JP2022095037A - Power conversion device - Google Patents

Abstract

To provide a power conversion device capable of blocking flowing of current into a part where a power conversion is performed by a blocking switch and capable of easily improving a function by an element connected between the part where the power conversion is performed and the blocking switch.SOLUTION: A power conversion device 3 has a power conversion part 5, a blocking switch 70, and a diode 60. The power conversion part 5 has a second circuit 20. The second circuit 20 has an inductor 24 electrically connected to a second conducting path 52, and outputs DC voltage to the second conducting path 52 when AC voltage is generated in a second coil 32. A cathode of the diode 60 is electrically connected to a portion between the inductor 24 and the blocking switch 70 in the second conducting path 52. An anode of the diode 60 is electrically connected to ground.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a power converter.

Patent Document 1 discloses a redundant power supply system including a first battery, a second battery, a first DCDC converter, and a second DCDC converter. Further, the redundant power supply system is provided with a battery protection circuit.

JP-A-2019-187062

The redundant power supply system of Patent Document 1 includes a battery protection circuit, but this battery protection circuit is only for the purpose of preventing current from flowing from the second DCDC converter side to the second battery side, and is on the converter side. It does not have a function to prevent the flow into. For example, in the redundant power supply system of Patent Document 1, when a ground fault occurs in the second DCDC converter, a large current flows from the second battery to the second DCDC converter.

In the present disclosure, power conversion can be cut off by a cutoff switch from flowing current into a power conversion part, and the function can be easily enhanced by an element connected between the power conversion part and the cutoff switch. Provide the device.

The power conversion device, which is one of the present disclosures, is
The first circuit having a switching element, a transformer unit having a first coil and a second coil connected to the first circuit, and a second circuit connected to the second coil, said first. A power conversion device that performs voltage conversion between a first conductive path connected to one circuit and a second conductive path connected to the second circuit.
A cutoff switch that switches between a state in which the current flows to the second circuit side in the second conductive path and a state in which the current is allowed to flow to the second circuit side.
A diode electrically connected to the second conductive path and
Have,
The first circuit performs at least a first conversion operation of converting a DC voltage applied to the first conductive path by the switching operation of the switching element and generating an AC voltage in the first coil of the transformer unit.
When an AC voltage is generated in the first coil by the first conversion operation, the transformer unit generates an AC voltage in the second coil.
The second circuit includes an inductor that is electrically connected to the second conductive path, and outputs a DC voltage to the second conductive path when an AC voltage is generated in the second coil.
The cathode of the diode is electrically connected to the portion of the second conductive path between the inductor and the cutoff switch, and the anode of the diode is electrically connected to the ground.

The power conversion device, which is one of the present disclosures, is
The first circuit having a switching element, a transformer unit having a first coil and a second coil connected to the first circuit, and a second circuit connected to the second coil, said first. A power conversion device that performs voltage conversion between a first conductive path connected to one circuit and a second conductive path connected to the second circuit.
A cutoff switch that switches between a state in which the current flows to the second circuit side in the second conductive path and a state in which the current is allowed to flow to the second circuit side.
An element part having a diode or a switch,
A control unit that controls the cutoff switch, the first circuit, and the second circuit.
Have,
A capacitor is electrically connected to the first conductive path.
The first circuit has a first conversion operation of converting a DC voltage applied to the first conductive path by a switching operation of the switching element to generate an AC voltage in the first coil of the transformer unit, and the first conversion operation. At least the second conversion operation of converting the AC voltage generated in the coil and applying the DC voltage to the first conductive path is performed.
The second circuit has a third conversion operation of converting a DC voltage applied to the second conductive path to generate an AC voltage in the second coil and a third conversion operation of converting the AC voltage generated in the second coil. 2 Perform at least the fourth conversion operation of applying a DC voltage to the conductive path,
The transformer unit generates an AC voltage in the second coil when an AC voltage is generated in the first coil by the first conversion operation, and an AC voltage is generated in the second coil by the third conversion operation. In some cases, an AC voltage is generated in the first coil.
The second circuit comprises an inductor that is electrically connected to the second conductive path.
One end of the element portion is electrically connected to a portion of the second conductive path between the inductor and the cutoff switch, and the other end of the element portion is electrically connected to the ground.
The cutoff switch, the element unit, and the inductor form a chopper circuit that performs a voltage conversion operation in the second conductive path.
The control unit charges the capacitor by causing the voltage conversion operation of the chopper circuit, the third conversion operation of the second circuit, and the second conversion operation of the first circuit to be performed in parallel. Precharge control is performed.

The technique according to the present disclosure can cut off the flow of current to the part where power conversion is performed by a cutoff switch, and the function is easily enhanced by an element connected between the part where power conversion is performed and the cutoff switch. obtain.

FIG. 1 is a circuit diagram illustrating an in-vehicle system including the power conversion device of the first embodiment. FIG. 2 is a circuit diagram illustrating an in-vehicle system including the power conversion device of the second embodiment. FIG. 3 is a circuit diagram illustrating an in-vehicle system including the power conversion device of the third embodiment. FIG. 4 is a circuit diagram illustrating an in-vehicle system including the power conversion device of the fourth embodiment. FIG. 5 is an explanatory diagram illustrating the first switching control in the power conversion device of the fourth embodiment. FIG. 6 is an explanatory diagram illustrating a second switching control in the power conversion device of the fourth embodiment. FIG. 7 is an explanatory diagram illustrating a third switching control in the power conversion device of the fourth embodiment. FIG. 8 is an explanatory diagram illustrating a fourth switching control in the power conversion device of the fourth embodiment. The upper part of FIG. 9 is an explanatory diagram for explaining the change in the duty of each PWM signal with the passage of time when the precharge control is performed in the power conversion device of the fourth embodiment, and the lower part of FIG. 9 is the fourth diagram. It is explanatory drawing which shows the change of the charge voltage of a capacitor with the lapse of time when the precharge control is performed in the power conversion apparatus of embodiment.

[Explanation of Embodiments of the present disclosure]
Hereinafter, embodiments according to the present disclosure are listed and exemplified. The features [1] to [9] exemplified below may be combined in any combination without any contradiction.

[1] It has a first circuit having a switching element, a transformer unit having a first coil and a second coil connected to the first circuit, and a second circuit connected to the second coil. A power conversion device that performs voltage conversion between a first conductive path connected to the first circuit and a second conductive path connected to the second circuit.
A cutoff switch that switches between a state in which the current flows to the second circuit side in the second conductive path and a state in which the current is allowed to flow to the second circuit side.
A diode electrically connected to the second conductive path and
Have,
The first circuit performs at least a first conversion operation of converting a DC voltage applied to the first conductive path by the switching operation of the switching element and generating an AC voltage in the first coil of the transformer unit.
When an AC voltage is generated in the first coil by the first conversion operation, the transformer unit generates an AC voltage in the second coil.
The second circuit includes an inductor that is electrically connected to the second conductive path, and outputs a DC voltage to the second conductive path when an AC voltage is generated in the second coil.
A power conversion device in which the cathode of the diode is electrically connected to a portion of the second conductive path between the inductor and the cutoff switch, and the anode of the diode is electrically connected to the ground.

The power conversion device of the above [1] can cut off the current flowing to the second circuit side in the second conductive path when the cutoff switch is switched to the cutoff state. Therefore, this power conversion device can prevent the current from flowing into the second circuit through the second conductive path by the cutoff switch, and can protect the components related to the second circuit. Moreover, this power conversion device can suppress the influence of the energy stored in the inductor on the vicinity of the second circuit immediately after the cutoff switch is cut off by the presence of the diode. Therefore, this power conversion device can easily enhance the protection function by the element connected between the portion that performs power conversion and the cutoff switch.

The power conversion device of [2] has the following features in the power conversion device of [1] above. The power conversion device of [2] has a plurality of the above-mentioned second circuits. The transformer unit includes a plurality of the second coils. Each of the above second circuits is connected to each of the above second coils. The second conductive path has a common conductive path through which a current flows from any of the plurality of second circuits. The cutoff switch is provided in the common conductive path. In the common conductive path, the cathode of the diode is electrically connected between the plurality of second circuits and the cutoff switch.

In the power conversion device of the above [2], since a plurality of second circuits are connected in parallel between the transformer section and the common conductive path, one of the second circuits must be stopped for some reason. However, it is easy to continue the power conversion by the other second circuit. Moreover, this power conversion device has a configuration in which a cutoff switch is provided in a common conductive path, and the cathode of a diode is electrically connected between a plurality of second circuits and the cutoff switch. This power conversion device can realize a function of preventing current from flowing into the second circuit through the second conductive path by reducing the number of cutoff switches, and affects the vicinity of the second circuit immediately after the cutoff switch is cut off. The function of suppressing the number of diodes can be reduced.

