Vehicle power supply device and abnormality detection method for vehicle power supply device

Abstract

A vehicle power supply device (1) comprises: a power supply line that constitutes a part of a power supply path for supplying power from an external power supply to a power supply target; a discharge line (Lsu) that branches and extends from the power supply line; an auxiliary power supply (41) that is connected to the power supply line via the discharge line; a boost circuit (42) that is provided in the discharge line; a backup relay that is provided on the output side of the boost circuit in the discharge line; and a regenerative absorption circuit (46). The regenerative absorption circuit includes: an absorption line (Lab) for connecting the power supply line to the ground; and a Zener diode (71) provided in the absorption line. The vehicle power supply device further comprises: a high-voltage generation diode (81) that is provided upstream of the Zener diode in the absorption line; and a branch line (Lbr) that branches and extends from a connection point between the boost circuit and the backup relay in the discharge line and is connected to a connection point between the high-voltage generation diode and the Zener diode in the absorption line.

Description

Vehicle power supply device and method for detecting abnormalities in a vehicle power supply device

[0001] The present disclosure relates to a vehicle power supply device and a method for detecting an abnormality in 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. As described in the document, the motor used in the steering device may generate regenerative power due to a reaction force, for example, when a wheel hits a curb or the like.

[0003] In consideration of these points, the vehicle power supply device of Patent Document 1 includes a main battery, an auxiliary battery, a discharge circuit, a charge circuit, and a high-voltage suppression circuit. The discharge circuit and the charge circuit are connected in parallel between the auxiliary battery and the steering device. The discharge circuit operates when power from the auxiliary battery is supplied to the steering device, and the charge circuit operates when the auxiliary battery is charged using power from the main battery. The high-voltage suppression circuit is provided in a power line connecting the discharge circuit and the charge circuit to the steering device. The high-voltage suppression circuit is configured to pass current to ground when the voltage on the power line increases due to regenerative power generated by the steering device. This prevents components of the vehicle power supply device from failing due to an increase in the voltage on the power line.

[0004] JP 2018-113814 A

[0005] If an abnormality occurs in the high-voltage suppression circuit, the high-voltage suppression circuit may not operate properly, and the regenerative power generated by the steering device may not be absorbed. However, Patent Document 1 does not mention how to detect an abnormality in the high-voltage suppression circuit, and there is still room for improvement in this regard.

[0006] This problem is not limited to cases where the power supply target is a steering device, but can occur similarly as long as the power supply target generates regenerative power.

[0007] According to one aspect of the present disclosure, there is provided 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 drive relay provided on the power line; a discharge line branching from a connection point on the power line downstream of the drive relay and extending therefrom; an auxiliary power supply connected to the power line via the discharge line; a boost circuit provided on the discharge line and configured to boost and output a voltage of the auxiliary power supply; a backup relay provided on the discharge line on the output side of the boost circuit; and a regenerative absorption circuit configured to absorb regenerative power generated in the power supply target. The regenerative absorption circuit includes an absorption line connecting a portion of the power line downstream of the drive relay to ground; and a Zener diode provided on the absorption line, the Zener diode configured to allow a current to flow from the power line to ground when a reverse voltage applied to the Zener diode is equal to or greater than a Zener voltage. The vehicle power supply device further includes: a high-voltage generating diode provided upstream of the Zener diode in the absorption line, the high-voltage generating diode being configured to allow a current to flow from the power supply line toward the Zener diode and to regulate a current flow from the Zener diode toward the power supply line; and a branch line branching off from a connection point in the discharge line between the boost circuit and the backup relay, the branch line being connected to a connection point in the absorption line between the high-voltage generating diode and the Zener diode.

