Power source management system, method for charging secondary battery, and vehicle

Abstract

This power source management system includes a battery, which is a power source for a high-voltage system, a power supply unit that receives a supply of power from the outside to charge the battery, a DC-DC converter that steps down power of the battery and supplies the power to a low-voltage system, and a charge control device that controls charging of the battery, wherein the power source management system executes charge / discharge processing that promotes the elimination of battery polarization by alternately performing first control for supplying power from the power supply unit to the battery and the DC-DC converter, and second control for stopping the supply of power from the power supply unit to the battery and the DC-DC converter and supplying power from the battery to the DC-DC converter.

Description

Power supply management system, secondary battery charging processing method, and vehicle

[0001] The present disclosure relates to a power supply management system, a charging processing method for a secondary battery, and a vehicle.

[0002] Vehicles such as electric vehicles and hybrid vehicles are known that are configured to charge their onboard batteries externally. The batteries in such vehicles use lithium-ion secondary batteries that have large capacity and can output high voltage.

[0003] A battery is made up of multiple battery cells, and if there is variation in the remaining capacity of each battery cell, there will be differences in the voltage of each battery cell, which may shorten the battery's usable time. To address this issue, for example, by performing a cell balancing process that corrects the potential difference between the battery cells after the vehicle is stopped, the voltage of each battery cell can be made equal.

[0004] As a battery is used, polarization occurs, causing its internal resistance to rise. For example, if the battery becomes polarized, it must be stopped and left on standby for approximately one to two hours until the polarization is resolved. While the battery is polarized, the voltage of each battery cell cannot be accurately measured, making it impossible to perform cell balancing.

[0005] In response to this, Patent Document 1 proposes a method for estimating the state of charge of a secondary battery, in which, after interrupting the charge / discharge current in the input / output circuit of the secondary battery, a shortening processing circuit connected in parallel to the input / output circuit performs processing to shorten the polarization relaxation time of the secondary battery by successively performing single discharges and single charges from the secondary battery, and then, when it is determined that the open circuit voltage of the secondary battery is constant, the state of charge of the secondary battery is estimated based on the open circuit voltage.

[0006] JP 2017-32294 A

[0007] However, some vehicles are configured to run a high-capacity battery at all times while the vehicle is parked, operate a camera that monitors the vehicle's surroundings, record the behavior of suspicious individuals approaching the vehicle, and alert those around to threats by flashing the headlights, etc. However, if the battery is running while the vehicle is parked to operate low-voltage systems such as a monitoring system, it is not possible to provide a time period for the battery to be shut down to eliminate polarization. As a result, cell balancing cannot be performed, which may result in a decrease in external charging performance or battery degradation.

[0008] The present disclosure has been made in consideration of the above problems, and an object of the present disclosure is to provide a power supply management system, a battery charging processing method, and a vehicle that enable operation of a low-voltage system while the vehicle is stopped, while eliminating polarization of battery cells, performing cell balancing processing, and charging the battery in a short period of time.

[0009] In order to solve the above problem, according to one aspect of the present disclosure, there is provided a power supply management system including a battery that is a power source for a high-voltage system, a power supply unit that receives power from an external source for charging the battery, a DC-DC converter that reduces the power of the battery and supplies it to a low-voltage system, and a charge control device that controls charging of the battery, wherein the charge control device alternately performs a first control that supplies power from the power supply unit to the battery and the DC-DC converter, and a second control that stops the power supply from the power supply unit to the battery and the DC-DC converter and supplies power from the battery to the DC-DC converter, thereby performing a charge and discharge process that promotes elimination of polarization in the battery.

[0010] In order to solve the above problem, according to another aspect of the present disclosure, there is provided a charging processing method for a battery in a power supply management system including a battery that is a power source for a high-voltage system, a power supply unit that receives power supplied from an external source for charging the battery, a DCDC converter that reduces the power of the battery and supplies it to a low-voltage system, and a charging control device that controls charging of the battery, the charging control device alternately performing a first control of supplying power from the power supply unit to the battery and the DCDC converter and a second control of stopping the power supply from the power supply unit to the battery and the DCDC converter and supplying power from the battery to the DCDC converter, performing a cell balancing process for the battery after a predetermined time has elapsed to eliminate polarization of the battery, and after completion of the cell balancing process, supplying power from the power supply unit to the battery and the DCDC converter to charge the battery.

[0011] In addition, in order to solve the above problem, according to another aspect of the present disclosure, there is provided a vehicle equipped with a power supply management system including a battery that is a power source for a high-voltage system, a power supply unit that receives power from an external source for charging the battery, a DC-DC converter that reduces the power of the battery and supplies it to a low-voltage system, and a charge control device that controls charging of the battery, wherein the charge control device alternately performs a first control that supplies power from the power supply unit to the battery and the DC-DC converter, and a second control that stops the power supply from the power supply unit to the battery and the DC-DC converter and supplies power from the battery to the DC-DC converter, thereby performing a charge and discharge process that promotes elimination of polarization in the battery.

