Electric circuit and program for charging treatment

Abstract

To suppress deterioration of a relay switch.SOLUTION: An electric circuit mounted on a vehicle has a first battery, a second battery, a three-phase motor, an inverter circuit, a charging port, a first relay switch, a second relay switch, a third relay switch, and a control circuit. The first relay switch is provided between a high-potential wiring of the inverter circuit and a high-potential charging terminal of the charging port. The second relay switch is provided between a low-potential wiring of the inverter circuit and a low-potential charging terminal of the charging port. The third relay switch is provided between the positive electrode of the second battery and the neutral point. When the charging operation is terminated, the control circuit turns off the third relay switch, then turns off the first relay switch and the second relay switch.SELECTED DRAWING: Figure 4

Description

Technical Field

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

[0002] Patent Document 1 discloses an electric circuit mounted on a vehicle. This electric circuit has a series circuit of two batteries, an inverter circuit, and a three-phase motor. The inverter circuit drives the three-phase motor by converting the DC power supplied from the series circuit of the batteries into AC power and supplying it to the three-phase motor. Further, this electric circuit has a wiring connecting the connection point of the two batteries and the neutral point of each coil of the three-phase motor. By transferring power between the two batteries through this wiring, each battery can be heated up.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In an electric circuit having two batteries, an inverter circuit, and a three-phase motor, there is a technology for charging each battery using a charging facility outside the vehicle. One battery is connected to the charging facility via a wiring. The other battery is connected to the charging facility via the inverter circuit and the three-phase motor. According to this configuration, the two batteries can be charged in parallel. This type of electric circuit has a relay switch, and the relay switch is turned off at the end of the charging process. In this specification, a technology for suppressing the deterioration of the relay switch is proposed.

Means for Solving the Problems

[0005] The first electrical circuit disclosed in this specification is mounted on a vehicle. This electrical circuit includes a first battery, a second battery, a three-phase motor, an inverter circuit, a charging port, a first relay switch, a second relay switch, a third relay switch, 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 thereof and a second connection terminal provided at the other end thereof. The second connection terminals of the three windings are connected to each other at the 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 charging port has a high-potential charging terminal and a low-potential charging terminal, and is connected to a charging facility outside the vehicle. 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 includes an upper reverse-conducting switching element, which 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, which is a reverse-conducting switching element connected between the first connection terminal of the corresponding winding and the low-potential wiring. The first relay switch is provided between the high-potential wiring and the high-potential charging terminal. The second relay switch is provided between the low-potential wiring and the low-potential charging terminal. The third relay switch is provided between the positive electrode of the second battery and the neutral point. When charging the first battery and the second battery through the charging port, the control circuit can execute a charging operation in which the high-potential wiring is connected to the positive electrode of the first battery, the low-potential wiring is connected to the negative electrode of the first battery and the negative electrode of the second battery, the first relay switch, the second relay switch, and the third relay switch are controlled to be turned on, the three lower reverse-conducting switching elements are controlled to be turned off, and at least one specific upper reverse-conducting switching element among the three upper reverse-conducting switching elements is continuously or intermittently turned on.When ending the charging operation, the control circuit turns off the third relay switch and then turns off the first relay switch and the second relay switch.

[0006] In this specification, a reverse-conducting switching element is an element in which a switching element and a diode are connected in parallel, the cathode of the diode is connected to the high-potential side terminal of the switching element, and the anode of the diode is connected to the low-potential side 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. Further, the switching element and the diode may be provided on a common semiconductor substrate or on separate semiconductor substrates. Also, in this specification, the on of the reverse-conducting switching element means the on of the switching element included in the reverse-conducting switching element, and the off of the reverse-conducting switching element means the off of the switching element included in the reverse-conducting switching element.

[0007] When ending the charging operation, the first electric circuit turns off the third relay switch and then turns off the first relay switch and the second relay switch. According to this configuration, deterioration of the first relay switch and the second relay switch can be suppressed.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0009] In the first electric circuit, in one example, when ending the charging operation, the control circuit may turn off the specific upper reverse conduction switching element, and then turn off the third relay switch.

