Current backflow prevention device

Abstract

To provide a current backflow prevention device capable of preventing a current from flowing back to an external power supply when a vehicle is started by jumping start.SOLUTION: The current backflow prevention device includes an electric power reception detector that detects an electric power reception state in which electric power supply from an external power supply is received by the low-voltage battery, an activation detector that detects an activation operation for activating the electric vehicle, and a condition setting unit that sets a starting condition of the voltage converter such that an output voltage of the voltage converter becomes equal to or lower than a voltage of the external power supply when the electric power reception detector detects the electric power reception state and the activation detector detects the activation operation.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a current backflow prevention device. [Background technology]

[0002] Patent Document 1 discloses an electric vehicle that includes a high-voltage battery for driving, a low-voltage battery for electrical components, and a DC-DC converter, with the input side of the DC-DC converter electrically connected to the high-voltage battery and the output side electrically connected to the low-voltage battery. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-010280 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned electric vehicle, when the power stored in the low-voltage battery is consumed significantly and the voltage of the low-voltage battery drops, the low-voltage battery is electrically connected to an external power source having a voltage higher than the maximum voltage of the low-voltage battery, and the electric vehicle is started using the power supplied from the external power source to the low-voltage battery, in a process known as a jump start.

[0005] However, if the output voltage of the DC-DC converter is higher than the voltage of the external power supply, when the electric vehicle is started by jump-starting, a current corresponding to the voltage difference between the voltage of the external power supply and the output voltage of the DC-DC converter may flow back into the external power supply, which may have an adverse effect on the external power supply.

[0006] The present invention has been made in consideration of the above-mentioned situation, and aims to provide a current backflow prevention device that can prevent current from flowing back to an external power source when a vehicle is started by jump-starting. [Means for solving the problem]

[0007] The present invention has been made to solve at least some of the above-mentioned problems, and can be realized as the following aspects or application examples.

[0008] The current backflow prevention device according to this application example is a current backflow prevention device provided in an electric vehicle that includes a high-voltage battery for driving, a low-voltage battery having a lower voltage than the high-voltage battery, and a voltage converter having an input side connected to the high-voltage battery and an output side connected to the low-voltage battery, and includes a power reception detection unit that detects a power receiving state in which the low-voltage battery receives power supply from an external power source, a start detection unit that detects a start operation for starting the electric vehicle, and a condition setting unit that sets a start condition for the voltage converter so that the output voltage of the voltage converter is equal to or lower than the voltage of the external power source when the power reception detection unit detects the power receiving state and the start detection unit detects the start operation.

[0009] The current backflow prevention device according to this application example can prevent current from flowing back to the external power supply when the electric vehicle is started by jump-starting. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a block diagram showing an example of an electrical configuration of a vehicle according to an embodiment of the present invention; [Figure 2] 1 is a block diagram showing an example of the electrical configuration of a current backflow prevention device according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0011] 1. Vehicle configuration Fig. 1 is a block diagram showing an example of the electrical configuration of a vehicle 1 according to this embodiment. The electrical configuration of the vehicle 1 will be described below with reference to Fig. 1. In Fig. 1, a power circuit for supplying power is shown by a solid line, and a control circuit for transmitting and receiving various signals is shown by a dashed line.

[0012] The vehicle 1 is an electric vehicle such as an electric vehicle or a hybrid vehicle, and is equipped with a control unit (VCU: Vehicle Control Unit) 12, a high-voltage battery 14, a motor 16, a DC-DC converter (voltage converter) 18, a low-voltage battery 20, a voltage measurement unit 22, a power reception detection unit 24, and a start button 26, etc.

[0013] The control unit 12 is a computer that performs overall control of the vehicle 1. The control unit 12 is electrically connected to each of the DC-DC converter 18, the voltage measurement unit 22, the power reception detection unit 24, the start button 26, etc. via a control circuit.

[0014] The high-voltage battery 14 is a high-voltage, large-capacity battery and is the power source for the vehicle 1. For example, a lithium-ion battery with a maximum voltage set to about 200 V is used as the high-voltage battery 14. The high-voltage battery 14 is electrically connected to the motor 16 via a power circuit and a traction inverter (not shown).

