Abstract:
A method of detecting the type of a battery pack in a mobile electronic device is provided, which detects the type of a battery pack connected in a mobile electronic device even if no dedicated terminals are provided to a battery pack. (a) A first battery pack connectable to the body is provided. (b) A second battery pack connectable to the body and different in characteristic from the first pack is provided. Each of the first and second packs has a battery cell, first and second terminals respectively connected to high- and low-potential side terminals of the cell, a third terminal, and a temperature detection element connected across the first and second terminals. (c) The body is provided with fourth, fifth, and sixth terminals connectable respectively to the first, second, and third terminals of the first or second battery pack. The body has a resistive voltage divider circuit connected among the fourth, fifth, and sixth terminals. (d) The first or second pack is connected to the body in such a way that the fourth, fifth, and sixth terminals of the body are connected to the first, second, and third terminals of the first or second battery pack, respectively. (c) An output voltage of the divider is detected to thereby generate a detection result. (f) Whether the first or second pack is connected to the body is detected based on the detection result.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method of detecting the connection of a battery pack to a portable or mobile electronic device such as mobile phones and a mobile electronic device using the method. More particularly, the invention relates to a method of detecting whether or not a specific battery pack is connected to the body of a mobile electronic device that makes it possible to recognize the connection and type of the battery pack without providing discrimination-dedicated terminals, and a mobile electronic device capable of connection of battery packs having different characteristics. 
     2. Description of the Related Art 
     In recent years, various portable or mobile electronic equipment such as mobile or cellular phones, personal handyphone systems (PHSs), notebook computers, and digital cameras, have been developed and extensively used. The mobile electronic equipment, which may be termed “mobile electronic devices” later, require high-level transportability and therefore, they need to be compact and light-weight and operable with a battery pack as its power supply. 
     Typically, the battery pack applicable to portable electronic equipment comprises at least one chargeable battery cell in its inside. Several types of chargeable battery cells have been already developed and commercially produced and sold for this purpose. They are different in battery characteristics such as capacity, discharge characteristic, and necessary charging period from each other. According to the types of chargeable battery cells, several types of battery packs have been already commercially produced and sold so far. 
     To make it possible to apply different types of battery packs to mobile electronic devices of this sort, mobile electronic devices need to discriminate the type of sort of battery packs connected or installed and to switch their operating condition according to the current type/sort of battery packs. Also, with mobile electronic devices chargeable without separating battery packs, the charging voltage to battery packs is required to be controlled or adjusted in the devices according to the current type/sort of battery packs. 
     To meet the above-described requirement, conventionally, prior-art mobile electronic devices capable of using different types of battery packs comprises dedicated terminals for discriminating the type of battery packs connected. The discrimination-dedicated terminals are provided in both battery packs and the body of devices. 
     As an example of mobile electronic devices of this sort, a conventional mobile phase capable of the alternative use of two different types of battery packs is explained below with reference to FIGS. 1 to  3 . 
     FIGS. 1 and 2 are schematic, partial circuit diagrams of two different-type battery packs for a conventional mobile phone, respectively. FIG. 3 is a schematic, partial circuit diagram of the body of the same phone. 
     As shown in FIG. 1, a first battery pack  40  comprises a switch (SW)  41 , a protection circuit  42 , a lithium (Li)-ion battery cell  43 , a thermistor  44 , a resistor  45 , a power supply terminal (i.e., +V terminal)  401 , a discrimination terminal (i.e., SEL terminal)  402 , a temperature detection terminal (i.e., TH terminal)  403 , and a ground terminal (i.e., GND terminal)  404 . The switch  41 , the protection circuit  42 , the cell  43 , the thermistor  44 , and the resistor  45  are provided in the enclosure or casing (not shown) of the first battery pack  40 . The power-supply terminal  401 , the discrimination terminal  402 , the temperature detection terminal  403 , and the ground terminal  404  are exposed to the outside from the enclosure. 
     The positive terminal of the battery cell  43  is connected to the power-supply terminal  401  by way of the switch  41 . The negative terminal of the battery cell  43  is directly connected to the ground terminal  401 . The battery voltage V BAT1 , which is generated between the positive and negative terminals of the cell  43 , is outputted from the power supply and ground terminals  401  and  404 . 
     The protection circuit  42  is supplied with the battery voltage V BAT1  from the cell  43 . The circuit  42  generates the switch control signal V SW1  on the basis of the voltage V BAT1  and then, supplies the signal V SW1  thus generated to the switch  41 . The ground terminal of the circuit  42  is connected to the ground terminal  404 . 
     The switch  41  serves to connect the positive terminal of the battery cell  43  to the power supply terminal  401  or disconnects the same from the terminal  401  according to the switch control signal V S1  from the protection circuit  42 . 
     The resistor  45  is connected across the discrimination terminal  402  and the ground terminal  404 . 
     The thermistor  44  is connected across the temperature detection terminal  403  and the ground terminal  404 . To facilitate detection of the temperature of the cell  43 , the thermistor  44  is located in the vicinity of the battery cell  43  in the battery enclosure. 
     With the first battery pack  40  having the above-described configuration, the switch  41  is turned on or off by the control signal V SW1  from the protection circuit  42 , thereby controlling the output of the battery voltage V BAT1  from the power-supply and ground terminals  401  and  404 . Specifically, in the normal operation state where the voltage V BAT1  is equal to or higher than a specific value, the switch  41  is turned on by the control signal V SW1 , outputting the voltage V BAT1  from the terminals  401  and  404 . On the other hand, in the abnormal operation state where the voltage V BAT1  is less than the specific value, the switch  41  is turned off by the control signal V SW1 , stopping the output of the voltage V BAT1  from the terminals  401  and  404 . 
     The resistance R TH1  of the thermistor  44  varies according to the temperature of the battery cell  43 . Thus, when a proper circuit that generates a voltage corresponding to the resistance R TH1  is connected to the temperature detection terminal  403 , the temperature of the cell  43  can be detected on the basis of the voltage thus generated. 
     When a specific circuit is connected to the discrimination terminal  403 , the type or sort of the first battery pack  40  can be discriminated. 
     Next, a second battery pack  50  is explained below. 
     As shown in FIG. 2, the second battery pack  50  has approximately the same configuration as the first battery pack  40  except that a resistor  55  corresponding to the resistor  45  is connected across a power supply terminal  501  and a discrimination terminal  502 . 
     Specifically, the second battery pack  50  comprises a switch  51 , a protection circuit  52 , a Li-ion battery cell  53 , a thermistor  54 , a resistor  55 , a power-supply terminal  501 , a discrimination terminal  502 , a temperature detection terminal  503 , and a ground terminal  504 . The switch  51 , the protection circuit  52 , the cell  53 , the thermistor  54 , and the resistor  55  are provided in the enclosure (not shown) of the pack  50 . The power-supply terminal  501 , the discrimination terminal  502 , the temperature detection terminal  503 , and the ground terminal  504  are exposed to the outside from the enclosure. The battery cell  53  is different in characteristic from the battery cell  43 . 
     The positive terminal of the cell  53  is connected to the power-supply terminal  501  by way of the switch  51 . The negative terminal of the cell  53  is directly connected to the ground terminal  504 . The battery voltage V BAT2 , which is generated between the positive and negative terminals of the cell  53 , is outputted from the power-supply and ground terminals  501  and  504 . 
     The protection circuit  52  is supplied with the battery voltage V BAT2  from the cell  53 . The circuit  52  generates the switch control signal V SW2  on the basis of the voltage B BAT2  and then, supplies the signal V SW2  thus generated to the switch  51 . The ground terminal of the circuit  52  is connected to the ground terminal  504 . 
     The switch  51  serves to connect the positive terminal of the battery cell  53  to the power supply terminal  501  or disconnects the same from the terminal  501  according to the switch control signal V SW2  from the protection circuit  52 . 