The power conversion device of [3] has the following features in the power conversion device of [1] above. The power conversion device of [3] has a plurality of the second circuits, a plurality of cutoff switches, and a plurality of the diodes. The transformer unit includes a plurality of the second coils. Each of the above second circuits is connected to each of the above second coils. The second conductive path includes a plurality of individual conductive paths and a common conductive path. Each of the individual conductive paths is electrically connected to each of the plurality of second circuits, and the end opposite to the second circuit is connected to the common conductive path. One end of the common conductive path is connected to the plurality of individual conductive paths, and a current flows from any of the plurality of individual conductive paths. Each of the above cutoff switches is provided in each of the above individual conductive paths. The cathode of each diode is electrically connected between the cutoff switch and the inductor of each second circuit in each individual conduction path.

In the power conversion device of the above [3], since each second circuit is provided between the transformer section and each individual conductive path, even if one of the second circuits has to be stopped for some reason, the other It is easy to continue power conversion by the second circuit of. Further, this power conversion device can realize a function of preventing current from flowing into the second circuit and a function of suppressing the influence on the vicinity of the second circuit immediately after the cutoff switch is cut off in each individual conductive path. .. For example, in this power conversion device, even when the cutoff switch of any one of the individual conductive paths is turned off, the power conversion by the second circuit is performed by operating the second circuit corresponding to the other individual conductive path. Can be continued. Moreover, when the second circuit corresponding to the other individual conductive path is operated in the state where one individual conductive path is cut off, this power conversion device functions as a cutoff switch and a diode in the other individual conductive path. The function of can be maintained separately from the above-mentioned individual conductive path.

The power conversion device according to [4] has the following features in the power conversion device according to any one of the above [1] to [3]. The power conversion device of [4] includes a control unit that controls the cutoff switch. The cutoff switch, the diode, and the inductor form a chopper circuit. The control unit causes the chopper circuit to perform a voltage conversion operation.

The power conversion device of the above [4] not only suppresses the energy stored in the inductor from affecting the vicinity of the second circuit immediately after the cutoff switch is cut off, but also uses a diode as a part of the chopper circuit. be able to. Therefore, this power conversion device can realize further high functionality with a simple configuration.

The power conversion device of [5] has the following features in the power conversion device of [4] above. A capacitor is electrically connected to the first conductive path. The first circuit at least performs a second conversion operation of converting an AC voltage generated in the first coil and applying a DC voltage to the first conductive path. The second circuit converts the DC voltage applied to the second conductive path to generate an AC voltage in the second coil, and converts the AC voltage generated in the second coil into the second coil. (2) At least the fourth conversion operation of applying a DC voltage to the conductive path is performed. The transformer unit generates an AC voltage in the first coil when an AC voltage is generated in the second coil by the third conversion operation. The control unit charges the capacitor by performing the voltage conversion operation of the chopper circuit, the third conversion operation of the second circuit, and the second conversion operation of the first circuit in parallel. Precharge control is performed.

In the power conversion device of the above [5], not only the diode is used as a part of the chopper circuit, but also the precharge operation can be performed by this chopper circuit. Therefore, this power conversion device can be further enhanced in functionality with a simple configuration. Moreover, this power conversion device can adjust the input voltage in the third conversion operation by the voltage conversion operation in the chopper circuit.

[6] It has a first circuit having a switching element, a transformer unit having a first coil and a second coil connected to the first circuit, and a second circuit connected to the second coil. A power conversion device that performs voltage conversion between a first conductive path connected to the first circuit and a second conductive path connected to the second circuit.
A cutoff switch that switches between a state in which the current flows to the second circuit side in the second conductive path and a state in which the current is allowed to flow to the second circuit side.
An element part having a diode or a switch,
A control unit that controls the cutoff switch, the first circuit, and the second circuit.
Have,
A capacitor is electrically connected to the first conductive path.
The first circuit has a first conversion operation of converting a DC voltage applied to the first conductive path by a switching operation of the switching element to generate an AC voltage in the first coil of the transformer unit, and the first conversion operation. At least the second conversion operation of converting the AC voltage generated in the coil and applying the DC voltage to the first conductive path is performed.
The second circuit has a third conversion operation of converting a DC voltage applied to the second conductive path to generate an AC voltage in the second coil and a third conversion operation of converting the AC voltage generated in the second coil. 2 Perform at least the fourth conversion operation of applying a DC voltage to the conductive path,
The transformer unit generates an AC voltage in the second coil when an AC voltage is generated in the first coil by the first conversion operation, and an AC voltage is generated in the second coil by the third conversion operation. In some cases, an AC voltage is generated in the first coil.
The second circuit comprises an inductor that is electrically connected to the second conductive path.
One end of the element portion is electrically connected to a portion of the second conductive path between the inductor and the cutoff switch, and the other end of the element portion is electrically connected to the ground.
The cutoff switch, the element unit, and the inductor form a chopper circuit that performs a voltage conversion operation in the second conductive path.
The control unit charges the capacitor by causing the voltage conversion operation of the chopper circuit, the third conversion operation of the second circuit, and the second conversion operation of the first circuit to be performed in parallel. A power conversion device that performs precharge control.

The power conversion device of the above [6] can cut off the current flowing to the second circuit side in the second conductive path when the cutoff switch is switched to the cutoff state. Therefore, this power conversion device can prevent the current from flowing into the second circuit through the second conductive path by the cutoff switch, and can protect the components related to the second circuit. Further, in this power conversion device, an element portion is connected to a path between the inductor and a cutoff switch, and a chopper circuit is formed by these. Therefore, the function of this power conversion device can be easily enhanced by an element connected between the portion that performs power conversion and the cutoff switch. Further, since this power conversion device can perform a precharge operation by using such a chopper circuit, it is possible to realize further high functionality with a simple configuration. Moreover, this power conversion device can adjust the input voltage in the third conversion operation by the voltage conversion operation in the chopper circuit.

The power conversion device according to [7] has the following features in the power conversion device according to any one of the above [1] to [6]. The first conductive path is a conductive path that is electrically connected to the first battery and to which a DC voltage is applied from the first battery. The second conductive path is a conductive path that is electrically connected to the second battery and to which a DC voltage is applied from the second battery.

The power conversion device can transmit electric power between a first battery electrically connected to the first conductive path and a second battery electrically connected to the second conductive path. Then, this power conversion device can prevent a large current from flowing from the second battery to the second circuit by shutting off the cutoff switch when a ground fault occurs in the second circuit.

The power conversion device according to [8] is the power conversion device according to any one of the above [2] or [3], or the power conversion device according to any one of the above [4] to [7]. In quoting the above [2] or [3], it has the following features. The power conversion device of [8] includes a plurality of the first circuits and a plurality of transformer units. The first coil of each of the plurality of transformer portions is magnetically coupled to the second coil of each of the plurality of transformer portions. One side of each of the first circuits is connected to the first conductive path, and the other side is connected to each of the first coils. A power conversion unit formed by connecting each of the first circuits, each of the transformer units, and each of the second circuits is connected in parallel between the first conductive path and the common conductive path.

The power conversion device of the above [8] can operate with higher independence in each power conversion unit.

The power conversion device according to [9] is the power conversion device according to any one of the above [5] or [6], or the power conversion device according to any one of the above [7] or [8]. In quoting the above [5] or [6], it has the following features. In the power conversion device of [9], when the control unit starts the precharge control at a predetermined time, the control unit gives a PWM signal to the cutoff switch of the chopper circuit to give the second conductive path in the second conductive path. The step-down control is performed so that the voltage applied to the portion on the opposite side of the circuit is stepped down and the step-down operation of applying the DC voltage to one end side of the inductor is performed. In the precharge control, the control unit performs the step-down control and the control for causing the second circuit to perform the third conversion operation in parallel. Further, the control unit starts the precharge control at the predetermined time, and then performs the soft start control in which the duty of the PWM signal is gradually increased in the step-down control.

The power conversion device of [9] can perform the third conversion operation in a state where the voltage on one end side of the inductor is lowered in the initial period immediately after the start of the precharge control. Therefore, this power conversion device tends to increase the duty given to the second circuit when the third conversion operation is performed even in the initial period.
[Details of Embodiments of the present disclosure]

<First Embodiment>
1. 1. Basic Configuration of In-Vehicle System FIG. 1 illustrates the power conversion device 3 according to the first embodiment. The power conversion device 3 is used as a part of the in-vehicle system 1 mounted on the vehicle. The vehicle on which the in-vehicle system 1 is mounted is, for example, a vehicle such as a PHEV (Plug-in Hybrid Electric Vehicle) or an EV (Electric Vehicle). The in-vehicle system 1 includes a high-voltage battery 181 and a low-voltage battery 182, a power conversion device 3, a low-voltage load 190, and the like. The high-voltage battery 181 and the low-voltage battery 182, and the power conversion device 3 constitute an in-vehicle power supply system.

