Electric circuit and program for battery temperature rise processing

Abstract

To execute battery temperature rise processing in an electric circuit in which power is transferred as being stepped down in a specific power transfer direction.SOLUTION: An electric circuit comprises a first battery, a second battery, a three-phase motor, an inverter circuit, and a control circuit. Battery temperature rise processing comprises: voltage difference adjustment processing for adjusting voltage difference obtained by subtracting output voltage of the second battery from output voltage of the first battery so that the voltage difference becomes a reference value or larger; and periodic power transfer processing for causing a converter circuit constituted of the inverter circuit and a winding of the three-phase motor to alternately and repeatedly execute a first power transfer operation for transferring power as being stepped up from the second battery to the first battery and a second power transfer operation for transferring power as being stepped down from the first battery to the second battery. Amplitude of the voltage difference in the periodic power transfer processing is smaller than the reference value.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to an electric circuit and a program for battery temperature increase 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. This electric circuit can perform a battery heating process to heat each battery by transferring power between the two batteries via the neutral point. [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] Depending on the configuration of the electric circuit, power may be transferred while increasing the voltage in a specific power transfer direction (e.g., from the second battery to the first battery), but may be transferred while decreasing the voltage in another power transfer direction (e.g., from the first battery to the second battery). When transferring power while decreasing the voltage, power cannot be transferred unless the output voltage of the battery from which the power is being transferred is higher than the output voltage of the battery to which the power is being transferred. This may prevent the battery warming process from being performed appropriately. This specification proposes a technology for suitably performing battery warming process in an electric circuit in which power is transferred while decreasing the voltage in a specific power transfer direction. [Means for solving the problem]

[0005] (Configuration 1) The electric circuit of Configuration 1 disclosed in this specification is mounted on a vehicle. The electric circuit includes a first battery, a second battery, a three-phase motor, an inverter 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 provided at one end and a second connection terminal provided 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 inverter circuit includes 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 control circuit is capable of executing a battery warm-up process. The battery warm-up process includes a voltage difference adjustment process and a periodic power transfer process. The voltage difference adjustment process is a process of adjusting a voltage difference obtained by subtracting the output voltage of the second battery from the output voltage of the first battery so that the voltage difference is equal to or greater than a reference value. The periodic power transfer process is a process of causing a converter circuit formed by a specific series switch circuit that is at least one of the three series switch circuits and a specific winding of the three windings that corresponds to the specific series switch circuit to alternately and repeatedly execute a first power transfer operation that transfers power from the second battery to the first battery while increasing voltage, and a second power transfer operation that transfers power from the first battery to the second battery while decreasing voltage. The amplitude of the voltage difference during the periodic power transfer process is less than the reference value.

[0006] In this specification, a reverse-conducting switching element refers to an element in which a switching element and a diode are connected in parallel, with the cathode of the diode connected to the high-potential terminal of the switching element and the anode of the diode connected to the low-potential terminal of the switching element. The switching element may be a semiconductor switching element such as a field-effect transistor or an insulated gate bipolar transistor. The diode may be a pn diode or a Schottky barrier diode. The switching element and the diode may be provided on a common semiconductor substrate or on different semiconductor substrates. In this specification, "on" of a reverse-conducting switching element means that the switching element of the reverse-conducting switching element is on, and "off" of a reverse-conducting switching element means that the switching element of the reverse-conducting switching element is off.

[0007] In this electric circuit, in the voltage difference adjustment process, the voltage difference obtained by subtracting the output voltage of the second battery from the output voltage of the first battery is adjusted so that the voltage difference is equal to or greater than a reference value, and then the periodic power transfer process is executed. That is, the periodic power transfer process is started in a state in which the output voltage of the first battery is higher than the output voltage of the second battery by equal to or greater than a reference value. Also, the amplitude of the voltage difference in the periodic power transfer process is smaller than the reference value. Therefore, it is possible to prevent the output voltage of the first battery from becoming lower than the output voltage of the second battery in the periodic power transfer process. As a result, it is possible to appropriately transfer power from the first battery to the second battery in the second power transfer operation (i.e., the operation of transferring power while lowering the voltage) of the periodic power transfer process, and it is possible to appropriately heat the first battery and the second battery. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a circuit diagram of an electric circuit according to a first embodiment (a diagram showing a current path when a lower reverse-conducting switching element 35VL is on during boost converter operation). FIG. [Figure 2]1 is a circuit diagram of an electric circuit according to a first embodiment (a diagram showing a current path when a lower reverse-conducting switching element 35VL is turned off during boost converter operation). FIG. [Figure 3] 1 is a circuit diagram of an electric circuit according to a first embodiment (a diagram showing a current path when an upper reverse-conducting switching element 35VU is on during operation as a step-down converter). FIG. [Figure 4] 1 is a circuit diagram of an electric circuit according to a first embodiment (a diagram showing a current path when an upper reverse-conducting switching element 35VU is turned off during operation of a step-down converter). FIG. [Figure 5] 4 is a flowchart showing a battery temperature increasing process. [Figure 6] 3 is a circuit diagram showing currents I1, I2, and I3 flowing in the electric circuit of the first embodiment. FIG. [Figure 7] 6 is a graph showing changes in currents I1 and I2 in the voltage difference adjustment process of the first embodiment. [Figure 8] 6 is a graph showing changes in output voltages V1 and V2 during the entire battery temperature increase process. [Figure 9] 6 is a graph showing changes in currents I1 and I2 during periodic power transfer processing in Example 1. [Figure 10] 6 is a graph showing a change in voltage difference ΔV in the periodic power transfer process of the first embodiment. [Figure 11] 10 is a graph showing changes in currents I1 and I2 in a voltage difference adjustment process according to the first modification. [Figure 12] 10 is a graph showing changes in currents I1 and I2 in a voltage difference adjustment process according to Modification 2. [Figure 13] 10 is a graph showing changes in currents I1 and I2 in a periodic power transfer process according to the second modification. [Figure 14] 10 is a graph showing changes in output voltages V1 and V2 throughout the entire battery temperature increase process of Modification 2. [Figure 15] 10 is a graph showing changes in currents I1 and I2 in the voltage difference adjustment process of the second embodiment. [Figure 16] FIG. 10 is a circuit diagram of an electric circuit according to a third embodiment. [Figure 17] FIG. 10 is a circuit diagram of an electric circuit according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Following the above configuration 1, additional configurations of the electric circuit disclosed in this specification will be described below.

