Automotive power supply device and method for controlling automotive power supply device

Abstract

A control circuit of an automotive power supply device (1) is configured to: execute, when a startup switch of a vehicle is switched to the on state, initial check processing, including one or more abnormality determinations to detect abnormalities of the automotive power supply device (1); and execute, when the startup switch is switched to the off state, a discharge process to discharge via a boost circuit (42) until the voltage of an auxiliary power supply (41) reaches a prescribed voltage. The control circuit is further configured to perform, before executing the one or more abnormality determinations, a restart determination as to whether or not at least one of the voltages on a discharge line (Lsu) on the input and output sides of the boost circuit (42) is at or above a voltage threshold, and if at least one of the voltages is at or above the voltage threshold, not determine that an abnormality has occurred in the automotive power supply device (1) according to a prescribed abnormality determination.

Description

Vehicle power supply device and control method for vehicle power supply device

[0001] The present disclosure relates to a vehicle power supply device and a method for controlling a vehicle power supply device.

[0002] For example, Patent Document 1 discloses a vehicle power supply device that supplies power to a steering device of a vehicle. The vehicle power supply device is provided in a power supply path that supplies power from an external power supply mounted on the vehicle to the steering device. The power supply device includes an auxiliary power supply, multiple switching elements that change the connection state of the auxiliary power supply to the power supply path, and a power supply control device that controls the multiple switching elements. The power supply control device switches the on / off state of the switching elements so that when the voltage of the external power supply is normal, power from the external power supply is supplied to the steering device, and when the voltage of the external power supply drops, power from the auxiliary power supply is supplied to the steering device.

[0003] JP 2023-63741 A

[0004] In the above-described vehicle power supply device, an abnormality such as a short circuit may occur in one of the multiple switching elements. Therefore, the vehicle power supply device is required to not only detect the abnormality that occurs in the device, but also to not erroneously determine that an abnormality has occurred in the device when no abnormality has actually occurred.

[0005] It should be noted that such a requirement is not limited to the case where power is supplied to the steering device, but also applies to the case where power is supplied to other power supply targets.

[0006] One aspect of the present disclosure provides a vehicle power supply device configured to supply power to a power supply target. The vehicle power supply device includes a power line constituting a part of a power supply path that supplies power from an external power source to the power supply target, a discharge line branching from the power line, a charge line branching from the power line and connected in parallel to the discharge line, an auxiliary power source connected to the power line via the discharge line and the charge line, a boost circuit provided in the discharge line, a step-down circuit provided in the charge line, multiple switching elements provided in the discharge line and the charge line, and a control circuit configured to control the multiple switching elements. The control circuit is configured to perform an initial check process including one or more abnormality determinations to detect an abnormality in the vehicle power supply device when a vehicle start switch is switched on, and to perform a discharge process to discharge the auxiliary power source via the boost circuit until the voltage of the auxiliary power source reaches a predetermined voltage when the start switch is switched off. The one or more abnormality determinations include a predetermined abnormality determination affected by the voltage of at least one of the discharge line and the charge line. The control circuit is further configured to perform a restart determination as to whether or not the voltage of at least one of the input side and output side of the boost circuit in the discharge line is equal to or greater than a voltage threshold before executing the one or more abnormality determinations, and if the at least one voltage is equal to or greater than the voltage threshold, not to determine that an abnormality has occurred in the vehicle power supply device based on the specified abnormality determination.

[0007] Another aspect of the present disclosure provides a control method for a vehicle power supply device configured to supply power to a power supply target. The vehicle power supply device includes a power line constituting a part of a power supply path that supplies power from an external power source to the power supply target, a discharge line branching from the power line, a charge line branching from the power line and connected in parallel to the discharge line, an auxiliary power supply connected to the power line via the discharge line and the charge line, a boost circuit provided in the discharge line, a step-down circuit provided in the charge line, and a plurality of switching elements provided in the discharge line and the charge line. The control method includes: when a vehicle start switch is switched to an ON state, performing an initial check process including one or more abnormality determinations to detect an abnormality in the vehicle power supply device; and when the start switch is switched to an OFF state, performing a discharge process to discharge the auxiliary power supply via the boost circuit until the voltage of the auxiliary power supply reaches a predetermined voltage. The one or more abnormality determinations include a predetermined abnormality determination affected by the voltage of at least one of the discharge line and the charge line. The method further includes, before executing the one or more abnormality determinations, performing a restart determination to determine whether the voltage of at least one of the input side and output side of the boost circuit in the discharge line is above a voltage threshold, and if the at least one voltage is above the voltage threshold, the specified abnormality determination does not determine that an abnormality has occurred in the vehicle power supply device.

[0008] 1 is a schematic diagram of a vehicle power supply device and a steering device to which power is supplied by the vehicle power supply device of an embodiment. 2 is a block diagram showing the electrical configuration of the vehicle power supply device of Fig. 1. 3 is a flowchart showing the procedure of various processes executed by a power supply control circuit of Fig. 2. 4 is a graph showing an example of changes in the boost input voltage, the boost output voltage, the buck input voltage, and the buck output voltage before and after the power supply control circuit of Fig. 2 executes a discharge process.

[0009] An embodiment of a vehicle power supply device and a control method for a vehicle power supply device will be described below with reference to the drawings. (Overall Configuration) As shown in Fig. 1, a vehicle power supply device 1 of this embodiment supplies power to a steering device 2 of a vehicle to be powered. The steering device 2 is a steer-by-wire steering device. The steering device 2 includes an operation unit 4 operated by a driver via a steering wheel 3, a steering unit 6 that steers steered wheels 5, and a steering control device 7 that controls the operation of the operation unit 4 and the steering unit 6. The steering device 2 may be configured such that the power transmission path between the operation unit 4 and the steering unit 6 is always mechanically separated, or may be configured such that the operation unit 4 and the steering unit 6 can be selectively mechanically separated by a clutch.

[0010] The operation unit 4 includes an operation-side motor 11. The operation-side motor 11 generates an operation reaction force that resists the operation of the steering wheel 3 by the driver. The turning unit 6 includes a turning-side motor 12. The turning-side motor 12 generates a turning force that steers the steered wheels 5.

