Patent Application
20080264464
The present invention relates to the field of electronics, and more particularly, to thermoelectric devices and methods.
Thermoelectric materials may be used to provide cooling and/or power generation according to the Peltier effect. Thermoelectric materials are discussed, for example, in the reference by Venkatasubramanian et al. entitled “Phonon-Blocking Electron-Transmitting Structures” (18th International Conference On Thermoelectrics, 1999), the disclosure of which is hereby incorporated herein in its entirety by reference.
Application of solid state thermoelectric cooling may be expected to improve the performance of electronics and sensors such as, for example, RF receiver front-ends, infrared (IR) imagers, ultra-sensitive magnetic signature sensors, and/or superconducting electronics. Bulk thermoelectric materials typically based on p-BixSb2−xTe3 and n-Bi2Te3−xSex alloys may have figures-of-merit (ZT) and/or coefficients of performance (COP) which result in relatively poor thermoelectric device performance.
The performance of a thermoelectric device may be a function of the figure(s)-of-merit (ZT) of the thermoelectric material(s) used in the device, with the figure-of-merit being given by:
ZT=(α2Tσ/KT), (equation 1)
where α, T, σ, KT are the Seebeck coefficient, absolute temperature, electrical conductivity, and total thermal conductivity, respectively. The material-coefficient Z can be expressed in terms of lattice thermal conductivity (KL), electronic thermal conductivity (Ke) and carrier mobility (μ), for a given carrier density (ρ) and the corresponding α, yielding equation (2) below:
Z=α2σ/(KL+Ke)=α2/[KL/(μρpq)+L0T)], (equation 2)
where, L0 is the Lorenz number (approximately 1.5×10−8V2/K2 in non-degenerate semiconductors). State-of-the-art thermoelectric devices may use alloys, such as p-BixSb2−xTe3−ySey (x≈0.5, y≈0.12) and n-Bi2(SeyTe1−y)3 (y≈0.05) for the 200 degree K to 400 degree K temperature range. For certain alloys, KL may be reduced more strongly than μ leading to enhanced ZT.
A ZT of 0.75 at 300 degree K in p-type BixSb2−xTe3 (x≈1) was reported forty years ago. See, for example Wright, D. A., Nature vol. 181, pp. 834 (1958). Since then, there has been relatively modest progress in the ZT of thermoelectric materials near 300 degree K (i.e., room temperature). A ZT of about 1.14 at 300 degree K for bulk p-type (Bi2Te3)0.25 (Sb2Te3)0.72 (Sb2Se3)0 03 alloy has been discussed for example, in the reference by Ettenberg et al. entitled “A New N-Type And Improved P-Type Pseudo-Ternary (Bi2Te3)(Sb2Te3)(Sb2Se3) Alloy For Peltier Cooling,” (Proc. of 15th Inter. Conf. on Thermoelectrics, IEEE Catalog. No. 96TH8169, pp. 52-56, 1996), the disclosure of which is hereby incorporated herein in its entirety by reference.
According to some embodiments of the present invention, a temperature control system may include a thermoelectric device, and a controller electrically coupled to the thermoelectric device. The controller may be configured to apply an AC signal to the thermoelectric device and to sense an electrical characteristic of the thermoelectric device using the AC signal. The controller may be further configured to generate an electrical control signal to pump heat through the thermoelectric device responsive to sensing the electrical characteristic of the thermoelectric device using the AC signal.
The controller may be configured to superimpose the AC signal on the electrical control signal so that both of the AC signal and the electrical control signal are applied to the thermoelectric device at the same time. Moreover, a frequency of the AC signal may be at least 10 times greater than a frequency of the electrical control signal, and/or at least 10 times greater than a thermal bandwidth of the thermoelectric device. Sensing an electrical characteristic of the thermoelectric device using the AC signal may include determining an electrical resistance of the thermoelectric device using the AC signal, and/or sensing an electrical characteristic of the thermoelectric device using the AC signal may include sensing an electrical characteristic of the thermoelectric device that varies in response to variations of a thermal gradient across the thermoelectric device.
Sensing an electrical characteristic of the thermoelectric device may include sensing a first value of the electrical characteristic at a first time and sensing a second value of the electrical characteristic at a second time, with the first and second times being different and with the first and second values being different. Generating the electrical control signal may include generating a first electrical control signal responsive to the first value of the electrical characteristic and generating a second electrical control signal responsive to the second value of the electrical characteristic with the first and second electrical control signals being different. The controller may be configured to generate the first electrical control signal so that heat is pumped through the thermoelectric device in a first direction, and to generate the second electrical control signal so that heat is pumped through the thermoelectric device in a second direction opposite the first direction. The controller may be configured to generate the first electrical control signal so that a first electrical current flows through the thermoelectric device in a first direction, and to generate the second electrical control signal so that a second electrical current flows through the thermoelectric device in a second direction opposite the first direction.
The thermoelectric device may include a thermoelectric material such as bismuth telluride. The thermoelectric device may include a P-type thermoelectric element and an N-type thermoelectric element electrically coupled in series and thermally coupled in parallel. In addition, a heat transfer structure may be thermally coupled to a first side of the thermoelectric device, and a temperature controlled medium may be thermally coupled to a second side of the thermoelectric device so that the thermoelectric device is thermally coupled between the heat transfer structure and the temperature controlled medium.