[0010] According to this configuration, deterioration of the third relay switch can be suppressed.

[0011] In the first electric circuit, in one example, after the control circuit turns off the specific upper reverse conduction switching element, it detects the leakage current flowing from the positive electrode of the second battery to the positive electrode of the first battery via the neutral point, and when the leakage current is smaller than the reference value, it may turn off the third relay switch.

[0012] According to this configuration, deterioration of the third relay switch can be more effectively suppressed.

[0013] In the first electric circuit, in one example, after the control circuit turns off the specific upper reverse conduction switching element, it increases the supply current to the charging port until the leakage current flowing from the positive electrode of the second battery to the positive electrode of the first battery via the neutral point becomes smaller than the reference value, and when the leakage current is smaller than the reference value, it may turn off the third relay switch.

[0014] According to this configuration, deterioration of the third relay switch can be more effectively suppressed.

[0015] In the first electric circuit, for example, after the control circuit outputs a signal to turn off the third relay switch, a stuck determination process may be executed to detect the current flowing through the second battery in a state where the specific upper reverse conduction switching element is on and a state where it is off.

[0016] According to this configuration, it is possible to detect the sticking of the third relay switch.

[0017] The second electrical circuit disclosed in this specification is mounted on a vehicle. The electrical circuit includes a first battery, a second battery, a three-phase motor, an inverter circuit, a charging port, a first relay switch, a second relay switch, a third relay switch, 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 thereof and a second connection terminal provided at the other end thereof. The second connection terminals of the three windings are connected to each other at the 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 charging port has a high-potential charging terminal and a low-potential charging terminal and is connected to a charging facility outside the vehicle. 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 includes an upper reverse-conducting switching element, which 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, which is a reverse-conducting switching element connected between the first connection terminal of the corresponding winding and the low-potential wiring. The first relay switch is provided between the high-potential wiring and the high-potential charging terminal. The second relay switch is provided between the low-potential wiring and the low-potential charging terminal. The third relay switch is provided between the positive electrode of the second battery and the neutral point. When charging the first battery and the second battery through the charging port, the control circuit can perform a charging operation in which the high-potential wiring is connected to the positive electrode of the first battery and the low-potential wiring is connected to the negative electrode of the first battery and the negative electrode of the second battery, and in this state, the control circuit controls the first relay switch, the second relay switch, and the third relay switch to be turned on, controls the three lower reverse-conducting switching elements to be turned off, and continuously or intermittently turns on a specific upper reverse-conducting switching element, which is at least one of the three upper reverse-conducting switching elements.When ending the charging operation, the control circuit turns off the specific upper reverse-conducting switching element, and then charges the first battery until the OCV of the first battery becomes higher than the OCV of the second battery, and then turns off the third relay switch.

[0018] When ending the charging operation, the second electric circuit turns off the specific upper reverse-conducting switching element, and then charges the first battery until the OCV of the first battery becomes higher than the OCV of the second battery, and then turns off the third relay switch. According to this configuration, deterioration of the third relay switch can be suppressed.

Embodiment

[0019] 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. Thereby, the three-phase motor 40 rotates the drive wheels and the vehicle travels.

[0020] 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. The terminals 42U, 42V, and 42W are connected to each other at the neutral point 46.

[0021] The inverter circuit 30 is connected to the terminals 41U, 41V, and 41W of the three-phase motor 40. The inverter circuit 30 has 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 is composed of two reverse-conducting switching elements 35 connected in series between the high-potential wiring 31 and the low-potential wiring 32. Hereinafter, among the two reverse-conducting switching elements 35 connected in series, 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 (for example, an insulated gate bipolar transistor or a field-effect transistor) and a diode (for example, a pn diode or a Schottky barrier diode) are connected in antiparallel. In each reverse-conducting switching element 35, the cathode of the diode is connected to the high-potential terminal (that is, the collector or drain) of the switching element, and the anode of the diode is connected to the low-potential terminal (that is, the emitter or source) of the switching element.

