Vehicle power supply

Abstract

This invention provides a vehicle power supply device that can shorten the time required to start charging batteries connected in parallel. [Solution] The vehicle's power supply unit 1 can change the connection of the first battery 20A and the second battery 20B by a switching mechanism SC, so as to connect them in parallel or in series. When the control device 100 starts charging the batteries connected in parallel, it first detects the voltages of the first battery 20A and the second battery 20B using the first sensor 24A and the second sensor 24B. Next, the control device 100 charges capacitors C1 and C2 using the battery with the lower battery voltage among the first battery 20A and the second battery 20B, and then controls the switching mechanism SC to connect the first battery 20A and the second battery 20B in parallel.

Description

Technical Field

[0001] This disclosure relates to a power supply device for a vehicle.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2023-047162 (Patent Document 1) discloses a vehicle power supply device capable of achieving both switching between series / parallel connection of a power supply during charge / discharge and power reception between power supplies during parking. This vehicle power supply device includes a DC-DC converter including a first switch connected to the low potential side of a first power storage device and the high potential side of a second power storage device, a second switch connected between the high potential side of the first power storage device, the low potential side of the second power storage device, and the first switch, and a third switch connected between the low potential side of the second power storage device, the low potential side of the first power storage device, and the first switch.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the vehicle power supply device disclosed in Japanese Patent Application Laid-Open No. 2023-047162 (Patent Document 1), a DC-DC converter between upper and lower batteries adjusts the battery voltage before parallel connection to reduce the voltage difference between the upper and lower batteries and suppress the generation of inrush current. However, in this method, it may take time to adjust the battery voltage, and there is a risk that the adjustment may not be completed within a predetermined time.

[0005] An object of this disclosure is to provide a power supply device for a vehicle that can shorten the time until the start of charging or the like of parallel-connected batteries.

Means for Solving the Problems

[0006] This disclosure relates to a vehicle power supply unit. The vehicle power supply unit includes a first battery, a first sensor for detecting the voltage of the first battery, a second battery, a second sensor for detecting the voltage of the second battery, a capacitor connected between a first node and a second node, a switching mechanism for switching the connection relationship between the first battery and the second battery and the first node and the second node, and a control device for controlling the switching mechanism. The switching mechanism is configured to switch the configuration of connecting the first battery and the second battery between the first node and the second node to first to fifth states. The first state is a state in which the first battery and the second battery are connected in series between the first node and the second node. The second state is a state in which the first battery and the second battery are connected in parallel between the first node and the second node. The third state is a state in which the first battery is connected without connecting the second battery between the first node and the second node. The fourth state is a state in which the second battery is connected without connecting the first battery between the first node and the second node. The fifth state is a state in which neither the first battery nor the second battery is connected between the first node and the second node. When the control device transitions the state of the switching mechanism from the fifth state to the second state, it is configured to detect the voltages of the first battery and the second battery in advance using the first sensor and the second sensor, and to control the switching mechanism so that it passes through either the third state or the fourth state so that the battery with the lower battery voltage is connected between the first node and the second node first.

[0007] With the above configuration, the capacitor is charged by the battery with the lower voltage among the first and second batteries, thus minimizing the peak charging current to the capacitor when the batteries are connected in parallel. Furthermore, when the batteries are connected in parallel, it is possible to prevent current from flowing from the capacitor to the battery with the lower voltage. Therefore, the batteries can be connected in parallel without the need to adjust the voltage of the two batteries using a DC-DC converter or similar device. [Effects of the Invention]

[0008] According to the vehicle power supply device of this disclosure, it is possible to transition to charging with batteries connected in parallel without performing voltage adjustment of the batteries, and it is possible to prevent the preparation time for charging from exceeding a specified time. [Brief explanation of the drawing]

[0009] [Figure 1] This diagram shows the configuration of the power supply unit for the vehicle according to this embodiment. [Figure 2] This diagram shows the current flow during pre-charging when the switching mechanism SC is in the third state. [Figure 3] This diagram shows the current flow during pre-charging immediately after switching the switching mechanism SC from the third state to the second state. [Modes for carrying out the invention]

[0010] Embodiments of this disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated.

[0011] Figure 1 shows the configuration of the vehicle power supply unit according to this embodiment. The vehicle's power supply unit 1 includes a first battery 20A, a first sensor 24A for detecting the voltage of the first battery 20A, a second battery 20B, a second sensor 24B for detecting the voltage of the second battery 20B, capacitors C1 and C2 connected between first nodes N11, N21 and second nodes N12, N22, a switching mechanism SC for switching the connection relationship between the first battery 20A and the second battery 20B and the first nodes N11, N21 and second nodes N12, N22, and a control device 100 for controlling the switching mechanism SC. The control device 100 includes a processor 101 and a memory 102.