The high voltage battery 181 is a battery capable of outputting a relatively high voltage. The high voltage battery 181 outputs a predetermined voltage (for example, 300V) when fully charged. The high voltage battery 181 supplies power to, for example, a drive unit (not shown). The drive unit includes, for example, an inverter and a motor, and is a device that applies a rotational force to the wheels of a vehicle on which the in-vehicle system 1 is mounted by a motor. The output voltage when the high-voltage battery 181 is fully charged is higher than the output voltage when the low-voltage battery 182 is fully charged. The high voltage battery 181 may be composed of a lithium ion battery or another type of storage battery. In the high-voltage battery 181 the high-potential side electrode is electrically connected to the wiring portion 171 and the low-potential side electrode is electrically connected to the wiring portion 172. The wiring unit 171 is a conductive path to which a predetermined voltage is applied from the high-voltage battery 181 and the wiring unit 173 is a reference conductive path maintained at the ground potential. The high-voltage battery 181 applies the predetermined voltage (for example, 300 V) between the first conductive path 51 and the third conductive path 53 via the wiring portions 171 and 173. The electrode on the high potential side of the high voltage battery 181 and the first conductive path 51 have, for example, the same potential.

In the present specification, the “voltage” is a voltage based on the ground potential unless otherwise specified. In the present specification, "electrically connected" may be connected in a configuration that allows current to flow, may be short-circuited without interposing an element, and may be connected by interposing a conductive element. It may be connected by letting it.

Although not shown in FIG. 1, another load (for example, an air conditioner, a heater, etc.) that can be operated by being supplied with electric power from the high-voltage battery 181 in a configuration in which electric power can be supplied through the first conductive path 51. (Electrical equipment) may be provided.

The low voltage battery 182 is a battery capable of outputting a relatively low voltage. The low voltage battery 182 supplies power to the low voltage load 190. The low voltage battery 182 may be composed of a lead storage battery or another type of storage battery. The low voltage battery 182 outputs a predetermined voltage (for example, 12V) when fully charged. In the low voltage battery 182, the electrode on the high potential side is electrically connected to the wiring portion 172, and the electrode on the low potential side is electrically connected to the ground. The electrode on the high potential side of the low voltage battery 182 and the wiring portion 172 are, for example, at the same potential.

The low voltage load 190 is an electric component that operates by being supplied with electric power from the low voltage battery 182. The low voltage load 190 is a known in-vehicle electric component. The low pressure load 190 may include, for example, an electric power steering system, an electric parking brake, a lighting device, a wiper drive unit, a navigation device, an audio device, and the like.

2. 2. Outline of the Power Conversion Device The power conversion device 3 is configured as a converter capable of performing voltage conversion between the first conductive path 51 and the second conductive path 52. In the example of FIG. 1, the power conversion device 3 is configured as an isolated DCDC converter. The power conversion device 3 includes a conversion circuit unit 4 and a control unit 7 that controls the conversion circuit unit 4. The conversion circuit unit 4 is a part of the power conversion device 3 excluding the capacitor 41 and the control unit 7. The conversion circuit unit 4 includes a power conversion unit 5, a capacitor 42, a cutoff switch 70, and a diode 60.

3. 3. Configuration of Power Conversion Unit The power conversion unit 5 includes a first circuit 10, a second circuit 20, and a transformer 30. The power conversion unit 5 may perform a step-down operation in which a voltage applied to the first conductive path 51 is used as an input voltage, the input voltage is stepped down, and an output voltage is applied to the second conductive path 52. The power conversion device 3 can perform a boosting operation in which a voltage applied to the second conductive path 52 is used as an input voltage, the input voltage is boosted, and an output voltage is applied to the first conductive path 51.

The first circuit 10 is a switching circuit configured as a full bridge circuit. The first circuit 10 includes a plurality of switching elements 10A, 10B, 10C, 10D and an inductor 13. The first circuit 10 is electrically connected to the first conductive path 51 and the third conductive path 53. In the example of FIG. 1, each of the switching elements 10A, 10B, 10C, and 10D is configured by an N-channel type MOSFET (Metal Oxide Semiconductor Field Effect Transistor). However, the switching elements 10A, 10B, 10C, and 10D may be composed of other types of switching elements.

The switching element 10A and the switching element 10B are connected in series between the first conductive path 51 and the third conductive path 53. The switching element 10C and the switching element 10D are connected in series between the first conductive path 51 and the third conductive path 53. The drains of the switching elements 10A and 10C are electrically connected to the first conductive path 51. Each source of the switching elements 10B and 10D is electrically connected to the third conductive path 53. The source of the switching element 10A is electrically connected to the drain of the switching element 10B. The source of the switching element 10C is electrically connected to the drain of the switching element 10D.

One end of the inductor 13 is electrically connected to the second connection point P2 between the switching element 10C and the switching element 10D, and is electrically connected to the source of the switching element 10C and the drain of the switching element 10D. The other end of the inductor 13 is electrically connected to one end of the first coil 31. The other end of the first coil 31 is electrically connected to the first connection point P1 between the switching element 10A and the switching element 10B, and is electrically connected to the source of the switching element 10A and the drain of the switching element 10B.

The first circuit 10 may perform the first conversion operation and the second conversion operation. In the first conversion operation, the DC voltage applied to the first conductive path 51 by the switching operation of the switching elements 10A, 10B, 10C, and 10D is used as an input voltage, and this input voltage is converted into an AC voltage to the first coil 31. This is an operation to generate an AC voltage. The second conversion operation is a rectification operation in which the AC voltage generated in the first coil 31 is converted and a DC voltage is applied to the first conductive path 51.

The transformer 30 corresponds to an example of the transformer unit. The transformer 30 has a first coil 31 connected to the first circuit 10 and a second coil 32 connected to the second circuit 20. The transformer 30 is configured as a center tap type transformer. The second coil 32 has coils 32A and 32B, and a center tap is provided between the coils 32A and the coils 32B. The transformer 30 generates an AC voltage in the second coil 32 when, for example, an AC voltage is generated in the first coil 31 by the above-mentioned first conversion operation. The transformer 30 generates an AC voltage in the first coil 31 when an AC voltage is generated in the second coil 32 by, for example, a third conversion operation described later.

The second circuit 20 is electrically connected to the second conductive path 52 and the second coil 32. The second circuit 20 includes switch elements 21 and 22, and an inductor 24. In the example of FIG. 1, each of the switch elements 21 and 22 is composed of an N-channel MOSFET. The switch element 21 is connected between one end of the coil 32A of the transformer 30 and the ground. The drain of the switch element 21 is electrically connected to one end of the coil 32A and the source is electrically connected to the ground. When the switch element 21 is in the off state, no current flows from the coil 32A side to the ground side. The switch element 22 is connected between one end of the coil 32B of the transformer 30 and the ground. The drain of the switch element 22 is electrically connected to one end of the coil 32B and the source is electrically connected to the ground. When the switch element 22 is in the off state, no current flows from the coil 32B side to the ground side.

One end of the inductor 24 is electrically connected to the center tap between the coil 32A and the coil 32B, and is electrically connected to the other end of the coil 32A and the other end of the coil 32B. The other end of the inductor 24 is electrically connected to the second conductive path 52. The other end of the inductor 24 has the same potential as the second conductive path 52.

The second circuit 20 has a third conversion operation of converting the DC voltage applied to the second conductive path 52 to generate an AC voltage in the second coil 32 and a second conversion operation of converting the AC voltage generated in the second coil 32. At least the fourth conversion operation of applying a DC voltage to the conductive path 52 is performed. The fourth conversion operation is a rectification operation that outputs a DC voltage to the second conductive path 52 when an AC voltage is generated in the second coil 32 in response to the first conversion operation described above. This rectification operation may be a diode rectification operation performed while the switch elements 21 and 22 are maintained in the off state, or may be a known synchronous rectification operation in which the switch elements 21 and 22 are synchronized and turned on and off. When the second circuit 20 outputs a DC voltage to the second conductive path 52 by performing a rectifying operation, the output voltage is smoothed by the inductor 24 and the capacitor 42 described later.

The control unit 7 is an information processing device having a calculation function, an information processing function, a detection function, and the like. The control unit 7 is mainly composed of, for example, a microcomputer, and has an arithmetic unit such as a CPU (Central Processing Unit), a semiconductor memory, an A / D converter, and the like.

The control unit 7 can acquire a value indicating the voltage of the first conductive path 51 directly or from a first voltage detection unit (not shown). The control unit 7 can acquire a value indicating the voltage of the second conductive path 52 directly or from a second voltage detection unit (not shown). Further, although not shown in FIG. 1, a current sensor for detecting the value of the current flowing through the first conductive path 51 may be provided, and the current sensor for detecting the value of the current flowing through the second conductive path 52 may be provided. May be provided. In this case, the control unit 7 may be configured to be able to acquire the value of the current flowing through the first conductive path 51 from the current sensor, or to acquire the value of the current flowing through the second conductive path 52 from the current sensor. It may be.

