JP2011139614A - Power supply system, power supply module used in the same, and portable equipment having the system and module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply system which responds to an instantaneous high energy requirement, and suppresses early deterioration of a lithium ion capacitor while achieving maximum use of power capacity. <P>SOLUTION: The power supply system 10 includes a lithium ion secondary battery 3, a monitoring circuit 6 which monitors terminal voltage of the battery 3, a lithium ion capacitor 4 connected in parallel to the battery 3, an FET 9 which opens and closes to connect and disconnect the capacitor 4, and a protective circuit 5 which monitors the terminal voltage of the capacitor 4. The protective circuit 5 opens and closes the FET 9 to control the full charge voltage of the capacitor 4 to be equal to or lower than an upper-limit voltage determined to be lower than the maximum operating voltage of the lithium ion secondary battery 3. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a power supply system having a secondary battery that can be repeatedly charged and discharged, and in particular, a power supply that can be suitably used for portable devices such as notebook computers, digital cameras, video cameras, portable game machines, and mobile phones. The present invention relates to a supply system, a power supply module used for the supply system, and a portable device including these.

  As a power supply module (power supply device) used in this type of power supply system, a cell (single cell) having a lithium ion secondary battery as a minimum component is used in many portable devices. As shown in FIG. 8, in this type of power supply module 101, the monitoring circuit 106 monitors the terminal voltage of the cell 102 (see, for example, Patent Document 1). This type of power supply module 101 is normally charged by a “constant current / constant voltage charging method (CCCV)”. In this charging method, charging is first started by constant current charging, and when a predetermined voltage is reached, switching to constant voltage charging is performed and charging is performed up to a fully charged voltage.

  Here, a lithium ion secondary battery is not necessarily suitable for responding to an instantaneous high energy demand because the response time is slower than that of a capacitor. Therefore, conventionally, with respect to this type of power supply module, there has been a proposal of connecting a capacitor in parallel with a battery in order to improve the responsiveness of an instantaneous high energy request (see, for example, Patent Documents 2 to 3).

For example, in the technology disclosed in Patent Document 2, in a power supply device for a vehicle, a power supply module having a lithium ion secondary battery in which capacitors are connected in parallel, the input / output current to the secondary battery is less than the charge / discharge limit current. By providing the current control means for limiting the charging, it is possible to charge the battery to near full charge while preventing deterioration of the secondary battery due to overcharging.
For example, the technique described in Patent Document 3 improves the responsiveness of instantaneous high energy requirements by connecting a capacitor to the power supply device in parallel as a power supply device that is not limited to a secondary battery.

Japanese Patent Laid-Open No. 2004-120849 JP 2009-44808 A (FIG. 1) JP 2002-330548 A (FIGS. 2 and 3)

  As a capacitor used for such an application, a lithium ion capacitor can be considered in addition to the electric double layer capacitor described in Patent Document 2, the capacitor described in Patent Document 3, an ultracapacitor, and a supercapacitor. A lithium ion capacitor is a capacitor having a positive electrode made of activated carbon, a negative electrode made of an active material that absorbs and desorbs lithium ions, and a non-aqueous electrolyte solution containing a lithium salt electrolyte. Since the maximum operating voltage is higher than that of an electric double layer capacitor having a non-aqueous electrolyte containing an electrolyte, the output characteristics are excellent.

  However, it is known that the lithium ion capacitor has a maximum operating voltage of about 4 V, and its life is remarkably reduced when a predetermined voltage that is a full charge voltage exceeds the maximum operating voltage. Therefore, in a power supply module or power supply system that has a lithium ion secondary battery with a maximum operating voltage of about 4.2 V in the cell, one lithium ion capacitor is simply connected in parallel to one lithium ion secondary battery. As a result, although it can respond to an instantaneous high energy demand, the lithium ion capacitor deteriorates remarkably in the region of about 4 V or more. That is, when using one lithium ion capacitor for one lithium ion secondary battery, do not use the region of 4V or more of the lithium ion secondary battery, or the deterioration of the lithium ion capacitor progresses early. However, it is impossible to solve the problem that it is necessary to choose between the use of up to 4.0 to 4.2 V with the knowledge of the fact.

  That is, the power supply module having a lithium ion secondary battery in the cell includes a monitoring circuit 106 as illustrated in FIG. 8, and the monitoring circuit 106 has a predetermined voltage for stopping the constant current charging described above and a full voltage. In addition to a charging function for monitoring a predetermined voltage (or a predetermined current, a predetermined time) as a charging voltage, it also has an overcharge protection function for monitoring a predetermined voltage for overcharging. The overcharge protection function of the monitoring circuit 106 is configured to stop the charging by interrupting the charging current when the overcharge detection voltage is higher than the overcharge detection voltage in order to prevent overheating and rupture of the module due to overcharging. .

