Power supply system

The disclosure of Japanese Patent Application No. 2014-185458 filed on Sep. 11, 2014 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

1. Field of the Invention

The present invention relates to a power supply system in which voltage conversion is performed bidirectionally between either or both of two batteries and an output electric circuit.

2. Description of Related Art

A hybrid vehicle and an electric vehicle that employ a rotary electric machine as a driving source are provided with a power supply system including a battery, which is a direct-current power supply, and a voltage transducer for stepping up a battery voltage and stepping down a regenerative electric power caused by the rotary electric machine. As the voltage transducer, there has been known a buck-boost converter as illustrated in FIG. 28 . The buck-boost converter steps up/down a voltage by ON/OFF operations of two switching elements S 1 , S 2 .

Further, as a voltage transducer having an expanded function of the buck-boost converter, Japanese Patent Application Publication No. 2012-070514 (JP 2012-070514 A), for example, describes a voltage transducer including four switching elements S 1 to S 4 and connected to two batteries B 1 , B 2 , as illustrated in FIG. 29 . The voltage transducer can step up/down a voltage by ON/OFF operations of the four switching elements S 1 to S 4 , and can switch the two batteries between series connection and parallel connection by changing ON-OFF patterns of the switching elements.

In the meantime, in a conventional voltage transducer, it is difficult to perform voltage conversion at the time of an ON fault (short-circuit fault) of a switching element. For example, in a buck-boost converter illustrated in FIG. 28 , as generally known, a voltage is stepped up/down by an ON/OFF operation of a switching element S 2 in synchronization with an ON/OFF operation of a switching element S 1 . Accordingly, when either one of the switching elements S 1 , S 2 has an ON fault and is turned on continuously, a voltage cannot be stepped up/down in the above manner.

In the voltage transducer illustrated in FIG. 29 , even if either of the switching elements S 1 to S 4 has an ON fault, a voltage can be stepped up/down theoretically by use of either of the batteries B 1 , B 2 . However, in this case, another problem is caused such that the stepping up/down of a voltage should be stopped from the viewpoint of safety. For example, at the time of an ON fault of the switching element S 3 , the battery B 1 is connected in series with the battery B 2 , so that an output voltage is a voltage sum of the battery B 1 and the battery B 2 . This voltage might exceed withstanding voltages of system main relays SMR 1 , SMR 2 , and the like, so the voltage transducer illustrated in FIG. 29 eventually cannot help but stop the stepping up/down of a voltage at the time of an ON fault of the switching element.

The present invention provides a power supply system that can perform voltage conversion even at the time of an ON fault of a switching element.

A power supply system related an aspect of the present invention includes a first battery, a second battery, an output electric circuit, a first switching element, a second switching element, and a third switching element. The output electric circuit is configured to perform voltage conversion bidirectionally with either one or both of the first battery and the second battery. The output electric circuit includes a first electric circuit and a second electric circuit. The second electric circuit has a potential lower than a potential of the first electric circuit. The first switching element, the second switching element, and the third switching element are provided in series with each other from the first electric circuit toward the second electric circuit. The first battery is provided in parallel with the second switching element. The second battery is provided in parallel with a series connection between the second switching element and the third switching element.

According to the power supply system of the present invention, it is possible to perform voltage conversion even at the time of an ON fault of a switching element

The power supply system may further includes a first system main relay, a second system main relay and a controlling portion. The first system main relay may be configured such that the first battery is connected in parallel with the second switching element via the first system main relay. The second system main relay may be configured such that the second battery is connected in parallel with the series connection between the second switching element and the third switching element via the second system main relay. The controlling portion may be configured to perform ON-OFF controls on the first switching element, the second switching element, the third switching element, the first system main relay and the second system main relay. The controlling portion may be configured to, at a time of an ON fault of the first switching element, turn off the second system main relay and execute a first failsafe mode by performing ON-OFF controls on the second switching element and the third switching element. The controlling portion may be configured to step up a voltage of the first battery in the first failsafe mode.

The power supply system may further includes a first system main relay, a second system main relay and a controlling portion. The first system main relay may be configured such that the first battery is connected in parallel with the second switching element via the first system main relay. The second system main relay may be configured such that the second battery is connected in parallel with the series connection between the second switching element and the third switching element via the second system main relay. The controlling portion may be configured to perform ON-OFF controls on the first switching element, the second switching element, the third switching element, the first system main relay and the second system main relay. The controlling portion may be configured to, at a time of an ON fault of the second switching element, turn off the first system main relay and execute a second failsafe mode by performing ON-OFF controls on the first switching element and the third switching element. The controlling portion may be configured to step up a voltage of the second battery in the second failsafe mode.

Furthermore, the second battery may have a voltage higher than a voltage of the first battery. The first battery and the second battery may be placed in a loop circuit via the third switching element. The controlling portion may be configured to control connection or disconnection between the first battery and the second battery by performing an ON-OFF control on the third switching element.

The controlling portion may be configured to control a charging current by adjusting a conduction resistance of the third switching element, when an electric power is supplied to the first battery from the second battery by connecting the first battery to the second battery.

A power supply system related to the other aspect of the present invention includes a first battery, a second battery, an output electric circuit, a first switching element, a second switching element, and a third switching element. The output electric circuit is configured to perform voltage conversion bidirectionally with either one or both of the first battery and the second battery. The output electric circuit includes a first electric circuit and a second electric circuit. The second electric circuit has a potential lower than a potential of the first electric circuit. The first switching element, the second switching element, and the third switching element are provided in series with each other from the first electric circuit toward the second electric circuit. The first battery is provided in parallel with the third switching element. The second battery is provided in parallel with a series connection between the second switching element and the third switching element.

The power supply system may further includes a first system main relay, a second system main relay and a controlling portion. The first system main relay is configured such that the first battery is connected in parallel with the third switching element via the first system main relay. The second system main relay is configured such that the second battery is connected in parallel with the series connection between the second switching element and the third switching element via the second system main relay. The controlling portion may be configured to perform ON-OFF controls on the first switching element, the second switching element, the third switching element, the first system main relay and the second system main relay. The controlling portion may be configured to, at a time of an ON fault of the first switching element, turn off the second system main relay and execute a first failsafe mode by performing ON-OFF controls on the second switching element and the third switching element. The controlling portion may be configured to step up a voltage of the first battery in the first failsafe mode.

