Abstract:
A light emitting device can comprise a light emitter for emitting light at a defined light intensity and circuitry connecting a power source to the light emitter. The circuitry can adjust power provided to the light emitter over time to compensate for inefficiencies due to circuit and light emitter degradation. A more consistent light intensity of the emitted light over a life of the light emitting device and an improved life expectancy of the light emitter can be achieved than what would result if the power was not adjusted over time to offset degradation effects.

Description:
BACKGROUND 
     The present invention relates to the field of lighting and, more particularly, to using individual cluster-level power regulation circuits to extend light-emitting diode (LED) light life. 
     Recent trends have made it commonplace to replace energy-inefficient incandescent and fluorescent light bulbs with energy-efficient light-emitting diode (LED) bulbs. The benefits of LED light bulbs include low energy consumption, long life, low heat production, slow failure, and the ability to be quickly cycled on and off. The life of an LED light is affected by environmental variables like temperature and operational variables like current and voltage. These variables are often difficult to control, particularly in large indoor spaces (i.e., industrial lighting) or outdoor spaces (i.e., streetlights) and systems where the LED lights have been retrofitted. 
     Heat sinks are generally used to address the issue of temperature fluctuations, while power conversion and/or regulation circuitries are used to control power fluctuations. However, conventional power regulation approaches address the LED light as a whole. This approach is insufficient for high-powered LED light fixtures that support multiple, distinct clusters or arrangements of LEDs like those taught in U.S. Patent Application GTL12001. 
     The conventional approach assumes that the LED arrangements are identical in composition (e.g., quantity of LEDs) as well as usage. Such an approach would drastically decrease the overall performance of the LED light fixtures described in U.S. Patent Application GTL12001. That is, the power regulation for an LED arrangement having seven LEDs will be different than the power regulation for an LED arrangement having three LEDs. Treating these LED arrangements identically, in terms of power regulation, will affect the performance of the LEDs of the arrangements. 
     BRIEF SUMMARY 
     One aspect of the present invention can include a light emitting device comprising a light emitter for emitting light at a defined light intensity and circuitry connecting a power source to the light emitter. The circuitry can adjust power provided to the light emitter over time to compensate for inefficiencies due to circuit and light emitter degradation. A more consistent light intensity of the emitted light over a life of the light emitting device and an improved life expectancy of the light emitter can be achieved than what would result if the power was not adjusted over time to offset degradation effects. 
     Another aspect of the present invention can include a method where a light emitting device can adjust power supplied to a light emitter over time to compensate for circuit degradation effects. A more consistent light intensity of the emitted light over a life of the light emitting device can be achieved than what would result if the power was not increased over time to offset circuit degradation effects. 
     Yet another aspect of the present invention can include a method for independently regulating current to LED clusters. Such a method can begin when a control signal is received by a master power controller to activate one or more LED clusters of an LED light fixture. Each LED cluster can be comprised of multiple LEDs electrically connected in series and arranged in a circular configuration. The master power controller can provide a power signal to the power regulation circuit of each LED cluster. The provided power signal can be adjusted over time by the power regulation circuit of each LED cluster to compensate for circuit degradation effects. A more consistent light intensity of the emitted light over a life of the light emitting device can be achieved than what would result if the power was not increased over time to offset circuit degradation effects. The LED cluster can then be powered with the adjusted power signal. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating a light-emitting diode (LED) light fixture that utilizes cluster-level power regulation circuits in accordance with embodiments of the inventive arrangements disclosed herein. 
         FIG. 1A  is a graph illustrating LED degradation over time. 
         FIG. 1B  is a graph illustrating the decrease in LED light output as a result of degradation and aging over time. 
         FIG. 1C  is a graph illustrating the current provided by the power regulation circuit to compensate for degradation over time. 
         FIG. 1D  is a graph illustrating the LED output over time as a result of the compensation provided by the power regulation circuit. 
         FIG. 2  is a block diagram illustrating the components of the cluster-level power regulation circuit in accordance with an embodiment of the inventive arrangements disclosed herein. 
         FIG. 3  is a circuit diagram for a sample topology for a portion of the power regulation circuit in accordance with an embodiment of the inventive arrangements disclosed herein. 
         FIG. 3A  is a circuit diagram of the high-side current sense circuit. 
         FIG. 3B  is a detailed example of the power regulation circuit that can be used to implement an energy savings program for an LED light. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention discloses a power regulation circuit that can automatically and dynamically compensate for degradation experienced over time by the LED light. The power regulation circuit can be implemented at the cluster-level to allow for individualized compensation in configurations where multiple LED lights are contained in the same fixture and may have different operating variables over time. The power regulation circuit can be configured to compensate for an optimum LED life and/or a specific level of luminance. 
     As will be appreciated by one skilled in the art, aspects of the present invention may be embodied as a system, method or. Accordingly, aspects of the present invention may take the form of an entirely hardware embodiment or an embodiment combining software (including firmware, resident software, micro-code, etc.) and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system”. Aspects of the present invention are described below with reference to flowchart illustrations and/or block diagrams of methods and/or apparatus (systems) according to embodiments of the invention. 
