Abstract:
An electronic device includes a secondary battery having at least one bare cell, the secondary battery including a charge/discharge switching module for placing the secondary battery in one of a charging state for charging the at least one bare cell or a discharging state for discharging the at least one bare cell; and an analog front end for generating an analog signal based on information of the secondary battery and for transmitting the analog signal out of the secondary battery; and a processor external to the secondary battery for receiving the analog signal from the analog front end and for controlling the charge/discharge switching module in accordance with the analog signal.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to and the benefit of U.S. Provisional Patent Application No. 61/149,964, filed on Feb. 4, 2009, the entire content of which is incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a secondary battery, and more particularly to a charge and discharge system of a secondary battery and a method of controlling charge and discharge of a secondary battery. 
         [0004]    2. Description of the Related Art 
         [0005]    In recent years, due to rapid development of electronics, portable electronic devices are being more widely distributed. Rechargeable secondary batteries are widely used as power sources of many of these portable electronic devices. 
         [0006]    A conventional rechargeable secondary battery installed in a portable electronic device, such as a portable computer, to be charged and discharged generally includes a bare cell, a charge/discharge switching module, a current detector, a temperature detector, a microprocessor unit (hereinafter referred to as an “MPU”), and an analog front end (hereinafter referred to as an “AFE”). The AFE converts analog information on the secondary battery into digital data and transmits the converted digital data to the MPU. The information on the secondary battery may include a voltage of the bare cell, charge/discharge currents, temperature of the bare cell, and similar information detected from the bare cell, the current detector, the temperature detector, and/or various other diagnostic devices. The MPU determines a status of the secondary battery based on the information transmitted from the AFE, and transmits a corresponding control signal to the AFE. The AFE controls the charge/discharge switching module in accordance with the control signal transmitted from the MPU, so that charge and discharge of the secondary battery is controlled. The MPU of the secondary battery transmits the information on the secondary battery, that is, the converted digital data, to another MPU of a portable electronic device through a system management (SM) bus. The MPU of the portable electronic device controls charging and discharging current using the information on the secondary battery transmitted from the MPU of the secondary battery. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention provides a system for controlling charge and discharge of a secondary battery using a microprocessor unit (MPU) of a portable electronic device, to which a secondary battery is connected, and a charge and discharge controlling method of the secondary battery. 
         [0008]    In accordance with an aspect of an exemplary embodiment of the present invention, there is provided an electronic device including: a secondary battery having at least one bare cell, the secondary battery including: a charge/discharge switching module for placing the secondary battery in one of a charging state for charging the at least one bare cell or a discharging state for discharging the at least one bare cell; and an analog front end for generating an analog signal based on information of the secondary battery and for transmitting the analog signal out of the secondary battery; and a processor external to the secondary battery for receiving the analog signal from the analog front end and for controlling the charge/discharge switching module in accordance with the analog signal. 
         [0009]    In accordance with an aspect of another exemplary embodiment of the present invention, there is provided a method of controlling charging and discharging of a secondary battery, including: requesting information from the secondary battery; receiving an analog signal from the secondary battery corresponding to the requested information; determining a status of the secondary battery based on the analog signal; and transmitting a control signal to the secondary battery to control charging and discharging of the secondary battery in accordance with the status of the secondary battery. 
         [0010]    In accordance with an aspect of yet another exemplary embodiment of the present invention, there is provided a secondary battery including: at least one bare cell; a charge/discharge switching module for charging and discharging the at least one bare cell; and an analog front end for generating an analog signal including information of the at least one bare cell and for transmitting the analog signal to an external device. 
         [0011]    According to exemplary embodiments of the present invention, since the charge and discharge of a secondary battery are controlled by the MPU of the portable electronic device to which the second battery is connected, the secondary battery may not include an internal MPU. As such, the secondary battery in one embodiment does not include its own processor (i.e., its own MPU for processing the analog information). Therefore, a simplified secondary battery can be achieved, and manufacturing costs can be reduced. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a block diagram illustrating a charge and discharge system of a secondary battery according to an embodiment of the present invention; and 
           [0013]      FIG. 2  is a flow chart illustrating a method of charging and discharging a secondary battery by utilizing the charge and discharge system shown in  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    Hereinafter, exemplary embodiments of the present invention will be described in detail, with reference to the accompanying drawings. 
         [0015]      FIG. 1  shows a block diagram of a charge and discharge system of a secondary battery according to an embodiment of the present invention. 
