EP0910934B1 - Circuit for signal transmitters with leds - Google Patents

Abstract

This invention concerns a circuit for signal transmitters in traffic control systems with LEDs (4 to 15) for emitting colored light. Said circuit is supplied with a.c. voltage and has two groups of LEDs (4 to 9 and 10 to 15), which are connected antiparallel to one another. This creates a simple and easy to monitor inherently safe system for signal transmission.

Description

The invention relates to a circuit arrangement for signal transmitters with light emitting diodes (LEDs) for emitting colored light, according to the preamble of claim 1. It relates in particular on such a circuit arrangement for Signalers in road traffic signal systems.

So far has been used in traffic signal systems or traffic lights Generation of colored light a common light bulb used in front of which a colored filter plate is placed. there However, it can be caused by reflection from light sources Add to this that the colored filter plate is switched off Traffic light lights up and it is not clear whether that is corresponding signal is switched on or off. Another Disadvantage when using light bulbs is that these emit light in a broadband radiation spectrum and only filtered out a small percentage in the desired color and therefore only a fraction of the used Energy is used.

These disadvantages are overcome by the use of LEDs (Light Emitting Diode) as a radiation source, since the LEDs are almost Produce monochrome light in the desired color and therefore do not need filters that match those described above can cause deceptive reflection. In addition, at Using LEDs almost 100% of the energy generated in light the desired color.

The use of LEDs, also known as luminescent diodes are in traffic light systems so far only in prototypes and still has a number of problems. The LEDs are operated with a ballast, which a power supply, possibly a controller and possibly includes a pulse generator for pulse operation of the LEDs. The problem here is that those used in the ballasts Components in accordance with DIN 0832 no error exclusions include. The ballasts can therefore not be regarded as an intrinsically safe assembly. For this reason and since the ballasts are so complex overall that a internal monitoring can no longer be carried out safely can, a sensory measurement or monitoring in particular of a blocking signal. At traffic lights a red light is usually used as a blocking signal. Such complex ballasts that also have a failure detection need can only be produced at high costs.

From US-A-4,939,426 it is known to have several rectified Arrange LEDs in one strand and two such strands to switch anti-parallel to each other. Every strand is there when applying an AC voltage through the two AC phases controlled alternately. This has the disadvantage that if a single LED fails, the entire associated one Strand becomes inoperable, so that flickering light is generated becomes.

In addition, from FR-A-2 350 034, several strands are known Arrange rectified LEDs next to each other. Within this arrangement of strands with rectified LEDs Connection points between two LEDs of a string each with a connection point between LEDs of an adjacent one Strands connected to form a matrix.

The invention is based on the object of specifying a circuit arrangement of the type mentioned at the outset in which the reliability is improved while maintaining the luminosity as unchanged as possible.

This task is accomplished by a circuit arrangement with the Features of claim 1 solved. Advantageous further training the circuit arrangement according to the invention are the subject of subclaims 2 to 6.

According to the invention it is provided that in the circuit arrangement an LED of the first type Group with an LED of the second group are combined in one housing and at least a connection point between two LEDs of the first Group with at least one connection point between two LEDs of the second group through a cross connection line connected is.

According to an alternative solution, in particular for Is used if the LEDs only allow a low reverse voltage, the LEDs are arranged in a circuit with an AC voltage is supplied, and in which at least a bridge rectifier is arranged by the LEDs are controlled.

According to a basic idea of the invention, the LEDs are anti-parallel on an alternating voltage via a series resistor operated. Each LED only lights up for half a period, which lead to a noticeable flickering at a mains frequency could. However, this effect is due to the anti-parallel Switching of the groups of LEDs avoided. So there is for the entire module almost no dark times. For the alternative required components, e.g. the bridge rectifier, can claim errors according to DIN 0832 become.

The first group of LEDs is preferably the same size as that second group of LEDs. That means half each Number of LEDs used in the circuit arrangement anti-parallel operated to the remaining LEDs of the circuit arrangement is, so that in both half-periods of the AC voltage the same number of LEDs are lit.

The AC voltage is preferably from a transformer generates a mains voltage of 220 V to a supply voltage transformed between 10 and 40 V. An error exclusion after the DIN 0832. The AC voltage is too insofar cheap, as well as the advantages of a pulse operation can be availed because the half wave is a sinusoidal AC voltage lead to similar effects can, like a rectangular pulse. This is cheap because achieves a higher luminous efficacy when the LEDs are in pulse mode can be as with DC operation.

By the measure that two operated antiparallel LEDs are combined in a housing, is advantageous achieved that the number of components is reduced is. A jumping of light points is therefore advantageous also reduced because the same-color emitting LEDs are so close together that they look like on the outside one red dot appears. The remaining one There would then be a flickering between different illuminated dots Frequency of 100 Hz, which is for a human viewer is no longer perceptible. For example, so-called MULTILEDs are used (MULTILED is a registered Siemens AG brand).

