Thermoelectric cooling and/or moderation of transient thermal load using phase change material
Techniques described and illustrated herein can permit high luminous flux and/or longer lifetimes for a class of photoemissive device configurations and/or uses that generate intense highly localized, but transient heat flux. For example, certain Light Emitting Diode (LED) applications, e.g., for flash illumination, certain solid state laser configurations and other similar configurations and uses may benefit from the developed techniques. In particular, it has been discovered that by locating an amount of appropriate phase change material in close thermal proximity to such a photoemissive device, substantial generated heat fluxes may be “absorbed” into a phase transition of the phase change material. In some configurations, a thermoelectric is employed in conjunction with the phase change material. For example, the thermoelectric may at least partially define a heat transfer path from the photoemissive device to the phase change material. Similar configurations may be employed for photosensitive devices. In such configurations, the phase change material may effectively clamp one side (typically the hot side) of the thermoelectric as heat transferred across the thermoelectric is absorbed into the transition of at least some of the phase change material from a first state thereof to a second state. The thermoelectric may be transiently operated in substantial synchrony with operation of the photoemissive or photosensitive device to provide extremely high density spot cooling when and where desired.
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This application claims benefit of U.S. Provisional Application No. 60/621,382 entitled “TRANSIENT THERMOELECTRIC COOLING OF OPTOELECTRONIC DEVICES,” filed on Oct. 22, 2004.
In addition, this application is related to commonly-owned U.S. patent application Ser. No. ______ entitled “TRANSIENT THERMOELECTRIC COOLING OF OPTOELECTRONIC DEVICES,” and naming Uttam Ghoshal as inventor, filed on even date herewith, the entirety of which is incorporated herein by reference.
BACKGROUND1. Field of the Invention
The present invention relates to management of transient thermal loads, such as exhibited by some optoelectronic devices, and particularly to thermoelectric cooling and/or moderation of transient thermal loads using phase change material.
2. Related Art
Modern digital devices including consumer electronics increasingly employ optoelectronic devices. Digital cameras (as well as phones that include camera features) are good examples. Arrays of charge coupled devices (CCDs) or complementary metal oxide semiconductor (CMOS) sensors are used for image capture. In some devices, a flash may be employed, which may itself employ light emitting diodes (LEDs) or other technologies.
Individual elements of a CCD array convert energy from incoming light into electrons. The higher the intensity of incoming light (or the longer an element is exposed), the more free electrons an element accumulates. Of course, like most sensors, CCD's (and CMOS devices) are susceptible to noise because the materials and device structures exhibit a baseline level of electron “action” (or current). In sensors, this current is usually called dark current (the “dark” in the name implies that the current was formed without exposure to light). Dark current increases with temperature.
Sensitivity is typically limited by background noise. In general, smaller elements must tolerate higher noise for a given level of sensitivity. Accordingly, as higher and higher pixel densities are supported (often with smaller and smaller sensor elements), sensitivity and noise issues may become increasingly important. Efficient techniques for cooling arrays of optoelectronic sensors are therefore desired.
In addition to photosensitive devices, some photoemissive devices exhibit temperature sensitivity. For example, luminous flux and lifetime of white flash LEDs can be affected by operating temperatures. Most approaches to cooling flash LEDs and CCD have been limited to passive heat spreading packages. Unfortunately, it is difficult to increase the performance of white LEDs and CCDs with known passive methods. Alternative techniques are desired.
SUMMARYThe invented techniques described and illustrated herein can permit high luminous flux and/or longer lifetimes for a class of photoemissive device configurations and/or uses that generate intense highly localized, but transient heat flux. For example, certain Light Emitting Diode (LED) applications, e.g., for flash illumination, certain solid state laser configurations and other similar configurations and uses may benefit from the developed techniques. In particular, it has been discovered that by locating an amount of appropriate phase change material in close thermal proximity to such a photoemissive device, substantial generated heat fluxes may be “absorbed” into a phase transition of the phase change material.
Although particular phase change materials and particular phase transitions can vary from exploitation to exploitation, solid-liquid phase transitions exhibited in low-melt point solders or gallium confined in a nickel cavity are typically suitable for many of the optoelectronic device cooling implementations described herein. More generally, other endothermic phase transitions (whether solid-liquid, liquid-gas, solid-gas or solid-solid) of other materials may be exploited as long as transition temperatures, latent heats of transition and thermal conductivities of the materials are suitable for the heat fluxes involved and suitable material confinement/compatibility techniques are available.
