Auxiliary power supply device

Abstract

To limit a current flowing from a power path into a first conducting path to an upper-limit current value or less by controlling a charging operation of a charging section provided on a second conducting path which branches from the first conducting path.SOLUTION: An auxiliary power unit 60 includes: a first conducting path 61 through which a current supplied from a power path 30 flows; a second conducting path 62 and a third conducting path 63 which branch from the first conducting path 61; a charging section 64 that performs at least a charging operation of supplying a charging current to a power storage section 40 based on power supplied from the second conducting path 62; and a control unit 65 that controls the charging section 64. The control section 65 makes the charging section 64 perform the charging operation so as to limit the current flowing from the power path 30 to the first conducting path 61 to an upper-limit value or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an auxiliary power supply device.

Background Art

[0002] In a configuration where there are a plurality of electric wires (branch portions) branched from one electric wire (main trunk portion) and power is supplied from each of the branch portions to a load, a current obtained by superimposing the currents flowing through the respective branch portions flows through the main trunk portion. In such a configuration, depending on the number of loads and the current value required by the load, heat generation in the main trunk portion increases, and it is necessary to increase the wire diameter of the main trunk portion in order to suppress overheating.

[0003] Therefore, it is conceivable to apply a configuration such as the power control device disclosed in Patent Document 1. The power control device of Patent Document 1 is configured to be connected to a power source and supply power to a plurality of loads via a plurality of electric wires respectively. An upper limit of an allowable temperature is predetermined for each of the electric wires. When the temperature of an electric wire is equal to or higher than the upper limit temperature, the control unit of the power control device stops power supply to the load to protect the electric wire.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] For example, a configuration can be considered in which charging current is supplied to an energy storage element via a branching section, and current is supplied to a load via another branching section. However, if the power control device configuration of Patent Document 1 is applied to each branching section of such a configuration, the charging time of the energy storage element will be prolonged by interrupting the charging current to the energy storage element. For loads where interruption of current supply is undesirable, it is difficult to apply the interruption configuration. Therefore, there is a need for a configuration that can control the current flowing through the main section without interrupting the current flowing through the branching sections.

[0006] The purpose of this disclosure is to control the charging operation of a charging unit provided in a second conductive path that branches off from the first conductive path, thereby suppressing the current flowing from the power path to the first conductive path to an upper limit current value or less. [Means for solving the problem]

[0007] One of the disclosures is an auxiliary power supply device, An auxiliary power supply device used in a power supply system having a power supply unit, a power line which is a path through which power is supplied from the power supply unit, and a power storage unit, A first conductive path electrically connected to the aforementioned power path, through which current supplied from the aforementioned power path flows, A second conductive path and a third conductive path branching from the first conductive path, A charging unit is provided between the second conductive path and the energy storage unit, and performs at least a charging operation that supplies a charging current to the energy storage unit based on the power supplied from the second conductive path, A control unit that controls the charging unit, It has, The control unit causes the charging unit to perform the charging operation so as to keep the current flowing from the power line to the first conductive line below the upper limit current value. [Effects of the Invention]

[0008] The technology disclosed herein controls the charging operation of a charging unit provided in a second conductive path branching from the first conductive path, thereby suppressing the current flowing from the power path to the first conductive path to an upper limit current value or less. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a block diagram illustrating a power supply system including an auxiliary power supply device according to the first embodiment. [Figure 2] Figure 2 is an explanatory diagram illustrating the state in which current flows from the power supply unit to the energy storage unit and the load in the block diagram of Figure 1. [Figure 3] Figure 3 is an explanatory diagram illustrating the changes in each current value with respect to elapsed time in the auxiliary power supply device of the first embodiment. [Figure 4] Figure 4 is an explanatory diagram illustrating the changes in each current value with respect to elapsed time in the auxiliary power supply device of the second embodiment. [Figure 5] Figure 5 is a block diagram illustrating a power supply system including an auxiliary power supply device according to the third embodiment. [Figure 6] Figure 6 is an explanatory diagram illustrating the fuse tripping characteristics in the power supply system of the fourth embodiment. [Modes for carrying out the invention]

[0010] Embodiments of the present disclosure are listed and illustrated below. The features [1] to [8] illustrated below may be combined in any way that is not contradictory.

