Patent Application
20100127299
The present invention relates to illumination systems that utilize light emitting diodes (“LEDs”) to provide light, and more specifically to LED illumination systems that incorporate active cooling, so the LEDs operate in a favorable temperature range.
LEDs offer benefits over incandescent, high energy discharge (“HID”) and fluorescent lights as sources of illumination. Such benefits include high energy efficiency and longevity. To produce a given output of light, an LED consumes less electricity than an incandescent or a fluorescent light. And, in general, the LED will last longer before failing.
The level of light that a typical LED outputs depends upon the amount of electrical current supplied to the LED and the operating temperature of the LED. Thus, the intensity of light emitted by an LED changes when electrical current is constant and the LED's temperature varies and when electrical current varies and temperature remains constant. Operating temperature also impacts the usable lifetime of most LEDs. Accordingly, an LED typically has a temperature range that can sustain efficient operation for many years without failure.
The conventional technologies available for maintaining an LED at a desired operating temperature are generally limited. Conventional technologies frequently involve inefficient manufacturing procedures, can be costly to implement, are often inflexible, and may lack sufficient finesse for maintaining an LED at optimal operating conditions.
Accordingly, to address these representative deficiencies in the art, what is needed is an improved technology for operating an LED at a desired temperature or within a specified range of temperatures. Moreover, a need exists for applying temperature control or thermal regulation to an LED in a manner that supports cost-effective manufacturing. Such need encompasses not only product architectures that promote manufacturability, but also processes for fabrication and manufacturing. Another need exists for processes and designs that tightly integrate thermal regulation or cooling with an LED. Yet another need exists for efficiently removing heat generated by an LED. Still another need exists for attaching a cooling circuit and an LED drive circuit to one substrate, for example to reduce size, to control cost, to minimize manufacturing steps, or to improve flexibility. A capability addressing one or more of the aforementioned needs, or some similar want in the field, would advance LED lighting.
In one aspect of the present invention, a lighting system, apparatus, or device can comprise one or more LEDs. The LEDs can emit or produce visible light, for example light that is white, red, blue, green, purple, violet, yellow, multicolor, etc. Thus, the light can have a wavelength or frequency that a typical human being can perceive visually. Furthermore, the emitted light can have spectral content invisible to a human observer, for example in an ultraviolet or near-ultraviolet spectral range. The emitted light can comprise photons, luminous energy, electromagnetic waves, radiation, or radiant energy.
In addition to one or more LEDs, the lighting system can comprise a system that thermally regulates or controls at least one LED, for example via cooling or extracting heat from the LED. Accordingly, a thermal regulation system can provide the LED with a temperature or a thermal condition that benefits the LED's operation, for example enhancing efficiency, reducing risk of failure, providing desirable spectral content, or extending the LED's useful life.
The thermal regulation system can comprise a substrate, at least part of which is electrically insulative (or inhibits flow of electricity) and is thermally conductive (or promotes heat transfer). The term “substrate,” as used herein, generally refers to a material, or an integrated combination of materials, upon which circuits, circuit elements, LEDs, conductors, or components that are electrical (or optical, semiconductor, electronic, etc.) can be mounted. A substrate can comprise a plate, wafer, sheet, or material having at least one flat surface, to name a few possibilities. Moreover, a substrate can comprise a base material that is coated, plated, layered, deposited, or filmed with another material. The base material can comprise an electrically insulating material, while the coating can comprise a metallic plating, for example. Candidate base materials for the substrate of the thermal regulation system can comprise ceramic, alumina, aluminum oxide, aluminum nitride, boron nitride, diamond, silicon dioxide, or some other inorganic substance (not an exhaustive list). As an alternative to applying a coating on the base material, the substrate can be uncoated.
