Power supply device

Abstract

To provide a power supply device capable of suppressing deterioration of an auxiliary power supply due to overdischarge.SOLUTION: A power supply device 10 has an auxiliary power supply 10A backing up an on-vehicle main power supply 20, and a control circuit 10C controlling charge of the auxiliary power supply 10A by power from the main power supply 20 and discharge of the auxiliary power supply 10A. When a power supply switch 23 of a vehicle is turned ON, the control circuit 10C executes an initial check that is an initial inspection at the time of startup, and charges the auxiliary power supply 10A when traveling preparation of the vehicle is completed after the completion of the initial check. The control circuit 10C charges the auxiliary power supply 10A when both a first condition that an elapsed time after the completion of the initial check is equal to or more than a threshold value, regardless after the completion of the initial check or before the completion of the travelling preparation of the vehicle, and a second condition that voltage of the auxiliary power supply 10A is less than a voltage threshold value are satisfied.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a power supply device. [Background technology]

[0002] Conventionally, there is known a power supply device that uses an auxiliary power supply to back up power supply to a power supply target when a main power supply fails. For example, the power supply device of Patent Document 1 is provided in a power supply path between a main power supply and a steering control device of a vehicle. The power supply device has an auxiliary power supply and a charging circuit. The auxiliary power supply is, for example, a lithium ion capacitor. The charging circuit is a circuit for charging the auxiliary power supply. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-18841 A Summary of the Invention [Problem to be solved by the invention]

[0004] The auxiliary power supply has a self-discharge characteristic. Therefore, even when the auxiliary power supply is not in use, the capacity of the auxiliary power supply gradually decreases over time. Therefore, if the auxiliary power supply is not charged for a long period of time for some reason, the auxiliary power supply may reach an over-discharge state. There is a concern that the deterioration of the auxiliary power supply may be accelerated if the over-discharge state continues for a long period of time. The power supply device is required to suppress the deterioration of the auxiliary power supply due to over-discharge. [Means for solving the problem]

[0005] A power supply device that can solve the above problem includes an auxiliary power supply configured to back up an on-board main power supply that supplies power to a power supply target, and a control circuit configured to control charging of the auxiliary power supply with power from the main power supply and discharging of the auxiliary power supply. When a power switch of a vehicle is turned on, the control circuit is configured to execute an initial check that is an initial inspection at start-up, and to wait until the vehicle is ready to run after the initial check is completed, and then charge the auxiliary power supply. After the initial check is completed, but before the vehicle is ready to run, the control circuit is configured to charge the auxiliary power supply when both a first condition that the elapsed time since the completion of the initial check is equal to or greater than a time threshold value and a second condition that the voltage of the auxiliary power supply is less than a voltage threshold value are satisfied.

[0006] It is conceivable that the vehicle does not become ready to run for a long time due to some reason. In this case, the auxiliary power supply may discharge or consume power during the period from when the power switch is turned on until the vehicle becomes ready to run, and the auxiliary power supply may reach an over-discharged state. In this regard, according to the above configuration, when the power switch is turned on, even if the vehicle is not yet ready to run, if the elapsed time since the initial check is completed is equal to or greater than the time threshold value and the voltage of the auxiliary power supply is less than the voltage threshold value, the auxiliary power supply is charged. Therefore, during the period from when the power switch is turned on until the vehicle becomes ready to run, it is possible to suppress the auxiliary power supply from discharging or consuming power, and thus the auxiliary power supply from reaching an over-discharged state. Therefore, it is possible to suppress the deterioration of the auxiliary power supply due to over-discharge.

[0007] In the power supply device, the auxiliary power supply may have an output voltage lower than an output voltage of the main power supply and may be charged by a voltage of the main power supply that is stepped down by an on-board DC / DC converter. The preparation for running of the vehicle may include a process of starting up the DC / DC converter.

