Vehicle control device

Abstract

To enable inexpensive detection that stop of power supply to a DC / DC converter is no longer being normally performed.SOLUTION: A vehicle control device includes: an inverter for driving an electric motor; a DC / DC converter that reduces a voltage of a high-voltage battery; a main relay that switches on / off of an input of the voltage of the high-voltage battery to the inverter and the DC / DC converter; a precharge circuit including a precharge relay; a voltage detection unit that detects an input voltage V of the inverter and the DC / DC converter; and a controller. After the precharge is completed and before the main relay is turned on and the precharge relay is turned off, when the level of the input voltage V of the inverter and the DC / DC converter is lowered below the level at the time of precharge completion of the inverter, the controller determines that the stop of the power supply to the DC / DC converter is not normally performed.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a vehicle control device that controls an electric vehicle. [Background technology]

[0002] Electric vehicles, hybrid vehicles, and other electrically powered vehicles include an electric motor as a power source for driving, a high-voltage battery that outputs high voltage to drive the electric motor, on-board equipment that is an electric / electronic device that operates at a low voltage of, for example, 12 V, a low-voltage battery that supplies power to the on-board equipment, and a vehicle control device that controls the electric vehicle.

[0003] The vehicle control device includes an inverter that drives the electric motor, and a DC (Direct Current) / DC converter that reduces the voltage of the high-voltage battery to, for example, 12 V in order to charge the low-voltage battery and supply power to on-board equipment.

[0004] The vehicle control device also includes a main relay that switches on / off the input of voltage from the high-voltage battery to the inverter and the DC / DC converter, and a precharge circuit that precharges the inverter. The precharge circuit includes a precharge resistor that generates a precharge current by reducing the current value from the high-voltage battery, and a precharge relay that switches on / off the input of the precharge current to the inverter.

[0005] The vehicle control device also includes a voltage detection circuit that detects the input voltage input from the high-voltage battery to the inverter and the DC / DC converter, and a controller that performs various controls related to the electric vehicle, such as open / close switching control of the main relay, open / close switching control of the pre-charge relay, operation / stop switching control of the inverter, and operation / stop switching control of the DC / DC converter.

[0006] In the vehicle control device, the inverter and the DC / DC converter are connected in parallel to the high-voltage battery, and the main relay and the precharge circuit are connected in parallel to each other midway along a path connecting the high-voltage battery to the inverter and the DC / DC converter.

[0007] When the main relay is open and the pre-charge relay is closed, a pre-charge current is input from the high-voltage battery to the inverter via the pre-charge circuit. On the other hand, when the main relay is closed and the pre-charge relay is open, a drive current required for inverter operation is input from the high-voltage battery to the inverter. Furthermore, when either the main relay or the pre-charge relay is closed, the voltage output from the high-voltage battery is input to the inverter and the DC / DC converter, respectively.

[0008] The DC / DC converter receives voltage from a high-voltage battery to step down the voltage of the high-voltage battery, but also receives power from a low-voltage battery to operate the DC / DC converter itself. The DC / DC converter also has an operation control circuit that controls itself. This operation control circuit has the function of switching whether the DC / DC converter receives power from the low-voltage battery or not.

[0009] The controller controls the operation control circuit of the DC / DC converter to switch between operation and stop of the DC / DC converter. Specifically, the controller outputs an operation control signal to the DC / DC converter. For example, when the voltage level of the operation control signal output from the controller is at a first level, the operation control circuit of the DC / DC converter puts the DC / DC converter into a state in which it receives power supply from the low-voltage battery. This causes the DC / DC converter to operate. On the other hand, when the voltage level of the operation control signal output from the controller is at a second level, the operation control circuit of the DC / DC converter puts the DC / DC converter into a state in which it cuts off the power supply from the low-voltage battery. This causes the DC / DC converter to stop.

[0010] A vehicle control device configured as described above operates as follows. While the vehicle's power switch is off, the controller is in an idle state. Also, while the vehicle's power switch is off, the operation control circuit of the DC / DC converter sets the DC / DC converter to a state in which power supply from the low-voltage battery is cut off in accordance with a second-level operation control signal output from the idle controller to the DC / DC converter. As a result, the DC / DC converter is stopped. Also, while the vehicle's power switch is off, the inverter is stopped, and the main relay and pre-charge relay are both open.

[0011] When the vehicle's power switch is turned on, the controller becomes active. The controller closes the precharge relay while leaving the main relay open. This allows precharge current to be input from the high-voltage battery to the inverter via the precharge circuit, precharging the inverter.

[0012] When the pre-charging of the inverter is completed, the input voltage input from the high-voltage battery to the inverter becomes approximately equal to the normal discharge voltage of the high-voltage battery. The controller recognizes the input voltage input from the high-voltage battery to the inverter based on the detection signal output from the voltage detection circuit and recognizes that the pre-charging of the inverter is completed. The controller then closes the main relay and opens the pre-charge relay.

[0013] The controller then switches the voltage level of the operation control signal output to the DC / DC converter from the second level to the first level. This causes the DC / DC converter's operation control circuit to set the DC / DC converter to a state where it receives power from the low-voltage battery. This causes the DC / DC converter to start operating and begin stepping down the voltage output from the high-voltage battery. The voltage stepped down by the DC / DC converter then charges the low-voltage battery and supplies power to the on-board equipment. The controller also operates the inverter.

[0014] After that, when the vehicle's power switch is turned off, the controller opens the main relay, which stops the input of drive current from the high-voltage battery to the inverter and causes the input voltages of the inverter and DC / DC converter to drop to zero. Next, the controller switches the voltage level of the operation control signal output to the DC / DC converter from the first level to the second level. This causes the DC / DC converter's operation control circuit to put the DC / DC converter into a state that cuts off the power supply from the low-voltage battery. This stops the DC / DC converter, preventing charging of the low-voltage battery or power supply to on-board equipment. The controller also stops the inverter.

