Charging system

Abstract

To provide a charging system that can reliably fully charge multiple batteries. [Solution] The ECU 100 has the first circuit and the second circuit connected in parallel, and during charging when the inlet 82 is connected to the charging device 200, it completes charging of the second battery 52 using the second circuit, then controls the first switching element and the second switching element to disconnect the connection to the first inverter 11 and the second inverter 12, and then completes charging of the first battery 51 using the first circuit.

Description

Technical Field

[0001] The present disclosure relates to a charging system.

Background Art

[0002] Japanese Unexamined Patent Application Publication No. 2024-110701 (Patent Document 1) discloses a power supply system that switches the connection state of a plurality of batteries between series connection and parallel connection by turning on and off a plurality of relays.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When charging a vehicle equipped with a plurality of batteries as in Patent Document 1, the connection state of the plurality of batteries may be switched to parallel connection for charging. However, since each of the plurality of batteries may have polarization or variations in full charge capacity, even if the same value of current flows through each battery, the timing of reaching full charge may be different. Since the determination of full charge is performed based on voltage, when the voltage of one battery reaches the voltage for determining full charge, charging may end while the voltage of the other battery has not reached the voltage for determining full charge.

[0005] An object of the present disclosure is to provide a charging system capable of stably fully charging a plurality of batteries.

Means for Solving the Problems

[0006] A charging system according to one aspect of the present disclosure comprises a motor generator, a first inverter connected to one end of the motor generator and having a first switching element, a second inverter connected to the other end of the motor generator and having a second switching element, an inlet detachably connected to an external charging device, a first battery and a second battery connected to the inlet, a switching circuit for switching the connection state between the charging device and the first battery and the second battery, and a control device for controlling the first switching element, the second switching element, and the switching circuit. When the inlet is connected to the charging device for charging, the control device controls the switching circuit to connect a first circuit connecting the first battery and the inlet, and a second circuit connecting the second battery, the first inverter, the second inverter, and the inlet in parallel, and after completing the charging of the second battery using the second circuit, it controls the first switching element and the second switching element to disconnect the connection to the first inverter and the second inverter, and then complete the charging of the first battery using the first circuit. [Effects of the Invention]

[0007] According to this disclosure, the control device completes the charging of the second battery using the second circuit, then controls the first and second switching elements to disconnect the connection to the first and second inverters, and then completes the charging of the first battery using the first circuit. As a result, the first battery can be fully charged using the first circuit without supplying current to the second circuit after the second battery has been fully charged, thus enabling stable full charging of multiple batteries. [Brief explanation of the drawing]

[0008] [Figure 1] This is a diagram showing an example of a charging system. [Figure 2] This diagram shows an example of the connection relationship between the battery and the drive unit. [Figure 3] This figure shows an example of a charging circuit. [Figure 4]This figure shows an example of the charging power and voltage state when the battery is nearly fully charged. [Figure 5] This flowchart shows an example of the process performed by the ECU. [Modes for carrying out the invention]

[0009] The embodiments of this disclosure will be described in detail below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated.

[0010] Figure 1 shows an example of a charging system 1. The charging system 1 is installed in a vehicle (not shown). The vehicle is, for example, an electric vehicle. The charging system 1 comprises a drive unit 300, a first battery 51, a second battery 52, switches 45-48, an inlet 82, and an electronic control unit (ECU) 100, which is an example of a control device. The drive unit 300 comprises a motor generator 13, a first inverter 11, a second inverter 12, switches 41-44, and a resistor R3. The charging system 1 is detachably connected to an external charging device 200 via the inlet 82.

[0011] The motor-generator 13 is, for example, an embedded permanent magnet synchronous motor (IPM motor) that has both motor and generator functions. The motor-generator 13 includes three windings that are electrically isolated from each other.

[0012] The first inverter 11 includes switches 21-26, which are first switching elements connected to one end of the winding of the motor generator 13, capacitors C1, C3, C4, C5, and resistors R1, R4, R5, R6. The second inverter 12 includes switches 31-36, which are second switching elements connected to the other end of the winding of the motor generator 13, capacitors C2, C6, C7, C8, and resistors R2, R7, R8, R9.

