Patent Publication Number: US-11050096-B2

Title: Battery protection circuit and battery pack including same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and benefit of Korean Patent Application No. 10-2018-0066250, filed on Jun. 8, 2018 in the Korean Intellectual Property Office, the entire content of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     Aspects of embodiments of the present invention relate to a battery protection circuit and a battery pack including the same. 
     2. Description of the Related Art 
     A rechargeable battery, or secondary cell, is one that may perform charging and discharging alternately and repeatedly. The rechargeable battery may convert chemical energy into electrical energy to discharge it, and, conversely, when electrical energy is charged to the discharged rechargeable battery, it may be stored again in the form of chemical energy. 
     The rechargeable battery may be applied to various portable electronic devices. For example, a laptop computer may be equipped with a battery pack of a multi-series structure in which a plurality of rechargeable batteries (herein referred to as “cells”) connected in series with each other are combined with a charge and discharge circuit. 
     A thermal cut-off (TCO) may be installed in a battery pack of a multi-series structure in which square cells or polymer cells are coupled in series. The TCO is an element for securing the safety of each cell from the risk of overcharging or short-circuiting by cutting off a current according to the temperature. 
     Since the TCO is operated by temperature, it should be closely attached to the cell such that temperature of the cell can be easily detected. Accordingly, additional components, such as tape, a Ni-plate, etc., are required to mount the TCO on the battery pack, or additional processes, such as welding, cell adhesion, and tape processing, are required. In addition, when the cell temperature is not properly detected due to the TCO mounting defect, such a protection operation of the TCO may not be performed properly. 
     The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and, therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
     SUMMARY 
     According to aspects of embodiments of the present invention, a battery protection circuit, and a battery pack including the same, that are capable of supporting a safety operation by detecting the temperature of each cell constituting a battery pack instead of using a TCO are provided. 
     According to one or more exemplary embodiments of the present invention, a battery protection circuit includes: a plurality of pack terminals configured to connect a battery module to an external device; a first fuse element located on a current path between the battery module and the pack terminals to block a current flow between the battery module and the pack terminals depending on a voltage applied to a control terminal thereof; a first integrated circuit configured to include a first input terminal and control a voltage outputted to the control terminal of the first fuse element depending on a voltage applied to the first input terminal; and a plurality of thermistors connected in series between a positive electrode of the battery module and a first input terminal of the first integrated circuit and having resistance that is varied depending on a temperature of a corresponding cell among cells constituting the battery module. 
     In the battery protection circuit, the thermistors may correspond to the cells, respectively, and each of the thermistors may be located adjacent to the corresponding cell of the cells. 
     In the battery protection circuit, each of the thermistors may be a positive temperature coefficient thermistor. 
     In the battery protection circuit, each of the thermistors may include a chip mounted on a printed circuit board. 
     In the battery protection circuit, the first fuse element may be connected between the battery module and the pack terminals. 
     In the battery protection circuit, the first fuse element may be connected between two adjacent cells of the cells. 
     In the battery protection circuit, the first integrated circuit may include a plurality of second input terminals that are electrically connected at opposite ends of each of the cells, detect an over-voltage state of the battery module based on a voltage applied to the second input terminals, and control a voltage applied to the control terminal of the first fuse element depending on a detected result of the over-voltage state. 
     The battery protection circuit may include a second fuse element located on a current path between the battery module and the pack terminals to block a current flow between the battery module and the pack terminals depending on a voltage applied to a control terminal thereof, and may further include a second integrated circuit configured to include a plurality of input terminals that are electrically connected at opposite ends of each of the cells, to detect an over-voltage state of the battery module based on a voltage applied to the input terminals, and to control a voltage applied to the control terminal of the first fuse element depending on a detected result of the over-voltage state. 
     The battery protection circuit may further include: a charging control switch located on a current path between the battery module and the pack terminals to control a charging current flow between the battery module and the pack terminals; a discharging control switch disposed on a current path between the battery module and the pack terminals to control a discharging current flow between the battery module and the pack terminals; and a battery controller configured to control switching of the charging control switch and the discharging control switch based on a cell voltage of each of the cells or a current flowing between the battery module and the pack terminals. 
     In the battery protection circuit, the first integrated circuit and the battery controller may operate independently. 
