Vehicle power supply device

Abstract

To provide a power supply device for a vehicle capable of suppressing the occurrence of power supply voltage fluctuation affecting the operation of an auxiliary machine load even if there is a large change in power demand in the auxiliary machine load when a power supply source is only a DC-DC converter (DDC).SOLUTION: A vehicle power supply device that supplies electric power to a plurality of auxiliary loads mounted on a vehicle, the vehicle power supply device comprising: a power supply source; an auxiliary battery including a lithium ion battery that can be charged by the power supply source; a DDC that is provided between the power supply source and the plurality of auxiliary loads and controls electric power supply from the power supply source to the plurality of auxiliary loads; A control device includes a switch that switches an electrical connection state between a plurality of auxiliary loads and an auxiliary battery, and a control unit that controls a DCDC converter and the switch, and the control unit controls the DCDC converter such that an output voltage of the DCDC converter is higher when the switch is turned off than when the switch is turned on.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a power supply device mounted on a vehicle. [Background technology]

[0002] Patent Document 1 discloses a vehicle power supply device that controls the power supply from a driving battery to an auxiliary battery. This vehicle power supply device increases the power supply to the auxiliary battery by controlling the output voltage of a DC-DC converter based on the operation of an electronically controlled brake system, which is one of the auxiliary loads, and prevents the voltage of the auxiliary battery from dropping below a threshold. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-213456 Summary of the Invention [Problem to be solved by the invention]

[0004] When a lithium-ion battery is used as the auxiliary battery, a switch is generally provided to disconnect the auxiliary battery from the power system (DC-DC converter) to protect the lithium-ion battery. In this configuration where a switch is inserted between the auxiliary battery and the DC-DC converter, when the switch is in a conductive state (electrically connected), the power supply source to the auxiliary load is both the auxiliary battery and the DC-DC converter, so problematic fluctuations in power supply voltage are unlikely to occur even if the power demand of the auxiliary load changes significantly. However, when the switch is in a disconnected state (electrically disconnected), the power supply source to the auxiliary load is only the DC-DC converter, which creates the problem of power supply voltage fluctuations being easily affected by large changes in the power demand of the auxiliary load.

[0005] Therefore, there is room for further study on the control method for supplying power to the auxiliary load when the switch is in the OFF state and the only power supply source to the auxiliary load is the DC-DC converter.

[0006] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a power supply device for a vehicle that can suppress power supply voltage fluctuations that affect the operation of an auxiliary load even if there is a large change in power demand in the auxiliary load when the power supply source is only a DC-DC converter. [Means for solving the problem]

[0007] In order to solve the above problem, one aspect of the disclosed technology is a vehicle power supply device that supplies power to multiple auxiliary loads mounted on a vehicle, and includes: a power supply source; an auxiliary battery including a lithium-ion battery that can be charged by the power supply source; a DC-DC converter that is provided between the power supply source and the multiple auxiliary loads and controls the power supply from the power supply source to the multiple auxiliary loads; a switch that is provided between the DC-DC converter, the multiple auxiliary loads, and the auxiliary battery and switches the electrical connection state between the multiple auxiliary loads and the auxiliary battery; and a control unit that controls the DC-DC converter and the switch, wherein the control unit controls the output voltage of the DC-DC converter so that a second voltage when the switch is turned off is higher than a first voltage when the switch is turned on. [Effects of the Invention]

[0008] According to the vehicle power supply device of the present disclosure, even if there is a large change in the power demand of the auxiliary load when the switch inserted between the auxiliary battery and the DC-DC converter is in the cut-off state, it is possible to suppress the occurrence of power supply voltage fluctuations that affect the operation of the auxiliary load. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic configuration diagram of a vehicle power supply device according to an embodiment of the present disclosure; [Figure 2]Processing flowchart of switch cutoff determination control performed by a vehicle power supply device [Figure 3] First sequence diagram of switch tripping process in switch tripping judgment control [Figure 4] Second sequence diagram of switch tripping process in switch tripping judgment control [Figure 5] Process flowchart of switch conduction determination control performed by a vehicle power supply device [Figure 6] Third sequence diagram of switch continuity processing in switch continuity determination control [Figure 7] Fourth sequence diagram of switch continuity processing in switch continuity determination control DETAILED DESCRIPTION OF THE INVENTION

[0010] The vehicle power supply device of the present disclosure controls the output voltage of the DC-DC converter to be higher when the switch inserted between the auxiliary battery and the DC-DC converter is in the OFF state than when the switch is in the ON state, thereby suppressing fluctuations in the power supply voltage due to large changes in the power demand of the auxiliary load when the switch is in the OFF state. Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0011] <Embodiment> [composition] FIG. 1 is a diagram illustrating a schematic configuration of a vehicle power supply device 1 according to an embodiment of the present disclosure. The vehicle power supply device 1 is a device that supplies power for driving a plurality of auxiliary loads 101, 102, and 103. The vehicle power supply device 1 illustrated in FIG. 1 includes a power supply source 10, a DC-DC converter (DDC) 20, an auxiliary battery (auxiliary LiB) 30, a switch (SW) 40, a first control unit 51, and a second control unit 52. In FIG. 1, solid lines indicate wiring through which power is transmitted and received, and dotted lines indicate wiring through which signals such as control, request, and notification are transmitted and received. The vehicle power supply device 1 and the plurality of auxiliary loads 101, 102, and 103 can be mounted on a vehicle or the like.

