Power supply device and vehicle

Abstract

A backup power supply device (10) comprises: a first power storage element (11); a first DC / DC converter (12) that carries out a first conversion in which the voltage from the first power storage element (11) is converted and output to an output terminal (20); a second power storage element (13); a second DC / DC converter (14) that carries out a third conversion in which the voltage from the second power storage element (13) is converted and output to the output terminal (20), and a fourth conversion in the reverse direction; a first control circuit (15); and a second control circuit (16). The backup power supply device (10) has a normal current mode in which the first DC / DC converter (12) is caused to carry out the first conversion, and the second DC / DC converter (14) is caused to carry out the fourth conversion, and a large current mode in which the first DC / DC converter (12) is caused to carry out the first conversion, and the second DC / DC converter (14) is caused to carry out the third conversion.

Description

Power supply device and vehicle

[0001] The present disclosure relates to a power supply device and a vehicle equipped with the power supply device.

[0002] 2. Description of the Related Art Various power supply devices have been proposed as power supply devices used as backup power supply devices that back up vehicle power sources (see, for example, Patent Document 1).

[0003] The power supply device of Patent Document 1 includes a first storage element, a second storage element connected in parallel to the first storage element and having a smaller internal resistance and storage capacity than the first storage element, an opening / closing unit connected between the first storage element and the second storage element and switching between a disconnected state and a connected state, a charging circuit connected to the input path of the first storage element and performing a step-down operation, a discharging circuit connected to the output path of the second storage element and performing a step-up operation, and a control circuit that controls the operation of the opening / closing unit, the charging circuit, and the discharging circuit.

[0004] This realizes a backup power supply device that combines the two advantages of efficiently supplying current over a long period of time without having to include a storage element with a large overall capacity, and of supplying large current during peak loads.

[0005] International Publication No. 2018 / 056190

[0006] In the technology of Patent Document 1, the first storage element and the second storage element are connected via an opening / closing unit, and therefore, in order to ensure that the second storage element can be charged from the first storage element via the opening / closing unit, it is necessary for the voltage of the first storage element to be higher than the voltage of the second storage element.

[0007] This limits the types of storage elements that can be combined as the first and second storage elements used in the backup power supply, and also necessitates an expensive switch that can withstand large currents.

[0008] a first DC / DC converter inserted in a path between the first storage element and the output terminal, the first DC / DC converter performing at least a first conversion of converting a voltage input from the first storage element and outputting it to the output terminal, and a second conversion of converting a voltage input from the output terminal and outputting it to the first storage element; a second storage element; a second DC / DC converter inserted in a path between the second storage element and the output terminal, the second DC / DC converter performing a third conversion of converting a voltage input from the second storage element and outputting it to the output terminal, and a fourth conversion of converting a voltage input from the output terminal and outputting it to the second storage element; and a control circuit controlling the first DC / DC converter and the second DC / DC converter, the control circuit having a large current mode in which the first DC / DC converter performs the first conversion and the second DC / DC converter performs the third conversion.

[0009] A vehicle according to one embodiment of the present disclosure includes a load including a steering device, and the power supply device that supplies power to the load.

[0010] The present disclosure provides a power supply device that includes two storage elements, does not require a switch to connect the two storage elements, and is not restricted by the component types of the two storage elements, and a vehicle that includes such a power supply device.

[0011] FIG. 1 is a block diagram showing the configuration of a backup power supply device according to an embodiment. FIG. 2 is a circuit diagram showing a specific example of the first DC / DC converter and the second DC / DC converter shown in FIG. 1. FIG. 3A is a diagram showing the current flow in normal current mode of the backup power supply device according to an embodiment. FIG. 3B is a diagram showing the current flow in high current mode of the backup power supply device according to an embodiment. FIG. 4 is a diagram showing an example of operation in normal current mode of the backup power supply device according to an embodiment. FIG. 5A is a flowchart showing operation when the backup power supply device according to an embodiment switches from normal current mode to high current mode. FIG. 5B is a diagram showing state changes of the backup power supply device when switching from the normal current mode to the high current mode shown in FIG. 5A. FIG. 6A is a flowchart showing a procedure when the backup power supply device according to an embodiment switches from the normal current mode to the high current mode in a manner different from that shown in FIG. 5A. FIG. 6B is a diagram supplementarily explaining the switching from the normal current mode to the high current mode shown in FIG. 6A. FIG. 7 is a diagram for explaining a control procedure for avoiding continuous switching between the charge mode and the stop mode. FIG. 8 is a block diagram showing the configuration of a backup power supply device according to a first modified embodiment. Fig. 9 is a block diagram showing the configuration of a backup power supply device according to a second modified example of the embodiment. Fig. 10 is a block diagram showing the configuration of a vehicle equipped with a backup power supply device according to a third modified example of the embodiment. Fig. 11 is a block diagram showing the configuration of the backup power supply device in Fig. 10. Fig. 12 is a diagram showing the current flow in the vehicle power supply mode of the backup power supply device shown in Fig. 11.

[0012] Embodiments of the present disclosure will be described in detail below with reference to the drawings. Each embodiment described below represents a specific example of the present disclosure. The numerical values, numbers, types of energy storage elements, components, component placement and connection configurations, steps, step order, charge / discharge characteristic examples, and the like shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Furthermore, each figure is not necessarily an exact illustration. In each figure, substantially identical components are assigned the same reference numerals, and redundant explanations are omitted or simplified. Furthermore, "A and B are connected" means that A and B are electrically connected, and includes not only a case where A and B are directly connected, but also a case where A and B are indirectly connected with another circuit element interposed between A and B. Furthermore, unless otherwise specified, "voltage," "current," and "power" mean "DC voltage," "DC current," and "DC power," respectively.

