Vehicle power supply device and door latch device

Abstract

To provide a vehicular power supply device which is capable of stably operating a motor even when a battery voltage fluctuates significantly.SOLUTION: A vehicular power supply device 1 comprises: a backup power supply 6 which is supplied with power by a battery 3 mounted on a vehicle; a voltage boosting part 20 for boosting the voltage of the backup power supply 6 to a predetermined boosted voltage Vb; a motor driving part 7 which is connected to the battery 3 and the voltage boosting part 20 and is capable of driving an electric motor 2 by being supplied with power by either one of the battery 3 and the voltage boosting part 20; a first switching part 60 for connecting / disconnecting supply of power between the battery 3 and the motor driving part 7; a control part 8 for controlling the first switching part 60; and a second switching part 70 which is provided between the voltage boosting part 20 and the first switching part 60 and turns the first switching part 60 off when the voltage output from the voltage boosting part 20 becomes equal to or greater than the predetermined boosted voltage Vb.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a vehicle power supply device and a door latch device. [Background technology]

[0002] Cited Document 1 discloses a vehicle door lock system that locks and unlocks vehicle doors by operating a door lock motor with power supplied from a battery installed in the vehicle body. In this system, a backup power supply that is charged with power from the battery is installed in the vehicle door, and when the power supply from the battery to the door lock motor is cut off, the door lock motor is operated by supplying power from the backup power supply. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-144441 Summary of the Invention [Problem to be solved by the invention]

[0004] In a power supply device capable of supplying power to a motor from a backup power source, such as the vehicle door lock system of Patent Document 1, when the power supply from the battery to the motor is not interrupted, i.e., under normal conditions, the motor always operates on power from the battery. However, the battery voltage can fluctuate significantly from its rated voltage, making it impossible to operate the motor stably.

[0005] An object of the present invention is to provide a vehicle power supply device that can operate a motor stably even when the battery voltage fluctuates greatly. [Means for solving the problem]

[0006] One aspect of the present invention is a backup power supply supplied with power from an on-board battery; a booster unit that boosts the voltage of the backup power supply to a predetermined boost voltage; a motor drive unit connected to the battery and the voltage step-up unit, and capable of driving an electric motor by receiving power from either the battery or the voltage step-up unit; a first switching unit that connects / disconnects power supply between the battery and the motor driving unit; a control unit that controls the first switching unit; a second switching unit that is provided between the boosting unit and the first switching unit and turns off the first switching unit when the voltage output from the boosting unit becomes equal to or higher than the predetermined boosted voltage; A vehicle power supply device comprising:

[0007] According to the present invention, when the voltage output from the booster unit reaches or exceeds a predetermined boost voltage, the power supply from the battery to the motor drive unit is cut off and power is supplied from the booster unit. Therefore, by supplying power from the booster unit, which has a stable voltage, rather than from the battery, which is prone to voltage fluctuations, the motor can be operated stably. [Effects of the Invention]

[0008] According to the present invention, the motor can be operated stably even when the battery voltage fluctuates greatly. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a circuit diagram of a vehicle power supply device according to a first embodiment of the present invention. [Figure 2] FIG. 5 is a circuit diagram of a vehicle power supply device according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] A vehicle power supply device according to one embodiment of the present invention will now be described with reference to the accompanying drawings. Note that the following description is merely exemplary in nature and is not intended to limit the present invention, its applications, or its uses.

[0011] [First embodiment] 1 is a circuit diagram of a vehicle power supply device 1 according to a first embodiment of the present invention. The vehicle power supply device 1 is a device for supplying power to an electric motor 2 that performs locking and unlocking operations of a door latch device 10 provided in a vehicle door (not shown).

[0012] The door latch device 10 has a fork 12 that can rotate between a latched position where it engages with a striker 11 on the vehicle body and an open position where the engagement is released, and a claw 13 that can rotate between a locked position where the fork 12 is held in the latched position and an unlocked position where the engagement is released. The vehicle door is also provided with a door lock switch 14 that a user operates to lock and unlock the door latch device 10. Operating the door lock switch 14 rotates the claw 13 via the electric motor 2, thereby locking or unlocking the vehicle door.

