figur 2 sowie die Differenzkurve der beiden Kennlinien eingetragen sind;

Figur 4,

ein Schaltdiagramm des Ausführungsbeispiels;

Figur 5,

ein Strom-Spannungsdiagramm, in dem schematisch die Strom-Spannungskennlinien des maximalen Stromes durch den Lastwiderstand und des maximalen Stromes durch die Sicherung der Schaltungsanordnung gemäß dem Ausführungsbeispiel und die Summe der beiden Ströme aufgetragen sind;

Figur 6,

ein Strom-Spannungsdiagramm, in dem schematisch die Strom-Spannungskennlinien einer herkömmlichen Signallampe, einer LED-Anordnung im fehlerfreien Zustand und einer LED-Anordnung mit maximal anzunehmendem Fehlerstrom der Schaltungsanordnung zur Kennlinienanpassung aufgetragen sind; und

Figur 7,

ein Schaltdiagramm eines Ausführungsbeispieles für eine erfindungsgemäße Schaltungsanordnung für Wechselspannungsbetrieb.

Show it:

Figure 1

(already explained in more detail above), a diagram in which the resistance-voltage characteristics of a conventional signal lamp and an LED arrangement according to FIG. 2 are shown schematically;

Figure 2

(already explained in more detail above), a circuit diagram of an LED arrangement for use in a light signal system instead of a conventional signal lamp;

Figure 3,

a current-voltage diagram in which the current-voltage characteristics of a conventional signal lamp and an LED arrangement according to Figure 2 and the difference curve of the two characteristics are entered schematically;

Figure 4,

a circuit diagram of the embodiment;

Figure 5,

a current-voltage diagram in which the current-voltage characteristics of the maximum current through the load resistor and the maximum current through the fuse of the circuit arrangement according to the embodiment and the sum of the two currents are schematically plotted;

Figure 6,

a current-voltage diagram in which the current-voltage characteristic curves of a conventional signal lamp, an LED arrangement in the fault-free state and an LED arrangement with the maximum fault current of the circuit arrangement for adapting the characteristic curve are plotted; and

Figure 7,

a circuit diagram of an embodiment of an inventive circuit arrangement for AC operation.

In the current-voltage diagram of Figure 3 is on the ordinate the lamp current I in arbitrary units and on the abscissa the operating voltage U is plotted in any units. The curves make it clear how the current-voltage characteristic curve a conventional signal lamp (solid Line) of a (conventional) LED arrangement according to the figure 2 (dotted line), the circuit part according to the invention for adapting the characteristic curve. In addition, the difference curve (dashed line) is the entered both characteristics, that is, the proportion of electricity, which, depending on the voltage, is missing in order to LED array to get the same electrical current as at, the conventional signal lamp. It is clear from the diagram to recognize that in the area of a reduced operating voltage, such as in railway signal systems in night-time dining conditions, this current is a maximum has. In the upper operating voltage range, such as with daytime feed conditions in railway signal systems, the Difference against zero.

The circuit diagram of FIG. 4 shows a circuit arrangement which is connected in parallel to an LED arrangement according to FIG. 2 and which absorbs the differential current shown in FIG. 3 (dashed line) as a function of an operating voltage U _{B of} the LED arrangement.

The circuit arrangement essentially has an operational amplifier OPV, a reference voltage source Uref, and a series circuit comprising a transistor T and a load resistor R _L , which is connected in parallel to the LED arrangement.

The sum of the current through the LED array and the current through the load resistor RL essentially gives the current by the LED signal lamp, which the rest of the light signal system "sees" as lamp current.

In detail, in the circuit arrangement according to the specific exemplary embodiment, a series circuit comprising a load resistor R _L and the current path EC (emitter collector) of a transistor T is connected in parallel with the LED arrangement to the operating voltage (U _B ) source. In the present case, the transistor T is, for example, a pnp bipolar transistor. In principle, however, any other type of transistor can also be used.

Parallel to the LED arrangement is a voltage divider device, consisting of a series connection of a first electrical resistance R1 and a second electrical resistance R2, connected upstream of a fuse Si is.