[0013] 1 is a block diagram showing the configuration of a backup power supply device 10 according to an embodiment. A load 50 is also shown. The backup power supply device 10 is an example of a power supply device that supplies power to the load 50 via an output terminal 20, and includes a first storage element 11, a first DC / DC converter 12, a second storage element 13, a second DC / DC converter 14, a first control circuit 15, a second control circuit 16, a first current detection circuit 17, a second current detection circuit 18, a voltage detection circuit 19, and the output terminal 20.

[0014] The first storage element 11 is a storage element capable of storing and supplying electric charge, and in this embodiment, is a storage element having a larger storage capacity and a smaller output current (i.e., a larger internal resistance) than the second storage element 13. For example, the first storage element 11 is a single lithium-ion battery (hereinafter also referred to as "LiB"). Generally, an LiB has a voltage of 1.8 V to 4.2 V depending on the state of charge.

[0015] First DC / DC converter 12 is an example of a DC / DC converter that is inserted in a path between first storage element 11 and output terminal 20 and performs at least a first conversion of converting a voltage input from first storage element 11 and outputting it to output terminal 20 (i.e., discharging from first storage element 11), and a second conversion of converting a voltage input from output terminal 20 and outputting it to first storage element 11 (i.e., charging first storage element 11). In this embodiment, first DC / DC converter 12 is a unidirectional DC / DC converter that performs only the first conversion of the first and second conversions.

[0016] The second storage element 13 is a storage element capable of storing and supplying electric charge, and in this embodiment, as described above, is a storage element having a smaller storage capacity and a larger output current (i.e., a smaller internal resistance) than the first storage element 11. For example, the second storage element 13 is four electric double layer capacitors (hereinafter also referred to as "EDLC") or lithium-ion capacitors (hereinafter also referred to as "LiC"). Generally, EDLC and LiC have a voltage of 0 V to 10.0 V depending on the charge storage state.

[0017] The second DC / DC converter 14 is a bidirectional DC / DC converter that is inserted into the path between the second storage element 13 and the output terminal 20 and performs a third conversion (i.e., discharging from the second storage element 13) of converting the voltage input from the second storage element 13 side and outputting it to the output terminal 20 side, and a fourth conversion (i.e., charging the second storage element 13) of converting the voltage input from the output terminal 20 side and outputting it to the second storage element 13 side.

[0018] The first control circuit 15 is a circuit that controls the first conversion by the first DC / DC converter 12, and controls the first DC / DC converter 12 to start, stop, and maintain a constant output voltage, as well as control a constant power output mode that sets a limit value for the output power (or output current).

[0019] The second control circuit 16 is a circuit that controls the third and fourth conversions performed by the second DC / DC converter 14, and performs controls such as starting up the second DC / DC converter 14, switching between the third and fourth conversions, stopping the converter, maintaining the output voltage constant, and controlling the constant power output mode that sets a limit value for the output power (or output current).

[0020] The first control circuit 15 and the second control circuit 16 constitute a control circuit that controls the first DC / DC converter 12 and the second DC / DC converter 14. The control circuit has a normal current mode in which the first DC / DC converter 12 performs the first conversion and the second DC / DC converter 14 performs the fourth conversion, and a large current mode in which the first DC / DC converter 12 performs the first conversion and the second DC / DC converter 14 performs the third conversion. Note that the normal current mode may also include a case in which the first DC / DC converter 12 performs the first conversion and the second DC / DC converter 14 is stopped. Here, the control circuit is specifically realized by an A / D converter, a D / A converter, a processor with a built-in control program, a drive circuit that amplifies power, etc.

[0021] The first current detection circuit 17 is a circuit that detects the current flowing from the output terminal 20 to the load 50, and is configured, for example, with a shunt resistor and an amplifier that amplifies the voltage drop across the shunt resistor.

[0022] Second current detection circuit 18 is a circuit that detects the current output from first storage element 11, and is configured with, for example, a shunt resistor and an amplifier that amplifies the voltage drop across the shunt resistor.

[0023] The voltage detection circuit 19 is a circuit that detects the voltage at the output terminal 20, and is, for example, a buffer amplifier.

[0024] The output terminal 20 is a terminal through which the backup power supply 10 supplies power to the load 50 .

[0025] 2 is a circuit diagram showing a specific example of the first DC / DC converter 12 and the second DC / DC converter 14 in FIG. 2A to 2E, the left side is the side connected to the storage element, and the right side is the side connected to the output terminal 20. FIG. 2A shows an example of a step-down converter that steps down a voltage from the storage element side to the output terminal 20 side, FIG. 2B shows an example of a step-up converter that steps up a voltage from the storage element side to the output terminal 20 side, FIG. 2C shows an example of a synchronous rectification bidirectional converter that steps down a voltage from the storage element side to the output terminal 20 side and steps up a voltage from the output terminal 20 side to the storage element side, FIG. 2D shows an example of a bidirectional step-up / step-down converter, and FIG. 2E shows an example of a circuit in which DC / DC converters are connected in parallel. Although (e) of FIG. 2 shows an example in which the step-down converters shown in (a) of FIG. 2 are connected in parallel, the present invention is not limited to this, and other types of DC / DC converters may be connected in parallel, or different types of DC / DC converters may be connected in parallel, or multiple paralleled DC / DC converters may each be controlled in an independent conversion direction.

