Abstract:
The present invention generally relates to thermal management of electronic devices and systems. More specifically, the present invention relates to heat dissipation in a telecommunication device. A method for cooling a telecommunication device, wherein cooling capacity is provided by natural cooling capacity and forced cooling capacity which is adjustable, the method comprising: estimating a thermal state of the telecommunication device; and if cooling capacity mismatches the thermal state, making an adjustment to the forced cooling capacity.

Description:
TECHNICAL FIELD 
       [0001]    The present invention generally relates to thermal management of electronic devices and systems. More specifically, the present invention relates to heat dissipation in a telecommunication device. 
       BACKGROUND 
       [0002]    Heat generated by electronic devices and circuitry must be dissipated to improve reliability and prevent premature failure. Remote Radio Unit (RRU), Digital Unit (DU) and microwave communication device are examples of telecommunication equipment that need heat dissipation to reduce their temperature. As one important member in Radio Base Station (RBS) product family, RRU is widely deployed. However, RRU with high coverage generates large amount heat, which will decrease its reliability due to high temperature. 
         [0003]    Techniques for heat dissipation include natural cooling and forced cooling. Natural cooling needs no extra devices or energy input. It is featured with low airflow rate, bulky heat sinks, energy saving and noise-free environment. Typically, a heat sink consists of a metal plate with one or more flat surfaces to ensure good thermal contact with the components to be cooled, and an array of comb or fin like protrusions to increase the surface contacting with the air. The high thermal conductivity of the metal combined with its large surface area result in the rapid transfer of thermal energy to the surrounding. 
         [0004]    RRU is usually installed near antenna, and thus for easy installation, it shall be designed to be as compact and light as possible. However, heat sinks impose a severe restriction on RRU in terms of volume and weight, and in this sense, natural cooling is unsatisfied. 
         [0005]    A heat sink is sometimes used in conjunction with a fan to increase the rate of airflow over the heat sink and a larger temperature gradient is maintained by replacing warmed air faster than convection would. As a result, a compact heat sink is available. This is known as forced cooling approach. However, it is featured with high energy consumption and high acoustic noise level. For some base stations with forced cooling mechanism, their sound power levels can reach at 79 dBA, which is harmful to health. 
         [0006]    Often, RRUs are necessarily installed near residential areas where their noise level shall be strictly controlled. In such a case, these RRUs have to be equipped with bulky heat sinks. As for the forced cooling, another issue involves in fan failure, which is a fatal menace for RRUs. 
       SUMMARY OF THE INVENTION 
       [0007]    In light of the above, one of the objects of the present invention is to provide a solution which can gratify at least one of the problems as described above. 
         [0008]    According to one aspect of the present invention, a method for cooling a telecommunication device, wherein cooling capacity is provided by natural cooling capacity and forced cooling capacity which is adjustable, the method comprising:
       estimating a thermal state of the telecommunication device; and   if the cooling capacity mismatches the thermal state, making an adjustment to the forced cooling capacity.       
 
         [0011]    In the above-mentioned method, natural cooling function and forced cooling function can be effected either concurrently or separately based on the thermal state. This makes it possible to tailor heat sinks and air flow generators to various applications. 
         [0012]    In a preferred embodiment according to the present invention, wherein the thermal state is represented by temperature measured inside or outside the telecommunication device, and the cooling capacity is deemed to mismatch the thermal state if the temperature exceeds a first threshold above which the telecommunication device is not permitted to operate or shall reduce its load. 
         [0013]    In a preferred embodiment according to the present invention, wherein the thermal state is represented by temperature measured inside or outside the telecommunication device, and the cooling capacity is deemed to mismatch the thermal state if the temperature is below a second threshold and the forced cooling capacity is in operation, the second threshold is not greater than the first threshold. 
         [0014]    According to another aspect of the present invention, an apparatus for cooling a telecommunication device, wherein cooling capacity is provided by natural cooling capacity and forced cooling capacity which is adjustable, the apparatus comprising:
       at least one sensor configured to detect a thermal state of the telecommunication device;   a natural cooling unit adapted to be integrated with or mounted on the telecommunication device and to provide the natural cooling capacity;   a forced cooling unit adapted to be mounted on the telecommunication device and to provide the forced cooling capacity; and   a controller communicatively coupled to the at least one sensor and the forced cooling unit, and configured to adjust the forced cooling capacity if cooling capacity mismatches the thermal state.       
