Abstract:
A secondary battery comprises a bare cell and a protection circuit module comprising a printed circuit board and a thermistor. The thermistor comprises: a supporting member comprising an elastic material; a temperature sensor formed on the supporting member; a terminal configured to couple to a printed circuit board; and a conductive portion formed on the supporting member, wherein the conductive portion is connected to the terminal and to the temperature sensor.

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 61/413,351 filed with the United States Patent and Trademark Office on Nov. 12, 2010, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Field 
     The present technology relates to protection circuit modules that include a thermistor and a secondary battery pack having the same, and more particularly, to a secondary battery pack and a protection circuit module in which a thermistor is fixed. 
     2. Description of the Related Technology 
     A thermistor is a protection element used for secondary battery packs and a type of resistor whose unique resistance varies with temperature. Thermistors can be classified into a negative temperature coefficient (NTC) thermistor formed of a NTC material, which has a resistance that decreases with increasing temperature, and a positive temperature coefficient thermistor (PTC) formed of a PTC material, which has a resistance that increases with increasing temperature. The PTC material has a relatively low resistance at normal temperatures, allowing current to flow smoothly. However, when the PTC material increases in temperature due to increases in the ambient temperature or an overcurrent, resistance can increase about 1000 to 10000 times or more compared to the initial resistance, to block flowing current. Thus, the PTC material is widely used to protect various electronic components from overheating or overcurrents. 
     SUMMARY 
     An aspect of the present invention is to provide a protection circuit module including a means to fix a thermistor in a secondary battery pack without additional components or processes, and a secondary battery pack including the protection circuit module. 
     Further, an aspect of the present invention is to provide a protection circuit module including a means to prevent a thermistor from abnormally being detached even though a fabricated secondary battery pack has an impact while being transferred or used, and a secondary battery pack. 
     According to an aspect of the present invention, a protection circuit module includes a printed circuit board having a protection circuit, and a thermistor connected to the protection circuit of the protection circuit module. 
     According to an aspect, the thermistor includes a supporting member comprising an elastic material; a temperature sensor formed on the supporting member; a terminal configured to couple to a printed circuit board; and a conductive portion formed on the supporting member, wherein the conductive portion is connected to the terminal and to the temperature sensor. 
     According to an aspect, the conductive portion of the thermistor comprises a conductive film. The conductive portion may comprise a conductive wire printed on an insulating film. The conductive portion may be formed over substantially every surface of the supporting member. The conductive portion may be formed over every surface except the lateral sides of the supporting member. The conductive portion may be formed over a portion of the supporting member. 
     According to an aspect, the supporting member has a cross section that is rectangular, pentagonal or hexagonal. The supporting member may have a portion that has a curved shape. 
     According to an aspect, the temperature sensor is formed on a surface of the supporting member that is curved. 
     According to an aspect, the thermistor comprises a second temperature sensor and a second terminal, wherein the second temperature sensor is electrically connected to the second terminal. 
     According to an aspect, the thermistor comprises a hole that extends through the supporting member. 
     Further, an aspect of the present invention also provides a secondary battery pack comprising a bare cell, and a protection circuit module comprising a printed circuit board and a thermistor, wherein the thermistor comprises a supporting member comprising an elastic material, a temperature sensor formed on the supporting member, a terminal coupled to the printed circuit board, and a conductive portion formed on the supporting member, wherein the conductive portion is connected to the terminal and to the temperature sensor. 
     According to an aspect, the printed circuit board comprises a hole through which the terminal of the thermistor is inserted. 
     According to an aspect, the printed circuit board comprises a recess in a region adjacent to the hole, and wherein the recess is configured to accommodate the thermistor. 
     According to an aspect, the terminal comprises a portion extended through the hole and bent along a surface of the printed circuit board. 
     According to an aspect, the bent portion of terminal is soldered to the printed circuit board. 
     According to an aspect, the temperature sensor contacts an external surface of the bare cell. 
     According to an aspect, the secondary battery comprises a plurality of bare cells. 
     According to an aspect, the thermistor contacts more than one bare cell. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, together with the specification, illustrate certain embodiments of the present invention, and, together with the description, serve to explain the principles of the present invention. 