[0022] 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. The high-potential terminal of the upper reverse-conducting switching element 35UU is connected to the high-potential wiring 31. The low-potential terminal of the upper reverse-conducting switching element 35UU and the high-potential terminal of the lower reverse-conducting switching element 35UL are connected to the terminal 41U. The low-potential terminal of the lower reverse-conducting switching element 35UL is connected to the low-potential wiring 32.

[0023] The series switch circuit 34V is provided for the winding 44V. The series switch circuit 34V has an upper reverse conduction switching element 35VU and a lower reverse conduction switching element 35VL. The high potential terminal of the upper reverse conduction switching element 35VU is connected to the high potential wiring 31. The low potential terminal of the upper reverse conduction switching element 35VU and the high potential terminal of the lower reverse conduction switching element 35VL are connected to the terminal 41V. The low potential terminal of the lower reverse conduction switching element 35VL is connected to the low potential wiring 32.

[0024] The series switch circuit 34W is provided for the winding 44W. The series switch circuit 34W has an upper reverse conduction switching element 35WU and a lower reverse conduction switching element 35WL. The high potential terminal of the upper reverse conduction switching element 35WU is connected to the high potential wiring 31. The low potential terminal of the upper reverse conduction switching element 35WU and the high potential terminal of the lower reverse conduction switching element 35WL are connected to the terminal 41W. The low potential terminal of the lower reverse conduction switching element 35WL is connected to the low potential wiring 32.

[0025] A capacitor 36 is connected between the high potential wiring 31 and the low potential wiring 32. Also, a voltmeter 37 is connected between the high potential wiring 31 and the low potential wiring 32.

[0026] A neutral point wiring 50 is connected to the neutral point 46 of the three-phase motor 40. A capacitor 60 is connected between the neutral point wiring 50 and the low potential wiring 32. Also, a voltmeter 61 is connected between the neutral point wiring 50 and the low potential wiring 32.

[0027] 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 a connector of the charging facility is connected to the charging port 70, a DC voltage is applied between the high potential charging terminal 71 and the low potential charging terminal 72 by the charging facility in such a direction that the high potential charging terminal 71 becomes the high potential.

[0028] The electric circuit 10 has a plurality of relay switches 81 to 88. By switching each relay switch, the mutual connection relationships among 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 are changed.

[0029] 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.

[0030] The relay switch 82 is provided between the negative electrodes of the first battery 11 and the second battery 12. When the relay switch 82 is turned on, the negative electrodes of the first battery 11 and the second battery 12 are connected.

[0031] A galvanometer 20 and a relay switch 83 are provided 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.

[0032] The relay switch 84 is provided between the negative electrode of the second battery 12 and the low-potential wiring 32. When the relay switch 84 is turned on, the negative electrode of the second battery 12 is connected to the low-potential wiring 32.

[0033] 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.

[0034] 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.

[0035] An ammeter 52 and a relay switch 87 are provided in series between the positive electrode of the second battery 12 and the neutral point wiring 50. Also, a relay switch 88 is provided in the neutral point wiring 50. When the relay switches 87 and 88 are turned on, the positive electrode of the second battery 12 is connected to the neutral point 46.

[0036] 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 conduction switching element 35 and the relay switches 81 to 88 according to the program. The control circuit 90 can execute a normal operation and a charging operation.

[0037] In the normal operation, the control circuit 90 turns on the relay switches 81, 83, and 84 and turns off the relay switches 82, 85, 86, 87, and 88. 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 DC voltage output by 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 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 the switching elements of each reverse conduction switching element 35, and supplies the AC power to the three-phase motor 40. As a result, the three-phase motor 40 rotates. The control circuit 90 controls the torque and the 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.

[0038] In the charging operation, the control circuit 90 executes a charging program to charge the first battery 11 and the second battery 12. When a connector of an external charging facility is connected to the charging port 70, the control circuit 90 starts the charging operation. In the charging operation, the control circuit 90 turns on the relay switches 82, 83, 84, 85, 86, 87, and 88 and turns off the relay switch 81. In the charging operation, the first battery 11 and the second battery 12 are charged in parallel.