  In general, when a lithium ion capacitor is connected in parallel to a power supply module under the monitoring of such a monitoring circuit, the monitoring range of the monitoring circuit is the cell of the lithium ion secondary battery constituting the power supply module. It is not limited to the conventional one. Therefore, the maximum operating voltage of the lithium ion secondary battery is insufficient to suppress the early deterioration of the lithium ion capacitor having a high degree of deterioration.

  Thus, for example, it is conceivable to connect a lithium ion capacitor in parallel to a cell made of a lithium ion secondary battery and monitor the terminal voltage of each cell including the capacitor with a monitoring circuit. However, in this case, it is possible to prevent the early deterioration of the lithium ion capacitor by lowering the upper limit voltage set as the maximum operating voltage in the monitoring circuit, giving priority to the prevention of the early deterioration of the lithium ion capacitor. Therefore, the region near the maximum operating voltage of the lithium ion secondary battery cannot be used effectively. For this reason, this measure still leaves room for further study on the issue of improving power supply capacity. In particular, improvement of power supply capacity in portable devices is an important issue.

  Therefore, the present invention has been made paying attention to such problems, and is capable of responding to instantaneous high energy demands, while preventing the early deterioration of the lithium ion capacitor and maximizing the power source capacity. It is an object of the present invention to provide a power supply system that can be used for a mobile device, a power supply module used for the power supply system, and a portable device including these.

  In order to solve the above problems, a first aspect of the present invention is a power supply system having a secondary battery capable of repeated charge and discharge, the lithium ion secondary battery and the lithium ion secondary battery. A monitoring circuit for monitoring the terminal voltage of the battery, a lithium ion capacitor connected in parallel to the lithium ion secondary battery, a switching element capable of opening and closing the connection of the lithium ion capacitor, and a protection circuit for opening and closing the switching element A lithium ion capacitor in which a full charge voltage of the lithium ion capacitor is set to a value lower than a maximum operating voltage of the lithium ion secondary battery based on a terminal voltage of the lithium ion secondary battery. The switching element is opened and closed so as to control the maximum operating voltage.

Here, the “maximum operating voltage” is essentially a value determined by the material, but is a value set by the battery manufacturer as a specification after evaluating safety and cycle characteristics. For example, in the case of a general lithium ion secondary battery using lithium cobaltate for the positive electrode, it is often set to 4.2V.
According to the power supply system according to the first aspect, since the lithium ion capacitor connected in parallel to the lithium ion secondary battery is provided, it is possible to respond to an instantaneous high energy demand. Further, as will be described later, by allowing a margin for the lower limit voltage controlled on the main body side of the system at the end of discharge, circuit disconnection due to unexpected IR drop can be prevented. Therefore, an effective usable area of the power supply system can be expanded to the low voltage side. Therefore, the usability of the power supply system on the main body side of the system is greatly improved.

  The power supply system according to the first aspect includes a switching element that opens and closes the connection of the lithium ion capacitor, and a protection circuit that can open and close the switching element, and the protection circuit is supplied to the power line. Based on the voltage of the lithium ion secondary battery, the full charge voltage of the lithium ion capacitor is controlled to the maximum operating voltage of the lithium ion capacitor set to a value lower than the maximum operating voltage of the lithium ion secondary battery. Since the switching element is opened and closed, only the lithium ion capacitor is disconnected from the circuit, and use in a region exceeding the upper limit voltage and reaching the maximum operating voltage of the lithium ion secondary battery can be avoided. On the other hand, for the lithium ion secondary battery, unless the monitoring circuit for monitoring the voltage of the lithium ion secondary battery detects overcharge, overdischarge, etc., the connection with the circuit is maintained regardless of opening and closing of the switching element. Therefore, the area up to the maximum operating voltage can be used continuously. Therefore, it is possible to use the power source capacity to the maximum while preventing early deterioration of the lithium ion capacitor.

 In the region between the maximum operating voltage of the lithium ion capacitor and the maximum operating voltage of the lithium ion secondary battery, the lithium ion capacitor is separated from the circuit by the switching element, but in this region, the lithium ion secondary battery Because of its relatively low internal resistance, only a lithium ion secondary battery can respond to instantaneous high energy requirements. Further, when the voltage of the power supply line supplied from the lithium ion secondary battery becomes lower than the maximum operating voltage of the lithium ion capacitor due to the response, the lithium ion capacitor is immediately connected in parallel by closing the switching element. This makes it possible to respond to instantaneous high energy demands.

  In the power supply system according to the first aspect, the lithium ion secondary battery includes a positive electrode using a composite oxide of a transition metal and lithium as a positive electrode active material, and a material capable of occluding and releasing lithium ions. A negative electrode as a substance, and a non-aqueous electrolyte solution in which an electrolyte containing lithium ions is dissolved in an organic solvent, wherein the lithium ion capacitor includes a positive electrode using activated carbon as a positive electrode active material, and a carbonaceous material on the surface of the activated carbon. It is preferable to have a negative electrode using a composite porous carbon material coated with a negative electrode active material and a non-aqueous electrolyte solution in which an electrolyte containing lithium ions is dissolved in an organic solvent.

