Power supply control device and power supply control method

Abstract

This power supply control device comprises: a parallel battery circuit in which battery circuits M1, M2 are connected in parallel; a capacitor 3 which is connected in parallel to the parallel battery circuit; a capacitor-side relay N; and a controller 10 which controls whether battery-side relays P1, P2, charge relays C1, C2, and the capacitor-side relay N are on or off. In the parallel battery circuit, each battery-side relay P1, P2 is connected in parallel to a series circuit in which a charge relay C1, C2 and a charge resistor R1, R2 are connected in series, and the parallel circuit of the series circuit and the battery-side relay P1, P2 is electrically connected to one of the terminals of a battery B1, B2. The capacitor-side relay N is provided on one of a pair of power supply lines Lp, Ln which connect between the capacitor 3 and the parallel battery circuit, and is not provided on the other line.

Description

Power supply control device and power supply control method

[0001] The present invention relates to a power supply control device and a power supply control method.

[0002] Conventionally, a power supply system has been known in which a main battery and a sub-battery are mounted on a vehicle, converter units are arranged in a path between a load such as a motor and the main battery, and in a path between the load and the sub-battery, and relays are connected between the main battery and the converter units and between the sub-battery and the converter units (for example, see Patent Document 1).The power supply system described in Patent Document 1 uses converter units connected in parallel to boost the voltages output by the main battery and the sub-battery.

[0003] International Publication No. 2014 / 057321

[0004] In the above power supply system, even if the main relays connected to the main battery and the sub-battery are turned on, the converter unit prevents conduction between the main battery and the sub-battery. Therefore, when the relays are turned on, a large inrush current does not flow due to the voltage difference between the main battery and the sub-battery. However, a problem occurs in that a boost circuit such as the converter unit has poor system efficiency.

[0005] The problem to be solved by the present invention is to provide a power supply control device and a power supply control method that can perform circuit operation in a circuit with good system efficiency so that a large inrush current does not flow when a relay operates.

[0006] The present invention solves the above problem by comprising a battery parallel circuit in which battery circuits are connected in parallel, a capacitor connected in parallel to the battery parallel circuit, a capacitor-side relay, and a controller that controls the on / off of the relay, wherein the battery parallel circuit connects the battery-side relay in parallel to a series circuit that connects a charging relay and a charging resistor in series, and the parallel circuit of the series circuit and the battery-side relay is electrically connected to either one of the terminals across the battery, and the capacitor-side relay is provided on one of a pair of power supply lines that connect the capacitor and the battery parallel circuit, but not on the other line.

[0007] According to the present invention, in a circuit with good system efficiency, it is possible to perform circuit operation in which a large inrush current does not flow when the relay operates.

[0008] FIG. 1 is a block diagram of a vehicle power supply system according to an embodiment of the present invention. FIG. 2 is a conceptual diagram showing current conduction paths when SOC leveling is performed in the power supply circuit of the vehicle power supply system shown in FIG. 1. FIG. 3 is a conceptual diagram showing current conduction paths when precharging a capacitor in the power supply circuit of the vehicle power supply system shown in FIG. 1. FIG. 4 is a conceptual diagram showing current conduction paths after voltage adjustment of the capacitor and batteries B1 and B2 in the power supply circuit of the vehicle power supply system shown in FIG. 1. FIG. 5 is a conceptual diagram showing current conduction paths in the power supply circuit of the vehicle power supply system shown in FIG. 1 when the voltage difference between batteries B1 and B2 is large while the vehicle is running or stopped. FIG. 6 is a conceptual diagram showing a power supply circuit of a vehicle power supply system according to a first modification of this embodiment. FIG. 7 is a conceptual diagram showing a power supply circuit of a vehicle power supply system according to a second modification of this embodiment. FIG. 8 is a conceptual diagram showing a power supply circuit of a vehicle power supply system according to a third modification of this embodiment.

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described with reference to the accompanying drawings. Fig. 1 is a block diagram of a vehicle power supply system according to an embodiment of the present invention.

[0010] The vehicle power supply system 1 according to this embodiment includes a plurality of battery circuits M1, M2, a capacitor-side relay N, an inverter 2, a capacitor 3, a discharge resistor 4, a control battery 5, a DC-DC converter 6, and a controller 10. The vehicle power supply system 1 is a system mounted on a vehicle and supplies power to a load mounted on the vehicle. The plurality of battery circuits M1, M2 are configured as a parallel battery circuit in which the battery circuits M1, M2 are connected in parallel. The plurality of battery circuits M1, M2 are circuits that switch between supplying and cutting off power between the vehicle power supply and the load. Note that a circuit including at least the plurality of battery circuits M1, M2, the capacitor-side relay N, and the capacitor 3 corresponds to the "power supply circuit" of the present invention.

[0011] The battery circuit M1 includes a battery B1, a battery-side relay P1, a charging relay C1, a current sensor S1, and a charging resistor R1. The battery-side relay P1 and the charging relay C1 are relay switches with mechanical contacts that are switched on and off under the control of the controller 10. The battery-side relay P1 and the charging relay C1 may also be semiconductor switches. The battery B1 is a battery group in which multiple secondary batteries, such as lithium-ion batteries or lead batteries, are connected in parallel and / or series. The battery B1 corresponds to a vehicle power source. The battery B1 is electrically connected to the circuit elements, such as the battery-side relay P1, included in the battery circuit M1, and the capacitor 3.

