Power supply system

Abstract

A power supply system, comprising a first battery, a second battery whose voltage is higher when the first battery is fully charged than when the first battery is fully charged, a connection circuit configured to form a parallel circuit, and a first relay and a second relay provided in the connection circuit to turn on and off power from an external power supply to the first battery and to the second battery, respectively, in the parallel circuit, and a control device configured to execute a charging process of charging the first battery and the second battery. The charging process includes a process of turning off the first relay to turn off power from the external power source to the first battery while continuing charging the second battery when the first battery is fully charged.

Description

Technical Field

[0001] The technology disclosed in this specification relates to a power supply system. Background Art

[0002] Japanese Unexamined Patent Application Publication No. 2021-16234 (JP 2021-16234A) discloses a power supply device that charges a first battery and a second battery in a parallel circuit in which the first battery and the second battery are connected in parallel. JP 2021-16234A describes that even in a state where the state of charge of the first battery and the state of charge of the second battery are different, the first battery and the second battery can be appropriately charged while suppressing a circulating current flowing from one of the first battery or the second battery to the other. Summary of the invention

[0003] In JP 2021-16234A, the first battery and the second battery have the same discharge capacity. That is, the voltages of the first battery and the second battery when fully charged are equal, and it is not expected that the voltages of the first battery and the second battery when fully charged are different. Accordingly, in the technology of JP 2021-16234, in this case, a battery with a high voltage when fully charged may not be fully charged, or a battery with a low voltage when fully charged may be overcharged. This specification provides a technology for properly charging two batteries with different full-charge voltages in a circuit in which the two batteries are connected in parallel.

[0004] According to one aspect of the present invention, a power supply system includes: a first battery that can be charged by an external power source; a second battery that can be charged by an external power source, the voltage of the second battery when fully charged is higher than the voltage of the first battery when fully charged; a connecting circuit configured to form a parallel circuit in which the first battery and the second battery are connected in parallel; a first relay that is provided in the connecting circuit, the first relay conducts and cuts off the power from the external power source to the first battery in the parallel circuit; a second relay that is provided in the connecting circuit, the second relay conducts and cuts off the power from the external power source to the second battery in the parallel circuit; and a control device configured to perform a charging process for charging the first battery and the second battery using the external power source. The charging process may include the following process: when the first battery reaches full charge, the first relay is cut off to cut off the power from the external power source to the first battery, while continuing to charge the second battery.

[0005] With the above configuration, when the first battery whose voltage when fully charged is lower than the voltage of the second battery when fully charged reaches full charge, the first relay is cut off to stop charging the first battery and continue charging the second battery. This allows both the first battery and the second battery to be properly charged to full charge.

[0006] In the power supply system according to the above aspect, the first relay may include a contactless relay. In the power supply system according to the above aspect, the contactless relay may include a semiconductor switching device. In the power supply system according to the above aspect, the contactless relay may include a first diode connected in anti-parallel with the semiconductor switching device. The first diode may be oriented to allow discharge of the first battery and also prohibit charging of the first battery.

[0007] With the above configuration, disconnection or welding of the first relay can be suppressed.

[0008] In the power supply system according to the above aspect, the connection circuit may include a second diode connected in series with the second battery in a parallel circuit. The second diode may be oriented to inhibit discharge of the second battery and also allow charging of the second battery.

[0009] With the above configuration, it is possible to suppress the circulating current flowing from the second battery to the first battery in the parallel circuit.

[0010] In the power supply system according to the above aspect, the charging process may include: before cutting off the power to the first battery, turning on the first relay to charge the first battery, and when the voltage of the first battery reaches the voltage of the second battery, starting to charge the second battery with the second relay in the on state.

[0011] With the above configuration, charging of the first battery is started before charging of the second battery. Generally, a battery having a lower voltage when fully charged will have a lower voltage before charging. Therefore, by charging the first battery first, it is not necessary to measure the voltages of the first battery and the second battery, and the process can be simplified accordingly.

[0012] The power supply system according to the above aspect may further include: a charging relay that turns on and off power from an external power source to a connection circuit; and a first capacitor that is connected in parallel with a first battery and a second battery in a parallel circuit. The charging process may include: before a process of charging the first battery, a process of pre-charging the first capacitor by the first battery by turning on the first relay in a state where the charging relay is turned off, and during the process of charging the first battery, the charging relay may be turned on.