[0012] As described above, according to the present disclosure, it is possible to eliminate polarization of battery cells, perform cell balancing processing, and charge the battery in a short period of time while enabling operation of low-voltage systems while the vehicle is stopped.

[0013] FIG. 1 is a schematic diagram showing a configuration example of a vehicle to which a power management system according to a first embodiment of the present disclosure can be applied; FIG. 2 is a block diagram showing a configuration example of the power management system according to the same embodiment; FIG. 3 is a block diagram showing a configuration example of a charge control device of the power management system according to the same embodiment; FIG. 4 is a flowchart showing an example of a processing operation by the charge control device of the power management system according to the same embodiment; FIG. 5 is a flowchart showing an example of a charge / discharge processing operation by the charge control device of the power management system according to the same embodiment; FIG. 6 is an explanatory diagram showing a reference example of the same embodiment; FIG. 7 is an explanatory diagram showing the function of the same embodiment; FIG. 8 is a flowchart showing an example of a charge / discharge processing operation by the charge control device of the power management system according to a second embodiment of the present disclosure; FIG. 9 is a block diagram showing a configuration example of a power management system according to a third embodiment of the present disclosure.

[0014] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0015] <<1. First embodiment>> <1-1. Overall configuration of vehicle> First, the overall configuration of a vehicle to which a power supply management system according to an embodiment of the present disclosure is applied will be described.

[0016] FIG. 1 is a schematic diagram showing an example of the overall configuration of a vehicle. The illustrated vehicle 1 is a front-wheel-drive electric vehicle equipped with a drive motor 3 that drives the front wheels. However, the vehicle may also be a four-wheel-drive electric vehicle in which the front and rear wheels are driven by a drive motor, a four-wheel-drive electric vehicle equipped with a front-wheel drive motor and a rear-wheel drive motor, or a four-wheel-drive electric vehicle equipped with a drive motor (in-wheel motor) for each wheel. The vehicle may also be a hybrid vehicle equipped with an internal combustion engine in addition to a drive motor.

[0017] The vehicle 1 includes a drive motor 3, an inverter unit 5, a high-voltage battery 7, a power supply unit 9, a DCDC converter 11, an auxiliary battery (low-voltage battery) 13, a monitoring system 15, and a connection switching unit 21.

[0018] The high-voltage battery 7 is a rechargeable secondary battery. The high-voltage battery 7 may be, for example, a lithium-ion battery rated at 200 V, but the rated voltage and type of the high-voltage battery 7 are not particularly limited. The high-voltage battery 7 includes a plurality of battery cells connected in series. The high-voltage battery 7 is connected to the drive motor 3 via the inverter unit 5 and supplies power to the drive motor 3.

[0019] The high-voltage battery 7 is equipped with a battery management unit 31 that detects the voltage and temperature of the high-voltage battery 7, as well as the voltage of each battery cell. The battery management unit 31 has a configuration that is capable of performing cell balancing processing to correct the potential difference between the battery cells.

[0020] The drive motor 3 outputs drive torque that is transmitted to the left and right front wheels. For example, the drive motor 3 is configured as a three-phase AC motor. The drive motor 3 outputs drive torque by rotating its rotor due to a rotating magnetic field formed by supplying three-phase AC current to its stator. Furthermore, the drive motor 3 has the function of generating electricity by receiving rotational torque from the front wheels and rotating its rotor when three-phase AC current is not supplied to the stator.

[0021] The inverter unit 5 converts DC power swept from the high-voltage battery 7 into three-phase AC power and supplies it to the stator of the drive motor 3. The inverter unit 5 also converts three-phase AC power regenerated by the stator into DC power and supplies it to the high-voltage battery 7.

[0022] The power supply unit 9 is a component that receives power from the external power supply device 17. For example, the external power supply device 17 is a device that can supply high-voltage DC power, and the power supply unit 9 is configured as an inlet connector that can connect to a power supply connector 19 of the external power supply device 17. The power supply unit 9 includes a switch or sensor that detects that the power supply connector 19 of the external power supply device 17 is connected. The power supply unit 9 also includes means for communicating with the external power supply device 17 when the power supply connector 19 is connected. The communication means may be, for example, a wired communication means achieved by connecting a communication line, or a wireless communication means such as infrared communication. The power supplied from the external power supply device 17 via the power supply unit 9 charges the high-voltage battery 7.

[0023] If the external power supply device 17 is a device that supplies power at a voltage lower than the voltage of the high-voltage battery 7, a boost circuit that boosts the power supplied via the power supply unit 9 may be provided. If the power supplied via the power supply unit 9 is AC power, a power supply circuit that rectifies and smoothes the AC power supplied via the power supply unit 9 may be provided. If the system that charges the high-voltage battery 7 with power supplied from the external power supply device 17 is a contactless charging system, the power supply unit 9 may have a contactless configuration such as a charging coil.