[0011] [1] An auxiliary power supply device used in a power supply system having a power supply unit, a power line which is a path through which power is supplied from the power supply unit, and a power storage unit, A first conductive path electrically connected to the aforementioned power path, through which current supplied from the aforementioned power path flows, A second conductive path and a third conductive path branching from the first conductive path, A charging unit is provided between the second conductive path and the energy storage unit, and performs at least a charging operation that supplies a charging current to the energy storage unit based on the power supplied from the second conductive path, A control unit that controls the charging unit, It has, The control unit causes the charging unit to perform the charging operation so as to suppress the current flowing from the power path into the first conductive path to be equal to or less than the upper limit current value. Auxiliary power supply device.

[0012] In the auxiliary power supply device of [1] above, by controlling the charging operation of the charging unit provided in the second conductive path branched from the first conductive path, the current flowing from the power path into the first conductive path can be suppressed to be equal to or less than the upper limit current value. Therefore, without controlling the current in the third conductive path branched from the first conductive path, the current flowing into the first conductive path can be suppressed to be equal to or less than the upper limit current value.

[0013] 〔2〕The auxiliary power supply device according to [1] has the following features. The auxiliary power supply device has a current sensor that detects the current value of the first conductive path. The control unit controls the charging operation of the charging unit based on the detection result of the current sensor so that the current flowing from the power path into the first conductive path is equal to or less than the upper limit current value.

[0014] In the auxiliary power supply device of [2] above, the current value of the first conductive path can be directly grasped by the current sensor, and it becomes easier to improve the accuracy of suppressing the current flowing into the first conductive path to be equal to or less than the upper limit current value by controlling the charging operation of the charging unit.

[0015] 〔3〕The auxiliary power supply device according to [1] has the following features. The auxiliary power supply device has a second current sensor that detects the current value of the second conductive path, and one or more third current sensors arranged so as to be able to detect the current flowing from the first conductive path into the third conductive path. The control unit controls the charging operation of the charging unit based on the detection result of the second current sensor and the detection result of the third current sensor so that the current flowing from the power path into the first conductive path is equal to or less than the upper limit current value.

[0016] In the auxiliary power supply device of [3] above, the current flowing through the first conductive path can be indirectly grasped by using the second current sensor provided in the second conductive path and the third current sensor provided in the third conductive path.

[0017] The auxiliary power supply device described in any of [4] [1] to [3] has the following features: The control unit performs a first control to bring the current value of the second conductive path closer to the target current value, provided that the sum of a predetermined target current value smaller than the upper limit current value and the current value of the third conductive path is less than or equal to the upper limit current value. If the charge unit is to perform the charging operation when the sum of the target current value and the current value of the third conductive path exceeds the upper limit current value, the control unit performs a second control to limit the current value of the second conductive path to a value lower than the target current value while suppressing the current flowing into the first conductive path to less than or equal to the upper limit current value.

[0018] In the auxiliary power supply device described in [4] above, when the sum of a predetermined target current value, which is smaller than the upper limit current value, and the current value of the third conductive path is less than or equal to the upper limit current value, it is permissible to allow the first conductive path to flow a current of the target value so as not to exceed the upper limit current value. Therefore, when the conditions for this state are met, the first control (control to bring the current value of the second conductive path closer to the target current value) can be performed to allow the second conductive path to flow a current of the desired target value. If the sum of the target current value and the current value of the third conductive path exceeds the upper limit current value, it is necessary to reduce the current value of the first conductive path so as not to exceed the upper limit current value. Therefore, the current of the first conductive path can be kept below the upper limit current value by performing the second control (control to limit the current value of the second conductive path to a value lower than the target current value while keeping the current flowing into the first conductive path below the upper limit current value).