The power supply system may further includes a first system main relay, a second system main relay and a controlling portion. The first system main relay imay be configured such that the first battery is connected in parallel with the third switching element via the first system main relay. The second system main relay may be configured such that the second battery is connected in parallel with the series connection between the second switching element and the third switching element via the second system main relay. The controlling portion may be configured to perform ON-OFF controls on the first switching element, the second switching element, the third switching element, the first system main relay and the second system main relay. The controlling portion may be configured to, at a time of an ON fault of the third switching element, turn off the first system main relay and execute a second failsafe mode by performing ON-OFF controls on the first switching element and the second switching element. The controlling portion may be configured to step up a voltage of the second battery in the second failsafe mode.

Furthermore, the second battery may have a voltage higher than a voltage of the first battery. The first battery and the second battery may be placed in a loop circuit via the second switching element. The controlling portion may be configured to control connection or disconnection between the first battery and the second battery by controlling ON-OFF of the second switching element.

The controlling portion may be configured to control a charging current by adjusting a conduction resistance of the second switching element, when an electric power is supplied to the first battery from the second battery by connecting the first battery to the second battery.

Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is a configuration diagram of an electric system of a vehicle which electric system includes a power supply system according to the present embodiment;

FIG. 2 is a configuration diagram of the power supply system according to the present embodiment;

FIG. 3 is a view of a first buck-boost circuit extracted from the power supply system according to the present embodiment;

FIG. 4 is a view of a second buck-boost circuit extracted from the power supply system according to the present embodiment;

FIG. 5 is a view exemplifying an operation at the time of step-up storage in a parallel step-up/step-down mode in a normal time, among step-up/step-down operations using the power supply system according to the present embodiment;

FIG. 6 is a view exemplifying an operation at the time of step-up discharge in the parallel step-up/step-down mode in a normal time, among the step-up/step-down operations using the power supply system according to the present embodiment;

FIG. 7 is a view exemplifying an operation at the time of step-down storage in the parallel step-up/step-down mode in a normal time, among the step-up/step-down operations using the power supply system according to the present embodiment;

FIG. 8 is a view exemplifying an operation at the time of step-down discharge in the parallel step-up/step-down mode in a normal time, among the step-up/step-down operations using the power supply system according to the present embodiment;

FIG. 9 is a view exemplifying an operation at the time of step-up storage and step-down discharge in a step-up/step-down mode in an ON fault of a switching element S 1 , among the step-up/step-down operations using the power supply system according to the present embodiment;

FIG. 10 is a view exemplifying an operation at the time of step-up discharge and step-down storage in the step-up/step-down mode in the ON fault of the switching element S 1 , among the step-up/step-down operations using the power supply system according to the present embodiment;

FIG. 11 is a view exemplifying an operation at the time of step-up storage and step-down discharge in a step-up/step-down mode in an ON fault of a switching element S 2 , among the step-up/step-down operations using the power supply system according to the present embodiment;

FIG. 12 is a view exemplifying an operation at the time of step-up discharge and step-down storage in the step-up/step-down mode in the ON fault of the switching element S 2 , among the step-up/step-down operations using the power supply system according to the present embodiment;

FIG. 13 is a view exemplifying an operation in a B 1 single direct connection mode using the power supply system according to the present embodiment;

FIG. 14 is a view exemplifying an operation in a B 2 single direct connection mode using the power supply system according to the present embodiment;

FIG. 15 is a view to describe an inter-battery current;

FIG. 16 is a view to describe a half-ON control by a switching element S 3 ;

FIG. 17 is a configuration diagram of a power supply system according to another embodiment;

FIG. 18 is a view of a first buck-boost circuit extracted from the power supply system according to the another embodiment;

FIG. 19 is a view of a second buck-boost circuit extracted from the power supply system according to the another embodiment;

FIG. 20 is a view exemplifying an operation at the time of step-up storage and step-down discharge in a parallel step-up/step-down mode in a normal time, among step-up/step-down operations using the power supply system according to the another embodiment;

FIG. 21 is a view exemplifying an operation at the time of step-up discharge and step-down storage in the parallel step-up/step-down mode in a normal time, among the step-up/step-down operations using the power supply system according to the another embodiment;

FIG. 22 is a view exemplifying an operation at the time of step-up storage and step-down discharge in a step-up/step-down mode in an ON fault of a switching element S 1 , among the step-up/step-down operations using the power supply system according to the another embodiment;

FIG. 23 is a view exemplifying an operation at the time of step-up discharge and step-down storage in the step-up/step-down mode in the ON fault of the switching element S 1 , among the step-up/step-down operations using the power supply system according to the another embodiment;

FIG. 24 is a view exemplifying an operation at the time of step-up storage and step-down discharge in a step-up/step-down mode in an ON fault of a switching element S 3 , among the step-up/step-down operations using the power supply system according to the another embodiment;

FIG. 25 is a view exemplifying an operation at the time of step-up discharge and step-down storage in the step-up/step-down mode in the ON fault of the switching element S 3 , among the step-up/step-down operations using the power supply system according to the another embodiment;

FIG. 26 is a view exemplifying an operation in a B 1 single direct connection mode using the power supply system according to the another embodiment;

FIG. 27 is a view exemplifying an operation in a B 2 single direct connection mode using the power supply system according to the another embodiment;

FIG. 28 is a view exemplifying a conventional buck-boost converter; and

FIG. 29 is a view exemplifying a conventional voltage transducer.

With reference to the drawings, the following describes an embodiment of the present invention. FIG. 1 exemplifies a configuration diagram of an electric system of a vehicle which electric system includes a power supply system 10 according to the present embodiment. Note that an alternate long and short dash line in FIG. 1 indicates a signal line.