[0024] The DC-DC converter 11 includes a step-down circuit. The DC-DC converter 11 steps down the high-voltage power of the high-voltage battery 7 and supplies the resulting step-down power to a low-voltage system including the auxiliary battery 13. The auxiliary battery 13 may be, for example, a lead-acid battery rated at 50 V, but the rated voltage and type of the auxiliary battery 13 are not particularly limited. The monitoring system 15 includes, for example, a pair of left and right stereo cameras 15L, 15R, which operate on low-voltage power to capture images of the surroundings of the vehicle 1.

[0025] The low-voltage system includes various control devices, lighting devices, air conditioning devices, and other electrical equipment mounted on the vehicle 1. The monitoring system 15 is an example of a low-voltage system that continues to operate even after the systems of the vehicle 1 have stopped, and the low-voltage system may include other systems that continue to operate even after the systems of the vehicle 1 have stopped.

[0026] The connection switching unit 21 includes a plurality of relay switches and switches the connection states between the high-voltage battery 7, the power supply unit 9, and the DCDC converter 11. Note that the connection switching unit 21 may represent a group of a plurality of relay switches, or may be configured as a unit such as a junction box.

[0027] <1-2. Power Management System> Next, the configuration of the power management system according to this embodiment will be described.

[0028] 2 is an explanatory diagram showing an example of the configuration of a power supply management system according to this embodiment. The power supply management system 10 includes a high-voltage battery 7, a power supply unit 9, a DC-DC converter 11, an auxiliary battery 13, a battery management system (BMS) 31, a power control device 40, and a charge control device 50.

[0029] A first relay 23a, a second relay 23b, a third relay 25a, and a fourth relay 25b are provided in a current path that connects the positive and negative sides of the high-voltage battery 7 to the power supply unit 9. The first relay 23a, the second relay 23b, the third relay 25a, and the fourth relay 25b switch between connection and disconnection of the current path by the charging control device 50 controlling the supply and stop of current to a coil (not shown).

[0030] The first relay 23a and the third relay 25a are provided on a current path connecting the positive electrode side of the high-voltage battery 7 and the power supply unit 9. The second relay 23b and the fourth relay 25b are provided on a current path connecting the negative electrode side of the high-voltage battery 7 and the power supply unit 9. The DCDC converter 11 is connected in parallel with the high-voltage battery 7 and the power supply unit 9 between the first relay 23a and the second relay 23b and the third relay 25a and the fourth relay 25b.

[0031] The first relay 23a and the second relay 23b have a function of disconnecting the high-voltage battery 7 from the low-voltage system. The third relay 25a and the fourth relay 25b have a function of disconnecting the power supply unit 9 from the high-voltage system and the low-voltage system.

[0032] The battery management unit 31 includes a step-up / step-down circuit 33, a battery state detection unit 35, and a cell balancing processing unit 37. Of these, the functions of the battery state detection unit 35 and the cell balancing processing unit 37 are realized by a processor executing a computer program. Note that part of the battery state detection unit 35 and the cell balancing processing unit 37 may be configured by hardware such as an analog circuit.

[0033] The step-up / step-down circuit 33 is, for example, a bidirectional DC-DC converter, and transfers electric charges between a plurality of battery cells.

[0034] The battery state detection unit 35 detects the open circuit voltage of the high-voltage battery 7 and the voltage of each battery cell based on a sensor signal from a voltage sensor (not shown). The voltage of the battery cell indicates the remaining capacity (SOC: State Of Charge) of the battery cell.

[0035] The cell balancing processing unit 37 executes a process to correct the potential difference between the battery cells when there is a variation in the voltages of the battery cells. The cell balancing processing unit 37 determines whether to execute the cell balancing process when it receives a signal from the charge control device 50 indicating the start of charging by the external power supply device 17. For example, when the SOCs of the battery cells differ by a predetermined difference or more at the start of charging, the cell balancing processing unit 37 controls the drive of the step-up / step-down circuit 33 to transfer charge between the battery cells and execute a process to equalize the potentials.

[0036] However, if polarization occurs in the high-voltage battery 7, the voltage of each battery cell cannot be detected correctly, and the accuracy of the cell balancing process may not be guaranteed. For example, the high-voltage battery 7 transports electrons via ions during charging and discharging, and this causes a bias in the ion concentration inside the battery cell. As a result, the potential tends to decrease during discharging and increase during charging. Although this polarization will disappear over time, the voltage of each battery cell cannot be detected correctly until the polarization is eliminated.

[0037] The cell balancing process may be performed by a conventionally known method, and therefore a detailed description thereof will be omitted.