[0019] The auxiliary power supply device described in any of [5] [1] to [4] has the following features: The control unit performs control to increase the target current value so that the current value of the first conductive path approaches the upper limit current value when the sum of a predetermined target current value which is smaller than the upper limit current value and the current value of the third conductive path is smaller than the upper limit current value.

[0020] In the auxiliary power supply device described in [5] above, when the sum of a predetermined target current value, which is smaller than the upper limit current value, and the current value of the third conductive circuit is smaller than the upper limit current value, there is room to increase the target current value as long as the current value of the first conductive circuit does not exceed the upper limit current value. In such cases, by controlling the device to increase the target current value so that the current value of the second conductive circuit approaches the target current value, the charging current can be increased while keeping the current value of the first conductive circuit below the upper limit current value.

[0021] The auxiliary power supply device described in any of [6] [1] to [5] has the following features: The power supply system has a cutoff unit that cuts off the energization of the first conductive path when the current value of the power path reaches the cutoff current value. The upper limit current value is less than the cutoff current value.

[0022] In the auxiliary power supply device described in [6] above, since the upper limit current value is less than the cutoff current value, the cutoff unit can be prevented from being cut off by keeping the current flowing into the first conductive path below the upper limit current value.

[0023] The auxiliary power supply device described in any of [7], [1] to [5] has the following features: The control unit changes the upper limit current value based on the current value of the first conductive path.

[0024] In the auxiliary power supply device described in [7] above, changing the upper limit current value makes it easier to appropriately change the current state of the first conductive circuit according to the load connected to the third conductive circuit.

[0025] The auxiliary power supply device described in [8] and [7] has the following features: The power supply system is provided with a fuse in the power path. The fuse operates to interrupt the current in the first conductive path when a current of any value flows for a period of time corresponding to any of the values ​​in the interruption characteristics. The control unit reduces the upper limit current value to less than the current value corresponding to the allowable time corresponding to the elapsed time in the interruption characteristics, for a predetermined elapsed time after the current value of the first conductive path becomes equal to or greater than a predetermined lower limit current value.

[0026] In the auxiliary power supply device described in [8] above, it is possible to determine, based on the fuse's tripping characteristics, how long (allowable time) the current in the first conductive path will flow at a given current value before the current in the first conductive path is cut off. Therefore, if the current in the first conductive path exceeds a predetermined lower limit current value that causes the tripping characteristics to occur, the upper limit current value can be reduced to a value lower than the current value corresponding to the allowable time equivalent to the elapsed time, thereby preventing the fuse from cutting off the current in the first conductive path for a predetermined period of time.

[0027] <First Embodiment> [Power supply system configuration] The power supply system 10 shown in Figure 1 comprises a power supply unit 20, a power line 30, a power storage unit 40, loads 51 and 52, and an auxiliary power supply device 60. The power supply system 10 is mounted, for example, in a vehicle. The power supply system 10 is used as a power source to operate the loads 51 and 52 mounted in the vehicle.

[0028] The power supply unit 20 functions as a main power source that continuously supplies power to loads 51 and 52. The power supply unit 20 is a DC power source that generates a DC voltage. The power supply unit 20 is composed of a battery, such as a lead-acid battery. The high-potential terminal of the power supply unit 20 is electrically connected to the power line 30, and the low-potential terminal of the power supply unit 20 is electrically connected to ground. The power supply unit 20 applies a predetermined voltage to the power line 30. The power line 30 is the path through which power is supplied from the power supply unit. In this specification, unless otherwise specified, voltage refers to a voltage with respect to ground.