[0010] (Configuration 2) 2. The electric circuit of claim 1, wherein in the voltage difference adjustment process, the control circuit causes the converter circuit to perform the first power transfer operation. (Configuration 3) The electric circuit according to configuration 1, wherein in the voltage difference adjustment process, the control circuit charges the first battery by applying a supply voltage supplied from a charging facility external to the vehicle to the first battery, and charges the second battery by applying a voltage obtained by stepping down the supply voltage using the converter circuit to the second battery. (Configuration 4) 2. The electric circuit according to claim 1, wherein the control circuit consumes power from the second battery during the voltage difference adjustment process. (Configuration 5) 5. The electric circuit according to any one of configurations 1 to 4, wherein the control circuit executes the battery temperature increasing process while charging the first battery and the second battery in parallel by a charging facility external to the vehicle. (Configuration 6) 6. The electric circuit according to any one of configurations 1 to 5, wherein the control circuit executes a process for reducing the voltage difference after executing the periodic power transfer process. (Configuration 7) The electric circuit according to any one of configurations 1 to 6, wherein the control circuit executes the periodic power transfer process in a state in which the positive electrode of the first battery is connected to the high potential wiring, the negative electrode of the first battery is connected to the low potential wiring, the positive electrode of the second battery is connected to the neutral point, and the negative electrode of the second battery is connected to the low potential wiring. (Configuration 8) The electric circuit according to any one of configurations 1 to 8, wherein the control circuit executes the periodic power transfer process in a state in which the positive electrode of the first battery is connected to the high potential wiring, the negative electrode of the first battery is connected to the low potential wiring, the positive electrode of the second battery is connected to the high potential wiring, and the negative electrode of the second battery is connected to the neutral point.

[0011] According to the second aspect, the output voltage of the first battery can be increased, and the voltage difference can be increased to the reference value or more.

[0012] According to the third aspect, the first battery can be charged faster than the second battery, so that the voltage difference can be increased to or above the reference value.

[0013] According to the fourth aspect, the output voltage of the second battery can be reduced, and the voltage difference can be increased to or above the reference value.

[0014] According to configuration 5, the first battery and the second battery can be charged efficiently.

[0015] According to the sixth aspect, after the temperature of the battery is increased, the output voltages of the first battery and the second battery can be balanced.

[0016] According to the seventh configuration, the first power transfer operation and the second power transfer operation can be performed.

[0017] According to the eighth aspect, the first power transfer operation and the second power transfer operation can be performed. [Example]

[0018] The electric circuit 10 shown in Fig. 1 is mounted on a vehicle. The electric circuit 10 has an upper battery 11, a lower 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 upper battery 11 and the lower 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] A 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.

[0025] A neutral point wiring 50 is connected to the neutral point 46 of the three-phase motor 40. The other end of the neutral point wiring 50 is connected to the positive electrode of the lower battery 12. An ammeter 54 is provided at the positive electrode of the lower battery 12. The ammeter 54 detects the current flowing through the lower battery 12. A capacitor 60 is connected between the neutral point wiring 50 and the low potential wiring 32. A voltmeter 61 is connected between the neutral point wiring 50 and the low potential wiring 32.

[0026] The electric circuit 10 has a charging port 70. A connector of a charging facility outside the vehicle can be connected to the charging port 70. The charging port 70 has a high-potential charging terminal 71 and a low-potential charging terminal 72. When the connector of the charging facility is connected to the charging port 70, the charging facility applies a DC voltage between the high-potential charging terminal 71 and the low-potential charging terminal 72 in a direction such that the high-potential charging terminal 71 has a high potential.

