Abstract:
A thermoelectric power supply converts thermal energy into a high power output with voltages in the Volt-range for powering a microelectronic device and comprises an in-plane thermoelectric generator, a cross-plane thermoelectric generator, an initial energy management assembly, a voltage converter and a final energy management assembly. The in-plane thermoelectric generator produces a high thermoelectric voltage at low power output. The initial energy management assembly rectifies and limits the thermoelectric voltage and stores and releases power to the voltage converter. The cross-plane thermoelectric generator generates a high power output at low thermoelectric voltage. Once activated by the in-plane thermoelectric generator, the voltage converter multiplies the low thermoelectric voltage output of the cross-plane thermoelectric generator. After multiplying the relatively low voltage provided by the cross-plane thermoelectric generator, the voltage converter supplies electrical energy to the final energy management assembly which rectifies and limits the voltage and stores and releases energy to an external power receiver such as the microelectronic device.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims the benefit of co-pending U.S. Provisional Application No. 60/814,648, entitled THERMOELECTRIC POWER SUPPLY and filed on Jun. 16, 2006, the entire contents of which is herein incorporated by reference. The present application is also related to commonly-owned U.S. patent application Ser. No. 11/352,113 filed on Feb. 10, 2006 and entitled IMPROVED LOW POWER THERMOELECTRIC GENERATOR, which is a continuation-in-part application of U.S. application Ser. No. 11/185,312, filed on Nov. 17, 2005 and entitled LOW POWER THERMOELECTRIC GENERATOR, which is a continuation application of U.S. application Ser. No. 10/440,992 filed on May 19, 2003 and entitled LOW POWER THERMOELECTRIC GENERATOR, now U.S. Pat. No. 6,958,443, the entire contents of each being expressly incorporated by reference herein. 
     
     STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT 
       [0002]    (Not Applicable) 
       BACKGROUND 
       [0003]    The present invention pertains generally to thermoelectric devices and, more particularly, to a self-sufficient thermoelectric power supply that is specifically adapted to produce a relatively high-voltage power output such as for powering microelectronic devices. 
         [0004]    The increasing trend toward miniaturization of microelectronic devices necessitates the development of miniaturized power supplies. Batteries and solar cells are traditional power sources for such microelectronic devices. However, the power that is supplied by batteries dissipates over time requiring that the batteries be periodically replaced. Solar cells, although having an effectively unlimited useful life, may only provide a transient source of power as the sun or other light sources may not always be available. Furthermore, solar cells require periodic cleaning of their surfaces in order to maintain efficiency of energy conversion. 
         [0005]    Thermoelectric generators are self-sufficient energy sources that convert thermal energy into electrical energy according to the Seebeck effect—a phenomenon whereby heat differences may be converted into electricity due in large part to charge carrier diffusion in a conductor. Electrical power may be generated under the Seebeck effect by utilizing thermocouples which are each comprised of a pair of dissimilar metals (n-type and p-type) joined at one end. N-type and p-type refers to the respective negative and positive types of charge carriers within the material. 
         [0006]    The temperature gradient that exists between the ends of the thermocouple may be artificially applied or it may be naturally-occurring as waste heat or as dissipated heat that is constantly rejected by the human body. In a wristwatch, one side is typically exposed to air at ambient temperature while the opposite side is exposed to the higher temperature of the wearer&#39;s skin. Thus, a small temperature gradient is present across the thickness of the wristwatch. A thermoelectric generator may be incorporated into the wristwatch to take advantage of the dissipated or waste heat and generate a supply of power sufficient to operate the wristwatch as a self-contained unit. Advantageously, many microelectronic devices that are similar in size to a typical wristwatch require only a small amount of power and therefore may also be compatible for powering by a thermoelectric generator. 
         [0007]    The continuous development that is occurring in the microelectronics industry has led to the increasing miniaturization of certain electronic applications with a concomitant reduction in power consumption of many modern electronic devices. This reduction in power requirements for such electronic devices has enabled the employment of alternative energy sources such as thermoelectric generators. 
         [0008]    When used as thermal energy harvesting devices for recovering thermal energy as dissipated heat which is typically lost to the environment, such thermoelectric generators may be utilized to power microelectronics or sensor systems. As the functional density of such modern electronic devices increases due in part to the integration of the many subcomponents that make up such electronic devices, power consumption of the devices has shrunk to the micro-watt and nano-watt level. Often however, a higher power is required for many microelectronic devices. This higher power requirement is often in the milli-watt range. 