An electrical circuit that cools the substrate can be attached to one side (or face) of the substrate. That cooling electrical circuit can comprise at least two different materials, which may be dissimilar metals or semiconductors, cooperatively extracting heat from the substrate in response to a flow of electricity. The cooling electrical circuit, which can be viewed as a type of heat pump, can cool via thermal electric (“TE”) cooling or via the Peltier effect, for example. One of the two different materials, or some other portion of the cooling electrical circuit that conducts electricity, can adjoin, contact, or touch that side of the substrate.
The LED can be mounted to another side (or face) of the substrate (e.g. opposite the electrical cooling circuit), for example via soldering to a metal overcoat. In this configuration, the substrate can provide an electrical barrier or electrical insulation between the cooling electrical circuit and another circuit that supplies electrical power to the LED. Meanwhile, the substrate can exhibit low thermal resistance to provide sufficient transmission of heat or thermal conductivity. Via low thermal resistance, the cooling effect of the cooling circuit reaches the LED, and the LED can be cooled efficiently. That is, heat generated by the LED can transmit preferentially through the substrate to facilitate active heat removal by the cooling electrical circuit.
The discussion of cooling or thermally regulating LEDs presented in this summary is for illustrative purposes only. Various aspects of the present invention may be more clearly understood and appreciated from a review of the following detailed description of the disclosed embodiments and by reference to the drawings and the claims that follow. Moreover, other aspects, systems, methods, features, advantages, and objects of the present invention will become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such aspects, systems, methods, features, advantages, and objects are to be included within this description, are to be within the scope of the present invention, and are to be protected by the accompanying claims.
Many aspects of the invention can be better understood with reference to the above drawings. The elements and features shown in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of exemplary embodiments of the present invention. Moreover, certain dimensions may be exaggerated to help visually convey such principles. In the drawings, reference numerals designate like or corresponding, but not necessarily identical, elements throughout the several views.
An exemplary embodiment of the present invention supports operating an LED under conditions that provide efficient or reliable illumination. The LED can be mounted, for example via soldering, solder bumps, or bonding, to a surface of a generally flat piece of material, such as a plate or a sheet of ceramic material. The term “plate”, as used herein, generally refers to a piece or body of material having at least one side or area that is approximately flat or planar, and the term can encompass a piece of material that incorporates layered or laminated structures. Thus, the mounted LED can adjoin, contact, or touch the generally flat piece of material. An electrical circuit for removing heat generated by the LED can also adjoin, contact, or touch the generally flat piece of material, for example on a surface that is opposite the LED. The electrical circuit can comprise one or more components that cool the generally flat piece of material when the circuit is energized.
A lighting fixture will now be described more fully hereinafter with reference to
The invention can be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those having ordinary skill in the art. Furthermore, all “examples” or “exemplary embodiments” given herein are intended to be non-limiting, and among others supported by representations of the present invention.
Turning now to
The term “luminaire”, as used herein, generally refers to a system for producing, controlling, and/or distributing light for illumination. A luminaire can be a system that outputs or distributes light into an environment so that people can observe items in the environment. Such a system could be a complete lighting unit comprising one or more LEDs; sockets, connectors, or receptacles for mechanically mounting and/or electrically connecting components to the system; optical elements for distributing light; and mechanical components for supporting or attaching the luminaires Luminaires are sometimes referred to as “lighting fixtures” or as “light fixtures.” A lighting fixture that has a socket for a light source, but no light source installed in the socket, can still be considered a luminaires That is, a lighting system lacking some provision for full operability may still fit the definition of a luminaires
As discussed in further detail below, the LEDs 175 are mounted on a ceramic substrate 125 that is printed with electrical connections 130 and/or other electrical circuitry features that provide electrical power to the LEDs 175. In addition to functioning as and LED circuit board, the ceramic substrate 125 is also an element of a thermal electric cooler (“TEC”) 150. In terms of composition, the substrate 125, as well as the substrate 120 can comprise alumina, aluminum nitride, boron nitride, diamond, ceramic materials, etc.