[0013] The first battery 51 and the second battery 52 are connected to the charging device 200 via an inlet 82. The charging device 200 includes an AC power supply 70, a charger 80, and a connector 81. The charger 80 converts the AC power supplied from the AC power supply 70 into DC power and also converts it to a voltage that can be charged to the first battery 51 and the second battery 52. ​​The first battery 51 and the second battery 52 are charged by the DC power supplied from the connector 81 of the charging device 200 through the inlet 82.

[0014] Switches 45-48 function as switching circuits that switch the connection state between the charging device 200 and the first battery 51 and the second battery 52. ​​The connection state between the first battery 51 and the second battery 52 can be switched between series connection and parallel connection.

[0015] The circuit of the charging system 1 has multiple sensors. These multiple sensors include current sensors 14a to 14i and voltage sensors 15a to 15c. Current sensors 14a to 14i are sensors for detecting current. Voltage sensors 15a to 15c are sensors for detecting voltage.

[0016] The ECU100 includes a CPU (Central Processing Unit), memory such as ROM (Read Only Memory) and RAM (Random Access Memory), and input / output ports for inputting and outputting various signals (not shown). The ECU100 controls switches 21-26, which are first switching elements, switches 31-36, which are second switching elements, switches 45-48, which function as switching circuits, and switches 41-44.

[0017] When the ECU 100 is charging with the inlet 82 connected to the charging device 200, it constitutes a plurality of circuits shown in FIG. 1. The ECU 100 connects the first circuit (broken line) connecting the first battery 51 and the inlet 82 and the second circuit (dashed line) connecting the second battery 52, the first inverter 11, the second inverter 12, and the inlet 82 in parallel by switching the connection states of the switches 45 to 48. During charging when the first circuit and the second circuit are connected in parallel, the switches 41 and 42 are OFF and the switch 43 is ON.

[0018] During charging when the first circuit and the second circuit are connected in parallel, the ECU 100 detects the current value of the first battery 51 based on the detection signal from the current sensor 14a, for example, and detects the current value of the second battery 52 based on the detection signal from the current sensor 14b. During charging when the first circuit and the second circuit are connected in parallel, the ECU 100 detects the voltage value of the first battery 51 based on the detection signal from the voltage sensor 15a, for example, and detects the voltage value of the second battery 52 based on the detection signal from the voltage sensor 15b. The current values and voltage values of the first battery 51 and the second battery 52 may be measured using other sensors or by arranging sensors at positions not shown in the figure and using those sensors.

[0019] FIG. 2 is a diagram showing an example of the connection relationship between the battery and the drive device 300. The ECU 100 switches the connection states of the first battery 51, the second battery, and the drive device 300 by controlling the switches 45 to 48 that function as a switching circuit. For example, when the ECU 100 connects the first battery 51 and the second battery 52 in series, it turns on the switches 45 and 46 and turns off the switches 47 and 48. Thereby, the ECU 100 can drive the drive device 300 with the high-voltage battery connected in series.

[0020] For example, when the ECU 100 connects the first battery 51 and the second battery 52 in parallel, it turns off the switch 45 and turns on the switches 46, 47, and 48. As a result, the ECU 100 can be driven by the low-voltage batteries connected in parallel to the drive device 300.

[0021] The same applies during charging. For example, when the ECU 100 connects the first battery 51 and the second battery 52 in series, it turns on the switches 45 and 46 and turns off the switches 47 and 48. As a result, the ECU 100 can perform rapid charging (for example, 800 V) by connecting the batteries in series. For example, when the ECU 100 connects the first battery 51 and the second battery 52 in parallel, it turns off the switch 45 and turns on the switches 46, 47, and 48. As a result, the ECU 100 can perform normal charging (for example, 400 V) by connecting the batteries in parallel.

[0022] FIG. 3 is a diagram showing an example of a circuit during charging. FIG. 3(A) is a diagram schematically showing the first circuit (broken line) shown in FIG. 1. FIG. 3(B) is a diagram schematically showing the second circuit (dash-dotted line) shown in FIG. 1.

