Abstract:
An electronic apparatus system includes a battery pack housing batteries and a battery pack connection section connecting the battery pack to the electronic apparatus, the electronic apparatus operable with one of electric power from an external power supply and electric power from the battery pack. A pseudo battery pack includes a power holding unit holding electric power to be supplied to the electronic apparatus, wherein if the external power supply is used and the external power supply fails to supply the electric power, the pseudo battery pack is mounted on the battery pack connection section.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a battery pack, which is mounted on a portable type of electronic apparatus such as a note type of personal computer, a PDA, a mobile personal computer, or another type of electronic apparatus, a pseudo battery pack modeled on the battery pack, an electronic apparatus, and an electronic apparatus system. 
     2. Description of the Related Art 
     Different types portable of electronic apparatuses, such as notebook computers and the like are arranged so that they are operable by electric power obtained from an external power supply, for example, a commercial power supply via an AC adapter, a car adapter wherein voltage from a car battery is converted into regular voltage, or a battery pack incorporated in the computer as well. Here, a notebook personal computer will be explained by way of example. 
     A battery pack is very convenient for a user who often uses the personal computer where an external power supply, such as a commercial power supply is not available. There are, however, many users who use the personal computer as a desk computer. 
     Recently, as the higher-level function and the higher speed of processing are required of the personal computer, the dissipation power of the personal computer is increased, while miniaturization of an AC adapter is required because of improvement of portability of the personal computer. Miniaturization of an AC adapter is implemented, to some extent, through improvement of efficiency for a control circuit. However, as larger tolerance and miniaturization of the AC adapter are implemented, it becomes difficult to expect an assurance for a momentary power cut of the external power supply, such as the commercial power supply by the AC adapter. Specifically, to ensure operation of the personal computer for the momentary power cut from the external power supply, such as the commercial power supply, there is a need to store energy at a predetermined level ensuring operation of the personal computer until the power supply is recovered. However, in view of the tendency that the dissipation power of the personal computer is increased and the AC adapter is miniaturized, it is difficult to make the AC adapter to ensure operation during the momentary power cut. In view of the foregoing, in general AC adapters do not ensure operation during the momentary power cut of the external power supply such as the commercial power supply. 
     The personal computer is an electronic apparatus in which it is essentially expected that a battery pack is mounted therein, assuring operation during the momentary power cut of the external power supply such as the commercial power supply, the battery pack rather than the AC adapter provides power to the personal computer. 
     However, because typical battery packs incorporate thereinto secondary batteries, these battery packs are relatively expensive. The secondary battery is an expendable source and is not long in life time. Also the battery pack is large in load for the user who uses the personal computer on a desk, where the battery pack is mounted for momentary power cuts. 
     SUMMARY OF THE INVENTION 
     It is intended that an AC adapter is minimized, it is considered that the current (rated current), which can be derived from the AC adapter, is decreased. A notebook personal computer is not operated always at a constant power, but is usually operated at a current level, which is considerably lower than a current of a level near the rated current. Consequently, the battery pack is mounted on the personal computer where the rated current of the AC adapter is lowered, and when the personal computer is operated in the usual low current level, the secondary battery of the battery pack is charged. When a large current is needed instantaneously, a shortage of the current capacity of the AC adapter is complemented with the secondary battery in the battery pack. In this manner, it is ensured that the battery pack is mounted on the personal computer and it is possible to miniaturize the AC adapter through lowering the rated current of the AC adapter. In this case, however, it is obliged to mount the battery pack on the personal computer. Thus, this case also brings about too much load for a user who uses the personal computer on a desk. 
     In view of the foregoing, it is an object of the present invention to measure a momentary power cut and a large current, which will be needed momentarily, upon reducing a load. 
     An electronic apparatus system, including: a battery pack housing batteries; a battery pack connection section connecting the battery pack to the electronic apparatus, the electronic apparatus operable with one of electric power from an external power supply and electric power from the battery pack; and a pseudo battery pack including a power holding unit holding electric power to be supplied to the electronic apparatus, wherein if the external power supply is used and the external power supply fails to supply the electric power, the pseudo battery pack is mounted on the battery pack connection section. 
