Patent Publication Number: US-2015075186-A1

Title: Method of and an apparatus for maintaining constant phone skin temperature with a thermoelectric cooler and increasing allowable power/performance limit for die in a mobile segment

Description:
BACKGROUND 
     1. Field 
     The present disclosure relates generally to a mobile device, and more particularly, to optimizing performance and user experience of the mobile device. 
     2. Background 
     Devices such as mobile devices and computing devices have components that generate heat. Mobile device components generally generate more heat as the components perform at a higher level. Heat removal is often necessary to ensure optimal user experience with a device. Further, if a user directly contacts the device, then a device portion contacted should be maintained within a certain temperature range to optimize the user&#39;s experience with the device. For example, if heat from the device causes the device to become hot, a user that is in contact with the device may find the high temperature in the device unpleasant. Manufacturers design devices to efficiently remove the heat from mobile devices without significantly reducing performance of the mobile devices. Therefore, an approach to maintain a desired temperature while optimizing the performance of the device is desired. 
     SUMMARY 
     In an aspect of the disclosure, a method, a computer program product, and an apparatus are provided. The apparatus may determine whether a skin temperature at a skin portion of a mobile device is greater than a threshold temperature. The apparatus may provide power to a thermoelectric cooler (TEC) to cool a first side of the TEC while heating a second side of the TEC if the skin temperature is greater than the threshold temperature, wherein the first side of the TEC contacts the skin portion to cool the skin portion and the second side of the TEC faces a core of the mobile device. The skin temperature may be determined based on at least one of a die temperature, a power management integrated circuit (PMIC) power output, or a PMIC temperature. 
     The apparatus may further generate power via a temperature difference between the first side and the second side of the TEC if the determined skin temperature is equal to or less than the threshold temperature. The generated power may be stored in a battery of the mobile device or is provided directly to components of the mobile device. 
     The apparatus may further refrain from providing power to the TEC when the skin temperature is determined to be equal to or less than the threshold temperature. 
     The second side of the TEC may contact a thermal solution to cool heat generated from the second side of the TEC. The thermal solution may comprise at least one of a copper heat spreader, an aluminum heat spreader, a carbon heat spreader, or phase change material (PCM). The skin portion of the mobile device at which the skin temperature is measured may be at a display side of the mobile device. Alternatively, the skin portion of the mobile device at which the skin temperature is measured may be at a non-display side of the mobile device. 
     The apparatus may further determine whether a second skin temperature at a second skin portion of the mobile device is greater than the threshold temperature. The apparatus may further provide power to a second TEC to cool a first side of the second TEC while heating a second side of the second TEC if the second skin temperature is greater than the threshold temperature, wherein the first side of the second TEC contacts the second skin portion to cool the second skin portion and the second side of the second TEC faces the core of the mobile device. 
     The apparatus may further generate power via a temperature difference between a first side of a second TEC and a second side of the second TEC, the second TEC being located at an opposing side from the TEC within the apparatus. The first side of the second TEC may contact a second skin portion of the mobile device and the second side of the second TEC faces the core of the mobile device. Alternatively, the first side of the second TEC may face the core of the mobile device and the second side of the second TEC may contact a second skin portion of the mobile device. At least one of the first side and the second side of the second TEC may contact a thermal solution. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  are diagrams illustrating an example of a mobile device. 
         FIGS. 2A and 2B  are diagrams illustrating cross sections of an exemplary mobile device. 
         FIG. 3  is a diagram illustrating a thermoelectric cooler used for a Peltier effect 
         FIG. 4  is a diagram illustrating a thermoelectric cooler used for a Seebeck effect. 
         FIG. 5  illustrates an exemplary thermoelectric cooler structure implemented in a mobile device. 
         FIGS. 6A-6C  illustrate exemplary implementations of a thermoelectric cooler in a mobile device. 
         FIG. 7  illustrates a closed-loop temperature control system using a thermoelectric cooler according to an embodiment. 
         FIG. 8  is a diagram illustrating a cross section of a mobile device including a thermoelectric cooler according to one embodiment. 
         FIG. 9  is a diagram illustrating a cross section of a mobile device including a thermoelectric cooler according to another embodiment. 
         FIG. 10  is a diagram illustrating a cross section of a mobile device including two thermoelectric coolers according to an embodiment. 
         FIG. 11  is a diagram illustrating a cross section of a mobile device including two thermoelectric coolers according to another embodiment. 
         FIG. 12  is a diagram illustrating a cross section of a mobile device including a thermoelectric cooler according to another embodiment. 
         FIG. 13  is a diagram illustrating a cross section of a mobile device including two thermoelectric coolers according to another embodiment. 
         FIGS. 14A and 14B  are flow charts of a method of utilizing one or more thermoelectric coolers. 
         FIG. 15  is a conceptual data flow diagram illustrating the data flow between different modules/means/components in an exemplary apparatus. 
         FIG. 16  is a diagram illustrating an example of a hardware implementation for an apparatus employing a processing system. 
     
    
    
     DETAILED DESCRIPTION 
     The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well known structures and components are shown in block diagram form in order to avoid obscuring such concepts. 
     Several aspects of the present disclosure will now be presented with reference to various apparatus and methods. These apparatus and methods will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, modules, components, circuits, steps, processes, algorithms, etc. (collectively referred to as “elements”). These elements may be implemented using electronic hardware, computer software, or any combination thereof Whether such elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. 
     By way of example, an element, or any portion of an element, or any combination of elements may be implemented with a “processing system” that includes one or more processors. Examples of processors include microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. One or more processors in the processing system may execute software. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. 
     Accordingly, in one or more exemplary embodiments, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or encoded as one or more instructions or code on a computer-readable medium. Computer-readable media includes computer storage media. Storage media may be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise a random-access memory (RAM), a read-only memory (ROM), an electrically erasable programmable ROM (EEPROM), compact disk ROM (CD-ROM) or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Disk and disc, as used herein, includes CD, laser disc, optical disc, digital versatile disc (DVD), and floppy disk where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media. 
       FIGS. 1A and 1B  illustrate an exemplary mobile device  100 . The mobile device  100  may be a mobile phone, a tablet, a portable media player, a camera, high-tech glasses, a set-top box, audio/video appliances or any electronic device which operates via human interaction or skin contact.  FIG. 1A  illustrates a front view  110  of the mobile device  100 , and  FIG. 1B  illustrates a rear view  150  of the mobile device  100 . The mobile device  100  has a front cover  120 , a display screen  130  and a power button  140  on a front surface of the mobile device  100 . The front cover  120  covers a front portion of the mobile device  100 . The display screen  130  may include a liquid crystal display (LCD) unit and/or a touch screen that covers the front portion of the mobile device  100 . The power button  140  is used to turn on or off the power of the mobile device  100 . The mobile device  100  has a back cover  160  to cover a back portion of the mobile device  100 . A camera  170  may be mounted on a back surface of the mobile device  100 . An additional camera may be mounted on the front cover  120 . 
       FIGS. 2A and 2B  are diagrams illustrating cross sections of an exemplary mobile device. The mobile device  100  of  FIG. 1  may include structures illustrated in  FIGS. 2A and 2B .  FIG. 2A  is a first cross section view  200  illustrating a cross section I 1  of the mobile device  100  of  FIG. 1A .  FIG. 2B  is a side view illustrating a cross section I 2  of  FIG. 1A . According to  FIG. 2A , the mobile device  100  illustrated in the first cross section view  200  has a front portion  210  and a back portion  230 , and an inside portion  240  located between the front portion  210  and the back portion  230 . The front portion  210  includes a touch screen display  212  that includes a touch screen  214  located on a display stack  216 . The display stack  216  may be an LCD stack. The front portion  210  includes a first heat dissipation layer  218  located below the touch screen display  212  to reduce heat generated from the mobile device  100 . The first heat dissipation layer  218  may include a graphite layer  220  and a heat spreader  222  on which the graphite layer  220  is located. The heat spreader  222  may include at least one of a copper heat spreader, an aluminum heat spreader, a carbon heat spreader, a vapor chamber, a heat pipe, or phase change material (PCM). In the front portion  210 , there may optionally be an air gap  224  between the touch screen display  212  and the first heat dissipation layer  218 . The back portion  230  includes a back cover  232  to cover the back portion  230  and a second heat dissipation layer  234  to reduce heat generated from the mobile device  100 . The second heat dissipation layer  234  may include a graphite layer, and may additionally include a copper heat spreader or an aluminum heat spreader. 