         [0009]    In view of the above-described developments in microelectronic miniaturization, there exists a need in the art for a power supply for such microelectronic devices that is capable of providing an essentially continuous supply of power thereto. Furthermore, there exists a need in the art for a power supply for microelectronic devices that does not require periodic replacement of the power source. 
         [0010]    In addition, there exists a need in the art for a power supply for microelectronic devices that can provide a stable and efficient source of power thereto and which has an effectively unlimited useful life. Finally, there exists a need in the art for a power supply such as may be used for microelectronic devices that is capable of converting essentially constant energy sources into electrical energy using only small temperature gradients. 
       BRIEF SUMMARY 
       [0011]    The present invention specifically address and alleviates the above-mentioned needs associated with power supplies for microelectronic devices by providing a thermoelectric power supply that is specifically adapted to convert thermal energy into electrical energy from only small temperature gradients such as those occurring due to body or waste heat. More particularly, the present invention provides thermoelectric power supply that is capable of converting thermal energy into a relatively high power output with voltages in the Volt-range and which provides such power in a stable and reliable manner in order to power microelectronic devices such as sensor systems. 
         [0012]    In its broadest sense, the invention comprises an in-plane thermoelectric generator, a cross-plane thermoelectric generator, an initial energy management assembly, a voltage converter and a final energy management assembly. The in-plane thermoelectric generator may be constructed similar to that shown and described in U.S. Pat. No. 6,958,443 issued to Stark et al., the entire contents of which is expressly incorporated by reference herein. The in-plane thermoelectric generator is generally constructed having a high number of thermocouples arranged in series and deposited on a substrate in order to produce a relatively high thermoelectric voltage but with low power output. 
         [0013]    The initial energy management system receives the relatively high voltage and low power output from the in-plane thermoelectric generator and is specifically configured to rectify the thermoelectric voltage, protect against excess voltage via a diode, and store or accumulate a sufficient amount of energy in an energy storage element in order to activate the voltage converter. The initial energy management assembly may further include a voltage detector which is adapted to release power to the voltage converter upon obtaining a certain voltage threshold. 
         [0014]    The voltage converter is specifically adapted to be activated or powered by voltage from the in-plane thermoelectric generator after processing by the initial energy management assembly. The voltage converter then is capable of converting the low voltage output from the cross-plane thermoelectric generator into a relatively high voltage using the principle of voltage multiplication such as by using a charge pump. More specifically, the voltage converter is adapted to multiply the relatively low thermoelectric voltage output of the cross-plane thermoelectric generator. 
         [0015]    Advantageously, the cross-plane thermoelectric generator is adapted to generate a relatively high power output but at low voltage. Unfortunately, due to the geometric arrangement of the thermocouples that make up the cross-plane thermoelectric generator, the high power output is provided at a relatively low voltage at small temperature gradients such that the voltage is too low to drive most modern electronic circuitry. However, by combining the in-plane thermoelectric generator with the cross-plane thermoelectric generator, the combined advantages of each may be utilized to overcome the individual disadvantages in order to provide a thermoelectric power supply having an electric power output that is compatible for use in electronic devices requiring a high power consumption. 
         [0016]    In the thermoelectric power supply of the present invention, after multiplying the relatively low voltage provided by the cross-plane thermoelectric generator, the voltage converter supplies electrical energy directly to the final energy management assembly which, like the initial energy management assembly, also rectifies and limits the voltage, charges an integrated energy storage element, detects the charging state of the stored energy via a voltage detector for release to an external power receiver such as a microelectronic device. 