[0012] The battery circuit M1 has a battery-side relay P1 connected in parallel to a series circuit connecting a charging relay C1 and a charging resistor R1 in series, and a parallel circuit connecting the series circuit of the charging relay C1 and the charging resistor R1 and the battery-side relay P1 in parallel, which is electrically connected to one of the terminals of the battery B1. A current sensor S1 is also connected in series to the battery B1. That is, the battery-side relay P1 and the series circuit connecting the charging relay C1 and the charging resistor R1 in series are each connected in parallel to the battery B1, and the current sensor S1 is also connected in series to the battery B1. The series circuit of the charging relay C1 and the charging resistor R1 is a pre-charge circuit that charges the capacitor 3. The charging resistor R1 limits the current value during capacitor charging. The charging relay C1 and the battery-side relay P1 are also electrically connected to the inverter 2. The current sensor S1 detects the charge / discharge current of the battery B1 and outputs the detected value to the controller 10.

[0013] The battery circuit M2 has the same circuit configuration as the battery circuit M1, and includes a battery B2, a battery-side relay P2, a charging relay C2, a current sensor S2, and a charging resistor R2. The battery circuits M1 and M2 are connected in parallel. The battery circuits M1 and M2 are designed so that the component layout and power supply busbar structure are symmetrical. The battery circuits M1 and M2 have a junction A on the positive and negative sides, respectively. １ , a ２ It includes the junction point a１ , a ２ and the capacitor 3 are connected by a pair of power supply lines Lp and Ln.

[0014] The capacitor-side relay N is a switch that switches between electrical conduction and interruption between the multiple parallel circuits M1, M2 and the capacitor 3. The capacitor-side relay N is a relay switch having mechanical contacts, and is switched on and off under the control of the controller 10. The capacitor-side relay N may be a semiconductor switch. The capacitor-side relay N is provided on one of the pair of power supply lines Lp, Ln, but not on the other power supply line Lp. In other words, the capacitor-side relay N is provided on only one of the pair of power supply lines Lp, Ln. Note that the capacitor-side relay N may not be provided on one of the power supply lines Ln, but may be provided on the other power supply line Lp.

[0015] The inverter 2 is an example of a load of the vehicle, includes a power conversion circuit, converts the power output from the batteries B1 and B2, and outputs the converted power to the motor. During regenerative operation of the motor, the inverter 2 converts the power generated by the motor and outputs the converted power to the batteries B1 and B2.

[0016] A smoothing capacitor 3 and a discharge resistor 4 are connected to the input side of the inverter 2 (the connection side of the batteries B1 and B2). The capacitor 3 is connected in parallel to a battery pack parallel circuit in which multiple battery circuits M1 and M2 are connected in parallel. The discharge resistor 4 discharges the capacitor 3. The capacitor 3 and the capacitor-side relay N are connected at a pair of junction points A. １ , a ２ are connected in series between

[0017] The control battery 5 is a power source for driving the controller 10 and supplies power to the controller 10. The DCDC converter 6 converts the DC voltage input from the batteries B1 and B2, and outputs the converted DC voltage to the control battery 5 to charge the control battery 5.

[0018] The controller 10 has functions such as detecting the status of batteries B1 and B2, detecting the status of inverter 2, and switching on and off the charging relays C1 to Cn, battery-side relays P1 to Pn, and negative electrode relays N1 to Nn. The controller 10 includes a processor for implementing various functions and a memory for storing programs executed by the processor. The controller 10 also includes functional blocks for executing various functions, such as a battery management unit 11, an inverter (INV) control unit 12, and a relay drive unit 13. The battery management unit 11, inverter control unit 12, and relay drive unit 13 each include a detection circuit for detecting the status of batteries B1 and B2, a detection circuit for detecting the status of inverter 2, and a drive circuit for driving the relay. The individual circuits are connected by information and communication lines, allowing them to share sensor information and status information about batteries B1 and B2 and the inverter. While FIG. 1 illustrates the controller 10 as a single control unit, the controller 10 may also be composed of, for example, multiple ECUs.

[0019] The battery management unit 11 measures the voltages of batteries B1 and B2 using voltage sensors connected to batteries B1 and B2, respectively. The battery management unit 11 also measures the charge / discharge currents of batteries B1 and B2 using current sensors S1 and S2, calculates the remaining capacities of batteries B1 and B2 from the integrated values ​​of the charge / discharge currents, and calculates the SOCs of batteries B1 and B2. The battery management unit 11 may also calculate the SOCs from the voltages of batteries B1 and B2. The battery management unit 11 also controls the charging and discharging of batteries B1 and B2 while managing the states of batteries B1 and B2 and control battery 5.

[0020] The inverter control unit 12 transmits switching commands to switch on and off the switching elements included in the inverter 2, and controls the inverter 2 so as to convert the output voltages of the batteries B1 and B2 and output the converted voltages to the motor.

[0021] The relay driving unit 13 drives the battery side relays P1, P2, the charging relays C1, C2, and the capacitor side relay N to adjust the capacity between the batteries B1, B2 (adjust the SOC), precharge the capacitor 3, adjust the voltage of the batteries B1, B2 and the capacitor 3, and supply power to loads such as the inverter 2 and the batteries M1, M2.

