Electrical circuit and program for parallel charging startup

Abstract

To provide an electrical circuit and a program for parallel charging startup to start parallel charging of batteries in a short time.SOLUTION: An electrical circuit mounted on a vehicle includes processes for: discharging a high-voltage capacitor through an inverter circuit and a three-phase motor in a state where a parallel charging startup process controls a connection switching circuit to stop voltage application from a series circuit of first and second batteries to the high-voltage capacitor; charging the high-voltage capacitor by applying the output voltage of the first battery to the high-voltage capacitor; and charging the first and second batteries in parallel by connecting the first battery between a high-potential wiring and a low-potential wiring, connecting the second battery between an intermediate point and the low-potential wiring, and controlling the connection switching circuit so that a charging voltage generated by a power supplied from an external charging installation is applied between the high-potential wiring and the low-potential wiring.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to an electric circuit and a program for parallel charging start processing.

[0002] Patent Document 1 discloses an electric circuit mounted on a vehicle. This electric circuit includes a series circuit of two batteries, an inverter circuit, and a three-phase motor. The inverter circuit converts DC power supplied from the series circuit of batteries into AC power and supplies it to the three-phase motor to drive the three-phase motor. The electric circuit also includes wiring that connects the connection point of the two batteries with the neutral point of each coil of the three-phase motor. By transferring power between the two batteries via this wiring, it is possible to raise the temperature of each battery. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-120566 Summary of the Invention [Problem to be solved by the invention]

[0004] A capacitor (hereinafter referred to as a high-voltage capacitor) is provided between the high-potential wiring and the low-potential wiring of an inverter circuit. Furthermore, in an electric circuit in which a wiring is connected to the neutral point of a three-phase motor, a capacitor (hereinafter referred to as a low-voltage capacitor) may be connected between the neutral point and the low-potential wiring. In this type of electric circuit, the output voltage of a series circuit of two batteries is applied to the high-voltage capacitor, and then a process is executed to charge the batteries in parallel using an external charging device. In this case, a conventional process first discharges the high-voltage capacitor and the low-voltage capacitor. Next, one battery is connected to the high-voltage capacitor, and the other battery is connected to the low-voltage capacitor. The supply voltage of the external charging device is then applied to the batteries in parallel to charge them. This process adjusts the voltage of each capacitor to an appropriate voltage corresponding to the battery, preventing inrush current from the high-voltage capacitor when changing the circuit connection. However, this process has a problem in that it takes a long time to change the circuit connection. As a result, a timeout error may occur if the waiting time for reception from the external charging device is exceeded. This specification proposes a technology that enables parallel charging of batteries to start in a shorter time. [Means for solving the problem]

[0005] The electric circuit disclosed in this specification is mounted on a vehicle. The electric circuit includes a first battery, a second battery, a high-voltage capacitor, a low-voltage capacitor, a three-phase motor, an inverter circuit, a charge port, a connection switching circuit, and a control circuit. The three-phase motor has three windings: a U-phase winding, a V-phase winding, and a W-phase winding. Each of the three windings has a first connection terminal at one end and a second connection terminal at the other end, and the second connection terminals of the three windings are connected to each other at a neutral point. The inverter circuit is connected to the first connection terminal of the U-phase winding, the first connection terminal of the V-phase winding, and the first connection terminal of the W-phase winding. The charge port is connected to an external charging facility. The connection switching circuit changes the mutual connections of the first battery, the second battery, the inverter circuit, the neutral point, and the charge port. The inverter circuit has a high-potential wiring, a low-potential wiring, and three series switch circuits provided for each of the three windings. Each of the series switch circuits has an upper reverse-conducting switching element that is a reverse-conducting switching element connected between the first connection terminal of the corresponding winding and the high-potential wiring, and a lower reverse-conducting switching element that is a reverse-conducting switching element connected between the first connection terminal of the corresponding winding and the low-potential wiring. The high-voltage capacitor is connected between the high-potential wiring and the low-potential wiring. The low-voltage capacitor is connected between the neutral point and the low-potential wiring. When an external charging facility is connected to the charging port during series operation in which the connection switching circuit is controlled so that the output voltage of the series circuit of the first battery and the second battery is applied to the high-potential capacitor, the control circuit executes a parallel charging start process.The parallel charging start process includes a process of discharging the high-voltage capacitor via the inverter circuit and the three-phase motor while controlling the connection switching circuit so that application of voltage from the series circuit to the high-voltage capacitor is stopped; a process of charging the high-voltage capacitor by controlling the connection switching circuit so that the output voltage of the first battery is applied to the high-voltage capacitor; and a process of charging the first battery and the second battery in parallel by connecting the first battery between the high-potential wiring and the low-potential wiring, connecting the second battery between the neutral point and the low-potential wiring, and controlling the connection switching circuit so that a charging voltage generated by power supplied from an external charging facility is applied between the high-potential wiring and the low-potential wiring.