     The inside portion  240  includes a printed circuit board (PCB)  242  having one or more electrical components located thereon. A die or a processor  244  to perform tasks of the mobile device  100  is located on the PCB  242 . Communication components such as a wireless communication device (WCD)  246 , a wireless modem  248 , and a radio transceiver  250  may be located on the PCB  242 . The wireless communication device  246  may be used to communicate with a core network of a cellular network. The wireless modem  248  may be used for local area network communication. Storage-related components such as an embedded multimedia card (EMMC)  252 , micro subscriber identification module (micro-SIM) card connector  254 , and micro secure digital (micro-SD) card connecter  256  may be located on the PCB  242 . PCB  242  may include one or more power management integrated circuits (PMIC)  258 ,  260  to manage power to various components of the mobile device  100 , and one or more power amplifiers  262 ,  264 ,  266  located thereon. An audio codec chip  268  may be located on the PCB  242 . A first die thermal interface material portion (TIM-I)  270  may be provided on the die  244  and a second die thermal interface material portion (TIM-II)  272  may be provided on the TIM-I  270  and may contact the heat spreader  222 . Other thermal interface material portions (TIM)  274 ,  276 ,  278  may be implemented on and around the electrical components located on the PCB  242 . It is noted that the layout of the PCB components illustrated in  FIG. 2A  is an example and the layout of the PCB components on top and bottom sides of the PCB  242  may vary. For example, if TIM  274  and TIM  278  on the back side of the PCB are omitted from the PCB layout, there may be a small air gap between the components on the back side of the PCB  242  and the back portion  230  including the second heat dissipation layer  234  and the back cover  232 . 
       FIG. 2B  is a second cross section view  280  illustrating a cross section I 2  of the mobile device  100  of  FIG. 1A .  FIG. 2B  illustrates a side view of the front portion  210 , the back portion  230 , and the inside portion  240  that are illustrated in  FIG. 2A .  FIG. 2B  illustrates a side view of the touch screen display  212  including the touch screen  214  and the display stack  216 , the first heat dissipation layer  218  including the graphite layer  220  and the heat spreader  222 , the air gap  224 , the back cover  232 , and the second heat dissipation layer  234  that are illustrated in  FIG. 2A .  FIG. 2B  also illustrates a side view of the PCB  242 , the die  244 , the PMIC  258 , the TIM-I  270 , the TIM-II  272 , and the TIM  274  that are illustrated in  FIG. 2A . As shown in  FIG. 2B , the mobile device  100  includes a battery  282 . 
     In a mobile device (e.g., the mobile device  100 ) heat within the mobile device may be removed via conduction inside the mobile device and via natural convection and radiation on the surface of a skin of the mobile device. In the present disclosure, the mobile device skin may be the portion of the mobile device  100  that faces an exterior of the mobile device, such as the touch screen display  212  and the back cover  232 . For example, heat from the mobile device components (e.g., the die  244 ) in the inside portion  240  of the mobile device  100  may be conducted within the mobile device  100 . The heat may reach the device skin through conduction. The heat may then be removed through natural convection and radiation on the surface of the device skin. Inside the mobile device  100 , there is little space that can be utilized to remove the heat from the die  244 . Thus, heat generated from the die  244  is removed mainly through the device skin. As the die power consumption increases, the die  244  generates heat that causes an increase in the die temperature. The device skin temperature increases as well due to the heat from the die  244 . The increased die temperature may cause the device skin temperature to exceed a maximum allowable device skin temperature for human interaction (e.g., approximately 40˜45° C.). The increased die temperature may also generate a hot spot on a portion of a mobile device surface corresponding to a location of the die, where the hot spot on the mobile device surface is hotter than the rest of the mobile device surface. Notably, a maximum allowable temperature limit for a die  244  to maintain reliability generally ranges from 105˜125° C., which is much higher than the maximum allowable device skin temperature. 
     Conventionally, temperature mitigation is used to maintain the device skin temperature below the maximum allowable device skin temperature. For example, the device skin temperature is maintained below the maximum allowable device skin temperature of 45° C. when the die temperature reaches approximately 70˜85° C. Temperature mitigation refers to reducing the power and performance at the die to reduce the die temperature, thereby reducing the skin temperature. Because the die temperature above 70˜85° C. causes the skin temperature to rise above the allowable temperature of 45° C., the temperature mitigation ensures that the die temperature does not exceed 70˜85° C. In a mobile device, a maximum allowable skin temperature (e.g., 40˜45° C.) is the critical temperature that limits the die temperature to a certain mitigation temperature level (e.g., 70˜85° C.). For example, conventional mobile phones may be configured such that the die temperature of a most intensive central processing unit/graphics processing unit (CPU/GPU) is approximately 70˜85° C., with the skin temperature of 45° C. However, higher die performance can be achieved if the die temperature is allowed to reach a higher temperature since the die generates more heat as the die provides higher performance at higher power. For example, higher die performance can be achieved if the die temperature is allowed to reach 105˜125° C., compared to the die performance at 70˜85° C., assuming that the same components (e.g., the same thermal solution) are used for the die. In a conventional mobile phone, the skin temperature reaches the allowable skin temperature of (e.g., 40˜45° C.) before the die temperature reaches its allowable limit of 105˜125° C. Thus, when temperature mitigation with respect to the skin temperature is implemented, the die temperature is not allowed to reach the maximum allowable limit of 105˜125° C. to maintain the allowable skin temperature of 45° C. or below, and therefore die performance is limited by a mobile device skin temperature and the hot spot on the mobile device surface. 
     For at least the reasons discussed supra, an effective approach to maintain a suitable mobile device skin temperature with improved die performance is desired to achieve an optimal mobile device experience. 
       FIG. 3  is a diagram  300  illustrating a thermoelectric cooler (TEC) utilizing a Peltier effect. The Peltier effect is a presence of heating or cooling at an electrified junction of two different conductors. The TEC utilizing the Peltier effect uses power (e.g., direct current power) to move heat from a first portion of the TEC to a second portion of the TEC, thus cooling the first portion while heating the second portion. Therefore, the first portion of the TEC utilizing the Peltier effect may be used to cool the device skin to reduce the device skin temperature. 
     In particular, a TEC  310  utilizing the Peltier effect includes an N-semiconductor  312  and a P-semiconductor  314 . The TEC  310  also includes a P-N junction conductor  316  contacting a first side of the N-semiconductor  312  and a first side of the P-semiconductor  314  that are in a first junction  318 . In the TEC  310 , a second side of the N-semiconductor  312  contacts an N-side junction conductor  320  and a second side of the P-semiconductor  314  contacts a P-side junction conductor  322 , where the N-side junction conductor  320  and the P-side junction conductor  322  are in a second junction  324 . For the TEC  310  utilizing the Peltier effect, a voltage source  326  is connected to the N-side junction conductor  320  and a ground  328  is connected to the P-side junction conductor  322 . When the voltage source  326  supplies an input voltage (Vin) to the TEC  310 , the input voltage (Vin) causes electrons to flow from the P-semiconductor  314  to the N-semiconductor  312  through the P-N junction conductor  316 , as shown by arrow  330 . With the electrons flowing in the direction of the arrow  330 , heat from a cooling side  332  and the first junction  318  is transferred to the second junction  324  and a heating side  334 , thereby cooling the cooling side  332  and heating the heating side  334 . In summary, the TEC  310  utilizing the Peltier effect cools the cooling side  332  and heats the heating side  334  when the input voltage (Vin) is supplied by the voltage source  326 . 
       FIG. 4  is a diagram  400  illustrating a TEC used for a Seebeck effect. The Seebeck effect is a conversion of a temperature difference between two junctions directly into electricity. The TEC utilizing the Seebeck effect generates power when there is a temperature difference between a first portion of the TEC and a second portion of the TEC. Thus, when there is a temperature difference between different portions of the mobile device, the TEC utilizing the Seebeck effect may generate power using the temperature difference. 
