Power supply device

Abstract

To provide a power supply device capable of ensuring the calculation accuracy of the internal resistance of an auxiliary power supply.SOLUTION: A control circuit 24 of a power supply device 10 creates a state in which an auxiliary power supply 22 is connected to a main power supply 11 via a charging circuit 21 when a power switch 13 provided in a power supply path between the main power supply 11 and a power supply target 12 is turned on. The control circuit 24 calculates the internal resistance of the auxiliary power supply 22 on the basis of a charging current I supplied from the charging circuit 21 to the auxiliary power supply 22. When the power switch 13 is turned off, the control circuit 24 disconnects the power supply device 10 from the main power supply 11 and the power supply target 12, and creates a state in which only the auxiliary power supply 22 and the boost circuit 23 are connected. When a terminal voltage V2 of the auxiliary power supply 22 falls below a stop determination threshold, the control circuit 24 disconnects the auxiliary power supply 22 from the boost circuit 23.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 the 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. The charging circuit has a boost circuit that boosts the output voltage of the main 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] In a power supply device such as that described in Patent Document 1, a deterioration diagnosis is sometimes performed. For example, the internal resistance of the auxiliary power supply during charging is calculated, and the degree of deterioration of the auxiliary power supply is determined based on the calculated internal resistance. To ensure the reliability of the diagnosis, it is necessary to ensure the calculation accuracy of the internal resistance. [Means for solving the problem]

[0005] A power supply device that can solve the above problem includes an auxiliary power supply for a main power supply that supplies power to a power supply target, a charging circuit provided in a charging path between the main power supply and the auxiliary power supply, the charging circuit configured to charge the auxiliary power supply using power from the main power supply, a boost circuit provided in a discharging path between the auxiliary power supply and the power supply target, the boost circuit configured to boost the output voltage of the auxiliary power supply, and a control circuit configured to control opening and closing of the charging path and the discharging path. The control circuit is configured to create a state in which the auxiliary power supply is connected to the main power supply via the charging circuit when a power switch provided in the power supply path between the main power supply and the power supply target is turned on, and to calculate an internal resistance of the auxiliary power supply based on a charging current supplied from the charging circuit to the auxiliary power supply. The control circuit is configured to disconnect the power supply device from the main power supply and the power supply target when the power switch is turned off, and to create a state in which only the auxiliary power supply and the boost circuit are connected, and to disconnect the auxiliary power supply from the boost circuit when the voltage of the auxiliary power supply falls below a stop determination threshold.

[0006] With this configuration, the next time the power switch is turned on, the voltage of the auxiliary power supply will have dropped to below the shutdown threshold, allowing a sufficient charging current to flow from the charging circuit to the auxiliary power supply, ensuring the accuracy of the calculation of the internal resistance.

[0007] In the above power supply device, the control circuit is configured so that, when the power switch is turned on, power is supplied from the main power supply and power is supplied from the boost circuit by forming a state in which the auxiliary power supply and the boost circuit are connected, while the control circuit may be configured so that power continues to be supplied from the boost circuit for a period from when the power switch is turned off until the voltage of the auxiliary power supply falls below the stop determination threshold.

[0008] With this configuration, even if the power supply from the main power source to the control circuit is stopped due to the power switch being turned off, the power from the boost circuit is still supplied to the control circuit, so the control circuit can continue to operate by consuming the power from the boost circuit.

[0009] In the above power supply device, the control circuit may be configured not to calculate the internal resistance of the auxiliary power supply when the charging current is below the current threshold value if the power switch is turned on again within a period from when the power switch is turned off until the voltage of the auxiliary power supply falls below the stop determination threshold value.

[0010] When a sufficient charging current does not flow, there is a risk that it will be impossible to ensure the accuracy of the calculation of the internal resistance of the auxiliary power supply. With the above configuration, it is possible to avoid unnecessary calculation of the internal resistance that would make it impossible to ensure the accuracy of the calculation.

[0011] In the above power supply device, the control circuit may be configured not to calculate the internal resistance of the auxiliary power supply when the power switch is turned on and the voltage of the auxiliary power supply is not below the stop determination threshold.

