JP5664310B2 - DC power supply - Google Patents

Description

  The present invention relates to a DC power supply device that supplies DC power to a load by discharging from an electric storage means.

  Conventionally, some DC power supply devices for supplying DC power to a load such as a motor of an electric vehicle use a capacitor having a relatively large capacity (for example, Japanese Utility Model Publication No. 3-104002). . In addition, since a capacitor cannot supply electric power when it has run out of electric charge, there is also a DC power supply device that is devised to extend the usage time of a DC power supply by using it together with a secondary battery (battery) (for example, Japanese Patent Laid-Open No. Hei 6). No. -270695 [Patent Document 2], JP 2009-112122 A [Patent Document 3], JP 2004-266888 [Patent Document 4], and JP 2010-4587 [Patent Document 5]). In particular, Patent Documents 3 and 5 disclose that the required maximum power of a secondary battery is reduced by using a lithium ion capacitor as a large-capacity capacitor and does not cover the required maximum power.

Japanese Utility Model Publication No. 3-104002 JP-A-6-270695 JP 2009-112122 A JP 2004-266888 A JP 2010-4487 A

  However, compared with a lithium ion capacitor, the secondary battery is likely to be deteriorated by rapid charge / discharge, overdischarge / overcharge, and there is a problem that the secondary battery is deteriorated depending on the conventional control method. For example, in the configuration described in Patent Document 4, the secondary battery is connected in parallel via a main power supply and a relay, and a large load is connected to the secondary battery without limitation during charging and discharging. Further, the configuration described in Patent Document 5 has a problem that the usage frequency of the secondary battery is high, and the DC / DC converter is always used, so that power is always consumed.

  An object of the present invention is to use a lithium ion capacitor unit as a main power source, and in a DC power supply device using a secondary battery as a standby power source, to reduce the burden on the secondary battery, suppress the deterioration of the secondary battery, extend the life, It is another object of the present invention to provide a DC power supply device that can stably supply power.

  Another object of the present invention is to provide a direct current power supply device capable of charging a secondary battery together when charging a lithium ion capacitor unit with an external power source.

  Still another object of the present invention is to provide a DC power supply device capable of charging a secondary battery under conditions suitable for the environmental temperature in which the DC power supply device is used.

  The DC power supply device of the present invention includes a lithium ion capacitor unit connected in parallel to a load, a secondary battery connectable in parallel to the load and the lithium ion capacitor unit, and voltage detection for detecting the voltage of the lithium ion capacitor unit. And a switching circuit for connecting the secondary battery to the load and the lithium ion capacitor unit in parallel.

  Since a general lithium ion capacitor is about 3.8 V as a single unit, a plurality of lithium ion capacitors are connected in series according to the application to form a lithium ion capacitor unit, and a necessary output voltage is obtained. Moreover, the secondary battery should just be what can be charged / discharged, such as a lead storage battery and a lithium ion battery, for example, The kind is not limited.

  Lithium ion capacitors have the property that if they are overdischarged below a lower limit voltage that is inevitably determined in terms of characteristics, the original characteristics cannot be obtained even if recharged. Therefore, in the present invention, in order to prevent the voltage of each lithium ion capacitor constituting the lithium ion capacitor unit from interrupting the lower limit voltage, the voltage of the lithium ion capacitor unit is detected by the voltage detection means, When the voltage of the ion capacitor unit reaches the unit lower limit voltage, the switching circuit connects the secondary battery to the lithium ion capacitor unit in parallel, and the multiple lithium ion capacitors in the lithium ion capacitor unit drop below the lower limit voltage. To prevent it.

  In the present specification, “unit lower limit voltage” is a voltage value that is higher than the total value of the lower limit voltages of a plurality of lithium ion capacitors connected in series and lower than the rated voltage of the secondary battery. This is a value that can prevent the voltage of the capacitor from dropping below the lower limit voltage.