[0027] The electric circuit 10 has a plurality of relay switches 81 to 87. When each relay switch is switched, the mutual connection relationship between the upper battery 11, the lower battery 12, the high potential wiring 31, the low potential wiring 32, the neutral point 46, and the charging port 70 is changed.

[0028] The relay switch 81 is provided between the negative electrode of the upper battery 11 and the positive electrode of the lower battery 12. When the relay switch 81 is turned on, the negative electrode of the upper battery 11 is connected to the positive electrode of the lower battery 12 and the neutral point wiring 50.

[0029] The relay switch 82 is provided between the negative terminal of the upper battery 11 and the negative terminal of the lower battery 12. When the relay switch 82 is turned on, the negative terminal of the upper battery 11 and the negative terminal of the lower battery 12 are connected.

[0030] An ammeter 20 and a relay switch 83 are connected in series between the positive electrode of the upper battery 11 and the high-potential wiring 31. When the relay switch 83 is turned on, the positive electrode of the upper battery 11 is connected to the high-potential wiring 31. The ammeter 20 detects the current flowing through the upper battery 11.

[0031] The relay switch 84 is provided between the negative electrode of the lower battery 12 and the low potential wiring 32. When the relay switch 84 is turned on, the negative electrode of the lower battery 12 is connected to the low potential wiring 32.

[0032] The relay switch 85 is provided between the low potential charging terminal 72 and the low potential wiring 32. When the relay switch 85 is turned on, the low potential charging terminal 72 is connected to the low potential wiring 32.

[0033] The relay switch 86 is provided between the high-potential charging terminal 71 and the high-potential wiring 31. When the relay switch 86 is turned on, the high-potential charging terminal 71 is connected to the high-potential wiring 31.

[0034] The relay switch 87 is provided in the neutral point wiring 50. When the relay switch 87 is turned on, the positive electrode of the lower battery 12 is connected to the neutral point 46 via the neutral point wiring 50.

[0035] 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 87 in accordance with the program.

[0036] The control circuit 90 can perform normal operation to drive the three-phase motor 40. In normal operation, the control circuit 90 turns on the relay switches 81, 83, and 84 and turns off the relay switches 82, 85, 86, and 87. In this state, the upper battery 11 and the lower battery 12 are connected in series between the high-potential wiring 31 and the low-potential wiring 32. Therefore, the DC voltage output from the series circuit of the upper battery 11 and the lower battery 12 is applied between the high-potential wiring 31 and the low-potential wiring 32. The control circuit 90 converts the DC power applied between the high-potential wiring 31 and the low-potential wiring 32 into AC power by switching on and off the switching elements of each reverse-conducting switching element 35, 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 rotational speed of the three-phase motor 40 by changing the amplitude, frequency, etc. of the AC current supplied to the three-phase motor 40.

[0037] The control circuit 90 can operate the inverter circuit 30 and the three-phase motor 40 as a DC-DC converter circuit. Specifically, the inverter circuit 30 and the three-phase motor 40 are internally configured with a DC-DC converter circuit configured with the series switch circuit 34U and the winding 44U, a DC-DC converter circuit configured with the series switch circuit 34V and the winding 44V, and a DC-DC converter circuit configured with the series switch circuit 34W and the winding 44W. The control circuit 90 can synchronize the operation of the three DC-DC converter circuits, or can operate the remaining DC-DC converter circuits while stopping one or two of the three DC-DC converter circuits. In a DC-DC converter circuit that is stopped, both the upper and lower reverse-conducting switching elements are controlled to be off. The operation of a DC-DC converter circuit (i.e., a V-phase DC-DC converter circuit) configured with the series switch circuit 34V and the winding 44V will be described below as an example.

[0038] When operating the DC-DC converter circuit, the control circuit 90 turns on the relay switches 84 and 87. That is, the control circuit 90 connects the positive electrode of the lower battery 12 to the neutral point 46 and connects the negative electrode of the lower battery 12 to the low-potential wiring 32. In this state, the control circuit 90 can perform both the step-up converter operation and the step-down converter operation.

[0039] Boost converter operation is an operation in which the output voltage of the lower battery 12 is boosted and applied between the high-potential wiring 31 and the low-potential wiring 32. In boost converter operation, the control circuit 90 repeatedly switches the lower reverse-conducting switching element 35VL. The upper reverse-conducting switching element 35VU may be controlled in any manner as long as the condition that the lower reverse-conducting switching element 35VL and the upper reverse-conducting switching element 35VU are not simultaneously turned on is satisfied. For example, the control circuit 90 may alternately turn on the lower reverse-conducting switching element 35VL and the upper reverse-conducting switching element 35VU, or may maintain the upper reverse-conducting switching element 35VU off. Arrow 100 in FIG. 1 indicates the current path when the lower reverse-conducting switching element 35VL is turned on during boost converter operation. As shown by arrow 100, when the lower reverse-conducting switching element 35VL is turned on, a current flows from the positive electrode of the lower battery 12 to the negative electrode of the lower battery 12 via the neutral point 46, the winding 44V, the transistor of the lower reverse-conducting switching element 35VL, and the low-potential wiring 32. When the lower reverse-conducting switching element 35VL is then turned off, an induced voltage is generated in the winding 44V, and a current flows as shown by arrow 102 in FIG. 2. That is, a current flows from the positive electrode of the lower battery 12 to the high-potential wiring 31 via the neutral point 46, the winding 44V, and the diode of the upper reverse-conducting switching element 35VU. During boost converter operation, a current flows alternately through the paths shown by arrows 100 and 102. In boost converter operation, the voltage obtained by adding the induced voltage generated in the winding 44V to the output voltage of the lower battery 12 is applied to the high potential wiring 31, so that a voltage higher than the output voltage of the lower battery 12 is applied between the high potential wiring 31 and the low potential wiring 32.