The center tap M of the voltage divider circuit is R1, R2 to the non-inverting input "+" of an operational amplifier OPV laid. Parallel to the voltage divider device R1, R2 is a series connection of a third electrical Resistor R3, a fourth electrical resistor R4 and a reference voltage (Uref) source switched. The connecting line between the third R3 and the fourth electrical Resistor R4 is on inverting input "-" of the operational amplifier OPV. The inverting input of the op amp is over a fifth electrical resistance R5 with the output of the operational amplifier OPV connected, which in turn with the control input B (Base) of the transistor T is connected.

The following is the mode of operation of the circuit arrangement explained according to the embodiment.

As long as the operating voltage U _B divided by the voltage divider R1, R2, which is present at the non-inverting input of the operational amplifier OPV, is less than the voltage at the inverting input of the operational amplifier OPV, the output of the operational amplifier OPV has negative potential and the transistor T is conductive. As a result, the load resistor R _{L is connected in} parallel with the LED arrangement and thus also with the operating voltage (U _B ) source. This leads to an additional current flow parallel to the LED arrangement, as a result of which the rest of the signal system "sees" a small electrical resistance of the LED signal lamp, that is to say an LED arrangement including a circuit arrangement for matching characteristic curves connected in parallel therewith.

If the operating voltage U _{B increases} to a value such that the voltage at the non-inverting input "+" reaches and exceeds the reference voltage at the inverting input "-" of the operational amplifier OPV, the operational amplifier OPV regulates its output against + as long as until the voltages at the inverting input "-" and at the non-inverting input "+" match again. The output of the operational amplifier OPV thereby switches through depending on the operating voltage from "-" to "+". With the same dependency, the transistor T changes from the fully conductive to the blocked state, as a result of which the current flow through the fifth electrical resistor R5 is reduced to zero. The reference voltage at the inverting input of the operational amplifier OPV is determined by the reference voltage source Uref and the voltage divider, consisting of the electrical resistors R ₃ , R ₄ and R ₅ .

The increase in the output voltage of the operational amplifier OPV can be adjusted with the help of the third and fifth electrical resistance. The operating voltage U _B , at which the current is reduced by the load resistor RL, is set with the voltage divider R1, R2.

The arrangement is preferably set in such a way that at the lowest operating voltage U _B to be assumed (for example in the case of night food links in a railway light signal system) the transistor T is fully activated on the signal lamp, that is to say the current path EC is at most conductive and that with the largest operating voltage U _B to be assumed (for Example in daytime feed conditions in a railway light signal system) the transistor T is fully blocked, that is to say the current path EC has maximum electrical resistance. This results in a maximum current consumption of the circuit arrangement for adapting the characteristic curve, for example under make-up conditions and a minimum current consumption under day-make conditions.

In the case of railway light signal systems in particular, the fundamental problem arises that component failures either have to be recognized immediately or their effects must not cause any conditions which could endanger operation. For this reason, the load resistor R _L is designed as a safety design, which means that in the event of a fault, only a defined resistance reduction (for example 10%) has to be expected. However, an increase in electrical resistance can be assumed. The fuse Si is inserted in such a way that an assumed short circuit of the operational amplifier OPV, the transistor T, the reference voltage source Uref and the five electrical resistors R1 to R5 limits the resulting fault current.

• Verringerung des Stromflusses bis auf Null und
• Erhöhung des Stromflusses bis zu einem maximal möglichen Strom.

With these measures, only the following error states are to be expected at the connections of the circuit arrangement for adapting the characteristic curve according to FIG. 4:

• Reduction of current flow to zero and
• Increasing the current flow up to a maximum possible current.

This is shown schematically in the diagram of FIG. The current corresponding to the dash-dotted line 51 results when, for example, the collector-emitter path CE of the transistor T is short-circuited, but also when the output of the operational amplifier OPV is constantly at minus potential. Due to the fact that the electrical load resistance R _L cannot decrease significantly in the event of a fault, the current through the load resistance R _L cannot increase beyond the curve shown in dash-dotted line 51. Regardless of which component error is assumed in the circuit arrangement according to FIG. 4.