 
         [0019]    In a preferred embodiment according to the present invention, wherein the natural cooling unit comprises a heat sink having a plurality of fins being arranged in parallel on a surface of thereof, and the forced cooling unit comprises at least one air flow generator for generating air flowing along a surface of the heat sink. 
         [0020]    In a preferred embodiment according to the present invention, wherein the forced cooling unit is further configured to provide the forced cooling capacity with different levels and the controller is further configured to activate the forced cooling unit to operate at the different levels based on the thermal state. 
         [0021]    According to another aspect of the present invention, a telecommunication device comprising:
       a unit for performing telecommunication function; and   the apparatus according to anyone of claims  9 - 15 , mounted or integrated with the unit.       
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    The foregoing and other objects, features, and advantages of the present invention will be apparent from the following more particular description of preferred embodiments as illustrated in the accompanying drawings in which: 
           [0025]      FIG. 1  is a block diagram illustrating one exemplary embodiment of an apparatus for cooling a telecommunication device according to the present invention. 
           [0026]      FIG. 2  is a diagram illustrating one example of the combination of natural cooling unit and forced cooling unit used in the apparatus as shown in  FIG. 1 . 
           [0027]      FIG. 3  is a diagram illustrating another example of the combination of natural cooling unit and forced cooling unit used in the apparatus as shown in  FIG. 1 . 
           [0028]      FIG. 4  is a diagram illustrating heat flux flowing in the apparatus as shown in  FIG. 1 . 
           [0029]      FIG. 5  is a process flow diagram of a method for cooling a telecommunication device according to one exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0030]    While the invention covers various modifications and alternative constructions, embodiments of the invention are shown in the drawings and will hereinafter be described in detail. However, it should be understood that the specific description and drawings are not intended to limit the invention to the specific forms disclosed. On the contrary, it is intended that the scope of the claimed invention includes all modifications and alternative constructions thereof falling within the scope of the invention as expressed in the appended claims. 
         [0031]    Unless defined in the context of the present description, otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. 
         [0032]    For illustrative purpose, the following embodiments are described in the context of RRU. However, one skilled artisan in the art would recognize that the present invention is applicable to any telecommunication devices, such as Digital Unit (DU) and microwave communication device. 
         [0033]      FIG. 1  is a block diagram illustrating one exemplary embodiment of an apparatus for cooling a telecommunication device according to the present invention. 
         [0034]    With reference to  FIG. 1 , the apparatus  10  according to this embodiment comprises a sensor  110 , a natural cooling unit  120 , a forced cooling unit  130 , and a controller  140  which communicatively coupled to the sensor  110  and the forced cooling unit  130 . 
         [0035]    In the present embodiment, the heat generated in the telecommunication device is dissipated by the natural cooling unit  120  individually or both of the natural cooling unit  120  and the forced cooling unit  130 , depending on what thermal state the telecommunication device is in. No matter what the thermal state is like, the natural cooling unit  120  functions well. This means that in the event of failure of the forced cooling unit  130 , basic cooling capacity is always ensured and thus prevents the telecommunication device from undergoing fatal consequence. While the telecommunication device is in a high thermal state, i.e., above a critical level, the basic cooling capacity is insufficient to dissipate the heat, and hence the controller  140  will activate the forced cooling unit  130  to provide additional cooling capacity. 
         [0036]    On the other hand, if the telecommunication device is in a low thermal state far below the critical level and the forced cooling unit  130  is in operation, it is preferable to deactivate or decrease the forced cooling capacity to reduce power consumption, decrease noise level and extend its life expectancy. 
         [0037]    Preferably, a critical level is associated with one point, above which the telecommunication device is not permitted to operate or shall reduce its load, otherwise its life time will be significantly shortened. In the present embodiment, the thermal state is characterized by a temperature measured or obtained inside and/or outside the telecommunication device. This temperature is measured or obtained by the sensor  110  and then is compared with a critical temperature. Generally, the critical temperature for the high thermal state relies on what application the apparatus is applied to. For example, it can be set as one above which the telecommunication devices are not permitted to operate or shall reduce its load. Moreover, the setting of the critical temperature can aim at activating the forced cooling unit as little as possible while keeping the thermal state within a safe range. The examples of the temperature include but are not limited to a junction temperature inside a semiconductor chip or a temperature at one component pin. 