Furthermore, in the power supply system according to the first aspect, it is preferable that the composite porous carbon material that is the negative electrode active material of the lithium ion capacitor satisfies the following conditions (1) and (2).
(1) Mesopore amount (amount of pores having a diameter of 2 nm to 50 nm) Vm1 (cc / g) calculated by the BJH method is 0.01 ≦ Vm1 <0.10.
(2) The amount of micropores (amount of pores having a diameter of less than 2 nm) Vm2 (cc / g) calculated by the MP method is 0.01 ≦ Vm2 <0.30.

Still further, in the power supply system according to the first aspect, the activated carbon that is the positive electrode active material of the lithium ion capacitor preferably satisfies the following conditions (3) to (5).
(3) The mesopore amount V1 (cc / g) calculated by the BJH method is 0.3 ≦ V1 <0.8.
(4) The micropore volume V2 (cc / g) calculated by the MP method is 0.5 ≦ V2 <1.0.
(5) The measured specific surface area by the BET method is less than 1500 m ² / g or more 3000 m ² / g.
With such a configuration, it is possible to obtain a lithium ion capacitor that can more stably and repeatedly charge and discharge conditions such as the upper limit voltage (4.0 V) of the full charge voltage of the lithium ion capacitor described above.

  Furthermore, in order to solve the above-mentioned problem, a second aspect of the present invention is a power supply module that is used in the power supply system according to the first aspect and can be repeatedly charged and discharged, and is a lithium ion secondary A battery, a lithium ion capacitor connected in parallel to the lithium ion secondary battery, a switching element that opens and closes the connection of the lithium ion capacitor, and a monitor that monitors terminal voltages of the lithium ion secondary battery and the lithium ion capacitor The monitoring circuit also serves as the protection circuit, and based on the monitored terminal voltage, the full charge voltage of the lithium ion capacitor is lower than the maximum operating voltage of the lithium ion secondary battery Open and close the switching element to control the maximum operating voltage of the lithium ion capacitor set to the value And wherein the Rukoto.

  According to the power supply module according to the second aspect, since the lithium ion capacitor is connected in parallel to the lithium ion secondary battery, and the monitoring circuit also serves as a protection circuit, the power supply according to the first aspect When constructing the system, it is not necessary to add a lithium ion capacitor and a protection circuit to the device body side of the system. Therefore, the cost increase on the device main body side can be suppressed, and the power supply system according to the first aspect can be constructed without depending on the device main body side.

Furthermore, in order to solve the above-mentioned problem, a third aspect of the present invention is a portable portable device including a power supply system or a power supply module having a secondary battery capable of repeated charge and discharge, As a power supply system or a power supply module, the power supply system according to the first aspect or the power supply module according to the second aspect is provided.
According to the portable device according to the third aspect, since the portable device includes the power supply system according to the first aspect or the power supply module according to the second aspect, it is possible to respond to an instantaneous high energy request. Yes, it is possible to use the power supply capacity to the maximum while preventing early deterioration of the lithium ion capacitor.

  As described above, according to the present invention, a power supply system capable of responding to instantaneous high energy requirements and preventing the early deterioration of the lithium ion capacitor while using the power supply capacity to the maximum, and the use thereof It is possible to provide a power supply module and a portable device including these power supply modules.

It is a mimetic diagram explaining one embodiment of a power supply system concerning the present invention. It is a figure explaining one Embodiment of the charging method in the power supply system which concerns on this invention, The figure has shown the flowchart of the charge control process at the time of the charge performed with a monitoring circuit and a protection circuit. It is a figure explaining one Embodiment of the discharge method in the power supply system which concerns on this invention, The figure has shown the flowchart of the discharge control process at the time of the discharge performed with a monitoring circuit and a protection circuit. It is a graph for explaining the operation of the power supply system according to the present invention, the figure is the timing of switching element OFF during charging and switching element ON during discharging, and the relationship between constant current charging and constant voltage charging Timing is shown. It is a graph explaining the effect of the power supply system which concerns on this invention, The figure has shown the relationship between the discharge capacity of a lithium ion secondary battery, a voltage, and its internal resistance. It is a graph explaining the effect of the power supply system which concerns on this invention, The figure has shown the relationship where the internal resistance of a lithium ion secondary battery falls by cooperation with a lithium ion capacitor. It is a mimetic diagram explaining one embodiment of a power supply module concerning the present invention. It is a schematic diagram explaining an example of the conventional power supply device (power supply module).

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings as appropriate.
FIG. 1 shows an embodiment of a portable device including a power supply system according to the present invention. Here, the power supply system 10 has a secondary battery that can be repeatedly charged and discharged. Moreover, the portable device in this embodiment is a mobile phone, for example.
Specifically, as shown in the figure, the power supply system 10 is also referred to as a power supply module 1 including a lithium ion secondary battery and a load or a charger (hereinafter referred to as “apparatus body”) to which the power supply module 1 is connected. And an auxiliary module including the cell 7 connected to the side. This embodiment is an embodiment suitable for using an auxiliary module in a device main body that already uses a power supply module including a lithium ion secondary battery.

