A light emitting diode, led, based lighting source, comprising a plurality in series connected controllers in a string, as well as a corresponding method and controller

Abstract

A Light Emitting Diode, LED, based lighting source, comprising a plurality in series connected controllers in a string, wherein each of said plurality of in series connected controllers is arranged for controlling one or more LEDs and wherein each of said controller is arranged for receiving, from a previous controller in said string, data at an input of said respective controller, extracting, from said received data, control data intended for controlling respective one or more LEDs of said respective controller, forwarding, to a next controller in said string, data at an output of said respective controller, wherein the LED based lighting source further comprises filters placed at each of said outputs of said controllers, respectively, for filtering data being forwarded to said next controller, wherein each filter is at least a 2nd order filter.

Description

[0001] A Light Emitting Diode, LED, based lighting source, comprising a plurality in series connected controllers in a string, as well as a corresponding method and controller

[0002] TECHNICAL FIELD

[0003] The present disclosure generally relates to the field of lighting and, more specifically, to an LED based lighting source having a plurality of in series connected controllers in a string.

[0004] BACKGROUND OF THE INVENTION

[0005] In recent years, LED pixelated light sources have emerged as a promising technology, redefining the landscape of illumination and visual displays across a multitude of industries. These sources may consist of arrays of individually controllable Light Emitting Diodes, LEDs and have witnessed remarkable advancements in both hardware and software.

[0006] One of the most visible and widely adopted application of LED pixelated light sources is in LED displays. These displays have evolved from single-color scrolling text boards to high-resolution, full-color video walls provided in public spaces, stadiums, and corporate events. Advancements in LED technology have led to smaller pixel pitches, resulting in higher pixel density and, consequently, crisper and more immersive visual experiences. With pixel pitches now measured in millimeters, these displays can be viewed comfortably even at close distances, making them suitable for indoor and outdoor applications.

[0007] The control systems governing LED pixelated light sources have seen significant enhancements. Traditional central controllers are being replaced by distributed control architectures, where multiple controllers are connected in series or networked, allowing for more flexible and scalable control.

[0008] Cascaded serial datastreams are commonly employed to convey commands from one controller to the next, ensuring synchronized operation. Furthermore, the integration of powerful microcontrollers and advanced software algorithms has simplified content creation and scheduling, enabling dynamic lighting displays and animations with greater ease.

[0009] The LED pixelated light source systems empower users with a wide range of customization options. From changing the colour and intensity of individual pixels to creating lighting effects and animations, these systems cater to diverse artistic and functional requirements. Interactive features, such as touch-sensitive displays or sensors that respond to environmental conditions, have also been integrated into LED pixelated light sources, enhancing their adaptability in smart lighting and interactive installations.

[0010] The present disclosure focusses on an architecture in which multiple controller are connected in series, i.e. they form some sort of string or chain of controllers. Each controller may control one or multiple LEDs. Data is communicated from one controller to another controller in the string, and so on.

[0011] One of the issues with such an architecture is that unwanted high Electromagnetic Interference, EMI, emission levels may be generated, especially in the case of large system sizes.

[0012] SUMMARY

[0013] It would be advantageous to achieve a Light Emitting Diode, LED, based lighting source, comprising a plurality in series connected controllers in a string, wherein the LED based lighting source has improved Electromagnetic Compatibility, EMC, capabilities.

[0014] It would further be advantageous to achieve a corresponding method and controller.

[0015] In a first aspect of the present disclosure, there is provided a Light Emitting Diode, LED, based lighting source, comprising a plurality of in series connected controllers in a string, wherein each of said plurality of in series connected controllers is arranged for controlling one or more LEDs and wherein each of said controller is arranged for: receiving, from a previous controller in said string, data at an input of said respective controller; extracting, from said received data, control data intended for controlling respective one or more LEDs of said respective controller; forwarding, to a next controller in said string, data at an output of said respective controller; wherein the LED based lighting source further comprises filters placed at each of said outputs of said controllers, respectively, for filtering data being forwarded to said next controller, wherein each filter is at least a 2nd order filter.

[0016] The present disclosure is directed to a control architecture that uses a cascaded digital datastream. The controllers, for example Integrated Circuits, ICs, may be available as separate ICs or build-in in an LED package. The controllers may have a data input and a data output. The controller may “strip” its required data, i.e. data addressed to that specific controller, from the datastream and may pass the remaining data to the next controller in the string.

