Abstract:
Battery pack circuits are provided. In one embodiment, the invention relates to a battery pack including a rechargeable battery including a first battery terminal and a second battery terminal coupled to a common terminal, a discharge control switch coupled between the first battery terminal and a first discharging terminal, a charge control switch coupled between the first discharging terminal and a first charging terminal, wherein the battery pack is configured to provide a current to a load coupled between the first discharging terminal and the common terminal, and a processing circuitry configured to charge and discharge the battery by controlling the discharge control switch and the charge control switch.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to and the benefit of U.S. Provisional Application No. 61/257,789, filed on Nov. 3, 2009, in the United States Patent and Trademark Office, the disclosure of which is incorporated herein in its entirety by reference. 
     
    
     BACKGROUND 
       [0002]    1. Field 
         [0003]    Embodiments of the present invention relate to battery packs, and more particularly, to charging and discharging of the battery packs. 
         [0004]    2. Description of the Related Art 
         [0005]    Rechargeable batteries, unlike primary batteries, are chargeable and dischargeable, and are widely used in high-end electronic devices such as cellular phones, notebook computers, or camcorders. In addition, rechargeable batteries are also used as a battery for electric vehicles such as scooters or automobiles. For high power applications, a plurality of rechargeable battery cells are assembled together in a battery pack. Conventional charging and discharging circuits are used to charge and discharge battery packs. However, conventional charging and discharging circuits have limitations. 
       SUMMARY 
       [0006]    Aspects of the invention relate to battery pack circuits. In one embodiment, the invention relates to a battery pack including a rechargeable battery including a first battery terminal and a second battery terminal coupled to a common terminal, a discharge control switch coupled between the first battery terminal and a first discharging terminal, a charge control switch coupled between the first discharging terminal and a first charging terminal, wherein the battery pack is configured to provide a current to a load coupled between the first discharging terminal and the common terminal, and a processing circuitry configured to charge and discharge the battery by controlling the discharge control switch and the charge control switch. 
         [0007]    In another embodiment, the invention relates to a method for charging and discharging a rechargeable battery of a battery pack, the method including switching-on a charge control switch to charge the battery, the charge control switch coupled between a first charging terminal and a discharge control switch coupled to a first battery terminal of the battery, wherein a charging current flows through the charge control switch and the discharge control switch while charging the battery, switching-on the discharge control switch and switching off the charge control switch to discharge the battery, wherein a discharging current does not flow through the charge control switch while discharging the battery. 
         [0008]    In further embodiment, the invention relates to a method for discharging a rechargeable battery of a battery pack, the method including switching-off a charge control switch coupled between a charging device and a discharge control switch coupled to a first battery terminal of the battery, and switching-on the discharge control switch, wherein the battery is configured to supply a load coupled to a first discharging terminal and a second battery terminal of the battery, wherein the first discharging terminal is located between the charge control switch and the discharge control switch. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    These and other aspects will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which: 
           [0010]      FIG. 1  is a circuit diagram of a conventional battery pack; 
           [0011]      FIG. 2  is a circuit diagram of a battery pack illustrating the connection relationship between a battery pack, a load, and a charging device, according to an embodiment of the present invention; 
           [0012]      FIG. 3  is a circuit diagram of a battery pack illustrating the connection relationship between a battery pack, a load, and a charging device, according to another embodiment of the present invention; 
           [0013]      FIG. 4  is a circuit diagram of a battery pack illustrating the connection relationship between a battery pack, a load, and a charging device, according to another embodiment of the present invention; 
           [0014]      FIG. 5  is a flowchart illustrating a process for charging a battery pack according to another embodiment of the present invention; and 
           [0015]      FIG. 6  is a flowchart illustrating a process for discharging a battery pack according to another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. In this regard, the present embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the figures, to explain aspects of the present description. 
         [0017]      FIG. 1  is a circuit diagram of a conventional battery pack  100 . Referring to  FIG. 1 , the general battery pack  100  includes a chargeable battery cell  130  and a protection circuit. The battery pack  100  is installed at an external system (not shown) such as portable personal computer (PC, e.g., a notebook computer) and charges and discharges the battery cell  130 . 
         [0018]    The battery pack  100  includes the battery cell  130 , external charging and discharging terminals P+ and P− connected in parallel to the battery cell  130 , and the protection circuit including a charging element  140  and a discharging element  150  connected in series to a high current path (HCP) that is formed between the battery cell  130  and the external charging and discharging terminals P+ and P−, and an analog front end (AFE) integrated circuit (IC)  120  and a microcomputer  110  that are connected in parallel to the battery cell  130 , the charging element  140 , and the discharging element  150 . 