[0015] The motor 16 is a drive source for the vehicle 1 and also functions as a generator. The high-voltage battery 14 is also electrically connected to a low-voltage battery 20 via a power circuit and a DC-DC converter 18.

[0016] The DC-DC converter 18 converts the voltage of the power supplied from the high-voltage battery 14 to the low-voltage battery 20. The input side (primary side) of the DC-DC converter 18 is electrically connected to the high-voltage battery 14, and the output side (secondary side) is electrically connected to the low-voltage battery 20.

[0017] The low-voltage battery 20 is an auxiliary battery with a lower voltage than the high-voltage battery 14. For example, a lead battery with a maximum voltage set to about 12 V is used as the low-voltage battery 20. The low-voltage battery 20 is electrically connected to each of the electrical components 28 via a power circuit. In this embodiment, the low-voltage battery 20 is mounted under the hood of the vehicle 1.

[0018] The electrical components 28 are electronic components that operate by consuming the power stored in the low-voltage battery 20, and include the control unit 12, the voltage measurement unit 22, the power reception detection unit 24, and the start button 26. The electrical components 28 also include headlights, turn signals, audio, various sensors, and various switches.

[0019] The voltage measuring unit 22 is provided in the low-voltage battery 20 and measures the input voltage to the low-voltage battery 20 .

[0020] The power reception detection unit 24 detects the power reception state of the vehicle 1. The power reception state refers to a state in which an external power source 40 (described later) and the input side of the low-voltage battery 20 are electrically connected by an external cable 42, and the low-voltage battery 20 receives power supply from the external power source 40.

[0021] If the surroundings of the low-voltage battery 20 change depending on whether the low-voltage battery 20 and the external power supply 40 are connected via the external cable 42, it is possible to estimate from the change whether the vehicle 1 is in a power receiving state. Therefore, the power receiving detection unit 24 may detect the power receiving state of the vehicle 1 based on the change in the surroundings of the low-voltage battery 20.

[0022] Since the low-voltage battery 20 of this embodiment is mounted inside the hood of the vehicle 1, the hood of the vehicle 1 is always in an open state when the vehicle 1 is in a power receiving state. In other words, the open state of the hood can be assumed to be the power receiving state. Therefore, in this embodiment, an open / closed sensor that detects the open / closed state of the hood of the vehicle 1 is used as the power receiving detection unit 24.

[0023] The start button 26 is a button for starting the vehicle 1. The start button 26 can also be said to be a button for switching the vehicle 1 from a standby state to a running state.

[0024] The standby state of the vehicle 1 refers to a state in which power is supplied only to the electrical components 28 (partially or entirely) using the power stored in the low-voltage battery 20. Therefore, when the vehicle 1 is in the standby state, the power of the high-voltage battery 14 is not used and the operation of the DC-DC converter 18 is also stopped. The startup state of the vehicle 1 refers to a state in which power is supplied to the electrical components 28 using the power stored in the low-voltage battery 20, and further, power is supplied to the drive system such as the motor 16 using the power stored in the high-voltage battery 14.

[0025] Therefore, while the vehicle 1 is in an activated state, the control unit 12 controls the operation of the DC-DC converter 18, and the power stored in the high-voltage battery 14 is supplied (charged) to the low-voltage battery 20 via the DC-DC converter 18.

[0026] For example, if a lead battery with a maximum voltage of about 12 V is used as low-voltage battery 20, the operation of DC-DC converter 18 is basically controlled so that the output voltage is greater than 12 V. In this embodiment, the operation of DC-DC converter 18 is basically controlled so that the output voltage is 14 V.

[0027] For these reasons, the high-voltage battery 14 can be said to be a battery for driving the vehicle 1, as well as a battery for charging the low-voltage battery 20. On the other hand, the low-voltage battery 20 supplies power to the electrical components 28 regardless of whether the vehicle 1 is in a standby state or an activated state, so the low-voltage battery 20 can also be said to be a battery for the electrical components 28.

[0028] The high-voltage battery 14 is charged as needed. For example, when the high-voltage battery 14 is connected to an external charger for the high-voltage battery 14 via a connector, the high-voltage battery 14 is charged. Also, when electric power is generated by regenerative braking using the motor 16 as a generator and supplied to the high-voltage battery 14, the high-voltage battery 14 is charged.