The temperature controlled medium may include a semiconductor substrate of an integrated circuit device, an optical device configured to emit and/or receive optical radiation, and/or a medical instrument configured to contact living tissue. The controller may be configured to generate the first and second electrical control signals to maintain a stable temperature of the temperature controlled medium, to provide a temperature ramp for the temperature controlled medium, and/or to provide a cyclical temperature profile for the temperature controlled medium.
According to other embodiments of the present invention, a temperature control system may include a temperature controlled medium, a heat transfer structure thermally spaced apart from the temperature controlled medium, and a thermoelectric heat pumping device thermally coupled between the heat transfer structure and the temperature controlled medium. A thermoelectric sensing device may be thermally coupled to the temperature controlled medium with the thermoelectric sensing device being electrically isolated from the thermoelectric heat pumping device. A controller may be electrically coupled to the thermoelectric heat pumping device and to the thermoelectric sensing device. The controller may be configured to sense a first value of an electrical characteristic of the thermoelectric sensing device and to generate a first electrical control signal to pump heat through the thermoelectric heat pumping device between the heat transfer structure and the temperature controlled medium in response to sensing the first value of the electrical characteristic of the thermoelectric sensing device. The controller may be further configured to sense a second value of the electrical characteristic of the thermoelectric sensing device with the first and second values of the electrical characteristic being different, and to generate a second electrical control signal to pump heat through the thermoelectric heat pumping device between the heat transfer structure and the temperature controlled medium in response to sensing the second electrical characteristic of the thermoelectric sensing device with the first and second electrical control signals being different.
In addition, a reference medium may be spaced apart from the temperature controlled medium and spaced apart from the heat transfer structure, and the thermoelectric sensing device may be thermally coupled between the reference medium and the temperature controlled medium. The controller may be configured to sense the first and second electrical characteristics by sensing electrical signals generated by the thermoelectric sensing device responsive to first and second heat gradients across the thermoelectric sensing device.
The controller may be configured to generate the first electrical control signal so that heat is pumped through the thermoelectric heat pumping device in a first direction, and to generate the second electrical control signal so that heat is pumped through the thermoelectric heat pumping device in a second direction opposite the first direction. Accordingly, the controller and the thermoelectric heat pump may be configured to both heat and cool the temperature controlled medium. In addition or in an alternative, the controller may be configured to generate the first electrical control signal so that a first electrical current flows through the thermoelectric heat pumping device in a first direction, and to generate the second electrical control signal so that a second electrical current flows through the thermoelectric heat pumping device in a second direction opposite the first direction. Accordingly, the controller may be configured to reverse a polarity of electrical control signals applied to the thermoelectric heat pumping device.
The thermoelectric heat pumping device may include a thermoelectric material such as bismuth telluride. Moreover, the thermoelectric device may include a P-type thermoelectric element and an N-type thermoelectric element electrically coupled in series and thermally coupled in parallel. The temperature controlled medium may include a thermally conductive substrate, a semiconductor substrate of an integrated circuit device, an optical device configured to emit and/or receive optical radiation, and/or a medical instrument configured to contact living tissue. The controller may be configured to generate the first and second electrical control signals to maintain a stable temperature of the temperature controlled medium, to provide a temperature ramp for the temperature controlled medium, and/or to provide a cyclical temperature profile for the temperature controlled medium.
The present invention is described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the present invention are shown. This invention may, however, 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 present invention to those skilled in the art. In the drawings, the sizes and relative sizes of layers and regions may be exaggerated for clarity. Like numbers refer to like elements throughout.
It will be understood that when an element or layer is referred to as being “on”, “connected to” or “coupled to” another element or layer, it can be directly on, connected or coupled to the other element, or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly connected to” or “directly coupled to” another element or layer, there are no intervening elements or layers present. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
It will be understood that, although the terms first, second, third etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present invention.
Spatially relative terms, such as “beneath”, “below”, “lower”, “above”, “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. Also, as used herein, “lateral” refers to a direction that is substantially orthogonal to a vertical direction.
The terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting of the present invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
Example embodiments of the present invention are described herein with reference to cross-section illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of the invention. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments of the present invention should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, an region/shape illustrated as a rectangle will, typically, have rounded or curved features. Thus, the regions/shapes illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of the present invention.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Accordingly, these terms can include equivalent terms that are created after such time. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the present specification and in the context of the relevant art, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety.
As shown in
The temperature controlled medium 103 may be any substrate, surface, device, instrument, etc. for which temperature control is desired. The temperature controlled medium 103, for example, may be a semiconductor substrate of an integrated circuit (IC) electronic device (including a plurality of interconnected electronic devices such as transistors, diodes, capacitors, inductors, resistors, etc.); a substrate of a discrete electronic device (including a single transistor, diode, capacitor, inductor, resistor, etc.); an optical device configured to emit and/or receive optical radiation; and/or a medical instrument (such as a blade, scalpel, probe, implant, etc.) configured to contact living tissue. In medical applications, the temperature controlled medium may include living tissue, such as a portion of a human body.
