The present invention is related to a system for operating an electronic light arrangement.
It is known to offer systems for operating an electronic light arrangement, for instance using LED (light emitting diode) driver circuits or the like. It is important in this regard to ensure a constant voltage for the driver circuit so that a stable operation of the light arrangement is provided. In order to achieve this, it is known to use a constant voltage regulator which is connected to a further electronic device, which serves as a constant current driver for the light arrangement.
However, such an assembly is often expensive and technically complex. Additionally, it becomes further complex if different groups of LEDs are used in the light arrangement, each group requiring a different current supply.
Document
It is an object of the present invention to overcome aforesaid problems in systems for operating an electronic light arrangement at least partially. Particularly, it is an object of the present invention to provide an easy and cost-efficient solution for operating an electronic light arrangement, for example a LED arrangement.
The invention is defined by a system according to claim 1, with further embodiments set out in the dependent claims.
Particularly, aforesaid object is achieved by a system for operating an electronic light arrangement, for example an arrangement with light-emitting devices, for instance LEDs or laser diodes or the like. The system comprises:
The buck-boost-device is electrically connected to the at least one buck-device for providing a constant voltage (particularly for operating the buck-device and/or the light-emitting devices of the at least one secondary group) by using a voltage drop across the light-emitting devices of the primary group. In other words, the constant voltage is provided by the voltage drop of the primary group, particularly equals the voltage drop. This has the advantage that a very constant voltage can be provided for operating the buck-device and/or the secondary groups in an easy and cost-effective manner. Furthermore, it is not necessary to use an additional device for providing a constant supply voltage for the buck device.
Preferably, the "constant current" and/or "constant voltage" refers to a nearly constant current or voltage respectively, which may vary within a certain range. Particularly, also a current or voltage that varies within a certain tolerance, for instance in a range from 0.01 A (Ampere) to 1 A, especially from 0.1 A to 0.2 A, or in a range from 0.1 V (Volt) to 2 V, especially from 0.5 V to 1 V, is regarded as "constant".
The buck-boost-device can for example provide the first constant current, which causes the voltage drop across the light-emitting devices of the primary group. Preferably, the constant voltage for operating the at least one buck-device equals and/or depends on the voltage drop, which is supplied to the buck-device by the connection between the buck-boost-device and the buck-device(s). This can be a direct or indirect electrical connection, so that for instance other electronic components can be integrated in a current path of this connection between the buck-boost-device and the buck-device.
Preferably, it can be provided that the buck-boost-device is configured as DC-DC-buck-boost-converter for operating as constant current driver. Here, "DC-DC" refers to a DC-to-DC converter that converts a source of direct current (DC) from one voltage level to another. The buck-boost converter can be a type of DC-to-DC converter that has an output voltage magnitude that is either greater than or less than the input voltage magnitude. For instance, the buck-boost-device is configured as a buck (step-down) converter combined with a boost (step-up) converter, which refers to a certain topology of a buck-boost-converter (also referred to as "four-switch buck-boost converter"). Particularly, the buck-boost-converter can operate over a wide input range from 4.5 V to 75 V, preferably from 9 V to 60 V, particularly preferably from 20 V to 30 V, and can for example have further functions like an overvoltage protection or thermal shutdown or the like. Therefore, the buck-boost-device can provide a stable and safe operation for the light arrangement.
It can be another aspect of the invention that the buck-boost-device is electrically connected to a supply input of the at least one buck-device for providing an intermediate circuit voltage to the at least one buck-device, wherein particularly the at least one buck-device is configured to step down the intermediate circuit voltage for providing a supply (operating) voltage for the at least one secondary group (that means the light-emitting devices of the secondary group), wherein particularly preferably the voltage drop depends on the first constant current and the type of light-emitting devices of the primary group, wherein for example the intermediate circuit voltage equals the voltage drop. Surprisingly it has been found that the assembly of light-emitting devices of the primary group can serve as a supplier for a very constant voltage for operating the at least one buck-device. Particularly, LEDs as light-emitting devices can provide a very constant voltage drop. Therefore, it is not necessary to use an additional regulation device for providing a constant supply voltage for the buck device(s), which can reduce costs and technical complexity.
According to the invention, it can also be possible that an electrical primary potential is provided by the voltage drop (for instance a potential at the path through the light-emitting devices of the primary group), and the primary potential is electrically connected to a supply input of the at least one buck-device for providing a constant voltage for operating the at least one buck-device, wherein particularly the voltage drop is a voltage drop across a series connection of the light-emitting devices of the primary group. Therefore, it can be provided that the light-emitting devices of the primary and/or the secondary group(s) are connected in series such that the constant current provided by the buck-boost-device or the buck-device respectively is passed through a common current path of the light-emitting devices in series connection. This allows for a simple and cost-effective configuration of the arrangement.