[0013] The vehicle power supply device 1 has a battery 3 provided in the vehicle body. The vehicle power supply device 1 also has a motor drive unit 7 that is capable of driving the electric motor 2 within the vehicle door, and a control unit 8 that controls the operation of the vehicle power supply device 1. The battery 3 has a rated voltage of DC 12V.

[0014] The battery 3 stores the power required for the operation of the vehicle, supplies power to the prime mover, electrical equipment, and other on-board devices as needed, and when the stored power level decreases, is charged by, for example, a generator (not shown) rotated by the prime mover (not shown) or a regenerative brake (not shown). The battery 3 has an output terminal 3a from which the stored power is output, and a ground terminal 3b which is grounded.

[0015] The motor drive unit 7 has an input terminal 7a to which power is supplied, an output terminal 7b to which power is supplied to the electric motor 2, a control terminal 7c to which a control signal from the control unit 8 is input, and a ground terminal 7d which is grounded. The control terminal 7c is connected to the control unit 8 via a first control signal line 41. The motor drive unit 7 supplies power to the electric motor 2 so as to rotate the electric motor 2 forward or reverse based on the control signal input to the control terminal 7c.

[0016] The output terminal 3a of the battery 3 and the input terminal 7a of the motor drive unit 7 are connected by two systems including a first power supply line 31 and a second power supply line 32 connected in parallel to each other. A first switching unit 60 is provided on the first power supply line 31. The first switching unit 60 has a first relay 61 (first switching element) and a first transistor 64.

[0017] The first relay 61 has a contact 62 and a coil 63. The contact 62 is provided on the first power supply line 31. One end 63a of the coil 63 is connected on the first power supply line 31 between the battery 3 and the contact 62, and the other end 63b is connected via a resistor 65 to a first transistor 64 (second switching element).

[0018] The first transistor 64 has a collector 64a, an emitter 64b, and a base 64c. The collector 64a is connected to the other end 63b of the coil 63. The emitter 64b is grounded. The base 64c is connected to the control unit 8 via the second control signal line 42.

[0019] The first relay 61 is configured to be normally open, and when a control signal is input from the control unit 8, the collector 64a and emitter 64b of the first transistor 64 become conductive, causing current to flow from the battery 3 to the coil 63, and the contact 62 is turned on (closed) using the magnetic force generated in the coil 63. As a result, power is supplied from the battery 3 to the motor drive unit 7 via the first relay 61.

[0020] Meanwhile, a backup power supply 6 and a booster unit 20 are provided on the second power supply line 32, and a predetermined boosted voltage Vb obtained by boosting the power output from the backup power supply 6 by the booster unit 20 is supplied to the motor drive unit 7. That is, the motor drive unit 7 is supplied with either the output voltage of the battery 3 supplied via the first power supply line 31 or the predetermined boosted voltage Vb supplied from the booster unit 20 via the second power supply line 32.

[0021] A second relay 9 is provided on the second power supply line 32 between the battery 3 and the backup power supply 6. The second relay 9 is connected to the control unit 8 via a third control signal line 43. The second relay 9 is configured to be normally open, and is turned on when a control signal is input from the control unit 8. When the second relay 9 is turned on, the backup power supply 6 is turned on and is electrically connected to the battery 3, and stores the power supplied from the battery 3.

[0022] The booster 20 includes a booster circuit 26 that boosts the voltage of the backup power supply 6 to a predetermined boosted voltage Vb, and a voltage divider circuit 50 that divides the predetermined boosted voltage Vb.

[0023] The backup power supply 6 is interposed between the second relay 9 and the boost circuit 26 on the second power supply line 32. One end 6a of the backup power supply 6 is connected to the second power supply line 32, and the other end 6b is grounded. In this embodiment, the backup power supply 6 is a capacitor, and stores electricity at a voltage of about DC 3V to DC 5V.

[0024] The boost circuit 26 has a coil 21 and a diode 22 provided on the second power supply line 32, and arranged in series in this order from the battery 3 side.

