Patent Application
20160100469
The invention relates to a lighting device. In particular, the invention relates to lighting devices which include OLEDs.
OLED technology has significantly advanced such that today OLED elements start to become available which are suited for lighting applications. OLED elements include a layer of organic semiconductive material which is driven as an electroluminescent layer to emit light.
Lighting devices intended for general lighting applications, i. e. for illumination of a room, space etc., generally have to fulfill certain requirements both regarding the geometric parameters such as size and shape as well as illumination parameters, such as luminous flux. One possible approach to satisfy these requirements is to design, for each lighting task, a single custom OLED element or module of required geometrical and illumination properties. However, this concept is not very flexible and requires an extra design for any of several different required types of lighting devices.
WO 2009/048951 A2 describes a method and apparatus for controlling load currents of multiple series-connected loads. In an embodiment, the apparatus is a luminaire comprising multiple series-connected LED loads to provide coloured and/or white light having a variety of colours. The apparatus includes a power supply and control electronics that provide an operating voltage for the LED light sources, which are connected in series.
The LED light sources are of different types having different spectra of emitted light. The power supply includes a load control stage to control a flow of the series current, including a controllable current path coupled between the different LEDs so as to partially divert the series current around one of the LED. The controllable current pass may be controlled based on a temperature signal.
It may be considered an object of the invention to provide an OLED lighting device with a very flexible design for different lighting tasks.
This object is solved by a lighting device according to claim 1. Dependent claims refer to preferred embodiments of the invention.
According to an aspect of the invention, the lighting device comprises more than one OLED module, specifically at least a first and a second OLED module. Each OLED module includes at least one OLED element, which may preferably be of flat shape and include front and back surfaces. In the present context, the light emitting surface will be referred to as the front surface, whereas the back surface of the OLED element is the surface opposite to the front surface. While the term “OLED element” refers to the actual light emitting part and decisive electrical component, i.e generally preferred an OLED board with an organic luminous layer, the term “OLED module” shall refer to a physical unit, which may comprise further elements of mechanical nature (e.g. a module housing) and/or electrical nature (e.g. connector plugs, conductors and/or circuitry). In the simplest case, an OLED module may also be comprised of the OLED element alone, if no further parts are necessary.
Each OLED element may be operated by supplying electrical power thereto, specifically to electrical terminals provided for this purpose. According to the generally known structure of an OLED element, such terminals may be connected to electrodes provided adjacent to the organic semiconductor layer. In the context of the present invention, the specifics of the internal structure of the OLED elements, such as the material of the organic compound or of the electrodes, will not be further discussed.
According to an aspect of the invention, at least the first and the second OLED elements are different with regard to their size; in particular have a different surface area of the respective front surfaces. As will be appreciated by the skilled person, the first and second OLED elements may differ by their shape and dimensions. As will become apparent in connection with preferred embodiments, the invention is not limited to lighting devices comprising only two different OLED modules or elements; in fact, it may be preferred to provide, within the lighting device, several OLED modules or elements of two or more different types.
Combining such different OLED modules or elements together in a lighting device allows for a very flexible design, and facilitates to provide lighting devices for different lighting tasks, i. e. of different dimensions. For example, the first OLED device (or: first type of several OLED modules in the lighting device) may comprise a relatively large, e.g. rectangular OLED element, whereas the second OLED module (or: second type of several OLED modules in the lighting device) may comprise an OLED element of substantially smaller surface area, e. g. of square shape.
Such different OLED modules with OLED elements of different shape and size allow efficient combinations suitable for a variety of different lighting tasks. For example, a lighting device suited for a lighting tasks demanding a certain overall length or area may be made up of a combination of OLED modules with larger OLED elements to fill the largest part of the required length or area, and one or more OLED devices with smaller OLED elements to fill the rest of the required length or area.
Thus, the concept of using differently shaped and/or sized OLED elements is quite flexible. To obtain efficient combinations, it is in particular proposed to provide a first OLED element that is at least 50% larger than the second OLED element, preferably more than 100% larger in area. Particularly preferred, the surface area of the front surface of the first OLED element is more than twice the size of the surface area of the front surface of the second OLED element. Such a relatively large difference in size between the OLED elements allows to fill a required overall size of a lighting device quite efficiently. For embodiments where the OLED elements and modules are arranged in a line one behind the other, it is particularly preferred to provide first and second OLED elements of the same width, but of different length.