[0029] In such a vehicle 1, the operation of the DC-DC converter 18 stops while the vehicle 1 is in a standby state, and if the power stored in the low-voltage battery 20 is significantly consumed during that time, the voltage of the low-voltage battery 20 drops, and the power supply to the control unit 12 and electrical components 28 such as the start button 26 becomes insufficient. Therefore, if the power stored in the low-voltage battery 20 is significantly consumed while the vehicle 1 is in a standby state, it becomes necessary to start the vehicle 1 using the external power source 40, i.e., to perform a jump start.

[0030] When performing a jump start, as shown in Fig. 1, an external power source 40 and the input side of the low-voltage battery 20 are electrically connected by an external cable 42, and power is supplied from the external power source 40 to the low-voltage battery 20 to make up for any power shortage. As the external power source 40, for example, a low-voltage battery of another vehicle or an external charger for the low-voltage battery 20 is used.

[0031] In addition, when the vehicle 1 is started by jump-starting, the output voltage of the DC-DC converter 18 is greater than the voltage of the external power supply 40, and in order to prevent current from flowing back into the external power supply 40, the vehicle 1 of this embodiment is further equipped with a current backflow prevention device 50.

[0032] 2. Electrical configuration of current backflow prevention device 2 is a block diagram showing an example of the electrical configuration of the current backflow prevention device 50 of this embodiment. As described above, the current backflow prevention device 50 prevents current from flowing back to the external power supply 40 when the vehicle 1 is started by jump-starting. The current backflow prevention device 50 will be described below using an example in which the voltage of the external power supply 40 is 12 V.

[0033] The current backflow prevention device 50 includes a control unit 12, a voltage measurement unit 22, and a power reception detection unit 24. The control unit 12 is also a computer that performs overall control of the current backflow prevention device 50, and as described above, is connected to each of the DC-DC converter 18, the voltage measurement unit 22, the power reception detection unit 24, and the start button 26 via control circuits.

[0034] The control unit 12 includes a CPU (Central Processing Unit) 60 and a storage unit 70 that can be directly accessed by the CPU 60. The storage unit 70 is, for example, a hard disk drive (HDD), a read only memory (ROM), a random access memory (RAM), a solid state drive (SSD), or any combination thereof.

[0035] The storage unit 70 stores programs, data, and the like for controlling the operation of the current backflow prevention device 50. Data acquired by components connected to the control unit 12 via a control circuit is stored in the storage unit 70 and is updated as necessary.

[0036] As described above, the voltage measurement unit 22 measures the input voltage to the low-voltage battery 20. Therefore, the voltage measurement unit 22 stores input voltage information indicating the input voltage to the low-voltage battery 20 as input voltage data 72 in the storage unit 70.

[0037] When the vehicle 1 is in standby mode and the external power supply 40 and the low-voltage battery 20 are electrically connected by the external cable 42, i.e., when preparations for jump-starting are complete, the DC-DC converter 18 is not operating, and therefore the input voltage data 72 indicates the voltage of the external power supply 40, i.e., 12V.

[0038] As described above, the power reception detection unit 24 detects the power reception state of the vehicle 1. Therefore, the power reception detection unit 24 stores detection information indicating the detection result of whether the vehicle 1 is in a power reception state as detection data 74 in the storage unit 70.

[0039] The CPU 60 executes the programs stored in the storage unit 70 to function as a start-up detection unit 62, a condition setting unit 64, and the like.

[0040] The start-up detection unit 62 detects a start-up operation to start the vehicle 1. Specifically, the start-up detection unit 62 detects a signal input from the start button 26 to the control unit 12 in response to the start button 26 being operated, thereby detecting the start-up operation.

[0041] When the power receiving detection unit 24 detects the power receiving state of the vehicle 1 and the start detection unit 62 detects a start operation, that is, when a start operation corresponding to a jump start is detected, the condition setting unit 64 refers to the input voltage data 72 and sets the start conditions for the DC-DC converter 18 so that the output voltage of the DC-DC converter 18 is equal to or lower than the voltage of the external power source 40, that is, 12 V or lower.