[0039] The arrow 100 in FIG. 1 indicates the charging path for the first battery 11. In the charging operation, the positive electrode of the first battery 11 is connected to the high-potential charging terminal 71 via the relay switches 83 and 86, and the negative electrode of the first battery 11 is connected to the low-potential charging terminal 72 via the relay switches 82, 84, and 85. Therefore, the voltage supplied from the external charging facility (hereinafter referred to as the charging facility supply voltage) is applied to the first battery 11, and a charging current flows through the first battery 11 along the path indicated by the arrow 100 in FIG. 1. As a result, the first battery 11 is charged.

[0040] Also, in the charging operation, the high-potential wiring 31 is connected to the high-potential charging terminal 71 via the relay switch 86, and the low-potential wiring 32 is connected to the low-potential charging terminal 72 via the relay switch 85. Also, the positive electrode of the second battery 12 is connected to the neutral point 46 via the relay switches 87 and 88, and the negative electrode of the second battery 12 is connected to the low-potential charging terminal 72 and the low-potential wiring 32 via the relay switches 84 and 85. Further, in the charging operation, the control circuit 90 turns off the lower reverse-conducting switching elements 35UL, 35VL, and 35WL. In a state where each part is controlled in this way, the control circuit 90 controls at least one of the upper reverse-conducting switching elements 35UU, 35VU, and 35WU (hereinafter referred to as the specific upper switching element) to perform charging on the second battery 12. Note that when there are elements other than the specific upper switching element among the upper reverse-conducting switching elements 35UU, 35VU, and 35WU, the control circuit 90 maintains the elements other than the specific upper switching element in the off state.

[0041] In the charging operation, the control circuit 90 can perform a direct charging operation and a step-down charging operation on the second battery 12.

[0042] In the direct charging operation, the control circuit 90 maintains the specific upper switching element in the ON state (i.e., continuously turns on the specific upper switching element). Arrow 102 in FIG. 2 indicates the current path when the upper reverse conduction switching element 35VU is ON as the specific upper switching element. When the upper reverse conduction switching element 35VU is turned on, the positive electrode of the second battery 12 is connected to the high-potential charging terminal 71 via the relay switches 87, 88, the neutral point 46, the winding 44V, the upper reverse conduction switching element 35VU, the high-potential wiring 31, and the relay switch 86. Therefore, the charging facility supply voltage is applied to the second battery 12. As a result, a charging current flows through the path indicated by arrow 102, and the second battery 12 is charged.

[0043] In the step-down charging operation, the control circuit 90 periodically switches the specific upper switching element (i.e., intermittently turns on the specific upper switching element). Arrows 102 and 104 in FIGS. 2 and 3 illustrate the current path of the step-down charging operation when the upper reverse conduction switching element 35VU is the specific upper switching element. When the upper reverse conduction switching element 35VU is turned on, a charging current flows as shown by arrow 102 in FIG. 2. After the upper reverse conduction switching element 35VU is turned off, an induced electromotive force is generated in the winding 44V. As a result, as shown by arrow 104 in FIG. 3, a reflux current flows through the diode of the lower reverse conduction switching element 35VL, the winding 44V, and the second battery 12. In the step-down charging operation, the second battery 12 is charged by the current flowing alternately through the paths indicated by arrows 100 and 102. Thus, in the step-down operation, the inverter circuit 30 and the windings of the three-phase motor 40 function as a step-down converter circuit. For this reason, a voltage lower than the charging facility supply voltage is applied to the second battery 12, and the second battery 12 is charged with a low charging current.

[0044] As described above, in the charging operation, the first battery 11 is charged through the path indicated by the arrow 100, and the second battery 12 is charged by a direct charging operation or a step-down charging operation. That is, the first battery 11 and the second battery 12 are charged in parallel. Note that the control circuit 90 may be configured to execute only one of the direct charging operation and the step-down charging operation.