In some configurations, a thermoelectric is employed in conjunction with the phase change material. For example, the thermoelectric may at least partially define a heat transfer path from the photoemissive device to the phase change material. Similar configurations may be employed for photosensitive devices. In such configurations, the phase change material may effectively clamp one side (typically the hot side) of the thermoelectric as heat transferred across the thermoelectric is absorbed into the transition of at least some of the phase change material from a first state thereof to a second state. The thermoelectric may be transiently operated in substantial synchrony with operation of the photoemissive or photosensitive device to provide extremely high density spot cooling when and where desired.
Alternatively (or additionally), phase change material may be disposed in close thermal proximity to the photoemissive device, absorbing substantial transient heat flux into the transition of at least some of the phase change material from a first state thereof to a second state. In this way, a phase change material (and an appropriate amount thereof) can be selected to absorb the transient heat flux generated or evolved by the photoemissive device, thereby avoiding large localized excursions in temperature of the device that may otherwise occur when the heat flux generated or evolved overwhelms conventional heat transfer pathways away from the photoemissive device. In some such configurations, the phase change material may be employed with a thermoelectric (e.g., between the photoemissive device and the thermoelectric). In some configurations, phase change material may be employed without a thermoelectric simply to moderate thermal transients generated by photoemissive device.
BRIEF DESCRIPTION OF THE DRAWINGSThe present invention may be better understood, and its numerous objects, features, and advantages made apparent to those skilled in the art by referencing the accompanying drawings.
The use of the same reference symbols in different drawings indicates similar or identical items.
DESCRIPTION OF THE PREFERRED EMBODIMENT(S)While not limited thereto, the invented techniques described and illustrated herein can permit high luminous flux and greater lifetimes for flash LEDs, and greater photon sensitivity and lower dark currents for CCD/CMOS imagers. Accordingly, we describe aspects of the inventive concepts in the context of configurations, optoelectronic devices, materials and heat fluxes typical of consumer electronics such as digital cameras and mobile phones that incorporate similar technologies. However, as more completely described herein, the invention is not limited to such exploitations.
In particular, the description that follows emphasizes exploitations of the present invention in which a light emitting diode, e.g., a white LED, or other photoemissive device is used in a flash mode of operation, e.g., as flash illumination to support digital imaging. In such exploitations, extremely high transient thermal flux can be generated. Particularly for white LEDs, quality of the luminance, including intensity and in some cases spectral characteristics may be affected by operating temperature of the LED. Furthermore, useful operating life of such LEDs can be adversely affected by operation at high temperatures. In addition, in typical exploitations for small form factor electronics, such as digital cameras, phones, etc., thermal sensitivity of other optoelectronic devices, e.g., CCD or CMOS imagers, RF electronics, etc may be adversely affected by thermal issues related to operation of such an LED.
Sensitivity and therefore performance of certain photosensitive devices such as CCD or CMOS imagers is typically limited by thermal background noise. In general, smaller or faster responding elements must tolerate higher levels of noise for a given level of sensitivity. Accordingly, as higher and higher pixel densities are supported (often with smaller and smaller sensor elements), sensitivity and noise issues become increasingly important. Efficient techniques for cooling arrays of optoelectronic sensors are desirable. Since many CCD or CMOS imagers (e.g., those employed for image capture) are operated intermittently, rather than continuously, transiently applied cooling power can be advantageously employed as described herein.
For these and other reasons, cooling of a white LED flash illuminator to overcome a transient thermal load (or moderation thereof) and/or transient cooling of a CCD or CMOS imager serve as a useful descriptive context for certain inventive concepts and designs. However, based on the description persons of ordinary skill in the art will appreciate other exploitations of the described techniques. Accordingly, without limitation on the scope of inventive concepts described and claimed herein, we now describe certain exemplary embodiments.
General Techniques
In some, though not all, embodiments in accordance with the present invention, we exploit two basic technologies. First, we use transient cooling properties of thermoelectric coolers to get large cooling powers and temperature differentials. For example, in some embodiments, a thermoelectric cooler for an illuminator or imager is operated in a generally synchronous manner with flash illumination or image capture. Peltier cooling provided by a typical thermoelectric cooler is nearly instantaneous, but evolution of Joule heat and its subsequent back flow to a cold end of the thermoelectric element is comparatively slow. As a result, the cooling power transiently delivered can be much higher than steady-state performance would suggest.