[0025] A field effect transistor 23 is provided between the coil 21 and the diode 22 on the second power supply line 32. The field effect transistor 23 has a source 23a, a drain 23b, and a gate 23c. The source 23a is grounded. The drain 23b is connected to the second power supply line 32. The gate 23c is connected to an output terminal 24a of a boost IC 24.

[0026] The boost IC 24 has an output terminal 24a, a feedback terminal 24b, and a control terminal 24c. A voltage obtained by dividing a predetermined boost voltage Vb by a voltage divider circuit 50 is input to the feedback terminal 24b as a feedback voltage Vf. The control terminal 24c is connected to the control unit 8 via a fourth control signal line 44. The boost IC 24 outputs a control signal from the output terminal 24a to the gate 23c based on a control signal from the control unit 8.

[0027] Specifically, the field-effect transistor 23 is turned on in response to a control signal input to the gate 23c, and causes conduction between the source 23a and the drain 23b, thereby supplying current from the backup power supply 6 to the coil 21 and storing electrical energy as magnetic energy in the coil 21. Next, the boost IC 24 turns off the field-effect transistor 23, thereby canceling the conduction between the source 23a and the drain 23b and causing the magnetic energy stored in the coil 21 to be released as electrical energy.

[0028] The boost IC 24 outputs a control signal to the field-effect transistor 23 so as to repeatedly turn the field-effect transistor 23 on and off, thereby repeatedly storing and releasing energy in the coil 21. The boost IC 24 boosts the voltage from the backup power supply 6 until the feedback voltage Vf reaches a predetermined target voltage V0. As a result, the voltage output from the backup power supply 6 is output as a predetermined boosted voltage Vb.

[0029] A capacitor 25 is provided on the second power supply line 32 on the motor drive unit 7 side with respect to the diode 22. One end 25a of the capacitor 25 is connected to the second power supply line 32, and the other end 25b is grounded. Since the diode 22 and the capacitor 25 are located on the motor drive unit 7 side with respect to the field-effect transistor 23, voltage fluctuations of the predetermined boost voltage Vb are suppressed by the diode 22 and the capacitor 25. Therefore, the diode 22 and the capacitor 25 constitute a first voltage stabilizer 28.

[0030] As described above, the coil 21, diode 22, field-effect transistor 23, boost IC 24, and capacitor 25 constitute a boost circuit 26 that boosts the voltage output from the backup power supply 6 to a predetermined boosted voltage Vb. In the following description, the line through which the electricity boosted by the boost IC 24 flows, i.e., the portion of the second power supply line 32 that is located from the drain 23b of the field-effect transistor 23 to the motor drive unit 7, will be referred to as an output line 27.

[0031] The voltage-dividing circuit 50 is disposed on the second power supply line 32 on the motor drive unit 7 side of the capacitor 25. The voltage-dividing circuit 50 has a first resistor 51 and a second resistor 52. One end 51a of the first resistor 51 is connected to the output terminal 26b of the boost circuit 26, and the other end 51b is connected to the feedback terminal 24b of the boost IC 24. One end 52a of the second resistor 52 is connected to the other end 51b of the first resistor 51, and the other end 52b is grounded.

[0032] In the voltage-dividing circuit 50, the first resistor 51 and the second resistor 52 are connected in series, and therefore the voltage-dividing ratio of the first resistor 51 is expressed as the ratio of the resistance R1 of the first resistor 51 to the total resistance R0 of the resistance R1 of the first resistor 51 and the resistance R2 of the second resistor 52. Therefore, the predetermined boosted voltage Vb output from the boost circuit 26 drops in accordance with the voltage-dividing ratio of the first resistor 51, and is input to the feedback terminal 24b of the booster IC 24 as the feedback voltage Vf.

[0033] As described above, the boost IC 24 adjusts the predetermined boost voltage Vb so that the feedback voltage Vf input from the feedback terminal 24b becomes a predetermined value. The first resistor 51 and the second resistor 52 are set so that the predetermined boost voltage Vb is equal to or higher than the minimum voltage at which the electric motor 2 operates and is lower than the rated voltage of the battery 3. The operating voltage of the electric motor 2 is equal to or higher than DC 9V and equal to or lower than DC 16V.