[0006] The charging voltage may be a voltage supplied from an external charging facility to the charging port, or may be a voltage obtained by converting the voltage supplied from the external charging facility to the charging port (for example, a DC voltage converted from an AC voltage).

[0007] In the parallel charging start process of this electric circuit, the high-voltage capacitor is discharged and charged by the first battery, and then parallel charging of the first and second batteries is performed. Because the low-voltage capacitor is not charged or discharged, parallel charging of the batteries can be started in a short time. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a circuit diagram of an electric circuit according to an embodiment. [Figure 2] 10 is a flowchart of a parallel charging start process. DETAILED DESCRIPTION OF THE INVENTION

[0009] In the electric circuit, the parallel charging start process may be executed when the charging voltage is lower than the output voltage of the series circuit.

[0010] In the above electric circuit, the series operation may be an operation of alternately performing a process of transferring power from the first battery to the second battery via the inverter circuit and the three-phase motor and a process of transferring power from the second battery to the first battery via the inverter circuit and the three-phase motor.

[0011] This configuration allows the temperature of each battery to increase during series operation.

[0012] The electric circuit 10 shown in FIG. 1 is mounted on a vehicle. The electric circuit 10 has a first battery 11, a second battery 12, an inverter circuit 30, and a three-phase motor 40. The three-phase motor 40 is a motor for driving the vehicle. The inverter circuit 30 converts DC power supplied from the first battery 11 and the second battery 12 into AC power and supplies it to the three-phase motor 40. As a result, the three-phase motor 40 rotates the drive wheels, causing the vehicle to travel. The output voltage V1 of the first battery 11 is approximately equal to the output voltage V2 of the second battery 12.

[0013] The three-phase motor 40 has a U-phase winding 44U, a V-phase winding 44V, and a W-phase winding 44W. Terminals 41U and 42U are provided at both ends of the winding 44U. Terminals 41V and 42V are provided at both ends of the winding 44V. Terminals 41W and 42W are provided at both ends of the winding 44W. Terminals 42U, 42V, and 42W are connected to each other at a neutral point 46.

[0014] The inverter circuit 30 is connected to terminals 41U, 41V, and 41W of a three-phase motor 40. The inverter circuit 30 includes a high-potential wiring 31, a low-potential wiring 32, and three series switch circuits 34U, 34V, and 34W. Each of the series switch circuits 34U, 34V, and 34W includes two reverse-conducting switching elements 35 connected in series between the high-potential wiring 31 and the low-potential wiring 32. Hereinafter, of the two series-connected reverse-conducting switching elements 35, the one connected to the high-potential wiring 31 may be referred to as the upper reverse-conducting switching element, and the one connected to the low-potential wiring 32 may be referred to as the lower reverse-conducting switching element. Each reverse-conducting switching element 35 has a structure in which a switching element (e.g., an insulated gate bipolar transistor or a field-effect transistor) and a diode (e.g., a pn diode or a Schottky barrier diode) are connected in anti-parallel. In each reverse-conducting switching element 35, the cathode of the diode is connected to the high potential terminal (i.e., collector or drain) of the switching element, and the anode of the diode is connected to the low potential terminal (i.e., emitter or source) of the switching element.

[0015] The series switch circuit 34U is provided for the winding 44U. The series switch circuit 34U has an upper reverse-conducting switching element 35UU and a lower reverse-conducting switching element 35UL. A high potential terminal of the upper reverse-conducting switching element 35UU is connected to the high potential wiring 31. A low potential terminal of the upper reverse-conducting switching element 35UU and a high potential terminal of the lower reverse-conducting switching element 35UL are connected to the terminal 41U. A low potential terminal of the lower reverse-conducting switching element 35UL is connected to the low potential wiring 32.