[0013] With the above configuration, the first capacitor is precharged using the first battery, a surge current from the external power source to the connection circuit is suppressed, and a load on the charging relay can be suppressed.

[0014] In the power supply system according to the above aspect, the connection circuit may include a third diode connected in series with the first battery in a parallel circuit. The third diode may be oriented to inhibit discharge of the first battery and also allow charging of the first battery.

[0015] With the above configuration, it is possible to suppress the circulating current flowing from the first battery to the second battery in the parallel circuit.

[0016] In the power supply system according to the above aspect, the control device can be configured to perform a power feeding process of supplying power to the external load through the connection circuit using the first battery and the second battery. The power feeding process may include a process of cutting off the first relay and also turning on the second relay to supply power from the second battery to the external load.

[0017] With the above configuration, by turning off the first relay, the circulating current from the second battery toward the first battery can be suppressed, and also by turning on the second relay, the external load can be fed using only the second battery.

[0018] The power supply system according to the above aspect may further include: a feed relay that turns on and off power from the connection circuit to the external load, and a second capacitor that is connected in parallel with the first battery and the second battery in a parallel circuit. The power feeding process may include: before the process of supplying power from the second battery to the external load, the second capacitor is pre-charged by the second battery by cutting off the first relay in a state where the feed relay is cut off and also turning on the second relay, and in the process of supplying power from the second battery to the external load, the feed relay may be turned on.

[0019] With the above configuration, the second capacitor is precharged using the second battery, an excessive current is suppressed from flowing from the connection circuit to the external load, and the load on the feeding relay can be suppressed.

[0020] In the power supply system according to the above aspect, the first relay may include a semiconductor switching device, and a first diode connected in antiparallel to the semiconductor switching device, and the first diode may be oriented to allow discharge of the first battery and also inhibit charge of the first battery.

[0021] With the above configuration, when the second battery is performing power feeding to the external load and the voltages of the first battery and the second battery become approximately equal to each other, power feeding to the external load can be performed from both the first battery and the second battery while suppressing the flow of circulating current between the first battery and the second battery.

[0022] In the power supply system according to the above aspect, the connection circuit may be configured to selectively constitute a parallel circuit or a series circuit in which the first battery and the second battery are connected in series.

[0023] With the above configuration, the first battery and the second battery can be appropriately charged in the parallel circuit, and a large amount of electric power can be supplied to the outside in the series circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like numerals represent like elements, and in which: Figure 1 is a diagram schematically showing a configuration of a power supply system according to a first embodiment and a vehicle in which the system is installed; Figure 2 is a flowchart of a charging process performed by the power supply system according to the first embodiment; Figure 3 is a diagram for describing a charging process performed by the power supply system according to the first embodiment; Figure 4 is a diagram for describing a charging process performed by the power supply system according to the first embodiment; Figure 5 is a diagram for describing a charging process performed by the power supply system according to the first embodiment; Figure 6 is a diagram for describing a charging process performed by the power supply system according to the first embodiment; Figure 7 is a diagram for describing a charging process performed by the power supply system according to the first embodiment; Figure 8 is a diagram for describing a charging process performed by the power supply system according to the first embodiment; Fig. 9 is a diagram schematically showing a configuration of a power supply system according to a second embodiment and a vehicle in which the system is installed; Fig.10 is a flow chart of a power feeding process performed by the power supply system according to the second embodiment; Fig.11 is a diagram for describing a power feeding process performed by the power supply system according to the second embodiment; Fig.12 is a diagram for describing a power feeding process performed by the power supply system according to the second embodiment; Fig.13 is a diagram for describing a power feeding process performed by the power supply system according to the second embodiment; and Fig.14 2 is a diagram for describing a power feeding process performed by the power supply system according to the second embodiment. DETAILED DESCRIPTION First embodiment

[0025] Figure 1 A power supply system 1 according to a first embodiment is shown. The power supply system 1 is installed in a vehicle 100 and supplies power to a load 3 (e.g., a power control unit (PCU)) provided in the vehicle 100. The vehicle 100 is an electric vehicle such as, for example, a battery electric vehicle (BEV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), or a fuel cell electric vehicle (FCEV).

[0026] like Figure 1 As shown in , the power supply system 1 includes a first battery 21 , a second battery 22 , a connection circuit 24 , a control device 26 , and a first capacitor 28 .