       FIG. 1  is a block diagram illustrating a light-emitting diode (LED) light fixture  100  that utilizes cluster-level power regulation circuits  120  in accordance with embodiments of the inventive arrangements disclosed herein. The LED light fixture  100  can be designed for high-power applications, indoor and/or outdoor, where luminance is desired at distances of 100 ft. or more. Example applications of the LED light fixture  100  can include, but are not limited to, streetlights, industrial (e.g., warehouse, factories, etc.) lighting systems, office lighting systems, sports stadiums, parking lots/garages, and the like. 
     The LED light fixture  100  can have a primary component comprised of a printed circuit board  105 . The printed circuit board  105  can be manufactured in accordance with standard methods that acceptable for use with LED technology. Components coupled to a surface of the printed circuit board  105  can include multiple LED clusters  110 , a master power controller  125 , and interface elements  130 . 
     In another contemplated embodiment, the LED light fixture  100  can have an alternate primary component to which multiple printed circuit boards  105  can be attached; each printed circuit board  105  can support an LED cluster  110 , while the master power controller  125  and interface elements  130  can be elements of the alternate primary component. 
     For example, the alternate primary component can be a plastic disc having receptacles in which the printed circuit board  105  of each LED cluster  110  can be placed. The disc can have openings for wiring and/or connection points (i.e., interface elements  130 ) for each LED cluster  110  to be connected to the master power controller  125  and/or other necessary elements. 
     The LED clusters  110  can be positioned upon the printed circuit board  105  in a predetermined configuration. Each LED cluster  110  can include multiple LEDs  115  and a power regulation circuit  120 . The arrangement of LEDs  115  in an LED cluster  110  can be detailed in U.S. Patent Application GTL12001. 
     The quantity of LED clusters  110  included in the LED light fixture  100  can vary based on intended application and/or design. Further, LED clusters  110  having different quantities of LEDs  115  can be incorporated onto the same printed circuit board  105 . That is, the LED clusters  110  contained on the printed circuit board  105  need not be homogenous. 
     The LEDs  115  of the LED cluster  110  can be produced in accordance with standard semiconductor manufacturing practices and can have characteristics (e.g., color, luminance, power consumption, size, etc.) applicable for the specific type of LED light fixture  100 . For example, LUXEON REBEL (LXML-PWC1-100) LEDs  115  can be used. 
     The power regulation circuit  120  can regulate the current received by the LEDs  115  of the LED cluster  110  from the master power controller  125  to compensate for LED  115  aging and/or environmental factors. The effect of aging and/or environmental factors can manifest within the operating parameters of the LED  115  and/or LED cluster  110  in various ways, as shown by the graphs  150  and  160  of  FIGS. 1A and 1B . Graph  150  can illustrate how the forward voltage  152  required by the LED  115  to operate can increase over time  154  due to circuit degradation and/or aging. As a result, the light output  162  of the LED  115  can decrease or dim over time  164 , as shown in graph  160 . 
     The power regulation circuit  120  can be designed to detect changes to the most common affected parameters like light output, temperature, and forward voltage. The compensation provided by the power regulation circuit  120  can be for optimizing the life of the LED cluster  110  and/or producing a constant level of luminance. For example, the forward voltage of the LEDs  115  can be 3.0 Vdc and can require a current of 700 mA to produce 4000 lumens. The power regulation circuit  120  can then adjust the voltage and/or current to maintain these parameter values. If the forward voltage needed for the LEDs  115  starts to decrease, over time, the power regulation circuit  120  can compensate by increasing the supplied voltage to compensate for the decrease, if better LED  115  life is desired, or by adjusting the current, if constant lumen output is desired. 
     Conventional power regulation circuits can typically only regulate one parameter (current or voltage) to a predetermined, fixed value. The power regulation circuit  120  of the present invention can provide better regulation and flexibility over conventional implementations. 
     Graphs  170  and  180  can show the effect of the compensation of the power regulation circuit  120 . Compensating for the increasing required forward voltage  152  shown in graph  150 , graph  170  can illustrate how the power regulation circuit  120  can correspondingly increase the current  172  it provides to the LED  115  over time  174 . Such compensation can then stabilize the light output  182  of the LED  115  over time  184  as shown in graph  180 , as opposed to the uncompensated curve shown in graph  160 . 
     Operation of the power regulation circuit  120  of each LED cluster  110  can be governed by the master power controller  125 . The master power controller  125  can be an electronic component that controls the power distributed to the power regulation circuits  120  of the LED clusters  110  from the power source  140 . 
     It is important to emphasize that the current supplied to the LEDs  115  of each LED cluster  110  can be individually adjusted to meet the needs of the specific LED cluster  110  regardless of the power supplied by the master power controller  125 , allowing optimal operation of the LEDs  115 . For example, the master power controller  125  can be configured to provide all LED clusters  110  with the same current. The power regulation circuit  120  can then adjust, increase or decrease, the current to achieve the appropriate voltage for the number of LEDs  115  in the LED cluster  110 . 