The power supply module 1 includes a cell 8 composed of a lithium ion secondary battery (hereinafter also simply referred to as “battery”) 3 and a monitoring circuit 6 that individually monitors the terminal voltage of the cell 8. Although FIG. 1 shows a case where there is one cell 8, when a plurality of cells 8 are connected in series, a monitoring circuit 6 is provided for each.
The cell 8 (battery 3) has a terminal T1 on its positive line and a terminal T2 on its negative line, and the device body 2 is connected between these terminals. In addition, the negative line of the cell 8 is connected in series with an FET 9a and an FET 9b for interrupting the circuit when the cell 8 is overcharged or overdischarged.

  The monitoring circuit 6 is connected so that each terminal voltage of the cell 8 (that is, the minimum component consisting of the battery 3) can be individually monitored, and the full charge voltage is the maximum operating voltage of the battery 3 (4 in the example of this embodiment). .2V), the charging current or the charging current and voltage are controlled. The battery 3 is used in the range of the upper limit voltage (4.2 V) to the lower limit voltage (3.0 V) which is the maximum operating voltage, and the monitoring circuit 6 monitors them (overcharge protection, end of charge detection). , Over discharge protection, and constant current charge stop and switch to constant voltage charge if necessary).

  Specifically, the monitoring circuit 6 includes detection circuits such as overcharge, overdischarge, overcurrent, and temperature protection, and a logic circuit that generates a control signal based on detection signals from the built-in detection circuits. It has. The monitoring circuit 6 includes a VSS terminal 6a, a VDD terminal 6b, a DOUT terminal 6c, a COUT terminal 6d, a V- (minus) terminal 6e, and a TEMP terminal 6t for connection with the outside.

  The VSS terminal 6 a is a GND terminal and is connected to the negative line of the battery 3. The VDD terminal 6b is a power input terminal and is connected to the positive line of the battery 3. The DOUT terminal 6c outputs a corresponding control signal when an overdischarge or overcurrent is detected from the built-in detection circuit, and is connected to the gate of the FET 9a. The COUT terminal 6d outputs a corresponding control signal when overcharge is detected, and is connected to the gate of the FET 9b.

  The V-terminal 6e is connected to a negative line to be connected to a load or a charger via a resistor R, and is used for overcurrent detection. The TEMP terminal 6t is an input terminal of the temperature protection circuit, detects the ambient temperature of the place where the battery 3 is installed, and outputs a temperature detection signal when the ambient temperature rises to a preset temperature. ing. Although not shown in the figure, an increase in the ambient temperature is detected by a temperature detection element such as a thermistor and input to the monitoring circuit 6.

On the other hand, the cell 7 of the spare module includes a lithium ion capacitor (hereinafter also simply referred to as a “capacitor”) 4 and is connected in parallel to the battery 3 of the cell 8. Further, the spare module has a protection circuit 5 for monitoring the voltage supplied to the power supply lines (T1 and T2), and an FET 9 connected in series with the capacitor 4.
The FET 9 is a switching element that opens and closes the connection of the capacitor 4. Then, the protection circuit 5 sets the full charge voltage of the capacitor 4 to a value lower than the maximum operating voltage of the cell 8 (4.2 V in the example of the present embodiment) based on the voltage of the power supply line being monitored. The FET 9 is opened and closed so as to control to the set upper limit voltage of the cell 7 (4.0 V in the example of this embodiment).

 Although FIG. 1 shows the case where there is one cell 8, when a plurality of cells 8 are connected in series, the voltage for opening and closing the FET 9 may be appropriately changed. For example, when three cells 8 are connected in series, the maximum voltage supplied to the power supply lines (T1 and T2) is 4.2V × 3 = 12.6V in the embodiment, but in this case, What is necessary is just to control FET9 which is a switching element which opens and closes the connection of the capacitor 4 by making 4.0V * 3 = 12.0V into an upper limit.

  Here, the battery 3 includes a positive electrode using a composite oxide of transition metal and lithium as a positive electrode active material, a negative electrode using a material capable of occluding and releasing lithium ions as a negative electrode active material, and an electrolyte containing lithium ions as an organic material. A non-aqueous electrolyte solution dissolved in a solvent. Preferably, lithium cobaltate, lithium manganate, or lithium nickelate is used as the positive electrode active material, and graphite or coke is used as the negative electrode active material. In the following, a battery 3 using lithium cobaltate as a positive electrode active material and graphite as a negative electrode active material will be described as a representative example. The maximum operating voltage of the battery 3 is 4.2V.