[0026] In this embodiment, first DC / DC converter 12 is a DC / DC converter that performs the first conversion (i.e., discharging first storage element 11), and therefore may be any of the types shown in (a) to (e) of Fig. 2. Furthermore, second DC / DC converter 14 is a bidirectional DC / DC converter that performs the third conversion (i.e., discharging second storage element 13) and the fourth conversion (i.e., charging second storage element 13), and therefore may be any of the types of bidirectional DC / DC converters that are paralleled as shown in (c) and (d) of Fig. 2 and (e) of Fig. 2.

[0027] Next, the operation of the backup power supply device 10 according to this embodiment configured as described above will be described.

[0028] FIG. 3A is a diagram showing the current flow in the normal current mode of the backup power supply 10 according to the embodiment.

[0029] In the normal current mode, under the control of the first control circuit 15, the first DC / DC converter 12 performs a first conversion in which it converts the voltage input from the first storage element 11 side into a predetermined load voltage and outputs it to the output terminal 20 side, that is, it discharges the first storage element 11. In parallel with this, under the control of the second control circuit 16, the second DC / DC converter 14 performs a fourth conversion in which it converts the load voltage input from the output terminal 20 side into a voltage suitable for charging the second storage element 13 and outputs it to the second storage element 13 side, that is, it charges the second storage element 13.

[0030] In this normal current mode, the current discharged from the first storage element 11, which has a large storage capacity, is supplied to the load 50 as shown in Figure 3A, and is also supplied to the second storage element 13, thereby charging the second storage element 13.

[0031] FIG. 3B is a diagram showing the current flow in the large current mode of the backup power supply device 10 according to the embodiment.

[0032] In the large current mode, under the control of the first control circuit 15, the first DC / DC converter 12 performs a first conversion in which, as in the normal current mode, the first DC / DC converter 12 converts the voltage input from the first storage element 11 side into a predetermined load voltage and outputs it to the output terminal 20 side, i.e., discharges the first storage element 11. In parallel with this, under the control of the second control circuit 16, the second DC / DC converter 14 performs a third conversion in which the second DC / DC converter 14 converts the voltage input from the second storage element 13 side into a predetermined load voltage and outputs it to the output terminal 20 side, i.e., discharges the second storage element 13. As a result, the current output from the first DC / DC converter 12 and the current output from the second DC / DC converter 14 are superimposed and supplied to the load 50 via the first current detection circuit 17 and the output terminal 20.

[0033] In such a high current mode, the current discharged from the first storage element 11 is added to the current discharged from the second storage element 13, which has a large output current, and the large current after addition is supplied to the load 50, as shown in Figure 3B.

[0034] Here, the second storage element 13, which is specialized for large currents, has a smaller capacity than the first storage element 11 and becomes empty in a short period of time, but by switching to the normal current mode shown in Figure 3A after the large current mode, it can be charged by the current from the large-capacity first storage element 11.

[0035] In this way, the backup power supply device 10 of this embodiment has a normal current mode that makes use of the advantage of the first storage element 11, which has a small output current but a large capacity, and a large current mode that makes use of the advantage of the second storage element 13, which has a small capacity but a large output current.As a result, it is possible to efficiently supply current over a long period of time and to supply large currents at peak loads without having to provide storage elements with a large overall capacity.

[0036] This advantage will be explained in more detail as follows. If the energy storage elements of the backup power supply 10 were composed only of energy storage elements A with small output currents but large capacities, a large number of energy storage elements A would be required to provide the ability to output a large current. For example, to construct an energy storage element capable of outputting a maximum output current of 200 A using only energy storage elements A with a maximum output current of 40 A and having the capacity of one energy storage element A in terms of the duration of current output (amount of energy), five energy storage elements A would be required.

[0037] On the other hand, if the storage elements of the backup power supply unit 10 are constructed using only storage elements B, which have a small capacity but a large output current (for example, a maximum output current of 200 A and a duration (amount of energy) for outputting current that is one-tenth of that of storage element A), ten storage elements B would be required to construct a storage element with the same capacity as above.

[0038] In contrast, the backup power supply device 10 according to this embodiment only needs to have one storage element A and one storage element B as the first storage element 11 and the second storage element 13, which is the optimal solution.

[0039] Here, the features of the present embodiment compared to the prior art will be described using a specific example. Suppose that energy storage element A is an LiB having a voltage of 1.8 V to 4.2 V and energy storage element B is an LiC having a voltage of 2.2 V to 3.6 V. According to the prior art, when the remaining capacity of energy storage element A decreases to a state where the voltage is only 2.0 V, the voltage of energy storage element A is lower than the minimum voltage of 2.2 V of the LiC constituting energy storage element B, and therefore a problem occurs in that energy storage element A cannot charge energy storage element B.

[0040] In contrast, in backup power supply device 10 according to the present embodiment, first storage element 11 and second storage element 13 are not connected via a switch, but rather via first DC / DC converter 12 and second DC / DC converter 14. As a result, as described above, backup power supply device 10 is only provided with one LiB and one LiC, which are the optimal solution, as first storage element 11 and second storage element 13, respectively, and can operate in both normal current mode and large current mode without being subject to constraints that depend on the voltages of first storage element 11 and second storage element 13.