Thermoelectric devices and materials are well-known in the art and a wide variety of configurations, systems and exploitations thereof will be appreciated by those skilled in the art. In general, exploitations include those in which a temperature difference is developed as a consequence of a current or electromotive force (typically voltage) across an appropriate material, material interface or quantum structure. Often, such exploitations operate based on the Peltier effect. Peltier effects arise at interfaces between dissimilar conductive (or semiconductive) materials. However, more generally, other effects or actions may be similarly exploited, including related or similar effects (e.g., Thomson, quantum tunneling and thermoionic effects) in materials, at material interfaces or as a result of quantum scale confinement.
Accordingly, for purposes of the present description, the term “thermoelectric cooler” is meant in the broadest sense of the term in which current or electromotive force is traded for temperature difference across a thermoelectric module, couple, element, device, material etc, and therefore includes those thermoelectric cooler configurations which exploit Peltier effects, as well as those that operate based upon Thomson, quantum tunneling, thermoionic or other similar effect or combination of effects. That said, for clarity of description, we focus on Peltier-type thermoelectric coolers; however, based on such description, persons of ordinary skill in the art will appreciate applications of the described inventive concepts to devices and configurations in which other thermoelectric-type effects are employed.
Second, we employ a phase-change material. Phase-change material may be positioned at either the hot-end or the cooled-end (or both the hot-end and the cooled-end) of a thermoelectric module, couple, element, device, material etc. When positioned at the hot-end, the phase-change material effectively clamps the hot side temperature of the thermoelectric as heat transferred across the thermoelectric is absorbed into the transition of at least some of the phase change material from a first state thereof to a second state. Because the thermoelectric nearly instantaneously develops a temperature differential between cooled and hot sides thereof, if the particular phase change material and amounts thereof are appropriately selected in relation to operating temperatures and expected thermal flux, virtually all of the temperature change will be delivered as cold-side cooling. Typically, the thermoelectric is transiently operated in substantial synchrony with operation of the photoemissive or photosensitive device to provide extremely high density spot cooling when and where desired.
When positioned at the cooled-end (i.e., when positioned thermally between the photoemissive device and the thermoelectric), the phase-change material can effectively absorb a large transient heat flux generated or evolved by a photoemissive device, thereby avoiding large localized excursions in temperature of the device that may otherwise occur when the heat flux generated or evolved overwhelms a conventional heat transfer pathway away from the photoemissive device. The thermoelectric then acts as part of a heat transfer pathway away from the phase-change material, eventually reversing the phase change into which the large transient heat flux was absorbed. Because of the large heat capacity represented by a phase change, the thermoelectric need not be operated simultaneously (in a transient mode) with operation of the photoemissive device. Rather, the thermoelectric may be operated continuously or semicontinuously, e.g., at low power levels. Alternatively the thermoelectric may be operated intermittently at times that need not precisely correspond to operation of the photoemissive device. In this way, peak power requirements may be reduced for a system that includes both the thermoelectric and the photoemissive device.
In general, a thermoelectric cooler may be advantageously employed when the heat rejection thermal resistance (Rth) of the cooled device (e.g., an optoelectronic device alone or in combination with an attendant body of phase change material) is less than the product of the thermodynamic efficiency of the cooler (ε) and the operating temperature (Tg) of the optoelectronic device divided by the total power dissipation of the optoelectronic device (Q). In the case of a continuously operated thermoelectric cooler, this relation can be expressed as:
Rth<εTs/Q (1)
For example, if ε=0.1 for thermoelectric devices with ZT=1, Ts=330K (57° C.), and Q=1W, then thermoelectric cooling delivered by continuous operation of the thermoelectric will be beneficial if Rth<33 K/W.
In general, depending on the phase change material employed and on ambient conditions, embodiments that place phase change material at (in thermal communication with) a cooled-end of a thermoelectric may operate to restore the phase change material to a phase compatible with ambient conditions or may operate to pre-transition the phase change material to an appropriate phase state. For example, in some embodiments, a thermoelectric may operate to return (post photoemission) a liquid-phase phase change material to an ambient-stable, solid state. Furthermore, in some embodiments, a thermoelectric may operate to presolidify (prior to photoemission) an ambient-stable liquid-phase phase change material. In short, both post-chill and pre-chill realizations are possible.