         [0017]    Optionally, a portion of the power released by the final energy management assembly may be re-circulated back to the voltage converter to drive the voltage converter which may provide the capability for reducing the power requirement, size and cost of the in-plane thermoelectric generator. Therefore, the initial energy management assembly is used to initially activate the voltage converter after which the initial energy management assembly may be used to provide energy to the final device. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    These and other features and advantages of the various embodiments disclosed herein will be better understood with respect to the following description and drawings, in which like numbers refer to like parts throughout, and in which: 
           [0019]      FIG. 1  is a schematic illustration of a thermoelectric power supply in one embodiment and which is comprised of an in-plane thermoelectric generator, a cross-plane thermoelectric generator, an initial energy management assembly, a voltage converter and a final energy management assembly; 
           [0020]      FIG. 2  is a perspective view of the in-plane thermoelectric generator illustrating the basic configuration of p-type and n-type thermoelectric legs deposited onto a substrate using thin film technologies; 
           [0021]      FIG. 3  is a perspective view of the cross-plane thermoelectric generator wherein a spaced pair of heat couple plates is configured in a checkerboard arrangement of p-type and n-type thermoelectric legs; 
           [0022]      FIG. 4  is a schematic diagram of the thermoelectric power supply in an alternative embodiment wherein the in-plane and cross-plane thermoelectric generators are constructed as separate elements and wherein the initial energy management assembly, voltage converter and final energy management assembly are integrated, for example, into a unitary electronic assembly; and 
           [0023]      FIG. 5  is a schematic diagram of the thermoelectric power supply in a further alternative embodiment wherein the in-plane and cross-plane thermoelectric generators share the same heat couple plates similar to that illustrated in  FIG. 1  but wherein the initial and final energy management assemblies are integrated with the voltage converter into a unitary electronic assembly. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    Referring now to the drawings wherein the showings are for purposes of illustrating preferred embodiments of the present invention and not for purposes of limiting the same, shown in  FIG. 1  is a schematic diagram of a thermoelectric power supply  10  that is specifically adapted to convert thermal energy into electrical energy from only small temperature gradients such as emitted by the body or waste heat. Advantageously, the power supply  10  of the present invention is adapted to produce electrical energy from such small temperature gradients with a high power output and with a stable and relatively high level voltage sufficient to power modern microelectronic devices and sensor systems. 
         [0025]    In its broadest sense, the thermoelectric power supply  10  comprises an in-plane thermoelectric generator  12 , a cross-plane thermoelectric generator  14 , an initial energy management assembly  40 , a voltage converter  58  and a final energy management assembly  64 . The in-plane thermoelectric generator  12  provides the advantage of generating a relatively high voltage at even small temperature gradients. 
         [0026]    Arranged with a relatively high number of thermocouples  38  connected in series, the in-plane thermoelectric generator  12  has a relatively high thermal resistance due to the arrangement of relatively long and thin n-type and p-type thermoelectric legs  34 ,  36  which are disposed in generally parallel and spaced relation to one another. More specifically, the length of such thermoelectric legs is in the millimeter range wherein the thickness of such legs is in the order of magnitude of microns up to tens of microns. In this regard, the ratio of length of the thermoelectric legs to the thickness thereof is such that the amount of heat flowing through the in-plane thermoelectric generator  12  is relatively small. 
         [0027]    Unfortunately, the arrangement of the in-plane thermoelectric generator  12  results in the creation of a relatively high electrical resistance due as well as to the relatively large number of thermocouples  38  that are electrically connected in series. In addition, high electrical resistance is a result of the relatively large ratio of length of the thermoelectric legs to cross-section thereof. This high electrical resistance results in a relatively low power output. Furthermore, the in-plane thermoelectric generator  12  arrangement results in a relatively low level of efficiency as a result of parasitic heat flow through the substrate  26  onto which the n-type and p-type thermoelectric legs  34 ,  36  are deposited. 
         [0028]    As was earlier mentioned, a common arrangement for in-plane thermoelectric generator  12  configurations is to construct such devices as a foil segment  24  or series of foil segments  24  having a relatively large number of thermocouples  38  which are themselves electrically connected in series. The p-type and n-type thermoelectric legs  36 ,  34  which make up the thermocouples  38  are connected using metal bridges  30  and metal contacts  32  as is shown in  FIG. 2 . Such metal bridges  30  and metal contacts  32  may be deposited onto the substrate  26  after deposition of the p-type and n-type thermoelectric legs  36 ,  34  in order to form the thin film thermoelectric structure that makes up the in-plane thermoelectric generator  12  configuration. 
         [0029]    The in-plane thermoelectric generator may be fabricated by a number of alternative technologies. For example, the in-plane thermoelectric generator may be fabricated using MEMS silicon-based technology such as that described in the document entitled “A Thermoelectric Converter for Energy Supply” by H. Glosch et al. and reprinted in the publication entitled Sensors and Actuators, No. 74 (1999) Pages 246-250. Additionally, the in-plane thermoelectric generator may be fabricated using silicon technology such as that described in the document entitled “Miniaturized Thermoelectric Generators Based on Poly-Si and Poly-SiGe Surface Micromachining” by M. Strasser et al. of Infineon Technologies A.G., Wireless Products, Microsystems and Munich University of Technology, Institute for Physics of Electrotechnology. 