[0034] In this embodiment, the resistance value R1 of the first resistor 51 is set to 142 kΩ, the resistance value R2 of the second resistor 52 is set to 22 kΩ, and the target voltage V0 of the feedback voltage Vf is set to DC 1.274 V so that the predetermined boost voltage Vb is DC 9.5 V.

[0035] Specifically, the voltage division ratio between the first resistor 51 and the second resistor 52 is 142:22, and the predetermined boost voltage Vb when the feedback voltage Vf becomes the target voltage V0 is calculated to be approximately 9.5 V from the following equation (1).

[0036]

number

[0037] Therefore, by the boost IC 24 controlling the field effect transistor 23 so that the feedback voltage Vf becomes the target voltage V0, the voltage output from the backup power supply 6 can be boosted to a predetermined boost voltage Vb.

[0038] Here, the vehicle power supply device 1 connects the second power supply line 32 and the second control signal line 42, and has a fifth control signal line 45 for controlling the on / off of the first switching unit 60. A second switching unit 70 is provided on the fifth control signal line 45. The second switching unit 70 has a diode 71, a Zener diode 73, a resistor 74, and a second transistor 75 (third switching element) arranged in series in this order from the second power supply line 32 side. A capacitor 72 is interposed between the diode 71 and the Zener diode 73.

[0039] One end 72a of the capacitor 72 is connected to the fifth control signal line 45, and the other end 72b is grounded. The anode 71a of the diode 71 is connected between the field effect transistor 23 and the diode 22 on the second power supply line 32, and the cathode 71b is connected to one end 72a of the capacitor 72. The diode 71 allows electricity to flow on the fifth control signal line 45 from the second power supply line 32 side to the second control signal line 42 side, but does not allow electricity to flow in the opposite direction.

[0040] The voltage fluctuation of the electricity flowing through the fifth control signal line 45 is suppressed by the diode 71 and the capacitor 72. Thus, the diode 71 and the capacitor 72 constitute a second voltage stabilization unit .

[0041] The Zener diode 73 has a cathode 73a connected to the cathode 71b of the diode 71 and an anode 73b connected to the second control signal line 42. That is, the cathode 73a of the Zener diode 73 is connected to the output line 27 via the diode 71. The Zener diode 73 allows electricity to flow in the fifth control signal line 45 from the second control signal line 42 toward the second power supply line 32 but does not allow electricity to flow in the opposite direction. However, when the applied voltage reaches or exceeds a predetermined voltage, the Zener diode 73 also allows electricity to flow in the opposite direction (i.e., from the second power supply line 32 toward the second control signal line 42). In this embodiment, the predetermined voltage for the Zener diode 73 is set to a predetermined boost voltage Vb. The predetermined voltage for the Zener diode 73 may be set lower than the predetermined boost voltage Vb. In that case, it may be set to the minimum operating voltage of the electric motor 2, i.e., 9 V or higher.

[0042] The second transistor 75 has a collector 75a, an emitter 75b, and a base 75c. The collector 75a is connected to the second control signal line 42. The emitter 75b is grounded. The base 75c is connected to the anode 73b of the Zener diode 73 via a resistor 74. A resistor 77 is provided on the second control signal line 42 between the control unit 8 and the collector 75a of the second transistor 75.

[0043] According to the fifth control signal line 45, when the voltage on the output line 27 is less than the predetermined boost voltage Vb, the Zener diode 73 blocks the flow of electricity from the second power supply line 32 side to the second control signal line 42 side. On the other hand, when the voltage on the output line 27 becomes equal to or greater than the predetermined boost voltage Vb, the Zener diode 73 causes electricity to flow from the second power supply line 32 side to the second control signal line 42 side, and the current is input to the base 75c of the second transistor 75.

[0044] As a result, the second transistor 75 is turned on, the collector 75a and the emitter 75b are conductive, and the second control signal line 42 is grounded via the second transistor 75. Therefore, the control signal from the control unit 8 to the first transistor 64 via the second control signal line 42 reaches ground via the second transistor 75, so the first transistor 64 is not turned on but is turned off.