[0012] The vehicle's power supply unit 1 further includes a motor generator 11, an inverter 12, a high-voltage device 13, a motor generator 21, and an inverter 22. The motor generator 11, inverter 12, high-voltage device 13, motor generator 21, and inverter 22 constitute a load device such as a vehicle drive system, but they may also constitute a generator that generates electricity.

[0013] The switching mechanism SC includes system main relays SMR11 to SMR13, system main relays SMR21 to SMR23, and relays R1 to R3.

[0014] The vehicle power supply unit 1 shown in Figure 1 can be connected in parallel or in series using a switching mechanism SC, allowing the connection of the first battery 20A and the second battery 20B to be changed.

[0015] The vehicle's power supply unit 1 further includes an inlet 34 to which the connector for the charging station 30 is connected, charging relays DCR1 and DCR2, and a charging voltage sensor 35 for detecting the charging voltage.

[0016] While 400V chargers are currently the mainstream, 800V chargers that allow for faster charging are being considered. The vehicle power supply unit 1 shown in Figure 1 can accommodate both chargers by connecting the batteries in series when charging with 800V and in parallel when charging with 400V.

[0017] Figure 1 shows the charging stand 30, which supplies 400V, connected. The charging stand 30 includes a DC power supply 31, a smoothing capacitor 32, a current sensor 33A, and a voltage sensor 33V.

[0018] However, there are some points to note when connecting the charging stand 30 that supplies 400V and starting charging. If there is variation in the charge state of the first battery 20A and the second battery 20B, when the batteries are connected in parallel during 400V charging, the voltage variation between the parallel batteries will cause the voltage precharged to the smoothing capacitors C1 and C2 of the high-voltage equipment and inverter to flow as a short-circuit current between the batteries. This may damage the batteries and the high-voltage equipment.

[0019] For example, before charging, it is conceivable to adjust the voltage between the parallel batteries with a converter so that the charge states of the first battery 20A and the second battery 20B become uniform, and then perform pre-charging. However, since it takes time to adjust the voltage between the batteries, there is a risk that the voltage cannot be adjusted within the specified time defined by the standard during charging, and charging cannot start due to a timeout or the like.

[0020] Therefore, the control device 100 controls the switching mechanism SC as follows. When starting to charge the batteries connected in parallel, the control device 100 detects the voltages of the first battery 20A and the second battery 20B in advance by the first sensor 24A and the second sensor 24B. Next, the control device 100 charges the capacitors C1 and C2 using the battery with the lower battery voltage among the first battery 20A and the second battery 20B, and then controls the switching mechanism SC so that the first battery 20A and the second battery 20B are connected in parallel.

[0021] Specifically, the switching mechanism SC is configured to be able to switch the mode of connecting the first battery 20A and the second battery 20B between the first node N11, N21 and the second node N12, N22 to the first to fifth states.

[0022] The first state is a state in which the first battery 20A and the second battery 20B are connected in series between the first node N11, N21 and the second node N12, N22.

[0023] The second state is a state in which the first battery 20A and the second battery 20B are connected in parallel between the first node N11, N21 and the second node N12, N22.

[0024] The third state is a state in which the first battery 20A is connected between the first node N11, N21 and the second node N12, N22 without connecting the second battery 20B.

[0025] The fourth state is a state in which the second battery 20B is connected between the first node N11, N21 and the second node N12, N22 without connecting the first battery 20A.

[0026] The fifth state is a state where neither the first battery 20A nor the second battery 20B is connected between the first nodes N11, N21 and the second nodes N12, N22.

[0027] When the control device 100 transitions the state of the switching mechanism SC from the fifth state to the second state, it previously detects the voltages of the first battery 20A and the second battery 20B by the first sensor 24A and the second sensor 24B. Next, the control device 100 controls the switching mechanism SC so as to pass through either the third state or the fourth state such that the battery with the lower battery voltage among the first battery 20A and the second battery 20B is first connected between the first nodes N11, N21 and the second nodes N12, N22.

[0028] The following explains the control of the switching mechanism SC at the start of charging when the initial state is V(20A) < V(20B) when the voltage of the first battery 20A is V(20A) and the voltage of the second battery 20B is V(20B).

[0029] The initial state is the fifth state described above. In the fifth state, specifically, the system main relays SMR11 to SMR13, the system main relays SMR21 to SMR23, and the relays R1 to R3 are all in the OFF state, and the first battery 20A and the second battery 20B are disconnected from the first nodes N11, N21 and the second nodes N12, N22.

[0030] In this state, the control device 100 detects the battery voltages of the first battery 20A and the second battery 20B by the first sensor 24A and the second sensor 24B. When the detected initial state is V(20A) < V(20B), the control device 100 sets the switching mechanism SC to the third state described above and pre-charges the capacitors C1 and C2 using the first battery 20A.