[0027] The first battery 21 and the second battery 22 are storage batteries that can be charged and discharged using direct current power, and each storage battery has a plurality of battery cells arranged in a stack. Each battery cell is composed of a secondary battery that can be repeatedly charged and discharged, such as, for example, a lithium-ion battery, an all-solid-state battery, a nickel-hydrogen battery, etc. The number of battery cells in the first battery 21 and the second battery 22 is not particularly limited, but the voltage of the second battery 22 when fully charged is higher than the voltage of the first battery 21 when fully charged. Specifically, in the present embodiment, the number of battery cells of the second battery 22 is greater than the number of battery cells of the first battery 21. The voltage of the first battery 21 when fully charged is about 390V, and the voltage of the second battery 22 when fully charged is about 410V. However, it should be noted that the voltage of the first battery 21 and the second battery 22 when fully charged can be changed as appropriate according to the required output voltage. Each of the first battery 21 and the second battery 22 is arranged between the high potential conductive trace 12 (the conductive trace connected to the cathode of the first battery 21 and the second battery 22) and the low potential conductive trace 14 (the conductive trace connected to the anode of the first battery 21 and the second battery 22) of the power supply system 1.

[0028] The connection circuit 24 has a first switching device 30, a second switching device 32, a third switching device 34, a fourth switching device 36, a first switching relay 38, a second switching relay 40, and a third switching relay 42. The control device 26 controls the operation of the switching devices 30, 32, 34, and 36 and the switching relays 38, 40, and 42. In the present embodiment, each of the switching devices 30, 32, 34, and 36 is an n-channel Metal-Oxide Semiconductor Field-Effect Transistor (MOSFET). The control device 26 is an Electronic Control Unit (ECU) or a Power Control Unit (PCU), etc.

[0029] The first switching device 30, the second switching device 32, and the first switching relay 38 are connected in series between the high potential conductive trace 12 and the cathode of the first battery 21. The drain of the first switching device 30 is connected to the high potential conductive trace 12, the source of the first switching device 30 is connected to the source of the second switching device 32, and the drain of the second switching device 32 is connected to the cathode of the first battery 21 via the first switching relay 38. That is, the first switching device 30 is oriented so as to conduct and cut off the power from the high potential conductive trace 12 to the first battery 21. The second switching device 32 is oriented so as to conduct and cut off the power from the first battery 21 to the high potential conductive trace 12. In addition, the first switching device 30 and the second switching device 32 have a diode 31 and a diode 33 respectively connected in anti-parallel thereto. The diode 31 has an anode connected to the source of the first switching device 30 and also has a cathode connected to the drain of the first switching device 30. That is, the diode 31 is oriented so as to allow the first battery 21 to be discharged and also prohibit the first battery 21 from being charged. The diode 33 has an anode connected to the source of the second switching device 32 and also has a cathode connected to the drain of the second switching device 32. That is, the diode 33 is oriented so as to allow the first battery 21 to be charged and also inhibit the first battery 21 from being discharged.

[0030] The third switching device 34, the fourth switching device 36, and the second switching relay 40 are connected in series between the low potential conductive trace 14 and the anode of the second battery 22. The source of the third switching device 34 is connected to the low potential conductive trace 14, the drain of the third switching device 34 is connected to the drain of the fourth switching device 36, and the source of the fourth switching device 36 is connected to the anode of the second battery 22 via the second switching relay 40. That is, the third switching device 34 is oriented so as to conduct and cut off the power from the second battery 22 to the low potential conductive trace 14 (in other words, the power from the high potential conductive trace 12 to the second battery 22). The fourth switching device 36 is oriented so as to conduct and cut off the power from the low potential conductive trace 14 to the second battery 22 (in other words, the power from the second battery 22 to the high potential conductive trace 12). In addition, the third switching device 34 and the fourth switching device 36 have a diode 35 and a diode 37 respectively connected in anti-parallel thereto. The diode 35 has an anode connected to the source of the third switching device 34 and also has a cathode connected to the drain of the third switching device 34. That is, the diode 35 is oriented so as to allow the second battery 22 to be discharged and also prohibit the second battery 22 from being charged. The diode 37 has an anode connected to the source of the fourth switching device 36 and also has a cathode connected to the drain of the fourth switching device 36. That is, the diode 37 is oriented so as to allow the second battery 22 to be charged and also prohibit the second battery 22 from being discharged.