[0023] As shown in FIG. 3(A), during charging when the inlet 82 is connected to the connector 81, the first circuit becomes a circuit connecting the first battery 51 and the inlet 82. As shown in FIG. 3(B), during charging when the inlet 82 is connected to the connector 81, the second circuit becomes a circuit connecting the second battery 52, the first inverter 11, the second inverter 12, and the inlet 82.

[0024] The second circuit includes, for example, capacitors C1 and C2 and switches 22, 25, 32, and 35. The second circuit shown in Figure 3(B) can achieve boost mode and buck mode for the second battery 52 by switching switches 22, 25, 32, and 35. In boost mode, for example, the ECU 100 repeatedly controls the system to turn switches 22 and 35 ON and switch 25 and 32 OFF, and then turns switches 22 and 32 ON and switches 22 and 35 OFF. This achieves boost mode and increases the voltage of the second battery 52.

[0025] In step-down mode, for example, the ECU 100 repeatedly controls switches 22 and 32 to ON and switches 25 and 35 to OFF, and then controls switches 25 and 32 to ON and switches 22 and 35 to OFF. This enables step-down mode and reduces the voltage of the second battery 52.

[0026] Although the second circuit was described as a circuit containing one winding, it may also be a circuit containing two windings or three windings. In the case of a circuit containing two windings, the ECU100 controls eight switches corresponding to the two windings, and in the case of a circuit containing three windings, the ECU100 controls twelve switches corresponding to the three windings, thereby achieving both boost mode and buck mode in the same way as a circuit containing one winding.

[0027] The ECU 100 can increase the voltage of the second battery 52 by switching to boost mode and adjust the amount of current used to charge the second battery 52. ​​The ECU 100 can also decrease the voltage of the second battery 52 by switching to buck mode and adjust the amount of current used to charge the second battery 52.

[0028] Here, variations in polarization or full charge capacity may occur in the first battery 51 and the second battery 52. ​​Therefore, even if the same current is applied to the first battery 51 and the second battery 52, the timing of full charge may differ. Since full charge is determined based on voltage, when the voltage of one battery reaches the voltage for full charge determination, charging may end even if the voltage of the other battery has not yet reached the voltage for full charge determination. Below, a charging system 1 that stably fully charges multiple batteries by adjusting the charging current near full charge will be described in detail.

[0029] Figure 4 shows an example of the charging power and voltage state near full charge. In Figure 4, the dashed line shows the voltage and charging power state of the first battery 51, and the solid line shows the voltage and charging power state of the second battery 52. ​​In the graph showing charging power, the arrow indicates that the power is decreasing, and in the graph showing voltage, the arrow indicates that the voltage is increasing.

[0030] As shown in Figure 4, the ECU 100 performs constant-power charging on the first battery 51 and the second battery 52 until the current voltage of either the first battery 51 or the second battery 52 reaches a predetermined first threshold. During constant-power charging, the ECU 100 applies voltage to the first battery 51 and the second battery 52 at the same rate of increase.

[0031] As shown in Figure 4, when the current voltage of the first battery 51 or the second battery 52 reaches a predetermined first threshold, the ECU 100 changes to a charging method that alternates between reducing the charging power and constant power charging. This is because, as the battery approaches full charge, it becomes difficult to store electricity with a large charging power. In this charging method, the ECU 100 increases the voltage of the second battery 52 to be greater than the voltage of the first battery 51, and controls the charging power of the second battery 52 to be greater than the charging power of the first battery 51. This allows the second battery 52, which is included in the second circuit to which the first inverter 11 and the second inverter 12 are connected, to approach full charge before the first battery 51.

[0032] The ECU 100 controls the first switching elements, switches 21-26, and the second switching elements, switches 31-36, to lower the voltage when reducing the charging power and to raise the voltage when the charging power is kept constant. As a result, the ECU 100 reduces the current by lowering the voltage during the period when the charging power is reduced, and reduces the current by raising the voltage during the period when the charging power is kept constant, thereby bringing the first battery 51 and the second battery 52 closer to full charge.