[0016] Series switch circuit 34V is provided for winding 44V. Series switch circuit 34V has an upper reverse-conducting switching element 35VU and a lower reverse-conducting switching element 35VL. A high potential terminal of upper reverse-conducting switching element 35VU is connected to high potential wiring 31. A low potential terminal of upper reverse-conducting switching element 35VU and a high potential terminal of lower reverse-conducting switching element 35VL are connected to terminal 41V. A low potential terminal of lower reverse-conducting switching element 35VL is connected to low potential wiring 32.

[0017] The series switch circuit 34W is provided for the winding 44W. The series switch circuit 34W has an upper reverse-conducting switching element 35WU and a lower reverse-conducting switching element 35WL. The high potential terminal of the upper reverse-conducting switching element 35WU is connected to the high potential wiring 31. The low potential terminal of the upper reverse-conducting switching element 35WU and the high potential terminal of the lower reverse-conducting switching element 35WL are connected to the terminal 41W. The low potential terminal of the lower reverse-conducting switching element 35WL is connected to the low potential wiring 32.

[0018] A high-voltage capacitor 36 is connected between the high-potential wiring 31 and the low-potential wiring 32. A voltmeter 37 is also connected between the high-potential wiring 31 and the low-potential wiring 32.

[0019] A neutral point wiring 50 is connected to the neutral point 46 of the three-phase motor 40. The neutral point wiring 50 is connected to the positive electrode of the second battery 12. A low-voltage capacitor 60 is connected between the neutral point wiring 50 and the low-potential wiring 32. In addition, a voltmeter 61 is connected between the neutral point wiring 50 and the low-potential wiring 32.

[0020] The electric circuit 10 has a charging port 70. A connector of a charging facility external to the vehicle can be connected to the charging port 70. An AC voltage is applied to the charging port 70 from the external charging facility. The charging port 70 is connected to a conversion circuit 73. When an AC voltage is applied to the charging port 70, the conversion circuit 73 converts the AC voltage into a DC voltage and outputs it to output wirings 71 and 72. The conversion circuit 73 outputs the DC voltage in a direction such that the output wiring 71 has a higher potential than the output wiring 72.

[0021] The electric circuit 10 has a plurality of relay switches 81 to 89. The switching of each relay switch changes the mutual connections between the first battery 11, the second battery 12, the high potential wiring 31, the low potential wiring 32, the neutral point 46, and the charging port 70. In other words, the relay switches 81 to 89 form a connection switching circuit.

[0022] The relay switch 81 is provided between the negative electrode of the first battery 11 and the positive electrode of the second battery 12. When the relay switch 81 is turned on, the first battery 11 and the second battery 12 are connected in series.

[0023] The relay switch 82 is provided between the negative electrode of the first battery 11 and the negative electrode of the second battery 12. When the relay switch 82 is turned on, the negative electrode of the first battery 11 and the negative electrode of the second battery 12 are connected.

[0024] An ammeter 20 and a relay switch 83 are connected in series between the positive electrode of the first battery 11 and the high-potential wiring 31. When the relay switch 83 is turned on, the positive electrode of the first battery 11 is connected to the high-potential wiring 31.

[0025] A relay switch 84, an ammeter 52, and a relay switch 85 are provided in the neutral point wiring 50. The relay switch 84 and the ammeter 52 are provided in the neutral point wiring 50 between the low-voltage capacitor 60 and the battery 12. The relay switch 85 is provided in the neutral point wiring 50 between the low-voltage capacitor 60 and the neutral point 46. When the relay switches 84 and 85 are turned on, the positive electrode of the second battery 12 is connected to the neutral point 46 via the neutral point wiring 50.

[0026] The relay switch 86 is provided between the negative electrode of the second battery 12 and the low potential wiring 32. When the relay switch 86 is turned on, the negative electrode of the second battery 12 is connected to the low potential wiring 32.

[0027] A series circuit of a relay switch 87 and a resistor 87r is connected in parallel to the relay switch 86. When the relay switch 87 is turned on, the negative electrode of the second battery 12 is connected to the low potential line 32 via the resistor 87r.

[0028] The relay switch 88 is provided between the positive electrode of the first battery 11 and the output wiring 71. When the relay switch 88 is turned on, the output wiring 71 is connected to the positive electrode of the first battery 11.

[0029] The relay switch 89 is provided between the negative electrode of the second battery 12 and the output wiring 72. When the relay switch 89 is turned on, the output wiring 72 is connected to the negative electrode of the second battery 12.

