EP3503688B1 - Flood light - Google Patents

Description

The invention relates to a spotlight which is intended in particular for illuminating a stage or a building facade.

Movable headlight heads are known from the general state of the art, which are often referred to as moving heads in English usage. Such headlights are used, for example, in scenic lighting and are used there as so-called wash lights or projectors. Furthermore, mirror scanners are known in which a movable mirror can be controlled in such a way that the light generated by an illuminant is deflected according to a control by a user. In addition, bar-shaped headlights are known in the form of elongated multiple arrangements that contain a large number of light sources.

While the first-mentioned spotlights are usually used to illuminate a stage, an event location or the like, the last-mentioned spotlights are used in architectural lighting to achieve optical effects on buildings or building facades.

Light-emitting diodes (LEDs) or groups of LEDs are increasingly being used as light sources in these headlights, since, compared to other light sources, they have the advantages of a long service life with little degradation in brightness and high stability of the color point over this service life, while at the same time being highly efficient (light output based on the supplied electrical energy) can offer.

The relationships described below can be established for LEDs. The efficiency of an LED decreases as the current through the LED increases. The service life of the LED is defined by its junction temperature and the current through the LED and reduces with increasing junction temperature and current. The amount of light emitted by the LED is also defined by its junction temperature and the current through the LED. This also decreases with increasing junction temperature, but increases with increasing current intensity.

It is therefore important to dissipate the heat loss efficiently using a powerful cooling concept and thus keep the junction temperature as low as possible.

One way to cool LEDs in headlights of the type mentioned is in DE10 2011 053 493 A1 shown. There, a cooling device for dissipating heat losses occurring in the individual light-emitting diode arrangements is described for a headlight with a plurality of light-emitting diodes distributed over a surface area on a carrier plate, in which a plurality of flow channels running parallel in terms of flow are provided. The individual flow ducts each contain a heat sink, around which the partial air flow flows through the flow duct for the purpose of transferring heat and which is connected to the associated light-emitting diode arrangement in a manner that conducts heat well.

The maximum current through the LED is usually set in such a way that an acceptable compromise between brightness and service life is achieved, which can vary depending on the application. For example, architectural spotlights can be optimized in terms of service life, and stage spotlights for short stroboscopic use can be optimized in terms of brightness take place. In the case of previously known headlight designs, this maximum current is already defined during the development of the headlight and can no longer be changed in later use.

The control of the light intensity, which is usually required by the user, is carried out via a modulation circuit, in which the specified maximum current of the LED is modulated by means of pulse width modulation. That's it EP1195740 B2 a device for lighting is known, comprising a plurality of light emitters in two different colors, which are coupled to a circuit having a current source and a common potential reference, a driver for the light emitters, which comprises two switches connected to the plurality of light emitters and connected to the circuit and to respective current paths of the light emitters, respectively, a controller for periodically and independently opening and closing the two switches, the controller having a variable address to identify a respective portion of an input data stream assigned thereto, each light emitter being an LED and the controller generates a plurality of PWM signals having a uniform frequency, each signal corresponding to a respective color of the plurality of LEDs of different colors, each said PWM signal causing each of the two switches to operate at the uniform frequency is opened and closed according to independent duty cycles, and wherein said data flow portion includes data for determining the respective duty cycles of the at least two LEDs of different colors.

From the U.S. 2014/152187 A1 discloses a circuit including a bridge circuit, a converter and a controller which receives power from the first and second power lines of a switch and produces a rectified voltage. The switch is able in a first state in which the switch was conducting current to the first power line but not the second power line, operating in a second state in which the switch was conducting current to the second power line but not the first power line, and in a third state in which the switch was conducting current to both first and also leads to the second power line.

From the WO 2008/157772 A1 a lighting device with a user adjustable intensity control is known. To this end, the device has a user-operable switch to turn the light source on and off and also to adjust the intensity of the light beam.

the US 8,058,815 B1 describes LED drivers and associated controllers that are designed to control high-power LEDs. Using the LED drivers, a current boost can be achieved for momentary illumination of the LEDs at levels that exceed their maximum continuous current rating.