The power supply system 10 is an electric power supply for a rotary electric machine 12 serving as a drive source of a vehicle. A vehicle in which the power supply system 10 is provided is constituted by a hybrid vehicle or an electric vehicle, for example. The power supply system 10 includes a first battery B 1 , a second battery B 2 , a voltage transducer 14 , an inverter 16 , system main relays SMR 1 , SMR 2 , and a controlling portion 18 .

As illustrated in FIG. 1 , the first battery B 1 and the second battery B 2 are connected to the voltage transducer 14 . The voltage transducer 14 steps up direct voltages VL 1 , VL 2 from the first battery B 1 and the second battery B 2 , and outputs them to the inverter 16 .

The inverter 16 is constituted by a three-phase inverter, and is connected to the rotary electric machine 12 . The inverter 16 converts a direct-current power stepped up by the voltage transducer 14 into a three-phase alternating-current power, and outputs it to the rotary electric machine 12 . Hereby, the rotary electric machine 12 is rotationally driven. A driving force of the rotary electric machine 12 is transmitted to driving wheels (not shown).

Further, at the time of braking of the vehicle, regenerative braking is performed by the rotary electric machine 12 . A regenerative electric power obtained at this time is subjected to AC/DC conversion performed by the inverter 16 so as to be converted into a direct-current power, and the direct-current power is then stepped down by the voltage transducer 14 so as to be supplied to the first battery B 1 and the second battery B 2 .

The controlling portion 18 controls step-up/step-down (voltage conversion) of a direct voltage by controlling ON/OFF of switching elements S 1 , S 2 , S 3 of the voltage transducer 14 . Further, the controlling portion 18 controls DC/AC conversion and AC/DC conversion by controlling ON/OFF of a switching element (not shown) of the inverter 16 . Through the controls on the voltage transducer 14 and the inverter 16 , the controlling portion 18 controls driving of the rotary electric machine 12 .

The first battery B 1 and the second battery B 2 are direct-current power supplies each constituted by a secondary battery, and are each constituted by a lithium-ion storage battery or a nickel metal hydride storage battery, for example. Further, at least one of the first battery B 1 and the second battery B 2 may be a storage element such as an electric double layer capacitor, instead of the secondary battery. Further, as will be described later, respective battery voltages of the first battery B 1 and the second battery B 2 are managed so that a voltage VL 2 of the second battery B 2 is higher than a voltage VL 1 of the first battery B 1 .

The first battery B 1 is connected in parallel with the switching element S 2 of the voltage transducer 14 via the system main relay SMR 1 . Further, the second battery B 2 is connected in parallel with the switching elements S 2 and S 3 of the voltage transducer 14 via the system main relay SMR 2 .

The system main relays SMR 1 , SMR 2 each include three types of relays. That is, positive relays 20 A, 20 B are connected to respective positive sides of the batteries B 1 , B 2 , and negative relays 22 A, 22 B are connected to respective negative sides thereof. Further, as a configuration to prevent rush current at the time when the first battery B 1 and the second battery B 2 are connected to a circuit, precharge relays 24 A, 24 B are connected in parallel with the negative relays 22 A, 22 B. Resistors 26 A, 26 B are connected in series with the precharge relays 24 A, 24 B, respectively.

The voltage transducer 14 performs ON/OFF operations on the switching elements S 1 , S 2 , S 3 , so as to perform voltage conversion bidirectionally from the first battery B 1 and the second battery B 2 to output electric circuits 28 , 30 (and the rotary electric machine 12 as their destinations) and vice versa.

FIG. 2 exemplifies an extracted view of the voltage transducer 14 and its peripherals. The output electric circuits 28 , 30 constituting an output of the voltage transducer 14 are connected to a load such as the rotary electric machine 12 . The output electric circuits 28 , 30 are constituted by a high-voltage electric circuit 28 , which is a first electric circuit, and a reference electric circuit 30 , which is a second electric circuit with a potential lower than that of the high-voltage electric circuit 28 . A smoothing capacitor 31 is provided in parallel with the load between the high-voltage electric circuit 28 and the reference electric circuit 30 .

The voltage transducer 14 is provided with the first, second, third switching elements S 1 , S 2 , S 3 in series from the high-voltage electric circuit 28 toward the reference electric circuit 30 . The switching elements S 1 , S 2 , S 3 are each constituted by, for example, an IGBT (an insulated gate bipolar transistor). The switching elements S 1 , S 2 , S 3 are each provided so that a forward current direction between its collector and its emitter is the same as a direction from a high-voltage side to a low-voltage side, that is, a direction from the high-voltage electric circuit 28 to the reference electric circuit 30 .

In the voltage transducer 14 , diodes D 1 , D 2 , D 3 are connected in reverse-parallel to the switching elements S 1 , S 2 , S 3 , respectively. That is, each of the diodes D 1 , D 2 , D 3 is provided so as to flow a current from the reference electric circuit 30 to the high-voltage electric circuit 28 .

In general, a set of a switching element and a diode connected in reverse-parallel thereto is referred to as an arm. In the present embodiment, a set of the switching element S 1 and the diode D 1 , a set of the switching element S 2 and the diode D 2 , and a set of the switching element S 3 and the diode D 3 constitute respective arms.

Further, the voltage transducer 14 is provided with a first reactor 34 connected in series with the first battery B 1 , and a first capacitor 36 connected in parallel with the first battery B 1 . Similarly, the voltage transducer 14 is provided with a second reactor 40 connected in series with the second battery B 2 , and a second capacitor 42 connected in parallel with the second battery B 2 .

The voltage transducer 14 , the first battery B 1 , and the second battery B 2 are connected in the following manner. That is, a positive electrode of the first battery B 1 is connected to a first node N 1 between the switching elements S 1 and S 2 of the voltage transducer 14 via the first reactor 34 , and a negative electrode of the first battery B 1 is connected to a second node N 2 between the switching elements S 2 and S 3 . A positive electrode of the second battery B 2 is connected to the first node N 1 via the second reactor 40 , and a negative electrode of the second battery B 2 is connected to the reference electric circuit 30 .

Referring back to FIG. 1 , the controlling portion 18 performs various operation controls of the vehicle, including voltage conversion to the voltage transducer 14 and the inverter 16 , as will be described later. The controlling portion 18 may be constituted by a computer such that a CPU 44 , a storage portion 46 , and a device/sensor interface 48 are connected to each other via an internal bus 50 .