4. Configuration of Capacitor, Cutoff Switch, and Diode The capacitor 41 is provided between the high voltage battery 181 and the first circuit 10. In the capacitor 41, one electrode is electrically connected to the first conductive path 51, and the other electrode is electrically connected to the third conductive path 53. A voltage between the first conductive path 51 and the third conductive path 53 is applied to both ends of the capacitor 41.

In the capacitor 42, one electrode is electrically connected to the second conductive path 52, and the other electrode is electrically connected to the ground. A voltage between the second conductive path 52 and the ground is applied to both ends of the capacitor 42.

The cutoff switch 70 is provided in the second conductive path 52. The cutoff switch 70 switches between a state in which the current flows from the wiring portion 172 side to the second circuit 20 side in the second conductive path 52 and a state in which the current is allowed to flow. In the example of FIG. 1, the cutoff switch 70 includes switch elements 71 and 72. The switch elements 71 and 72 are both configured as N-channel MOSFETs. The switch elements 71 and 72 are arranged in opposite directions to each other and are connected in series.

When both the switch elements 71 and 72 are in the off state, the current flow from the wiring portion 172 side to the second circuit 20 side in the second conductive path 52 is cut off, and the current flows from the second circuit 20 side to the wiring portion 172 side. The flow of current toward is also cut off. That is, when both the switch elements 71 and 72 are in the off state, bidirectional energization is cut off. When both the switch elements 71 and 72 are in the ON state, a current flows from the wiring portion 172 side to the second circuit 20 side in the second conductive path 52, and also toward the wiring portion 172 side from the second circuit 20 side. It is also permissible for current to flow. That is, when both the switch elements 71 and 72 are in the ON state, bidirectional energization is allowed.

The diode 60 is electrically connected to the second conductive path 52. The cathode of the diode 60 is electrically connected to the portion 52A between the inductor 24 and the cutoff switch 70 in the second conductive path 52. The anode of the diode 60 is electrically connected to the ground. In the example of FIG. 1, one electrode of the capacitor 42 is electrically connected between the connection point P3 to which the anode of the diode 60 is electrically connected and the inductor 24 in the second conductive path 52.

5. Operation of the power conversion device In the power conversion device 3, the control unit 7 causes the power conversion unit 5 to perform a conversion operation. The control unit 7 causes the power conversion unit 5 to perform a step-down operation at a predetermined first period in the normal state. When the power conversion unit 5 is caused to perform the step-down operation, the control unit 7 causes the first circuit 10 to perform the above-mentioned first conversion operation and the second circuit 20 to perform the above-mentioned fourth conversion operation. The fourth control is performed in parallel. By performing such control by the control unit 7, the output voltage of the first target value is applied to the second conductive path 52. The first target value may be a value slightly higher than the output voltage when the low-voltage battery 182 is fully charged, and may be about the same as the output voltage when the low-voltage battery 182 is fully charged. When the power conversion unit 5 is to perform a step-down operation, the control unit 7 adopts a known phase shift method and outputs a PWM signal toward each gate of the switching elements 10A, 10B, 10C, and 10D.

The control unit 7 causes the power conversion unit 5 to perform a boosting operation at a predetermined second period in the normal state. When the power conversion unit 5 causes the power conversion unit 5 to perform the boosting operation, the control unit 7 causes the first circuit 10 to perform the above-mentioned second conversion operation and the second circuit 20 to perform the above-mentioned third conversion operation. The third control is performed in parallel. By performing such control by the control unit 7, the output voltage of the second target value is applied to the first conductive path 51. The second target value may be a value slightly higher than the output voltage when the high voltage battery 181 is fully charged, or may be about the same as the output voltage when the high voltage battery 181 is fully charged.

The above-mentioned normal state is a state in which a predetermined abnormal state has not occurred. The predetermined abnormal state is, for example, a state in which the voltage of the second conductive path 52 is less than the threshold value. This threshold value is lower than the output voltage when the low-voltage battery 182 is fully charged, and is higher than 0V.

When the abnormal state occurs while the step-down operation or the step-up operation is performed in the normal state, the control unit 7 switches the cutoff switch 70 to the off state. When the control unit 7 switches the cutoff switch 70 to the off state, both the switch elements 71 and 72 are turned off, and the energization straddling the cutoff switch 70 is cut off. For example, when a ground fault occurs in the second circuit 20 and the voltage of the second conductive path 52 drops sharply below the threshold value, the control unit 7 switches the cutoff switch 70 to the off state via the cutoff switch 70. It is possible to block the flow of current to the second circuit 20 side. Therefore, the parts related to the second circuit 20 are protected.

On the other hand, if the control unit 7 shuts off the cutoff switch 70 while the power conversion unit 5 is performing the conversion operation, the path for releasing the energy stored in the inductor 24 is cut off at the time of the cutoff. There is a concern about the influence on the element (such as the capacitor 42 becoming overvoltage). However, in the configuration of FIG. 1, since the diode 60 is provided, when the control unit 7 shuts off the cutoff switch 70 while the power conversion unit 5 is performing the conversion operation, it is accumulated in the inductor 24 at the time of cutoff. The energy that is being used can be converted and consumed. Therefore, the presence of the diode 60 can suppress the energy stored in the inductor 24 from affecting the vicinity of the second circuit 20 immediately after the cutoff switch 70 is cut off. As described above, the power conversion device 3 can easily enhance the protection function by the element connected between the portion performing power conversion and the cutoff switch 70.

<Second Embodiment>
The following description relates to the power conversion device 203 of the second embodiment.
The vehicle-mounted system 201 shown in FIG. 2 is different from the vehicle-mounted system 1 of FIG. 1 only in that the power conversion device 3 is changed to the power conversion device 203, and is the same as the vehicle-mounted system 1 in other points. Therefore, in the vehicle-mounted system 201, the parts having the same configuration as the vehicle-mounted system 1 are designated by the same reference numerals as those of the vehicle-mounted system 1, and detailed description thereof will be omitted.

The power conversion device 203 of the second embodiment is different from the power conversion device 3 of the first embodiment in that the conversion circuit unit 204 is provided in addition to the conversion circuit unit 4. That is, the power conversion device 3 of the first embodiment has a configuration in which the conversion circuit unit 204 is omitted from the power conversion device 203 of the second embodiment.

The power conversion device 203 of the second embodiment is provided with a conversion circuit unit 204 in addition to the conversion circuit unit 4 of FIG. 1, and a conversion circuit unit 4 and a conversion circuit unit are provided between the first conductive path 51 and the wiring unit 172. 204 is connected in parallel. The conversion circuit unit 4 and the conversion circuit unit 204 have the same circuit configuration as each other. Since the power conversion device 203 is provided with a plurality of conversion circuit units (conversion circuit unit 4 and conversion circuit unit 204), the first circuit 10, the second circuit 20, the transformer 30, the capacitor 42, the diode 60, and the cutoff switch are provided. It is a configuration in which a plurality of 70s and the like are provided.

In the configuration of FIG. 2, each of the plurality of first circuits 10 is connected to the first conduction path 51, and each first coil 31 of the plurality of transformers 30 is connected to each first circuit 10. In this example, a plurality of transformers 30 correspond to an example of the transformer unit. Then, each second coil 32 of the plurality of transformers 30 is connected to each second circuit 20.

In the configuration of FIG. 2, a second conductive path 252 is provided in place of the second conductive path 52. The second conductive path 252 includes a plurality of individual conductive paths 252A and 252B, and a common conductive path 252C. Each of the individual conductive paths 252A and 252B has one end electrically connected to each of the plurality of second circuits 20, and the end opposite to the second circuit 20 is electrically connected to the common conductive path 252C. Connected to. The common conductive path 252C has one end connected to a plurality of individual conductive paths 252A and 252B, and forms a path through which a current flows from any of the plurality of individual conductive paths 252A and 252B. The other end of the common conductive path 252C is electrically connected to the wiring portion 172.

The power conversion unit 5 of the conversion circuit unit 4 performs voltage conversion between the first conductive path 51 and the individual conductive path 252A. The power conversion unit 5 of the conversion circuit unit 4 can perform a step-down operation of stepping down the DC voltage applied to the first conductive path 51 and applying the DC voltage to the individual conductive path 252A. The power conversion unit 5 of the conversion circuit unit 4 can perform a step-up operation of boosting the DC voltage applied to the individual conductive path 252A and applying the DC voltage to the first conductive path 51. The power conversion unit 5 of the conversion circuit unit 204 performs voltage conversion between the first conductive path 51 and the individual conductive path 252B. The power conversion unit 5 of the conversion circuit unit 204 may perform a step-down operation of stepping down the DC voltage applied to the first conductive path 51 and applying the DC voltage to the individual conductive path 252B. The power conversion unit 5 of the conversion circuit unit 204 may perform a step-up operation of boosting the DC voltage applied to the individual conductive path 252B and applying the DC voltage to the first conductive path 51.