  The capacitor 4 includes a positive electrode using activated carbon as a positive electrode active material, a negative electrode using a material capable of occluding and releasing lithium ions as a negative electrode active material, and a non-aqueous electrolyte solution in which an electrolyte containing lithium ions is dissolved in an organic solvent. It has. Preferably, as the negative electrode active material, graphite, a non-graphitizable carbon material (hard carbon), or a composite porous carbon material in which a carbonaceous material is deposited on the surface of activated carbon is used.

Instead of the capacitor 4, an electric double layer capacitor having a non-aqueous electrolyte solution in which both the positive electrode active material and the negative electrode active material are activated carbon and a quaternary ammonium salt such as a tetraalkylammonium salt is dissolved in an organic solvent is used. It is also possible to do. However, since the electric double layer capacitor has a maximum operating voltage of 2.5 to 3.0 V, the above-described lithium ion two-dimensional capacitor is often used with a full charge voltage set to 4.2 to 4.3 V. In order to use it in combination with a secondary battery, two are required in series. For this reason, in particular, when employed in a power supply system for a portable device, the volume and cost increase, which is not preferable.
Capacitor 4 is formed by laminating one or a plurality of positive electrodes, negative electrodes, and separators to form an electrode, which is packaged with a laminate film having an outer resin layer, an aluminum foil, and an inner resin layer. It is preferable to use a thin outer package that is hermetically sealed after injection.

The negative electrode active material of the capacitor 4 described above is more preferably a composite porous carbon material that satisfies the following conditions (1) and (2).
(1) Mesopore amount (amount of pores having a diameter of 2 nm to 50 nm) Vm1 (cc / g) calculated by the BJH method is 0.01 ≦ Vm1 <0.10.
(2) The amount of micropores (amount of pores having a diameter of less than 2 nm) Vm2 (cc / g) calculated by the MP method is 0.01 ≦ Vm2 <0.30.

Moreover, it is preferable that the positive electrode active material of the capacitor 4 described above is activated carbon that satisfies the following conditions (3) to (5).
(3) The mesopore amount V1 (cc / g) calculated by the BJH method is 0.3 ≦ V1 <0.8.
(4) The micropore volume V2 (cc / g) calculated by the MP method is 0.5 ≦ V2 <1.0.
(5) The measured specific surface area by the BET method is less than 1500 m ² / g or more 3000 m ² / g.

  If the negative electrode active material or the positive electrode active material of the capacitor 4 satisfies the above (1) to (5), the upper limit of the above-described battery 3 is obtained by the battery 3 having the above-described conditions and the capacitor 4 connected in parallel thereto. The voltage (4.2 V) condition can be repeatedly charged and discharged more stably. In the power supply system of this embodiment, the battery 3 and the capacitor 4 that satisfy these conditions (1) to (5) are employed.

  Next, a charging / discharging method for a portable device including the power supply system 10 will be described with reference to FIGS. 2, 3, and 4. FIG. 2 is an explanatory diagram of a charging method in a portable device including the above-described power supply system 10, in which the charge control executed by the power supply system 10 including the protection circuit 5 and the monitoring circuit 6 is illustrated. The flowchart of a process is shown. In FIG. 4, the upper diagram is a charge / discharge curve (time on the horizontal axis, voltage on the vertical axis), the symbol V1 is the maximum operating voltage of the battery (for example, 4.2V), and V2 is the maximum operating voltage of the capacitor ( For example, 4.0 V), V3 is the lower limit voltage (for example, 3.0 V) of the battery, and the lower diagram shows the applied current.

  As shown in FIG. 4, in the charging method of the power supply system 10, charging is started by constant current charging (symbol CC in the figure). For the capacitor 4, the maximum operating voltage is set as the full charge voltage without intentionally using the voltage region exceeding the maximum operating voltage (4.0 V) and reaching the maximum voltage of the battery 3. On the other hand, for the cell 8 of the battery 3, the monitoring circuit 6 allows charging up to the maximum operating voltage (4.2V) of the battery 3 by applying a constant current when the battery 3 is charged, In this case, charging is performed by constant voltage charging (symbol CV in the figure).

  Specifically, when a charge control process is executed in the power supply system 1 in a state of charge less than the capacitor end-of-charge detection voltage (4.0 V), as shown in FIG. Start constant current charging (CC). In the initial stage of charging, since the charging state is less than the detection voltage (4.0 V), the FET 9 that opens and closes the connection of the capacitor 4 is in the connection (ON) state of the capacitor 4 (step S1). In subsequent step S2, the protection circuit 5 monitors the terminal voltage of the cell 7 (capacitor 4) and determines whether or not the terminal voltage of the cell 7 has reached the charge end detection voltage (4.0 V). If the end-of-charge detection voltage has been reached (Yes), the process proceeds to step S3. If not (No), constant current charging (CC) is continued. In step S3, the protection circuit 5 disconnects the capacitor 4 from the circuit by opening the FET 9 (OFF), and proceeds to step S4.