[0011] An operating-side motor 11 and a turning-side motor 12 are connected to the steering control device 7. The operating-side motor 11 may have multiple coil groups that are supplied with power via multiple electrically independent power supply systems. In other words, the operating-side motor 11 may be an electrically redundant motor. Similarly, the turning-side motor 12 may be an electrically redundant motor. Furthermore, the operating-side motor 11 and the turning-side motor 12 may be motors that are not electrically redundant. In the illustrated example, the operating-side motor 11 and the turning-side motor 12 are motors that are not electrically redundant. The steering control device 7 controls the operation of the operating-side motor 11 and the turning-side motor 12 by supplying power to the operating-side motor 11 and the turning-side motor 12. Power supplied to the operating-side motor 11 and the turning-side motor 12 is supplied from an external power source 13 mounted on the vehicle via the vehicle power supply device 1.

[0012] In more detail, the steering control device 7 has an operating-side control unit 21 and a turning-side control unit 22. The operating-side control unit 21 controls the operation of the operating-side motor 11. The turning-side control unit 22 controls the operation of the turning-side motor 12. The operating-side control unit 21 and the turning-side control unit 22 are connected to each other so that they can communicate with each other via a local network 23 such as serial communication. The steering control device 7 of this embodiment is a single control device that has the operating-side control unit 21 and the turning-side control unit 22. In other embodiments, the steering control device 7 may be equipped with a control device that includes the operating-side control unit 21 and another control device that is mechanically separated from the control device and includes the turning-side control unit 22.

[0013] The operation-side control unit 21 includes an operation-side drive circuit 24 and an operation-side control circuit 25 that controls the operation-side drive circuit 24. In a configuration in which the operation-side motor 11 is electrically redundant, the operation-side control unit 21 may include multiple operation-side drive circuits 24 corresponding to multiple coil groups. In this case, the operation-side control unit 21 may include multiple operation-side control circuits corresponding to the multiple operation-side drive circuits 24, or may include a single operation-side control circuit.

[0014] The operating-side drive circuit 24 is a typical PWM inverter having multiple switching elements such as FETs and IGBTs. The operating-side control circuit 25 controls the operation of the operating-side drive circuit 24 by outputting control signals that define the duty ratio of each switching element. In other words, the control signals are gate on / off signals that define the on / off states. The duty ratio refers to the proportion of the on time of a switching element in a pulse period.

[0015] The operating-side control circuit 25 can be configured as (1) one or more processors operating according to a computer program (software), (2) one or more dedicated hardware circuits such as an application-specific integrated circuit (ASIC) that executes at least some of the various processes, or (3) a combination thereof. The processor includes a central processing unit (CPU) and memory such as RAM and ROM, which store program code or instructions configured to cause the CPU to execute the processes. The memory, i.e., non-transitory computer-readable medium, includes any available medium accessible by a general-purpose or dedicated computer. Various controls by the operating-side control circuit 25 are performed by the CPU executing the programs stored in the memory at predetermined calculation intervals.

[0016] The operating-side control circuit 25 calculates a reaction force control amount, which is a target value for the actuation reaction force, based on the detection results of various sensors (not shown) and information obtained from the steering-side control unit 22 via the local network 23. The operating-side control circuit 25 then generates a control signal having a duty ratio corresponding to the reaction force control amount. In this way, the operating-side control circuit 25 controls the supply of power to the operating-side motor 11.

[0017] The steering-side control unit 22 is configured in the same manner as the operation-side control unit 21. That is, the steering-side control unit 22 includes a steering-side drive circuit 26 and a steering-side control circuit 27 that controls the steering-side drive circuit 26.

[0018] The steering-side control circuit 27 calculates a steering control amount, which is a target value of the steering force, based on the detection results of the various sensors and information obtained from the operation-side control unit 21 via the local network 23. Then, the steering-side control circuit 27 generates a control signal having a duty ratio according to the steering control amount. In this way, the steering-side control circuit 27 controls the supply of power to the steering-side motor 12.

[0019] (Power Supply Path) The steering control device 7 is connected to an external power source 13 via the vehicle power supply device 1. As a result, power is supplied to the steering control device 7 from the external power source 13 via the vehicle power supply device 1. The external power source 13 is, for example, a secondary battery. The external power source 13 can be charged by a generator such as an alternator (not shown).

[0020] Specifically, the steering control device 7 is connected to the external power supply 13 via a drive power line Lp and a control power line Lc. The control power line Lc branches off from a connection point P0 of the drive power line Lp. The vehicle power supply device 1 is provided across both the drive power line Lp and the control power line Lc. The drive power line Lp includes an upstream drive power line Lpu, which is a power supply path upstream of the vehicle power supply device 1, and a downstream drive power line Lpd, which is a power supply path downstream of the vehicle power supply device 1. The control power line Lc includes an upstream control power line Lcu, which is a power supply path upstream of the vehicle power supply device 1, and a downstream control power line Lcd, which is a power supply path downstream of the vehicle power supply device 1.

[0021] The upstream control power line Lcu is provided with a control relay 32 that is linked to a vehicle start switch 31. The start switch 31 is a switch that is operated to start or stop the drive source for running the vehicle, and is, for example, an ignition switch or a power switch. When the start switch 31 is operated to the on state, the control relay 32 is switched to the on state, and the control power line Lc is made conductive. When the start switch 31 is operated to the off state, the control relay 32 is switched to the off state, and the control power line Lc is interrupted.

[0022] The downstream drive power line Lpd branches downstream and is connected to the operation side drive circuit 24 and the turning side drive circuit 26. The downstream control power line Lcd branches downstream and is connected to the operation side control circuit 25 and the turning side control circuit 27.

[0023] (Vehicle power supply device 1) An activation signal Sig indicating the on / off state of the activation switch 31 and an external power supply voltage signal Sve indicating the external power supply voltage Vex, which is the voltage of the external power supply 13, are input to the vehicle power supply device 1. The external power supply voltage signal Sve is output from a voltage sensor 33. When the external power supply voltage Vex of the external power supply 13 is equal to or greater than a drop determination threshold Vthlo, the vehicle power supply device 1 determines that the external power supply 13 is normal, and supplies power from the external power supply 13 to the steering device 2. On the other hand, when the external power supply voltage Vex is less than the drop determination threshold Vthlo, the vehicle power supply device 1 supplies power from an auxiliary power supply 41, described below, to the steering device 2.