Each of the plurality of cutoff switches 70 is provided in each of the plurality of individual conductive paths 252A and 252B, respectively. The cutoff switch 70 of the conversion circuit unit 4 is provided between the connection point P4 to which the diode 60 is connected and the common conductive path 252C in the individual conductive path 252A. The cutoff switch 70 of the conversion circuit unit 4 cuts off the energization of the individual conductive path 252A in both directions when it is switched to the off state, and energizes the individual conductive path 252A in both directions when it is switched to the on state. Tolerate. The cutoff switch 70 of the conversion circuit unit 204 is provided between the connection point P5 to which the diode 60 is connected and the common conductive path 252C in the individual conductive path 252B. The cutoff switch 70 of the conversion circuit unit 204 cuts off the energization of the individual conductive path 252B in both directions when it is switched to the off state, and energizes the individual conductive path 252B in both directions when it is switched to the on state. Tolerate.

In the diode 60 of the conversion circuit unit 4, the cathode is electrically connected to the portion between the cutoff switch 70 and the inductor 24 in the individual conductive path 252A, and the anode is electrically connected to the ground. In the diode 60 of the conversion circuit unit 204, the cathode is electrically connected to the portion between the cutoff switch 70 and the inductor 24 in the individual conductive path 252B, and the anode is electrically connected to the ground.

The control unit 7 causes each power conversion unit 5 to perform a step-down operation at a predetermined first time in a normal state. At the time of the step-down operation, the control unit 7 causes each first circuit 10 to perform the same first conversion operation as in the first embodiment, and causes each second circuit 20 to perform the same first conversion operation as in the first embodiment. The same fourth conversion operation described above is performed. The output voltage of the first target value is applied to the second conductive path 252 by the control unit 7 performing control to cause each power conversion unit 5 to perform a step-down operation. The first target value is set in the same manner as in the first embodiment.

The control unit 7 causes each power conversion unit 5 to perform a boosting operation at a predetermined second period in the normal state. At the time of the boosting operation, the control unit 7 causes each first circuit 10 to perform the same second conversion operation as in the first embodiment, and causes each second circuit 20 to perform the same second conversion operation as in the first embodiment. The same third conversion operation described above is performed. The output voltage of the second target value is applied to the first conductive path 51 by the control unit 7 executing the control to cause each power conversion unit 5 to perform the boosting operation. The second target value is set in the same manner as in the first embodiment.

The above-mentioned normal state in the power conversion device 203 is a state in which a predetermined abnormal state has not occurred. The abnormal state in the power conversion device 203 is, for example, a state in which the voltage of any of the individual conductive paths 252A and 252B is less than the threshold value. This threshold value is lower than the output voltage when the low-voltage battery 182 is fully charged, and is higher than 0V. The control unit 7 acquires the voltage values of the individual conductive paths 252A and 252B directly or via another voltage detection unit.

When the abnormal state occurs while the step-down operation or the step-up operation is being performed in the normal state, the control unit 7 switches the cutoff switch 70 of the path where the abnormality has occurred to the off state. For example, when the voltage of one individual conductive path 252A suddenly drops below the threshold value due to the occurrence of a ground fault in one of the second circuits 20, the control unit 7 controls the cutoff switch of the individual conductive path 252A. Switch 70 to the off state. As a result, it is possible to block the current from flowing from the low voltage battery 182 to the second circuit 20 side via the individual conductive path 252A. In this case, if the voltage of the individual conductive path 252B exceeds the above threshold value, the cutoff switch 70 of the individual conductive path 252B does not have to be switched to the off state. Therefore, the voltage conversion can be continued in the conversion circuit unit 204 corresponding to the other individual conductive path 252B. Similarly, when the voltage of the individual conductive path 252B drops sharply below the threshold value due to the occurrence of a ground fault in the other second circuit 20, the control unit 7 controls the cutoff switch of the individual conductive path 252B. Switch 70 to the off state. As a result, it is possible to block the current from flowing from the low voltage battery 182 to the second circuit 20 side via the individual conductive path 252B. In this case, if the voltage of the individual conductive path 252A exceeds the above threshold value, the cutoff switch 70 of the individual conductive path 252A does not have to be switched to the off state. Therefore, the voltage conversion can be continued in the conversion circuit unit 4 corresponding to one of the individual conductive paths 252A.

Even in such a power conversion device 203, the same effect as that of the first embodiment can be obtained by the presence of the cutoff switch 70 and the diode 60. Further, in the power conversion device 203, each second circuit 20 is provided between the transformer unit (plurality of transformers 30) and each of the individual conductive paths 252A and 252B. Even if one of the second circuits 20 has to be stopped for some reason, the power conversion device 203 can easily continue the power conversion by the other second circuit 20. Further, the power conversion device 203 has a function of preventing current from flowing into the second circuit 20 and a function of suppressing the influence on the vicinity of the second circuit 20 immediately after the cutoff switch 70 is cut off. It can be realized in each of 252B. For example, the power conversion device 203 operates a conversion circuit unit (second circuit 20, etc.) corresponding to the other individual conductive path even when the cutoff switch 70 of any one of the individual conductive paths is turned off. Then, the power conversion can be continued. Moreover, when the power conversion device 203 operates the conversion circuit unit corresponding to the other individual conductive path in a state where one individual conductive path is cut off, the function of the cutoff switch 70 in the other individual conductive path and the diode The function of 60 can be maintained separately from the above-mentioned one individual conductive path.

<Third Embodiment>
The following description relates to the power conversion device 303 of the third embodiment.
The in-vehicle system 301 shown in FIG. 3 is different from the in-vehicle system 1 in FIG. 1 only in that the power conversion device 3 is changed to the power conversion device 303, and is the same as the in-vehicle system 1 in other points. Therefore, in the vehicle-mounted system 301, the parts having the same configuration as the vehicle-mounted system 1 are designated by the same reference numerals as those of the vehicle-mounted system 1, and detailed description thereof will be omitted.

The first aspect of the power conversion device 303 of the third embodiment is that a power conversion unit 305 is provided in addition to the power conversion unit 5 of FIG. 1, and a cutoff switch 370 is provided instead of the cutoff switch 70. It is different from the power conversion device 3 of the embodiment. That is, the power conversion device 3 of the first embodiment has a configuration in which the power conversion unit 305 is omitted from the power conversion device 303 of the third embodiment.

The power conversion device 303 of the third embodiment is provided with a power conversion unit 305 in addition to the power conversion unit 5, and the power conversion unit 5 and the power conversion unit 305 are provided between the first conductive path 51 and the second conductive path 52. Are connected in parallel. The power conversion unit 5 and the power conversion unit 305 have the same circuit configuration as each other. Since the power conversion device 303 is provided with a plurality of power conversion units (power conversion unit 5 and power conversion unit 305), a configuration in which a plurality of first circuit 10, second circuit 20, transformer 30, and the like are provided. Is.

In the configuration of FIG. 3, each of the plurality of first circuits 10 is connected to the first conductive path 51, and the first coil 31 of each of the plurality of transformers 30 is connected to each of the plurality of first circuits 10. .. In this example, the plurality of transformers 30 correspond to an example of the transformer unit. Then, each second coil 32 of the plurality of transformers 30 is connected to each second circuit 20. In the example of FIG. 3, the second conductive path 52 corresponds to an example of the common conductive path, and forms a path through which a current flows from any of the plurality of second circuits 20.

In the configuration of FIG. 3, a cutoff switch 370 is provided in the second conductive path 52 (common conductive path). The cutoff switch 370 is provided with a pair of switch elements 371 and 372 connected in series in opposite directions to each other and a pair of switch elements 373 and 374 connected in series in opposite directions to each other in parallel. In the example of FIG. 3, the switch elements 371, 372, 373, and 374 are all MOSFETs. The off state of the cutoff switch 370 is a state in which all the switch elements 371, 372, 373, and 374 are in the off state. When the cutoff switch 370 is in the off state, the energization across the cutoff switch 370 is cut off in both directions in the second conductive path 52.

The diode 60 is electrically connected to the second conductive path 52. The cathode of the diode 60 is electrically connected to the portion 52A between the inductor 24 and the cutoff switch 370 in the second conductive path 52. The anode of the diode 60 is electrically connected to the ground. In the example of FIG. 3, one electrode of the capacitor 42 is electrically connected between the connection point P3 to which the anode of the diode 60 is electrically connected and the inductor 24 in the second conductive path 52.

The control unit 7 causes each of the power conversion units 5 and 305 to perform a step-down operation at a predetermined first period in the normal state. At the time of the step-down operation, the control unit 7 causes each first circuit 10 to perform the same first conversion operation as in the first embodiment, and causes each second circuit 20 to perform the same first conversion operation as in the first embodiment. The same fourth conversion operation described above is performed. The control unit 7 executes a control for causing each of the power conversion units 5 and 305 to perform a step-down operation, so that the output voltage of the first target value is applied to the second conductive path 52. The first target value is set in the same manner as in the first embodiment.

