A light source based on light emitting diodes (LEDs) comprising a plurality of controllers connected in series in a string, and corresponding methods and controllers
By introducing a second-order EMI filter at the output of each controller in the LED pixelated light source system, the problem of high electromagnetic interference is solved, resulting in lower EMI emissions and higher electromagnetic compatibility, and improving the system's communication efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SIGNIFY HOLDING BV
- Filing Date
- 2024-12-10
- Publication Date
- 2026-07-31
AI Technical Summary
In LED pixelated light source systems, the series connection of multiple controllers can lead to unnecessarily high levels of electromagnetic interference (EMI) emissions, especially in larger systems.
A second-order EMI filter is introduced at the output of each controller, including a first impedance and a first capacitor connected to the output and the midpoint, a second impedance and a second capacitor connected between the midpoint and ground, to filter the data forwarded to the next controller.
It effectively reduces EMI levels, ensures the system's electromagnetic compatibility (EMC) meets standards and regulations, and improves communication efficiency between controllers.
Smart Images
Figure CN122498237A_ABST
Abstract
Description
Technical Field
[0001] This disclosure generally relates to the field of lighting, and more specifically, to an LED-based lighting source having multiple controllers connected in series in a string. Background Technology
[0002] In recent years, pixelated LED light sources have emerged as a promising technology, reshaping the lighting and visual display landscape across numerous industries. These light sources can comprise arrays of individually controllable light-emitting diodes (LEDs) and have witnessed significant advancements in both hardware and software.
[0003] One of the most prominent and widespread applications of LED pixelation light sources is LED displays. These displays have evolved from monochrome scrolling text boards to high-resolution, full-color video walls provided for public spaces, stadiums, and corporate events. Advances in LED technology have enabled smaller pixel pitches, resulting in higher pixel densities and consequently, sharper, more immersive visual experiences. Because pixel pitch is now measured in millimeters, these displays are comfortable to view even at close range, making them suitable for both indoor and outdoor applications.
[0004] Control systems for LED pixelated light sources have also been significantly enhanced. Traditional central controllers are being replaced by distributed control architectures, where multiple controllers are connected in series or networked, enabling more flexible and scalable control.
[0005] Cascaded serial data streams are typically used to transmit commands from one controller to the next, ensuring synchronized operation. Furthermore, the integration of powerful microcontrollers and advanced software algorithms simplifies content creation and scheduling, making the production of dynamic lighting displays and animations easier.
[0006] LED pixelated light source systems offer users a wide range of customization options. From altering the color and intensity of individual pixels to creating lighting effects and animations, these systems meet diverse artistic and functional needs. Interactive features, such as touch-sensitive displays or sensors responsive to environmental conditions, have also been integrated into LED pixelated light sources, enhancing their adaptability in smart lighting and interactive installations.
[0007] This disclosure focuses on an architecture in which multiple controllers are connected in series, i.e., they form a controller string or chain. Each controller can control one or more LEDs. Data is transmitted from one controller to another in the controller string, and so on.
[0008] One of the problems with this architecture is that it can generate unnecessarily high levels of electromagnetic interference (EMI) emissions, especially in the case of large-scale systems. Summary of the Invention
[0009] It is advantageous to implement a light-emitting diode (LED) based lighting source, which includes multiple controllers connected in series in a string, wherein the LED-based lighting source has improved electromagnetic compatibility (EMC) capabilities.
[0010] A further advantage is the implementation of the corresponding methods and controllers.
[0011] According to a first aspect of this disclosure, a light-emitting diode (LED) based lighting source is provided, comprising a plurality of controllers connected in series in a string, wherein each of the plurality of controllers connected in series is configured to control one or more LEDs, and wherein each of the controllers is arranged for:
[0012] - Receive data from the previous controller in the string at the input of the corresponding controller;
[0013] - From the received data, extract control data intended for controlling one or more LEDs of the corresponding controller;
[0014] - Forward the data from the output of the corresponding controller to the next controller in the string;
[0015] The LED-based lighting source also includes filters placed at each of the output terminals of the controller for filtering data forwarded to the next controller, wherein each filter is at least a second-order filter.
[0016] This disclosure relates to a control architecture using cascaded digital data streams. The controller, such as an integrated circuit (IC), may be provided as a separate IC or integrated within an LED package. The controller may have data inputs and data outputs. The controller can "strip" the data it needs from the data stream, i.e., address the data to that particular controller, and can pass the remaining data to the next controller in the string.
[0017] Typically, the distance between controllers is short, such as a few centimeters, but there may also be large systems with pixel distances as high as several meters.