[0008] Another aspect of the present disclosure provides a method for detecting an abnormality in 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 drive relay provided on the power line; a discharge line branching from a connection point on the power line downstream of the drive relay and extending therefrom; an auxiliary power supply connected to the power line via the discharge line; a boost circuit provided on the discharge line and configured to boost and output a voltage of the auxiliary power supply; a backup relay provided on the discharge line on the output side of the boost circuit; and a regenerative absorption circuit configured to absorb regenerative power generated in the power supply target. The regenerative absorption circuit includes an absorption line connecting a portion of the power line downstream of the drive relay to ground; and a Zener diode provided on the absorption line, the Zener diode configured to allow a current to flow from the power line to ground when a reverse voltage applied to the Zener diode is equal to or greater than a Zener voltage. The vehicle power supply device further includes: a high-voltage generating diode provided in the absorption line upstream of the Zener diode, the high-voltage generating diode being configured to allow a current to flow from the power line toward the Zener diode and to restrict a current to flow from the Zener diode toward the power line; and a branch line extending from a connection point in the discharge line between the boost circuit and the backup relay, the branch line being connected to the connection point in the absorption line between the high-voltage generating diode and the Zener diode. The abnormality detection method includes detecting a determination voltage that is a voltage on the branch line, and determining that an abnormality has occurred in the Zener diode when the determination voltage is outside a predetermined voltage range that includes the Zener voltage, with the backup relay switched to an off state and the boost circuit controlled to output a voltage higher than the Zener voltage.

[0009] 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 according to an embodiment of the present invention. FIG. 2 is a block diagram showing the electrical configuration of the vehicle power supply device of FIG. 1. FIG. 3 is a flowchart showing the procedure of various processes executed by a power supply control circuit of FIG. 2. FIG. 4 is a graph showing an example of a change in output voltage when the power supply control circuit of FIG. 2 executes backup processing.

[0010] An embodiment of a vehicle power supply device and a method for detecting an abnormality in 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 mechanically separated at all times, or may be configured such that the operation unit 4 and the steering unit 6 can be selectively mechanically separated by a clutch.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] (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).

[0021] 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.

[0022] 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.

[0023] 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.

[0024] (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.

[0025] More specifically, as shown in FIG. 2, the vehicle power supply device 1 includes an auxiliary power supply 41, a voltage step-up circuit 42, a voltage step-down circuit 43, a regulator 44, a power supply control circuit 45 which is an abnormality detection circuit, a regenerative absorption circuit 46, and electric wires which interconnect these circuit components.

[0026] 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.

[0027] 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.

[0028] The auxiliary power supply 41 is, for example, a capacitor. The auxiliary power supply 41 can be charged and discharged. 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.

[0029] The boost circuit 42 is provided on the discharge line Lsu. The boost circuit 42 boosts and outputs an auxiliary power supply voltage Vsp, which is the voltage of the auxiliary power supply 41. A first switching element 51 is provided on the input side of the boost circuit 42 of the discharge line Lsu, i.e., the side to which the auxiliary power supply 41 is connected. A second switching element 52, which is a backup relay, is provided on the output side of the boost circuit 42 of 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 element 52 are provided in this order on the discharge line Lsu 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 predetermined boost voltage Vsu and outputs the boosted voltage by adjusting the on / off ratio of the internal switching elements by the boost control circuit. The activation and deactivation of the boost control circuit, that is, the activation and deactivation of the boost circuit 42 is controlled by the power supply control circuit 45 .

[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] The drive relay 47, the first switching element 51, the second switching element 52, 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.

[0032] 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.

[0033] 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 52. The first backup line Lbk1 is connected to the first internal control power line Lci1 at a connection point P2. The second backup line Lbk2 is connected to the second internal control power line Lci2 at a connection point P3.

[0034] Diodes 61 and 62 are provided upstream of connection point P2 between the first internal control power line Lci1 and the first backup line Lbk1. 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 regulator 44 with the larger voltage of either the voltage supplied from the external power supply 13 or the voltage supplied from the auxiliary power supply 41.

[0035] Diodes 63 and 64 are provided upstream of connection point P3 on the second internal control power supply line Lci2 and the second backup line Lbk2. 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 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.

[0036] 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.

[0037] The start signal Sig and the external power supply voltage signal Sve are input to the power supply control circuit 45. A voltage sensor 65 that detects the auxiliary power supply voltage Vsp of the auxiliary power supply 41 is also connected to the power supply control circuit 45. The power supply control circuit 45 performs various processes (controls) based on the input signals and the detected auxiliary power supply voltage Vsp.

[0038] The regenerative absorption circuit 46 absorbs regenerative power generated in the steered-side motor 12 by a reaction force when, for example, the steered wheel 5 hits a curb or the like. The regenerative absorption circuit 46 includes an absorption line Lab, a Zener diode 71, a fuse 72, a regenerative switching element 73, and an absorption operation switching circuit 74.