  In step S4, charging is continued only for the cell 8 (battery 3), and the monitoring circuit 6 has reached the charging end detection voltage (4.2V) of the battery 3 by gradually increasing the charging amount of the battery 3. Monitor whether or not. That is, if the cell 8 has reached the charge end detection voltage (4.2 V) (Yes), the process proceeds to step S5, and if not (No), the constant current charging (CC) is continued. In step S5, charging is continued by switching from constant current charging (CC) to constant voltage charging (CV). In the subsequent step S6, it is monitored whether or not the charging time (t) or the charging end detection current (I) has been reached, and when it is reached (t ≧ t1orI ≦ I1), the processing is ended (Yes), so Otherwise (No), constant voltage charging (CV) to the cell 8 is continued.

Next, a method for discharging a portable device including the above-described power supply system 10 will be described with reference to FIG. 1 is an explanatory diagram of a discharging method using a power supply device including the power supply system 1, and FIG. 3 is a flowchart of a charging control process executed in a system including the protection circuit 5 and the monitoring circuit 6. Show.
When the discharge control process is executed in the power supply system 1, as shown in FIG. 3, the process proceeds to step S1, and the protection circuit 5 of the cell 7 is charged at the charge end detection voltage (4.0V) or higher. If the charge end detection voltage (4.0V) or higher is monitored (Yes), the process proceeds to step S2 where the protection circuit 5 opens the FET 9 and disconnects the capacitor 4 from the circuit. (OFF). On the other hand, if it is less than the end-of-charge detection voltage (4.0 V) (No), the process proceeds to step S3, where the protection circuit 5 switches the FET 9 to the closed state, and the capacitor 4 is connected (ON). As a result, the cell 7 and the cell 8 are connected in parallel. In the subsequent step S4, the protection circuit 5 and the monitoring circuit 6 monitor whether or not the charge amount has gradually decreased to reach the discharge end detection voltage (3.0V). That is, if the cells 7 to 8 have reached the discharge end detection voltage (3.0 V) (Yes), the discharge is terminated, and if not (No), the discharge is continued.

  Next, the operation and effect of the power supply system 10 and the operation and effect of the portable device including the power supply system 10 will be described with reference to FIGS. In the discharge curve shown in FIG. 5 (the horizontal axis is the discharge capacity, the vertical axis is the voltage or the internal resistance), V1 is the maximum operating voltage of the battery (for example, 4.2 V), and V2 is the maximum operating voltage of the capacitor (for example, 4. 0V), V3 is a lower limit voltage (eg, 3.3V) controlled on the system side, and V4 is a lower limit voltage (eg, 3V) of the battery.

Here, when it is employed in a mobile phone, the power supply module 1 only needs to have one cell 8, and the power supply system 10 can be configured only by the configuration of FIG.
By the way, as shown in FIG. 6, the internal resistance c of the lithium ion secondary battery is small when it is close to the fully charged state V1 (for example, 4.2V), and increases as the discharge progresses and the usable capacity decreases. Come. However, the increase of the internal resistance c is a big problem in using the device.

  For example, in a communication method such as GSM for a mobile phone, a base current that is constantly flowing is a very small value (for example, 1 mA or 10 mA), whereas a large value (for example, 1 A) is passed at a peak. Is doing. However, in the case of a large current, the discharge amount of the lithium ion secondary battery can be reduced as compared with the case of a small current.

  Now, in the case of a large current discharge, if the module (battery pack) is discharged and the internal resistance c is in a large state C1, as shown in FIG. 6, an IR drop is generated by the internal resistance C1, thereby monitoring. The voltage of the cell 8 detected by the circuit 6 may be lower than a specified voltage (for example, 3 V and the lower limit voltage V4 shown in FIG. 5). Then, in order to prevent the deterioration of the battery due to overdischarge, the overdischarge protection function of the monitoring circuit 6 determines that the discharge has ended, interrupts the discharge current and stops the discharge (step S4 in FIG. 3). Therefore, the mobile phone suddenly becomes unusable. Therefore, as the main body system side 2 of the mobile phone, the lower limit voltage V3 controlled on the main body system side is expected to have a margin (eg, 0.3V) for the lower limit voltage V4 (eg, 3V) of the battery, and the lower limit shown in FIG. By setting the voltage V3 (for example, 3.2V, 3.4V, 3.5V, etc.), circuit disconnection due to such an unexpected IR drop is prevented. That is, the range actually used is controlled by the system side of the device, and the system side is substantially cut off by the voltage V3, and the end-of-discharge portion is not effectively used.

  That is, the first merit by the power supply system 10 of the present invention is that the cell 7 (capacitor 4) is connected in parallel to the cell 8 (battery 3), so that 1A flows at the peak. In addition, the capacitor 4 assists the battery 3 and can supply current from the capacitor 4 side. As a result, as shown in FIG. 6, the internal resistance can be changed to a graph indicated by reference numeral C2 in FIG. Therefore, according to the power supply system 10, the voltage drop due to the IR drop of the cell 8 can be kept small even at the peak time. Thereby, the lower limit voltage V3 controlled on the system side 2 of the mobile phone can be lowered to the end of discharge (moved downward in FIG. 5). Therefore, by adopting this power supply system 10, the end-of-discharge side region that has not been used can be used effectively. For this reason, not only is it possible to respond to instantaneous high energy demands, but it is also possible to secure a longer use time than in the past from the viewpoint of the user.