  In the present invention, the switching circuit is configured to switch between two circuit configurations. First, when the secondary battery is connected in parallel to the load and the lithium ion capacitor unit, the switching circuit first passes the secondary battery through the first discharge circuit including current limiting means in the load and the lithium ion capacitor unit. The first circuit configuration is connected in parallel. Thereafter, it is detected that the voltage of the lithium ion capacitor unit has risen to a first set voltage higher than the unit lower limit voltage, or the voltage of the lithium ion capacitor unit is lowered to a second set voltage lower than the unit lower limit voltage. When this is detected, the switching circuit has a second circuit configuration in which the secondary battery is connected in parallel to the load and the lithium ion capacitor unit via a second discharge circuit that does not include current limiting means.

  “When detecting that the voltage of the lithium ion capacitor unit has risen to the first set voltage higher than the unit lower limit voltage”, use the secondary battery after the switching circuit is in the first circuit configuration. This is a case where necessary electric power can be supplied without flowing an overcurrent to the load, and the lithium ion capacitor unit can be charged by the secondary battery. For this reason, the voltage rises to a first set voltage that is higher than the unit lower limit voltage. The first set voltage is a voltage that can prevent the discharge current from the secondary battery to the load from becoming an overcurrent. Therefore, in this state, the presence of the current limiting element causes the generation of power loss and does not fulfill the function of preventing the occurrence of overcurrent. Therefore, by switching to the second circuit configuration, the current limiting means is disconnected, the occurrence of loss in the current limiting means is prevented, and the load on the secondary battery is reduced. As a result, the capacity reduction rate of the secondary battery can be slow.

  On the other hand, in the case of “detecting that the voltage of the lithium ion capacitor unit has dropped to the second set voltage lower than the unit lower limit voltage”, the load at the time when the switching circuit becomes the first circuit configuration If the current is supplied to the load via the current limiting element because it is too large, sufficient power cannot be supplied, and the discharge of the lithium ion capacitor unit is continued. Therefore, in this case, if the current limiting element is present in the discharge circuit, there is a risk that the discharge from the lithium ion capacitor unit is continued and the voltage of each lithium ion capacitor is lowered to the lower limit voltage. Therefore, by switching to the second circuit configuration, the current limiting means is disconnected, thereby supplying necessary power to the load and preventing a voltage drop of the lithium ion capacitor unit. From such a viewpoint, the second set voltage is a voltage that can prevent the voltage of the lithium ion capacitor from becoming lower than the lower limit voltage.

  As described above, according to the present invention, by switching from the first circuit configuration to the second circuit configuration in the case of a specific condition, it is possible to prevent overcurrent discharge from the secondary battery and Deterioration can be suppressed and power loss can be suppressed, and power necessary for the load can be supplied.

  Specifically, the second discharge circuit can be constituted by a short circuit that short-circuits the current limiting means of the first discharge circuit. With this configuration, the configuration of the switching circuit can be simplified.

  The DC power supply device of the present invention is suitable for an automatic guided vehicle (AGV) driven by a motor. Generally, when the voltage of the lithium ion capacitor unit decreases, if it is an automatic transport vehicle, charging is performed by a charging device (external charger) when the automatic transport vehicle returns to the standby station. At this time, if the lithium ion capacitor unit is further equipped with a charging circuit that enters an operating state when a charging voltage is applied from an external charger and charges the secondary battery, the secondary battery is also charged. can do. However, the charging characteristics and charging time of the lithium ion capacitor unit and the secondary battery are greatly different. As a result, the problem arises that the lithium ion capacitor unit cannot be effectively used because it extends more than necessary. If the charging circuit is always connected, the secondary battery can always be charged from the lithium ion capacitor unit, resulting in power loss. Therefore, it is desirable to include a switching circuit in the charging circuit so that the secondary battery is charged when the switching circuit is in a conductive state. By including a switching circuit in the charging circuit, it is possible to charge a secondary battery with a long charging time using a standby time after charging a lithium ion capacitor unit with a short charging time. . Further, when such a switching circuit is provided, the operation of charging the secondary battery from the lithium ion capacitor unit can be arbitrarily stopped. The charging voltage of the lithium ion capacitor unit is higher than the charging voltage of the secondary battery. Therefore, the charging circuit can include a DC / DC converter that steps down the charging voltage to a voltage suitable for charging the secondary battery. Since the voltage of the DC / DC converter can be arbitrarily controlled, the secondary battery can be charged with an appropriate charging voltage to suppress the life reduction of the secondary battery.