         FIG. 1A  is an exploded perspective view illustrating a battery pack according to an embodiment; 
         FIG. 1B  is a plan view illustrating the battery pack of  FIG. 1A ; 
         FIG. 2  is a cross-sectional view illustrating that a thermistor is combined with a circuit board according to an embodiment; 
         FIG. 3A  is a perspective view illustrating a thermistor according to an embodiment; 
         FIG. 3B  is a lateral view of the thermistor of  FIG. 3A ; 
         FIG. 3C  is a lateral view of a thermistor according to another embodiment; 
         FIG. 3D  is a lateral view of a thermistor according to still another embodiment; 
         FIG. 3E  is a perspective view of a thermistor according to still another embodiment; 
         FIG. 4A  is a lateral view of a thermistor having a curved side; 
         FIG. 4B  is a lateral view illustrating the thermistor of  FIG. 4A  is in contact with a bare cell; 
         FIG. 5  is a perspective view of a thermistor formed with a penetration hole; 
         FIG. 6  is a cross-sectional view illustrating a thermistor is combined with a circuit board according to an embodiment; 
         FIG. 7  is a schematic plan view illustrating a battery pack according to another embodiment; 
         FIG. 8  is a schematic front view illustrating a position of a thermistor according to an embodiment; 
         FIG. 9  is a lateral view of a thermistor according to another embodiment; and 
         FIG. 10  is a front view illustrating that the thermistor of  FIG. 9  is used. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, certain embodiments of the present invention will be described with reference to the accompanying drawings. In the specification, terms to indicate directions “up,” “down,” “right,” and “left” are based on directions in the drawings unless the context clearly indicates otherwise. Further, like reference numerals refer to like elements in the embodiments. 
     First Embodiment 
       FIG. 1A  is an exploded perspective view illustrating a battery pack according to an embodiment of the present invention,  FIG. 1B  is a plan view illustrating the battery pack of  FIG. 1A , and  FIG. 2  is a cross-sectional view illustrating that a thermistor is combined with a circuit board according to an embodiment of the present invention. 
     As shown in  FIGS. 1A and 1B , a secondary battery pack according to the present embodiment includes a protection circuit module  100  including a thermistor  300  and at least one bare cell  200  electrically connected to the protection circuit module  100 . The thermistor  300  may include a temperature sensor, which will be described, and closely contacts an external surface of the bare cell  200  between the protection circuit module  100  and the bare cell  200 . 
     First, the protection circuit module  100  of an embodiment may be formed of a module and a protection circuit seated on a printed circuit board, the module performing charging and discharging and performing communication with an outside, and the protection circuit securing stability while charging and discharging are performed. The protection circuit module  100  may include a terminal  105  connected to each bare cell  200 . Each bare cell  200  may be electrically connected to the terminal formed in the protection circuit module  100  through a member functioning as an electrical conducting wire, such as a nickel tab  250 . Further, as shown in  FIG. 1B , a connector  150  may be formed on the outside of the protection circuit module  100  to be connected to an external device. 
     Terminal accommodation holes  120  may be formed in pairs of cathodes and anodes in the protection circuit module  100 , a terminal of the thermistor  300  being accommodated in the terminal accommodation holes  120 . Here, a seating part  110  may be formed in the protection circuit module  100  to improve fixing of the thermistor  300  to the protection circuit module  100 . The seating part  110  may be formed with a stepped part in a similar shape to a contact surface with the thermistor  300 . 
     As shown in  FIG. 2 , a pair of terminals  310  of the thermistor  300  is inserted into the terminal accommodation holes  120  formed in the protection circuit module  100  and fixed by welding or soldering. Here, as described above, in order to prevent the thermistor  300  from being shaken or being easily detached, the seating part  110  recessed in a region adjacent to the terminal accommodation holes  120  may be formed to seat the thermistor  300 . Thus, due to the recessed seating part  100 , the thermistor  300  may be securely mounted in the printed circuit board of the protection circuit module  100 . The seating part  110  may be formed in a groove stepped and recessed in a region of the protection circuit module  100 , particularly the printed circuit board of the protection circuit module  100 , to accommodate the thermistor  300 . 
     Then, the protection circuit module  100  combined with the thermistor  300  can be connected to the bare cell  200 . One side of the nickel tab  250  connecting terminals of bare cells  200  in parallel or in series may be connected to a corresponding protection circuit module through soldering or welding. Here, as shown in  FIG. 1B , the thermistor  300  may be disposed between the protection circuit module  100  and the bare cell  200  and closely attached to the external surface of the bare cell  200  to be pressed. The thermistor  300  may be pressed by the bare cell  200 , being fixed to the protection circuit module  100  when the battery pack is formed, and thus the thermistor  300  can have a stable structure that is not easily detached. 
     Here, in order to improve fixing of the thermistor  300 , as shown in  FIG. 6 , a pair of terminals  310   a  may be bent at an end portion and connected through welding or soldering. Here, due to the bent end portion of the terminals  310   a , the thermistor  300  is not easily detached even though solder comes off. 