[0040] The buck converter operation is an operation in which the voltage between the high-potential wiring 31 and the low-potential wiring 32 is stepped down and applied to the lower-side battery 12. In the buck converter operation, the control circuit 90 repeatedly switches the upper reverse-conducting switching element 35VU. The lower reverse-conducting switching element 35VL may be controlled in any manner as long as the condition that the lower reverse-conducting switching element 35VL and the upper reverse-conducting switching element 35VU are not simultaneously turned on is satisfied. For example, the control circuit 90 may alternately turn on the lower reverse-conducting switching element 35VL and the upper reverse-conducting switching element 35VU, or may keep the lower reverse-conducting switching element 35VL off. Arrow 104 in FIG. 3 indicates the current path when the upper reverse-conducting switching element 35VU is turned on during the buck converter operation. As shown by arrow 104, when the upper reverse-conducting switching element 35VU is turned on, a current flows from the high-potential wiring 31 to the positive electrode of the lower battery 12 via the upper reverse-conducting switching element 35VU, the winding 44V, and the neutral point 46. When the upper reverse-conducting switching element 35VU is subsequently turned off, an induced voltage is generated in the winding 44V, and a current flows as shown by arrow 106 in FIG. 4. That is, a current flows from the negative electrode of the lower battery 12 to the positive electrode of the lower battery 12 via the diode of the lower reverse-conducting switching element 35VL, the winding 44V, and the neutral point 46. In step-down converter operation, a current flows alternately through the paths shown by arrows 104 and 106. In step-down converter operation, the voltage between the high potential wiring 31 and the low potential wiring 32 is divided and applied to the winding 44V and the lower battery 12, so that a voltage lower than the voltage between the high potential wiring 31 and the low potential wiring 32 is applied to the lower battery 12.

[0041] The control circuit 90 can also perform a direct connection operation in the DC-DC converter circuit. The direct connection operation is an operation in which the voltage between the high potential wiring 31 and the low potential wiring 32 is applied directly to the lower battery 12. In the direct connection operation, the control circuit 90 keeps the upper reverse conducting switching element 35VU on and keeps the lower reverse conducting switching element 35VL off. Therefore, in the direct connection operation, a direct current flows through the path indicated by the arrow 104 in FIG. 3, and the voltage between the high potential wiring 31 and the low potential wiring 32 is applied to the lower battery 12.

[0042] Next, the operation of the electric circuit 10 when the upper battery 11 and the lower battery 12 are charged by a charging facility external to the vehicle will be described. When charging the upper battery 11 and the lower battery 12, the connector of the external charging facility is connected to the charging port 70. The control circuit 90 then turns on relay switches 82, 83, 84, 85, 86, and 87 and turns off relay switch 81. The external charging facility also applies a DC voltage between the high-potential charging terminal 71 and the low-potential charging terminal 72 in a direction such that the high-potential charging terminal 71 has a high potential. As a result, the supply voltage of the external charging facility is applied between the high-potential wiring 31 and the low-potential wiring 32. The control circuit 90 executes the battery heating process shown in FIG. 5 according to a program stored in memory.

[0043] In step S2, the control circuit 90 detects the output voltage V1 of the upper battery 11 and the output voltage V2 of the lower battery 12. The output voltage V2 can be detected, for example, by the voltmeter 61. The output voltage V1 can be calculated, for example, by subtracting the output voltage V2 from the value detected by the voltmeter 37. The control circuit 90 calculates the voltage difference ΔV (= V1 - V2) by subtracting the output voltage V2 from the output voltage V1. In step S2, the control circuit 90 determines whether the voltage difference ΔV is equal to or greater than a reference value Vref. The reference value Vref is a predetermined value. If the voltage difference ΔV is smaller than the reference value Vref, the control circuit 90 executes the voltage difference adjustment process of step S4.

[0044] FIG. 6 shows currents I1 to I3 flowing through the electric circuit 10. Current I1 is the current flowing through the upper battery 11, current I2 is the current flowing through the lower battery 12, and current I3 is the current supplied from the external charging equipment to the high-potential charging terminal 71. For current I1, the direction in which the upper battery 11 is charged is shown as positive. For current I2, the direction in which the lower battery 12 is discharged is shown as positive. FIG. 7 also shows changes in currents I1 and I2 during the voltage difference adjustment process. During the voltage difference adjustment process, the control circuit 90 alternately performs boost converter operation and direct charging operation. In FIG. 7, period T1 is the period in which boost converter operation is performed, and period T2 is the period in which direct connection operation is performed.

