Power supply system and control program

Abstract

A power supply system (10) comprises: a plurality of main machine batteries (31, 61) connected in parallel to power supply buses (11, 12); and at least one conversion circuit (40), each of which converts power input to a primary-side terminal pair (41, 42) from one of the main machine batteries and outputs the converted power from a secondary-side terminal pair (47, 48). The positive electrode and negative electrode of said main machine battery are respectively connected to the primary-side terminal pair of the conversion circuit, the secondary-side terminal pair of the conversion circuit can be connected in series with the main machine battery, and the secondary-side terminal pair of the conversion circuit can be connected in parallel to a low-voltage load (22).

Description

Power supply system and control program CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Application No. 2023-108740 filed on June 30, 2023, the contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a power supply system.

[0003] For example, there is a power supply system that includes a first converter and a second converter that receive power from a high-voltage battery, and a low-voltage load that receives power from at least one of the first converter and the second converter (see Patent Document 1). In the power supply system described in Patent Document 1, if the first converter fails, power can be supplied to the low-voltage load from the second converter, thereby providing redundancy to the power source of the low-voltage load.

[0004] Patent No. 7198606

[0005] In a power supply system in which multiple high-voltage batteries (main batteries) are connected in parallel to a power supply bus, a partial power converter (PPC) is required to adjust the voltage difference between the high-voltage batteries. The present inventors have noticed that if a PPC can be used as a power source for low-voltage loads, it will be possible to reduce the number of redundant power sources.

[0006] The present disclosure has been made to solve the above-mentioned problems, and its main purpose is to enable a PPC to be used as a power source for a low-voltage load in a power supply system in which multiple main batteries are connected in parallel to a power supply bus.

[0007] A first means for solving the above problem is a power supply system including a plurality of main batteries connected in parallel to a power supply bus, and at least one conversion circuit that converts power input from the main batteries to a primary terminal pair and outputs the power from a secondary terminal pair, wherein the positive and negative electrodes of the main batteries are respectively connected to the primary terminal pair of the conversion circuit, the secondary terminal pair of the conversion circuit can be connected in series to the main battery, and the secondary terminal pair of the conversion circuit can be connected in parallel to a low-voltage load.

[0008] According to the above configuration, the plurality of main batteries are connected in parallel to the power supply bus, so that power can be supplied from the plurality of main batteries to the power supply bus. At least one conversion circuit converts power input from the main battery to a pair of primary terminals and outputs the converted power from a pair of secondary terminals.

[0009] Here, the positive and negative electrodes of the main battery are respectively connected to the primary terminal pair of the conversion circuit, and the secondary terminal pair of the conversion circuit can be connected in series to the main battery. Therefore, when the secondary terminal pair of the conversion circuit is connected in series to the main battery, the output voltage Vo of the conversion circuit can be added to the output voltage Vb of the main battery, and the voltage difference between the main batteries can be adjusted by the conversion circuit (PPC). In this case, the output voltage Vo required of the conversion circuit can be lowered compared to a configuration in which the main battery is connected in parallel to the secondary terminal pair of the conversion circuit. This allows the rated voltage of the conversion circuit to be lowered, which in turn allows the rated capacity of the conversion circuit to be reduced, thereby enabling the conversion circuit to be made more compact.

[0010] Furthermore, the secondary terminal pair of the conversion circuit can be connected in parallel to a low-voltage load. Therefore, when the secondary terminal pair of the conversion circuit is connected in parallel to the low-voltage load, power can be supplied to the low-voltage load from the secondary terminal pair of the conversion circuit. Here, because the output voltage Vo required of the conversion circuit when adjusting the voltage difference between the main batteries is low, the conversion circuit is suitable for supplying power to the low-voltage load. Therefore, the conversion circuit can be used as a power source for the low-voltage load, thereby reducing the need for redundant power sources.

[0011] The second means includes a series path that connects the secondary terminal pair of the conversion circuit in series to the main battery, a first relay that disconnects and connects the series path, a bus connection path that connects the secondary terminal of the secondary terminal pair of the conversion circuit opposite the main battery to the power supply bus, a second relay that disconnects and connects the bus connection path, a negative side path and a positive side path that connect the secondary terminal pair of the conversion circuit in parallel to the low-voltage load, a third relay that disconnects and connects the negative side path, and a fourth relay that disconnects and connects the positive side path.

[0012] According to the above configuration, when the first relay and the second relay are connected, the output voltage Vo of the conversion circuit can be added to the output voltage Vb of the main battery, and the voltage difference between the main batteries can be adjusted by the conversion circuit. At this time, by disconnecting the third relay and the fourth relay, a high-voltage path that supplies a high voltage to the power supply bus and a low-voltage path that supplies a low voltage to the low-voltage load can be isolated. Furthermore, when the third relay and the fourth relay are connected, power can be supplied to the low-voltage load from the secondary terminal pair of the conversion circuit. At this time, by disconnecting the first relay and the second relay, the high-voltage path and the low-voltage path can be isolated.

[0013] The third means includes a control unit that connects the first relay and the second relay and disconnects the third relay and the fourth relay when executing a voltage adjustment mode in which power is supplied from the secondary terminal pair of the conversion circuit to the power supply bus, and that disconnects the first relay and the second relay and connects the third relay and the fourth relay when executing a low-voltage power supply mode in which power is supplied from the secondary terminal pair of the conversion circuit to the low-voltage load.

[0014] According to the above configuration, when executing a voltage regulation mode in which power is supplied from the secondary terminal pair of the conversion circuit to the power supply bus, the control unit connects the first relay and the second relay and disconnects the third relay and the fourth relay. Therefore, in the voltage regulation mode, the conversion circuit can adjust the voltage difference between the main batteries while isolating the high-voltage path and the low-voltage path. Furthermore, when executing a low-voltage power supply mode in which power is supplied from the secondary terminal pair of the conversion circuit to the low-voltage load, the control unit disconnects the first relay and the second relay and connects the third relay and the fourth relay. Therefore, in the low-voltage power supply mode, power can be supplied from the secondary terminal pair of the conversion circuit to the low-voltage load while isolating the high-voltage path and the low-voltage path.

[0015] In a fourth means, when executing the voltage adjustment mode, the control unit disconnects the third relay and the fourth relay and then connects the first relay and the second relay, and when executing the low-voltage power supply mode, the control unit disconnects the first relay and the second relay and then connects the third relay and the fourth relay.

[0016] According to the above configuration, when executing the voltage adjustment mode, the control unit closes the third relay and the fourth relay and then connects the first relay and the second relay. Therefore, the voltage adjustment mode can be executed after the high-voltage path and the low-voltage path are reliably insulated. Furthermore, when executing the low-voltage power supply mode, the control unit closes the first relay and the second relay and then connects the third relay and the fourth relay. Therefore, the low-voltage power supply mode can be executed after the high-voltage path and the low-voltage path are reliably insulated.

[0017] A fifth means includes a step-down converter connected to the power supply bus, which steps down the power input from the power supply bus and outputs the power to the low-voltage load, and the control unit switches from the low-voltage power supply mode to the voltage adjustment mode after starting the step-down converter, and stops the step-down converter after switching from the voltage adjustment mode to the low-voltage power supply mode.

[0018] According to the above configuration, the step-down converter is connected to the power supply bus and steps down the power input from the power supply bus and outputs the power to the low-voltage load. Therefore, power can be supplied to the low-voltage load from the conversion circuit and the step-down converter operating in a low-voltage power supply mode. The control unit switches from the low-voltage power supply mode to the voltage regulation mode after starting the step-down converter. Therefore, the transition from the low-voltage power supply mode to the voltage regulation mode can be made without interruption of the power supply to the low-voltage load. Furthermore, the control unit stops the step-down converter after switching from the voltage regulation mode to the low-voltage power supply mode. Therefore, the step-down converter can be stopped without interruption of the power supply to the low-voltage load.

[0019] In a sixth aspect, the power supply system is mounted on a vehicle and includes a state determination unit that determines a state of the vehicle, and a control unit that, when the state determination unit determines that the vehicle is in a mode in which the multiple main batteries are connected in parallel to the power supply bus and charged / discharged, executes a voltage adjustment mode in which power is supplied from the secondary terminal pair of the conversion circuit to the power supply bus, and, when the state determination unit determines that the vehicle is in a mode in which the multiple main batteries are not connected in parallel to the power supply bus or a mode in which the multiple main batteries are not charged / discharged, executes a low-voltage power supply mode in which power is supplied from the secondary terminal pair of the conversion circuit to the low-voltage load.

[0020] According to the above configuration, when the state determination unit determines that the vehicle is in a mode in which the multiple main batteries are connected in parallel to the power supply bus and charged / discharged (e.g., the vehicle is in operation), the control unit executes a voltage regulation mode in which power is supplied from the secondary terminal pair of the conversion circuit to the power supply bus. Therefore, for example, when the vehicle is in operation, by executing the voltage regulation mode, power can be supplied from the main batteries to the power supply bus while the conversion circuit adjusts the voltage difference between the main batteries. Furthermore, when the state determination unit determines that the vehicle is in a mode in which the multiple main batteries are not connected in parallel to the power supply bus or a mode in which the multiple main batteries are not charged / discharged (e.g., the vehicle is stopped), the control unit executes a low-voltage power supply mode in which power is supplied from the secondary terminal pair of the conversion circuit to the low-voltage load. Therefore, for example, when the vehicle is stopped, power can be supplied from the conversion circuit to the low-voltage load by executing the low-voltage power supply mode. This eliminates the need for a dedicated low-voltage power supply to supply power to the low-voltage load while the vehicle is stopped.