[0045] A third power supply line 33, to which the voltage of the battery 3 is supplied, is connected to the control unit 8. The third power supply line 33 supplies operating power from the battery 3 to the control unit 8, and one end 33a is connected to the second power supply line 32 on the battery 3 side with respect to the second relay 9, and the other end 33b is connected to the control unit 8. A regulator 5 is provided on the third power supply line 33, and the power from the battery 3 is stepped down to 5 V and supplied to the control unit 8.

[0046] Furthermore, a control signal output from a door lock switch 14 is input to the control unit 8. Based on the control signal from the door lock switch 14, the control unit 8 determines whether or not the door lock switch 14 has been operated.

[0047] As described above, the first to fourth control signal lines 41 to 44 are connected to the control unit 8. The control unit 8 outputs control signals to the motor drive unit 7, the first relay 61, the second relay 9, and the boost IC 24 via the first to fourth control signal lines 41 to 44.

[0048] The control unit 8 is configured by a known computer equipped with a memory, a storage device, and a central processing unit (CPU), and software installed on the computer. The control unit 8 has a second relay control unit 81, a door lock switch operation determination unit 82, a first relay control unit 83, a boost IC control unit 84, and a motor drive control unit 85.

[0049] The second relay control unit 81 appropriately charges the backup power supply 6 from the battery 3 by conducting (turning on) the second relay 9. The door lock switch operation determination unit 82 determines whether the door lock switch 14 has been operated based on a signal from the door lock switch 14. The first relay control unit 83 inputs a control signal to the first relay 61 to conduct (turn on) the first relay 61. The boost IC control unit 84 controls the boost IC 24 based on the operation of the door lock switch 14 to boost the voltage of the power output from the backup power supply 6 to a predetermined boost voltage Vb. The motor drive control unit 85 controls the motor drive unit 7 to rotate the electric motor 2 forward or reverse.

[0050] Next, the operation of the vehicle power supply device 1 will be described.

[0051] First, at a predetermined timing, the control unit 8 causes the second relay control unit 81 to conduct the second relay 9, thereby supplying power from the battery 3 to the backup power supply 6. As a result, the backup power supply 6 is appropriately charged in preparation for the locking or unlocking operation of the door latch device 10.

[0052] When the control unit 8 determines through the door lock switch operation determination unit 82 that the door lock switch 14 has been operated, the control unit 8 causes the boost IC control unit 84 to operate the boost IC 24 to boost the voltage output from the backup power supply 6 to a predetermined boost voltage Vb so that the feedback voltage Vf becomes the target voltage V0, and also causes the first relay control unit 83 to output a control signal to the first relay 61 via the second control signal line 42.

[0053] When the backup power supply 6 is sufficiently charged, the power from the backup power supply 6 is boosted to a predetermined boost voltage Vb. As a result, the second transistor 75 in the second switching unit 70 is turned on, so that the second control signal line 42 is connected to ground via the second transistor 75, and the control signal from the control unit 8 is not input to the first switching unit 60, so that the first switching unit 60 is not turned on but is turned off.

[0054] Therefore, in this case, the battery 3 and the motor drive unit 7 are disconnected by the first relay 61 of the first power supply line 31, and power is supplied to the motor drive unit 7 at a predetermined boost voltage Vb via the second power supply line 32.

[0055] On the other hand, when the charge level of backup power supply 6 is insufficient, the power from backup power supply 6 is not boosted up to the predetermined boost voltage Vb. As a result, the second transistor 75 in second switching unit 70 is not turned on, so the second control signal line 42 is not connected to ground via the second transistor 75, and the control signal from control unit 8 is input to first switching unit 60, turning first switching unit 60 on.

[0056] Therefore, in this case, the battery 3 and the motor drive unit 7 are electrically connected via the first relay 61 of the first power supply line 31, and power is supplied to the motor drive unit 7 from the battery 3 via the first power supply line 31.

[0057] The vehicle power supply device 1 according to the embodiment described above provides the following effects.