[0012] When the voltage of the auxiliary power supply is not below the stop determination threshold, there is a risk that the calculation accuracy of the internal resistance of the auxiliary power supply cannot be ensured due to insufficient charging current. With the above configuration, it is possible to avoid unnecessary calculation of the internal resistance that cannot ensure the calculation accuracy.

[0013] In the above power supply device, the power supply target may include a control device of a vehicle. Vehicle control devices are required to have high operational reliability, and the above-described power supply device is suitable for use in vehicle control devices. Effect of the Invention

[0014] According to the power supply device of the present invention, it is possible to ensure the accuracy of calculation of the internal resistance of the auxiliary power supply. [Brief description of the drawings]

[0015] [Figure 1] 1 is a circuit diagram of a power supply device according to an embodiment; [Diagram 2] FIG. 2 is a circuit diagram of an auxiliary power supply according to an embodiment when not charging. [Diagram 3] FIG. 2 is a circuit diagram of an auxiliary power supply during charging according to one embodiment. [Figure 4] 4 is a graph showing a voltage rise at the start of charging of an auxiliary power supply according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] An embodiment of a power supply device will be described below. As shown in Fig. 1, a power supply device 10 is provided in a power supply path between a main power supply 11 and a power supply target 12. The main power supply 11 is, for example, a battery. The power supply target 12 is, for example, a vehicle control device that operates by consuming power supplied via the power supply device 10. The control device is, for example, a steering control device that controls a motor that is a drive source for a steering device of the vehicle. Examples of steering devices include an electric power steering device or a steer-by-wire type steering device.

[0017] The power supply path includes a first power line L1 and a second power line L2. The second power line L2 branches off from a first connection point P1 set on the first power line L1. The first connection point P1 is set between the main power supply 11 and the power switch 13 on the first power line L1.

[0018] The power of the main power supply 11 is supplied, for example, to an electric circuit of a power system of the power supply target 12 via a first power supply line L1. The electric circuit of the power system is a circuit that handles larger power, and includes, for example, an inverter that converts the DC power of the main power supply 11 into AC power. Moreover, the power of the main power supply 11 is supplied, for example, to an electric circuit of a control system of the power supply target 12 via a second power supply line L2. The electric circuit of the control system is, for example, a circuit for controlling a motor, and includes a processing circuit such as a microcomputer.

[0019] A power switch 13 is provided in the first power line L1 between the power supply device 10 and the main power supply 11. The power switch 13 includes, for example, an ignition switch, and is operated when starting to run the vehicle. Through the operation of the power switch 13, the conduction of the first power line L1 is switched between on and off.

[0020] The first power line L1 and the second power line L2 form a power supply path between the main power supply 11 and the power supply target 12. <Configuration of power supply device 10> Next, the configuration of the power supply device 10 will be described.

[0021] The power supply device 10 has a charging circuit 21, an auxiliary power supply 22, a boost circuit 23, and a control circuit 24. The power supply device 10 also has first to fifth switches 31 to 35, a first voltage sensor 41, a second voltage sensor 42, and a current sensor 43.

[0022] The charging circuit 21 is a circuit for charging the auxiliary power supply 22 using power from the main power supply 11. An input terminal of the charging circuit 21 is connected to a second connection point P2 set on the second power supply line L2 via a third power supply line L3. An output terminal of the charging circuit 21 is connected to the auxiliary power supply 22 via a fourth power supply line L4.

[0023] Auxiliary power supply 22 is a power storage device capable of charging and discharging electric charge, and may be, for example, a lithium ion capacitor or a lithium ion battery. The voltage of auxiliary power supply 22 is set lower than the voltage of main power supply 11. The voltage of auxiliary power supply 22 and the voltage of main power supply 11 are each a terminal voltage, and are actual output voltages.

[0024] The boost circuit 23 is a circuit for boosting the output voltage of the auxiliary power supply 22. The boost circuit 23 boosts the output voltage of the auxiliary power supply 22 to, for example, a voltage higher than the terminal voltage of the auxiliary power supply 22 and lower than the terminal voltage of the main power supply 11. An input terminal of the boost circuit 23 is connected to the auxiliary power supply 22 via a fifth power supply line L5. The boost circuit 23 has two output terminals. A first output terminal of the boost circuit 23 is connected to a third connection point P3 set on the first power supply line L1 via a sixth power supply line L6. A second output terminal of the boost circuit 23 is connected to a fourth connection point P4 set on the second power supply line L2 via a seventh power supply line L7. The fourth connection point P4 is set between the second connection point P2 on the second power supply line L2 and the power supply target 12.