[0021] In the seventh means, a low-voltage power supply is connected to the low-voltage load, and the seventh means includes an abnormality determination unit that determines whether the low-voltage power supply is abnormal, and a control unit that, when the abnormality determination unit determines that the low-voltage power supply is not abnormal, executes a voltage adjustment mode in which power is supplied from the secondary terminal pair of the conversion circuit to the power supply bus, and, when the abnormality determination unit determines that the low-voltage power supply is abnormal, executes a low-voltage power supply mode in which power is supplied from the secondary terminal pair of the conversion circuit to the low-voltage load.

[0022] According to the above configuration, when the abnormality determination unit determines that the low-voltage power supply is not abnormal, the control unit executes a voltage adjustment mode in which power is supplied from the secondary terminal pair of the conversion circuit to the power supply bus. Therefore, when the low-voltage power supply is not abnormal, the control unit executes the voltage adjustment mode, allowing the conversion circuit to adjust the voltage difference between the main batteries while supplying power from the main battery to the power supply bus. Furthermore, when the abnormality determination unit determines that the low-voltage power supply is abnormal, the control unit executes a low-voltage power supply mode in which power is supplied from the secondary terminal pair of the conversion circuit to the low-voltage load. Therefore, when the low-voltage power supply is abnormal, the control unit executes the low-voltage power supply mode, allowing power to be supplied from the conversion circuit to the low-voltage load. This makes it possible to reduce redundant power supplies.

[0023] In an eighth means, a high-voltage load is connected to the power supply bus, and the eighth means includes a power calculation unit that calculates a high-voltage power request value that is the power required by the high-voltage load and a low-voltage power request value that is the power required by the low-voltage load, and a control unit that executes a voltage adjustment mode in which power is supplied from the secondary-side terminal pair of the conversion circuit to the power supply bus when the high-voltage power request value calculated by the power calculation unit is greater than a first specified value or when the low-voltage power request value calculated by the power calculation unit is smaller than a second specified value, and executes a low-voltage power supply mode in which power is supplied from the secondary-side terminal pair of the conversion circuit to the low-voltage load when the high-voltage power request value calculated by the power calculation unit is smaller than the first specified value or when the low-voltage power request value calculated by the power calculation unit is greater than the second specified value.

[0024] According to the above configuration, the control unit executes a voltage adjustment mode in which power is supplied from the secondary terminal pair of the conversion circuit to the power supply bus when the high-voltage power request value calculated by the power calculation unit is greater than a first specified value or when the low-voltage power request value calculated by the power calculation unit is less than a second specified value. Therefore, by executing the voltage adjustment mode in which the high-voltage power request value is greater than the first specified value or the low-voltage power request value is less than the second specified value, power can be supplied from the main battery to the power supply bus while adjusting the voltage difference between the main batteries using the conversion circuit. Furthermore, the control unit executes a low-voltage power supply mode in which power is supplied from the secondary terminal pair of the conversion circuit to the low-voltage load when the high-voltage power request value calculated by the power calculation unit is less than the first specified value or when the low-voltage power request value calculated by the power calculation unit is greater than the second specified value. Therefore, when the high-voltage power requirement value is smaller than the first specified value or when the low-voltage power requirement value is greater than the second specified value, the low-voltage power supply mode is executed, so that power can be supplied from the conversion circuit to the low-voltage load. Therefore, the voltage regulation mode and the low-voltage power supply mode can be switched depending on the high-voltage power requirement value and the low-voltage power requirement value.

[0025] In a ninth aspect, the conversion circuit includes a secondary-side voltage sensor that detects the voltage between the secondary-side terminal pair, and a control unit that controls the output voltage of the conversion circuit based on the voltage detected by the secondary-side voltage sensor when executing a voltage adjustment mode in which power is supplied from the secondary-side terminal pair of the conversion circuit to the power supply bus, and controls the output voltage of the conversion circuit based on the voltage detected by the secondary-side voltage sensor when executing a low-voltage power supply mode in which power is supplied from the secondary-side terminal pair of the conversion circuit to the low-voltage load.

[0026] According to the above configuration, the control unit can use the voltage detected by the secondary voltage sensor both when the voltage adjustment mode is being executed and when the low-voltage power supply mode is being executed.

[0027] In the tenth means, a high-voltage load is connected to the main battery in which the secondary terminal pair of the conversion circuit can be connected in series, or a charging device is connected to the main battery in which the secondary terminal pair of the conversion circuit cannot be connected in series.

[0028] According to the above configuration, the charge level of a main battery connected to a high-voltage load can be reduced, thereby lowering the output voltage Vb of the main battery. Alternatively, the charge level of a main battery connected to a charging device can be increased, thereby raising the output voltage Vb of the main battery. In other words, the output voltage Vb of the main battery whose secondary terminal pair of the conversion circuit can be connected in series can be relatively lower than the output voltage Vb of the main battery whose secondary terminal pair of the conversion circuit cannot be connected in series. This makes it easier to control the addition of the output voltage Vo of the conversion circuit to the output voltage Vb of the main battery, making it easier to adjust the voltage difference between the main batteries using the conversion circuit.

[0029] The eleventh aspect of the present invention includes a predetermined path connecting a primary terminal of the conversion circuit, the primary terminal being connected between the main battery and the secondary terminal, to the power supply bus, and a predetermined relay for connecting and disconnecting the predetermined path. With this configuration, power can be directly supplied from the main battery to the power supply bus by connecting the predetermined path using the predetermined relay. Therefore, for example, when the first relay and the second relay are disconnected and the third relay and the fourth relay are connected, power can be supplied to the power supply bus and the low-voltage load while isolating the high-voltage path from the low-voltage path.

[0030] The twelfth means includes a plurality of main batteries connected in parallel to a power supply bus, at least one conversion circuit that converts power input from the main battery to a primary terminal pair and outputs the converted power from a secondary terminal pair, a series path that connects the secondary terminal pair of the conversion circuit in series to the main battery, a first relay that connects and disconnects the series path, a bus connection path that connects a secondary terminal of the secondary terminal pair of the conversion circuit opposite to the main battery to the power supply bus, a second relay that connects and disconnects the bus connection path, and a relay that connects and disconnects the bus connection path. a negative side path and a positive side path that connect the secondary side terminal pair of a circuit in parallel to a low-voltage load, a third relay that connects and disconnects the negative side path, and a fourth relay that connects and disconnects the positive side path, wherein the positive and negative poles of the main battery are respectively connected to the primary side terminal pair of the conversion circuit, the secondary side terminal pair of the conversion circuit can be connected in series to the main battery, and the secondary side terminal pair of the conversion circuit can be connected in parallel to the low-voltage load. The control program is applied to a power supply system that includes: a negative side path and a positive side path that connect the secondary side terminal pair of a circuit in parallel to a low-voltage load, a third relay that connects and disconnects the negative side path, and a fourth relay that connects and disconnects the positive side path, wherein the positive and negative poles of the main battery are respectively connected to the primary side terminal pair of the conversion circuit, the secondary side terminal pair of the conversion circuit can be connected in series to the main battery, and the secondary side terminal pair of the conversion circuit can be connected in parallel to the low-voltage load, and causes a computer to execute a process of connecting the first relay and the second relay and disconnecting the third relay and the fourth relay when executing a voltage adjustment mode in which power is supplied from the secondary side terminal pair of the conversion circuit to the power supply bus, and

[0031] According to the above configuration, by causing a computer to execute a control program applied to the power supply system, it is possible to achieve the same effects as those of the third means.

[0032] The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which Fig. 1 is a circuit diagram of a power supply system, Fig. 2 is a circuit diagram showing an example of a conversion circuit, Fig. 3 is a circuit diagram showing relay states and currents in a voltage regulation mode, Fig. 4 is a circuit diagram showing relay states and currents in a 12V-DCDC mode, Fig. 5 is a flowchart showing a mode switching procedure of a first embodiment, Fig. 6 is a flowchart showing a mode switching procedure of a second embodiment, Fig. 7 is a flowchart showing a mode switching procedure of a third embodiment, and Fig. 8 is a flowchart showing a mode switching procedure of a fourth embodiment. 9 is a circuit diagram of a modified example of the power supply system, FIG. 10 is a circuit diagram of another modified example of the power supply system, FIG. 11 is a circuit diagram of another modified example of the power supply system, FIG. 12 is a circuit diagram of another modified example of the power supply system, FIG. 13 is a circuit diagram of another modified example of the power supply system, FIG. 14 is a circuit diagram of a modified example of the conversion circuit, FIG. 15 is a circuit diagram of another modified example of the conversion circuit, FIG. 16 is a circuit diagram of another modified example of the conversion circuit, and FIG. 17 is a circuit diagram of a modified example of the storage battery module.

[0033] First Embodiment A first embodiment of a power supply system mounted on a vehicle to supply power to a load will be described below with reference to the drawings. The vehicle may be, for example, a hybrid vehicle or an electric vehicle, and is equipped with an activation switch (e.g., an IG switch or a start switch) for activating the vehicle. The vehicle is placed in an operating state (in operation) by turning on the activation switch (not shown), and placed in a stopped state (stopped) by turning off the activation switch.

[0034] 1 , the power supply system 10 includes buses 11 and 12 (power supply buses), a first storage battery module 30, a second storage battery module 60, a voltage sensor 13, a current sensor 19, an ECU (Electronic Control Unit) 16, etc. The positive side of the buses is referred to as bus 11, and the negative side of the buses is referred to as bus 12. The bus 12 is grounded.

[0035] A first storage battery module 30 (storage battery module), a second storage battery module 60 (storage battery module), a high-voltage load 21, a 12VDCDC 23, and a voltage sensor 13 are connected in parallel to the buses 11 and 12. The storage battery modules 30 and 60 input and output power to the buses 11 and 12. The high-voltage load 21 inputs high-voltage power (e.g., several hundred volts) from the buses 11 and 12, or inputs and outputs high-voltage power to the buses 11 and 12. The voltage sensor 13 detects a bus voltage Vbus, which is the voltage between the buses 12 and 11. The current sensor 19 detects a current flowing through the bus 12 (high-voltage load 21).