The controlling portion 18 receives signals from various sensors via the device/sensor interface 48 . More specifically, as signals related to the first battery B 1 and the second battery B 2 , the controlling portion 18 receives respective detection values from battery voltage sensors 52 A, 52 B for measuring voltage values VL 1 , VL 2 of respective batteries, battery current sensors 54 A, 54 B for measuring current values IB 1 , IB 2 of respective batteries, and an output voltage sensor 56 for measuring output voltage values VH in the output electric circuits 28 , 30 .

Further, the controlling portion 18 receives detection signals of a rotation angle and a three-phase alternating current of the rotary electric machine 12 from a resolver 58 and current sensors 60 A, 60 B, as signals related to the rotary electric machine 12 . Further, the controlling portion 18 receives detection signals of stepping-in amounts of respective pedals from an accelerator pedal stepping-in amount sensor and a brake pedal stepping-in amount sensor (not shown) as other vehicle information.

Further, the controlling portion 18 supplies control signals to the switching elements S 1 , S 2 , S 3 of the voltage transducer 14 and the switching element of the inverter 16 via the device/sensor interface 48 . The CPU 44 of the controlling portion 18 executes various control programs stored in the storage portion 46 , and performs arithmetic processing on detection signals received from various sensors, so as to perform ON/OFF controls on the switching elements S 1 , S 2 , S 3 of the voltage transducer 14 and an ON/OFF control on the switching element of the inverter 16 . By performing ON/OFF controls on the switching elements of the voltage transducer 14 and the inverter 16 , driving of the rotary electric machine 12 is controlled.

Further, the controlling portion 18 performs ON/OFF (contact closing/contact opening) controls on the system main relays SMR 1 , SMR 2 . As will be described later, by performing ON/OFF controls on the system main relays SMR 1 , SMR 2 according to ON-fault states of the switching elements S 1 , S 2 , S 3 , a step-up/step-down operation can be performed at the time of an ON fault of the switching elements S 1 , S 2 , S 3 .

The voltage transducer 14 according to the present embodiment has an expanded function of a conventional buck-boost converter illustrated in FIG. 28 . In view of this, the following description describes an operation of the voltage transducer 14 according to the present embodiment based on an operation of the conventional buck-boost converter.

Further, the operation of the voltage transducer 14 according to the present embodiment is obtained such that respective operations of a first buck-boost circuit CNV 1 on a first-battery-B 1 side and a second buck-boost circuit CNV 2 on a second-battery-B 2 side are superimposed on top of each other by a so-called principle of superposition (superposition theorem). In view of this, the following description describes a buck-boost circuit of the voltage transducer 14 according to the present embodiment based on two buck-boost circuits CNV 1 , CNV 2 , separately, for convenience.

First, the conventional buck-boost converter illustrated in FIG. 28 is described. In this converter, two arms are divided into an “upper arm” and a “lower arm.”

Conventionally, the lower arm indicates an arm forming a loop circuit including a battery and a reactor. The upper arm indicates an arm that connects a battery, a reactor, and a load (a high-voltage electric circuit 28 ).

Switching elements of the upper arm and the lower arm are turned on/off complementarily. That is, when the switching element of the lower arm is turned on, the switching element of the upper arm is turned off. Conversely, when the switching element of the upper arm is turned on, the switching element of the lower arm is turned off.

Note that, in the following description, a state where a switching element of an arm is turned on is just referred to as “arm ON” and a state where a switching element of an arm is turned off is just referred to as “arm OFF.”

A step-up/step-down operation by the conventional buck-boost converter is well known, but is described here briefly. When an electric power is transferred to an output side, an electric energy from a battery is first stored in a reactor by lower-arm ON as a step-up process. Then, the electric power thus stored in the reactor is added to an electric power of the battery by lower-arm OFF, and then sent to the output side. When the electric power is transferred to a battery side, an electric energy from the output side is stored in the reactor by upper-arm ON as a step-down process. Further, the electric power thus stored in the reactor is sent to the battery by upper-arm OFF. By controlling a ratio between ON times of the upper and lower arms that are turned on/off complementarily, an output voltage of the buck-boost converter is controlled.

FIG. 3 is a view of the first buck-boost circuit CNV 1 extracted from the voltage transducer 14 according to the present embodiment. From the viewpoint of the aforementioned functions of the upper arm and the lower arm, in the first buck-boost circuit CNV 1 illustrated in FIG. 3 , an arm (an S 1 -arm) including the switching element Si and an arm (an S 3 -arm) including the switching element S 3 serve as upper arms, and an arm (an S 2 -arm) including the switching element S 2 serves as a lower arm.

FIG. 4 is an extracted view of the second buck-boost circuit CNV 2 on a second-battery-B 2 side. Similarly to the first buck-boost circuit CNV 1 , in terms of roles of respective arms when viewed from the second buck-boost circuit CNV 2 , the S 1 -arm serves as an upper arm, and the S 2 -arm and the S 3 -arm serve as lower arms.

From the above description, the S 1 -arm, the S 2 -arm, and the S 3 -arm when viewed from each of the buck-boost circuits CNV 1 , CNV 2 have roles as described in Table 1 below.

As illustrated in Table 1, the voltage transducer 14 according to the present embodiment includes the S 3 -arm that functions as the upper arm for the first buck-boost circuit CNV 1 and also functions as the lower arm for the second buck-boost circuit CNV 2 , in addition to the S 1 -arm as the upper arm and the S 2 -arm as the lower arm.

In such a configuration, the first buck-boost circuit CNV 1 includes the S 3 -arm as another upper arm, and therefore, even if the S 1 -arm serving as the upper arm has an ON fault, a step-up/step-down operation is performable by using the S 2 -arm (the lower arm) and the S 3 -arm (the upper arm). Further, the second buck-boost circuit CNV 2 includes the S 3 -arm as another lower arm, and therefore, even if the S 2 -arm serving as the lower arm has an ON fault, a step-up/step-down operation is performable by using the S 1 -arm (the upper arm) and the S 3 -arm (the lower arm). As such, the voltage transducer according to the present embodiment is configured such that a step-up/step-down operation is performable even at the time of an ON fault of a switching element. Note that a step-up/step-down operation by the S 1 -arm and the S 2 -arm is performable with the S 3 -arm being turned on continuously.

