Patent Publication Number: US-2019171260-A1

Title: Electronic apparatus with heat-dissipation system and heat-dissipation device thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This Application claims priority of Taiwan Patent Application No. 106142133 filed on Dec. 1, 2017, the entirety of which is incorporated by reference herein. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present disclosure relates to an electronic apparatus, and in particular to an electronic apparatus with a heat-dissipation system. 
     Description of the Related Art 
     There are many high-efficiency processing chips disposed in computers for improving the efficiency of those computers, which may include servers. However, when processing chips are operated at full speed, the processing chips generate a lot of heat in the computer. 
     For dissipating the heat in the computer, the conventional heat-dissipation system used in computers includes heat-dissipation structures disposed on each of the processing chips, and many fans disposed in the computer so as to increase the amount of airflow flowing to the heat-dissipation structures. 
     However, when some of the fans stop working, the distribution of the airflow inside the computer changes, and thus the heat-dissipation efficiency of the heat-dissipation structures decreases. Moreover, if the temperature of the processing chips reaches a critical temperature, the temperature of the processing chips must be lowered by decreasing the operation speed of the processing chips. However, this also decreases the efficiency of the computer. 
     Although conventional heat-dissipation systems for computers have generally been adequate for their intended purposes, they have not been entirely satisfactory in all respects. Consequently, it is desirable to provide a solution for improving heat-dissipation systems. 
     BRIEF SUMMARY OF THE INVENTION 
     The disclosure provides an electronic apparatus with a heat-dissipation system. The efficiency of the heat-dissipation system can be improved by rotating heat-dissipation structures to various orientations. Moreover, the electronic apparatus can rotate the heat-dissipation structure according to the operation conditions of fans or heat sources, so as to prevent the electronic apparatus from overheating or decreasing the operation speed of heat sources. 
     The disclosure provides a heat-dissipation device configured to be disposed in an electronic apparatus. The heat-dissipation device includes a bottom base, a heat-dissipation structure and a driving mechanism. The heat-dissipation structure includes a heat-dissipation base rotatably disposed on the bottom base; and heat-dissipation fins disposed on the heat-dissipation base. The driving mechanism is configured to selectively rotate the heat-dissipation structure to one of predetermined orientations. 
     In some embodiments, the driving mechanism further includes a first connection element connected to the heat-dissipation structure; a first magnetic element disposed on the first connection element; and a first electromagnet adjacent to the first magnetic element, and configured to generate a first magnetic field. The heat-dissipation structure is rotated to one of the predetermined orientations by changing the intensity of the first magnetic field. 
     In some embodiments, the driving mechanism further includes a second connection element pivoted on the first connection element; a second magnetic element disposed on the second connection element; and a second electromagnet adjacent to the second magnetic element, and configured to generate a second magnetic field. The heat-dissipation structure is rotated to one of the predetermined orientations by changing strengths of the first magnetic field and the second magnetic field. 
     In some embodiments, the driving mechanism further includes a connection assembly connected to the heat-dissipation structure; and a motor connected to the connection assembly. The heat-dissipation structure is rotated to one of the predetermined orientations by the motor driving the connection assembly. 
     In some embodiments, the connection assembly includes a connection element disposed on the heat-dissipation structure; a rack pivoted on the connection element; and a gear engaged with the rack, and connected to the motor. 
     The disclosure provides an electronic apparatus with a heat-dissipation system including a housing, a heat-dissipation device, a fan, sensors and a processing device. The heat-dissipation device includes a bottom base located in the housing; a heat-dissipation structure rotatably disposed on the bottom base; and a driving mechanism configured to rotate the heat-dissipation structure. The fan is disposed in the housing, and configured to generate an airflow passing through the heat-dissipation structure; sensors disposed in the housing, and configured to generate a plurality of sensing signals; and a processing device selectively rotating the heat-dissipation structure to one of the predetermined orientations according to the sensing signals, so as to increase the intensity of the airflow passing through the heat-dissipation structure. 