[0036] The high-voltage load 21 is, for example, a combination of an inverter and a motor generator (MG) (a motor unit with an inverter), an electric heater, etc. The MG (motor generator) drives, for example, an electric vehicle using power supplied from the inverter, or generates electricity regeneratively using rotational force applied from the electric vehicle. The inverter converts power between the buses 11, 12 and the MG. The electric heater generates heat using high voltage supplied from the buses 11, 12, for example, to warm the interior of the vehicle or the battery. The high-voltage load 21 may be singular or plural.

[0037] The 12V DCDC 23 is, for example, a well-known isolated DCDC converter. The 12V DCDC 23 (step-down converter, low-voltage power supply, high-voltage load) is connected in parallel to the buses 11 and 12. A low-voltage load 22 is connected in parallel to the 12V DCDC 23. The 12V DCDC 23 steps down (converts) high-voltage DC power supplied from the buses 11 and 12 to supply 12 V (low-voltage) DC power to the low-voltage load 22, or converts DC power supplied from a solar panel or the like to supply DC power to the buses 11 and 12. The 12V DCDC 23 is controlled by the control unit 16b of the ECU 16.

[0038] The low-voltage load 22 is an on-board auxiliary device, a control device, or the like that is driven by a supply of 12 V (low voltage) power. The low-voltage load 22 may include the ECU 16. The low-voltage load 22 is maintained supplied with power from at least one of the 12 V DCDC 23 and a first conversion circuit 40 (described later).

[0039] The first storage battery module 30 includes a first storage battery 31, a first current sensor 33, a first drive circuit 35, a first conversion circuit 40, a first path 36, a second path 37, a third path 38, a fourth path 39, a first relay 36a, a second relay 37a, a third relay 38a, a fourth relay 39a, and a relay 40b. The relays 36a, 37a, 38a, 39a, and 40b are configured by semiconductor relays such as FETs and IGBTs (Insulated Gate Bipolar Transistors), and are controlled by the control unit 16b of the ECU 16. The relay 40b connects and disconnects the storage battery module 30 to and from the bus 12.

[0040] The first storage battery 31 (high-voltage battery, main battery, storage battery) is a high-voltage (e.g., several hundred volts) secondary battery, such as a lithium-ion battery or a nickel-metal hydride battery, and may be of any type. The first storage battery 31 is generally configured as a battery pack in which multiple unit batteries are connected in series. A first current sensor 33 (current sensor) detects the current flowing through the first storage battery 31. The value detected by the first current sensor 33 is input to the ECU 16 and used, for example, to calculate the state of charge (SOC) of the first storage battery 31. A first drive circuit 35 (drive circuit) drives a switching element (described below) included in the first conversion circuit 40 to turn on and off. The first drive circuit 35 is controlled by the ECU 16.

[0041] The first conversion circuit 40 (PPC, conversion circuit) includes a primary side terminal pair consisting of a primary side positive terminal 41 and a negative terminal 42 (primary side terminals) and a secondary side terminal pair consisting of a secondary side positive terminal 47 and a negative terminal 48 (secondary side terminals). The negative terminal of the first storage battery 31 is connected to the bus 12. The primary side positive terminal 41 is connected to the positive terminal of the first storage battery 31, and the primary side negative terminal 42 is connected to the negative terminal of the first storage battery 31. That is, the positive terminal and the negative terminal of the first storage battery 31 are connected to the primary side terminal pair 41, 42 of the first conversion circuit 40, respectively.

[0042] A secondary-side negative terminal 48 is connected to the positive electrode of the first storage battery 31 via a first path 36. The first path 36 (series path) connects the secondary-side negative terminal 48 (secondary-side terminal pair 47, 48) of the first conversion circuit 40 in series with the first storage battery 31. A first relay 36a is provided in the first path 36 to interrupt and connect the first path 36. The secondary-side positive terminal 47 is connected to the bus 11 via a second path 37. The second path 37 (bus connection path) connects the secondary-side positive terminal 47 of the secondary-side terminal pair 47, 48 of the first conversion circuit 40 opposite the first storage battery 31 to the bus 11. A second relay 37a is provided in the second path 37 to interrupt and connect the second path 37. That is, the first path 36, the second path 37, the first relay 36a, and the second relay 37a enable the secondary terminal pair 47, 48 of the first conversion circuit 40 to be connected in series to and disconnected from the first storage battery 31.

[0043] Furthermore, the negative terminal 48 on the secondary side is connected to the negative side of the low-voltage load 22 via a third path 38. A third relay 38a is provided in the third path 38 (negative path) to connect and disconnect the third path 38. The positive terminal 47 on the secondary side is connected to the positive side of the low-voltage load 22 via a fourth path 39. A fourth relay 39a is provided in the fourth path 39 (positive path) to connect and disconnect the fourth path 39. That is, the third path 38, the fourth path 39, the third relay 38a, and the fourth relay 39a enable parallel connection and disconnection of the secondary terminal pair 48, 47 of the first conversion circuit 40 to and from the low-voltage load 22.

[0044] The first conversion circuit 40 converts the power input from the first storage battery 31 to the pair of primary side terminals 41 and 42 and outputs it from the pair of secondary side terminals 47 and 48. Note that the first conversion circuit 40 may be a bidirectional conversion circuit that is also capable of converting the power input to the pair of secondary side terminals 47 and 48 and outputting it from the pair of primary side terminals 41 and 42.

[0045] The second storage battery module 60 has a configuration similar to that of the first storage battery module 30, except that it does not include the third path 38, the fourth path 39, and the relays 36a, 37a, 38a, and 39a. The second storage battery module 60 includes a second storage battery 61 (high-voltage battery, main battery, storage battery), a second current sensor 63 (current sensor), a second drive circuit 65 (drive circuit), a second conversion circuit 70, and relays 70a and 70b. The second conversion circuit 70 (conversion circuit) has a configuration similar to that of the first conversion circuit 40 and includes a primary-side terminal pair consisting of a primary-side positive terminal 71 and a negative terminal 72 (primary-side terminals) and a secondary-side terminal pair consisting of a secondary-side positive terminal 77 and a negative terminal 78 (secondary-side terminals). The connection configuration of these components is also similar to that of the first storage battery module 30, and therefore the above description of the first storage battery module 30 is applicable. The relays 70a and 70b respectively connect and disconnect the storage battery module 60 to the buses 11 and 12. Although the first storage battery module 30 and the second storage battery module 60 have configurations with similar functions, the ratings and withstand voltages of the respective configurations may be different from each other.

[0046] FIG. 2 shows an example of a first conversion circuit 40. The first conversion circuit 40 is a well-known center-tap isolated DC-DC converter. The first conversion circuit 40 includes switching elements 43 to 46, diodes 54A and 55A, smoothing capacitors 50 and 57, a transformer 53, a reactor 56, voltage sensors 51 and 59, and current sensors 52 and 58. The switching elements 43 to 46 are, for example, FETs, IGBTs, or the like. The switching elements 43 to 46 form a full-bridge circuit. The connection point between the switching elements 43 and 44 and the connection point between the switching elements 45 and 46 are connected to both ends of the primary coil of the transformer 53, respectively. The diodes 54A and 55A are connected between both ends of the secondary coil of the transformer 53 and the negative terminal 48, respectively. The anodes of the diodes 54A and 55A are connected to the negative terminal 48, and the cathodes are connected to both ends of the secondary coil of the transformer 53. The voltage sensor 51 detects the voltage between the negative terminal 42 and positive terminal 41 on the primary side, i.e., the output voltage Vb of the first storage battery 31. The current sensor 52 detects the input current Ii, which is the current input to the primary side circuit. The voltage sensor 59 detects the voltage between the negative terminal 48 and positive terminal 47 on the secondary side, i.e., the output voltage Vo of the first conversion circuit 40. The current sensor 58 detects the current flowing through the reactor 56, i.e., the output current Io of the first conversion circuit 40. The detected values ​​of the voltage sensors 51, 59 and the current sensors 52, 58 are input to the ECU 16.

[0047] The ECU 16 (control device) is configured as a microcomputer (computer) including, for example, a CPU, ROM, RAM, an input / output interface, etc. The ECU 16 controls the states of the relays 15 and 17, the drive state of the 12V DCDC 23, the states of the relays 36a, 37a, 38a, 39a, 40b, 70a, and 70b, and the state of the high-voltage load 21. Furthermore, the ECU 16 executes a control program applied to the power supply system 10 to realize functions of a bus voltage setting unit 16a, a control unit 16b, a state determination unit 16c, an abnormality determination unit 16d, a power calculation unit 16e, etc.

[0048] The bus voltage setting unit 16a sets a bus voltage request value Vbus*, which is a voltage that is requested to be supplied from the buses 11 and 12 to the high-voltage load 21. The bus voltage setting unit 16a sets the bus voltage request value Vbus* based on the state of the high-voltage load 21.

[0049] The control unit 16b controls the output voltages Vo1 and Vo2 of the conversion circuits 40 and 70 so that the output voltages Vm1 and Vm2 of the storage battery modules 30 and 60 become equal to the requested bus voltage value Vbus* (approach the requested bus voltage value Vbus*). For example, the control unit 16b controls the switching elements 43 to 46 based on the detected values ​​of the voltage sensors 51 and 59 and the current sensors 52 and 58 to control the first output voltage Vo1 of the first conversion circuit 40 to become equal to the requested first output voltage value Vo1*. Specifically, the control unit 16b sets the requested first output voltage value Vo1* to a voltage obtained by subtracting the first output voltage Vb1 of the first storage battery 31 from the requested bus voltage value Vbus* (Vo1* = Vbus* - Vb1). Similarly, the control unit 16b controls the second output voltage Vo2 of the second conversion circuit 70 to become equal to the requested second output voltage value Vo2*. Specifically, the second output voltage request value Vo2* is set to a voltage obtained by subtracting the second output voltage Vb2 of the second storage battery 61 from the bus voltage request value Vbus* (Vo2*=Vbus*−Vb2).