[0030] The electric circuit 10 has a control circuit 90. The control circuit 90 is composed of a CPU, a memory, etc. A program for controlling the electric circuit 10 is stored in the memory of the control circuit 90. The control circuit 90 controls the switching elements of each reverse conducting switching element 35 and the relay switches 81 to 89 in accordance with the program.

[0031] In normal operation, the control circuit 90 turns on the relay switches 81, 83, and 86 and turns off the relay switches 82, 84, 85, 87, 88, and 89. In this state, the first battery 11 and the second battery 12 are connected in series between the high-potential wiring 31 and the low-potential wiring 32. Therefore, the output voltage V3 output from the series circuit of the first battery 11 and the second battery 12 is applied between the high-potential wiring 31 and the low-potential wiring 32. The output voltage V3 is the sum of the output voltage V1 of the first battery 11 and the output voltage V2 of the second battery 12. The control circuit 90 switches on and off the switching elements of each reverse-conducting switching element 35 to convert the DC power applied between the high-potential wiring 31 and the low-potential wiring 32 into AC power and supplies the AC power to the three-phase motor 40. This causes the three-phase motor 40 to rotate. The control circuit 90 controls the torque and rotation speed of the three-phase motor 40 by changing the amplitude, frequency, etc. of the AC current supplied to the three-phase motor 40 .

[0032] The control circuit 90 can execute a battery heating operation while the vehicle is stopped. For example, in a low-temperature environment, the performance of the batteries 11, 12 can be improved by raising the temperature of the batteries 11, 12 through the battery heating operation. In the battery heating operation, the control circuit 90 operates the inverter circuit 30 and the three-phase motor 40 as a converter circuit. More specifically, in the battery heating operation, the control circuit 90 operates at least one of the U phase, V phase, and W phase as a converter circuit. Since the U phase, V phase, and W phase operate in the same way, the operation of the U phase will be described below.

[0033] During the battery temperature increase operation, the control circuit 90 turns on relay switches 81, 83, 84, 85, and 86 and turns off relay switches 82, 87, 88, and 89. The control circuit 90 also switches reverse-conducting switching elements 35UU and 35UL depending on the situation. When the reverse-conducting switching element 35UU is turned on, a current flows from the positive electrode of the first battery 11 to the negative electrode of the first battery 11 via the high-potential wiring 31, the reverse-conducting switching element 35UU, the winding 44U, and the neutral point wiring 50. When the reverse-conducting switching element 35UU is subsequently turned off, an induced voltage is generated in the winding 44U, and a current flows from the negative electrode of the second battery 12 to the positive electrode of the second battery 12 via the low-potential wiring 32, the diode of the reverse-conducting switching element 35UL, the winding 44U, and the neutral point wiring 50. In this way, when the reverse conducting switching element 35UU switches on, the first battery 11 is discharged and the second battery 12 is charged, and power is transferred from the first battery 11 to the second battery 12. When the reverse conducting switching element 35UL is turned on, a current flows from the positive electrode of the second battery 12 to the negative electrode of the second battery 12 via the neutral point wiring 50, the winding 44U, the reverse conducting switching element 35UL, and the low potential wiring 32. When the reverse conducting switching element 35UL is subsequently turned off, an induced voltage is generated in the winding 44U, and a current flows from the negative electrode of the first battery 11 to the positive electrode of the first battery 11 via the neutral point wiring 50, the winding 44U, the diode of the reverse conducting switching element 35UU, and the high potential wiring 31. In this way, when the reverse conducting switching element 35UL switches on, the second battery 12 is discharged and the first battery 11 is charged, and power is transferred from the second battery 12 to the first battery 11. In the battery temperature raising operation, the control circuit 90 alternately transfers power from the first battery 11 to the second battery 12 and from the second battery 12 to the first battery 11. In this way, the control circuit 90 raises the temperatures of the first battery 11 and the second battery 12.

[0034] During the battery warming operation, an external charging device may be connected to the charging port 70, and charging of the batteries 11, 12 may begin. In this case, the charging voltage Vc output from the conversion circuit 73 between the output wirings 71, 72 is lower than the output voltage V3 of the series circuit of the batteries 11, 12, and higher than the output voltages V1, V2 of the batteries 11, 12. Therefore, the control circuit 90 applies the charging voltage Vc to the batteries 11, 12 in parallel to charge the batteries 11, 12 (hereinafter referred to as the parallel charging operation). When transitioning from the battery warming operation to the parallel charging operation, the control circuit 90 executes the parallel charging start process shown in FIG. 2 according to a program.