[0031] The third switching relay 42 is provided between the conductive trace connecting the first battery 21 and the first switching relay 38 and the conductive trace connecting the second battery 22 and the second switching relay 40. The first switching relay 38, the second switching relay 40 and the third switching relay 42 are provided to switch the connection form of the first battery 21 and the second battery 22. That is, the control device 26 is configured to control the opening and closing of each of the switching relays 38, 40 and 42 so that the connection circuit 24 selectively forms Figure 3 The series circuit shown in Figure 4 Specifically, when the control device 26 disconnects the first switching relay 38 and the second switching relay 40 and closes the third switching relay 42, the connection circuit 24 forms a parallel circuit as shown in FIG. Figure 3 In this series circuit, the first battery 21 is connected in series with the second battery 22. On the other hand, when the control device 26 closes the first switching relay 38 and the second switching relay 40 and opens the third switching relay 42, the connection circuit 24 is formed as shown in FIG. Figure 4 The parallel circuit shown in FIG. 1 , etc. In this parallel circuit, the first battery 21 and the second battery 22 are connected in parallel.

[0032] The first capacitor 28 is provided between the high potential conductive trace 12 and the low potential conductive trace 14. The first capacitor 28 is connected to the first battery 21 and the second battery 22 in parallel.

[0033] The power supply system 1 further includes a charging relay 52 and a discharging relay 54. The charging relay 52 is provided between the connection circuit 24 and the charging inlet 50 of the vehicle 100. The charging relay 52 conducts and cuts off the power between the connection circuit 24 and the charging inlet 50. The charging inlet 50 is configured so that an external power source 60 (see Figure 4 ) is detachably attached thereto. The charging inlet 50 is electrically connected to the external power source 60 via a connector, for example, when charging the first battery 21 and the second battery 22. Therefore, power is input from the external power source 60 to the charging inlet 50. In this case, the control device 26 causes the connection circuit 24 to form a parallel circuit and also closes the charging relay 52. ​​As a result, the first battery 21 and the second battery 22 are connected to the charging inlet 50 in parallel. Therefore, the first battery 21 and the second battery 22 can be charged at a relatively low voltage. The external power source 60 is, for example, a power source that supplies power, such as a household commercial power source or a charging station.

[0034] The discharge relay 54 is provided between the connection circuit 24 and the load 3 of the vehicle 100. The discharge relay 54 conducts and cuts off the power between the connection circuit 24 and the load 3. When the vehicle 100 is traveling, the control device 26 causes the connection circuit 24 to form a series circuit and also closes the discharge relay 54. Thus, the first battery 21 and the second battery 22 are connected in series to the load 3, and power can be supplied to the load 3 at a relatively high voltage.

[0035] The control device 26 monitors each of the state of charge (SOC) of the first battery 21 and the state of charge of the second battery 22. The method of monitoring the state of charge is not particularly limited. For example, the control device 26 can calculate the state of charge of the first battery 21 by accumulating the charging current and discharging current of the first battery 21 over time. The same is true for the second battery 22. The control device 26 can estimate the voltage of the first battery 21 and the second battery 22 based on the state of charge of the first battery 21 and the state of charge of the second battery 22, respectively. It should be noted that the voltage of the first battery 21 and the second battery 22 can be directly detected by a voltage sensor.

[0036] Next, the operation of the power supply system 1 will be described. Figure 2 2 is a flowchart showing a process of charging the first battery 21 and the second battery 22 by the external power source 60 . Figure 2 The process shown in FIG. 1 starts when the circuit 24 is connected to form a series circuit. Specifically, Figure 3As shown in FIG. 1 , the first switching relay 38, the second switching relay 40 and the charging relay 52 are disconnected, and the third switching relay 42 and the discharging relay 54 are closed. In addition, the switching devices 30, 32, 34, 36 are turned off (OFF). That is, this state is a state in which power can be supplied from the first battery 21 and the second battery 22 to the load 3, and the current flows as indicated by the dotted arrow. Figure 3 In the same manner as in FIG. 1 , the flow of current in the power supply system 1 is indicated by a dotted arrow. It should be noted that in this embodiment, it is assumed that at the beginning Figure 2 During the processing, the voltage of the first battery 21 is about 190V, and the voltage of the second battery 22 is about 200V.

