EP3038433A2 - Led light module, signal light with such a light module and method for operating such a light module - Google Patents

Abstract

LED light module comprising at least one string (10) of serially connected LEDs (18), means for monitoring (26, 28, 30) the current flowing through the string during operation of the string, and / or the voltage dropping across the string, a power supply the LEDs, means for detecting at least one further operating parameter of the LEDs, which comprise a sensor (24) for detecting a value proportional to a luminous flux emitted during operation of the light module and outputting a signal based on the value, and an evaluation unit (16). The evaluation unit (16) controls the power supply (10) of the LEDs for a current supplied to the LED string as a function of the signal by pulse width modulation and is powered during operation of the light module also via the power supply (20) of the LEDs (18) with power.

Description

TECHNICAL FIELD OF THE INVENTION

The invention relates to an LED light module, a signal light with such a light module, in particular for rail, water, air or road traffic and a method for operating such a light module.

BACKGROUND OF THE INVENTION

Due to their characteristics such as low power consumption and long service life, light-emitting diodes (LEDs) are being used more and more frequently as a substitute for conventional light sources, including in safety-relevant luminaires, such as light sources. Traffic lights, marker lights and vehicle lights, which here lights are understood for all types of land, water and air vehicles.

Many luminaires require or even require automated monitoring of correct operation. While in classical light sources the monitoring of the correct functioning can usually be realized easily (in general, it is sufficient to monitor whether current flows through the light source or not, if, despite the voltage applied, no current flows through the light source, it can be assumed that that the lamp is defective and needs to be replaced), the function monitoring of LEDs is not trivial for various reasons. So it can be e.g. In addition, an LED will not light even though current is flowing through it.

The total failure of an LED can be detected by a combined current-voltage monitoring. However, this type of monitoring does not make it possible to detect a change in the luminous flux (degradation) caused, for example, by aging of the LEDs.

It is known to use LED light modules, i. Arrangements with usually multiple LEDs and other elements such as Vorschalteinheiten for operating the LEDs to be provided with a Betriebszeitzähler that detects the actual operating life of the LEDs. If a certain operating time is reached, the LEDs are replaced, regardless of whether the light emitted by them is still sufficient to fulfill the possibly prescribed requirements or not. This procedure leads to regular replacement of LEDs, which still work correctly.

It has been shown that the aging of LEDs depends not only on their pure operating time, but also on other factors, in particular the operating current and the operating temperature.

An obvious solution to the problem of detecting an aging-related decrease in light output is direct monitoring of the light emitted during operation of an LED by means of corresponding sensors. This suggests the DE 197 54 222 a monitoring unit of an LED, in which the light emitted by an LED light is measured by means of a photosensor. If the brightness of the light falls below a certain limit value, a warning signal is generated which indicates to an operator of the LED that the LED should be replaced.

The from the DE 197 54 222 known type of monitoring is just in so-called. Track signals for rail transport associated with possibly very high cost of materials, because the monitoring unit is supplied with its own operating voltage, the corresponding cable not infrequently over a few hundred, sometimes even a thousand and more meters from a corresponding Connection point must be led to the monitoring unit.

The US 6,078,148 describes a controller for a transformer having primary and secondary windings with a plurality of turns and taps for changing the number of effective turns and thus a LED full-wave power. In this case, the taps are controlled as a function of an operating parameter of the LEDs for maintaining the light output LEDs above a predetermined level based on a combination of measurements of voltages and currents on the LEDs.

The EP 0 974 947 A1 shows a traffic signal with at least one signal generator whose light source is formed by arranged in the form of a matrix LEDs, and with a monitoring device for checking the LEDs on their error-free operating state, which arranged in the beam path of the LEDs and a light sensor associated with this evaluation for comparing a light sensor signal generated by the light sensor having a predetermined setpoint corresponding to a normal operating state of the light-emitting diodes.

The DE 10 2005 032 719 A1 shows a traffic signal with at least one light-emitting diode having signal generator for emitting a light signal, with a control unit for controlling, evaluation and monitoring of the signal generator, with lines for power supply and lines for data transmission between the controller and the signal generators, and with a circuit device for controlling the signal generator, and each signal generator arranged in its immediate vicinity circuit device, wherein the signal generator are connected via a the power supply lines and the data transmission lines having wiring harness with the control unit.

According to the DE 10 2010 026 012 A1 has a signal generator for generating different colored light points with RGB LEDs on an optical sensor for fail-safe monitoring of the color locus and the light level of the signal generator on.

To operate a fan shows DE 10 2010 013 310 A1 an output circuit connected to an output of a ballast for supplying a lighting module with electrical energy, wherein both the fan and a control circuit for supplying electrical energy are connected to the output circuit.

DISCLOSURE OF THE INVENTION

The invention has for its object to provide an LED light module with a monitoring unit and a signal lamp equipped therewith, in which the monitoring unit with minimum material costs and therefore can be made particularly cost-effective.

The invention is also based on the object of specifying a method for operating an LED light module, which can be carried out in a cost-saving manner while ensuring a high degree of operational reliability.