From the US 9,807,839 B1 a lighting system is known in which individual light sources are designed with a first operating power for the majority of the time, but with the possibility of increasing the operating power for increased light output for the same light sources of the system for a small proportion of the cumulative operating time of the light sources or to increase.

the EP 2 026 634 A1 describes an LED with a current control circuit that can output different control currents to an LED array according to the flashing times of a switch to modulate the intensity of the light emitted by the LED array.

Against this background, the inventor has now set himself the task of further improving such headlights without providing significant changes in the maximum service life.

This object is solved by the features of claim 1. Further advantageous configurations of the invention are the subject matter of the dependent claims. These can be combined with one another in a technologically sensible manner. The description, in particular in connection with the drawing, additionally characterizes and specifies the invention.

According to the invention a headlight according to claim 1 is provided.

Accordingly, for example in a first mode, which corresponds to normal operation, the maximum intensity and the associated maximum current are limited in such a way that an appropriate service life for permanent operation with maximum intensity is achieved for the respective application. This corresponds to the already known limitation of the operating current with regard to normal operation. However, in order to make it possible to operate with a changed maximum intensity, the headlight can be switched to a second mode in which the light-emitting diode is operated either with a higher maximum intensity with a simultaneously reduced service life and efficiency or with a lower maximum intensity with a simultaneously increased service life and efficiency becomes.

Although operation in the second mode with a higher maximum intensity and the associated higher maximum current reduces the service life of the light-emitting diode, it can produce special lighting effects that cannot be achieved with conventional headlights by merely activating it for a short time. For example, at the end of an event, a concluding sequence could be shown with significantly increased intensity, which leaves a special impression on visitors. If operation in this second mode is limited to such short-term sequences, the expected overall reduction in service life is typically not significant. In other Use cases it would be possible to provide a correspondingly higher light intensity, for example in strong sunlight.

Another example of operation in the second mode with a higher maximum intensity would be an architectural application in which a building is to be illuminated for a few seconds with bright flashes of light every hour on the hour, but the spotlight is generally not operated with an increased maximum current. The disadvantages of a reduced service life occurring in the prior art due to the permanently increased maximum current and increased energy consumption, since the efficiency of the LED could not be optimally used during operating times with lower brightness, are avoided according to the invention.

Alternatively, a second mode with a lower maximum intensity could be optimized with regard to the efficiency and service life of the light-emitting diode and with regard to the noise development of the headlight. In areas of application that allow a reduced maximum intensity, this would give the user the opportunity to reduce the energy consumption and thus the energy costs and, through the associated reduction in the power loss, to reduce the volume of a fan used for cooling, for example, which in turn would make the use of the headlight easier in noise-sensitive environments. For this interpretation of the second mode, applications would also be conceivable which make use of the switchover to this mode only occasionally.

For example, the lighting of a play for quieter scenes that require less light intensity and tolerate less background noise could be temporarily switched to this more efficient mode with less noise. A more significant color locus shift by changing the maximum current occurs at most at low intensities when changing modes on, wherein within an operating mode, brightness control can be done true to color, for example, by means of the aforementioned modulation circuit.

According to an embodiment of the invention, each light-emitting diode can be provided with a control unit. It is also conceivable to provide groups of light-emitting diodes with a control unit or to equip light-emitting diodes with a color characteristic with a control unit.

Accordingly, it is possible to set up the control of the maximum light intensity with different complexities, with the selection of certain light-emitting diodes with the same color characteristics being provided in particular in addition to a group-wise assignment. For example, it would be possible to equip the light-emitting diodes that emit white light with a higher maximum intensity, for example to make flashes of white light have a particularly impressive effect on visitors. This would of course also be possible for other colors or color mixtures.

According to one embodiment of the invention, the maximum intensity is set to be the same for groups. Accordingly, operating currents can be chosen to be the same or approximately the same for groups, so that the wear values are also approximately the same.