         [0019]    As illustrated in  FIG. 1 , the general battery pack  100  has a single charging and discharging path. The general battery pack  100  has a structure in which a load  170  and a charging device  180  are connected to the external charging and discharging terminals P+ and P−. In more detail, during a discharging operation, the battery pack  100  supplies power to terminals P+ and P− such as a mobile phone or a notebook computer acting as the load of the external system, via both the charging element  140  and the discharging element  150  in the battery cell  130 . During a charging operation, the battery pack  100  performs charging by using the discharging element  150  and the charging element  140  via the terminals P+ and P− or while being connected directly to the charging device  180 . In this case, charging or discharging is performed via one of the external charging and discharging terminals P+ and P− so that charging or discharging may be easily performed with a simple mechanical configuration. There is a small difference between the charging current and the discharging current in portable electronic devices such as a mobile phone and a notebook computer. Thus, a field effect transistor (FET) used for the charging element may have an allowable current (e.g., current rating) that is the same as or similar to a FET that is used for the discharging element  140 , and a price difference thereof is also not large. 
         [0020]    However, in the case of an electrical moving body such as an electric bike, an electric scooter, an electric wheelchair, and a motor-operated cart, there is a significant difference between the charging current and the discharging current. For example, in the case of the electric bike, the charging current is about 1.5 to about 2.0 A, and the discharging current is 10 A (average) and 20 A (maximum). In such case, there is a large difference between the charging current and the discharging current. Also, in the case of the electric scooter, the discharging current is 30 A (average) and 80 A (maximum), and thus there is much larger difference between the discharging current and the charging current. Thus, when a battery pack having a single charging and discharging path is used, as in related art, the FET for charging has to have a high allowable current rating that is similar to the rating for the FET for discharging. 
         [0021]      FIG. 2  is a circuit diagram of a battery pack  200  illustrating the connection relationship between the battery pack  200 , a load  270 , and a charging device  280 , according to an embodiment of the present invention. Referring to  FIG. 2 , the battery pack  200  according to the present embodiment includes a microcomputer  210 , a battery cell  230 , a charging element  240 , a discharging element  250 , a discharging terminal  290 , a charging terminal  291 , and a charging and discharging terminal  292  (e.g., common terminal). Also, the battery pack  200  further includes a load  270  that is connected to the battery pack  200  via the discharging terminal  290  and the charging and discharging terminal  292 . The charging device  280  is connected to the battery pack  200  via the charging terminal  291  and the charging and discharging terminal  292 . 
         [0022]    Although not shown, the battery pack  200  may further include a current detector that is connected in series to a HCP formed between the battery cell  230  and the discharging terminal  290  and connected to the microcomputer  210 , and a temperature detector that detects the temperature of the battery cell  230 , and a self protection controller that blows a fuse located in the HCP according to control signals generated by the microcomputer  210  or an external system (not shown). The microcomputer  210  turns off the charging element  240  and the discharging element  250  or blows the fuse to prevent over-charging or over-discharging of the battery cell  230  when it is determined that the battery cell  230  is in an overcharged state or an over-discharged state. Also, the microcomputer  210  may include a system management BUS (SMBUS) for communication with the external system. 
         [0023]    The battery cell  230  is a secondary battery cell that may be charged and discharged. In  FIG. 2 , B+ and B− denote high current terminals of the battery cell  230 , e.g., power supply terminals of the battery cell  230 . The battery cell  230  provides various information about the battery cell  230 , such as temperature and a charging voltage of the battery cell  230 , to the microcomputer  210 . 
         [0024]    The discharging element  250  is connected between the battery cell  230  and the discharging terminal  290 . The discharging element  250  performs a switching function for discharging the battery cell  230  and prevents over-discharging when it is turned off according to control signals generated by the microcomputer  210  when the battery cell  230  is over-discharged. The discharging element  250  may include an FET. However, the discharging element  250  may be an electric element that performs a different type of switch function. Through this configuration, when the load  270  is connected to the discharging terminal  290  and the charging and discharging terminal  292 , a discharging path from the battery cell  230  to the load  270  is formed by the battery cell  230 , the discharging element  250 , the discharging terminal  290 , and the load  270 , and a current is supplied from the battery pack  200  along the discharging path. Thus, the charging element  240  is not included in the discharging path so that the charging element  240  may be a switch element having a lower current rating than the current rating of the discharging element  250 . In other words, even when a comparatively large discharging current flows to the load  270 , the charging element  240  may be implemented without regard to the magnitude of the discharging current. 