       FIG. 3A  is a perspective view illustrating a thermistor according to an embodiment of the present invention, and  FIG. 3B  is a lateral view of the thermistor of  FIG. 3A .  FIGS. 3C to 3E  are lateral views and a perspective view of various thermistors according to embodiments of the present invention. 
     As shown in  FIGS. 3A and 3B , the thermistor  300  includes a supporting body  340 , a conductive connection part  320 , a temperature sensor  330 , and a pair of terminals  310 . In the present embodiment, the thermistor  300  collectively refers to a means for measuring temperature using the temperature sensor  330 . The thermistor  300  is a device whose resistance varies with ambient temperature and may use a positive temperature coefficient (PTC) thermistor and a negative temperature coefficient (NTC) thermistor. 
     The supporting body  340  may be formed of an elastic material that is contractable by an external force. The supporting body  340  of the elastic material can enable the thermistor  300  to be more attached to the bare cell  200  elastically. The supporting body  340  of the present embodiment has a cuboid shape. However, as shown in  FIG. 3C , the supporting body  340  may have a hexagonal longitudinal section, and a conductive connection part  320   a  may be formed on an external surface of the hexagonal supporting body  340 . Further, as shown in  FIG. 3D , the supporting body  340  may have a round longitudinal section without an edge, and a conductive connection part  320   b  may be formed on an external surface of the round supporting body  340 . The supporting body  340  may have various shapes. 
     The conductive connection part  320  is an element that can electrically connect the temperature sensor  330  with the pair of terminals  310 . The conductive connection part  320  is formed to enclose the external surface of the supporting body  340  of the elastic material. Here, the conductive connection part  320  may use a film-type conductive member or an insulating film on which a conducting wire is printed. The conductive connection part  320  can also function to fix the supporting body  340 . Thus, as shown in  FIG. 3A , the conductive connection part  320  may be formed to enclose four sides of the supporting body  340  while the remaining opposite two sides are exposed. Further, when the conductive connection part  320  has a hexagonal longitudinal section or a round longitudinal section, as shown in  FIGS. 3C and 3D , the conductive connection part  320  can enclose the external surface of the supporting body  340 . As shown in  FIG. 3E , a conductive connection part  320   c  may be formed on a portion of the external surface of the supporting body  340  to have a minimum area just for connection of the temperature sensor  330  with the pair of terminals  310 . 
     The conductive connection part  320  of the thermistor  300  is referred to as  320   a ,  320   b ,  320   c , and  320   d  depending on the shapes but is collectively referred to as  320  hereinafter. 
     The temperature sensor  330  may be formed on an external surface of the conductive connection part  320 . The temperature sensor  330  may be closely attached to and in contact with the external surface of the bare cell  200 . The temperature sensor  330  can convert information based on ambient temperature into electrical characteristics, and can transmit the electrical characteristics to the protection circuit module  100 . That is, the temperature sensor  330  may be formed on the conductive connection part  320  so that the temperature sensor  330  is electrically connected to the protection circuit module  100  through the conductive connection part  320  and the pair of terminals  310 . 
     In detail, the temperature sensor  330  measures the temperature of the bare cell  200  and may be connected to the protection circuit of the protection circuit module  100  through the conductive connection part  320 ,  320   a ,  320   b ,  320   c , and  320   d  and the pair of terminals  310 . 
     The pair of terminals  310 , the conductive connection part  320 , and the temperature sensor  330  may be formed a film structures. For example, if an integrated film-type thermistor is used, the respective components may not need separate manufacturing, thereby facilitating fabrication and reducing manufacturing costs. 
     Second Embodiment 
       FIG. 4A  is a lateral view of a thermistor having a curved or round side according to another embodiment of the present invention, and  FIG. 4B  is a lateral view illustrating that the thermistor of  FIG. 4A  is in contact with a bare cell. 
     As shown in  FIGS. 4A and 4B , the thermistor  300  of the present embodiment may include a supporting body  340   d  having one side curved or round. A conductive connection part  320   d  may be formed on an external surface of the supporting body  340   d . A temperature sensor  330  may be attached to a round external surface of the conductive connection part  320   d  or the supporting body  340   d.    