According to a further embodiment of the invention, a circuit for pulse width modulation is provided as the modulation circuit in the first operating mode and in the second operating mode, which circuit can be operated with an adjustable maximum current in each case.

Accordingly, within each operating mode, the color-accurate control of the illuminance is carried out by a pulse width modulation circuit. Such a Modulation circuitry allows the light intensity to be regulated in a simple manner without color shifts occurring. The radiated light intensity can be controlled true to color, for example, by means of a modulation circuit. The emitted light intensity of the light-emitting diodes can thus be regulated in every operating mode up to the maximum intensity that can be set via the maximum current, without color deviations occurring when the brightness is varied.

According to a further embodiment, a third operating mode can also be provided.

The operating modes can thus be selected, for example, in such a way that it is possible to switch between normal operation, operation with increased intensity and stroboscopic operation.

This makes it possible to operate the headlight flexibly between different brightnesses, with stroboscopic operation being understood here as such is intended that only a very short light pulse with high intensity is to be generated.

In this case, the control unit can be programmable via an interface with regard to the maximum intensity.

The use of a programmable interface is provided as standard in headlights, so that the maximum intensities provided and the maximum currents associated therewith can also be designed to be programmable by a user. The programmable interface can thus be used to select which maximum intensity or which associated maximum current is to be specified, which in turn means that a number of modes can be implemented. The different modes can therefore not only be understood as discrete values of the maximum current of the light-emitting diodes, but can also be continuously changed from the outside.

According to a further embodiment of the invention, the control unit is equipped with a monitoring unit that records an operating time in an operating mode with a reduced service life. In this case, for example, when a definable threshold is reached, switching to an operating mode with a shorter service life can be prevented.

In order not to reduce the service life of the light-emitting diodes of the headlight to a certain extent, this embodiment provides for a monitoring unit to be integrated into the control unit, so that the operating time in the operating mode with a reduced service life is recorded. It can thus be prevented, for example, that the second operating mode activated too frequently or accidentally, which would result in a significant reduction in service life.

According to a further embodiment of the invention, the headlight has a temperature sensor that can be used to determine the maximum intensities.

Since the temperature of the light-emitting diode also has an influence on the service life, this procedure makes it possible to adapt the maximum currents of the light-emitting diode as a function of the temperature.

Fig. 1

schematisch eine Leuchtdiode mit einer Steuerschaltung als Bestandteil eines Scheinwerfers gemäß der Erfindung,

Fig. 2

schematisch eine Leuchtdiode mit einer Steuerschaltung als Bestandteil eines Scheinwerfers gemäß einer Ausführungsform,

Fig. 3

ein Teil einer Steuereinheit nach Fig. 1 in einer schematischen Darstellung, und

Fig. 4

eine zweite Ausführungsform einer Steuereinheit nach Fig. 1 oder 2 in einer schematischen Darstellung.

Some exemplary embodiments are explained in more detail below with reference to the drawing. Show it:

1

schematically a light-emitting diode with a control circuit as part of a headlight according to the invention,

2

schematically a light-emitting diode with a control circuit as part of a headlight according to one embodiment,

3

part of a control unit 1 in a schematic representation, and

4

according to a second embodiment of a control unit Fig. 1 or 2 in a schematic representation.

In the figures, identical or functionally identical components are provided with the same reference symbols.

In 1 a light-emitting diode 5 is shown schematically, which forms part of a headlight according to the invention. It goes without saying that an actual headlight can comprise a large number of such light-emitting diodes 5 . The light-emitting diode 5 is connected to a terminal with a potential that is in 1 is denoted by V ₁ . The other terminal of the light-emitting diode 5 is connected to a control unit, the first part of which is referred to as the first control unit 10 , the second part of which is referred to as the second control unit 12 and the third part of which is referred to as the third control unit 14 .

