Vehicle power supply device

Abstract

In this vehicle power supply device, an electricity storage unit (3) is provided with: a plurality of switches (SW1-SW4) that selectively switch between connecting a plurality of capacitors (C1-C3) in series or in parallel; and a voltage detection unit that measures the voltage across both ends of each of the plurality of capacitors (C1-C3). When a voltage detection unit (30) detects, as a voltage at both ends, a predetermined voltage at which at least one of the plurality of capacitors (C1-C3) cannot be further discharged, the control unit (4) distributes the residual charge of the at least one of the plurality of capacitors (C1-C3) to the other capacitors by controlling the plurality of switches (SW1-SW4) to be connected in parallel. Therefore, power can be supplied to the load again without recharging.

Description

Technical Field

[0001] The present invention relates to a power supply device for a vehicle. Background Art

[0002] In recent years, due to environmental considerations and the like, the electrification of automobiles (hereinafter referred to as vehicles) has been continuously promoted. Electrification is not limited to the power of the vehicle, and the conversion from conventional mechanical control to electrical control is also being continuously promoted for vehicle control systems including brakes, steering wheels, etc. In such an electrical control situation, when the storage battery becomes abnormal, there is a risk of falling into a very dangerous state where not only the power is lost but also the vehicle control system no longer operates and it is impossible to stop safely.

[0003] In response to these problems, a vehicle power supply device as an auxiliary power supply has been proposed for supplying power to a vehicle control system when the storage battery is abnormal such as a temporary voltage drop of the storage battery or a permanent storage battery failure state (for example, refer to Patent Document 1).

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2020-120464 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] However, in the storage unit used in the vehicle power supply device as described above, a plurality of storage elements are connected in series. When one of the plurality of storage elements reaches the discharge limit (for example, the charge is zero), even if there is remaining charge in other storage elements, further discharge cannot be performed. That is, although there is remaining charge in the storage unit as a whole, the power supply to the load (for example, the vehicle control system) ends without exhausting these charges.

[0009] An object of the present disclosure is to provide a vehicle power supply device that can effectively utilize the remaining charge to supply power to the load again even in a vehicle power supply device in which a plurality of storage elements of the storage unit discharge in an unbalanced manner as described above and cannot supply power to the load (for example, the vehicle control system) due to a storage element that has reached the discharge limit and there is remaining charge in other storage elements.

[0010] Means for Solving the Problems

[0011] A vehicle power supply device according to one aspect of the present disclosure includes:

[0012] A power supply unit that supplies power to a load;

[0013] A power storage unit that supplies power in an abnormal state of the power supply unit;

[0014] A charging circuit that charges the power storage unit;

[0015] A voltage conversion circuit that converts the voltage of the power storage unit into a specified voltage and outputs the specified voltage to the load; and

[0016] A control unit that controls the operations of the power storage unit, the charging circuit, and the voltage conversion circuit,

[0017] wherein the power storage unit includes:

[0018] A plurality of capacitors;

[0019] A plurality of switches that selectively switch to connect the plurality of capacitors in series or in parallel; and

[0020] A voltage detection unit that measures the voltages across both ends of each of the plurality of capacitors,

[0021] When the voltage detection unit detects a specified voltage at which at least one of the plurality of capacitors cannot be further discharged as the voltage across both ends, the control unit distributes the remaining charge of at least one of the plurality of capacitors to other capacitors by controlling the plurality of switches to be connected in parallel, so as to be able to supply power to the load again without recharging.

[0022] Effects of the Invention

[0023] Therefore, in a vehicle power supply device in which the plurality of power storage elements of the power storage unit discharge in an unbalanced manner and power cannot be supplied to a load (such as a vehicle control system) due to a power storage element that has reached the discharge limit and there is remaining charge in other power storage elements, the remaining charge can be effectively utilized to supply power to the load again. As a result, power can be ensured after the power supply is lost, and initial diagnosis of defective parts can be performed quickly. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a block diagram showing a structural example of a vehicle power supply device according to Embodiment 1.