[0012] The power supply source 10 is configured to supply power to a plurality of auxiliary loads 101, 102, and 103 via a DC-DC converter 20. The power supply source 10 is also configured to charge an auxiliary battery 30. For example, the power supply source 10 may be a secondary battery (high-voltage battery) such as a lithium-ion battery configured to be chargeable and dischargeable, or a generator (alternator) that generates electric power.

[0013] The DC-DC converter 20 is a power converter that can convert input power into power of a predetermined voltage and output it. One end of this DC-DC converter 20 is connected to a power supply source 10, and the other end is connected to a plurality of auxiliary loads 101, 102, and 103. The DC-DC converter 20 can supply the power output from the power supply source 10 connected to one end to the plurality of auxiliary loads 101, 102, and 103 connected to the other end. The operation of this DC-DC converter 20 is controlled by a second control unit 52.

[0014] The auxiliary battery 30 is a secondary battery configured to be chargeable and dischargeable using a lithium ion battery (LiB). The auxiliary battery 30 is connected to the DC-DC converter 20 via a switch 40 so that it can be charged with power from the power supply source 10, and is also connected to a plurality of auxiliary loads 101, 102, and 103 so that it can supply its own stored power. The state of the auxiliary battery 30 is monitored by a first control unit 51.

[0015] The switch 40 is a switching element (such as a semiconductor relay or a mechanical relay) that is provided between the DC-DC converter 20 and the auxiliary loads 101, 102, and 103 and the auxiliary battery 30, and can switch between an electrically conductive state and an electrically cut-off state between the two. The connection state of the switch 40 is controlled by the first control unit 51.

[0016] The multiple auxiliary loads 101, 102, and 103 are predetermined in-vehicle devices that are driven by power supplied from the DC-DC converter 20 (power supply source 10) and / or the auxiliary battery 30, such as electronic devices and equipment that are not involved in the running of the vehicle. At least one of the multiple auxiliary loads 101, 102, and 103 is a load that can request the DC-DC converter 20 to increase its output voltage in order to intentionally increase the power it consumes. Note that the number of auxiliary loads to which the vehicle power supply device 1 supplies power is not limited to three as shown in FIG. 1.

[0017] The first control unit 51 is configured to have at least a function of monitoring the state of the auxiliary battery 30 and a function of controlling the connection state of the switch 40. The first control unit 51 can monitor the state of the auxiliary battery 30 for abnormalities (such as a ground fault or a short to power) in the auxiliary battery 30 that prevent the auxiliary battery 30 from maintaining its connection with the DC-DC converter 20. The first control unit 51 can also monitor whether the auxiliary battery 30 is in a charging state where current is flowing in or a discharging state where current is flowing out. These states of the auxiliary battery 30 can be detected using detection elements (not shown) such as a voltage sensor and a current sensor provided in the auxiliary battery 30. Furthermore, the first control unit 51 can control the connection state of the switch 40 to a conductive state using a predetermined ON signal that activates the switch 40, or to a cut-off state using a predetermined OFF signal that deactivates the switch 40, for example.

[0018] Furthermore, when the first control unit 51 controls the switch 40 to a cut-off state or a conduction state, it can notify the second control unit 52 that the switch 40 has been cut off or conducted. Furthermore, the first control unit 51 can control the switch 40 to a cut-off state by accepting a cut-off request for the switch 40 notified from the second control unit 52. Furthermore, the first control unit 51 constantly monitors the output voltage of the DC-DC converter 20, and can control the switch 40 to a conduction state in response to a change in the output voltage.

[0019] The second control unit 52 is configured to have at least a function of controlling the operation of the DC-DC converter 20 and a function of making requests to the multiple auxiliary loads 101, 102, and 103. The second control unit 52 can adjust the output voltage of the DC-DC converter 20 as the operation of the DC-DC converter 20. More specifically, the second control unit 52 increases or decreases the output voltage of the DC-DC converter 20 in response to notifications received from the first control unit 51 and requests received from the multiple auxiliary loads 101, 102, and 103. The second control unit 52 can also transmit, as requests to the multiple auxiliary loads 101, 102, and 103, instructions to temporarily limit fluctuations in power demand in the auxiliary loads and instructions to release this limit.