[0039] The absorption line Lab connects to ground a portion of the internal drive power supply line Lpi downstream of the drive relay 47. In the illustrated example, the absorption line Lab extends from a connection point on the internal drive power supply line Lpi downstream of the connection point P1.

[0040] The Zener diode 71 is provided on the absorption line Lab. When the applied reverse voltage exceeds a predetermined Zener voltage Vze (also referred to as a breakdown voltage), the Zener diode 71 allows current to flow from the cathode to the anode while maintaining the voltage at a value close to the Zener voltage Vze. Applying a reverse voltage to the Zener diode 71 means applying a voltage such that the cathode has a higher potential than the anode. Specifically, the Zener diode 71 has a cathode connected to the internal drive power line Lpi via a high-voltage generating diode 81 and a fuse 72 (described later), and an anode connected to ground via a regenerative switching element 73. As a result, when the reverse voltage applied to the Zener diode 71 exceeds the Zener voltage Vze, current flows through the Zener diode 71 to ground.

[0041] The fuse 72 is provided on the absorption line Lab upstream of the Zener diode 71. The fuse 72 blows when a current equal to or greater than a predetermined current flows through the absorption line Lab, thereby shutting off the absorption line Lab. The predetermined current is a preset current that flows when, for example, the internal drive power supply line Lpi is grounded via the absorption line Lab while power from the external power supply 13 is being supplied to the internal drive power supply line Lpi.

[0042] The regenerative switching element 73 is provided on the absorption line Lab downstream of the Zener diode 71. The regenerative switching element 73 is a semiconductor switch such as an FET or an IGBT.

[0043] The absorbing operation switching circuit 74 controls the on / off state of the regenerative switching element 73 based on the output voltage Vout output from the internal drive power supply line Lpi to the operating side drive circuit 24 (operating side motor 11) and the turning side drive circuit 26 (turning side motor 12). In the illustrated example, a voltage sensor 75 that detects the output voltage Vout is provided downstream of the connection point P1 on the internal drive power supply line Lpi. The voltage sensor 75 outputs the detected output voltage Vout to the absorbing operation switching circuit 74. The absorbing operation switching circuit 74 controls the regenerative switching element 73 to be in the on state when the output voltage Vout becomes equal to or greater than a preset on voltage Von. When the output voltage Vout becomes less than a preset off voltage Voff while controlling the regenerative switching element 73 to be in the on state, the absorbing operation switching circuit 74 controls the regenerative switching element 73 to be in the off state. In the initial state, the on-voltage Von is set to a value greater than the external power supply voltage Vex, the boost voltage Vsu, and the Zener voltage Vze. In other embodiments, the on-voltage Von may be set to a value substantially equal to the Zener voltage Vze. In the initial state, the off-voltage Voff is set to a value smaller than the on-voltage Von. In this embodiment, the on-voltage Von and the off-voltage Voff can be changed from their initial values ​​by the power supply control circuit 45.

[0044] 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.

[0045] 3, when the power supply control circuit 45 starts its operation, it executes an initial check process (step 101). In the initial check process, one or more abnormality determinations are executed to detect an abnormality in the vehicle power supply device 1. The one or more abnormality determinations include, for example, determining whether or not a short-circuit fault has occurred in the first switching element 51, the second switching element 52, the third switching element 53, and the fourth switching element 54. The one or more abnormality determinations also include determining an abnormality in the regenerative absorption circuit 46, which will be described later. If the power supply control circuit 45 determines that an abnormality has occurred in the vehicle power supply device 1, it may, for example, display that fact on an indicator (not shown).

[0046] 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 auxiliary power supply voltage Vsp of the auxiliary power supply 41 reaches the standby voltage Vsb.

[0047] 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.

[0048] 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 element 52 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 step-down circuit 43.

[0049] 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.

[0050] In the backup process, the power supply control circuit 45 controls the first switching element 51 and the second switching element 52 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 element 52 is switched to the ON state by executing the backup process, power is immediately supplied from the auxiliary power supply 41 to the steering control device 7.

[0051] 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.

[0052] If the start switch 31 is turned off during standby mode (YES in step 103b), the power supply control circuit 45 executes a discharge mode (step 105). The discharge mode is a mode in which the auxiliary power supply 41 is discharged until the auxiliary power supply voltage Vsp of the auxiliary power supply 41 reaches a stop voltage Vst. The stop voltage Vst is set to a value lower than the standby voltage Vsb.