[0025] Figure 2 is a diagram showing Figure 1 a structural example of the power storage unit 3.

[0026] Figure 3 is a diagram showing Figure 1 a flowchart of a power storage control process executed by the control unit 4.

[0027] Figure 4 is a block diagram showing a structural example of the power storage unit 3A according to Modification 1.

[0028] Figure 5 is a block diagram showing a structural example of the vehicle power supply device according to Embodiment 2.

[0029] Figure 6 is a block diagram showing a structural example of the vehicle power supply device according to Embodiment 3.

[0030] Figure 7 is a flowchart showing the charge storage control process executed by Figure 6 the vehicle ECU 8 and the control unit 4.

[0031] Figure 8 is a block diagram showing a structural example of the vehicle power supply device according to Embodiment 4.

[0032] Figure 9 is a block diagram showing the structure of the vehicle power supply device according to the conventional example.

[0033] Figure 10 is a flowchart showing the charge storage control process executed by Figure 9 the control unit 104. Detailed Embodiments

[0034] Hereinafter, embodiments and modifications of the present invention will be described with reference to the drawings. In addition, the same or similar components are denoted by the same reference numerals.

[0035] (Inventor's Opinion)

[0036] Figure 9 is a block diagram showing the structure of the vehicle power supply device according to the conventional example. In Figure 9 the vehicle power supply device according to the conventional example is configured to include a power supply unit 101, a load 102, a power storage unit 103, a control unit 104, a charging circuit 105, and a voltage conversion circuit 106. Here, as a charge storage element for storing charge as an auxiliary power supply, for example, an electric double layer capacitor is used, and a plurality of charge storage elements are connected to form the power storage unit 103.

[0037] In the vehicle power supply device configured as described above, during normal operation, the power supply unit 101 including the storage battery supplies the power required by the load 102, and the power supply unit 101 charges the power storage unit 103 via the charging circuit 105 to prevent an abnormal state of the storage battery. In the case where an abnormal state occurs in the storage battery, by supplying the charge accumulated in the power storage unit 103 to the load 102 via the voltage conversion circuit 106, the power storage unit 103 can supply the charge as much as possible to supply the power required for vehicle control, so that safe parking can be achieved without losing vehicle control.

[0038] Figure 10 It is a flowchart showing the charge storage control process executed by Figure 9 the control unit 104. In Figure 10 it, it is assumed that an abnormal state has occurred in the power supply unit 101 including the storage battery.

[0039] In Figure 10 it, first, when an abnormal state of the power supply unit 101 is detected (S101: "Yes"), the discharge (standby operation) of supplying DC power from the power storage unit 103 to the load 102 is started (S102). By the discharge, the charge of the power storage unit 103 decreases, and when further power supply cannot be performed (S103: "Yes"), the system of the control unit 104 is normally ended (S104) before getting out of control to stop the function.

[0040] Figure 9 The power storage unit 103 used in the vehicle power supply device according to the conventional example shown in the figure is formed by connecting a plurality of power storage elements in series. When one of the plurality of power storage elements reaches the discharge limit (for example, the charge is zero), even if there is remaining charge in other power storage elements, further discharge cannot be performed. That is, although there is remaining charge in the power storage unit 103 as a whole, the power supply to the load 2 (for example, the vehicle control system) is ended without using up these charges.

[0041] The inventors have devised a technical solution that can effectively utilize the remaining charge to supply power to the load again even in a vehicle power supply device in which a plurality of power storage elements of the power storage unit discharge in an unbalanced manner as described above and power supply to the load (vehicle control system) cannot be performed due to a power storage element that has reached the discharge limit. The vehicle power supply device is designed as follows.