         [0016]    Referring to  FIG. 1 , a charge and discharge system  100  of a secondary battery includes a secondary battery  200  and a portable electronic device  300  to which the secondary battery  200  is connected. 
         [0017]    The secondary battery  200  includes a bare cell  210 , a charge/discharge switching module  220 , a current detector  230 , a temperature detector  240 , an analog front end (AFE)  250 , and a plurality of external terminals  260   a ,  260   b ,  260   c , and  260   d.    
         [0018]    The bare cell  210  is a device for storing electrical energy and for supplying the electrical energy to the outside, and includes a positive electrode  211  and a negative electrode  212 . The bare cell  210  may be, for example, a lithium ion battery or a lithium polymer battery. An open circuit voltage of the bare cell  210  is an analog signal, which is transmitted to the AFE  250 . In  FIG. 1 , a number of bare cells  210  are connected to each other in series, but the present invention is not limited thereto. A number of bare cells  210  can be connected to each other in parallel, or connected in a combination of both series and parallel. In some embodiments, a single bare cell  210  may be used. 
         [0019]    The charge/discharge switching module  220  includes a charge switching device  221  and a discharge switching device  222 . The charge/discharge switching module  220  determines a direction of current in charge and discharge modes. 
         [0020]    The charge switching device  221  includes a charge field effect transistor (hereinafter referred to as “FET”)  221   a  and a parasitic diode  221   b  connected to the charge FET  221   a  in parallel. The charge FET  221   a  is mounted such that a drain and a source of the charge FET  221   a  are placed on a high current path  10  of the bare cell  210 . In the present embodiment, the high current path  10  is a path through which charge and discharge currents of the bare cell  210  flow. The charge FET  221   a  is turned on and off by a control signal from the AFE  250  through a gate of the charge FET  221   a . The charge FET  221   a  is turned on together with a discharge FET  222   a  of the discharge switching device  222  for charging of the secondary battery  200 , and supplies the charge current from the portable electronic device  300  to the bare cell  210  through the first positive terminal  260   a  and the first negative terminal  260   b.    
         [0021]    The parasitic diode  221   b  corresponding to the charge FET  221   a  is connected to the charge FET  221  a in a reverse biased direction relative to the charge current direction. When the charge FET  221   a  is turned off, the parasitic diode  221   b  corresponding to the charge FET  221   a  provides a path through which the discharge current may flow. 
         [0022]    The discharge switching device  222  includes a discharge FET  222   a  and a parasitic diode  222   b  connected in parallel to the discharge FET  222   a.    
         [0023]    The discharge FET  222   a  is mounted such that a drain and a source of the discharge FET  222   a  are placed on the high current path  10  of the bare cell  210 . The discharge FET  222   a  is turned on and off by a control signal from the AFE  250  through a gate of the discharge FET  222   a . The discharge FET  222   a  is turned on together with the charge FET  221   a  for discharging of the secondary battery  200 , and supplies the discharge current from the bare cell  210  to the portable electronic device  300  through the first positive terminal  260   a  and the first negative terminal  260   b.    
         [0024]    The parasitic diode  222   b  corresponding to the discharge FET  222   a  is connected to the discharge FET  222   a  in a reverse biased direction relative to the discharge current direction. When the discharge FET  222   a  is turned off, the parasitic diode  222   b  corresponding to the discharge FET  222   a  provides a path through which the charge current may flow. 
         [0025]    The current detector  230  is installed on the high current path  10 . Both ends of the current detector  230  are electrically connected to the AFE  250 . In one embodiment of the present invention, a resistor (e.g., a sense resistor) is used as the current detector  230 . A voltage difference between the two ends of the current detector  230  is transmitted as an analog signal to the AFE  250 , and the transmitted voltage difference is used to estimate the amount of electric current flowing through the high current path  10 . 
         [0026]    The temperature detector  240  is positioned near the bare cell  210  and is electrically connected to the AFE  250 . In one embodiment of the present invention, a thermistor is used as the temperature detector  240 . The temperature detector  240  detects a temperature of the bare cell  210 , and the detected temperature of the bare cell  210  is transmitted as an analog signal to the AFE  250 . 