Further, as a second merit of the power supply system 10, the capacitor 4 is set to 4.0 V as the upper limit voltage without intentionally using the initial discharge region exceeding the maximum operating voltage. The power source capacity of the battery 3 can be used to the maximum while preventing the early deterioration of the battery.
Usually, the lithium ion capacitor is deteriorated by repeated use. Such deterioration due to repeated use is caused by decomposition of the electrolytic solution in the lithium ion capacitor to generate gas, and deterioration proceeds by the generation of this gas. In the discharge curve of the capacitor 4, the repeated use in the region of 4.2V to 4.0V is more remarkable than the repeated use in the region where the voltage is lower than this.

That is, according to the power supply system 10, the protection circuit 5 of the capacitor 4 manages the cell 7 with the maximum operating voltage as the upper limit voltage (4.0V), so that the region of 4.2V to 4.0V By not intentionally using the capacitor 4, it is possible to suppress the deterioration of the capacitor 4. For this reason, it is possible to extend the lifetime by avoiding a region where the deterioration is severe.
On the other hand, since the monitoring circuit 6 charges the cell 8 of the battery 3 also using the region from 4.2 to 4.0 V at the initial stage of discharge, the power supply capacity can be used to the maximum. In other words, as indicated by the symbol Vs in FIG. 5, the region from 4.2 to 4.0 V at the initial stage of discharge with respect to the full charge is about the total usage time with respect to the discharge curve from 4.2 to 3.0 V. Although it has a capacity of 10 to 20%, this area can be used effectively. Therefore, combined with the first advantage described above, the effective use range can be expanded as a whole. Therefore, when this is used for a mobile phone, the actual call time can be further extended and the power supply capacity can be maximized while preventing the capacitor 4 from prematurely deteriorating.

  As described above, according to the power supply system 10, since the lithium ion capacitor 4 (cell 7) connected in parallel to the lithium ion secondary battery 3 (cell 8) is provided, it is possible to respond to instantaneous high energy requirements. In addition, circuit disconnection due to unexpected IR drop can be prevented even at the end of discharge. Therefore, the effective usable area of the power supply system 10 can be expanded to the low voltage side. Therefore, it is possible to allow a margin for the lower limit voltage controlled by the system main body side 2 at the end of discharge, and the usable time per charge of the portable device can be extended, so that the usability is remarkably improved.

  The power supply system 10 includes the FET 9 that opens and closes the connection of the capacitor 4 and the protection circuit 5 that can open and close the FET 9. The protection circuit 5 is connected to the capacitor 3 based on the terminal voltage of the battery 3. Since the FET 9 is opened and closed so as to control the full charge voltage of 4 to an upper limit voltage set to a value lower than the maximum operating voltage of the battery 3, only the capacitor 4 is disconnected from the circuit. Use in a region exceeding the maximum operating voltage can be avoided. On the other hand, since the connection with the circuit is maintained for the battery 3, the region up to the maximum operating voltage (4.2V) can be continuously used. Therefore, the power supply capacity can be used to the maximum while preventing the capacitor 4 from premature deterioration.

  Note that the critical significance of setting the upper limit voltage of the cell 7 including the capacitor 4 to 4.0 V is set to 4.1 V as opposed to the maximum operating voltage 4.2 V of the battery 3 of the present embodiment described above. This is because the deterioration of the capacitor 4 easily proceeds. On the other hand, when the voltage is set to 4.0 V, the cycle life is greatly improved although the charging capacity is reduced by about 10% with respect to the 4.1 V charging. On the other hand, if the upper limit voltage of the capacitor 4 is set to 3.9 V, the charging capacity naturally decreases when the voltage is low, so that, for example, the call time when employed in a mobile phone is shortened.

As described above, according to the power supply system 10 and the mobile phone including the power supply system 10, it is possible to respond to a momentary high energy demand, and while preventing the early deterioration of the lithium ion capacitor 4, the power supply capacity is maximized. Can be used to the limit. The power supply system according to the present invention and the portable device including the power supply system are not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.
For example, in the above embodiment, the example of the mobile phone in which the power supply system 10 is constructed by the power supply module 1 and the device main body side 2 has been described. However, the mobile device on the main body side is not limited to this. For example, it can be used for portable devices such as notebook computers, digital cameras, video cameras, portable game machines, and other portable electronic devices.

In the above embodiment, for example, the protection circuit 5 has been described in which the full charge voltage to be controlled is the maximum operating voltage 4.0 V of the lithium ion capacitor. The full charge voltage can be controlled to be equal to or lower than the upper limit voltage set to a value lower than the maximum operating voltage of 3.
Furthermore, although an example of the charging method and the discharging method of the power supply system 10 has been described in the above embodiment, the charge / discharge method for the power supply system according to the present invention is not limited to this.