[0020] The second control unit 52 is also configured to be able to grasp the states of the multiple auxiliary loads 101, 102, and 103, and to acquire information such as the amount of power (current) consumed by each auxiliary load and the operation (scheduled operation) status of its functions. This information can be used to determine whether to transmit various requests to the multiple auxiliary loads 101, 102, and 103.

[0021] The first control unit 51 and the second control unit 52 described above may be integrated into a single configuration, or may be subdivided into configurations for each function. Furthermore, some or all of the functions of the first control unit 51 and the second control unit 52 may be configured as one or more electronic control units (ECUs) that typically include a processor, a memory, an input / output interface, and the like. The electronic control units configured in this manner realize the respective functions of the first control unit 51 and the second control unit 52 by the processor reading and executing a program stored in the memory.

[0022] [control] Next, with further reference to FIGS. 2 to 7, the control executed by the vehicle power supply device 1 according to this embodiment will be described.

[0023] [1] SW cutoff judgment control 2 is a flowchart illustrating the procedure of the SW cutoff determination control executed by the first control unit 51 and the second control unit 52 of the vehicle power supply device 1. The SW cutoff determination control illustrated in FIG. 2 is executed when the switch 40 is in a conductive state.

[0024] (Step S201) The first control unit 51 determines whether or not an abnormality has occurred in the auxiliary battery 30. An abnormality in the auxiliary battery 30 refers to an abnormality such as a ground fault or a power fault that unintentionally affects the power supply from the DC-DC converter 20 to the auxiliary loads 101, 102, and 103.

[0025] If the first control unit 51 determines that an abnormality has occurred in the auxiliary battery 30 (abnormality detection) (step S201, YES), the process proceeds to step S204. On the other hand, if the first control unit 51 determines that an abnormality has not occurred in the auxiliary battery 30 (step S201, NO), the process proceeds to step S202.

[0026] (Step S202) The second control unit 52 determines whether or not it has received a "voltage increase request" from at least one of the auxiliary loads 101, 102, and 103, which requests an increase in the output voltage of the DC-DC converter 20. This voltage increase request is a prior request for the execution of a specific operation, with the aim of preventing an extreme drop in the power supply voltage (a change below the lower limit of the operable voltage of the auxiliary load) due to a specific operation that consumes a large current performed by the auxiliary load. In this embodiment, since the auxiliary battery 30 is a lithium-ion battery (LiB), the voltage increase request for increasing the output voltage of the DC-DC converter 20 to a voltage that exceeds the allowable operating voltage range of the lithium-ion battery is the subject of the determination.

[0027] If the second control unit 52 determines that a voltage increase request has been received from the auxiliary load (YES in step S202), the process proceeds to step S203. On the other hand, if the second control unit 52 determines that a voltage increase request has not been received from the auxiliary load (NO in step S202), the process proceeds to step S201.

[0028] (Step S203) The first control unit 51 determines whether the auxiliary battery 30 is in a charging state. This determination is made to confirm that the current state of the DC-DC converter 20 is in a state where there is a margin in the power supply capacity (such as a predetermined margin with respect to the rated output) that is sufficient to charge the auxiliary battery 30. If the auxiliary battery 30 is in a discharging state, it can be assumed that the auxiliary loads 101, 102, and 103 are consuming a large amount of power that cannot be supplied by the DC-DC converter 20 alone.

[0029] If the first control unit 51 determines that the auxiliary battery 30 is in a charging state (step S203, Yes), the process proceeds to step S205. On the other hand, if the first control unit 51 determines that the auxiliary battery 30 is not in a charging state (step S203, No), the process proceeds to step S201.

[0030] (Step S204) In order to switch the switch 40 from a conductive state to a cut-off state, the first control unit 51 and the second control unit 52 execute a SW cut-off process (FIG. 3) according to a first sequence based on the occurrence of an abnormality in the auxiliary battery 30. The SW cut-off process according to this first sequence will be described later. When the switch 40 is brought into the cut-off state according to the first sequence, the SW cut-off determination control ends.

[0031] (Step S205) In order to switch the switch 40 from the conductive state to the cut-off state, the first control unit 51 and the second control unit 52 execute a SW cut-off process (FIG. 4) according to a second sequence based on a voltage increase request from the auxiliary load. This SW cut-off process according to the second sequence will be described later. When the switch 40 is brought into the cut-off state according to the second sequence, the SW cut-off determination control ends.

[0032] [1-1]. First sequence SW shutoff process 3, a description will be given of a SW shutoff process according to a first sequence executed by first control unit 51, second control unit 52, and auxiliary loads 101, 102, and 103. In this first sequence, the following steps a1 to h1 are executed.