The outputs of the first, second and third control unit 10, 12, 14 are in turn connected to a potential in 1 is denoted by V ₂ . The first control unit 10, the second control unit 12 and the third control unit 14 are each connected to an input signal 16, 18 and 20, which in turn are fed by a programmable interface 22. The programmable interface 22 can thus select one of the first, second or third control units 10, 12 or 14 by means of corresponding control signals, so that this branch is activated.

Each of the first, second or third control units 10, 12 or 14 can specify a maximum current with which the light-emitting diode 5 is operated between the potential difference between the potentials V ₁ and V ₂ . In the simplest case, each of the first, second or third control units 10, 12 or 14 can therefore contain a resistor, so that a corresponding operating mode can be selected by switching using the interface 22, as below with reference to FIG 3 is explained in more detail. A voltage source can be attached between the potentials V ₁ and V ₂ , for example, so that a maximum current that can be predetermined by means of the resistor flows through the light-emitting diode 5 . In this case, V ₂ could correspond to a ground connection, and a positive voltage could be applied to V ₁ . The brightness of the light-emitting diode 5 can be adjustable for each operating mode via an analog current control or via a modulation circuit.

With reference to 2 an example is explained for better understanding, but not belonging to the invention. Again, a light-emitting diode 5 is shown, which forms part of a headlight according to the invention. The light-emitting diode 5 is connected to the control unit 10, which is constructed here as an adjustable current source, so that the current flowing between the points V ₁ and V ₂ is specified by means of the input signal 16. The input signal 16 can in turn be fed by a programmable interface 22 . The programmable interface 22 can thus use appropriate control signals to select which current is to be specified, as a result of which a plurality of modes can in turn be implemented. The different modes can thus not only be understood as discrete values of the operating current of the light-emitting diode 5, but can definitely also be changed continuously from the outside.

With reference to 3 1 shows an exemplary structure of the first control unit 10 1 explained in more detail. It can be seen that the terminal connected to the light-emitting diode is connected to a resistor RI, which can be switched back and forth between V ₁ and V ₂ via a switch SI by means of a pulse width modulation circuit 24, which is fed by the signal 16 of the programmable interface 22 . Thus, with potential conditions as above in connection with 1 specified, current can only flow through the light-emitting diode 5 if the switch is connected to V ₂ . This corresponds to a pulse width modulated maximum current through the resistor RI, which can also be set externally via a further line 26 . The first control unit 10, the second control unit 12 and the third control unit 14 have an identical structure, with only a different resistance RI being provided for each of the first, second and third control units 10, 12 and 14, so that the light-emitting diode 5 depending on the activated first , second or third control unit 10, 12 or 14 can be operated with a different maximum current. At this maximum current, the intensity of the light-emitting diode 5 is correspondingly controlled by means of the pulse width modulation circuit 24 .

In the example shown, for example, the first control unit 10 can correspond to the normal operation of the light-emitting diode 5 . The second control unit 12 can have a higher light intensity, which can be generated via a lower resistance RI. However, statistically speaking, this is associated with a shorter service life. The third control unit 14 can in turn have an even lower internal resistance, so that when it is activated via the signal 20, a kind of stroboscopic illumination can be achieved by means of the light-emitting diode 5. The second control unit 12 and the third control unit 14 are constructed identically to the first control unit 10 except for the value of the resistor RI.

According to the invention, for example in the first mode, which corresponds to normal operation, the maximum current is set via the first control unit 10 such that an appropriate service life of the light-emitting diode 5 is achieved at the selected maximum intensity of the amount of light emitted. This corresponds to the already known limitation of the operating current with regard to normal operation by means of the resistor RI. However, in order to create the possibility of a higher maximum intensity, the headlight can be switched to a second mode in which the light-emitting diode with a higher maximum intensity is activated by means of the second control unit 12 is operated with a reduced service life at the same time. Although operation in the second mode reduces the service life of the light-emitting diode, it can produce special lighting effects that cannot be achieved with conventional headlights if it is only activated for a short time. If the operation in the second mode is limited to such short-term sequences, the reduction in the service life of the light-emitting diode 5 that is to be expected overall is typically not significant. An operation in the third mode can take place by means of the third control unit 14, for example in order to provide even higher or also lower intensities. The latter corresponds, for example, to operation with reduced energy consumption or operation with reduced noise development due to a lower cooling requirement, which is usually associated with reduced noise from a fan.