  Moreover, although the said embodiment demonstrated the example which employ | adopted what satisfy | filled the said conditions (1)-(5) as the negative electrode active material thru | or positive electrode active material of the capacitor 4, it is not limited to this, Various negative electrodes The present invention is applicable to cells and capacitors using active materials and positive electrode active materials. However, in configuring the cell 7 that can more stably and repeatedly charge and discharge the upper limit voltage (4.0 V) condition of the capacitor 4 described above, a cell that satisfies the above conditions (1) to (5) should be adopted. Is preferred.

Further, for example, in the above-described embodiment, the example in which the power supply system 10 is constructed by the power supply module 1 and the device main body side 2 has been described, but the power supply system according to the present invention is configured without depending on the device main body side. May be.
Specifically, as illustrated in FIG. 7, the power supply system 10 includes the capacitor 4, the FET 9, and the protection circuit (5) only by the power supply module 1 side in the above-described embodiment. May be built. That is, the monitoring circuit 6 of the battery 3 shown in FIG. 2 also serves as the protection circuit 5 for the capacitor 4. The monitoring circuit 6 determines the full charge voltage of the capacitor 4 based on the terminal voltage monitored by the The FET 9 is opened and closed so as to control to an upper limit voltage set to a value lower than the maximum operating voltage of the ion secondary battery. This embodiment is an embodiment suitable for a case where a power supply module that already has a lithium ion secondary battery is used and replaced with the power supply module or when a new power supply module is redesigned. is there.

Here, in the case of constructing the power supply system 10 using only the power supply module 20, if the bottom area of the battery 3 and the bottom area of the capacitor 4 are substantially equal, the amount of the battery 3 is slightly smaller than that of the battery 3 alone. The increase in thickness is preferable because the capacitor 4 can be mounted without requiring a useless space.
And if it is such a structure, the power supply system 10 can be constructed | assembled, without changing the control circuit and program on the main body system side of a portable apparatus. Therefore, while suppressing the cost increase of portable devices, it can respond to instantaneous high energy demands without depending on the main system, and uses the power supply capacity to the maximum while preventing early deterioration of the lithium ion capacitor. can do.

  The power supply system according to the present invention and the power supply module used therefor can be suitably used in the field of power supply devices, such as notebook computers, digital cameras, video cameras, portable game machines, and other portable electronic devices. It can be particularly suitably used as a power supply device for portable equipment.

1 power supply module 2 device body side 3 battery (lithium ion secondary battery)
4 Capacitor (lithium ion capacitor)
5 protection circuit 6 monitoring circuit 7 cell 8 cell 9, 9a, 9b FET (switching element)
10 Power supply system 20 Power supply module

Claims (4)

A power supply system having a secondary battery capable of repeated charge and discharge,
Lithium ion secondary battery, monitoring circuit for monitoring terminal voltage of the lithium ion secondary battery, lithium ion capacitor connected in parallel to the lithium ion secondary battery, and switching element for opening and closing the connection of the lithium ion capacitor And a protection circuit capable of opening and closing the switching element,
The protection circuit controls the full charge voltage of the lithium ion capacitor to an upper limit voltage set to a value lower than the maximum operating voltage of the lithium ion secondary battery based on the terminal voltage of the lithium ion secondary battery. A power supply system that opens and closes the switching element. The lithium ion secondary battery includes a positive electrode using a composite oxide of transition metal and lithium as a positive electrode active material, a negative electrode using a material capable of occluding and releasing lithium ions as a negative electrode active material, and an electrolyte containing lithium ions. A non-aqueous electrolyte solution dissolved in a solvent,
The lithium ion capacitor includes a positive electrode using activated carbon as a positive electrode active material, a negative electrode using a composite porous carbon material having a carbonaceous material deposited on the surface of activated carbon as a negative electrode active material, and an electrolyte containing lithium ions as an organic solvent. The power supply system according to claim 1, further comprising a non-aqueous electrolyte solution dissolved in the water. A power supply module having a secondary battery that can be used for the power supply system according to claim 1 or 2 and that can be repeatedly charged and discharged.
Lithium ion secondary battery, lithium ion capacitor connected in parallel to the lithium ion secondary battery, switching element for opening / closing the connection of the lithium ion capacitor, terminal voltage of the lithium ion secondary battery and the lithium ion capacitor And a monitoring circuit for monitoring
The monitoring circuit also serves as the protection circuit, and based on the terminal voltage to be monitored, the full charge voltage of the lithium ion capacitor is set to a value lower than the maximum operating voltage of the lithium ion secondary battery. A power supply module, wherein the switching element is opened and closed so as to control to an upper limit voltage. A portable portable device comprising a power supply system or a power supply module having a secondary battery capable of repeated charge and discharge,
A portable device comprising the power supply system according to claim 1 or 2 or the power supply module according to claim 3 as the power supply system or power supply module.

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