[0053] In the discharge process, the power supply control circuit 45 controls the first switching element 51 to be turned on and the second switching element 52, the third switching element 53, and the fourth switching element 54 to be turned off. 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.

[0054] When the discharge process is completed, the power supply control circuit 45 stops the power supply to itself (step 106). Specifically, when the discharge is continued until the voltage of the auxiliary power supply 41 reaches the stop 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.

[0055] When the standby process is being executed, if the external power supply voltage Vex of the external power supply 13 is equal to or greater than the drop determination threshold Vthlo (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.

[0056] Here, for example, assume a situation in which regenerative power is generated in the steered-side motor 12. If regenerative power is generated during the charging process or the standby process, the drive relay 47 is in the ON state, and therefore the regenerative power generated in the steering device 2 is absorbed by the external power supply 13. Therefore, the output voltage Vout does not increase, and the regenerative switching element 73 is not switched ON. In other words, the regenerative absorption circuit 46 does not operate. On the other hand, if regenerative power is generated during the backup process, the drive relay 47 is in the OFF state, and therefore the regenerative power is not absorbed by the external power supply 13. Furthermore, because the switching element inside the boost circuit 42 is repeatedly turned ON and OFF, the regenerative power is not absorbed by the auxiliary power supply 41 either. Therefore, as the output voltage Vout increases, the regenerative switching element 73 is switched ON, and the regenerative power is absorbed by the regenerative absorption circuit 46.

[0057] Next, a change in the output voltage Vout when regenerative power is generated during backup processing will be described with reference to Fig. 4. Fig. 4 shows an example of the change over time in the output voltage Vout and the on / off state of the regenerative switching element 73 when regenerative power is generated in the steered-side motor 12 at time t1.

[0058] As shown in FIG. 4A, before time t1, the magnitude of the output voltage Vout is the boosted voltage Vsu output from the boost circuit 42. Because the boosted voltage Vsu is smaller than the on-voltage Von, the regenerative switching element 73 is in the off state, as shown in FIG. 4B. As shown in FIG. 4A, when regenerative power is generated in the turning-side motor 12 at time t1, the output voltage Vout rises. Then, at time t2, when the output voltage Vout reaches the on-voltage Von, the regenerative switching element 73 switches to the on state, as shown in FIG. 4B. As a result, the output voltage Vout is maintained at a value close to the Zener voltage Vze, and current flows to ground via the Zener diode 71. In other words, the regenerative power generated in the turning-side motor 12 is absorbed by the regenerative absorption circuit 46. Thereafter, as shown in FIG. 4(a), the regenerative power generated by the steered-side motor 12 is gradually absorbed, and at time t3, the output voltage Vout becomes less than the off-voltage Voff, and the regenerative switching element 73 switches to the off state, as shown in FIG. 4(b).

[0059] Incidentally, the regenerative absorption circuit 46 may experience, for example, the following abnormalities. One abnormality in the regenerative absorption circuit 46 is an abnormality in the Zener diode 71. When an abnormality occurs in the Zener diode 71, for example, current may not flow even when the reverse voltage applied to the Zener diode 71 exceeds the Zener voltage Vze, or current may flow even when the reverse voltage is less than the Zener voltage Vze. Another abnormality in the regenerative absorption circuit 46 is an abnormality in the path that absorbs regenerative power, such as a break in the absorption line Lab. Another abnormality in the regenerative absorption circuit 46 is an operation abnormality in which the regenerative switching element 73 is switched to the on state even though the output voltage Vout is less than the on-voltage Von, due to an abnormality occurring in at least one of the regenerative switching element 73 and the absorption operation switching circuit 74.

[0060] If such an abnormality occurs in the regenerative absorption circuit 46, when regenerative power is generated during backup processing, the regenerative power cannot be absorbed, and the output voltage Vout may greatly exceed the Zener voltage Vze. As a result, there is a risk of failure of components of the vehicle power supply device 1, such as the boost control circuit. In consideration of this, the vehicle power supply device 1 of this embodiment is equipped with a configuration for detecting an abnormality in the regenerative absorption circuit 46.

[0061] 2, the vehicle power supply device 1 includes a high-voltage generating diode 81 provided on the absorption line Lab and a branch line Lbr branching from the discharge line Lsu. The vehicle power supply device 1 further includes a resistor 82 and a fifth switching element 83 provided on the branch line Lbr.