[0033] Step a1: The first control unit 51 determines whether there is an abnormality in the auxiliary battery 30 (step S201 in FIG. 2). Step b1: The first control unit 51 switches the switch 40 from the conductive state to the cut-off state. Step c1: The first control unit 51 transmits to the second control unit 52 a SW cutoff completion notification indicating that the switch 40 has been switched to the cutoff state.

[0034] Step d1: In response to receiving the SW cutoff completion notification, the second control unit 52 transmits a temporary load limit request to the auxiliary loads 101, 102, and 103, instructing the auxiliary loads to temporarily limit an increase in current consumption. This temporary load limit request is a request to suppress the operation of a function that generates power demand that exceeds the rated performance of the DC-DC converter 20. For example, in a vehicle, this request can be a limit request issued to a comfort-related function that does not affect the actions of "driving," "turning," and "stopping." The temporary load limit request also serves to notify the auxiliary loads 101, 102, and 103 that voltage fluctuations are likely to occur. Step e1: The auxiliary loads 101, 102, and 103 each implement a shedding response in response to receiving the temporary load shedding request.

[0035] Step f1: The second control unit 52 performs a process of increasing (UP) the output voltage of the DC-DC converter 20 from a first voltage to a second voltage. The first voltage is the output voltage of the DC-DC converter 20 that is set when the switch 40 is in a conductive state and the auxiliary battery 30 is connected to the DC-DC converter 20. The second voltage is the output voltage of the DC-DC converter 20 that is set when the switch 40 is in a cut-off state and the auxiliary battery 30 is disconnected from the DC-DC converter 20. This second voltage can be, for example, the maximum voltage that the DC-DC converter 20 can output.

[0036] Step g1: After the output voltage of the DC-DC converter 20 increases, the second control unit 52 transmits a temporary load limit release request to the auxiliary loads 101, 102, and 103 to instruct them to release the limit on the increase in current consumption that had been instructed to the auxiliary loads. This temporary load limit release request also serves to notify the auxiliary loads 101, 102, and 103 that even if a voltage fluctuation occurs, it will not affect their operation (the fluctuation can be absorbed). Step h1: In response to receiving the request to release the temporary load shedding, the auxiliary loads 101, 102, and 103 each take action to release the shedding.

[0037] The above-described steps e1 and f1 may be performed in order. That is, the output voltage of the DC-DC converter 20 may be increased before the auxiliary loads 101, 102, and 103 complete their respective limiting actions in response to the temporary load limiting request.

[0038] [1-2]. Second sequence SW shutoff process 4, a description will be given of the SW shutoff process according to the second sequence executed by the first control unit 51, the second control unit 52, and the auxiliary loads 101, 102, and 103. In this second sequence, the following steps a2 to j2 are executed.

[0039] Step a2: The second control unit 52 receives a voltage increase request from at least one of the auxiliary loads 101, 102, and 103 (step S202 in FIG. 2). Step b2: In response to receiving the voltage increase request, the second control unit 52 transmits a temporary load limit request to the auxiliary loads 101, 102, and 103, instructing the auxiliary loads to temporarily limit an increase in current consumption. This temporary load limit request is a request to suppress the operation of a function that generates power demand that exceeds the rated performance of the DC-DC converter 20. For example, in a vehicle, this request can be a limit request issued to a comfort-related function that does not affect the actions of "driving," "turning," and "stopping." The temporary load limit request also serves to notify the auxiliary loads 101, 102, and 103 that voltage fluctuations are likely to occur. Step c2: The auxiliary loads 101, 102, and 103 each implement a load shedding response in response to receiving the temporary load shedding request. Step d2: The auxiliary loads 101, 102, and 103 transmit a restriction completion notification to the second control unit 52, indicating that the restriction response has been completed.

[0040] Step e2: The second control unit 52 transmits to the first control unit 51 a SW cutoff request requesting that the switch 40 be put into the cutoff state. Step f2: In response to the reception of the SW cutoff request, the first control unit 51 switches the switch 40 from the conductive state to the cutoff state. Step g2: The first control unit 51 transmits to the second control unit 52 a SW cutoff completion notification indicating that the switch 40 has been switched to the cutoff state.

[0041] Step h2: The second control unit 52 performs a process of increasing (UP) the output voltage of the DC-DC converter 20 from the first voltage to the second voltage. The first voltage is the output voltage of the DC-DC converter 20 that is set when the switch 40 is in a conductive state and the auxiliary battery 30 is connected to the DC-DC converter 20. The second voltage is the output voltage of the DC-DC converter 20 that is set when the switch 40 is in a cut-off state and the auxiliary battery 30 is disconnected from the DC-DC converter 20. This second voltage may be the maximum voltage that the DC-DC converter 20 can output, or may be a value specified by a voltage increase request (for example, the maximum value if there are multiple requests).