[0018] The aforementioned data stream typically operates at a fairly high symbol rate. This refers to the data transmitted between controllers. Therefore, there may be many high-to-low and low-to-high transitions within the data stream.
[0019] One of the drawbacks of this characteristic is that signal conversion can lead to unwanted electromagnetic interference (EMI).
[0020] With increased system size, such as a large number of controllers or relatively long cables between these controllers, the coupling capacitance to the environment (i.e., parasitic capacitance) may increase. This can lead to higher EMI levels.
[0021] The inventors have discovered that it may be beneficial to introduce a second-order filter at each output of the controller.
[0022] A second-order filter is an electronic filter that affects the amplitude and phase of a signal (i.e., a data stream) as it passes through the filter circuit. The characteristics of a second-order filter are determined by its order, which is determined by the number of energy storage elements (usually capacitors or inductors) in the filter circuit topology. In the case of a second-order filter, there are two such energy storage elements.
[0023] Filters can be EMI filters, designed to suppress electromagnetic interference in electronic circuits and systems, including conducted and radiated interference. These filters are introduced to ensure, for example, that LED-based lighting equipment 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 well it attenuates unwanted electromagnetic interference.
[0025] For example, a second-order EMI filter typically consists of two filtering stages, each with energy storage components such as capacitors and inductors. These stages are designed to attenuate interference across different frequency ranges. The combined effect of these two stages produces the second-order filter response.
[0026] The first stage of a filter can, for example, consist of a low-pass filter that attenuates high-frequency common-mode interference. It can be designed to block signals above a certain cutoff frequency.
[0027] The second stage may include additional filtering elements or components, such as capacitors and inductors, to further attenuate interference signals, typically differential-mode interference signals or lower-frequency interference signals.
[0028] It is important to note that the connection between controllers can be based on two separate lines / wires. One line / wire is intended for the data to be transmitted, and the other line / wire serves as a return line, such as a grounding wire.
[0029] In one example, each filter includes:
[0030] - A first impedance connected between the corresponding output terminal of the controller and the first intermediate point;
[0031] - A first capacitor connected between the first intermediate point and ground;
[0032] - A second impedance connected between the first intermediate point and the second intermediate point;
[0033] - A second capacitor connected between the second intermediate point and ground.
[0034] The inventors have discovered that first-order impedance-capacitor filters may not produce sufficiently large attenuation at high frequencies to keep EMI levels low enough. Lowering the corner frequency (i.e., increasing the resistor-capacitor time constant) may not be ideal because it may violate time-domain and voltage-level requirements.
[0035] This disclosure aims to use higher-order filtering devices, such as second-order filters, to reduce high-frequency components.
[0036] In one example, at least one of the following is satisfied:
[0037] The first impedance is any one of a resistor, an inductor, or a ferrite bead; the second impedance is any one of a resistor, an inductor, or a ferrite bead.
[0038] A resistor is a passive component that primarily limits the flow of 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 in current (frequency). 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 inductor at high frequencies and reduces noise transmission on signal or power lines.
[0039] In another example, the second intermediate point is connected to the corresponding input of the next controller in the string.
[0040] In one example, the second capacitor is any of the following:
[0041] - Independent capacitors;
[0042] - A capacitor consisting of a cable connecting the controller to the next controller in the string;
[0043] - A combination of an independent capacitor and the capacitor formed by the cable connecting the controller to the next controller in the string.
[0044] The inventors have discovered that the cables connecting adjacent controllers to each other can also act as capacitors. This capacitance can be used to create second-order filters. Discrete, independent capacitors can be used as second capacitors, whose values can be selected to compensate for the cable capacitance.
[0045] This is especially true for relatively long cables, which have relatively high capacitance.
[0046] In a specific example, any of the following is satisfied:
[0047] - The value of the first impedance is between 50 Ohm and 5000 Ohm;
[0048] - The value of the first capacitor is between 20 picofarads and 2 nanofarads;
[0049] - The value of the second impedance is between 50 Ohm and 5000 Ohm;
[0050] - The value of the second capacitor is between 20 picofarads and 5 nanofarads.
[0051] In another example, each controller is configured to remove extracted data from the received data before forwarding the data to the next controller in the string.
[0052] This example is for a specific communication topology. Data can be sent by a first controller and forwarded by each intermediate controller in the string to its adjacent controller. One advantageous scenario is that each controller uses the first X bits (e.g., 6 bits) of the received data to control its corresponding LED. These X bits can then be removed from the data stream before forwarding the data stream to the next controller in the string. The next controller can then subsequently remove the next X bits from the data stream and forward the remaining data stream to the next controller in the string, and so on.