     In some embodiments, at least one of the sensors is located between the heat-dissipation structure and the fan. In some embodiments, the heat-dissipation structure is located between the fan and the sensors. 
     In some embodiments, the electronic apparatus further includes heat sources disposed in the housing. The sensors are located between the heat sources and the heat-dissipation structure, and adjacent to the heat sources or integrated in the heat sources. The processing device is configured to selectively rotate the heat-dissipation structure to one of the predetermined orientations according to the sensing signals, so as to enhance the intensity of the airflow toward to one of the heat sources. 
     The disclosure provides an electronic apparatus with heat-dissipation system including a housing, a heat-dissipation device, fans, and a processing device. The heat-dissipation device includes a bottom base located in the housing; a heat-dissipation structure rotatably disposed on the bottom base; and a driving mechanism configured to rotate the heat-dissipation structure. The fans is disposed in the housing, and configured to generate an airflow passing through the heat-dissipation structure. The processing device is configured to detect an operation condition of the fans, and generating an operation signal. The processing device controls the driving mechanism to make the heat-dissipation structure rotate to a predetermined orientation according to the operation signal. 
     In conclusion, the electronic device of the disclosure improves the heat-dissipation efficiency of the heat-dissipation device by adjusting the orientation of the heat-dissipation structure. In some embodiments, when at least one of the fans is not working, the heat-dissipation system can provide good heat-dissipation efficiency, so as to prevent the electronic device from overheating and crashing. In some embodiments, the heat-dissipation system selectively increases the amount of the airflow flowing to some of the heat sources, so as to prevent from decreasing the efficiency of some heat sources due to overheating. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
         FIG. 1  is a schematic view of an electronic apparatus in accordance with a first embodiment of the disclosure, wherein the heat-dissipation structure is located at a first predetermined orientation. 
         FIG. 2  is a system diagram of the processing device in accordance with the first embodiment of the disclosure. 
         FIG. 3  is a schematic view of the electronic apparatus in accordance with the first embodiment of the disclosure, wherein the heat-dissipation structure of the heat-dissipation device is located at a second predetermined orientation. 
         FIG. 4  is a schematic view of an electronic apparatus in accordance with a second embodiment of the disclosure, wherein the heat-dissipation structure is located at a first predetermined orientation. 
         FIG. 5  is a schematic view of an electronic apparatus in accordance with the second embodiment of the disclosure, wherein the heat-dissipation structure is located at a second predetermined orientation. 
         FIG. 6  is a perspective view of the heat-dissipation devices in accordance with the first embodiment of the disclosure. 
         FIG. 7  is a cross-sectional view of the heat-dissipation devices in accordance with the first embodiment of the disclosure. 
         FIG. 8A  and  FIG. 8B  are top views of the heat-dissipation devices in accordance with the first embodiment of the disclosure. 
         FIG. 9  is a perspective view of a heat-dissipation device in accordance with a second embodiment of the disclosure. 
         FIG. 10A  and  FIG. 10B  are top views of the heat-dissipation device in accordance with the second embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following disclosure provides many different embodiments, or examples, for implementing different features of the present disclosure. Specific examples of components and arrangements are described below to simplify the present disclosure. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. 
     The words, such as “first” or “second”, in the specification are for the purpose of clarity of description only, and are not relative to the claims or meant to limit the scope of the claims. In addition, terms such as “first feature” and “second feature” do not indicate the same or different features. 
     Spatially relative terms, such as upper and lower, may be used herein for ease of description to describe one element or feature&#39;s relationship to other elements or features as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. Moreover, the shape, size, and thickness depicted in the drawings may not be drawn to scale or may be simplified for clarity of discussion; these drawings are merely intended for illustration. 