[0042] (Embodiment 1)

[0043] Figure 1 It is a block diagram showing a structural example of the vehicle power supply device according to Embodiment 1. In Figure 1In the vehicle power supply device according to Embodiment 1, it is configured to include a power supply unit 1, a load 2, a power storage unit 3, a control unit 4, a charging circuit 5, and a voltage conversion circuit 6. Here, the power supply unit 1 includes, for example, a secondary battery such as a storage battery, and the load 2 is, for example, a load such as a vehicle control system. In addition, as a power storage element for storing charge as an auxiliary power supply, an electric double layer capacitor is used, for example, and these multiple electric double layer capacitors are connected in series, for example, to form the power storage unit 3.

[0044] In the vehicle power supply device configured as described above, DC power is supplied from the power supply unit 1 to the load 2 during normal operation of the vehicle. In addition, the control unit 4 operates the charging circuit 5, for example, to charge the power storage unit 3 to prevent an abnormal state of the power supply unit 1 including the storage battery. When the power supply unit 1 becomes an abnormal state such as a voltage drop or failure, the control unit 4 senses the voltage drop and supplies DC power from the power storage unit 3 to the load 2. At this time, the voltage conversion circuit 6 is used as needed to perform voltage conversion to obtain the voltage required by the load 2.

[0045] Figure 2 is a block diagram showing Figure 1 a structural example of the power storage unit 3.

[0046] In Figure 2 it, the power storage unit 3 is connected between the charging circuit 5 and the voltage conversion circuit 6. The power storage unit 3 is configured to include:

[0047] (1) Capacitors C1 to C3 that store charge;

[0048] (2) Switches SW1 to SW6 that selectively switch to connect the capacitors C1 to C3 in series or in parallel based on control from the control unit 4; and

[0049] (3) A voltage detection unit 30 that measures the voltages V1 to V3 across each of the capacitors C1 to C3 and the output voltage Vout (= V1 + V2 + V3; which refers to the voltage between one end of the charging circuit 5 side of the capacitor C3 and the ground terminal), and outputs the measurement results to the control unit 4.

[0050] Here, the control unit 4 uses control signals S1 to S6 to control the on or off of the switches SW1 to S6 respectively. In addition, during normal operation and standby operation when an abnormal state of the power supply unit 1 occurs, the capacitors C1 to C3 are in an on state through the switches SW1 and SW2 and the switches SW3, SW4, SW5, and SW6 are in an off state (hereinafter, referred to as the "initial state of the switches SW1 to SW6") and are connected in series.

[0051] Figure 3 is a flowchart showing the power storage control process executed by Figure 1 the control unit 4.

[0052] In Figure 3 step S1, first, after setting the initial states of switches SW1 to SW6, when an abnormal state occurs in the power supply unit 1 (S2: "Yes"), power supply from the power storage unit 3 to the load 2 (backup operation) is started (S3). Moreover, due to the power supply from the power storage unit 3, the amount of charge stored in capacitors C1 to C3 decreases. Here, when any one of capacitors C1 to C3 has no charge, even if there is remaining charge in other capacitors, further charge supply is not possible. Therefore, the voltage detection unit 30 monitors the remaining charge amount in each of capacitors C1 to C3 by measuring the voltage of each of capacitors C1 to C3.

[0053] When it is detected through voltage monitoring by the voltage detection unit 30 that the voltage across one or more of capacitors C1 to C3 has dropped below the threshold voltage Vth1 (S4: "Yes"), the control unit 4 stops the power supply from the power storage unit 3 and makes the switches SW1 and SW2 open and the switches SW3 to SW6 closed (hereinafter, referred to as "parallel connection state of capacitors C1 to C3 achieved by switches SW1 to SW6") (S5), to distribute the remaining charge in capacitors C1 to C3 to each of capacitors C1 to C3, thereby enabling the charge amounts among capacitors C1 to C3 to be made uniform (S6). That is, by supplying charge to the capacitor that has no charge, charge supply can be resumed.