[0041] 4A and 4B are diagrams illustrating an example of operation in the normal current mode of the backup power supply device 10 according to the embodiment. More specifically, (a) of Fig. 4A illustrates an example of operation when the second storage element 13 is charged in the normal current mode when the voltage of the second storage element 13 is zero, and (b) of Fig. 4B illustrates an example of operation when the second storage element 13 is charged in the normal current mode when the voltage of the second storage element 13 is not zero.

[0042] As shown in (a) of Figure 4, when the voltage of the second storage element 13 is zero, the "output current of the first storage element" is the sum of the "load current" supplied from the output terminal 20 to the load 50 and the "charging current" used to charge the second storage element 13. As shown in the figure, the "charging current" used to charge the second storage element 13 is constant. This "charging current" causes the "voltage of the second storage element" to rise.

[0043] As shown in (b) of Figure 4, when the voltage of second storage element 13 is not zero, the "output current of the first storage element" is the sum of the "load current" supplied from output terminal 20 to load 50 and the "charging current" used to charge second storage element 13, similar to (a) of Figure 4. However, as shown in the figure, the "charging current" used to charge second storage element 13 decreases toward zero after a certain period of time has elapsed (i.e., when second storage element 13 is fully charged). Due to this "charging current," the "voltage of the second storage element" rises and then reaches a saturation voltage.

[0044] FIG. 5A is a flowchart showing the operation of the backup power supply 10 according to the embodiment when it switches from the normal current mode to the large current mode.

[0045] Now, it is assumed that second DC / DC converter 14 is stopped or is performing the fourth conversion (that is, charging second storage element 13) (S10).

[0046] The second control circuit 16 determines whether the load current detected by the first current detection circuit 17 has reached a predetermined allowable current of the first storage element 11 (S11), and if it determines that the load current has reached the predetermined allowable current of the first storage element 11 (Yes in S11), it switches to the large current mode and operates (S12). That is, in the large current mode, the second control circuit 16 causes the second DC / DC converter 14 to perform the third conversion, i.e., discharge from the second storage element 13. The above procedure (steps S10 to S12) is repeated in the normal current mode until the mode is switched to the large current mode.

[0047] In addition, in the above step S11, the second control circuit 16 may make a similar judgment using the discharge current of the first storage element 11 detected by the second current detection circuit 18 instead of the load current detected by the first current detection circuit 17.

[0048] 5B is a diagram showing the state change of backup power supply 10 when switching from the normal current mode shown in FIG. 5A to the large current mode. As shown in FIG. 5B, assume that the "load current" begins to increase at a certain point and exceeds the "allowable current of the first storage element" at some point. This is detected by second control circuit 16, which monitors the "load current" via first current detection circuit 17. Under the control of second control circuit 16, second DC / DC converter 14 starts the third conversion, thereby starting discharge from second storage element 13 (the "output current of the second storage element").

[0049] As a result, as shown in the figure, the "output current of the first storage element" increases to the "allowable current of the first storage element" and then maintains the "allowable current of the first storage element." In parallel with this, the "output current of the second storage element" increases as the "load current" increases. In other words, the "output current of the first storage element" and the "output current of the second storage element" are superimposed to generate the "load current."

[0050] FIG. 6A is a flowchart showing a procedure for switching the backup power supply 10 according to the embodiment from the normal current mode to the large current mode in a manner different from that shown in FIG. 5A.

[0051] This procedure is based on the premise that the first DC / DC converter 12 is operating in constant power output mode under the control of the first control circuit 15. In other words, under the control of the first control circuit 15, the first DC / DC converter 12 has a limit value for the output power (or the output current during constant voltage output), and more specifically, has the characteristic that when the first DC / DC converter 12 outputs a current exceeding a certain limit value during constant voltage output, the output voltage is reduced in accordance with the current that exceeds the limit value.

[0052] Now, it is assumed that second DC / DC converter 14 is stopped or is performing the fourth conversion (that is, charging second storage element 13) (S20).

[0053] Using voltage detection circuit 19, second control circuit 16 determines whether it has detected that the voltage at output terminal 20 has dropped below a predetermined voltage (S21), and if it determines that the voltage at output terminal 20 has dropped below the predetermined voltage (Yes in S21), it switches to the large current mode and operates (S22). That is, in such a case, second control circuit 16 determines that the current discharging from first storage element 11 has reached the allowable current of first storage element 11, and causes second DC / DC converter 14 to perform the third conversion, i.e., discharge from second storage element 13. The above procedure (steps S20 to S22) is repeated in the normal current mode until switching to the large current mode is performed.

[0054] Fig. 6B is a diagram supplementarily explaining the switching from the normal current mode to the large current mode shown in Fig. 6A. Fig. 6B(a) is a diagram explaining the constant power output mode of the first DC / DC converter 12. As shown in this figure, the first DC / DC converter 12 operates in the constant power output mode under the control of the first control circuit 15. In this mode, the output voltage of the first DC / DC converter 12 normally maintains a constant value even when the output current increases, but when the output current exceeds a "limit value," the output voltage is reduced in accordance with the current exceeding the "limit value" ("output of the first DC / DC converter").