     An electronic apparatus system, including: a battery pack housing batteries; a battery pack connection section connecting the battery pack to the electronic apparatus, the electronic apparatus operable with one of electric power from an external power supply and electric power from the battery pack; and a pseudo battery pack including a power holding unit holding electric power to be supplied to the electronic apparatus, wherein if the external power supply is used and the external power supply is short in supplying electric power, the pseudo battery pack is mounted on the battery pack connection section. 
     A battery pack in an electronic apparatus including a battery pack connection section connecting the battery pack, the electronic apparatus being operable with one of electric power from an external power supply and electric power from the battery pack, the battery pack including: a battery; and a power holding unit holding electric power to be supplied to the electronic apparatus when the external power supply is short in power supply. 
     An electronic apparatus operative with electric power from an external power supply, the electronic apparatus including: a power holding unit charged with electric power from the external power supply to hold electric power to be supplied to the electronic apparatus, when the external power supply fails to supply the electric power; a charging path preventing or reducing in-rush current and charging the power holding unit upon receipt of a supply of the electric power from the external power supply; and a power supplying path supplying charged electric power stored in the power holding unit to the electronic apparatus while preventing a backflow of the power, the power supplying path being different from the charging path. 
     An electronic apparatus operative with electric power from an external power supply, the electronic apparatus including: a power holding unit charged with electric power from the external power supply to hold electric power to be supplied to the electronic apparatus, when the external power supply is short in power supply; a charging path preventing or reducing in-rush current and charging the power holding unit upon receipt of a supply of the electric power from the external power supply; and a power supplying path supplying charged electric power stored in the power holding unit to the electronic apparatus while preventing a backflow of the power, the power supplying path being different from the charging path. 
     A pseudo battery pack for an electronic apparatus, including: a battery pack mounting section to which a battery pack for housing batteries is detachably mounted, the electronic apparatus being operable with one of electric power from an external power supply and electric power from the battery pack, wherein the pseudo battery pack includes capacitors connected in parallel, and the pseudo battery pack is mounted on the battery pack mounting section. 
     An electronic apparatus system, including: a battery pack housing batteries; an electronic apparatus including a battery pack mounting section to which the battery pack is detachably mounted, the electronic apparatus being operable with one of electric power from an external power supply and electric power from the battery pack; and a pseudo battery pack including capacitors connected in parallel, the pseudo battery pack being mounted on the battery pack mounting section. 
     A system, including: an electronic apparatus; a pseudo battery pack; and a battery pack housing batteries detachably mounted to the electronic apparatus, the electronic apparatus being operable with one of electric power from an external power supply and electric power from the battery pack, wherein the pseudo battery pack includes capacitors connected in parallel, and the pseudo battery pack includes substantially same configuration as the battery pack. 
     An electronic apparatus system, including: an electronic apparatus; a battery pack housing batteries detachably mounted to the electronic apparatus, the electronic apparatus being operable with one of electric power from an external power supply and electric power from the battery pack; and a pseudo battery pack including capacitors connected in parallel, the pseudo battery pack including substantially same configuration as the battery pack, and being detachably mounted on the electronic apparatus. 
     An electronic apparatus system, including: a battery pack housing secondary batteries; an electronic apparatus to which the battery pack is detachably mounted, the electronic apparatus being operable with one of electric power from an external power supply and electric power from the battery pack; and a pseudo battery pack including capacitors connected in parallel, the pseudo battery pack including substantially same configuration as the battery pack, and being detachably mounted on the electronic apparatus. 
     A system, including: a battery pack housing batteries; an electronic apparatus to which the battery pack is detachably mounted, the electronic apparatus being operable with one of electric power from an external power supply and electric power from the battery pack; and a capacitor in the battery pack connected in parallel with the housed batteries. 