     In particular, the TEC  410  utilizing the Seebeck effect includes an N-semiconductor  412  and a P-semiconductor  414 . The TEC  410  further includes a P-N junction conductor  416  that contacts a first side of the N-semiconductor  412  and a first side of the P-semiconductor  414  that are in a first junction  418 . In the TEC  410 , a second side of the N-semiconductor  412  contacts an N-side junction conductor  420  and a second side of the P-semiconductor contacts a P-side junction conductor  422 , where the N-side junction conductor  420  and the P-side junction conductor  422  are in the second junction  424 . When using the Seebeck effect, a power output destination  426  is connected to the N-side junction conductor  420  and the P-side junction conductor  422 . When a heat input side  430  of the TEC  410  is hotter than a heat removal side  432  of the TEC  410 , the temperature difference between the heat input side  430  and the heat removal side  432  causes electrons to flow from the P-semiconductor  414  to the N-semiconductor  412  through the P-N junction conductor  416 , as shown by arrow  428 . With the electrons flowing in the direction of the arrow  428 , power with positive voltage is generated and is output to the power output destination  426 . Further, when the heat removal side  432  of the TEC  410  is hotter than the heat input side  430  of the TEC  410 , power with negative voltage is generated and is output to the power output destination  426 . In summary, the TEC  410  utilizing the Seebeck effect generates power when there is a temperature difference between the heat input side  430  and the heat removal side  432 . 
       FIG. 5  illustrates an exemplary TEC structure  500  implemented in a mobile device. A TEC structure  500  may include multiple TECs  504  forming a TEC layer. A mobile device skin surface  502  may be placed on the multiple TECs  504 . The TECs  504  may be thin TECs such that thicknesses of the TECs  504  do not affect a thickness of the mobile device significantly. Each of the TECs  504  may be connected to an N connector  506  that is connected to an N semiconductor of each of the TECs  504 . Each of the TECs  504  may also be connected to a P connector  508  that is connected to a P semiconductor of each of the TECs  504 . To utilize the Peltier effect, the N connector  506  and the P connector  508  may be connected to a power source supplying power to the TECs  504 . If the TECs  504  utilize the Seebeck effect to generate power via a temperature difference across the TECs  504 , the N connector  506  and the P connector  508  may be connected to a battery to store the generated power and/or maybe connected to various parts of the mobile device to directly provide the generated power thereto. For simplicity, a TEC and a TEC layer may both be referred to as a TEC hereinafter. It is noted that the layout of the TECs illustrated in  FIG. 5  is an example and the layout of the TECs may vary. For example, there may be a single layer or multiple layers of TECs covering an entire area or a small area under the mobile device skin surface  502 . 
       FIGS. 6A-6C  illustrate exemplary implementations of a TEC in a mobile device. In particular,  FIG. 6A  illustrates an exemplary implementation  600  of a TEC using the Peltier effect. In  FIG. 6A , the TEC implementation  600  in a mobile device includes an outer portion  610  representing an outer shell of a mobile device. The outer portion  610  includes a TEC  612  that corresponds with the TEC  310  of  FIG. 3  using the Peltier effect. TEC  612  may have two junctions including Junction A  614  and Junction B  616 . Junction A  614  of the TEC  612  is located on one side of the TEC  612  contacting a skin layer  618 . Junction B  616  of the TEC  612  is located on an opposite side of the TEC  612  contacting a core layer  620 . The skin layer  618  faces an exterior of the mobile device, and may include a touch screen display and/or a cover of the mobile device. The skin layer  618  has a temperature sensor  622  to measure a skin temperature. The core layer  620  faces an inner portion  630  of the mobile device, and thus faces an interior of the mobile device. The core layer  620  may include, for example, a thermal solution layer to dissipate heat from Junction B  616  of the TEC  612 . The core layer  620  may be an optional component if there is a separate thermal solution to dissipate heat from Junction B  616  of the TEC  612 . The TEC  612  utilizes the Peltier effect and is connected to a battery  634  via a power connection  624  to supply power to the TEC  612 . The TEC  612  uses power (e.g., direct current power) to move heat from Junction A  614  of the TEC  614  to Junction B  616  of the TEC  616 . That is, when the power is applied to the TEC  612 , the heat is carried from one side (e.g., Junction A  614 ) to other side (e.g., Junction B  616 ) of the TEC  612  by electron transport. The thermal solution layer may be a custom designed light weight thermal solution and may be made of at least one of a copper heat spreader, an aluminum heat spreader, a carbon heat plate, or PCM, for example. The TEC  612 , the skin layer  618 , and the core layer  620  are included in the outer portion  610  of the mobile device. The inner portion  630  of the mobile device may include at least a die  632  and a battery  634 . 
     As discussed supra, when power is supplied to the TEC utilizing the Peltier effect, one junction of the TEC is cooled while another junction of the TEC is heated as heat is pumped from one side to another side of TEC by electron transport, depending on a direction of the current applied. Thus, in one configuration where Junction A  614  corresponds with the first junction  318  of  FIG. 3  and Junction B  616  corresponds with the second junction  324  of  FIG. 3 , Junction A  614  is cooled while Junction B  616  is heated when the battery  634  supplies power to the TEC  612 . Hence, the TEC  612  utilizing the Peltier effect can be used to cool Junction A  614  and pump heat to Junction B  616  of the TEC  612 . 
     As the die  632  performs mobile device tasks, die temperature rises, causing temperatures of various portions of the mobile device  800  to increase. For example, the increase in the die temperature may cause the skin temperature sensed via the temperature sensor  618  to increase. When the skin temperature sensed via the temperature sensor  618  rises above the threshold temperature (e.g., 40˜45° C.), the TEC  612  utilizing the Peltier effect can be powered (e.g., via the battery  632 ) to cool one side of the TEC  612  corresponding to Junction A  614  that contacts the skin layer  618  to lower the skin temperature of the skin layer  618 , thereby maintaining the skin temperature at the threshold temperature (e.g., 40˜45° C.) or below. While the TEC  612  is powered, the other side of the TEC  612  corresponding to Junction B  616  is heated. The heat from the temperature increase at Junction B  616  may also be cooled with the thermal solution included in the core layer  620 . The die temperature may reach the maximum allowable die temperature limit of the die  632  while maintaining a desired skin temperature at the skin layer  618 . That is, the die temperature is allowed to reach maximum allowable temperature while the skin temperature is maintained at 45° C. 
     As discussed supra, the allowable die temperature limit in conventional mobile devices is 105˜125° C. Therefore, the TEC  612  is powered to cool the skin layer  618  and to maintain the skin temperature of the skin layer  618  at the threshold temperature (e.g., 40˜45° C.) or below, while the temperature at Junction B  616  and the inner portion  630  increases due to the heat from Junction B  616  and an increase in the die temperature. That is, because the TEC  612  is used to maintain the skin temperature of the skin layer  618  at the threshold temperature (e.g., 40˜45° C.) or below, the die  632  can perform at a high level that causes the die temperature to rise above a conventional mitigation temperature of 70˜85° C. Further, the die  632  may have its own independent cooling component such as a die thermal solution  636  to cool the die  632 . The die thermal solution  632  may include at least one of a vapor chamber, a heat pipe or PCM. 