[0045] When the control circuit 90 ends the charging operation, it executes the charging end process shown in FIG. 4 according to the charging end program. The charging end process is executed when the first battery 11 and the second battery 12 are fully charged or when a predetermined time has elapsed since the start of the charging operation.

[0046] In step S2, the control circuit 90 turns off the specific upper switching element. As a result, all the reverse conduction switching elements are in the off state. When all the reverse conduction switching elements are off, the application of the charging facility supply voltage to the second battery 12 is stopped. At this stage, as shown in FIG. 1, the charging facility supply voltage is applied to the first battery 11.

[0047] When the voltage V2 between both ends of the second battery 12 is higher than the voltage V1 between both ends of the first battery 11 in a state where all the reverse conduction switching elements are off, a leakage current I1 flows from the second battery 12 to the first battery 11 as shown in FIG. 5. The leakage current I1 flows from the positive electrode of the second battery 12, through the neutral point 46, the diodes of the upper reverse conduction switching elements 35U, 35VU, 35WU, and the high-potential wiring 31, to the positive electrode of the first battery 11. Note that in FIG. 5, as an example, the path passing through the diode of the upper reverse conduction switching element 35VU is shown. On the other hand, when the voltage V2 of the second battery 12 is lower than the voltage V1 of the first battery 11, the leakage current I1 does not flow. When trying to turn off the relay switch 87 in a state where the leakage current I1 is flowing, sticking may occur at the contacts of the relay switch 87, and the relay switch 87 may not be turned off.

[0048] In step S4, the control circuit 90 detects the leakage current I1 by the ammeter 20 or 52, and determines whether the leakage current I1 is smaller than the reference value Iref. The reference value Iref is a current level at which the sticking of the relay switch does not occur, and is a value at which the leakage current I1 can be regarded as zero. When the leakage current I1 is greater than or equal to the reference value Iref, the control circuit 90 waits for a predetermined time in step S6. The control circuit 90 repeats steps S4 and S6 until the leakage current I1 becomes smaller than the reference value Iref. During the standby of the control circuit 90, the leakage current I1 flows and the voltage V2 of the second battery 12 decreases. Also, during the standby of the control circuit 90, the first battery 11 is charged and the voltage V1 increases. Therefore, the leakage current I1 gradually decreases during the standby of the control circuit 90. When the leakage current I1 becomes smaller than the reference value Iref, the control circuit 90 determines YES in step S4 and outputs an off signal to the relay switch 87 in step S8. As a result, the relay switch 87 turns off. Since the relay switch 87 can be turned off in a state where the leakage current I1 is low, sticking of the relay switch 87 can be suppressed.

[0049] Next, in step S10, the control circuit 90 executes a sticking determination process for the relay switch 87. In the sticking determination process, the control circuit 90 switches at least one of the upper reverse conduction switching elements 35UU, 35VU, and 35WU and monitors the current value detected by the ammeter 52. If the relay switch 87 is properly off, the current value does not change in the sticking determination process. On the other hand, if the relay switch 87 cannot be turned off due to sticking, the current value changes when the upper reverse conduction switching element is switched. When the control circuit 90 detects the sticking of the relay switch 87, it causes an alarm to be displayed on the vehicle or the charging facility in step S12.

[0050] When the control circuit 90 does not detect the sticking of the relay switch 87 in step S10, in step S14, it stops the charging current supplied from the charging facility and turns off the relay switches 85 and 86. Next, the control circuit 90 turns off the relay switch 88 in step S16. Thereby, the charging process is completed, and the connector of the charging facility can be removed from the charging port 70.

[0051] As described above, in the first embodiment, since the relay switch 87 is turned off after the leakage current I1 stops, sticking of the relay switch 87 can be suppressed.

Embodiment

[0052] As shown in FIG. 6, in the electrical circuit of the second embodiment, step S6a is executed instead of step S6 in the first embodiment. Other configurations of the second embodiment are the same as those of the first embodiment.