[0033] The ECU 100 stops charging the second battery 52 when its current voltage reaches a second threshold, which is the threshold for determining full charge, and this threshold is greater than the first threshold. Stopping charging the second battery 52 results in its charging power becoming 0W. Since the ECU 100 was controlling the charging power of the second battery 52 to be greater than that of the first battery 51, the second battery 52 reaches the second threshold before the first battery 51.

[0034] The ECU 100 gradually increases the voltage over a period from the first threshold to the second threshold. During this period, the ECU 100 controls the second battery 52 to have a greater charging power than the first battery 51, and the voltage of the second battery 52 to have a greater voltage than the first battery 51. As a result, the ECU 100 controls the second battery 52 to have a greater charging current than the first battery 51 during this period. This allows the ECU 100 to gradually bring both the first battery 51 and the second battery 52 closer to full charge, and to bring the second battery 52 closer to full charge than the first battery 51, thereby ensuring sufficient accumulation of electricity in both the first battery 51 and the second battery 52.

[0035] After the voltage of the second battery 52 reaches the second threshold and the charging of the second battery 52 is complete, the ECU 100 controls the first switching elements, switches 21-26 and the second switching elements, switches 31-36, to disconnect the connection to the first inverter 11 and the second inverter 12. Subsequently, the ECU 100 completes the charging of the first battery 51 using the first circuit. This interrupts the current flow in the second circuit and sets the charging current to 0A, thereby preventing overcharging of the second battery 52 while allowing the first battery 51 to continue charging.

[0036] The ECU 51 performs constant-power charging as the charging method for the first battery 51 after the second battery 52 has been fully charged. By doing so, the ECU 51 controls the voltage of the first battery 51 to gradually increase until it reaches a second threshold, thereby gradually decreasing the current and bringing the first battery 51 closer to full charge. In this way, the ECU 51 can fully charge the first battery using the first circuit without supplying current to the second circuit after the second battery 52 has been fully charged, thus enabling stable full charging of multiple batteries.

[0037] The explanation described a case where the ECU 100 performs constant-power charging until a first threshold is reached, and then changes to a charging method that alternates between reducing the charging power and performing constant-power charging once the first threshold is reached. However, as a charging method near full charge, it is also possible to perform CCCV charging (Constant Current-Constant Voltage), which involves maintaining the magnitude of the charging current to perform CC (Constant Current) charging until the battery voltage reaches a first threshold, and then performing CV (Constant Voltage) charging while maintaining the battery voltage. Alternatively, the ECU 100 may perform constant-power charging until a first threshold is reached, and then perform CV charging once the first threshold is reached. In this way, the charging method can be appropriately changed to a method that enables full charge.

[0038] The specific control actions performed by the ECU100 will now be explained. Figure 5 is a flowchart showing an example of the process performed by the ECU100. In step 1 (hereinafter referred to as step S), the ECU100 starts charging when the inlet 82 is connected to the connector 81 and DC power is supplied to the first battery 51 and the second battery 52.

[0039] Next, the ECU 100 determines whether or not the voltage has reached the first threshold for switching the charging method (S2). In S2, the ECU 100 determines whether or not the voltage of the second battery 52 has reached the first threshold based on the voltage value detected by the voltage sensor 15b. If the ECU 100 determines in S2 that the voltage has not reached the first threshold (NO in S2), it repeats the process in S2.

[0040] If the ECU 100 determines in S2 that the first threshold has been reached (YES in S2), it changes the charging method from constant power charging to a charging method that alternates between reducing the charging power and constant power charging (S3). Next, the ECU 100 controls the first switching elements, switches 21-26, and the second switching elements, switches 31-36, to adjust the current used to charge the second battery 52 to be greater than the current used to charge the first battery 51 (S4), and then proceeds to the process in S5.

[0041] In S5, the ECU 100 determines whether the second battery 52 has reached a fully charged state. The ECU 100 determines whether the second battery 52 has reached a fully charged state by determining whether the voltage of the second battery 52 has reached a second threshold based on the voltage value detected by the voltage sensor 15b.

[0042] If ECU100 determines in S5 that the second battery 52 is not fully charged (NO in S5), it repeats the process from S4 to S5. If ECU100 determines in S5 that the second battery 52 is fully charged (YES in S5), it stops charging the second battery 52 (S6).