[0042] Step i2: After the output voltage of the DC-DC converter 20 increases, the second control unit 52 transmits a temporary load limit release request to the auxiliary loads 101, 102, and 103 to instruct them to release the limit on the increase in current consumption that had been instructed to the auxiliary loads. This temporary load limit release request also serves to notify the auxiliary loads 101, 102, and 103 that even if a voltage fluctuation occurs, it will not affect their operation (the fluctuation can be absorbed). Step j2: In response to receiving the request to release the temporary load shedding, the auxiliary loads 101, 102, and 103 each take action to release the shedding.

[0043] In this second sequence, in order to prevent the switch 40 from being turned off while leaving the possibility of the auxiliary loads 101, 102, and 103 increasing their power consumption, the second control unit 52 confirms that it has received a restriction completion notification from each of the auxiliary loads 101, 102, and 103 (step d2), and then sends a SW turning-off request to the first control unit 51 (step e2).

[0044] [2] SW continuity determination control 5 is a flowchart illustrating the procedure of the SW continuity determination control executed by the first control unit 51 and the second control unit 52 of the vehicle power supply device 1. The SW continuity determination control illustrated in FIG. 5 is executed when the switch 40 is in the interrupted state.

[0045] (Step S501) The first control unit 51 determines whether or not there is an abnormality in the auxiliary battery 30. This determination is made to confirm whether or not the abnormality in the auxiliary battery 30 is non-sustained and the auxiliary battery 30 has recovered to a normal state, even though the abnormality in the auxiliary battery 30 has been determined in the above-described SW cutoff determination control (FIG. 2).

[0046] If the first control unit 51 determines that there is no abnormality in the auxiliary battery 30 (step S501, NO), the process proceeds to step S502. On the other hand, if the first control unit 51 determines that there is an abnormality in the auxiliary battery 30 (step S501, YES), the process proceeds to step S501.

[0047] (Step S502) The second control unit 52 determines whether or not it has received a “voltage increase cancellation request” from at least one of the auxiliary loads 101, 102, and 103, requesting cancellation of the increase in the output voltage of the DC-DC converter 20. This voltage increase cancellation request is a request intended to inform the second control unit 52 that the auxiliary loads are no longer planning to perform a specific operation that consumes a large current.

[0048] If the second control unit 52 determines that it has received a voltage increase cancellation request from the auxiliary load (YES in step S502), the process proceeds to step S504. On the other hand, if the second control unit 52 determines that it has not received a voltage increase cancellation request from the auxiliary load (NO in step S502), the process proceeds to step S503.

[0049] (Step S503) The second control unit 52 determines whether the output current of the DC-DC converter 20 exceeds a predetermined threshold. This determination is made to confirm that the current state of the DC-DC converter 20 has a sufficient power supply capacity to allow the output voltage to be reduced (e.g., there is a predetermined margin relative to the rated output current). The threshold is set based on the specification value of the DC-DC converter 20. For example, if the output current of the DC-DC converter 20 exceeds the threshold, it can be easily inferred that the output voltage cannot be reduced because a large current is being supplied from the DC-DC converter 20 to the auxiliary loads 101, 102, and 103. In this case, since the DC-DC converter 20 may reach its output limit, it can be determined that it is better to prioritize restoring the auxiliary battery 30, which is normal, to a conductive state even if there is no particular request from the auxiliary load to cancel the voltage increase.

[0050] If the second control unit 52 determines that the output current of the DC-DC converter 20 exceeds the threshold value (step S503, Yes), the process proceeds to step S505. On the other hand, if the second control unit 52 determines that the output current of the DC-DC converter 20 does not exceed the threshold value (step S503, No), the process proceeds to step S501.

[0051] (Step S504) In order to switch the switch 40 from the cut-off state to the conduction state, the first control unit 51 and the second control unit 52 execute a SW conduction process (FIG. 6) according to a third sequence based on a voltage increase cancellation request from the auxiliary load. The SW conduction process according to the third sequence will be described later. When the switch 40 enters the conduction state according to the third sequence, the SW conduction determination control ends.

[0052] (Step S505) In order to switch the switch 40 from the interrupted state to the conductive state, the first control unit 51 and the second control unit 52 execute a SW continuity process (FIG. 7) according to a fourth sequence based on the normal recovery of the auxiliary battery 30. The SW continuity process according to the fourth sequence will be described later. When the switch 40 enters the conductive state according to the fourth sequence, the SW continuity determination control ends.

[0053] [2-1]. SW conduction processing of the third sequence 6, a description will be given of the SW conduction process according to a third sequence executed by first control unit 51, second control unit 52, and auxiliary loads 101, 102, and 103. In this third sequence, the following steps a3 to i3 are executed.