[0054] The threshold voltage Vth1 in step S4 is set as follows. In the vehicle power supply device, in the case of an abnormal state where the power supply unit 1 fails and the power storage unit 3 is also unable to supply charge, the control unit 4 becomes a state where it loses its own power supply and is unable to perform control to make the charge of capacitors C1 to C3 of the power storage unit 3 uniform. In Embodiment 1, in order to avoid falling into such an abnormal state, the threshold voltage Vth1 of each of capacitors C1 to C3 is set in a state where there is remaining power for charge equalization processing. That is, the threshold voltage Vth1 is set to the voltage across each of capacitors C1 to C3 before reaching the abnormal state.

[0055] Next, the control unit 4 determines whether the charge equalization of the capacitors C1 to C3 is completed (S7) based on the voltage monitoring performed by the voltage detection unit 30, according to the absolute value of each voltage difference between the respective terminal voltages V1 to V3 of the capacitors C1 to C3 becoming equal to or less than a specified threshold voltage difference ΔV. If "Yes", it proceeds to step S8. On the other hand, if "No", it returns to step S7. In step S8, the connection of the capacitors C1 to C3 is restored to the series connection state by returning the switches SW1 to SW6 to their initial states. Next, it is determined whether the output voltage Vout of the power storage unit 3 is equal to or higher than the threshold voltage Vth2 (S9).

[0056] The threshold voltage Vth2 in step S9 is set as follows. The threshold voltage Vth2 is set to an output voltage Vout that is sufficient for the system of the load 2 to operate in a normal state after the charge equalization of the capacitors C1 to C3 is completed.

[0057] In step S9, if "Yes", it proceeds to step S10. On the other hand, if "No", it proceeds to step S11. In step S10, it is set to a state (standby state) where DC power can be supplied to the load 2, and this charge storage control process is ended. In this case, when the user turns on the ignition device, the power supply to the load 2 starts, and initial diagnosis such as investigating the cause of the vehicle becoming abnormal can be performed quickly. On the other hand, when the voltage of the power storage unit 3 is equal to or lower than the threshold voltage Vth2 (S9: "No"), the state is such that the charge that can be supplied to the load 2 is insufficient and restart is not possible, and the system of the control unit 4 is directly ended (S11) to end this charge storage control process.

[0058] According to the vehicle power supply device according to Embodiment 1 configured as described above, even in a vehicle power supply device that cannot supply power to the load 2 (e.g., the vehicle control system) when the charge amounts of the plurality of power storage elements, i.e., the capacitors C1 to C3, of the power storage unit 3 are discharged in an unbalanced manner and there is remaining charge in other capacitors due to a capacitor that has reached the discharge limit, the remaining charge can be effectively utilized to supply power to the load 2 again. As a result, power can be ensured after power loss, and initial diagnosis of defective parts can be performed quickly.

[0059] In the above Embodiment 1, the case where the number of capacitors in the power storage unit 3 is three has been described. However, the present disclosure is not limited to this, and as long as there are two or more capacitors. This is the same in other embodiments and modification examples.

[0060] (Modification Example 1)

[0061] Figure 4It is a block diagram showing a structural example of the power storage unit 3A according to Modification 1. Figure 4 The vehicle power supply device is different from Figure 1 the vehicle power supply device.

[0062] (1) It has a power storage unit 3A instead of the power storage unit 3, and the power storage unit 3A has the following resistors R1 to R2 for preventing inrush current.

[0063] (A) A resistor R1 is inserted between the switches SW3 and SW4.

[0064] (B) A resistor R2 is inserted between the switch SW3 and one end on the charging circuit 5 side of the capacitor C3.

[0065] Next, the differences will be described.

[0066] In the vehicle power supply device configured as described above, when multiple capacitors C1 to C3 with a potential difference are connected, a large current will flow instantaneously, causing abnormal heating, melting of wiring, etc. To prevent such inrush current, the current amount can be suppressed by connecting the resistors R1 and R2. Here, the capacitors C1 to C3 are, for example, electric double layer capacitors.

[0067] In the above Modification 1, the resistors R1 and R2 are also provided, but the present disclosure is not limited thereto, and it may also be configured to connect a resistor connected in parallel with at least one of the multiple capacitors when the switches SW3 and SW4 are turned on. In addition, Modification 1 and its modifications can also be applied to other embodiments and modifications.