[0025] The first switch 31 is provided on the third power line L3. The first switch 31 opens and closes the third power line L3. The second switch 32 is provided on the fourth power line L4. The second switch 32 opens and closes the fourth power line L4. The third switch 33 is provided on the fifth power line L5. The third switch 33 opens and closes the fifth power line L5. The fourth switch 34 is provided on the sixth power line L6. The fourth switch 34 opens and closes the sixth power line L6. The fifth switch 35 is provided on the seventh power line L7. The fifth switch 35 opens and closes the seventh power line L7.

[0026] The first voltage sensor 41 is provided between the power switch 13 and the third connection point P3 in the first power line L1. The first voltage sensor 41 detects a voltage V1 occurring in the first power line L1. The second voltage sensor 42 is provided between the second switch 32 and the auxiliary power supply 22 in the fourth power line L4. The second voltage sensor 42 detects a terminal voltage V2 of the auxiliary power supply 22. The terminal voltage V2 is a voltage actually output from the auxiliary power supply 22. The current sensor 43 is provided between the charging circuit 21 and the second switch 32 in the fourth power line L4. The current sensor 43 detects a current occurring in the fourth power line L4, i.e., a charging current I for the auxiliary power supply 22. The charging current I is a current supplied to the auxiliary power supply 22 when the auxiliary power supply 22 is charged.

[0027] The control circuit 24 is connected to a fifth connection point P5 set on the sixth power line L6 via an eighth power line L8. The fifth connection point P5 is set between the fourth switch 34 and the boost circuit 23 on the sixth power line L6. The control circuit 24 controls the on and off of the first to fifth switches 31 to 35. The control circuit 24 detects the on and off of the power switch 13 based on the voltage V1 detected through the first voltage sensor 41. The control circuit 24 monitors the voltage of the main power supply 11. When the value of the voltage VB of the main power supply 11 is smaller than a predetermined voltage threshold, the control circuit 24 determines that the voltage VB of the main power supply 11 has dropped. The voltage threshold is a criterion for determining a voltage drop of the main power supply 11.

[0028] The third power supply line L3 and the fourth power supply line L4 form a charging path between the main power supply 11 and the auxiliary power supply 22. The fifth power supply line L5, the sixth power supply line L6, and the seventh power supply line L7 form a discharging path between the auxiliary power supply 22 and the power supply target 12. The control circuit 24 controls the opening and closing of the charging path and the discharging path by controlling the on and off of the first to fifth switches 31 to 35.

[0029] <Operation of power supply device 10> Next, a description will be given of the operation of the power supply device 10. In the initial state, the power switch 13 and the first to fifth switches 31 to 35 are turned off.

[0030] When the power switch 13 is turned on, power from the main power supply 11 is supplied to the electric circuit of the control system of the power supply target 12 via the first power supply line L1. When the power switch 13 is turned on, power from the main power supply 11 is also supplied to the control circuit 24 via a power supply line (not shown). Regardless of whether the power switch 13 is on or off, power from the main power supply 11 is supplied to the electric circuit of the power system of the power supply target 12 via the second power supply line L2.

[0031] When the power switch 13 is turned on, the control circuit 24 turns on the first to fourth switches 31 to 34 while maintaining the fifth switch 35 in an off state. Therefore, the power from the main power supply 11 is charged into the auxiliary power supply 22 via the charging circuit 21. The charging circuit 21 controls charging while monitoring, for example, the charging current and the charging voltage.

[0032] The output voltage of the auxiliary power supply 22 is boosted by the boost circuit 23. When the voltage VB of the main power supply 11 is not lowered, the voltage V3 boosted by the boost circuit 23 is lower than the voltage VB of the main power supply 11. Therefore, the voltage V3 boosted by the boost circuit 23 is not supplied to the electric circuit of the control system of the power supply target 12 via the sixth power supply line L6 and the first power supply line L1. A first diode for preventing reverse current (not shown) is provided between the third connection point P3 in the sixth power supply line L6 and the fourth switch 34. The first diode prevents power from flowing from the main power supply 11 to the boost circuit 23 via the first power supply line L1 and the sixth power supply line L6. The voltage boosted by the boost circuit 23 is supplied to the control circuit 24 via the eighth power supply line L8.