         [0030]    A further description of silicon-based technology for fabricating the in-plane thermoelectric generator is provided in the document entitled “Analysis of a CMOS Low Power Thermoelectric Generator” by M. Strasser et al. of Infineon Technologies and Munich University of Technology. The in-plane thermoelectric generator may further fabricated using electroplating technology similar to that disclosed in the document entitled “Microfabrication of Thermoelectric Generators on Flexible Foil Substrates as Power Source for Autonomous Microsystems” by Wenmin Qu et al. and published in The Journal of Micromechanics and Microengineering, 11 (2001), pages 146-152. 
         [0031]    In an alternative arrangement, the relatively high density of thermocouples  38  can be achieved utilizing stacking of the substrates  26 . Furthermore, the foil segment  24  or substrate  26  may be rolled into a spiral shape in order to produce a round-shaped thermoelectric generator similar to that disclosed in U.S. Patent Publication Serial No. 20060151021 and entitled LOW POWER THERMOELECTRIC GENERATOR. A spaced pair of heat couple plates  22  (i.e., top and bottom plates) may be attached such as by bonding to the stack or roll of thin films (i.e., thermocouples  38  deposited on substrate  26 ) in order to provide thermal connection thereacross and also to allow for connection of the thermoelectric generator to an external heat source  18  and a heat sink  20 . 
         [0032]    Electrical connection of the in-plane thermoelectric generator  12  to the initial energy management assembly  40  can be facilitated using at least one of the heat couple plates  22  (i.e., one of the top and bottom plates) or by directly connecting opposing ends of the thermocouple chain to the initial energy management assembly  40 . In using the heat couple plates  22  to make the connection, the top plate and bottom plate are preferably fabricated of electrically conductive material such as metallic material. 
         [0033]    An inner surface of the heat couple plates  22  is preferably coated with a non-electrically conductive coating except at the extreme ends of the series of alternating n-type and p-type thermoelectric legs  34 ,  36  wherein the non-electrically conductive coating is locally omitted. The heat couple plates  22  (i.e., top or bottom plate) are, in turn, electrically connected to respective ones of opposing ends of the series of alternating n-type and p-type thermoelectric legs  34 ,  36 . The heat couple plates  22  are then electrically connectable to the initial energy management assembly  40  similar to the electrical connection of a watch battery to a watch. 
         [0034]    Alternatively, the in-plane thermoelectric generator  12  may be connected to the initial energy management assembly  40  by direct connection to the ends of the thermocouple chain of the in-plane thermoelectric generator  12 . More specifically, in such an arrangement, the heat couple plates  22  (i.e., top and bottom plated) may be fabricated of electrically non-conductive material such as relatively-highly-thermally-conductive ceramic material or other suitable material with a relatively high thermal conductivity. Alternatively, at least one of the inside surfaces of the heat couple plates  22  may be coated with a non-electrically conductive coating. 
         [0035]    In another embodiment, the thermally conductive glue or adhesive which bonds the top and bottom plates to the foil segments as described in U.S. Pat. No. 6,958,443 is preferably electrically non-conductive and therefore eliminates the need for a separate non-electrically conductive coating. Furthermore, it is contemplated that the heat couple plates  22  (i.e., top and bottom plates) may be fabricated of electrically conductive material (e.g., metallic) which is electrically insulated from the foil segments  24  by the non-electrically conductive coating and/or by the non-electrically conductive glue which bonds the foil segments  24  to the top and bottom plates. The thermoelectric power supply  10  may include electrically conductive wiring for connecting the respective ones of opposing ends of the series of alternating n-type and p-type thermoelectric legs  34 ,  36  to the initial energy management assembly  40 . 
         [0036]    Regarding the construction of the cross-plane thermoelectric generator  14 , its configuration as shown in  FIG. 3  may be fabricated using bulk polycrystalline material such as is utilized in standard Peltier coolers known in the art. In this typical configuration, the length of the p-type and n-type thermoelectric legs  36 ,  34  is in the millimeter range for configurations utilizing bulk polycrystalline material. Alternatively, for construction methodologies using thin film technology in order to produce the cross-plane thermoelectric generator  14 , the length of the thermoelectric legs may be in a range of several tens of microns. In this configuration, heat couple plates  22  that are arranged on upper and lower ends of the spaced pair of thermoelectric legs act as the substrate  26  for the thin film deposition. 
