Abstract:
A heat dissipation device for cooling a heat generating component, includes a fins module, a heat pipe, a fan, at least two temperature sensors, and a control system. The heat pipe includes an evaporation section absorbing heat from the heat generating component, and a condensation section thermally connected to the fins module. The fan is for driving airflow towards the fins module. The at least two temperature sensors are arranged on the evaporation section of the heat pipe, for continuously sensing temperatures of their respective positions on the heat pipe. The control system adjusts the speed of the fan and/or the operating power of the heat generating component according to the sensed temperatures of the at least two temperature sensors. A method for controlling the heat dissipation device is also provided.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present disclosure generally relates to heat dissipation devices, and control method for the heat dissipation devices. 
         [0003]    2. Description of Related Art 
         [0004]    During operation of electronic devices such as computer central processing units (CPUs), a large amount of heat is often produced. The heat must be quickly removed from the electronic devices to prevent them from becoming unstable or being damaged. Many heat dissipation devices are employed to dissipate heat produced by the electric device. A heat dissipation device generally comprises a base attached to the electric device, a plurality of fins thermally connected to the base by heat pipes, and a fan for driving airflow towards the fins. The base is intimately attached to the CPU for absorbing the heat generated by the CPU. Most of the heat accumulated on the base is transferred to the fins by the heat pipes and then the fins are cooled by airflow driven by the fan. 
         [0005]    To achieve high efficiency heat transfer, a fan speed of the heat dissipation device is high, which is not energy saving. 
         [0006]    Therefore, what is needed is to provide a heat dissipation device capable of effectively improving heat dissipating efficiency under different temperatures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Many aspects of the disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the disclosure. 
           [0008]      FIG. 1  is a schematic view of a heat dissipation device in accordance with an embodiment of the present disclosure. 
           [0009]      FIG. 2  is similar to  FIG. 1 , but showing another aspect of the heat dissipation device. 
           [0010]      FIG. 3  is an exploded view of the heat dissipation device of  FIG. 1 . 
           [0011]      FIG. 4  is a function block diagram of the circuit of the mobile phone of  FIG. 1 . 
           [0012]      FIG. 5  is a plot of the thermal resistance versus the fan speed of the heat dissipation device. 
           [0013]      FIG. 6  is a flowchart illustrating a principle of fan speed and processor power adjustment of the heat dissipation device. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    Reference will now be made to the drawings to describe the present embodiment of a heat dissipation device, in detail. 
         [0015]    Referring to  FIGS. 1-4 , a heat dissipation device  10  according to an embodiment includes a fan  11 , a fins module  12 , a heat pipe  13 , a base  14 , two fixing plates  15 , and a control system  16 . 
         [0016]    The fan  11  is for driving airflow towards the fins module  12 . The fan  11  includes a housing  111 , a hub  112  and a plurality of blades  113  radially and extending outward from the hub  112 . The housing  111  defines an air outlet  1111  at a lateral side. The hub  112  and the plurality of blades  113  are received in the housing  111 . 
         [0017]    The fins module  12  is arranged adjacent to the air outlet  1111 . The fins module  12  includes a plurality of fins  121  arranged in parallel to each other. Air channels  122  are formed between each two neighboring fins  121 . The fins  121  each define a rectangular through hole  123  with a size matching the heat pipe  13 . The through holes  123  of the plurality of fins  121  are arranged in alignment, thereby the heat pipe  13  can penetrate through the plurality of fins  121  via the through holes  123 . 
         [0018]    The heat pipe  13  has a curved shape with a flat profile. The heat pipe  13  is made of metal pipe with excellent heat conductivity and phase-change media sealed in the metal pipe. The heat pipe  13  includes an evaporation section  131  and a condensation section  132 . 
         [0019]    The evaporation section  131  of the heat pipe  13  is thermally attached to a central portion of the base  14  and fixed to the base  14  by the fixing plate  15 . At least two temperature sensors  133  are arranged at different positions of the evaporation section  131 . At the position where each temperature sensor  133  sits, a temperature is sensed, and a sensed result is sent to the control system  16 , by the temperature sensor  133 . The number of temperature sensors  133  can be two, three, four, or more. In this embodiment, there are three temperature sensors  133  arranged on the evaporation section  131 . 