[0062] The high-voltage generating diode 81 is provided on the absorption line Lab between the fuse 72 and the Zener diode 71. The high-voltage generating diode 81 allows current to flow from the upstream side to the downstream side and regulates current flow from the downstream side to the upstream side. That is, the high-voltage generating diode 81 allows current to flow from the internal drive power supply line Lpi to the Zener diode 71 and regulates current flow from the Zener diode 71 to the internal drive power supply line Lpi.

[0063] The branch line Lbr branches off from a connection point P4 on the discharge line Lsu between the boost circuit 42 and the second switching element 52, and is connected to a connection point P5 on the absorption line Lab between the high-voltage generating diode 81 and the Zener diode 71. A resistor 82 and a fifth switching element 83 are provided in this order on the branch line Lbr from the connection point P4 toward the connection point P5.

[0064] The fifth switching element 83 is a semiconductor switch such as an FET or an IGBT. The on / off state of the fifth switching element 83 is controlled by the power supply control circuit 45. For ease of explanation, a line indicating a signal output from the power supply control circuit 45 to the fifth switching element 83 is not shown. The fifth switching element 83 is controlled to be in the on state only when an abnormality determination is performed on the regenerative absorption circuit 46, and is controlled to be in the off state at other times. This prevents the configuration for detecting an abnormality in the regenerative absorption circuit 46 from affecting the execution of the charging process, standby process, backup process, and discharge process.

[0065] In addition, the branch line Lbr is provided with a voltage sensor 84 that detects a determination voltage Vde, which is a voltage between the resistor 82 on the branch line Lbr and the fifth switching element 83. The determination voltage Vde detected by the voltage sensor 84 is output to the power supply control circuit 45, which is an abnormality detection circuit.

[0066] The power supply control circuit 45 performs an abnormality determination for the regenerative power absorption circuit 46 based on the input determination voltage Vde. As described above, the power supply control circuit 45 of this embodiment performs an abnormality determination for the regenerative power absorption circuit 46 as one of the abnormality determinations performed in the initial check process. The power supply control circuit 45 performs three abnormality determinations: an abnormality in the Zener diode 71, an abnormality in the path that absorbs regenerative power, and an abnormality in the operation of the regenerative switching element 73. For example, the power supply control circuit 45 performs the determinations in the order of an abnormality in the path that absorbs regenerative power, an abnormality in the operation of the regenerative switching element 73, and an abnormality in the Zener diode 71, although the order in which the abnormality determinations are performed can be changed as appropriate.

[0067] Specifically, when determining whether the Zener diode 71 is malfunctioning, the power supply control circuit 45 controls the second switching element 52 to be turned off and the fifth switching element 83 to be turned on, and controls the boost circuit 42 to output a voltage higher than the Zener voltage Vze. In this case, the power supply control circuit 45 controls the drive relay 47 to be turned on and changes the on-voltage Von of the absorption operation switching circuit 74 from its initial value to a value lower than the external power supply voltage Vex. As a result, the output voltage Vout becomes equal to or higher than the on-voltage Von, and the regenerative switching element 73 is controlled to be turned on by the absorption operation switching circuit 74. In this state, the power supply control circuit 45 determines whether the Zener diode 71 is malfunctioning based on whether the determination voltage Vde is outside a predetermined voltage range that includes the Zener voltage Vze. The predetermined voltage range is a voltage range within which it can be determined that the Zener diode 71 is maintaining a normal voltage when a current flows through the Zener diode 71, and is set in advance. If the determination voltage Vde is outside a predetermined voltage range, the power supply control circuit 45 determines that an abnormality has occurred in the Zener diode 71 .

[0068] When determining whether an abnormality exists in the path that absorbs regenerative power, the power supply control circuit 45 controls the drive relay 47 and the fifth switching element 83 to be turned on, the second switching element 52 (which serves as a backup relay) to be turned off, and the boost circuit 42 to be stopped. In this state, the power supply control circuit 45 determines whether an abnormality exists in the path that absorbs regenerative power based on whether the determination voltage Vde is less than the open circuit abnormality determination threshold Vthop. In this state, if no abnormality, such as a break, exists in the absorption line Lab, a voltage based on the external power supply voltage Vex is generated in the branch line Lbr. The open circuit abnormality determination threshold Vthop is, for example, a value that allows the determination voltage Vde to be considered zero and is set to a value slightly greater than zero to take into account the effects of noise, etc. If the determination voltage Vde is less than the open circuit abnormality determination threshold Vthop, the power supply control circuit 45 determines that an abnormality exists in the path that absorbs regenerative power.