[0017] Typically, the distance between controllers is quite short, for example in the order of several centimeters, but larger systems may also exist having pixel distances up to several meters.

[0018] The above identified datastream typically operates at quite a high symbol rate. This refers to the data that is being communicated between the controllers. As such, in the datastream many high-to-low and low-to-high transitions of the signal may exist.

[0019] One of the downsides of such a characteristic is that the signal transitions may cause undesired Electromagnetic Interference, EMI.

[0020] The coupling capacitance to the environment, i.e. the parasitic capacitance, may increase for increasing system sizes. For example a high number of controllers or relatively long cables between those controllers. This may result in higher EMI levels.

[0021] The inventors have found that it may be beneficial to introduce 2ndorder filters at each of the outputs of the controllers, respectively.

[0022] A second-order filter is a type of electronic filter that affects the amplitude and phase of a signal, i.e. the datastream, as it passes through the filter circuit. Second-order filters are characterized by their order, which is determined by the number of energy-storage elements, which are typically capacitors or inductors, in the filter's circuit topology. In the case of a second-order filter, there are two such energy-storage elements.

[0023] The filters may be EMI filters which are designed to suppress electromagnetic interference, both conducted and radiated, in electronic circuits and systems. These filters are introduced to ensure, for example, that the LED based lighting device complies with electromagnetic compatibility, EMC, standards and regulations.

[0024] EMI filters come in various configurations, including common-mode and differential-mode filters. The order of an EMI filter refers to the complexity of its filtering circuitry and how it attenuates unwanted electromagnetic interference.

[0025] A second-order EMI filter, for example, typically includes two filtering stages, each with energy -storage components such as capacitors and inductors. These stages are designed to attenuate interference at different frequency ranges. The combined effect of these two stages results in a second-order filter response. A first stage of the filter may, for example, consist of a low-pass filter that attenuates high-frequency common-mode interference. It may be designed to block signals above a certain cutoff frequency.

[0026] The second stage may include additional filtering elements or components like capacitors and inductors to further attenuate interference signals, often in the differential mode or at lower frequencies.

[0027] It is noted that the connections between the controllers may be based on two separate lines / wires. One line / wire is intended for the data that is to be transmitted and the other line / wire is used as a return line, for example ground.

[0028] In an example, each filter comprises: a first impedance connected to said corresponding output of said controller and a first intermediate point; a first capacitor connected between said first intermediate point and ground; a second impedance connected between said first intermediate point and a second intermediate point; a second capacitor connected between said second intermediate point and ground.

[0029] The inventors have found that a first order impedance-capacitance filter may not be able to create a large enough roll-off at high frequencies to keep the EMI levels low enough. Decreasing the comer frequency, i.e. increase the resistance-capacitance time constant, may not be desired as it may violate time domain and voltage level requirements.

[0030] The present disclosure is directed to use a higher order filter arrangement, for example a 2ndorder filter, to decrease the high frequency content.

[0031] In an example, at least one of: said first impedance is any of a resistor, inductor or ferrite bead; said second impedance is any of a resistor, inductor or ferrite bead.

[0032] A resistor is a passive component that primarily restricts the flow of electrical current in a circuit. An inductor is a passive component that stores electrical energy in the form of a magnetic field when current flows through it. It resists changes ( / frequencies) in current. A ferrite bead, also known as a ferrite choke or ferrite core, is a passive component designed to suppress high-frequency electromagnetic interference, EMI. It acts as an inductive element at high frequencies and reduces the transmission of noise on a signal or power line. In a further example, the second intermediate point is connected to a respective input of a next controller in said string.

[0033] In an example, the second capacitor being any of: a standalone capacitor; a capacitance constituted by a cable connecting said controller to said next controller in said string; a combination of a standalone capacitor and said capacitance constituted by said cable connecting said controller to said next controller in said string.

[0034] The inventors have found that the cable that connects subsequent controllers to one another may also act as a capacitance. This capacitance may be utilized to create the 2ndorder filter. A discrete, standalone, capacitor may be used as the second capacitor, wherein the value for this second capacitor may be chosen such to compensate for the capacitance of the cable.

[0035] The above is especially true for relatively long cables, which have a relatively high capacitance.

[0036] In a specific example, any of: a value for said first impedance is between 50 Ohm - 5000 Ohm; a value for said first capacitor is between 20 Pico Farad - 2 nano Farad; a value for said second impedance is between 50 Ohm - 5000 Ohm; a value for said second capacitor is between 20 Pico Farad - 5 nano Farad.