[0008] According to this configuration, the auxiliary power supply is charged by the voltage of the main power supply stepped down by the DC / DC converter. Therefore, when the power switch is turned on, it is basically preferable to wait for the DC / DC converter to start up before charging the auxiliary power supply.

[0009] In the power supply device described above, the voltage threshold value may be set to a minimum voltage value required for backing up the main power supply. The auxiliary power supply is charged by power from the main power supply. Therefore, when the auxiliary power supply is charged, power from the main power supply is consumed. In this regard, according to the above configuration, the time from when the initial check by the control circuit is completed until the second condition that the voltage of the auxiliary power supply is less than the voltage threshold value is satisfied can be made longer than when the voltage threshold value is set to a value greater than the minimum voltage value required for backing up the main power supply. Therefore, power consumption from the main power supply before the start-up of the DC / DC converter can be suppressed.

[0010] In the above power supply device, the power supply target may be a control device of the vehicle configured to transmit a charge permission signal to the control circuit when the vehicle is ready to run. The control circuit may be configured to recognize that the vehicle is ready to run when the charge permission signal is received.

[0011] According to this configuration, the control circuit can easily recognize that the vehicle is ready to travel by receiving the charge permission signal from the control device of the vehicle. In the above power supply device, the control device may be a steering control device configured to control a motor that is a drive source for a steering device of the vehicle.

[0012] A steering control device is required to have high operational reliability. The above power supply device is suitable for a steering control device. Effect of the Invention

[0013] According to the power supply device of the present invention, deterioration of the auxiliary power supply due to over-discharge can be suppressed. [Brief description of the drawings]

[0014] [Figure 1] 1 is a block diagram of a vehicle power supply system including a power supply device and a steering control device according to an embodiment. [Diagram 2] 5 is a flowchart illustrating an example of a process executed by a control circuit of the power supply device according to one embodiment. [Diagram 3] 4 is a graph showing a voltage usage range of an auxiliary power supply according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] An embodiment of a power supply device will be described below. As shown in Fig. 1, the power supply device 10 is provided in a power supply path between a main power supply 20 and a steering control device 30 to be powered. The main power supply 20 is connected to the power supply device 10 via a DC / DC converter 21. The power supply device 10 is located between the DC / DC converter 21 and the steering control device 30, and backs up the main power supply 20. "DC" is an abbreviation for "Direct Current" and means "direct current." The main power supply 20 is also connected to an auxiliary battery 22 via the DC / DC converter 21.

[0016] The main power supply 20 is, for example, a lithium ion battery or a nickel-metal hydride battery. The main power supply 20 is an in-vehicle power supply backed up by the power supply device 10. The DC / DC converter 21 steps down the output voltage of the main power supply 20. Power from the DC / DC converter 21 is supplied to the steering control device 30 via the power supply device 10.

[0017] The auxiliary battery 22 is, for example, a lead storage battery. The output voltage of the auxiliary battery 22 is lower than the output voltage of the main power supply 20. The DC / DC converter 21 steps down the output voltage of the main power supply 20 and charges the auxiliary battery 22 with the stepped-down voltage. The power of the auxiliary battery 22 is supplied to the on-board auxiliaries.

[0018] The steering control device 30 is one of the control devices of the vehicle. The steering control device 30 controls a motor that is a drive source of a steering device of the vehicle. The steering device is, for example, a steer-by-wire type steering device, in which the power transmission between the steering wheel and the steered wheels is separated. The motor includes a reaction motor 41 and a steering motor 42.

[0019] The reaction motor 41 is a generating source of a steering reaction force. The steering reaction force is a force in a direction opposite to the operation direction of the steering wheel. The reaction motor 41 is, for example, a three-phase brushless motor and has two winding groups. The winding groups include a first winding group N11 and a second winding group N12. The torque of the reaction motor 41 is applied to the steering shaft via a reducer.