         [0027]    The AFE  250  may include an application specific integrated circuit (ASIC). The AFE  250  may detect an open circuit voltage of the bare cell  210 , scale an analog signal to a voltage level of the portable electronic device  300 , and transmit the scaled analog signal to the portable electronic device  300  through the first information terminal  260   c . Moreover, the AFE  250  may transmit the voltage difference between the two ends of the current detector  230  as an analog signal to the portable electronic device  300  through a first information terminal  260   c . The AFE  250  may also transmit the detected temperature of the bare cell  210  from the temperature detector  240  as an analog signal to the portable electronic device  300  through the first information terminal  260   c . The AFE  250  receives a digital control signal from the portable electronic device  300  through a first control signal terminal  260   d , and controls the charge FET  221   a  and the discharge FET  222   a  of the charge/discharge switching module  220  based on the signal to activate (i.e., accommodate the flow of) either the charge current or the discharge current. 
         [0028]    The plurality of external terminals  260   a ,  260   b ,  260   c , and  260   d  includes the first positive terminal  260   a , the first negative terminal  260   b , the first information terminal  260   c , and the first control signal terminal  260   d . The first positive terminal  260   a  and the first negative terminal  260   b  are electrically connected to the positive electrode  211  and the negative electrode  212  of the bare cell  210 , respectively, along the high current path  10 . The first positive terminal  260   a  and the first negative terminal  260   b  are electrically connected to the portable electronic device  300  to accommodate the charge and discharge currents. 
         [0029]    The first information terminal  260   c  is electrically connected to the AFE  250 . The AFE  250  transmits information about the secondary battery  210  to the portable electronic device  300  through the first information terminal  260   c , typically in the form of an analog signal. In this case, information about the secondary battery  210 , which is transmitted through the first information terminal  260   c  to the portable electronic device  300 , contains information such as the voltage of the bare cell  210 , the voltage difference between the two ends of the current detector  230 , and the temperature of the bare cell  210  detected by the temperature detector  240 . 
         [0030]    The first control signal terminal  260   d  is electrically connected to the AFE  250 . A digital control signal is transmitted from the portable electronic device  300  to the AFE  250  through the first control signal terminal  260   d . An existing SM bus can provide a path through which the digital control signal is transmitted from the portable electronic device  300  to the AFE  250 . 
         [0031]    The portable electronic device  300  includes a power supply  310 , an A/D converter  312 , an MPU  320 , and a plurality of external terminals  330   a ,  330   b ,  330   c , and  330   d.    
         [0032]    The power supply  310  includes a switching device controlled by the MPU  320  and an adaptor for converting external AC power into DC power to supply to the portable electronic device  300 . The power supply  310  supplies the charge current to the secondary battery  200  and supplies the discharge current from the secondary battery  200  to the portable electronic device  300  as electric power. The power supply  310  can also supply external electric power directly to the portable electronic device  300 . 
         [0033]    The A/D converter  312  converts information about the secondary battery  200 , transmitted from the secondary battery  200  as an analog signal, into a digital signal, and transmits the converted digital signal to the MPU  320 . 
         [0034]    The MPU  320  includes a microprocessor a passive device, an active device, and a memory, which are electrically connected to the microprocessor. The MPU  320  outputs a digital control signal requesting information about the secondary battery  200  to the AFE  250  of the secondary battery  200 . The MPU  320  receives information about the secondary battery  200  in the form of a digital signal through the A/D convertor  312 . The information about the secondary battery  200  contains information such as the voltage of the bare cell  210 , the voltage difference between the two ends of the current detector  230 , and/or the temperature of the bare cell  210  detected by the temperature detector  240 . The MPU  320  determines a status of the bare cell  210 , for example, whether the bare cell  210  is over-discharged, fully-discharged, fully-charged, or over-charged, based on the voltage information of the bare cell  210 , and outputs a digital control signal corresponding to the determined status of the bare cell  210  to the AFE  250 . The MPU  320  calculates charge and discharge currents flowing through the high current path  10  of the secondary battery  200  using the voltage difference information between the two ends of the current detector  230 . When an abnormal status is detected, the MPU  320  outputs a digital control signal for stopping charge or discharge of the secondary battery  200  to the AFE  250  of the secondary battery  200 . The MPU  320  checks the information on the temperature of the bare cell  210  of the secondary battery  200  and outputs a digital control signal for stopping the charge or discharge of the secondary battery  200  to the AFE  250  of the secondary battery  200  when an abnormal status is detected. The MPU  320  also outputs a signal to control the power supply  310 . 
         [0035]    The plurality of external terminals  330   a ,  330   b ,  330   c , and  330   d  includes a second positive terminal  330   a , a second negative terminal  330   b , a second information terminal  330   c , and a second control signal terminal  330   d . The second positive terminal  330   a  and the second negative terminal  330   b  are electrically connected to the power supply  310 , and are respectively connected to the first positive terminal  260   a  and the first negative terminal  260   b  of the secondary battery  200 , for forming a path through which the charge and discharge currents may flow when the secondary battery  200  is installed in or connected to the portable electronic device  300 . 