       FIG. 1  is a schematic view of an electronic apparatus A 1  in accordance with a first embodiment of the disclosure, wherein the heat-dissipation structure  20  is located at a first predetermined orientation. The electronic apparatus A 1  may be a computer host. In some embodiments, the electronic apparatus A 1  may be a server. The electronic apparatus A 1  includes a housing A 10 , heat sources A 20  (such as the heat sources A 20   a  to A 20   d ), heat-dissipation devices A 30  (such as heat-dissipation devices A 30   a  to A 30   d ), electronic devices A 40 , fans A 50 , sensors A 60  (such as sensors A 60   a  to A 60   c ), and a processing device A 70 . The heat-dissipation devices A 30 , the fans A 50 , the sensors A 60 , and the processing device A 70  are formed as a heat-dissipation system. 
     The heat sources A 20  are disposed in the housing A 10 . When the electronic apparatus A 1  is operated, the heat sources A 20  generates heat. In some embodiments, the heat sources A 20  may be chips, but there are not limited thereto. For example, the chips may be central processing chips, memories, or display chips. In the embodiment, there are four heat sources A 20 , but it is not limited thereto. Moreover, the position of the heat sources A 20  distributed in the housing A 10  can be changed according to the design requirements. 
     The heat-dissipation devices A 30  are disposed in housing A 10 , and connected to the heat sources A 20 . In the embodiment, there are four heat-dissipation devices A 30 , but it is not limited thereto. The number of the heat-dissipation devices A 30  may correspond to the number of the heat sources A 20 . In some embodiments, the number of the heat-dissipation devices A 30  is less than the number of the heat sources A 20 . In some embodiments, the number of the heat-dissipation devices A 30  is greater than the number of the heat sources A 20 . 
     In the embodiment, each of the heat-dissipation devices A 30  includes a bottom base  10 , a heat-dissipation structure  20 , a pivot structure  30  (as shown in  FIG. 7 ), and a driving mechanisms  40 . The bottom base  10  is disposed in the housing A 10 , and may be disposed on the heat source A 20 . The heat-dissipation structures  20  are rotatably disposed on the bottom bases  10  by the pivot structures  30 . The driving mechanisms  40  are configured to rotate the heat-dissipation structures  20  relative to the bottom bases  10 . 
     In some embodiments, some of the heat-dissipation devices A 30  (such as the heat-dissipation devices A 30   b,  A 30   c  and A 30   d ) may not include the bottom bases  10  and/or the driving mechanisms  40 . When the heat-dissipation devices A 30  do not include the bottom bases  10  and the driving mechanisms  40 , the heat-dissipation structures  20  are detachably disposed on the heat sources A 20 , or the heat-dissipation structures  20  are connected to the heat sources A 20  via heat-conducting elements (not shown in figures). 
     The electronic devices A 40  are disposed in the housing A 10 . In the embodiment, there are two electronic devices A 40 , and disposed on two opposite sides of the heat-dissipation device A 30   a,  but the position and number of the electronic devices A 40  are not be limited thereto. For example, the electronic devices A 40  are storage devices, such as hard disks or optical drives, but there are not limited thereto. 
     The fans A 50  are disposed in the housing A 10 , and configured to generate an airflow. The airflow may pass through the heat-dissipation devices A 30  and the heat-dissipation structures  20 . In the embodiment, the fans A 50  are configured to inhale the air outside of the housing A 10  into the housing A 10 . In some embodiments, the fans A 50  exhaust the air in the housing A 10  to the outside of the housing A 10 . 
     In the embodiment, there are six fans A 50 , but it is not limited thereto. In some embodiments, there are one or at least one fans A 50 . In the embodiment, the fans A 50  are arranged on the rear side A 11  of the housing A 10 , but the arrangement of the fans A 50  may be varied according to different designs. 
     The sensors A 60  are disposed in the housing A 10 , and configured to generate sensing signals S 1  (as shown in  FIG. 2 ). In the embodiment, the sensors A 60  are adjacent to the fans A 50 . The sensors A 60  are disposed between the heat-dissipation structure  20  of the heat-dissipation device A 30   a  and the fans A 50 . 
     In some embodiments, the sensors A 60  are thermistors, and generate sensing signals S 1  (as shown in  FIG. 2 ) according to the changes of the resistances of the thermistors. In a case, the sensors A 60  are thermistors. The intensity of the airflow flowing to the sensors A 60  affects the resistances of the thermistors, and thus the amount of airflow passing through the sensors A 60  can be inferred based on the resistances of the thermistors. 