The objects are achieved by an LED light module having the features of claim 1, a signal light having the features of claim 4 and a method having the features of claim 3.

The LED light module according to the invention does not require a separate power supply of the monitoring unit, but this can use the light module with pulse width modulation of the supplied power to monitor the emitted luminous flux and thereby to dispense with a complex out-calculation of stray light components, which are miterfasst of conventional monitoring units , These and other advantages will become apparent from the following, purely exemplary and non-limiting description of exemplary embodiments in conjunction with the drawing, which consists of two drawing figures.

BRIEF DESCRIPTION OF THE DRAWING

Fig. 1

shows a highly schematic block diagram for a basic understanding of the operation of the invention.

Fig. 2

shows a highly schematic of an embodiment of a light module according to the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

In the Fig. 1 is very schematic illustrates the basic idea of the invention, according to which a strand 10 of series-connected LEDs of a corresponding LED light module, in particular a light module for signal lights of road and rail transport, in a conventional manner via a line 12, a current with a certain voltage and then a portion of the supplied current via a parallel to at least some of the LEDs of the strand circuit for operating a monitoring unit 14 is used. The monitoring unit 14 can detect certain operating parameters of the light module, such as the current flowing through the string during operation, the voltage dropping across the string, the temperature in the vicinity of the string and the luminous flux generated by the string, and characteristic values for these operating parameters to a higher level Output evaluation unit 16.

The monitoring unit 14 can be completely powered by the power supply of the LED string so that advantageously dispensed with a separate power supply and thus in particular when the light module is used in signal lights for rail transport, sometimes quite considerable amounts of cable can be saved. Means such as voltage meters for the forward LED voltage may be provided, which are connected in parallel to one or more LEDs 18 of the strand 10. These means can be powered during operation of the light module via the power supply 20 of the LEDs.

The higher-level evaluation unit 16 is supplied via the power supply of the LED string, thus avoiding a scattered light detection in particular pulsed switched off LED string. The necessary modern components, such as e.g. Temperature or photosensor and microcontroller, have such a low power consumption, that it has no significant effect on the luminous flux of the LED strand when a branch of the power supply to the units 14 and 16 is diverted via said parallel circuit.

Typically, an LED string 10 of the type in question, for example, eight LEDs in series with a current consumption of 350 mA, while a Photo sensor as means for detecting a further operating parameter and a corresponding microcontroller for evaluating the signal of the photo sensor have a current consumption in the range of about 1 to 2 mA. It has been found that a circuit according to the invention works particularly well, in particular, when the current consumption of the units 14 and 16 is more than 20 times smaller than the current consumption of the LED string, preferably about 50 to 100 times smaller.

In the Fig. 2 an embodiment of the invention is shown, in which case two operating parameters detected and used to monitor and control the LED string in the inventive manner. The units of the Fig. 1 corresponding units were with the also in Fig. 1 provided reference numerals.

The light module shown forms in this embodiment, a unit that can be installed in particular in a signal light and powered externally via a line 12. The LED string is formed by a number of serially connected LEDs 18, only a few of which are shown, with the supply voltage and current being controlled by a ballast 20. In this embodiment, the ballast unit 20, like the evaluation unit 16, is part of the light module, but, like the evaluation unit 16, can also be arranged outside the actual light module. Evaluation unit 16 and ballast unit can be part of a single control unit.

As indicated by the line 22, power is supplied to a monitoring unit 14 at a first location via a circuit parallel to the series connection of the LEDs 18, wherein the various rectangular signals symbolically represented in the figure are intended to indicate that the current is pulse width modulated.

As indicated by the corresponding circuit diagram, the monitoring unit 14 in this embodiment comprises a photosensor 24, which is arranged in the light module and detects a proportional to the luminous flux, which is generated during operation of the LEDs, value. In light modules of the type in question, the LEDs are typically arranged rotationally symmetric, and the light module is provided with a header or lens, whereby a part of the emitted light is reflected back, which can then be detected by the photosensor 24.

The monitoring unit 14 further comprises, in this embodiment, two voltmeters 26 which, together with respective shunt resistors 28 and lines 30, enable indirect current measurement of the current flowing through the LED string in operation.

Not shown, but provided in a preferred embodiment, is a voltmeter which measures the total voltage drop across the LED string, which may be particularly advantageous in light modules for use in signal lights for rail traffic. The advantages of a combined current-voltage monitoring in the monitoring of LED strings are known and, for example in the EP 1 992 524 A2 , the contents of which are hereby incorporated by reference. In one embodiment of the invention means provided for detecting the current and / or the voltage may be pulsed with power via the power supply of the LEDs.