         [0037]    Advantageously, the arrangement as shown in  FIG. 3  for the cross-plane thermoelectric generator  14  provides a relatively low electrical resistance due to the relatively small quantity of thermocouples  38  that are arranged in series. In addition, low electric resistance of the cross-plane thermoelectric generator  14  configuration is a result of the relatively small ratio of length of n-type and p-type thermoelectric legs  34 ,  36  to cross-sections thereof. In contrast to the arrangement for the in-plane thermoelectric generator  12 , the relatively small aspect ratio of the thermoelectric legs in the cross-plane thermoelectric generator  14  results in a relatively high power output. 
         [0038]    In addition, due to the lack of a substrate  26  interconnecting the heat couple plates  22  as is present in the in-plane thermoelectric generator  12 , the cross-plane thermoelectric generator  14  provides a relatively high efficiency capability for converting thermal energy into electrical energy. This is a result of the lack of parasitic heat flow through the substrate  26  as is present in the in-plane thermoelectric generator  12  configuration. Advantageously, this arrangement results in heat flowing only through the thermoelectric legs. Unfortunately, the advantages provided by the small aspect ratio (i.e., low electrical resistance and high power output) also means that the cross-plane thermoelectric generator  14  exhibits relatively low thermal resistance due to the same low aspect ratio. 
         [0039]    More specifically, the relatively low ratio of length of the thermoelectric legs to cross-section thereof leads to low thermal resistance resulting in a relatively large amounts of heat flow through the device. An unfavorable characteristic of the cross-plane thermoelectric generator  14  are associated with the relatively limited quantity of thermocouples  38  that may be electrically connected in series while still minimizing the overall size of the device. This limited number of thermocouples  38  results in a relatively low voltage output at small temperature gradients despite the high power capabilities. 
         [0040]    The cross-plane thermoelectric generator  14  may be fabricated by a variety of thin film technologies described in the documents mentioned below. For example, the cross-plane thermoelectric generator  14  may be fabricated by using thin film technologies described in the document entitled “Micropelt Miniaturized Thermoelectric Devices: Small Size, High Cooling Power Densities, Short Response Time” by H. Boettner of the Fraunhofer Institute Physikalische Messtechnik (IPM), Freiburg, Germany, or in the article entitled “Micropelt: State of the Art, Roadmap and Applications” also by H. Boettner as well as that described in the document entitled “New Thermoelectric Components Using Microsystem Technologies” also by H. Boettner et al. Various electroplating technology techniques (e.g., galvanic processing) for the cross-plane thermoelectric generator  14  can be used such as is described in the disclosure entitled “Thermoelectric Microdevice Fabricated by a MEMS-Like Electrochemical Process” by G. Jeffrey Snyder et al. of Jet Propulsion Laboratory, California Institute of Technology and published on-line on 27 Jul. 2003, incorporated by reference in its entirety. 
         [0041]    In addition, the cross-plane thermoelectric generator  14  may be fabricated using bulk polycrystalline thermoelectric material and mechanical cutting technology of bulk polycrystalline thermoelectric material. The bulk polycrystalline thermoelectric material may be prepared from melts (i.e., liquids) and/or by powder technology techniques and/or by mechanical alloying. 
         [0042]    Advantageously, the thermoelectric power supply  10  of the present invention combines in-plane and cross-plane thermoelectric generators  12 ,  14  in a unique arrangement that takes advantage of the benefits of each device in order to provide electrical power output that is compatible for many microelectronic devices that consume relatively high power. More specifically, the in-plane thermoelectric generator  12  configuration is capable of providing the necessary voltage for operating many modern microelectronic devices in the 1.5 to 3 volt range but are incapable of producing the required amount of power due to the relatively low current at which such electrical energy is provided. Such low electrical current is a result of the high electric internal resistance of the in-plane thermoelectric generator  12  design. 
         [0043]    Conversely, the cross-plane thermoelectric generator  14  configuration is capable of producing the amount of power compatible for many electronic devices  62  due to its low internal resistance which results in a relatively high electrical current. However, the power output of the cross-plane thermoelectric generator  14  at the relatively small temperature gradients results in a thermoelectric voltage that is generally too low for operating many electronic circuitry. 