[0058] (1) The vehicle power supply device 1 includes a backup power supply 6 supplied with power from a battery 3 mounted on the vehicle, a boost unit 20 that boosts the voltage of the backup power supply 6 to a predetermined boost voltage Vb, a motor drive unit 7 connected to the battery 3 and the boost unit 20 and capable of driving the electric motor 2 by receiving power from either the battery 3 or the boost unit 20, a first switching unit 60 that conducts / cuts off the power supply between the battery 3 and the motor drive unit 7, a control unit 8 that controls the first switching unit 60, and a second switching unit 70 that is provided between the boost unit 20 and the first switching unit 60 and turns off the first switching unit 60 when the voltage output from the boost unit 20 becomes equal to or higher than the predetermined boost voltage Vb.

[0059] As a result, when the voltage output from the boost unit 20 reaches or exceeds the predetermined boost voltage Vb, the power supply from the battery 3 to the motor drive unit 7 is cut off, and power is supplied from the boost unit 20. Therefore, by supplying power from the boost unit 20, which has a stable voltage, rather than from the battery 3, which is prone to voltage fluctuations, the electric motor 2 can be driven stably.

[0060] (2) The first switching unit 60 includes a first relay 61 provided between the battery 3 and the motor drive unit 7, and a first transistor 64 connected to the other end 63b of the coil 63 of the first relay 61 and configured to turn on the first relay 61 in response to a control signal from the control unit 8. The second switching unit 70 includes a Zener diode 73 having a cathode 73a connected to the output line 27 of the voltage step-up unit 20 and configured to be turned on when the voltage output from the voltage step-up unit 20 reaches or exceeds a predetermined boosted voltage Vb, and a second transistor 75 having a base 75c connected to the anode 73b of the Zener diode 73 and configured to be turned on when the Zener diode 73 is turned on. A collector 75a of the second transistor 75 is connected to the base 64c of the first transistor 64, and the first transistor 64 is configured to be turned off when the second transistor 75 is turned on.

[0061] As a result, power from the backup power supply 6 can be supplied to the motor drive unit 7 with only a simple circuit configuration, eliminating the need for complex control processing.

[0062] (3) A second voltage stabilization unit 76 for stabilizing the voltage output from the boost unit 20 is further provided between the output line 27 of the boost unit 20 and the cathode 73a of the Zener diode 73. The second voltage stabilization unit 76 has a diode 71 having an anode 71a connected to the output line 27 of the boost unit 20 and a cathode 71b connected to the cathode 73a of the Zener diode 73, and a capacitor 72 having one end 72a connected to the cathode 71b of the diode 71 and the other end 72b grounded.

[0063] As a result, by providing a second voltage stabilization unit 76 that stabilizes the voltage output from the boost unit 20, the stabilized voltage is input to the Zener diode 73, so that the second transistor 75 can be turned on / off accurately.

[0064] (4) The predetermined boost voltage Vb is lower than the rated voltage of the battery 3. As a result, the boosting by the booster 20 does not need to be higher than the rated voltage of the battery 3, thereby reducing power consumption.

[0065] [Second embodiment] 2 is a circuit diagram of a vehicle power supply device 100 according to the second embodiment. The vehicle power supply device 100 according to the second embodiment differs from the vehicle power supply device 1 according to the first embodiment in the configuration of the second switching unit 170. In the following explanation, the same elements as those in the vehicle power supply device 1 according to the first embodiment are given the same reference numerals, and explanations thereof will be omitted.

[0066] The second switching unit 170 differs from the first switching unit 170 in that it does not have a second voltage stabilization unit 76, and that the cathode 73a of the Zener diode 73 is connected to the output terminal 26b of the boost circuit 26 on the output line 27. That is, the Zener diode 73 is supplied with power whose voltage fluctuations are suppressed via the first voltage stabilization unit 28 provided on the output line 27.

[0067] Furthermore, a diode 171 is provided on the second power supply line 32, closer to the motor driver 7 than the output terminal 26b of the boost circuit 26. The diode 171 allows electricity to flow from the boost circuit 26 toward the motor driver 7, while blocking the flow of electricity in the opposite direction. As a result, even if the battery 3 and the motor driver 7 are electrically connected via the first power supply line 31 and the voltage of the first power supply line 31 is higher than the voltage of the second power supply line 32, the diode 171 prevents current from flowing from the input terminal 7a of the motor driver 7 to the second switching unit 170 via the second power supply line 32.