     According to one or more exemplary embodiments of the present invention, a battery pack includes: a battery module including a plurality of cells; and a battery protection circuit, wherein the battery protection circuit includes: a plurality of pack terminals configured to connect the battery module to an external device; a first fuse element located on a current path between the battery module and the pack terminals to block a current flow between the battery module and the pack terminals depending on a voltage applied to a control terminal thereof; a first integrated circuit configured to include a first input terminal and control a voltage outputted to the control terminal of the first fuse element depending on a voltage applied to the first input terminal; and a plurality of thermistors connected in series between a positive electrode of the battery module and a first input terminal of the first integrated circuit and having resistance that is varied depending on a temperature of a corresponding cell among the plurality of cells. 
     The battery pack may further include a printed circuit board including the battery protection circuit mounted thereon and a plurality of conductive tabs coupled to a positive or negative electrode of each of the cells, and the thermistors may be mounted on the printed circuit board as a chip type. 
     In the battery pack, the thermistors may correspond to the cells, respectively, and each of the thermistors may be located adjacent to a conductive tab that is coupled to a corresponding one of the conductive tabs. 
     The battery pack may further include an adhesive member to cover together electrode terminals, conductive tabs, and thermistors, which face each other among electrode terminals of the cells, the conductive tabs, and the thermistors. 
     In the battery pack, each of the thermistors may be a positive temperature coefficient thermistor. 
     The battery pack may include a second fuse element located on a current path between the battery module and the pack terminals to block a current flow between the battery module and the pack terminals depending on a voltage applied to a control terminal thereof, and may further include a second integrated circuit configured to include a plurality of input terminals that are electrically connected at opposite ends of each of the cells, to detect an over-voltage state of the battery module based on a voltage applied to the input terminals, and to control a voltage applied to the control terminal of the first fuse element depending on a detected result of the over-voltage state. 
     In the battery pack, the first integrated circuit may include a plurality of second input terminals that are electrically connected at opposite ends of each of the cells, detect an over-voltage state of the battery module based on a voltage applied to the second input terminals, and control a voltage applied to the control terminal of the first fuse element depending on a detected result of the over-voltage state. 
     The battery pack may include: a charging control switch located on a current path between the battery module and the pack terminals to control a charging current flow between the battery module and the pack terminals; a discharging control switch located on a current path between the battery module and the pack terminals to control a discharging current flow between the battery module and the pack terminals; and a battery controller configured to control switching of the charging control switch and the discharging control switch based on a cell voltage of each of the cells or a current flowing between the battery module and the pack terminals. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  schematically illustrates a battery pack according to an exemplary embodiment of the present invention. 
         FIG. 2  schematically illustrates a battery pack according to another exemplary embodiment of the present invention. 
         FIG. 3  schematically illustrates an example of a PCB on which a battery protection circuit is mounted according to an exemplary embodiment of the present invention. 
     
    
    
     DESCRIPTION OF SYMBOLS 
     
         
           10 A,  10 B: battery pack 
           100 A,  100 B: battery protection circuit 
           111 : thermistor 
           120 : controller 
           130 ,  131 ,  132 : integrated circuit 
         F 1 , F 2 : fuse element 
         C_FET: charging control switch 
         D_FET: discharging control switch 
         P+, P−: pack terminal 
       
    
     DETAILED DESCRIPTION 
     The present invention will be described more fully herein with reference to the accompanying drawings, in which some exemplary embodiments of the invention are shown. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. 
     To clearly describe the exemplary embodiments, parts that are irrelevant to the description may be omitted, and like numerals refer to like or similar constituent elements throughout the specification. Therefore, the reference numbers of the constituent elements used in a previous drawing may be used in a next drawing. 
     Further, since sizes and thicknesses of constituent members shown in the accompanying drawings may be arbitrarily given for better understanding and ease of description, the exemplary embodiments are not limited to the illustrated sizes and thicknesses. In the drawings, the thickness of layers, films, panels, regions, etc., may be exaggerated for clarity. 
     A case of electrically connecting two constituent elements includes not only a case of directly connecting the constituent elements but also a case of connecting the constituent elements via another constituent element therebetween. The constituent element therebetween may include a switch, a resistor, a capacitor, and the like. In describing exemplary embodiments, an expression of connection indicates electrical connection unless explicitly described to be direct connection. 
     It is to be understood that, although the terms “first,” “second,” etc. may be used herein to describe various elements, components, regions, layers, and/or sections, these elements, components, regions, layers, and/or sections should not be limited by these terms. These terms are used to distinguish one element, component, region, layer, or section from another element, component, region, layer, or section. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section without departing from the teachings of example embodiments. 
     Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. It is to be understood that 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. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
     The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting of example embodiments. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It is to be further understood that the terms “comprises,” “comprising,” “includes,” and/or “including,” if used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments of the inventive concept belong. It is to be further understood that terms, such as those defined in commonly-used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     Herein, a battery protective circuit and a battery pack including the same according to some exemplary embodiments will be described with reference to the drawings. 
       FIG. 1  schematically illustrates a battery pack according to an exemplary embodiment of the present invention. 
     Referring to  FIG. 1 , a battery pack  10 A according to the present exemplary embodiment may include a battery module and a battery protection circuit  100 A. Constituent elements are illustrated in  FIG. 1  according to an exemplary embodiment, and the battery pack  10 A according to embodiments of the present invention may be implemented to include more or fewer components. 
     The battery module may include a plurality of cells connected in series with each other. Although a case in which the battery module includes three cells is illustrated in  FIG. 1  as an example for convenience of description, the present invention is not limited thereto. According to another exemplary embodiment, the battery module may be configured to include fewer or more than three cells connected in series. 
     According to an embodiment, the battery protection circuit  100 A includes a plurality of pack terminals P+ and P−, a charging control switch C_FET, a discharging control switch D_FET, a fuse element F 1 , a plurality of thermistors  111 , a battery controller  120 , and an integrated circuit (IC)  130 . 
     The pack terminals P+ and P− may be electrically connected to external devices (e.g., charging devices, loads, etc.) to supply electrical energy of the battery module to the external devices or to receive electrical energy from the external devices. That is, the pack terminals P+ and P− may supply the electrical energy of the battery module to the load or receive electrical energy from an external charging device. 
     The charging control switch C_FET is coupled in series to a charging path of the battery module, and may cut off or supply a charging current of the battery module. The charging path is a current flow path between the battery module and a charging device (not shown) connected through the pack terminals P+ and P− of the battery pack  10 A, and serves to transfer a charging current supplied from the charging device to the battery module. 
     The discharging control switch D_FET is coupled in series to a discharge path of the battery module, and may cut off or supply a discharge current of the battery module. The discharge path is a current flow path between the battery module and a load (not shown) connected through the pack terminals P+ and P− of the battery pack  10 A, and serves to transfer a discharging current supplied from the battery module to the load. 
     The charging path and the discharging path are relatively large in magnitude of the current flowing through the path compared to other current paths in the battery pack  10 A. In this specification, the discharging path and the charging path are sometimes referred to as “high current paths.” 
     In an embodiment, the charging control switch C_FET and the discharging control switch D_FET may each include a field effect transistor (FET). For example, each of the charging control switch C_FET and the discharging control switch D_FET may include an N-channel FET. 
     Although a case in which the charging control switch C_FET and the discharging control switch D_FET are connected between a positive electrode of the battery module and the positive pack terminal P+ of the battery pack  10 A is illustrated in  FIG. 1  as an example, the present invention is not limited thereto. According to another exemplary embodiment, the charging control switch C_FET or the discharging control switch D_FET may be connected between a negative electrode of the battery module and the negative electrode pack terminal P− of the battery pack  10 A. 
     The fuse element F 1  may be connected in series to a high current path, i.e., between one of electrode terminals of the battery module and a pack terminal corresponding thereto (e.g., between a positive electrode of the battery module and the positive pack terminal P+), to block a current flow between the battery module and an external device. 
     In an embodiment, the fuse element F 1  may be a self-control protection (SCP) element including a control terminal to which a control voltage is externally applied, at least one fuse, and heating resistors. In this case, the heating resistor included in the fuse element F 1  may generate heat depending on a voltage applied to the control terminal of the fuse element F 1 , and the fuses may be disconnected by the heat of the heating resistors to block the high current path of the battery module. The control terminal of the fuse element F 1  may be connected to an output terminal of the integrated circuit  130 , and may receive a control voltage for controlling the heat generation of the heating resistors constituting the fuse element F 1  from the output terminal of the integrated circuit  130 . 
     The plurality of thermistors  111  may be connected in series between the positive electrode of the battery module and an input terminal of the integrated circuit  130 . In an embodiment, the plurality of thermistors  111  are disposed to correspond one-to-one to each cell constituting the battery module, and can be thermally coupled to corresponding cells. 
     The thermistors  111  are elements having resistance that is varied depending on temperature. Accordingly, resistance of the thermistors  111  thermally coupled to the respective cells varies depending on temperatures of the corresponding cells. As a result, a voltage that drops by the thermistors  111  and then is inputted into the input terminal of the integrated circuit  130  (herein referred to as a “temperature sensing voltage”) may vary depending on the cell temperature of the battery module. 