         [0025]    The charging element  240  is connected between the discharging terminal  290  and the charging terminal  291 . The charging element  240  performs a switching function for charging the battery cell  230  and prevents over-charging when it is turned off according to control signals generated by the microcomputer  210  when the battery cell  230  is over-charged. Like the discharging element  250 , the charging element  240  may include an FET. However, the charging element  240  may be an electric element that performs a different type of switch function. Through this configuration, when the charging device  280  is connected to the charging terminal  291  and the charging and discharging terminal  292 , a charging path from the charging device  280  to the battery cell  230  is formed by the charging device  280 , the charging terminal  291 , the charging element  240 , the discharging terminal  290 , the discharging element  250 , and the battery cell  230 . 
         [0026]    The microcomputer  210  controls the discharging element  250  and the charging element  240  to perform charging and discharging functions of the battery pack  200  and to thereby prevent over-charging and over-discharging. When the load  270  is connected to the discharging terminal  290  and the charging and discharging terminal  292 , the microcomputer  210  may turn on the discharging element  250  to discharge the battery cell  230 . Also, when the charging device  280  is connected to the charging terminal  291  and the charging and discharging terminal  292 , the microcomputer  210  may turn on the charging element  240  and the discharging element  250  to charge the battery cell  230 . Also, when the microcomputer  210  measures a voltage of the battery cell  230  and determines that over-discharging to the load  270  is occurring, the microcomputer  210  may turn off the discharging element  250  to prevent over-discharging. Also, when the microcomputer  210  determines that over-charging from the charging device  280  is occurring, the microcomputer  210  may turn off the charging element  240  to prevent over-charging. 
         [0027]    Based on the configuration of the battery pack  200 , the load  270 , and the charging device  280 , when there is a large difference between a charging current and a discharging current in the load  270  such as an electric moving body, during a discharging operation, the discharging current does not flow through the charging element  240 . In such case, the charging element  240  may be a switching element that does not need a high current rating like that of the discharging element  250 . 
         [0028]    Also, in  FIG. 2 , the discharging element  250  and the charging element  240  are located along the HCP at the positive side of the battery cell  230 . However, the discharging element  250  and the charging element  240  may also be located along the HCP at the negative side of the battery cell  230 . 
         [0029]      FIG. 3  is a circuit diagram of a battery pack  300  illustrating the connection relationship between the battery pack  300 , a load  370 , and a charging device  380 , according to another embodiment of the present invention. Referring to  FIG. 3 , the battery pack  300  according to the present embodiment includes a microcomputer  310 , an AFE IC  320 , a battery cell  330 , a charging element  340 , a discharging element  350 , a discharging terminal  390 , a charging terminal  391 , and a charging and discharging element  392 . The battery pack  300  further includes the load  370  that is connected to the battery pack  300  via the discharging terminal  390  and the charging and discharging terminal  392 , and the charging device  380  that is connected to the battery pack  300  via the charging terminal  391  and the charging and discharging terminal  392 . The difference between  FIGS. 2 and 3  is that the battery pack  300  includes the AFE IC  320  that controls the discharging element  350  and the charging element  340  and detects a voltage from the battery cell  330 , and a charging FET FET 1  and a discharging FET FET 2  that constitute the charging element  340  and the discharging element  350 , respectively. 
         [0030]    When the charging device  380  is connected to the battery pack  300  via the charging terminal  391  and the charging and discharging terminal  392 , the AFE IC  320  sets the charging FET FET 1  of the charging element  340  to be in an on state and the discharging FET FET 2  of the discharging element  350  to be in the on state so that the battery cell  330  may be charged. Similarly, when the load  370  is connected to the battery pack  300  via the discharging terminal  390  and the charging and discharging terminal  392 , the AFE IC  320  sets the discharging FET FET 2  of the discharging element  350  to be in the on state so that the battery cell  330  may be discharged. The AFE IC  320  controls switching operations of the charging FET FET 1  for the charging element  340  and the discharging FET FET 2  for the discharging element  350  according to control signals generated by the microcomputer  310 . 