[0015] Patent Document 1 listed below describes a device similar to the above vehicle control device. [Prior art documents] [Patent documents]

[0016] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-10280 Summary of the Invention [Problem to be solved by the invention]

[0017] In the vehicle control device, when the vehicle's power switch is turned off, the DC / DC converter's operation control circuit, in accordance with the operation control signal output from the controller, puts the DC / DC converter into a state in which power supply from the low-voltage battery is cut off. This stops the power supply from the low-voltage battery to the DC / DC converter. However, an abnormality may occur in which the power supply from the low-voltage battery to the DC / DC converter does not stop even when the vehicle's power switch is turned off.

[0018] For example, the operation control circuit of the DC / DC converter is configured to place the DC / DC converter in a state where it receives power from the low-voltage battery when the operation control signal output from the controller is at ground level, and to place the DC / DC converter in a state where it cuts off the power supply from the low-voltage battery when the operation control signal output from the controller is at a non-ground level. In this case, if a ground fault occurs in the path that sends the operation control signal from the controller to the DC / DC converter for some reason, the DC / DC converter enters a state equivalent to a constant input of a ground-level operation control signal. Therefore, the DC / DC converter is unable to cut off the power supply from the low-voltage battery in accordance with the operation control signal from the controller. As a result, the low-voltage battery continues to supply power to the DC / DC converter even when the power switch is turned off.

[0019] While the power switch is off, both the main relay and precharge relay are open, preventing the high-voltage battery voltage from being input to the DC / DC converter. Therefore, even if the DC / DC converter is receiving power from the low-voltage battery, the DC / DC converter does not perform step-down operation. However, in this state, the DC / DC converter still consumes power from the low-voltage battery, albeit a small amount compared to when the DC / DC converter is performing step-down operation. This power consumption is wasteful and must be reduced. Therefore, it is necessary to detect an abnormality in which the power supply from the low-voltage battery to the DC / DC converter does not stop even when the vehicle's power switch is off.

[0020] In this regard, it is conceivable to add a circuit (hardware) for detecting this abnormality, but adding such a circuit would increase manufacturing costs, which is not desirable.

[0021] The present invention has been made in view of the problems described above, and an object of the present invention is to provide a vehicle control device that can inexpensively detect when power supply to a DC / DC converter is no longer being stopped normally. [Means for solving the problem]

[0022] In order to solve the above problems, the present invention provides a vehicle control device for controlling an electric vehicle having an electric motor as a power source for traveling, a high-voltage battery that outputs a high voltage for driving the electric motor, on-board equipment that operates at a low voltage, and a low-voltage battery that outputs a low voltage for operating the on-board equipment, the vehicle control device including an inverter that drives the electric motor using a voltage output from the high-voltage battery, a DC / DC converter that steps down the voltage output from the high-voltage battery and outputs a voltage used to charge the low-voltage battery or operate the on-board equipment, a main switch that switches on / off the input of the voltage output from the high-voltage battery to the inverter and the DC / DC converter, a pre-charge circuit having a pre-charge current generation unit that generates a pre-charge current using a current output from the high-voltage battery and a pre-charge switch that switches on / off the input of the pre-charge current to the inverter, and a low-voltage battery that outputs a low voltage for operating the on-board equipment from the high-voltage battery. a controller that inputs the precharge current to the inverter by turning the main switch off and the precharge switch on to start precharging of the inverter, and turns the main switch on and the precharge switch off after precharging of the inverter is completed, wherein the inverter and the DC / DC converter are connected in parallel to the high-voltage battery, and the main switch and the precharge circuit are connected in parallel to each other in a path connecting the high-voltage battery with the inverter and the DC / DC converter, and the controller determines whether or not the input voltage detected by the voltage detection unit has dropped below the input voltage input from the high-voltage battery to the inverter and the DC / DC converter at the time precharging of the inverter is completed before turning the main switch on and the precharge switch offWhen the input voltage detected by the voltage detection unit becomes lower than the input voltage input from the high-voltage battery to the inverter and the DC / DC converter at the time when precharging of the inverter is completed, it is determined that the power supply from the power supply of the DC / DC converter to the DC / DC converter has not been stopped normally. [Effects of the Invention]

[0023] According to the present invention, it is possible to inexpensively detect that the power supply to a DC / DC converter is not being stopped normally. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a circuit diagram showing an electric motor, a high-voltage battery, on-board equipment, a low-voltage battery, and a vehicle control device according to an embodiment of the present invention. [Figure 2] 3 is a characteristic diagram showing changes in input voltage of an inverter and a DC / DC converter during precharge in the vehicle control device according to the embodiment of the present invention. FIG. [Figure 3] 4 is a flowchart showing a vehicle start process in a controller of the vehicle control device according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] A vehicle control device according to an embodiment of the present invention is a vehicle control device that controls an electric vehicle equipped with an electric motor that serves as a power source for driving the vehicle, a high-voltage battery that outputs a high voltage to drive the electric motor, on-board equipment that operates at a low voltage, and a low-voltage battery that outputs a low voltage to operate the on-board equipment.

[0026] The vehicle control device of this embodiment includes an inverter, a DC / DC converter, a main switch, a precharge circuit, a voltage detection unit, and a controller.

[0027] An inverter is a circuit that drives an electric motor using the voltage output from a high-voltage battery, while a DC / DC converter is a circuit that steps down the voltage output from the high-voltage battery and outputs a voltage that is used to charge a low-voltage battery or operate on-board equipment.

[0028] The main switch is a switch that switches on / off the input of the voltage output from the high-voltage battery to the inverter and the DC / DC converter. The precharge circuit is a circuit that precharges the inverter. The precharge circuit has a precharge current generator that generates a precharge current using the current output from the high-voltage battery, and a precharge switch that switches on / off the input of the precharge current to the inverter.

[0029] The voltage detection unit is a circuit that detects the input voltage input from the high-voltage battery to the inverter and the DC / DC converter.

[0030] The controller has a function of inputting a precharge current to the inverter by turning the main switch off and the precharge switch on to start precharging the inverter, and after completing precharging of the inverter, turning the main switch on and the precharge switch off.