[0020] The steering motor 42 is a source of steering force. The steering force is a force for steering the steered wheels of a vehicle. The steering motor 42 is, for example, a three-phase brushless motor, and has two winding groups. The winding groups include a first winding group N21 and a second winding group N22. The torque of the steering motor 42 is applied to a steering shaft via a reducer. The steering shaft steers the steered wheels.

[0021] The steering control device 30 has a reaction force control device 31 and a turning control device 32. The reaction force control device 31 and the turning control device 32 exchange information with each other via a communication line (not shown).

[0022] The reaction force control device 31 controls the power supply to the reaction force motor 41. The reaction force control device 31 has a first reaction force control unit 31A and a second reaction force control unit 31B. The first reaction force control unit 31A controls the power supply to the winding group N11 of the first system of the reaction force motor 41. The second reaction force control unit 31B controls the power supply to the winding group N12 of the second system of the reaction force motor 41.

[0023] The steering control device 32 controls the power supply to the steering motor 42. The steering control device 32 has a first steering control section 32A and a second steering control section 32B. The first steering control section 32A controls the power supply to the winding group N21 of the first system of the steering motor 42. The second steering control section 32B controls the power supply to the winding group N22 of the second system of the steering motor 42.

[0024] <Power supply path> Next, the power supply path between the main power source 20 and the steering control device 30 will be described. As shown in FIG. 1, the power supply device 10 is connected to a DC / DC converter 21 via a first power line L1. The power supply device 10 is also connected to the DC / DC converter 21 via a second power line L2. A power switch 23 is provided on the second power line L2. The power switch 23 includes, for example, an ignition switch, and is operated when starting or stopping a drive source for running the vehicle. The drive source for running is, for example, an engine or a motor for running. Through the operation of the power switch 23, the conduction of the second power line L2 is switched between on and off.

[0025] The first reaction force control unit 31A is connected to the DC / DC converter 21 via the power supply unit 10. The first reaction force control unit 31A is connected to the power supply unit 10 via a third power supply line L3. The third power supply line L3 branches off from the first power supply line L1 inside the power supply unit 10. The first reaction force control unit 31A is connected to the power supply unit 10 via a fourth power supply line L4. The fourth power supply line L4 branches off from the second power supply line L2 inside the power supply unit 10.

[0026] The power from the DC / DC converter 21 is supplied to the power circuit of the first reaction force control unit 31A via the first power line L1, the power supply unit 10, and the third power line L3. The power circuit is an electric circuit that handles larger power, and includes, for example, an inverter that converts the DC power from the DC / DC converter 21 into AC power. The power from the DC / DC converter 21 is also supplied to the control circuit of the first reaction force control unit 31A via the second power line L2, the power supply unit 10, and the fourth power line L4. The control circuit is an electric circuit for controlling the reaction force motor 41, and includes, for example, a CPU (Central Processing Unit) and a memory. The memory includes a RAM (Random Access Memory) and a ROM (Read Only Memory).

[0027] The first turning control unit 32A is connected to the DC / DC converter 21 via the power supply device 10. The first turning control unit 32A is connected to the power supply device 10 via a fifth power supply line L5. The fifth power supply line L5 branches off from the first power supply line L1 inside the power supply device 10. The first turning control unit 32A is connected to the power supply device 10 via a sixth power supply line L6, and the sixth power supply line L6 branches off from the second power supply line L2 inside the power supply device 10.

[0028] Power from DC / DC converter 21 is supplied to a power circuit of first steering control unit 32A via first power line L1, power supply device 10, and fifth power line L5. Power from DC / DC converter 21 is also supplied to a control circuit of first steering control unit 32A via second power line L2, power supply device 10, and sixth power line L6.

[0029] The second reaction force control unit 31B is connected to the DC / DC converter 21 without going through the power supply device 10. The second reaction force control unit 31B is connected to the DC / DC converter 21 through a seventh power supply line L7. The second reaction force control unit 31B is also connected to the DC / DC converter 21 through an eighth power supply line L8. More specifically, the second reaction force control unit 31B is connected to a first connection point P1 set on the second power supply line L2 through the eighth power supply line L8. The first connection point P1 is set between the power switch 23 and the power supply device 10 on the second power supply line L2.