  It is known that the voltage suitable for charging the secondary battery varies depending on the environmental temperature at which the secondary battery is placed. Therefore, in order to charge the secondary battery so as to prevent overcharging and insufficient charging, the battery further includes temperature detecting means for detecting the environmental temperature, and the output voltage of the DC / DC converter included in the charging circuit is determined according to the environmental temperature. It is preferable to change. Specifically, when the detected temperature detected by the temperature detecting means is higher than a predetermined reference upper limit temperature, the voltage suitable for charging the secondary battery is lowered, and the detected temperature detected by the temperature detecting means is a predetermined reference. What is necessary is just to make it raise the voltage suitable for charge of a secondary battery when it becomes lower than minimum temperature.

  The charging circuit is configured to include one or more diodes, and when the charging voltage is applied to the lithium ion capacitor unit from an external charger, the charging voltage is reduced to a voltage suitable for charging the secondary battery. You may comprise so that it may apply to a secondary battery. Specifically, one or more diodes are connected in series, the anode side is connected to the anode terminal of the lithium ion capacitor unit, and the cathode is connected to the anode terminal of the secondary battery. If comprised in this way, it is possible to adjust the charging voltage of a secondary battery easily only by determining the number of diodes according to the rated voltage of the secondary battery to be used. Therefore, a complicated circuit such as a switching circuit or a DC / DC converter is not required. In this case as well, it is desirable to include a switching circuit in the charging circuit so that the secondary battery is charged only when the switching circuit is in a conductive state.

  As described above, the first set voltage is a voltage that can prevent the discharge current from the secondary battery to the load from becoming an overcurrent. The first set voltage is thus determined when the voltage of the secondary battery is higher than the voltage of the lithium ion capacitor unit when the switching circuit switches from the first circuit configuration to the second circuit configuration. This is because if the voltage difference between the two voltages exceeds a predetermined value, a current exceeding the maximum discharge current of the secondary battery may flow. The “maximum discharge current of the secondary battery” is the maximum current that can be discharged without shortening the life of the secondary battery, and is defined by the specifications of the secondary battery. Depending on the performance of the secondary battery and the usage environment of the secondary battery, a fixed value may be used as the first set voltage. However, when the first set voltage is set to a fixed value, if the voltage change rate of the secondary battery at the time of discharge increases due to deterioration of the secondary battery, individual differences, environmental temperature, and the like, the first discharge circuit When the current limiting means is short-circuited, there is a possibility that the discharge current becomes larger than the maximum discharge current. Therefore, the first set voltage can be a voltage obtained by subtracting a tolerance voltage that allows the discharge current to be prevented from becoming an overcurrent from the voltage value (terminal voltage) of the secondary battery. By setting the first set voltage in this way, the voltage difference between the secondary voltage and the lithium ion capacitor unit becomes sufficiently small when switching from the first circuit configuration to the second circuit configuration. A discharge current exceeding the maximum discharge current of the secondary battery will not flow.

In the case of the second circuit configuration, the lithium ion capacitor unit and the secondary battery are directly connected, and the resistance component in the discharge circuit including the lithium ion capacitor unit and the secondary battery is the lithium ion capacitor unit. Only the internal resistance (R _C ) of the unit and the internal resistance (R _B ) of the secondary battery. In this discharge circuit, in order to prevent the discharge current from exceeding the maximum discharge current of the secondary battery, the voltage difference (V _dif ) between the secondary battery and the lithium ion capacitor unit is set to the total value of the internal resistance (R _C The current value (I) obtained by dividing by + R _B ) may be set to be equal to or less than the maximum discharge current (I _ref ) of the secondary battery. Therefore, as the tolerance voltage, the voltage value obtained by the product of the total value of the internal resistance of the lithium ion capacitor unit and the internal resistance of the secondary battery (R _C + R _B ) and the maximum discharge current (I _ref ) of the secondary battery is If used, the discharge current from the secondary battery can be prevented from exceeding the maximum discharge current, and the power loss due to the current limiting means can be minimized while preventing the secondary battery from deteriorating.