In each of the operating modes, an intensity control can also be carried out up to the respective maximum current, for which purpose a modulation circuit, in particular a circuit for pulse width modulation, or a combination of the modulation circuit and a circuit for current limitation, which can be operated with the adjustable maximum current, can be provided.

In 4 In a further embodiment, the first control unit 10 is shown, which is expanded by a monitoring unit 28 . The monitoring unit 28 is connected to a current signal 30, for example. In addition to being activated via a signal 32, the monitoring unit 28 can, of course, also be provided with further control signals. The monitoring unit 28 signals at its output 34, for example, that a maximum operating time has been reached in the intended operating state. In yet other embodiments, the control unit may be according to FIG 4 be extended by a temperature sensor, which is also used to monitor the lifetime can be used. Furthermore, it is conceivable to provide a programmable change of operating modes via the interface 22 via the control, for example, of a power source for the light-emitting diode.

Instead of the first, second and third control units 10, 12 and 14 shown, it is of course also possible to provide only two control units or more than three control units for a light-emitting diode. It is thus possible to switch from normal operation using first control unit 10 to at least one additional operating mode using second control unit 12 or to a third operating mode using third control unit 14 . The other operating modes can have a higher light intensity, so that special optical effects can be achieved with certain scenic lighting.

The features specified above and in the claims, as well as the features that can be inferred from the illustrations, can be advantageously implemented both individually and in various combinations. The invention is not limited to the exemplary embodiments described, but can be modified in many ways within the scope of specialist knowledge.

Claims (9)

1. Flood light, in particular for illuminating a stage or a building facade, which contains a multiplicity of light-emitting diodes (5) as light sources, at least some of the light-emitting diodes (5) being switchable between operation in a first operating mode with a first maximum intensity and operation in a second operating mode with a second maximum intensity differing from the first maximum intensity, a plurality of control units (10; 12; 14) being present for the variable control of an emitted light intensity of the part of the light-emitting diodes (5) as a component of the spotlight; 12; 14) are present, the plurality of control units (10; 12; 14) specifying for each operating mode a maximum current, which can be selected by switching over, for setting the respective maximum intensity, characterized in that the plurality of control units (10; 12; 14) each use a modulation circuit to carry out intensity control of the part of the light-emitting diodes (5) up to the respective maximum current, and a brightness of the light-emitting diodes (5) can be set with the respective modulation circuit within a respective operating mode.
2. Flood light according to claim 1, wherein each light emitting diode (5) is provided with a control unit (10; 12; 14), groups of light emitting diodes (5) are provided with a control unit (10; 12; 14) or light emitting diodes (5) of a colour characteristic are provided with a control unit (10; 12; 14).
3. Flood light according to claim 1 or 2, in which brightness control is colour-true within an operating mode.
4. Flood light according to any one of claims 1 to 3, wherein for controlling the emitted light intensity the respective modulation circuit is a pulse width modulation circuit (24).
5. Flood light according to any one of claims 1 to 4, wherein a third operating mode is further provided.
6. Flood light according to any one of claims 1 to 5, wherein the modes of operation are selected to be switchable between a normal operation, an increased intensity operation, a reduced power consumption operation, a reduced noise operation or a strobe operation.
7. Flood light according to any one of claims 1 to 6, wherein the respective control units (10; 12; 14) are each provided with a monitoring unit (28), the monitoring unit (28) recording an operating time in a reduced life operating mode.
8. Flood light according to claim 7, in which a switchover to an operating mode with a shorter service life can be prevented when a specifiable threshold of the operating time is reached.
9. Flood light according to any one of claims 1 to 8, comprising a temperature sensor which can be used to determine the maximum intensities.

Images