[0050] The present inventors have noted that if the first conversion circuit 40 can be used as a power supply for the low-voltage load 22, it is possible to reduce the number of redundant power supplies. In other words, by using the first conversion circuit 40, which is used to adjust the voltage difference between the first storage battery 31 and the second storage battery 61, as a redundant power supply for the 12V DCDC 23, it is not necessary to provide a redundant power supply. Specifically, the control unit 16b executes a voltage adjustment mode in which power is supplied from the secondary-side terminal pair 47, 48 of the first conversion circuit 40 to the buses 11, 12, and a 12V-DCDC mode (low-voltage power supply mode) in which power is supplied from the secondary-side terminal pair 47, 48 of the first conversion circuit 40 to the low-voltage load 22. The control unit 16b controls the output voltage Vo of the first conversion circuit 40 based on the voltage detected by the voltage sensor 59 (secondary-side voltage sensor) when the 12V-DCDC mode is executed. In detail, the control unit 16b controls the switching elements 43 to 46 based on the detected values ​​by the voltage sensors 51, 59 and the current sensors 52, 58 so that the voltage detected by the voltage sensor 59 becomes, for example, 12 [V] (the voltage required by the low-voltage load 22).

[0051] FIG. 3 is a circuit diagram showing relay states and currents in the voltage regulation mode. When executing the voltage regulation mode, the control unit 16b connects the first relay 36a and the second relay 37a and disconnects the third relay 38a and the fourth relay 39a. This isolates the high-voltage path supplying the high voltage to the buses 11 and 12 from the low-voltage path supplying the low-voltage load 22. In the voltage regulation mode, the first output voltage Vm1 of the first storage battery module 30 is adjusted to a voltage obtained by adding the first output voltage Vb1 of the first storage battery 31 to the first output voltage Vo1 of the first conversion circuit 40 (Vm1 = Vb1 + Vo1), and power is supplied from the first storage battery module 30 to the buses 11 and 12. At this time, power is not supplied from the first conversion circuit 40 to the low-voltage load 22. Note that the high-voltage path and the low-voltage path are also isolated within the 12V DCDC 23.

[0052] 4 is a circuit diagram showing the relay states and currents in the 12V-DCDC mode. When executing the 12V-DCDC mode, the control unit 16b disconnects the first relay 36a and the second relay 37a and connects the third relay 38a and the fourth relay 39a. This isolates the high-voltage path that supplies high voltage to the buses 11 and 12 from the low-voltage path that supplies low voltage to the low-voltage load 22. In the 12V-DCDC mode, power of the first output voltage Vo1 is supplied from the secondary-side terminal pair 47 and 48 of the first conversion circuit 40 to the low-voltage load 22. At this time, power is not supplied from the first storage battery module 30 to the buses 11 and 12. Note that the high-voltage path and the low-voltage path are also isolated within the 12V-DCDC 23.

[0053] 5 is a flowchart showing the mode switching procedure of this embodiment. This series of processes is repeatedly executed by the ECU 16 at a predetermined interval.

[0054] First, it is determined whether the vehicle is in operation (S10). Specifically, the state of the vehicle's start switch is input, and if the start switch is on, it is determined that the vehicle is in operation. If the start switch is off, it is determined that the vehicle is not in operation (stopped). If it is determined that the vehicle is not in operation (S10: NO), the first relay 36a and the second relay 37a are disconnected, and then the third relay 38a and the fourth relay 39a are connected (S11). Then, the 12V-DCDC mode is executed (S12). Note that the processing of S10 corresponds to the processing of the state determination unit 16c. When the vehicle is in operation, it corresponds to a mode in which the storage batteries 31, 61 are connected in parallel to the buses 11, 12 and charged / discharged. When the vehicle is stopped, it corresponds to a mode in which the storage batteries 31, 61 are not charged / discharged.

[0055] Next, it is determined whether or not there is a vehicle startup request (S13). Specifically, it is determined that there is a startup request when the vehicle startup switch is turned from off to on, and it is determined that there is no startup request when the vehicle startup switch remains off. If it is determined that there is a vehicle startup request (S13: YES), the 12V DCDC 23 is started (S14). That is, the 12V DCDC 23 starts to be driven, and power is supplied from the 12V DCDC 23 to the low-voltage load 22.

[0056] Next, after the third relay 38a and the fourth relay 39a are disconnected, the first relay 36a and the second relay 37a are connected (S15). After that, the voltage adjustment mode is executed (S16), and this series of processes is temporarily ended (END). That is, after the 12V DCDC 23 is started, switching from the 12V-DCDC mode to the voltage adjustment mode is executed. Note that, if it is determined in S10 that the vehicle is in operation (S10: YES), the voltage adjustment mode is executed (S16), and this series of processes is temporarily ended (END). That is, the voltage adjustment mode is continued.

[0057] Furthermore, if it is determined in step S13 that there is no request to start the vehicle (S13: NO), the 12V DCDC 23 is stopped (S17). That is, after switching from the voltage regulation mode to the 12V-DCDC mode (after executing the 12V-DCDC mode), the 12V DCDC 23 is stopped. Then, this series of processes is temporarily ended (END).

[0058] The present embodiment described above in detail has the following advantages.

[0059] The positive and negative electrodes of the first storage battery 31 are connected to the primary-side terminal pair 41, 42 of the first conversion circuit 40, respectively, and the secondary-side terminal pair 47, 48 of the first conversion circuit 40 can be connected in series to the first storage battery 31. Therefore, when the secondary-side terminal pair 47, 48 of the first conversion circuit 40 are connected in series to the first storage battery 31, the first output voltage Vo1 of the first conversion circuit 40 can be added to the first output voltage Vb1 of the first storage battery 31, and the voltage difference between the storage batteries 31, 61 can be adjusted by the first conversion circuit 40. In this case, the first output voltage Vo1 required of the first conversion circuit 40 can be lowered compared to a configuration in which the first storage battery 31 is connected in parallel to the secondary-side terminal pair 47, 48 of the first conversion circuit 40. Therefore, the rated voltage of the first conversion circuit 40 can be lowered, and the rated capacity of the first conversion circuit 40 can be reduced, so that the first conversion circuit 40 can be made smaller.

[0060] The secondary-side terminal pair 47, 48 of the first conversion circuit 40 can be connected in parallel to the low-voltage load 22. Therefore, when the secondary-side terminal pair 47, 48 of the first conversion circuit 40 is connected in parallel to the low-voltage load 22, power can be supplied from the secondary-side terminal pair 47, 48 of the first conversion circuit 40 to the low-voltage load 22. Here, because the first output voltage Vo1 required of the first conversion circuit 40 when adjusting the voltage difference between the storage batteries 31, 61 is low, the first conversion circuit 40 is suitable for supplying power to the low-voltage load 22. Therefore, the first conversion circuit 40 can be used as a power supply for the low-voltage load 22, making it possible to reduce the number of redundant power supplies.

[0061] When the first relay 36a and the second relay 37a are connected, the first output voltage Vo1 of the first conversion circuit 40 can be added to the first output voltage Vb1 of the first storage battery 31, and the voltage difference between the storage batteries 31 and 61 can be adjusted by the first conversion circuit 40. At this time, by disconnecting the third relay 38a and the fourth relay 39a, it is possible to isolate the high-voltage path that supplies a high voltage to the buses 11 and 12 from the low-voltage path that supplies a low voltage to the low-voltage load 22. Furthermore, when the third relay 38a and the fourth relay 39a are connected, power can be supplied to the low-voltage load 22 from the secondary-side terminal pair 47 and 48 of the first conversion circuit 40. At this time, by disconnecting the first relay 36a and the second relay 37a, it is possible to isolate the high-voltage path from the low-voltage path.

[0062] When executing a voltage adjustment mode in which power is supplied from the secondary-side terminal pair 47, 48 of the first conversion circuit 40 to the buses 11, 12, the control unit 16b connects the first relay 36a and the second relay 37a and disconnects the third relay 38a and the fourth relay 39a. Therefore, in the voltage adjustment mode, the first conversion circuit 40 can adjust the voltage difference between the storage batteries 31, 61 while isolating the high-voltage path and the low-voltage path. Furthermore, when executing a 12V-DCDC mode in which power is supplied from the secondary-side terminal pair 47, 48 of the first conversion circuit 40 to the low-voltage load 22, the control unit 16b disconnects the first relay 36a and the second relay 37a and connects the third relay 38a and the fourth relay 39a. Therefore, in the 12V-DCDC mode, power can be supplied from the secondary-side terminal pair 47, 48 of the first conversion circuit 40 to the low-voltage load 22 while isolating the high-voltage path and the low-voltage path.

[0063] When executing the voltage adjustment mode, the control unit 16b closes the third relay 38a and the fourth relay 39a and then connects the first relay 36a and the second relay 37a. Therefore, the high-voltage path and the low-voltage path can be reliably insulated before executing the voltage adjustment mode. Furthermore, when executing the 12V-DCDC mode, the control unit 16b closes the first relay 36a and the second relay 37a and then connects the third relay 38a and the fourth relay 39a. Therefore, the 12V-DCDC mode can be reliably insulated before executing the 12V-DCDC mode.

[0064] The 12V DCDC 23 is connected to the buses 11 and 12 and reduces the high-voltage power input from the buses 11 and 12 to 12 V and outputs it to the low-voltage load 22. Therefore, power can be supplied to the low-voltage load 22 from the first conversion circuit 40 and the 12V DCDC 23, which are operating in the 12V-DCDC mode. Here, the control unit 16b switches from the 12V-DCDC mode to the voltage regulation mode after starting the 12V DCDC 23. Therefore, the power supply to the low-voltage load 22 can be transitioned from the 12V-DCDC mode to the voltage regulation mode without interruption. Furthermore, the control unit 16b stops the 12V DCDC 23 after switching from the voltage regulation mode to the 12V-DCDC mode. Therefore, the 12V DCDC 23 can be stopped without interruption of the power supply to the low-voltage load 22. If there is no problem with a temporary interruption of the power supply to the low-voltage load 22, the voltage adjustment mode may be executed before the 12V DCDC 23 is started, or the 12V DCDC 23 may be stopped before the 12V-DCDC mode is executed.