[0069] When determining whether the regenerative switching element 73 is malfunctioning, the power supply control circuit 45 controls the second switching element 52 to be turned off and the fifth switching element 83 to be turned on, and controls the boost circuit 42 to output a voltage higher than the Zener voltage Vze. In this case, the power supply control circuit 45 of this embodiment controls the drive relay 47 to be turned on and does not change the on-voltage Von of the absorption operation switching circuit 74 from its initial value. As a result, the output voltage Vout becomes less than the on-voltage Von, and the regenerative switching element 73 is controlled to be turned off by the absorption operation switching circuit 74. In this state, the power supply control circuit 45 determines whether the regenerative switching element 73 is malfunctioning based on whether the determination voltage Vde is less than the conduction malfunction determination threshold Vthco. In this state, if the regenerative switching element 73 is properly switched off, no current flows through the Zener diode 71 even if the reverse voltage applied to the Zener diode 71 exceeds the Zener voltage Vze. Therefore, the determination voltage Vde has a value corresponding to a voltage higher than the Zener voltage Vze output from the boost circuit 42. On the other hand, when the regenerative switching element 73 is not switched to the OFF state, i.e., when the regenerative switching element 73 is in the ON state, the Zener diode 71 maintains the voltage at a value close to the Zener voltage Vze, and current flows. In consideration of this, the conduction abnormality determination threshold Vthco is preset to a value close to the upper limit of the above-mentioned predetermined voltage range. When the determination voltage Vde is lower than the conduction abnormality determination threshold Vthco, the power supply control circuit 45 determines that an abnormality has occurred in at least one of the regenerative switching element 73 and the absorbing operation switching circuit 74.

[0070] Next, the operation and effects of this embodiment will be described. (1) The vehicle power supply device 1 includes a high-voltage generating diode 81 that is provided upstream of the Zener diode 71 on the absorption line Lab, and a branch line Lbr that branches off from the connection point P4 of the discharge line Lsu and is connected to the connection point P5 of the absorption line Lab.

[0071] According to the above configuration, when the second switching element 52 is switched to the off state, the boost circuit 42 can apply a reverse voltage exceeding the Zener voltage Vze to the Zener diode 71. This makes it possible to determine whether the Zener diode 71 is abnormal.

[0072] (2) When the second switching element 52 is switched off, the regenerative switching element 73 is controlled to be on, and the boost circuit 42 is controlled to output a voltage higher than the Zener voltage Vze, the power supply control circuit 45 determines that an abnormality has occurred in the Zener diode 71 if the determination voltage Vde is outside a predetermined voltage range. This allows the power supply control circuit 45 to appropriately determine whether an abnormality has occurred in the regenerative absorption circuit 46.

[0073] (3) When the drive relay 47 is switched on, the second switching element 52 is controlled to be switched off, and the boost circuit 42 is controlled to be stopped, the power supply control circuit 45 determines that an abnormality has occurred in the path that absorbs regenerative power if the determination voltage Vde is less than the open circuit abnormality determination threshold Vthop. This allows the power supply control circuit 45 to appropriately determine whether there is an abnormality in the regenerative absorption circuit 46.

[0074] (4) The regenerative absorption circuit 46 includes a regenerative switching element 73 provided downstream of the Zener diode 71 on the absorption line Lab, and an absorption operation switching circuit 74 configured to control the on / off state of the regenerative switching element 73 based on the output voltage Vout.

[0075] Depending on the vehicle conditions, the external power supply voltage Vex may temporarily become high. In such a case, if an abnormality occurs in the Zener diode 71 that causes the Zener voltage Vze to become low, the internal drive power supply line Lpi will be grounded via the absorption line Lab. As a result, there is a risk that power from the external power supply 13 will not be properly supplied to the steering device 2. In this regard, in the above configuration, the regenerative switching element 73 is maintained in the off state unless the generation of regenerative power causes the output voltage Vout to become so high that it adversely affects the boost control circuit, etc. This makes it possible to suppress the occurrence of a ground fault in the internal drive power supply line Lpi, and to stably supply power from the external power supply 13 to the steering device 2.