       FIG. 6B  illustrates an exemplary implementation  640  of a TEC that corresponds with the TEC  410  of  FIG. 4  utilizing the Seebeck effect. In  FIG. 6B , the TEC  652  may have two junctions including Junction A  654  and Junction B  656 . Junction A  654  of the TEC  652  is located on one side of the TEC  652  facing the inner portion  630  and Junction B  656  of the TEC  652  is located on an opposite side of the TEC  652  contacting a core layer  660 . The skin layer  658  faces an exterior of the mobile device and is located on the core layer  660 . The skin layer  658  may include a touch screen display or a cover. The core layer  660  is located between the skin layer  658  and the TEC  652 . The core layer  660  may include, for example, a thermal solution layer to dissipate heat at Junction B  656 . The thermal solution layer may be a custom designed light weight thermal solution and may be made of at least one of a copper heat spreader, an aluminum heat spreader, a carbon heat plate, or PCM, for example. The TEC  652 , the skin layer  658  and the core layer  660  are included in the outer portion  650  of the mobile device. The inner portion  630  of the mobile device may include at least a die  632  and a battery  634 . The die  632  may also have the die thermal solution  636  located on the die  632  to cool the die  632 . The battery is connected to the TEC  652  via a power storage connection  662 . When there is a temperature difference across the TEC  652  between Junction A  654  and Junction B  656 , a power may be generated at the TEC  652  due to the Seebeck effect. The generated power may be stored in the battery  634  or may be supplied directly to other components of the mobile device. More specifically, in a first configuration where Junction A  654  corresponds with the first junction  418  of  FIG. 4  and Junction B  656  corresponds with the second junction  424  of  FIG. 4 , power with positive voltage is generated when Junction A  654  has a higher temperature than Junction B  656  and power with negative voltage is generated when Junction B  656  has a higher temperature than Junction A  654 . In a second configuration where Junction A  654  corresponds with the second junction  424  of  FIG. 4  and Junction B  656  corresponds with the second junction  418  of  FIG. 4 , power with positive voltage is generated when Junction B  656  has a higher temperature than Junction A  654  and power with negative voltage is generated when Junction A  656  has a higher temperature than Junction A  654 . 
     In an aspect, when the temperature of the inner portion of the mobile device is higher than the skin temperature when the die is performing, the TEC utilizing the Seebeck effect can be used to generate power with the temperature difference between the inner portion and the skin portion of the mobile device. In another aspect, when the display device operates at a high resolution, the display generates heat, and thus the skin side may have a higher temperature than the die portion of the mobile device. The TEC utilizing the Seebeck effect can then be used to generate power using the temperature difference. The generated power may be used to supply power to components or a battery, which can contribute to longer battery life. 
       FIG. 6C  illustrates an exemplary implementation  670  of a TEC that corresponds to a combination of uses of the TEC  310  of  FIG. 3  using the Peltier effect and the TEC  410  of  FIG. 4  using the Seebeck effect. In  FIG. 6C , the TEC implementation  670  in a mobile device includes an outer portion  680  representing an outer shell of a mobile device. The outer portion  680  includes a TEC  682  that is used for the Peltier effect of the TEC  310  of  FIG. 3  and for the Seebeck effect of the TEC  410  of  FIG. 4 . TEC  682  may have two junctions including Junction A  684  and Junction B  686 . Junction A  684  of the TEC  682  is located on one side of the TEC  682  contacting a skin layer  688  and Junction B  686  of the TEC  682  is located on an opposite side of the TEC  682  contacting a core layer  690 . The skin layer  688  faces an exterior of the mobile device, and may include a touch screen display and/or a cover of the mobile device. The skin layer  688  has a temperature sensor  692  to measure a skin temperature. The core layer  690  faces an inner portion  630  of the mobile device, and thus faces an interior of the mobile device. The core layer  690  may include, for example, a thermal solution layer to dissipate heat from Junction B  686  of the TEC  682 . The core layer  690  may be an optional component, especially if there is a separate thermal solution to cool Junction B  686  of the TEC  682 . The TEC  682 , the skin layer  688  and the core layer  690  are included in the outer portion  680  of the mobile device. The inner portion  630  of the mobile device may include at least a die  632  and a battery  634 . The die  632  may also have the die thermal solution  636  located on the die  632  to dissipate heat from the die  632 . The battery  634  is connected to the TEC  682  via a power connection  694  to supply power to the TEC  612  and via a power storage connection  696  to supply power to the battery  634 . 
     When the skin temperature sensed via the temperature sensor  692  is equal to or less than the threshold temperature, the TEC  682  is used for the Seebeck effect to generate power via a temperature difference between Junction A  684  and Junction B  686 . The generated power may be stored in the battery  634  via the power storage connection  696  or may be supplied directly to other components of the mobile device. More specifically, in a configuration where Junction A  684  corresponds with the first junction  418  of  FIG. 4  and Junction B  686  corresponds with the second junction  424  of  FIG. 4 , power with positive voltage is generated when Junction A  684  has a higher temperature than Junction B  686  and power with negative voltage is generated when Junction B  686  has a higher temperature than Junction A  684 . On the other hand, when the skin temperature sensed via the temperature sensor  692  is greater than the threshold temperature (e.g., 40˜45° C.), the TEC  682  utilizing the Peltier effect can be powered (e.g., via the battery  634  and the power connection  694 ) to cool one side of the TEC  682  corresponding to Junction A  684  that contacts the skin layer  688  to lower the skin temperature of the skin layer  688 , thereby maintaining the skin temperature at the threshold temperature or below. While the TEC  682  is powered, the other side of the TEC  682  corresponding to Junction B  686  is heated. The die temperature may reach close to the maximum allowable die temperature limit while maintaining the desired skin temperature using the TEC  682 . 
     In another configuration of the exemplary implementation  670  of  FIG. 6C , the TEC  682  may include two or more separate TECs. The TEC  682  may include a first TEC on the left side of the TEC  682  corresponding to the location of the die  632 , and a second TEC on the right side of the TEC  682  corresponding to the location of the battery  634 . In a first example, the first TEC on the left side may utilize both the Peltier effect and the Seebeck effect and thus may be connected to the power connection  694  and the power storage connection  696 . In the first example, the second TEC on the right side of the TEC  682  may utilize only the Seebeck effect, and thus may be connected only with the power storage connection  696 . In a second example, the first TEC on the left side may utilize only the Seebeck effect, and thus may be connected only with the power storage connection  696 . In the second example, the second TEC on the right side may utilize both the Peltier effect and the Seebeck effect and thus may be connected to the power connection  694  and the power storage connection  696 . 
     It is noted that any combinations of  FIGS. 6A-6C  may be implemented in a mobile device. For example, a mobile device may implement the outer portion  610  of  FIG. 6A  at one side of the mobile device and further provide an additional implementation of the outer portion  610  of  FIG. 6A  at another side of the mobile device, to provide two TECs utilizing the Peltier effect on different sides of the mobile device. As another example, a mobile device may implement the outer portion  610  of  FIG. 6A  at one side of the mobile device to provide a TEC utilizing the Peltier effect and further implement the outer portion  650  of  FIG. 6B  at another side of the mobile device to provide a TEC utilizing the Seebeck effect. As another example, a mobile device may implement the outer portion  680  of  FIG. 6C  at one side of the mobile device to provide a TEC using both the Peltier effect and the Seebeck effect, and further provide one or more of the outer portion  610  of  FIG. 6A  and the outer portion  650  of  FIG. 6B  at another side of the mobile device. Examples illustrating implementations of the features of  FIGS. 6A-6B  are provided infra. 
       FIG. 7  illustrates a closed-loop temperature control system  700  using a TEC according to an embodiment. A temperature sensor  702  senses a temperature near a first junction of a TEC  704 . The sensed temperature from the temperature sensor  702  is sent to a temperature control module  706 . The temperature module  706  computes a temperature difference value by subtracting a threshold temperature from the sensed temperature. The threshold temperature is set to an allowable temperature limit (e.g., 40˜45° C.) for a mobile device skin. The temperature difference value is sent from the temperature control module  706  to a power supply controller  708 . If the temperature difference value is less than or equal to zero, the power supply controller  708  controls so that power is not supplied to the TEC  704 . If the temperature difference value is greater than zero, the power supply controller  708  controls to supply power to the TEC  704  utilizing the Peltier effect to cool a portion near a first junction of the TEC  704  while heating a portion near a second junction of the TEC  704 . As the TEC  704  cools the portion near the first junction of the TEC  704 , the sensor  702  senses a lowered temperature near the first junction. If the cooling by the TEC  704  causes the temperature near the first junction to decrease to the threshold temperature or below, the difference value computed at the temperature module  706  becomes zero or below zero. If the power supply controller  708  receives the computed difference value of zero or below zero, the power supply controller  708  controls to stop supplying power to the TEC  704 , thereby stopping the cooling process by the TEC  704  using the Peltier effect. 