         [0020]    The condensation section  132  of the heat pipe  13  is perpendicular to the evaporation section  131  and thermally connected to the fins module  12 . In addition, the condensation section  132  penetrates through the plurality of fins  121  via the through holes  123 . 
         [0021]    The base  14  is a flat heat conductive plate with the four corners cut off. The base  14  has its bottom intimately attached to a processor  17  in use. The base  14  has its top attached to the evaporation section  131  of the heat pipe  13 . 
         [0022]    The fixing plates  15  each include a central portion  151 , a first side portion  152  and a second side portion  153 . The central portion  151  is a strip-like portion fixed with the base  14 . The first and second side portions  152 ,  153  respectively extend from an end of the central portion  151  along a direction inclined to the central portion  151 . The first and second side portions  152 ,  153  each include a distal end, in which a through hole  154  is defined. Accordingly, the base  14  can be fixed to a circuit board (not illustrated) by bolts  155  penetrating through the through holes  154 . In this embodiment, a plurality of gaskets  156  engage with corresponding bolts  155  under the fixing plates  15 . 
         [0023]    Referring to  FIG. 4 , the control system  16  communicates with the processor  17  and the fan  11 , thereby adjusting a heat dissipating efficiency of the heat dissipation device  10 . 
         [0024]    Referring to  FIG. 5 , a plot of the thermal resistance versus the fan speed of the heat dissipation device  10  is illustrated. When the processor  17  has a relatively low power, for example 35 watts (Q in =35 W), the thermal resistance of the heat dissipation device  10  decreases as the fan speed increases. When the processor  17  has a higher power, for example 40 and 45 watts (Q in =40 W, Q in =45 W), the thermal resistance of the heat dissipation device  10  first decreases and then increases, as the fan speed increases. Generally, the processor  17  has an operation power greater than 40 watts. 
         [0025]    Referring to  FIG. 6 , the control system  16  is capable of adjusting the speed of the fan  11  and the operation power of the processor  17 , according to temperatures respectively sensed by the three temperature sensors  133 . The principle of fan speed and processor power adjustment of the heat dissipation device  10  is described in detail as follows. 
         [0026]    First, the three temperature sensors  133  continuously sense temperatures S 1 , S 2  and S 3  of the respective positions where they sit. The control system  16  respectively compares the temperatures S 1 , S 2  and S 3  with a first critical temperature T 1  which stands for a normal operating temperature of the processor  17 . 
         [0027]    In condition that the temperatures S 1 , S 2  and S 3  are all lower than or equal to the first critical temperature T 1 , the control system  16  keeps the operation power of the processor  17  unchanged. If the temperatures S 1 , S 2  and S 3  are all lower than or equal to the first critical temperature T 1 , it shows that heat dissipating efficiency of the heat dissipation device  10  satisfactorily meets the cooling needs of the processor  17 . Accordingly, there is no need to adjust the operation power of the processor  17 . 
         [0028]    In condition, that anyone of the temperatures S 1 , S 2 , and S 3  is higher than the first critical temperature T 1 , the control system  16  increases the speed of the fan  11 . If anyone of the temperatures S 1 , S 2 , and S 3  is higher than the first critical temperature T 1 , it shows that heat dissipating efficiency of the heat dissipation device  10  fails to meet the cooling needs of the processor  17 . Accordingly, the speed of the fan  11  increases to improve the heat dissipating efficiency of the heat dissipation device  10 . Successively, the control system  16  compares a difference between S 1  and S 2  with a first critical temperature difference N 1 , to check out whether there is a nonuniform temperature distribution caused by drying-out of the heat pipe  13 . The first critical temperature difference N 1  is defined with a value representing a threshold of normal temperature difference between two of the temperature sensors  133  on the heat pipe  13 . 