[0031] In the vehicle control device of this embodiment, the inverter and the DC / DC converter are connected in parallel to the high-voltage battery, and the main switch and the precharge circuit are connected in parallel to each other midway along a path connecting the high-voltage battery to the inverter and the DC / DC converter.

[0032] Furthermore, after precharging of the inverter is completed, but before the main switch is turned on and the precharge switch is turned off, the controller determines whether the input voltage detected by the voltage detection unit has dropped below the input voltage input from the high-voltage battery to the inverter and DC / DC converter at the time precharging of the inverter is completed, and if the input voltage detected by the voltage detection unit has dropped below the input voltage input from the high-voltage battery to the inverter and DC / DC converter at the time precharging of the inverter is completed, the controller determines that the power supply from the DC / DC converter power supply to the DC / DC converter has not been stopped normally.

[0033] In the vehicle control device of this embodiment, for example, when the power switch of the electric vehicle is turned on, the controller inputs a pre-charge current to the inverter by turning off the main switch and turning on the pre-charge switch, thereby starting pre-charging of the inverter. As a result, the input voltages of the inverter and the DC / DC converter connected in parallel with the inverter to the high-voltage battery gradually increase, and when pre-charging of the inverter is completed, the input voltage becomes approximately equal to the normal discharge voltage of the high-voltage battery.

[0034] After the inverter precharge is complete, almost no precharge current flows into the inverter. Furthermore, if the power supply from the DC / DC converter power supply to the DC / DC converter is stopped normally, the DC / DC converter is stopped when the power switch of the electric vehicle is turned off. The power switch of the electric vehicle is then turned on, the inverter is precharged, and the DC / DC converter remains stopped even when the inverter precharge is complete. If the DC / DC converter is stopped after the inverter precharge is complete, almost no precharge current flows into the DC / DC converter. This state in which almost no precharge current flows into either the inverter or the DC converter is maintained by keeping the main switch off and the precharge switch on. As a result, by keeping the main switch off and the precharge switch on after the inverter precharge is complete, the input voltages of the inverter and the DC / DC converter are maintained at approximately the same level as the normal discharge voltage of the high-voltage battery.

[0035] On the other hand, if the power supply from the DC / DC converter power supply to the DC / DC converter is not stopped normally when the power switch of the electric vehicle is turned off. Then, when the power switch of the electric vehicle is turned on, the inverter is precharged, and the DC / DC converter is not stopped even when the inverter precharge is completed. In this case, during the inverter precharge, the input voltage of the inverter and the DC / DC converter reaches an input voltage at which the DC / DC converter can perform a step-down operation. After a certain time has passed, the DC / DC converter begins to perform a step-down operation. As a result, a precharge current begins to flow into the DC / DC converter. The precharge current usually begins to flow into the DC / DC converter after the precharge is completed. As a result, the input voltage of the inverter and the DC / DC converter temporarily becomes approximately equal to the normal discharge voltage of the high-voltage battery when the inverter precharge is completed, and then begins to decrease.

[0036] To summarize the above, if the power supply from the DC / DC converter power supply to the DC / DC converter is stopped normally, the input voltage levels of the inverter and DC / DC converter will maintain the level at which the inverter precharge was completed while the main switch is off and the precharge switch is on after the inverter precharge is completed. On the other hand, if the power supply from the DC / DC converter power supply to the DC / DC converter is not stopped normally, the input voltage levels of the inverter and DC / DC converter will drop below the level at which the inverter precharge was completed while the main switch is off and the precharge switch is on after the inverter precharge is completed.

[0037] After the pre-charging of the inverter is completed, but before the main switch is turned on and the pre-charge switch is turned off, the controller determines whether the input voltage detected by the voltage detection unit has dropped below the input voltage input from the high-voltage battery to the inverter and the DC / DC converter at the time of completion of the pre-charging of the inverter, thereby enabling the controller to determine whether the power supply from the power supply of the DC / DC converter to the DC / DC converter has been stopped normally.

[0038] This determination can be realized by using a voltage detection unit provided in an existing vehicle control device as a means for determining whether precharging is complete, and by adding or modifying a computer program executed by the controller. That is, this determination can be realized by adding or modifying software to an existing vehicle control device, and there is no need to add new hardware to the existing vehicle control device to make this determination. Therefore, the vehicle control device of this embodiment can inexpensively detect whether the power supply to the DC / DC converter has been stopped normally. [Example]

[0039] Hereinafter, an embodiment of a vehicle control device according to the present invention will be described.

[0040] (Vehicle control device) FIG. 1 is a circuit diagram showing a vehicle control device 11 and the like according to an embodiment of the present invention. The vehicle control device 11 is a device that controls a vehicle. The vehicle is an automobile that uses an electric motor as a power source for traveling, such as an electric vehicle, a fuel cell vehicle, or a hybrid vehicle. The vehicle may also be a four-wheeled motor vehicle, a three-wheeled motor vehicle, a two-wheeled motor vehicle, or the like.

[0041] As shown in FIG. 1, a vehicle is provided with an electric motor 1, a high-voltage battery 2, on-board equipment 3, a low-voltage battery 4, a vehicle power switch 5, and a vehicle control device 11. The electric motor 1 is a power source for driving the vehicle. The high-voltage battery 2 is a storage battery that outputs a voltage for driving the electric motor 1. The nominal voltage of the high-voltage battery 2 is, for example, 100 V to 500 V or higher. The on-board equipment 3 is an electric / electronic device that operates at a low voltage (for example, 12 V). The low-voltage battery 4 is a storage battery that outputs a voltage for operating the on-board equipment 3. The nominal voltage of the low-voltage battery 4 is, for example, 12 V. The power switch 5 is a switch that allows the user to turn the overall power of the vehicle on and off.