An operation of the voltage transducer 14 in a normal time in which none of the switching elements S 1 , S 2 , S 3 has an ON fault is described with reference to FIGS. 5 to 8 .

FIGS. 5, 6 illustrate an operation at the time when voltages of the first battery B 1 and the second battery B 2 are stepped up by the voltage transducer 14 . FIG. 5 illustrates currents to cause an electric energy to be stored in the first reactor 34 and the second reactor 40 from the first battery B 1 and the second battery B 2 .

As described above, at the time of step-up storage, lower-arm ON is achieved, and upper-arm OFF is achieved accordingly. That is, in the first buck-boost circuit CNV 1 , the S 1 -arm and the S 3 -arm are turned off, and the S 2 -arm is turned on. In the meantime, in the second buck-boost circuit CNV 2 , the S 1 -arm is turned off, and the S 2 -arm and the S 3 -arm are turned on. The controlling portion 18 finds a logical sum (ON=1, OFF=0) thereof, and achieves S 1 -arm OFF, S 2 -arm ON, and S 3 -arm ON.

FIG. 6 illustrates an operation at the time when the electric energy thus stored is discharged to the load. As described above, at the time of step-up discharge, lower-arm OFF is achieved, and upper-arm ON is achieved accordingly. That is, in the first buck-boost circuit CNV 1 , the S 1 -arm and the S 3 -arm are turned on, and the S 2 -arm is turned off. In the meantime, in the second buck-boost circuit CNV 2 , the S 1 -arm is turned on, and the S 2 -arm and the S 3 -arm are turned off. The controlling portion 18 finds a logical sum thereof, and achieves S 1 -arm ON, S 2 -arm OFF, and S 3 -arm ON.

FIGS. 7, 8 illustrate an operation at the time when an output-side energy from the rotary electric machine 12 is stepped down. FIG. 7 exemplifies an operation at the time when the output-side energy is stored in the first reactor 34 and the second reactor 40 . At the time of step-down storage, upper-arm ON is achieved, and lower-arm OFF is achieved accordingly. That is, similarly to FIG. 6 , in the first buck-boost circuit CNV 1 , the S 1 -arm and the S 3 -arm are turned on, and the S 2 -arm is turned off. In the meantime, in the second buck-boost circuit CNV 2 , the S 1 -arm is turned on, and the S 2 -arm and the S 3 -arm are turned off. The controlling portion 18 finds a logical sum thereof, and achieves S 1 -arm ON, S 2 -arm OFF, and S 3 -arm ON.

FIG. 8 illustrates an operation at the time when electric energies stored in the first reactor 34 and the second reactor 40 in FIG. 7 are discharged to the first battery B 1 and the second battery B 2 . At the time of step-down discharge, upper-arm OFF is achieved, and lower-arm ON is achieved accordingly. That is, similarly to FIG. 5 , in the first buck-boost circuit CNV 1 , the S 1 -arm and the S 3 -arm are turned off, and the S 2 -arm is turned on. In the meantime, in the second buck-boost circuit CNV 2 , the S 1 -arm is turned off, and the S 2 -arm and the S 3 -arm are turned on. The controlling portion 18 finds a logical sum thereof, and achieves S 1 -arm OFF, S 2 -arm ON, and S 3 -arm ON.

As illustrated in FIGS. 5 to 8 , in a parallel step-up/step-down operation in a normal time, the switching element S 3 is in a continuously ON state, so that the batteries B 1 , B 2 are connected in parallel with each other, and the S 1 -arm and the S 2 -arm are controlled to be ON/OFF complementarily.

Note that, in the parallel step-up/step-down as illustrated in FIGS. 5 to 8 , the first buck-boost circuit CNV 1 and the second buck-boost circuit CNV 2 are controlled so as to become generally equipotential. For example, when there are predetermined voltage request and current request to the load, a voltage control to step up an output voltage to a requested voltage is performed in the second buck-boost circuit CNV 2 . In the meantime, in the first buck-boost circuit CNV 1 , a current control to output a current that compensates a difference between a requested current and an output current of the second buck-boost circuit CNV 2 is performed.

An operation of the voltage transducer 14 at the time when the switching element S 1 has an ON fault (short-circuit fault) is described with reference to FIGS. 9, 10 . Note that, in the descriptions of FIGS. 5 to 8 , the arms perform the same operations at the time of step-up storage and at the time of step-down discharge, and also at the time of step-up discharge and at the time of step-down storage. In view of this, in the following description, operations at the time of step-up storage and at the time of step-down discharge are described collectively, and operations at the time of step-up discharge and at the time of step-down storage are also described collectively.

As illustrated in FIG. 9 , at the time of an ON fault of the switching element S 1 (an ON fault of the S 1 -arm), an upper arm, viewed from the second buck-boost circuit CNV 2 , has an ON fault, so that an step-up/step-down operation using the circuit CNV 2 cannot be performed. In view of this, the controlling portion 18 performs the following switch control as a first failsafe mode. That is, the controlling portion 18 turns off the system main relay SMR 2 (contact opening) so as to separate the second battery B 2 from the voltage transducer 14 , thereby stopping an operation of the second buck-boost circuit CNV 2 . Then, a step-up/step-down operation is performed by the first buck-boost circuit CNV 1 .

FIG. 9 illustrates an operation at the time of step-up storage and at the time of step-down discharge, when the switching element S 1 has an ON fault. As described above, at the time of step-up storage and step-down discharge, an upper arm is turned off and a lower arm is turned on. That is, in the first buck-boost circuit CNV 1 (the S 1 -arm has an ON fault), the S 2 -arm is turned on, and the S 3 -arm is turned off. In the meantime, since the second buck-boost circuit CNV 2 stops its operation, an operation of the first buck-boost circuit CNV 1 is just reflected as a logical sum.