[0022] As an example of a power supply control method executed by the controller 10, SOC leveling, precharging of the capacitor 3, voltage control between the capacitor 3 and the batteries B1 and B2, and power supply to the load will be described. FIG. 2 is a conceptual diagram showing the current conduction path when SOC leveling is performed. FIG. 3 is a conceptual diagram showing the current conduction path when precharging the capacitor 3. FIG. 4 is a conceptual diagram showing the current conduction path after voltage adjustment of the capacitor 3 and the batteries B1 and B2. In FIGS. 2 to 4, among the wiring forming the circuit, solid lines indicate electrically conducting wiring, and dotted lines indicate electrically non-conducting wiring. Also, FIGS. 2 to 4 show circuit diagrams of the power supply circuit in the vehicle power supply system 1, and the DC-DC converter 6, the controller 10, and the like are not shown.

[0023] SOC leveling by the relay driving unit 13 will now be described. While the vehicle is running and / or stopped, the controller 10 manages the states of the batteries B1 and B2 using the battery management unit 11, and charges and discharges the batteries B1 and B2 in response to torque requests due to accelerator operation, power requests from the system, and the like. After charging and discharging the batteries B1 and B2, if the states of the batteries B1 and B2 are within a usable range and the SOC difference between the batteries B1 and B2 is equal to or greater than a predetermined SOC difference, the controller 10 performs SOC leveling. The usable range is a range that specifies conditions under which the batteries B1 and B2 are stable and do not deteriorate, and is indicated, for example, by battery temperature. The relay driving unit 13 turns off the multiple charging relays C1 and C2, turns on the battery-side relays P1 and P2, and turns off the capacitor-side relay N to level the SOC variation between the batteries B1 and B2. That is, the relay driver 13 forms a closed loop including batteries B1, B2 and battery-side relays P1, P2 (see FIG. 2). When the SOC of battery B1 is higher than the SOC of battery B2, current flows from battery B1 to battery B2, discharging battery B1 and charging battery B2. As a result, SOC equalization is performed so that the SOC difference between batteries B1 and B2 is equal to or less than a predetermined SOC. SOC equalization is performed for a predetermined period after the vehicle's main switch (also referred to as a power switch or ignition switch) is turned off, while the vehicle is parked, etc.

[0024] While the vehicle is running or stopped, batteries B1 and B2 are repeatedly charged and discharged. Due to individual differences and other factors, the degree of deterioration of batteries B1 and B2 may differ, resulting in variations in the voltages of batteries B1 and B2. For example, if electrical conduction is established between batteries B1 and B2 and a load such as inverter 2 when the voltages of batteries B1 and B2 are high, a large inrush current may flow when the relays are turned on. In this embodiment, after batteries B1 and B2 are charged and discharged, capacitor-side relay N is turned off and battery-side relays P1 and P2 are turned on to perform SOC equalization. This suppresses the inrush current that occurs when capacitor-side relay N and battery-side relays P1 and P2 are turned on.

[0025] Next, precharging of the capacitor 3 by the relay driving unit 13 will be described. When the vehicle's main switch is turned on and the controller 10 receives a vehicle start command, it precharges the capacitor 3. Note that the relay driving unit 13 may turn off all relays before precharging. When the vehicle is started, if the voltage difference between batteries B1 and B2 is equal to or greater than a predetermined voltage difference, the controller 10 charges the capacitor 3 with the power of the battery B1 or B2, whichever has the higher voltage. For example, if the voltage of battery B1 is higher than the voltage of battery B2, the relay driving unit 13 drives the relays as follows to charge the capacitor 3 with battery B1. The relay driving unit 13 turns on the charging relay C1, turns off the battery-side relay P1, turns off the charging relay C2 and the battery-side relay P2, and turns on the capacitor-side relay N. Starting from the positive electrode of battery B1, the charging relay C1, the charging resistor R1, and the junction point A are connected. １ , power supply line Lp, capacitor 3, power supply line Ln, capacitor side relay N, and connection point a ２ In this order, a closed loop for precharging is formed up to the negative electrode of battery B1 (see FIG. 3). Battery B1 is electrically connected to capacitor 3, and capacitor 3 is charged with the power of battery B1.

[0026] Next, the voltage adjustment of batteries B1, B2 and capacitor 3 after precharging will be described. After precharging capacitor 3, relay driver 13 turns off capacitor-side relay N. Capacitor 3 is discharged through discharge resistor 4, and the voltage of capacitor 3 drops. While capacitor 3 is discharging through the discharge resistor, relay driver 13 turns on battery-side relays P1, P2 and turns off charging relays C1, C2. As with SOC leveling, a closed loop is formed including batteries B1, B2 and battery-side relays P1, P2. A current determined by the inter-battery voltage difference, which is the internal resistance of batteries B1, B2, flows through battery-side relays P1, P2 included in the closed loop. Furthermore, because battery circuits M1 and M2 have symmetrical circuit structures, the voltage at the connection point between power supply line Lp and capacitor 3 and the voltage at the connection point between capacitor-side relay N and battery circuits M1, M2 are equal to or close to the average voltage of batteries B1, B2. The average voltage of batteries B1 and B2 is the average voltage of the voltage of battery B1 and the voltage of battery B1.