[0030] The power from the DC / DC converter 21 is supplied to the power circuit of the second reaction force control unit 31B via the seventh power line L7. The power from the DC / DC converter 21 is also supplied to the control circuit of the second reaction force control unit 31B via a part of the second power line L2 and the eighth power line L8.

[0031] The second turning control unit 32B is connected to the DC / DC converter 21 without going through the power supply device 10. The second turning control unit 32B is connected to the DC / DC converter 21 via a ninth power supply line L9. The second turning control unit 32B is also connected to the DC / DC converter 21 via a tenth power supply line L10. In detail, the second turning control unit 32B is connected to a second connection point P2 set on the eighth power supply line L8 via the ninth power supply line L9.

[0032] The power from the DC / DC converter 21 is supplied to the power circuit of the second turning control unit 32B via the ninth power supply line L9. The power from the DC / DC converter 21 is also supplied to the control circuit of the second turning control unit 32B via a part of the second power supply line L2, a part of the eighth power supply line L8, and the tenth power supply line L10.

[0033] The main power supply 20, the DC / DC converter 21, the auxiliary battery 22, the power supply device 10, and the steering control device 30 constitute a vehicle power supply system. <Power supply> Next, the configuration of the power supply device 10 will be described.

[0034] The power supply device 10 includes an auxiliary power supply 10A, a switching circuit 10B, and a control circuit 10C. The auxiliary power supply 10A is a power storage device capable of charging and discharging an electric charge, such as a lithium ion capacitor or a lithium ion battery. The voltage of the auxiliary power supply 10A is, for example, higher than the lower limit of the voltage required for backup of the auxiliary battery 22, i.e., the lower limit of the voltage required for proper operation of the steering control device 30, and lower than the voltage of the auxiliary battery 22.

[0035] Based on a command from the control circuit 10C, the switching circuit 10B switches the connection state of the auxiliary power supply 10A to the first power supply line L1 so that the auxiliary power supply 10A is charged. That is, the switching circuit 10B opens and closes the charging path between the auxiliary power supply 10A and the first power supply line L1. Based on a command from the control circuit 10C, the switching circuit 10B also switches the power supply of the first reaction force control unit 31A and the first steering control unit 32A between the main power supply 20 and the auxiliary power supply 10A. That is, the switching circuit 10B opens and closes the discharge path between the auxiliary power supply 10A and the third power supply line L3 and between the auxiliary power supply 10A and the fourth power supply line L4. Based on a command from the control circuit 10C, the switching circuit 10B also opens and closes the discharge path between the auxiliary power supply 10A and the fifth power supply line L5 and between the auxiliary power supply 10A and the sixth power supply line L6.

[0036] The power of the main power supply 20 or the auxiliary power supply 10A switched by the switching circuit 10B is supplied to the first reaction force control unit 31A via the third power supply line L3 and the fourth power supply line L4. Also, the power of the main power supply 20 or the auxiliary power supply 10A switched by the switching circuit 10B is supplied to the first steering control unit 32A via the fifth power supply line L5 and the sixth power supply line L6.

[0037] The control circuit 10C has a processing circuit including any one of the following three configurations A1, A2, and A3. A1. One or more processors that operate according to a computer program that is software. The processor includes a CPU and a memory.

[0038] A2. One or more dedicated hardware circuits, such as an application-specific integrated circuit (ASIC), that perform at least some of the processing. A3. A hardware circuit that combines two configurations A1 and A2.

[0039] The memory is a computer-readable medium that stores a program that describes processes or instructions for the computer. In this embodiment, the computer is a CPU. The memory includes RAM and ROM. The CPU executes various controls by executing the programs stored in the memory at a set calculation cycle.