The dotted line 52 of the diagram in FIG. 5 represents the current profile which is limited by the fuse Si. This current value is preferably substantially smaller than the current according to the dash-dotted line 51. This is ensured by the selection of suitable components. In an exemplary configuration, the response value of the fuse Si is 30 mA, a current of 500 mA flowing through the load resistor R _L and a current of 300 mA flowing through the LED in the event of post-tensioning.

The solid line 53 of the diagram in FIG. 5 shows the maximum total current to be assumed for the circuit arrangement in accordance with FIG. 4 in the event of a fault and is the sum of the current through the load resistor R _L (dash-dotted line 51) and the current through the fuse Si (dotted line 52).

In the diagram of Figure 6 (current-voltage diagram) is the current consumption of an LED signal lamp, consisting of a LED arrangement according to Figure 2 and a circuit arrangement for Characteristic curve adaptation according to FIG. 4 in the error-free state (dotted Line), as well as at the maximum fault current to be assumed the circuit arrangement for characteristic curve adaptation (solid Line) compared to the current consumption of a conventional one Signal lamp (dash-dotted line) shown.

The diagram in FIG. 6 shows a good agreement of the Current consumption of an LED signal, consisting of an LED arrangement according to Figure 2 and one connected in parallel Circuit arrangement according to Figure 4, in the fault-free state with the current consumption of a conventional signal lamp. Below of the night voltage value NS is the current consumption of the LED signal lamp slightly smaller than the current consumption of one conventional signal lamp. But it comes with small ones Operating voltages to a current flow, causing the LED signal lamp behaves with low resistance and is therefore insensitive against interference voltages.

In the event of a faulty circuit arrangement for adapting the characteristic (maximum possible current flow to be assumed) is the current consumption the LED signal lamp up to the night voltage value NS almost identical to the current consumption with faultless circuit arrangement. Only increased from the post tension value NS the span between error-free and incorrect characteristic curve adjustment.

The characteristic curve shown in the diagram in FIG. 6 in the event of a fault Circuit arrangement represents a maximum value which is not exceeded, no matter what error in the Circuit arrangement is adopted. The behavior of the LED signal lamp is thus almost up to the night voltage value NS identical to the behavior of the conventional signal lamp. Above of the night voltage value NS in the event of a fault Circuit arrangement come to an additional current flow, which is also capped.

With this information, the behavior of the LED signal lamp in the light signal circuit in the event of a fault and the safe Function can be demonstrated.

The circuit arrangement according to FIG. 4 represents only one possible variant of the circuit arrangement according to the invention. Of course, any type of electronic switch can be used instead of the transistor T. The use of mechanical switches, such as relays, is also conceivable, but depending on the respective operating voltage, electrical load resistors R _{L of} different sizes must be switched (with a low operating voltage, a smaller load resistor, with a large operating voltage, a larger load resistor).

AC operation is another application A circuit arrangement is preferably suitable for this according to the circuit diagram of Figure 7. In this is a rectifier bridge GR1 and a filter element for the generation of a internal DC voltage before the input of the evaluation device 4 switched. The fuse Si is in front of the rectifier bridge GR1 arranged. Component defects on the Rectifier bridge (short circuit of a diode) through the fuse Si be caught with. Parallel to the LED arrangement is a parallel arrangement 3 from a first series connection off, load resistor RL1, transistor T1 and diode D1 and one second series connection of load resistor RL2, transistor T2 and diode D2 connected. The pass directions of the two Series connections are directed in opposite directions. The two control connections B1 and B2 of the two transistors T1 and T2 are connected to the output of the operational amplifier OPV connected, the input circuit of which described above Circuit arrangement according to Figure 4 corresponds. The Rectifier bridge GR1 with the filter element is between the operating voltage connection and operational amplifier OPV switched and supplies the voltage divider R1, R2 with DC voltage.

The load resistors RL1 and RL2 and the transistors T1 and T2 are arranged in front of the fuse Si. For every half wave is a transistor T1 or T2 and a load resistor RL1 or RL2 used. The diodes D1 and D2 prevent this Kind of switches a current of the other half wave flows into the collector of the transistors T1 and T2.

When using other switches, for example relay contacts, is a division for the individual half-waves not mandatory. It all depends depending on the switch types used.