The control unit 7 causes each of the power conversion units 5 and 305 to perform a boosting operation at a predetermined second period in the normal state. At the time of the boosting operation, the control unit 7 causes each first circuit 10 to perform the same second conversion operation as in the first embodiment, and causes each second circuit 20 to perform the same second conversion operation as in the first embodiment. The same third conversion operation described above is performed. The output voltage of the second target value is applied to the first conductive path 51 by the control unit 7 executing a control for causing each of the power conversion units 5 and 305 to perform a boosting operation. The second target value is set in the same manner as in the first embodiment.

The above-mentioned normal state in the power conversion device 303 is a state in which a predetermined abnormal state has not occurred. The abnormal state in the power conversion device 303 is, for example, a state in which the voltage of the second conductive path 52 is less than the threshold value. This threshold value is lower than the output voltage when the low-voltage battery 182 is fully charged, and is higher than 0V. The control unit 7 can grasp the voltage value of the second conductive path 52 by the same method as in the first embodiment.

When the abnormal state occurs while the step-down operation or the step-up operation is being performed in the normal state, the control unit 7 switches the cutoff switch 370 to the off state. For example, when the voltage of the second conductive path 52 drops sharply below the threshold value due to the occurrence of a ground fault in any of the second circuits 20, the control unit 7 turns off the cutoff switch 370. Switch. As a result, it is possible to block the current from flowing from the low voltage battery 182 toward the ground fault generating portion.

In the power conversion device 303 shown in FIG. 3, a plurality of second circuits 20 are connected in parallel between the transformer unit (plurality of transformers 30) and the second conductive path 52 (common conductive path). Even if one of the second circuits 20 has to be stopped for some reason, the power conversion device 303 can easily continue the power conversion by the other second circuit 20. Moreover, in this power conversion device 303, a cutoff switch 370 is provided in the second conductive path 52 (common conductive path), and the cathode of the diode 60 is electrically connected between the plurality of second circuits 20 and the cutoff switch 370. It is a configuration. This power conversion device 303 can realize a function of preventing current from flowing into the second circuit 20 via the second conductive path 52 by reducing the number of cutoff switches, and is near the second circuit 20 immediately after the cutoff switch 370 is cut off. The function of suppressing the influence on the power can be realized by reducing the number of diodes.

<Fourth Embodiment>
The in-vehicle system 401 shown in FIG. 4 is different from the in-vehicle system 1 in FIG. 1 only in that the power conversion device 3 is changed to the power conversion device 403, and is the same as the in-vehicle system 1 in other points. Therefore, in the vehicle-mounted system 401, the parts having the same configuration as the vehicle-mounted system 1 are designated by the same reference numerals as those of the vehicle-mounted system 1, and detailed description thereof will be omitted.

The circuit configuration of the power conversion device 403 of the fourth embodiment is that a capacitor 442 is provided instead of the capacitor 42, and the switch element 71 and the switch element 72 in the cutoff switch 70 of FIG. 1 are replaced to form a cutoff switch 470. Only the circuit configuration of the power converter 3 is different. In the power conversion device 403, the power conversion unit 5 is the same as the power conversion unit 5 in the first embodiment. That is, the above-mentioned explanation of "3. Configuration of power conversion unit" is also the explanation of the power conversion unit 5 of the power conversion device 403.

The capacitor 41 is provided between the high voltage battery 181 and the first circuit 10. In the capacitor 41, one electrode is electrically connected to the first conductive path 51, and the other electrode is electrically connected to the third conductive path 53. A voltage between the first conductive path 51 and the third conductive path 53 is applied to both ends of the capacitor 41.

In the capacitor 442, one electrode is electrically connected to the second conductive path 52, and the other electrode is electrically connected to the ground. A voltage between the second conductive path 52 and the ground is applied to both ends of the capacitor 442. The capacitor 442 is electrically connected to the cutoff switch 470 in the second conductive path 52 on the side opposite to the second circuit 20 side. That is, the capacitor 442 is electrically connected to a portion between the cutoff switch 470 and the wiring portion 172.

The cutoff switch 470 is provided in the second conductive path 52. The cutoff switch 470 switches between a state in which the current flows from the wiring portion 172 side to the second circuit 20 side in the second conductive path 52 and a state in which the current is allowed to flow. In the example of FIG. 4, the cutoff switch 470 includes switch elements 71 and 72. The switch elements 71 and 72 are both configured as N-channel MOSFETs. The switch elements 71 and 72 are arranged in opposite directions to each other and are connected in series. When both the switch elements 71 and 72 are in the off state, bidirectional energization is cut off in the second conductive path. When both the switch elements 71 and 72 are in the ON state, bidirectional energization is allowed in the second conductive path.

The diode 60 is electrically connected to the second conductive path 52. The cathode of the diode 60 is electrically connected to the portion 52A between the inductor 24 and the cutoff switch 470 in the second conductive path 52. The anode of the diode 60 is electrically connected to the ground. Specifically, the anode of the diode 60 and one end of the inductor 24 are electrically connected to the source of the switch element 72. The drain of the switch element 72 is electrically connected to the drain of the switch element 71, and the source of the switch element 71 is electrically connected to one electrode of the capacitor 442 and the wiring portion 172.

In the power conversion device 403, the cutoff switch 470, the diode 60, and the inductor 24 form a chopper circuit 480. This chopper circuit 480 constitutes a diode-type non-isolated DCDC converter. The control unit 7 causes the chopper circuit 480 to perform a voltage conversion operation by controlling the on / off of the switch element 71 while keeping the switch element 72 in the on state. The chopper circuit 480 steps down the voltage applied to the portion 52B between the switch element 72 and the wiring portion 172 in the second conductive path 52, and lowers the voltage applied to the conductive path 26 between the inductor 24 and the center tap of the second coil 32. It is possible to perform a step-down operation in which a DC voltage is applied to. Specifically, the control unit 7 gives an on / off signal (for example, a PWM signal) to the switch element 72 to cause the switch element 72 to perform an on / off operation, whereby the chopper circuit 480 performs the above-mentioned step-down operation.

In the power conversion device 403, the control unit 7 controls the cutoff switch 470, the first circuit 10, and the second circuit 20. The control unit 7 may cause the first circuit 10 to perform the above-mentioned first conversion operation and the above-mentioned second conversion operation similar to those in the first embodiment. The control unit 7 causes the second circuit 20 to perform the above-mentioned third conversion operation and the above-mentioned fourth conversion operation similar to those in the first embodiment.

The control unit 7 performs a step-down operation on the power conversion unit 5 at a predetermined first time in the above-mentioned normal state (for example, a state where the voltage of the second conductive path 52 is equal to or higher than the threshold value) as in the first embodiment. Let me. When the power conversion unit 5 is to perform the step-down operation, the control unit 7 performs the first control for the first circuit 10 and the fourth control for the second circuit 20 in parallel. In the first control, a control signal is given to the switching elements 10A, 10B, 10C, and 10D of the first circuit 10, the DC voltage applied to the first conductive path 51 is converted, and the AC voltage is applied to the first coil 31 of the transformer 30. This is a control for causing the first circuit 10 to perform an operation (first conversion operation) for generating the above. When an AC voltage is generated in the first coil 31 by the first conversion operation, the transformer 30 (transformer unit) generates an AC voltage in the second coil 32 according to the AC voltage of the first coil 31. The fourth control is a control in which the second circuit 20 performs a rectifying operation (fourth conversion operation) in which an AC voltage generated in the second coil 32 is converted and a DC voltage is applied to the second conductive path 52.

The control unit 7 performs a boosting operation on the power conversion unit 5 at a predetermined second period in the above-mentioned normal state (for example, a state where the voltage of the second conductive path 52 is equal to or higher than the threshold value) as in the first embodiment. Precharge control is performed to charge the capacitor 41. The control unit 7 controls the chopper circuit 480 to perform a voltage conversion operation (voltage conversion control), controls the second circuit 20 to perform a third conversion operation (third control), and causes the first circuit 10 to perform a second conversion operation. The precharge control is executed so as to perform the control for performing the conversion operation (second control) in parallel.

When the control unit 7 causes the chopper circuit 480 to perform a voltage conversion operation by the voltage conversion control, which is one of the precharge controls, the control unit 7 gives an on / off signal (PWM signal or the like) to the switch element 72. The switch element 72 is turned on and off. In response to this voltage conversion control, the chopper circuit 480 performs a step-down operation using the DC voltage applied to the portion 52B on one side of the switch element 72 as an input voltage, and performs a step-down operation with respect to the conductive path 26 on the other end side of the inductor 24. A DC voltage (output voltage) lower than the voltage of the portion 52B is applied.

When the second circuit 20 is to perform the third conversion operation, the control unit 7 performs the third control so as to push-pull the switch elements 21 and 22. Specifically, the control unit 7 switches to the first switching control for switching to the state of FIG. 5, the second switching control for switching to the state of FIG. 6, and the state of FIG. 7 while continuing the step-down operation of the chopper circuit 480. The third switching control and the fourth switching control for switching to the state of FIG. 8 are sequentially executed in this order, and the third control is performed so as to repeat such a series of controls (first to fourth switching controls).