[0065] When the state determination unit 16c determines that the vehicle is operating, the control unit 16b executes a voltage adjustment mode in which power is supplied from the secondary-side terminal pair 47, 48 of the first conversion circuit 40 to the buses 11, 12. Therefore, by executing the voltage adjustment mode while the vehicle is operating, power can be supplied from the first storage battery 31 to the buses 11, 12 while the voltage difference between the storage batteries 31, 61 is adjusted by the first conversion circuit 40. Furthermore, when the state determination unit 16c determines that the vehicle is stopped, the control unit 16b executes a 12V-DCDC mode in which power is supplied from the secondary-side terminal pair 47, 48 of the first conversion circuit 40 to the low-voltage load 22. Therefore, by executing the 12V-DCDC mode while the vehicle is stopped, power can be supplied from the first conversion circuit 40 to the low-voltage load 22. This eliminates the need for a dedicated low-voltage power source to supply power to the low-voltage load 22 while the vehicle is stopped.

[0066] The control unit 16b can use the voltage detected by the voltage sensor 59 both when the voltage adjustment mode is being executed and when the 12V-DCDC mode is being executed.

[0067] The above-described advantageous effects can be achieved by causing the ECU 16 (computer) to execute the control program applied to the power supply system 10 .

[0068] Second Embodiment The second embodiment will be described below, focusing on the differences from the first embodiment. Note that the same parts as those in the first embodiment are denoted by the same reference numerals and the description thereof will be incorporated herein.

[0069] In this embodiment, the ECU 16 executes a control program to implement the function of an abnormality determination unit 16d that determines whether or not the low-voltage power supply is abnormal. The low-voltage power supply is, for example, the 12V DCDC 23 shown in FIG. 1 and is capable of being disconnected from the low-voltage load 22. The low-voltage power supply may also be, for example, an auxiliary battery (low-voltage battery) that supplies a voltage of 12 V.

[0070] 6 is a flowchart showing the mode switching procedure of this embodiment. This series of processes is repeatedly executed by the ECU 16 at a predetermined interval.

[0071] First, it is determined whether the low-voltage power supply is normal (S20). For example, if the 12V DCDC 23 is not malfunctioning and is not grounded, it is determined that the low-voltage power supply is normal (not abnormal). On the other hand, if the 12V DCDC 23 is malfunctioning or has a ground fault, it is determined that the low-voltage power supply is abnormal (abnormal). If it is determined that the low-voltage power supply is abnormal (NO in S20), the low-voltage power supply is disconnected from the low-voltage load 22 (S21). The first relay 36a and the second relay 37a are disconnected, and the third relay 38a and the fourth relay 39a are connected (S22). Thereafter, the 12V-DCDC mode is executed (S23), and this series of processes is temporarily terminated (END). Note that the process in S20 corresponds to the process performed by the abnormality determination unit 16d.

[0072] On the other hand, if it is determined in S20 that the low-voltage power supply is normal (S20: YES), the voltage adjustment mode is executed (S24), and this series of processes is temporarily ended (END). When executing the voltage adjustment mode, the first relay 36a and the second relay 37a are closed, and the third relay 38a and the fourth relay 39a are closed.

[0073] According to the above configuration, when the abnormality determination unit 16d determines that the 12V-DCDC 23 is normal (not abnormal), the control unit 16b executes a voltage adjustment mode in which power is supplied from the secondary-side terminal pair 47, 48 of the first conversion circuit 40 to the buses 11, 12. Therefore, when the 12V-DCDC 23 is normal, by executing the voltage adjustment mode, power can be supplied from the first storage battery 31 to the buses 11, 12 while the voltage difference between the storage batteries 31, 61 is adjusted by the first conversion circuit 40. Furthermore, when the abnormality determination unit 16d determines that the 12V-DCDC 23 is abnormal (abnormal), the control unit 16b executes a 12V-DCDC mode in which power is supplied from the secondary-side terminal pair 47, 48 of the first conversion circuit 40 to the low-voltage load 22. Therefore, when the 12V-DCDC 23 is abnormal, power can be supplied from the first conversion circuit 40 to the low-voltage load 22 by executing the 12V-DCDC mode. Therefore, it is possible to reduce the number of redundant power supplies.

[0074] Third Embodiment Hereinafter, a third embodiment will be described, focusing on differences from the first embodiment. Note that the same parts as those in the first embodiment are denoted by the same reference numerals and the description thereof will be incorporated.

[0075] In this embodiment, the ECU 16 executes a control program to realize the function of a power calculation unit 16e that calculates a high-voltage power requirement value, which is the power required by the high-voltage load 21, and a low-voltage power requirement value, which is the power required by the low-voltage load 22. The power calculation unit 16e calculates the high-voltage power requirement value based on the state of the high-voltage load 21, and calculates the low-voltage power requirement value based on the state of the low-voltage load 22.

[0076] 7 is a flowchart showing the mode switching procedure of this embodiment. This series of processes is repeatedly executed by the ECU 16 at a predetermined interval.

[0077] First, it is determined whether the required high-voltage power value is greater than a first specified value (S30). The first specified value is set, for example, to a value that allows determination that the difference between the maximum power that can be supplied by the second storage battery module 60 and the required high-voltage power value is small (smaller than a predetermined difference). If it is determined that the required high-voltage power value is greater than the first specified value (S30: YES), the third relay 38a and the fourth relay 39a are disconnected, and then the first relay 36a and the second relay 37a are connected (S31). Thereafter, the voltage adjustment mode is executed (S32), and this series of processes is temporarily terminated (END). The process of S30 corresponds to the process performed by the power calculation unit 16e.

[0078] On the other hand, if the determination in S30 determines that the high-voltage power request value is not greater than the first specified value (S30: NO), the control unit 100 determines whether the low-voltage power request value is greater than a second specified value (S33). The second specified value is set, for example, to a value that allows determination that the difference between the maximum power that can be supplied by the 12V DCDC 23 and the low-voltage power request value is small (smaller than a predetermined difference). If the determination determines that the low-voltage power request value is greater than the second specified value (S33: YES), the control unit 100 turns off the first relay 36a and the second relay 37a, and then turns on the third relay 38a and the fourth relay 39a (S34). Then, the 12V DCDC mode is executed (S35), and this series of processes is temporarily terminated (END). If the determination in S33 determines that the low-voltage power request value is not greater than the second specified value (S33: NO), this series of processes is temporarily terminated (END). Note that the process in S33 corresponds to the process of the power calculation unit 16e.

[0079] According to the above configuration, the control unit 16b executes the voltage adjustment mode when the high-voltage power request value calculated by the power calculation unit 16e is greater than the first specified value. Therefore, when the high-voltage power request value is greater than the first specified value, the control unit 16b executes the voltage adjustment mode, thereby enabling the first conversion circuit 40 to adjust the voltage difference between the storage batteries 31 and 61 and supply power from the first storage battery 31 to the buses 11 and 12. Furthermore, when the low-voltage power request value calculated by the power calculation unit 16e is greater than the second specified value, the control unit 16b executes the 12V-DCDC mode. Therefore, when the low-voltage power request value is greater than the second specified value, the control unit 16b executes the 12V-DCDC mode, thereby enabling power to be supplied from the first conversion circuit 40 to the low-voltage load 22. Therefore, switching between the voltage adjustment mode and the 12V-DCDC mode is possible depending on the high-voltage power request value and the low-voltage power request value.

[0080] Alternatively, instead of the process of S30, it may be determined whether the low-voltage power request value is smaller than a second specified value. If it is determined that the low-voltage power request value is smaller than the second specified value, the process may proceed to S31. Alternatively, instead of the process of S33, it may be determined whether the high-voltage power request value is smaller than a first specified value. If it is determined that the high-voltage power request value is smaller than the first specified value, the process may proceed to S34. With this configuration, when the low-voltage power request value is smaller than the second specified value, the voltage adjustment mode is executed, so that power can be supplied from the first storage battery 31 to the buses 11 and 12 while the voltage difference between the storage batteries 31 and 61 is adjusted by the first conversion circuit 40. When the high-voltage power request value is smaller than the first specified value, the 12V-DCDC mode is executed, so that power can be supplied from the first conversion circuit 40 to the low-voltage load 22. Therefore, it is possible to switch between the voltage adjustment mode and the 12V-DCDC mode depending on the high-voltage power request value and the low-voltage power request value.

[0081] Fourth Embodiment The following describes the fourth embodiment, focusing on differences from the third embodiment. The same components as those in the first and third embodiments are denoted by the same reference numerals and the same descriptions are incorporated herein. In this embodiment, the ECU 16 also executes a control program to implement the functions of the power calculation unit 16e.

[0082] 8 is a flowchart showing the mode switching procedure of this embodiment. This series of processes is repeatedly executed by the ECU 16 at a predetermined interval.

[0083] The processes of S40 to S42 are the same as the processes of S30 to S32 in Fig. 7. If it is determined in S40 that the requested high-voltage power value is not greater than the first specified value (S40: NO), the voltage adjustment mode is stopped (S43). That is, the supply of power from the first storage battery 31 to the buses 11 and 12 is stopped while the voltage difference between the storage batteries 31 and 61 is adjusted by the first conversion circuit 40.

[0084] The processes of S44 to S46 are the same as the processes of S33 to S35 in Fig. 7. Here, in the process of S46, the state in which the voltage adjustment mode is stopped is switched to the 12V-DCDC mode.