[0024] More specifically, as shown in FIG. 2, the vehicle power supply device 1 includes an auxiliary power supply 41, a boost circuit 42, a step-down circuit 43, a regulator 44, a power supply control circuit 45, a voltage monitoring circuit 46, electric wires connecting these circuit components to each other, and a plurality of switching elements.

[0025] The electric wires of the vehicle power supply device 1 include an internal drive power supply line Lpi that constitutes a part of the drive power supply line Lp, and an internal control power supply line Lci that constitutes a part of the control power supply line Lc. The internal drive power supply line Lpi is provided between the upstream drive power supply line Lpu and the downstream drive power supply line Lpd. A drive relay 47 is provided on the internal drive power supply line Lpi. The internal control power supply line Lci is provided between the upstream control power supply line Lcu and the downstream control power supply line Lcd.

[0026] The electric wires of the vehicle power supply device 1 include a discharge line Lsu branching off from the internal drive power line Lpi and a charge line Lsd branching off from the internal drive power line Lpi and connected in parallel to the discharge line Lsu. The discharge line Lsu and the charge line Lsd both branch off from a connection point P1 on the internal drive power line Lpi downstream of the drive relay 47. The discharge line Lsu and the charge line Lsd meet on the opposite side of the connection point P1.

[0027] The auxiliary power supply 41 is, for example, a capacitor. The auxiliary power supply 41 is capable of charging and discharging. In this embodiment, the auxiliary power supply 41 includes two capacitors (cells) connected in series. The auxiliary power supply 41 is connected to the internal drive power supply line Lpi via a discharge line Lsu and a charge line Lsd.

[0028] The boost circuit 42 is provided on the discharge line Lsu. The boost circuit 42 boosts and outputs the voltage of the auxiliary power supply 41 (i.e., the second voltage Vi2 described later). A first switching element 51 is provided on the input side of the boost circuit 42 on the discharge line Lsu, i.e., the side to which the auxiliary power supply 41 is connected. Two second switching elements 52a, 52b connected in series are provided on the output side of the boost circuit 42 on the discharge line Lsu, i.e., the side where the connection point P1 is located. That is, the first switching element 51, the boost circuit 42, and the second switching elements 52a, 52b are provided on the discharge line Lsu in this order from the auxiliary power supply 41 toward the connection point P1. The boost circuit 42 is, for example, a DC-DC converter. The boost circuit 42 includes a boost control circuit (not shown). The boost circuit 42 boosts the input voltage to a preset boost voltage Vsu by adjusting the on / off ratio of the internal switching elements of the boost control circuit, and outputs the boosted voltage. The activation and deactivation of the boost control circuit, i.e., the activation and deactivation of the boost circuit 42, are controlled by the power supply control circuit 45.

[0029] Specifically, the boost control circuit of this embodiment is configured to operate based on the voltage between the first switching element 51 and the boost circuit 42 (i.e., the boost input voltage Vui, which will be described later). The power supply control circuit 45 indirectly controls the operation and stop of the boost control circuit by switching the on / off state of the first switching element 51. In other embodiments, the power supply control circuit 45 may directly control the operation and stop of the boost control circuit.

[0030] The step-down circuit 43 is provided on the charging line Lsd. The step-down circuit 43 steps down the external power supply voltage Vex of the external power supply 13 and outputs the resulting voltage. A third switching element 53 is provided on the input side of the step-down circuit 43, i.e., the side where the connection point P1 is located, of the charging line Lsd. A fourth switching element 54 is provided on the output side of the step-down circuit 43, i.e., the side where the auxiliary power supply 41 is connected, of the charging line Lsd. That is, the third switching element 53, the step-down circuit 43, and the fourth switching element 54 are provided in this order on the charging line Lsd from the connection point P1 toward the auxiliary power supply 41. The step-down circuit 43 is, for example, a DC-DC converter. The step-down circuit 43 has a step-down control circuit (not shown). The step-down control circuit adjusts the on / off ratio of the internal switching elements of the step-down circuit 43 to step down the input voltage to a predetermined step-down voltage Vsd and output the resulting voltage. The activation and deactivation of the step-down control circuit, that is, the activation and deactivation of the step-down circuit 43, is controlled by the power supply control circuit 45.

[0031] Specifically, the power supply control circuit 45 in this embodiment directly controls the activation and deactivation of the step-down control circuit. In other embodiments, the power supply control circuit 45 may indirectly control the activation and deactivation of the step-up control circuit, for example, by switching the third switching element 53 between on and off.

[0032] The drive relay 47, the first switching element 51, the second switching elements 52a and 52b, the third switching element 53, and the fourth switching element 54 are semiconductor switches such as FETs and IGBTs. The on / off states of these switching elements are controlled by the power supply control circuit 45. For ease of explanation, lines indicating signals output from the power supply control circuit 45 to each circuit component are not shown.

[0033] The electric wires of the vehicle power supply device 1 include a discharge branch line Lsub branching from the discharge line Lsu and a charge branch line Lsdb branching from the charge line Lsd. The discharge branch line Lsub branches off from the discharge line Lsu between the boost circuit 42 and the second switching element 52a. The charge branch line Lsdb branches off from the charge line Lsd between the step-down circuit 43 and the third switching element 53. The discharge branch line Lsub and the charge branch line Lsdb are connected to each other at a connection point P2 and then connected to the voltage monitoring circuit 46.

[0034] Diodes 61 and 62 are provided upstream of the connection point P2 between the discharge branch line Lsub and the charge branch line Lsdb. The diodes 61 and 62 allow current to flow from the upstream side to the downstream side and regulate current to flow from the downstream side to the upstream side. The diodes 61 and 62 form a selection circuit that supplies the voltage monitoring circuit 46 with the larger voltage of the discharge line Lsu or the voltage of the charge line Lsd.

[0035] The voltage monitoring circuit 46 detects the voltage of the auxiliary power supply 41. The hardware configuration of the voltage monitoring circuit 46 may be the same as that of the operation-side control circuit 25. The voltage monitoring circuit 46 of this embodiment detects a first voltage Vi1 between two capacitors connected in series in the auxiliary power supply 41. When power is being supplied, the voltage monitoring circuit 46 outputs a voltage monitoring signal Svm indicating the detected first voltage Vi1 to the power supply control circuit 45. When the supply of power is stopped, the voltage monitoring circuit 46 stops outputting the voltage monitoring signal Svm. For ease of explanation, some of the lines indicating the signals output from the voltage monitoring circuit 46 to the power supply control circuit 45 are omitted.