Moreover, the thermoelectric device 101 may be configured to act as both a heat pump and as a heat sensor. The thermoelectric device 101 may thus provide temperature feedback to the controller 107, and the controller 107 may use temperature feedback information from the thermoelectric device 101 to determine a control signal used to pump heat through the thermoelectric device 101. Accordingly, a separate temperature sensor may not be required thereby simplifying a structure of the temperature controlled apparatus.
Thermoelectric (TE) devices 101a and 101b according to different embodiments of the present invention are respectively illustrated by way of example in
By generating an electrical current through the TE elements P and N having a first polarity between the electrically conductive traces 121a and 121d responsive to an electrical control signal generated by the controller 107, heat can be pumped from the temperature controlled medium 103 to the heat transfer structure 105 to thereby cool the temperature controlled medium 103. By generating an electrical current through the TE elements P and N having a second polarity (opposite the first polarity) between the electrically conductive traces 121a and 121d responsive to an electrical control signal generated by the controller 107, heat can be pumped from the heat transfer structure 105 to the temperature controlled medium 103 to thereby heat the temperature controlled medium 103. By sensing an electrical characteristic of the TE device 101 a (e.g., a voltage across the TE device 101 a, a current through the TE device l01 a, and/or a resistance of the TE device 101 a), a temperature gradient across the TE device 101 a and/or a temperature of the temperature controlled medium 103 may be determined.
Each of the p-type and n-type TE elements P and N may include a layer of a thermoelectric material such as bismuth telluride (Bi2Te3). Each of the TE elements P and N may be electrically and mechanically coupled to respective traces 121a-d and 123a-c, for example, using solder together with a barrier metal, an adhesion metal, and/or other metallization layers. Materials, formation, and/or assembly of TE elements/structures are discussed, for example, in: U.S. Pat. Pub. No. 2003/0099279 entitled “Phonon-Blocking, Electron-Transmitting Low-Dimensional Structures”; U.S. Pat. Pub. No. 2007/0028956 entitled “Methods Of Forming Thermoelectric Devices Including Superlattice Structures Of Alternating Layers With Heterogeneous Periods And Related Devices”; U.S. Pat. Pub. No. 2006/0086118 entitled “Thin Film Thermoelectric Devices For Hot-Spot Thermal Management In Microprocessors And Other Electronics”; U.S. Pat. Pub. No. 2006/0289052 entitled “Methods Of Forming Thermoelectric Devices Including Conductive Posts And/Or Different Solder Materials And Related Methods And Structures”; U.S. Pat. Pub. No. 2006/0289050 entitled “Methods Of Forming Thermoelectric Devices Including Electrically Insulating Matrixes Between Conductive Traces And Related Structures”; U.S. Pat. Pub. No. 2007/0215194 entitled “Methods Of Forming Thermoelectric Devices Using Islands Of Thermoelectric Material And Related Structures”; U.S. Pat. Pub. No. 2007/0089773 entitled “Methods Of Forming Embedded Thermoelectric Coolers With Adjacent Thermally Conductive Fields and Related Structures”; U.S. Pat. No. 6,300,150 entitled “Thin-Film Thermoelectric Device And Fabrication Method Of Same”; U.S. Pat. No. 7,164,077 entitled “Thin-Film Thermoelectric Cooling And Heating Devices For DNA Genomic And Proteomic Chips, Thermo-Optical Switching Circuits, And IR Tags”; U.S. Pat. No. 7,235,735 entitled “Thermoelectric Devices Utilizing Double-Sided Peltier Junctions And Methods Of Making The Devices”; and International PCT Pub. No. WO/2005/074463 entitled “Thin Film Thermoelectric Devices For Power Conversion And Cooling”. The disclosures of each of the above referenced patent publications and patents are hereby incorporated herein in their entirety by reference.
Each of the TE elements P and N may include a thin film layer of a thermoelectric material having a thickness (in a direction between the electrically conductive traces 121a-d and 123a-c) that is less than about 100 μm (micrometers) and more particularly less than about 50 μm (micrometers). Moreover, the layers of the thermoelectric material may have substantially single crystal and/or substantially oriented polycrystalline structures (e.g., formed by epitaxial growth), or amorphous structures (e.g., formed by sputtering). Accordingly, the TE device 101a and/or portions thereof may be manufactured using semiconductor processing techniques (e.g., epitaxial growth and/or sputtering). By using semiconductor processing techniques to manufacture a thin film TE device, the thin film TE device may be more easily isolated to accommodate biocompatibility for medical applications.
As shown in
By generating an electrical current through the TE elements having a first polarity between the electrically conductive traces 131 and 133 responsive to an electrical control signal generated by the controller 107, heat can be pumped from the temperature controlled medium 103 to the heat transfer structure 105 to thereby cool the temperature controlled medium 103. By generating an electrical current through the TE elements having a second polarity (opposite the first polarity) between the electrically conductive traces 131 and 133 responsive to an electrical control signal generated by the controller 107, heat can be pumped from the heat transfer structure 105 to the temperature controlled medium 103 to thereby heat the temperature controlled medium 103. By sensing an electrical characteristic of the TE device 101b (e.g., a voltage across the TE device 101b, a current through the TE device 101b, and/or a resistance of the TE device 101b), a temperature gradient across the TE device 101b and/or a temperature of the temperature controlled medium 103 may be determined.