[0037] First, if Figure 2 As shown in , it is determined in S10 whether charging of the first battery 21 and the second battery 22 has started. For example, when the voltage on the charging inlet 50 side becomes higher than the voltage on the connection circuit 24 side, the control device 26 determines that the connector of the external power source 60 has been connected to the charging inlet 50 and charging has started.

[0038] When it is determined that charging of the first battery 21 and the second battery 22 has started (Yes in S10), in S12, the control device 26 causes the connection circuit 24 to form a parallel circuit. Specifically, the control device 26 disconnects the discharge relay 54, disconnects the third switching relay 42, and also closes the first switching relay 38 and the second switching relay 40. Accordingly, the connection circuit 24 is switched from the series circuit to the parallel circuit. Figure 4 The parallel circuit shown in .

[0039] Next, in S14, the control device 26 precharges the first capacitor 28. Specifically, the control device 26 turns on the second switch device 32, and also turns on the first switch device 30 and the third switch device 34. The second switch device 32 is turned on, and the fourth switch device 36 is turned off, and accordingly, the discharge of the first battery 21 is allowed, and the discharge of the second battery 22 is prohibited. Figure 4 As shown in FIG. 2 , there is no circulating current flowing from the second battery 22 to the first battery 21, and the first capacitor 28 is pre-charged by the first battery 21. Therefore, the first capacitor 28 is charged to the voltage of the first battery 21 (ie, about 190V).

[0040] When the pre-charging of the first capacitor 28 is finished, in S16, the control device 26 turns off the second switching device 32 and also closes the charging relay 52. ​​This electrically connects the connection circuit 24 to the external power source 60. The voltage of the first battery 21 at the start of charging (about 190V) is lower than the voltage of the second battery 22 at the start of charging (about 200V). Accordingly, when S16 is executed, power is only supplied to the first battery 21. That is, as Figure 5 As shown in FIG. 5 , no current flows at the second battery 22, and only the charging of the first battery 21 is started. Figure 8 , the load 3 and the discharge relay 54 are omitted from the illustration.

[0041] Thereafter, in S18, the control device 26 monitors whether any current is flowing at the second battery 22. In other words, the control device 26 monitors whether the second battery 22 is being charged. As described above, in S16, current flows only to the first battery 21, and charging of the second battery 22 does not start until the voltage of the first battery 21 reaches the voltage of the second battery 22. When the voltage of the first battery 21 is charged to the voltage of the second battery 22, current also starts to flow at the second battery 22, as shown in FIG. Figure 6 When the control device 26 determines that current is flowing at the second battery 22 (Yes in S18), the flow proceeds to S20.

[0042] In S20, the control device 26 outputs a command to the external power source 60 to increase the current supplied to the connection circuit 24. Accordingly, the charging of the first battery 21 and the second battery 22 is continued while the charging rates of the first battery 21 and the second battery 22 are maintained.

[0043] Thereafter, in S22, the control device 26 determines whether the first battery 21 has reached full charge. The control device 26, for example, calculates the state of charge of the first battery 21, and estimates the voltage of the first battery 21 based on the calculated state of charge. When the control device 26 determines that the first battery 21 has reached full charge (Yes in S22), the process proceeds to S24.

[0044] In S24, the control device 26 cuts off the power from the external power source 60 to the first battery 21. Specifically, the control device 26 turns off the first switching device 30, and then disconnects the first switching relay 38. Therefore, the charging of the first battery 21 is stopped. On the other hand, the third switching device 34 is turned on, and the charging of the second battery 22 is continued accordingly, as shown in FIG. Figure 7 as shown in .

[0045] Thereafter, in S26, the control device 26 determines whether the second battery 22 has reached full charge. Whether the second battery 22 has reached full charge may be determined in the same manner as in S22.

[0046] When the control device 26 determines that the second battery 22 has reached full charge (Yes in S26), in S28, the power from the external power source 60 to the second battery 22 is cut off. Specifically, the control device 26 turns off the third switching device 34, and then disconnects the second switching relay 40 and the charging relay 52. ​​As a result, Figure 8 As shown in , the power from the external power source 60 to the second battery 22 (connection circuit 24) is cut off. After executing S28, the control device 26 ends this series of processing.

[0047] As described above, in the power supply system 1 according to the present embodiment, when the first battery 21 whose voltage when fully charged is lower than the voltage of the second battery 22 when fully charged reaches full charge (Yes in S22), the first switching device 30 is turned off (S24) to stop charging the first battery 21 and continue charging the second battery 22. This allows both the first battery 21 and the second battery 22 to be properly charged to full charge.