[0045] During the execution of the process of FIG. 5, the relay switches 82, 83, and 84 are on, so that the positive electrode of the upper battery 11 is connected to the high-potential wiring 31, and the negative electrode of the upper battery 11 is connected to the low-potential wiring 32. During period T1, current flows from the lower battery 12 to the high-potential wiring 31 due to the boost converter operation, so that current I2 becomes positive. In addition, current I3 is supplied to the high-potential wiring 31 from the external charging equipment. Therefore, current I1 flowing to the upper battery 11 is a relatively high current obtained by adding current I2 and current I3 together. Therefore, during period T1, the upper battery 11 is charged, and the lower battery 12 is discharged.

[0046] During period T2, the high-potential wiring 31 is connected to the positive electrode of the lower battery 12 by a direct connection operation. As a result, the current I3 supplied from the external charging equipment is branched and supplied to the upper battery 11 and the lower battery 12. As a result, the current I1 becomes a relatively low positive value, and the current I2 becomes a negative value. As a result, during period T2, the upper battery 11 and the lower battery 12 are charged.

[0047] As described above, in the voltage difference adjustment process, the upper battery 11 is charged during both periods T1 and T2. Therefore, as shown in FIG. 8, the output voltage V1 of the upper battery 11 increases during the voltage difference adjustment process. Furthermore, in the voltage difference adjustment process, the lower battery 12 is discharged during period T1, and the lower battery 12 is charged during period T2. The control circuit 90 controls the amount of charge charged to the lower battery 12 during period T2 to be greater than the amount of charge discharged from the lower battery 12 during period T1. Therefore, as shown in FIG. 8, the output voltage V2 of the lower battery 12 increases at a slower rate than the output voltage V1 of the upper battery 11 during the voltage difference adjustment process. Therefore, the voltage difference ΔV increases during the voltage difference adjustment process.

[0048] During the period T2, the step-down converter operation may be performed instead of the direct connection operation. In this case, a current also flows from the high-potential wiring 31 to the lower battery 12, so that the lower battery 12 can be charged. In the step-down converter operation, the charging current to the lower battery 12 can be made smaller than in the direct connection operation.

[0049] The control circuit 90 repeats steps S2 and S4 until the voltage difference ΔV becomes equal to or greater than the reference value Vref. When the voltage difference ΔV becomes equal to or greater than the reference value Vref, the control circuit 90 determines YES in step S2 and executes the periodic power transfer process in step S6.

[0050] 9 shows the changes in currents I1 and I2 during the periodic power transfer process. During the periodic power transfer process, the control circuit 90 alternately performs boost converter operation and buck converter operation. In FIG. 9, the boost converter operation is performed during period T3, and the buck converter operation is performed during period T4.

[0051] During period T3, current I2 becomes positive because the boost converter operates to cause current to flow from the lower battery 12 to the high-potential wiring 31. In addition, current I3 is supplied from the external charging equipment to the high-potential wiring 31. Therefore, current I1 flowing to the upper battery 11 becomes a relatively high current obtained by adding current I2 and current I3 together. Therefore, during period T3, the upper battery 11 is charged and the lower battery 12 is discharged.

[0052] During period T4, current I2 becomes negative because current flows from the high-potential wiring 31 to the lower battery 12 due to the operation of the step-down converter. During period T4a in period T4 when the absolute value of current I2 is small, part of current I3 flows to the upper battery 11, so current I1 is positive. Thereafter, during period T4b when the absolute value of current I2 is large, all of current I3 flows to the lower battery 12, discharging the upper battery 11. Therefore, during period T4b, current I1 becomes negative. Thereafter, during period T4c when the absolute value of current I2 is small, current I1 becomes positive, just like during period T4a.

[0053] As described above, in the periodic power transfer process, the lower battery 12 is discharged and the upper battery 11 is charged during the period T3. That is, during the period T3, a first power transfer operation is performed in which power is transferred from the lower battery 12 to the upper battery 11 while increasing the voltage. Also, during the period T4b, the upper battery 11 is discharged and the lower battery 12 is charged. That is, during the period T4b, a second power transfer operation is performed in which power is transferred from the upper battery 11 to the lower battery 12 while decreasing the voltage. Therefore, as shown in FIG. 10 , the voltage difference ΔV periodically fluctuates during the periodic power transfer process. The control circuit 90 performs the periodic power transfer process so that the amount of charge transferred from the upper battery 11 to the lower battery 12 is equal to the amount of charge transferred from the lower battery 12 to the upper battery 11. Therefore, during the periodic power transfer process, the average value of the voltage difference ΔV is maintained at the reference value Vref. Furthermore, the control circuit 90 ensures that the amplitude A of the voltage difference ΔV during the periodic power transfer process (i.e., half the difference between the maximum and minimum values of the voltage difference ΔV within one cycle of the fluctuating voltage difference ΔV) is smaller than the reference value Vref. Therefore, the voltage difference ΔV does not become negative during the periodic power transfer process. In other words, the output voltage V1 does not become lower than the output voltage V2 during the periodic power transfer process. Therefore, the first power transfer operation (i.e., boost converter operation) and the second power transfer operation (i.e., buck converter operation) can be suitably executed during the periodic power transfer process.