FIG. 10 illustrates an operation at the time of step-up discharge and at the time of step-down storage, when the switching element S 1 has an ON fault. As described above, at the time of step-up discharge and at the time of step-down storage, an upper arm is turned on and a lower arm is turned off. That is, in the first buck-boost circuit CNV 1 (the S 1 -arm has an ON fault), the S 2 -arm is turned off, and the S 3 -arm is turned on.

An operation of the voltage transducer 14 at the time when the switching element S 2 has an ON fault is described with reference to FIGS. 11, 12 . As illustrated in these figures, at the time of an ON fault of the switching element S 2 (an ON fault of the S 2 -arm), a lower arm, viewed from the first buck-boost circuit CNV 1 , has an ON fault, so that a step-up/step-down operation using the circuit CNV 1 cannot be performed. In view of this, the controlling portion 18 performs the following switch control as a second failsafe mode. That is, the controlling portion 18 turns off the system main relay SMR 1 so as to separate the first battery B 1 from the voltage transducer 14 , thereby stopping an operation of the first buck-boost circuit CNV 1 . Further, a step-up/step-down operation is performed by the second buck-boost circuit CNV 2 .

FIG. 11 illustrates an operation at the time of step-up storage and at the time of step-down discharge, when the switching element S 2 has an ON fault. At the time of step-up storage and at the time of step-down discharge, an upper arm is turned off and a lower arm is turned on. That is, in the second buck-boost circuit CNV 2 , the S 1 -arm is turned off (the S 2 -arm has an ON fault), and the S 3 -arm is turned on. In the meantime, since the first buck-boost circuit CNV 1 stops its operation, an operation of the second buck-boost circuit CNV 2 is just reflected as a logical sum.

FIG. 12 illustrates an operation at the time of step-up discharge and at the time of step-down storage, when the switching element S 2 has an ON fault. At the time of step-up discharge and at the time of step-down storage, an upper arm is turned on and a lower arm is turned off. That is, in the second buck-boost circuit CNV 2 , the S 1 -arm is turned on (the S 2 -arm has an ON fault), and the S 3 -arm is turned off.

As illustrated in FIGS. 9 to 12 , at the time when the S 1 -arm or the S 2 -arm has an ON fault, the S 3 -arm is controlled to be ON/OFF instead of the arm thus having an ON fault. Hereby, one of two buck-boost circuits CNV 1 , CNV 2 is usable, which makes it possible to perform a step-up/step-down operation at the time of an ON fault of a switching element, which cannot be performed in the related art.

An operation at the time of an ON fault of the switching element S 3 is the same as the parallel step-up/step-down operation ( FIGS. 5 to 8 ) in a normal time in which the switching element S 3 is turned on continuously. That is, fields for S 3 in an upper table in FIGS. 5 to 8 are replaced with “S 3 : ON fault,” so that an operation at the time of an ON fault of the switching element S 3 is obtained. In view of this, illustration and detailed descriptions thereof are omitted herein.

Note that the voltage transducer 14 according to the present embodiment is not limited to the aforementioned step-up/step-down operations, but can perform various operations. FIG. 13 illustrates an operation at the time when the first battery B 1 singularly supplies an electric power to the load without performing a step-up/step-down operation. At this time, the first buck-boost circuit CNV 1 and the second buck-boost circuit CNV 2 may not become equipotential, unlike the step-up/stepdown operation. In this case, an inter-battery current (current loop) via the S 3 -arm might occur between the first battery B 1 and the second battery B 2 depending on a potential difference. In view of this, in a B 1 single direct connection mode, the controlling portion 18 turns off the system main relay SMR 2 so as to separate the second battery B 2 from the voltage transducer 14 .

In the B 1 single direct connection mode, only the operation of the first buck-boost circuit CNV 1 at the time of step-up discharge in the parallel step-up/step-down operation in a normal time as illustrated in FIG. 6 is picked out and fixed. That is, in the B 1 single direct connection mode, the S 1 -arm is fixed to an ON state, the S 2 -arm is fixed to an OFF state, and the S 3 -arm is fixed to an ON state. Note that, in this mode, the S 1 -arm and the S 3 -arm are fixed to an ON state. Accordingly, even in a case where the S 1 -arm and the S 3 -arm have an ON fault, this mode can be used.

FIG. 14 illustrates an operation at the time when the second battery B 2 singularly supplies an electric power to the load, instead of FIG. 13 . In a B 2 single direct connection mode, the controlling portion 18 turns off the system main relay SMR 1 so as to separate the first battery B 1 from the voltage transducer 14 .

In the B 2 single direct connection mode, only the operation of the second buck-boost circuit CNV 2 at the time of step-up discharge in the parallel step-up/step-down operation in a normal time is picked out and fixed. That is, in the B 2 single direct connection mode, the S 1 -arm is fixed to an ON state, the S 2 -arm is fixed to an OFF state, and the S 3 -arm is fixed to an OFF state. Note that, in this mode, the S 1 -arm is fixed to an ON state. Accordingly, even in a case where the S 1 -arm has an ON fault, this mode can be used.

As described above, in the power supply system according to the present embodiment, an inter-battery current (current loop) via the S 3 -arm might occur between the first battery B 1 and the second battery B 2 . For example, as illustrated in FIG. 15 , in a case where the system main relays SMR 1 and SMR 2 are ON states and the first battery voltage VL 1 has a higher voltage than the second battery voltage VL 2 , even if the switching elements S 1 to S 3 are turned off, a current loop is formed between the first battery B 1 and the second battery B 2 via the diode D 3 of the S 3 -arm. Such an operation state can occur at the time when the power supply system starts, that is, after the system main relays SMR 1 , SMR 2 are turned on but before a step-up/step-down operation starts.

In view of this, in the power supply system 10 according to the present embodiment, a second battery voltage VL 2 is set higher than a first battery voltage VL 1 , thereby preventing the occurrence of the inter-battery current via the diode D 3 of the S 3 -arm. If the switching element S 3 is turned off in such a voltage relationship, it is possible to prevent the occurrence of the inter-battery current. That is, by controlling ON/OFF of the switching element S 3 , connection/disconnection between the first battery B 1 and the second battery B 2 can be controlled.