The values which are representative of the current flowing through the LED string and the current value proportional to the luminous flux emitted during the operation of the LEDs and measured by the photosensor 24 are fed to the evaluation unit 16, which is in this case Embodiment comprises a microcontroller 32 and a controller 34, which is designed to output a control value to the ballast unit 20. It should be noted that the evaluation unit 16 does not have its own power supply, as in the case of previously known light modules, but advantageously, just like the monitoring unit 14, it is fed by the current fed to the LEDs 18. If the photosensor now detects that the luminous flux emitted during operation, for example due to degradation of the LEDs, decreases, the evaluation unit 16 can generate a corresponding control signal, by means of which the ballast unit 20 causes the current supplied to the LEDs to increase so that the desired luminous flux results. With the above-mentioned boundary condition that the current consumption of monitoring unit 14 and Evaluation unit 16 is significantly smaller than the current consumption of the LEDs, the reduction of the brightness of the LEDs due to the Stromabzweigung can be neglected, especially since such a detected anyway by the photosensor 24 and led to a readjustment of the current.

The evaluation unit 16 is designed to directly or indirectly control the current supplied to the LED string as a function of the so-called "further operating parameter", in this case the luminous flux, ie to influence the current either directly as part of a more complex control circuit or with a separate unit, here the Vorschalteinheit 20 to communicate and transmit this information, which are the basis for a control of the current, and so indirectly control the power.

At the in Fig. 2 In the embodiment shown, the actual current detection is dual-channel, thus redundant, so that incorrect measurements are practically excluded because the microcontroller 32 may be designed so that it can generate a corresponding error message in case of deviations between the two signals representative of the actual current then in a conventional manner to a parent body, for example, a maintenance center, can be transmitted.

In addition to the already mentioned assurance of a stable color location, the pulse-width modulated operation provided in a preferred embodiment of the invention has two significant further advantages. It is unnecessary in those cases in which the means for detecting at least one further operating parameter a photosensor as in Fig. 2 include, a complex calculation of the scattered light component, since the sensor is only in operation by the supply according to the invention via the LED current, even if the LEDs are turned on, in which case stray light components can be neglected. Light falling on the sensor when the LEDs are turned off between two current pulses is not included in the usual summation by the sensor, so advantageously low cost standard photosensors that sum light to output a reading over a certain period of time are used can be.

Another advantage of the pulse width modulated operation is that the evaluation unit 16 can check whether the photosensor 24 or the voltmeter 26 deliver signals during the time between two current pulses, from which then a malfunction of the photosensor and / or the voltmeter closed and in per se known Way a corresponding error message can be generated. Thus, the evaluation unit 16 has virtually a function for testing the means for detecting the at least one further operating parameter. It is therefore checked whether the signals output by the ammeter and / or the photosensor show a course which corresponds to the course of the pulse-width-modulated current.

In the context of the inventive concept, numerous modifications and developments are possible, which relate in particular to the type and number of means for detecting operating parameters of the LEDs. Thus, it is provided in a preferred embodiment of the invention to detect the temperature in the vicinity of the LEDs of the strand, in which case with this value via the evaluation unit, for example, a fan can be turned on. Such a fan can also be advantageously supplied with power via the operating current of the LEDs since, in typical applications, the fan only has to have a low power.

The invention allows in a particularly simple and cost-effective manner for the first time the realization of a particularly secure monitoring of the correct functioning of an LED light module, as three different monitoring methods - monitoring the voltage drop across the LED string, monitoring the current flowing through the strand and detection of the delivered Luminous flux proportional value - can be combined.

LIST OF REFERENCE NUMBERS

10

LED cluster

12

management

14

monitoring unit

16

evaluation

18

LEDs

20

upstream unit

22

management

24

photosensor

26

voltmeter

28

Shunt resistors

30

cables

32

microcontroller

34

regulation

Claims (4)

LED light module, in particular for signal lights of the road and rail traffic, comprising at least one strand (10) of LEDs (18) connected in series, Means for monitoring (26, 28, 30) the current flowing through the strand during operation of the strand and / or the voltage dropping across the strand, - a power supply of the LEDs and Means for detecting at least one further operating parameter of the LEDs, which comprise a sensor (24) for detecting a value proportional to a luminous flux emitted during operation of the light module and outputting a signal based on the value,
marked by an evaluation unit (16) which is designed to control the power supply (10) of the LEDs for a current supplied to the LED string as a function of the signal by pulse width modulation, and during operation of the light module also via the power supply (20) of the LEDs ( 18) is supplied with electricity. LED light module according to claim 1, characterized in that the evaluation unit (16) has a function for testing the means for detecting the at least one further operating parameter. Method for operating an LED light module, in particular for signal lights of the road and rail traffic, wherein the light module has a string of LEDs connected in series, the current flowing through the strand during operation and / or the voltage dropping across the strand are monitored, - With a sensor (24) detects a value proportional to a luminous flux emitted during operation of the light module and a signal is output on the basis of the value to a higher-level evaluation unit, and
characterized in that the current supplied to the train during operation is controlled as a function of the value by pulse width modulation of the power supply of the LEDs and the The higher-level evaluation unit is also supplied with power via the power supply of the LEDs during operation of the light module. Signal light, in particular for road and rail traffic, characterized in that it comprises an LED light module according to claim 1 or 2.

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