     In an embodiment, each of the thermistors  111  may be a positive temperature coefficient (PTC) thermistor having resistance that increases when the temperature increases. In this case, as the temperature of each cell increases, the resistance value of the corresponding thermistor increases and the temperature sensing voltage applied to the input terminal of the integrated circuit  130  decreases. 
     In an embodiment, each of the thermistors  111  may be a negative temperature coefficient (NTC) thermistor having resistance that increases when the temperature decreases. In this case, as the temperature of each cell increases, the resistance value of the corresponding thermistor decreases and the temperature sensing voltage applied to the input terminal of the integrated circuit  130  increases. 
     The battery controller  120  may control a general operation of the battery protection circuit  100 A. 
     The battery controller  120  may be electrically connected to opposite ends of each cell constituting the battery module or opposite ends of the battery module, and may detect the voltage of each cell constituting the battery module or the voltage of the battery module. 
     The battery controller  120  may measure a magnitude of the current flowing through the high current path. 
     The battery controller  120  may control on and off of the charging control switch C_FET or the discharging control switch D_FET based on the cell voltage of each cell, the module voltage of the battery module, a magnitude of the current flowing through the high current path, and the like. For example, the battery controller  120  may detect an overvoltage state of the battery module by comparing the cell voltage of each cell with a reference voltage for determining overvoltage, and may turn off the charging control switch C_FET or may turn off the charging control switch C_FET and the discharging control switch D_FET when the battery module is in the overvoltage state. In addition, for example, the battery controller  120  may detect an overcurrent (overcharge current or over-discharge current) state of the battery module based on a magnitude of the current flowing through the high current path, and may turn off the charging control switch C_FET or may turn off the charging control switch C_FET and the discharging control switch D_FET when the battery module is in the overcurrent state. 
     Each function of the battery controller  120  may be performed by a processor implemented as at least one central processing unit (CPU) or another chipset, a microcontroller unit (MCU), a microprocessor, or the like. 
     The integrated circuit  130  may be electrically connected to opposite ends of each cell constituting the battery module through voltage detection input terminals, to detect the cell voltage of each cell. The integrated circuit  130  may detect the overvoltage state of each cell based on the cell voltage of each cell, and may block the high current path by controlling the fuse element F 1  when at least one cell is in the overvoltage state. 
     The integrated circuit  130  may be connected to the thermistors  111  connected in series to each other through a temperature-detecting input terminal to detect a temperature sensing voltage through the thermistors  111 . The integrated circuit  130  may detect an over-temperature state by comparing the temperature sensing voltage with a reference voltage when the temperature sensing voltage is inputted through the thermistors  111 , and may block the high current path by controlling the fuse element F 1  when the temperature sensing voltage is detected. Herein, a fixed value may be used as the reference voltage to be compared with the temperature sensing voltage, or the reference voltage may be varied depending on the cell voltage of the battery module. 
     According to the present exemplary embodiment, although a case in which the over-temperature and the over-voltage are detected by one integrated circuit  130  in the battery pack  10 A has been described as an example, the present invention is not limited thereto. 
       FIG. 2  schematically illustrates a battery pack according to another exemplary embodiment of the present invention, wherein the battery pack further includes an integrated circuit and a fuse element for temperature detection using thermistors. 
     Referring to  FIG. 2 , according to an embodiment of the present invention, the battery pack  10 B may include a plurality of integrated circuits  131  and  132  for detecting the state (voltage, temperature, etc.) of the battery module and thus for a safety operation. 
     Among the integrated circuits, the integrated circuit  131  may detect the cell voltage of each cell constituting the battery module through voltage detection input terminals, and may detect the overvoltage state of each cell based on the detected cell voltage. When at least one cell is in the overvoltage state, the high current path may be blocked by controlling the fuse element F 1 . 
     Among the integrated circuits, the integrated circuit  132  may be connected to the thermistors  111  connected in series to each other through a temperature-detecting input terminal to receive a temperature sensing voltage through the thermistors  111 . Then, an over-temperature state of the cells may be detected by comparing the inputted temperature sensing voltage with the reference voltage, and when the over-temperature state is detected, a fuse element F 2  may be controlled to block the high current path. 
     In an embodiment, the fuse elements F 1  and F 2  may be disposed at different portions for improved stability. As illustrated in  FIG. 1 , as an example, the fuse element F 1  is disposed between the positive electrode of the battery module and the positive pack terminal P+, and the fuse element F 2  may be disposed between two neighboring cells among the cells constituting the battery module. 