[0042] The vehicle control device 11 includes an inverter 12, a DC / DC converter 13, a main relay 15 as a main switch, a pre-charge circuit 16, a voltage detection unit 19, and a controller 20. The inverter 12 and the DC / DC converter 13 are connected in parallel to the high-voltage battery 2. The main relay 15 and the pre-charge circuit 16 are connected in parallel to each other midway along a path connecting the positive terminal of the high-voltage battery 2 to the positive input terminal of the inverter 12 and the positive input terminal of the DC / DC converter 13 (between the positive terminal of the high-voltage battery 2 and point P). The electric motor 1 is connected to the output side of the inverter 12. The on-board device 3 and the low-voltage battery 4 are each connected to the output side of the DC / DC converter 13. The controller 20 is connected to a control terminal of the main relay 15, a control terminal of a pre-charge relay 18 in the pre-charge circuit 16, a control terminal of the DC / DC converter 13, a control terminal of the inverter 12, and the voltage detection unit 19. The controller 20 is also connected to a power switch 5 of the vehicle.

[0043] The inverter 12 is a circuit that controls the driving of the electric motor 1 using the power output from the high-voltage battery 2.

[0044] The DC / DC converter 13 is a circuit that steps down the voltage output from the high-voltage battery 2 and outputs a voltage used to charge the low-voltage battery 4 and operate the in-vehicle device 3 .

[0045] The power source for the DC / DC converter 13 itself is the low-voltage battery 4. The DC / DC converter 13 operates by receiving power from the low-voltage battery 4. The DC / DC converter 13 also has an operation control circuit 14 that controls the DC / DC converter 13. The operation control circuit 14 has a function of switching whether the DC / DC converter 13 receives power from the low-voltage battery 4. The DC / DC converter 13 also has a control terminal that controls the operation control circuit 14 via the controller 20. An operation control signal output from the controller 20 is input to this control terminal. The operation control circuit 14 switches whether the DC / DC converter 13 receives power from the low-voltage battery 4 in accordance with the operation control signal.

[0046] When the voltage level of the operation control signal is at the ground level, the operation control circuit 14 sets the state of the DC / DC converter 13 to a state in which it receives power supply from the low-voltage battery 4. This causes the DC / DC converter 13 to operate. On the other hand, when the voltage level of the operation control signal is at the non-ground level, the operation control circuit 14 sets the state of the DC / DC converter 13 to a state in which it cuts off the power supply from the low-voltage battery 4. This causes the DC / DC converter 13 to stop.

[0047] The main relay 15 is a switch that switches on / off the input of the voltage output from the high-voltage battery 2 to the inverter 12 and the DC / DC converter 13. The pre-charge circuit 16 is a circuit for pre-charging the inverter 12. Pre-charging the inverter 12 is a process that charges an input current smoothing capacitor provided in the inverter 12 when the input of voltage from the high-voltage battery 2 to the inverter 12 begins. The pre-charge circuit 16 includes a pre-charge resistor 17 that serves as a pre-charge current generator, and a pre-charge relay 18 that serves as a pre-charge switch. The pre-charge resistor 17 is a resistor that generates a pre-charge current by reducing the current value of the current output from the high-voltage battery 2. The pre-charge relay 18 is a switch that switches on / off the input of the pre-charge current to the inverter 12.

[0048] The voltage detection unit 19 detects the input voltage input from the high-voltage battery 2 to the inverter 12 and the DC / DC converter 13. Since the inverter 12 and the DC / DC converter 13 are connected in parallel to the high-voltage battery 2, the input voltage of the inverter 12 and the input voltage of the DC / DC converter 13 are equal to each other.

[0049] The controller 20 includes a CPU (Central Processing Unit), a memory, and the like. The controller 20 enters an active state (normal operation state) when the vehicle's power switch 5 is turned on, and enters an idle state (power-saving operation state) when the vehicle's power switch 5 is turned off. The controller 20 also outputs a main relay control signal to the main relay 15 to control the opening / closing of the main relay 15. The controller 20 also outputs a pre-charge relay control signal to the pre-charge relay 18 to control the opening / closing of the pre-charge relay 18. The controller 20 also outputs an operation control signal to the DC / DC converter 13 to control the operation control circuit 14 of the DC / DC converter 13. The controller 20 also outputs another operation control signal to the inverter to control the operation / stop of the inverter 12. The controller 20 can recognize the input voltages of the inverter 12 and the DC / DC converter 13 based on the detection results of the voltage detection unit 19. The controller 20 can also measure time.

[0050] Normally, after the vehicle's power switch 5 is turned on, pre-charging of the inverter 12 is completed, and the main relay 15 is closed and the pre-charge relay 18 is open, the controller 20 sets the voltage level of the operation control signal to the ground level while the power switch 5 is on. This causes the operation control circuit 14 of the DC / DC converter 13 to set the DC / DC converter 13 to a state in which it receives power supply from the low-voltage battery 4. On the other hand, while the vehicle's power switch 5 is off, the controller 20 sets the voltage level of the operation control signal to the non-ground level. This causes the operation control circuit 14 of the DC / DC converter 13 to set the DC / DC converter 13 to a state in which it cuts off the power supply from the low-voltage battery 4.

[0051] Furthermore, the controller 20 has a function to detect the occurrence of an abnormality in which the power supply from the low-voltage battery 4 to the DC / DC converter 13 does not stop even when the vehicle's power switch 5 is turned off (hereinafter, this will be referred to as an "abnormality in the DC / DC converter 13"). An abnormality in the DC / DC converter 13 occurs when, for some reason, a ground fault occurs in the path that transmits the operation control signal from the controller 20 to the DC / DC converter 13. If a ground fault occurs in the path that transmits the operation control signal from the controller 20 to the DC / DC converter 13, the DC / DC converter 13 enters a state equivalent to a ground-level operation control signal being constantly input. Therefore, the DC / DC converter 13 cannot cut off the power supply from the low-voltage battery 4 in accordance with the operation control signal from the controller 20. As a result, the power supply from the low-voltage battery 4 to the DC / DC converter 13 continues even when the vehicle's power switch 5 is turned off.