[0053] In the second embodiment, when it is determined in step S4 that the leakage current I1 is equal to or greater than the reference value Iref, the control circuit 90 increases the supply current of the charging facility (that is, the current supplied from the external charging facility through the path indicated by the arrow 100 in FIG. 1) in step S6a. When the supply current of the charging facility increases, the potential of the high-potential wiring 31 rises, and the leakage current I1 decreases. The control circuit 90 repeats steps S4 and S6a until the leakage current I1 becomes smaller than the reference value Iref, and turns off the relay switch 87 in step S8 when the leakage current I1 becomes smaller than the reference value Iref. Thereby, sticking of the relay switch 87 can be prevented.

[0054] As described above, in the second embodiment, the leakage current I1 is reduced by increasing the supply current of the charging facility. According to this configuration, the leakage current I1 can be reduced in a shorter time than in the first embodiment. Therefore, the charging end process can be completed in a shorter time.

Embodiment

[0055] The electric circuit of Example 3 executes the charge completion process shown in FIG. 7. Other configurations of Example 3 are the same as those of Example 1.

[0056] In step S22, the control circuit 90 turns off the specific upper switching element. As a result, all the reverse-conducting switching elements are in the off state. When all the reverse-conducting switching elements are off, the application of the charging facility supply voltage to the second battery 12 is stopped. At this stage, the charging facility supply voltage is applied to the first battery 11.

[0057] Next, in step S24, the control circuit 90 commands an external charging facility to reduce the supply current of the charging facility (that is, the current supplied from the external charging facility through the path indicated by the arrow 100 in FIG. 1). Thereby, the charging current to the first battery 11 decreases.

[0058] After executing steps S22 and S24, in step S26, the control circuit 90 determines whether the voltage V1 across both ends of the first battery 11 (that is, the CCV (Closed Circuit Voltage) of the first battery 11) is higher than the voltage V2 across both ends of the second battery 12 (that is, the OCV (Open Circuit Voltage) of the second battery 12). When the voltage V2 is higher than the voltage V1, a leakage current I1 flows as shown in FIG. 5. Since the supply current of the charging facility is decreased, the CCV in the first battery 11 is substantially equal to the OCV. Therefore, the determination in step S26 is equivalent to determining whether the OCV of the first battery is higher than the OCV of the second battery. The voltage V2 can be detected by the voltmeter 61. The voltage V1 can be detected by subtracting the detected value of the voltmeter 61 from the detected value of the voltmeter 37. The control circuit 90 can detect the voltages V1 and V2 and execute the determination in step S26 based on these detected values. Also, as described above, when the voltage V2 is higher than the voltage V1, the leakage current I1 flows. Therefore, the control circuit 90 may execute the determination in step S26 by determining whether the leakage current I1 is flowing.

[0059] The control circuit 90 repeatedly executes step S26 during the charging of the first battery 11. When the voltage V1 becomes higher than the voltage V2 due to the charging of the first battery, the control circuit 90 executes step S28.

[0060] In step S28, the control circuit 90 turns off the relay switches 85 and 86. Thereby, the charging of the first battery 11 ends. As described above, since the first battery 11 is charged until the OCV of the first battery 11 becomes higher than the OCV of the second battery, the state where the voltage V1 is higher than the voltage V2 is maintained even after the relay switches 85 and 86 are turned off. Therefore, the leakage current I1 does not flow even after step S28.

[0061] In step S30, the control circuit 90 turns off the relay switch 87. Since the leakage current I1 does not flow, sticking of the relay switch 87 can be prevented when turning off the relay switch 87.

[0062] In step S32, the control circuit 90 executes a sticking determination process for the relay switch 87 in the same manner as step S10 in FIG. 4. When detecting sticking of the relay switch 87, the control circuit 90 causes the vehicle or the charging facility to display an alarm in step S34. When the relay switch 87 is not stuck, the control circuit 90 turns off the relay switch 88 in step S36 and completes the charging end process. Thereby, it becomes possible to remove the connector of the charging facility from the charging port 70.