[0055] 6B(b) is a diagram showing the state change of the backup power supply 10 when switching from the normal current mode shown in FIG. 6A to the large current mode. As shown in this figure, assume that the "load current" begins to increase at a certain point and exceeds the "allowable current of the first storage element" at some point. Then, the first DC / DC converter 12 drops the output voltage (i.e., the "load voltage") in constant power output mode. This is detected by the second control circuit 16, which monitors the "load voltage" using the voltage detection circuit 19. Under the control of the second control circuit 16, the second DC / DC converter 14 starts the third conversion, which starts discharging the second storage element 13 (the "output current of the second storage element").

[0056] As a result, as shown in the figure, the "output current of the first storage element" rises to the "allowable current of the first storage element" and then maintains the "allowable current of the first storage element." In parallel with this, as the "load current" rises, the "output current of the second storage element" increases, and the decrease in the "load voltage" is maintained at a constant value. As a result, the "output current of the first storage element" and the "output current of the second storage element" are superimposed to generate a "load current."

[0057] Next, we will explain the control to avoid an event in which the second control circuit 16 repeatedly switches between charging (also called "charging mode") and stopping (also called "stopping mode") the second storage element 13 (i.e., an event in which the charging mode, stopping mode, charging mode, stopping mode, etc. occur).

[0058] Now, suppose that first DC / DC converter 12 is performing the first conversion (i.e., discharging first storage element 11) and, in parallel, second DC / DC converter 14 is performing the fourth conversion (i.e., charging second storage element 13) (i.e., charging mode). Then, suppose that an increase in the load current causes the current discharged from first storage element 11 to reach the allowable current of first storage element 11. Therefore, suppose that the fourth conversion (i.e., charging second storage element 13) by second DC / DC converter 14 is stopped (i.e., stop mode).

[0059] As a result, the current discharged from first storage element 11 decreases, and the current discharged from first storage element 11 falls below the allowable current of first storage element 11. As a result, if charging of second storage element 13 is not completed, second DC / DC converter 14 may again perform the fourth conversion (i.e., charging second storage element 13, i.e., charge mode). This may result in continuous switching between charge mode, stop mode, charge mode, etc.

[0060] Therefore, the backup power supply device 10 according to this embodiment has two types of control procedures (i.e., a first measure and a second measure) described below as a function for avoiding such continuous switching between the charging mode and the stop mode.

[0061] 7A and 7B are diagrams illustrating a control procedure for avoiding successive switching between the charging mode and the stop mode. More specifically, (a) of Fig. 7A is a diagram illustrating a control procedure for a first measure, and (b) of Fig. 7B is a diagram illustrating a control procedure for a second measure.

[0062] As shown in (a) of Figure 7, in the first measure, in the normal current mode in which the first DC / DC converter 12 performs the first conversion and the second DC / DC converter 14 performs the fourth conversion (i.e., the charging mode), the second control circuit 16 stops the fourth conversion (i.e., the "charging current" in the figure) by the second DC / DC converter 14 (i.e., enters the stop mode) when the current detected by the first current detection circuit 17 (i.e., the "load current" in the figure) exceeds the first threshold value (i.e., the "charging stop threshold" in the figure).

[0063] As a result, even if the "load current" continues to increase, charging to the second storage element 13 is stopped, so the "output current of the first storage element" does not reach the "allowable current of the first storage element," and the stop mode is maintained.

[0064] It is preferable that the "charge stop threshold" be set to the value of the "load current" when the sum of the "load current" and the "charge current" is lower than the "allowable current of the first storage element."

[0065] On the other hand, as shown in (b) of Figure 7, in the second measure, in the normal current mode in which the first DC / DC converter 12 performs the first conversion and the second DC / DC converter 14 performs the fourth conversion (i.e., the charging mode), the second control circuit 16 controls the magnitude of the charging current output from the second DC / DC converter 14 to the second storage element 13 so that the current detected by the second current detection circuit 18 (i.e., the "output current of the first storage element" in the figure) does not exceed a second threshold value (i.e., the "discharge threshold value" in the figure) that is lower than the "allowable current of the first storage element."

[0066] As a result, even if the "load current" continues to increase, the "output current of the first storage element" does not exceed the "allowable current of the first storage element", and the charging mode is maintained.

[0067] The "discharge threshold" may be set to any value as long as it is lower than the "allowable current of the first storage element." Furthermore, only one of the first and second measures described above may be implemented in the backup power supply device 10, or both may be implemented in the backup power supply device 10 and selected by a user setting.

[0068] As described above, backup power supply device 10 according to this embodiment is a power supply device having output terminal 20 connected to load 50 and supplying power to load 50 via output terminal 20, and includes first storage element 11, first DC / DC converter 12 inserted in a path between first storage element 11 and output terminal 20 and performing at least the first conversion of converting a voltage input from first storage element 11 and outputting it to output terminal 20, and the second conversion of converting a voltage input from output terminal 20 and outputting it to first storage element 11, second storage element 13, and first DC / DC converter 12 inserted in a path between second storage element 13 and output terminal 20 and performing at least the first conversion of converting a voltage input from second storage element 13 and outputting it to first storage element 11. The power supply circuit includes a second DC / DC converter 14 that performs a third conversion in which a voltage input from the output terminal 20 is converted and output to an output terminal 20, and a fourth conversion in which a voltage input from the output terminal 20 is converted and output to a second storage element 13, and a control circuit (a first control circuit 15 and a second control circuit 16) that controls the first DC / DC converter 12 and the second DC / DC converter 14, and the control circuit has a normal current mode in which the first DC / DC converter 12 performs the first conversion and the second DC / DC converter 14 performs the fourth conversion, and a large current mode in which the first DC / DC converter 12 performs the first conversion and the second DC / DC converter 14 performs the third conversion.