[0043] In S6, the ECU 100 controls the first switching elements, switches 21-26, and the second switching elements, switches 31-36, to disconnect the connection between the first inverter 11 and the second inverter 12, thereby preventing current from flowing to the second battery 52.

[0044] Next, the ECU 100 controls the first battery 51 to continue charging (S7). In S7, the ECU 100 performs, for example, constant power charging. Next, the ECU 100 determines whether the first battery 51 has reached a fully charged state (S8). The ECU 100 determines whether the first battery 51 has reached a fully charged state by determining whether the voltage of the first battery 51 has reached a second threshold based on the voltage value detected by the voltage sensor 15a.

[0045] If ECU100 determines in S8 that the first battery 51 is not fully charged (NO in S8), it repeats the process from S7 to S8. If ECU100 determines in S8 that the first battery 51 is fully charged (YES in S8), it stops charging the first battery 51 (S9) and terminates the process.

[0046] As described above, in this embodiment, when the first circuit and the second circuit are connected in parallel and the inlet 82 is connected to the charging device 200, the ECU 100 completes charging of the second battery 52 using the second circuit, then controls the first switching element and the second switching element to disconnect the connection to the first inverter 11 and the second inverter 12, and then completes charging of the first battery 51 using the first circuit. As a result, the charging system 1 of this disclosure can fully charge the first battery 51 using the first circuit without supplying current to the second circuit after fully charging the second battery 52, and can stably fully charge multiple batteries.

[0047] In the above embodiment, during charging, when the current voltage of the second battery 52 reaches a predetermined first threshold, the ECU 100 controls the first switching element and the second switching element to adjust the amount of power used to charge the second battery 52 to be greater than the amount of power used to charge the first battery 51. As a result, the ECU 100 can fully charge the second battery 52, to which the first inverter 11 and the second inverter 12 are connected, before fully charging the first battery 51.

[0048] In the above embodiment, the ECU 100 stops charging the second battery 52 when it reaches a second threshold that is greater than the first threshold during charging. This allows the ECU 100 to complete full charging of the second battery 52 based on the second threshold.

[0049] In the above embodiment, the ECU 100 gradually increases the voltage over a period from the first threshold to the second threshold. This allows the ECU 100 to gradually reduce the charging power, slowly bringing the first battery 51 and the second battery 52 closer to full charge, and enabling sufficient accumulation of electricity in the batteries.

[0050] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of this disclosure is indicated by the claims rather than by the description of the embodiments above, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of symbols]

[0051] 1 Charging system, 11 First inverter, 12 Second inverter, 13 Motor generator, 14a~14i Current sensor, 15a~15c Voltage sensor, 21~26, 31~36, 41~48 Switches, 51 First battery, 52 Second battery, 70 AC power supply, 80 Charger, 81 Connector, 82 Inlet, 200 Charging device, 300 Drive device.

Claims

1. Motor generator and, A first inverter connected to one end of the motor generator and having a first switching element, A second inverter connected to the other end of the motor generator and having a second switching element, An inlet that can be detachably connected to an external charging device, The first battery and the second battery connected to the inlet, A switching circuit for switching the connection state between the charging device and the first battery and the second battery, The system comprises a first switching element, a second switching element, and a control device for controlling the switching circuit, The control device, when the inlet is connected to the charging device during charging, By controlling the switching circuit, a first circuit connecting the first battery and the inlet, and a second circuit connecting the second battery, the first inverter, the second inverter, and the inlet are connected in parallel. A charging system that, after completing the charging of the second battery using the second circuit, controls the first switching element and the second switching element to disconnect the connection to the first inverter and the second inverter, and then completes the charging of the first battery using the first circuit.

2. The charging system according to claim 1, wherein the control device, during charging, controls the first switching element and the second switching element when the current voltage of the second battery reaches a predetermined first threshold, so that the amount of power used to charge the second battery is greater than the amount of power used to charge the first battery.

3. The charging system according to claim 2, wherein the control device stops charging the second battery when it reaches a second threshold greater than the first threshold during charging.

4. The charging system according to claim 3, wherein the control device gradually increases the voltage over a period from the first threshold to the second threshold.

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