Abstract:
A heat dissipation device for a light emitting diode (LED) module includes a liquid cooling system. The liquid cooling system includes a heat-absorbing member, which includes an inlet, an outlet and at least one pipe extending between the inlet and the outlet. The inlet and the outlet are provided for permitting liquid to flow through the at least one pipe, which is in thermal contact with at least one LED of the LED module.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a heat dissipation device, more particularly to a heat dissipation device for a light emitting device module. 
       DESCRIPTION OF RELATED ART 
       [0002]    A light emitting diode (LED) is a device for transferring electricity to light by using a theory that, if a current is made to flow in a forward direction in a junction comprising two different semiconductors, electrons and holes are coupled at a junction region to generate a light beam. The LED has an advantage in that it is resistant to shock, and has an almost eternal lifetime under a specific condition, so more and more LED modules with different capabilities are being developed. 
         [0003]    LED modules for use in a display or an illumination device require many LEDs, and most of the LEDs are driven at the same time, which results in a quick rise in temperature of the LED module. Since generally the LED modules do not have heat dissipation devices with good heat dissipating efficiencies, operation of the general LED modules has a problem of instability because of the rapid build up of heat. Consequently, the light from the LED module often flickers, which degrades the quality of the display or illumination. 
         [0004]    What is needed, therefore, is a heat dissipation device for an LED module, which can overcome the above-described disadvantages. 
       SUMMARY OF THE INVENTION 
       [0005]    A heat dissipation device for a light emitting diode (LED) module is disclosed. The heat dissipation device comprises a liquid cooling system. The liquid cooling system comprises a heat-absorbing member, which comprises an inlet, an outlet and at least one pipe extending between the inlet and the outlet. The inlet and the outlet are provided for permitting liquid to flow through the at least one pipe, which is in thermal contact with at least one LED of the LED module. 
         [0006]    Other advantages and novel features will become more apparent from the following detailed description of preferred embodiments when taken in conjunction with the accompanying drawings, in which: 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Many aspects of the present embodiments 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 present embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
           [0008]      FIG. 1  is an isometric view of a heat dissipation device in accordance with a first preferred embodiment, together with an LED module, wherein one of printed circuit boards of the LED module is removed away to clearly show relationship between the heat dissipation device and LEDs of the LED module; 
           [0009]      FIG. 2  is similar to  FIG. 1 , but viewed from another aspect; 
           [0010]      FIG. 3  is an isometric view of a heat-absorbing member of a heat dissipation device in accordance with another preferred embodiment, together with an LED module; 
           [0011]      FIG. 4  is similar to  FIG. 3 , but viewed from another aspect; 
           [0012]      FIG. 5  is an exploded view of the heat-absorbing member in  FIG. 3 ; and 
           [0013]      FIG. 6  is an isometric view of a heat-absorbing member of a heat dissipation device in accordance with another preferred embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]    Referring to  FIG. 1 , a heat dissipation device  100  in accordance with a first preferred embodiment is illustrated. The heat dissipation device  100  is used to cool down an LED module  200  to keep the LED module  200  working within an acceptable temperature range. 
         [0015]    In this embodiment, the LED module  200  comprises several juxtaposed printed circuit boards  220  and a plurality of LEDs  240  electrically bonded to the printed circuit boards  220 . Each printed circuit board  220  has a plurality of through holes  222  defined therein. The through holes  222  are arrayed in rows and lines for the LEDs  240  extending therethrough. Alternatively, these printed circuit boards  220  can be replaced by a larger single printed circuit board, which has a matrix of through holes defined therein. The LEDs  240  are installed into the corresponding through holes  222  of the printed circuit boards  220 , and electrically connected to circuits (not shown) provide on the printed circuit boards  220 . Therefore, the LED module  200  is formed. For facilitating heat dissipation of the LEDs  240 , bottom surfaces of the LEDs  240  commonly define a surface coplanar with a bottom surface commonly defined by the printed circuit boards  220 , or located in a level below the bottom surface of the printed circuit boards  220 . 
         [0016]    Before the LED module  200  is driven to generate light, the heat dissipation device  100  is mounted on the bottom surface of the printed circuit boards  220 . 
         [0017]    The heat dissipation device  100  is a liquid cooling system, and comprises a heat-absorbing member  120 , a heat-dissipating member  140 , a pump  160 , a supply pipe  170  and a delivery pipe  180 . The hear-absorbing member  120 , the heat-dissipating member  140 , the pump  160 , the supply pipe  170  and the delivery pipe  180  together form a loop for circulation of liquid. The pump  160  draws the liquid from the heat-absorbing member  120  via the delivery pipe  180 , and supplies the liquid back to the heat-absorbing member  120  via the supply pipe  170 . The heat-dissipating member  140  is mounted on the supply pipe  170  such that the liquid is sufficiently cooled while passing the supply pipe  170 . 