Each of the TE elements may include a layer of a thermoelectric material such as bismuth telluride (Bi2Te3). Each of the TE elements may be electrically and mechanically coupled to respective traces 131 and 133, for example, using solder together with a barrier metal, an adhesion metal, and/or other metallization layers. Materials, formation, and/or assembly of TE elements/structures are discussed, for example, in: U.S. Pat. Pub. No. 2003/0099279 entitled “Phonon-Blocking, Electron-Transmitting Low-Dimensional Structures”; U.S. Pat. Pub. No. 2007/0028956 entitled “Methods Of Forming Thermoelectric Devices Including Superlattice Structures Of Alternating Layers With Heterogeneous Periods And Related Devices”; U.S. Pat. Pub. No. 2006/0086118 entitled “Thin Film Thermoelectric Devices For Hot-Spot Thermal Management In Microprocessors And Other Electronics”; U.S. Pat. Pub. No. 2006/0289052 entitled “Methods Of Forming Thermoelectric Devices Including Conductive Posts And/Or Different Solder Materials And Related Methods And Structures”; U.S. Pat. Pub. No. 2006/0289050 entitled “Methods Of Forming Thermoelectric Devices Including Electrically Insulating Matrixes Between Conductive Traces And Related Structures”; U.S. Pat. Pub. No. 2007/0215194 entitled “Methods Of Forming Thermoelectric Devices Using Islands Of Thermoelectric Material And Related Structures”; U.S. Pat. Pub. No. 2007/0089773 entitled “Methods Of Forming Embedded Thermoelectric Coolers With Adjacent Thermally Conductive Fields and Related Structures”; U.S. Pat. No. 6,300,150 entitled “Thin-Film Thermoelectric Device And Fabrication Method Of Same”; U.S. Pat. No. 7,164,077 entitled “Thin-Film Thermoelectric Cooling And Heating Devices For DNA Genomic And Proteomic Chips, Thermo-Optical Switching Circuits, And IR Tags”; U.S. Pat. No. 7,235,735 entitled “Thermoelectric Devices Utilizing Double-Sided Peltier Junctions And Methods Of Making The Devices”; and International PCT Pub. No. WO/2005/074463 entitled “Thin Film Thermoelectric Devices For Power Conversion And Cooling”. The disclosures of each of the above referenced patent publications and patents are hereby incorporated herein in their entirety by reference.
Each of the TE elements TE of
As shown in
According to some embodiments of the present invention, the switches 117 may couple the driver circuit 111 to the TE device 101 during heat pump periods to provide heat pumping interrupted by brief sensing intervals when the switches 117 couple the sensor circuit 115 to the TE device 101. During a first sensing interval, for example, the sensor circuit 115 may be electrically coupled with the TE device 101 through switches 117 to sense a first value of an electrical characteristic of the TE device 101. During a first drive period following the first sense interval, the driver circuit 111 may be electrically coupled with the TE device 101 through switches 117 to generate a first electrical control signal to pump heat through the thermoelectric device 101 between the heat transfer structure 105 and the temperature controlled medium 103 in response to sensing the first value of the electrical characteristic of the thermoelectric device. During a second sensing interval following the first drive period, the sensor circuit 115 may be electrically coupled with the TE device 101 through switches 117 to sense a second value of an electrical characteristic of the TE device 101, and the first and second values of the electrical characteristic may be different. During a second drive period following the second sense interval, the driver circuit 111 may be electrically coupled with the TE device 101 through switches 117 to generate a second electrical control signal to pump heat through the thermoelectric device between the heat transfer structure and the temperature controlled medium in response to sensing the second electrical characteristic of the thermoelectric device.
According to some other embodiments of the present invention, the driver circuit 111 and the sensor circuit 115 may be electrically coupled in parallel with the TE device 101 without the switches 117 so that interruption of the control signal is not required during sensing intervals. The sensor circuit 115, for example, may be configured to sense a voltage across the TE device 101 and a current through the TE device 101 to determine a temperature gradient across the TE device 101 without interrupting a current through the TE device 101 generated responsive to a control signal from the driver circuit 111. A continuous control signal generated by the driver circuit 111 may thus be varied responsive to the sensor circuit 115.
As the value of the electrical characteristic changes (due to changing temperatures of the temperature controlled medium 103), the controller 107 may change a control signal generated by the driver circuit 111 during different drive periods to maintain a desired temperature of the temperature controlled medium 103. During sensing intervals, for example, the sensor circuit 115 may sense an electrical characteristic of the TE device 101 such as a voltage generated by the TE device 101, a current generated by the TE device 101, a resistance of the TE device 101, etc. During drive periods, the driver circuit 111 may provide a drive current through the TE device 101 with increased magnitudes of the driver current providing increased heat pumping, with decreased magnitudes of the driver current providing decreased heat pumping, with a first polarity of the driver current providing cooling of the temperature controlled medium 103, and with a second polarity (opposite the first polarity) of the driver current providing heating of the temperature controlled medium 103. The electrical control signals may differ, for example, so that a current through the TE device 101 is either on or off during different drive periods; so that currents through the TE device 101 have different magnitudes during different drive periods; so that currents through the TE device 101 have different polarities during different drive periods; and/or so that currents through the TE device 101 have different duty cycles during different drive periods.
