Abstract:
A battery protection circuit and a battery pack are disclosed. The battery pack includes the battery protection circuit, which has a switching unit and a control circuit, which controls the switching unit with a control signal. The battery protection circuit also has an external terminal, which is configurable to electrically connect the control signal to a circuit external to the battery protection circuit.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application No. 61/696,672, filed on Sep. 4, 2012, the entire content of which is incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    1. Field 
         [0003]    The disclosed technology relates to a battery protection circuit and a battery pack including the same, and more particularly, to a battery protection circuit and a battery pack that includes a terminal capable of being connected to a gate electrode of a transistor for charging/discharging control, so that the turn-on resistance of the transistor can be easily controlled. Accordingly, efficient battery management is possible. 
         [0004]    2. Description of the Related Technology 
         [0005]    Recently, portable electronic/electrical devices which are compact in size and light in weight, such as cellular phones, notebook computers, and camcorders, have been actively developed and produced. The portable electronic/electrical devices have batteries so as to be operated locations where a separate power source is not provided. 
         [0006]    Damage to a battery may occur due to its ignition, rupture, or explosion if the battery experiences overcharging, overdischarging, or overcurrent caused by a short circuit between terminals because of, for example, chemical properties of the battery. Therefore, as can be seen in a battery pack  100  shown in  FIG. 1 , a battery protection circuit  120  that protects a bare cell  110  by detecting overcharging, overcurrent and over discharging of the bare cell  110  is included in the related art battery pack  100 . 
         [0007]    The battery protection circuit  120  may be manufactured in the form of an integrated circuit (IC) chip. The battery protection circuit  120  includes a control IC  130  and a switching unit  140  therein, so as to perform a protecting operation of the bare cell  110 . Generally, the switching unit  140  is configured to include a transistor  141  for discharging control and a transistor  142  for charging control, which are controlled by the control IC  130 . 
         [0008]    As can be seen in  FIG. 1 , the battery protection circuit  120  includes separate terminals T 1 , T 2  and T 3  through which external connection to source/drain electrodes of each of the transistors  141  and  142  for charging/discharging control is made. However, the battery protection circuit  120  does not include a separate external terminal for electrical connection to a gate electrode of the transistors  141  and  142  for charging/discharging control. 
         [0009]    The gate electrodes of the transistors  141  and  142  may be controlled to adjust the internal resistance of the battery pack  100 . However, since the gate electrodes of the transistors  141  and  142  for charging/discharging control are not exposed to the outside, there exists a problem that the turn-on resistance of the transistors  141  and  142  for charging/discharging control cannot be controlled by an external source. 
       SUMMARY 
       [0010]    Another inventive aspect is a battery pack, including a battery cell, and a battery protection circuit formed as an integrated circuit and configured to protect the battery cell, the battery protection circuit including a switching unit, configured to control charging and discharging of the battery cell according to a control signal received at a control input, a control circuit configured to generate the control signal, and at least one external terminal configured to electrically connect the control input to a circuit external to the battery protection circuit. 
         [0011]    Another inventive aspect is a battery protection circuit formed as an integrated circuit and configured to protect a battery cell, the battery protection circuit including a switching unit, configured to control charging and discharging of the battery cell according to a control signal received at a control input, a control circuit configured to generate the control signal, and an external terminal configurable to electrically connect the control input to a circuit external to the battery protection circuit. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The accompanying drawings, together with the specification, illustrate exemplary embodiments, and, together with the description, serve to explain various inventive principles and aspects. 
           [0013]      FIG. 1  is a circuit diagram showing a battery pack. 
           [0014]      FIG. 2  is a circuit diagram showing a battery pack according to an embodiment. 
           [0015]      FIG. 3  is a circuit diagram showing a configuration of a control IC for the embodiment of  FIG. 2 . 
           [0016]      FIG. 4  is a circuit diagram showing a battery pack according to another embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    Hereinafter, certain exemplary embodiments are described with reference to the accompanying drawings. When a first element is described as being connected to a second element, the first element may be not only directly connected to the second element but may alternatively be indirectly connected to the second element via a third element. Further, some of the elements that are not essential to the complete understanding of the invention may be omitted for clarity. Also, like reference numerals generally refer to like elements throughout. 
         [0018]      FIG. 2  is a circuit diagram showing a battery pack according to an embodiment. Referring to  FIG. 2 , the battery pack  200  according to this embodiment includes a bare cell  210  and a battery protection circuit  220 . 
         [0019]    The bare cell  210  may one or more bare cells, and a plurality of bare cells  210  may be connected in series and/or parallel. Positive and negative electrode terminals  281  and  282  connectable to a charger (not shown), electronic product (not shown), or the like may be formed on a high current path of the bare cell  210 . 
         [0020]    The battery protection circuit  220  is used to solve a problem that occurs due to an abnormal state (e.g. overcharging, overdischarging, overcurrent or the like) of the bare cell  210 . The battery protection circuit  220  is connected to the bare cell  210  so as to perform a protecting operation of the bare cell  210 . The battery protection circuit  220  may be manufactured as an integrated circuit (IC) chip. 