The term “ceramic” or “ceramic material”, as used herein, generally refers to an article or material comprising a crystalline or partially crystalline structure or glass that is produced from substantially inorganic, non-metallic substances and is either formed from a molten mass which solidifies on cooling, or is formed and simultaneously or subsequently matured by action of heat. Such non-metallic substances can comprise metal oxides, for example. A ceramic material can have a glazed or unglazed surface. A ceramic article having a coating of a pure metal or some other non-ceramic material would still be a ceramic article. By way of example, ceramic materials can comprise aluminum oxide, alumina, aluminum nitride, barium titanate, bismuth strontium calcium copper oxide, boron carbide, boron nitride, ferrite, lead zirconate titanate, magnesium diboride, sialons, silicon carbide, silicon nitride, steatite, magnesium silicate, titanium oxide, yttrium barium copper oxide, zinc oxide, zirconium dioxide, zirconia, etc.
Referring to
As an optional feature, the lighting system 100 comprises two holes 115 extending through the TEC to facilitate mounting in a luminaire or some other lighting fixture or device. Each hole 115 can receive a fastener, such as a screw, that attaches to the luminaires
The TEC 150 receives electricity via the connectors 105, 110, one comprising a positive lead and the other comprising a negative lead. In an exemplary embodiment, the connectors 105, 110 provide mechanical support in addition to electricity. The connectors 105, 110 can be rigidly attached to the TEC 150. In this configuration, the connectors 105, 110 can plug into a female receptacle of a luminaire so the mounting holes 115 can be optional. Alternatively, the connectors 105, 110 can be flexible leads, wires, or pigtails that are coupled to an electrical supply line.
In the exemplary embodiment that
In an alternative exemplary embodiment, the connectors 105, 110 can provide electrical power to both the TEC 150 and the LEDs 175. In this situation, the contact pads 130 can be optional. Accordingly, in one exemplary embodiment, the connectors 105, 110 provide essentially full electrical and mechanical support for mounting and operating the lighting system 100 in a luminaire or some other support structure.
Turning now to
Although the cross sectional view of
The cooling power supply 235 supplies direct current (“DC”) voltage and current to a network or series of members, semiconductors, or conductors (also referred to as “TE elements” 210, 215 and interconnect 220) that cool the substrate 125 and the LEDs 175 attached thereto when electrically energized. The cooling circuit 250 comprises a system or circuit 250 of TE elements 210, 215 that extract heat from the substrate 125 to provide a beneficial thermal environment for the LEDs 175. The circuit 250 is referred to herein as a “TE circuit”. The TEC 150 can function in a capacity of an active heat pump.
The TE elements 210, 215 can respectively comprise two different materials or dissimilar metals that are in the electricity's path. The cooling power supply 235 provides a voltage differential across the two TE elements 210, 215 of dissimilar metals, causing a temperature differential that is similar to operating a thermal couple in reverse. In an exemplary embodiment, the temperature differential is a result of the Peltier effect, Peltier cooling, Peltier-Seebeck cooling, or a thermal electric effect. The TEC 150 typically comprises numerous junctions between dissimilar metals. Those junctions are electrically in series with one another and thermally in parallel with one another. As an alternative to having an intervening conductor 220 disposed between the two dissimilar metals as shown in
As an alternative to dissimilar or different metals, the TE circuit 250 can provide thermal regulation via semiconductor-based cooling. The TE elements 210, 215 can respectively be N- and P-type semiconductors with high Seeback coefficients, high thermal conductivity, high figure or merit, and/or low thermal resistance. The TE elements can comprise bismuth telluride, lead telluride, silicon germanium, or cobalt lead (not an exhaustive list). In one embodiment, the semiconductor materials can be layered in thin-films to create micro-sized devices that enhance cooling density without sacrificing cooling capacity.