With a semiconductor substrate of an integrated circuit electronic device, a medical probe, and/or living tissue as the temperature controlled medium 103, for example, the controller 107 may be configured to provide that the TE device 101 cools a hot spot of the temperature controlled medium 103 when a temperature gradient across the TE device 101 exceeds a threshold. Accordingly, the controller 107 may be configured to provide cooling only. With an optical electronic device as the temperature controlled medium 103, for example, the controller 107 may be configured to provide that the TE device 101 heats the temperature controlled medium 103 when a temperature gradient across the TE device is less than a low temperature threshold and to provide that the TE device 101 cools the temperature controlled medium 103 when a temperature gradient across the TE device 101 is greater than a high temperature threshold.
Accordingly, the controller 107 may be configured to provide heating and cooling to maintain a relatively stable temperature. With a medical scalpel as the temperature controlled medium 103, for example, the controller 107 may be configured to provide that the TE device 101 heats the scalpel when a temperature gradient across the TE device 101 is less than a threshold. Accordingly, the controller 107 may be configured to provide heating only.
According to some embodiments of the present invention, the electrical control signal generated at block 203 may be interrupted when sensing the electrical characteristic of the TE device 101 at block 201. According to other embodiments of the present invention, the electrical characteristic of the TE device 101 may be sensed at block 201 without interrupting the electrical control signal generated at block 203. The electrical control signals generated at block 203 may differ, for example, so that a current through the TE device 101 is either on or off during different drive periods; so that currents through the TE device 101 have different magnitudes during different drive periods; so that currents through the TE device 101 have different polarities during different drive periods; and/or so that currents through the TE device 101 have different duty cycles during different drive periods. Sensing the electrical characteristic of the TE device 101 at block 201 may include sensing a current through the TE device 101; sensing a voltage across the TE device 101; sensing a current through the TE device 101 and a corresponding voltage across the TE device 101; sensing a resistance of the TE device 101; etc. Moreover, the electrical characteristic of the TE device 101 sensed at block 201 may be representative of a temperature gradient across the TE device 101 and/or a temperature of the temperature controlled medium 103.
According to some embodiments of the present invention, the controller 107 may be configured to generate the electrical control signal at block 203 to maintain a stable temperature for the temperature controlled medium 103. For example, the controller 107 may be configured to generate the electrical control signal at block 203 to provide that the temperature controlled medium 103 does not exceed a high temperature threshold, to provide that the temperature controlled medium 103 is maintained between high and low temperature thresholds, or to provide that the temperature controlled medium 103 is maintained above a low temperature threshold. According to some other embodiments of the present invention, the controller 107 may be configured to generate the electrical control signal at block 203 to provide a temperature ramp for the temperature controlled medium 103. According to still other embodiments of the present invention, the controller 107 may be configured to generate the electrical control signal at block 203 to provide a cyclical temperature profile for the temperature controlled medium 103.
As noted above, electrical characteristics of a TE device may be sensed without interrupting an electrical control signal used to power the TE device.
According to some embodiments of the present invention shown in
The controller 107′ (including driver circuit 111′ and sensor circuit 115′), for example, may be configured to superimpose the AC signal (generated by sensor circuit 115′) on the electrical control signal (generated by the driver circuit 111′) so that both of the AC signal and the electrical control signal are applied to the thermoelectric device 101 at the same time. Accordingly, the electrical control signal may be maintained without interruption even when sensor circuit 115′is sensing electrical characteristics of the thermoelectric device. According to other embodiments of the present invention, the electrical control signal may be interrupted during sense intervals when the AC signal is applied to the thermoelectric device 101. A frequency of the AC signal, for example, may be at least 10 times greater than a frequency of the electrical control signal, and/or a frequency of the AC signal may be at least 10 times greater than a thermal bandwidth of the thermoelectric device 101. Moreover, a magnitude of the electrical control signal may be at least 10 times greater than a magnitude of the AC signal.
Sensor circuit 115′ may sense an electrical characteristic of the thermoelectric device using the AC signal by sensing an electrical characteristic of the thermoelectric device that varies in response to variations of a thermal gradient across the thermoelectric device. For example, sensor circuit 115′ may sense the electrical characteristic of the thermoelectric device 111 using the AC signal by determining an electrical resistance of the thermoelectric device 101 using the AC signal.
Sensor circuit 115′ may be configured to sense an electrical characteristic of the thermoelectric device 101 by sensing a first value of the electrical characteristic at a first time and sensing a second value of the electrical characteristic at a second time (different than the first time). If a temperature of the temperature controlled medium 103 changes and/or if a temperature gradient between temperature controlled medium 103 and heat transfer structure 105 changes from the first time to the second time, the first and second values of the electrical characteristic may be different. Accordingly, driver circuit 111′ may generate the electrical control signal by generating a first electrical control signal responsive to the first value of the electrical characteristic, and by generating a second electrical control signal responsive to the second value of the electrical characteristic and the first and second electrical control signals may be different to accommodate the change in temperature and/or temperature gradient. While first and second values of the electrical characteristic of thermoelectric device 101 and first and second electrical control signals are discussed by way of example, it will be understood that controller 107′ may be configured to provide a continuous feedback control loop as discussed above with respect to
For example, the driver circuit 111′ may be configured to generate the first electrical control signal so that heat is pumped through the thermoelectric device 101 in a first direction (e.g., from temperature controlled medium 103 to heat transfer structure 105), and to generate the second electrical control signal so that heat is pumped through the thermoelectric device 101 in a second direction (e.g., from heat transfer structure 105 to temperature controlled medium 103) opposite the first direction. According to other embodiments of the present invention, the driver circuit 111′ may be configured to generate the first electrical control signal so that a first electrical current flows through the thermoelectric device 101 in a first direction, and to generate the second electrical control signal so that a second electrical current flows through the thermoelectric device 101 in a second direction opposite the first direction. By reversing a direction of current though the thermoelectric device, a direction of heat pumping may be reversed. The driver circuit 111′ may be configured, for example, to vary the electrical control signal to maintain a stable temperature of the temperature controlled medium 103, to provide a temperature ramp for the temperature controlled medium, and/or to provide a cyclical temperature profile for the temperature controlled medium.