Furthermore, it is advantageous if each of the two groups of LEDs from several electrical strings connected in parallel exists, each having several LEDs connected in series. These electrical strands are still among themselves connected at all connection points of the individual LEDs.

Overall, this results in a grid or array and is thereby and also due to the parallel connection of different electrical LED strings can be classified as multiple redundant.

In a preferred embodiment of the invention is a Diffuser attached in front of the LEDs, through which a possibly for the viewer recognizable flickering through and jumping luminous dots is avoided because of the Diffuser the local assignment of the visible light for the viewer becomes impossible.

Furthermore, it is favorable to have a semiconductor diode in the individual strands to switch or one in each individual strand To use bridge rectifiers. Such a bridge rectifier can also be connected in front of the entire LED array. These measures are particularly advantageous if the LEDs only allow a low reverse voltage.

Current monitoring is simple in the primary circuit possible so that a complex ballast is not required becomes.

Seen overall, for the transformer and the series resistor Error exclusions in accordance with DIN 0832 apply be made. The semiconductor diodes and possibly the Bridge rectifiers, like the LED strings, are multiple available and therefore also multiple redundant.

Figur 1 eine schematische Darstellung des Auführungsbeispieles und

Figur 2 eine schematische Darstellung eines LED-Gehäuses.

The invention is explained in more detail below using an exemplary embodiment in conjunction with FIGS. 1 and 2.
Show it

Figure 1 is a schematic representation of the performance example and

Figure 2 is a schematic representation of an LED housing.

In the drawing are a secondary circuit 1, a Transformer 2, a series resistor 3, twelve LEDs 4 to 15 and Cross connections 16 and 17 shown. Total make up six LEDs 4 to 9 and six LEDs 10 to 15 a first or a second group of LEDs that are connected anti-parallel to each other are, d. that is, LEDs 4 through 9 of the first group are located directed in the opposite direction with respect to their forward direction in the circuit, like LEDs 10 to 15 of the second Group. Each group consists of several connected in parallel Strands 18, 19, 20, 21 in a row and in the same Direction of passage of switched LEDs. For example, make up LEDs 4, 5 and 6 a strand 18 of the first group and are anti-parallel to the strand 19 with the LEDs 10, 11 and 12 the second group. Through electrical cross connections 16 and 17 between connection points of each LEDs of a strand 18, 19, 20, 21 among themselves are the individual strands 18, 19, 20, 21 also interconnected and thus form an array or a matrix. This is preferred each connection point between two LEDs one Stranges 18, 19, 20, 21 each with exactly one connection point between two LEDs of each other strand connected by such cross-connections. Of course but it is also conceivable that two antiparallel to each other switched strands only interconnections have and the strand pairs thus formed with each other are only connected in parallel and no cross connections exhibit.

One group of LEDs is replaced by a half wave of the AC and the other group through the other half wave driven.

When using components, each two LEDs in one Combine LED housings, such as in a MUL-TILED-SMD housing 22 (Figure 2) (registered trademark of Siemens AG), LEDs 4 and 12, 5 and 11, for example and 9 and 13 to a component with two chips of the same color summarized.

The circuit 1 is powered by the transformer 2 with an alternating voltage from 10 to 40 V to operate LEDs 4 to 15 provided. The primary 220 V AC power supply is therefore outside the LED circuit arrangement.

LIST OF REFERENCE NUMBERS

1

circuit

2

transformer

3

dropping resistor

4 - 15

LEDs

16, 17

cross connections

18-21

strands

22

LED housing

Claims (6)

1. Circuit arrangement with LEDs for emitting coloured light, in which the LEDs (4 to 15) are arranged in an electrical circuit (1) supplied with an AC voltage, one group of LEDs (4 to 9) is connected anti-parallel to a second group of LEDs (7 to 15), the LEDs (4 to 15) are arranged in electrical sections which are connected anti-parallel to one another, and only LEDs of one group are arranged in each section, and,
   the two groups of LEDs (4 to 15) are driven by the two AC phases,
   characterized

   in that two LEDs operated anti-parallel are in each case combined in a housing, and

   in that the electrical sections are interconnected by cross connections (16, 17) at all the junction points of the individual LEDs, with the result that the LEDs are connected in the form of a multiply redundant matrix.
2. Circuit arrangement according to Claim 1, characterized in that the first group of LEDs (4 to 9) is just as large as the second group of LEDs (10 to 15).
3. Circuit arrangement according to Claim 1 or 2, characterized in that a transformer (2) is provided, via which the electrical circuit (1) is supplied with an AC voltage of between 10 and 40 V during operation of the circuit arrangement.
4. Circuit arrangement according to one of the preceding claims, characterized in that semiconductor diodes for protecting the LEDs (4 - 15) are connected into the individual sections.
5. Circuit arrangement according to one of the preceding claims, characterized in that a series resistor (3) is arranged in the electrical circuit (1).
6. Circuit arrangement according to one of the preceding claims, characterized in that each junction point between two LEDs (4 to 15) of one section (18 to 21) is in each case connected to exactly one junction point between in each case two LEDs of every other section by means of a respective cross connection.

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