[0031] Figure 2 shows the current flow during pre-charging in the third state. In Figure 2, the switching mechanism SC is set to the third state described above. Specifically, the control device 100 controls system main relays SMR12, SMR13, system main relays SMR22, SMR23, and relay R1 to the ON (connected) state. On the other hand, the control device 100 controls system main relay SMR11, system main relay SMR21, and relays R2 and R3 to the OFF (disconnected) state.

[0032] As shown by the dashed arrows in Figure 2, a charging current flows from the first battery 20A to capacitors C1 and C2. Since the voltage of the first battery 20A is lower than that of the second battery 20B, precharging capacitors C1 and C2 using the first battery 20A results in a smaller inrush current than precharging them using the second battery 20B.

[0033] When the pre-charging of capacitors C1 and C2 has progressed to a certain extent in the state shown in Figure 2, the control device changes the state of the switching mechanism SC from the third state described above to the second state.

[0034] Figure 3 shows the current flow during pre-charging immediately after switching the switching mechanism SC from the third state to the second state. Specifically, in the latter half of the pre-charging period, relay R2 is changed from the OFF state to the ON state from the state shown in Figure 2. As a result, the first battery 20A and the second battery 20B are connected in parallel to capacitors C1 and C2. This causes the second battery 20B to add charge to capacitors C1 and C2 by the voltage difference between the batteries.

[0035] Subsequently, the system main relays SMR12 and SMR22 are changed from OFF to ON, the charging relays DCR1 and DCR2 are changed from OFF to ON, and charging of the first battery 20A and the second battery 20B from the charging stand 30 begins. If the initial state is V(20A)>V(20B), the control device 100 sets the switching mechanism SC to the fourth state described above, precharges capacitors C1 and C2 using the second battery 20B, and then sets the switching mechanism SC to the second state.

[0036] As described above, in this embodiment, capacitors C1 and C2 are pre-charged by the battery with the lower voltage among the two batteries, then the two batteries are connected in parallel to perform an additional pre-charge equal to the voltage difference, and then charging is performed.

[0037] Conversely, if capacitors C1 and C2 are pre-charged by the battery with the higher voltage, when the battery with the lower voltage is connected, the current from capacitors C1 and C2 and the current from the battery with the higher voltage will flow into the battery with the lower voltage, potentially shortening its lifespan due to excessive current.

[0038] In this embodiment, precharging of the capacitor is performed in stages, which reduces the precharging current. Furthermore, when two batteries are connected in parallel, the current flowing is distributed between the batteries and the capacitor, starting with the battery with the higher voltage. Therefore, charging can begin without adjusting the voltage between the batteries. Consequently, precharging of the capacitor can be completed and charging can begin within the specified time frame defined by the standard.

[0039] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of this disclosure is indicated by the claims rather than by the description of the embodiments above, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of Symbols]

[0040] 1 Power supply unit, 11, 21 Motor generator, 12, 22 Inverter, 13 High-voltage equipment, 20A 1st battery, 20B 2nd battery, 24A 1st sensor, 24B 2nd sensor, 30 Charging stand, 31 DC power supply, 32, C1, C2 Smoothing capacitors, 33A Current sensor, 33V Voltage sensor, 34 Inlet, 35 Charging voltage sensor, 100 Control unit, 101 Processor, 102 Memory, C1, C2 Capacitors, DCR1, DCR2 Charging relays, N11, N21 1st node, N12, N22 2nd node, R1, R2, R3 Relays, SC Switching mechanism, SMR11, SMR12, SMR13, SMR21, SMR22, SMR23 System main relays.

Claims

[Claim 1] The first battery and A first sensor for detecting the voltage of the first battery, The second battery, A second sensor for detecting the voltage of the second battery, A capacitor connected between the first node and the second node, A switching mechanism for switching the connection relationship between the first battery and the second battery and the first node and the second node, The system includes a control device that controls the switching mechanism, The switching mechanism is configured to switch between first to fifth states in which the first battery and the second battery are connected between the first node and the second node. The first state is a state in which the first battery and the second battery are connected in series between the first node and the second node. The second state is a state in which the first battery and the second battery are connected in parallel between the first node and the second node. The third state is a state in which the first battery is connected without connecting the second battery between the first node and the second node, The fourth state is a state in which the second battery is connected between the first node and the second node without the first battery being connected, The fifth state is a state in which neither the first battery nor the second battery is connected between the first node and the second node. The control device is configured to, when transitioning the state of the switching mechanism from the fifth state to the second state, detect the voltages of the first battery and the second battery in advance using the first sensor and the second sensor, and control the switching mechanism so that it passes through either the third state or the fourth state so that the battery with the lower battery voltage is connected first between the first node and the second node.

Images