[0085] If it is determined in S44 that the low-voltage power request value is not greater than the second specified value (S44: NO), the 12V-DCDC mode is stopped (S47). That is, the supply of power from the first conversion circuit 40 to the low-voltage load 22 is stopped. Then, the first conversion circuit 40 is stopped (S48). At this time, the relays 36a, 37a, 38a, and 39a may be shut off. Then, this series of processes is temporarily ended (END). This configuration allows the power consumption of the power supply system 10 to be reduced.

[0086] Furthermore, in the third and fourth embodiments, the power supply system 10 may include a plurality of first storage battery modules 30 capable of operating in the voltage regulation mode and the 12V-DCDC mode. The number of first storage battery modules 30 operating in the voltage regulation mode may be increased each time the high-voltage power request value increases by a first request value. The first request value is, for example, a value corresponding to the power that can be supplied by one first storage battery 31 (first storage battery module 30) in the voltage regulation mode. Meanwhile, the number of first storage battery modules 30 operating in the voltage regulation mode may be decreased each time the high-voltage power request value decreases by the first request value. Furthermore, the number of first storage battery modules 30 operating in the 12V-DCDC mode may be increased each time the low-voltage power request value increases by a second request value. The second request value is, for example, a value corresponding to the power that can be supplied by one first storage battery 31 (first storage battery module 30) in the 12V-DCDC mode. Meanwhile, the number of first storage battery modules 30 operating in the 12V-DCDC mode may be decreased each time the low-voltage power request value decreases by a second request value. Then, the first storage battery module 30 that is not operating in either the voltage regulation mode or the 12V-DCDC mode may be stopped. At this time, the relays 36a, 37a, 38a, and 39a may be shut off.

[0087] The first to fourth embodiments can be modified as follows: The same parts as those in the first to fourth embodiments are denoted by the same reference numerals and the description thereof will be incorporated herein.

[0088] When switching from the 12V-DCDC mode to the voltage adjustment mode, the first relay 36a and the second relay 37a may be connected at the same time as the third relay 38a and the fourth relay 39a are disconnected. Also, when switching from the 12V-DCDC mode to the voltage adjustment mode, the first relay 36a and the second relay 37a may be connected before the third relay 38a and the fourth relay 39a are disconnected. In this case, a state occurs in which the high-voltage path and the low-voltage path are not insulated, but no short-circuit current flows between the high-voltage path and the low-voltage path.

[0089] When switching from the voltage regulation mode to the 12V-DCDC mode, the first relay 36a and the second relay 37a may be disconnected and the third relay 38a and the fourth relay 39a may be connected at the same time. Also, when switching from the voltage regulation mode to the 12V-DCDC mode, the third relay 38a and the fourth relay 39a may be connected before the first relay 36a and the second relay 37a are disconnected. In this case, a state occurs in which the high-voltage path and the low-voltage path are not insulated, but no short-circuit current flows between the high-voltage path and the low-voltage path.

[0090] In the voltage adjustment mode, when the first output voltage Vo1 of the first conversion circuit 40 is approximately 12 V (approximately equal to the voltage required by the low-voltage load 22), the relays 36 a, 37 a, 38 a, and 39 a can be connected to simultaneously execute the 12 V-DCDC mode.

[0091] As shown by the dashed line in the first storage battery module 30 in FIG. 1 , the first storage battery module 30 may include a predetermined path 49 and a predetermined relay 49a. The predetermined path 49 connects the primary-side positive terminal 41 of the first conversion circuit 40 to the bus 11. That is, the predetermined path 49 connects the primary-side positive terminal 41 (primary-side terminal) of the primary-side terminal pair 41, 42 of the first conversion circuit 40, which is connected between the first storage battery 31 and the secondary-side negative terminal 48 (secondary-side terminal pair), to the bus 11 (power supply bus). The predetermined relay 49a is configured, for example, with an FET or an IGBT and connects and disconnects the predetermined path 49. With this configuration, power can be directly supplied from the first storage battery 31 to the buses 11 and 12 by connecting the predetermined path 49 using the predetermined relay 49a. Therefore, for example, when the first relay 36a and the second relay 37a are disconnected and the third relay 38a and the fourth relay 39a are connected, power can be supplied to the buses 11, 12 and the low-voltage load 22 while isolating the high-voltage path and the low-voltage path.

[0092] In the second storage battery module 60 that does not execute the 12V-DCDC mode, the voltage sensor 59 (secondary-side voltage sensor) of the second conversion circuit 70 can be omitted. In this case, the second output voltage Vo2 of the second conversion circuit 70 in the voltage regulation mode can be calculated by subtracting the second output voltage Vb2 of the second storage battery 61 detected by the voltage sensor 51 from the bus voltage Vbus detected by the voltage sensor 13 (Vo2 = Vbus - Vb2).

[0093] FIG. 9 is a circuit diagram of a modified example of the power supply system 10. Here, the first conversion circuit 40 is represented as PPC, and the connections of the primary-side terminal pair 41, 42 and the secondary-side terminal pair 47, 48 are shown in a simplified form. This is also true in subsequent drawings showing the power supply system 10. The power supply system 10 may include only the second storage battery 61 instead of the second storage battery module 60. In other words, the second storage battery 61 does not need to be connected in series with the second conversion circuit 70. Even with this configuration, the voltage difference between the storage batteries 31, 61 can be adjusted by the first conversion circuit 40.

[0094] 10 , a high-voltage load 21A and a power supply 21B may be connected in parallel to the buses 11 and 12. The high-voltage load 21A is a low-voltage power supply similar to, for example, a 12V DCDC converter 23. With this configuration, even if any of the first storage battery 31, the first conversion circuit 40, the second storage battery 61, and the power supply 21B fails, power can be supplied to the high-voltage load 21A from at least one of these. Furthermore, the first storage battery 31 and the second storage battery 61 can be charged from the power supply 21B.

[0095] As shown in FIG. 11 , a high-voltage load 21C may be connected in parallel to the first storage battery 31, whose secondary-side terminal pair 47, 48 (not shown) of the first conversion circuit 40 can be connected in series. With this configuration, the charge amount of the first storage battery 31 can be reduced by supplying power from the first storage battery 31 to the high-voltage load 21C, thereby lowering the first output voltage Vb1 of the first storage battery 31. That is, the first output voltage Vb1 of the first storage battery 31 can be lowered relatively to the second output voltage Vb2 of the second storage battery 61, which is not connected in series to the second conversion circuit 70 (i.e., the secondary-side terminal pair 77, 78 of the second conversion circuit 70 cannot be connected in series). This facilitates control to add the first output voltage Vo1 of the first conversion circuit 40 to the first output voltage Vb1 of the first storage battery 31, making it easier for the first conversion circuit 40 to adjust the voltage difference between the storage batteries 31 and 61.

[0096] Furthermore, the power source 21B (charging device) is connected to the second storage battery 61 to which the second conversion circuit 70 is not connected. Therefore, by charging the second storage battery 61 from the power source 21B, the charge amount of the second storage battery 61 can be increased, and the second output voltage Vb2 of the second storage battery 61 can be raised. In this case, too, the first output voltage Vb1 of the first storage battery 31 can be relatively lower than the second output voltage Vb2 of the second storage battery 61. Therefore, it becomes easier to perform control to add the first output voltage Vo1 of the first conversion circuit 40 to the first output voltage Vb1 of the first storage battery 31, and the first conversion circuit 40 can easily adjust the voltage difference between the storage batteries 31 and 61.

[0097] 12 , the power supply system 10 may include a plurality of first storage battery modules 30. That is, secondary-side terminal pairs 47, 48 (not shown) of a plurality of first conversion circuits 40 may be connectable in parallel to the low-voltage load 22.

[0098] As shown in FIG. 13 , the power supply system 10 may include a switching circuit that switches between a state in which the storage batteries 31, 61 are connected in parallel to the buses 11, 12 and a state in which they are connected in series. The switching circuit includes, for example, a path 24 and relays 25 to 27. The relay 25 (switch) is provided between the negative electrode of the first storage battery 31 and the bus 12. The relay 27 (switch) is provided between the positive electrode of the second storage battery 61 and the bus 11. The path 24 connects a connection point N1 between the negative electrode of the first storage battery 31 and the relay 25, and a connection point N2 between the positive electrode of the second storage battery 61 and the relay 27. The relay 26 (switch) is provided on the path 24. The relays 25 to 27 are controlled by the ECU 16.

[0099] According to the above configuration, the ECU 16 can switch the first storage battery 31 and the second storage battery 61 to a parallel connection with the buses 11 and 12 by turning on (connecting) the relays 25 and 27 and turning off (connecting) the relay 26. The ECU 16 can also switch the first storage battery 31 and the second storage battery 61 to a series connection with the buses 11 and 12 by turning off (disconnecting) the relays 25 and 27 and turning on (connecting) the relay 26. When the storage batteries 31 and 61 are switched to a parallel connection by the switching circuit, power can be supplied from the storage batteries 31 and 61 to the buses 11 and 12. Therefore, the storage batteries 31 and 61 can be used as redundant high-voltage power supplies. When the storage batteries 31 and 61 are switched to a parallel connection by the switching circuit, the ECU 16 can execute the above-described control of the power supply system 10 and control similar to the modified example. Furthermore, when the storage batteries 31, 61 are switched to a series connection by the switching circuit, the sum of the output voltages of the first storage battery 31, the first conversion circuit 40, and the second storage battery 61 can be supplied to the buses 11, 12. This allows the storage batteries 31, 61 to be used as a higher voltage power supply. Furthermore, when the storage batteries 31, 61 are switched to a series connection by the switching circuit (a mode in which the storage batteries 31, 61 are not connected in parallel to the buses 11, 12), the ECU 16 can execute a 12V-DCDC mode (low-voltage power supply mode).

[0100] As the high-voltage load 21, for example, two or more combinations of an inverter and an MG (Motor Generator) (motor units with inverters) may be connected in parallel to the buses 11 and 12. In this case, the number of storage battery modules or storage batteries connected to the buses 11 and 12 may be increased according to the number of motor units with inverters.