When switching to the state shown in FIG. 5 by the first switching control, the control unit 7 keeps the switch element 71 in the on state and causes the switch element 72 to perform an on / off operation while switching the switch elements 21 and 22 and the switching elements 10A and 10C. Is turned on. On the other hand, the control unit 7 turns off the switching elements 10B and 10D in the first switching control. When the control unit 7 performs the first switching control as shown in FIG. 5, a DC voltage is output to the first conductive path 51 based on the electric charge accumulated in the capacitor 41.

After the first switching control, the control unit 7 executes the second switching control to switch to the state shown in FIG. In the second switching control, the control unit 7 turns the switch element 21 into the on state and the switch element 22 into the off state while keeping the switch element 71 in the on state and causing the switch element 72 to perform the on / off operation. On the other hand, in the second switching control, the control unit 7 turns on the switching elements 10B and 10C and turns off the switching elements 10A and 10D. When the control unit 7 performs the second switching control, a current flows from the coil 32A side to the ground side via the switch element 21 in the second circuit 20. On the other hand, in the first circuit 10, a current flows from the first coil 31 side toward the switching element 10C side, and an output voltage is applied to the first conductive path 51. The capacitor 41 is charged by such an output voltage.

After the second switching control, the control unit 7 executes the third switching control to switch to the state shown in FIG. 7. In the third switching control, the control unit 7 turns on the switch elements 21 and 22 and the switching elements 10B and 10D while keeping the switch element 71 in the on state and causing the switch element 72 to perform the on / off operation. Turn 10A and 10C off. When the control unit 7 performs the third switching control, a DC voltage is output to the first conductive path 51 based on the electric charge accumulated in the capacitor 41.

After the third switching control, the control unit 7 executes the fourth switching control to switch to the state shown in FIG. In the fourth switching control, the control unit 7 turns on the switch element 22 and turns the switch element 21 off while keeping the switch element 71 in the on state and causing the switch element 72 to perform the on / off operation. On the other hand, in the fourth switching control, the control unit 7 turns on the switching elements 10A and 10D and turns off the switching elements 10B and 10C. When the control unit 7 performs the fourth switching control, a current flows from the coil 32B side to the ground side via the switch element 22 in the second circuit 20. On the other hand, in the first circuit 10, a current flows from the first coil 31 side toward the switching element 10A side, and an output voltage is applied to the first conductive path 51. The capacitor 41 is charged by such an output voltage. The control unit 7 executes the first switching control after the fourth switching control.

The control unit 7 performs precharge control so as to execute the above-mentioned first to fourth switching controls in order, and repeats a series of these controls (first to fourth switching controls). In the precharge control, the DC voltage applied to the second conductive path 52 by performing the push-pull operation of the second circuit 20 and the rectifying operation of the first circuit 10 in parallel while the step-down operation by the chopper circuit 480 is performed. Is boosted and applied to the first conductive path 51 to charge the capacitor 41.

The operation performed by the second circuit 20 during the above-mentioned precharge control is the third conversion operation, which is an operation of converting the DC voltage applied to the second conductive path 52 to generate an AC voltage in the second coil 32. .. As shown in FIGS. 6 and 8, when an AC voltage is generated in the second coil 32 by the third conversion operation, the transformer 30 generates an AC voltage in the first coil 31 according to the AC voltage of the second coil 32. .. The operation performed by the first circuit 10 during the above-mentioned precharge control is the first conversion operation, and the first circuit 10 converts the AC voltage generated in the first coil 31 as shown in FIGS. 5 to 8. , A DC voltage (a DC voltage higher than the DC voltage applied to the second conductive path 52) is applied to the first conductive path 51.

When the above-mentioned precharge control is started at a predetermined time, the control unit 7 executes the control so as to repeat the control of sequentially executing the first to fourth switching controls from the start time to the predetermined time. .. The predetermined time is, for example, a time after the start switch of the vehicle is turned on and before charging of the capacitor 41 is started, and is a time when the charging voltage of the capacitor 41 is equal to or lower than the predetermined voltage. The upper part of FIG. 9 shows an example of a change in the duty of each PWM signal when the precharge control is performed at the predetermined time. The lower part of FIG. 9 shows the change in the charging voltage of the capacitor 41 when the control is performed as in the upper part of FIG. In the example of FIG. 9, the charging voltage of the capacitor 41 is 0 at the start time (time 0).

In the example of FIG. 9, the time t2 is the predetermined time. In the example of FIG. 9, the control unit 7 repeats the control of sequentially executing the first to fourth switching controls from the start time point (time 0) to the time t2. In the example of FIG. 9, the control unit 7 sets the duty of the PWM signal (on / off signal for causing the chopper circuit 480 to perform the step-down operation) given to the switch element 72 from the start time (time 0) to the time t2. Soft start control is performed so that it gradually rises.

In the example of FIG. 9, when the control unit 7 performs the precharge control at the predetermined time, the duty of the PWM signal given to the switch element 72 is set to 0 from the start time (time 0) of the precharge control to the time t1. The chopper circuit 480 is made to perform a step-down operation while gradually increasing from the first value to the first value D1 (for example, 0.8). The time t1 is the time when the duty of the PWM signal given to the switch element 72 reaches the first value D1. After the duty of the PWM signal given to the switch element 72 reaches the first value D1, the control unit 7 sets the duty of the PWM signal given to the switch element 72 from the first value D1 to the second value D2 (until the time t2). For example, the chopper circuit 480 is made to perform a step-down operation while gradually increasing to 1.0). The time t2 is the time when the duty of the PWM signal given to the switch element 72 reaches the second value D2.

In the example of FIG. 9, the control unit 7 increases the duty of the PWM signal given to the switch element 72 from the start time point (time 0) to the time t1 from 0 to the first value D1. It is made larger than the ascending speed for increasing from the 1st value D1 to the 2nd value D2. That is, the value of D1 / t1 is made larger than the value of (D2-D1) / (t2-t1). After the duty of the PWM signal given to the switch element 72 reaches the second value D2 at the time t2, the control unit 7 continues to maintain the duty at the second value D2. That is, the control unit 7 keeps the switch element 72 in the on state after the time t2.

In the example of FIG. 9, the control unit 7 starts the above-mentioned third control from the above-mentioned start time (time 0), and causes the switch elements 21 and 22 to perform the push-pull operation in parallel with the step-down operation of the chopper circuit 480. .. The control unit 7 assigns the duty to the switch elements 21 and 22 when the switch elements 21 and 22 perform the push-pull operation from the start time (time 0) to the predetermined time after the time t1 elapses from 0. It is set to a value larger than 1 and smaller than 1. In the example of FIG. 9, the control unit 7 sets the duty given to the switch elements 21 and 22 to the third value D3 from the time 0 to the predetermined time. The control unit 7 gradually increases the duty given to the switch elements 21 and 22 after reaching the predetermined time from the third value D3, and when the predetermined value (for example, the first value D1) is reached, the control unit 7 gradually increases the duty. The duty given to the switch elements 21 and 22 is maintained at the predetermined value. The third value D3 is a value larger than 0 and smaller than the first value D1 (for example, 0.6). The predetermined time may be, for example, a time t2, a time earlier than the time t2, or a time later than the time t2. In the example of FIG. 9, the switch element 21 is used for a part or all of the period during which the soft start control is performed so as to gradually increase the duty of the PWM signal given to the switch element 72 in the control for stepping down the chopper circuit 480. , The push-pull operation can be performed while increasing the duty given to 22 to some extent. According to this configuration, the period of control (soft start control of switch elements 21 and 22) that gradually increases while lowering the duty given to the switch elements 21 and 22 can be shortened, and the inrush current to the capacitor 41 can be suppressed. However, the precharge control that gradually raises the charging voltage of the capacitor 41 can be performed at a higher speed.

When the abnormal state (for example, the voltage of the second conductive path 52 is less than the threshold value) occurs while the step-down operation or the step-up operation is performed in the normal state, the control unit 7 sets the cutoff switch 70. Switch to the off state. When the control unit 7 switches the cutoff switch 70 to the off state, both the switch elements 71 and 72 are turned off, and bidirectional energization is cut off in the second conductive path 52. When such a cutoff operation is performed, the energy stored in the inductor 24 by the diode 60 may be commutated or consumed.

The power conversion device 403 can cut off the current flowing to the second circuit 20 side in the second conductive path 52 when the cutoff switch 70 is switched to the cutoff state. Therefore, the power conversion device 403 can prevent the current from flowing into the second circuit 20 through the second conductive path 52 by the cutoff switch, and can protect the components related to the second circuit. Further, in this power conversion device, an element portion is connected to a path between the inductor and a cutoff switch, and a chopper circuit is formed by these. Therefore, the function of this power conversion device can be easily enhanced by an element connected between the portion that performs power conversion and the cutoff switch. Further, since this power conversion device can perform a precharge operation by using such a chopper circuit, it is possible to realize further high functionality with a simple configuration. Moreover, this power conversion device can adjust the input voltage in the third conversion operation by the voltage conversion operation in the chopper circuit.