[0053] This could improve addressing and potentially improve efficient communication between controllers in the string.
[0054] In one example, each controller includes the corresponding filter.
[0055] The filter can be integrated into the controller, for example, within an integrated circuit. Alternatively, the filter can be mounted on a substrate (e.g., a printed circuit board (PCB)) to which the controller is attached. Ideally, the filter should be placed near the controller's output port.
[0056] The controller can be an integrated circuit (IC), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or any similar device.
[0057] In another example, each controller is arranged to receive data at a symbol rate of at least 400 kHz from the preceding controller in the string at the input of the respective controller.
[0058] The distance between adjacent controllers in the string can be between 5 cm and 1000 cm.
[0059] In a second aspect of this disclosure, a method is provided for controlling one or more LEDs of a light-emitting diode (LED)-based lighting source according to any of the foregoing examples, wherein the method includes the following steps:
[0060] - The controller in the string receives data at the input terminal from the previous controller in the string.
[0061] - The controller extracts control data for controlling one or more corresponding light-emitting diodes;
[0062] - The controller forwards the data to the next controller in the string via its output.
[0063] - The data forwarded to the next controller is filtered by a filter placed at the output of the controller.
[0064] It should be noted that the advantages explained with respect to the first aspect of this disclosure (i.e., a light source based on light-emitting diodes) also apply to the second aspect of this disclosure (i.e., a method for controlling one or more light-emitting diodes).
[0065] In one example, the method also includes the following steps:
[0066] - The controller removes the extracted data from the received data before forwarding the data to the next controller in the string.
[0067] In a third aspect of this disclosure, a controller is provided, which is arranged for operation in a light-emitting diode (LED)-based lighting system according to any of the foregoing examples, wherein the controller is configured to:
[0068] - Receive data from the previous controller in the string at the input of the corresponding controller;
[0069] - Extract control data from the received data intended for controlling one or more corresponding light-emitting diodes of the respective controller;
[0070] - Forward the data at the output of the corresponding controller to the next controller in the string;
[0071] The controller also includes filters placed at each of the output terminals of the controller for filtering data forwarded to the next controller, wherein each filter is at least a second-order filter.
[0072] In one example, the filters include:
[0073] - A first impedance connected to the corresponding output terminal of the controller and the first intermediate point;
[0074] - A first capacitor connected between the first intermediate point and ground;
[0075] - A second impedance connected between the first intermediate point and the second intermediate point;
[0076] - A second capacitor connected between the second intermediate point and ground.
[0077] This disclosure is described in conjunction with the accompanying drawings. It should be emphasized that, in accordance with industry standard practice, the various features in the drawings are not drawn to scale. In fact, for clarity of discussion, the dimensions of various features may be arbitrarily enlarged or reduced.
[0078] In the accompanying drawings, similar parts and / or features may have the same reference numerals. Furthermore, parts of the same type can be distinguished by a dashed underline following the reference numeral and a second reference numeral used to differentiate similar parts. If only the first reference numeral is used in the specification, the description applies to any similar parts having the same first reference numeral, regardless of the second reference numeral.
[0079] The foregoing and other aspects of this disclosure will become apparent and elucidated in conjunction with the examples described below. Attached Figure Description
[0080] Figure 1 An example of a light-emitting diode-based lighting source according to this disclosure is disclosed;
[0081] Figure 2 Charts were published showing the differences between using first-order filters and second-order filters;
[0082] Figure 3 An example method according to this disclosure is provided. Detailed Implementation
[0083] Please note that in the description of the accompanying drawings, the same reference numerals refer to the same or similar components that perform the same or substantially similar functions.
[0084] The description will be further detailed with reference to specific examples, some of which are illustrated in the accompanying drawings, to provide a more detailed understanding of the features of this disclosure. Please note that the drawings show only typical examples and should not be construed as limiting the scope of the claims. The drawings are provided for ease of understanding of this disclosure and are not necessarily drawn to scale. The advantages of the claimed subject matter will become apparent to those skilled in the art upon reading this description in conjunction with the accompanying drawings.
[0085] The following description provides only preferred exemplary embodiments and is not intended to limit the scope, applicability, or configuration of this disclosure. Rather, the subsequent description of preferred exemplary embodiments will provide those skilled in the art with an illustrative description of preferred exemplary embodiments for implementing this disclosure. It should be understood that various changes can be made to the function and arrangement of elements without departing from the scope of this disclosure, including combining features from different embodiments.