In the illustrated exemplary embodiment, the TE elements 210, 215 are attached to electrical interconnects 220 that attach to the substrates 120, 125. In exemplary embodiments, the electrical interconnects 220 comprise metallic materials plated, coated, deposited, layered, or filmed on the substrates 120, 125. For example, the full surfaces 201, 208 of the substrates 120, 125 facing the TE circuit 250 can be plated. Following plating, acid etching can selectively remove regions of the plating so the electrical interconnects 220 remain. The TE members 210, 215 can then be attached, for example via welding, soldering, or bonding, to the patches of interconnect material layer that remain. Via such a process, the TE circuit 250 is in electrical and physical contact with the substrates 120, 125. More specifically, the TE circuit 250 touches and contacts the substrate surface 201, both physically and electrically. In one exemplary embodiment, physical and electrical contact results from urging or pressing the TE elements 210, 215 to the electrical interconnects 220, without necessarily incorporating permanent bonding.
In another exemplary embodiment, the TE circuit 250 can be formed as a separate structure that is attached to the substrates 120, 125. More specifically, a series network can be fabricated by welding, bonding, or otherwise attaching the TE elements 210, 215 to the interconnection elements 220, thus forming a stand-alone structure. That structure, which comprises the TE circuit 250, can be sandwiched between the two substrates 120, 125. The TE circuit 250, so formed, can be bonded, glued, welded, soldered, or otherwise attached (chemically, metallically, via heat, etc.) to the substrates 120, 125. Accordingly, the TE circuit 250 can adjoin, contact, or touch the substrates 120, 125 and specifically the substrate surface 201. Electricity flowing in the TE circuit 250 can thereby adjoin, contact, or touch each of the substrates 120, 125, and the substrates 120, 125 can electrically insulate the TE circuit 250. The electrical insulation of the substrate 120 prevents electrical shorting or unwanted/uncontrolled flow of electricity while providing thermal conductivity to improve TEC efficiency and to lower the junction temperature of the LEDs 175.
The heatsink 205 dissipates heat that the TEC 150 draws from the substrate 125 and the LEDs 175. A system of fins, channels, or grooves 203 comprises open areas through which air flows and circulates to promote convection. In an exemplary embodiment, the heatsink 205 can be made of aluminum or another metal with reasonably high thermal conductivity. In certain exemplary embodiments, the heatsink 205 comprises one or more heat pipes, a water cooler, or some other appropriate heat management system.
The outer surface 200 of the substrate 125, opposite the surface 201, comprises facilities for attaching the LEDs 175 thereto. In one exemplary embodiment, that surface 202 comprises pads 202 to which LEDs 175 are attached. In an exemplary embodiment, the pads 202 comprise a metal plating, coating, or layer. The material of the pads 202 can comprise copper, nickel, silver, gold, etc. In one embodiment, the surface 200 comprises a coat of nickel or other material that promotes adherence of a copper film to the substrate 125. The pads 202 can, in other words, comprise multiple layers of metal or other materials to support adhesion, bonding, etc.
The LEDs 175 can be soldered, bonded, or attached with electrically conductive adhesive, for example. With the LEDs 175 in “die” form, the die-to-substrate attachments and electrical connections can be implemented with eutectic bonds. The material of the eutectic bonds can comprise bismuth tin or some other material that supports low-temperature bonding. Epoxies can also be used to die bond the LED 175 to the substrate 125.
In addition to the pads 202, the surface 200 comprises electrical conductors in the form of electrical traces 275 that feed or provide electricity to the LEDs 175. The feed traces 275 can be defined via photolithography or via essentially any other known process or procedure for imprinting a surface with electrical conductors or elements.
The LEDs 175 are wirebonded to the feed trace 275 via one or more microwires 204. Wirebonding typically involves soldering each microwire, which can comprise gold, aluminum, or copper, for example. In certain exemplary embodiments, the LEDs 175 can be attached via flip-chip assembly.