         [0038]    Additionally, the low thermal state can be also characterized by temperature. For example, it is considerable to specify a threshold for the low thermal state, which is equal to or lower than the critical temperature. If the temperature is below the threshold and the forced cooling unit  130  is in operation, the controller  130  deactivates or decreases the forced cooling capacity. 
         [0039]    In the present embodiment, the sensor  110  is mounted inside or outside a RRU and is coupled to the controller  140  via wireless or cable connection. The sensor  110  is configured to transmit the measured temperature to the controller  140  periodically or in response to a query from the controller  140 . 
         [0040]    Alternatively, a set of temperatures measured at different positions can be combined to more accurately represent the thermal state. In such a case, a plurality of sensors are mounted inside and/or outside the RRU and are coupled to the controller  140  via wireless or cable connection. 
         [0041]      FIG. 3  is a diagram illustrating one example of the combination of natural cooling unit and forced cooling unit used in the apparatus for cooling a telecommunication device as shown in  FIG. 1 . 
         [0042]    Typically, the natural cooling unit  120  consists of a metal plate and a plurality of fins. Referring to  FIG. 2 , however, the natural cooling unit  120  in this example is in form of a heat sink only consisting of a plurality of fins  1201  arranged in parallel on the surface of the RRU  20 . The absence of the metal plate leads to a more compact structure. However, it shall be noted that the natural cooling unit  120 , e.g., the fins  1201  may be integrated with or be parts of the RRU  20 . In the present embodiment, the fins  1201  are made of metal such as aluminum, copper and their alloy. 
         [0043]    Regardless of the thermal state of the RRU, the natural cooling unit  120  always functions well so as to provide basic cooling capacity. While the thermal state of RRU  20  is above a predetermined level, e.g., the temperature measured by the sensor  110  exceeds a critical temperature, the controller  140  will activate the forced cooling unit  130  or instruct it to increase its output power. 
         [0044]    In the present embodiment, as shown in  FIG. 2 , the forced cooling unit  130  is implemented in form of a fan array which is installed on the top of RRU  20  and acts as one or more air flow generators. Specifically, in operation, sucking force is generated by the fan array to make air flow along the surface of the RRU  20  with the fins  1201 , carrying one portion of the heat from the RRU  20 . Therefore, besides the basic cooling capacity by the fins  1201 , an additional capacity is furnished. 
         [0045]      FIG. 3  is a diagram illustrating another example of the combination of natural cooling unit and forced cooling unit used in the apparatus for cooling a telecommunication device as shown in  FIG. 1 . 
         [0046]    In this example, the natural cooling unit  120  also consists of a plurality of fins  1201  arranged in parallel on the surface of the RRU  20  and provides basic cooling capacity. Moreover, while the thermal state of RRU  20  is above a predetermined level, the controller  140  will activate the forced cooling unit  130  or instruct it to increase its output power. 
         [0047]    In this example, however, as shown in  FIG. 3 , the forced cooling unit  130  is implemented in form of a Synthetic Jet actuator array which is installed on the bottom of RRU  20  and is regarded as a set of air flow generators. In operation, the actuator array generates a continual flow of vortices that are formed by alternating brief ejection and suction of air across an opening such that the net mass flux is zero. With the continual flow rapidly passing along the surface of the RRU  20 , one portion of the heat from the RRU  20  is carried away and thus an additional capacity is furnished. Various examples of Synthetic Jet actuator are known to the art, including one disclosed in U.S. application Ser. No. 12/288,144 (John Stanley Booth et al.,), entitled “Light Flexture With Multiple LEDs And Synthetic Jet Thermal Management System”, which is incorporated herein by reference. 
         [0048]    In the examples as shown in  FIGS. 2 and 3 , the forced cooling unit  130  comprises a plurality of air flow generators. Therefore, by turning on or turning off some of the air flow generators, the forced cooling unit  130  can provide additional cooling capacity with multiple-level. Moreover, one or more among the air flow generators may be reserved for backup so as to improve the reliability. However, the above multiple-level scheme can be performed by the forced cooling unit  130  having one air flow generator with a tunable output power. 
         [0049]    In the present embodiment, the fins  1201  are designed to have a tradeoff between the natural cooling capacity and the forced cooling capacity. For example, the optimized geometry of the fins  1201  makes a balance between natural cooling performance and forced cooling performance. As a result, neither the natural cooling performance nor the forced cooling performance reaches its best point, but cooling performance in total is optimal. In another example, the optimization may be directed to make the basic natural cooling capacity as large as possible. A number of factors may be considered in the optimization, including but not limited to the critical temperature, the upper limit of the weight of the natural cooling unit, the restriction on geometry of the natural cooling unit, the minimum basic cooling capacity as required, the maximum noise level as permitted, and the like. As for the telecommunication devices, preferably, the fins  1201  are optimized to have a spacing of 5 mm-15 mm and an average thickness of 0.8 mm-3 mm. 