[0038] The power control device 40 controls the power of the high-voltage system. The power control device 40 is communicably connected to the battery management device 31 and the charge control device 50. The power control device 40 includes a step-down processing unit 41 that controls the drive of the DC-DC converter 11. The power control device 40 may also have a function of controlling the drive of the inverter unit 5 to control the drive and regeneration of the drive motor 3. The function of the step-down processing unit 41 is realized by the execution of a computer program by a processor. Note that a part of the step-down processing unit 41 may be configured by hardware such as an analog circuit.

[0039] The step-down processing unit 41 drives the DCDC converter 11 to step down the output voltage of the high-voltage battery 7 and supply it to the low-voltage system. Furthermore, in this embodiment, the step-down processing unit 41 has a function of driving the DCDC converter 11 to step down the voltage of the power supplied from the power supply unit 9 and supply the resulting step-down power to the low-voltage system.

[0040] In this embodiment, the battery management unit 31 and the power control unit 40 are kept active even when the systems of the vehicle 1 are stopped, and the output voltage of the high-voltage battery 7 is stepped down and supplied to the low-voltage system, thereby allowing the monitoring system 15, for example, to continue operating.

[0041] The charge control device 50 includes a processor such as a CPU (Central Processing Unit) and storage elements such as a RAM (Random Access Memory) and a ROM (Read Only Memory), and functions as a device that controls charging of the high-voltage battery 7 by the processor executing a computer program. The computer program is a computer program that causes the processor to execute operations to be performed by the charge control device 50, which will be described later. The computer program executed by the processor may be recorded on a recording medium that functions as a storage unit (memory) provided in the charge control device 50, or may be recorded on a recording medium built into the charge control device 50 or any recording medium that can be externally attached to the charge control device 50.

[0042] The recording medium for recording a computer program may be a magnetic medium such as a hard disk, a floppy disk, or a magnetic tape; an optical recording medium such as a CD-ROM (Compact Disk Read Only Memory), a DVD (Digital Versatile Disk), or a Blu-ray (registered trademark); a magneto-optical medium such as a floptical disk; a memory element such as a RAM or a ROM; a flash memory such as a USB (Universal Serial Bus) memory or an SSD (Solid State Drive); or any other medium capable of storing a program.

[0043] Although the illustrated charging control device 50 is shown as a single control device, it may be configured as multiple control devices that can communicate with each other. Also, a part or all of the charging control device 50 may be configured with updatable firmware or the like, or may be a program module or the like that is executed by commands from a CPU or the like.

[0044] 3 is an explanatory diagram showing an example configuration of the charge control device 50. The charge control device 50 includes a processing unit 51 and a storage unit 57. The processing unit 51 is configured with one or more processors such as CPUs. The storage unit 57 is configured to be able to communicate with the processing unit 51. The storage unit 57 stores programs executed by the processing unit 51, parameters used in various calculations, information on calculation results, etc. A portion of the storage unit 57 is used as a work area for the processing unit 51.

[0045] The charging control device 50 is connected to the power supply unit 9 and the power control device 40 via a communication means such as a dedicated line or a CAN (Controller Area Network) so as to be able to communicate with them. The charging control device 50 is also connected to the first relay 23a, the second relay 23b, the third relay 25a, and the fourth relay 25b via a communication means such as a dedicated line or a CAN (Controller Area Network) so as to be able to output command signals thereto.

[0046] The processing unit 51 includes a relay control unit 53 and a charging processing unit 55. The functions of the relay control unit 53 and the charging processing unit 55 are realized by a processor executing a computer program. Note that part of the relay control unit 53 and the charging processing unit 55 may be configured by hardware such as an analog circuit.

[0047] The relay control unit 53 controls the driving of the first relay 23 a, the second relay 23 b, the third relay 25 a, and the fourth relay 25 b. For example, the relay control unit 53 switches between connection and disconnection of the first relay 23 a, the second relay 23 b, the third relay 25 a, and the fourth relay 25 b in accordance with the calculation processing of the charging processing unit 55.

[0048] The charging processing unit 55 controls the charging of the high-voltage battery 7 by the external power supply device 17. For example, the charging processing unit 55 starts the charging process when it receives a signal from the power supply unit 9 indicating that the power supply connector 19 of the external power supply device 17 has been connected. After starting the charging process, the charging processing unit 55 executes a charge / discharge process that promotes elimination of polarization in the high-voltage battery 7, and after the polarization elimination period and cell balancing process period have elapsed, maintains the high-voltage battery 7 in a charged state.

[0049] In the charge / discharge process, the charge processing unit 55 alternately performs a first control in which power is supplied from the power supply unit 9 to the high-voltage battery 7 and the DCDC converter 11, and a second control in which power supply from the power supply unit 9 to the high-voltage battery 7 and the DCDC converter 11 is stopped and power is supplied from the high-voltage battery 7 to the DCDC converter 11. By alternately repeating the first control and the second control continuously in a short period of time, elimination of polarization in the high-voltage battery 7 is promoted, and the time until the polarization is eliminated can be shortened.