[0029] In this disclosure, "electrically connected" preferably means a configuration in which the two connected objects are connected in a state of conduction (a state in which current can flow) such that the potentials of both objects are equal. However, the disclosure is not limited to this configuration. For example, "electrically connected" may mean a configuration in which the two connected objects are connected in a state in which they can conduct electricity while an electrical component is interposed between them.

[0030] A fuse 32 is provided in the power line 30. The fuse 32 corresponds to the "interruption unit" in this disclosure. The fuse 32 interrupts the flow of power to the first conductive line 61 when the current value in the power line 30 reaches the interruption current value. The interruption current value is, for example, a fixed value.

[0031] Loads 51 and 52 are, for example, automotive electrical equipment. Loads 51 and 52 may also be actuators such as motors. Alternatively, loads 51 and 52 may be ECUs and actuators in an electric parking brake system, or ECUs and actuators in a shift-by-wire control system. Alternatively, they may be other automotive electrical equipment.

[0032] The energy storage unit 40 functions as an auxiliary power source for loads 51 and 52. The energy storage unit 40 is a DC power source that outputs a DC voltage, and is, for example, an electric double-layer capacitor. The energy storage unit 40 is charged and discharged via the charging unit 64, which will be described later.

[0033] The auxiliary power supply unit 60 supplies power from the power supply unit 20 to the energy storage unit 40 and loads 51 and 52. The auxiliary power supply unit 60 includes a first conductive path 61, a second conductive path 62, a third conductive path 63, a charging unit 64, a control unit 65, and a current sensor 66.

[0034] Current supplied from the power line 30 flows through the first conductive path 61. One end of the first conductive path 61 is electrically connected to the power line 30. The other end of the first conductive path 61 is electrically connected to the second conductive path 62 and the third conductive path 63.

[0035] The second conductive path 62 and the third conductive path 63 branch off from the first conductive path 61. One end of the second conductive path 62 is electrically connected to the other end of the first conductive path 61. The other end of the second conductive path 62 is electrically connected to the charging section 64.

[0036] The third conductive path 63 comprises a power supply side conductive path 63A and load side conductive paths 63B and 63C. The load side conductive paths 63B and 63C branch off from the power supply side conductive path 63A. One end of the power supply side conductive path 63A is electrically connected to the other end of the first conductive path 61. The other end of the power supply side conductive path 63A is electrically connected to one end of the load side conductive path 63B and one end of the load side conductive path 63C.

[0037] The other end of the load-side conductive path 63B is electrically connected to the load 51. A switch element 63D is provided in the load-side conductive path 63B. The switch element 63D is composed of a relay switch or a semiconductor switch such as a MOSFET. The switch element 63D is switched by the control unit 65 between an ON state, which allows energization of the load-side conductive path 63B, and an OFF state, which cuts off the energization.

[0038] The other end of the load-side conductive path 63C is electrically connected to the load 52. A switch element 63E is provided on the load-side conductive path 63C. The switch element 63E is composed of a relay switch or a semiconductor switch such as a MOSFET. The switch element 63E is switched by the control unit 65 between an ON state, which allows energization of the load-side conductive path 63C, and an OFF state, which cuts off the energization.

[0039] The charging unit 64 is located between the second conductive path 62 and the energy storage unit 40. The charging unit 64 performs charging and discharging operations for the energy storage unit 40. The charging unit 64 performs a charging operation by supplying a charging current to the energy storage unit 40 based on the power supplied from the second conductive path 62. The charging unit 64 operates based on the control of the control unit 65, which will be described later. The charging unit 64 is configured, for example, as a DC-DC converter. The charging unit 64 performs constant current operation and constant voltage operation. In constant current operation, the charging current is output at a target charging current (also called a target current value) by feedback control. In constant voltage operation, the output voltage is output at a target charging voltage by feedback control. In constant voltage operation, the charging current is not necessarily constant. As a discharge operation, the charging unit 64 performs a voltage conversion operation by boosting or lowering the voltage output from the energy storage unit 40 and applying it to the second conductive path 62.