[0035] At the start of Fig. 2, the control circuit 90 is executing the battery temperature raising operation. That is, at the start of Fig. 2, the relay switches 81, 83, 84, 85, and 86 are on, and the relay switches 82, 87, 88, and 89 are off. In this state, the output voltage V3 of the series circuit of the batteries 11 and 12 is applied to the high-voltage capacitor 36, and the output voltage V2 of the second battery 12 is applied to the low-voltage capacitor 60.

[0036] In step S2, external charging equipment is connected to the charging port 70. The control circuit 90 then turns off all reverse-conducting switching elements 35 and ends the battery warming operation. When the user then operates the external charging equipment to start charging, the external charging equipment transmits a charge start instruction to the control circuit 90. Therefore, in step S4, the control circuit 90 receives the charge start instruction. The control circuit 90 then sequentially executes the processes from step S6 onwards.

[0037] In step S6, the control circuit 90 turns off the relay switch 86. This causes the potential of the low-potential wiring 32 to float. Even when the relay switch 86 is turned off, charges are still held in the high-voltage capacitor 36 and the low-voltage capacitor 60. Therefore, after the relay switch 86 is turned off, the voltage across the high-voltage capacitor 36 is approximately equal to the output voltage V3, and the voltage across the low-voltage capacitor 60 is approximately equal to the output voltage V2.

[0038] Next, in step S8, the control circuit 90 executes a high-voltage capacitor discharge process. Here, the control circuit 90 turns on the upper reverse-conducting switching element 35 of one phase of the series switch circuits 34U-34W and the lower reverse-conducting switching element 35 of another phase. As an example, a case where the upper reverse-conducting switching element 35UU and the lower reverse-conducting switching element 35VL are turned on will be described. In this case, current flows from the high-potential terminal of the high-voltage capacitor 36 to the low-potential terminal of the high-voltage capacitor 36 via the upper reverse-conducting switching element 35UU, the winding 44U, the winding 44V, and the lower reverse-conducting switching element 35VL. This discharges the high-voltage capacitor 36. In the high-voltage capacitor discharge process, the control circuit 90 repeatedly switches at least one of the reverse-conducting switching elements 35UU and 35VL to prevent the discharge current from becoming excessively high. In step S8, the control circuit 90 discharges the high-voltage capacitor 36 until the voltage across the high-voltage capacitor 36 (i.e., the voltage detected by the voltmeter 37) reaches 0 V. When the voltage across the high-voltage capacitor 36 drops to 0 V, the control circuit 90 turns off both reverse-conducting switching elements 35UU and 35VL, and ends the high-voltage capacitor discharge process. Note that, because the low-voltage capacitor 60 is not discharged in step S8, the voltage across the low-voltage capacitor 60 remains substantially equal to the output voltage V2 after step S8 is completed.

[0039] Generally, a relay switch may not be able to be turned off due to a stuck contact. If the relay switch 86 is not turned off due to a stuck contact, the voltage across the high-voltage capacitor 36 does not drop in step S8. Therefore, step S8 also serves as a check to see if the relay switch 86 is stuck. If the relay switch 86 is stuck, the control circuit 90 halts processing.

[0040] Next, in step S10, the control circuit 90 turns the relay switch 81 off.

[0041] Next, in step S12, the control circuit 90 turns on the relay switch 87. Furthermore, the control circuit 90 monitors the voltage across the high-voltage capacitor 36 with the voltmeter 37. If the relay switch 81 is not stuck and off, turning on the relay switch 87 charges the high-voltage capacitor 36 through the series circuit of the batteries 11 and 12, and the voltage across the high-voltage capacitor 36 increases. On the other hand, if the relay switch 81 is off, turning on the relay switch 87 does not increase the voltage across the high-voltage capacitor 36. Therefore, step S12 makes it possible to check whether the relay switch 81 is stuck. If the relay switch 81 is stuck, the control circuit 90 stops processing.

[0042] Next, in step S14, the control circuit 90 turns off the relay switch 87, and ends the check for whether the relay switch 81 is stuck.

[0043] Next, in step S16, the control circuit 90 turns on the relay switch 82. As a result, the negative electrode of the first battery 11 is connected to the negative electrode of the second battery 12.