[0054] As described above, in the periodic power transfer process, charging and discharging are repeated in the upper battery 11 and the lower battery 12. This makes it possible to efficiently increase the temperatures of the upper battery 11 and the lower battery 12. As the temperatures of the upper battery 11 and the lower battery 12 increase, the upper battery 11 and the lower battery 12 can be efficiently charged.

[0055] The periodic power transfer process is performed while the upper battery 11 and the lower battery 12 are being charged in parallel by an external charging device. As described above, the control circuit 90 maintains the voltage difference ΔV at the reference value Vref. Therefore, as shown in FIG. 8, in the periodic power transfer process, the output voltage V1 and the output voltage V2 increase at approximately the same rate.

[0056] After step S6, the control circuit 90 detects the battery temperature Tb in step S8. The battery temperature Tb may be the temperature of the upper battery 11, the temperature of the lower battery 12, or a value calculated from the temperatures of the upper battery 11 and the lower battery 12 (for example, an average value). The control circuit 90 repeats steps S6 and S8 until the battery temperature Tb becomes higher than the reference temperature Tref. When the battery temperature Tb becomes higher than the reference temperature Tref, the control circuit 90 executes a voltage difference reduction process in step S10.

[0057] In the voltage difference reduction process, the control circuit 90 executes a direct connection operation. As a result, the current I3 flows split into a path that charges the upper battery 11 (i.e., the path of the current I1) and a path that charges the lower battery 12 (i.e., the path indicated by the arrow 104 in FIG. 3). This causes the upper battery 11 and the lower battery 12 to be charged in parallel. A larger charging current flows to the lower battery 12, which has a lower output voltage. Therefore, as shown in FIG. 8, in the voltage difference reduction process, the output voltage V2 of the lower battery 12 increases at a faster rate than the output voltage V1 of the upper battery 11. As a result, the voltage difference ΔV decreases during the voltage difference reduction process. When the batteries 11 and 12 are fully charged, the control circuit 90 turns off the relay switches 82 to 87 and terminates charging of the batteries 11 and 12.

[0058] In the above-described embodiment, the control circuit 90 controls the current I2 to have a half-wave rectified waveform in the voltage difference adjustment process, as shown in Fig. 7. However, the control circuit 90 may also control the current I2 to have a full-wave rectified waveform in the voltage difference adjustment process, as shown in Fig. 11. In other words, the waveform of the current I2 may be any waveform as long as it can increase the voltage difference ΔV in the voltage difference adjustment process.

[0059] In the first embodiment described above, the voltage difference adjustment process, periodic power transfer process, and voltage difference reduction process are performed while the batteries 11 and 12 are being charged by the external charging equipment. However, these processes may be performed when the batteries 11 and 12 are not being charged. In other words, these processes may be performed when the relay switches 85 and 86 are turned off. Figures 12 to 14 show the changes in each value in this case.

[0060] As shown in FIG. 12, in the voltage difference adjustment process, the control circuit 90 performs boost converter operation during period T1, thereby transferring power from the lower battery 12 to the upper battery 11 while boosting the voltage. Note that the currents I1 and I2 may be controlled to have other waveforms (for example, full-wave rectified waveforms) instead of the half-wave rectified waveforms shown in FIG. 12. Furthermore, when there is no current supplied by the external charging equipment, the boost converter operation may be performed so that the currents I1 and I2 become direct currents. In the voltage difference adjustment process when there is no current supplied by the external charging equipment, the upper battery 11 is charged and the lower battery 12 is discharged. Therefore, as shown in FIG. 14, in the voltage difference adjustment process, the output voltage V1 increases and the output voltage V2 decreases. This causes the voltage difference ΔV to increase to the reference value Vref.

[0061] As shown in FIG. 13, in the periodic power transfer process, the control circuit 90 performs boost converter operation during period T3 and performs buck converter operation during period T4. During period T3, power is transferred from the lower battery 12 to the upper battery 11 while increasing the voltage, and during period T4, power is transferred from the upper battery 11 to the lower battery 12 while decreasing the voltage. The control circuit 90 performs the periodic power transfer process so that the amplitude A of the voltage difference ΔV is smaller than the reference value Vref. This allows the boost converter operation and the buck converter operation to be performed appropriately during the periodic power transfer process. Charging and discharging are repeated between the upper battery 11 and the lower battery 12, causing the temperatures of the upper battery 11 and the lower battery 12 to rise. As shown in FIG. 14, during the periodic power transfer process, the output voltages V1 and V2 are maintained substantially constant, and the voltage difference ΔV is also maintained substantially constant.

[0062] Thereafter, in the voltage difference reduction process, a direct connection operation is performed, and the output voltage V1 and the output voltage V2 are controlled to be approximately the same value.