         [0031]    As described above with reference to  FIG. 2 , the load  370  connected to the battery pack  300  may be a load in which the discharging current is larger than the charging current, and may be an electric moving body such as an electric bike or an electric scooter. Thus, the charging FET FET 1  is not positioned in the discharging path. Thus, a comparatively large current, for example, current of several amps does not flow through the charging FET FET 1 . Thus, the charging FET FET 1  may be an FET that has a low current rating. For example, the discharging FET FET 2  may be an FET that has an allowable current (e.g., current rating) of 20 A, and the charging FET FET 1  may be an FET that has an allowable current (e.g., current rating) of 2 A. 
         [0032]    The source and drain of the charging FET FET 1  (e.g., the charging element  340 ) are positioned opposite to the source and drain of the discharging FET FET 2  (e.g., the discharging element  350 ). More specifically, the source of the charging FET FET 1  (e.g., the charging element  340 ) is coupled to the source of the discharging FET FET 2  (e.g., the discharging element  350 ). Using this configuration, the charging FET FET 1  (e.g., the charging element  340 ) is configured to limit flow of current from the charging device  380  to the battery cell  330 . On the other hand, the discharging FET FET 2  (e.g., the discharging element  350 ) is configured to limit flow of current from the battery cell  330  to the load  370 . Here, the FETs FET 1  and FET 2  are turned on or off according to control signals of the AFE IC  320 , e.g., a switch control signal at a high level or a low level. 
         [0033]    The AFE IC  320  is connected to the battery cell  330 , the charging element  340 , and the discharging element  350  and is connected in series between the battery cell  330  and the microcomputer  310 . The AFE IC  320  detects a voltage of the battery cell  330 , transmits the detected voltage to the microcomputer  310 , and controls switch operations of the charging FET FET 1  and the discharging FET FET 2  according to control signals provided by the microcomputer  310 . 
         [0034]    In more detail, when the charging device  380  is connected to the battery pack  300  via the charging terminal  391  and the charging and discharging terminal  392 , the AFE IC  320  sets the charging FET FET 1  (e.g., the charging element  340 ) to be in an on state and the discharging FET FET 2  (e.g., the discharging element  350 ) to be in the on state so that the battery cell  330  may be charged. Similarly, when the load  370  is connected to the battery pack  300  via the discharging terminal  390  and the charging and discharging terminal  392 , the AFE IC  320  outputs a control signal that is used to set the discharging FET FET 2  (e.g., the discharging element  350 ) to be in the on state so that the battery cell  330  may be discharged. 
         [0035]    The microcomputer  310  is an IC that is connected in series between the AFE IC  320  and the external system. The microcomputer  310  controls the charging element  340  and the discharging element  350  via the AFE IC  320  so as to prevent over-charging, over-discharging, and overcurrent of the battery cell  330 . In other words, the microcomputer  310  compares a voltage of the battery cell  330  that is received via the AFE IC  320  with a voltage that is at a level that is set in the microcomputer  310  (e.g., a preselected voltage), outputs a control signal that is generated according to the result of the comparison to the AFE IC  320 , and, if necessary, turns off the charging element  340  and the discharging element  350 , thereby preventing over-charging, over-discharging, and overcurrent of the battery cell  330 . 
         [0036]    When the microcomputer  310  determines that the battery cell  330  is in an over-discharged state, it outputs a control signal that is generated according to the result of such determination to the AFE IC  320 , thereby turning off the discharging FET FET 2  (e.g., the discharging element  350 ), and any discharge to the load  370  from the battery cell  330  may be prevented. Although not shown, the battery pack  300  may further include a parasitic diode connected in parallel to the discharging FET FET 2  (e.g., the discharging element  350 ) so that, even when the discharging FET FET 2  (e.g., the discharging element  350 ) is turned off, a charging function of the battery cell  330  may be performed. 
         [0037]      FIG. 4  is a circuit diagram of a battery pack  400  illustrating the connection relationship between the battery pack  400 , a load  470 , and a charging device  480 , according to another embodiment of the present invention. Referring to  FIG. 4 , the battery pack  400  includes a microcomputer  410 , an AFE IC  420 , a battery cell  430 , a charging element  440 , a discharging element  450 , a current limit element  460 , a discharging terminal  490 , a charging terminal  491 , and a charging and discharging terminal  492 . Also, the battery pack  400  is coupled to the load  470  via the discharging terminal  490  and the charging and discharging terminal  492 . The battery pack  400  is further coupled to the charging device  480  via the charging terminal  491  and the charging and discharging terminal  492 . The primary difference between the embodiments illustrated in  FIGS. 3 and 4  is that the battery pack  400  further includes the current limit element  460  that is disposed between the discharging terminal  490  and the charging element  440 . As such, descriptions of the structure and function for the same portions as the battery pack  300  of  FIG. 3  will not be provided here, and only the current limit element  460  will now be described. 