Note that, in order to start the parallel step-up/step-down operation after the power supply system starts, charging may be necessary due to a decrease in an SOC of the first battery B 1 . In such a case, the switching element S 3 is operated so as to charge the first battery B 1 from the second battery B 2 .

At the time of the charging, if a potential difference between the first battery voltage VL 1 and the second battery voltage VL 2 is large, a heavy-current may flow into the first battery B 1 , which might lead to deterioration of the first battery B 1 . In view of this, in the power supply system 10 according to the present embodiment, a collector-emitter conduction resistance of the switching element S 3 is adjusted, so as to control a charging current.

FIG. 16 exemplifies a control at the time of charging the first battery B 1 . The controlling portion 18 decreases a conduction ratio of the switching element S 3 as compared with a normal ON operation, thereby reducing a charging current amount to be supplied to the first battery B 1 via the switching element S 3 .

More specifically, the controlling portion 18 adjusts a gate voltage V G of the switching element S 3 , so that a collector-emitter voltage V CE of the switching element S 3 is set so as to be higher than that of a normal ON operation (half-ON). For example, the collector-emitter voltage V CE is adjusted so that a sum of the first battery voltage VL 1 and the collector-emitter voltage V CE of the switching element S 3 is slightly lower than the second battery voltage VL 2 . For example, the collector-emitter voltage V CE is adjusted so as to satisfy (VL 1 +V CE )−VL 2 =5V.

Alternatively, instead of the aforementioned voltage control, the controlling portion 18 may perform a current control of controlling the gate voltage V G of the switching element S 3 so that a first battery current IB 1 detected by a battery current sensor 54 A falls within a predetermined threshold.

FIG. 17 exemplifies a voltage transducer 14 according to another embodiment. The voltage transducer 14 is different from the voltage transducer 14 of FIG. 2 in a configuration of a first buck-boost circuit CNV 1 .

That is, a first battery B 1 is connected in parallel with a switching element S 3 , instead of a switching element S 2 . More specifically, the first battery B 1 is connected to a second node N 2 between the switching elements S 2 and S 3 , and a reference electric circuit 30 .

Further, the voltage transducer 14 is configured such that a first reactor 34 is connected in series with the first battery B 1 , and a first capacitor 36 is connected in parallel with the first battery B 1 . Further, a system main relay SMR 1 is provided between the voltage transducer 14 and the first battery B 1 . The other configuration is the same as the voltage transducer 14 illustrated in FIG. 2 .

FIG. 18 is an extracted view of a first buck-boost circuit CNV 1 . As illustrated in the figure, in the first buck-boost circuit CNV 1 , an S 1 -arm and an S 2 -arm serve as upper arms, and an S 3 -arm serves as a lower arm.

FIG. 19 is an extracted view of a second buck-boost circuit CNV 2 . As illustrated in the figure, in the second buck-boost circuit CNV 2 , the S 1 -arm serves as an upper arm, and the S 2 -arm and the S 3 -arm serve as lower arms.

The S 1 -arm, the S 2 -arm, and the S 3 -arm, viewed from each of the buck-boost circuits CNV 1 , CNV 2 , have roles as described in Table 2 below. The first buck-boost circuit CNV 1 includes the upper arms redundantly, and the second buck-boost circuit CNV 2 includes the lower arms redundantly.

An operation of the voltage transducer 14 in a normal time in which none of the switching elements S 1 , S 2 , S 3 has an ON fault is described with reference to FIGS. 20, 21 .

FIG. 20 illustrates an operation at the time of step-up storage and at the time of step-down discharge in a parallel step-up/step-down mode of the first battery B 1 and the second battery B 2 . As described above, at the time of step-up storage and at the time of step-down discharge, an upper arm is turned off and a lower arm is turned on. That is, in the first buck-boost circuit CNV 1 , the S 1 -arm and the S 2 -arm are turned off, and the S 3 -arm is turned on. In the meantime, in the second buck-boost circuit CNV 2 , the S 1 -arm is turned off, and the S 2 -arm and the S 3 -arm are turned on. The controlling portion 18 finds a logical sum thereof, and achieves S 1 -arm OFF, S 2 -arm ON, and S 3 -arm ON.

FIG. 21 illustrates an operation at the time of step-up discharge and at the time of step-down storage similarly in the parallel step-up/step-down mode. At the time of step-up discharge and at the time of step-down storage, an upper arm is turned on and a lower arm is turned off. That is, in the first buck-boost circuit CNV 1 , the S 1 -arm and the S 2 -arm are turned on, and the S 3 -arm is turned off. In the meantime, in the second buck-boost circuit CNV 2 , the S 1 -arm is turned on, and the S 2 -arm and the S 3 -arm are turned off. The controlling portion 18 finds a logical sum thereof, and achieves S 1 -arm ON, S 2 -arm ON, and S 3 -arm OFF.

As illustrated in FIGS. 20, 21 , in a parallel step-up/step-down operation in a normal time, the switching element S 2 is in a continuously ON state, and the S 1 -arm and the S 3 -arm are controlled to be ON/OFF complementarily.

An operation of the voltage transducer 14 at the time when the switching element S 1 has an ON fault (short-circuit fault) is described with reference to FIGS. 22, 23 . As illustrated in FIG. 22 , at the time of an ON fault of the switching element S 1 (an ON fault of the S 1 -arm), an upper arm, viewed from the second buck-boost circuit CNV 2 , has an ON fault, so that a step-up/step-down operation using the circuit CNV 2 cannot be performed. In view of this, the controlling portion 18 performs the following switch control as a first failsafe mode. That is, the controlling portion 18 turns off the system main relay SMR 2 (contact opening) so as to separate the second battery B 2 from the voltage transducer 14 , thereby stopping an operation of the second buck-boost circuit CNV 2 . Further, a step-up/step-down operation is performed by the first buck-boost circuit CNV 1 .