         [0021]    Referring  FIG. 2 , the battery protection circuit  220  includes a control circuit, such as exemplary control circuit control IC  230  and a switching unit  240 . The control IC  230  performs a function of detecting an abnormal state of the bare cell  210 . For example, the control IC  230  may detect an abnormal state such as overcharging, overdischarging or over current. 
         [0022]    The control IC  230  may control a charging/discharging state of the bare cell  210  by controlling the switching unit  240 . The switching unit  240  includes at least one transistor for controlling the charging/discharging of the bare cell  210 , and the operation of the switching unit  240  may be controlled by the control IC  230 . 
         [0023]    A gate electrode of the at least one transistor included in the switching unit  240  may be connected to a gate connection terminal of the battery protection circuit  220 , which is also an electrode terminal for a connection outside of the battery protection circuit  220 . The switching unit  240  may include a switch, such as a transistor  241  for discharging control and a switch, such as a transistor  242  for charging control, which will be described further below. 
         [0024]    In this case, a gate electrode of the transistor  241  for discharging control may be connected to a first external terminal, such as first gate connection terminal G 1  of the battery protection circuit  220 , which is exposed to the outside, and a gate electrode of the transistor  242  for charging control may be connected to a second external terminal, such as second gate connection terminal G 2  of the battery protection circuit  220 , which is also exposed to the outside. 
         [0025]    As can be seen in  FIG. 1 , the gate electrodes of the transistors  141  and  142  included in the switching unit  140  are connected to the control IC  130  in the battery protection circuit  120 . Accordingly, the gate electrodes of the transistors  141  and  142  cannot be directly accessed from the outside, and therefore, the gate electrodes of the transistors  141  and  142  cannot be controlled from the outside to, for example, adjust internal resistance. 
         [0026]    In contrast, the gate electrodes of the transistors  241  and  242  included in the switching unit  240  are exposed to the outside through the respective gate connection terminals G 1  and G 2 , and thus the turn-on resistance of each of the transistors  241  and  242  can be controlled from the outside. 
         [0027]    The connection relationship between the transistor  241  for discharging control and the transistor  242  for charging control is described. A first electrode of the transistor  241  for discharging control may be connected to a first terminal T 1  of the battery protection circuit  220 , which is exposed to the outside, and a second electrode of the transistor  241  for discharging control may be connected to a second electrode of the transistor  242  for charging control. In addition a first electrode of the transistor  242  for charging control may be connected to a second terminal T 2  of the battery protection circuit  220 , which is exposed to the outside. 
         [0028]    For example, the first and second electrodes of the transistor  241  for discharging control may be source and drain electrodes, respectively. In addition, the first and second electrodes of the transistor  242  for charging control may source and drain electrodes, respectively. 
         [0029]    The transistor  241  for discharging control and the transistor  242  for charging control are associated with diodes  251  and  252  connected in parallel thereto, respectively. Thus, power can be supplied to the transistor  241  for discharging control and the transistor  242  for charging control through the respective diodes  251  and  252  in the charging or discharging of the transistor  241  for discharging control and the transistor  242  for charging control, in which either the transistor  241  for discharging control or the transistor  242  for charging control is turned off 
         [0030]    The second electrode of the transistor  241  for discharging control and the second electrode of the transistor  242  for charging control may be connected to a third terminal T 3  of the battery protection circuit  220 , which is exposed to the outside. 
         [0031]    The transistor  241  for discharging control and the transistor  242  for charging control may be either N-MOS or P-MOS transistors. 
         [0032]    The battery protection circuit according to this embodiment include the first and second gate connection terminals G 1  and G 2  and the first, second and third terminals T 1 , T 2  and T 3 . 
         [0033]    In this embodiment, the first terminal T 1  is connected to a negative electrode of the bare cell  210 , and the second terminal T 2  is connected to the negative electrode terminal  282  of the battery pack  200 . 
         [0034]    The battery protection circuit  220  may include a power terminal VDD connected to a positive electrode of the bare cell  210  and an auxiliary terminal V− connected to the negative electrode terminal  282  of the battery pack  200 . 
         [0035]    As shown in  FIG. 2 , a resistor R 1  may be provided between the positive electrode of the bare cell  210  and the power terminal VDD, and a capacitor C may be provided between the power terminal VDD and the first terminal T 1  of the battery protection circuit  220 . Furthermore, a resistor R 2  may be provided between the auxiliary terminal V− and the negative electrode terminal  282  of the battery pack  200 . 
         [0036]    In this embodiment, the first and second gate connection terminals G 1  and G 2  are formed at positions opposite to each other for convenience of circuit design. In a case where the first gate connection terminal G 1  is formed at one side of the battery protection circuit  220 , the second gate connection terminal G 2  may be formed at the other side of the battery protection circuit  220 . 
         [0037]    In this embodiment, the first terminal T 1  is formed adjacent to the first gate connection terminal G 1 , and the second terminal T 2  is formed adjacent to the second gate connection terminal G 2 . As an example, as shown in  FIG. 2 , the power terminal VDD, the first gate connection terminal G 1  and the first terminal T 1  are sequentially positioned at the one side of the battery protection circuit  220  from the top of this figure, and the auxiliary terminal V−, the second gate connection terminal G 2  and the second terminal T 2  are sequentially positioned at the other side of the battery protection circuit  220  from the top of this figure. 