[0036] The internal control power supply line Lci branches downstream into a first internal control power supply line Lci1 and a second internal control power supply line Lci2. The first internal control power supply line Lci1 is connected to regulator 44. The second internal control power supply line Lci2 is connected to the operating side control circuit 25 and the steering side control circuit 27 via the downstream side control power supply line Lcd.

[0037] The electric wires of the vehicle power supply device 1 include a first backup line Lbk1 and a second backup line Lbk2 branching off from the discharge line Lsu. The first backup line Lbk1 and the second backup line Lbk2 branch off from the discharge line Lsu between the boost circuit 42 and the second switching element 52a. The first backup line Lbk1 is connected to the first internal control power line Lci1 at a connection point P3. The second backup line Lbk2 is connected to the second internal control power line Lci2 at a connection point P4.

[0038] Diodes 63 and 64 are provided upstream of connection point P3 between first internal control power line Lci1 and first backup line Lbk1. The diodes 63 and 64 allow current to flow from the upstream side to the downstream side and regulate current to flow from the downstream side to the upstream side. The diodes 63 and 64 form a selection circuit that supplies the regulator 44 with the larger voltage of either the voltage supplied from external power supply 13 or the voltage supplied from auxiliary power supply 41.

[0039] Diodes 65 and 66 are provided upstream of connection point P4 on the second internal control power supply line Lci2 and the second backup line Lbk2. The diodes 65 and 66 allow current to flow from the upstream side to the downstream side and regulate current to flow from the downstream side to the upstream side. The diodes 65 and 66 form a selection circuit that supplies the larger of the voltage supplied from the external power supply 13 and the voltage supplied from the auxiliary power supply 41 to the operating side control circuit 25 and the steering side control circuit 27.

[0040] The regulator 44 adjusts the input voltage to a preset voltage for the control circuit. The power supply control circuit 45 is connected to the regulator 44 and operates based on the power supplied from the regulator 44. The hardware configuration of the power supply control circuit 45 may be the same as that of the operation-side control circuit 25.

[0041] The power supply control circuit 45 receives the start signal Sig and the external power supply voltage signal Sve as well as the voltage monitoring signal Svm output from the voltage monitoring circuit 46. Voltage sensors 71-74 are connected to the power supply control circuit 45 to detect voltages on the discharge line Lsu and the charge line Lsd. Specifically, the discharge line Lsu is provided with a voltage sensor 71 that detects a boost input voltage Vui between the first switching element 51 and the boost circuit 42, a voltage sensor 72 that detects a boost output voltage Vuo between the boost circuit 42 and the second switching element 52a, and a voltage sensor 73 that detects a switching element voltage Vbs between the second switching element 52a and the second switching element 52b. The charge line Lsd is provided with a voltage sensor 74 that detects a step-down output voltage Vdo between the step-down circuit 43 and the fourth switching element 54. Furthermore, the power supply control circuit 45 of this embodiment is connected with a voltage sensor 75 that detects a second voltage Vi2 on the high potential side of the auxiliary power supply 41 and a current sensor 76 that detects a current I flowing through the auxiliary power supply 41. For ease of explanation, some of the lines indicating the signals output from the voltage sensors 71 to 75 and the current sensor 76 to the power supply control circuit 45 are omitted. The power supply control circuit 45 then executes various processes (controls) based on the various input signals and the detected voltages, currents, etc.

[0042] Next, a description will be given of various processes executed by the power supply control circuit 45. When the start switch 31 is operated to be turned on, the control relay 32 is switched on, and power from the external power supply 13 is supplied to the power supply control circuit 45. This causes the power supply control circuit 45 to start operating.

[0043] As shown in FIG. 3, when the power supply control circuit 45 starts its operation, it controls the drive relay 47 to be turned on, thereby supplying power from the external power supply 13 to the operating side drive circuit 24 and the steering side drive circuit 26 and executing an initial check process (step 101).

[0044] Next, when the initial check process is completed, the power supply control circuit 45 executes a charging process (step 102). The charging process is a process for charging the auxiliary power supply 41 until the voltage of the auxiliary power supply 41, more specifically, the second voltage Vi2, becomes equal to the standby voltage Vsb.

[0045] When the charging process is completed, the power supply control circuit 45 executes a standby process (step 103) while supplying power from the external power supply 13 to the steering control device 7. The standby process includes determining whether the external power supply voltage Vex of the external power supply 13 has dropped (step 103a) and determining whether the start switch 31 has been switched to the OFF state (step 103b). Whether the external power supply voltage Vex has dropped is determined based on whether the external power supply voltage Vex is equal to or higher than a drop determination threshold Vthlo.

[0046] If the external power supply voltage Vex of the external power supply 13 drops during standby processing, i.e., if the external power supply voltage Vex is less than the drop determination threshold Vthlo (step 103a: NO), the power supply control circuit 45 executes backup processing (step 104). The backup processing is processing in which the power supply from the external power supply 13 to the steering control device 7 is stopped and power from the auxiliary power supply 41 is supplied to the steering control device 7.

[0047] If the start switch 31 is operated to be in the OFF state during standby processing (step 103b: YES), the power supply control circuit 45 executes a discharge processing (step 105). The discharge processing is a processing for discharging the auxiliary power supply 41 until the voltage of the auxiliary power supply 41, more specifically, the second voltage Vi2, reaches a predetermined voltage Vst. The predetermined voltage Vst is a voltage such that, if the internal resistance of the auxiliary power supply 41 is normal, the current I flowing through the auxiliary power supply 41 based on the step-down voltage Vsd becomes equal to or greater than the current threshold Ith in the abnormality determination of the auxiliary power supply 41 described below. The predetermined voltage Vst is set to a value lower than the standby voltage Vsb.

[0048] When the discharge process is completed, the power supply control circuit 45 stops the power supply to itself (step 106). If the external power supply voltage Vex of the external power supply 13 is equal to or higher than the drop determination threshold Vthlo during the standby process (step 103a: YES) and the start switch 31 is not operated to be in the OFF state (step 103b: NO), the processes of steps 103a and 103b are repeated.