         [0038]    The current limit element  460  is connected between the discharging terminal  490  and the charging element  440 . Here, when the load  470  is connected to the discharging terminal  490  and the charging and discharging terminal  492  and a discharging current flows to the load  470  from the battery cell  430 , the current limit element  460  cuts off flow of any discharging current to the charging element  440 . The current limit element  460  may be a diode or a switch. 
         [0039]    In the case where the current limit element  460  is a diode, the current limit element  460  is connected between the discharging terminal  490  and the charging element  440  and may cut off the flow of discharging current to the charging element  440 . Thus, the diode cuts off the flow of the discharging current to the charging element  440  while allowing the charging current to flow to the battery cell  430  via the discharging element  450 . 
         [0040]    In the case where the current limit element  460  is a switch, the current limit element  460  is connected between the discharging terminal  490  and the charging element  440 , as described above. The current limit element  460  is turned on or off according to control signals provided by the AFE IC  420 . When the load  470  is connected to the discharging terminal  490  and the charging and discharging terminal  492  and the discharging current flows to the load  470  from the battery  430 , the switch is turned off and cuts off flow of the discharging current to the charging element  440 . However, during a charging operation, the switch is turned on and allows a charging current to flow through the charging element  440  and the discharging element  450  to the battery cell  430 . Here, the switch may be an FET or another suitable electric element that performs a switching function. 
         [0041]    In  FIG. 4 , a discharging path includes the battery cell  430 , the discharging element  450 , the discharging terminal  490 , and the load  470 , and a charging path includes the charging device  480 , the charging terminal  491 , the charging element  440 , the current limit element  460 , the discharging terminal  490 , the discharging element  450 , and the battery cell  430 . Similar to embodiments described for  FIGS. 2 and 3 , the charging element  440 , unlike the discharging element  450  that generally has to be rated for a comparatively large discharging current, may be a switching element that does not have a high current rating while securely preventing the discharging current from flowing through the charging element  440  during a discharging operation. 
         [0042]      FIGS. 5 and 6  are flowcharts illustrating a process for charging a battery pack and a process for discharging the battery pack, respectively, according to other embodiments of the present invention. Referring to  FIG. 5 , in block  500 , a charging device is connected to a charging terminal of the battery pack. In blocks  502  and  504 , the charging element and discharging element are turned on. A charging path includes a charging device, a charging terminal, a charging element, a discharging terminal, a discharging element, and a battery cell. Optionally, a current limit element may be disposed between the charging element and the discharging terminal. Here, the current limit element does not cut off the charging current but allows the charging current to flow through the battery cell. The charging current that flows through the charging element and the discharging element during a charging operation is relatively small compared to the corresponding discharging current. Thus, an allowable current (e.g., current rating) of the charging element does not have to be high and the charging element may be implemented to correspond to the magnitude of the charging current of the charging device. In block  506 , the battery cell is charged. 
         [0043]    Referring to  FIG. 6 , in block  600 , the load is connected to the discharging terminal of the battery pack. The discharging terminal is configured different from the charging terminal of  FIG. 5 . In other words, in order to separate charging and discharging paths from each other, the load is connected to the battery pack via an additional discharging terminal. 
         [0044]    In blocks  602  and  604 , the discharging element is turned on, and the battery cell is discharged. The discharging path includes the battery cell, the discharging element, the discharging terminal, and the load. Thus, when the load needs a comparatively large output current, for example, a maximum current required when an electric bike travels uphill, the output current may be supplied to the load without passing through the charging element. In order to securely prevent the discharging current from flowing through the charging element during the discharging operation, the current limit element may be disposed between the charging element and the discharging terminal in several embodiments. The current limit element may be a diode or a switch and prevents the discharging current from flowing through the charging element via the discharging terminal during the discharging operation. 
         [0045]    As described above, according to several embodiments of the present invention, the battery pack includes an additional discharging element to separate the charging and discharging paths from each other. Thus, when a current is supplied to a load that requires a comparatively large output current, a large current does not flow through the charging element so that an allowable current (e.g., current rating) of the charging element may be reduced. Also, a discharging operation may be performed without discharging current passing through the charging element so that efficiency of output of the battery pack may be improved and the amount of heat-dissipation may be reduced. 
         [0046]    Furthermore, the charging and discharging circuitry may be implemented so that a charging operation may be performed without separating the battery pack. 
         [0047]    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 included within the spirit and scope of the appended claims, and equivalents thereof.