     In some embodiments, the sensors A 60  may be temperature sensors. Since the intensity of the airflow flowing to the sensors A 60  affects the temperatures of the sensors A 60 , the amount of the airflow passing through the sensors A 60  can be inferred based on the temperatures of the sensors A 60 . 
       FIG. 2  is a system diagram of the processing device A 70  in accordance with the first embodiment of the disclosure. The processing device A 70  is disposed in the housing A 10 , and connected to the sensors A 60  and the driving mechanisms  40 . The processing device A 70  can selectively rotate the heat-dissipation structures  20  to many predetermined orientations according to the sensing signals S 1 , so as to change the movement direction of the airflow, and to enhance the intensity of the airflow passing through the heat-dissipation structures  20 . Moreover, the driving mechanisms  40  can maintain the position of the heat-dissipation structures  20  on one of the predetermined orientations. 
     The processing device A 70  is configured to receive the sensing signals S 1 , and generate a control signal S 3  according to the sensing signals S 1 . In the embodiment, the processing device A 70  may include an amplifying circuit A 71 , a comparison circuit A 72 , and a control circuit A 73 . The amplifying circuit A 71  is configured to amplify the sensing signals S 1 , and transmit the amplified sensing signals S 1  to the comparison circuit A 72 . The comparison circuit A 72  is configured to generate a comparison signal S 2  according to the sensing signals S 1 . The control circuit A 73  generates a control signal S 3  according to the comparison signal S 2 . 
     In the embodiment, the heat source A 20   a  may be a central processing chip. The processing device A 70  may be integrated in the central processing chip. 
     As shown in  FIGS. 1 and 2 , in some embodiments, when all of the fans A 50  are working normally, the airflow are uniformly flowing to each of the sensors A 60 . Therefore, the sensors A 60  (such as the sensors A 60   a,  A 60   b  and A 60   c ) generate the same or substantially the same sensing signals S 1 . After the comparison circuit A 72  processes the sensing signals S 1 , the comparison circuit A 72  generates a comparison signal S 2  having a first comparison value. 
     The control circuit A 73  generates a first control signal S 3  according to the first comparison value, so as to control the driving mechanisms  40  to rotate the heat-dissipation structure  20  of the heat-dissipation device A 30   a  to a first predetermined orientation as shown in  FIG. 1 . Moreover, the driving mechanism  40  can maintain the heat-dissipation structure  20  of the heat-dissipation device A 30   a  on the first predetermined orientation. When all of the fans A 50  are working normally, the intensity of the airflow passing through the heat-dissipation structure  20  at the first predetermined orientation is greater. Therefore, the heat-dissipation efficiency of the heat-dissipation device A 30   a  is improved. 
     In the embodiment, the heat-dissipation structure  20  includes heat-dissipation fins  22  parallel to and separated from each other. When all of the fans A 50  are working normally, the extension direction of the heat-dissipation fins  22  at the first predetermined orientation is substantially parallel to the direction of the airflow flowing to the heat-dissipation structure  20 . Therefore, the airflow can smoothly pass through the gaps between the heat-dissipation fins  22 . 
       FIG. 3  is a schematic view of the electronic apparatus A 1  in accordance with the first embodiment of the disclosure, wherein the heat-dissipation structure  20  of the heat-dissipation device A 30   a  is located at a second predetermined orientation. Moreover, the driving mechanism  40  can maintain the heat-dissipation structure  20  of the heat-dissipation device A 30   a  on the second predetermined orientation. In some embodiments, when the fan A 50   a  is not working, the distribution of the airflow generated by the fans A 50  changes. The intensity of the airflow flowing to the sensor A 60   a  is less than the intensity of the airflow flowing to the sensor A 60   b  and A 60   c.    