     Hence, the TEC utilizing the Peltier effect can be used at a mobile device skin near a display (e.g., touch screen) side and/or back cover side to cool the skin and maintain the skin temperature at the threshold temperature (e.g., 40˜45° C.) by using the temperature control loop discussed supra. That is, when the sensor  702  determines that the skin temperature is above the threshold temperature, the controller  708  powers the TEC  704  utilizing the Peltier effect to cool the skin. When the skin temperature is not greater than the threshold temperature, the controller  708  deactivates the TEC  704  utilizing the Peltier effect. Because the skin temperature can be maintained at the threshold temperature (e.g., 40˜45° C.) via the cooling effect of the TEC  704 , the die temperature may be allowed to increase above a conventional mitigation temperature (e.g., 70˜85° C.) and reach the allowable limit (e.g., 105˜125° C.) of the die temperature, which enables the die to perform at a higher level than a conventional mobile device. 
     In addition, at least one of a die temperature, PMIC power output, or a PMIC temperature may be considered in determining whether to power the TEC  704 . For example, a die temperature sensor may be embedded in the die to sense the die temperature, and a PMIC temperature sensor may be embedded in the PMIC to measure the PMIC temperature. The correlation between the skin temperature and at least one of the die temperature, the PMIC power output, or the PMIC temperature may be determined during a development stage of the mobile device. In particular, during the development stage, for each of various use cases (e.g., a CPU intensive case, a graphic intensive case, etc.), at least one of the die temperature, the PMIC power output, or the PMIC temperature may be determined and correlated with a corresponding skin temperature measured by a sensor. 
     Therefore, a database including information about relationship between a device skin temperature and its corresponding die temperature, PMIC power output, and PMIC temperature may be built and stored in the mobile device. Then, the mobile device being used by a user may measure at least one of the measured die temperature, PMIC power output, or PMIC temperature, and then estimate the skin temperature based on the measured values and the correlation in the database, without using the skin temperature sensor.  FIGS. 8-12  illustrate various embodiments of uses of one or more TECs in a mobile device.  FIGS. 8-12  show a cross sectional view similar to a cross section I 2  of  FIG. 1A . Thus, several of components illustrated in  FIGS. 8-12  are similar to the components illustrated in  FIG. 2B . 
       FIG. 8  is a diagram illustrating a cross section of a mobile device including a TEC according to one embodiment. According to  FIG. 8 , the mobile device  800  has a front portion  810  and a back portion  830 , and an inside portion  850  located between the front portion  810  and the back portion  830  of the mobile device  800 . The front portion  810  includes a front TEC  812  and a touch screen display  814 . The touch screen display  814  is similar to the touch screen display  212  of  FIG. 2B  that includes a touch screen  214  located on a display stack  216 . The front portion  810  includes a front thin heat spreader plate  816  located between the touch screen display  814  and the front TEC  812  to spread heat. The front portion  810  includes a front thermal solution layer  818  located on the front TEC  812  and facing the inside portion  850 . The front thin heat spreader plate  816  may be made of copper or aluminum, and the front thermal solution layer  818  may be made of at least one of a copper heat spreader, an aluminum heat spreader, a carbon heat spreader, or PCM, for example. A front temperature sensor  820  is included in the front portion  810  to sense a front skin temperature at the touch screen display  814 . The front temperature sensor can be placed on a hot spot area of the touch screen display  814 , where the hot spot area corresponds with the location of the die  854  and thus is hotter than other areas of the touch screen display  814 . The back portion  830  includes a back cover  832  and a back graphite layer  834  located on the back cover  832  to dissipate heat. The inside portion  850  includes a printed circuit board (PCB)  852  having a die  854  and electrical components  858  located thereon. A die thermal interface material portion (TIM)  856  is provided on the die  854 . A component TIM  859  is provided on the electrical components  858  and may contact the back graphite layer  834 . The inside portion  850  includes a battery  860  to supply power to the mobile device  800 . It is noted that the die  854  may have its own die thermal solution  862  to dissipate heat from the die  854 . The die thermal solution  862  may include at least one of a heat pipe, a vapor chamber, or PCM. 
     As the mobile device  800  utilizes the die  854  to perform various tasks of the mobile device  800 , the die temperature rises, which causes temperatures of various portions of the mobile device  800  to increase. Thus, with the increase in the die temperature, the front skin temperature sensed by the front temperature sensor  820  rises. The touch screen display  814  providing a high resolution may also generate heat that additionally contributes to the rise in the front skin temperature. When the front skin temperature is greater than a threshold temperature (e.g., 40˜45° C.), the mobile device  800  supplies power from the battery  860  to the front TEC  812  through a power connection  826  in order to cool Junction A  822  of the front TEC  812  facing toward the touch screen display  814 . While Junction A  822  is cooled, Junction B  824  of the front TEC  812  facing toward the front thermal solution layer  818  and the die  854  is heated. Thus, the front skin portion including the touch screen display  814  is cooled via Junction A  822  of the front TEC  812  until the mobile device  800  determines that the front temperature sensed by the front temperature sensor  820  is less than or equal to the threshold temperature. The cooling of the front skin portion via the front TEC  812  allows the front temperature at the touch screen display  814  to be maintained at the threshold temperature or below. An inside temperature of the inside portion  850  increases due to an increased die temperature and the heating of Junction B  824  while the front TEC  812  is activated. However, the increase in the inside temperature does not affect the die performance since the allowable die temperature limit for reliable performance is much higher (e.g., 105˜125° C.) than the threshold temperature (e.g., 40˜45° C.). While power is supplied to the front TEC  812 , the heat from the heated Junction B  824  may be dissipated via the front thermal solution layer  818 . The heat from the inside portion  850  may further be dissipated via the die thermal solution  862 . 
       FIG. 9  is a diagram illustrating a cross section of a mobile device including a TEC according to another embodiment. According to  FIG. 9 , the mobile device  900  has a front portion  910  and a back portion  930 . The mobile device  900  has an inside portion  950  that is located between the front portion  910  and the back portion  930  of the mobile device  800 . The front portion  910  includes a touch screen display  814  that is located on a front graphite layer  916  for dissipating heat. The back portion  930  includes a back TEC  932  and a back cover  832 . The back portion  930  includes a back heat spreader plate  933  located between the back cover  832  and a back TEC  932  to spread heat. The back portion  930  includes a back thermal solution layer  935  located on the back TEC  932  and facing the inside portion  950 . The back thin heat spreader plate  933  may be made of copper or aluminum, and the back thermal solution layer  935  may be made of at least one of a copper heat spreader, an aluminum heat spreader, a carbon heat spreader, or PCM, for example. The temperature sensor  934  is included in the back portion  930  to sense a back side skin temperature at the back cover  832 . The die  854  may have its own die thermal solution  862  to dissipate heat from the die  854 . 
     When the die temperature of the die  854  increases while the die  854  performs various tasks of the mobile device  900 , the back side skin temperature sensed by the back side temperature sensor  934  rises. When the back side skin temperature is greater than a threshold temperature (e.g., 40˜45° C.), the mobile device  900  supplies power from the battery  860  to the back TEC  932  through a power connection  940  in order to cool Junction A  936  of the back TEC  932  facing toward the back cover  832  while heating Junction B  938  of the back TEC  932  facing toward the back thermal solution layer  935  and the die  854 . Thus, the back side skin portion including the back cover  832  is cooled via Junction A  936  of the back TEC  932  until the mobile device  900  determines that the back side skin temperature sensed by the back side temperature sensor  934  is less than or equal to the threshold temperature. The cooling of the back side skin portion via the back TEC  932  allows the temperature at the back cover  934  to be maintained at the threshold temperature or below. An inside temperature of the inside portion  950  increases due to a increased die temperature and the heating of Junction B  938  while the back TEC  932  is activated. However, the increase in the inside temperature does not affect the die performance since the allowable die temperature limit for reliable performance is much higher (e.g., 105˜125° C.) than the threshold temperature. While power is supplied to the back TEC  932 , the heat from the heated Junction B  938  is cooled via the back thermal solution layer  935 . The heat from the inside portion  950  may further be dissipated via the independent thermal solution on top of the die  862  and the front graphite  916 . 