     The resistor  55  is connected across the discrimination terminal  502  and the ground terminal  504 . 
     The thermistor  54  is connected across the temperature detection terminal  503  and the ground terminal  504 . To facilitate detection of the temperature of the cell  53 , the thermistor  54  is located in the vicinity of the battery cell  53  in the battery enclosure. 
     With the second battery pack  50  having the above-described configuration, similar to the first battery pack  40  shown in FIG. 1, the switch  51  is turned on or off by the control signal V SW2  generated by the protection circuit  52 , thereby controlling the output of the battery voltage V BAT2  from the power-supply and ground terminals  501  and  504 . Specifically, in the normal operation state where the voltage V BAT2  is equal to or higher than a specific value, the switch  51  is turned on by the control signal V CON2 , outputting the voltage V BAT2  through the terminals  501  and  504 . On the other hand, in the abnormal operation state where the voltage V BAT2  is less than the specific value, the switch  51  is turned off by the signal V SW2 , stopping the output of the voltage V BAT2  through the terminals  501  and  504 . 
     The resistance R TH2  of the thermistor  54  varies according to the temperature of the battery cell  53 . Thus, the similar to the first battery pack  40 , when a proper circuit that generates a voltage corresponding to the resistance R SW2  is connected to the temperature detection terminal  503 , the temperature of the cell  53  can be detected on the basis of the voltage thus generated. 
     When a specific circuit is connected to the discrimination terminal  503 , the type or sort of the second battery pack  50  can be discriminated. 
     Subsequently, the body of the mobile phone, i.e., the phone body  60 , is explained below with reference to FIG.  3 . 
     As shown in FIG. 3, the phone body  60  comprises a switch  61 , a charging controller  62 , two comparators  63  and  64 , a diode  65  for stopping the reverse current, four resistors  66 ,  67 ,  68 , and  69 , a power supply IC (Integrated Circuit)  70  with specific control functions, a power supply terminal  60 , a discrimination terminal  602 , a temperature detection terminal  603 , two ground terminals  604  and  606 , and a charging terminal  605 . The switch  61 , the charge control section  62 , two comparators  63  and  64 , the diode  65 , the resistors  66 ,  67 ,  68 , and  69 , and the power supply IC  70  are provided in the enclosures (not shown) of the body  60 . The power supply terminal  601 , the discrimination terminal  602 , the temperature detection terminal  603 , the ground terminals  604  and  606 , and the charging terminal  605  are exposed to the outside from the enclosure. The ground terminal  604  is used for connection of the first or second battery pack  40  or  50 . The ground terminal  606  is used for connection of a specific charging device. 
     The power supply terminal  601  is connected to the ground terminals  604  and  606  by way of the serially-connected resistors  66  and  67 . Also, the terminal  602  is connected to the charge input terminal  605  by way of the switch  61  and the diode  65 . The terminal  601  is further connected to the power supply IC  70  incorporated into the inside of the body  60 . 
     The serially-connected resistors  68  and  69  are connected parallel to the serially-connected resistors  66  and  67  between the power supply terminal  601  and the ground terminal  604 . 
     The discrimination terminal  602  is connected to the connection point of the resistors  68  and  69  and the input terminal of the first comparator  63 . The resistors  68  and  69  serve as a pull-up resistor and a pull-down resistor for the terminal  602 , respectively. The output terminal of the first comparator  63  is connected to the charging controller  62  and thus, the output signal V COMP1  of the first comparator  63  is inputted in to the controller  62 . 
     The temperature detection terminal  603  is connected to the connection point of the resistors  66  and  67  and the input terminal of the second comparator  64 . The resistors  66  and  67  serve as a pull-up resistor and a pull-down resistor for the terminal  603 , respectively. The output terminal of the second comparator  64  to connected to the charging controller  62  and thus, the output signal V COMP2  of the second comparator  64  is inputted in to the controller  62 . 
     The charging controller  62 , which is connected to the cathode of the diode  65  and the ground terminal  606 , receives the output signals V COM1  and V COM2  from the first and second comparators  63  and  64 . The charging controller  62  controls or adjusts the charge voltage V CHG  at the connection point of the switch  61  and the diode  65  on the basis of the output signal V COM1  of the first comparator  63  thus received. The charging controller  62  outputs the control signal V CW3  to the switch  61  on the basis of the output signal V COM2  of the second comparator  64  thus received. 
     The switch  61  serves to connect the diode  65  to the power supply terminal  601  or disconnect if from the terminal  601  according to the control signal V SW  sent from the controller  62 . 
     One of the first and second battery packs  10  and  50  is alternately connected to the phase body  60 , constituting the mobile phone. This phone to which the first or second battery pack  40  or  50  is connected operates in the following way. 
     FIG. 4 shows the configuration of the conventional mobile phone having the first battery pack  40 , in which the power supply terminal  401 , the discrimination terminal  402 , the temperature detection terminal  403 , and the ground terminal  404  of the first battery pack  40  are connected to the power supply terminal  601 , the discrimination terminal  602 , the temperature detection terminal  603 , and the ground terminal  604  of the phone body  60 , respectively. 
     When the phone body  60  is in its normal operation, the power supply terminal  601  is supplied with the first battery voltage V BAT1  of the first battery pack  40 . The first battery voltage V BAT1  thus supplied is then supplied to the power supply IC  70 , generating specific inner-circuit voltages with specific values. These inner-circuit voltages are respectively supplied to the inner circuit blocks of the phone body  60 , such as the ratio, display, and control sections (not shown). 
     The first battery voltage V BAT1  supplied by the first pack  40  is divided by the resistor  45  of the pack  40  and the resistors  68  and  69  of the body  60 , generating a first discrimination voltage V A  at the connection point of the resistor  68  and  69 . The first discrimination voltage V A , which has a relatively lower value, is inputted into the first comparator  63 . The first comparator  63  generates the output signal V COM1  having a logic value corresponding to the value of the discrimination voltage V A  thus inputted and then, sends the output signal V COM1  to the charging controller  62  of the phone body  60 . According to the output signal V COM1  thus sent, the controller  62  recognizes that the first battery pack  40  is connected to the body  60 . 
     On the other hand, when the phone body  60  is in its charging operation, a specific charging apparatus (not shown) is connected across the charging terminal  605  and the ground terminal  606 , supplying a charge current I CHG  to the body  60  through the terminal  605 . Part of the charge current I CHG  is sent to the charging controller  62  as a control current I COS , thereby generating the charge voltage V CHG  at the connection point of the switch  61  and the diode  65  in the body  60 . As explained above, the controller  62  is recognized that the first battery pack  40  has been connected to the body  60  and therefore, the controller  62  controls the value of the control current I CON  to thereby adjust the value of the charge voltage V CHG  according to the charge characteristic of the battery cell  43 . 
     The charge voltage V CHG  thus generated is outputted through the power supply terminal  601  by way of the switch  61  and then, is supplied to the battery cell  43  of the first battery pack  40  by way of the power supply terminal  401  and the switch  41 . As a result, a specific charging current is supplied to the cell  43  to charge the same. 
     The diode  65  of the body  60  serves to prevent the reverse current from flowing toward the charge apparatus from the cell  43 . 
     During the charging operation, the charging voltage V CHG  is divided by the thermistor  44  of the pack  40  and the resistors  66  and  67  of the body  60 , thereby generating the temperature detection voltage V B  that varies dependent on the resistance value R TH1  of the thermistor  44  at the connection point of the resistors  66  and  67 . The detection voltage V B  thus generated is then inputted into the second comparator  64  of the body  60 . The second comparator  64  generates the output signal V COM2  having a logic value corresponding to the detection voltage V B  thus inputted and then, sends the signal V COM2  to the charging controller  62 . Thus, the controller  62  controls the turn on and off operation of the switch  61  according to the signal V COM2  from the second comparator  64 . 