     In one embodiment, the value of the sensing signal S 1  generated by the sensor A 60   a  is less than the value of the sensing signals S 1  generated by the sensor A 60   b  and A 60   c.  Therefore, after the comparison circuit A 72  processes the sensing signals S 1 , the comparison circuit A 72  generates a comparison signal S 2  having a second comparison value. The control circuit A 73  generates a control signal S 3  according to the second comparison value, so as to control the driving mechanism  40  to rotate the heat-dissipation device A 30   a  of the heat-dissipation structure  20  to a second predetermined orientation as shown in  FIG. 3 . 
     Therefore, when the fan A 50   a  is not working, the intensity of the airflow passing through the heat-dissipation structure  20  at the second predetermined orientation is greater than the intensity of the airflow passing through the heat-dissipation structure  20  at the first predetermined orientation. Therefore, the heat-dissipation efficiency of the heat-dissipation device A 30   a  is improved. Moreover, when the fan A 50   a  is not working, the extension direction of the heat-dissipation fins  22  at the second predetermined orientation is substantially parallel to the direction of the airflow flowing to the heat-dissipation structure  20 . Therefore, the airflow can smoothly pass through the gaps between heat-dissipation fins  22  at the second predetermined orientation. 
     The embodiment is not limited to the situation of the fan A 50   a,  which is not working. The processing device A 70  controls the driving mechanism  40  to rotate the heat-dissipation structure  20  to various predetermined orientation according to the position and number of inoperable fans A 50 . 
     For example, when the fan A 50   b  is not working, and the other fans A 50  are working normally, the processing device A 70  controls the driving mechanism  40  to rotate the heat-dissipation structure  20  of the heat-dissipation device A 30   a  to a third predetermined orientation according to the sensing signals S 1 . Moreover, the driving mechanism  40  can maintain the heat-dissipation structure  20  of the heat-dissipation device A 30   a  at the third predetermined orientation. When the fan A 50   a  and the fan A 50   b  are not working, and the other fans A 50  are working normally, the processing device A 70  controls the driving mechanism  40  to rotate the heat-dissipation structure  20  of the heat-dissipation device A 30   a  to a fourth predetermined orientation according to the sensing signals S 1 . Moreover, the driving mechanism  40  can maintain the heat-dissipation structure  20  of the heat-dissipation device A 30   a  at the fourth predetermined orientation. 
     In some embodiments, the processing device A 70  can rotate the heat-dissipation structures  20  of the heat-dissipation devices A 30   b,  A 30   c  and A 30   d  by the disclosed methods, so as to improve the heat-dissipation efficiency of the heat-dissipation devices A 30   b,  A 30   c  and A 30   d.    
     Accordingly, in the embodiment, the heat-dissipation system can adjust the orientations of the heat-dissipation structures  20  according to the operation conditions of the fans A 50 , so as to improve the heat-dissipation efficiency of the heat-dissipation devices A 30 . Moreover, when some of the fans A 50  are not working, the heat-dissipation system also provides great heat-dissipation efficiency, so as to prevent the electronic apparatus A 1  from overheating and crashing. 
     In some embodiments, the electronic apparatus A 1  may not include the sensors A 60 , and the processing device A 70  is directly electrically connected to each of the fans A 50 . Therefore, the processing device A 70  can detect the operation conditions of the fans A 50 , and generate an operation signal. Afterwards, the processing device A 70  controls the driving mechanisms  40  to rotate the heat-dissipation structures  20  to various predetermined orientations according to the operation signal, so as to change the flowing direction of the airflow. 
     For example, when all of the fans A 50  are working normally, the processing device A 70  controls the driving mechanism  40  to rotate the heat-dissipation structure  20  to the first predetermined orientation according to the operation signal. Alternately, when the fan A 50   a  is not working, the processing device A 70  controls the driving mechanism  40  to rotate the heat-dissipation structure  20  to the second predetermined orientation according to the operation signal. When the fan A 50   b  is not working, the processing device A 70  controls the driving mechanism  40  to rotate the heat-dissipation structure  20  to the third predetermined orientation according to the operation signal. 