[0054] Step a3: The second control unit 52 receives a voltage increase cancellation request from at least one of the auxiliary loads 101, 102, and 103 (step S502 in FIG. 5). Step b3: In response to receiving the voltage increase cancellation request, the second control unit 52 transmits a temporary load limit request to the auxiliary loads 101, 102, and 103, instructing the auxiliary loads to temporarily limit an increase in current consumption. This temporary load limit request is a request to suppress the operation of a function that generates power demand that exceeds the rated performance of the DC-DC converter 20. For example, in a vehicle, this request can be a limit request issued to a comfort-related function that does not affect the actions of "driving," "turning," and "stopping." The temporary load limit request also serves to notify the auxiliary loads 101, 102, and 103 that voltage fluctuations are likely to occur. Step c3: The auxiliary loads 101, 102, and 103 each implement a load shedding response in response to receiving the temporary load shedding request. Step d3: The auxiliary loads 101, 102, and 103 transmit a restriction completion notification to the second control unit 52, indicating that the restriction response has been completed.

[0055] Step e3: The second control unit 52 performs a process to decrease (DOWN) the output voltage of the DC-DC converter 20 from the second voltage to a predetermined voltage. The second voltage is the output voltage of the DC-DC converter 20 that is set when the switch 40 is in the cut-off state and the auxiliary battery 30 is disconnected from the DC-DC converter 20. The voltage value to be decreased may be the first voltage, which is the output voltage of the DC-DC converter 20 that is set when the switch 40 is in the conduction state and the auxiliary battery 30 is connected to the DC-DC converter 20, or a value specified by the voltage UP cancellation request (the minimum value if there are multiple requests).

[0056] Step f3: When the first control unit 51 detects that the output voltage of the DC-DC converter 20 has dropped, it switches the switch 40 to the conductive state. This detection is possible because the first control unit 51 constantly monitors the output voltage of the DC-DC converter 20. Step g3: The first control unit 51 transmits to the second control unit 52 a SW conduction completion notification indicating that the switch 40 has been switched to the conductive state.

[0057] Step h3: In response to receiving the SW conduction completion notification, the second control unit 52 transmits a temporary load limit release request to the auxiliary loads 101, 102, and 103, instructing them to release the limit on the increase in current consumption that had been instructed to the auxiliary loads. This temporary load limit release request also serves to notify the auxiliary loads 101, 102, and 103 that voltage fluctuations are unlikely to occur (high robustness to voltage fluctuations). Step i3: In response to receiving the request to release the temporary load shedding, the auxiliary loads 101, 102, and 103 each take action to release the shedding.

[0058] In the above example, the first control unit 51 actively switches the switch 40 from the off state to the on state (step f3) based on the output voltage of the DC-DC converter 20, but the switching may be performed passively by receiving a predetermined notification from the second control unit 52 after the output voltage of the DC-DC converter 20 is lowered (step e3).

[0059] [2-2]. SW conduction process of the 4th sequence 7, a description will be given of the SW conduction process according to a fourth sequence executed by first control unit 51, second control unit 52, and auxiliary loads 101, 102, and 103. In this fourth sequence, the following steps a4 to i4 are executed.

[0060] Step a4: Based on the fact that the auxiliary battery 30 has returned to a normal state, the first control unit 51 sends a "voltage DOWN request" to the second control unit 52, which is a request to lower the output voltage of the DCDC converter 20, which has been increased. Step b4: In response to receiving the voltage DOWN request, the second control unit 52 transmits a temporary load limit request to the auxiliary loads 101, 102, and 103, instructing the auxiliary loads to temporarily limit an increase in current consumption. This temporary load limit request is a request to suppress the operation of a function that generates power demand that exceeds the rated performance of the DC-DC converter 20. For example, in a vehicle, this request can be a limit request issued to a comfort-related function that does not affect the actions of "driving," "turning," and "stopping." The temporary load limit request also serves to notify the auxiliary loads 101, 102, and 103 that voltage fluctuations are likely to occur. Step c4: The auxiliary loads 101, 102, and 103 each implement a load shedding response in response to receiving the temporary load shedding request. Step d4: The auxiliary loads 101, 102, and 103 transmit a restriction completion notification to the second control unit 52, indicating that the restriction response has been completed.

[0061] Step e4: The second control unit 52 performs a process to decrease (DOWN) the output voltage of the DC-DC converter 20 from the second voltage to a predetermined voltage. The second voltage is the output voltage of the DC-DC converter 20 that is set when the switch 40 is in the cut-off state and the auxiliary battery 30 is disconnected from the DC-DC converter 20. The voltage value to be decreased may be the first voltage, which is the output voltage of the DC-DC converter 20 that is set when the switch 40 is in the conduction state and the auxiliary battery 30 is connected to the DC-DC converter 20, or a value specified by the voltage UP cancellation request (the minimum value if there are multiple requests).