Of course, in some exploitations, thermally decoupled amounts of phase-change material may be positioned at both ends of a thermoelectric, if desired. Similarly, a thermoelectric may be omitted in certain configurations wherein the large transient heat flux generated or evolved by a photoemissive device and absorbed by the phase-change material may be effectively dissipated using other active or passive mechanisms sufficient to reverse the phase-change prior to a next operation of the photoemissive device.
Although particular phase change materials and particular phase transitions can vary from exploitation to exploitation, solid-liquid phase transitions exhibited in low-melt point solders or gallium confined in a nickel cavity are typically suitable for many of the optoelectronic device cooling implementations described herein. In some embodiments, the phase-change material may include a dielectric thermal interface material. More generally, an endothermic phase transition (whether solid-liquid, liquid-gas, solid-gas or solid-solid) of other materials may be exploited as long as transition temperatures, latent heats of transition and thermal conductivities of the materials are suitable for the heat fluxes involved and suitable material confinement/compatibility techniques are available.
EXEMPLARY EMBODIMENTS
The photoemissive device 20 may be mounted on a separate board, or on the same printed wiring board 30, as shown in
In general, any of a wide variety of synchronization circuits or mechanisms may be employed. Suitable realizations of such synchronization circuits or mechanisms are typically application-specific and may constitute a matter of design choice. Indeed, suitable realizations of such synchronization circuits or mechanisms range from the sophisticated to the trivial. For example, many digital imaging exploitations in accordance with the present invention(s) may opportunistically exploit sophisticated programmable timing control facilities that may already be available to support the for the significantly more demanding timing requirements of shutter control, imager travel, auto focus processing, flash synchronization, etc. Alternatively, in some realizations, suitable synchronization may be provided simply as a byproduct of series or parallel coupling of current supply leads or paths for thermoelectric current and target device (e.g., LED) excitation. Based on the description herein and the design alternatives available to a given exploitation, persons of ordinary skill in the art will appreciate suitable synchronization circuits or mechanisms.
In general, selection of appropriate target devices (e.g., LEDs), associated driver circuits, package configurations etc. are matters of design choice and subject to numerous application-specific constraints and/or figures of merit that are largely independent of the thermoelectric and/or phase change material design factors described herein. Nonetheless, based on the description herein, persons of ordinary skill in the art will appreciate suitable selections and/or adaptations of their own configurations, parts or assemblies or those commercially-available now or in the future, to exploit techniques of the present invention. In this regard, LEDs available from various commercial sources, including Lumileds Lighting, U.S. LLC and Cree, Inc., are suitable for many exploitations. In general, devices and/or configurations that provide or allow a low thermal impedance path to a thermoelectric and/or phase change material are desirable. Unpackaged LED device or wafer configurations can offer flexibility in thermal design, though at the potential expense of additional packaging and test steps that could be avoided with use of a suitable packaged component. Selections of driver circuits may vary depending on a particular device selected.
Of course, commercial requirements and therefore suitable device selections are application-specific and may vary depending on the particular commercial exploitation. As a result, a person of skill in the art will typically consult manufacturer or supplier specifications or recommendations. In this regard, as of the filing date of this application, Lumileds Lighting, U.S. LLC provides (on it's website, www.lumileds.com) datasheets, reference design information and application briefs (including driver integrated circuit recommendations) and Cree, Inc. provides (on it's website, www.cree.com) specifications and application notes (including die attach recommendations) for their respective products.
Referring to the upper graph of
Referring to
Another method of forming PCM modules is shown in
Thermoelectrics, Generally
While embodiments of the present invention are not limited to any particular thermoelectric module or device configuration, certain illustrative configurations will be understood in the context of advanced thin-film thermoelectrics. Accordingly, merely for purposes of additional description and without limitation on the broad range of thermoelectric configurations that fall within the scope of any claim herein that recites a thermoelectric, thermoelectric element, thermoelectric device, thermoelectric structure, thermoelectric couple, thermoelectric module or the like, applicants hereby incorporate herein by reference the disclosure of commonly-owned U.S. patent application Ser. No. ______, entitled “LATERAL THERMOELECTRIC DEVICE STRUCTURE AND RELATED APPARATUS,” naming Ghoshal, Ngai, Samavedam and Miner as inventors, and filed on even date herewith.