<Other embodiments>
The present disclosure is not limited to the embodiments described above with reference to the description and drawings. For example, the features of the embodiments described above or below can be combined in any combination within a consistent range. Further, any of the features of the above-mentioned or later-described embodiments may be omitted unless it is clearly stated as essential. Further, the above-described embodiment may be modified as follows.

In the above-described embodiment, the isolated DCDC converter that operates by the phase shift method has been exemplified, but a general isolated DCDC converter that operates by a normal method other than the phase shift method may be used. As the first circuit and the second circuit constituting the isolated DCDC converter, other known configurations are adopted as long as they are circuits capable of bidirectional voltage conversion between the first conductive path 51 and the second conductive path 52. May be done.

In the above-described embodiment, the predetermined abnormal state is a state in which the voltage of the second conductive path 52 is less than the threshold value, but the present invention is not limited to this example. For example, the predetermined abnormal state may be a state in which the current of the second conductive path 52 becomes a predetermined value or more. In this example, when the current of the second conductive path 52 becomes a predetermined value or more, the control unit 7 switches the cutoff switch 70 to the off state and cuts off the bidirectional energization.

In the above-described embodiment, the configuration in which the diode 60 is provided is exemplified, but the diode 60 may be a body diode of a MOSFET.

In the above-described embodiment, an example of the cutoff switch is shown, but the cutoff switch has another configuration using a semiconductor switch as long as it can cut off the energization in both directions at the place where the cutoff switch is provided. It may be a mechanical relay.

In the fourth embodiment, the chopper circuit 480 configured as a diode type DCDC converter is exemplified, but a switch element similar to the switch element 71 is provided in place of the diode 60, and the chopper circuit is provided as a synchronous rectification type DCDC converter. It may be operated.

In the fourth embodiment, an example of forming a chopper circuit using the diode 60 is shown. For example, in the configuration of FIG. 2, the positions of the switch elements 71 and 72 are exchanged in each of the conversion circuit units 4 and 204, and the positions of the switch elements 71 and 72 are exchanged. The position of the capacitor 42 may be arranged between the cutoff switch 70 and the common conductive path 252C in the individual conductive path. In this way, the chopper circuit can be configured by the inductor 24, the diode 60, and the switch element 72 in each of the conversion circuit units 4, 204. Alternatively, the chopper circuit as shown in FIG. 4 may be configured with a configuration in which a part of the configuration of FIG. 3 is modified.

In the fourth embodiment, the diode rectification type chopper circuit 480 is configured, but the diode 60 may be replaced with a switching element such as a MOSFET, and a synchronous rectification type chopper circuit may be configured. In this case, the control unit may cause the chopper circuit to perform a step-down operation by a synchronous rectification method.

It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is not limited to the embodiments disclosed here, but may be indicated by the scope of claims and include all modifications within the meaning and scope equivalent to the scope of claims. Intended.

1,201,301,401: In-vehicle system 3,203,303,403: Power conversion device 4,204: Conversion circuit unit 5,305: Power conversion unit 7: Control unit 10: First circuit 10A, 10B, 10C, 10D: Switching element 13: Inductor 20: Second circuit 21 and 22: Switch element 24: Inductor 26: Conductive path 30: Transformer 31: First coil 32: Second coil 32A, 32B: Coil 41: Condenser 42, 442: Condenser 51: 1st conductive path 52: 2nd circuit 52, 252: 2nd conductive path 53: 3rd conductive path 60: Diode 70, 370, 470: Cutoff switch 71, 72, 371, 372, 373, 374: Switch Elements 171,172,173: Wiring part 181: High-pressure battery 182: Low-pressure battery 190: Low-voltage load 252A, 252B: Individual conductive path 252C: Common conductive path 480: Chopper circuit

Claims (6)

The first circuit having a switching element, a transformer unit having a first coil and a second coil connected to the first circuit, and a second circuit connected to the second coil, said first. A power conversion device that performs voltage conversion between a first conductive path connected to one circuit and a second conductive path connected to the second circuit.
A cutoff switch that switches between a state in which the current flows to the second circuit side in the second conductive path and a state in which the current is allowed to flow to the second circuit side.
A diode electrically connected to the second conductive path and
Have,
The first circuit performs at least a first conversion operation of converting a DC voltage applied to the first conductive path by the switching operation of the switching element and generating an AC voltage in the first coil of the transformer unit.
When an AC voltage is generated in the first coil by the first conversion operation, the transformer unit generates an AC voltage in the second coil.
The second circuit includes an inductor that is electrically connected to the second conductive path, and outputs a DC voltage to the second conductive path when an AC voltage is generated in the second coil.
A power conversion device in which the cathode of the diode is electrically connected to a portion of the second conductive path between the inductor and the cutoff switch, and the anode of the diode is electrically connected to the ground. It has a plurality of the above-mentioned second circuits and has a plurality of said second circuits.
The transformer unit includes a plurality of the second coils.
Each of the second circuits is connected to each of the second coils.
The second conductive path has a common conductive path through which a current flows from any of the plurality of second circuits.
The cutoff switch is provided in the common conductive path, and the cutoff switch is provided.
The power conversion device according to claim 1, wherein the cathode of the diode is electrically connected between the plurality of second circuits and the cutoff switch in the common conductive path. With the plurality of the second circuits
With the plurality of the cutoff switches,
With the plurality of diodes
Have,
The transformer unit includes a plurality of the second coils.
Each of the second circuits is connected to each of the second coils.
The second conductive path includes a plurality of individual conductive paths and a common conductive path.
Each of the individual conductive paths is electrically connected to each of the plurality of second circuits, and the end opposite to the second circuit is connected to the common conductive path.
The common conductive path has one end connected to the plurality of individual conductive paths and forms a path through which a current flows from any of the plurality of individual conductive paths.
Each of the cutoff switches is provided in each of the individual conductive paths.
The power conversion device according to claim 1, wherein the cathode of each diode is electrically connected between the cutoff switch and the inductor of the second circuit in each individual conductive path. A control unit for controlling the cutoff switch is provided.
The cutoff switch, the diode, and the inductor form a chopper circuit.
The power conversion device according to any one of claims 1 to 3, wherein the control unit causes the chopper circuit to perform a voltage conversion operation. A capacitor is electrically connected to the first conductive path.
The first circuit performs at least a second conversion operation of converting an AC voltage generated in the first coil and applying a DC voltage to the first conductive path.
The second circuit has a third conversion operation of converting a DC voltage applied to the second conductive path to generate an AC voltage in the second coil and a third conversion operation of converting the AC voltage generated in the second coil. 2 Perform at least the fourth conversion operation of applying a DC voltage to the conductive path,
When an AC voltage is generated in the second coil by the third conversion operation, the transformer unit generates an AC voltage in the first coil.
The control unit charges the capacitor by causing the voltage conversion operation of the chopper circuit, the third conversion operation of the second circuit, and the second conversion operation of the first circuit to be performed in parallel. The power conversion device according to claim 4, wherein the precharge control is performed. The first circuit having a switching element, a transformer unit having a first coil and a second coil connected to the first circuit, and a second circuit connected to the second coil, said first. A power conversion device that performs voltage conversion between a first conductive path connected to one circuit and a second conductive path connected to the second circuit.
A cutoff switch that switches between a state in which the current flows to the second circuit side in the second conductive path and a state in which the current is allowed to flow to the second circuit side.
An element part having a diode or a switch,
A control unit that controls the cutoff switch, the first circuit, and the second circuit.
Have,
A capacitor is electrically connected to the first conductive path.
The first circuit has a first conversion operation of converting a DC voltage applied to the first conductive path by a switching operation of the switching element to generate an AC voltage in the first coil of the transformer unit, and the first conversion operation. At least the second conversion operation of converting the AC voltage generated in the coil and applying the DC voltage to the first conductive path is performed.
The second circuit has a third conversion operation of converting a DC voltage applied to the second conductive path to generate an AC voltage in the second coil and a third conversion operation of converting the AC voltage generated in the second coil. 2 Perform at least the fourth conversion operation of applying a DC voltage to the conductive path,
The transformer unit generates an AC voltage in the second coil when an AC voltage is generated in the first coil by the first conversion operation, and an AC voltage is generated in the second coil by the third conversion operation. In some cases, an AC voltage is generated in the first coil.
The second circuit comprises an inductor that is electrically connected to the second conductive path.
One end of the element portion is electrically connected to a portion of the second conductive path between the inductor and the cutoff switch, and the other end of the element portion is electrically connected to the ground.
The cutoff switch, the element unit, and the inductor form a chopper circuit that performs a voltage conversion operation in the second conductive path.
The control unit charges the capacitor by causing the voltage conversion operation of the chopper circuit, the third conversion operation of the second circuit, and the second conversion operation of the first circuit to be performed in parallel. A power conversion device that performs precharge control.

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