[0048] In addition, in the power supply system 1 according to the present embodiment, the fourth switching device 36 connected in series with the second battery 22 includes a diode 37. The diode 37 is oriented so as to inhibit the discharge of the second battery 22 while allowing the charging of the second battery 22, thereby being able to suppress the flow of the circulating current from the second battery 22 to the first battery 21 when the connection circuit 24 forms a parallel circuit.

[0049] In addition, in the power supply system 1 according to the present embodiment, before the charging relay 52 is closed, both the first switching device 30 and the third switching device 34 are turned on (S14). Therefore, when the charging relay 52 is closed, the current begins to flow to the battery with a lower voltage before charging (the first battery 21 in the present embodiment). In this way, according to the present embodiment, the charging process is performed so that the battery with a lower voltage is charged first without measuring the voltage of the first battery 21 and the second battery 22, thereby simplifying the process. In addition, when the first battery 21 is charged to the voltage of the second battery 22, the current also begins to flow to the second battery 22, and accordingly both the first battery 21 and the second battery 22 can be charged.

[0050] In addition, in the power supply system 1 according to the present embodiment, after the first capacitor 28 is pre-charged using the first battery 21 (S14), the charging relay 52 is closed (S16). This can suppress the surge current from the external power supply 60 to the connection circuit 24 and suppress the charging relay 52 from being loaded.

[0051] Furthermore, in the power supply system 1 according to the present embodiment, the second switching device 32 connected in series with the first battery 21 includes a diode 33. The diode 33 is oriented so as to inhibit the discharge of the first battery 21 while allowing the charge of the first battery 21, thereby being able to suppress the flow of circulating current from the first battery 21 to the second battery 22 when the connection circuit 24 forms a parallel circuit. Second embodiment

[0052] In the second embodiment, in addition to the charging process of the first embodiment, the power supply system 1 can also perform a feeding process for supplying power to an external load 62 (eg, an electrical device, etc.) using the first battery 21 and the second battery 22. Fig. 9 As shown in FIG. 1 , the power supply system 1 according to the second embodiment includes a second capacitor 29 and a feeding relay 56. Fig. 9 and Figures 11 to 14 In the embodiment, the first battery 21, the second battery 22, the switching devices 30, 32, 34, 36 and the switching relays 38, 40, 42 are omitted. Figure 1 An illustration of the configuration in .

[0053] like Fig. 9 As shown in FIG. 1 , the second capacitor 29 is disposed between the high potential conductive trace 12 and the low potential conductive trace 14. The second capacitor 29 is connected in parallel with the first battery 21 and the second battery 22.

[0054] The feed relay 56 is provided between the connection circuit 24 and the power supply outlet 58 of the vehicle. The feed relay 56 conducts and cuts off the power between the connection circuit 24 and the power supply outlet 58. The power supply outlet 58 is configured so that an external load 62 (see Fig.11 ) is detachably connected thereto. For example, when feeding power to the external load 62 is performed, the power supply outlet 58 is electrically connected to the external load 62 via the connector. Accordingly, the power input from the first battery 21 and / or the second battery 22 to the power supply outlet 58 is supplied to the external load 62.

[0055] Next, the operation of the power supply system 1 will be described. Fig.10 2 is a flowchart showing a power feeding process in which the first battery 21 and the second battery 22 supply power to the external load 62. Figure 2 In the same way, Fig.10 The process shown in FIG. 1 starts when the circuit 24 is connected to form a series circuit. Fig.10At the start of the process in , both the first battery 21 and the second battery 22 are fully charged. That is, the voltage of the first battery 21 is about 390V, and the voltage of the second battery 22 is about 410V.

[0056] First, if Fig.10 As shown in , in S40, the control device 26 determines whether power feeding has started from the first battery 21 and the second battery 22. For example, when the voltage on the power supply outlet 58 side becomes lower than the voltage on the connection circuit 24 side, the control device 26 determines that the connector of the external load 62 has been connected to the power supply outlet 58 and power feeding has started.

[0057] When it is determined that the feeding from the first battery 21 and the second battery 22 has started (Yes in S40), in S42, the control device 26 causes the connection circuit 24 to form a parallel circuit. Specifically, the control device 26 opens the third switching relay 42, and also closes the first switching relay 38 and the second switching relay 40. Figure 4 In the same manner as in FIG. 1 , the connection circuit 24 is switched from a series circuit to a parallel circuit.