         [0044]    However, by including the voltage converter  58  in the thermoelectric power supply  10  of the present invention, the relatively high power output at low voltage of the cross-plane thermoelectric generator  14  may be exploited by the voltage converter  58  by increasing the voltage of the cross-plane thermoelectric generator  14 . The voltage converter  58  does this using the principle of a charge pump  60 . The voltage converter  58  then supplies electrical energy directly to the final energy management assembly  64 . 
         [0045]    As illustrated in  FIG. 1 , the final energy management assembly  64  is connected to the voltage converter  58  and receives power therefrom. The voltage converter  58  is activated or powered by electrical energy produced initially by the in-plane thermoelectric generator  12  after processing thereof by the initial energy management assembly  40 . More specifically, the final energy management assembly  64  is adapted to rectify and limit voltage received from the cross-plane thermoelectric generator  14 , charge an energy storage element  50  such as a capacitor  52  or a rechargeable thin film battery  54  contained within the final energy management assembly  64 , and detect the charging state of the energy storage element  50  utilizing a voltage detector  56 . 
         [0046]    More specifically, the detection capability of the voltage detector  56  allows the final energy management assembly  64  to release power to the electronic device  62  upon detection of a sufficient level of electrical energy in the energy storage element  50 . As shown in  FIG. 1 , the final energy management assembly  64  releases power to a device such as a microelectronic device in order to power the device which may be any number of applications including, but not limited to, microelectronics, and sensor systems. 
         [0047]    Optionally, a portion of the energy released by the final energy management assembly  64  may be re-circulated back to the voltage converter  58  in order to provide power for its voltage multiplication purposes. In such a configuration, the power requirements as well as size and, ultimately, cost, of the in-plane thermoelectric generator  12  may be reduced. In addition, the power requirements, size and cost of the initial energy management assembly  40  may also be reduced as the initial energy management assembly  40  would then only be required to operate to initiate or start the voltage converter  58  after which operation of the initial energy management assembly  40  would no longer be required. Optionally, if power produced by the initial energy management assembly  40  is not required to drive the voltage converter  58 , such power may be delivered to the final energy management assembly  64  where it may be stored in the energy storage element  50 . 
         [0048]    In addition, the thermoelectric power supply  10  of the present invention may be configured to include a relatively large energy storage element  50  such as a rechargeable thin film battery  54  or a capacitor  52  in electrical communication with the final energy management assembly  64 . Such relatively large energy storage element  50  may be configured to store excess energy not required by the final electronic device  62  and/or voltage converter  58 . 
         [0049]    Regarding the specific architecture of the initial energy management assembly  40 , it is contemplated that the initial energy management assembly  40  functions to rectify and limit the thermoelectric voltage produced by the in-plane thermoelectric generator  12 , protect against the generation of excess voltage, initially provide energy storage capability in the form of an energy storage element  50 , as well as provide the capability of voltage regulation in order to regulate the point at which power is released to the voltage converter  58 . 
         [0050]    Rectifying of the thermoelectric voltage may be facilitated through the use of a diode  44  in order to provide voltage with only one polarity regardless of the direction of temperature flow or temperature gradient. Alternatively, the rectifier  42  may be adapted to enable exploitation of temperature gradient regardless of the direction of heat flow by utilizing a diode bridge  46 . Further embodiments may include at least one diode to block the discharge of energy storage by the in-plane and/or cross-plane thermoelectric generators  12 ,  14 . 
         [0051]    The initial energy management assembly  40  may also provide excess voltage protection such as by utilizing a Zener diode, a single diode  44  or a plurality of diodes  44  arranged in series in a manner well known in the art. Initial energy storage elements  50  may include small capacitors  52  or a rechargeable thin film battery configured to accumulate sufficient energy in order to activate the voltage converter  58 . Voltage detection may be facilitated through the use of a switch or switches at defined voltage thresholds which correspond to the amount of energy stored. Over a pre-determined threshold, charges in the storage element may be released as power to the voltage converter  58 . Under that pre-determined threshold, electrical current flow may be interrupted or prevented. 
         [0052]    As was earlier mentioned, the voltage converter  58  is specifically adapted to convert the relatively low voltage but high power output of the cross-plane thermoelectric generator  14  into a usable high voltage using the principle of voltage multiplication in the manner of a charge pump  60 . In this manner, the thermoelectric power supply  10  is capable of powering or driving electronics such as energy management systems, a final electronic application and/or the voltage converter  58  itself. 