[0068] (Embodiment 2)

[0069] Figure 5 It is a block diagram showing a structural example of the vehicle power supply device according to Embodiment 2. Figure 5 The vehicle power supply device is different from Figure 1 the vehicle power supply device.

[0070] (1) Another power supply unit 7 is connected to the control unit 4. Here, the other power supply unit 7 is, for example, a secondary battery such as a storage battery or a lithium ion battery.

[0071] Next, the differences will be described.

[0072] In Figure 5In the vehicle power supply device, when it enters an abnormal state where the power supply unit 1 fails and the power storage unit 3 cannot supply charge either, the control unit 4 loses its own power supply and cannot perform the control to equalize the charges of the capacitors C1 to C3 in the power storage unit 3. In Embodiment 1, to avoid entering such a state, the threshold voltages Vth1 of the respective capacitors C1 to C3 are set in a state where there is remaining power for performing charge equalization processing.

[0073] However, the original purpose of the power storage unit 3 is to supply DC power for ensuring safety during an abnormal state of the power supply unit 1. Therefore, in Embodiment 1, the charge cannot be exhausted for the original purpose. To address such a problem, in Embodiment 2, by additionally connecting another power supply unit 7 to the control unit 4, the control unit 4 can be supplied with DC power from the other power supply unit 7. Thus, even when it enters an abnormal state where the power supply unit 1 fails and the power storage unit 3 cannot supply charge either, the charge equalization processing of the capacitors C1 to C3 can be performed. Moreover, the vehicle power supply device according to Embodiment 2 has the same effects as those of Embodiment 1.

[0074] (Embodiment 3)

[0075] Figure 6 is a block diagram showing a structural example of the vehicle power supply device according to Embodiment 3. Figure 6 The vehicle power supply device differs from Figure 1 the vehicle power supply device in the following aspects.

[0076] (1) A vehicle ECU (Electronic Control Unit) 8 is connected to the control unit 4.

[0077] Next, the differences will be described.

[0078] In Figure 6 the vehicle power supply device, the control unit 4 communicates with the vehicle ECU 8 via a specified communication line. The vehicle ECU 8 is a control device that controls the entire vehicle, and the vehicle power supply device also operates under the control of the vehicle ECU 8. In Embodiments 1 and 2, the vehicle power supply device performs control in a manner that can be restarted through its own judgment, but it is also assumed that there may be risks such as fire when power is applied again according to the fault state of the vehicle. All information related to the vehicle is aggregated in the vehicle ECU 8, and in such a state, the control of the vehicle power supply device can be performed based on the overall condition of the vehicle.

[0079] Figure 7 is shown by Figure 6Flowchart of the charge storage control process executed by the vehicle ECU 8 and the control unit 4.

[0080] In Figure 7 the control unit 4 similarly executes Figure 3 the processes of steps S1 to S3. That is, in step S3, the standby operation by the charge storage unit 3 is started, and the charges of the capacitors C1 to C3 are released. When it is detected that the voltage across one or more of the capacitors C1 to C3 has dropped below the threshold voltage Vth1 (S3: "Yes"), the control unit 4 sends a single-cell voltage drop notification signal to the vehicle ECU 8.

[0081] In response to this, the vehicle ECU 8 receives the single-cell voltage drop notification signal from the control unit 4 (S31). When it is determined that restart is possible based on the vehicle state (S32: "Yes"), an instruction signal including equalization of the capacitor charges is sent to the control unit 4 (S33). On the other hand, when it is determined that restart is not possible based on the vehicle state (S32: "No"), an instruction signal not including equalization of the capacitor charges is sent to the control unit 4 (S34).