[0050] 1-3. Example of Operation of Charging Control Device So far, we have described an example of the configuration of the power management system 10. Next, an example of operation of the charging control device 50 will be described.

[0051] Fig. 4 is a flowchart showing an example of a processing operation by the charging control device 50. Note that the flowchart shown in Fig. 4 is executed in a state where the vehicle 1 is stopped.

[0052] First, the charging processing unit 55 of the charging control device 50 detects that the external power supply device 17 has been connected (step S1). For example, the charging processing unit 55 detects that the external power supply device 17 has been connected by receiving a signal from the power supply unit 9 indicating that the power supply connector 19 of the external power supply device 17 has been connected. Next, the charging processing unit 55 executes a charging / discharging process (step S3).

[0053] 5 is a flowchart showing the operation of the charge / discharge process. First, the charge processing unit 55 performs a first control in which the first relay 23a, the second relay 23b, the third relay 25a, and the fourth relay 25b are all connected, and power is supplied from the power supply unit 9 to the high-voltage battery 7 and the DCDC converter 11 (step S21). In the first control, a portion of the power supplied from the external power supply device 17 is charged into the high-voltage battery 7, and another portion of the power is stepped down by the DCDC converter 11 and supplied to the low-voltage system. Therefore, the monitoring system 15 is maintained in an activated state.

[0054] Next, the charging processing unit 55 performs second control to supply power from the high-voltage battery 7 to the DCDC converter 11 by maintaining the first relay 23a and the second relay 23b in a connected state while maintaining the third relay 25a and the fourth relay 25b in a disconnected state (step S23). In the second control, the power supply from the external power supply device 17 is interrupted, and the power of the high-voltage battery 7 is stepped down by the DCDC converter 11 and supplied to the low-voltage system. Therefore, the monitoring system 15 is maintained in an activated state.

[0055] Next, the charging processing unit 55 increments the counter by 1 (step S25). This counter counts the number of times the first control and the second control are executed consecutively.

[0056] Next, the charging processing unit 55 determines whether the counter value has reached a predetermined threshold value (step S27). If the charging processing unit 55 determines that the counter value has not reached the predetermined threshold value (S27 / No), the charging processing unit 55 returns to step S21 and repeatedly executes the first control and the second control. On the other hand, if the charging processing unit 55 determines that the counter value has reached the predetermined threshold value (S27 / Yes), the charging processing unit 55 ends the charging / discharging process.

[0057] In this way, in the charge / discharge process, the first control and the second control are repeated, thereby repeatedly charging and discharging the high-voltage battery 7 while maintaining power supply to the low-voltage system. The execution time and the number of repetitions (predetermined counter thresholds) of the first control and the second control when executing the charge / discharge process may be set to any appropriate values ​​based on the polarization relaxation / shortening effect determined in advance by tests or simulations using an actual device. As an example, the execution time of each of the first control and the second control may be set to 4 to 8 seconds, and the number of repetitions may be set to 2 to 3. However, it has been found that the longer the execution time of each of the first control and the second control, or the more repetitions, the more the polarization relaxation / shortening effect decreases. Therefore, it is preferable to set conditions that result in a relatively high polarization relaxation / shortening effect, taking into account, for example, the response speed from when current is supplied to the high-voltage battery 7 until the voltage rises.

[0058] Furthermore, it is preferable to set the difference between the amount of power supplied to the DCDC converter 11 during execution of the first control and the amount of power supplied to the DCDC converter 11 during execution of the second control to be equal within a predetermined range. This ensures that power consumed by low-voltage systems such as the monitoring system 15 is secured while the surplus power is charged to the auxiliary battery 13, preventing the control of the DCDC converter 11 from becoming complicated. On the other hand, the amount of power supplied to the DCDC converter 11 during execution of the first control and the amount of power supplied to the DCDC converter 11 during execution of the second control may be variable according to the power consumption of the low-voltage systems. This eliminates power waste.

[0059] Returning to Fig. 4, after the charge / discharge process is completed, the charge processing unit 55 keeps the first relay 23a and the second relay 23b in an OFF state, while keeping the third relay 25a and the fourth relay 25b in an ON state, thereby putting the high-voltage battery 7 into a standby state for charging from the external power supply 17 (step S5). In the standby state, the high-voltage battery 7 is not charged. Instead, the battery management unit 31 waits until the polarization of the battery cells is eliminated, and then performs cell balancing. Also, in the standby state, the power supplied from the external power supply 17 is stepped down by the DCDC converter 11 and supplied to the low-voltage system. Therefore, the monitoring system 15 is kept activated.