         [0050]      FIG. 4  is a diagram illustrating heat flux flowing in the apparatus as shown in  FIG. 1 . 
         [0051]    Referring to  FIG. 4 , the natural cooling unit  120  and the forced cooling unit  130  provide two paths for heat flux from the RRU  20 , i.e., a natural path and a forced cooling path. The sensor  110  transmits the measured temperature to the controller  140 , which compares the measurement with the critical temperature. While the RRU  20  operates in a normal thermal state, e.g., the measured temperature is not greater than the critical temperature, the heat flux flows to the surrounding only via the natural cooling path. On the other hand, the forced cooling path is switched on or off by the controller  140 . If the controller  140  determines the thermal state is above the critical temperature, it switches on the forced cooling path, and thus a part of the heat flux flow along this path. 
         [0052]    As described above, the forced cooling unit  130  may comprise a plurality of air flow generators. Therefore, the forced cooling path may consist of two or more branches connected in parallel between the RRU  20  and the surrounding and each of the branches may contain one or more air flow generators. With such a structure, the controller  140  may selectively switch on or off one or more of the branches so as to provide multiple-level forced cooling capacity. 
         [0053]    In the above embodiment, the apparatus  10  is described as an individual entity in relation to a telecommunication device. However, the present invention shall not be limited to such architecture. In fact, the apparatus  10  may be regarded as one part of the telecommunication device. 
         [0054]      FIG. 5  is a process flow diagram of a method for cooling a telecommunication device according to one exemplary embodiment of the present invention. For illustrative purpose, the present embodiment is described in the context of the apparatus as shown in  FIGS. 1-4 . However, one skilled artisan in the art would recognize that the present embodiment is applicable to any other apparatuses comprising a natural cooling unit and a forced cooling unit. 
         [0055]    With reference to  FIG. 5 , at step S 510 , the controller  140  determines whether it receives from the sensor  110  a message indicating a thermal state of the RRU  20 , e.g., temperature measured inside or outside the RRU  20 . The sensor  110  may transmit the message periodically or in response to a query from the controller  140 . In the event of the receipt of the message, the process proceeds to step S 520 , which will be described in detail; otherwise, the controller  140  continues to wait for the message. 
         [0056]    Then, at step S 520 , the controller  140  determines whether the current cooling capacity is sufficient to the thermal state of the RRU  20 . In the present embodiment, this is accomplished by comparing the measured temperature with a first threshold, i.e. the critical temperature. If the measured temperature is not greater than the first threshold, the process proceeds to step S 530  for maintaining or decreasing the current cooling capacity; otherwise, the process proceeds to step S 540 , increasing the current cooling capacity or warning the cooling capacity cannot match the thermal state. 
         [0057]    Referring to  FIG. 5 , at step S 530 , the controller  140  further determines whether the measured temperature is lower than a second threshold and the forced cooling unit  130  is in operation. The second threshold is set to be equal to or lower than the first threshold. If it is true, the process proceeds to step S 550  for deactivating the forced cooling unit  130  or turning off one or more of the air flow generators and then returns to step S 510 ; otherwise, the process returns to step S 510  directly. 
         [0058]    For another branch, at step S 540 , the controller  140  further determines whether the forced cooling unit  130  operates at its peak load. If it is true, the process proceeds to step S 560 , warning the RRU  20  that no more cooling capacity is available; otherwise, the process proceeds to step S 570  for activating the forced cooling unit  130  or turning on more air flow generators. After steps S 560  and S 570 , the process returns to step S 510 . 
         [0059]    It should be noted that the aforesaid embodiments are illustrative of this invention instead of restricting this invention, substitute embodiments may be designed by those skilled in the art without departing from the scope of the claims enclosed. The wordings such as “include”, “including”, “comprise” and “comprising” do not exclude elements or steps which are present but not listed in the description and the claims. It also shall be noted that as used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. This invention can be achieved by means of hardware including several different elements or by means of a suitably programmed computer. In the unit claims that list several means, several ones among these means can be specifically embodied in the same hardware item. The use of such words as first, second, third does not represent any order, which can be simply explained as names.