[0086] Unless the context explicitly requires otherwise, throughout the description and claims, the words “comprising,” “including,” and “including” should be interpreted as inclusive, not exclusive or exhaustive; that is, meaning “including but not limited to.” As used herein, the terms “connection,” “coupling,” or any variation thereof mean any connection or coupling between two or more elements, whether direct or indirect; the coupling or connection between elements can be physical, logical, electromagnetic, or a combination thereof. Furthermore, the words “this article,” “above,” “below,” and similar terms, when used in this application, refer to the entire application and not a specific part thereof. Where the context permits, singular or plural terms used in the detailed description may also include the plural or singular, respectively. The word “or,” when referring to a list of two or more items, covers all of the following interpretations: any item in the list, all items in the list, and any combination of items in the list.
[0087] These and other changes to the technology can be made based on the following detailed description. While the description depicts certain examples of the technology and describes the best envisioned mode, the technology can be implemented in many ways, no matter how detailed the description. The details of the system may vary considerably in its specific implementation, but are still included within the scope of the technology disclosed herein. As noted above, specific terms used in describing certain features or aspects of the technology should not be construed as implying that the term is redefined herein as limited to any specific feature or aspect of the technology associated with that term. In general, the terms used in the following claims should not be construed as limiting the technology to the specific examples disclosed in the specification, unless such terms are expressly defined in the detailed description section. Therefore, the actual scope of the technology includes not only the disclosed examples but also all equivalent ways of practicing or implementing the technology under the claims.
[0088] Figure 1 An example of a light-emitting diode-based lighting source 1 according to the present disclosure is disclosed.
[0089] The LED-based lighting source 1 may include multiple controllers 2 connected to each other in a series topology (i.e., chain). Each controller 2 can control a single LED, as shown by reference numeral 10 in the figure. Alternatively, the controller 2 can control multiple LEDs simultaneously.
[0090] Each controller 2 may have an input terminal 11 for receiving a data stream. This data stream is received from the previous controller in the same chain / string. Data intended for use by controller 2 is extracted from the data stream, wherein the extracted data is used to control at least one light-emitting diode 10.
[0091] Then, the data is forwarded via output 3 to the subsequent controller in the string (not shown).
[0092] Communication between adjacent controllers can be based on two separate lines: a data line and a return line. The return line can be referred to as ground line 4.
[0093] The inventors have discovered that LED-based lighting sources 1 can generate significant amounts of electromagnetic interference (EMI). This is undesirable because EMI can interfere with other devices. Furthermore, existing standards limit EMI to specific limits.
[0094] To suppress EMI as much as possible, the LED-based lighting source 1 also includes filters placed at each of the output terminals 3 of the controller for filtering data forwarded to the next controller, wherein each filter is at least a second-order filter.
[0095] The filter may include a first impedance 5 connected between the corresponding output terminal of the controller and the first intermediate point 12, a first capacitor 7 connected between the first intermediate point 12 and ground 7, a second impedance 6 connected between the first intermediate point 12 and the second intermediate point 13, and second capacitors 8 and 9 connected between the second intermediate point 13 and ground 7.
[0096] Please note that the second capacitors 8 and 9 are formed by combining the discrete capacitor 8 and the cable capacitor 9.
[0097] Figure 2 A chart was published showing the difference between using a first-order filter and a second-order filter.
[0098] Digital baseband signals may have strict timing and level requirements, which limits the options for filtering out higher harmonics of the signal.
[0099] A first-order RC filter (i.e., -20 dB / decathlon, as shown by reference numeral 21) may not produce sufficiently large attenuation at higher frequencies to keep the transmit level low enough. Simply lowering the corner frequency (increasing the RC time constant) may violate time-domain and voltage level requirements. This disclosure proposes using a higher-order filter configuration (i.e., -40 dB / decathlon attenuation, as shown by reference numeral 22) to reduce high-frequency components.
[0100] The main difference compared to a first-order filter is the addition of an extra series impedance C before the cable. This increases the filter's order, thereby increasing the attenuation from -20dB / decathlon to -40dB / decathlon.
[0101] This filter may need to be introduced between the data output pins and the interconnects between the individual pixels.
[0102] The square wave source signal may have an attenuation of -20 dB / decibels. The coupling path to the environment is capacitive, and the current flowing through this capacitor has a transfer function of +20 dB / decibels. This produces an effective transmit spectrum, which is 0 dB / decibels in the unfiltered case.
[0103] Figure 3 An example method according to this disclosure is provided.