     When the cell  43  of the first battery pack  40  is excessively charged, the temperature of the cell  43  rises and the resistance R TH1  of the thermistor  44  decreases. Thus, the temperature detection voltage V D  at the connection point of the resistors  66  and  67  lowers. The second comparator  64  compares the value of the detection voltage V D  with the predetermined threshold value and then, outputs the output signal V COM2  having a specific logic value if the value of the detection voltage V D  is equal to or less than its threshold value. As a result, the charging controller  62  turns the switch  61  off to stop the charging operation toward the first battery pack  40 . 
     Next, the operation of the conventional mobile phone having the second battery pack  50  is explained with reference to FIG.  5 . 
     FIG. 5 shows the configuration of the conventional mobile phone with the second battery pack  50 , in which the power supply terminal  501 , the discrimination terminal  502 , the temperature detection terminal  503 , and the ground terminal  504  of the second battery pack  50  are connected to the power supply terminal  601 , the discrimination terminal  602 , the temperature detection terminal  603 , and the ground terminal  604  of the phone body  60 , respectively. 
     When the phone body  60  is in its normal operation, the power supply terminal  601  is supplied with the second battery voltage V BAT2  of the second battery pack  50 . The second battery voltage V BAT2  thus supplied is then supplied to the power supply IC  70 , generating the specific inner-circuit voltages will specific values. These inner-circuit voltages are respectively sent to the inner circuit blocks or the phone body  60 , such as the radio section, the display section, and the control section. This is the same as that of the first battery pack  40 . 
     The second battery voltage V BAT2  supplied by the second pack  50  is divided by the resistor  55  of the pack  50  and the resistors  68  and  69  of the body  60 , generating a second discrimination voltage V A ′ at the connection point of the resistors  68  and  69 . The second discrimination voltage V A ′, which has a higher value than the first discrimination voltage V A , is inputted into the first comparator  63 . The first comparator  63  generates the output signal V COM1  having a logic value corresponding to the value of the discrimination voltage V A ′ thus inputted and then, sends the output signal V COM1  to the charging controller  62  of the phone body  60 . According to the output signal V COM1  thus sent, the controller  62  recognizes that the second battery pack  50  is connected to the body  60 . 
     The charging operation is approximately the same as that using the first battery pack  40 . Specifically, when the phone body  60  is in its charging operation, a specific charging apparatus (not shown) is connected across the charge input terminal  605  and the ground terminal  606 . Thus, a charge current I CHG  is supplied to the body  60  through the terminal  605 . Part of the current I CHG  is sent to the charge controller  62  as the control current I CON , thereby generating the charge voltage V CHG  at the connection point of the switch  61  and the diode  65  in the body  60 . As explained above, the controller  62  is recognized that second battery pack  50  has been connected to the body  60  and therefore, the controller  62  controls the value of the control current I CON  to thereby adjust the value of the charge voltage V CHG  according to the charge characteristic of the battery cell  53 . 
     The charge voltage V CHG  thus generated is outputted through the power supply terminal  601  by way of the switch  61  and then, is supplied to the battery cell  53  of the second pack  50  by way of the power supply terminal  501  and the switch  51 . As a result, a specific current flows to the cell  53  to charge the same. 
     The diode  65  of the body  60  serves to prevent the reverse current from flowing toward the charge apparatus from the cell  53 . 
     During the charging operation, the charging voltage V CHG  is divided by the thermistor  54  of the pack  50  and the resistors  66  and  67  of the body  60 , thereby generating the temperature detection voltage V B ′ that varies dependent on the resistance value R TH2  of the thermistor  54  at the connection point of the resistors  66  and  67 . The detection voltage V B ′ thus generated is inputted into the second comparator  64  of the body  60 . The second comparator  64  generates the output signal V COM2  having a logic value corresponding to the voltage V B ′ thus inputted and then, sends the signal V COM2  to the charging controller  62 . Thus, the controller  62  controls the turn on and off operation of the switch  61  according to the signal V COM2  from the second comparator  64 . 
     When the cell  53  of the second battery pack  50  is excessively charged, the temperature of the cell  53  rises and the resistance of the thermistor  54  decreases. Thus, the temperature detection voltage V B ′ at the connection point of the resistors  66  and  67  decreases. The second comparator  61  compares the value of the detection voltage V B ′ with the predetermined threshold value and then, outputs the output signal V COM2  having a specific logic value if the value of the detection voltage V B ′ is equal to or less than its threshold value. As a result, the charging controller  62  turns the switch  61  off to stop the charging operation toward the second battery pack  50 . 
     As explained above in detail, with the conventional mobile phone shown in FIGS. 1 to  5 , the phone body  60  can recognize whether the first or second battery pack  40  or  50  is connected thereto according to the discrimination voltage V A  or V A ′ generated at the connection point of the resistors  68  and  69 , i.e., the discrimination terminal  602 . Also, the value of the charging voltage V CHG  is adjusted or controlled to be proper for the charging characteristic of the battery pack  40  or  50  recognized. 
     However, to discriminate between the first and second packs  40  and  50 , the discrimination-dedicated terminals  402 ,  502 , and  602  are essentially provided respectively in the first and second packs  40  and  50  and the phone body  60 . Thus, there arises a problem that the count of necessary terminals is large and therefore, the mobile phone is unable or difficult to be made more compact and light-weight. 
     SUMMARY OF THE INVENTION 
     Accordingly, an object of the present invention is to provide a method of detecting the type of a battery pack in a mobile electronic device that detects the type of a battery pack connected in a mobile electronic device even if no dedicated terminals are provided to a battery pack. 
     Another object of the present invention is to provide a mobile electronic device capable of detecting the type of a battery pack connected even if no dedicated terminals are provided to a battery pack. 
     Still another object of the present invention is to provide a method of detecting the type of a battery pack in a mobile electronic device that makes the device more compact and more light-weight easily. 
     A further object of the present invention is to provide a mobile electronic device that can be easily made more compact and more light-weight. 
     The above objects together with others not specifically mentioned will become clear to those skilled in the art from the following description. 
     According to a first aspect of the present invention, a method of detecting the type of a battery pack in a mobile electronic device is provided, which comprises the steps of: 
     (a) providing a first battery pack connectable to a body of a mobile electronic device; 
     the first battery pack having a battery cell, a first terminal connected to a high-potential side terminal of the cell, a second terminal connected to a low-potential side terminal of the cell, a third terminal, and a temperature detection element connected across the second and third terminals; 
     (b) providing a second battery pack connectable to the body of the device; 
     the second battery pack being different in characteristic from the first battery pack; 
     the second battery pack having a battery cell, a first terminal connected to a high-potential side terminal of the cell, a second terminal connected to a low-potential side terminal of the cell, a third terminal, and a temperature detection element connected across the first and second terminals; 
     (c) providing the body of the device with a fourth terminal connectable to the first terminal of the first or second battery pack, a fifth terminal connectable to the second terminal of the first or second battery pack, a sixth terminal connectable to the third terminal of the first or second battery pack; 
     the body of the device having a resistive voltage divider circuit connected among the fourth, fifth, and sixth terminals; 
     (d) connecting the first or second battery pack to the body of the device in such a way that the fourth, fifth, and sixth terminals of the body of the device are connected to the first, second, and third terminals of the first or second battery pack, respectively; 
     (e) detecting an output voltage of the resistive voltage divider of the body of the device, generating a detection result; and 
     (f) judging whether the first or second battery pack is connected to the body of the device base on the detection result. 