     An electronic apparatus operative with electric power from an external power supply, the electronic apparatus, including: a capacitor charged with electric power from the external power supply and supplying a charged electric power to the electronic apparatus to operate during a predetermined time, when the external power supply fails to supply the electronic power; a charging path preventing or reducing in-rush current and charging the capacitor upon receipt of a supply of the electric power from the external power supply; and a power supplying path supplying charged electric power stored in the capacitor while preventing a backflow of the power, the power supplying path being different from the charging path. 
     An electronic apparatus operative with electric power from an external power supply, the electronic apparatus, including: a capacitor charged with electric power from the external power supply and supplying a charged electric power to the electronic apparatus to operate during a predetermined time, when the external power supply is short in power supply; a charging path preventing or reducing in-rush current and charging the capacitor upon receipt of a supply of the electric power from the external power supply; and a power supplying path supplying charged electric power stored in the capacitor while preventing a backflow of the power, the power supplying path being different from the charging path. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above objects and advantages will be more apparent by describing the preferred embodiment of the present invention with reference to the accompanied reference drawings, in which: 
     FIG. 1 is a schematic diagram of a system comprising a note type of personal computer, a battery pack, and a pseudo battery pack. 
     FIG. 2 is a block diagram showing a circuit structure of a power supply section in a state that a battery pack is mounted on a personal computer. 
     FIG. 3 is a block diagram showing a circuit structure of a power supply section where a pseudo battery pack is mounted on a personal computer. 
     FIG. 4 is a circuit diagram of an internal structure of a charger shown in FIGS. 2 and 3. 
     FIG. 5 is a circuit diagram of an internal structure of a DC—DC converter shown in FIGS. 2 and 3. 
     FIG. 6 is a block diagram showing an internal structure of a control circuit of a DC—DC converter shown in FIG.  5 . 
     FIG. 7 is a block diagram showing a circuit structure of a power supply section in a state that a pseudo battery pack is mounted on a note type of personal computer, in a system according to a second embodiment. 
     FIG. 8 is a block diagram showing a circuit structure of a power supply section in a state that a battery pack is mounted on the personal computer, in a system according to a second embodiment. 
     FIG. 9 is a circuit diagram showing an example of a constant current source provided on the battery pack and the pseudo battery pack shown in FIGS. 7 and 8, respectively. 
     FIG. 10 is a diagram showing an embodiment of a battery pack according to the present invention. 
     FIG. 11 is a circuit diagram of a power supply section of a note type of personal computer, which is an embodiment of an electronic apparatus according to the present invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Embodiments of the present invention will be described with reference to the accompanying drawings. 
     FIG. 1 is a schematic diagram of a system comprising a personal computer, such as a notebook personal computer, a battery pack, and a pseudo battery pack. 
     The personal computer  100  is provided with a battery pack mounting slot  101  which is an example of a battery pack mounting section. A battery pack  200  is mounted through the battery pack mounting slot  101 . Further, it is possible to mount on the battery pack mounting slot  101  a pseudo battery pack  300  having the substantially same configuration as the battery pack  200 , instead of the battery pack  200 . 
     In FIG. 1, it is possible to mount on the battery pack mounting slot  101  a pseudo battery pack  300  having the substantially same configuration as the battery pack  200 . The pseudo battery pack has substantially the same configuration as the battery pack, but it is not restricted to this configuration. As far as it is possible to mount a pseudo battery pack on the battery pack mounting slot  101 , which is an example of the battery pack mounting section of the electronic apparatus, it is acceptable that the pseudo battery pack  300  has any other types of configurations which are not substantially same as the battery pack  200 . For example, it is acceptable that the pseudo battery pack  300  has thinner configuration, shorter configuration, smaller configuration or thicker configuration than the battery pack  200 . Particularly, in such a type of electronic apparatus where the battery pack  200  is inserted from a side of a cover member into an insertion slot, and the battery pack  200  is completely housed inside the electronic apparatus, those features are effective. According to the personal computer  100  shown in FIG. 1, the bottom of the battery pack  200  forms the bottom of the personal computer  100  when the battery pack  200  is mounted. Thus, in this case, the pseudo battery pack  300  may have substantially the same configuration as the battery pack  200 . However, in the event that the bottom of the battery pack  200  does not form the bottom of the personal computer  100 , it is acceptable that the pseudo battery pack  300  does not have substantially the same configuration as the battery pack  200 . Further, as shown in FIG. 1, even in a case where the battery pack  200  is mounted on the bottom, it is acceptable that the pseudo battery pack  300 , which is larger than the battery pack  200 , is used to provide a tilt function. As mentioned above, the present invention does not exclude a case where the pseudo battery pack  300  is different in shape from the battery pack  200 . 