[0044] Next, in step S18, the control circuit 90 turns on the relay switch 87. This connects the negative electrode of the first battery 11 and the negative electrode of the second battery 12 to the low-potential line 32 via the resistor 87r. Then, the output voltage V1 of the first battery 11 is applied to the high-voltage capacitor 36. Therefore, the high-voltage capacitor 36 is charged by the output voltage V1. At this time, the resistor 87r prevents the charging current from becoming extremely high. The control circuit 90 charges the high-voltage capacitor 36 until the voltage across the high-voltage capacitor 36 becomes equal to the output voltage V1. Furthermore, when the relay switch 87 is turned on, the output voltage V2 of the second battery 12 is applied to the low-voltage capacitor 60. However, because the voltage across the low-voltage capacitor 60 is approximately equal to the output voltage V2 before step S18 is performed, the voltage across the low-voltage capacitor 60 changes very little even when the relay switch 87 is turned on.

[0045] When the voltage across the high-voltage capacitor 36 rises to the output voltage V1, the control circuit 90 turns on the relay switch 86 in step S20. This directly connects the negative electrode of the first battery 11 and the negative electrode of the second battery 12 to the low-potential wiring 32. After turning on the relay switch 86, the control circuit 90 turns off the relay switch 87 in the subsequent step S22.

[0046] Next, the control circuit 90 starts the parallel charging operation in step S24. That is, the control circuit 90 first instructs the external charging equipment to start parallel charging. The external charging equipment then applies an AC voltage to the charging port 70. The conversion circuit 73 then converts the AC voltage into a DC charging voltage Vc and outputs it between the output wirings 71 and 72. The control circuit 90 also turns on the relay switches 88 and 89. This control results in the first battery 11 being connected between the high potential wiring 31 and the low potential wiring 32, the second battery 12 being connected between the neutral point 46 and the low potential wiring 32, and the charging voltage Vc being applied between the high potential wiring 31 and the low potential wiring 32.

[0047] A charging voltage Vc is applied to the first battery 11. As described above, the charging voltage Vc is higher than the output voltage V1 of the first battery 11. Therefore, the first battery 11 is charged.

[0048] Furthermore, in the parallel charging operation, the control circuit 90 turns on at least one of the upper reverse-conducting switching elements 35UU, 35VU, and 35WU. The following describes the case where the upper reverse-conducting switching element 35UU is turned on as an example. When the upper reverse-conducting switching element 35UU is turned on, the high-potential wiring 31 is connected to the positive electrode of the second battery 12 via the upper reverse-conducting switching element 35UU, the winding 44U, and the neutral point wiring 50. Therefore, a charging voltage Vc is applied to the second battery 12. As described above, the charging voltage Vc is higher than the output voltage V2 of the second battery 12. Therefore, the second battery 12 is charged. Note that the charging current for the second battery 12 may be reduced by repeatedly switching the upper reverse-conducting switching element 35UU.

[0049] In this way, in the parallel charging operation, the first battery 11 and the second battery 12 are charged in parallel, thereby allowing the charged states of the first battery 11 and the second battery 12 to be restored.

[0050] As described above, in the parallel charging start process of Fig. 2, the high-voltage capacitor 36 is discharged without charging or discharging the low-voltage capacitor 60, and then the first battery 11 can be connected to the high-voltage capacitor 36. Therefore, preparation for parallel charging of the batteries 11 and 12 can be completed in a short time. This prevents a timeout error in the external charging equipment due to a long preparation time.

[0051] In the above embodiment, the case where the operation transitions from the battery warming operation to the parallel charging operation has been described. However, the operating state before the parallel charging start process is not limited to the battery warming operation. In other words, the operating state before the parallel charging start process may be any operating state as long as the batteries 11 and 12 are connected in series, the output voltage V3 is applied to the high-voltage capacitor 36, and the output voltage V2 is applied to the low-voltage capacitor 60.

[0052] Although the embodiments have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings simultaneously achieves multiple objectives, and achieving one of these objectives itself has technical utility. [Explanation of symbols]

[0053] 11: First battery 12: Second battery 30: Inverter circuit 36: High-voltage capacitor 40: Three-phase motor 46: Neutral point 60: Low voltage capacitor 70: Charging port