[0104] This method aims to control one or more LEDs of a light-emitting diode (LED)-based lighting source according to any of the preceding claims. The method includes the following steps:
[0105] - The controller in the string receives 31 data points at the input terminal from the previous controller in the string.
[0106] - The controller extracts control data from 32 for controlling one or more corresponding LEDs;
[0107] - The controller forwards 33 data to the next controller in the string via its output.
[0108] - The data forwarded to the next controller is filtered by a filter placed at the output of the controller 34.
[0109] To reduce the number of claims, certain aspects of the present technology are presented in the form of specific claims as described below, but the applicant considers that various aspects of the present technology can be embodied in any number of claims. For example, while some aspects of the present technology may be described as computer-readable medium claims, others may also be embodied as computer-readable medium claims, or in other forms, such as means plus function claims.
[0110] In the foregoing description, numerous specific details have been set forth for illustrative purposes in order to provide a thorough understanding of the implementation of the disclosed technology. However, it will be apparent to those skilled in the art that embodiments of the disclosed technology can be practiced without some of these specific details.
[0111] Those skilled in the art, upon studying the accompanying drawings, disclosure, and appended claims, will be able to understand and implement other variations of the disclosed embodiments. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude multiple. The fact that certain measures are recited in mutually different dependent claims does not mean that a combination of these measures cannot be used to achieve beneficial effects. Any reference numerals in the claims should not be construed as limiting their scope.
Claims
1. A lighting source based on a light-emitting diode (LED), comprising a plurality of controllers connected in series in a string, wherein each of the plurality of series-connected controllers is arranged to control one or more LEDs, and wherein each of the controllers is arranged as follows: - Receive data from the previous controller in the string at the input of the corresponding controller; - From the received data, extract control data intended for controlling one or more LEDs of the corresponding controller; - Forward the data from the output of the corresponding controller to the next controller in the string; The LED-based lighting source also includes filters placed at each of the output terminals of the controller for filtering data forwarded to the next controller, wherein each filter is at least a second-order filter.
2. The LED-based lighting source of claim 1, wherein each filter comprises: - A first impedance is connected to the corresponding output terminal of the controller and a first midpoint; - A first capacitor is connected between the first intermediate point and ground; - A second impedance is connected between the first midpoint and the second midpoint; - A second capacitor is connected between the second intermediate point and ground.
3. The LED-based lighting source according to claim 2, wherein at least one of the following is present: - The first impedance is any one of a resistor, an inductor, or a ferrite bead; - The second impedance is any one of a resistor, an inductor, or a ferrite bead.
4. The LED-based lighting source according to any one of claims 2 to 3, wherein the second intermediate point is connected to the corresponding input of the next controller in the string.
5. The LED-based lighting source according to any one of claims 2 to 4, wherein the second capacitor is any one of the following: - Independent capacitors; - A capacitor, consisting of a cable connecting the controller to the next controller in the string; - A combination of an independent capacitor and the capacitor formed by the cable connecting the controller to the next controller in the string.
6. The LED-based lighting source according to any one of claims 2 to 5, wherein any one of the following is present: - The value of the first impedance is between 50 Ohm and 5000 Ohm; - The value of the first capacitor is between 20 picofarads and 2 nanofarads; - The value of the second impedance is between 50 Ohm and 5000 Ohm; - The value of the second capacitor is between 20 picofarads and 5 nanofarads.
7. The LED-based lighting source according to any one of the preceding claims, wherein each controller is arranged to remove extracted data from the received data before forwarding the data to the next controller in the string.
8. The LED-based lighting source according to any one of the preceding claims, wherein each controller includes the corresponding filter.
9. The LED-based lighting source according to any one of the preceding claims, wherein each controller is an integrated circuit IC.
10. An LED-based lighting source according to any one of the preceding claims, wherein each controller is arranged to receive data at a symbol rate of at least 400 kHz from the preceding controller in the string at the input of the respective controller.
11. The LED-based lighting source according to any one of the preceding claims, wherein the distance between adjacent controllers in the string is between 5 cm and 1000 cm.
12. A method for controlling one or more LEDs of a light-emitting diode (LED)-based lighting source according to any one of the preceding claims, wherein the method comprises the following steps: - The controller in the string receives data at the input terminal from the previous controller in the string. - The controller extracts control data for controlling one or more corresponding LEDs; - The controller forwards data to the next controller in the string via its output. - The filter placed at the output of the controller filters the data forwarded to the next controller.
13. The method of claim 12, wherein the method further comprises the following step: - The controller removes the extracted data from the received data before forwarding the data to the next controller in the string.