     FIG. 2 is a block diagram showing a circuit structure of a power supply section in a state that a battery pack is mounted on the personal computer, such as a notebook personal computer. 
     An AC adapter  110  is attached or connected to the note type of personal computer  100 . The AC adapter  110  has a function where electric power of the external power supply, such as a commercial power supply  11  is converted into electric power of DC voltage of, for example, 16.0V, and then supplied to a power supply section  120 . The electric power supplied from the AC adapter  110  to the power supply section  120  of the personal computer  100  is supplied via a charger  121  to the battery pack  200 , and is also supplied via a diode D 1  to a DC—DC converter  123 . 
     According to the present embodiment, as a preferable embodiment, there is shown the AC adapter  110  by way of example. However, it is acceptable that electric power is supplied from a car battery adapter for converting a voltage of a car battery. 
     Further it is noted that the external power supply is not restricted to the commercial power supply, and it is acceptable that a car battery is adopted as the external power supply. 
     The battery pack  200  houses therein total six chargeable secondary batteries E 11 , E 12 , E 13 , E 21 , E 22  and E 23  connected as shown in FIG. 2. A comparator COMP 1 , which is provided on the power supply section  120  of the personal computer  100 , compares a voltage from the external power supply such as the AC adapter  110  with a reference voltage e 1 , so that it is determined whether electronic power is supplied from the commercial power supply  11  via the AC adapter  110 . A comparator COMP 2  compares a voltage from the battery pack  200  with a reference voltage e 2 , so that it is determined whether the battery pack  200  is mounted. Determination results of the comparators COMP 1  and COMP 2  are fed to a charge control unit  122 . The charge control unit  122  activates a charger  121  in accordance with the determination results in the event that the power is supplied from the AC adapter  110 , and the battery pack  200  is mounted. The charger  121  charges, upon receipt of control of the charge control unit  122 , the secondary batteries E 11 , E 12 , E 13 , E 21 , E 22  and E 23  of the battery pack  200  with the electric power from the AC adapter  110 . 
     The power from the AC adapter  110  is transferred via the diode D 1  to the DC—DC converter  123 . The DC—DC converter  123  converts the power from the AC adapter  110  into an electric power of a voltage to be used by the personal computer  100 . According to the embodiment shown in FIG. 2, there are provided two lines of output from the DC—DC converter  123 . This means that the DC—DC converter  123  generates powers of two types of voltage mutually different. Capacitor C 1 , which is disposed at the input side of the DC—DC converter  123 , and capacitors C 2  and C 3 , which are disposed at the output side of the DC—DC converter  123  are capacitors for voltage stabilizing. The electric powers generated in the DC—DC converter  123  are supplied to associated circuits, which are operative with the associated voltages, respectively, in the personal computer  100  in accordance with the voltages. 
     When the AC adapter  110  is not connected, power (e.g. power of 12.6V or so) of the secondary batteries E 11 , E 12 , E 13 , E 21 , E 22  and E 23  housed in the battery pack  200  is converted through the diode D 2  by the DC—DC converter  123  into a predetermined voltage of power, so that the converted power is supplied to the associated circuit of the note type of personal computer  100 . 