     The external surface of the supporting body  340   d  or the conductive connection part  320   d  in contact with the bare cell may be formed to have a round shape so that the thermistor  300  is closely in contact with the cylindrical bare cell. Further, due to the round shape of the supporting body  340   d , the thermistor  300  of the present embodiment may have its structure improved in attachment and stability when the bare cell  200  is cylindrical.  FIG. 4B  shows that the temperature sensor  330  attached to one round side of the conductive connection part  320   b  or the supporting body  340   d  is attached and fixed to the bare cell  200 . 
     Third Embodiment 
       FIG. 5  is a perspective view of a thermistor formed with a porous hole according to still another embodiment of the present invention. In the present embodiment, a supporting body  340   c  may be formed of an elastic material and have a porous shape. Although the supporting body  340   c  of the elastic material can include one porous hole  345  in  FIG. 5 , a plurality of porous holes  345  may be formed. When the supporting body  340   c  has the porous hole  345  therein, a thermistor  300  may be improved in elasticity. That is, the supporting body  340   c  may be improved in contraction and expansion. The porous hole  340   c  may be formed parallel with a pivot of the bare cell  200  with which the thermistor  300  is closely in contact, or be formed perpendicularly to a direction in which the supporting body  340   c  contracts. The porous hole  340   c  may have a longitudinal section which is not limited in shape. 
     Fourth Embodiment 
       FIG. 7  is a schematic plan view illustrating a battery pack according to still another embodiment of the present invention, and  FIG. 8  is a schematic front view illustrating a position of a thermistor. 
     In the present embodiment, as shown in  FIGS. 7 and 8 , a protection circuit module  100  is disposed perpendicular to a plurality of bare cells  200 . Here, when the thermistor  300   e  is in contact with only one of the bare cells  200 , as shown in  FIG. 8 , the present embodiment is similar to the first embodiment. Thus, a structure and a method of connecting the thermistor  300   e  and the protection circuit module  100  may be the same as described above. 
     Fifth Embodiment 
       FIG. 9  is a lateral view of a thermistor according to still another embodiment of the present invention, and  FIG. 10  is a front view illustrating that the thermistor of  FIG. 9  is used. 
     In the present embodiment, as shown in  FIGS. 9 and 10 , a protection circuit module  100  is disposed over a bare cell  200 , and the thermistor  300   e  is simultaneously in contact with two cylindrical bare cells. Here, the thermistor  300   e  may include a supporting body  340   f  being formed of an elastic material and having a shape to fill a spatial shape or a space between the two neighbouring bare cells  200 , as shown in  FIG. 10 . Here, the supporting body  340   f  may have a cross section having the shape of a space formed between the supporting body  340   f  and the two bare cells  200  so that the thermistor  300   e  closely contacts the two neighboring bare cells  200 . In  FIGS. 9 and 10 , the supporting body  340   f  has a roughly pentagonal shape. Further, in order to improve attachment or adhesion, the thermistor  300   f  may be formed to have a round surface which contacts the bare cells  200 . When the thermistor  300   f  is attached to the protection circuit module  100 , and then the protection circuit module  100  is connected with the bare cells  200 , two surfaces of the thermistor  300   f  closely contact the neighboring bare cells  200  simultaneously to form a stable structure, as shown in  FIG. 10 . Although the present embodiment illustrates the thermistor  300   f  closely contacts the two bare cells  200 , the thermistor  300   f  may closely contact more than two bare cells. The thermistor  300   f  may include at least one temperature sensor  330  formed between the supporting body  340   f  and the bare cells  200 . Here, when two or more temperature sensors  330  are provided, the same number of pairs of terminals  310  as the temperature sensors  330  may be provided so that the terminals  310  are connected to the temperature sensors  330 . For example, when two temperature sensors  330  are provided, two pairs of terminals  310  connected to the respective temperature sensors  330  may be provided. Alternatively, when one or more temperature sensors  330  are provided, the one or more temperature sensors  330  may be connected to a pair of terminals  310  in parallel or in series to measure temperature. 
     As described above, according to embodiments of the present invention, a thermistor may be stably fixed in a secondary battery pack without an additional fixing component, such as a fixing tape. 
     Further, embodiments of the present invention may eliminate a process in which the thermistor is fixed in the secondary battery pack using the fixing tape or the like. 
     Sixth Embodiment 
     The present embodiment relates a conductive connection part  320   g  according to an embodiment. 
     As described above, the conductive connection part  320   g  is an element to electrically connect a temperature sensor  330  and a pair of terminals  310 . The conductive connection part  320   g  of the present embodiment may be formed to pass through a supporting body  340   g . Further, the conductive connection part  320   g  has the elasticity to bend in a predetermined direction when the supporting body  340   g  contracts by an external force. 
     While the present invention has been described in connection with certain embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.