[0052] While the power switch 5 is off, both the main relay 15 and the pre-charge relay 18 are open, and therefore the voltage of the high-voltage battery 2 is not input to the DC / DC converter 13. Therefore, even when power is being supplied to the DC / DC converter 13 from the low-voltage battery 4, the DC / DC converter 13 does not perform a voltage step-down operation. However, in this state, the DC / DC converter 13 still consumes power from the low-voltage battery 4, although this amount is smaller than when the DC / DC converter 13 is performing a voltage step-down operation. The controller 20 can detect the occurrence of such an abnormality in the DC / DC converter 13 and notify the user of the occurrence of the abnormality in the DC / DC converter 13.

[0053] (Principle of DC / DC converter abnormality detection) The principle of abnormality detection of DC / DC converter 13 by controller 20 will be described. When vehicle power switch 5 is turned on, controller 20 precharges inverter 12. When precharging inverter 12, controller 20 detects the occurrence of an abnormality in DC / DC converter 13.

[0054] Figure 2(A) shows the change in input voltage of inverter 12 and DC / DC converter 13 during pre-charge when no abnormality has occurred in DC / DC converter 13. Figure 2(B) shows the change in input voltage of inverter 12 and DC / DC converter 13 during pre-charge when an abnormality has occurred in DC / DC converter 13. Hereinafter, the input voltage of inverter 12 and DC / DC converter 13 will be referred to as "input voltage V".

[0055] First, some terms used in explaining the principles of abnormality detection in DC / DC converters will be explained.

[0056] The reference voltage used to determine whether precharging of the inverter 12 is complete based on the input voltage V is called the "precharge completion reference voltage." The precharge completion reference voltage is set to, for example, the lower limit of the normal discharge voltage of the high-voltage battery 2. Va in FIG. 2 is the precharge completion reference voltage. The lower limit of the normal discharge voltage of the high-voltage battery 2 is, for example, a value lower than the nominal voltage of the high-voltage battery 2 but higher than the discharge end voltage.

[0057] The time required from the start to the completion of precharging the inverter 12 is referred to as the “precharge required time.” Pa in FIG. 2 is the precharge required time.

[0058] The lower limit of the input voltage of DC / DC converter 13 at which DC / DC converter 13 can perform the operation of stepping down the input voltage and outputting the stepped-down voltage (step-down operation) is called the "step-down operation lower limit voltage." Vb in Figure 2 is the step-down operation lower limit voltage. The step-down operation lower limit voltage Vb is lower than the precharge completion reference voltage Va.

[0059] Furthermore, the time required for DC / DC converter 13 to step down the input voltage and output the stepped-down voltage after a voltage equal to or greater than step-down operation lower-limit voltage Vb is input to DC / DC converter 13 when no voltage equal to or greater than step-down operation lower-limit voltage Vb has been input is referred to as the "step-down operation start time." The step-down operation start time is set, for example, based on data obtained by conducting a test or the like in advance. Pb in Figure 2 is the step-down operation start time.

[0060] Next, referring to FIG. 2A, a change in the input voltage V when no abnormality occurs in the DC / DC converter 13 will be described. Precharging of the inverter 12 begins when the main relay 15 is open and the precharge relay 18 is closed. During precharging, the inverter 12 is stopped or in a ready-to-operate state. In FIG. 2A, when precharging of the inverter 12 begins at time t1, a precharge current flows into the inverter 12. Thereafter, the input voltage V of the inverter 12 and the DC / DC converter 13 gradually increases and reaches the step-down operation lower-limit voltage Vb at time t2. Thereafter, the input voltage V further increases and reaches the precharge completion reference voltage Va at time t3. When the input voltage V reaches the precharge completion reference voltage Va, precharging of the inverter 12 is completed. When precharging of the inverter 12 is completed, almost no precharge current flows into the inverter 12, which is stopped or in a ready-to-operate state. As described above, the controller 20 sets the voltage level of the operation control signal to a non-grounded level while the vehicle's power switch 5 is off. This causes the operation control circuit 14 of the DC / DC converter 13 to set the state of the DC / DC converter 13 to a state in which power supply from the low-voltage battery 4 is cut off. As a result, the DC / DC converter 13 is stopped while the vehicle's power switch 5 is off. Therefore, even if the vehicle's power switch 5 is switched from off to on, the state in which power supply from the low-voltage battery 4 to the DC / DC converter 13 is cut off is maintained, and the DC / DC converter 13 remains stopped, unless the controller 20 changes the voltage level of the operation control signal from the non-grounded level to the grounded level. The pre-charge current hardly flows into the stopped DC / DC converter 13 (strictly speaking, since a smoothing capacitor is provided on the input side of the DC / DC converter 13, when pre-charging of the inverter 12 starts, the pre-charge current flows into the stopped DC / DC converter 13, but when pre-charging of the inverter 12 is completed, almost no pre-charge current flows into the stopped DC / DC converter 13).Therefore, after time t3, as long as the main relay 15 is open, the pre-charge relay 18 is closed, the inverter 12 is in a stopped state or a ready-to-operate state, and the DC / DC converter 13 is in a stopped state, the input voltage V remains approximately constant.

[0061] Next, referring to FIG. 2B, a description will be given of changes in the input voltage V of the inverter 12 and the DC / DC converter 13 during precharging when an abnormality occurs in the DC / DC converter 13. In FIG. 2B, after precharging of the inverter 12 starts at time t1, the input voltage V of the inverter 12 and the DC / DC converter 13 gradually increases and reaches the step-down operation lower-limit voltage Vb at time t2. The input voltage V then increases further and reaches the precharge completion reference voltage Va at time t3. When the input voltage V reaches the precharge completion reference voltage Va, precharging of the inverter 12 is completed. Once precharging of the inverter 12 is completed, almost no precharge current flows into the inverter 12, which is in a stopped state or in an operation preparation state. However, when an abnormality occurs in the DC / DC converter 13, the controller 20's control of the DC / DC converter 13 (operation control circuit 14) is ineffective, and power continues to be supplied to the DC / DC converter 13 from the low-voltage battery 4 even after the vehicle's power switch 5 is turned off. Even after the vehicle's power switch 5 is switched from off to on and pre-charging of the inverter 12 is initiated, power continues to be supplied from the low-voltage battery 4 to the DC / DC converter 13. In this case, even during pre-charging of the inverter 12, if a voltage equal to or greater than the step-down operation lower-limit voltage Vb is input from the high-voltage battery 2 to the DC / DC converter 13, the DC / DC converter 13 will step down the input voltage and output the stepped-down voltage after the step-down operation start required time Pb has elapsed. When the DC / DC converter 13 is in this state, a pre-charge current begins to flow into the DC / DC converter 13. As a result, the input voltage V drops after time t4.