[0027] That is, the controller 10 turns on the battery-side relays P1, P2 to establish electrical continuity between the batteries B1, B2, and turns off the capacitor-side relay N to discharge the capacitor 3 through the discharge resistor 4, and to set the voltage difference between the batteries B1, B2 to a predetermined first voltage difference or less. The first voltage difference is a threshold value indicating a small variation in the voltages of the batteries B1, B2, and is set to zero or close to zero. In this embodiment, the vehicle power supply system is provided with the capacitor-side relay N on one of the power supply lines Lp, Ln, and no relay on the other line. With this circuit configuration, when the battery-side relays P1, P2 are turned on, current flows between the batteries B1 and B2. However, because the capacitor-side relay N is turned off, no current flows from the capacitor 3 to the batteries B1, B2. As a result, the voltage of the capacitor 3 is regulated by discharge through the discharge resistor 4, and the voltage of the batteries B1, B2 is regulated by the power supply between the batteries B1, B2.

[0028] In this embodiment, the circuit elements and circuit wiring included in the battery circuits M1 and M2 are laid out symmetrically between the battery circuits M1 and M2. Therefore, the connection point of the pair of power supply lines Lp and Pn connected to the capacitor 3 is located at the middle position (connection point A) of the parallel circuit of the battery circuits M1 and M2. １ , a ２ When the battery side relays P1 and P2 are turned on, the voltage of the capacitor 3 becomes the average voltage of the batteries B1 and B2.

[0029] If the voltage difference between batteries B1 and B2 is equal to or greater than a second voltage difference after precharging capacitor 3, controller 10 may turn on charging relay C1 and / or charging relay C2 to reduce the voltage difference between batteries B1 and B2 so that the batteries B1 and B2 are electrically connected. The second voltage difference is a threshold value for determining the regulation circuit when regulating the voltage between batteries B1 and B2. The second voltage difference is greater than the first voltage difference. Battery management unit 11 of controller 10 detects the voltages of batteries B1 and B2. If the voltage difference between batteries B1 and B2 is equal to or greater than the second voltage difference, battery-side relays B1 and B2 are turned on, and batteries B1 and B2 are electrically connected without passing through charging resistors R1 and R2, the inrush current may exceed a specified value. Therefore, controller 10 turns on battery-side relay P1 and charging relay C2 and turns off battery-side relay P2 and charging relay C1. Alternatively, the controller 10 may turn off the battery-side relay P1 and the charging relay C2 and turn on the battery-side relay P2 and the charging relay C1. That is, the relay drive unit 13 of the controller 10 may drive the relays so that the current path electrically connecting the batteries B1 and B2 includes one charging resistor R1, R2. This makes it possible to adjust the voltage difference between the batteries B1 and B2 to a predetermined first voltage difference or less while suppressing the current flowing between the batteries B1 and B2.

[0030] Furthermore, if the voltage difference between battery B1 and battery B2 is larger, the controller 10 may turn off battery-side relays P1 and P2 and turn on battery-side relays P1 and P2. Because the current path between the multiple batteries B1 and B2 includes two charging resistors R1 and R2, the value of the current flowing between the multiple batteries B1 and B2 can be further suppressed. Note that limiting the current using charging resistors R1 and R2 reduces the amount of regulated current and slows down the regulation speed. Therefore, the controller 10 may appropriately select whether to turn on one of charging relays C1 and C2 or both of charging relays C1 and C2, depending on the voltage difference between battery B1 and battery B2.

[0031] When adjusting the voltages of batteries B1 and B2, controller 10 selects an adjustment circuit from among a current path without current limitation by charging resistors R1 and R2, a path that limits current by one of charging resistors R1 and R2, and a path that limits current by both charging resistors R1 and R2. When leveling the SOC, controller 10 may select an adjustment circuit using a method similar to that described above. This allows current to flow through charging resistors R1 and R2 based on the voltage difference between batteries B1 and B2, thereby suppressing SOC variations between batteries B1 and B2.

[0032] The controller 10 detects the voltages of the capacitor 3 and the batteries B1 and B2 using voltage sensors connected to the capacitor 3 and the batteries B1 and B2, respectively. When the voltage difference between the batteries B1 and B2 becomes equal to or less than a first voltage difference and the voltage of the capacitor 3 becomes the average voltage of the batteries B1 and B2 or a value close to the average voltage, the controller 10 turns on the battery-side relays P1 and P2, turns off the charging relays C1 and C2, and turns on the capacitor-side relay (see FIG. 4 ). That is, when the controller 10 detects that the voltage of the capacitor 3 has dropped to a value close to the average voltage of the batteries B1 and B2, the controller 10 turns on the capacitor-side relay from off, establishing electrical continuity between the batteries B1 and B2 and the capacitor 3 via the pair of power supply lines.

[0033] After charging capacitor 3 using batteries B1 and B2 with a higher voltage, controller 10 switches capacitor-side relay N from off to on in a state in which the voltage of capacitor 3 has dropped to the average voltage of batteries B1 and B2 through natural discharge of discharge resistor 4. When capacitor-side relay N is turned on, the difference between the voltage of capacitor 3 and the voltages of batteries B1 and B2 is small, so the current that flows when capacitor-side relay N is on can be reduced. Then, when the vehicle's main switch is on and the vehicle is running or stopped and there is little variation between the voltage of capacitor 3 and the voltages of batteries B1 and B2, controller 10 drives the relay to the state shown in FIG. 4 to supply power to a load such as inverter 2 (power supply to load).