         [0018]    The heat-absorbing member  120  is tightly attached to the bottom surface of the printed circuit boards  220  so as to absorb heat originated from the LEDs  240 . In this embodiment, the heat-absorbing member  120  comprises a serpentine flattened pipe  122 . The serpentine flattened pipe  122  comprises four juxtaposed straight pipes  1222  and three elbows  1224 . The straight pipes  1222  are parallel to each other and separated from each other by a certain distance determined by the arrangement of the LEDs  240  on the printed circuit boards  220 . The rightmost straight pipe  1222  has an end connected to the delivery pipe  180 , thereby serving as an outlet (not labeled) for the flatten pipe  122 ; the leftmost straight pipe  1222  has an end connected to the supply pipe  170 , thereby serving as an inlet (not labeled) for the flatten pipe  122 . The elbows  1224  hermetically interconnect the remaining ends of the neighboring straight pipes  1222  to form a serial and serpentine channel extending between the inlet and the outlet. 
         [0019]    Additionally, the number of the straight pipes  1222  may be increased or decreased via increasing or decreasing the number of the elbows  1224 , according to the requirement of heat dissipating. Therefore, the heat-absorbing member  120  has a high versatility of use. 
         [0020]    When the LEDs  240  are driven to luminance, the liquid is driven to flow along the serpentine channel of the heat-absorbing member  120  by the pump  160 , and heated up by the heat produced by the LEDs  240  which are directly contact with the straight pipes  1222 . The heated liquid is then forced to flow across the heat-dissipating member  140  to dissipate the heat to ambient air, whereby the heated liquid is cooled before it returns back to the heat-absorbing member  120  for another circulation. Therefore, the heat of the LEDs  240  is removed away, and the LEDs  240  can work within an acceptable temperature range. 
         [0021]    As described above, the straight pipes  1222  of the heat-absorbing member  120  are directly contacted with the LEDs  240 , wherein the LEDs  240  in contact with one of the straight pipes  1222  are arranged in two parallel lines. The straight pipes  1222  transfer the heat from the LEDs  240  to the liquid flowing past the heat-absorbing member  120 . 
         [0022]    For further improving the heat dissipating efficiency, the heat-absorbing member  120  further comprises a plurality of fins  124  tightly attached to the bottom surface of the printed circuit boards  220 , and transverse to the straight pipes  1222 . Each fin  124  has four cutouts  1242  defined in a top portion thereof. When the fins  124  are combined together, the cutouts  1242  cooperatively define four straight grooves lengthwise extending in a top portion of the fins  124 , for accommodating the straight pipes  1222  therein. Each fin  124  has flanges  1244  each perpendicularly extending from the fin at a periphery of the corresponding cutout  1242 , to increase the contacting area between the fins  124  and the straight pipes  1222 . Therefore, part of the heat carried by the liquid is first transferred to the fins  124  via the flanges  1244  to be dissipated, prior to the liquid flowing into the heat-dissipating member  140  to be cooled. 
         [0023]      FIGS. 3-5  show another heat-absorbing member  120   a.  The heat absorbing-member  120   a  comprises a diverging member  126   a,  a converging member  128   a  and four straight pipes  1222   a.  The diverging member  126   a  comprises an inlet  1262   a  for being coupled to a supply pipe (not shown), and four outlets  1264   a  branching from the diverging member  126   a.  The converging member  128   a  comprises an outlet  1282   a  for being coupled to a delivery pipe, and four inlets  1284   a  converged at the converging member  128   a  to the outlet  1282   a.  Opposite ends of each straight pipe  1222   a  are respectively coupled to a corresponding inlet  1284   a  of the converging member  128   a  and a corresponding outlet  1264   a  of the diverging member  126   a.  In other words, each straight pipe  1222   a  interconnects one outlet  1264   a  of the diverging member  126   a  and a corresponding inlet  1284   a  of the converging member  128   a,  whereby the straight pipes  1222   a  are positioned between the diverging member  126   a  and converging member  128   a  in parallel. 
         [0024]    Liquid flowing into the inlet  1262   a  of the diverging member  126   a  will be divided into four branches at the outlets  1264   a.  Then the four branches of the liquid simultaneously flow towards the inlets  1284   a  of the converging member  128   a  along the straight pipes  1222   a  as shown by arrows of  FIG. 4 . Finally, the four branches of the liquid converge at the converging member  128   a  before the liquid flows into the delivery pipe from the outlet  1282   a  of the converging member  128   a.  When the liquid flows past the straight pipes  1222   a  of the heat-absorbing member  120   a,  the heat produced by the LEDs  240  is conducted to the liquid, and then conveyed to the heat-dissipating member remote from the heat-absorbing member  120   a  to be dissipated into the ambient air. 
         [0025]    In this embodiment, the liquid flowing in each straight pipe  1222   a  is diverged in parallel from the diverging member  126   a  and then respectively flows in different straight pipes  1222   a.  The liquid in one straight pipe  1222   a  can not enter another straight pipe  1222   a  so that the liquid in different straight pipes  1222   a  does not interact with each other. Therefore, heat in liquid flowing in one straight pipe  1222   a  can not transferred to the liquid flowing in a different straight pipe  1222   a,  whereby even if the liquid in one straight pipe  1222   a  is overheated, the overheated liquid will not increase the temperature of the liquid in a different straight pipe  1222   a.    
         [0026]    Referring to  FIG. 6 , for further improving the heat dissipating efficiency, a plurality of fins  124   a  are attached to the bottom surface of the printed circuit boards  220   a  and transverse to the straight pipes  1222   a  in a similar manner as shown in  FIG. 2 . A part of heat received by the straight pipes  1222   a  is dissipated to the ambient air by the fins  124   a.    
         [0027]    It is believed that the present embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the invention.