A relatively low amplitude and high frequency AC signal (generated by sensor circuit 115′) may thus be superimposed on a relatively slowly varying (e.g., relatively low frequency) relatively high amplitude control signal (generated by driver circuit 111′), and the combined signal may be applied to the thermoelectric heat pumping device 101. The AC signal can thus be used to measure a resistance of the thermoelectric heat pumping device 101 while maintaining the control signal used to provide heat pumping through the thermoelectric heat pumping device 101. The measured resistance may be used together with a measured voltage across the thermoelectric heat pumping device by sensor circuit 115′ to determine/estimate a temperature gradient across thermoelectric device 101. Temperature sensing discussed above with respect to claim 12 can thus be used to determine/estimate temperatures continuously, at desired sampling intervals, and/or at controller 107′ determined times without interrupting heat pumping.
According to embodiments of the present invention shown in
More particularly, the temperature control system of
Controller 107″ may include driver circuit 111″ electrically coupled to thermoelectric heat pumping device 101 and sensor circuit 111″ electrically coupled to thermoelectric sensing device 1351. Accordingly, sensor circuit 115″ may be configured to sense a first value of an electrical characteristic of thermoelectric sensing device 1351, and driver circuit 111″ may be configured to generate a first electrical control signal to pump heat through thermoelectric heat pumping device 101 between heat transfer structure 105 and temperature controlled medium 103″ in response to sensor circuit 115″ sensing the first value of the electrical characteristic of the thermoelectric sensing device 1351. At a different time (e.g., at a next sensing interval), sensor circuit 115″ may be configured to sense a second value of the electrical characteristic of thermoelectric sensing device 1351, and the first and second values of the electrical characteristic may be different. Accordingly, driver circuit 111″ may be configured to generate a second electrical control signal to pump heat through thermoelectric heat pump device 101 between heat transfer structure 105 and temperature controlled medium 103″ in response to sensing the second electrical characteristic of thermoelectric sensing device 1351.
Accordingly, driver circuit 111″ may provide different electrical control signals (e.g., electrical control signals having different magnitudes, polarities, duty cycles, etc.) responsive to different electrical characteristics of thermoelectric sensing device 1351 (e.g., indicating different temperatures of temperature controlled medium 103″). While first and second electrical characteristics of thermoelectric sensing device 1351 and fist and second electrical control signals are discussed by way of example, it will be understood that controller 107″ may be configured to provide a continuous feedback control loop as discussed above with respect to
As -further shown in
Sensor circuit 115″ may be configured to sense first and second electrical characteristics of thermoelectric sensing device 1351 by sensing electrical signals generated by thermoelectric sensing device 1351 responsive to first and second heat gradients across thermoelectric sensing device 1351. Driver circuit 111″ may be configured to generate the first electrical control signal so that heat is pumped through the thermoelectric heat pumping device in a first direction, and to generate the second electrical control signal so that heat is pumped through the thermoelectric heat pumping device in a second direction opposite the first direction. Driver circuit 111″ may be configured to generate the first electrical control signal so that a first electrical current flows through the thermoelectric heat pumping device in a first direction, and to generate the second electrical control signal so that a second electrical current flows through the thermoelectric heat pumping device in a second direction opposite the first direction.
Driver circuit 111″ may be configured to generate electrical control signals to maintain a stable temperature of temperature controlled medium 103″. According to other embodiments of the present invention, driver circuit 111″ may be configured to generate electrical control signals to provide a temperature ramp for temperature controlled medium 103″. According to still other embodiments of the present invention, driver circuit may be configured to generate electrical control signals to provide a cyclical temperature profile for temperature controlled medium 103″.
Thermoelectric sensing device 1351 may have a structure as discussed above with respect to
Thermoelectric heat pumping device 101 may thus include one or more “active” P-N thermoelectric couples that actively pump heat between temperature controlled medium 103″ and heat transfer structure 105 responsive to electrical control signals generated by driver circuit 111″. In contrast, thermoelectric sensing device 1351 may include one or more “passive” P-N thermoelectric couples that are used by sensor circuit 115″ to estimate a temperature of temperature controlled medium 103″ and/or a load element/structure thermally coupled thereto. Accordingly, temperature controlled medium 103″ may provide thermal coupling between temperature controlled medium sides of thermoelectric sensing device 1351 and thermoelectric heat pumping device 101. In contrast, reference medium 1355 and heat transfer structure 105 may be thermally isolated. Driver and sensor circuits 111″ and 115″ may thus be simplified by providing separate couplings to separate thermoelectric heat pumping and sensing devices 101 and 1351.