[0034] After precharging of capacitor 3 is completed, if the voltage of battery B1 is higher than the voltage of battery B2 while the vehicle is running or stopped, the controller 10 may turn on battery-side relay P1, turn off charging relay C1, turn off battery-side relay P2 and charging relay C2, and turn on capacitor-side relay N to supply power from battery B1 to a load such as inverter 2 (power supply to load). FIG. 5 is a conceptual diagram showing the current conduction path of the power supply circuit when the voltage difference between batteries B1 and B2 is large while the vehicle is running or stopped. That is, as shown in FIG. 5, if the voltage difference between batteries B1 and B2 is large, the battery-side relays P1 and P2 and charging relays C1 and C2 of the battery with the lower voltage or SOC are turned off, and the vehicle runs using only the battery B1 or B2 with the higher voltage or SOC. Note that if the voltage of battery B2 is higher than the voltage of battery B1, the controller 10 turns on battery-side relay P2 and capacitor-side relay N and turns off battery-side relay P1 and charging relays C1 and C2.

[0035] In addition, when only the battery B1, B2 with the higher voltage or SOC is used to supply power to the load, the maximum output value of the batteries B1, B2 is halved, so the controller 10 may send an alert display instruction to the HMI display ECU.

[0036] Furthermore, after precharging of capacitor 3 is completed, while the vehicle is running or stopped, if the voltage difference between battery B1 and battery B2 is equal to or less than a predetermined third voltage difference, controller 10 may turn on battery-side relays P1 and P2, turn off charging relays C1 and C2, and turn on capacitor-side relay N to supply power from battery B1 and battery B2 to a load such as inverter 2. The third voltage difference is a voltage difference threshold for determining whether the voltages or SOCs of battery B1 and battery B2 are the same or similar. Note that the third voltage difference may be the same value as the first voltage difference. While the vehicle is running or stopped, if the voltage difference between battery B1 and battery B2 is equal to or less than the third voltage difference, the current conduction path of the power supply circuit becomes the path shown in FIG. 4.

[0037] The controller 10 may charge the control battery 5 with the power of the batteries B1 and B2 while the vehicle is running or parked. The controller 10 may charge the control battery 5 so that the remaining capacity of the control battery 5 when the vehicle is parked is sufficient to power the controller 10. A lower limit value for the voltage or SOC of the control battery 5 is preset so that the controller 10 can be powered solely by the power of the control battery 5 without using the power of the batteries B1 and B2. The lower limit value is indicated by the SOC or voltage. While the vehicle is running or parked, the battery management unit 11 of the controller 10 manages the voltage or SOC of the control battery 5. If the SOC or voltage of the control battery 5 is below the lower limit value, the controller 10 drives the DC-DC converter 6 to charge the control battery 5 with the power of the batteries B1 and B2, thereby raising the SOC or voltage of the control battery 5 to or above the lower limit value. Then, when the vehicle is parked, the controller 10 raises the SOC or voltage of the control battery 5 to or above the lower limit value. That is, while the vehicle is parked, the control battery 5 is charged more than necessary to ensure a power source for driving the controller 10. As a result, while the vehicle is parked or when the vehicle is started, the controller 10 can be driven by the power of the control battery 5, and SOC or voltage leveling can be performed.

[0038] The controller 10 may store vehicle driving history data and data on the SOC difference between batteries B1 and B2, and set the voltage or SOC lower limit of the control battery 5 based on the stored data. Specifically, while the vehicle is traveling, the controller 10 stores in memory driving history data such as the vehicle speed, torque, and driving distance, as well as battery data such as the voltage, SOC, and charge / discharge current of batteries B1 and B2. For example, if there is a correlation between the vehicle driving distance and the magnitude of the SOC difference between batteries B1 and B2, the controller 10 measures the distribution of the SOC difference according to the driving distance. From the measured SOC distribution, the controller 10 measures the maximum deviation and calculates the current conduction time required for batteries B1 and B2 to change from a state where the SOC difference is maximum to a state where the SOC is equalized. The conduction time corresponds to the time during which current flows between batteries B1 and B2 during SOC equalization. Then, the controller 10 calculates the voltage or SOC required to drive the controller 10 for at least the conduction time, and sets the calculated voltage or SOC to the lower limit value.

[0039] As described above, the power supply control device according to this embodiment includes a battery parallel circuit in which battery circuits M1 and M2 are connected in parallel, a capacitor 3 connected in parallel to the battery parallel circuit, a capacitor-side relay N, and a controller 10 that controls the on / off of the battery-side relays P1 and P2, the charging relays C1 and C2, and the capacitor-side relay N. The battery parallel circuit connects the battery-side relays P1 and P2 in parallel to a series circuit that connects the charging relays C1 and C2 and the charging resistors R1 and R2 in series. The parallel circuit of the series circuit and the battery-side relays P1 and P2 is electrically connected to either one of the terminals across the batteries B1 and B2. The capacitor-side relay N is provided on one of a pair of power supply lines Lp and Ln that connect the capacitor 3 and the battery parallel circuit, but not on the other line. This allows for circuit operation with high system efficiency to be performed without a large inrush current flowing during relay operation.

[0040] In this embodiment, the controller 10 equalizes the SOCs of the batteries B1 and B2 by turning off the charging relays C1 and C2, turning on the battery-side relays P1 and P2, and turning off the capacitor-side relay N. This reduces SOC variations among the parallel-connected batteries B1 and B2.