     With the method of detecting the type of a battery pack in a mobile electronic device according to the first aspect of the invention, the first and second battery packs connectable to the body of the mobile electronic device are provided. Each of the first and second packs has the battery cell, the first terminal connected to the high-potential side terminal of the cell, the second terminal connected to the low-potential side terminal of the cell, the third terminal, and the temperature detection element connected across the second and third terminals. 
     On the other hand, the body of the device is provided with the fourth terminal connectable to the first terminal of the first or second battery pack, the fifth terminal connectable to the second terminal of the first or second battery pack, the sixth terminal connectable to the third terminal of the first or second battery pack. The body of the device further has the resistive voltage divider circuit connected among the fourth, fifth, and sixth terminals. 
     When the first or second battery pack is connected to the body of the device in such a way that the fourth, fifth, and sixth terminals of the body of the device are connected to the first, second, and third terminals of the first or second battery pack, respectively, the output voltage of the resistive voltage divider is detected, generating the detection result. Thereafter, it is judged whether the first or second battery pack is connected to the body of the device based on the detection result. 
     Because the temperature detection element is connected across the second and third terminals in the first battery pack while the temperature detection element is connected across the first and second terminals in the second battery pack, the content of the detection result varies according to whether the first or second battery pack is connected to the body of the device. 
     Accordingly, the fact whether the first or second battery pack is connected to the body of the device can be detected (i.e., recognized). Thus means that the type of the first or second battery pack can be discriminated even if no dedicated terminals are provided to the first and second battery packs. Thus, the mobile electronic device can be made more compact and more light-weight easily. 
     In a preferred embodiment of the method according to the first aspect of the invention, each of the first and second battery packs comprises a circuit for detecting whether or not the battery cell is in its normal condition; and a switch for stopping an output of the battery cell if the battery cell is not in its normal condition. 
     In another preferred embodiment of the method according to the first aspect of the invention, the body of the device comprises first, second, and third comparators having threshold values different from each other; and a discrimination circuit for discriminating between the first and second battery packs. The first, second, and third comparators compares the output of the resistive voltage-divider circuit with their threshold values, generating an comparison result signal to the discrimination circuit. The discrimination circuit discriminates between the first and second battery packs based on the comparison result signal. 
     In this embodiment, it is preferred that the comparison result signal is a combination of three logic signals from the first, second, and third comparators. 
     According to a second aspect of the present invention, a mobile electronic device is provided, which comprises: 
     (a) a first battery pack connectable to a body of a mobile electronic device; 
     the first battery pack having a battery cell, a first terminal connected to a high-potential side terminal of the cell, a second terminal connected to a low-potential side terminal of the cell, a third terminal, and a temperature detection element connected across the second and third terminals; 
     (b) a second battery pack connectable to the body; 
     the second battery pack being different in characteristic from the first battery pack; 
     the second battery pack having a battery cell, a first terminal connected to a high-potential side terminal of the cell, a second terminal connected to a low-potential side terminal of the cell, a third terminal, and a temperature detection element connected across the first and second terminals; 
     (c) the body of the mobile electronic device having a fourth terminal, a fifth terminal, a sixth terminal, and a resistive voltage divider circuit connected among the fourth, fifth, and sixth terminals; 
     the first terminal of the first or second battery pack being connectable to the fourth terminal of the body, the second terminal of the first or second battery pack being connectable to the fifth terminal of the body, the third terminal of the first or second battery pack being connectable to the sixth terminal of the body; 
     (d) an output voltage of the resistive voltage divider of the body being detected to generate a detection result, when the first or second battery pack is connected to the body in such a way that the fourth, fifth, and sixth terminals of the body are connected to the first, second, and third terminals of the first or second battery pack, respectively; and 
     (e) whether the first or second battery pack is connected to the body is judged based on the detection result. 
     With the mobile electronic device according to the second aspect of the present invention, because of substantially the same reason as the method according to the first aspect of the invention, the fact that the first or second battery pack is connected to the body of the mobile electronic device can be detected (i.e., recognized) and discriminated without providing dedicated terminals for discriminating between the first and second battery packs. 
     Also, since no discrimination-dedicated terminals are required, the mobile electronic device according to the second embodiment can be easily made more compact and more light-weight. 
     In a preferred embodiment of the deice according to the second aspect of the invention, each of the first and second battery packs comprises a circuit for detecting whether or not the battery cell is in its normal condition; and a switch for stopping an output of the battery cell if the battery cell is not in its normal condition. 
     In another preferred embodiment of the device according to the second aspect of the invention, the body comprises first, second, and third comparators having threshold values different from each other; and a discrimination circuit for discriminating between the first and second battery packs. The first, second, and third comparators compares the output of the resistive voltage-divider circuit with their threshold values, generating an comparison result signal to the discrimination circuit. The discrimination circuit discriminates between the first and second battery packs based on the comparison result signal. 
     In this embodiment, it is preferred that the comparison result signal is a combination of three logic signals from the first, second, and third comparators. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In order that the present invention may be readily carried into effect, it will now be described with reference to the accompanying drawings. 
     FIG. 1 is a schematic, partial circuit diagram showing the configuration of the first battery pack of a prior-art mobile phone. 
     FIG. 2 is a schematic, partial circuit diagram showing the configuration of the second battery pack of the prior art mobile phone. 
     FIG. 3 is a schematic, partial circuit diagram showing the configuration of the body of the prior-art mobile phone. 
     FIG. 4 is a schematic, partial circuit diagram showing the configuration of the prior-art mobile phone, in which the first battery pack is connected to the phone body. 
     FIG. 5 is a schematic, partial circuit diagram showing the configuration of the prior-art mobile phone, in which the second battery pack is connected to the phone body. 
     FIG. 6 is a schematic, partial circuit diagram showing the configuration of the first battery pack of a mobile phone according to an embodiment of the invention. 
     FIG. 7 is a schematic, partial circuit diagram showing the configuration of the second battery pack of the mobile point according to the embodiment of FIG.  6 . 
     FIG. 8 is a schematic, partial circuit diagram showing the configuration of the body of the mobile phone according to the embodiment of FIG.  6 . 
     FIG. 9 is a schematic, partial circuit diagram showing the configuration of the mobile phone according to the embodiment of the invention, in which the first battery pack shown in FIG. 6 is connected to phone body shown in FIG.  8 . 
     FIG. 10 is a schematic, partial circuit diagram showing the configuration of the portable telephone according to the embodiment of the invention, in which the second battery pack shown in FIG. 7 is connected to the phone body shown in FIG.  8 . 
     FIG. 11 is a graph showing the relationship between the temperature detection voltage and the temperature of the first or second battery pack in the mobile phone according to the embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiment of the present invention will be described in detail below while referring to the drawings attached. 
     A mobile phone according to an embodiment of the present invention is shown in FIGS. 6 to  8 . 
     As shown in FIG. 6, a first battery pack  1  comprises a switch  11 , a protection circuit  12 , a Li-ion battery cell  18 , a thermistor  14 , a power-supply terminal (i.e., +V terminal)  101 , a temperature detection terminal (i.e., TH terminal)  102 , and a ground terminal (i.e., GND terminal)  103 . The switch  11 , the protection circuit  12 , the cell  13 , and the thermistor  14  are provided in the enclosure or casing (not shown) of the first battery pack  1 . The power-supply terminal  101 , the temperature detection terminal  102 , and the around terminal  103  are exposed to the outside from the enclosure. 