[0101] As shown in Fig. 14, in the first conversion circuit 40 (conversion circuit), the diodes 54A and 55A in Fig. 2 may be replaced with switching elements 54 and 55. The control unit 16b may then control the switching elements 43 to 46, 54, and 55 based on the values ​​detected by the voltage sensors 51 and 59 and the current sensors 52 and 58. With this configuration, it is possible to achieve the same effects as the first conversion circuit 40 in Fig. 2. The same applies to the second conversion circuit 70 and other conversion circuits (conversion circuits).

[0102] As shown in Fig. 15, in the first conversion circuit 40 (conversion circuit), the switching elements 54 and 55 in Fig. 14 may be connected between the secondary coil of the transformer 53 and the reactor 56. With this configuration, it is possible to achieve the same effects as the first conversion circuit 40 in Figs. 2 and 14. The same applies to the second conversion circuit 70 etc. (conversion circuit).

[0103] 16, the first conversion circuit 40 (conversion circuit) may be a well-known isolated DC-DC converter including a non-center-tapped transformer 153 and a secondary-side full-bridge circuit composed of switching elements 143 to 146. The switching elements 143 to 146 are, for example, FETs or IGBTs. The switching elements 143 to 146 are controlled by the ECU 16. The same applies to the second conversion circuit 70 and other conversion circuits.

[0104] A resonant DC-DC converter may be used as the first conversion circuit 40 (conversion circuit). Also, a non-isolated DC-DC converter such as a buck converter may be used as the first conversion circuit 40 (conversion circuit). The same applies to the second conversion circuit 70 and other conversion circuits.

[0105] The battery modules 30, 60 may be configured as shown in FIG. 17 . That is, the positive electrode of the first storage battery 31 is connected to the bus 11. The positive electrode of the first storage battery 31 is connected to the primary-side positive terminal 41 of the first conversion circuit 40, and the negative electrode of the first storage battery 31 is connected to the primary-side negative terminal 42 of the first conversion circuit 40. The negative electrode of the first storage battery 31 is connected to the secondary-side positive terminal 47 of the first conversion circuit 40 via a first path 36. The secondary-side negative terminal 48 of the first conversion circuit 40 is connected to the bus 12 via a second path 37. In this case, too, the positive and negative electrodes of the first storage battery 31 are connected to the primary-side terminal pair 41, 42 of the first conversion circuit 40, respectively. The first path 36 (series path) connects the secondary-side positive terminal 47 (secondary-side terminal pair 47, 48) of the first conversion circuit 40 in series with the first storage battery 31. The first path 36 is provided with a first relay 36a. The second path 37 (bus connection path) connects a negative terminal 48 of the secondary side of the pair of secondary terminals 47, 48 of the first conversion circuit 40, the negative terminal 48 being on the opposite side from the first storage battery 31, to the bus 12. The second path 37 is provided with a second relay 37a. The third path 38, the third relay 38a, the fourth path 39, and the fourth relay 39a are the same as those in the power supply system 10 of FIG. 1. Therefore, the pair of secondary terminals 47, 48 of the first conversion circuit 40 can be connected in series to the first storage battery 31, and the pair of secondary terminals 47, 48 of the first conversion circuit 40 can be connected in parallel to the low-voltage load 22. Even with this configuration, it is possible to achieve the same effects as those of the above-described embodiments and modified examples.

[0106] The first storage battery module 30 may also include a predetermined path 49 and a predetermined relay 49a. The predetermined path 49 connects the primary-side negative terminal 42 of the first conversion circuit 40 to the bus 12. That is, the predetermined path 49 connects the primary-side negative terminal 42 (primary-side terminal) of the primary-side terminal pair 41, 42 of the first conversion circuit 40, which is connected between the first storage battery 31 and the secondary-side positive terminal 47 (secondary-side terminal pair), to the bus 12 (power supply bus). The predetermined relay 49a is configured, for example, with an FET or an IGBT, and interrupts and connects the predetermined path 49. With this configuration, power can be directly supplied from the first storage battery 31 to the buses 11, 12 by connecting the predetermined path 49 using the predetermined relay 49a. Therefore, for example, when the first relay 36a and the second relay 37a are disconnected and the third relay 38a and the fourth relay 39a are connected, power can be supplied to the buses 11, 12 and the low-voltage load 22 while isolating the high-voltage path and the low-voltage path.

[0107] At least one of the functions of the bus voltage setting unit 16 a, the control unit 16 b, the state determination unit 16 c, the abnormality determination unit 16 d, and the power calculation unit 16 e of the ECU 16 can be realized by, for example, a power control ECU (Electronic Control Unit) that controls the power of the vehicle or a vehicle control ECU (host ECU) that controls the overall vehicle. The power supply system 10 can also be mounted on an electric vehicle such as an electric airplane or an electric ship.

[0108] The storage battery 31, 61 (main battery) may be a battery that supplies a voltage lower than several hundred volts, such as 24 V, 48 V, or 60 V, and the low-voltage load 22 may be a load that receives power that is a stepped-down version of the power supplied from the storage battery 31, 61 (bus 11, 12). Alternatively, the storage battery 31, 61 (main battery) may be a battery that supplies a high voltage higher than several hundred volts, and the low-voltage load 22 may be a load that receives power that is a stepped-down version of the power supplied from the storage battery 31, 61 (bus 11, 12).

[0109] At least one of the functions of the bus voltage setting unit 16 a, the control unit 16 b, the state determination unit 16 c, the abnormality determination unit 16 d, and the power calculation unit 16 e of the ECU 16 can be realized by, for example, a power control ECU (Electronic Control Unit) that controls the power of the electric vehicle or a vehicle control ECU (host ECU) that controls the electric vehicle in an integrated manner. Furthermore, when the power supply system 10 is used as, for example, a stationary power source, the functions of the bus voltage setting unit 16 a, the control unit 16 b, the state determination unit 16 c, the abnormality determination unit 16 d, and the power calculation unit 16 e of the ECU 16 can be realized by a stationary power source control ECU (control device) that controls the stationary power source.

[0110] The ECU 16 and the methods described herein may be implemented by a special-purpose computer configured with a processor and memory programmed to execute one or more functions (instructions) embodied in a computer program. Alternatively, the ECU 16 and the methods described herein may be implemented by a special-purpose computer configured with a processor implemented by one or more dedicated hardware logic circuits. Alternatively, the ECU 16 and the methods described herein may be implemented by one or more special-purpose computers configured with a processor and memory programmed to execute one or more functions and a processor implemented by one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions executed by a computer on a computer-readable non-transitory storage medium.

[0111] The above-described embodiments and modifications may be combined within the scope of possible combinations.

[0112] The following describes characteristic configurations extracted from the above-described embodiments and modified examples. [Configuration 1] A power supply system (10) including a plurality of main batteries (31, 61) connected in parallel to a power supply bus (11, 12), and at least one conversion circuit (40) that converts power input from the main batteries to primary terminal pairs (41, 42) and outputs the converted power from secondary terminal pairs (47, 48), wherein the positive and negative electrodes of the main batteries are connected to the primary terminal pairs of the conversion circuit, respectively, the secondary terminal pairs of the conversion circuit can be connected in series to the main batteries, and the secondary terminal pairs of the conversion circuit can be connected in parallel to a low-voltage load (22). [Configuration 2] The power supply system according to Configuration 1, comprising: a series path (36) connecting the secondary terminal pair of the conversion circuit in series to the main battery; a first relay (36a) disconnecting and connecting the series path; a bus connection path (37) connecting a secondary terminal of the secondary terminal pair of the conversion circuit opposite the main battery to the power supply bus; a second relay (37a) disconnecting and connecting the bus connection path; a negative side path (38) and a positive side path (39) connecting the secondary terminal pair of the conversion circuit in parallel to the low-voltage load; a third relay (38a) disconnecting and connecting the negative side path; and a fourth relay (39a) disconnecting and connecting the positive side path. [Configuration 3] The power supply system according to Configuration 2, further comprising a control unit (16b) that connects the first relay and the second relay and disconnects the third relay and the fourth relay when executing a voltage adjustment mode in which power is supplied from the secondary terminal pair of the conversion circuit to the power supply bus, and that disconnects the first relay and the second relay and connects the third relay and the fourth relay when executing a low-voltage power supply mode in which power is supplied from the secondary terminal pair of the conversion circuit to the low-voltage load. [Configuration 4] The power supply system according to Configuration 3, wherein the control unit connects the first relay and the second relay after disconnecting the third relay and the fourth relay when executing the voltage adjustment mode, and connects the third relay and the fourth relay after disconnecting the first relay and the second relay when executing the low-voltage power supply mode.[Configuration 5] The power supply system according to Configuration 3 or 4, further comprising a step-down converter (23) connected to the power supply bus, stepping down the power input from the power supply bus and outputting the power to the low-voltage load, wherein the control unit switches from the low-voltage power supply mode to the voltage regulation mode after starting the step-down converter, and stops the step-down converter after switching from the voltage regulation mode to the low-voltage power supply mode. [Configuration 6] The power supply system according to Configuration 1 or 2, wherein the power supply system is mounted on a vehicle and includes: a state determination unit (16c) that determines a state of the vehicle; and a control unit (16b) that, when the state determination unit determines that the vehicle is in a mode in which the multiple main batteries are connected in parallel to the power supply bus and charged / discharged, executes a voltage adjustment mode that supplies power from the secondary-side terminal pair of the conversion circuit to the power supply bus, and, when the state determination unit determines that the vehicle is in a mode in which the multiple main batteries are not connected in parallel to the power supply bus or a mode in which the multiple main batteries are not charged / discharged, executes a low-voltage power supply mode that supplies power from the secondary-side terminal pair of the conversion circuit to the low-voltage load. [Configuration 7] The power supply system according to configuration 1 or 2, wherein a low-voltage power supply (23) is connected to the low-voltage load, and the power supply system comprises: an abnormality determination unit (16d) that determines whether or not the low-voltage power supply is abnormal; and a control unit (16b) that, when the abnormality determination unit determines that the low-voltage power supply is not abnormal, executes a voltage adjustment mode in which power is supplied from the secondary-side terminal pair of the conversion circuit to the power supply bus, and, when the abnormality determination unit determines that the low-voltage power supply is abnormal, executes a low-voltage power supply mode in which power is supplied from the secondary-side terminal pair of the conversion circuit to the low-voltage load.[Configuration 8] The power supply system according to Configuration 1 or 2, wherein a high-voltage load (21, 21A) is connected to the power supply bus, and the power supply system comprises: a power calculation unit (16e) that calculates a high-voltage power request value that is the power required by the high-voltage load and a low-voltage power request value that is the power required by the low-voltage load; and a control unit (16b) that executes a voltage adjustment mode in which power is supplied from the secondary-side terminal pair of the conversion circuit to the power supply bus when the high-voltage power request value calculated by the power calculation unit is greater than a first specified value or when the low-voltage power request value calculated by the power calculation unit is smaller than a second specified value, and executes a low-voltage power supply mode in which power is supplied from the secondary-side terminal pair of the conversion circuit to the low-voltage load when the high-voltage power request value calculated by the power calculation unit is smaller than the first specified value or when the low-voltage power request value calculated by the power calculation unit is greater than the second specified value. [Configuration 9] The power supply system according to Configuration 1 or 2, wherein the conversion circuit includes a secondary-side voltage sensor (59) that detects a voltage between the pair of secondary-side terminals, and a control unit (16b) that controls an output voltage of the conversion circuit based on the voltage detected by the secondary-side voltage sensor when executing a voltage adjustment mode in which power is supplied from the pair of secondary-side terminals of the conversion circuit to the power supply bus, and controls the output voltage of the conversion circuit based on the voltage detected by the secondary-side voltage sensor when executing a low-voltage power supply mode in which power is supplied from the pair of secondary-side terminals of the conversion circuit to the low-voltage load. [Configuration 10] The power supply system according to any one of Configurations 1 to 9, wherein a high-voltage load (21C) is connected to the main battery (31) to which the pair of secondary-side terminals of the conversion circuit can be connected in series, or a charging device (21B) is connected to the main battery (61) to which the pair of secondary-side terminals of the conversion circuit cannot be connected in series. [Configuration 11] The power supply system according to any one of configurations 1 to 10, comprising: a predetermined path (49) that connects a primary terminal of the primary terminal pair of the conversion circuit, the primary terminal being connected between the main battery and the secondary terminal pair, to the power supply bus; and a predetermined relay (49 a) that cuts off and connects the predetermined path.