     In an embodiment, each of the fuse elements F 1  and F 2  may be a self-control protection (SCP) element including a control terminal to which a control voltage is externally applied, at least one fuse, and heating resistors. In this case, the heating resistor included in each of the fuse elements F 1  and F 2  may generate heat depending on a voltage applied to the control terminal of the fuse element F 1  or F 2 , and the fuses may be disconnected by the heat of the heating resistors to block the high current path of the battery module. In addition, control terminals of the fuse elements F 1  and F 2  may be respectively connected to output terminals of the corresponding integrated circuit  131  and  132  to receive control voltages for controlling heat generation of the heating resistors included in the fuse elements F 1  and F 2  from output terminals of the corresponding integrated circuits  131  and  132 . 
     In the exemplary embodiments described above, the battery controller  120  and the integrated circuits  130 ,  131 , and  132  may assist each other in protecting each other. Even when one of the battery controller  120  and the integrated circuits  130 ,  131 , and  132  malfunctions to disable a battery protection function from being properly performed, the others may serve to perform the battery protection function to secure the safety of the battery packs  10 A and  10 B. To this end, the battery controller  120  and the integrated circuits  130 ,  131 , and  132  may be driven independently of each other. 
     In the above embodiments, the temperature sensing voltage inputted through the thermistors  111  is compared with the reference voltage, and the integrated circuits  130 ,  131 , and  132  may be used to improve the accuracy and safety of the control compared with the use of a transistor such as a FET. In the above exemplary embodiments, the integrated circuits  130 ,  131 , and  132  may clearly distinguish between a high level voltage and a low level voltage depending on the resistance of the thermistors  111 , and, thus, the fuse element may be accurately disconnected in a situation in which the fuse element needs to be disconnected, thereby ensuring control accuracy and stability of the fuse element. 
     In contrast, when a transistor such as a FET is used as a control switch and a thermistor is connected to a control terminal of the control switch as a voltage-distributing resistor, a small voltage may be applied to the control terminal of the control switch such that a small current flows in the fuse element. In this case, the inside of the fuse element may be slowly melted and deformed, which may affect a characteristic of the fuse element, and, thus, the control accuracy of the fuse element may deteriorate. 
     The battery protection circuits  100 A and  100 B according to the above-described exemplary embodiments may be mounted on a printed circuit board (PCB) and combined with the battery module. 
       FIG. 3  schematically illustrates an example of a PCB  300  on which the battery protection circuits  100 A and  100 B may be mounted according to exemplary embodiments of the present invention, and some constituent elements (e.g., the battery controller  120  and the like) of the battery protection circuits  100 A and  100 B are not shown. 
     Referring to  FIG. 3 , the PCB  300  may include a plurality of conductive tabs  301 , and each of the conductive tabs  301  may be coupled to a positive or negative electrode of a corresponding cell. For example, each conductive tab  301  may be coupled to the positive or negative electrode of the corresponding cell. In an embodiment, for example, each of the conductive tabs  301  may be coupled to the positive or negative electrode of the corresponding cell using an adhesive member (e.g., silicone, adhesive tape, etc.). In the latter case, the adhesive members may be coated or attached to cover not only the terminals of the respective cells but also the corresponding conductive tabs  301  and thermistors  111  to effectively transmit the heat of each cell to the corresponding thermistor  111 . 
     According to an exemplary embodiments of the present invention, a chip type of thermistor  111  may be mounted on the PCB  300 . 
     In exemplary embodiments, each of the thermistors  111  is disposed at a position where the heat of each cell is effectively transferred in order to react sensitively to the temperature change of the corresponding cell. For example, as illustrated in  FIG. 3 , each of the thermistors  111  may be disposed adjacent to a conductive tab  301  that is coupled to a positive or negative electrode of the corresponding cell. In addition, for example, each of the thermistors  111  may be disposed on one of opposite surfaces of the PCB  300  which face the respective cells. 
     Referring to  FIG. 3 , the chip type of thermistor  111  may be mounted on a PCB  300 , unlike a TCO, such that it is not necessary to separately attach the thermistors  111  to each cell. Therefore, the assembling complexity of the battery packs  10 A and  10 B may be reduced as compared with a conventional battery pack using a TCO for the safety operation of the battery module, thereby lowering the unit cost. 
     While some exemplary embodiments of the present invention have been particularly shown and described with reference to the accompanying drawings, the specific terms used herein are used for the purpose of describing the invention and are not intended to be limiting of the scope of the invention set forth in the claims. Therefore, those skilled in the art will understand that various modifications and other equivalent embodiments of the present invention are to be included within the technical spirit of the appended claims.