[0049] More specifically, the initial check process executes one or more abnormality determinations to detect an abnormality in the vehicle power supply device 1. The one or more abnormality determinations include determining whether a short-circuit failure has occurred in the second switching elements 52 a, 52 b, the third switching element 53, and the fourth switching element 54. The one or more abnormality determinations also include determining whether an abnormality has occurred in the auxiliary power supply 41. If the power supply control circuit 45 determines that an abnormality has occurred in the vehicle power supply device 1, it may display that fact on an indicator (not shown), for example.

[0050] A short-circuit fault in the second switching element 52a is determined based on whether the voltage Vbs across the switching elements is equal to or greater than the short-circuit threshold Vthsc while the first switching element 51 is controlled to be in the on state, the boost circuit 42 is operating, and the second switching elements 52a, 52b are controlled to be in the off state. The short-circuit threshold Vthsc is a value for detecting a short circuit in the switching elements and is set to an appropriate value greater than zero. When a short-circuit fault occurs in the second switching element 52a, the voltage Vbs across the switching elements increases based on the boosted voltage Vsu output from the boost circuit 42, and it can be determined that a short-circuit fault has occurred in the second switching element 52a. A short-circuit fault in the second switching element 52b is determined based on whether the voltage Vbs across the switching elements is equal to or greater than the short-circuit threshold Vthsc while the second switching elements 52a, 52b are controlled to be in the off state. If a short-circuit fault occurs in the second switching element 52b, the voltage Vbs across the switching element increases based on the external power supply voltage Vex supplied from the external power supply 13, and therefore it can be determined that a short-circuit fault has occurred in the second switching element 52b.

[0051] A short-circuit fault in the third switching element 53 is determined based on whether or not the voltage monitoring circuit 46 outputs a voltage monitoring signal Svm when the boost circuit 42 is not operated and the second switching elements 52a, 52b and the third switching element 53 are controlled to be in the off state. This determination is made after it is determined that no short-circuit fault has occurred in the second switching elements 52a, 52b. Therefore, if no short-circuit fault has occurred in the third switching element 53, no power is supplied to the voltage monitoring circuit 46 and the voltage monitoring signal Svm is not output. Therefore, if the voltage monitoring signal Svm is output, it can be determined that a short-circuit fault has occurred in the third switching element 53.

[0052] A short-circuit fault in the fourth switching element 54 is determined based on whether the step-down output voltage Vdo is equal to or greater than the short-circuit determination threshold Vthsc while the third switching element 53 and the fourth switching element 54 are controlled to be in the off state. If a short-circuit fault occurs in the fourth switching element 54, the step-down output voltage Vdo becomes large based on the second voltage Vi2 supplied from the auxiliary power supply 41, and therefore it can be determined that a short-circuit fault has occurred in the fourth switching element 54.

[0053] The abnormality determination of the auxiliary power supply 41 includes a determination of whether the internal resistance of the auxiliary power supply 41 is excessive. This determination is made based on the current I flowing into the auxiliary power supply 41, i.e., the charging current of the auxiliary power supply 41, while the first switching element 51, the third switching element 53, and the fourth switching element 54 are controlled to be in the on state and the step-down circuit 43 is operating. The power supply control circuit 45 can determine that the internal resistance of the auxiliary power supply 41 is excessive when the current I is less than the current threshold Ith. The abnormality determination of the auxiliary power supply 41 also includes a determination of whether the auxiliary power supply 41 is in an over-discharge state. The abnormality determination of the auxiliary power supply 41 is made based on the first voltage Vi1 or the second voltage Vi2. The power supply control circuit 45 can determine that over-discharge of the auxiliary power supply 41 is occurring when the first voltage Vi1 is less than the first voltage threshold Vth1 or when the second voltage Vi2 is less than the second voltage threshold Vth2.

[0054] In the charging process and standby process, the power supply control circuit 45 controls the first switching element 51, the third switching element 53, and the fourth switching element 54 to be in the ON state and the second switching elements 52 a, 52 b to be in the OFF state. The power supply control circuit 45 also activates the voltage step-up circuit 42 and the voltage step-down circuit 43. As a result, the auxiliary power supply 41 is charged based on the step-down voltage Vsd output from the voltage step-down circuit 43.

[0055] In the backup process, the power supply control circuit 45 controls the first switching element 51 and the second switching elements 52a, 52b to be in the ON state, and the drive relay 47, the third switching element 53, and the fourth switching element 54 to be in the OFF state. The power supply control circuit 45 also continues to operate the voltage step-up circuit 42 and stops the voltage step-down circuit 43. As a result, the voltage output from the voltage step-up circuit 42 is supplied to the steering control device 7. Because the voltage step-up circuit 42 is operating even when the standby process is being executed as described above, when the second switching elements 52a, 52b are switched to the ON state by the execution of the backup process, power is immediately supplied from the auxiliary power supply 41 to the steering control device 7.

[0056] The power supply control circuit 45 of this embodiment continues the backup process to the extent possible based on the power of the auxiliary power supply 41, and stops the backup process when the power of the auxiliary power supply 41 runs out. In another embodiment, the power supply control circuit 45 may determine whether the external power supply voltage Vex of the external power supply 13 has become equal to or greater than a drop-determination threshold Vthlo while the backup process is being performed. In this embodiment, the power supply control circuit 45 returns to standby processing when the external power supply voltage Vex has become equal to or greater than the drop-determination threshold Vthlo.

[0057] In the discharge process, the power supply control circuit 45 controls the first switching element 51 to be in the ON state and the second switching elements 52a and 52b, the third switching element 53, and the fourth switching element 54 to be in the OFF state. The power supply control circuit 45 then operates the boost circuit 42 to continue supplying power to the power supply control circuit 45 itself, thereby discharging the power of the auxiliary power supply 41. When the discharge has been performed until the voltage of the auxiliary power supply 41 reaches a predetermined voltage Vst, the power supply control circuit 45 controls the first switching element 51 to be in the OFF state and stops the operation of the boost circuit 42. As a result, power is no longer supplied to the power supply control circuit 45, and the power supply control circuit 45 stops.

[0058] Next, the changes in the voltages of the discharge line Lsu and the charge line Lsd before and after the discharge process will be described with reference to Fig. 4. Fig. 4 shows the changes over time in the boost input voltage Vui, the boost output voltage Vuo, the buck output voltage Vdo, and the buck input voltage Vdi between the buck circuit 43 and the third switching element 53.