     This is the same also in the event that the momentary power cut occurs on the external power supply such as the commercial power supply  11 . The note type of personal computer  100  continues to operate during the momentary power cut upon receipt of the power from the battery pack  200 . The above-mentioned momentary power cut is an example in the event that power is not supplied from the external power supply. Further, in the even that while the AC adapter  110  is sufficient for supplying power corresponding to the steady-state dissipation power of the note type of personal computer  100 , the AC adapter  110  is insufficient for supplying a momentary peak power needed for an operation of the note type of personal computer  100 , the battery pack  200  has a function of supplementing the shortage of the supplying power from the AC adapter  110  at a timing where the momentary peak power is needed. The timing where the momentary peak power is needed is an example of a case where a power supply ability of the external power supply is insufficient. 
     FIG. 3 is a block diagram showing a circuit structure of a power supply section in a state that a pseudo battery pack is mounted on the personal computer. 
     A different point of the circuit structure of a power supply section from the circuit structure shown in FIG. 2 resides in the point that the battery pack  200  shown in FIG. 2 is replaced by a pseudo battery pack  300 . The pseudo battery pack  300  incorporates therein a plurality of capacitors C 11 , C 12 , . . . C 1 n which are connected in parallel. 
     In the event that the pseudo battery pack  300  shown in FIG. 3, instead of the battery pack  200  shown in FIG. 2, is mounted on the note type of personal computer  100 , it is impossible to operate the personal computer  100  in a state that the AC adapter  110  is removed from the personal computer  100 . However, in the event that the personal computer  100  is used as a desktop computer there is no problem. That is, when momentary power cut occurs on the external power supply such as the commercial power supply  11 , it is possible to continue to operate the personal computer  100  by electric power stored in the internal capacitors C 11 , C 12 , . . . C 1 n of the pseudo battery pack  300  as far as it concerns with a short time such as a momentary power cut or so, thereby the internal capacitors C 1 , C 12 , . . . C 1 n act as power holding units or power storing units. In a timing that the personal computer  100  is operated while the AC adapter  110  is connected, a peak power is required momentarily, the electric power stored in the internal capacitors C 11 , C 12 , . . . C 1 n of the pseudo battery pack  300  is outputted so that the shortage of the supplying power from the AC adapter  110  is complemented. 
     The capacitors C 11 , C 12 , . . . C 1 n are rather inexpensive as compared with the secondary batteries E 11  . . . E 23  in the battery pack  200  shown in FIG. 2, and therefore the pseudo battery pack  300  is inexpensive compared to the battery pack  200  whereby it is avoided that a user, who uses the personal computer  100  as a desktop is forced to be subjected to too much load. 
     FIG. 4 is a circuit diagram of an internal structure of the charger  121  shown in FIGS. 2 and 3. 
     The charger  121  is provided with a charge control IC  1211 . The charge control IC  1211  receives via a control terminal CTL from the charger control unit  122  shown in FIGS. 2 and 3 an instruction for a charge indicating that the AC adapter  110  and the battery pack  200  (or the pseudo battery pack  300 ) are properly connected or mounted. Upon receipt of the charge instruction, the charge control IC  1211  controls a MOS transistor for current control. In case of the pseudo battery pack  300 , however, the pseudo battery pack  300  is mounted in a state that an electric power is not stored at all. Consequently, the charger control unit  122  shown in FIG. 3 outputs the charge instruction to the charger  121  using a signal as well from a switch (not illustrated) for detecting whether the pseudo battery pack  300  is mounted. 
     An input terminal IN of the charger  121  shown in FIG. 4 is a terminal for receiving an electric power from the AC adapter  110 . An output terminal OUT is a terminal for supplying electric power to the battery pack  200  (or the pseudo battery pack  300 ). 
     Upon receipt of an instruction of a charge via the control terminal CTL, the charge control IC  1211  controls a gate voltage of a MOS transistor  1212  so that a predetermined current conducts through the MOS transistor  1212 . The current conducted through the MOS transistor  1212  is outputted via an in-rush current preventing filter, which comprises a coil  1213  and a capacitor  1215 , and further via a diode  1216  through an output terminal OUT and is supplied to the battery pack  200  or the pseudo battery pack  300 . A Zener diode  1214  is a voltage limiting device for preventing a sudden high voltage from being applied to the battery pack  200  or the pseudo battery pack  300 . 