[0068] According to this embodiment, the second voltage stabilization unit 76 can be eliminated from the vehicle power supply device 1 according to the first embodiment, and the power supply device can be configured with a single first voltage stabilization unit .

[0069] The vehicle power supply device according to the present invention is not limited to the configuration of the above embodiment, and various modifications are possible.

[0070] In the above embodiment, the vehicle power supply device for controlling the power supply to a door latch device has been described as an example, but the present invention is not limited to this. The present invention can be applied to any on-board device that operates by receiving power, such as an on-board device equipped with an electric motor, and can also be used to supply power to electric motors, electromagnetic valves, etc. used in power windows, electric tailgates, electric fuel lid caps, electric sliding doors, etc. [Explanation of symbols]

[0071] 1 Vehicle power supply unit 2 electric motors 3 Battery 6. Backup power supply 7 Motor drive unit 8 Control Unit 9. Second Relay 10 Door latch device 14 Door lock switch 20 Booster section 21 Coil 22 Diode 23 Field-effect transistor 24 Boost IC 25 capacitors 26 Boost circuit 27 Output Line 28 First voltage stabilization unit 31 1st power supply line 32 2nd power supply line 41 First control signal line 42 Second control signal line 43 Third control signal line 44 4th control signal line 45 5th control signal line 50 Voltage divider circuit 51 1st resistance 52 2nd resistor 60 First Switching Section 61 1st Relay 64 First Transistor 70 Second Switching Section 71 Diode 72 Capacitor 73 Zener diode 75 Second transistor 76 Second voltage stabilization section 81 Second relay control section 82 Door lock switch operation determination unit 83 First relay control section 84 Boost IC control section 85 Motor drive control unit

Claims

1. a backup power supply supplied with power from an on-board battery; a booster unit that boosts the voltage of the backup power supply to a predetermined boost voltage; a motor drive unit connected to the battery and the voltage step-up unit, and capable of driving an electric motor by receiving power from either the battery or the voltage step-up unit; a first switching unit that connects / disconnects power supply between the battery and the motor drive unit; a control unit that controls the first switching unit; a second switching unit that is provided between the boosting unit and the first switching unit and turns off the first switching unit when the voltage output from the boosting unit becomes equal to or higher than the predetermined boosted voltage; A vehicle power supply device comprising:

2. The first switching unit a first switching element provided between the battery and the motor drive unit; a second switching element connected to a control terminal of the first switching element and receiving the control signal from the control unit to turn on the first switching element; have The second switching unit a Zener diode having a cathode connected to an output line of the booster unit and turning on when the voltage output from the booster unit becomes equal to or higher than the predetermined boosted voltage; a third switching element having a control terminal connected to an anode of the Zener diode and turned on when the Zener diode is brought into a conductive state; and The third switching element is connected to a control terminal of the second switching element, and when the third switching element is turned on, the second switching element is turned off.

2. A vehicle power supply device according to claim 1.

3. a voltage stabilizing unit between the output line of the voltage boosting unit and the cathode of the Zener diode, the voltage stabilizing unit stabilizing the voltage output from the voltage boosting unit; The voltage stabilization unit a diode having an anode connected to the output line of the booster unit and a cathode connected to the cathode of the Zener diode; a capacitor having one end connected to the cathode of the diode and the other end grounded; having The vehicle power supply device according to claim 2.

4. The predetermined boost voltage is lower than the rated voltage of the battery. The vehicle power supply device according to any one of claims 1 to 3.

5. A vehicle power supply device according to any one of claims 1 to 4, a fork that is rotatable between a latched position where it engages with a striker on the vehicle body side and an open position where the engagement is released; a claw rotatable between a locked position that holds the fork in the latched position and an unlocked position that releases the hold; and The door latch device includes an electric motor that is powered by the vehicle power supply device and drives the claw to rotate.

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