When thin film thermoelectric heat pumping devices are used as discussed above with respect to
A differential temperature (e.g., temperature gradient) across the thermoelectric heat pumping device may be measured directly (as discussed above with respect to
According to other embodiments of the present invention, a differential temperature (e.g., temperature gradient) across a thermoelectric sensing device may be measured (as discussed above with respect to
With each of the embodiments discussed above with respect to
While the sensor circuit may actually measure a thermal gradient across the thermoelectric heat pumping device and/or a separate thermoelectric sensing device (as opposed to a temperature on a load side of the temperature controlled medium), information relating to the thermal gradient can be used to estimate a load temperature with a sufficient degree of accuracy. Moreover an accuracy of the estimates may be improved by reducing a thermal resistance between the thermoelectric pumping/sensing device and the load.
According to some embodiments of the present invention, a thermoelectric (TE) cooling/heating device (also referred to as a Peltier cooling device) may provide a cold probe that can be used for medical and/or other purposes. Such as device can be used to create local cold and/or hot areas for medical applications. A TE cooling/heating device, for example, may be used to provide a scalpel with a controlled temperature at the blade, and/or to provide a medical implant that delivers controlled temperatures to localized areas in the human body. An implantable medical TE cooling device may be used to provide medical treatment such as to cool nerves, tumors, and/or portions of the brain, to reduce pain, treat cancer, and/or to stop/reduce seizures. Use of thermoelectric devices to stop seizures is discussed, for example, in the publication by Maria Fontanazza entitled “A Cooler Way To Stop Seizures” (Medical Device & Diagnostic Industry Magazine, October 2005), the disclosure of which is hereby incorporated herein in its entirety by reference.
The TE device 301 may include a plurality of n-type TE elements 309 and p-type TE elements 311 electrically coupled in series and thermally coupled in parallel as discussed above with respect to
In the probe of
According to other embodiments of the present invention, both electrical current and heat may flow in series. For example, the temperature controlled medium may be provided between n-type and p-type TE elements. As shown in
The TE device 401 may include an n-type TE element 409 and a p-type TE element 411 electrically coupled in series and thermally coupled to pump heat from opposite sides of the cold probe 421. As shown in
Accordingly, heat may be pumped from the cold probe 421 through the n-type and p-type TE elements 409 and 411 to the electrically conductive traces 405 on opposite sides of the cold probe 421. Portions of the cold probe 421 extending beyond the TE elements 409 and 411 may be shaped as a blade to provide a thermoelectrically cooled (or heated) scalpel. According to other embodiments of the present invention, portions of the probe 421 extending beyond the TE elements 409 and 411 may be shaped to provide a probe that may be inserted with precision in a human body to provide heating and/or cooling.
According to embodiments of the present invention, a TE device may be used to provide cooling, heating, and/or temperature control at a portion of a human body (or other living tissue) to provide medical treatment in areas such as neurological seizure control, pain management, transdermal delivery of pharmaceutical agents, and/or caloric stimulation of retrocortical cerebral enhancement. Such medical TE devices may be implantable, insertable, hypodermic, attachable, and/or wearable. Moreover, a medical TE device may provide both heat pumping functionality and temperature feedback functionality as discussed above with respect to
In general, a cooling device may include a cold surface at the tip of a probe with a sub-ambient temperature that is maintained using a solid-state device, such as a TE device (also referred to as a thermoelectric cooler or TEC), which in turn is attached to a body of a thermal mass configured to retain, transfer, transport and/or remove the heat from the hot-side of the solid-state device to the surrounding body tissues and/or ambient heat sink.
According to embodiments of the present invention, heat may be removed from the TE device to a surrounding heat-sink without incurring significant thermal damage to tissues between the TE device and an internal or external heat-sink. This heat removal may be accomplished by maintaining an amount of heat dissipation from an exposed surface(s) of the device to within a pre-determined level of heat-flux and temperature that can be tolerated by the tissue. Different embodiments of the present invention may include transporting heat away from a hot-side of a TEC to either a thermal mass and/or a heat sink, and diluting a level of heat density at a surface that is in intimate contact with the tissues. Dilution of heat may occur in spatial and/or temporal dimensions.
With an implantable TE heating/cooling device, heat-energy may be absorbed and/or dispersed in such a way that, by the time that the heat-flow reaches the surrounding tissue(s), the heat-density is low enough that the surrounding tissues themselves may serve as a heat-sink. A thermal mass including materials of high-thermal-diffusivity and/or high-thermal-capacitance (i.e., phase change materials or PCM's) may be attached to a hot-side of the TE device to absorb and/or diffuse heat relatively uniformly throughout the mass.