     This approach can allow for LED clusters  110  having different quantities of LEDs  115  to be incorporated into a LED light fixture  100  and driven by a single power signal. Conventional power regulation can be performed at the LED light fixture  100  level and would be unable to provide this granular level of control to support multiple LED clusters  110  of different types or LED  115  compositions. 
     Further, the conventional approach cannot provide adequate regulation for LED clusters  110  that have different usage times. For example, in a four-LED cluster  110  LED light fixture  100 , all four LED clusters  110  can be used when the LED light fixture  100  is “ON” and each pair of LED clusters  110  can be activated by separate motion sensors when the LED light fixture  100  is “OFF”. Thus, each pair of LED clusters  110  can accumulate different amounts of usage time, depending on how often each motion sensor is triggered. Over time, the LED clusters  110  that are more frequently activated can require more adjustment to the power signal by the power regulation circuit  120  to compensate for loss than the other pair of LED clusters  110 . 
     The interface elements  130  can represent a variety of items required to couple the printed circuit board  105  to other components like a heat sink  145 , attachment mechanism  135 , and power source  140 . For example, the attachment mechanism  135  can be coupled to the printed circuit board  105  via a housing using screws  130 . 
     A heat sink  145  can be used to dissipate excess heat generated by the LED clusters  110  as well as counteract heat from the external environment. This can be of particular importance due to the temperature-sensitivity of the LEDs  115  with respect to performance as well as the high-power nature of the application (i.e., more power tends to equal more heat). 
     The attachment mechanism  135  can represent the mechanical components require to affix the LED light fixture  100  to a desired physical location within an appropriate fixture or mounting surface. The attachment mechanism  135  can include elements that retrofit the LED light fixture  100  into existing, non-LED lighting systems. 
     The power source  140  can provide the LED light fixture  100  with power. The power source  140  can be a stand-alone element like a solar panel or battery, or can be a connection to a commercial power network. The power source  140  can be capable of providing the LED light fixture  100  with power in a specified operating range. 
       FIG. 2  is a block diagram illustrating the components of the power regulation circuit  200  in accordance with embodiments of the inventive arrangements disclosed herein. The power regulation circuit  200  can be utilized within the context of the LED light fixture  100  of  FIG. 1 . 
     The power regulation circuit  200  can include a logic controller  205 , high-side current sense circuit  210 , a metal-oxide semiconductor field effect transistor (MOSFET) switch  215 , an inductor  220 , a freewheeling diode  225 , and a ripple capacitor  230 . As the operation of these components is well known in the art, their specifics will not be discussed herein. 
     However, it should be noted that many conventional power regulation circuits lack a ripple capacitor  230 . The use of a ripple capacitor  230  in this improved power regulation circuit  200  can prevent high current switching noises from feeding back to the logic controller  205 . This feedback can be the source of poor current regulation and inconsistent performance in conventional power regulation circuits. 
       FIG. 3  is a circuit diagram  300  for a sample topology for a portion of the power regulation circuit in accordance with embodiments of the inventive arrangements disclosed herein. Circuit diagram  300  can be for illustrative purposes and is not meant as an exhaustive or limiting representation of the power regulation circuit. 
     The power regulation circuit of diagram  300  can be connected to the current high-side current sense circuit  340  of  FIG. 3A .  FIG. 3B  can illustrate a more detailed example  345  of the power regulation circuit that can be used to implement an energy savings program for the LED light. 
     In this example, the power regulation circuit of circuit diagram  300  can be used with an LED cluster of seven LUXEON REBEL (LXML-PWC1-100) LEDs. Power supply input  305  to the power regulation circuit can be 24V. The power supply input  305  can be connected to the appropriate pin (Vin) of the logic controller  205 . In this example, the logic controller  205  can be a hysteretic PFET controller for high power LEDs (LM3401MM). A 66.5 kΩ resistor  325  can be connected to the power supply input  305  and current limiting pin (ILIM) of the logic controller  205 . 
     An input capacitor  310  can be connected to the power supply input  305  and ground  335 . A 12.4 kΩ resistor  315  can be connected to the hysteresis pin (HYS) of the logic controller  205  and ground  335  to set the hysteretic limit. The ground pin (GND) of the logic controller  205  can also be connected to ground  335 . A separate dimmer input signal  320  can be connected to the dimmer pin (DIM) of the logic controller  205 , when dimmer functionality is implemented in the LED light fixture. 
     Activation of the LED cluster can be controlled by the output signal of the gate drive pin (HG) of the logic controller  205  and the MOSFET switch  215  (FDC5614P). When conditions for activating the LED cluster are met, current can flow out of the MOSFET switch  215  and onto the line  327  that connects to the current sensing pin (CS) of the logic controller  205  and the LED cluster. 
     The freewheeling diode  225  can be connected to line  327  and ground  335 . Line  327  can also include an 18 uH inductor  220 . Line  327  can then continue to the LED cluster with line  328  returning from the LED cluster. Line  328  can be connected to the current feedback pin of the logic controller  205 . A 220 nF ripple capacitor  230  can connect lines  327  and  328  to reduce noise feedback. A 0.22Ω resistor  330  can also be connected to line  328 . 
     The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems and/or methods according to various embodiments of the present invention. It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.