[0060] Next, the charging processing unit 55 determines whether the cell balancing process is complete (step S7). For example, the charging processing unit 55 determines that the cell balancing process is complete when it receives a signal via the power control device 40 indicating that the cell balancing process by the battery management unit 31 has ended. If the charging processing unit 55 does not determine that the cell balancing process is complete (S7 / No), it remains in the standby state.

[0061] On the other hand, if the charging processing unit 55 determines that the cell balancing process is complete (S7 / Yes), it connects all of the first relay 23a, the second relay 23b, the third relay 25a, and the fourth relay 25b, and supplies power from the power supply unit 9 to the high-voltage battery 7 and the DCDC converter 11 (step S9). Thereafter, until charging of the high-voltage battery 7 is completed, part of the power supplied from the external power supply device 17 is charged into the high-voltage battery 7, and the other part of the power is stepped down by the DCDC converter 11 and supplied to the low-voltage system. Therefore, the monitoring system 15 is maintained in an activated state.

[0062] Next, the charging processing unit 55 determines whether charging of the high-voltage battery 7 has been completed (step S11). For example, the charging processing unit 55 determines that charging of the high-voltage battery 7 has been completed when it receives a signal via the power control device 40 indicating that the SOC of the high-voltage battery 7, detected by the battery management unit 31, has reached a predetermined termination threshold. If the charging processing unit 55 does not determine that charging of the high-voltage battery 7 has been completed (S11 / No), the process returns to step S9 and the power supply unit 9 continues to supply power to the high-voltage battery 7 and the DCDC converter 11.

[0063] On the other hand, when the charging processing unit 55 determines that charging of the high-voltage battery 7 is completed (S13 / Yes), it switches the first relay 23a and the second relay 23b to the disconnected state, while maintaining the third relay 25a and the fourth relay 25b in the connected state, and stops the power supply from the external power supply device 17 to the high-voltage battery 7 (step S13). Thereafter, the power supplied from the external power supply device 17 is stepped down by the DCDC converter 11 and supplied to the low-voltage system. Therefore, the monitoring system 15 is maintained in the activated state.

[0064] When the user subsequently uses the vehicle 1, the charging processing unit 55 turns off all of the first relay 23a, the second relay 23b, the third relay 25a, and the fourth relay 25b, and ends the charging process.

[0065] <1-4. Action> Next, the action of the present disclosure will be described.

[0066] 6 shows a reference example in which the charge / discharge process according to the present disclosure is not performed. In this reference example, at time t10 when the power supply connector 19 is connected to the power supply unit 9 after driving, polarization of the high-voltage battery 7 has progressed, making it impossible to perform the cell balancing process. Therefore, the first relay 23a and the second relay 23b are turned off to stop the supply of power to the high-voltage battery 7, allowing the polarization to be eliminated and waiting until the cell balancing process can be performed. During this time, the third relay 25a and the fourth relay 25b are turned on to supply power from the power supply unit 9 to the DCDC converter 11, thereby maintaining the power supply to the low-voltage system, such as the monitoring system 15.

[0067] At time t11, when it can be determined that polarization has been eliminated, the battery management unit 31 starts executing the cell balancing process. Then, at time t12, when the cell balancing process period ends, the first relay 23a and the second relay 23b are switched to the connected state, and charging of the high-voltage battery 7 begins. In the reference example, the first relay 23a and the second relay 23b are kept in the disconnected state until time t12, when the cell balancing process ends, and charging of the high-voltage battery 7 cannot begin.

[0068] Furthermore, the polarization elimination period in the reference example (time t10 to t11) is longer than the period until polarization is eliminated in this embodiment (time t0 to t3 in FIG. 7), so charging of the high-voltage battery 7 cannot be started for a long period of time. This may result in a decrease in the charging performance of the external power supply 17 or deterioration of the high-voltage battery 7.

[0069] FIG. 7 is an explanatory diagram showing the connection states of the first relay 23 a, the second relay 23 b, the third relay 25 a, and the fourth relay 25 b, and the changes in the amount of power supplied between the power supply unit 9, the high-voltage battery 7, and the DCDC converter 11 when the charging process is performed by the charging processing unit 55 according to this embodiment.

[0070] After the power supply connector 19 is connected to the power supply unit 9 at time t0, a charge / discharge process is performed between times t1 and t2. During the charge / discharge process, the first relay 23a and the second relay 23b are maintained in a connected state, while the third relay 25a and the fourth relay 25b are alternately switched between a connected state and a disconnected state at predetermined intervals. This causes the first control and the second control to be alternately and continuously repeated. During the first control, power is supplied from the power supply unit 9 to the DCDC converter 11, and during the second control, power is supplied from the high-voltage battery 7 to the DCDC converter 11, maintaining the power supply to low-voltage systems such as the monitoring system 15.