[0041] In this embodiment, when the battery circuit M1 includes a high-voltage battery B1 and the battery circuit M2 includes a low-voltage battery B2, upon receiving a vehicle start command, the controller 10 turns on the charging relay C1, turns off the battery-side relay P1, turns off the charging relay C2 and the battery-side relay P2, and turns on the capacitor-side relay N to charge the capacitor 3 with the battery B1. This charges the capacitor 3 and puts the vehicle into a state where it can be driven.

[0042] In this embodiment, the controller 10 turns on at least two of the plurality of battery-side relays P1, P2 and the plurality of charging relays C1, C2 so as to establish electrical continuity between the plurality of batteries B1, B2, turns off the capacitor-side relay N, discharges the capacitor 3 through the discharge resistor 4, and sets the voltage difference between the plurality of batteries B1, B2 to a predetermined first voltage difference or less. This makes it possible to make the voltage of the capacitor 3 and the voltages of the plurality of batteries B1, B2 the same or similar values, suppress inrush current when the relays are turned on, and prevent welding of the relay contacts.

[0043] Furthermore, in this embodiment, when the voltage difference between the multiple batteries B1, B2 becomes equal to or less than the first voltage difference and the voltage of the capacitor 3 becomes the average voltage of the multiple batteries B1, B2 or a value close to the average voltage, the controller 10 turns on the multiple battery-side relays P1, P2, turns off the multiple charging relays C1, C2, and turns on the capacitor-side relay N. This suppresses the inrush current when the relays are turned on, and prevents the relay contacts from welding.

[0044] In this embodiment, the controller 10 turns on at least two of the battery-side main relays P1, P2 and the charging relays C1, C2 to establish electrical continuity between the batteries B1, B2. When the voltage difference between the batteries B1, B2 is equal to or greater than a predetermined second voltage difference, the two relays that are turned on include at least one of the charging relays C1, C2. This suppresses the current flowing between the batteries B1, B2 when the relays are turned on, preventing the relay contacts from welding.

[0045] In this embodiment, when the voltage of battery B1 is higher than the voltage of battery B2 after charging capacitor 3, controller 10 turns on battery-side relay P1, turns off charging relay C1, turns off charging relay C2 and battery-side relay P2, and turns on capacitor-side relay N to supply the power of battery B1 to the load. Furthermore, when the voltage difference between batteries B1 and B2 is equal to or less than a predetermined third voltage difference after charging capacitor 3, controller 10 turns on battery-side relays P1 and P2, turns off charging relays C1 and C2, and turns on capacitor-side relay N to supply the power of batteries B1 and B2 to the load. This reduces SOC variations between parallel-connected batteries B1 and B2. It also suppresses inrush current when the relays are turned on, preventing relay contacts from welding.

[0046] In this embodiment, the control battery 5 is charged so that the remaining capacity when the vehicle is parked is sufficient to drive the controller 10. This allows SOC or voltage leveling to be performed while the vehicle is parked or when the vehicle is started.

[0047] As a first modification of the present embodiment, the vehicle power supply system 1 may include a plurality of inverters 2, capacitors 3, discharge resistors 4, and capacitor-side relays N1. FIG. 6 shows a circuit diagram of a power supply circuit in the first modification of the vehicle power supply system 1. Note that FIG. 6 does not illustrate the control battery 5, the DC-DC converter 6, the controller 10, and the like. The capacitor 3 is connected to the input sides of the plurality of inverters 2. A plurality of capacitor-side relays N1, N2 are provided on the plurality of power supply lines Ln corresponding to the plurality of inverters 2. When the vehicle is started, if the voltage difference between battery B1 and battery B2 is equal to or greater than a predetermined voltage difference, the controller 10 charges the capacitor 3 with power from battery B1 or B2, whichever has the higher voltage. For example, if the voltage of battery B1 is higher than the voltage of battery B2, the relay driver 13 drives the relay as follows to charge the plurality of capacitors 3 with battery B1. The relay driver 13 turns on the charging relay C1, turns off the battery-side relay P1, turns off the charging relay C2 and the battery-side relay P2, and turns on the capacitor-side relays N1 and N2. １ , a plurality of power supply lines Lp, a plurality of capacitors 3, a plurality of power supply lines Ln, capacitor-side relays N1 and N2, and a connection point a ２ In this order, a closed loop for precharging is formed up to the negative electrode of battery B1. That is, a closed loop for precharging is formed in which a charging current flows from battery B1 through charging resistor R1 and multiple capacitor-side relays N1 and N2 to multiple capacitors C. Battery B1 is electrically connected to multiple capacitors 3, and multiple capacitors 3 are charged with power from battery B1.

[0048] In addition, in Modification 1 shown in FIG. 6 , after batteries B1 and B2 are charged and discharged, if the states of batteries B1 and B2 are within the usable range and the SOC difference between batteries B1 and B2 is equal to or greater than a predetermined SOC difference, controller 10 performs SOC equalization. Relay driver 13 turns off charging relays C1 and C2, turns on battery-side relays P1 and P2, and turns off capacitor-side relays N1 and N2 to equalize the SOC variation between batteries B1 and B2. That is, relay driver 13 forms a closed loop including batteries B1 and B2 and battery-side relays P1 and P2. If the SOC of battery B1 is higher than the SOC of battery B2, current flows from battery B1 to battery B2, discharging battery B1 and charging battery B2. In this way, SOC equalization is performed so that the SOC difference between batteries B1 and B2 is equal to or less than the predetermined SOC.