[0040] The control unit 65 controls the operation of supplying power from the power supply unit 20 to the energy storage unit 40 and loads 51 and 52. The control unit 65 is an information processing device having information processing functions, calculation functions, control functions, etc. The control unit 65 is mainly composed of a microcomputer and has calculation devices such as a CPU (Central Processing Unit), memory such as ROM (Read Only Memory) or RAM (Random Access Memory), A / D converter, etc. The control unit 65 has the function of controlling the charging unit 64 and the switch elements 63D and 63E.

[0041] The current sensor 66 detects the current value of the first conductive path 61. The current value detected by the current sensor 66 is a value that can identify the current value of the first conductive path 61 (specifically, an analog voltage value). The current sensor 66 is configured, for example, as a current detection circuit. The first conductive path 61 is electrically connected to the power path 30 and is at the same potential as the power path 30. Therefore, the current sensor 66 can detect the current of the power path 30.

[0042] [Operation of the auxiliary power supply] When the auxiliary power supply unit 60 supplies power from the power supply unit 20 to the energy storage unit 40 and loads 51 and 52, as shown in Figure 2, the switch elements 63D and 63E are turned ON, and current flows through each conductive path 61, 62, and 63. Let Iin be the current value of the current flowing from the power supply unit 20 to the first conductive path 61. Let I2 be the current flowing from the first conductive path 61 to the second conductive path 62. Let I3 be the current flowing from the first conductive path 61 to the third conductive path 63. The current in the first conductive path 61 is the sum of the currents in the second conductive path 62 and the third conductive path 63. That is, Iin is the sum of I2 and I3.

[0043] Based on the detection result of the current sensor 66, the control unit 65 causes the charging unit 64 to perform a charging operation so as to keep the current flowing from the power line 30 to the first conductive line 61 below the upper limit current value. Specifically, the control unit 65 performs the first control and the second control described below. The control unit 65 performs the first control to bring the current value of the second conductive line 62 closer to the target current value, provided that the sum of the target current value and the current value of the third conductive line 63 is below the upper limit current value. The target current value is the target current value of the current supplied to the energy storage unit 40 (the current flowing through the first conductive line 61). The target current value is smaller than the upper limit current value. When the sum of the target current value and the current value I3 of the third conductive line 63 is below the upper limit current value, for example, as shown in Figure 3 during times T1 to T2, the charging operation is performed so that the current value I2 of the second conductive line 62 becomes the target current value.

[0044] When the sum of the target current value, which is smaller than the upper limit current value, and the current value I3 of the third conductive circuit is less than or equal to the upper limit current value, it is permissible to allow the first conductive circuit 61 to flow a current of the target value so as not to exceed the upper limit current value. Therefore, when the conditions for this state are met, the first control (control to bring the current value I2 of the second conductive circuit 62 closer to the target current value) can be performed to allow current to flow through the second conductive circuit 62 at the desired target current value.

[0045] When the control unit 65 causes the charging unit 64 to perform a charging operation while the sum of the target current value and the current value I3 of the third conductive path 63 exceeds the upper limit current value, it performs a second control that limits the current value I2 of the second conductive path 62 to a value lower than the target current value, while keeping the current Iin flowing into the first conductive path 61 below the upper limit current value. For example, when the sum of the target current value and the current value I3 of the third conductive path 63 exceeds the upper limit current value, for example, as shown in the time T2 to T3 in Figure 3, I2 is limited to a value lower than the target current value, while Iin is kept below the upper limit current value. As a result, the current Iin flowing into the first conductive path 61 can be kept below the upper limit current value without controlling the current value I3 of the third conductive path 63.

[0046] Since the upper limit current value is less than the tripping current value of fuse 32, the fuse 32 can be prevented from tripping by keeping the current flowing into the first conductive path 61 below the upper limit current value. By keeping the current flowing into the first conductive path 61 below the upper limit current value without controlling the current in the third conductive path 63, it is not necessary to interrupt the power supply to the third conductive path 63, and the power supply to the third conductive path 63 can be continued, allowing the loads 51 and 52 to continue operating.