         [0029]    In condition that the difference between S 1  and S 2  is lower than or equal to the first critical temperature difference N 1  (S 1 −S 2 &lt;N 1 , or S 1 −S 2 =N 1 ), the control system  16  keeps the operation power of the processor  17  unchanged. The condition S 1 −S 2 &lt;N 1  or S 1 −S 2 =N 1  shows that there is no nonuniform temperature distribution on the heat pipe  13 , and the heat dissipating efficiency can be finely improved by only increasing the speed of the fan  11 . As such, there is no need to adjust the operation power of the processor  17 . 
         [0030]    In condition that the difference between S 1  and S 2  is larger than the first critical temperature difference N 1  (S 1 −S 2 &gt;N 1 ), the control system  16  decreases the speed of the fan  11  and then compares the difference between S 2  and S 3  with a second critical temperature difference N 2 . The condition S 1 −S 2 &gt;N 1  shows that there is a nonuniform temperature distribution on the heat pipe  13 , and the heat dissipating efficiency cannot be finely improved by increasing the speed of the fan  11 . That is because the increased speed of the fan  11  leads to higher thermal resistance of the heat dissipation device  10 . As such, the speed of the fan  11  is decreased to reduce the thermal resistance of the heat dissipation device  10 , according to what is illustrated in  FIG. 5 . Then a difference between S 2  and S 3  is compared with second critical temperature difference N 2  to further check whether there is a nonuniform temperature distribution on the heat pipe  13 . The second critical temperature difference N 2  is defined with a value representing another threshold of normal temperature difference between another two of the temperature sensors  133  on the heat pipe  13 . 
         [0031]    In condition that the difference between S 2  and S 3  is lower than or equal to the second critical temperature difference N 2  (S 2 −S 3 &lt;N 2 , or S 2 −S 3 =N 2 ), the control system  16  keeps the operation power of the processor  17  unchanged. The condition S 2 −S 3 &lt;N 2  or S 2 −S 3 =N 2  shows that the nonuniform temperature distribution on the heat pipe  13  is eliminated by decreasing the speed of the fan  11 , and it is the drying-out condition of the heat pipe  13  which leads to former low heat dissipating efficiency. As such, the heat dissipating efficiency can be improved by only decreasing the speed of the fan  11  to achieve lower thermal resistance of the heat dissipation device  10 . 
         [0032]    In condition that the difference between S 2  and S 3  is larger than the second critical temperature difference N 2  (S 2 −S 3 &gt;N 2 ), the control system  16  decreases the speed of the fan  11  and respectively compares the temperatures S 1 , S 2  and S 3  with a second critical temperature T 2 . The condition S 2 −S 3 &gt;N 2  shows that the thermal resistance of the heat dissipation device  10  has not been reduced to a minimum value by decreasing the speed of the fan  11 , according to  FIG. 5 . As such, the speed of the fan  11  further decreases to achieve a lower thermal resistance of the heat dissipation device  10 , and the temperatures S 1 , S 2  and S 3  with a second critical temperature T 2  to check out whether the processor  17  has been cooled to a satisfied temperature lower than or equal to the second critical temperature T 2 . 
         [0033]    In condition that the temperatures S 1 , S 2 , and S 3  are all lower than or equal to the second critical temperature T 2 , the control system  16  keeps the operation power of the processor  17  unchanged. The condition that the temperatures S 1 , S 2 , and S 3  are all lower than or equal to the second critical temperature T 2  shows that, the processor  17  has been cooled to a satisfied temperature by further decreasing the speed of the fan  11 . As such, there is no need to lower the operation power of the processor  17 . 
         [0034]    In condition, that anyone of the temperatures S 1 , S 2 , and S 3  is higher than T 2 , the control system  16  decreases the operation power of the processor  17 . The condition that the anyone of the temperatures S 1 , S 2 , and S 3  is higher than T 2  shows that, it is impossible to cool the processor  17  to the satisfied temperature range only by achieving lowest thermal resistance of the heat dissipation device  10 . As such, the processor  17  can only be cooled by reducing the operation power thereof. 
         [0035]    It is to be understood that the above-described embodiments are intended to illustrate rather than limit the disclosure. Variations may be made to the embodiments without departing from the spirit of the disclosure as claimed. The above-described embodiments illustrate the scope of the disclosure but do not restrict the scope of the disclosure.