[0049] In the first modification, when adjusting the voltages of the batteries B1, B2 and the capacitor 3 after precharging, the relay driver 13 may turn off the capacitor-side relays N1, N2 after precharging the plurality of capacitors 3. The plurality of capacitors 3 are discharged through the plurality of discharge resistors 4, respectively, and the voltages of the plurality of capacitors 3 decrease. While the capacitors 3 are discharging through the discharge resistors 4, the relay driver 13 turns on the battery-side relays P1, P2 and turns off the charge relays C1, C2. As in SOC leveling, a closed loop is formed that includes the batteries B1, B2 and the battery-side relays P1, P2, and a current determined by the inter-battery voltage difference corresponding to the internal resistance of the batteries B1, B2 flows through the battery-side relays P1, P2. Because the battery circuits M1 and M2 have a symmetrical circuit structure, the voltages at the connection points between the multiple power supply lines Lp and the multiple capacitors 3, and the voltages at the connection points between the capacitor-side relays N1 and N2 and the battery circuits M1 and M2, are equal to or close to the average voltage of the batteries B1 and B2. The controller 10 then switches the capacitor-side relays N1 and N2 from off to on after the voltage of the capacitor 3 has dropped to the average voltage of the batteries B1 and B2 through natural discharge of the discharge resistor 4. This charges the capacitor 3, enabling the vehicle to be driven. Furthermore, the inrush current when the relay is turned on is suppressed, preventing the relay contacts from welding.

[0050] As a second modification of this embodiment, the vehicle power supply system 1 may include a charging circuit that charges the capacitor 3. Fig. 7 shows a circuit diagram of the power supply circuit in the second modification of the vehicle power supply system 1. Note that the control battery 5, the controller 10, and the like are not shown in Fig. 7. In Fig. 7, among the wiring that forms the circuit, solid lines indicate electrically conductive wiring, and dotted lines indicate electrically non-conductive wiring. Fig. 7 also shows the current conduction path when SOC leveling is performed and the current conduction path when pre-charging the capacitor 3.

[0051] In the second modification, a charging battery 7 is used as a power source for precharging the capacitor 3, and the charging battery 7 is connected to the capacitor 3 via a DC-DC converter 6. The DC-DC converter 6 is connected to the capacitor 3 via precharging lines Lc1 and Lc2. The circuit including the DC-DC converter 6, the charging battery 7, and the lines Lc1 and Lc2 corresponds to the "charging circuit" of the present invention. When precharging the capacitor 3, the controller 10 turns on the battery-side relays P1 and P2 and turns off the capacitor-side relay N to charge the capacitor 3 with the charging battery 7 and to equalize the SOCs of the batteries B1 and B2. The controller 10 precharges the capacitor 3 until its voltage reaches the average voltage of the batteries B1 and B2. Alternatively, after precharging the capacitor 3, the voltage of the capacitor 3 may be lowered to the average voltage of the batteries B1 and B2 by natural discharge of the discharge resistor 4. The controller 10 then turns on the capacitor-side relay N after equalizing the SOC. This charges capacitor 3, enabling the vehicle to be driven. It also suppresses the inrush current when the relay is turned on, preventing the relay contacts from welding. As an additional modification to Modification 2, the charging relays C1 and C2 and the charging resistors R1 and R2 may be omitted from the power supply circuit, and a circuit configuration may be adopted in which one charging relay and one discharging resistor are used to connect between batteries B1 and B2.

[0052] As a third modification of this embodiment, the vehicle power supply system 1 may additionally include a discharge circuit 20 that discharges the capacitor 3. FIG. 8 shows a circuit diagram of the power supply circuit in the third modification of the vehicle power supply system 1. Note that the control battery 5, the DC-DC converter 6, the controller 10, and other components are not shown in FIG. 8 . The discharge circuit 20 is connected in parallel with the capacitor 3 and includes a discharge resistor 21 and a discharge relay 22 that switches the discharge resistor 21 between electrical conduction and interruption. When discharging the capacitor 3, if natural discharge of the discharge resistor 4 alone would result in a long discharge time, the controller 10 turns on the discharge relay 22 to shorten the discharge time. For example, after precharging the capacitor 3, the controller 10 turns on the discharge relay 22 to discharge the capacitor 3 and reduce the voltage of the capacitor 3 to the average voltage of the batteries B1 and B2. Then, when the voltage of the capacitor 3 reaches or approaches the average voltage of the batteries B1 and B2, the controller 10 switches the capacitor-side relay N from off to on. This promotes the discharge of the capacitor 3, and shortens the start-up time of the vehicle (the time until the vehicle is ready to run).

[0053] In this embodiment, the controller 10 does not need to perform all of the SOC leveling, precharging of the capacitor 3, and voltage control between the capacitor 3 and the batteries B1 and B2, but only needs to perform at least one of the control processes.