[0071] In the illustrated example, after switching between the first control and the second control twice, charging and discharging of the high-voltage battery 7 is stopped and the system enters a standby state between times t2 and t3. In the standby state, the first relay 23a and the second relay 23b are switched to a disconnected state, while the third relay 25a and the fourth relay 25b are switched to a connected state. This allows power to be supplied from the power supply unit 9 to the DCDC converter 11, maintaining the power supply to low-voltage systems such as the monitoring system 15. Furthermore, the battery management unit 31 can perform cell balancing after a period of time has passed during which it can be determined that the polarization of the high-voltage battery 7 has been eliminated.

[0072] After time t3 when the cell balancing process is completed, the first relay 23 a, the second relay 23 b, the third relay 25 a, and the fourth relay 25 b are all switched to the connected state. As a result, a portion of the power supplied from the power supply unit 9 is charged to the high-voltage battery 7, and another portion of the power is supplied to the DCDC converter 11. This allows the high-voltage battery 7 to be charged while maintaining power supply to the low-voltage system such as the monitoring system 15.

[0073] <1-5. Effects> As described above, the power supply management system 10 according to this embodiment includes the high-voltage battery 7, which is a power source for the high-voltage system, the power supply unit 9 that receives an external power supply for charging the high-voltage battery 7, the DCDC converter 11 that steps down the power of the high-voltage battery 7 and supplies it to the low-voltage system, and the charge control device 50 that controls the charging of the high-voltage battery 7. The charge control device 50 is configured to execute a charge / discharge process that promotes elimination of polarization in the high-voltage battery 7 by alternately performing a first control that supplies power from the power supply unit 9 to the high-voltage battery 7 and the DCDC converter 11 and a second control that stops the power supply from the power supply unit 9 to the high-voltage battery 7 and the DCDC converter 11 and supplies power from the high-voltage battery 7 to the DCDC converter 11.

[0074] This reduces the time required for the high-voltage battery 7 to be depolarized, and shortens the time required for the cell balancing process to be performed and charging to begin, thereby preventing a decrease in charging performance from the external power supply 17 and deterioration of the high-voltage battery 7.

[0075] Furthermore, the power supply management system 10 according to this embodiment is an in-vehicle system, and the step-down voltage obtained by the DC-DC converter 11 is used to drive low-voltage electrical components while the vehicle 1 is stopped. Therefore, even while the vehicle 1 is stopped, a security system such as a monitoring system 15 equipped with stereo cameras 15L and 15R can be kept running, and the remaining capacity of the high-voltage battery 7 can be prevented from decreasing due to the operation of the security system.

[0076] 2. Second Embodiment Next, a power supply management system according to a second embodiment of the present disclosure will be described. The power supply management system according to this embodiment controls the output voltage from the external power supply device 17 to charge and discharge the high-voltage battery 7. This differs from the first embodiment in that the charge and discharge processes of the high-voltage battery 7 are performed by switching between connection and disconnection of the third relay 25 a and the fourth relay 25 b.

[0077] 8 is a flowchart showing the operation of the charge / discharge process by the charge control device 50 of the power supply management system according to this embodiment. First, the charge processing unit 55 connects all of the first relay 23 a, the second relay 23 b, the third relay 25 a, and the fourth relay 25 b (step S41).

[0078] Next, the charging processing unit 55 communicates with the external power supply device 17 via the power supply unit 9 and performs first control to supply high voltage from the external power supply device 17 (step S43). As a result, power is supplied from the power supply unit 9 to the high-voltage battery 7 and the DCDC converter 11, and part of the power supplied from the external power supply device 17 is charged to the high-voltage battery 7, while the other part of the power is stepped down by the DCDC converter 11 and supplied to the low-voltage system. Therefore, the monitoring system 15 is maintained in an activated state.

[0079] Next, the charging processing unit 55 communicates with the external power supply device 17 via the power supply unit 9 and performs a second control to set the output voltage of the external power supply device 17 to 0 V (step S45). As a result, the power supply from the external power supply device 17 is interrupted, and the power of the high-voltage battery 7 is stepped down by the DCDC converter 11 and supplied to the low-voltage system. Therefore, the monitoring system 15 is maintained in an activated state.

[0080] Next, the charging processing unit 55 increments the counter by one (step S47) and determines whether the counter value has reached a predetermined threshold value (step S49), as in the first embodiment. If the charging processing unit 55 determines that the counter value has not reached the predetermined threshold value (S49 / No), the charging processing unit 55 returns to step S43 and repeatedly executes the first control and the second control. On the other hand, if the charging processing unit 55 determines that the counter value has reached the predetermined threshold value (S49 / Yes), the charging processing unit 55 ends the charging / discharging process.

[0081] In this way, the first control and the second control are repeated by controlling the output voltage of the external power supply device 17, thereby maintaining the power supply to the low-voltage system and repeatedly charging and discharging the high-voltage battery 7. Therefore, the same effect as that of the power supply management system according to the first embodiment can be obtained without performing processing to drive a relay switch.