     The positive terminal of the battery cell  13  is connected to the power supply terminal  101  by way of the switch  11 . The negative terminal of the battery cell  13  is directly connected to the ground terminal  103 . The first battery voltage V BAT1 , which is generated between the positive and negative terminals of the cell  43 , is outputted from the power-supply and ground terminals  101  and  104 . 
     The protection circuit  12  is supplied with the first battery voltage V BAT1  from the cell  13 . The circuit  12  generates the switch control signal V SW1  on the basis of the battery voltage V BAT1  and then, supplies the control signal V SW1  thus generated to the switch  11 . The ground terminal of the circuit  12  is connected to the ground terminal  103 . 
     The switch  11  serves to connect the positive terminal of the first battery cell  13  to the power supply terminal  101  and disconnects the same from the terminal  101  according to the switch control signal V CON1  from the protection circuit  12 . 
     The thermistor  14  is connected to the temperature detection terminal  102  and the ground terminal  103 . The thermistor  14  is located in the vicinity of the battery cell  13  to facilitate detection of the temperature of the cell  13 . 
     With the first battery pack  1  having the above described configuration, the switch  11  is turned on or off by the control signal V SW1  generated by the protection circuit  12 , thereby controlling the output of the first battery voltage V BAT1  through the power supply terminals  101  and  103 . Specifically, in the normal operation state where the battery voltage V BAT1  is equal to or higher than a specific value, the switch  11  is turned on by the control signal V SW1 , outputting the battery voltage V BAT1  through the terminal  101 . On the other hand, in the abnormal operation state where the battery voltage V BAT1  is less than the specific value, the switch  11  is turned off by the control signal V SW1 , stopping the output of the battery voltage V BAT1  through the terminals  101  and  103 . 
     The resistance R TH1  of the thermistor  44  varies according to the temperature of the battery cell  13 . Thus, when a circuit generating a voltage corresponding to the resistance R TH1  is connected to the temperature detection terminal  102 , the temperature of the cell  13  can be detected on the basis of the voltage thus generated. 
     As explained later, the voltage corresponding to the resistance R TH1  of the thermistor  44  becomes lower as the temperature of the cell  13  rises. Also, the voltage corresponding to the resistance R TH1  can be set at a value equal to or greater than the specific threshold value. Accordingly, the first battery pack  1  can be recognized and discriminated by detecting the voltage corresponding to the resistance R TH1 . 
     FIG. 7 shows a second battery pack  2 , which has approximately the same configuration as the first battery pack  1 , except that a thermistor  24  corresponding to the thermistor  14  in the first pack  1  is connected across a power supply terminal  201  and a temperature detection terminal  202 . 
     Specifically, as shown in FIG. 7, the second battery pack  2  comprises a switch  21 , a protection circuit  22 , a Li-ion battery cell  23 , a thermistor  24 , a power-supply terminal  201 , a temperature detection terminal  202 , and a ground terminal  203 . The switch  21 , the protection circuit  22 , the cell  23 , and the thermistor  24  are provided in the enclosure (not shown) of the second battery pack  2 . The power-supply terminal  201 , the temperature detection terminal  202 , and the ground terminal  203  are exposed to the outside from the enclosure. 
     The battery cell  23  is different in characteristics from the battery cell  13  of the first battery pack  1 . The positive terminal of the battery cell  23  is connected to the power-supply terminal  201  by way of the switch  21 . The negative terminal of the battery cell  23  is directly connected to the ground terminal  203 . The second battery voltage V BAT2 , which is generated across the positive and negative terminals of the cell  23 , is outputted from the terminal  201  by way of the switch  21 . 
     The protection circuit  22  is supplied with the second battery voltage V BAT2  from the cell  23 . The circuit  22  generates the switch control signal V SW2  on the basis of the battery voltage V BAT2  and then, supplies the control signal V SW2  thus generated to the switch  21 . The ground terminal of the circuit  22  is connected to the ground terminal  203 . 
     The switch  21  serves to connect the positive terminal of the second battery cell  23  to the power supply terminal  201  and disconnects the same from the terminal  201  according to the switch control signal V SW2  from the protection circuit  22 . 
     Unlike the thermistor  14  in the first battery pack  1 , the thermistor  24  is connected across the temperature detection terminal  202  and the ground terminal  203 . The thermistor  24  is located in the vicinity of the battery cell  23  to facilitate detection of the temperature of the cell  23 . 
     With the second battery pack  2  having the above-described configuration, the switch  21  is turned on or off by the control signal V SW2  generated by the protection circuit  22 , thereby controlling the output of the second battery voltage V BAT2  from the power-supply and ground terminals  201  and  203 . Specifically, in the normal operation state where the second battery voltage V BAT2  is equal to or higher than a specific value, the switch  21  is turned on by the control signal V SW2 , outputting the battery voltage V BAT2  through the terminals  201  and  203 . On the other hand, in the abnormal operation state where the voltage V BAT2  is less than the specific value, the switch  21  is turned off by the control signal V SW2 , stopping the output of the voltage V BAT2  through the terminals  201  and  203 . 
     Similar to the first battery pack  1  shown in FIG. 6, the resistance R TH2  of the thermistor  24  varies according to the temperature of the battery cell  23 . Thus, when a circuit generating a voltage corresponding to the resistance R TH2  is connected to the temperature detection terminal  202 , the temperature of the cell  23  can be detected on the basis of the voltage thus generated. 
     As explained later, the voltage corresponding to the resistance R TH2  of the thermistor  24  becomes lower as the temperature of the cell  23  rises. Also, the voltage corresponding to the resistance R TH2  can be set at a value equal to or greater than the specific threshold value. Accordingly, the second battery pack  2  can be recognized and discriminated by detecting the voltage corresponding to the resistance R TH2 . 
     Subsequently, the body of the mobile phone according to the embodiment of the invention, i.e., the phone body  3 , is explained below with reference to FIG.  8 . 
     The phone body  3  comprises a switch  31 , a charge control section  32 , three comparators  33 ,  34 , and  35 , two resistors  36  and  37 , a diode  38  for stopping the reverse current, a power supply terminal  301 , a temperature detection terminal  302 , two ground terminals  303  and  306 , and a charge input terminal  305 . The switch  31 , the charge control section  32 , the comparators  33 ,  34 , and  35 , the resistors  36  and  37 , and the diode  38  are provided in the enclosure (not shown) of the body  3 . The power supply terminal  301 , the temperature detection terminal  302 , the ground terminals  303  and  306 , and the charge input terminal  305  are exposed to the outside from the enclosure. The ground terminal  303  is used for connection of the first and second battery packs  1  and  2 , respectively. The ground terminal  306  is used for connection of a specific charging apparatus. 
     The power supply terminal  301  is connected to the ground terminals  303  and  306  by way of the serially-connected resistors  36  and  37  and to the charge input terminal  305  by way of the switch  31  and the diode  38 . The terminal  301  is further connected to a power supply IC  39  with specific control functions incorporated into the inside of the body  3 . 
     The temperature detection terminal  302  is connected to the connection point of the resistors  36  and  37  and is connected to common to the input terminals of the first, second, and third comparators  33 ,  34 , and  35 . The resistors  36  and  37  serve as a pull-up resistor and a pull-down resistor for the terminal  302 , respectively. Those comparators  33 ,  34 , and  35  produce first, second, and third output signals V COM1 , V COM2 , and V COM3 , respectively, and supplies them to the charging controller  32 . 
     The charging controller  32  is connected between the cathode of the diode  38  and the ground terminal  306 . The charging controller  32  receives the first to third control signals V COM1 , V COM2 , and V COM3  outputted respectively from the first to third comparators  33 ,  34 , and  35  and discriminates whether the first or second battery pack  1  or  2  is connected to the body  3 . Also, the controller  32  adjusts the charge voltage V CHG  at the connection point of the switch  31  and the diode  38  according to the charging characteristic of the pack  1  or  2  connected. Moreover, the controller  32  generates the control signal V SW3  to the switch  31  according to the control signals V COM1 , V COM2 , and V COM3  from the first to third comparators  33 ,  34 , and  35 . 