     FIG. 5 is a circuit diagram of an internal structure of the DC—DC converters shown in FIGS. 2 and 3. While FIGS. 2 and 3 show the DC—DC converters each for generating two lines of power mutually different in voltage, FIG. 5 shows only a line of circuit. 
     The DC power generated by the AC adapter  110  shown in FIGS. 2 and 3 is fed via the diode D 1  to an input terminal IN of the DC—DC converter  123  shown in FIG.  5 . The DC power supplied through the input terminal IN passes through a main switching transistor  1232  and a coil  1235  and is converted into predetermined voltage (e.g. 5.0V), which is lower than the input voltage (e.g. 16.0V), and then supplied through an output terminal OUT to the internal circuits of the note type of personal computer  100 . 
     A control circuit  1231  applies to a gate of the main switching transistor  1232  a pulse signal to intermittently turn on and off the main switching transistor  1232 . The control circuit  1231  also applies to a gate of a synchronization rectifying transistor  1233  a pulse signal to intermittently turn on and off the synchronization rectifying transistor  1233 . The control circuit  1231  receives a reference voltage Vref from the exterior and a voltage of the output terminal OUT as well. The control circuit  1231  controls a pulse width of the pulse signal to be applied to the gate of the main switching transistor  1232  so that a voltage of the output terminal OUT becomes a voltage (typically the same voltage as the reference voltage Vref) associated with the reference voltage Vref. And also, with respect to the pulse signal to be applied to the synchronization rectifying transistor  1233 , the control circuit  1231  performs a pulse timing control and a pulse width control so as not to overlap with a pulse to be applied to the main switching transistor  1232  (so as not to simultaneously turn on the main switching transistor  1232  and the synchronization rectifying transistor  1233 ). 
     A diode  1234 , which is connected in parallel with the synchronization rectifying transistor  1233 , is a flywheel diode which is operative when both, the main switching transistor  1232  and the synchronization rectifying transistor  1233  turn off. 
     When the main switching transistor  1232  turns on, an electric power is stored in the coil  1235 . And when the main switching transistor  1232  turns off, a current conducts through the diode  1234  or the synchronization rectifying transistor  1233 , so that the power stored in the coil  1235  is discharged through the output terminal OUT. Repeat of this cycle and voltage smoothing effect by the capacitor C 2  makes it possible to output an electric power of DC voltage according to a pulse width of the pulse to be applied via the output terminal OUT to the main switching transistor  1232 . 
     Since the flywheel diode  1234  is associated with a forward potential drop, the combination use of the flywheel diode  1234  with the synchronization rectifying transistor  1233  makes it possible to perform effective power conversion. 
     FIG. 6 is a block diagram showing an internal structure of the control circuit  1231  of the DC—DC converter  123  shown in FIG.  5 . 
     An error amplifier  12312  receives a reference voltage Vref from a reference voltage input terminal VREF, and also receives from a monitor voltage input terminal MTR a voltage (output voltage) of the output terminal OUT of the DC—DC converter  123  shown in FIG.  5 . The error amplifier  12312  determines an error (difference) from the reference voltage Vref of the output voltage. The error amplifier  12312  feeds the error thus determined to a PWM comparator  12313 . 
     The PWM comparator  12313  also receives a triangle wave generated by a triangle wave oscillator  12311 . The PWM comparator  12313  compares the triangle wave entered from the triangle wave oscillator  12311  with a predetermined voltage value adjusted in accordance with the error output from the error amplifier  12312  to generate a pulse train. Each pulse of the pulse train has a pulse width adjusted in accordance with the output of the error amplifier  12312  (or an error of the output voltage from the reference voltage Vref). The pulse train is fed to a drive circuit  12315  as a control signal for turning on and off the main switching transistor  1232  of the DC—DC converter  123  shown in FIG.  5 . 