[0037] In another example, each controller is arranged for removing extracted data from said received data before forwarding said data to said next controller in said string.

[0038] This example is directed to a specific communication topology. Data may be transmitted by a first controller and may be forwarded by each of the intermediate controllers in the string to their neighboring controllers, respectively. One of the advantageous situations may occur in which each controller uses the first X received bits, for example 6 bits, for controlling their respective LEDs. These X bits may then be removed from the datastream before forwarding the datastream to the next controller in the string. The next controller may then, subsequently, remove the next X bits from the datastream and may forward the remaining datastream to the next controller in the string, etc.

[0039] This may be beneficial to improve the addressing and may improve effective communication between the controllers in the string.

[0040] In an examples, each controller comprises said respective filter. The filters may be integrated in the controller, for example in the Integrated Circuit. Another option is that the filter is assembled on the substrate, for example Printed Circuit Board, PCB, to which the controller is attached. Ideally the filter is placed closed to the output port of the controller.

[0041] The controller may be an Integrated Circuit, IC, an Application Specific Integrated Circuit, ASIC, a Field Programmable Gate Array, FPGA, or anything similar.

[0042] In a further example, each controller is arranged for receiving, from a previous controller in said string, data at an input of said respective controller operating at a symbol rate of at least 400kHz.

[0043] The distance between subsequent controllers in said string may be between 5cm - 1000cm.

[0044] In a second aspect of the present disclosure, there is provided a method of controlling one or more Light Emitting Diodes, LEDs, of an LED based lighting source in accordance with any of the previous examples, wherein said method comprises the steps of: receiving, by a controller in said string, from a previous controller in said string, data at an input, extracting, by said controller, control data for controlling respective one or more LEDs; forwarding, by said controller, to a next controller in said string, data via an output; filtering, by said filter placed at said output of said controller, data being forwarded to said next controller.

[0045] It is noted that the advantages as explained with respect to the first aspect of the present disclosure, being the LED based lighting source, are also applicable to the second aspect of the present disclosure, being the method of controlling one or more LEDs.

[0046] In an example, the method further comprises the step of: removing, by said controller, extracted data from said received data before forwarding said data to said next controller in said string.

[0047] In a third aspect of the present disclosure, there is provided a controller arranged for operating in an Light Emitting Diode, LED, based lighting system in accordance with any of the previous examples, wherein said controller is arranged for receiving, from a previous controller in said string, data at an input of said respective controller; extracting, from said received data, control data intended for controlling respective one or more LEDs of said respective controller; forwarding, to a next controller in said string, data at an output of said respective controller; wherein the controller further comprises filters placed at each of said outputs of said controllers, respectively, for filtering data being forwarded to said next controller, wherein each filter is at least a 2nd order filter.

[0048] In an example, the filter comprises: a first impedance connected to said corresponding output of said controller and a first intermediate point; a first capacitor connected between said first intermediate point and ground; a second impedance connected between said first intermediate point and a second intermediate point; a second capacitor connected between said second intermediate point and ground.

[0049] The present disclosure is described in conjunction with the appended figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

[0050] In the appended figures, similar components and / or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.

[0051] The above and other aspects of the disclosure will be apparent from and elucidated with reference to the examples described hereinafter.

[0052] BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Fig. 1 discloses an example of a Light Emitting Diode, LED, based lighting source in accordance with the present disclosure;

[0054] Fig. 2 discloses a graph showing the difference between utilizing a 1storder filter and a 2ndorder filter; Fig. 3 discloses an example of a method in accordance with the present disclosure.

[0055] DETAILED DESCRIPTION

[0056] It is noted that in the description of the figures, same reference numerals refer to the same or similar components performing a same or essentially similar function.

[0057] A more detailed description is made with reference to particular examples, some of which are illustrated in the appended drawings, such that the manner in which the features of the present disclosure may be understood in more detail. It is noted that the drawings only illustrate typical examples and are therefore not to be considered to limit the scope of the subject matter of the claims. The drawings are incorporated for facilitating an understanding of the disclosure and are thus not necessarily drawn to scale. Advantages of the subject matter as claimed will become apparent to those skilled in the art upon reading the description in conjunction with the accompanying drawings.