[0058] Next, in S44, the control device 26 pre-charges the second capacitor 29. Specifically, the control device 26 turns on the third switch device 34 and the fourth switch device 36. The second switch device 32 is turned off, and the fourth switch device 36 is turned on, and accordingly, the discharge of the second battery 22 is allowed, and the discharge of the first battery 21 is prohibited. And, the first switch device 30 is turned off, and the charging of the first battery 21 is prohibited accordingly. Therefore, as Fig.11 As shown in FIG. 2 , there is no circulating current flowing from the second battery 22 to the first battery 21, and the second capacitor 29 is pre-charged by the second battery 22. Therefore, the second capacitor 29 is charged to the voltage of the second battery 22 (ie, about 410V).

[0059] When the pre-charging of the second capacitor 29 is finished, in S46, the control device 26 turns on the second switching device 32, turns off the third switching device 34, and also closes the feeding relay 56. This electrically connects the connection circuit 24 to the external load 62. At this time, the fourth switching device 36 is turned on, and accordingly the discharge of the second battery 22 is allowed. The voltage of the second battery 22 is higher than the voltage of the first battery, and accordingly when S46 is executed, power is supplied only from the second battery 22 to the external load 62. That is, as Fig.12 As shown in , no current flows from the first battery 21 , and power is fed only from the second battery 22 .

[0060] The second switching device 32 is turned on and accordingly allows the discharge of the first battery 21. Accordingly, when the feeding of the second battery 22 is being performed after S46 is performed and the voltage of the second battery 22 drops to the voltage of the first battery 21, power will also start to be supplied from the first battery 21 to the external load 62, as shown in FIG. Fig.13 That is, power is fed to the external load 62 from both the first battery 21 and the second battery 22 .

[0061] In S48, the control device 26 determines whether the power feeding has been stopped. For example, when the control device 26 receives a notification that the external load 62 has been disconnected from the power supply outlet 58, it determines that the power feeding has been stopped. When it is determined that the power feeding has been stopped (yes in S48), in S50, the control device 26 cuts off the connection between the connection circuit 24 and the external load 62. Specifically, the control device 26 turns off the second switching device 32 and the fourth switching device 36, and then disconnects the first switching relay 38, the second switching relay 40 and the feeding relay 56. Therefore, if Fig.14 As shown in , the power from the first battery 21 and the second battery 22 to the external load 62 is cut off. After executing S50, the control device 26 ends this series of processing.

[0062] As described above, in the power supply system 1 according to the present embodiment, while the circulating current from the second battery 22 to the first battery 21 is suppressed by turning off the first switching device 30, the discharge of the second battery 22 is allowed through the third switching device 34 and the fourth switching device 36, thereby enabling the external load 62 to be fed with power using only the second battery 22 (S46).

[0063] In addition, in the power supply system 1 according to the present embodiment, after the second capacitor 29 is precharged using the second battery 22 (S44), the feed relay 56 is closed (S46). Accordingly, it is possible to suppress excessive current from flowing from the connection circuit 24 to the external load 62, thereby suppressing the feed relay 56 from being loaded.

[0064] Also, in the power supply system 1 according to the present embodiment, the first switching device 30 connected in series with the first battery 21 includes a diode 31. The diode 31 is oriented to allow the first battery 21 to discharge. Accordingly, when the second battery 22 is supplying power to the external load 62, and the voltage of the second battery 22 drops to the voltage of the first battery 21, feeding of power from both the first battery 21 and the second battery 22 to the external load 62 can be performed while suppressing the flow of circulating current between the first battery 21 and the second battery 22. Correlation

[0065] The first switching device 30 and the third switching device 34 are examples of a “first relay” and a “second relay”, respectively. The diode 31, the diode 37, and the diode 33 are examples of a “first diode”, a “second diode”, and a “third diode”, respectively.

[0066] Although the embodiments are described in detail above, these are merely exemplary and are not intended to limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples shown above. Modifications

[0067] In the above-described embodiment, a case where the number of battery cells of the second battery 22 is greater than the number of battery cells of the first battery 21 is described as an example in which the voltage of the second battery 22 when fully charged is higher than the voltage of the first battery 21 when fully charged. However, even if the two batteries have the same number of battery cells, the voltages when fully charged may be different, for example, due to deterioration, etc. The technology disclosed in this specification can also be applied to such a case.