     The PWM comparator  12313  generates a pulse signal comprising a pulse train in timing not overlapping with the pulse train generated through comparison with the triangle wave (or the pulse train) as the control signal for turning on and off the main switching transistor  1232 . The pulse signal is fed to another drive circuit  12316  as a control signal for turning on and off the synchronization rectifying transistor  1233  of the DC—DC converter  123  shown in FIG.  5 . 
     The control circuit  1231  further comprises a charge pump  12314 . The charge pump  12314  is a circuit for generating a voltage which is somewhat higher than a voltage of a power generated from the AC adapter  110  (cf. FIGS.  2  and  3 ). 
     The reason the charge pump  12314  is provided is because in order to surely turn on the main switching transistor  1232  and the synchronization rectifying transistor  1233 , which constitute the DC—DC converter  123  shown in FIG. 5, there is a need to provide a high voltage to some extent. 
     The drive circuits  12315  and  12316  generate drive signals of the voltage generated in the charge pump  12314  to drive the main switching transistor  1232  and the synchronization rectifying transistor  1233  in accordance with the applied pulse signals, respectively. The drive signals thus generated are transmitted via drive signal output terminals HD and DL to the main switching transistor  1232  and the synchronization rectifying transistor  1233 , respectively. 
     Next, there will be explained a second embodiment of a system comprising a personal computer, such as a notebook personal computer, a battery pack, and a pseudo battery pack. The second embodiment of the system is the same as the system shown in FIG. 1 in structure, and thus redundant explanation will be omitted. 
     FIG. 7 is a block diagram showing a circuit structure of a power supply section in a state that a pseudo battery pack is mounted on the personal computer, in the system according to the second embodiment. 
     A power supply section  120  shown in FIG. 7 comprises a DC—DC converter  123 , capacitors C 1 , C 2  and C 3  for stabilizing voltages, and a diode D 1  for transmitting an electric power from the AC adapter  110  to the DC—DC converter  123 , and is not provided with charging facilities comprising the charger  121 , the charge control section  122  and two comparators COMP 1  and COMP 2  as shown in FIGS. 2 and 3. The diode D 2 , as shown in FIGS. 2 and 3, which is provided on the path for transmitting the power from the battery pack  200  or the pseudo battery pack  300  to the DC—DC converter  123 , is provided inside a pseudo battery pack  300 ′ in FIG.  7 . 
     The pseudo battery pack  300 ′ in FIG. 7 comprises internal capacitors C 11 , C 12 , . . . , C 1 n, a constant current source  301  for charging those internal capacitors, and a diode D 2  disposed on a path for transmitting electric power stored in those internal capacitors to the DC—DC converter  123 . 
     In case of the pseudo battery pack  300 ′ in FIG. 7, the charging path for charging the internal capacitors C 11 , C 12 , . . . , C 1 n and the power supplying path for supplying charged electric power stored in those internal capacitors to the DC—DC converter  123  are separated from one another. On the charging path, there is disposed the constant current source  301  for charging those internal capacitors of the pseudo battery pack  300 ′, and thereby preventing an in-rush current from occurring even if the internal capacitors are empty. On the power supplying path, there is disposed the diode D 2  to prevent the backflow of the power. 
     FIG. 8 is a block diagram showing a circuit structure of a power supply section where a battery pack is mounted on the personal computer, in the system according to the second embodiment. 
     Here, there is shown a battery pack  200 ′ instead of the pseudo battery pack shown in FIG.  7 . 
     The battery pack  200 ′ comprises secondary batteries E 11  to E 23 , a constant current source  201  for preventing in-rush current, and a diode D 2  for preventing a backflow. Operations of the constant current source  201  and the diode D 2  are the same as the constant current source  301  and the diode D 2  of the pseudo battery pack  300 ′, respectively, and thus redundant explanation will be omitted. 