[0059] First, the voltages during standby processing will be described. As shown in (a) of Fig. 4, the boost input voltage Vui becomes the second voltage Vi2 of the auxiliary power supply 41. As shown in (b) of Fig. 4, the boost output voltage Vuo becomes the boost voltage Vsu output from the boost circuit 42. As shown in (c) of Fig. 4, the step-down input voltage Vdi becomes the external power supply voltage Vex of the external power supply 13. As shown in (d) of Fig. 4, the step-down output voltage Vdo becomes the step-down voltage Vsd output from the step-down circuit 43.

[0060] As shown in FIG. 4 , the power supply control circuit 45 starts a discharge process, for example, at time T1. As a result, as shown in FIG. 4 (a), the boost input voltage Vui gradually decreases as the charge in the auxiliary power supply 41 is discharged. The boost circuit 42 boosts the input voltage to the boost voltage Vsu and outputs it, even if the input voltage decreases to a certain extent. Therefore, as shown in FIG. 4 (b), the boost output voltage Vuo remains at the boost voltage Vsu even if the boost input voltage Vui decreases. As shown in FIG. 4 (c), the step-down input voltage Vdi decreases and becomes zero when the third switching element 53 is switched off. As shown in FIG. 4 (d), the step-down output voltage Vdo decreases and becomes zero as the step-down input voltage Vdi decreases. The step-down input voltage Vdi and the step-down output voltage Vdo usually decrease faster than the step-up input voltage Vui and the step-up output voltage Vuo.

[0061] Subsequently, at time T2, when the voltage of the auxiliary power supply 41 reaches the predetermined voltage Vst, the power supply control circuit 45 completes the discharge process and switches the first switching element 51 to the off state. As a result, as shown in FIG. 4A, the boost input voltage Vui drops to zero. As shown in FIG. 4B, the boost output voltage Vuo drops to zero as the boost input voltage Vui drops. Typically, the time from time T1 to time T2 is, for example, several tens of minutes, and the time from time T2 until the boost output voltage Vuo drops to zero is, for example, several minutes.

[0062] As can be seen from these voltage changes, if the start switch 31 is switched on after the start of the discharge process until the boost output voltage Vuo reaches zero, charge may remain in the discharge line Lsu and the charge line Lsd, generating voltage. Therefore, there is a risk that a short-circuit fault in the third switching element 53 and the fourth switching element 54 may be erroneously determined to have occurred, even though no short-circuit fault actually has occurred in these elements.

[0063] Specifically, for example, charge remaining in the discharge line Lsu may cause the boost output voltage Vuo to exceed zero, which may cause the voltage monitoring circuit 46 to operate and output the voltage monitoring signal Svm based on the boost output voltage Vuo. As a result, even if no short circuit has occurred in the third switching element 53, the voltage monitoring signal Svm may be output, which may result in a false determination that a short circuit has occurred in the third switching element 53. Furthermore, for example, charge remaining in the charge line Lsd may cause the buck output voltage Vdo to exceed the short circuit determination threshold Vthsc. As a result, even if no short circuit has occurred in the fourth switching element 54, a false determination that a short circuit has occurred in the fourth switching element 54 may occur.

[0064] On the other hand, with regard to the abnormality determination of the auxiliary power supply 41 and the short-circuit fault of the second switching elements 52 a, 52 b, even if a voltage is generated in the discharge line Lsu and the charge line Lsd when the start switch 31 is switched to the on state, it is not erroneously determined that a short-circuit fault has occurred. Also, with regard to the abnormality determination of the auxiliary power supply 41, even if a voltage is generated in the discharge line Lsu and the charge line Lsd when the start switch 31 is switched to the on state, it is not erroneously determined that an abnormality has occurred in the auxiliary power supply 41.

[0065] In other words, the determination of a short-circuit failure of the third switching element 53 and the fourth switching element 54 corresponds to a predetermined abnormality determination, among one or more abnormality determinations, that is affected by the voltage remaining in at least one of the discharge line Lsu and the charge line Lsd when the start switch 31 is switched to the on state. The predetermined abnormality determination can also be said to be an abnormality determination whose result changes depending on whether a voltage remains in at least one of the discharge line Lsu and the charge line Lsd. Furthermore, the abnormality determination of the auxiliary power supply 41 and the short-circuit failure determination of the second switching elements 52a, 52b correspond to an abnormality determination other than a predetermined abnormality determination, among one or more abnormality determinations.

[0066] Therefore, before executing one or more abnormality determinations, the power supply control circuit 45 performs a restart determination to determine whether at least one of the boost input voltage Vui and the boost output voltage Vuo is equal to or greater than the residual voltage threshold Vthre. If at least one of the boost input voltage Vui and the boost output voltage Vuo is equal to or greater than the residual voltage threshold Vthre, the power supply control circuit 45 does not determine, through the predetermined abnormality determination, that an abnormality has occurred in the vehicle power supply device 1. The residual voltage threshold Vthre is, for example, a value at which the boost input voltage Vui and the boost output voltage Vuo can be considered to be zero, and is set to a value slightly greater than zero in consideration of the influence of noise, etc.

[0067] The power supply control circuit 45 of this embodiment adds the following condition to the conditions for determining whether a short-circuit fault has occurred in the third switching element 53 and the fourth switching element 54: that at least one of the boost input voltage Vui and the boost output voltage Vuo is not equal to or greater than the residual voltage threshold Vthre, i.e., that the boost input voltage Vui and the boost output voltage Vuo are less than the residual voltage threshold Vthre. Specifically, in determining whether a short-circuit fault has occurred in the third switching element 53, the power supply control circuit 45 determines that a short-circuit fault has occurred in the third switching element 53 if the boost input voltage Vui and the boost output voltage Vuo are less than the residual voltage threshold Vthre and the voltage monitoring circuit 46 outputs the voltage monitoring signal Svm. In determining whether or not a short circuit has occurred in the fourth switching element 54, the power supply control circuit 45 determines that a short circuit has occurred in the fourth switching element 54 when the boost input voltage Vui and the boost output voltage Vuo are less than the residual voltage threshold Vthre and the buck output voltage Vdo is equal to or greater than the short circuit determination threshold Vthsc. As a result, when at least one of the boost input voltage Vui and the boost output voltage Vuo is equal to or greater than the residual voltage threshold Vthre, it is not determined that a short circuit has occurred in the third switching element 53 and the fourth switching element 54.