[0047] The following explanation concerns an example of the effects of this configuration. The auxiliary power supply unit 60 controls the charging operation of the charging unit 64 provided in the second conductive path 62 that branches off from the first conductive path 61, thereby suppressing the current flowing from the power path 30 into the first conductive path 61 to below the upper limit current value. Therefore, the current flowing into the first conductive path 61 can be suppressed to below the upper limit current value without controlling the current in the third conductive path 63 that branches off from the first conductive path 61.

[0048] Furthermore, the auxiliary power supply unit 60 has a current sensor 66 that detects the current value of the first conductive path 61. This allows the current value of the first conductive path 61 to be directly determined by the current sensor 66, making it easier to improve the accuracy of controlling the charging operation of the charging unit to keep the current flowing into the first conductive path 61 below the upper limit current value.

[0049] When the sum of a predetermined target current value, which is smaller than the upper limit current value, and the current value of the third conductive path is less than or equal to the upper limit current value, it is permissible to allow the first conductive path to flow a current of the target value so as not to exceed the upper limit current value. Therefore, when the conditions for this state are met, the auxiliary power supply 60 can supply current to the second conductive path at the desired target current value by performing a first control (control that brings the current value of the second conductive path closer to the target current value). If the sum of the target current value and the current value of the third conductive path exceeds the upper limit current value, it is necessary to reduce the current value of the first conductive path so as not to exceed the upper limit current value. Therefore, the auxiliary power supply 60 can keep the current of the first conductive path below the upper limit current value by performing a second control (control that limits the current value of the second conductive path to a value lower than the target current value while keeping the current flowing into the first conductive path below the upper limit current value).

[0050] Furthermore, since the auxiliary power supply 60 has an upper limit current value that is less than the cutoff current value, it is possible to prevent the fuse 32 from tripping by limiting the current flowing into the first conductive path 61 to less than or equal to the upper limit current value.

[0051] <Second Embodiment> The power supply system 10 of the second embodiment differs from the first embodiment in terms of the operation of the auxiliary power supply unit 60, but is otherwise similar. Components identical to those in the first embodiment are denoted by the same reference numerals, and detailed explanations are omitted.

[0052] Similar to the first embodiment, when the auxiliary power supply unit 60 supplies power from the power supply unit 20 to the energy storage unit 40 and loads 51 and 52, the switch elements 63D and 63E are turned ON, as shown in Figure 2, and current flows through the conductive paths 61, 62, and 63.

[0053] Based on the detection results of the current sensor 66, the control unit 65 causes the charging unit 64 to perform a charging operation so as to keep the current flowing from the power line 30 to the first conductive line 61 below the upper limit current value. Specifically, when the sum of the target current value, which is smaller than the upper limit current value, and the current value I3 of the third conductive line 63 is smaller than the upper limit current value, the control unit 65 controls the system to increase the target current value so that the current value Iin of the first conductive line 61 approaches the upper limit current value. When the sum of the target current value and the current value I3 of the third conductive line 63 is smaller than the upper limit current value, for example, as shown in the time intervals T21 to T22 in Figure 4, the target current value is increased so that the current value Iin of the first conductive line 61 approaches the upper limit current value.

[0054] When the sum of the target current value and the current value of the third conductive path 63 is less than the upper limit current value, there is room to increase the target current value as long as the current value of the first conductive path 61 does not exceed the upper limit current value. In such cases, by controlling the system to increase the target current value so that the current value of the second conductive path 62 approaches the target current value, the charging current can be increased while keeping the current value of the first conductive path 61 below the upper limit current value.