[0042] In such current backflow prevention device 50, the starting conditions of DC-DC converter 18 are set so that when vehicle 1 is started by jump start, the output voltage of DC-DC converter 18 is equal to or lower than the voltage of external power supply 40. Therefore, current backflow prevention device 50 can prevent current from flowing back into external power supply 40 when vehicle 1 is started by jump start, which would be caused by the output voltage of DC-DC converter 18 being higher than the voltage of external power supply 40.

[0043] In this embodiment, in order to prevent current from flowing from the external power supply 40 to the DC-DC converter 18, it is preferable to set the starting conditions of the DC-DC converter 18 so that the output voltage of the DC-DC converter 18 matches the voltage of the external power supply 40 when the vehicle 1 is started by jump-starting.

[0044] This concludes the description of the embodiment of the present invention, but the specific configurations and numerical values ​​shown in this embodiment are merely examples, and the aspects of the present invention are not limited to the configurations shown in this embodiment.

[0045] The vehicle 1 may be a large or small electric vehicle such as an electric truck or a hybrid truck, and there are no particular limitations on where the low-voltage battery 20 is mounted in the vehicle 1. For example, when the low-voltage battery 20 is mounted in a truck or the like, the low-voltage battery 20 may be attached to a side frame or the like.

[0046] Furthermore, a key switch may be used instead of the start button 26 as a means for starting the vehicle 1. In this case, the start detection unit 62 detects the start operation by detecting a signal input from the key switch to the control unit 12 in response to the operation of the key switch.

[0047] Furthermore, there are no particular limitations on the installation location or type of the power reception detection unit 24, as long as it is capable of detecting the power reception state of the vehicle 1. If the power reception state of the vehicle 1 is detected based on changes in the surroundings of the low-voltage battery 20, the power reception detection unit 24 is not limited to detecting the open / closed state of the hood of the vehicle 1, and may also detect, for example, the attachment / detachment state of a cover member of the low-voltage battery 20, or the open / close state of a battery box that houses the low-voltage battery 20, or the attachment / detachment of an external cable 42 to / from the low-voltage battery 20.

[0048] Furthermore, when the vehicle 1 is simply in a standby state, the input voltage to the low-voltage battery 20 is zero. On the other hand, when the vehicle 1 is in a standby state and the external power supply 40 and the low-voltage battery 20 are electrically connected by the external cable 42, that is, when the jump-start implementation stage has been completed, the input voltage to the low-voltage battery 20 is the same as the voltage of the external power supply 40. In other words, only when the vehicle 1 is in a standby state, whether or not the vehicle is in a power receiving state can also be determined by the presence or absence of input voltage to the low-voltage battery 20. Therefore, the power receiving detection unit 24 may be configured to detect the presence or absence of input voltage to the low-voltage battery 20.

[0049] Furthermore, if the external power supply 40 electrically connected to the low-voltage battery 20 of the vehicle 1 is limited to a power supply of a specific voltage, external power supply voltage data indicating the voltage of the external power supply 40 may be stored in advance in the storage unit 70. In this way, if the external power supply voltage data is stored in advance in the storage unit 70, even if the voltage measurement unit 22 is omitted, it is possible to set the start conditions of the DC-DC converter 18 by referring to the external power supply voltage data so that the output voltage of the DC-DC converter 18 is equal to or lower than the voltage of the external power supply 40. [Explanation of symbols]

[0050] 1 vehicle 12 Control Unit 14 High Voltage Battery 18 Voltage converter 20 Low voltage battery 40 External power supply 50 Current backflow prevention device 62 Startup detection unit 64 Condition Setting Degree

Claims

[Claim 1] A current backflow prevention device provided in an electric vehicle including a high-voltage battery for driving, a low-voltage battery having a lower voltage than the high-voltage battery, and a voltage converter having an input side connected to the high-voltage battery and an output side connected to the low-voltage battery, a power receiving detection unit that detects a power receiving state in which the low-voltage battery receives power supply from an external power source; a start detection unit that detects a start operation for starting the electric vehicle; and a condition setting unit that sets a start condition for the voltage converter so that the output voltage of the voltage converter becomes equal to or lower than the voltage of the external power source when the power receiving detection unit detects the power receiving state and the start-up detection unit detects the start-up operation.

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