     The switch  31  serves to connect the diode  38  to the power supply terminal  301  or disconnect the same from the terminal  301  according to the control signal V SW3  from the controller  32 . 
     One of the first and second battery packs  1  and  2  is alternately connected to the phone body  3 , constituting the mobile phone according to the embodiment of the invention. The operation of the phone having the first or second battery pack  1  or  2  connected is explained below. 
     FIG. 9 shows the configuration of the mobile phone having the first battery pack  1 , in which the power supply terminal  101 , the temperature detection terminal  102 , and the ground terminal  103  of the first battery pack  1  are connected to the power supply terminal  301 , the temperature detection terminal  302 , and the ground terminal  303  of the phone body  3 , respectively. 
     When the phone body  3  is in its normal operation, the first battery voltage V BAT1  of the first pack  1  is supplied across the power supply terminal  301  and the ground terminal  303 . The first battery voltage V BAT1  thus supplied is then supplied to the power supply IC  39 , generating specific inner-circuit voltages with specific values. These inner-circuit voltages thus generated are respectively sent to the inner circuit blocks of the phone body  3 , such as the radio section, the display section, and the control section. 
     The first battery voltage V BAT1  supplied by the first pack  1  is divided by the thermistor  14  of the pack  1  and the resistors  36  and  37  of the body  3 , generating a first temperature detection voltage V C1  at the connection point of the resistors  36  and  37  (i.e., at the temperature detection terminal  302 ). The temperature detection voltage V C1  thus generated is inputted commonly into the first to third comparators  33 ,  34 , and  35 . 
     The first, second, and third comparators  33 ,  34 , and  35  compare the first temperature detection voltage V C1  thus inputted with their predetermined threshold voltages V TH1 , V TH2 , and V TH3 , respectively. When the inputted detection voltage V C1  is greater than the threshold voltage V TH1 , V TH2 , or V TH3 , the comparators  33 ,  34 , and  35  produce the output signals V COM1 , V COM2 , and V COM3  with logic high (H) values and send them to the charging controller  32  of the phone body  3 , respectively. When the inputted voltage V C1  is less than the threshold voltage V TH1 , V TH2 , or V TH3 , the comparators  33 ,  34 , and  35  produce the output signals V COM1 , V COM2 , and V COM3  with logic low (L) values and send them to the charging controller  32 , respectively. According to these output signals V COM1 , V COM2 , and V COM3  thus sent, the charging controller  62  recognizes that the first battery pack  1  is connected to the body  3 . 
     On the other hand, when the phone body  3  is in its charging operation, a specific charging apparatus (not shown) is connected across the charge input terminal  305  and the ground terminal  306 . Thus, a charging current I CHG  is supplied to the body  3  through the terminal  305 . Part of the charging current I CHG  is sent to the charging controller  32  as control current I CON , thereby generating the charging voltage V CHG  at the connection point of the switch  31  and the diode  38  in the body  3 . As explained above, the controller  32  has recognized that the first battery pack  1  has been connected to the body  3  and therefore, the controller  32  controls the value of the control current I CON  to thereby adjust the value of the charging voltage V CHG  according to the charging characteristic of the battery cell  13  of the first pack  1 . 
     The charging voltage V CHG  thus generated is outputted from the terminals  301  and  303  of the body  3  by way of the switch  31  and then, is supplied to the battery cell  13  of the first pack  1  by way of the terminals  101  and  103  and the switch  11  of the pack  1 . As a result, a specific current flows to the cell  13  to charge the same. 
     Additionally, the diode  36  of the body  3  serves to prevent the reverse current from flowing toward the charge apparatus from the cell  13 . 
     During the charging operation, the charging voltage V CHG  is divided by the thermistor  14  of the pack  1  and the resistors  36  and  37  of the body  3 , thereby generating the temperature detection voltage V C1 ′ that varies dependent on the resistance value of the thermistor  14  at the connection point of the resistors  36  and  37  (i.e., the temperature detection terminal  302 ). The temperature detection voltage V C1 ′ thus generated is commonly inputted into the first to third comparators  33 ,  34 , and  35  of the body  3 . The first, second, and third comparators  33 ,  34 , and  35  generate the output signals V COM1 , V COM2 , and V COM3  having a logic value L or H corresponding to the result of comparison between the detection voltage V C1 ′ and the threshold voltage V TH1 , V TH2 , or V TH3  and then, it sends the output signals V COM1 , V COM2 , and V COM3  to the charging controller  32 . Thus, the controller  32  judges whether the cell  13  of the first battery pack  1  is excessively charged or not according to the output signals V COM1 , V COM2 , and V COM3 . If the controller  32  judges that the cell  13  is excessively charged, the controller  32  turns the switch  31  off immediately, thereby stopping the charging operation to the first pack  1 . 
     Next, the operation of the portable telephone having the second battery pack  2  is explained with reference to FIG.  10 . 
     FIG. 10 shows the configuration of the mobile phone having the second battery pack  2 , in which the power supply terminal  201 , the temperature detection terminal  202 , and the ground terminal  203  of the second battery pack  2  are connected to the power supply terminal  301 , the temperature detection terminal  302 , and the ground terminal  303  of the phone body  3 , respectively. 
     The operation of the portable telephone using the second pack  2  is approximately the same as that using the first pack  1 . 
     Specifically, when the phone body  3  is in its normal operation, the second battery voltage V BAT2  of the second pack  2  is supplied across the power supply terminal  301  and the ground terminal  303 . The second battery voltage V BAT2  thus supplied is then supplied to the power supply IC  39 , generating specific inner-circuit voltages with specific values. These inner-circuit voltages thus generated are respectively sent to the inner circuit blocks of the phone body  3 , such as the radio section, the display section, and the control section. 
     The second battery voltage V BAT2  supplied by the second pack  2  is divided by the thermistor  24  of the pack  2  and the resistors  36  and  37  of the body  3 , generating a second temperature detection voltage V C2  at the connection point of the resistors  36  and  37  (i.e., at the temperature detection terminal  302 ). The temperature detection voltage V C2  thus generated is inputted commonly into the first to third comparators  33 ,  34 , and  35 . 
     The first, second, and third comparators  33 ,  34 , and  35  compare the second temperature detection voltage V C2  thus inputted with their predetermined threshold voltages V TH1 , V TH2 , and V TH3 , respectively. When the inputted detection voltage V C2  is greater than the threshold voltage V TH1 , V TH2 , or V TH3 , the comparators  33 ,  34 , and  35  produce the output signals V COM1 , V COM2 , and V COM3  with logic H values and send them to the charging controller  32  of the phone body  3 , respectively. When the inputted voltage V C2  is less than the threshold voltage V TH1 , V TH2 , or V TH3 , the comparators  33 ,  34 , and  35  produce the output signals V COM1 , V COM2 , and V COM3  with logic L values and send them to the charging controller  32 , respectively. According to these output signals V COM1 , V COM2 , and V COM3  thus sent, the charging controller  32  recognizes that the second battery pack  2  is connected to the body  3 . 
     On the other hand, when the phone body  3  is in its charging operation, a specific charging apparatus (not shown) is connected across the charge input terminal  305  and the ground terminal  306 . Thus, a charging current I CHG  is supplied to the body  3  through the terminal  305 . Part of the charging current I CHG  is sent to the charging controller  32  as a control current I CON , thereby generating the charging voltage V CHG  at the connection point of the switch  31  and the diode  38  in the body  2 . As explained above, the controller  32  has recognized that second battery pack  2  has been connected to the body  3  and therefore, the controller  32  controls the value of the control current I CON  to thereby adjust the value of the charging voltage V CHG  according to the charging characteristic of the battery cell  23  of the second pack  2 . 
     The charging voltage V CHG  thus generated is outputted from the terminals  301  and  303  of the body  3  by way of the switch  31  and then, it supplied to the battery cell  23  of the second pack  2  by way of the terminals  201  and  203  and the switch  21  of the pack  2 . As a result, a specific current flows to the cell  23  to charge the same. 