[0076] The abnormality determination for the Zener diode 71 is performed in a state in which the regenerative switching element 73 is controlled to be in the on state. Therefore, even if the regenerative switching element 73 is provided, the abnormality determination for the Zener diode 71 can be performed appropriately.

[0077] (5) When the second switching element 52 is switched to the OFF state, the regenerative switching element 73 is controlled to be switched to the OFF state, and the boost circuit 42 is controlled to output a voltage higher than the Zener voltage Vze, if the determination voltage Vde is less than the conduction abnormality determination threshold Vthco, the power supply control circuit 45 determines that an abnormality has occurred in at least one of the regenerative switching element 73 and the absorption operation switching circuit 74. This makes it possible to appropriately determine whether or not an abnormality has occurred in the regenerative absorption circuit 46.

[0078] (6) The vehicle power supply device 1 includes a fuse 72 provided in the absorption line Lab. For example, if a short-circuit fault occurs in the regenerative switching element 73 and an abnormality occurs in the Zener diode 71 that causes the Zener voltage Vze to drop, and the external power supply voltage Vex temporarily increases, there is a risk that the internal drive power line Lpi will be grounded via the absorption line Lab. In the above configuration, in such a case, a large current will flow through the absorption line Lab, causing the fuse 72 to melt. This makes it possible to prevent a ground fault from occurring in the internal drive power line Lpi, and to stably supply power from the external power supply 13 to the steering device 2.

[0079] This embodiment can be implemented with the following modifications. This embodiment and the following modifications can be implemented in combination with each other as long as there is no technical contradiction. In the above embodiment, the fuse 72 is provided upstream of the high-voltage generating diode 81 in the absorption line Lab, but this is not limitative, and it may be provided downstream of the high-voltage generating diode 81, for example. Also, the fuse 72 does not need to be provided in the absorption line Lab.

[0080] In the above embodiment, the power supply control circuit 45 may acquire the output voltage Vout and control the on / off state of the regenerative switching element 73 based on the acquired output voltage Vout. In this case, the regenerative absorption circuit 46 may not include the absorption operation switching circuit 74.

[0081] In the above embodiment, the regenerative absorption circuit 46 does not have to include the regenerative switching element 73 and the absorption operation switching circuit 74. In the above embodiment, the power supply control circuit 45 is configured to perform three abnormality determinations: an abnormality in the Zener diode 71, an abnormality in the path that absorbs regenerative power, and an abnormal operation of the regenerative switching element 73. However, the present invention is not limited to this, and the power supply control circuit 45 may perform at least one of these three abnormality determinations.

[0082] In the above embodiment, the absorption line Lab extends from a connection point on the internal drive power supply line Lpi that is downstream of the connection point P1, but this is not limiting and the absorption line Lab may extend, for example, from a portion of the internal drive power supply line Lpi between the drive relay 47 and the connection point P1. The absorption line Lab may also extend from between the connection point P1 on the discharge line Lsu and the second switching element 52, or from between the connection point P1 on the charge line Lsd and the third switching element 53.

[0083] In the above embodiment, the power supply control circuit 45 may perform an abnormality determination for the regenerative absorption circuit 46 at any time other than when the initial check process is being performed. In the above embodiment, an abnormality detection circuit that performs an abnormality determination for the regenerative absorption circuit 46 may be provided in the vehicle power supply device 1 separately from the power supply control circuit 45, so that the power supply control circuit 45 does not have to perform an abnormality determination for the regenerative absorption circuit 46.

[0084] In the above embodiment, the vehicle power supply device 1 does not have to include the charging line Lsd, the step-down circuit 43, the third switching element 53, and the fourth switching element 54. In the above embodiment, the steering device 2 may be an electric power steering device that applies the torque of a motor to a steering shaft or a rack shaft.

[0085] In the above embodiment, the vehicle power supply device 1 supplies power to the steering device 2. However, the present invention is not limited to this. For example, the vehicle power supply device 1 may supply power to a motor used as a driving source for traveling.