[0068] In addition, each of the switching devices 30, 32, 34 and 36 may be a contactless relay different from a semiconductor switching device, or may be a contact relay. In addition, in the charging process according to the first embodiment, the second switching device 32 and the fourth switching device 36 may be replaced with diodes.

[0069] It should be noted that the switch devices 30, 32, 34 and 36 are not necessarily provided. In the present modification, the first switching relay 38 is an example of a "first relay", and the second switching relay 40 is an example of a "second relay".

[0070] Furthermore, the number of batteries provided in the power supply system 1 is not necessarily two, and may be three or more.

[0071] The technical elements described in this specification or drawings demonstrate their 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 techniques illustrated in this specification or drawings can achieve multiple purposes at the same time and demonstrate technical utility by achieving one of the purposes.

Claims

1. A power supply system, characterized in that include: a first battery that can be charged by an external power source; a second battery, which can be charged by the external power source, the voltage of the second battery when fully charged being higher than the voltage of the first battery when fully charged; a connecting circuit configured to form a parallel circuit in which the first battery and the second battery are connected in parallel; a first relay disposed in the connection circuit, the first relay conducting and interrupting power from the external power source to the first battery in the parallel circuit; a second relay provided in the connection circuit, the second relay switching on and off the power from the external power source to the second battery in the parallel circuit; as well as a control device configured to execute a charging process of charging the first battery and the second battery using the external power source, The charging process includes the following process: when the first battery is fully charged, the first relay is cut off to cut off the power from the external power source to the first battery, while the second battery continues to be charged.

2. The power supply system according to claim 1, characterized in that: The first relay includes a contactless relay.

3. The power supply system according to claim 2, characterized in that: The contactless relay includes a semiconductor switching device.

4. The power supply system according to claim 3, characterized in that: The contactless relay includes a first diode connected in anti-parallel with the semiconductor switching device, and The first diode is oriented to allow discharge of the first battery and also inhibit charging of the first battery.

5. The power supply system according to claim 1, characterized in that : The connecting circuit includes a second diode connected in series with the second battery in the parallel circuit; and The second diode is oriented to inhibit discharge of the second battery and also allow charging of the second battery.

6. The power supply system according to claim 1, characterized in that: The charging process includes, before the process of cutting off the power to the first battery, turning on the first relay to charge the first battery, and When the voltage of the first battery reaches the voltage of the second battery, a process of charging the second battery is started with the second relay being in an on state.

7. The power supply system according to claim 6, characterized in that: Also includes: a charging relay that switches power from the external power source on and off to the connection circuit; as well as a first capacitor connected in parallel with the first battery and the second battery in the parallel circuit; The charging process includes: before charging the first battery, turning on the first relay while the charging relay is turned off, so that the first capacitor is pre-charged by the first battery; and In the process of charging the first battery, the charging relay is turned on.

8. The power supply system according to claim 1, characterized in that: The connecting circuit includes a third diode connected in series with the first battery in the parallel circuit, and The third diode is oriented to inhibit discharge of the first battery and also allow charging of the first battery.

9. The power supply system according to claim 1, characterized in that: The control device is configured to perform a power feeding process of supplying electric power to an external load through the connection circuit using the first battery and the second battery, and The power feeding process includes a process of turning off the first relay and also turning on the second relay to supply power from the second battery to the external load.

10. The power supply system according to claim 9, characterized in that: Also includes: a feeding relay that switches power on and off from the connection circuit to the external load; as well as a second capacitor connected in parallel with the first battery and the second battery in the parallel circuit, wherein The power feeding process includes: before the process of supplying power from the second battery to the external load, by turning off the first relay in a state where the power feeding relay is turned off and also turning on the second relay, the second capacitor is pre-charged by the second battery, and In the process of supplying electric power from the second battery to the external load, the power feeding relay is turned on.

11. The power supply system according to claim 10, characterized in that: The first relay includes a semiconductor switch device and a first diode connected in anti-parallel with the semiconductor switch device, and The first diode is oriented to allow discharge of the first battery and also inhibit charging of the first battery.

12. The power supply system according to any one of claims 1 to 11, characterized in that: The connection circuit is configured to selectively constitute the parallel circuit or a series circuit in which the first battery and the second battery are connected in series.

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