As shown in
As shown in
In addition, an insulating layer 815 may be provided between the core (811 and/or 813) and an inner shell 817. The insulating layer 815 may include electrical power and/or ground connections between the TE device 809 and a controller, and the inner shell 817 may include a low thermal conductivity material with a low touch temperature and a low-q dissipation. While not shown in
As shown in
TE cooling/heating devices discussed above may use a control mechanism, internal and/or external, to monitor and/or maintain device functionalities within specifications and/or usage requirements. A size and/or performance of a thin-film TE cooling/heating device may enable an electrical circuit in which the TE cooling/heating device provides an integral function of the operation of the circuit. A micro-TE cooling/heating device can be a part of the circuit to influence its own performance through a feedback loop, for example, as discussed above with respect to
According to some embodiments of the present invention, a TE device may operate in a signal generating mode to sense a thermal gradient and to generate a current (or other electrical signal) in response to the temperature gradient. The current (or other electrical signal) may be used to influence operations of an electrical circuit (such as a controller), which in turn can control an operational characteristic(s) of the TE device when operating in a heating and/or cooling mode. Stated in other words, during a temperature sensing operation, a current generated by the TE device responsive to a heat gradient across the TE device may be used to determine a temperature of the surface being cooled. During a cooling operation, a current through the TE device may be controlled responsive to the temperature determined during the temperature sensing operation. The same TE device may thus provide both temperature sensing and cooling/heating.
According to some other embodiments of the present invention, a temperature sensitive device may be physically attached to the surface of a micro TE device, and the temperature sensitive device may also be electrically connected to the drive circuit (e.g. controller) of the TE device. The TE device (by way of its relatively fast response time) may rapidly influence the performance of the temperature sensitive device by heating and/or cooling, while feedback from the temperature sensitive device may modulate an amount of heating and/or cooling that the TE device does (e.g., a power transistor may actively cool and/or heat itself in advance of reaching a damaging or debilitating operating temperature). According to still other embodiments of the present invention, a TE device may rapidly switch from heating to cooling and/or from cooling to heating to achieve different operating characteristics.
Elements of a control circuit according to embodiments of the present invention may include:
1) a control circuit that resides on and/or within a medical probe and/or thermal control structure, residing either within or external to a living body;
2) a feedback sensor that measures temperature and/or heat flux either internally or externally to a thin film TE device using either an external sensor(s) (e.g., thermocouple) or an internal sensor(s) (i.e., the thin film TE device itself);
3) a control circuit (or controller) including a proportional-integral-derivative (PID) controller, where the PID controller uses a sensing mechanism internal and/or external to the thin film TE device to control the TE device;
4) a PID controller providing that a cooling/heating curve meets a desired cooling/heating curve profile, and the cooling/heating curve may be designed to meet a specific therapeutic need such as,
By inserting brief off-duty periods (also referred to as sensing intervals), when the TE device is not driven with current to heat or cool, into any of the profiles mentioned above, a signal generating mode can be incorporated into the system using the TE device to sense a temperature and/or heat flux. During each off-duty period or sensing interval, the TE device itself may be used as a sensor/thermocouple where the output signal (which has been calibrated to the temperature and/or heat flux) is fed back to the controller to dynamically determine a profile of a next round of cooling/heating duty cycles (also referred to as drive periods). Use of the TE device to both heat/cool and to sense may be feasible because a response time constant of a micro TEC may be on the order about 10 ms or less.
As used herein, the term thermoelectric element includes a structure having a layer of a thermoelectric material (e.g. Bi2Te3) with a Seebeck coefficient sufficient to provide thermoelectric heat pumping (heating or cooling) responsive to an electrical current therethrough and/or electrical power generation responsive to a temperature gradient across the thermoelectric element. A thermoelectric element, for example, may include one or more P-N couples with a P-N couple having a P-type thermoelectric element and an N-type thermoelectric element electrically coupled in series and thermally coupled in parallel and configured to provide thermoelectric heating, cooling, and/or power generation. According to other embodiments of the present invention, a thermoelectric element may include a single layer of a thermoelectric material (either P-type or N-type) configured to provide thermoelectric heating, cooling, and/or power generation.
As discussed above TE devices may be used to provide heating, cooling, power generation, and/or temperature sensing according to embodiments of the present invention. While some embodiments may be discussed with respect a TE device(s) to provide cooling, it will be understood that the TE device(s) of such embodiments may also be used to provide heating, power generation, and/or temperature sensing. While some embodiments may be discussed with respect a TE device(s) to provide heating, it will be understood that the TE device(s) of such embodiments may also be used to provide cooling, power generation, and/or temperature sensing. While some embodiments may be discussed with respect a TE device(s) to provide power generation, it will be understood that the TE device(s) of such embodiments may also be used to provide heating, cooling, and/or temperature sensing.
While the present invention has been particularly shown and described with reference to embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.
The present application claims the benefit of priority as a continuation-in-part of U.S. application Ser. No. 11/972,267 entitled “Temperature Control Including Integrated Thermoelectric Temperature Sensing And Related Methods And Systems” filed Jan. 10, 2008, which claims the benefit of priority from U.S. Provisional Application No. 60/884,546 entitled “Implantable Thermoelectric Cooling Device” filed Jan. 11, 2007, and from U.S. Provisional Application No. 60/908,261 entitled “Methods Of Thermal Management Of Implantable And Wearable Thermoelectric Components (TEC's) And Use Of TEC As Integral Part Of The Thermal Control Circuit” filed Mar. 27, 2007. The disclosures of each of the above referenced U.S. utility and provisional applications are hereby incorporated herein in their entirety by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60884546 | Jan 2007 | US | |
| 60908261 | Mar 2007 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11972267 | Jan 2008 | US |
| Child | 12166953 | US |