       FIG. 10  is a diagram illustrating a cross section of a mobile device including two TECs according to an embodiment. According to  FIG. 10 , the mobile device  1000  has a front portion  1010  and a back portion  1030 , and an inside portion  950  located between the front portion  1010  and the back portion  1030  of the mobile device  1000 . The front portion  1010  includes a front thin heat spreader plate  816  located between a touch screen display  814  and a front TEC  812  to spread heat. The front portion  1010  includes a front thermal solution layer  818  located on the front TEC  812  and facing the inside portion  950 . A front temperature sensor  820  is included in the front portion  1010  to sense a front skin temperature at the touch screen display  814 . The back portion  1030  includes a back heat spreader plate  933  located between the back cover  832  and a back TEC  932  to spread heat. The back portion  1030  includes a back thermal solution layer  935  located on the back TEC  932  and facing the inside portion  950 . A back temperature sensor  934  is included in the back portion  1030  to sense a back side skin temperature at the back cover  832 . The back portion  1030  includes a back thermal solution layer  935  located on the back heat spreader plate  933  and facing the inside portion  950 . 
     It is noted that the mobile device  1000  is a combination of the TEC implementation at the front portion  810  of the mobile device  800  of  FIG. 8  and the TEC implementation at the back portion  930  of the mobile device  900  of  FIG. 9 . Therefore, the front portion  1010  of the mobile device  1000  is the same as the front portion  810  of the mobile device  800  of  FIG. 8 , and the back portion  1030  of the mobile device  1000  is the same as the back portion  910  of the mobile device  900  of  FIG. 9 . In summary, when the front skin temperature is greater than a threshold temperature (e.g., 40˜45° C.), the front TEC  812  is powered to cool Junction A  822  of the front TEC  812 , and when the back side skin temperature is greater than the threshold temperature (e.g., 40˜45° C.), the back TEC  932  is powered to cool Junction A  936  of the back TEC  932 . Because the TEC operations utilizing the Peltier effect and the structures of the front portion  1010  and the back portion  1030  are respectively the same as the TEC operations and the structures of the front portion  810  of  FIG. 8  and the back portion  930  of  FIG. 9  that are discussed supra, discussions of the TEC operations and the structures of the front portion  1010  and the back portion  1030  are omitted for brevity. 
     An alternative approach may be utilized to maintain the skin temperature in the mobile device  1000 . The alternative approach implements the back TEC  932  such that the back TEC  932  may be powered to cool Junction B  938  and to heat Junction A  936 . Further, the alternative approach implements the front TEC  812  such that the front TEC  812  may be powered to cool Junction B  824  and to heat Junction A  822 . In particular, when the front skin temperature sensed by the front temperature sensor  820  is greater than the threshold temperature, the back TEC  932  may be powered to cool Junction B  938  of the back TEC  932 . In a mobile device structure where mobile device components are connected from the front side  1010  to the back side  1030 , as Junction B  938  of the back TEC  932  is cooled, heat from the front portion  1010  and the inside portion  950  flows toward the back portion  1030  through the mobile device components, thereby lowering the front skin temperature. When the front side skin temperature decreases to the threshold temperature or below, power is no longer supplied to the back TEC  932  in order to stop cooling Junction B  938  of the back TEC  932 . Similarly, when the back side skin temperature is greater than the threshold temperature, the front TEC  812  may be powered to cool Junction B  824  of the front TEC  812 . As Junction B  824  of the front TEC  812  is cooled, heat from the back portion  1030  flows toward the front portion  1010  through the mobile device components, thereby lowering the back side skin temperature. When the back side skin temperature decreases to the threshold temperature or below, power is cut off from the front TEC  812  to stop cooling Junction B  824  of the front TEC  812 . In the alternative approach, one of the front TEC  812  and the back TEC  932  may be powered at a time until a desired temperature (e.g., a temperature equal to or less than the threshold temperature) is achieved for the front skin temperature and the back side skin temperature. 
       FIG. 11  is a diagram illustrating a cross section of a mobile device including two 
     TECs according to another embodiment. According to  FIG. 10 , the mobile device  1100  has a front portion  1110  and a back portion  1130 , and an inside portion  850  located between the front portion  1110  and the back portion  1130  of the mobile device  800 . The front portion  1110  includes a front thin heat spreader plate  816  located between a touch screen display  814  and a front TEC  812  to spread heat. The front portion  1110  includes a front thermal solution layer  818  located on the front TEC  812  and facing the inside portion  850 . A front temperature sensor  820  is included in the front portion  1110  to sense a front skin temperature at the touch screen display  814 . The back portion  1130  includes a back heat spreader plate  933  located between the back cover  832  and a back TEC  1132  to spread heat. The component TIM  859  on the components  858  in the inside portion  850  may contact the back TEC  1132 . 
     It is noted that the TEC operation utilizing the Peltier effect and the structure of the front portion  1110  of the mobile device  1100  is the same as the TEC operation and the structure of the front portion  810  of the mobile device  800  of  FIG. 8 . Thus, discussions of the TEC operation and the structure of the front portion  1110  of the mobile device  1100  is omitted for brevity. 
     At the back portion  1130 , the back TEC  1132  uses the Seebeck effect to generate power when there is a temperature difference between Junction A  1134  and Junction B  1136 . In a first configuration, Junction A  1134  and Junction B  1136  may be equivalent to the first junction  418  and the second junction  424 , respectively, as illustrated in  FIG. 4 . Thus, power with positive voltage is generated when a temperature at Junction A  1134  is higher than a temperature at Junction B  1136  and power with negative voltage is generated when a temperature at Junction B  1136  is higher than a temperature at Junction A  1134 . For example, when the die temperature of the die  854  increases, the temperature of the inside portion  850  increases, and thus the temperature of Junction A  1134  facing the inside portion  850  increases. With the increased temperature at Junction A  1134 , the temperature at Junction A  1134  becomes higher than the temperature at Junction B  1136 . Consequently, power with positive voltage is generated due to the temperature difference between Junction A  1134  and Junction B  1136 . On the other hand, a second configuration may be implemented instead of the first configuration, such that Junction A  1134  and Junction B  1136  in the second configuration are equivalent to the second junction  424  and the first junction  424  of  FIG. 4 , respectively. Thus, in the second configuration, power with positive voltage is generated when Junction B  1136  has a higher temperature than Junction A  1134  and power with negative voltage is generated when Junction A  1134  has a higher temperature than Junction B  1136 . The back TEC  1132  utilizing the Seebeck effect generates power with a temperature difference between Junction A  1134  and Junction B  1136 . The power generated by the back TEC  1132  may be stored in the battery  860  via a power storage connection  1034  and/or may be provided directly to various components of the mobile device  1100 . 
       FIG. 12  is a diagram illustrating a cross section of a mobile device including a TEC according to another embodiment. According to  FIG. 12 , the mobile device  1200  has a front portion  1210  and a back portion  1230 , and an inside portion  850  located between the front portion  1210  and the back portion  1230  of the mobile device  1200 . The front portion  1210  includes a front TEC  1212  and a touch screen display  814 . The front portion  1210  includes a front thin heat spreader plate  816  located between the touch screen display  814  and the front TEC  1212  to spread heat. The front portion  1210  includes a front thermal solution layer  818  located on the front TEC  1212  and facing the inside portion  850 . A front temperature sensor  820  is included in the front portion  1210  to sense a front skin temperature at the touch screen display  814 . The back portion  1230  includes a back cover  832  and a back graphite layer  834  located on the back cover  832  to dissipate heat. The inside portion  850  includes a printed circuit board (PCB)  852  having a die  854  and electrical components  858  located thereon. A die thermal interface material portion (TIM)  856  is provided on the die  854 . A component TIM  859  is provided on the electrical components  858  and may contact the back graphite layer  834 . The inside portion  850  includes a battery  860  to supply power to the mobile device  1200 . The die  854  may have its own die thermal solution  862  to dissipate heat from the die  854 . 