       FIG. 4  is a schematic view of an electronic apparatus A 1  in accordance with a second embodiment of the disclosure, wherein the heat-dissipation structure  20  is located at a first predetermined orientation.  FIG. 5  is a schematic view of an electronic apparatus A 1  in accordance with the second embodiment of the disclosure, wherein the heat-dissipation structure  20  is located at a second predetermined orientation. The processing device A 70  selectively rotates the heat-dissipation structure  20  to various predetermined orientations according to the sensing signals S 1 , so as to enhance the intensity of the airflow flowing to one of the heat sources A 20 . 
     In the embodiment, the sensors A 60  according to the front side A 12  of the housing A 10 , and adjacent to the heat sources A 20   b,  A 20   c  and A 20   d  and the heat-dissipation devices A 30   b,  A 30   c  and A 30   d.  In some embodiments, the sensors A 60  are disposed on the heat-dissipation devices A 30   b,  A 30   c  and A 30   d.  In some embodiments, the sensors A 60  may be disposed between the heat-dissipation devices A 30   b,  A 30   c  and A 30   d  and the heat-dissipation structure  20  of the heat-dissipation device A 30   a.  Moreover, the heat-dissipation structure  20  of the heat-dissipation device A 30   a  may be disposed between the fans A 50  and the sensors A 60 . In some embodiments, the sensors A 60  are integrated in the heat sources A 20   b,  A 20   c  and A 20   d.    
     In the embodiment, the heat source A 20   a  may be a central processing chip. The processing device A 70  may be integrated in the central processing chip. 
     In the embodiment, the sensors A 60  may be temperature sensors. In some embodiments, when the sensing signal S 1  of the sensor A 60   b  has a greater value, it means that the heat source A 20   c  has greater temperature. The processing device A 70  can control the driving mechanism  40  to rotate the heat-dissipation structure  20  of the heat-dissipation device A 30   a  to the first predetermined orientation as shown in  FIG. 4  according to the sensing signals S 1 , so as to enhance the intensity of the airflow flowing to the heat source A 20   c.    
     In some embodiments, when the sensing signal S 1  of the sensor A 60   a  has greater value, it means the heat source A 20   b  has a greater temperature. The processing device A 70  controls the driving mechanism  40  to rotate the heat-dissipation structure  20  of the heat-dissipation device A 30   a  to the second predetermined orientation as shown in  FIG. 5  according to the sensing signals S 1 , so as to enhance the intensity of the airflow according to the heat source A 20   b.    
     Each of the heat sources A 20   b,  A 20   c  and A 20   d  has a critical temperature. When the temperature of the heat sources A 20   b,  A 20   c  or A 20   d  is close to, equal to or over the critical temperature, the processing device A 70  will decrease the operation speed of the heat sources A 20   b,  A 20   c  or A 20   d,  so as to decrease the temperature of the heat sources A 20   b,  A 20   c  or A 20   d.    
     In the embodiment, the processing device A 70  can generate a priority value according to each of the temperatures of the heat sources A 20   b,  A 20   c  and A 20   d  and the critical temperature. The priority value can be a difference value of one of the temperatures and the critical temperature. 
     When the heat source A 20   c  has a greater priority value, it means the heat source A 20   c  needs greater heat-dissipation efficiency. The processing device A 70  can control the driving mechanism  40  to rotate the heat-dissipation structure  20  of the heat-dissipation device A 30   a  to the first predetermined orientation as shown in  FIG. 4  according to the priority value, so as to enhance the intensity of the airflow flowing to the heat source A 20   c.    
     When the heat source A 20   b  has a greater priority value, it means the heat source A 20   b  needs greater heat-dissipation efficiency. The processing device A 70  controls the driving mechanism  40  to rotate the heat-dissipation structure  20  of the heat-dissipation device A 30   a  to the second predetermined orientation as shown in  FIG. 5  according to the priority value, so as to enhance the intensity of the airflow flowing to the heat source A 20   b.    