[0062] 2(A) and 2(B), the following two points can be understood. First, when no abnormality occurs in DC / DC converter 13, the input voltage V at precharge completion time t3 is maintained even after time t4, as shown in FIG. 2(A). In contrast, when an abnormality occurs in DC / DC converter 13, the input voltage V drops below the input voltage V at precharge completion time t3 after time t4, as shown in FIG. 2(B). Second, after precharge starts at time t1, the input voltage V reaches the step-down operation lower-limit voltage Vb at time t2. At time t4, which is when step-down operation start required time Pb has elapsed since time t2, the precharge required time Pa has already elapsed, and therefore precharging of inverter 12 has already been completed. From these two points, it is possible to detect whether or not an abnormality has occurred in DC / DC converter 13 by determining whether or not input voltage V has dropped below input voltage V at the completion of precharging of inverter 12 after the time required for starting step-down operation Pb has elapsed since input voltage V reached step-down operation lower-limit voltage Vb after precharging of inverter 12 has started.

[0063] The controller 20 detects the occurrence of an abnormality in the DC / DC converter 13 based on the above-described principle of abnormality detection for the DC / DC converter 13. Specifically, after starting precharging of the inverter 12, the controller 20 determines whether the input voltage V is lower than the precharge completion reference voltage Va at time t5, which is the elapse of a determination wait time Pw from the time when the input voltage V reached the step-down operation lower-limit voltage Vb. The determination wait time Pw is the time obtained by adding an additional time Pc to the step-down operation start time Pb. The additional time Pc is a margin for reliably detecting a drop in the input voltage V after the step-down operation start time Pb has elapsed if an abnormality has occurred in the DC / DC converter 13. Furthermore, the controller 20 determines whether the input voltage V has dropped below the input voltage V at time t5 when precharging of the inverter 12 is completed by comparing the input voltage V at time t5 with the precharge completion reference voltage Va.

[0064] If, at time t5, the input voltage V is not lower than the precharge completion reference voltage Va, it can be determined that no abnormality has occurred in the DC / DC converter 13. If, on the other hand, the input voltage V is lower than the precharge completion reference voltage Va at time t5, it can be determined that an abnormality has occurred in the DC / DC converter 13.

[0065] (Vehicle start processing) The controller 20 performs abnormality detection processing for the DC / DC converter 13 during vehicle start processing, which includes precharging processing for the inverter 12. Figure 3 shows the vehicle start processing.

[0066] In Fig. 3, when the vehicle power switch 5 is off, the controller 20 is in an idle state. The main relay 15 and the pre-charge relay 18 are both open. When no abnormality occurs in the DC / DC converter 13, the voltage level of the operation control signal is at a non-ground level. The inverter is also stopped.

[0067] When the power switch 5 of the vehicle is turned on, the controller 20 transitions from an idle state to an active state (step S1). Furthermore, if the inverter 12 needs to be put into an operation ready state for precharging, the controller 20 puts the inverter 12 into the operation ready state.

[0068] Next, the controller 20 closes the precharge relay 18 while keeping the main relay 15 open (step S2), thereby starting precharging of the inverter 12.

[0069] Subsequently, the controller 20 determines whether or not the input voltage V (input voltage of the inverter 12 and the DC / DC converter 13) detected by the voltage detection unit 19 has reached the step-down operation lower limit voltage Vb (step S3).

[0070] If the input voltage V detected by the voltage detection unit 19 has not reached the step-down operation lower limit voltage Vb (step S3: NO), the controller 20 waits for the input voltage V detected by the voltage detection unit 19 to reach the step-down operation lower limit voltage Vb while repeatedly determining whether the input voltage V detected by the voltage detection unit 19 has reached the step-down operation lower limit voltage Vb.

[0071] If the input voltage V detected by the voltage detection unit 19 reaches the step-down operation lower limit voltage Vb (step S3: YES), the controller 20 waits for the determination waiting time Pw to elapse from the time when the input voltage V detected by the voltage detection unit 19 reaches the step-down operation lower limit voltage Vb (step S4).

[0072] When the judgment waiting time Pw has elapsed since the input voltage V detected by the voltage detection unit 19 reached the step-down operation lower limit voltage Vb (step S4: YES), the controller 20 determines whether the input voltage V detected by the voltage detection unit 19 is lower than the precharge completion reference voltage Va (step S5).

[0073] As described above, if no abnormality has occurred in DC / DC converter 13, input voltage V detected by voltage detection unit 19 will not become lower than precharge completion reference voltage Va. Furthermore, precharging of inverter 12 is completed when determination wait time Pw has elapsed since input voltage V detected by voltage detection unit 19 reached step-down operation lower-limit voltage Vb. If input voltage V detected by voltage detection unit 19 is not lower than precharge completion reference voltage Va (step S5: NO), controller 20 closes main relay 15 (step S6) and then opens precharge relay 18 (step S7).

[0074] Next, the controller 20 changes the voltage level of the operation control signal from the non-grounded level to the grounded level (step S8). As a result, the operation control circuit 14 of the DC / DC converter 13 sets the state of the DC / DC converter 13 to a state in which it receives power supply from the low-voltage battery 4. As a result, the DC / DC converter 13 starts operation and performs a voltage step-down operation. Then, the voltage output from the DC / DC converter 13 is input to the low-voltage battery 4 and the in-vehicle equipment 3, charging the low-voltage battery 4 and supplying power to the in-vehicle equipment 3. The controller 20 also operates the inverter 12.