Phase Change Materials, Generally
While virtually all materials undergo phase changes with temperature, so-called “phase change materials” or PCMs have transition temperatures in a range useful for a given application. For example, polymers and waxes that melt between 28° C. and 37° C. that are used in outdoor clothing to help maintain a comfortable temperature for the wearer may be used in certain exploitations. Pure elements, like gallium, and compounds, like water, exhibit sharp phase transitions, for example, melting at a precise temperature. Alloys and solutions, however, often complete the phase transition between liquid and solid states over a range of temperatures. An alloy containing 95% by weight of gallium and 5% indium begins to melt when heated above 15.7° C., its solidus temperature. As the alloy is heated further, liquid and solid phases coexist, and their compositions continually change, but the overall composition remains constant. When the alloy is heated to 25° C., all of the solid phase material has melted and the liquid alloy has a uniform composition. Eutectic compositions are alloy compositions whose solidus and liquidus temperatures are the same, so they behave like pure elements and have sharp melting points.
Relevant design properties of PCMs include the transition temperature range, the temperature range over which the PCM can be used, the latent heat of the transition, thermal conductivity, and thermal capacity, which is a measure of the energy that can be stored in the material over a given temperature range and which correlates with the material's density. In general, based on the description herein persons of ordinary skill in the art will be able to select an appropriate PCM for a given application. PCMs are commercially available from a number of sources. Major classes of PCM include waxes, polymers, hydrated salts, and liquid metals alloys. Table 1 illustrates several examples of PCMs, including examples from each major class.
Waxes are used primarily for lower-temperature applications. Wax compositions have been developed for an almost continuous distribution of transition temperatures. They typically have low densities and therefore low thermal capacities, but their light weight can be useful for some applications. Thermal conductivities are also low for waxes. Polymers typically exhibit poor thermal conductivity and low latent heats, but they are relatively easy to form and are compatible with many containment materials. Hydrated salts are more appropriate than waxes for higher temperature applications, but they, too, have low thermal conductivities. These inorganic salts are relatively inexpensive and are often used, for example, in first aid cold and hot packs.
Metals and alloys can be used at temperatures ranging from about −39° C., the melting point of mercury, to well over 200° C. Gallium melts at just under 30° C., the approximate operating temperature for many electronic devices. Metal PCMs typically have high thermal conductivities and large latent heats of fusion. In general, they are many times denser than other classes of PCM, contributing to higher heat storage capacities. Some alloys that are otherwise useful as PCMs contain elements that are not environmentally attractive, such as cadmium and lead. Nonetheless these alloys and even elemental Mercury may be suitable for some applications. In general, Gallium Indium alloys such as those illustrated in Table 1 provide an attractive combination of melt points, high thermal conductivities and large latent heats of fusion.
*Eutectic compositions exhibit equal liquidus and solidus temperatures.
†The transition temperature is the melting point of the element.
Generally, any of a variety of phase change materials may be employed in conjunction with the structures and configurations described herein. However, for at least some of the configurations illustrated herein, metals and metal alloys offer an attractive combination of properties and compatibilities with materials, temperatures and/or process technologies that may be employed in the forming, packaging and/or assembly of illustrated configurations. In general, phase change materials with phase transition points at or above an expected ambient temperature will be suitable for thermal moderation and for thermoelectric configurations that employ a body of the material at hot- or cooled-end of a thermoelectric. Phase change materials with transition points at or below an expected ambient temperature will generally be suitable for thermoelectric configurations that pre-chill a body of the material at a cooled-end of a thermoelectric.
In some realizations, a body of phase change material may include additional materials introduced to provide nucleation sites during phase transitions. In some realizations, a body of phase change material may compressible material or structures (e.g., small polystyrene balls or the like) to relieve stresses associated with expansion and contraction of the phase change material during phase transitions.
OTHER EMBODIMENTSWhile the invention(s) is(are) described with reference to various implementations and exploitations, it will be understood that these embodiments are illustrative and that the scope of the invention(s) is not limited to them. Many variations, modifications, additions, and improvements are possible. For example, while a variety of packaging configurations have been illustrated, exploitations of the present invention(s) need not correspond to any particular illustrated packaging of emissive, sensor or thermoelectric device. In general, packaging and other aspects of physical configuration are matters of design choice and may be conformed to application, commercially available device and/or market constraints as appropriate.