[0068] On the other hand, the power supply control circuit 45 does not include the requirement that at least one of the boost input voltage Vui and the boost output voltage Vuo is not equal to or greater than the residual voltage threshold Vthre as a condition for determining a short-circuit fault in the second switching elements 52a, 52b and for determining an abnormality in the auxiliary power supply 41. Specifically, when determining a short-circuit fault in the second switching elements 52a, 52b, the power supply control circuit 45 determines that a short-circuit fault has occurred in the second switching elements 52a, 52b if the inter-switching element voltage Vbs is equal to or greater than the short-circuit determination threshold Vthsc. Furthermore, the power supply control circuit 45 determines that the internal resistance of the auxiliary power supply 41 is excessively high if the current I is less than the current threshold Ith. The power supply control circuit 45 determines that over-discharge of the auxiliary power supply 41 has occurred if the first voltage Vi1 is less than the first voltage threshold Vth1 or if the second voltage Vi2 is less than the second voltage threshold Vth2.

[0069] Next, the operation and effects of this embodiment will be described. (1) Assume that the start switch 31 is switched back on while the discharge process is being performed, such as at time Tx in FIG. 4 . In this case, charge may remain in the discharge line Lsu and the charge line Lsd, causing their voltages to not become zero. Therefore, if a predetermined abnormality determination is performed to determine whether an abnormality has occurred in the vehicle power supply device 1, there is a risk that an abnormality may be erroneously determined to have occurred even when no abnormality actually has occurred. In this regard, in this embodiment, if at least one of the boost input voltage Vui and the boost output voltage Vuo is equal to or greater than the residual voltage threshold Vthre, the power supply control circuit 45 does not determine that an abnormality has occurred in the vehicle power supply device 1 through the predetermined abnormality determination. This prevents an erroneous determination of an abnormality even when no abnormality actually has occurred.

[0070] (2) When the second voltage Vi2 of the auxiliary power supply 41 reaches the predetermined voltage Vst due to the discharge process, the power supply control circuit 45 stops supplying power to the power supply control circuit 45. This allows for more energy-efficient vehicle power supply device 1 than when power is continuously supplied to the power supply control circuit 45 even after the discharge process is completed.

[0071] Here, assume that after the start switch 31 is switched off, the start switch 31 is switched on again while power is being supplied to the power supply control circuit 45, i.e., while the power supply control circuit 45 is performing a discharging process. In this case, the power supply control circuit 45 can determine that charge remains in the discharge line Lsu and the charge line Lsd based on whether the start switch 31 was switched on during the discharging process, without performing a restart determination. Therefore, as a reference example, a configuration can be considered in which, if the start switch 31 is switched on again while power supply to the power supply control circuit 45 continues, it is not determined by the predetermined abnormality determination that an abnormality has occurred in the vehicle power supply device 1.

[0072] However, even if the power supply to the power supply control circuit 45 is stopped after the second voltage Vi2 of the auxiliary power supply 41 reaches the predetermined voltage Vst, charge remains in the discharge line Lsu for a while. Therefore, in the above-described reference example, if the start switch 31 is switched back on while charge remains in the discharge line Lsu after the power supply to the power supply control circuit 45 is stopped, for example, at time Ty in FIG. 4 , there is still a possibility of erroneous determination. Therefore, by performing the restart determination as in this embodiment, it is possible to more reliably reduce erroneous determination and achieve power saving in the vehicle power supply device 1.

[0073] (3) The power supply control circuit 45 controls the first switching element 51, the second switching elements 52a and 52b, the third switching element 53, and the fourth switching element 54 so that no voltage is generated on the output side of the step-down circuit 43 on the charging line Lsd, and when the step-down output voltage Vdo is equal to or greater than the short-circuit determination threshold Vthsc, the power supply control circuit 45 determines that a short-circuit fault has occurred in the fourth switching element 54. This makes it easy to determine whether the fourth switching element 54 has a short-circuit fault.

[0074] (4) The vehicle power supply device 1 includes a voltage monitoring circuit 46 configured to detect the first voltage Vi1 of the auxiliary power supply 41 and output a voltage monitoring signal Svm indicating the first voltage Vi1 to the power supply control circuit 45. The voltage monitoring circuit 46 operates based on the higher of the step-up output voltage Vuo and the step-down input voltage Vdi. The power supply control circuit 45 determines that a short-circuit fault has occurred in the third switching element 53 when the voltage monitoring signal Svm is output from the voltage monitoring circuit 46 while controlling the first switching element 51, the second switching elements 52a and 52b, the third switching element 53, and the fourth switching element 54 so that no voltage is generated on the output side of the step-up circuit 42 or the input side of the step-down circuit 43. This makes it possible to determine whether a short-circuit fault has occurred in the third switching element 53 without detecting the step-down input voltage Vdi.

[0075] This embodiment can be implemented with the following modifications. This embodiment and the following modifications can be implemented in combination with each other to the extent that no technical contradiction occurs. In the above embodiment, the auxiliary power supply 41 may be a single capacitor or may include three or more capacitors connected in series.

[0076] In the above embodiment, the voltage monitoring circuit 46 may detect a voltage other than the first voltage Vi1 of the auxiliary power supply 41, for example, the second voltage Vi2. In the above embodiment, the determination of a short-circuit fault in the third switching element 53 is made based on whether or not the voltage monitoring signal Svm is input from the voltage monitoring circuit 46. However, this is not limiting, and for example, the power supply control circuit 45 may detect the step-down input voltage Vdi and make a determination of a short-circuit fault in the third switching element 53 based on the detected step-down input voltage Vdi.

[0077] In the above embodiment, the predetermined abnormality determination includes a determination of a short-circuit fault in the third switching element 53 and the fourth switching element 54. However, other determinations may be included in addition to or instead of these determinations. For example, the other determination may be a determination of a short-circuit fault in a switching element inside the step-down circuit 43. A short-circuit fault in a switching element inside the step-down circuit 43 can be determined based on whether the step-down output voltage Vdo is equal to or greater than the short-circuit determination threshold Vthsc while the step-down circuit 43 is stopped, for example, by controlling the third switching element 53 to be in the ON state and the fourth switching element 54 to be in the OFF state. Furthermore, determinations other than the predetermined abnormality determination may include other appropriate determinations.