While it is generally possible that the different OLED modules and elements may have different spectra of emitted light, i.e. provide light of different color, it is preferred to provide first and second OLED devices which emit light of the same color, such that the front of the lighting device will appear as a unitary light emitting surface.
According to an aspect of the invention, the different OLED modules are commonly supplied with electrical power by a power supply circuit. The power supply circuit supplies a series operating current IS and the OLED modules are electrically connected in series to the power supply to be operated by the series operating current IS.
As explained above, the OLED elements of the first and second OLED modules differ in their geometrical parameters, and may preferably also differ in their electrical parameters, i. e. require different nominal current. To be able to obtain such different nominal currents despite the chosen series connection, there is provided, according to an aspect of the invention, an adjustment circuit to deliver a second operating current I2 to the second OLED element. The current value of the second operating current I2 is adjusted by the adjustment circuit to a value below the current value of the series operating circuit IS.
This design thus allows to drive different OLED modules and elements in a series connection. Thus, the invention provides for a very simple design of a lighting device, which is however quite flexible with regard to combination of different OLED modules and elements.
According to a preferred embodiment of the invention, an OLED module may comprise at least one OLED element which includes terminals for electrical supply. A conductor board, which comprises electrical conductors connected—directly or indirectly—to the power supply circuit, may be arranged in parallel to the back surface of the OLED element, and the terminals of the OLED element may be connected to the conductors of the conductor board. Thus, according to this preferred embodiment, electrical connection within the OLED modules effected by a flat conductor board, which may e.g. be a printed circuit board (PCB). This allows to provide electrical connection without wires. The OLED modules may thus be comprised of the OLED elements and conductor boards.
In a particularly preferred embodiment, at least two of the OLED modules are electrically connected by plug connectors. Thus, even between the individual OLED devices, no separate wires are necessary. This further provides for efficient manufacturing.
In a further preferred embodiment, the electrical contact between a conductor board and an OLED element may be effected by contact springs. In this case, electrical terminals are provided on the back surface of an OLED element. The contact springs are arranged between these terminals and electrical conductors on the conductor board. In particular, the contact springs may be provided as bent metal sheet elements, which are provided between the conductor board and the backside of the OLED element.
It is preferred to arrange the OLED modules within a common housing or frame. In particular, a top housing may be provided as a frame to hold the OLED modules without covering the front surface.
With regard to power supply and electrical connection, it has already been explained that the first and second OLED modules are driven by a series operating current. It is preferred that the OLED element of the first OLED module is directly operated by this series operating current, i.e. that no further switching or other current conversion circuits need to be provided. In preferred embodiments, not only the OLED element of the first OLED module, but a plurality of OLED modules with OLED elements of the same type and, in particular of the same size, are directly operated by the series operating current.
On the other hand the OLED element of the second OLED module is driven by a second operating current I2 lower than the series operating current IS. According to a preferred aspect, the adjustment circuit may comprise a controllable bypass element to bypass at least a portion of the series operating current IS from the second OLED element. In other words, the OLED element of the second OLED module provided in the series circuit may be partially bridged by the controllable bypass element, such that the second operating current I2 flowing through it is reduced with regard to the series operating current IS.
According to a preferred embodiment, a control circuit is provided for controlling the controllable bypass element. Control may be effected in dependence on the current through the second OLED element, i.e. on the second operating current. In particular, feedback control may be employed to limit the second operating current to a current value below the series operating current. To effect feedback control, it is particularly preferred to provide a current sensing element which is electrically connected in series with the second OLED element, and which thus allows to sense the value of the second device current. The current sensing element may e.g. be a resistor.
In one embodiment, the adjustment circuit may comprise a DC/DC driver circuit, which is supplied with electrical power by the series operating current, and which provides the second operating current to the second OLED module or element. The DC/DC driver circuit may thus serve to adjust the second operating current to a desired value as necessitated by the second OLED element. Various types of DC/DC drivers are per se known to the skilled person. In particular, controllable switching DC/DC converters are preferred, where a plurality of topologies such as e.g. a buck converter may be used.
These and other aspects of the invention will become apparent from and elucidated with reference to the embodiment described herein after.