     Therefore, in the embodiment, by increasing the amount of the airflow flowing to the heat sources A 20   b  (A 20   c  or A 20   d ), the heat-dissipation efficiency of the heat sources A 20   b  (A 20   c  or A 20   d ) is improved, and the operation efficiency of the heat sources A 20   b  (A 20   c  or A 20   d ) may not need to be decreased. 
       FIG. 6  is a perspective view of the heat-dissipation devices A 30  in accordance with the first embodiment of the disclosure.  FIG. 7  is a cross-sectional view of the heat-dissipation devices A 30  in accordance with the first embodiment of the disclosure. The bottom base  10  is detachably affixed to the heat source A 20 . In some embodiments, the bottom base  10  may not be located over the heat source A 20 , and the bottom base  10  is connected to the heat source A 20  via a heat-dissipation element (not shown in figures) connected to the heat source A 20 . For example, the heat-dissipation element may be a heat pipe. The bottom base  10  is made from thermal material, such as metal. 
     The heat-dissipation structure  20  may be made from thermal material, such as metal. The heat-dissipation structure  20  includes a heat-dissipation base  21  and heat-dissipation fins  22 . The heat-dissipation base  21  is rotatably disposed on the bottom base  10 , and the heat-dissipation fin  22  is disposed on heat-dissipation base  21 . In some embodiments, the heat-dissipation base  21  and the heat-dissipation fins  22  are formed as a single piece. 
     The pivot structure  30  is connected to the bottom base  10  and the heat-dissipation base  21 . The heat-dissipation structure  20  is rotated relative to the bottom base  10  via the pivot structure  30 . The pivot structure  30  includes a rotation shaft  31  and a rotation ball  32 . The rotation shaft  31  is connected to the bottom base  10 , and extends along an axis AX 1 . Therefore, the heat-dissipation structure  20  is rotated about the axis AX 1  relative to the bottom base  10 . The rotation ball  32  is disposed on the end of the rotation shaft  31 , and in contact with the heat-dissipation base  21 , so as to enhance the smoothness of the heat-dissipation base  21  rotated relative to the bottom base  10 . 
     The driving mechanisms  40  are configured to selectively rotate the heat-dissipation structures  20  to various predetermined orientations. Each of the driving mechanism  40  includes a first connection element  41 , a second connection element  42 , magnetic elements  43  (such as magnetic elements  43   a,    43   b  and  43   c ) and electromagnets  44  (such as the magnetic elements  44   a,    44   b  and  44   c ). The first connection element  41  is connected to the heat-dissipation structure  20 . In the embodiment, the first connection element  41  is a rod-shaped structure. One end of the first connection element  41  is connected to a side of the heat-dissipation base  21 , and the other end is connected to the magnetic element  43   a.    
     The second connection element  42  is pivoted on the first connection element  41 . In the embodiment, the second connection element  42  may be a rod-shaped structure. Two ends of the second connection element  42  are connected to the magnetic element  43   b  and the magnetic element  43   c.    
     The magnetic elements  43  (such as the magnetic elements  43   a,    43   b  and  43   c ) are permanent magnets. The electromagnets  44  (such as the magnetic elements  44   a,    44   b  and  44   c ) are electrically connected to the processing device A 70 , and configured to the magnetic field. Moreover, the electromagnet  44   a  is adjacent to the magnetic element  43   a,  the electromagnet  44   b  is adjacent to the magnetic element  43   b , and the electromagnet  44   c  is adjacent to the magnetic element  43   c.    
     The processing device A 70  changes the intensity of the magnetic field by adjusting the current transmitted to the electromagnets  44 . Moreover, the heat-dissipation structure  20  is rotated to a predetermined orientation by changing the intensity of the magnetic field, and maintained on the predetermined orientation. 
     As shown in  FIG. 6 , the processing device A 70  controls the intensity of the magnetic field of the electromagnet  44   a  to greater than the intensity of the magnetic field of the electromagnet  44   b  and the electromagnet  44   c,  so as to make the magnetic element  43   a  move close to the electromagnet  44   a.  As a result, the heat-dissipation structure  20  is rotated to a first predetermined orientation. 