It is also conceivable that a first buck-device is electrically connected to a first secondary group of the light arrangement for providing a constant current to the first secondary group, and a second buck-device is electrically connected to a second secondary group of the light arrangement for providing a constant current to the second secondary group, wherein both buck-devices are supplied by an intermediate circuit voltage provided by the buck-boost-device. This has the advantage that the buck-boost-device can serve as constant current driver for the primary group as well as intermediate circuit voltage supplier for operating the buck-devices, which reduces costs and complexity. Further, a further loss of efficiency is avoided since a separate constant voltage regulator for providing a constant supply voltage is not necessary.
Preferably, it can be provided that the at least one buck-device is configured as DC-DC-buck-converter for operating as constant current driver. This can be a DC-to-DC power converter which steps down voltage (while stepping up current) from its input (supply) to its output. However, the buck-device can have a lower complexity than the buck-boot-device. Therefore, costs and technical effort can be reduced when using (only) one buck-boost-converter and the voltage drop of the primary group for suppling downstream buck-devices with operation voltage.
Preferably, the operation voltage of the buck-device(s) can be regulated by the light-emitting devices of the primary group. Additionally, at least one or at least two or at least three buck-devices can be provided, each connected to a corresponding secondary group. This allows for a highly flexible configuration of the light arrangement.
It is also conceivable that the secondary group, preferably each of the secondary groups, comprises a smaller number of light-emitting devices than the primary group, particularly preferably the second secondary group comprises a smaller number of light-emitting devices than the first secondary group. In other words, each secondary group can have lower energy consumption than the primary group. This allows for using the voltage drop of the primary group as supply voltage for each of the buck-devices.
According to another aspect of the invention, it is provided that the secondary group, particularly each of the secondary groups, comprises light-emitting devices configured to be operated with a current lower than the current for operating the light-emitting devices of the primary group. Particularly, this can be the case if different light intensities are used for the different groups. For instance, the group with the highest energy consumption can serve as primary group for providing a supply (operation) voltage to the buck-devices of the secondary group(s).
It can be provided that the system is configured as a LED driver circuit for operating the light arrangement, wherein preferably the light arrangement is configured as a LED arrangement, particularly as a projection arrangement for projecting an image onto a surface, particularly preferably used for a vehicle. This has the advantage that a highly efficient system for operation of the LED arrangement can be used since the projection of images onto a surface (for instance in front or behind the vehicle) requires different groups of LED, each requiring different currents for providing different light intensities. This allows for a uniformly projected image on the surface. Particularly, the vehicle can be configured as a forklift truck or truck or passenger vehicle or the like.
Particularly, the primary group as a first group of light-emitting devices requires a supply current (provided by the buck-boost-device) in a range from 500 mA to 1200 mA, preferably from 700 mA to 1000 mA, particularly preferably 820 mA. Preferably, the secondary group (or a first secondary group) as a second group of light-emitting devices requires a supply current (provided by the buck-device or a first buck-device) in a range from 200 mA to 800 mA, preferably from 300 mA to 600 mA, particularly preferably 480 mA. Preferably, a second secondary group as a third group of light-emitting devices requires a supply current (provided by a second buck-device) in a range from 100 mA to 600 mA, preferably from 200 mA to 400 mA, particularly preferably 360 mA.
It is conceivable that the input voltage for the buck-boost-device is in a range from 9 V to 60 V, wherein the buck-boost-device is configured to step up and step down the input voltage. Therefore, the buck-boost-device can ensure that a constant supply voltage is provided for other buck-devices as well as serving as constant current driver for a set of light-emitting devices. This can have the effect that a highly efficient system for operating a light arrangement can be provided. Also, the buck-devices can work very efficiently since the input voltage provided by the voltage drop is very constant. Additionally, the operational safety can be enhanced since the number of necessary electrical components can be reduced.
In the following, preferred embodiments of the invention are described on the basis of supportive figures. It is shown in:
In the different figures same features always correspond to the same reference signs, therefore generally the features are only described once.
In
In
The constant current output "LED+" is connected to the light-emitting devices 30 of the primary group 2a so that a voltage drop across the light-emitting devices 30 is effected (also shown in
In
The different groups can comprise a different number of light-emitting devices 30. This is made clear referring to
A vehicle 5 is shown that comprises the inventive system 1. The light arrangement 2 is used to project an image 6 on the ground. As to see, light points having a higher distance from the vehicle 5 require a projection with higher intensity than light points having lower distance. Therefore, each group can be operated with a different supply current.
This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.