[0063] In this way, even when charging using an external charging facility is not performed, the voltage difference adjustment process and the periodic power transfer process can be performed to warm up the batteries 11 and 12. For example, by performing these processes in winter, the performance of the batteries 11 and 12 can be improved before the vehicle is used. [Example]

[0064] The configuration of the electric circuit in the second embodiment is the same as that in the first embodiment (i.e., FIG. 1). In the second embodiment, the control circuit 90 also executes the process in FIG. 5. However, in the second embodiment, the control circuit 90 always executes the process in FIG. 5 when the connector of the charging equipment is connected to the charging port 70. In the second embodiment, the voltage difference adjustment process is different from that in the first embodiment. Other processes in the second embodiment (i.e., the periodic power transfer process, the voltage difference reduction process, etc.) are the same as those in the first embodiment.

[0065] In the second embodiment, the voltage difference adjustment process is performed while relay switches 82, 83, 84, 85, 86, and 87 are on, relay switch 81 is off, and the supply voltage from the external charging equipment is applied between the high-potential charging terminal 71 and the low-potential charging terminal 72. In the voltage difference adjustment process of the second embodiment, the control circuit 90 continuously performs step-down converter operation. The control circuit 90 controls the duty ratio of the upper reverse-conducting switching element 35VU when switching to maintain the current I2 at a substantially constant negative value, as shown in FIG. 15 . The control circuit 90 controls the current I2 so that the absolute value of the current I2 is smaller than the absolute value of the current I1. The upper battery 11 is charged by the current I1, and the lower battery 12 is charged by the current I2. Because the absolute value of the current I1 is greater than the absolute value of the current I2, the output voltage V1 increases at a faster rate than the output voltage V2 during the voltage difference adjustment process, as shown in FIG. 8 . Therefore, in the voltage difference adjustment process, the voltage difference ΔV can be increased to the reference value Vref.

[0066] As described above, in the second embodiment as well, the voltage difference ΔV can be increased to the reference value Vref by the voltage difference adjustment process. Therefore, in the subsequent periodic power transfer process, the boost converter operation and the buck converter operation can be preferably performed, as in the first embodiment. [Example]

[0067] FIG. 16 is a circuit diagram of an electric circuit of Example 3. The electric circuit of Example 3 differs from the electric circuit 10 of Example 1 (i.e., FIG. 1) in that an electric device 92 is connected between the positive and negative electrodes of the lower battery 12. The electric device 92 may be any device that can consume power. Other configurations of the electric circuit of Example 3 are the same as those of Example 1. In Example 3, too, when a connector of external charging equipment is connected to the charging port 70, the control circuit 90 executes the flowchart of FIG. 5. In Example 3, the voltage difference adjustment process differs from that of Example 1. Other processes of Example 3 (i.e., periodic power transfer process, voltage difference reduction process, etc.) are the same as those of Example 1.

[0068] In the third embodiment, the voltage difference adjustment process is also performed while relay switches 82, 83, 84, 85, 86, and 87 are on, relay switch 81 is off, and the supply voltage from the external charging equipment is applied between high-potential charging terminal 71 and low-potential charging terminal 72. In the voltage difference adjustment process of the third embodiment, the control circuit 90 performs a direct connection operation. Therefore, current I3 supplied from the external charging equipment is equally divided and supplied to the upper battery 11 and the lower battery 12. This charges the upper battery 11 and the lower battery 12. Furthermore, in the voltage difference adjustment process of the third embodiment, the control circuit 90 turns on the electrical device 92 to consume power from the lower battery 12. Therefore, as shown in FIG. 8 , the output voltage V1 increases at a faster rate than the output voltage V2 in the voltage difference adjustment process. Therefore, the voltage difference ΔV can be increased to the reference value Vref in the voltage difference adjustment process.

[0069] As described above, in the third embodiment as well, the voltage difference ΔV can be increased to the reference value Vref by the voltage difference adjustment process. Therefore, in the subsequent periodic power transfer process, the boost converter operation and the buck converter operation can be preferably performed, as in the first embodiment.

[0070] In the third embodiment described above, the voltage difference adjustment process, periodic power transfer process, and voltage difference reduction process are performed while the batteries 11, 12 are being charged by an external charging facility. However, these processes may be performed when the batteries 11, 12 are not being charged. That is, these processes may be performed when the relay switches 85, 86 are turned off. In this case, the control circuit 90 may stop the DC-DC converter during the voltage difference adjustment process. That is, the lower battery 12 may be disconnected from the high-potential wiring 31. Even in this state, the voltage difference ΔV can be increased to the reference value Vref by having the electrical device 92 consume power from the lower battery 12 during the voltage difference adjustment process.