         [0053]    The final energy management assembly  64  may be adapted to provide similar capabilities as was described above for the initial energy management assembly  40 . In this regard, the final energy management assembly  64  is preferably adapted to rectify thermoelectric voltage in order to provide voltage at one polarity for heat flow in opposite directions utilizing a diode  44  or diode bridge  46 . The final energy management assembly  64  is also preferably adapted to provide for excess voltage protection to prevent damage to the final electronic application as well as including an energy storage element  50  such as a small capacitor  52  or rechargeable thin film battery  54  in order to power the application to which the thermoelectric power supply  10  is connected. 
         [0054]    Optionally, an additional energy storage element  50  such as a relatively large rechargeable thin film battery  54  or capacitor  52  may be integrated into the final energy management assembly  64  in order to allow for accumulation of excess energy that is not required to power the electrical device. Like the initial energy management assembly  40 , the final energy management assembly  64  may further include a voltage detector  56  to determine and regulate the release of energy to the microelectronic device or application to which the thermoelectric power supply  10  is connected. 
         [0055]    In each of the above arrangements, the features of the initial energy management assembly  40  and final energy management assembly  64  are optimized according to the specific application and thermal environment in which the thermoelectric power supply  10  operates. More specifically, the above described features of the initial and final energy management assemblies may be reduced according to the requirements of the device to be powered by the thermoelectric generator as well as in accordance with the characteristics of the thermal environment within which the thermoelectric power supply  10  operates. 
         [0056]    Alternative embodiments or arrangements for the components of the thermoelectric power supply  10  are shown in  FIGS. 4 and 5 . In  FIG. 4 , shown is an arrangement wherein the in-plane thermoelectric generator  12  is constructed as a separate entity from the cross-plane thermoelectric generator  14 . As shown in  FIG. 1 , the in-plane and cross-plane thermoelectric generators  12 ,  14  may be configured to share a common heat source  18  and heat sink  20 . 
         [0057]    Conversely, as shown in  FIG. 4 , it is contemplated that the thermoelectric power supply  10  may be arranged such that the in-plane and cross-plane thermoelectric generators  12 ,  14  have separate heat couple plates  22  for heat source  18  and heat sink  20  purposes. In addition,  FIG. 1  illustrates the other components of the initial and final energy management assemblies  40 ,  64  and voltage converter  58  being provided as separate components which are electrically connected together. 
         [0058]    In yet another alternative arrangement shown in  FIG. 5 , the thermoelectric power supply  10  may be arranged such that the in-plane and cross-plane thermoelectric generators  12 ,  14  share a common heat source  18  and heat sink  20  (i.e., common heat couple plates  22 ) as opposed to the separate heat couple plates  22  of  FIG. 4 . 
         [0059]    However, as shown in  FIG. 5 , the in-plane and cross-plane thermoelectric generators  12 ,  14  may be integrated into a unitary structure which may, in turn, be electrically connected to an assembly comprising the initial and final energy management assemblies  40 ,  64  and the voltage converter  58 . As was earlier mentioned, the in-plane thermoelectric generator  12  may be provided in several arrangements including, but not limited to, a stack of thermopiles each comprising a substrate  26  having the thermoelectric legs disposed thereon and which are interconnected using metal bridges  30  and metal contacts  32 . 
         [0060]    Alternatively, the in-plane thermoelectric generator  12  may be arranged as a spiral of a continuous substrate  26  wherein a relatively large number of thermoelectric legs are connected in series wherein substrate  26  portions may be connected end to end using metal contacts  32  between the substrates  26  to electrically connect the thermoelectric legs in series. The spiral or stack of the thermopile structure may have the heat couple plates  22  disposed on upper and lower ends in order to thermally connect to a heat source  18  and heat sink  20 . In a final embodiment, it is contemplated that each of the components that make-up the thermoelectric power supply  10  may be integrated into a unitary structure and encapsulated to form a convenient assembly which may be adapted for use in many common microelectronic devices. 
         [0061]    The description of the various embodiments of the present invention is presented to illustrate preferred embodiments thereof and other inventive concepts may be otherwise variously embodied and employed. The appended claims are intended to be construed to include such variations except insofar as limited by the prior art.