Plural instances may be provided for components, operations or structures described herein as a single instance. Finally, boundaries between various components and particular operations are illustrated in the context of specific illustrative configurations. Other allocations of functionality are envisioned and may fall within the scope of the invention(s). In general, structures and functionality presented as separate components in the exemplary configurations may be implemented as a combined structure or component. Similarly, structures and functionality presented as a single component may be implemented as separate components. These and other variations, modifications, additions, and improvements may fall within the scope of the invention(s).
Claims
1. An apparatus comprising:
- an optoelectronic device;
- a thermoelectric cooler thermally coupled to the optoelectronic device to at least partially define a heat transfer path from the optoelectronic device; and
- a phase change material disposed in the heat transfer path to undergo a transition from a first phase to a second phase thereof and thereby absorb heat transferred by the heat transfer path.
2. The apparatus of claim 1,
- wherein the optoelectronic device is transiently operable and wherein the phase change material undergoing the transition absorbs a substantial portion of heat evolved by the optoelectronic device coincident with such transient operation.
3. The apparatus of claim 2,
- wherein the thermoelectric cooler is operable to transfer to the phase change material the heat evolved by the optoelectronic device.
4. The apparatus of claim 2,
- wherein the thermoelectric cooler is operable to transfer heat from the phase change material.
5. The apparatus of claim 1,
- wherein the thermoelectric cooler is operable to transfer heat from the phase change material and thereby cause the phase change material to transition from the second phase thereof to the first phase thereof.
6. The apparatus of claim 5,
- wherein the second phase to first phase transition is performed prior to or in anticipation of a transient operation of the optoelectronic device.
7. The apparatus of claim 5,
- wherein the second phase to first phase transition is performed after a transient operation of the optoelectronic device, thereby reversing a prior first phase to second phase transition of the phase change material, which absorbed heat transferred across the thermoelectric cooler coincident with such transient operation.
8. The apparatus of claim 1,
- wherein the thermoelectric cooler is transiently operable and wherein the transition of the phase change material absorbs a substantial portion of heat transferred across the thermoelectric cooler coincident with such transient operation.
9. The apparatus of claim 8,
- wherein the optoelectronic device is a sensor device, and
- wherein the thermoelectric cooler is transiently operable to cool the optoelectronic device below an ambient temperature.
10. The apparatus of claim 9,
- wherein the sensor device includes one or more of: a charge coupled device (CCD); and a complementary metal oxide semiconductor (CMOS) array.
11. The apparatus of claim 8,
- wherein the optoelectronic device is an emissive device, and
- wherein the heat transferred across the thermoelectric cooler includes that evolved by operation of the emissive device.
12. The apparatus of claim 9,
- wherein the emissive device includes one or more of: a light emitting diode (LED); and a semiconductor laser.
13. The apparatus of claim 8,
- wherein the optoelectronic device is transiently operable is substantial synchrony with the thermoelectric cooler.
14. The apparatus of claim 1,
- wherein the thermoelectric cooler is operable to transfer heat from the phase change material and thereby reverse the first to second phase transition.
15. The apparatus of claim 1,
- wherein the thermoelectric cooler is thermally coupled between the optoelectronic device and the phase change material.
16. The apparatus of claim 15,
- wherein temperature of a phase change material facing side of the thermoelectric cooler is substantially clamped based on a latent heat of transformation for the phase change material.
17. The apparatus of claim 16,
- wherein the clamped temperature corresponds to a first to second phase transition temperature for the phase change material.
18. The apparatus of claim 15,
- wherein the optoelectronic device evolves, during operation, a substantial portion of the heat absorbed in the first to second phase transition.
19. The apparatus of claim 15,
- wherein the thermoelectric cooler transfers, during operation, a substantial portion of the heat absorbed in the first to second phase transition.
20. The apparatus of claim 19,
- wherein the optoelectronic device evolves, during operation, a substantial portion of the heat transferred by the thermoelectric cooler and absorbed in the first to second phase transition.
21. The apparatus of claim 19,
- wherein the optoelectronic device is cooled, by operation of the thermoelectric cooler, below an ambient temperature.