It is a circuit diagram which shows the structure of an example of 1st Embodiment of the DC power supply device of this invention. (A) And (B) is a time chart which shows the timing of switching in the switching circuit of the DC power supply device of this invention. It is a flowchart which shows the flow of the control circuit which controls the switching circuit of the DC power supply device of this invention. It is a circuit diagram which shows the structure of an example of 2nd Embodiment of the DC power supply device of this invention.

  Hereinafter, embodiments of a DC power supply device of the present invention will be described in detail with reference to the drawings.

〔Constitution〕
FIG. 1 is a circuit diagram showing a configuration of a first embodiment in which a DC power supply device of the present invention is applied to a DC power supply device of an automated guided vehicle. The DC power supply device of the present embodiment includes a lithium ion capacitor unit 1, a secondary battery 3 such as a lead storage battery, a voltage detection means 5, a control circuit 7, and a switching circuit 8. The lithium ion capacitor unit 1 and the secondary battery 3 are connected in parallel to the motor M that is a load. The lithium ion capacitor unit 1 of the present embodiment is composed of a module in which four capacitor arrays in which 16 lithium ion capacitors are connected in series are connected in parallel (however, the illustration of the capacitors is partially omitted in the figure). ) The capacity of the lithium ion capacitor unit 1 is 450 F (1800 F for a lithium ion capacitor single cell). When the upper limit voltage of the lithium ion capacitors C1 to C16 is 3.8 [V], the voltage of the lithium ion capacitor unit 1 is 60.8 [V]. Since the lower limit voltage of the lithium ion capacitors C1 to C16 is 2.2 [V], the unit lower limit of the present embodiment is set by not setting the voltage to be lower than 35.2 [V] and setting the voltage at which the load side system does not go down. The voltage is set to 40.0 [V]. Each of the lithium ion capacitors is connected in parallel with a resistance element constituting a voltage equalization circuit for equalizing the voltage of each lithium ion capacitor (not shown in the figure). For example, a 1 kΩ resistor is used as the voltage equalizing resistor. As the secondary battery 3, a control valve type lead storage battery with a rating of 48.0 [V] (24 cells with a rating of 2 V are connected in series) and 44 Ah is used.

  The voltage detection means 5 is connected to the pair of terminals T3 and T4 of the lithium ion capacitor unit 1 and the pair of secondary batteries 3 so that the voltage between the terminals of the lithium ion capacitor unit 1 and the secondary battery 3 can be detected. The terminals T5 and T6 are connected in parallel. The voltage detection means 5 can be configured using, for example, a resistance voltage dividing circuit. The control circuit 7 controls conduction and interruption of the switches SW1, SW3 and SW5 based on the voltage value detected by the voltage detection means 5. Specific control operations will be described later.

  The switching circuit 8 includes a first discharge circuit 81 and a second discharge circuit 83. The first discharge circuit 81 includes a switch SW1 and a current limiting resistor 4 connected in series to the switch SW1. The second discharge circuit 83 is configured to include a switch SW3. As will be described later, the current limiting resistor 4 is provided for the purpose of preventing an overcurrent from being discharged from the secondary battery 3 when the switch SW1 is turned on. Although not shown, a motor drive circuit including an inverter circuit that operates in response to a control command is connected to a motor circuit M including a motor as a load.

  In the present embodiment, the pair of terminals T3 and T4 of the lithium ion capacitor unit 1 are electrically connected to the pair of terminals T1 and T2 of the motor circuit M, respectively. The terminal T1 of the motor circuit M, the terminal T3 of the lithium ion capacitor unit 1, and the terminal T5 of the secondary battery 3 are anode terminals, and the terminal T2 of the motor circuit M, the terminals T4 of the lithium ion capacitor unit 1, and the second terminal T5. A terminal T6 of the secondary battery 3 is a negative terminal commonly connected to the ground terminal of the charger 9. The first discharge circuit 81 is disposed between the anode terminal T3 of the lithium ion capacitor unit 1 and the anode terminal T6 of the secondary battery 3. The second discharge circuit 83 is connected in parallel to the first discharge circuit 81. Therefore, the lithium ion capacitor unit 1 and the secondary battery 3 are connected in parallel via the switching circuit 8 including the first discharge circuit 81 and the second discharge circuit 83.