[0055] <Third Embodiment> The power supply system 210 of the third embodiment differs from the first embodiment in that it includes a second current sensor 266A and third current sensors 266B and 266C, respectively, which detect the current in the second conductive path 62 and the third conductive path 63 (specifically, the load-side conductive paths 63B and 63C), but is otherwise common to the first embodiment. Components identical to those of the first embodiment are denoted by the same reference numerals, and detailed explanations are omitted.

[0056] As shown in Figure 5, the auxiliary power supply unit 260 includes a second current sensor 266A and third current sensors 266B and 266C. The second current sensor 266A and the third current sensors 266B and 266C are configured, for example, as a current detection circuit. The second current sensor 266A detects the current value of the second conductive path 62. The current value detected by the second current sensor 266A is a value that can identify the current value of the second conductive path 62 (specifically, an analog voltage value). The third current sensors 266B and 266C are positioned in the third conductive path 63 so as to be able to detect the current flowing from the first conductive path 61 to the third conductive path 63. The third current sensor 266B detects the current value of the load-side conductive path 63B of the third conductive path 63. The current value detected by the third current sensor 266B is a value that can identify the current value of the load-side conductive path 63B (specifically, an analog voltage value). The third current sensor 266C detects the current value of the load-side conductive path 63C of the third conductive path 63. The current value detected by the third current sensor 266C is a value that can identify the current value of the load-side conductive path 63C (specifically, an analog voltage value).

[0057] The sum of the current in the second conductive path 62 detected by the second current sensor 266A and the current in the third conductive path 63 (load-side conductive paths 63B, 63C) detected by the third current sensors 266B, 266C is the current in the first conductive path 61. Therefore, the current flowing through the first conductive path 61 can be indirectly determined using the second current sensor 266A and the third current sensors 266B, 266C.

[0058] The auxiliary power supply unit 260 performs control similar to that of the first embodiment or the second embodiment based on the detection results of the second current sensor 266A and the third current sensors 266B and 266C. That is, the auxiliary power supply unit 260 causes the charging unit 64 to perform a charging operation so that the current flowing from the power line 30 to the first conductive line 61 is kept below the upper limit current value. This achieves the same effect as the first or second embodiment.

[0059] <Fourth Embodiment> The power supply system of the fourth embodiment differs from the first embodiment in the method of setting the upper limit current value, but is otherwise similar. Components identical to those in the first embodiment are denoted by the same reference numerals, and detailed explanations are omitted.

[0060] The control unit 65 changes the upper limit current value based on the current value Iin of the first conductive path 61. By changing the upper limit current value, it becomes easier to appropriately change the current state of the first conductive path 61 in accordance with loads 51, 52, etc., connected to the third conductive path 63.

[0061] The fuse 32 operates to interrupt the current in the first conductive path 61 when a current of any value flows for a period of time corresponding to that value in the interruption characteristics. The interruption characteristics define what current value and for what duration the path (power path 30) will be interrupted. For example, as shown in Figure 6, the larger the current value flowing through the fuse 32, the shorter the permitted time.

[0062] The control unit 65 controls the circuit to make the upper limit current value smaller than the current value corresponding to the allowable time corresponding to the elapsed time in the tripping characteristics, for a predetermined elapsed time after the current value Iin of the first conductive circuit 61 becomes equal to or greater than a predetermined lower limit current value. The lower limit current value is, for example, the lower limit current value of the current value associated with the allowable time in the tripping characteristics. The lower limit current value is, for example, a reference value that is greater than the rated current of the fuse 32. For example, the control unit 65 is equipped with a timer (not shown) that measures the elapsed time after the current value Iin of the first conductive circuit 61 becomes equal to a predetermined lower limit current value. If the elapsed time is t1, then from the tripping characteristics shown in Figure 6, it can be seen that the current value (also called the melting current value) corresponding to the allowable time t1 is Ia. Therefore, for a predetermined elapsed time t1 after the current value Iin of the first conductive circuit 61 becomes equal to or greater than the lower limit current value, the upper limit current value is set to a current value Ib that is smaller than the melting current value Ia. This prevents the fuse 32 from interrupting the current flow in the first conductive circuit 61.