     During the charging operation, the charging voltage V CHG  is divided by the thermistor  24  of the pack  2  and the resistors  36  and  37  of the body  3 , thereby generating the temperature detection voltage V C2 ′ that varies dependent on the resistance value of the thermistor  24  at the connection point of the resistors  36  and  37  (i.e., the temperature detection terminal  302 ). The temperature detection voltage V C2 ′ thus generated is commonly inputted into the first to third comparators  33 ,  34 , and  35  of the body  3 . The first, second, and third comparators  33 ,  34 , and  35  generate the first, second, and third output signals V COM1 , V COM2 , and V COM3  having a logic value L or H corresponding to the result of comparison between the voltage V C2 ′ and the threshold voltage V TH1 , V TH2 , or V TH3  and then, it sends the output signals V COM1 , V COM2 , and V COM3  to the charging controller  32 . Thus, the controller  32  judges whether the cell  23  of the second battery pack  2  is excessively charged or not according to the output signals V COM1 , V COM2 , and V COM3 . If the controller  32  judges that the cell  23  is excessively charged, the controller  32  turns the switch  31  off immediately, thereby stopping the charging operation to the second pack  2 . 
     Next, the operation of the first to third comparators  33 ,  34 , and  35  and the charging controller  32  of the phone body  3  is explained in detail below with reference to FIG.  11 . 
     FIG. 11 shows the relationship between the temperature of the first and second battery packs  1  and  2  (i.e., the battery cells  13  and  23 ) and the first and second temperature detection voltages V C1  and V C2 , in which the ordinate and abscissa denotes the temperature detection voltage and the battery pack temperature, respectively. 
     The curve I in FIG. 11 shows the change of the temperature detection voltage when the first battery pack  1  is connected to the body  3 . The curve II in FIG. 11 shows the same change when the second battery pack  2  is connected to the body  3 . 
     Here, for the sake of simplification of description, it is supposed that the first and second battery voltages V BAT1  and V BAT2  of the battery packs  1  and  2  and the charging voltage V CHG  are equal to a specific voltage value V (i.e., V BAT1 −V BAT2 −V CHG −v). In other words, it is supposed that the first temperature detection voltages V C1  and V C1 ′ are equal to the second temperature detection voltages V C2  and V C2 ′ (i.e., V C1 =V C1 ′=V C2 =V C2 ′). 
     The temperature t 1  shown in FIG. 11 is determined to ensure the safety of users with respect to the first and second battery packs  1  and  2 . The phone body  3  turns the switch  36  off to stop the charging operation if the battery pack temperature exceeds the temperature t 1 . The temperature t 2  shown in FIG. 11 is the upper limit temperature that assures the normal operation of the body  3 . 
     The value of the first temperature detection voltage V C1  of the first pack  1  at the temperature t 1  is defined as v 1  and the value of the second temperature detection voltage V C2  of the second pack  2  at the temperature t 1  is defined as V 2 . Moreover, the second temperature detection voltage V C3  is adjusted not to be greater than the voltage (V/ 2 ) at the temperature t 2 . The first temperature detection voltage V C1  is adjusted not to be less than the voltage (V/ 2 ) at the temperature t 2 . 
     the resistance values of the thermistors  14  and  24  of the first and second packs  1  and  2  and the pull-up and pull-down resistors  36  and  37  of the phone body  3  are determined so as to satisfy the relationship between the temperature of the battery packs  1  and  2  and the temperature detection voltages V C1  and V C2 . On the other hand, the values of the threshold voltages V TH1 , V TH2 , and V TH3  of the first, second, and third comparators  33 ,  34 , and  35  are set at V 1 , V 2 , and (V/ 2 ), respectively. 
     When the first battery pack  1  is connected to the phone body  3 , the mobile phone according to the embodiment of the invention operates in the following way. 
     The thermistor  14  of the pack  1  has a semiconductor resistive element having a negative temperature coefficient and therefore, the resistance value of the thermistor  14  decreases as the temperature rises. Thus, the resistance value of the thermistor  14  is large within the lower temperature range where the temperature of the pack  1  is lower than t 1 . Accordingly, the first temperature detection voltages V C1  (i.e., the divided voltage by the resistive voltage-divider circuit comprising the thermistor  14  and the resistors  36  and  37 ) is high. 
     As a result, as shown by the curve I in FIG. 11, the first temperature detection voltage V C1  varies within the range from V to V 1  when the temperature of the first pack  1  is equal to or less than t 1 . In this case, the first temperature detection voltage V C1  is equal to or higher than all the threshold voltages V TH1 , V TH2 , and V TH3  of the first to third comparators  33 ,  34 , and  35  and thus, all the first to third output voltages V COM1 , V COM2 , and V COM3  of the comparators  33 ,  34 , and  35  have the H level values. Consequently, according to the first to third output voltages V COM1 , V COM2 , and V COM3  applied, the charging controller  32  of the body  3  recognizes that the first battery pack  1  is connected to the body  3  and at the same time, the pack  1  is chargeable, thereby turning the switch  31  on. 
     On the other hand, when the temperature of the first pack  1  is in the high temperature range where the temperature is greater than t 1 , the resistance value of the thermistor  14  is lower than the above-described case that the temperature of the first pack  1  is equal to or less than t 1 . Thus, as shown by the curve I in FIG. 11, the first temperature detection voltages V C1  varies within the range from V 1  to (V/ 2 ). In this case, the first temperature detection voltages V C1  is equal to or higher than the threshold voltages V TH2  and V TH3  of the second and third comparators  34  and  35  and therefore, the second and third output voltages V COM2  and V COM3  have the H level values. Also, the first temperature detection voltages V C1  is less than threshold voltages V TH1  of the first comparator  33  and therefore, the first output voltage V COM1  has the L level value. Consequently, according to the first to third output voltages V COM1 , V COM2 , and V COM3  applied, the charging controller  32  of the body  3  recognizes that the first battery pack  1  is connected to the body  3  and at the same time, the pack  1  is not chargeable, thereby turning the switch  31  off. 
     Next, the operation of the mobile phone according to the embodiment having the second battery pack  2  is explained below. 
     Since the thermistor  24  of the pack  2  also has a semiconductor resistive element having a negative temperature coefficient, the resistance value of the thermistor  24  decreases as the temperature rises. Thus, the resistance value of the thermistor  24  is large within the lower temperature range where the temperature of the pack  2  is lower than t 1 . Accordingly, the first temperature detection voltages V C2  (i.e., the divided voltage by the resistive voltage-divider circuit comprising the thermistor  24  and the resistors  36  and  37 ) is low. 
     As a result, as shown by the curve II in FIG. 11, the second temperature detection voltages V C2  varies within the range from 0 to V 2  when the temperature of the second pack  2  is equal to or less than t 1 . In this case, the first temperature detection voltages V C2  is equal to or less than the threshold voltages V TH1 , V TH2 , and V TH3  of the first to third comparators  33 ,  34 , and  35  and thus, all the first to third output voltages V COM1 , V COM2 , and V COM3  of the first to third comparators  33 ,  34 , and  35  have the L level values. Consequently, according to the first to third output voltages V COM1 , V COM2 , and V COM3  applied, the charging controller  32  of the body  3  recognizes that the second battery pack  2  is connected to the body  3  and at the same time, the pack  2  is chargeable, thereby turning the switch  31  on. 
     On the other hand, when the temperature of the second pack  2  is greater than t 1 , the resistance value of the thermistor  24  is lower than the above-described case that the temperature of the second pack  2  is equal to or less than t 1 . Thus, as shown by the curve II in FIG. 11, the first temperature detection voltages V C2  varies within the range from (V/ 2 ) to V 2 . In this case, the second temperature detection voltage V C2  is less than the threshold voltages V TH1  and V TH3  of the first and third comparators  33  and  35  and therefore, the first and third output voltages V COM1  and V COM3  have the L level values. Also, the second temperature detection voltages V C2  is equal to or greater than the threshold voltages V TH2  of the second comparators  34  and therefore, the second output voltage V COM2  has the H level value. Consequently, according to the first to third output voltages V COM1 , V COM2 , and V COM3  applied, the charging controller  32  of the body  3  recognizes that the second battery pack  2  is connected to the body  3  and at the same time, the pack  2  is not chargeable, thereby turning the switch  31  off. 
     The above-explained operation of the first to third comparators  33 ,  34 , and  35  and the charging controller  32  of the phone body  3  can be summarized as shown in the Table 1 listed below. 
     