[0113] Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and equivalent modifications. In addition, various combinations and forms, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

Claims

1. A power supply system (10) comprising a plurality of main batteries (31, 61) connected in parallel to a power supply bus (11, 12) and at least one conversion circuit (40) that converts power input from the main batteries to a primary terminal pair (41, 42) and outputs the power from a secondary terminal pair (47, 48), wherein the positive and negative poles of the main battery are respectively connected to the primary terminal pair of the conversion circuit, the secondary terminal pair of the conversion circuit can be connected in series to the main battery, and the secondary terminal pair of the conversion circuit can be connected in parallel to a low-voltage load (22).

2. A power supply system as described in claim 1, comprising: a series path (36) connecting the secondary terminal pair of the conversion circuit in series to the main battery; a first relay (36a) for interrupting and connecting the series path; a bus connection path (37) connecting a secondary terminal of the secondary terminal pair of the conversion circuit opposite the main battery to the power supply bus; a second relay (37a) for interrupting and connecting the bus connection path; a negative side path (38) and a positive side path (39) connecting the secondary terminal pair of the conversion circuit in parallel to the low-voltage load; a third relay (38a) for interrupting and connecting the negative side path; and a fourth relay (39a) for interrupting and connecting the positive side path.

3. The power supply system of claim 2, further comprising a control unit (16b) that connects the first relay and the second relay and disconnects the third relay and the fourth relay when executing a voltage adjustment mode in which power is supplied from the secondary terminal pair of the conversion circuit to the power supply bus, and that disconnects the first relay and the second relay and connects the third relay and the fourth relay when executing a low-voltage power supply mode in which power is supplied from the secondary terminal pair of the conversion circuit to the low-voltage load.

4. The power supply system of claim 3, wherein the control unit, when executing the voltage adjustment mode, connects the first relay and the second relay after disconnecting the third relay and the fourth relay, and, when executing the low-voltage power supply mode, connects the third relay and the fourth relay after disconnecting the first relay and the second relay.

5. A power supply system as described in claim 3 or 4, further comprising a step-down converter (23) connected to the power supply bus for stepping down the power input from the power supply bus and outputting the power to the low-voltage load, wherein the control unit switches from the low-voltage power supply mode to the voltage adjustment mode after starting the step-down converter, and stops the step-down converter after switching from the voltage adjustment mode to the low-voltage power supply mode.

6. The power supply system according to claim 1 or 2, comprising: a state determination unit (16c) for determining a state of the vehicle; and a control unit (16b) for executing a voltage adjustment mode for supplying power from the secondary terminal pair of the conversion circuit to the power supply bus when the state determination unit determines that the vehicle is in a mode in which the multiple main batteries are connected in parallel to the power supply bus and charged / discharged, and for executing a low-voltage power supply mode for supplying power from the secondary terminal pair of the conversion circuit to the low-voltage load when the state determination unit determines that the vehicle is in a mode in which the multiple main batteries are not connected in parallel to the power supply bus or in a mode in which the multiple main batteries are not charged / discharged.

7. A power supply system as described in claim 1 or 2, comprising: a low-voltage power supply (23) connected to the low-voltage load; an abnormality determination unit (16d) which determines whether or not the low-voltage power supply is abnormal; and a control unit (16b) which, when the abnormality determination unit determines that the low-voltage power supply is not abnormal, executes a voltage adjustment mode in which power is supplied from the secondary terminal pair of the conversion circuit to the power supply bus, and, when the abnormality determination unit determines that the low-voltage power supply is abnormal, executes a low-voltage power supply mode in which power is supplied from the secondary terminal pair of the conversion circuit to the low-voltage load.

8. A power supply system as claimed in claim 1 or 2, comprising: a high-voltage load (21, 21A) connected to the power supply bus; a power calculation unit (16e) that calculates a high-voltage power request value that is the power required by the high-voltage load and a low-voltage power request value that is the power required by the low-voltage load; and a control unit (16b) that executes a voltage adjustment mode in which power is supplied from the secondary terminal pair of the conversion circuit to the power supply bus when the high-voltage power request value calculated by the power calculation unit is greater than a first specified value or when the low-voltage power request value calculated by the power calculation unit is smaller than a second specified value, and that executes a low-voltage power supply mode in which power is supplied from the secondary terminal pair of the conversion circuit to the low-voltage load when the high-voltage power request value calculated by the power calculation unit is smaller than the first specified value or when the low-voltage power request value calculated by the power calculation unit is greater than the second specified value.

9. The power supply system of claim 1 or 2, wherein the conversion circuit includes a secondary voltage sensor (59) that detects the voltage between the secondary terminal pair, and a control unit (16b) that controls the output voltage of the conversion circuit based on the voltage detected by the secondary voltage sensor when a voltage adjustment mode is executed in which power is supplied from the secondary terminal pair of the conversion circuit to the power supply bus, and controls the output voltage of the conversion circuit based on the voltage detected by the secondary voltage sensor when a low-voltage power supply mode is executed in which power is supplied from the secondary terminal pair of the conversion circuit to the low-voltage load.

10. A power supply system as described in any one of claims 1 to 4, wherein a high-voltage load (21C) is connected to the main battery (31) in which the secondary terminal pair of the conversion circuit can be connected in series, or a charging device (21B) is connected to the main battery (61) in which the secondary terminal pair of the conversion circuit cannot be connected in series.

11. A power supply system as claimed in any one of claims 1 to 4, comprising: a predetermined path (49) connecting a primary terminal of the primary terminal pair of the conversion circuit, the primary terminal being connected between the main battery and the secondary terminal pair, to the power supply bus; and a predetermined relay (49a) for interrupting and connecting the predetermined path.

12. A power supply bus (11, 12) including a plurality of main batteries (31, 61) connected in parallel to the main battery; at least one conversion circuit (40) that converts power input from the main battery to a primary terminal pair (41, 42) and outputs the converted power from a secondary terminal pair (47, 48); a series path (36) that connects the secondary terminal pair of the conversion circuit in series to the main battery; a first relay (36a) that interrupts and connects the series path; a bus connection path (37) that connects a secondary terminal of the secondary terminal pair of the conversion circuit opposite to the main battery to the power supply bus; and a second relay (36b) that interrupts and connects the bus connection path. a negative side path (38) and a positive side path (39) that connect the secondary side terminal pair of the conversion circuit in parallel to a low-voltage load (22), a third relay (38a) that connects and disconnects the negative side path, and a fourth relay (39a) that connects and disconnects the positive side path, wherein a positive electrode and a negative electrode of the main battery are respectively connected to the primary side terminal pair of the conversion circuit, the secondary side terminal pair of the conversion circuit can be connected in series to the main battery, and the secondary side terminal pair of the conversion circuit can be connected in parallel to the low-voltage load, a control program that causes a computer (16) to execute a process of connecting the first relay and the second relay and disconnecting the third relay and the fourth relay when executing a voltage adjustment mode in which power is supplied from the secondary terminal pair of the conversion circuit to the power supply bus, and of disconnecting the first relay and the second relay and connecting the third relay and the fourth relay when executing a low-voltage power supply mode in which power is supplied from the secondary terminal pair of the conversion circuit to the low-voltage load.

Images