[0054] REFERENCE SIGNS LIST 1 Vehicle power supply system 2 Inverter 3 Capacitor 4 Discharge resistor 5 Control battery 6 DCDC converter 10 Controller B1, B2 Battery C1, C2 Charging relay M1, M2 Battery circuit N Capacitor side relay P1, P2 Battery side relay R1, R2 Charging resistor

Claims

1. A power supply control device mounted on a vehicle, comprising: a battery parallel circuit in which a battery circuit including a battery, a battery-side relay, a charging relay, and a charging resistor is connected in parallel; a capacitor connected in parallel to the battery parallel circuit; a capacitor-side relay; and a controller that controls the on / off of the battery-side relay, the charging relay, and the capacitor-side relay, wherein the battery parallel circuit connects the battery-side relay in parallel to a series circuit that connects the charging relay and the charging resistor in series, and the parallel circuit of the series circuit and the battery-side relay is electrically connected to either one of the terminals on both ends of the battery, and the capacitor-side relay is provided on one of a pair of power supply lines connecting the capacitor and the battery parallel circuit, but not on the other line.

2. A power supply control device according to claim 1, wherein the controller turns off a plurality of the charging relays, turns on a plurality of the battery-side relays, and turns off the capacitor-side relay, thereby equalizing the SOC among the plurality of the batteries.

3. A power supply control device according to claim 1 or 2, wherein the plurality of battery circuits include a first battery circuit including a first battery having a higher voltage among the plurality of batteries, and a second battery circuit including a second battery having a lower voltage among the plurality of batteries, and wherein the controller, upon receiving a command to start the vehicle, turns on the charging relay included in the first battery circuit, turns off the battery-side relay included in the first battery circuit, turns off the charging relay and the battery-side relay included in the second battery circuit, and turns on the capacitor-side relay, thereby charging the capacitor with the first battery.

4. A power supply control device according to any one of claims 1 to 3, comprising a discharge resistor connected in parallel to the capacitor, wherein the controller turns on at least two of the battery-side relays and the charging relays so as to establish electrical continuity between the batteries, and turns off the capacitor-side relay, thereby discharging the capacitor through the discharge resistor, and reducing the voltage difference between the batteries to a predetermined first voltage difference or less.

5. A power supply control device according to claim 4, wherein the controller turns on the battery-side relays, turns off the charging relays, and turns on the capacitor-side relay when the voltage difference between the plurality of batteries becomes equal to or less than the first voltage difference and the capacitor voltage becomes the average voltage of the plurality of batteries or a value close to the average voltage.

6. A power supply control device according to any one of claims 1 to 3, wherein the controller turns on at least two relays out of the plurality of battery-side main relays and the plurality of charging relays so as to establish electrical continuity between the plurality of batteries, and when the voltage difference between the plurality of batteries is equal to or greater than a predetermined second voltage difference, the at least two relays include the charging relay.

7. A power supply control device according to claim 3, wherein the controller, after charging the capacitor, if the voltage of the first battery is higher than the voltage of the second battery, turns on the battery-side relay included in the first battery circuit, turns off the charging relay included in the first battery circuit, turns off the charging relay and the battery-side relay included in the second battery circuit, and turns on the capacitor-side relay, thereby supplying the power of the first battery to a load; and, after charging the capacitor, if the voltage difference between the first battery and the second battery is equal to or less than a predetermined third voltage difference, turns on the battery-side relays included in the first battery circuit and the second battery circuit, respectively, turns off the charging relays included in the first battery circuit and the second battery circuit, and turns on the capacitor-side relay, thereby supplying the power of the first battery and the second battery to a load.

8. A power supply control device according to any one of claims 1 to 7, wherein the capacitors are connected to the input sides of a plurality of inverters, respectively, and a plurality of the capacitor-side relays are provided on one of the lines corresponding to the plurality of inverters.

9. A power supply control device according to any one of claims 1 to 7, comprising a control power supply for driving the controller, wherein the control power supply is charged so that the remaining capacity when the vehicle is parked is sufficient to drive the controller.

10. A power supply control device according to claim 1, comprising a charging circuit for charging the capacitor, wherein the controller turns on the plurality of battery-side relays and turns off the capacitor-side relay, charges the capacitor using the charging circuit, and equalizes the SOC among the plurality of batteries, and turns on the capacitor-side relay after equalizing the SOC.

11. A power supply control device according to any one of claims 1 to 10, further comprising a discharge circuit connected in parallel to the capacitor for discharging the capacitor, the discharge circuit including a discharge resistor and a discharge relay for switching between electrical conduction and cut-off of the discharge resistor.

12. A power supply control method for controlling a power supply circuit mounted on a vehicle, wherein the power supply circuit comprises: a battery parallel circuit in which a battery circuit including a battery, a battery-side relay, a charging relay, and a charging resistor is connected in parallel; a capacitor connected in parallel to the battery parallel circuit; and a capacitor-side relay; the battery parallel circuit connects the battery-side relay in parallel to a series circuit that connects the charging relay and the charging resistor in series; and electrically connects one of the terminals on both ends of the battery to the parallel circuit of the series circuit and the battery-side relay; the capacitor-side relay is provided on one of a pair of power supply lines connecting between the capacitor and the battery parallel circuit, but not on the other line; the multiple battery circuits include a first battery circuit including a first battery having a higher voltage among the multiple batteries, and a second battery circuit including a second battery having a lower voltage among the multiple batteries; and the controller a power supply control method for controlling a vehicle, when a start command for the vehicle is received, turning on the charging relay included in the first battery circuit, turning off the battery-side relay included in the first battery circuit, turning off the charging relay and the battery-side relay included in the second battery circuit, and turning on the capacitor-side relay to charge the capacitor with the high-voltage battery;

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