[0082] Third Embodiment Next, a power management system according to a third embodiment of the present disclosure will be described. The power management system according to this embodiment differs from the first and second embodiments in that it includes a heating resistor that consumes the step-down voltage stepped down by the DC-DC converter.

[0083] 9 is an explanatory diagram showing an example of the configuration of a power supply management system according to this embodiment. A power supply management system 70 has a configuration in which a first changeover switch 71a, a second changeover switch 71b, and a heating resistor 73 are added to the configuration of the power supply management system shown in FIG. 2. The first changeover switch 71a and the second changeover switch 71b alternate between a first state in which the DC-DC converter 11 is connected to the auxiliary battery 13 and the monitoring system 15, and a second state in which the DC-DC converter 11 is connected to the heating resistor 73.

[0084] As a result, by setting the charging control device 50 to the second state in which the DCDC converter 11 is connected to the heating resistor 73, the step-down voltage stepped down by the DCDC converter 11 can be consumed by the heating resistor 73. Therefore, even when the monitoring system 15 is not operated while the vehicle is stopped or when there is no need to charge the auxiliary battery 13, it is possible to obtain the same effects as those of the power supply management system according to the first embodiment.

[0085] The power stepped down by the DC-DC converter may be used for any purpose other than consumption by the monitoring system 15 or the heating resistor 73 or charging the auxiliary battery 13 .

[0086] Although the preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings, the technology of the present disclosure is not limited to such examples. It is clear that a person skilled in the art of the technology to which the present disclosure pertains can conceive of various modified or altered examples within the scope of the technical ideas described in the claims, and it is understood that these also naturally fall within the technical scope of the present disclosure.

[0087] 1: Vehicle 3: Drive motor 5: Inverter unit 7: High-voltage battery 9: Power supply unit 10: Power supply management system 11: DCDC converter 13: Auxiliary battery 15: Monitoring system 17: External power supply device 19: Power supply connector 21: Connection switching unit 23a: First relay 23b: Second relay 25a: Third relay 25b: Fourth relay 31: Battery management device 37: Cell balancing processing unit 40: Power control device 50: Charging control device 51: Processing unit 53: Relay control unit 55: Charging processing unit 57: Storage unit

Claims

1. A power supply management system comprising: a battery that is a power source for a high-voltage system; a power supply unit that receives power from an external source to charge the battery; a DC-DC converter that reduces the power of the battery and supplies it to a low-voltage system; and a charge control device that controls the charging of the battery, wherein the charge control device alternately performs a first control that supplies power from the power supply unit to the battery and the DC-DC converter, and a second control that stops the power supply from the power supply unit to the battery and the DC-DC converter and supplies power from the battery to the DC-DC converter, thereby performing a charge and discharge process that promotes the elimination of polarization in the battery.

2. The power management system described in claim 1, wherein the charging control device controls the difference between the amount of power supplied to the DC-DC converter while the first control is being executed and the amount of power supplied to the DC-DC converter while the second control is being executed to be within a predetermined range.

3. The power management system according to claim 1, wherein the charge control device executes the polarization elimination process when it is necessary to execute a cell balancing process for equalizing the voltages of a plurality of battery cells that constitute the battery.

4. The power supply management system according to claim 1, wherein the power supply management system is an in-vehicle system, and the power stepped down by the DC-DC converter is used to drive the low-voltage electrical components while the vehicle is stopped.

5. The power management system according to claim 1, further comprising a heat generating resistor that consumes the voltage stepped down by the DC-DC converter.

6. A method for charging a battery in a power supply management system comprising: a battery that is a power source for a high-voltage system; a power supply unit that receives power from an external source for charging the battery; a DC-DC converter that reduces the power of the battery and supplies it to a low-voltage system; and a charge control device that controls the charging of the battery, wherein the charge control device alternately performs a first control that supplies power from the power supply unit to the battery and the DC-DC converter and a second control that stops the power supply from the power supply unit to the battery and the DC-DC converter and supplies power from the battery to the DC-DC converter; performs cell balancing of the battery after a predetermined time has elapsed to eliminate polarization of the battery; and after the cell balancing process is completed, supplies power from the power supply unit to the battery and the DC-DC converter to charge the battery.

7. A vehicle equipped with a power management system including a battery that is a power source for a high-voltage system, a power supply unit that receives power from an external source to charge the battery, a DC-DC converter that reduces the power of the battery and supplies it to a low-voltage system, and a charge control device that controls the charging of the battery, wherein the charge control device alternately performs a first control that supplies power from the power supply unit to the battery and the DC-DC converter, and a second control that stops the power supply from the power supply unit to the battery and the DC-DC converter and supplies power from the battery to the DC-DC converter, thereby performing a charge and discharge process that promotes the elimination of polarization in the battery.

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