[0062] Step f4: When the first control unit 51 detects that the output voltage of the DC-DC converter 20 has dropped, it switches the switch 40 from a cut-off state to a conduction state. This detection is possible because the first control unit 51 constantly monitors the output voltage of the DC-DC converter 20. Step g4: The first control unit 51 transmits to the second control unit 52 a SW conduction completion notification indicating that the switch 40 has been switched to the conductive state.

[0063] Step h4: In response to receiving the SW conduction completion notification, the second control unit 52 transmits a temporary load limit release request to the auxiliary loads 101, 102, and 103, instructing them to release the limit on the increase in current consumption that had been instructed to the auxiliary loads. This temporary load limit release request also serves to notify the auxiliary loads 101, 102, and 103 that voltage fluctuations are unlikely to occur (high robustness to voltage fluctuations). Step i4: In response to receiving the request to release the temporary load shedding, the auxiliary loads 101, 102, and 103 each take action to release the shedding.

[0064] In the above example, the first control unit 51 actively switches the switch 40 from the off state to the conductive state (step f4) based on the output voltage of the DC-DC converter 20, but the switching may be performed passively by receiving a predetermined notification from the second control unit 52 after lowering the output voltage of the DC-DC converter 20 (step e4).

[0065] <Actions and Effects> As described above, according to the vehicle power supply device 1 of one embodiment of the present disclosure, when the auxiliary battery 30, which uses a lithium-ion battery, is disconnected from the DCDC converter 20 by turning off the switch 40, the output voltage of the DCDC converter 20 after the auxiliary battery 30 is disconnected is controlled to be higher than the output voltage of the DCDC converter 20 before the auxiliary battery 30 is disconnected.

[0066] This control prevents the output voltage of the DC-DC converter 20 from dropping too much even if the current consumption increases due to a large change in the power demand of the auxiliary loads 101, 102, and 103 when the auxiliary battery 30, which is a lithium-ion battery, is disconnected from the power line to protect the battery. This prevents the output voltage of the DC-DC converter 20 from fluctuating too much in response to the change in the power demand of the auxiliary loads 101, 102, and 103, thereby affecting (instability, shutdown, etc.) the operation of the auxiliary loads 101, 102, and 103. Therefore, when the output voltage of the DC-DC converter 20 is increased, the robustness of the auxiliary load operation is improved compared to when the output voltage is not increased.

[0067] Furthermore, according to the vehicle power supply device 1 of one embodiment of the present disclosure, even if there is no abnormality in the auxiliary battery 30, if the auxiliary loads 101, 102, and 103 request a voltage from the DCDC converter 20 that exceeds the allowable operating voltage range of the lithium-ion battery, the auxiliary battery 30 is forcibly disconnected from the power line.

[0068] This disconnection allows the output voltage of the DC-DC converter 20 to be controlled while the auxiliary battery 30 is disconnected from the power line, thereby relaxing the restrictions on the product design and control methods of auxiliary loads and devices that are bound by the allowable operating voltage range of lithium-ion batteries (voltage that cannot be exceeded).

[0069] <Application example 1> The transmission of the temporary load shedding request executed in step d1 in the SW shutoff processing of the first sequence (Figure 3), step b2 in the SW shutoff processing of the second sequence (Figure 4), step b3 in the SW conduction processing of the third sequence (Figure 6), and step b4 in the SW conduction processing of the fourth sequence (Figure 7) may be performed not to all auxiliary loads 101, 102, and 103, but to some of the auxiliary loads.

[0070] In this case, the portion of the auxiliary loads that are subject to the temporary load shedding request can be determined, for example, as follows, based on information such as the output voltage (such as the rated voltage) of the DC-DC converter 20 before or after the increase or decrease, the minimum voltage at which all auxiliary loads 101, 102, and 103 can operate stably, and the maximum current consumption that may increase due to the activation of each auxiliary load's function and its operating time.

[0071] By activating a specific function, some auxiliary loads that may cause the output voltage of the DC-DC converter 20 to fall below the minimum voltage at which all auxiliary loads 101, 102, and 103 can stably operate can be subject to a temporary load shedding request. In this case, auxiliary loads related to the vehicle's driving functions, such as "running," "turning," and "stopping," may be excluded from the load shedding request. The target auxiliary loads may be determined based on a predetermined priority order or in descending order of maximum current consumption.

[0072] <Application example 2> The transmission of the request to release temporary load limiting, which is executed in step g1 in the SW shutoff processing of the first sequence (Figure 3) and step i2 in the SW shutoff processing of the second sequence (Figure 4) described above, may be sent to only some of the auxiliary loads 101, 102, and 103 that have requested temporary load limiting, rather than to all of them.