     In the mobile device  1200 , the front TEC  1212  utilizes the Peltier effect when the front skin temperature sensed by the front temperature sensor  820  is greater than a threshold temperature. The front TEC  1212  utilizes the Seebeck effect when the front skin temperature sensed by the front temperature sensor  820  is equal to or less than the threshold temperature (e.g., 40˜45° C.). In particular, when the front skin temperature is equal to or less than the threshold temperature, the front TEC  1212  utilizes the Seebeck effect to generate power via a temperature difference between Junction A  1214  and Junction B  1216 . In one configuration, Junction A  1214  and Junction B  1216  may be equivalent to the first junction  418  and the second junction  424  of  FIG. 4 , respectively, utilizing the Seebeck effect. Thus, when Junction A  1214  has a higher temperature than Junction B  1216 , the front TEC  1212  may be used to generate positive power via the temperature difference between Junction A and Junction B. For example, Junction A  1214  may have a higher temperature than Junction B  1216  when the touch screen display  814  generates heat from displaying high resolution images, causing Junction A  1214  to become warmer than Junction B  1216 . Further, when Junction B  1216  has a higher temperature than Junction A  1214 , the front TEC  1212  may be used to generate negative power via the temperature difference between Junction A and Junction B. For example, Junction B  1216  may have a higher temperature than Junction A  1216  when an increase in the temperature of the die  854  increase the temperature of the inside portion  850 . The power generated by the front TEC  1212  via the temperature difference Junction A and Junction B may be stored in the battery  860  via a power storage connection  828  and/or may be provided directly to various components of the mobile device  1200 . 
     When the die temperature of the die  854  increases as the die  854  is used for various tasks of the mobile device  1200 , temperatures of various portions of the mobile device  1200  also increase. Thus, with the increase in the die temperature, the front skin temperature sensed by the front temperature sensor  820  rises. When the front skin temperature is greater than the threshold temperature (e.g., 40˜45° C.), the mobile device  1200  supplies power from the battery  860  to the front TEC  1212  through a power connection  826  in order to cool Junction A  1214  of the front TEC  1212  facing toward the touch screen display  814  while heating Junction B  1216  of the front TEC  1212  facing toward the front thermal solution layer  818  and the die  854 . The front skin portion including the touch screen display  814  is cooled via Junction A  1214  of the front TEC  1212  until the mobile device  1200  determines that the front temperature sensed by the front temperature sensor  820  is less than or equal to the threshold temperature. The cooling of the front skin portion via the front TEC  1212  allows the front temperature at the touch screen display  814  to be maintained at the threshold temperature or below. An inside temperature of the inside portion  850  increases due to a increased die temperature and the heating of Junction B  1216  while the front TEC  1212  is activated. However, the increase in the inside temperature does not affect the die performance because the allowable die temperature limit for reliable performance is much higher (e.g., 105˜125° C.) than the device skin threshold temperature limit. While power is supplied to the TEC, the heat from the heated Junction B  1216  may be dissipated via the front thermal solution layer  818 . The heat from the inside portion  850  may further be dissipated via the graphite layer  834  and the die thermal solution  862  on top of the die. 
     In another configuration, the TEC  1212  may include two or more separate TECs. The TEC  1212  may include a first TEC on the left side of the TEC  1212  corresponding to the location of the die  854 , and a second TEC on the right side of the TEC  1212  corresponding to the location of the battery  860 . In one example, the first TEC on the left side may utilize both the Peltier effect and the Seebeck effect and thus may be connected to the power connection  826  and the power storage connection  828 . In the first example, the second TEC on the right side of the TEC  1212  may utilize only the Seebeck effect, and thus may be connected only with the power storage connection  828 . In a second example, the first TEC on the left side may utilize only the Seebeck effect, and thus may be connected only with the power storage connection  828 . In the second example, the second TEC on the right side may utilize both the Peltier effect and the Seebeck effect and thus may be connected to the power connection  826  and the power storage connection  828 . 
       FIG. 13  is a diagram illustrating a cross section of a mobile device including two TECs according to another embodiment. According to  FIG. 13 , the mobile device  1300  has a front portion  1310  and a back portion  1330 , and an inside portion  850  located between the front portion  1310  and the back portion  1330  of the mobile device  1300 . The front portion  1310  includes a front TEC  1212  and a touch screen display  814 . The front portion  1310  includes a front thin heat spreader plate  816  located between the touch screen display  814  and the front TEC  1212  to spread heat. The front portion  1310  includes a front thermal solution layer  818  located on the front TEC  1212  and facing the inside portion  850 . A front temperature sensor  820  is included in the front portion  1310  to sense a front skin temperature at the touch screen display  814 . The back portion  1330  includes a back heat spreader plate  933  located between the back cover  832  and a back TEC  1132  to spread heat. 
     It is noted that the TEC operation utilizing the Peltier effect and the Seebeck effect and the structure of the front portion  1310  of the mobile device  1300  is the same as the TEC operation and the structure of the front portion  1210  of the mobile device  1200  of  FIG. 12 . Further, it is also noted that the TEC operation utilizing the Seebeck effect and the structure of the back portion  1330  of the mobile device  1300  is the same as the TEC operation and the structure of the back portion  1130  of the mobile device  1100  of  FIG. 11 . Thus, discussions of the TEC operations and the structures of the front portion  1310  and the back portion  1330  of the mobile device  1300  are omitted for brevity. 
       FIG. 14A  is a flow chart  1400  of a method of utilizing a thermoelectric cooler (TEC).  FIG. 14B  is a flowchart  1450  of a method of utilizing a second TEC in addition to the TEC of  FIG. 14A . The methods may be performed by a mobile device. Referring to  FIG. 14A , at step  1402 , the mobile device obtains a skin temperature at a skin portion of the mobile device. In one configuration, the skin portion of the mobile device at which the skin temperature is measured may be at a display side of the mobile device. For example, referring back to  FIGS. 8 ,  10 - 13 , the mobile device may obtain the skin temperature at a display side at the touch screen display  814  via the front temperature sensor  820 . In an alternative configuration, the skin portion of the mobile device at which the skin temperature is measured may be at a non-display side of the mobile device. For example, referring back to  FIGS. 9 and 10 , the mobile device may obtain the skin temperature at a non-display side at the back cover  822  via the back side temperature sensor  934 . 
     At step  1404 , the mobile device determines whether the skin temperature is greater than a threshold temperature. For example, referring back to  FIG. 7 , the temperature module  706  computes a temperature difference value by subtracting the threshold temperature from the sensed skin temperature. The sensed skin temperature is greater than the threshold temperature if the temperature difference is greater than zero. The device skin threshold temperature may be approximately 40˜45° C. 
     At step  1406 , if the skin temperature is greater than the threshold temperature, the mobile device provides power to a thermoelectric cooler (TEC) to cool a first side of the TEC while heating a second side of the TEC. For example, referring back to  FIGS. 8 ,  10 - 13 , if the skin temperature at the touch screen display  814  is greater than the threshold temperature, the mobile device provides power from the battery  860  to the front TEC  816  or the front TEC  1212  to cool Junction A of the front TEC  816  or the front TEC  1212  while heating Junction B of the front TEC  816  or the front TEC  1212 . As another example, referring back to  FIGS. 9-10 , if the skin temperature at the back cover  832  is greater than the threshold temperature, the mobile device provides power from the battery  860  to the back TEC  932  to cool Junction A  936  of the back TEC  932  while heating Junction B  938  of the back TEC  932 . 
     The second side of the TEC may contact a thermal solution to cool heat from the second side of the TEC. For example, referring back to FIGS.  8  and  10 - 11 , the front TEC  816  contacts the first thermal solution layer  818  to cool heat generated from Junction B  824  of the front TEC  816 . As another example, referring back to  FIGS. 12-13 , the front TEC  1212  contacts the first thermal solution layer  818  to cool heat generated from Junction B  1216  of the front TEC  1212 . As another example, referring back to  FIGS. 9-10 , the back TEC  932  contacts the second thermal solution layer  935  to cool heat generated from Junction B  938  of the back TEC  932 . The thermal solution may be at least one of a copper heat spreader, an aluminum heat spreader, a, for example. 
     At step  1408 , if the skin temperature is not greater than the threshold temperature, the mobile device refrains from providing power to the TEC. Further, at step  1410 , if the skin temperature is not greater than the threshold temperature (e.g., if the determined skin temperature is equal to or less than the threshold temperature), the mobile device may generate power via a temperature difference between the first side and the second side of the thermoelectric cooler. For example, referring to  FIGS. 12-13 , if the skin temperature sensed by the temperature sensor  820  is equal to or less than the threshold temperature, the mobile device may generate power via a temperature difference between the first junction  1214  and the second junction  1216  of the front TEC  1212 . 