[0075] On the other hand, if an abnormality has occurred in the DC / DC converter 13, in step S5, the input voltage V detected by the voltage detection unit 19 becomes lower than the precharge completion reference voltage Va. If the input voltage V detected by the voltage detection unit 19 is lower than the precharge completion reference voltage Va (step S5: YES), the controller 20 opens the precharge relay 18 (step S9) and then performs abnormality response processing (step S10). For example, as the abnormality response processing, the controller 20 turns on a notification lamp provided on the instrument panel of the vehicle to notify the user that an abnormality has occurred in the DC / DC converter 13. This allows the user to recognize the occurrence of an abnormality in the DC / DC converter 13.

[0076] As described above, in the vehicle control device 11 according to the embodiment of the present invention, after precharging of the inverter 12 is started, the controller 20 determines whether the input voltage V detected by the voltage detection unit 19 is lower than the precharge completion reference voltage Va when the determination wait time Pw has elapsed since the input voltage V detected by the voltage detection unit 19 reached the step-down operation lower limit voltage Vb. This determines whether an abnormality has occurred in the DC / DC converter 13. This determination can be realized by using the voltage detection unit 19 provided in an existing vehicle control device as a means for determining precharge completion, and by adding or modifying the computer program executed by the controller 20. In other words, this determination can be realized by adding or modifying software to the existing vehicle control device, and does not require the addition of new hardware to the existing vehicle control device. Therefore, the vehicle control device 11 according to the embodiment can inexpensively detect an abnormality in the DC / DC converter 13.

[0077] Furthermore, according to the vehicle control device 11 of this embodiment, it is possible to detect the occurrence of an abnormality in the DC / DC converter 13 during pre-charging of the inverter 12, which is performed when the vehicle's power switch 5 is turned on. Therefore, when an abnormality in the DC / DC converter 13 is detected, for example, a notification lamp provided on the vehicle's instrument panel is turned on to notify the user of the occurrence of an abnormality in the DC / DC converter 13, so that the user can be reliably notified of the occurrence of an abnormality in the DC / DC converter 13 when the user turns on the vehicle's power switch 5 and prepares to drive.

[0078] Furthermore, in the vehicle control device 11 of this embodiment, the controller 20 detects the occurrence of an abnormality in the DC / DC converter 13 based on a drop in the input voltage V caused by a pre-charge current flowing into the DC / DC converter 13 from its input side. The drop in the input voltage V caused by a pre-charge current flowing into the DC / DC converter 13 from its input side occurs regardless of the output characteristics of the DC / DC converter 13, such as the maximum output and output voltage value. In particular, if the DC / DC converter 13 is an isolated type, the input and output sides are electrically isolated by an internal transformer, so the drop in the input voltage V caused by the pre-charge current flowing into the DC / DC converter 13 from its input side is less likely to be affected by the output characteristics of the DC / DC converter 13. Therefore, the vehicle control device 11 of this embodiment can prevent the output characteristics of the DC / DC converter 13 from causing a decrease in the accuracy of detecting the occurrence of an abnormality in the DC / DC converter 13.

[0079] Furthermore, in the vehicle control device 11 of this embodiment, after starting precharging of the inverter 12, the controller 20 determines whether the input voltage V is lower than the precharge completion reference voltage Va when the determination wait time Pw has elapsed since the input voltage V reached the step-down operation lower limit voltage Vb. Therefore, in FIG. 2 , if the time between the start time t1 of precharging and the time t2 when the input voltage V reached the step-down operation lower limit voltage Vb fluctuates due to, for example, the environment in which the vehicle control device 11 is placed, the time t5 when the determination wait time Pw has elapsed since the time t2 when the input voltage V reached the step-down operation lower limit voltage Vb also fluctuates in the same way. Therefore, when an abnormality occurs in the DC / DC converter 13, it is possible to prevent the timing when the input voltage V drops due to the precharge current flowing into the DC / DC converter 13 from coinciding with the timing when the controller 20 determines that the input voltage V has dropped, due to the environment in which the vehicle control device 11 is placed, from becoming inconsistent. This improves the accuracy of detecting an abnormality in the DC / DC converter 13.

[0080] Furthermore, in the vehicle control device 11 of this embodiment, the determination wait time Pw is set by adding the additional time Pc to the step-down operation start required time Pb, and the controller 20 determines whether the input voltage V detected by the voltage detection unit 19 is lower than the pre-charge completion reference voltage Va when the determination wait time Pw has elapsed since the input voltage V detected by the voltage detection unit 19 reached the step-down operation lower-limit voltage Vb. This ensures that, when an abnormality has occurred in the DC / DC converter 13, the timing at which the input voltage V drops due to the pre-charge current flowing into the DC / DC converter 13 and the timing at which the controller 20 determines that the input voltage V has dropped can be reliably matched, thereby improving the accuracy with which an abnormality in the DC / DC converter 13 is detected.

[0081] Furthermore, in the vehicle control device 11 of this embodiment, when the controller 20 compares the input voltage V detected by the voltage detection unit 19 with the input voltage V at the completion of precharging of the inverter 12 at time t5 in Figure 2(A) or 2(B), the controller 20 uses the precharge completion reference voltage Va as a reference voltage equivalent to the input voltage V at the completion of precharging of the inverter 12. This makes it possible to easily detect the occurrence of an abnormality in the DC / DC converter 13.

[0082] In the above embodiment, after starting precharging of the inverter 12, the controller 20 determines whether the input voltage V detected by the voltage detection unit 19 is lower than the precharge completion reference voltage Va when the determination wait time Pw has elapsed since the input voltage V detected by the voltage detection unit 19 reached the step-down operation lower-limit voltage Vb. However, the present invention is not limited to this. For example, in FIG. 2, if the range of time fluctuation between the precharge start time t1 and the time t2 at which the input voltage V reaches the step-down operation lower-limit voltage Vb can be predicted in advance, the total time from time t1 to time t5 may be set in advance, and a decrease in the input voltage V may be determined when time t5 is reached after the total time has elapsed since the precharge start time t1 of the inverter 12.