  A charger (DC power supply for charging) 9 is a charger provided at a standby station of an automatic guided vehicle. Each time the automated guided vehicle returns to the standby station, the terminals T1 and T2 are connected to the output terminals T7 and T8 of the charger 9, and a charging operation is performed. When the charger 9 and the DC power supply device of the automated guided vehicle are connected, the charger 9 charges the lithium ion capacitor unit 1 with a charging voltage slightly lower than the upper limit voltage of the lithium ion capacitor unit 1. In the present embodiment, the charging circuit 13 of the secondary battery 3 is connected between the terminal T1 and the terminal T5 of the secondary battery 3. The charging circuit 13 is configured by connecting a switch SW5 and a DC / DC converter 15 in series. When the charger 9 is connected to the DC power supply device, the switch SW5 is turned on in response to a conduction signal from the control circuit 7, whereby charging of the secondary battery 3 is started. When the control circuit 7 detects that the voltage of the secondary battery 3 detected by the voltage detection means 5 has dropped below a predetermined charging start voltage, the control circuit 7 switches when the charger 9 is connected to the DC power supply device. A conduction signal for making SW5 conductive is output. The switch SW5 maintains a conductive state while the ON command is output. The DC / DC converter 15 applies a charging voltage obtained by reducing the charging voltage of the lithium ion capacitor unit 1 to a voltage suitable for charging the secondary battery 3 to the secondary battery 3. If the charging current from the DC / DC converter 15 becomes too large, the secondary battery 3 is deteriorated. Therefore, the DC / DC converter 15 is configured to charge the secondary battery 3 with a current of about 1 to 7A. is there. When the voltage detection means 5 detects that the voltage between the terminals T5 and T6 of the secondary battery 3 has been charged to a predetermined set voltage (charging completion voltage), the control circuit 7 stops the output of the ON command and switches SW5 is shut off and charging ends. In the present embodiment, the standby power is not consumed because the switch SW5 is shut off except when the secondary battery 3 is charged. Therefore, the lithium ion capacitor unit 1 can be quickly charged without being affected by the charging of the secondary battery 3.

  Moreover, in this Embodiment, the temperature detection means 6 which detects the environmental temperature of the secondary battery 3 is also provided. The output of the temperature detector 6 is input to a control unit (not shown) of the DC / DC converter 15. A control unit (not shown) adjusts the output voltage of the DC / DC converter 15 according to the environmental temperature in which the secondary battery 3 is detected, which is detected by the temperature detection means 6. Specifically, the control unit (not shown) reduces the charging voltage to the secondary battery when the environmental temperature increases, and increases the charging voltage to the secondary battery when the environmental temperature decreases. 15 output voltage is adjusted. In this way, by charging the secondary battery at a charging voltage suitable for changes in the environmental temperature, the stress that the secondary battery receives due to overcharging or insufficient charging is reduced, and the life of the secondary battery 3 is reduced. Can be extended.

[Control of switching circuit]
Next, the switching operation of the switching circuit 8 controlled by the control circuit 7 will be described with reference to FIGS.

In the DC power supply device of the present embodiment, when the charging voltage of the lithium ion capacitor unit 1 is higher than the unit lower limit voltage V ₁ (40.0 [V]), only the lithium ion capacitor unit 1 is transferred to the motor circuit M. Supply power. At this time, both the switch SW1 and the switch SW3 in the switching circuit 8 are in a disconnected state. When the voltage detection means 5 detects that the inter-terminal voltage V _LIC of the lithium ion capacitor unit 1 has dropped to the unit lower limit voltage V ₁ (40.0 [V]) (step ST1), the control circuit 7 switches the switch SW1. A conduction signal for setting the conduction state is output (step ST2). In this state, the switching circuit 8 has the first circuit configuration. When the switch SW1 is turned on, the drive current is supplied to the motor circuit M from the secondary battery 3 charged to a voltage higher than the voltage of the lowered lithium ion capacitor unit 1, and at the same time the lithium ion capacitor A charging current is supplied to the unit 1