     As shown in FIGS. 7 and 8, it is acceptable that the battery pack and the pseudo battery pack are provided with a charging function per se. 
     FIG. 9 is a circuit diagram showing an example of a constant current source provided on the battery pack and the pseudo battery pack shown in FIGS. 7 and 8, respectively. 
     A certain constant voltage, which is generated in a Zener diode ZD 1 , is applied to a base of a transistor Tr 1 , so that a constant current conducts from a collector of the transistor Tr 1  to an emitter of the transistor Tr 1 . The current conducting through the transistor Tr 1  is controlled by a base voltage, so that the in-rush current is prevented from entering, even if the internal capacitors of the pseudo battery pack are empty. 
     FIG. 10 is a diagram showing an embodiment of a battery pack according to the present invention. 
     A battery pack  200 ″ may be adopted instead of the battery pack shown in FIGS. 1 and 2. As compared with the battery pack  200  shown in FIG. 2, the battery pack  200 ″ is few in the number of the secondary batteries, instead there are provided capacitors disposed in parallel with the secondary batteries. 
     As mentioned above, electric power needed for operation of the personal computer  100  is not always constant, but sometimes exceeds the usual electric power. In an exemplary embodiment, the AC adapter  110  is removed from the note type of personal computer  100  so as to operate only with the battery pack. In this case, there is a need for the secondary batteries in the battery pack to store an electric power corresponding to the electric power to be consumed in the note type of personal computer  100  within a certain time, and to be capable of sufficiently supplying a peak power which will sometimes occur. In view of the foregoing, in order to supply the peak power, in some case, there is a need for the secondary batteries to provide a power capacity exceeding the satisfaction of the mean dissipation power x the operation assurance time. In this case, the use of the capacitors instead of the secondary batteries reduced in number as shown in FIG. 10, makes it possible to measure the peak power by utilizing the electric power stored in the capacitors on a sharing basis, without the secondary batteries exceeding the satisfaction of the mean dissipation power x the operation assurance time when the sudden peak power is required. 
     FIG. 11 is a circuit diagram of a power supply section  120 ′ of a personal computer  100 ′, such as a notebook personal computer, which is an embodiment of an electronic apparatus according to the present invention. 
     An electric power of the commercial power supply  11  is fed via the AC adapter  110  to the power supply section  120 ′ and then transmitted via the diode D 1  for preventing a backflow to a DC—DC converter  123 . The DC—DC converter  123  is the same as the DC—DC converter  123  shown in FIGS. 2 and 3, for instance. Capacitors C 1 , C 2  and C 3  are capacitors for voltage stabilization. 
     The power supply section  120 ′ incorporates therein capacitors C 1 , C 12  . . . C 1 n which are charged via a constant current source  124  having an in-rush current preventing function. An electric power stored in the capacitors C 11 , C 12  . . . C 1 n is supplied via a diode D 2  for preventing a backflow to the DC—DC converter  123 . The charging path for charging the capacitors C 11 , C 12 , . . . , C 1 n and the power supplying path for supplying charged electric power stored in those capacitors to the DC—DC converter  123 , are separated from one another. On the charging path, the constant current source  124  prevents an in-rush current from occurring when the capacitors are charged. On the power supplying path, the diode D 2  prevents the backflow of the power. 
     In this manner, the use of the capacitors in the note type of personal computer  100 ′ makes it possible to provide a power supply at the time of the momentary power cut of the commercial power supply  11  and a peak power supply momentarily exceeding an ability of the AC adapter  110 . 
     While the present invention has been explained referring to a notebook personal computer by way of example, the present invention is applicable to a portable type of electronic apparatus such as a PDA, and a mobile type of personal computer, and also widely applicable to a general electronic apparatus. 
     As mentioned above, according to the present invention, it is possible to measure a momentary power cut and a large current which will be needed momentarily, upon reducing a load of a user. 
     While the present invention has been described with reference to the particular illustrative embodiments, it is not to be restricted by those embodiments but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present invention.