[0063] <Other Embodiments> This disclosure is not limited to the embodiments described above and in the drawings. For example, any combination of the features of the embodiments described above or below is possible as long as it does not contradict each other. Furthermore, any feature of the embodiments described above or below may be omitted unless explicitly stated as essential. In addition, the embodiments described above may be modified as follows.

[0064] In the first to fourth embodiments described above, a configuration in which two loads 51 and 52 are provided in the power supply system 10 is illustrated, but a configuration in which one or more loads are provided is also possible. Specifically, a configuration in which the third conductive path 63 branches into two and is connected to the loads 51 and 52 is illustrated, but a configuration in which the third conductive path 63 is connected to one load without branching is also possible, or a configuration in which the third conductive path 63 branches into three or more and a load is connected to each of them is also possible. By providing a current sensor in each of the branched conductive paths, the sum of the current values ​​detected by each current sensor can be determined as the current flowing through the third conductive path 63.

[0065] In the third embodiment described above, the third current sensors 266B and 266C were provided on the load-side conductive paths 63B and 63C, respectively. However, instead of these current sensors, a current sensor may be provided on the power supply-side conductive path 63A. Even with such a configuration, the current value flowing through the third conductive path 63 can be detected, and together with the current value flowing through the second conductive path 62, the current value flowing through the first conductive path 61 can be determined.

[0066] In the first embodiment described above, the control unit 65 performed control (first control) to bring the current value of the second conductive path 62 closer to the target current value, provided that the sum of the target current value and the current value of the third conductive path 63 was less than or equal to the upper limit current value. However, instead of such control, the control unit 65 may also perform control to increase the target current value so that the current value Iin of the first conductive path 61 approaches the upper limit current value, provided that the sum of the target current value and the current value I3 of the third conductive path 63 is less than the upper limit current value.

[0067] It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is not limited to the embodiments disclosed herein, and is intended to include all modifications within the scope set forth in the claims or within the scope equivalent to the claims. [Explanation of Symbols]

[0068] 10…Power System 20...Power supply section 30…Power line 32…Fuse (breaking mechanism) 40... Energy storage unit 51, 52… load 60…Auxiliary power supply device 61...First conductive path 62...Second conductive circuit 63...Third conductive circuit 63A…Power supply side conductive path 63B, 63C…Load side conductive path 63D, 63E… Switching elements 64...Charging part 65... Control Unit 66...Current sensor 210…Power System 260…Auxiliary power supply device 266A...Second current sensor 266B, 266C…Third current sensor

Claims

[Claim 1] An auxiliary power supply device used in a power supply system having a power supply unit, a power line which is a path through which power is supplied from the power supply unit, and a power storage unit, A first conductive path electrically connected to the aforementioned power path, through which current supplied from the power path flows, A second conductive path and a third conductive path branch off from the first conductive path, A charging unit is provided between the second conductive path and the energy storage unit, and performs at least a charging operation that supplies a charging current to the energy storage unit based on the power supplied from the second conductive path, A control unit that controls the charging unit, It has, The control unit causes the charging unit to perform the charging operation so as to keep the current flowing from the power line to the first conductive line below the upper limit current value. The control unit changes the upper limit current value based on the current value of the first conductive path. The power supply system is provided with a fuse in the power path. The fuse operates to interrupt the current in the first conductive path when a current of any value flows for a period of time corresponding to any of the values ​​in the interruption characteristics, based on interruption characteristics that define an allowable time for each current value. The control unit reduces the upper limit current value to less than the current value corresponding to the allowable time corresponding to the elapsed time in the interruption characteristics, for a predetermined elapsed time after the current value of the first conductive path becomes equal to or greater than a predetermined lower limit current value. Auxiliary power supply.

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