[0069] As a result, first storage element 11 and second storage element 13 are not connected via a switch, but rather via first DC / DC converter 12 and second DC / DC converter 14. Therefore, a power supply device is realized that does not require an expensive switch to connect the two storage elements and is not restricted by the combination of the two storage elements.

[0070] The backup power supply 10 further includes a first current detection circuit 17 that detects the current flowing from the output terminal 20 to the load 50, and the control circuits (first control circuit 15 and second control circuit 16) switch to the large current mode when the current detected by the first current detection circuit 17 reaches the allowable current of the first storage element 11 while the second DC / DC converter 14 is stopped or performing the fourth conversion. As a result, when it becomes necessary to supply a current to the load 50 that exceeds the allowable current of the first storage element 11, the mode is automatically switched to the large current mode.

[0071] The backup power supply 10 further includes a voltage detection circuit 19 that detects the voltage at the output terminal 20, the first DC / DC converter 12 operates in the constant power output mode, and the control circuits (the first control circuit 15 and the second control circuit 16) switch to the large current mode when the voltage detection circuit 19 detects that the voltage at the output terminal 20 has dropped below a predetermined voltage while the second DC / DC converter 14 is stopped or performing the fourth conversion. As a result, when it becomes necessary to supply a current to the load 50 that exceeds the allowable current of the first storage element 11, the mode is automatically switched to the large current mode.

[0072] The control circuit further has a normal current mode in which first DC / DC converter 12 performs the first conversion and second DC / DC converter 14 performs the fourth conversion, thereby performing a mode in which current is supplied from first storage element 11 to load 50 and second storage element 13.

[0073] Furthermore, backup power supply 10 further includes a first current detection circuit 17 that detects the current flowing from output terminal 20 to load 50, and first control circuit 15 stops the fourth conversion by second DC / DC converter 14 when the current detected by first current detection circuit 17 exceeds a first threshold in the normal current mode. This can prevent the second storage element 13 from being repeatedly switched between charge mode, stop mode, charge mode, and so on.

[0074] Furthermore, the backup power supply device 10 may further include a second current detection circuit 18 that detects the current output from the first storage element 11, and the control circuits (first control circuit 15 and second control circuit 16) may control the charging current output from the second DC / DC converter 14 to the second storage element 13 so that the current detected by the second current detection circuit 18 does not exceed a second threshold value in the normal current mode. This also makes it possible to prevent the second storage element 13 from being repeatedly switched between charge mode, stop mode, charge mode, etc.

[0075] Furthermore, first storage element 11 has a larger storage capacity and a smaller output current than second storage element 13. This allows for a normal current mode that makes use of the advantage of first storage element 11, that is, a small output current but a large capacity, and a large current mode that makes use of the advantage of second storage element 13, that is, a small capacity but a large output current, to be realized, thereby achieving both efficient supply of current over a long period of time and supply of a large current at peak loads without providing storage elements with a large overall capacity.

[0076] Figure 8 is a block diagram showing the configuration of a backup power supply 10a according to a first modification of the embodiment. Backup power supply 10a according to this modification has a configuration in which a third DC / DC converter 21, a third control circuit 22, a third current detection circuit 23, a first switch 24, and a second switch 25 are added to the configuration of backup power supply 10 according to the embodiment shown in Figure 1. The following description will focus on the differences from the embodiment.

[0077] The first switch 24 is a switch that turns on / off the connection between the first storage element 11 and the third current detection circuit 23. The second switch 25 is a switch that turns on / off the connection between the second storage element 13 and the third DC / DC converter 21. The third current detection circuit 23 is a circuit that detects the current output by the first storage element 11, and has the same function as the second current detection circuit 18.

[0078] The third DC / DC converter 21 has a first terminal T1 connected to the first storage element 11 via a third current detection circuit 23 and a first switch 24, and connected to the second storage element 13 via a second switch 25, and a second terminal T2 connected to the output terminal 20. The third DC / DC converter 21 is a bidirectional DC / DC converter that performs a fifth conversion in which a voltage input to the first terminal T1 is converted and output from the second terminal T2, and a sixth conversion in which a voltage input to the second terminal T2 is converted and output from the first terminal T1. The third DC / DC converter 21 has the same function as the second DC / DC converter 14.

[0079] The third control circuit 22 is a circuit that controls the fifth and sixth conversions performed by the third DC / DC converter 21 , and has the same function as the second control circuit 16 .

[0080] According to the backup power supply device 10a of this modification, if a failure occurs in the first system consisting of the first DC / DC converter 12, the first control circuit 15, and the second current detection circuit 18, the third system consisting of the third DC / DC converter 21, the third control circuit 22, and the third current detection circuit 23 can be operated in place of the first system by turning on the first switch 24. Similarly, if a failure occurs in the second system consisting of the second DC / DC converter 14 and the second control circuit 16, the third system can be operated in place of the second system by turning on the second switch 25.

[0081] As described above, the backup power supply device 10a according to this modification further includes the first switch 24, the second switch 25, and the third DC / DC converter 21. The third DC / DC converter 21 has a first terminal T1 connected to the first storage element 11 via the first switch 24 and connected to the second storage element 13 via the second switch 25, and a second terminal T2 connected to the output terminal 20. The third DC / DC converter 21 performs a fifth conversion in which it converts a voltage input to the first terminal T1 and outputs it from the second terminal T2, and a sixth conversion in which it converts a voltage input to the second terminal T2 and outputs it from the first terminal T1.