[0033] In contrast, when the voltage VB of the main power supply 11 drops, power from the boost circuit 23 is instantly supplied to the electric circuit of the control system of the power supply target 12 via the sixth power supply line L6 and the first power supply line L1. This is because, as the voltage VB of the main power supply 11 drops, the voltage V3 boosted by the boost circuit 23 becomes higher than the voltage of the main power supply 11 and, by extension, the voltage generated in the first power supply line L1. Therefore, even if the power supply from the main power supply 11 to the power supply target 12 is interrupted, the power supply to the electric circuit of the control system of the power supply target 12 is backed up by the auxiliary power supply 22.

[0034] A second diode (not shown) for preventing reverse current is provided between the first voltage sensor 41 and the third connection point P3 in the first power supply line L1. The second diode prevents power from flowing from the boost circuit 23 to the main power supply 11 via the sixth power supply line L6 and the first power supply line L1.

[0035] When the voltage VB of the main power supply 11 drops, the control circuit 24 turns on the fifth switch 35. As a result, power from the boost circuit 23 is supplied to the power system electric circuit of the power supply target 12 via the seventh power supply line L7 and the second power supply line L2. This is because, as the voltage VB of the main power supply 11 drops, the voltage V3 boosted by the boost circuit 23 becomes higher than the voltage of the main power supply 11 and, by extension, the voltage generated on the second power supply line L2. Therefore, even if the power supply from the main power supply 11 to the power supply target 12 is interrupted, the power supply to the power system electric circuit of the power supply target 12 is backed up by the auxiliary power supply 22.

[0036] A third diode (not shown) for preventing reverse current is provided between the second connection point P2 and the fourth connection point P4 in the second power line L2. The third diode prevents power from flowing from the boost circuit 23 to the main power supply 11 via the sixth power line L6 and the second power line L2.

[0037] <Deterioration Diagnosis Processing of Auxiliary Power Supply 22> The control circuit 24 diagnoses the deterioration of the auxiliary power supply 22 while the auxiliary power supply 22 is being charged. When the power switch 13 is turned on, the control circuit 24 determines the degree of deterioration of the auxiliary power supply 22 based on the internal resistance of the auxiliary power supply 22 during charging. This is based on the fact that the internal resistance of the auxiliary power supply 22 increases as the deterioration of the auxiliary power supply 22 progresses. The internal resistance is an electrical resistance that the auxiliary power supply 22 has inside.

[0038] As shown in FIG. 2, the auxiliary power supply 22 generates an electromotive force V s and internal resistance R s It can be represented by an electric circuit with and connected in series. s is the theoretical voltage of the auxiliary power supply 22. When the auxiliary power supply 22 is not being charged, i.e., when no charging current is being supplied from the charging circuit 21 to the auxiliary power supply 22, the internal resistance R s Therefore, the terminal voltage V2 of the auxiliary power supply 22 does not increase in proportion to the electromotive force V s The terminal voltage V2 is the voltage actually output from the auxiliary power supply 22.

[0039] As shown in FIG. 3, when the auxiliary power supply 22 is being charged, that is, when a charging current I is being supplied from the charging circuit 21 to the auxiliary power supply 22, the internal resistance R s Therefore, when the auxiliary power supply 22 is being charged, the terminal voltage V2 of the auxiliary power supply 22 is increased by an electromotive force V s The increased voltage ΔV is the voltage of the auxiliary power supply 22 that increases due to the charging of the auxiliary power supply 22.

[0040] 4, depending on the charging method of charging circuit 21, when charging of auxiliary power supply 22 starts (time T1), terminal voltage V2 of auxiliary power supply 22 rises instantaneously. After that, terminal voltage V2 gradually increases as charging progresses, and eventually is maintained at a constant voltage.

[0041] The voltage rise ΔV of auxiliary power supply 22 during charging is expressed by the following equation (1): "·" in equation (1) indicates multiplication. ΔV=I R s…(1) Terminal voltage V2 of auxiliary power supply 22 during charging is expressed by the following equation (2).