[0040] Control circuit 10C controls the switching of switching circuit 10B. Control circuit 10C also monitors the voltage of main power supply 20. When the value of the voltage of main power supply 20 is smaller than a voltage threshold value, control circuit 10C determines that the voltage of main power supply 20 has dropped. The voltage threshold value is a criterion for determining a voltage drop of main power supply 20. The voltage threshold value is set based on the lower limit value of the voltage required for properly operating reaction force motor 41 and steering motor 42, as well as first reaction force control unit 31A and first steering control unit 32A.

[0041] When no drop in the voltage of main power supply 20 is detected, control circuit 10C generates a first command for switching circuit 10B. The first command is a command to switch the power source of first reaction force control unit 31A and first steering control unit 32A to main power supply 20. The first command is also a command to switch the connection state of auxiliary power supply 10A to first power supply line L1 so that auxiliary power supply 10A is charged.

[0042] When a drop in the voltage of main power supply 20 is detected, control circuit 10C generates a second command to switching circuit 10B. The second command is a command to switch the power supply of first reaction force control unit 31A and first steering control unit 32A from main power supply 20 to auxiliary power supply 10A. The second command is also a command to switch the connection state of auxiliary power supply 10A to first power supply line L1 so that auxiliary power supply 10A is not charged.

[0043] The control circuit 10C detects the charge amount of the auxiliary power supply 10A. The control circuit 10C detects the voltage of the auxiliary power supply 10A through a voltage sensor provided in the auxiliary power supply 10A, and detects the charge amount of the auxiliary power supply 10A based on the detected voltage. The voltage is the voltage between the terminals of the auxiliary power supply 10A. The control circuit 10C determines that the charge amount of the auxiliary power supply 10A is insufficient when the value of the voltage of the auxiliary power supply 10A is smaller than the voltage threshold value. The control circuit 10C determines that the charge amount of the auxiliary power supply 10A is sufficient when the value of the voltage of the auxiliary power supply 10A is equal to or greater than the voltage threshold value. The voltage threshold value is a criterion for determining whether the charge amount of the auxiliary power supply 10A is sufficient. The voltage threshold value is set based on the lower limit value of the voltage required to properly operate the reaction force motor 41 and the steering motor 42, as well as the first reaction force control unit 31A and the first steering control unit 32A.

[0044] <Processing of the control circuit 10C> Next, an example of the process executed by the control circuit 10C will be described. In the initial state, the power switch 23 is turned off. The charging path between the auxiliary power supply 10A and the first power supply line L1 is open. The discharging paths between the auxiliary power supply 10A and the third power supply line L3 and between the auxiliary power supply 10A and the fourth power supply line L4 are open. The discharging paths between the auxiliary power supply 10A and the fifth power supply line L5 and between the auxiliary power supply 10A and the sixth power supply line L6 are also open.

[0045] 2, when the power switch 23 is turned on, the control circuit 10C executes an initial check (step S101). The initial check is an initial inspection performed when the power supply device 10 is started up, and is a series of processes required for the power supply device 10 to operate. The initial check includes processes such as a hardware check and initialization of the CPU (Central Processing Unit).

[0046] After the execution of the initial check is normally completed, the control circuit 10C transitions to a state waiting for charging permission (step S102). The state waiting for charging permission is a state in which charging of the auxiliary power supply 10A is not permitted and is a state in which the control circuit 10C waits for the DC / DC converter 21 to start up, that is, a state in which the control circuit 10C waits for the vehicle to be ready to run. This is to reduce the load on the auxiliary battery 22 before the DC / DC converter 21 starts up, that is, the power consumption. The power from the DC / DC converter 21 is not charged into the auxiliary battery 22 until the DC / DC converter 21 starts up.