       
         
               
               
               
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                   
                   
                 Comparator Output 
                   
               
               
                   
                   
                 Level 
                 Charging 
               
             
          
           
               
                   
                 Temp. 
                 First 
                   
                 Third 
                 Controller 
               
               
                   
                 Detect. 
                 Compara- 
                 Second 
                 Compara- 
                 Judgment 
               
             
          
           
               
                 Case 
                 Voltage 
                 tor 
                 Comparator 
                 tor 
                 Battery 
                 Charge- 
               
               
                 No. 
                 [V] 
                 33 
                 34 
                 35 
                 Pack 
                 ability 
               
               
                   
               
               
                 1 
                 0˜V2 
                 L 
                 L 
                 L 
                 2nd 
                 Able 
               
               
                 2 
                 V2˜V/2 
                 L 
                 H 
                 L 
                 2nd 
                 Unable 
               
               
                 3 
                 V/2˜V1 
                 L 
                 H 
                 H 
                 1st 
                 Unable 
               
               
                 4 
                 V1˜V 
                 H 
                 H 
                 H 
                 1st 
                 Able 
               
               
                   
               
             
          
         
       
     
     As seen from Table 1, the charging controller  32  can recognize whether the first or second battery pack  1  or  2  is connected to the phone body  3  according to the combination of the logic values of the output voltages V COM1 , V COM2 , and V COM3  of the first to third comparators  33 ,  34 , and  35 . Moreover, the controller  32  can recognize which temperature range the first and second packs  1  and  2  belongs to and whether they are chargeable or not. 
     Accordingly, with the mobile phone according to the embodiment of the invention, dedicated terminals for discriminating the type of the first and second battery packs  1  and  2  are unnecessary and therefore, the count of the necessary terminals can be decreased in the packs  1  and  2  and the body  3 . This means that the mobile phone can be made more compact and more light-weight easily. 
     In the above-explained embodiment of the invention, the invention is applied to a mobile phone and a thermistor is used as the temperature detection device. However, it is needless to say that the invention is not limited to this case and it can be applied to any other mobile or portable electronic devices and that any other type of temperature detection devices may be used for this purpose. 
     Furthermore, three comparators  33 ,  34 , and  35  are used for discrimination of the type of battery packs in the above-explained embodiment of the invention. However, any other configuration may be used for this purpose. 
     While the preferred forms of the present invention have been described, it is to be understood that modifications will be apparent to those skilled in the art without departing from the spirit of the invention. The scope of the present invention, therefore, is to be determined solely by the following claims.