[0073] In this case, the portion of the auxiliary loads that are subject to the request to remove temporary load restriction can be determined, for example, as follows, based on information such as the output voltage of the DC-DC converter 20 after the increase (such as the allowable upper limit voltage), the minimum voltage at which all auxiliary loads 101, 102, and 103 can operate stably, and the maximum current consumption that may increase due to the activation of each auxiliary load's function and its operating time.

[0074] A request to cancel temporary load shedding can be made to target some auxiliary loads that do not pose a risk of the output voltage of the DC-DC converter 20 falling below the minimum voltage at which all auxiliary loads 101, 102, and 103 can stably operate even when a specific function is activated. In this case, the number of target auxiliary loads among the auxiliary loads for which temporary load shedding is requested is determined according to the output voltage after the DC-DC converter 20 has increased. The number of target auxiliary loads may be determined based on whether the auxiliary loads are related to the vehicle's driving functions of "driving," "turning," and "stopping," or may be determined based on a predetermined priority order, or may be determined in ascending order of maximum current consumption.

[0075] The above describes one embodiment of the disclosed technology, but the present disclosure can be understood as not only a vehicle power supply device, but also a method executed by an electronic control unit mounted on the vehicle power supply device, a program for executing this method, a computer-readable non-transitory storage medium storing this program, and a vehicle equipped with the vehicle power supply device, etc. [Industrial Applicability]

[0076] The vehicle power supply device of the present disclosure can be used in vehicles that use lithium-ion batteries as auxiliary batteries. [Explanation of symbols]

[0077] 1 Vehicle power supply unit 10 Power supply source 20 DC-DC converter 30 Auxiliary battery 40 Switch 51 First Control Section 52 Second Control Section 101, 102, 103 Auxiliary load

Claims

1. A vehicle power supply device that supplies power to a plurality of auxiliary loads mounted on a vehicle, a power supply source; an auxiliary battery including a lithium ion battery that can be charged by the power supply source; a DC-DC converter provided between the power supply source and the plurality of auxiliary loads and configured to control power supply from the power supply source to the plurality of auxiliary loads; a switch provided between the DCDC converter and the auxiliary battery, and between the auxiliary loads and the auxiliary battery, for switching an electrical connection state between the auxiliary loads and the auxiliary battery; a control unit that controls the DC-DC converter and the switch, The control unit controls the output voltage of the DC-DC converter so that a second voltage when the switch is turned off is higher than a first voltage when the switch is turned on. Vehicle power supply unit.

2. When the control unit turns off the switch based on detection of an abnormality in the auxiliary battery, the control unit temporarily limits power consumption by the plurality of auxiliary loads and then increases the output voltage of the DC-DC converter from the first voltage to the second voltage. The vehicle power supply device according to claim 1 .

3. When the control unit receives a request from at least one of the plurality of auxiliary loads to increase the output voltage of the DC-DC converter, if the auxiliary battery is in a charged state, the control unit temporarily limits power consumption by the plurality of auxiliary loads and then turns off the switch, and after turning off the switch, increases the output voltage of the DC-DC converter from the first voltage to the second voltage. The vehicle power supply device according to claim 1 .

4. When the abnormality in the auxiliary battery is resolved after turning off the switch, if the control unit receives a request from at least one of the plurality of auxiliary loads to cancel increasing the output voltage of the DC-DC converter, the control unit temporarily limits power consumption by the plurality of auxiliary loads, then drops the output voltage of the DC-DC converter from the second voltage to the first voltage, and then turns on the switch.

4. The vehicle power supply device according to claim 2 or 3.

5. When the abnormality in the auxiliary battery is resolved after the switch is turned off and if the output current of the DC-DC converter exceeds a predetermined threshold, the control unit temporarily limits power consumption by the plurality of auxiliary loads, then drops the output voltage of the DC-DC converter from the second voltage to the first voltage, and then turns on the switch.

4. The vehicle power supply device according to claim 2 or 3.

6. the control unit acquires information about power consumption from the plurality of auxiliary loads, and determines, based on the information, auxiliary loads whose power consumption is to be temporarily limited among the plurality of auxiliary loads.

6. The vehicle power supply device according to claim 2.

7. the control unit temporarily limits the power consumption by the plurality of auxiliary loads, and then, when the increase or decrease of the output voltage of the DC-DC converter is completed, releases the temporary limit on the power consumption by the plurality of auxiliary loads.

6. The vehicle power supply device according to claim 2.

8. the control unit temporarily limits the power consumption by the plurality of auxiliary loads, and then, when the increase or decrease of the output voltage of the DC-DC converter is completed, releases the temporary limit on the power consumption by a specific auxiliary load among the plurality of auxiliary loads based on the information.

7. The vehicle power supply device according to claim 6.

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