[0047] The vehicle has a host control device 50. The host control device 50 controls the control devices of various in-vehicle systems including the steering control device 30. When the power switch 23 is turned on, the host control device 50 executes preparation for the vehicle to travel after completing an initial check. The preparation for travel includes, for example, an initial check by the host control device 50, a start-up process of the vehicle's powertrain, and a start-up process of the DC / DC converter 21. When the vehicle's preparation for travel is completed and the vehicle is in a state where it can travel, the host control device 50 transmits an assist start permission signal S1 to the first reaction force control unit 31A.

[0048] When the power switch 23 is turned on, the first reaction force control unit 31A transitions to an assist start waiting state after completing an initial check. The assist start waiting state is a state in which the vehicle is waiting for the vehicle to be ready to travel and become travellable. When the assist start permission signal S1 is received in the assist start waiting state, the first reaction force control unit 31A transitions to an assist start state. The assist start state is a state in which control of the steering reaction force by the reaction force motor 41 can be executed. When the first reaction force control unit 31A transitions to the assist start state, it transmits a charge permission signal S2 to the control circuit 10C.

[0049] The transition of the state of first reaction force control unit 31A to the assist start state is transmitted to second reaction force control unit 31B, first steering control unit 32A and second steering control unit 32B. Therefore, at the timing when the state of first reaction force control unit 31A transitions to the assist start state, the states of second reaction force control unit 31B, first steering control unit 32A and second steering control unit 32B also transition to the assist start state.

[0050] When the control circuit 10C receives the charging permission signal S2 while waiting for the DC / DC converter 21 to start up, the control circuit 10C recognizes that the DC / DC converter 21 has started up. The charging permission signal S2 is also an electric signal indicating that the vehicle is ready to run, and therefore that the DC / DC converter 21 has started up. When the control circuit 10C recognizes that the DC / DC converter 21 has started up, it transitions to a chargeable state (step S103).

[0051] The chargeable state is a state in which charging of auxiliary power supply 10A is permitted and it is possible to start charging auxiliary power supply 10A. When control circuit 10C transitions to the chargeable state, it checks the charging state of auxiliary power supply 10A and determines whether the amount of charge in auxiliary power supply 10A is sufficient to back up the power supply to first reaction force control unit 31A and first steering control unit 32A.

[0052] When control circuit 10C determines based on the voltage of auxiliary power supply 10A that the charge level of auxiliary power supply 10A is not sufficient, it starts charging auxiliary power supply 10A and waits until the charge level of auxiliary power supply 10A reaches a sufficient level. When control circuit 10C determines that the charge level of auxiliary power supply 10A is sufficient, it recognizes that a backup of power supply to first reaction force control unit 31A and first steering control unit 32A is possible.

[0053] When it is determined that the charge amount of the auxiliary power supply 10A is sufficient, the control circuit 10C stops charging the auxiliary power supply 10A, transitions to a backup standby state (step S104), and ends the process. The backup standby state is a state in which the power supply device 10 is capable of backing up the power supply to the first reaction force control unit 31A and the first steering control unit 32A, and the power supply device 10 is on standby to back up the power supply to the first reaction force control unit 31A and the first steering control unit 32A. When the power supply device 10 is maintained in the backup standby state, the voltage of the main power supply 20 does not drop, and power is supplied from the main power supply 20 to the steering control device 30.

[0054] <Over-discharge prevention treatment> The power supply device 10 configured in this manner has the following concerns. For example, charging of the auxiliary power supply 10A is not permitted until the DC / DC converter 21 starts up, that is, until the host control device 50 has completed preparations for the vehicle to run. For this reason, if the DC / DC converter 21 does not start up for a long period of time for some reason, the discharge or power consumption of the auxiliary power supply 10A will progress, and there is a risk that the auxiliary power supply 10A will reach an over-discharged state.

[0055] Therefore, in order to prevent over-discharge of the auxiliary power supply 10A, the control circuit 10C executes the following process. That is, when the control circuit 10C transitions to the charge permission waiting state (step S102), if both the first condition B1 and the second condition B2 are satisfied, the control circuit 10C transitions to the chargeable state even if the vehicle is not ready to run (step S103). The control circuit 10C can recognize that the vehicle is not ready to run by not receiving the charge permission signal S2.