[0063] As described above, in the third embodiment, the first battery 11 is charged so that the OCV of the first battery 11 becomes higher than the OCV of the second battery 12. Therefore, the relay switch 87 can be turned off in a state where the leakage current I1 does not flow, and sticking of the relay switch 87 can be prevented.

[0064] Note that in the third embodiment, the relay switch 87 may be turned off before the relay switches 85 and 86.

[0065] 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 changes of the specific examples illustrated above. The technical elements described in this specification or the 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. In addition, the technology illustrated in this specification or the drawings achieves multiple purposes simultaneously, and achieving one of these purposes itself has technical utility.

Explanation of Reference Numerals

[0066] 11: First battery 12: Second battery 30: Inverter circuit 31: High-potential wiring 32: Low-potential wiring 35: Reverse-conducting switching element 40: Three-phase motor 46: Neutral point 70: Charging port 81~88: Relay switch

Claims

1. An electric circuit mounted on a vehicle, comprising: a first battery; a second battery; a three-phase motor having three windings of 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 being connected to each other at the 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 having a high-potential charging terminal and a low-potential charging terminal and connected to a charging facility outside the vehicle; a first relay switch; a second relay switch; a third relay switch; a control circuit; wherein: the inverter circuit includes: a high-potential wiring; a low-potential wiring; three series switch circuits provided for each of the three windings; wherein: each of the series switch circuits has an upper reverse-conducting switching element, which 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, which is a reverse-conducting switching element connected between the first connection terminal of the corresponding winding and the low-potential wiring; the first relay switch is provided between the high-potential wiring and the high-potential charging terminal; the second relay switch is provided between the low-potential wiring and the low-potential charging terminal; the third relay switch is provided between the positive electrode of the second battery and the neutral point; when charging the first battery and the second battery through the charging port, the control circuit can execute a charging operation in which the high-potential wiring is connected to the positive electrode of the first battery and the low-potential wiring is connected to the negative electrode of the first battery and the negative electrode of the second battery, and in this state, the control circuit controls the first relay switch, the second relay switch, and the third relay switch to be turned on, controls the three lower reverse-conducting switching elements to be turned off, and continuously or intermittently turns on at least one specific upper reverse-conducting switching element among the three upper reverse-conducting switching elements; when ending the charging operation, the control circuit turns off the third relay switch and then turns off the first relay switch and the second relay switch; an electric circuit.

2. When ending the charging operation, the control circuit turns off the specific upper reverse-conducting switching element, and then turns off the third relay switch. The electric circuit according to claim 1.

3. After the control circuit turns off the specific upper reverse-conducting switching element, it detects the leakage current flowing from the positive electrode of the second battery through the neutral point to the positive electrode of the first battery, and when the leakage current is smaller than the reference value, it turns off the third relay switch. The electric circuit according to claim 2.

4. After the control circuit turns off the specific upper reverse-conducting switching element, it increases the current supplied from the external charging facility of the vehicle to the charging port until the leakage current flowing from the positive electrode of the second battery through the neutral point to the positive electrode of the first battery becomes smaller than the reference value, and when the leakage current is smaller than the reference value, it turns off the third relay switch. The electric circuit according to claim 2.

5. After the control circuit outputs a signal to turn off the third relay switch, it executes a sticking determination process for detecting the current flowing through the second battery in a state where the specific upper reverse-conducting switching element is on and off. The electric circuit according to any one of claims 1 to 4.