[0058] The ensuing description above provides preferred exemplary embodiment(s) only, and is not intended to limit the scope, applicability or configuration of the disclosure. Rather, the ensuing description of the preferred exemplary embodiment(s) will provide those skilled in the art with an enabling description for implementing a preferred exemplary embodiment of the disclosure, it being understood that various changes may be made in the function and arrangement of elements, including combinations of features from different embodiments, without departing from the scope of the disclosure.

[0059] Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise," "comprising," and the like are to be construed in an inclusive sense, as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to." As used herein, the terms "connected," "coupled," or any variant thereof means any connection or coupling, either direct or indirect, between two or more elements; the coupling or connection between the elements can be physical, logical, electromagnetic, or a combination thereof. Additionally, the words "herein," "above," "below," and words of similar import, when used in this application, refer to this application as a whole and not to any particular portions of this application. Where the context permits, words in the Detailed Description using the singular or plural number may also include the plural or singular number respectively. The word "or," in reference to a list of two or more items, covers all of the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list. These and other changes can be made to the technology in light of the following detailed description. While the description describes certain examples of the technology, and describes the best mode contemplated, no matter how detailed the description appears, the technology can be practiced in many ways. Details of the system may vary considerably in its specific implementation, while still being encompassed by the technology disclosed herein. As noted above, particular terminology used when describing certain features or aspects of the technology should not be taken to imply that the terminology is being redefined herein to be restricted to any specific characteristics, features, or aspects of the technology with which that terminology is associated. In general, the terms used in the following claims should not be construed to limit the technology to the specific examples disclosed in the specification, unless the Detailed Description section explicitly defines such terms. Accordingly, the actual scope of the technology encompasses not only the disclosed examples, but also all equivalent ways of practicing or implementing the technology under the claims.

[0060] Fig. 1 discloses an example of a Light Emitting Diode, LED, based lighting source 1 in accordance with the present disclosure.

[0061] The LED based lighting source 1 may comprises a plurality of controllers 2 that are connected to one another in a string like topology, i.e. a chain. Each controller 2 may control a single LED as indicated with reference numeral 10. Alternatively, the controller 2 may control a plurality of LEDs at the same time.

[0062] Each controller 2 may have an input 11 for receiving a datastream. The datastream is received from a previous controller in the same chain / string. The data intended for the controller 2 is extracted from the data stream, wherein the extracted data is used to control the at least one LED 10.

[0063] The data is then forwarded via the output 3 to a subsequent controller in the string (not shown).

[0064] The communication lines between adjacent controller may be based on two separate lines. A data line and a return line. The return line may be referred to as ground 4.

[0065] The inventors have found that the LED based lighting source 1 may create a lot of Electromagnetic Interference, EMI. This is undesired as the EMI may cause interference at other devices. Further, standards are in place limiting the EMI to certain limits.

[0066] In order to suppress the EMI as much as possible, the LED based lighting source 1 further comprises filters placed at each of said outputs 3 of said controllers, respectively, for filtering data being forwarded to said next controller, wherein each filter is at least a 2nd order filter.

[0067] The filter may comprise a first impedance 5 connected to said corresponding output of said controller and a first intermediate point 12, a first capacitor 7 connected between said first intermediate point 12 and ground 7, a second impedance 6 connected between said first intermediate point 12 and a second intermediate point 13 and a second capacitor 8, 9 connected between said second intermediate point 13 and ground 7.

[0068] It is noted that the second capacitor 8,9 is formed by a discrete capacitance 8 in combination with the cable capacitance 9.

[0069] Fig. 2 discloses a graph showing the difference between utilizing a 1storder filter and a 2ndorder filter.

[0070] Digital, baseband, signals may have strict timing and level requirements which limit to options for filtering out the higher order harmonics of the signal.

[0071] A first order RC filter, i.e. -20dB / decade as shown with reference numeral 21, may not be able to create a large enough roll-off at higher frequencies to keep the emission levels low enough. Just decreasing the comer frequency, increasing the RC time constant, may violate time domain and voltage level requirements. The present disclosure proposes to use a higher order filter arrangement, i.e. 40dB / decade roll-off as shown with reference numeral 22, to decrease the high frequency content.

[0072] Compared to the first order filter, the main difference is the extra series impedance C before the cable. This will increase to order of the filter and hence increase the roll-off from -20dB / decade to -40dB / decade.

[0073] The filter may need to be introduced between the data-out pin and the interconnect between individual pixels.

[0074] The, square wave, source signal may have a roll-off of -20dB / decade. The coupling path to the environment is capacitive and the current through this capacitance has a +20dB / decade transfer function. This yields an effective emission spectrum, i.e. without filtering, of OdB / decade.