[0082] As a result, if the first system consisting of the first DC / DC converter 12, the first control circuit 15, and the second current detection circuit 18 fails, or if the second system consisting of the second DC / DC converter 14 and the second control circuit 16 fails, the third system consisting of the third DC / DC converter 21, the third control circuit 22, and the third current detection circuit 23 can operate in place of the failed first or second system, thereby improving the failure tolerance of the backup power supply device 10a.

[0083] Figure 9 is a block diagram showing the configuration of a backup power supply 10b according to a second modification of the embodiment. Backup power supply 10b according to this modification has a configuration in which a third switch 26 and a fourth switch 27 are added to the configuration of backup power supply 10 according to the embodiment shown in Figure 1. The following description will focus on the differences from the embodiment.

[0084] The third switch 26 is a switch inserted in the path between the first storage element 11 and the first DC / DC converter 12, and in this embodiment, is inserted between the first storage element 11 and the second current detection circuit 18. The fourth switch 27 is a switch inserted in the path between the second storage element 13 and the first DC / DC converter 12.

[0085] According to backup power supply device 10b of this modified example, the storage element connected to first DC / DC converter 12 can be switched between first storage element 11 and second storage element 13. Therefore, under normal circumstances, third switch 26 is turned on and fourth switch 27 is turned off, thereby performing the same operation as in the embodiment, and when the charge capacity of first storage element 11 is exhausted or when first storage element 11 fails, third switch 26 is turned off and fourth switch 27 is turned on, thereby connecting first DC / DC converter 12 to second storage element 13 and maintaining current supply from first DC / DC converter 12 to load 50.

[0086] As described above, the backup power supply device 10b of this modified example has the same configuration as the backup power supply device 10 of the embodiment, and further includes a third switch 26 inserted in the path between the first storage element 11 and the first DC / DC converter 12, and a fourth switch 27 inserted in the path between the second storage element 13 and the first DC / DC converter 12.

[0087] This means that even if the charging capacity of the first storage element 11 is exhausted or the first storage element 11 fails, the normal current mode can be maintained by connecting the first DC / DC converter 12 to the second storage element 13.

[0088] 10 is a block diagram showing the configuration of a vehicle 60 equipped with a backup power supply device 10c according to a third modification of the embodiment. The vehicle 60 includes, as components related to the backup power supply device 10c, a vehicle power supply 55 such as a lead battery used to charge the backup power supply device 10c, an alternator generator 56, and door ECUs (Electronic Control Units) / ACTs 50a to 50c as loads 50, a steering device 50d, and a brake device 50e.

[0089] Figure 11 is a block diagram showing the configuration of backup power supply device 10c in Figure 10. Also shown here is a vehicle power supply 55 and a load 50. Backup power supply device 10c has a configuration in which, instead of the unidirectional first DC / DC converter 12 and the first control circuit 15 that controls it in backup power supply device 10 according to the embodiment, a bidirectional first DC / DC converter 12a and a first control circuit 15a that controls it are provided, and an interrupting element 28 and a backup detection circuit 29 are added. The following description will focus on the differences from the embodiment.

[0090] First DC / DC converter 12a is a bidirectional DC / DC converter and has the same function as second DC / DC converter 14. First control circuit 15a is a circuit that controls first DC / DC converter 12a and has the same function as second control circuit 16. Breaker element 28 is a circuit breaker that turns on / off the connection between vehicle power supply 55 and backup power supply device 10c, more specifically, the connection between vehicle power supply 55 and first current detection circuit 17.

[0091] The backup detection circuit 29 is a control circuit that monitors the output voltage of the vehicle power supply 55, and turns off the cut-off element 28 if the output voltage drops below a threshold, and turns on the cut-off element 28 if the output voltage does not drop below a threshold.

[0092] In backup power supply device 10c having such a configuration, in vehicle power supply mode where the output voltage of vehicle power supply 55 is equal to or higher than a threshold, interrupting element 28 is turned on by backup detection circuit 29, and as shown in Fig. 12, current supplied from vehicle power supply 55 passes through interrupting element 28 and first current detection circuit 17 to load 50, charges first storage element 11 via first DC / DC converter 12a and second current detection circuit 18, and is also supplied to charge second storage element 13 via second DC / DC converter 14. Fig. 12 is a diagram showing the current flow in the vehicle power supply mode of backup power supply device 10c shown in Fig. 11.

[0093] On the other hand, in the backup power supply mode in which the output voltage of the vehicle power supply 55 is lower than the threshold value, the backup detection circuit 29 turns off the cut-off element 28, and the same operation as that of the backup power supply device 10 of the embodiment is performed, that is, a normal current mode in which current is supplied from the first storage element 11 to the load 50, or a large current mode in which current is supplied from the first storage element 11 and the second storage element 13 to the load 50 is performed.

[0094] Thus, according to the backup power supply device 10c of this modified example, in the vehicle power supply mode where the output voltage of the vehicle power supply 55 is equal to or higher than the threshold value, current is supplied from the vehicle power supply 55 to the load 50, and current is also supplied to the first storage element 11 and the second storage element 13. On the other hand, in the backup power supply mode where the output voltage of the vehicle power supply 55 is lower than the threshold value, current is supplied from the backup power supply device 10c to the load 50 in the normal current mode or the large current mode.