[0083] 2, precharging is started at time t1, the input voltage V reaches the step-down operation lower-limit voltage Vb at time t2, and precharging of the inverter 12 is already completed at time t4, when the time Pb required to start step-down operation has elapsed since time t2. However, if precharging of the inverter 12 may not be completed when the time Pb required to start step-down operation has elapsed since the input voltage V reached the step-down operation lower-limit voltage Vb after precharging has started, the additional time Pc is lengthened so that a decrease in the input voltage V is reliably determined after precharging of the inverter 12 is completed.

[0084] Furthermore, in the above embodiment, the controller 20 outputs a ground level operation control signal when changing the state of the DC / DC converter 13 to a state where it receives power from the low-voltage battery 4, and outputs a non-ground level operation control signal when changing the state of the DC / DC converter 13 to a state where it cuts off the power supply from the low-voltage battery 4. However, it may also be configured to output a non-ground level operation control signal when changing the state of the DC / DC converter 13 to a state where it receives power from the low-voltage battery 4, and output a ground level operation control signal when changing the state of the DC / DC converter 13 to a state where it cuts off the power supply from the low-voltage battery 4. In this case, an abnormality in the DC / DC converter 13 occurs when, for some reason, a constant external current flows into the path that sends the operation control signal from the controller 20 to the DC / DC converter 13.

[0085] Furthermore, in the above embodiment, a case has been described in which the power supply to DC / DC converter 13 is not normally stopped due to a ground fault in the path for transmitting an operation control signal from controller 20 to DC / DC converter 13, but there are no particular limitations on the reason why the power supply to DC / DC converter 13 is not normally stopped. Furthermore, DC / DC converter 13 is not limited to an isolated type.

[0086] Furthermore, the present invention can be modified as appropriate within the scope that does not contradict the gist or idea of ​​the invention that can be read from the claims and the entire specification, and vehicle control devices that involve such modifications are also included in the technical idea of ​​the present invention. [Explanation of symbols]

[0087] 1 electric motor 2 High Voltage Battery 3 In-vehicle equipment 4 Low voltage battery 11 Vehicle control device 12 inverters 13 DC / DC converter 15 Main relay 16 Precharge circuit 17 Precharge resistor (precharge current generator) 18 Precharge relay 19 Voltage detection section 20 Controller

Claims

1. A vehicle control device for controlling an electric vehicle including an electric motor as a power source for traveling, a high-voltage battery that outputs a high voltage for driving the electric motor, on-board equipment that operates at a low voltage, and a low-voltage battery that outputs a low voltage for operating the on-board equipment, an inverter that drives the electric motor using a voltage output from the high-voltage battery; a DC / DC converter that reduces the voltage output from the high-voltage battery and outputs a voltage used to charge the low-voltage battery or to operate the in-vehicle device; a main switch that switches on / off the input of the voltage output from the high-voltage battery to the inverter and the DC / DC converter; a precharge circuit including a precharge current generating unit that generates a precharge current using a current output from the high-voltage battery, and a precharge switch that switches on / off the input of the precharge current to the inverter; a voltage detection unit that detects an input voltage input from the high-voltage battery to the inverter and the DC / DC converter; a controller that inputs the precharge current to the inverter by turning the main switch off and the precharge switch on to start precharging of the inverter, and turns the main switch on and the precharge switch off after precharging of the inverter is completed; the inverter and the DC / DC converter are connected in parallel to the high-voltage battery; the main switch and the precharge circuit are connected in parallel to each other in a path connecting the high-voltage battery to the inverter and the DC / DC converter; the controller determines whether the input voltage detected by the voltage detection unit has dropped below the input voltage input from the high-voltage battery to the inverter and the DC / DC converter at the time of completion of precharging of the inverter, after precharging of the inverter is completed and before the main switch is turned on and the precharge switch is turned off, and determines that the power supply from the power supply of the DC / DC converter to the DC / DC converter has not been stopped normally if the input voltage detected by the voltage detection unit has dropped below the input voltage input from the high-voltage battery to the inverter and the DC / DC converter at the time of completion of precharging of the inverter.

2. The lower limit of the input voltage of the DC / DC converter at which the DC / DC converter can step down an input voltage and output the stepped-down voltage is called the step-down operation lower limit voltage, and the time it takes from when a voltage equal to or higher than the step-down operation lower limit voltage is input to the DC / DC converter in a state where no voltage equal to or higher than the step-down operation lower limit voltage has been input, until the DC / DC converter steps down the input voltage and outputs the stepped-down voltage is called the step-down operation start time.

2. The vehicle control device according to claim 1, wherein after starting precharging of the inverter, the controller determines whether the input voltage detected by the voltage detection unit has dropped below the input voltage input to the inverter and the DC / DC converter from the high-voltage battery at the time precharging of the inverter is completed after the required time for starting the step-down operation has elapsed since the input voltage detected by the voltage detection unit reached the step-down operation lower-limit voltage and before the main switch is turned on and the precharge switch is turned off.

3. The lower limit of the input voltage of the DC / DC converter at which the DC / DC converter can step down an input voltage and output the stepped-down voltage is called the step-down operation lower limit voltage, and the time it takes from when a voltage equal to or higher than the step-down operation lower limit voltage is input to the DC / DC converter in a state where no voltage equal to or higher than the step-down operation lower limit voltage has been input, until the DC / DC converter steps down the input voltage and outputs the stepped-down voltage is called the step-down operation start time. the controller, after starting precharging of the inverter, determines whether or not the input voltage detected by the voltage detection unit has dropped below a lower limit value of a normal discharge voltage of the high-voltage battery after a determination wait time has elapsed since the input voltage detected by the voltage detection unit reached the step-down operation lower limit voltage and before precharging of the inverter is completed and before the main switch is turned on and the precharge switch is turned off; 2. The vehicle control device according to claim 1, wherein the determination waiting time is a time obtained by adding a predetermined additional time to the time required to start the voltage reduction operation.

Images