[0075] Fig. 3 discloses an example of a method in accordance with the present disclosure.

[0076] The method is directed to controlling one or more Light Emitting Diodes, LEDs, of an LED based lighting source in accordance with any of the previous claims. The method comprises the steps of: receiving 31, by a controller in said string, from a previous controller in said string, data at an input, extracting 32, by said controller, control data for controlling respective one or more LEDs; forwarding 33, by said controller, to a next controller in said string, data via an output; filtering 34, by said filter placed at said output of said controller, data being forwarded to said next controller.

[0077] To reduce the number of claims, certain aspects of the technology are presented below in certain claim forms, but the applicant contemplates the various aspects of the technology in any number of claim forms. For example, while some aspect of the technology may be recited as a computer-readable medium claim, other aspects may likewise be embodied as a computer-readable medium claim, or in other forms, such as being embodied in a means-plus-function claim.

[0078] In the description above, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of implementations of the disclosed technology. It will be apparent, however, to one skilled in the art that embodiments of the disclosed technology may be practiced without some of these specific details.

[0079] Other variations to 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 or steps, and the indefinite article “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 thereof.

Claims

CLAIMS:

1. A Light Emitting Diode, LED, based lighting source, comprising a plurality of in series connected controllers in a string, wherein each of said plurality of in series connected controllers is arranged for controlling one or more LEDs and wherein each of said controller is arranged to: receive, from a previous controller in said string, data at an input of said respective controller; extract, from said received data, control data intended for controlling respective one or more LEDs of said respective controller; forward, to a next controller in said string, data at an output of said respective controller; wherein the LED based lighting source further comprises filters placed at each of said outputs of said controllers, respectively, for filtering data being forwarded to said next controller, wherein each filter is at least a 2ndorder filter.

2. An LED based lighting source in accordance with claim 1, wherein each filter comprises: a first impedance connected to said corresponding output of said controller and a first intermediate point; a first capacitor connected between said first intermediate point and ground; a second impedance connected between said first intermediate point and a second intermediate point; a second capacitor connected between said second intermediate point and ground.

3. An LED based lighting source in accordance with claim 2, wherein at least one of: said first impedance is any of a resistor, inductor or ferrite bead; said second impedance is any of a resistor, inductor or ferrite bead.

4. An LED based lighting source in accordance with any of the claims 2 - 3, wherein said second intermediate point is connected to a respective input of a next controller in said string.

5. An LED based lighting source in accordance with any of the claims 2 - 4, wherein said second capacitor being any of: a standalone capacitor; a capacitance constituted by a cable connecting said controller to said next controller in said string; a combination of a standalone capacitor and said capacitance constituted by said cable connecting said controller to said next controller in said string.

6. An LED based lighting source in accordance with any of the claims 2 - 5, wherein any of: a value for said first impedance is between 50 Ohm - 5000 Ohm; a value for said first capacitor is between 20 Pico Farad - 2 nano Farad; a value for said second impedance is between 50 Ohm - 5000 Ohm; a value for said second capacitor is between 20 Pico Farad - 5 nano Farad.

7. An LED based lighting source in accordance with any of the previous claims, wherein each controller is arranged for removing extracted data from said received data before forwarding said data to said next controller in said string.

8. An LED based lighting source in accordance with any of the previous claims, wherein each controller comprises said respective filter.

9. An LED based lighting source in accordance with any of the previous claims, wherein each controller is an Integrated Circuit, IC.

10. An LED based lighting source in accordance with any of the previous claims, wherein each controller is arranged for receiving, from a previous controller in said string, data at an input of said respective controller operating at a symbol rate of at least 400kHz.

11. An LED based lighting source in accordance with any of the previous claims, wherein a distance between subsequent controllers in said string is between 5cm - 1000cm.

12. A method of controlling one or more Light Emitting Diodes, LEDs, of an LED based lighting source in accordance with any of the previous claims, wherein said method comprises the steps of: receiving, by a controller in said string, from a previous controller in said string, data at an input, extracting, by said controller, control data for controlling respective one or more LEDs; forwarding, by said controller, to a next controller in said string, data via an output; filtering, by said filter placed at said output of said controller, data being forwarded to said next controller.

13. A method in accordance with claim 12, wherein said method further comprises the step of: removing, by said controller, extracted data from said received data before forwarding said data to said next controller in said string.

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