FIG. 22 illustrates an operation at the time of step-up storage and at the time of step-down discharge, when the switching element S 1 has an ON fault. At the time of step-up storage and at the time of step-down discharge, an upper arm is turned off and a lower arm is turned on. That is, in the first buck-boost circuit CNV 1 (the S 1 -arm has an ON fault), the S 2 -arm is turned off and the S 3 -arm is turned on. In the meantime, since the second buck-boost circuit CNV 2 stops its operation, an operation of the first buck-boost circuit CNV 1 is just reflected as a logical sum.

FIG. 23 illustrates an operation at the time of step-up discharge and at the time of step-down storage, when the switching element S 1 has an ON fault. At the time of step-up discharge and at the time of step-down storage, an upper arm is turned on and a lower arm is turned off. That is, in the first buck-boost circuit CNV 1 (the S 1 -arm has an ON fault), the S 2 -arm is turned on and the S 3 -arm is turned off.

An operation at the time of an ON fault of the switching element S 2 is the same as the parallel step-up/step-down operation ( FIGS. 20, 21 ) in a normal time in which the switching element S 2 is turned on continuously. That is, fields for S 2 in an upper table in FIGS. 20, 21 are replaced with “S 2 : ON fault,” so that an operation at the time of an ON fault of the switching element S 2 is obtained. In view of this, illustration and detailed descriptions thereof are omitted herein.

An operation of the voltage transducer 14 at the time when the switching element S 3 has an ON fault is described with reference to FIGS. 24, 25 . As illustrated in these figures, at the time of an ON fault of the switching element S 3 (an ON fault of the S 3 -arm), a lower arm, viewed from the first buck-boost circuit CNV 1 , has an ON fault, so that a step-up/step-down operation using the circuit CNV 1 cannot be performed. In view of this, the controlling portion 18 performs the following switch control as a second failsafe mode. That is, the controlling portion 18 turns off the system main relay SMR 1 so as to separate the first battery B 1 from the voltage transducer 14 , thereby stopping an operation of the first buck-boost circuit CNV 1 . Further, a step-up/step-down operation is performed by the second buck-boost circuit CNV 2 .

FIG. 24 illustrates an operation at the time of step-up storage and at the time of step-down discharge, when the switching element S 3 has an ON fault. At the time of step-up storage and at the time of step-down discharge, an upper arm is turned off and a lower arm is turned on. That is, in the second buck-boost circuit CNV 2 , the S 1 -arm is turned off, and the S 2 -arm is turned on (the S 3 -arm has an ON fault). In the meantime, since the first buck-boost circuit CNV 1 stops its operation, an operation of the second buck-boost circuit CNV 2 is just reflected as a logical sum.

FIG. 25 illustrates an operation at the time of step-up discharge and at the time of step-down storage, when the switching element S 3 has an ON fault. At the time of step-up discharge and at the time of step-down storage, an upper arm is turned on and a lower arm is turned off. That is, in the second buck-boost circuit CNV 2 , the S 1 -arm is turned on, and the S 2 -arm is turned off (the S 3 -arm has an ON fault).

As illustrated in FIGS. 22 to 25 , at the time when the S 1 -arm or the S 3 -arm have an ON fault, the S 2 -arm is controlled to be ON/OFF instead of the arm thus having an ON fault. Hereby, at least one of two buck-boost circuits CNV 1 , CNV 2 is usable, which makes it possible to perform a step-up/step-down operation at the time of an ON fault of a switching element, which cannot be performed in the related art.

FIG. 26 illustrates an operation at the time when the first battery B 1 singularly supplies an electric power to a load without performing a step-up/step-down operation. As described above, in this case, the first buck-boost circuit CNV 1 and the second buck-boost circuit CNV 2 may not become equipotential, unlike the step-up/stepdown operation. In this case, an inter-battery current (current loop) via the S 2 -arm might occur between the first battery B 1 and the second battery B 2 depending on a potential difference. In view of this, in a B 1 single direct connection mode, the controlling portion 18 turns off the system main relay SMR 2 so as to separate the second battery B 2 from the voltage transducer 14 .

In the B 1 single direct connection mode, only the operation of the first buck-boost circuit CNV 1 at the time of step-up discharge in the parallel step-up/step-down operation in a normal time as illustrated in FIG. 21 is picked out and fixed. That is, in the B 1 single direct connection mode, the S 1 -arm and the S 2 -arm are fixed to an ON state, and the S 3 -arm is fixed to an OFF state. Note that, in this mode, the S 1 -arm and the S 2 -arm are fixed to an ON state. Accordingly, even in a case where the S 1 -arm and the S 2 -arm have an ON fault, this mode can be used.

FIG. 27 illustrates an operation at the time when the second battery B 2 singularly supplies an electric power to the load, instead of FIG. 26 . In a B 2 single direct connection mode, the controlling portion 18 turns off the system main relay SMR 1 so as to separate the first battery B 1 from the voltage transducer 14 .

In the B 2 single direct connection mode, only the operation of the second buck-boost circuit CNV 2 at the time of step-up discharge in the parallel step-up/step-down operation in a normal time as illustrated in FIG. 21 is picked out and fixed. That is, in the B 2 single direct connection mode, the S 1 -arm is fixed to an ON state, and the S 2 -arm and the S 3 -arm are fixed to an OFF state. Note that, in this mode, the S 1 -arm is fixed to an ON state. Accordingly, even in a case where the S 1 -arm has an ON fault, this mode can be used.

As described above, in the power supply system according to the present embodiment, an inter-battery current (current loop) via the S 2 -arm might occur between the first battery B 1 and the second battery B 2 . In view of this, in the power supply system 10 according to the present embodiment, a second battery voltage VL 2 is set higher than a first battery voltage VL 1 , thereby preventing the occurrence of the inter-battery current via a diode D 2 of the S 2 -arm. If the switching element S 2 is turned off in such a voltage relationship, it is possible to prevent the occurrence of the inter-battery current. That is, by controlling ON/OFF of the switching element S 2 , connection/disconnection between the first battery B 1 and the second battery B 2 can be controlled.

Further, at the time when the first battery B 1 is charged from the second battery B 2 , a half-ON control is performed on the switching element S 2 as mentioned earlier, so that a collector-emitter conduction resistance of the switching element S 2 is adjusted, so as to control a charging current.