[0056] B1.ΔT ≧ΔT th B2.V <V th Here, "ΔT" is the time that has elapsed since the transition to the charging permission waiting state. The elapsed time ΔT is also the time that has elapsed since the initial check is completed. th " is the time threshold. "V" is the voltage of the auxiliary power supply 10A. "V th " is the voltage threshold.

[0057] As shown in Figure 3, the voltage threshold V th is set to the minimum voltage value required for backing up the main power supply 20. Also, the voltage threshold V th is set to a value greater than the first voltage V1 at which the auxiliary power supply 10A becomes over-discharged and less than the second voltage V2 at which the auxiliary power supply 10A becomes over-charged. A voltage range less than the first voltage V1 is the over-discharge range, and a voltage range greater than the second voltage V2 is the over-charge range, which are voltage ranges in which degradation of the auxiliary power supply 10A may be a concern. The operating range of the voltage of the auxiliary power supply 10A is equal to or greater than the first voltage V1 and equal to or less than the second voltage V2.

[0058] First voltage V1 or more, voltage threshold V th The voltage range below this threshold is a margin of error until the auxiliary power supply 10A reaches an over-discharge state. This is because the elapsed time from when the control circuit 10C transitions to the charging permission waiting state is equal to or exceeds the time threshold ΔT th This is based on the viewpoint of preventing the auxiliary power supply 10A from reaching an over-discharge state during the period until the voltage threshold V th As described above, the voltage range equal to or lower than the second voltage V2 is a voltage range in which the device uses its own energy. This is based on the viewpoint of reducing the load on the main power supply 20.

[0059] <Effects of the embodiment> This embodiment provides the following advantages. (1) It is possible that, for some reason, the vehicle is not ready to run for a long time. In this case, in the period from when power switch 23 is turned on until the vehicle is ready to run, the discharge or power consumption of auxiliary power supply 10A progresses, and auxiliary power supply 10A may reach an over-discharged state. In this regard, according to the present embodiment, control circuit 10C determines whether or not the elapsed time ΔT from the completion of the initial check is greater than or equal to the time threshold value ΔT even if the vehicle is not ready to run after the completion of the initial check. th The first condition is that the voltage V of the auxiliary power supply 10A is equal to or greater than the voltage threshold V th When both the first condition that the charge current is less than 100mA and the second condition that the charge current is less than 100mA are satisfied, charging of auxiliary power supply 10A is performed. This makes it possible to prevent auxiliary power supply 10A from discharging or consuming power, and thus to prevent auxiliary power supply 10A from reaching an over-discharged state, during the period from when power switch 23 is turned on until the vehicle is ready to travel. This makes it possible to prevent deterioration of auxiliary power supply 10A due to over-discharge.

[0060] (2) Auxiliary power supply 10A has an output voltage lower than the output voltage of the vehicle's main power supply 20, and is charged by the voltage of main power supply 20 stepped down by an on-board DC / DC converter 21. Furthermore, preparation for the vehicle to travel includes a startup process for DC / DC converter 21. With this configuration, auxiliary power supply 10A is charged by the voltage of main power supply 20 stepped down by DC / DC converter 21. For this reason, when power switch 23 is turned on, it is basically preferable to wait for startup of DC / DC converter 21 before charging auxiliary power supply 10A.

[0061] (3) Auxiliary power supply 10A is charged by the power of main power supply 20. Therefore, when auxiliary power supply 10A is charged, the power of main power supply 20 is consumed. In this regard, according to the present embodiment, the voltage threshold value V th is set to the minimum voltage value required for backing up the main power supply 20. For this reason, for example, the voltage threshold value V this set to a value greater than the minimum voltage value required for backing up the main power supply 20, the voltage of the auxiliary power supply 10A is set to a value greater than the voltage threshold value V th This makes it possible to lengthen the time until the second condition, that is, the current I / O voltage Vcc is less than 1 V, is satisfied. This makes it possible to suppress the power consumption of main power supply 20 before start-up of DC / DC converter 21, that is, to reduce the load on main power supply 20.