In addition to those explicitly described above, there are also arrangements can be used with a variety of switches and load resistors are connected in parallel. This allows the Power loss on a variety of load resistors and switches can be distributed. This is especially so particularly advantageous if for economic reasons Manufacturing surface mount components with small Power loss can be used.

If an LED arrangement with a different connection of the individual LEDs is provided, there is usually also a different course of the differential current of the characteristic curve of conventional signal lamps and the LED signal lamp. Instead of the operational amplifier OPV, the resistors R1 to R5 and the reference voltage source Uref, another type of evaluation device can then be used, which evaluates the operating voltage U _B and controls an output in such a way that the switch T compensates the differential current via the load resistor R _L. Freely programmable arrangements with a microprocessor enable, for example, adaptation to any curve shape of the differential current.

In addition to the circuit arrangement for adapting the characteristic curve circuit parts for temperature compensation can be provided his. In this way, a temperature-dependent Compensate the current consumption of the LED arrangement.

Claims (9)

Circuit arrangement (1) for adapting the characteristics of a light-emitting diode arrangement (2), in which at least one series circuit (3) consisting of a load resistor (R _L ) and a controllable switching element (T), whose electrical resistance in the switched-on state via a control input, is connected in parallel to the light-emitting diode arrangement (2) is adjustable, is switched and the switching element (T) is coupled to an evaluation device (4) which detects the operating voltage (U _B ) of the light-emitting diode arrangement (2) and the switching element (T) as a function of the detected operating voltage (U _B ) controls that a load current (I _L ) flows through the load resistor (R _L ), and the sum of the load current (I _L ) and light emitting diode current (I _LED ) a current value (I) assigned to the operating voltage (U _B ) on a by external elements , in particular monitoring devices, results in predetermined current-voltage characteristic (UI characteristic). Circuit arrangement according to Claim 1, in which at low operating voltages (U _B ) the parallel strand of load resistor (R _L ) and switching element (T) has a low resistance and at high operating voltages (U _B ) it has a high resistance. Circuit arrangement according to Claim 1 or 2, in which the switching element (S) is a transistor (T), the current path of which is connected in series with the load resistor (R _L ) and the control connection of which is coupled to an operational amplifier (OPV) which is in operation Sends signal to the control terminal, which controls the conductivity of the current path of the transistor (T) depending on the level of the operating voltage (U _B ). Circuit arrangement according to claim 3, wherein a voltage divider circuit (R1, R2) parallel to the LED arrangement (2) is switched, the center tap on one non-inverting input (+) of the operational amplifier (OPV) is set, and in the case of an inverting Input (-) of the operational amplifier (OPV) a reference voltage is coupled. LED signal lamp with an LED arrangement, which in particular have a large number connected in series has individual light-emitting diodes or rows of light-emitting diodes, and with a circuit arrangement according to one of the preceding Claims. Luminous signal arrangement with a circuit arrangement or a light-emitting diode single lamp according to one of the preceding claims, in which the switching element (S) is maximally permeable under night-time feed conditions to reduce the light intensity with the lowest possible operating voltage (U _B ) and with the greatest possible operating voltage (U _B ) under day-feeding conditions the switching element (S) is locked. Use of a circuit arrangement, a light emitting diode signal lamp or a light signal arrangement according to a the preceding claims in a signal system, where the light emitting diode arrangement is far from one from this arranged power supply and control device is supplied, in particular in a rail traffic light system, Road Traffic Signal Conditioning or traffic light system. Method for adapting the current flow through a light-emitting diode signal lamp to a characteristic curve specified by external energy supply and monitoring devices, in which a load current dependent on the level of the operating voltage (U _B ) for the light-emitting diode arrangement is used by means of a controllable load circuit connected in parallel with the light-emitting diode arrangement (I _L ) is generated, so that the sum of the load current (I _L ) and a light-emitting diode current (I _LED ) through the light-emitting diode arrangement is assigned a current value (U _B ) that is just present from the plurality of possible operating voltages (UB) (I) results on the given characteristic. Method according to Claim 8, in which, at low operating voltages (U _B ), the controllable load circuit connected in parallel with the light-emitting diode arrangement is switched to low-resistance and at high operating voltages (U _B ) to high-resistance.

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