The present invention relates generally to light emitting diodes LEDs), and more particularly, some embodiments relate driving systems for LED lighting systems.
Some LED-based luminaires provide white light by mixing from a plurality of monochromatic LEDs. Such multi-color LEDs may utilize two, three, four, or more different colors of monochromatic LEDs. White light, and even other colors of light, is provided by modifying the relative outputs of the various monochromatic LEDs. Typically, these multi-color LED-based color luminaires often utilize three color LED modules which have red, green, and blue LEDs.
In the illustrated system, each driver utilizes a pair of wires 108 and 109, 110 and 110, or 112 and 113, to control its respective LED. Accordingly, the wire 107 used to connect the drivers to the module 100 requires a total of six wires. In some systems, a common anode or common cathode wire is used to reduce this total to four wires.
According to various embodiments of the invention, a multicolored LED luminaire module is provided that can be controlled using a single driver and only two wires. The LED luminaire module comprises a plurality of LEDs and a sequencer. The sequencer connects each LED to the circuit in a predetermined order. Synchronously with the sequencer, the driver transmits a control signal comprising a time division multiplexed (TDM) signal that combines the driving currents for each LED into one TDM signal. The sequencer and TDM rate are sufficiently fast such that the light emitted by the LED luminaire appears to be the combined light from all the LEDs.
According to an embodiment of the invention, a multicolor light emitting diode (LED) lighting system, comprises an LED module comprising a plurality of LEDs, and a sequencer electrically coupled to the plurality of LEDs configured to connect LEDs of the plurality to a circuit and isolate other LEDs of the plurality from the circuit in a predetermined sequence; and a driver electrically coupled to the circuit and configured to provide a driving signal to the plurality of LEDs according to the predetermined sequence and in synchronization with the sequencer.
Other features and aspects of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the features in accordance with embodiments of the invention. The summary is not intended to limit the scope of the invention, which is defined solely by the claims attached hereto.
The present invention, in accordance with one or more various embodiments, is described in detail with reference to the following figures. The drawings are provided for purposes of illustration only and merely depict typical or example embodiments of the invention. These drawings are provided to facilitate the reader's understanding of the invention and shall not be considered limiting of the breadth scope, or applicability of the invention. It should be noted that for clarity and ease of illustration these drawings are not necessarily made to scale.
The figures are not intended to be exhaustive or to limit the invention to the precise form disclosed. It should be understood that the invention can be practiced with modification and alteration, and that the invention be limited only by the claims and the equivalents thereof.
The present invention is directed toward an LED-based illumination system. Use of time division multiplexing allows a multi-color LED luminaire to be operated using a single driver and a single pair of wires.
A sequencer module 202 sequentially connects and disconnects individual LEDs of the plurality 203 to the circuit. In the illustrated embodiment, the sequence module 202 comprises a sequencer control module 201 that controls 207 a plurality of switches 208, 209, 210. Each switch is electrically coupled to an individual LED. By connecting and disconnecting the switches, the sequencer connects and disconnects LEDs to the leads 211 and 212. For example, by connecting switch 208 and disconnecting switches 209 and 210 the red LED 204 is coupled to the leads 211 and 212, and the green LED 205 and the blue LED 206 are isolated from the circuit.
In some embodiments, the sequencer operates on a predetermined switching sequence to sequentially isolate and connect individual LEDs to the circuit. A driving signal provided on the leads may then control each of the LEDs in the order determined by the sequencer in some embodiments, when the sequencer advances to the next element of the predetermined sequence is determined by the driver. In a particular embodiment, a synchronization signal is embedded in the driving signal. When the synchronization signal is received, the sequencer advances to the next element of the sequence. In other embodiments, the sequence module 202 operates independently and the driver synchronizes to the sequence module without transmitting control information. For example, each LED may be coupled in series with a resistor, with each resistor having a different resistance. In this example, a driver operating in a constant current mode can determine the sequence and sequence timing of the sequencer 201 and synchronize by monitoring the continuous voltage on the line.
In other embodiments, the sequence module 202 is coupled to a control line 213 to allow control signals to be transmitted to the sequencer 201. For example, a stop/start or restart control signal may comprise a low current signal at a predetermined current level. When the sequencer 201 receives this signal it restarts the sequence, allowing the external driver to synchronize. For example, the low current signal may comprise a current that is insufficient to produce a noticeable illumination level in the LEDs 203. For example, the current level may only produce a luminance between 0 and 10−2 cd/m2 in the LEDs 203. Accordingly, the control signals embedded in the driving signals may be imperceptible to those viewing the luminaire.
Additionally, in further embodiments, different periods for different LEDs may be different time lengths.
Additionally, embedded control signals may be used to initially activate the sequencer or LED luminaire.
As illustrated, a plurality of LEDs may driven in this manner through the use of only two wires. In addition to substantial materials savings in wires 215, this allows some embodiments to serve in otherwise unsuitable locations. For example, the illustrated system may be particularly suitable for situations involving long wire runs, or situations where only two conductors are available, such as track lighting or lighting upgrades in a vehicle with only two available conductors.
When large numbers of LED modules are connected in series with a driver, the failure of any given LED module might prevent the entire chain from operating. Accordingly, in some embodiments, LED modules are coupled to shunt circuits that shunt current around a failed LED module.