[0062] (4) The steering control device 30, which is one of the control devices of the vehicle, transmits a charge permission signal S2 to the control circuit 10C when the vehicle is ready to travel. When the control circuit 10C receives the charge permission signal S2, it recognizes that the vehicle is ready to travel. With this configuration, the control circuit 10C can easily recognize that the vehicle is ready to travel by receiving the charge permission signal S2 from the steering control device 30.

[0063] (5) The steering control device 30 controls a motor that is a drive source for the steering device of the vehicle. Higher operational reliability is required for the steering control device 30. The power supply device 10 of the present embodiment is suitable for the steering control device 30.

[0064] <Other embodiments> This embodiment may be modified as follows. After the initial check is completed, the control circuit 10C may transition to a chargeable state for the auxiliary power supply 10A as long as the DC / DC converter 21 is activated, even if the vehicle is not yet fully prepared for traveling. In this case, the control circuit 10C may obtain a signal indicating the activation state of the DC / DC converter 21 from the upper control device 50 or from the DC / DC converter 21.

[0065] Motors having one system of winding groups may be used as reaction force motor 41 and steering motor 42. In this case, it is possible to use a configuration having only one of first reaction force control section 31A and second reaction force control section 31B as reaction force control device 31. Also, it is possible to use a configuration having only one of first steering control section 32A and second steering control section 32B as steering control device 32.

[0066] The control target of the steering control device 30 may be an assist motor, which is a drive source of an electric power steering device. The assist motor is a source of assist force. The assist force is a force in the same direction as the steering wheel operation direction. As the assist motor, a motor having one system of winding groups may be used, or a motor having two systems of winding groups may be used.

[0067] The power supply target of the power supply device 10 is not limited to the steering control device 30. The power supply target may be a control device that controls the drive of a driving motor of an electric vehicle or a hybrid electric vehicle. The power supply target may also be a control device that controls the brakes of the vehicle. [Explanation of symbols]

[0068] 10…Power supply device 10A…Auxiliary power supply 10C…Control circuit 20…Main power supply 21...DC / DC converter 22...Auxiliary battery (on-board power supply) 23…Power switch 30...Steering control device (power supply target) 41...Reaction motor 42...Steering motor

Claims

1. An auxiliary power supply configured to back up an on-board main power supply that supplies power to a power supply target; a control circuit configured to control charging of the auxiliary power supply with power from the main power supply and discharging of the auxiliary power supply; When a power switch of a vehicle is turned on, the control circuit executes an initial check which is an initial check at the time of startup, and after the initial check is completed, waits until the vehicle is ready to run, and then charges the auxiliary power supply. The control circuit is configured to charge the auxiliary power supply when both a first condition that the elapsed time since completion of the initial check is greater than or equal to a time threshold and a second condition that the voltage of the auxiliary power supply is less than a voltage threshold are satisfied after completion of the initial check, even if the vehicle is not ready to run.

2. the auxiliary power supply has an output voltage lower than an output voltage of the main power supply, and is configured to be charged by a voltage of the main power supply that is stepped down by an on-board DC / DC converter; The power supply device according to claim 1 , wherein the preparation for running the vehicle includes a start-up process for the DC / DC converter.

3. 3. The power supply device according to claim 1, wherein the voltage threshold value is set to a minimum voltage value required for backing up the main power supply.

4. The power supply target is a control device of the vehicle configured to transmit a charging permission signal to the control circuit when the vehicle is ready to travel, 3. The power supply device according to claim 1, wherein the control circuit is configured to recognize that the vehicle is ready to travel when the charge permission signal is received.

5. 5. The power supply device according to claim 4, wherein the control device is a steering control device configured to control a motor that is a drive source for a steering device of the vehicle.

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