The LEDs 175 of the lighting system 100 comprise semiconductor diodes emitting incoherent light when electrically biased in a forward direction of a p-n junction. In an exemplary embodiment, each LED 175 emits blue or ultraviolet light, and the emitted light excites a phosphor that in turn emits red-shifted light. The LEDs 175 and the phosphors emit blue and red-shifted light that essentially matches blackbody radiation and may approximate or emulate incandescent light to a human observer. In one exemplary embodiment, the LEDs 175 and their associated phosphors emit substantially white light that may seem slightly blue, green, red, yellow, orange, or some other color ting or tint. Exemplary embodiments of the LEDs 175 in the system 100 can comprise indium gallium nitride (“InGaN”) or gallium Nitride (“GaN”) for emitting blue light.
In an alternative embodiment, the system 100 can comprise LEDs 175 that individually produce distinct colors of light while collectively producing substantially white light or light emulating a blackbody radiator. Some of the LEDs 175 can produce red light, while others produce, blue, green, orange, or red, for example.
In certain exemplary embodiments, the lighting system 100 is controlled via RGB (Red-Green-Blue) and/or tri-stimulus methodology to create white or off-white light shifted to provide desired colors. For example, the lighting system 100 can support a range of desired colors, decorative lighting effects, theatrical light, or architectural aesthetics (not an exhaustive list). Furthermore, the lighting system's LEDs 175 can be controlled to provide color shifts for biological purposes, such as in support of day/night cycles.
In one exemplary embodiment, active and passive electrical circuit components can be attached to the surface 200 in addition to the LEDs 175. For example, resistors, amplifiers, LED drivers, transistors, operational amplifiers, power supplies, sensors (including the sensor 405 illustrated in
In one exemplary embodiment, optically transparent or clear material encapsulates the LEDs 175, either individually or collectively. Thus, one body of optical material can encapsulate the full LED array 175 illustrated in
Turning now to
In one exemplary embodiment, the TEC 150 of
In an alternative exemplary embodiment, the feed traces 275 and LEDs 175 are applied to the surface 200 of the substrate 125 prior to integrating an active cooling capability to the substrate 200. Then, the TEC 150 is created from the substrate assembly.
Commercial suppliers of TEC components suitable for including in exemplary embodiments of the lighting system 100 and/or the TEC 150 include Custom Thermoelectic of Bishopville, Md.; Ferrotec (USA) Corporation of Santa Clara, Calif.; and Marlow Industries, Inc. of Dallas Tex.
Turning now to
In one exemplary embodiment, the sensor 405 detects the level or intensity of light emitted by the LEDs 175, and the feedback loop 410 controls the TEC 150 to maintain LED intensity at a target level. In another exemplary embodiment, the sensor 405 detects the spectral content or color of the emitted light and adjusts the TEC 150 accordingly. Accordingly, the sensor 405 can comprise a simple light detector, an intensity meter, or a spectrometer. In one exemplary embodiment, the sensor 405 mounts on or otherwise attaches to the surface 125.
In one exemplary embodiment, the feedback loop 410 feeds a temperature target (or “setpoint”) to the cooling power supply 235, and the cooling power supply 235 supplies sufficient electricity to maintain the LEDs 175 at the target temperature. In an alternative exemplary embodiment, the feedback loop 410 adjusts the electrical output of the cooling power supply 235 based on sensed light, without direct temperature feedback.
In either case, the sensor 405 provides the feedback controller 415 with information about performance or operating status of the LEDs 175. In one exemplary embodiment, the feedback controller 415 comprises a proportional-plus-integral-plus-derivative (“PID”) controller, which may be based on digital or analog circuitry. In one exemplary embodiment, the feedback controller 415 comprises a proportional-plus-integral (“PI”) controller, implemented via digital logic or an analog circuit. In one exemplary embodiment, the feedback controller 415 comprises a computer or microprocessor that controls the lighting system 100 according to programming instructions stored in memory.