In the drawings,
As shown in
In the shown example, the lighting device 10 of
This arrangement of OLED modules 14a, 14b, 16a-16c is shown exemplary only for the specific lighting device 10. The lighting device 10 is intended to be used as a lamp for general lighting applications, which may be fitted at the plug connectors 18a, 18b into corresponding luminaires. In particular, the proposed embodiment is intended as a retrofit lamp replacing previous fluorescent lamps.
Since various types of fluorescent lamps are required, characterized e.g. by different lengths, the present invention intends to provide an efficient and flexible structure for lighting devices 10 which may serve as replacement of fluorescent lamps of different sizes. Thus, beside the one example of a lighting devide 10 shown in
In
As visible from
The OLED boards 28a, b serve as the actual light emitting elements. They consist of a substrate, e. g. glass, on which the actual OLED layer is applied. The OLED boards 28a of the OLED modules 16a-c of the first type are significantly larger than the OLED boards 28b of the OLED modules 14a, 14b of the second type. In the shown example of a lighting device 10 intended as replacement of a fluorescent lamp, the OLED boards 28a, 28b have the same width but differ in length. The OLED boards 28a have a length of more than twice the length of the OLED boards 28b, and thus correspondingly a larger surface area.
Provided on the back surface of the OLED boards 28a, 28b are metal contacting pads (not shown) serving as electrical terminals. The terminals are internally connected to the electrodes of the OLED layer of the OLED board, such that, when electrical power is supplied to these terminals, light is emitted from the front surface of the OLED board 28a, 28b shown in
Within each OLED module, the terminals of the OLED boards 28a, 28b are electrically contacted by contact springs 34, provided as bent sheet metal strips and arranged between the printed circuit boards 32a and 32b and the back of the OLED boards 28a, 28b. Also arranged in between the OLED boards 28a, 28b and the PCBs 32a, 32b is the module bottom cover 30 which comprises a number of cut-outs, through which the contact springs 34 provide the electrical contact.
Electrical power is supplied to the lighting device 10 via the first plug connector 18a. Each of the OLED modules 14a, 14b, 16a-c comprises a module plug connector 36 on its side facing towards the first connector 18a, and a corresponding module socket connector 38 on the opposite side (not shown). The OLED modules 14a, 14b, 16a-c are interconnected by these plug/socket connections such that electrical power is supplied from the first plug connector 18a to each of the modules.
The individual modules 14a, 14b, 16a-c are electrically interconnected by the module plug/socket connections 36, 38 as explained above.
The OLED boards 28a of the larger first type of OLED modules 16a-c are larger than the OLED boards 28b of the OLED modules 14a, 14b of the smaller second type, and thus require a higher nominal current.
As shown in the circuit of
On the other hand, the smaller OLED boards 28b have a smaller surface area and require a smaller nominal operating current I2. To provide this lower operating current for the second type of OLED boards 28b, which may also be designated a second device current I2 adjustment circuits 40 are comprised within the PCBs 32a of the OLED modules 14a , 14b of the second type. The adjustment circuits 40 are driven by the series operating current IS, but provide an operating current I2 for the smaller OLED boards 28b which have a lower current value than the series operating current IS.
In operation of the adjustment circuit 40, a portion of the series operating current IS supplied at the terminals is conducted through the MOSFET bypass element 42, such that only a smaller portion I2 flows through the OLED board 28b. The portion I2 of the total series operating current IS may be adjusted by an appropriate choice of the component values of resistors R1-R3.
The DC/DC converter circuit 48, which may e. g. be an integrated circuit switching converter, delivers the second device current I2 to the OLED board 28b under control of the controller 50.
In operation of the adjustment circuit 40, the controller 50 operates the bypass MOSFET 52 to maintain a voltage over capacitance C appropriate as input voltage for the DC/DC converter 48. The controller 50 further controls the DC/DC converter circuit 48 to obtain a desired current value for the second device current I2.
While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments.
For example the number of OLED modules within the lighting device may vary according to the required length and surface area. Also, different types of DC/DC controllers may be employed in the embodiment of
Further variations from the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims the word “comprising” does not exclude other elements, and the indefinite articles “a” or “an” does not exclude a plurality.
The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.
| Number | Date | Country | Kind |
|---|---|---|---|
| PCT/CN2013/076458 | May 2013 | CN | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/IB2014/061462 | May 2014 | US |
| Child | 14953380 | US | |
| Parent | PCT/CN2013/076458 | May 2013 | US |
| Child | PCT/IB2014/061462 | US |