Claims

1. An electrical circuit mounted on a vehicle, A first battery; A second battery; A high-voltage capacitor A low-voltage capacitor a three-phase motor having three windings, namely a U-phase winding, a V-phase winding, and a W-phase winding, each of the three windings having a first connection terminal provided at one end thereof and a second connection terminal provided at the other end thereof, and the second connection terminals of the three windings are connected to each other at a neutral point; an inverter circuit connected to the first connection terminal of the U-phase winding, the first connection terminal of the V-phase winding, and the first connection terminal of the W-phase winding; a charging port connected to an external charging facility; a connection switching circuit that changes the mutual connections of the first battery, the second battery, the inverter circuit, the neutral point, and the charging port; control circuit, and The inverter circuit High-voltage wiring, Low potential wiring; three series switch circuits provided for each of the three windings; and each of the series switch circuits has an upper reverse-conducting switching element that is a reverse-conducting switching element connected between the first connection terminal of the corresponding winding and the high-potential wiring, and a lower reverse-conducting switching element that is a reverse-conducting switching element connected between the first connection terminal of the corresponding winding and the low-potential wiring; the high-voltage capacitor is connected between the high-potential wiring and the low-potential wiring; the low-voltage capacitor is connected between the neutral point and the low-potential wiring; when an external charging device is connected to the charging port during a series operation in which the connection switching circuit is controlled so that an output voltage of a series circuit of the first battery and the second battery is applied to the high-voltage capacitor, the control circuit executes a parallel charging start process; The parallel charging start process a process of discharging the high-voltage capacitor via the inverter circuit and the three-phase motor while controlling the connection switching circuit so that application of voltage from the series circuit to the high-voltage capacitor is stopped; a process of charging the high-voltage capacitor by controlling the connection switching circuit so that the output voltage of the first battery is applied to the high-voltage capacitor; a process of charging the first battery and the second battery in parallel by connecting the first battery between the high potential wiring and the low potential wiring, connecting the second battery between the neutral point and the low potential wiring, and controlling the connection switching circuit so that a charging voltage generated by power supplied from an external charging facility is applied between the high potential wiring and the low potential wiring; having Electrical circuit.

2. 2. The electric circuit of claim 1, wherein the control circuit executes the parallel charging initiation process when the charging voltage is less than the output voltage of the series circuit.

3. 3. The electric circuit according to claim 1, wherein the series operation alternately performs a process of transferring power from the first battery to the second battery via the inverter circuit and the three-phase motor and a process of transferring power from the second battery to the first battery via the inverter circuit and the three-phase motor.

4. A program that causes an electric circuit mounted on a vehicle to perform a charging process, The electrical circuit A first battery; A second battery; A high-voltage capacitor A low-voltage capacitor a three-phase motor having three windings, namely a U-phase winding, a V-phase winding, and a W-phase winding, each of the three windings having a first connection terminal provided at one end thereof and a second connection terminal provided at the other end thereof, and the second connection terminals of the three windings are connected to each other at a neutral point; an inverter circuit connected to the first connection terminal of the U-phase winding, the first connection terminal of the V-phase winding, and the first connection terminal of the W-phase winding; a charging port connected to an external charging facility; a connection switching circuit that changes the mutual connections of the first battery, the second battery, the inverter circuit, the neutral point, and the charging port; control circuit, and The inverter circuit High-voltage wiring, Low potential wiring; three series switch circuits provided for each of the three windings; and each of the series switch circuits has an upper reverse-conducting switching element that is a reverse-conducting switching element connected between the first connection terminal of the corresponding winding and the high-potential wiring, and a lower reverse-conducting switching element that is a reverse-conducting switching element connected between the first connection terminal of the corresponding winding and the low-potential wiring; the high-voltage capacitor is connected between the high-potential wiring and the low-potential wiring; the low-voltage capacitor is connected between the neutral point and the low-potential wiring; when an external charging device is connected to the charging port during a series operation in which the connection switching circuit is controlled so that an output voltage of the series circuit of the first battery and the second battery is applied to the high-voltage capacitor, the program causes the control circuit to execute a parallel charging start process; The parallel charging start process a process of discharging the high-voltage capacitor via the inverter circuit and the three-phase motor while controlling the connection switching circuit so that application of voltage from the series circuit to the high-voltage capacitor is stopped; a process of charging the high-voltage capacitor by controlling the connection switching circuit so that the output voltage of the first battery is applied to the high-voltage capacitor; a process of charging the first battery and the second battery in parallel by connecting the first battery between the high potential wiring and the low potential wiring, connecting the second battery between the neutral point and the low potential wiring, and controlling the connection switching circuit so that a charging voltage generated by power supplied from an external charging facility is applied between the high potential wiring and the low potential wiring; having program.

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