When the voltage of the secondary battery 3 at this time is 48.0 [V], the voltage of the lithium ion capacitor unit 1 lowered to the voltage of the secondary battery 3 and the unit lower limit voltage V ₁ (40.0 [V]). The voltage difference from the voltage is 8.0 [V]. When the internal resistance of the lithium ion capacitor unit 1 is 10 [mΩ] and the internal resistance of the secondary battery is also 10 [mΩ], the secondary battery 3 is calculated momentarily when there is no current limiting resistor 4. The maximum current discharges a large current of 400 [A]. Therefore, in order to limit the discharge current from the secondary battery 3, the lithium ion capacitor unit 1 is charged from the secondary battery 3 through the first discharge circuit 81 including the current limiting resistor 4. For example, when the potential difference between the secondary battery 3 and the lithium ion capacitor unit 1 is 8.0 [V], the resistance value of the current limiting resistor 4 is limited to about 3 [A] at maximum. It is preferable to select a resistance of about 0Ω50W. However, in actuality, it is necessary to determine the value of the current limiting resistor 4 in consideration of a power value at which there is no shortage in the power supplied to the load.

After the switch SW1 is in a conductive state, the voltage of the lithium ion capacitor unit 1 is set high first than the unit lower-limit voltages V ₁ voltage V ₂ (42.5 [V]) or more units lower limit voltages V ₁ When the voltage detection means 5 detects that the second set voltage V ₃ (37.5 [V]) is lower (step ST3), the control circuit 7 outputs a conduction signal for turning on the switch SW3. (Step ST4). When the switch SW3 is turned on, the switching circuit 8 has the second circuit configuration. Note that the switch SW1 may be shut off after the switch SW3 is turned on.

When the switch SW3 becomes conductive, the first discharge circuit 81 is short-circuited by the second discharge circuit 83. Thereafter, the discharge current from the secondary battery 3 is transferred from the second discharge circuit 83 to the motor circuit M and The lithium ion capacitor unit 1 is supplied. When the voltage of the lithium ion capacitor unit 1 rises to the first set voltage V ₂ , the motor circuit (load) M is used by using the secondary battery 3 after the switching circuit 8 has the first circuit configuration. In this case, necessary electric power can be supplied to the battery without overcurrent, and the lithium ion capacitor unit 1 can also be charged by the secondary battery 3 (FIG. 2A). The first set voltage V ₂ is a voltage that can prevent the discharge current from the secondary battery 3 to the load M from becoming an overcurrent. Therefore, in this state, the current limiting resistor 4 only causes the generation of power loss, and does not fulfill the function of preventing overcurrent. Therefore, by switching to the second circuit configuration, the current limiting resistor 4 is disconnected, the occurrence of power loss in the current limiting resistor 4 is prevented, and the load of the secondary battery 3 is reduced. As a result, the capacity reduction rate of the secondary battery 3 can be made slow.

The first set voltage V ₂ needs to be set so that the discharge current from the secondary battery 3 to the load does not exceed the maximum discharge current when the first circuit configuration is switched to the second circuit configuration. is there. As the first set voltage V ₂ , a fixed value can be used as described above. However, when the first set voltage V ₂ is set to a fixed value, if the voltage change rate at the time of discharge of the secondary battery increases due to deterioration of the secondary battery, individual differences, environmental temperature, etc., the first discharge When the current limiting means of the circuit is short-circuited, there is a possibility that the discharge current becomes larger than the maximum discharge current. Therefore, in such a case, as shown in the equation (1), a tolerance voltage that allows the discharge current from the voltage value (terminal voltage) V _{B of the} secondary battery to be prevented from becoming an overcurrent. The voltage value obtained by subtracting V _dif is preferably the first set voltage V ₂ .

V ₂ = V _B −V _dif (1)
The tolerance voltage V _dif can be calculated from the equation (2).

V _dif = I _ref · (R _C + R _B ) (2)
However, I _ref is the maximum discharging current of the secondary battery 3, R _C is the internal resistance of the lithium ion capacitor unit 1, R _B is the internal resistance of the secondary battery 3. For example, when I _ref = 10 [A], R _C = 10 [mΩ], and R _B = 10 [mΩ], V _dif = 200 [mV]. The control circuit 7 stores the tolerance voltage V _dif calculated in advance by the equation (2), and the control circuit 7 determines the first set voltage V ₂ based on the equation (1). When the voltage detecting means 5 detects that the voltage of the lithium ion capacitor unit has increased to the first set voltage V ₂ , the control circuit 7 outputs a switching command to the switching circuit 8.