The feedback controller issues instructions or prompts to the cooling power supply 235 that adjust the amount of electricity (e.g. current and/or voltage) delivered to the TEC 150. The electrical adjustments control the temperature of the LEDs 175 so the LEDs operate in a temperature region that provides power efficiency and long life.
Dynamically controlling or regulating the operating temperature of the LEDs 175 can further compensate for variations in the LED power supply 420. For example, a user may dim the LEDs 175 via modulating the time duration of current pulses delivered by the LED power supply 420 to the LEDs 175, in a process that can be described as “pulse width modulation”. The dimmed LEDs 175 generate less heat than they would at their full brightness. The feedback controller 415 adjusts the amount of heat extracted from the substrate 200 so the LEDs 175 continue to operate in favorable temperature conditions. Accordingly, the feedback controller 415 can compensate for changes in the LEDs 175, whether such changes are due to user adjustments, aging of the LEDs 175, ambient light, random fluctuations in the LED power supply 420, environmental influences due to seasonal or other changes, or some other variation.
Turning now to
As discussed above, one exemplary method for fabricating the lighting system 100 comprises attaching circuitry, for example the contact pads 130, the feed traces 275, and the mounting pad 202, on top of a previously constructed TEC 150. However, process 500 offers an alternative approach. Exemplary process 500 proceeds via first applying such circuitry to a ceramic substrate 125 and then applying an active cooling capability to the circuit-substrate assembly.
At step 505, an electrical or electronic circuit is printed on or otherwise added to the ceramic substrate 125, typically as a separate sheet or plate of ceramic material.
In an exemplary embodiment of step 505, a manufacturer or a fabricator procures a flat piece of ceramic material that is suitable stock for creating a ceramic circuit board. To facilitate making multiple lighting systems 100, the flat piece of ceramic material can comprise a ceramic wafer large enough to yield multiple lighting system substrates 125.
The fabricator plates one side of the ceramic stock with a conductive material such as copper, gold, silver, etc. An application of photoresist, or other material that responds to light, readies the stock for photolithography and etching. An engineer creates a circuit layout using circuit-design software executing on a personal computer. The personal computer exports the circuit layout to a photolithographic system. The photolithographic system projects the circuit image (or a negative thereof) onto the metal-plated stock and the photoresist coating. Typically, the system projects multiple images, displaced from one another, onto the ceramic stock.
Submerging the ceramic stock in an acid bath etches selective areas of metal plating according to the projected images. When etching completes, the desired circuit pattern remains, in a metallic pattern. A solvent wash removes residual photoresist. Multiple instances of the desired circuitry are thereby patterned onto one wafer of the ceramic stock.
Dicing the stock, for example with a diamond saw, between each circuit pattern yields multiple copies of the desired circuit. Accordingly, one large wafer of ceramic stock produces numerous circuits. Each patterned piece of ceramic or “die” can be the substrate 125 incorporating the circuit patterns 130, 275, 202.
At step 510 of process 500, the fabricator attaches one or more LEDs 175 to each patterned ceramic substrate 200. As discussed above with reference to
At step 515, the fabricator attaches TE circuit 250, including the TE elements 210, 215, to each ceramic substrate 125, specifically on the side 201 opposite from the LEDs 175. As discussed above, exemplary procedures for making this attachment can comprise soldering, gluing, applying ceramic adhesives or refractory bonding agents, welding, etc.
At step 520, the fabricator attaches another ceramic substrate 120 to each TE circuit 250, with the TE circuit sandwiched between the two ceramic substrates 120, 125. This attachment can comprise applications of glue, ceramic adhesive, solders, brazes, or fasteners, for example. In one exemplary embodiment, the TE circuit 250 is pressed between the two ceramic substrates 120, 125 with compression force holding the assembly together. Thus, one or more mechanical fasteners hold the assembly together without glues or adhesives.