     Referring to  FIG. 14B , the method of the flowchart  1450  may be performed in addition to the method of  FIG. 14A . At step  1452 , the mobile device may generate power via a temperature difference between a first side of a second TEC and a second side of the second TEC. The second TEC may be located opposite the TEC within the mobile device. For example, referring back to  FIG. 11 , the mobile device may generate power via a temperature difference between Junction A  1134  and Junction B  1136  of the back TEC  1132  that is located at an opposing end from the front TEC  812 . At least one of the first side and the second side of the second TEC contacts a thermal solution. For example, referring back to  FIG. 11 , Junction B  1136  of the back TEC  1132  contacts the thermal solution  836 . In one configuration, the first side of the second TEC contacts a second skin portion of the mobile device and the second side of the second TEC faces the core of the mobile device. For example, referring back to  FIG. 11 , Junction A  1136  contacts the back cover  832  and Junction B  1134  faces the inside portion  850 . In another configuration, the first side of the second TEC faces the core of the mobile device and the second side of the second TEC contacts the second skin portion. 
     At step  1454 , the mobile device obtains a second skin temperature at a second skin portion of the mobile device. For example, referring back to  FIG. 10 , the mobile device obtains the back side skin temperature at the back cover  832  via the temperature sensor  934 . At step  1456 , the mobile device determines whether the second skin temperature is greater than the threshold temperature. For example, referring back to  FIG. 7 , the temperature module  706  computes a temperature difference value by subtracting the threshold temperature from the sensed skin temperature. The sensed skin temperature is greater than the threshold temperature if the temperature difference is greater than zero. At step  1458 , if the second skin temperature is greater than the threshold temperature, the mobile device provides power to the second TEC to cool a first side of the second TEC while heating a second side of the second TEC. For example, referring back to  FIG. 10 , if the back side skin temperature sensed by the back side temperature sensor  934  is greater than the threshold temperature, the mobile device provides power to the TEC  934  to cool Junction A  936  of the TEC  934  while heating Junction B  938  of the TEC  934 . 
       FIG. 15  is a conceptual data flow diagram  1500  illustrating the data flow between different modules/means/components in an exemplary apparatus  1502 . The apparatus may be a mobile device. The apparatus includes a temperature module  1504  that determines whether a skin temperature at a skin portion of a mobile device is greater than a threshold temperature. The first temperature sensor  1550  measures the skin temperature at the skin portion of the mobile device. The apparatus further includes a power supply control module  1506  that provides power to a TEC  1560  to cool a first side of the TEC  1560  while heating a second side of the TEC  1560  if the skin temperature is greater than the threshold temperature, wherein the first side of the TEC  1560  contacts the skin portion to cool the skin portion and the second side of the TEC  1560  faces a core of the mobile device. The power supply control module  1506  may refrain from providing power to the TEC  1560  when the skin temperature is determined to be equal to or less than the threshold temperature. The apparatus further includes a power generation control module  1508  that generates power via a temperature difference between the first side and the second side of the TEC  1560  if the determined skin temperature is equal to or less than the threshold temperature. The power generation control module  1508  may also generate power via a temperature difference between a first side of a second TEC  1570  and a second side of the second TEC  1570 , the second TEC  1570  being located at an opposite side from the TEC. 
     The temperature module  1504  may determine whether a second skin temperature at a second skin portion of the mobile device is greater than the threshold temperature. The second temperature sensor  1580  measures second skin temperature at the second skin portion of the mobile device. Then, the power supply control module  1506  may provide power to a second TEC  1570  to cool a first side of the second TEC  1570  while heating a second side of the second TEC  1570  if the second skin temperature is greater than the threshold temperature. The first side of the second TEC  1570  contacts the second skin portion to cool the second skin portion. The second side of the second TEC  1570  faces the core of the mobile device. 
     The apparatus may include additional modules that perform each of the steps of the algorithm in the aforementioned flow charts of  FIGS. 14A-14B . As such, each step in the aforementioned flow charts of  FIGS. 14A-14B  may be performed by a module and the apparatus may include one or more of those modules. The modules may be one or more hardware components specifically configured to carry out the stated processes/algorithm, implemented by a processor configured to perform the stated processes/algorithm, stored within a computer-readable medium for implementation by a processor, or some combination thereof. 
       FIG. 16  is a diagram  1600  illustrating an example of a hardware implementation for an apparatus  1502 ′ employing a processing system  1614 . The processing system  1614  may be implemented with a bus architecture, represented generally by the bus  1624 . The bus  1624  may include any number of interconnecting buses and bridges depending on the specific application of the processing system  1614  and the overall design constraints. The bus  1624  links together various circuits including one or more processors and/or hardware modules, represented by the processor  1604 , the modules  1504 ,  1506 ,  1508 ,  1550 ,  1560 ,  1570 ,  1580 , and the computer-readable medium  1606 . The bus  1624  may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further. 
     The processing system  1614  may be coupled to a transceiver  1610 . The transceiver  1610  is coupled to one or more antennas  1620 . The transceiver  1610  provides a means for communicating with various other apparatus over a transmission medium. The transceiver  1610  receives a signal from the one or more antennas  1620 , extracts information from the received signal, and provides the extracted information to the processing system  1614 . In addition, the transceiver  1610  receives information from the processing system  1614 , and based on the received information, generates a signal to be applied to the one or more antennas  1620 . The processing system  1614  includes a processor  1604  coupled to a computer-readable medium  1606 . The processor  1604  is responsible for general processing, including the execution of software stored on the computer-readable medium  1606 . The software, when executed by the processor  1604 , causes the processing system  1614  to perform the various functions described supra for any particular apparatus. The computer-readable medium  1606  may also be used for storing data that is manipulated by the processor  1604  when executing software. The processing system further includes at least one of the modules  1504 ,  1506 ,  1508 ,  1550 ,  1560 ,  1570 , and  1580 . The modules may be software modules running in the processor  1604 , resident/stored in the computer readable medium  1606 , one or more hardware modules coupled to the processor  1604 , or some combination thereof. 
     In one configuration, the apparatus  1502 / 1502 ′ for wireless communication includes means for determining whether a skin temperature at a skin portion of a mobile device is greater than a threshold temperature, and means for providing power to a TEC to cool a first side of a TEC while heating a second side of the TEC if the skin temperature is greater than the threshold temperature, wherein the first side of the TEC contacts the skin portion to cool the skin portion and the second side of the TEC faces a core of the mobile device. The apparatus  1502 / 1502 ′ may further include means for generating power via a temperature difference between the first side and the second side of the TEC if the determined skin temperature is equal to or less than the threshold temperature. The apparatus  1502 / 1502 ′ may further include means for refraining from providing power to the TEC when the skin temperature is determined to be equal to or less than the threshold temperature. The apparatus  1502 / 1502 ′ may further include means for determining whether a second skin temperature at a second skin portion of the mobile device is greater than the threshold temperature, and means for providing power to a second TEC to cool a first side of the second TEC while heating a second side of the second TEC if the second skin temperature is greater than the threshold temperature, wherein the first side of the second TEC contacts the second skin portion to cool the second skin portion and the second side of the second TEC faces the core of the mobile device. The apparatus  1502 / 1502 ′ may further include means for generating power via a temperature difference between a first side of a second TEC and a second side of the second TEC, the second TEC being located at an opposing side from the TEC. 
     It is understood that the specific order or hierarchy of steps in the processes disclosed is an illustration of exemplary approaches. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the processes may be rearranged. Further, some steps may be combined or omitted. The accompanying method claims present elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented. 
     The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more.” The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects.” Unless specifically stated otherwise, the term “some” refers to one or more. Combinations such as “at least one of A, B, or C,” “at least one of A, B, and C,” and “A, B, C, or any combination thereof” include any combination of A, B, and/or C, and may include multiples of A, multiples of B, or multiples of C. Specifically, combinations such as “at least one of A, B, or C,” “at least one of A, B, and C,” and “A, B, C, or any combination thereof” may be A only, B only, C only, A and B, A and C, B and C, or A and B and C, where any such combinations may contain one or more member or members of A, B, or C. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed as a means plus function unless the element is expressly recited using the phrase “means for.”