[0095] While the power supply device and vehicle according to the present disclosure have been described above based on the embodiments and modifications, the present disclosure is not limited to these embodiments and modifications. As long as they do not deviate from the gist of the present disclosure, various modifications that would occur to a person skilled in the art to the present embodiments and modifications, and other forms constructed by combining some of the components of the embodiments and modifications, are also included within the scope of the present disclosure.

[0096] For example, the backup power supply device 10a according to the first modified example has a configuration in which a first switch 24, a second switch 25, a third DC / DC converter 21, etc. are added to the configuration of the backup power supply device 10 according to the embodiment, but this is not limited to this, and the backup power supply device 10b according to the second modified example or the backup power supply device 10c according to the third modified example may have a configuration in which a first switch 24, a second switch 25, a third DC / DC converter 21, etc. are added.

[0097] Similarly, the backup power supply unit 10b according to the second modified example has a configuration in which a third switch 26 and a fourth switch 27 are added to the configuration of the backup power supply unit 10 according to the embodiment, but this is not limited to this, and the backup power supply unit 10b may have a configuration in which a third switch 26 and a fourth switch 27 are added to the configuration of the backup power supply unit 10a according to the first modified example or the backup power supply unit 10c according to the third modified example.

[0098] The present disclosure can be used as a power supply device and a vehicle equipped with a power supply device, for example, as a backup power supply device that is not restricted by the combination of two storage elements, and as a vehicle equipped with such a backup power supply device.

[0099] 10, 10a, 10b, 10c Backup power supply device 11 First storage element 12, 12a First DC / DC converter 13 Second storage element 14 Second DC / DC converter 15, 15a First control circuit 16 Second control circuit 17 First current detection circuit 18 Second current detection circuit 19 Voltage detection circuit 20 Output terminal 21 Third DC / DC converter 22 Third control circuit 23 Third current detection circuit 24 First switch 25 Second switch 26 Third switch 27 Fourth switch 28 Interrupting element 29 Backup detection circuit 50 Load 50a, 50b, 50c Door ECU / ACT 50d Steering device 50e Brake device 55 Vehicle power supply 56 Alternator generator 60 Vehicle T1 First terminal T2 Second terminal

Claims

1. A power supply device having an output terminal connected to a load and supplying power to the load via the output terminal, comprising: a first storage element; a first DC / DC converter inserted in a path between the first storage element and the output terminal, the first DC / DC converter performing at least the first conversion of converting a voltage input from the first storage element and outputting it to the output terminal, and a second DC / DC converter performing a third conversion of converting a voltage input from the second storage element and outputting it to the output terminal, and a fourth conversion of converting a voltage input from the output terminal and outputting it to the second storage element; and a control circuit controlling the first DC / DC converter and the second DC / DC converter, the control circuit having a large current mode in which the first DC / DC converter performs the first conversion and the second DC / DC converter performs the third conversion.

2. The power supply device according to claim 1, further comprising a first current detection circuit that detects a current flowing from the output terminal to the load, and wherein the control circuit switches to the large current mode and operates when the current detected by the first current detection circuit reaches an allowable current of the first storage element while the second DC / DC converter is stopped or performing the fourth conversion.

3. The power supply device according to claim 1, further comprising a voltage detection circuit that detects the voltage at the output terminal, wherein the first DC / DC converter operates in a constant power output mode, and wherein the control circuit switches to the large current mode and operates when the voltage detection circuit detects that the voltage at the output terminal has dropped below a predetermined voltage while the second DC / DC converter is stopped or performing the fourth conversion.

4. The power supply device according to any one of claims 1 to 3, wherein the control circuit further has a normal current mode in which the first DC / DC converter performs the first conversion and the second DC / DC converter performs the fourth conversion.

5. The power supply device according to claim 4, further comprising a first current detection circuit that detects a current flowing from the output terminal to the load, and wherein the control circuit stops the fourth conversion by the second DC / DC converter when the current detected by the first current detection circuit exceeds a first threshold value in the normal current mode.

6. The power supply device according to claim 4, further comprising a second current detection circuit that detects the current output by the first storage element, and wherein the control circuit controls the charging current output from the second DC / DC converter to the second storage element so that the current detected by the second current detection circuit does not exceed a second threshold value in the normal current mode.

7. The power supply device according to any one of claims 1 to 6, further comprising: a first switch; a second switch; and a third DC / DC converter, wherein the third DC / DC converter has a first terminal connected to the first storage element via the first switch and connected to the second storage element via the second switch; and a second terminal connected to the output terminal, and performs a fifth conversion of converting a voltage input to the first terminal and outputting it from the second terminal, and a sixth conversion of converting a voltage input to the second terminal and outputting it from the first terminal.

8. A power supply device as claimed in any one of claims 1 to 6, further comprising: a third switch inserted in a path between the first storage element and the first DC / DC converter; and a fourth switch inserted in a path between the second storage element and the first DC / DC converter.

9. A power supply device according to any one of claims 1 to 8, wherein the storage capacity of the first storage element is greater than the storage capacity of the second storage element, and the output current of the first storage element is smaller than the output current of the second storage element.

10. A vehicle comprising: a load including a steering device; and a power supply device according to any one of claims 1 to 9 that supplies power to the load.

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