At step 525, the fabricator attaches the heatsink 205 to each ceramic substrate 120 opposite from the TE circuit 250. A intermediate layer of thermally conductive adhesive, thermal interface material (“TIM”), tape, or material can promote thermal transfer from the ceramic substrate 120 to the heatsink 205.
Process 500 ends following step 525. Via processing the substrates in batches, particularly at step 505, process 500 yields numerous copies of the system 100 with a high level of manufacturing efficiency.
Turning now
At step 605 of process 600, the cooling power supply 235 delivers electrical power to the TEC 150. In response to the electrical power, the TEC 150 actively extracts heat from the substrate 125, effectively reducing the temperature of the substrate 125 and the LEDs 175 attached thereto. As discussed above, the heat extraction can comprise pumping heat, TE cooling, utilizing Peltier cooling, passing electricity through semiconductor materials that produce a cooling effect, or some other means for actively removing heat known in the art.
At step 610, the LED power supply 420 delivers electrical current to the LEDs 175 via circuit traces (for example the contact pads 130) printed on the surface 200 at step 505 of process 500. The current can be pulsed or continuous and can be pulse width modulated to support user-controlled dimming. In response to the applied current, the LEDs 175 emit or produce substantially white light or some color of light that a person can perceive. As discussed above, in one exemplary embodiment, at least one of the LEDs 175 produces blue or ultraviolet light that triggers photonic emissions from a phosphor. Those emissions can comprise green, yellow, orange, and/or red light, for example.
In response to the environmental conditions provided by the TEC 150, the LEDs 175 operate efficiently and avoid premature failure. In an exemplary embodiment, the mean time before failure or average life of the LEDs 175 can exceed 50,000 hours in the thermal conditions provided by the TEC 150.
At step 615, the sensor 405 detects a portion of the light the LEDs 175 emit. In an exemplary embodiment, the sensor 405 determines light intensity from the LEDs 175 or light intensity in the vicinity of LEDs 175. The sensor 405 feeds an electrical signal carrying the intensity information to the feedback controller 415.
As an alternative to light intensity, the sensor 405 can detect another parameter that provides operational feedback about the LEDs 175. In certain exemplary embodiments, the sensor 405 comprises an RTD, a thermistor, a thermocouple, or some other means for measuring or assessing temperature of the LEDs 175. In certain exemplary embodiments, the sensor 405 comprises a component measuring a voltage associated with the LEDs 175 to provide an indication of operational state, temperature, performance, etc. of the LEDs 175. For example, the sensor 405 can sense a secondary voltage Vf of the LEDs 175 as an indication of the LEDs' operational temperature.
At step 620, the feedback controller 415 prompts the cooling power supply 235 to output electrical power to the TEC 150 according to the sensor input. When ambient temperature drops in the winter, for example, the cooling power supply 235 may decrease the power output to compensate for increased ambient cooling. Similarly, the feedback controller 415 can set the cooling power supply 235 to compensate for age-related degradation, changes in the electrical characteristics of the power supply 420, failure of one or more LEDs 175, chromatic changes, etc.
More generally, at step 620, the feedback control loop 410 regulates or manipulates the temperature of the LEDs 175 so that the LEDs 175 operate within a particular band of thermal conditions, despite fluctuating conditions, random events, and various perturbations.
Process 600 ends following step 620. In an exemplary embodiment, the LEDs 175 provide efficient illumination for many years.
Technology for cooling an LED of an illumination system, for fabricating an illumination system that comprises a cooled LED, and for operating such an illumination system has been described. From the description, it will be appreciated that an embodiment of the present invention overcomes the limitations of the prior art. Those skilled in the art will appreciate that the present invention is not limited to any specifically discussed application or implementation and that the embodiments described herein are illustrative and not restrictive. From the description of the exemplary embodiments, equivalents of the elements shown therein will suggest themselves to those skilled in the art, and ways of constructing other embodiments of the present invention will appear to practitioners of the art. Therefore, the scope of the present invention is to be limited only by the claims that follow.