       FIG. 8A  and  FIG. 8B  are top views of the heat-dissipation devices A 30  in accordance with the first embodiment of the disclosure. As shown in  FIG. 8A , the processing device A 70  controls the intensity of the magnetic field of the electromagnet  44   b  to greater than the intensity of the magnetic field of the electromagnet  44   c  (and the electromagnet  44   a ), so as to make the magnetic element  43   b  move close to the electromagnet  44   b.  As a result, the heat-dissipation structure  20  is rotated to a second predetermined orientation. As shown in  FIG. 8B , the processing device A 70  controls the intensity of the magnetic field of the electromagnet  44   c  to greater than the intensity of the magnetic field of the electromagnet  44   b  (and the electromagnet  44   a ), so as to make the magnetic element  43   c  move close to the electromagnet  44   c.  As a result, the heat-dissipation structure  20  is rotated to a third predetermined orientation. 
     Accordingly, in the embodiment, by adjusting the intensity of the magnetic field, the heat-dissipation structure  20  can be rotated to various predetermined orientations, but it is not limited to the predetermined orientations as shown in  FIGS. 6, 8A and 8B . 
       FIG. 9  is a perspective view of a heat-dissipation device A 30  in accordance with a second embodiment of the disclosure. In the embodiment, the heat-dissipation device A 30  includes a driving mechanism  50 . The driving mechanism  50  includes a connection assembly  51  and a motor  52 . The connection assembly  51  is connected to the heat-dissipation structure  20  and the motor  52 . The motor  52  is configured to drive the connection assembly  51  to make the connection assembly  51  rotate the heat-dissipation structure  20  to a predetermined orientation, and to maintain the heat-dissipation structure  20  at the predetermined orientation. 
     The connection assembly  51  includes a connection element  511 , a rack  512 , and a gear  513 . The connection element  511  is disposed on the heat-dissipation structure  20 . In the embodiment, the connection element  511  may be a rod-shaped structure, and connected to a side of the heat-dissipation base  21 . The rack  512  is pivoted on the connection element  511 . The gear  513  is engaged with the rack  512 , and connected to the motor  52 . In the embodiment, the connection assembly  51  may further includes a retaining structure  53  configured to retain the movement of the rack  512  along a movement direction D 1 . 
     As shown in  FIG. 9 , the processing device A 70  drives the motor  52  to move the rack  512  along the movement direction D 1 , so as to rotate the heat-dissipation structure  20  to a first predetermined orientation.  FIG. 10A  and  FIG. 10B  are top views of the heat-dissipation device A 30  in accordance with the second embodiment of the disclosure. As shown in  FIG. 10A , the processing device A 70  drives the motor  52  to move the rack  512  along the movement direction D 1 , so as to rotate the heat-dissipation structure  20  to a second predetermined orientation. As shown in  FIG. 10B , the processing device A 70  drives the motor  52  to move the rack  512  along the movement direction D 1 , so as to rotate the heat-dissipation structure  20  to a third predetermined orientation. 
     Accordingly, in the embodiment, the heat-dissipation structure  20  can be rotated to various predetermined orientations by driving the motor  52 , but it is not limited to the predetermined orientations as shown in  FIGS. 9, 10A and 10B . 
     The disclosed features may be combined, modified, or replaced in any suitable manner in one or more disclosed embodiments, but are not limited to any particular embodiments. 
     In conclusion, the electronic device of the disclosure improves the heat-dissipation efficiency of the heat-dissipation device by adjusting the orientation of the heat-dissipation structure. In some embodiments, when at least one of the fans is not working, the heat-dissipation system can provide good heat-dissipation efficiency, so as to prevent the electronic device from overheating and crashing. In some embodiments, the heat-dissipation system selectively increases the amount of the airflow flowing to some of the heat sources, so as to prevent from decreasing the efficiency of some of heat sources due to overheating. 
     While the invention has been described by way of example and in terms of preferred embodiment, it should be understood that the invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.