Equation (2) is determined for the following reason. That is, when it becomes a 2nd circuit structure, the lithium ion capacitor unit 1 and the secondary battery 3 will be in the state connected directly. At this time, the resistance in the discharge circuit including the lithium ion capacitor unit 1 and the secondary battery 3 is only the internal resistance (R _C ) of the lithium ion capacitor unit and the internal resistance (R _B ) of the secondary battery. . In this circuit configuration, in order to prevent the discharge current from exceeding the maximum discharge current of the secondary battery 3, the voltage difference between the secondary battery 3 and the lithium ion capacitor unit 1 is set to the total value of the internal resistance (R _C + R _The current value (I) obtained by dividing by _B ) may be set to be equal to or less than the maximum discharge current (I _ref ) of the secondary battery. That is, the following equation (3) may be established between the tolerance voltage V _dif and the maximum discharge current (I _ref ).

V _dif / (R _C + R _B ) = I <= I _ref (3)
Therefore, as the tolerance voltage V _dif , the product of the total value (R _C + R _B ) of the internal resistance of the lithium ion capacitor unit 1 and the internal resistance of the secondary battery 3 and the maximum discharge current (I _ref ) of the secondary battery [ If the voltage value obtained by the above equation (2)] is used, the power loss due to the current limiting resistor 4 can be minimized while preventing the secondary battery from deteriorating.

When the voltage of the lithium ion capacitor unit 1 drops to the second set voltage V ₃ , the load at the time when the switching circuit 8 is in the first circuit configuration (the switch SW1 is in a conductive state) is too large. If the current is supplied to the load via the current limiting resistor 4, sufficient power cannot be supplied, and the discharge of the lithium ion capacitor unit 1 is continued (FIG. 2 (B)). Accordingly, in this case, if the current limiting resistor 4 is present in the discharge circuit, there is a risk that the discharge from the lithium ion capacitor unit 1 is continued and the voltage of each lithium ion capacitor is lowered to the lower limit voltage. . Therefore, by switching to the second circuit configuration (the switch SW3 is in a conductive state), the current limiting resistor 4 is disconnected from the discharge circuit, thereby supplying necessary power to the motor circuit (load) M, and a lithium ion capacitor.・ Prevent voltage drop of unit 1. From this point of view, the second set voltage V ₃ is a voltage that can prevent the voltage of the lithium ion capacitor from becoming lower than the lower limit voltage.

  As shown in FIG. 4, in the charging circuit 113 of the secondary battery 3, it is possible to use a plurality of diodes connected in series instead of the DC / DC converter as means for reducing the charging voltage. FIG. 4 shows a configuration of the second embodiment in which a diode is used for the charging circuit 113. 4, the same members as those in the embodiment shown in FIG. 1 are denoted by the same reference numerals as those in FIG. In the present embodiment, a plurality of diodes are connected in series to form a diode array 117, the anode side of the diode array 117 is connected to the terminal T 3 of the lithium ion capacitor unit 101, and the cathode is the anode of the secondary battery 103. Connect to terminal T5. With this configuration, the charging voltage of the secondary battery 103 can be easily adjusted by simply determining the number of diodes according to the rated voltage of the secondary battery 103 to be used without using a DC / DC converter. Is possible.

  According to the present invention, in a DC power supply device using a lithium ion capacitor unit as a main power source and a secondary battery as a backup power source, the burden on the secondary battery is reduced, the deterioration of the secondary battery is suppressed, and the life is extended. Further, it is possible to provide a DC power supply device that can supply power stably.