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 for supplying power of an external power supply to the power supply target; A drive relay provided on the power line; A discharge line branching and extending from a connection point on the downstream side of the drive relay in the power line; An auxiliary power supply connected to the power line via the discharge line; A boost circuit provided on the discharge line and configured to boost the voltage of the auxiliary power supply and output it; A backup relay provided on the output side of the boost circuit in the discharge line; A regenerative absorption circuit configured to absorb regenerative power generated in the power supply target, The regenerative absorption circuit includes: An absorption line connecting a portion of the power line downstream of the drive relay to the ground; A Zener diode provided on the absorption line, configured to allow a current flow from the power line to the ground when the reverse voltage applied to the Zener diode is equal to or higher than the Zener voltage; The vehicle power supply device further includes: A high-voltage generating diode provided upstream of the Zener diode in the absorption line, configured to allow a current flow from the power line to the Zener diode and regulate a current flow from the Zener diode to the power line; A branch line branching and extending from a connection point between the boost circuit and the backup relay in the discharge line, and connected to a connection point between the high-voltage generating diode and the Zener diode in the absorption line.

2. The vehicle power supply device according to claim 1, further comprising: a voltage sensor that detects a determination voltage which is the voltage on the branch line; and an abnormality detection circuit configured to execute one or more abnormality determinations for detecting an abnormality in the regenerative absorption circuit, wherein the abnormality detection circuit is controlled such that the backup relay is switched to an off state, and in a state where the boost circuit is controlled to output a voltage higher than the Zener voltage, when the determination voltage is outside a predetermined voltage range including the Zener voltage, the abnormality detection circuit is further configured to determine that an abnormality has occurred in the Zener diode.

3. The vehicle power supply device according to claim 2, wherein the abnormality detection circuit is controlled such that the drive relay is switched to an on state and the backup relay is switched to an off state, and in a state where the boost circuit is controlled to stop, when the determination voltage is less than an open-circuit abnormality determination threshold value, the abnormality detection circuit is further configured to determine that an abnormality has occurred in the path for absorbing the regenerative power.

4. The vehicle power supply device according to claim 2 or 3, wherein the regenerative absorption circuit further comprises: a regenerative switching element provided downstream of the Zener diode in the absorption line; and an absorption operation switching circuit configured to control an on / off state of the regenerative switching element based on an output voltage output from the power supply line to the power supply target.

5. The vehicle power supply device according to claim 4, wherein the abnormality detection circuit is controlled such that the backup relay is switched to an off state and the regenerative switching element is switched to an off state, and in a state where the boost circuit is controlled to output a voltage higher than the Zener voltage, when the determination voltage is less than a conduction abnormality determination threshold value, the abnormality detection circuit is further configured to determine that an abnormality has occurred in at least one of the regenerative switching element and the absorption operation switching circuit.

6. The vehicle power supply device according to any one of claims 1 to 3, further comprising a fuse provided in the absorption line.

7. A method for detecting an abnormality in a vehicle power supply device configured to supply power to a power supply target, the vehicle power supply device including: - a power line that forms part of a power supply path for supplying power from an external power supply to the power supply target; - a drive relay provided on the power line; - a discharge line that branches and extends from a connection point on the power line downstream of the drive relay; - an auxiliary power supply connected to the power line via the discharge line; - a boost circuit provided on the discharge line and configured to boost the voltage of the auxiliary power supply and output it; - a backup relay provided on the output side of the boost circuit on the discharge line; - a regenerative absorption circuit configured to absorb regenerative power generated in the power supply target. The regenerative absorption circuit includes: - an absorption line that connects a portion of the power line downstream of the drive relay to ground; - a Zener diode provided on the absorption line and configured to allow a current flow from the power line to ground when the reverse voltage applied to the Zener diode is equal to or higher than the Zener voltage. The vehicle power supply device further includes: - a high-voltage generating diode provided upstream of the Zener diode on the absorption line and configured to allow a current flow from the power line to the Zener diode and regulate a current flow from the Zener diode to the power line; - a branch line that branches and extends from a connection point between the boost circuit and the backup relay on the discharge line and is connected to a connection point between the high-voltage generating diode and the Zener diode on the absorption line. The abnormality detection method includes: - detecting a determination voltage that is the voltage on the branch line; - determining that an abnormality has occurred in the Zener diode when the determination voltage is outside a predetermined voltage range including the Zener voltage in a state where the backup relay is switched to an off state and the boost circuit is controlled to output a voltage higher than the Zener voltage.

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