[0071] In the first to third embodiments, the upper battery 11 is an example of a first battery, and the lower battery 12 is an example of a second battery. [Example]

[0072] In the electric circuit of the fourth embodiment shown in FIG. 17, relay switches 82x, 87x, a capacitor 60x, and a voltmeter 61x are provided instead of the relay switches 82 and 87, the capacitor 60, and the voltmeter 61 of the first embodiment. The other configurations of the electric circuit of the fourth embodiment are the same as those of the first embodiment. The relay switch 82x is provided between the positive electrode of the upper battery 11 and the positive electrode of the lower battery 12. When the relay switch 82x is turned on, the positive electrode of the upper battery 11 is connected to the positive electrode of the lower battery 12. The relay switch 87x is provided between the negative electrode of the upper battery 11 and the neutral point wiring 50. When the relay switch 87x is turned on, the negative electrode of the upper battery 11 is connected to the neutral point 46. The capacitor 60x is connected between the high potential wiring 31 and the neutral point wiring 50. The voltmeter 61x is connected between the high potential wiring 31 and the neutral point wiring 50. Furthermore, when the electric circuit of the fourth embodiment includes an electric device 92 for consuming power, the electric device 92 is connected between the positive and negative electrodes of the upper battery 11 .

[0073] In the fourth embodiment, when the relay switches 83 and 87x are turned on, the upper battery 11 is connected between the high-potential wiring 31 and the neutral point 46. Also, in the fourth embodiment, when the relay switches 82x, 83, and 84 are turned on, the lower battery 12 is connected between the high-potential wiring 31 and the low-potential wiring 32. In this state, when the control circuit 90 repeatedly switches the upper reverse-conducting switching element, power is transferred from the upper battery 11 to the lower battery 12 while being boosted by a boost converter operation. Also, when the control circuit 90 repeatedly switches the lower reverse-conducting switching element, power is transferred from the lower battery 12 to the upper battery 11 while being lowered by a buck converter operation. Therefore, similar to the first to third embodiments, the voltage difference adjustment process, the periodic power transfer process, and the voltage difference reduction process can be executed.

[0074] In the fourth embodiment, the lower battery 12 is an example of a first battery, and the upper battery 11 is an example of a second battery.

[0075] 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]

[0076] 11: Upper battery 12: Lower battery 30: Inverter circuit 31: High potential wiring 32: Low potential wiring 34U~34W: Series switch circuit 35: Reverse conducting switching element 40: Three-phase motor 46: Neutral point 70: Charging port

Claims

1. An electrical circuit mounted on a vehicle, A first battery; A second battery; 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; 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 control circuit is capable of executing a battery temperature increase process; The battery temperature increasing process is a voltage difference adjustment process of adjusting a voltage difference obtained by subtracting the output voltage of the second battery from the output voltage of the first battery so that the voltage difference is equal to or greater than a reference value; a periodic power transfer process in which a converter circuit constituted by a specific series switch circuit that is at least one of the three series switch circuits and a specific winding of the three windings that corresponds to the specific series switch circuit is caused to alternately and repeatedly execute a first power transfer operation of transferring power from the second battery to the first battery while stepping up the voltage, and a second power transfer operation of transferring power from the first battery to the second battery while stepping down the voltage; and the amplitude of the voltage difference during the periodic power transfer process is smaller than the reference value; Electrical circuit.

2. The electric circuit of claim 1 , wherein the control circuit causes the converter circuit to perform the first power transfer operation in the voltage difference adjustment process.

3. 2. The electric circuit according to claim 1, wherein in the voltage difference adjustment process, the control circuit charges the first battery by applying a supply voltage supplied from a charging facility external to the vehicle to the first battery, and charges the second battery by applying a voltage obtained by stepping down the supply voltage using the converter circuit to the second battery.

4. 2. The electric circuit according to claim 1, wherein the control circuit consumes power from the second battery during the voltage difference adjustment process.

5. 5. The electric circuit according to claim 1, wherein the control circuit executes the battery temperature raising process while charging the first battery and the second battery in parallel by a charging facility external to the vehicle.

6. 5. The electric circuit according to claim 1, wherein the control circuit executes a process for reducing the voltage difference after the periodic power transfer process is executed.

7. The electric circuit according to any one of claims 1 to 4, wherein the control circuit executes the periodic power transfer process in a state in which a positive electrode of the first battery is connected to the high potential wiring, a negative electrode of the first battery is connected to the low potential wiring, a positive electrode of the second battery is connected to the neutral point, and a negative electrode of the second battery is connected to the low potential wiring.

8. The electric circuit according to any one of claims 1 to 4, wherein the control circuit performs the periodic power transfer process in a state in which a positive electrode of the first battery is connected to the high potential wiring, a negative electrode of the first battery is connected to the low potential wiring, a positive electrode of the second battery is connected to the high potential wiring, and a negative electrode of the second battery is connected to the neutral point.

9. A program for causing an electric circuit mounted on a vehicle to perform a battery warming process, The electrical circuit A first battery; A second battery; 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; 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 battery temperature increasing process is a voltage difference adjustment process of adjusting a voltage difference obtained by subtracting the output voltage of the second battery from the output voltage of the first battery so that the voltage difference is equal to or greater than a reference value; a periodic power transfer process in which a converter circuit constituted by a specific series switch circuit that is at least one of the three series switch circuits and a specific winding of the three windings that corresponds to the specific series switch circuit is caused to alternately and repeatedly execute a first power transfer operation of transferring power from the second battery to the first battery while stepping up the voltage, and a second power transfer operation of transferring power from the first battery to the second battery while stepping down the voltage; and the amplitude of the voltage difference during the periodic power transfer process is smaller than the reference value; program.

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