22. The apparatus of claim 1,
- wherein the phase change material is thermally coupled between the optoelectronic device and the thermoelectric cooler.
23. The apparatus of claim 22,
- wherein, during a heat-evolving transient operation of the optoelectronic device, temperature of the optoelectronic device is substantially moderated based on a latent heat of transformation for the phase change material.
24. The apparatus of claim 22,
- wherein the thermoelectric cooler is operable to transfer heat from the phase change material and thereby reverse the first to second phase transition.
25. The apparatus of claim 22,
- wherein the thermoelectric cooler is operable to transfer heat from the phase change material and thereby transition a substantial portion of the phase change material from the second phase to the first phase thereof prior to or in anticipation of a transient operation of the optoelectronic device.
26. The apparatus of claim 1,
- wherein at ambient conditions, the phase change material is in the first phase thereof.
27. The apparatus of claim 1,
- wherein at ambient conditions, the phase change material is in the second phase thereof.
28. The apparatus of claim 1,
- wherein the first phase is a solid phase, and
- wherein the second phase is a liquid phase.
29. The apparatus of claim 1,
- wherein the first phase is a liquid phase, and
- wherein the second phase is a gas phase.
30. The apparatus of claim 1,
- wherein the first phase is a solid phase, and
- wherein the second phase is a gas phase.
31. The apparatus of claim 1,
- wherein the first and second phases are both solid state phases.
32. The apparatus of claim 1, further comprising:
- confinement for the phase change material when in a non-solid state.
33. The apparatus of claim 32,
- wherein the confinement encapsulates the phase change material.
34. The apparatus of claim 32,
- wherein the confinement operates to inhibit flow of the phase change material when in a liquid state in part by surface tension of the liquid state phase change material.
35. An apparatus comprising:
- an optoelectronic device; and
- a phase change material thermally proximate to the optoelectronic device to undergo a transition from a first phase to a second phase thereof and thereby absorb at least a substantial portion of heat evolved by transient operation of the optoelectronic device.
36. The apparatus of claim 35, further comprising:
- a thermoelectric cooler operable to transfer heat from the phase change material and thereby reverse the first to second phase transition
37. The apparatus of claim 35, further comprising:
- a thermoelectric cooler operable to transfer heat from the phase change material and thereby transition a substantial portion of the phase change material from the second phase to the first phase thereof prior to or in anticipation of the transient operation of the optoelectronic device
38. A method of moderating temperature of an optoelectronic system, the method comprising:
- transiently operating an optoelectronic device that evolves heat; and
- absorbing at least a substantial portion of the heat evolved by transient operation of the optoelectronic device in a phase change material thermally proximate to the optoelectronic device, the phase change material undergoing a transition from a first phase to a second phase thereof.
39. The method of claim 38, further comprising:
- transferring heat from the phase change material and thereby reversing the first to second phase transition.
40. A method of cooling an optoelectronic device, the method comprising:
- transferring heat from the optoelectronic device along a heat transfer path that includes a thermoelectric cooler; and
- absorbing, in a phase change material undergoing a transition from a first phase to a second phase thereof, at least a substantial portion of the heat transferred in the heat transfer path.
41. The method of claim 40, further comprising:
- transiently operating the optoelectronic device and thereby evolving a substantial portion of the heat transferred and absorbed in the phase change material.
42. The method of claim 41, further comprising:
- transferring to the phase change material, using the thermoelectric cooler, the heat evolved by the optoelectronic device.
43. The method of claim 41, further comprising:
- transferring heat from the phase change material, using the thermoelectric cooler.
44. The method of claim 40, further comprising:
- transiently operating the thermoelectric cooler to transfer thereacross a substantial portion of the heat absorbed in the phase change material.
45. The method of claim 44, further comprising:
- transiently operating the optoelectronic device in substantial synchrony with the thermoelectric cooler.
46. The method of claim 40, further comprising:
- transferring heat from the phase change material, using the thermoelectric cooler, thereby reverse the first to second phase transition.
Type: Application
Filed: May 6, 2005
Publication Date: Apr 27, 2006
Applicant:
Inventor: Uttam Ghoshal (Austin, TX)
Application Number: 11/123,882
International Classification: F25B 21/02 (20060101); F25D 23/12 (20060101);