[0082] In response to the instruction signal from the vehicle ECU 8, the control unit 4 determines whether the instruction signal is an instruction signal including equalization of the capacitor charges (S23). When it is "Yes", it proceeds to step S5. On the other hand, when it is "No", it proceeds to step S24. The control unit 4 executes the same processes as Figure 3 the control process of

[0083] after step S5 (S5 to S11) and ends this charge storage control process. On the other hand, in step S24, the discharge from the charge storage unit 3 is ended, the system of the control unit 4 is ended, and then this charge storage control process is ended.

[0084] (Embodiment 4)

[0085] Figure 8 is a block diagram showing a structural example of the vehicle power supply device according to Embodiment 4. Figure 8 The vehicle power supply device of Figure 1 is different from the vehicle power supply device of

[0086] (1) It simultaneously includes the vehicle ECU 8 according to Embodiment 3 and the other power supply unit 7 according to Embodiment 2.

[0087] Next, the differences will be described.

[0088] In the vehicle power supply device according to the fourth embodiment configured as described above, even when an abnormal state occurs in which the power supply unit 1 fails and the power storage unit 3 cannot supply charge, it is possible to perform the charge equalization process of the capacitors C1 to C3, and the vehicle power supply device can be controlled by the determination of the vehicle ECU 8. In addition, the vehicle power supply device according to the fourth embodiment has the same effects as the vehicle power supply devices according to the first to third embodiments.

[0089] (Modification example)

[0090] In the above embodiments and modification examples, the power supply unit 1 and the other power supply unit 7 are, for example, batteries that supply DC power, but the present disclosure is not limited thereto, and AC power may be converted into DC power for supply. In addition, AC power may be supplied and an AC-DC converter may be provided on the power receiving side.

[0091] Industrial applicability

[0092] The vehicle power supply device according to the present invention is useful for rapid and safe recovery processing when an abnormality occurs in the power supply unit as an in-vehicle auxiliary power supply.

[0093] Description of reference numerals

[0094] 1: Power supply unit; 2: Load; 3: Power storage unit; 4: Control unit; 5: Charging circuit; 6: Voltage conversion circuit; 7: Power supply unit; 8: Vehicle ECU; 30: Voltage detection unit; C1 to C3: Capacitors; SW1 to SW6: Switches; R1 to R2: Resistors.

Claims

1. A vehicle power supply device, comprising: a power supply unit that supplies power to a load; a power storage unit that supplies electric power in an abnormal state of the power supply unit; a charging circuit for charging the power storage unit; a voltage conversion circuit that converts the voltage of the power storage unit into a predetermined voltage and outputs the predetermined voltage to the load; and a control unit that controls the operations of the power storage unit, the charging circuit, and the voltage conversion circuit, in, The power storage unit includes: Multiple capacitors; a plurality of switches that selectively switch to connect the plurality of capacitors in series or in parallel; and a voltage detection unit for measuring a voltage across both ends of each of the plurality of capacitors; When the voltage detection unit detects a specified voltage as the voltage across both ends that prevents at least one of the multiple capacitors from further discharging, the control unit controls the multiple switches to be connected in parallel to distribute the remaining charge of at least one of the multiple capacitors to other capacitors, so that power can be supplied to the load again without recharging.

2. The vehicle power supply device according to claim 1, wherein: The control unit controls the plurality of switches to be connected in parallel, thereby equalizing the amount of charge accumulated in the plurality of capacitors.

3. The vehicle power supply device according to claim 2, wherein: The control unit performs the equalization of the charge amount according to an instruction of a vehicle electronic control unit (vehicle ECU).

4. The vehicle power supply device according to claim 2, wherein: The control unit further comprises another power supply unit, the other power supply unit being connected to the control unit and configured to supply power to the load. The control unit receives power supply from the other power supply unit when performing the equalization of the charge amount.

5. The vehicle power supply device according to claim 1, wherein: The plurality of capacitors are electric double layer capacitors.

6. The vehicle power supply device according to any one of claims 1 to 5, wherein: The power storage unit further includes a resistor connected in parallel with at least one of the plurality of capacitors and configured to suppress an inrush current flowing through the plurality of capacitors when the plurality of switches are switched.

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