         [0036]    The second information terminal  330   c  is electrically connected to the A/D converter  312 . When the secondary battery  200  is connected to the portable electronic device  300 , the second information terminal  330   c  is connected to the first information terminal  260   c  of the secondary battery  200  and is utilized for transmitting analog signals from the first terminal  260   c  to the A/D converter  312 . 
         [0037]    The second control signal terminal  330   d  is electrically connected to the MPU  320 . When the secondary battery  200  is connected to the portable electronic device  300 , the second control signal terminal  330   d  is connected to the first control signal terminal  260   d  of the secondary battery  200  and is utilized for transmitting digital signals from the MPU  320  to the secondary battery  200 . 
         [0038]    Hereinafter, a method of controlling charge and discharge of a secondary battery, utilizing the charge and discharge system shown in  FIG. 1 , according to an embodiment of the present invention will be described in detail. 
         [0039]    Referring to  FIG. 2 , the charge and discharge controlling method of the secondary battery includes requesting information about a secondary battery (S 10 ), detecting the information about the secondary battery (S 20 ), transmitting the information about the secondary battery (S 30 ), determining a status of the secondary battery (S 40 ), and transmitting a control signal to the secondary battery (S 50 ). 
         [0040]    Referring to the  FIGS. 1 and 2 , each of the above steps will be described in more detail. 
         [0041]    In the request of information about the secondary battery (S 10 ), the MPU  320  of the portable electronic device  300  transmits a digital control signal requesting information about the secondary battery  200  to the AFE  250  of the secondary battery  200 . The digital control signal requesting information about the secondary battery  200  is transmitted through the connection between the first control signal terminal  260   d  of the secondary battery  200  and the second control signal terminal  330   d  of the portable electronic device  300 . 
         [0042]    In the detection of the information about the secondary battery (S 20 ), the AFE  250  detects an open circuit voltage of the bare cell  210 , a voltage difference between the two ends of the current detector  230 , and/or a temperature of the bare cell  210  from the temperature detector  240 . In one embodiment, all the detected values are analog signals. 
         [0043]    In the transmission of the information about the secondary battery (S 30 ), the AFE  250  transmits the voltage information of the bare cell  210 , the voltage difference between the two ends of the current detector  230 , and/or the temperature of the bare cell  210  detected by the temperature detector  240 , to the portable electronic device  300  in the form of analog signals through the first information terminal  260   c  and the second information terminal  330   c . In this case, the voltage signal of the bare cell  210  is scaled to the voltage level of the portable electronic device  300 , and the scaled signal is transmitted. After that, the information about the secondary battery  200 , in the form of the analog signal transmitted through the second information terminal  330   c , is converted into a digital signal by the A/D converter  312  of the portable electronic device  300 , and the converted digital signal is transmitted to the MPU  320  of the portable electronic device  300 . 
         [0044]    In the determining of the status of the secondary battery (S 40 ), the MPU  320  of the portable electronic device  300  checks the information of the secondary battery  200  input through the A/D converter  312 . The MPU  320  may determine whether the bare cell  210  is over-discharged, fully-discharged, fully-charged, or over-charged, based on the voltage information of the bare cell  210 . The MPU  320  may also calculate the charge and discharge currents flowing through the high current path  10  of the secondary battery  200  using the voltage difference between the two ends of the current detector  230  of the secondary battery  200  and determine whether there is an abnormality. The MPU  320  may also check the temperature of the bare cell  210  of the secondary battery  200  and determine whether there is an abnormality. 
         [0045]    In the transmission of the control signal to the secondary battery (S 50 ), the MPU  320  outputs a digital control signal to the AFE  250  through the first control signal terminal  260   d  and the second control signal terminal  330   d . The digital control signal is a signal for controlling the charge FET  221   a  and the discharge FET  222   a  of the charge and discharge switching device  220  of the secondary battery  200 . The MPU  320  outputs a digital control signal, which may, for example, stop the charge or discharge of the secondary battery  200  when the voltage of the bare cell  210 , the charge or discharge current, and/or the temperature of the bare cell  210  are determined to be abnormal. 
         [0046]    Although exemplary embodiments of the present invention have been described in detail hereinabove, it should be understood that variations and modifications of the basic inventive concept herein described which may be apparent to those skilled in the art will still fall within the spirit and scope of the exemplary embodiments of the present invention, as defined by the appended claims.