In general, the number of LED modules in series is limited by the available compliance voltage of the driver. In other words, the maximum voltage that the driver can output while maintaining current control. For typical laboratory drivers, this limit is 100-200V. With typical LEDs and circuit components, this corresponds to 20-40 LED modules.
To allow for longer chains of LED modules, repeating drivers may be implemented. Because control signals are transmitted within the driving signals themselves, repeating drivers may be connected to the same circuits without the use of separate control or signaling cables. A repeating driver is configured to sense the driving signal and retransmit it to allow for an increased number of LED modules within the circuit.
In some embodiments, analog driving signals may be employed, and a repeating LED driver may be configured to retransmit the analog driving signal as it senses the signal. However, in some applications, imperfections in signal reproduction can degrade the quality of the signal, and consequently impact the quality of the light produced by the luminaire. In these embodiments, a TDM modulation scheme is employed that uses discrete current levels and discrete LED period durations. A downstream repeating driver then senses a transmitted driving signal and repeats the closest discrete signal to the received signal. Accordingly, normal signal degradation does not impact the quality of downstream light, because the retransmitted signal is equivalent to the original driving signal. In this configuration, the overall error for any arbitrary length chain of drivers is equal to the error of one driver.
In some embodiments, repeating drivers may be provided with redundant fault protection.
In addition to series circuits of multiple LED modules, some embodiments of the invention may provide for multiple LED modules in parallel.
As used herein, the term module might describe a given unit of functionality that can be performed in accordance with one or more embodiments of the present invention. As used herein, a module might be implemented utilizing any form of hardware, software, or a combination thereof. For example, one or more processors, controllers. ASICs. PLAs, PALs, CPLDs. FPGAs, logical components, software routines, circuit elements, or other mechanisms might be used in a module. In implementation, the various modules described herein might be implemented as discrete modules or the functions and features described can be shared in part or in total among one or more modules. In other words, as would be apparent to one of ordinary skill in the art after reading this description, the various features and functionality described herein may be implemented in any given application and can be implemented in one or more separate or shared modules in various combinations and permutations. Even though various features or elements of functionality may be individually described or claimed as separate modules, one of ordinary skill in the art will understand that these features and functionality can be shared among one or more common software and hardware elements, and such description shall not require or imply that separate hardware or software components are used to implement such features or functionality.
While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not of limitation. Likewise, the various diagrams may depict an example architectural or other configuration for the invention, which is done to aid in understanding the features and functionality that can be included in the invention. The invention is not restricted to the illustrated example architectures or configurations, but the desired features can be implemented using a variety of alternative architectures and configurations. Indeed, it will be apparent to one of skill in the art how alternative functional, logical or physical partitioning and configurations can be implemented to implement the desired features of the present invention. Also, a multitude of different constituent module names other than those depicted herein can be applied to the various partitions. Additionally, with regard to flow diagrams, operational descriptions and method claims, the order in which the steps are presented herein shall not mandate that various embodiments be implemented to perform the recited functionality in the same order unless the context dictates otherwise.
Although the invention is described above in terms of various exemplary embodiments and implementations, it should be understood that the various features, aspects and functionality described in one or more of the individual embodiments are not limited in their applicability to the particular embodiment with which they are described, but instead can be applied, alone or in various combinations, to one more of the other embodiments of the invention, whether or not such embodiments are described and whether or not such features are presented as being a part of a described embodiment. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments.
Terms and phrases used in this document, and variations thereof, unless otherwise expressly stated, should be construed as open ended as opposed to limiting. As examples of the foregoing: the term “including” should be read as meaning “including, without limitation” or the like; the term “example” is used to provide exemplary instances of the item in discussion, not an exhaustive or limiting list thereof; the terms “a” or “an” should be read as meaning “at least one,” “one or more” or the like; and adjectives such as “conventional,” “traditional,” “normal,” “standard,” “known” and terms of similar meaning should not be construed as limiting the item described to a given time period or to an item available as of a given time, but instead should be read to encompass conventional, traditional, normal, or standard technologies that may be available or known now or at any time in the future. Likewise, where this document refers to technologies that would be apparent or known to one of ordinary skill in the art, such technologies encompass those apparent or known to the skilled artisan now or at any time in the future.
The presence of broadening words and phrases such as “one or more,” “at least,” “but not limited to” or other like phrases in some instances shall not be read to mean that the narrower case is intended or required in instances where such broadening phrases may be absent. The use of the term “module” does not imply that the components or functionality described or claimed as part of the module are all configured in a common package. Indeed, any or all of the various components of a module, whether control logic or other components, can be combined in a single package or separately maintained and can further be distributed in multiple groupings or packages or across multiple locations.
Additionally, the various embodiments set forth herein are described in terms of exemplary block diagrams, flow charts and other illustrations. As will become apparent to one of ordinary skill in the art after reading this document, the illustrated embodiments and their various alternatives can be implemented without confinement to the illustrated examples. For example, block diagrams and their accompanying description should not be construed as mandating a particular architecture or configuration.
This application claims the benefit of U.S. Provisional Application No. 61/271,954 filed Jul. 29, 2009.
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