[0042] V2=V s +ΔV …(2) Internal resistance R s is expressed by the following formula (3). Formula (3) is obtained from the previous formula (1). " / " in formula (3) indicates division.

[0043] R s =ΔV / I …(3) The control circuit 24 calculates the internal resistance R of the auxiliary power supply 22 using equation (3). s The control circuit 24 calculates, for example, the internal resistance R s is greater than a predetermined resistance threshold, the control circuit 24 determines that the auxiliary power supply 22 has deteriorated. When the control circuit 24 determines that the auxiliary power supply 22 has deteriorated, the control circuit 24 executes a predetermined process. The process includes, for example, visually or audibly notifying the user of the vehicle that the auxiliary power supply 22 has deteriorated.

[0044] However, when the deterioration of the auxiliary power supply 22 is diagnosed while the auxiliary power supply 22 is being charged, the following concerns arise. That is, when the auxiliary power supply 22 is nearly fully charged, a sufficient charging current I does not flow, so that, for example, the signal-to-noise ratio (SN ratio) of the current sensor 43 decreases, and the internal resistance R of the auxiliary power supply 22 increases. s Therefore, in this embodiment, the internal resistance R of the auxiliary power supply 22 is s In order to ensure the accuracy of the calculation, the control circuit 24 executes the following process.

[0045] <Internal resistance R s Processing to ensure the accuracy of calculations> When the power switch 13 is turned off, the control circuit 24 turns off the first switch 31, the second switch 32, the fourth switch 34, and the fifth switch 35. That is, the control circuit 24 keeps only the third switch 33 turned on. Therefore, the power of the auxiliary power supply 22 continues to be supplied to the boost circuit 23. As a result, the boost circuit 23 continues to operate. As the power of the auxiliary power supply 22 is consumed by the boost circuit 23, the charge amount of the auxiliary power supply 22 gradually decreases. As the charge amount decreases, the terminal voltage V2 of the auxiliary power supply 22 decreases.

[0046] The control circuit 24 operates by consuming power supplied via the eighth power line L8 from the boost circuit 23. The control circuit 24 determines whether or not the following equation (4) is satisfied. V2 <V th …(4) However, "V th " is the stop determination threshold. Stop determination threshold V th is a criterion for determining whether to completely stop the operation of the power supply device 10. th is set, for example, based on the terminal voltage V2 of the auxiliary power supply 22 at which a sufficient charging current I is expected to flow the next time the auxiliary power supply 22 is charged.

[0047] When the following formula (4) does not hold, that is, when the terminal voltage V2 of the auxiliary power supply 22 is equal to or lower than the stop determination threshold V th In this case, only the third switch 33 continues to be kept on. The power of the auxiliary power supply 22 continues to be consumed by the boost circuit .

[0048] When the following formula (4) is satisfied, that is, when the terminal voltage V2 of the auxiliary power supply 22 reaches the stop determination threshold value V thWhen the voltage Vcc falls below 1 V, the third switch 33 is turned off. This stops the supply of power from the auxiliary power supply 22 to the boost circuit 23, and the operation of the boost circuit 23 stops. When the operation of the boost circuit 23 stops, the supply of power from the boost circuit 23 to the control circuit 24 via the eighth power line L8 stops. This also stops the operation of the control circuit 24. In other words, the operation of the power supply device 10 stops completely.

[0049] Thereafter, when the power switch 13 is turned on again, the control circuit 24 turns on the first to fourth switches 31 to 34 while maintaining the fifth switch 35 in the off state. Based on the charging current I detected via the current sensor 43 and the terminal voltage V2 of the auxiliary power supply 22 detected via the second voltage sensor 42, the control circuit 24 calculates the internal resistance R s The terminal voltage V2 of the auxiliary power supply 22 is calculated as the stop determination threshold value V th Since the internal resistance R s It is possible to ensure the calculation accuracy.