6. An electric circuit mounted on a vehicle, A first battery, A second battery, A three-phase motor having three windings of 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 being connected to each other at the 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 having a high-potential charging terminal and a low-potential charging terminal and connected to an external charging facility of the vehicle, A first relay switch, A second relay switch, A third relay switch, A control circuit, having, The inverter circuit has A high-potential wiring, A low-potential wiring, Three series switch circuits provided for each of the three windings, having. Each of the series switch circuits includes an upper reverse-conducting switching element, which 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, which is a reverse-conducting switching element connected between the first connection terminal of the corresponding winding and the low-potential wiring. The first relay switch is provided between the high-potential wiring and the high-potential charging terminal. The second relay switch is provided between the low-potential wiring and the low-potential charging terminal. The third relay switch is provided between the positive electrode of the second battery and the neutral point. When charging the first battery and the second battery by the charging port, the control circuit controls the first relay switch, the second relay switch, and the third relay switch to be turned on in a state where the high-potential wiring is connected to the positive electrode of the first battery and the low-potential wiring is connected to the negative electrode of the first battery and the negative electrode of the second battery, controls the three lower reverse-conducting switching elements to be turned off, and can execute a charging operation of continuously or intermittently turning on a specific upper reverse-conducting switching element, which is at least one of the three upper reverse-conducting switching elements. When ending the charging operation, the control circuit turns off the specific upper reverse-conducting switching element, then charges the first battery until the OCV of the first battery becomes higher than the OCV of the second battery, and then turns off the third relay switch. Electrical circuit.

7. A program for executing a charging process on an electrical circuit mounted on a vehicle, wherein the electrical circuit includes 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 being connected to each other at the 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 having a high-potential charging terminal and a low-potential charging terminal and connected to a charging facility outside the vehicle, a first relay switch, a second relay switch, a third relay switch, and a control circuit. having, the inverter circuit a high potential wiring, a low potential wiring, three series switch circuits provided for each of the three windings, having, each of the series switch circuits being an upper reverse conduction switching element which is a reverse conduction switching element connected between the first connection terminal of the corresponding winding and the high potential wiring, and a lower reverse conduction switching element which is a reverse conduction switching element connected between the first connection terminal of the corresponding winding and the low potential wiring, the first relay switch being provided between the high potential wiring and the high potential charging terminal, the second relay switch being provided between the low potential wiring and the low potential charging terminal, the third relay switch being provided between the positive electrode of the second battery and the neutral point, the program being capable of causing the control circuit to execute a charging operation, when the charging operation is to charge the first battery and the second battery by the charging port, in a state where the high potential wiring is connected to the positive electrode of the first battery and the low potential wiring is connected to the negative electrode of the first battery and the negative electrode of the second battery, controlling the first relay switch, the second relay switch, and the third relay switch to be turned on, controlling the three lower reverse conduction switching elements to be turned off, and continuously or intermittently turning on a specific upper reverse conduction switching element which is at least one of the three upper reverse conduction switching elements, when ending the charging operation, the program causes the control circuit to turn off the third relay switch, and then turn off the first relay switch and the second relay switch, Program.

8. A program for causing an electric circuit mounted on a vehicle to execute a charging process, wherein the electric circuit a first battery, a second battery, a three-phase motor having three windings of 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 being 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, It has a high-potential charging terminal and a low-potential charging terminal, a charging port connected to a charging facility outside the vehicle, a first relay switch, a second relay switch, a third relay switch, a control circuit, and has, wherein the inverter circuit has a high-potential wiring, a low-potential wiring, and three series switch circuits provided for each of the three windings, and has, each of the series switch circuits has an upper reverse-conducting switching element which 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 which is a reverse-conducting switching element connected between the first connection terminal of the corresponding winding and the low-potential wiring, the first relay switch is provided between the high-potential wiring and the high-potential charging terminal, the second relay switch is provided between the low-potential wiring and the low-potential charging terminal, the third relay switch is provided between the positive electrode of the second battery and the neutral point, the program can cause the control circuit to execute a charging operation, when the charging operation is to charge the first battery and the second battery by the charging port, in a state where the high-potential wiring is connected to the positive electrode of the first battery and the low-potential wiring is connected to the negative electrode of the first battery and the negative electrode of the second battery, the first relay switch, the second relay switch, and the third relay switch are controlled to be turned on, the three lower reverse-conducting switching elements are controlled to be turned off, and a specific upper reverse-conducting switching element which is at least one of the three upper reverse-conducting switching elements is continuously or intermittently turned on, when ending the charging operation, the program causes the control circuit to turn off the specific upper reverse-conducting switching element, then charges the first battery until the OCV of the first battery becomes higher than the OCV of the second battery, and then turns off the third relay switch, program.

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