         [0038]      FIG. 3  is a circuit diagram showing an embodiment of the control IC  230  for the battery pack of  FIG. 2 . 
         [0039]    Referring to  FIG. 3 , the control IC  230  according to this embodiment includes an overcharging detection unit VD 1  that detects overcharging of the bare cell  210 , an overdischarging detection unit VD 2  that detects overdischarging of the bare cell  210 . The control IC  230  also includes discharging and charging overcurrent detection units VD 3  and VD 4  that detect overcurrent of the bare cell  210 , a first logic circuit  311 , a second logic circuit  312 , a delay circuit  320 , an oscillator  330 , a counter  340 , a level shift circuit  350 , and a short detection circuit  360 . 
         [0040]    The control IC  230  is connected to the power and auxiliary terminals VDD and V− of the battery protection circuit  220 . The control IC  230  includes a ground terminal VSS, a discharging control terminal Dout, and a charging control terminal Cout, which are connected to the switching unit  240 . The control IC  230  includes a DS terminal connected to the oscillator  330 . 
         [0041]    As shown, the ground terminal VSS of the control IC  230  may be connected to the first terminal T 1  and the first electrode of the transistor  241  for discharging control with the switching unit  240 , and the discharging control terminal Dout may be connected to the first gate connection terminal G 1  and the gate electrode of the transistor  241  for discharging control included in the switching unit  240 . The charging control terminal Cout may be connected the second gate connection terminal G 2  and the gate electrode of the transistor  242  for charging control with the switching unit  240 . 
         [0042]    Hereinafter, certain operations performed by the battery protection circuit  220  are described. 
         [0043]    If overcharging, overdischarging, discharging overcurrent, charging overcurrent or short circuit is detected by the overcharging detection unit VD 1 , the overdischarging detection unit VD 2 , the discharging overcurrent detection unit VD 3 , the charging overcurrent detection unit VD 4  or the short detection circuit  360 , the oscillator  330  is activated, and the counter  340  starts counting. 
         [0044]    In a case where the overcharging or charging overcurrent is detected, a predetermined detection delay time is measured with the counter  340 , and the output of the charging control terminal Cout is then switched to a low level through the logic circuit  311  and the level shift circuit  350 . As a result, the transistor  242  for charging control is turned off. 
         [0045]    In a case where the overdischarging, discharging overcurrent or short circuit is detected, the output of the discharging control terminal Dout is switched to a low level through the logic circuit  312 . As a result, the transistor  241  for charging control is turned off. 
         [0046]    The configuration and operation of the control IC  230  described above is merely an embodiment, and may be variously modified. 
         [0047]      FIG. 4  is a circuit diagram showing a battery pack according to another embodiment. Referring to  FIG. 4 , the battery pack  200  according to this embodiment further includes an auxiliary switching unit  300 . 
         [0048]    The auxiliary switching unit  300  is provided to adjust the internal resistance of the battery pack  200 , i.e., the resistance of the switching unit  240  on the high current path. The auxiliary switching unit  300  may include at least one transistor connected in parallel to the transistor  241  for discharging control and the transistor  242  for charging control, which are included in the switching unit  240 . 
         [0049]    In this case, the auxiliary switching unit  300  is configured in the same form as the switching unit  240 . Accordingly, the auxiliary switching unit  300  may include a first transistor  311  and a second transistor  312 . The first and second transistors  311  and  312  may be connected in series between the first and second terminals T 1  and T 2  so as to be positioned in parallel to the transistor  241  for discharging control and the transistor  242  for charging control. 
         [0050]    Specifically, a first electrode of the first transistor  311  is connected to the first terminal T 1 , and a second electrode of the first transistor  311  is connected to a second electrode of the second transistor  312 . In addition, a first electrode of the second transistor  312  may be connected to the second terminal T 2 . As an example, the first and second electrodes of the first transistor  311  may be source and drain electrodes, respectively. In addition, the first and second electrodes of the second transistor  312  may be source and drain electrodes, respectively. 
         [0051]    In order to perform the same function as the switching unit  240 , the auxiliary switching unit  300  may be provided with auxiliary diodes  321  and  322  respectively connected in parallel to the first and second transistors  311  and  312 . In order to perform the same operation as the transistor  241  for discharging control, a gate electrode of the first transistor  311  may be connected to the first gate connection terminal G 1 . In order to perform the same operation as the transistor  242  for charging control, a gate electrode of the second transistor  312  may be connected to the second gate connection terminal G 2 . 
         [0052]    Although one switching unit  240  is illustrated in  FIG. 4 , the number of switching units  240  may be variously changed. Accordingly, the separate gate connection terminals G 1  and G 2  are added to the battery protection circuit  220 , so that the auxiliary switching unit  300  for adjusting the internal resistance of the battery pack  200  can be added to the battery pack  200  without changing the form of the battery protection circuit  220  manufactured in the form of the IC chip. 
         [0053]    While the present invention has been described in connection with certain exemplary 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.