[0050] <Effects of the embodiment> This embodiment provides the following advantages. (1) When the power switch 13 is turned on, the control circuit 24 turns on the first switch 31 and the second switch 32, thereby creating a state in which the auxiliary power supply 22 is connected to the main power supply 11 via the charging circuit 21. The control circuit 24 calculates the internal resistance R s When the power switch 13 is turned off, the control circuit 24 turns off the first switch 31, the fourth switch 34, and the fifth switch 35, thereby isolating the power supply device 10 from the main power supply 11 and the power supply target 12. Furthermore, the control circuit 24 turns off the second switch 32 while maintaining the third switch 33 in an on state, thereby creating a state in which only the auxiliary power supply 22 and the boost circuit 23 are connected. The control circuit 24 determines whether the terminal voltage V2 of the auxiliary power supply 22 is equal to or lower than the stop determination threshold value V thWhen the voltage Vcc falls below 1 V, the third switch 33 is turned off to separate the auxiliary power supply 22 from the boost circuit 23.

[0051] According to this configuration, the next time the power switch 13 is turned on, the terminal voltage V2 of the auxiliary power supply 22 will be equal to or lower than the stop determination threshold V th Therefore, a sufficient charging current I flows from the charging circuit 21 to the auxiliary power supply 22. Therefore, the internal resistance R of the auxiliary power supply 22 s It is possible to ensure the accuracy of the calculation of the deterioration diagnosis of the auxiliary power supply 22. Furthermore, it is possible to appropriately perform the deterioration diagnosis of the auxiliary power supply 22 before the vehicle starts running, which is the timing when the deterioration diagnosis of the auxiliary power supply 22 is required. It is also possible to ensure the reliability of the deterioration diagnosis.

[0052] (2) After the power switch 13 is turned off, the power of the auxiliary power supply 22 consumed by the boost circuit 23 is small. For this reason, the terminal voltage V2 of the auxiliary power supply 22 does not reach the stop determination threshold V th It takes time for the terminal voltage V2 of the auxiliary power supply 22 to decrease to a level below 0V. However, the adjustment of the terminal voltage V2 of the auxiliary power supply 22 is performed when the vehicle is not in use, for example, when the vehicle is parked. Therefore, the adjustment of the terminal voltage V2 of the auxiliary power supply 22 does not affect the operation of the vehicle system.

[0053] (3) When power switch 13 is turned on, a sufficient charging current I flows. This prevents a decrease in the signal-to-noise ratio of current sensor 43 and, in turn, a decrease in the detection accuracy of current sensor 43. Therefore, a highly accurate current sensor 43 is not required.

[0054] (4) When the power switch 13 is turned on, power from the main power supply 11 is supplied to the control circuit 24. When the power switch 13 is turned on, the control circuit 24 turns on the third switch 33 to establish a state in which the auxiliary power supply 22 and the boost circuit 23 are connected. Therefore, power is supplied from the boost circuit 23 to the control circuit 24. When the terminal voltage V2 of the auxiliary power supply 22 becomes lower than the stop determination threshold value V after the power switch 13 is turned off, th, power from the boost circuit 23 continues to be supplied to the control circuit 24. Therefore, even if the supply of power from the main power supply 11 to the control circuit 24 is stopped when the power switch 13 is turned off, the control circuit 24 can continue to operate by consuming power from the boost circuit 23.

[0055] (5) When the auxiliary power supply 22 is discharged, that is, when a current is output from the auxiliary power supply 22, the internal resistance R s Therefore, when the auxiliary power supply 22 is discharged, the terminal voltage V2 of the auxiliary power supply 22 is increased by an amount corresponding to the voltage drop. s The voltage drop is the voltage of the auxiliary power supply 22 that drops due to the discharge of the auxiliary power supply 22. In contrast, when the auxiliary power supply 22 is not discharged, that is, when no current is output from the auxiliary power supply 22, the internal resistance R s Therefore, the terminal voltage V2 of the auxiliary power supply 22 does not drop in proportion to the electromotive force V s is equal to

[0056] Therefore, the internal resistance R of the auxiliary power supply 22 during discharge s It is also possible to determine the degree of deterioration of the auxiliary power supply 22 based on the internal resistance R s In order to ensure the accuracy of the calculation of the discharge current, and therefore the accuracy of the determination of the deterioration degree of the auxiliary power supply 22, it is necessary to pass a certain amount of discharge current. For this reason, the power supply device 10 is provided with a current path including special components such as a large-capacity discharge resistor. Providing a current path may increase the size or product cost of the power supply device 10. In this regard, the internal resistance R of the auxiliary power supply 22 during charging s When the deterioration degree of the auxiliary power supply 22 is determined based on the above, no special parts related to discharge are required. This is advantageous in terms of the size of the power supply device 10 or the product cost.