[0078] In the above embodiment, two second switching elements 52 a, 52 b are provided on the output side of the boost circuit 42 in the discharge line Lsu, but this is not limiting, and only a single second switching element may be provided on the output side of the boost circuit 42 in the discharge line Lsu. In this case, a short-circuit fault of the single second switching element can be determined based on the boost output voltage Vuo, and this determination may be a predetermined abnormality determination.

[0079] In the above embodiment, the condition for the predetermined abnormality determination to be established is that at least one of the boost input voltage Vui and the boost output voltage Vuo is less than the residual voltage threshold Vthre. However, the present invention is not limited to this. The power supply control circuit 45 may be configured to not perform the predetermined abnormality determination, i.e., to skip the predetermined abnormality determination, when at least one of the boost input voltage Vui and the boost output voltage Vuo is equal to or greater than the residual voltage threshold Vthre.

[0080] In the above embodiment, the power supply control circuit 45 is configured so that when at least one of the boost input voltage Vui and the boost output voltage Vuo is equal to or greater than the residual voltage threshold Vthre, the predetermined abnormality determination does not determine that an abnormality has occurred in the vehicle power supply device 1. However, the present invention is not limited to this, and the power supply control circuit 45 may be configured so that when the boost input voltage Vui or the boost output voltage Vuo is equal to or greater than the residual voltage threshold Vthre, the predetermined abnormality determination does not determine that an abnormality has occurred in the vehicle power supply device 1.

[0081] In the above embodiment, even after the discharge process is completed, power may continue to be supplied from another power source to the power supply control circuit 45. In the above embodiment, the steering device 2 may be an electric power steering device that applies torque from a motor to a steering shaft or a rack shaft.

[0082] In the above embodiment, the vehicle power supply device 1 supplies power to the steering device 2, but this is not limiting and the vehicle power supply device 1 may supply power to, for example, a motor used as a driving source for traveling. Next, the technical ideas that can be understood from the above embodiment and modified examples will be described below.

[0083] (Supplementary Note 1) The control circuit may be further configured to, after completion of the initial check process, execute a charging process to charge the auxiliary power supply until the voltage of the auxiliary power supply becomes a standby voltage higher than the predetermined voltage.

Claims

1. A vehicle power supply device configured to supply power to a power supply target, comprising: a power line constituting a part of a power supply path that supplies power from an external power supply to the power supply target; a discharge line branching off from the power line; a charge line branching off from the power line and connected in parallel to the discharge line; an auxiliary power supply connected to the power supply line via the discharge line and the charge line; a boost circuit provided in the discharge line; a step-down circuit provided in the charge line; a plurality of switching elements provided in the discharge line and the charge line; and a control circuit configured to control the plurality of switching elements, wherein the control circuit is configured to: when a start switch of a vehicle is switched to an on state, execute an initial check process including one or more abnormality determinations that detect an abnormality in the vehicle power supply device; and when the start switch is switched to an off state, execute a discharge process that discharges the auxiliary power supply via the boost circuit until the voltage of the auxiliary power supply reaches a predetermined voltage, and the one or more abnormality determinations include a predetermined abnormality determination that is influenced by the voltage of at least one of the discharge line and the charge line, The control circuit is further configured to perform a restart determination as to whether or not a voltage of at least one of the input side and output side of the boost circuit in the discharge line is equal to or higher than a voltage threshold before executing the one or more abnormality determinations, and if the at least one voltage is equal to or higher than the voltage threshold, not to determine that an abnormality has occurred in the vehicle power supply device through the specified abnormality determination.

2. A vehicle power supply device as claimed in claim 1, wherein the control circuit stops supplying power to the control circuit when the voltage of the auxiliary power supply reaches the predetermined voltage as a result of the discharge process being performed.

3. A vehicle power supply device as claimed in claim 1 or 2, wherein the plurality of switching elements include a first switching element provided on the input side of the boost circuit in the discharge line, a second switching element provided on the output side of the boost circuit in the discharge line, a third switching element provided on the input side of the step-down circuit in the charge line, and a fourth switching element provided on the output side of the step-down circuit in the charge line, and the specified abnormality determination includes a determination of a short-circuit fault of the third switching element and the fourth switching element.

4. A vehicle power supply device as described in claim 3, wherein the control circuit is further configured to determine that a short-circuit failure has occurred in the fourth switching element when the voltage on the output side of the step-down circuit in the charging line is equal to or higher than a short-circuit determination threshold while controlling the multiple switching elements so that no voltage is generated on the output side of the step-down circuit in the charging line.

5. A vehicle power supply device as described in claim 3, further comprising a voltage monitoring circuit configured to detect the voltage of the auxiliary power supply and output a voltage monitoring signal indicating the detected voltage of the auxiliary power supply to the control circuit, wherein the voltage monitoring circuit is configured to operate based on the higher of the voltage on the output side of the boost circuit in the discharge line and the voltage on the input side of the step-down circuit in the charging line, and wherein the control circuit is configured to determine that a short-circuit failure has occurred in the third switching element when the voltage monitoring signal is output from the voltage monitoring circuit while controlling the multiple switching elements so that no voltage is generated on the output side of the boost circuit in the discharge line and no voltage is generated on the input side of the step-down circuit in the charging line.

6. A control method for a vehicle power supply device configured to supply power to a power supply target, the vehicle power supply device comprising: a power line constituting a part of a power supply path that supplies power from an external power supply to the power supply target; a discharge line branching off and extending from the power line; a charge line branching off from the power line and connected in parallel to the discharge line; an auxiliary power supply connected to the power supply line via the discharge line and the charge line; a boost circuit provided in the discharge line; a step-down circuit provided in the charge line; and a plurality of switching elements provided in the discharge line and the charge line, the control method comprising: executing an initial check process including one or more abnormality determinations that detect an abnormality in the vehicle power supply device when a start switch of a vehicle is switched to an ON state; and executing a discharge process that discharges the auxiliary power supply via the boost circuit until a voltage of the auxiliary power supply reaches a predetermined voltage when the start switch is switched to an OFF state, the one or more abnormality determinations including a predetermined abnormality determination that is influenced by the voltage of at least one of the discharge line and the charge line, The control method further includes, before executing the one or more abnormality determinations, performing a restart determination as to whether or not a voltage on at least one of the input side and output side of the boost circuit in the discharge line is equal to or higher than a voltage threshold, and if the at least one voltage is equal to or higher than the voltage threshold, not determining that an abnormality has occurred in the vehicle power supply device through the specified abnormality determination.

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