DESCRIPTION OF SYMBOLS 1 Lithium ion capacitor unit 3 Secondary battery 4 Current limiting resistance 5 Voltage detection means 6 Temperature detection means 7 Control circuit 8 Switching circuit 9 DC power supply 13 for charging 13 Charging circuits C1-C16 Lithium ion capacitor M Motor SW1, SW3, SW5 Switching circuit

Claims (9)

A lithium ion capacitor unit connected in parallel to the load;
A secondary battery connectable in parallel to the load and the lithium ion capacitor unit;
Voltage detection means for detecting the voltage of the lithium ion capacitor unit;
Until the voltage detection means detects the unit lower limit voltage of the lithium ion capacitor unit, the secondary battery is electrically disconnected from the load and the lithium ion capacitor unit, and the voltage detection means detects the unit lower limit voltage. And a switching circuit for connecting the secondary battery in parallel to the load and the lithium ion capacitor unit,
When the secondary battery is connected in parallel to the load and the lithium ion capacitor unit, the switching circuit includes a current limiting unit that first includes the secondary battery in the load and the lithium ion capacitor unit. A first circuit configuration connected in parallel via a discharge circuit, and then detecting that the voltage of the lithium ion capacitor unit has risen to a first set voltage higher than the unit lower limit voltage or the lithium ion capacitor -When it is detected that the voltage of the unit has dropped to a second set voltage lower than the unit lower limit voltage, the secondary battery is not included in the load and the lithium ion capacitor unit. second circuitry connected in parallel across a discharge circuit and Do Ri,
DC power supply device according to claim that you have provided further charging circuit for charging the secondary battery is in the operating state when the charging voltage from the external charger is applied to the lithium-ion capacitor unit.   2. The DC power supply device according to claim 1, wherein the second discharge circuit is configured by a short circuit that short-circuits the current limiting unit of the first discharge circuit. The DC power supply device according to claim 1 , wherein the charging circuit includes a switching circuit, and the secondary battery is charged when the switching circuit becomes conductive. The charging circuit includes a DC power supply device according to the charging voltage to claim 1 or 3 contains a DC / DC converter that steps down the voltage suitable for charging the secondary battery. A temperature detecting means for detecting the environmental temperature;
The DC / DC converter reduces the voltage suitable for charging the secondary battery when the detected temperature detected by the temperature detecting means is higher than a predetermined reference upper limit temperature, and the detected temperature detected by the temperature detecting means. The DC power supply device according to claim 4 , wherein when the voltage becomes lower than a predetermined reference lower limit temperature, a voltage suitable for charging the secondary battery is increased. A lithium ion capacitor unit connected in parallel to the load;
A secondary battery connectable in parallel to the load and the lithium ion capacitor unit;
Voltage detection means for detecting the voltage of the lithium ion capacitor unit;
Until the voltage detection means detects the unit lower limit voltage of the lithium ion capacitor unit, the secondary battery is electrically disconnected from the load and the lithium ion capacitor unit, and the voltage detection means detects the unit lower limit voltage. And a switching circuit for connecting the secondary battery in parallel to the load and the lithium ion capacitor unit,
When the secondary battery is connected in parallel to the load and the lithium ion capacitor unit, the switching circuit includes a current limiting unit that first includes the secondary battery in the load and the lithium ion capacitor unit. A first circuit configuration connected in parallel via a discharge circuit, and then detecting that the voltage of the lithium ion capacitor unit has risen to a first set voltage higher than the unit lower limit voltage or the lithium ion capacitor -When it is detected that the voltage of the unit has dropped to a second set voltage lower than the unit lower limit voltage, the secondary battery is not included in the load and the lithium ion capacitor unit. The second circuit configuration is connected in parallel through the discharge circuit,
The secondary battery is configured to include one or more diodes, and when the charging voltage is applied to the lithium ion capacitor unit from an external charger, the charging voltage is reduced to a voltage suitable for charging the secondary battery. A DC power supply device further comprising a charging circuit applied to the battery. The DC power supply device according to claim 6 , wherein the charging circuit includes a switching circuit, and the secondary battery is charged when the switching circuit becomes conductive. The first set voltage is a voltage obtained by subtracting, from a voltage between terminals of the secondary battery, a tolerance voltage that allows the discharge current from the secondary battery to be prevented from becoming an overcurrent. The DC power supply device according to claim 1 or 6 . The tolerance voltage, according to claim 8, characterized in that determined by the product of the maximum discharge current of the total value and the secondary battery of the internal resistance of the internal resistance and the secondary battery of the lithium-ion capacitor unit DC power supply.

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