[0057] (6) The power supply target 12 includes a vehicle control device. Higher operational reliability is required for the vehicle control device. The power supply device 10 of the present embodiment is suitable for the vehicle control device. <Other embodiments> This embodiment may be modified as follows.

[0058] The control circuit 24 detects whether the terminal voltage V2 of the auxiliary power supply 22 reaches the stoppage determination threshold V th If the power switch 13 is turned on again within the period until the charging current I falls below the current threshold, the internal resistance R s The current threshold value is calculated by experiment or simulation using the internal resistance R s When a sufficient charging current I does not flow, the internal resistance R of the auxiliary power supply 22 is set to a value that is considered to ensure the accuracy of the calculation. s According to the above configuration, it is possible to avoid unnecessary calculation of the internal resistance, which would result in a failure to ensure the accuracy of the calculation.

[0059] When the power switch 13 is turned on, the control circuit 24 detects whether the terminal voltage V2 of the auxiliary power supply 22 is equal to or lower than the stop determination threshold V th When the internal resistance R of the auxiliary power supply 22 is not lower than s The terminal voltage V2 of the auxiliary power supply 22 may not be calculated. th If the charging current I is not below 100%, the internal resistance R of the auxiliary power supply 22 will not increase due to insufficient charging current I. s According to the above configuration, the calculation accuracy of the internal resistance R s This can avoid the calculation of [Explanation of symbols]

[0060] 10…Power supply device 11…Main power supply 12…Power supply target 13...Power switch 21…Charging circuit 22…Auxiliary power supply 23...Boost circuit 24...Control circuit L1: The first power line that constitutes the power supply path L2: The second power line that constitutes the power supply path L3: The third power line that constitutes the charging path L4: The fourth power line that constitutes the charging path L5: The fifth power line that constitutes the discharge path L6: The sixth power line that constitutes the discharge path L7: The seventh power line that constitutes the discharge path

Claims

1. An auxiliary power source for a main power source that supplies power to a power supply target; a charging circuit provided in a charging path between the main power supply and the auxiliary power supply, the charging circuit being configured to charge the auxiliary power supply using power from the main power supply; a boost circuit provided in a discharge path between the auxiliary power supply and the power supply target, the boost circuit being configured to boost an output voltage of the auxiliary power supply; A control circuit configured to control opening and closing of the charging path and the discharging path, the control circuit forms a state in which the auxiliary power supply is connected to the main power supply via the charging circuit when a power switch provided in a power supply path between the main power supply and the power supply target is turned on, and calculates an internal resistance of the auxiliary power supply based on a charging current supplied from the charging circuit to the auxiliary power supply, The control circuit is configured to disconnect the power supply device from the main power supply and the power supply target when the power switch is turned off, and to create a state in which only the auxiliary power supply and the boost circuit are connected, and to disconnect the auxiliary power supply from the boost circuit when the voltage of the auxiliary power supply falls below a stop determination threshold.

2. The control circuit is configured such that, when the power switch is turned on, power is supplied from the main power supply, and power is supplied from the boost circuit by establishing a state in which the auxiliary power supply and the boost circuit are connected, while 2. The power supply device according to claim 1, wherein the power supply is continued to be supplied from the boost circuit during a period from when the power switch is turned off until the voltage of the auxiliary power supply falls below the stop determination threshold.

3. 3. The power supply device according to claim 1, wherein the control circuit is configured not to calculate the internal resistance of the auxiliary power supply when the charging current is below the current threshold value if the power switch is turned on again within a period from when the power switch is turned off until the voltage of the auxiliary power supply falls below the stop determination threshold value.

4. 3. The power supply device according to claim 1, wherein the control circuit is configured not to calculate the internal resistance of the auxiliary power supply when the power switch is turned on and the voltage of the auxiliary power supply is not below the stop determination threshold.

5. The power supply device according to claim 1 or 2, wherein the power supply target includes a control device of a vehicle.

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