Power System

Abstract

To provide a power supply system that can detect an open failure of a capacitor, while preventing overcharge and shortage in the remaining amount of the capacitor.SOLUTION: A power supply system 1 comprises: a DC / DC converter 8; a first battery 6 that is electrically connected with the DC / DC converter 8; a current sensor 10 that detects a current value of a current input to the first battery 6 and a current value of a current output from the first battery 6; a charge-discharge control unit 14 that, in a state in which the first battery 6 is normal, executes open failure detection control of varying output power of the DC / DC converter 8 so that the value of the current input to the first battery 6 and the value of the current output from the first battery 6 are alternately detected by the current sensor 10; and an open failure determination unit 15 that, when the current is not detected by the current sensor 10 during the execution of the open failure detection control, determines that an open failure of the first battery 6 occurs.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] In recent years, with technological advances such as automatic driving of vehicles, there has been much discussion about a stable supply of power to a load of a vehicle. As a power supply system for supplying power to a load, for example, a configuration in which a battery and a load are connected in parallel to an output terminal of a DC / DC converter is known. In such a configuration, in an emergency such as when the output power of the DC / DC converter cannot be supplied to the load, power can be supplied from the battery to the load. For this reason, it is desirable to periodically detect the presence or absence of an open circuit fault in the battery so that power can be supplied from the battery to the load in an emergency.

[0003] For example, Patent Document 1 describes a disconnection detection system for a power supply battery of an automobile. The power supply battery disconnection detection system described in Patent Document 1 includes a DC / DC converter, a low-voltage battery connected to an output terminal of the DC / DC converter, a load connected in parallel with the low-voltage battery, a current sensor that detects the current value of the current flowing through the low-voltage battery, and a load connected in parallel with the low-voltage battery. of The device is provided with an electronic control unit that controls the DC / DC converter to charge or discharge, and detects whether the low-voltage battery is disconnected based on the detection value of the current sensor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2016-528870 Summary of the Invention [Problem to be solved by the invention]

[0005] In the above conventional technology, a low-voltage battery The output power from the DC / DC converter is supplied to The presence or absence of a disconnection in the low-voltage battery is detected when the DC / DC converter is controlled so that the low-voltage battery is charged, or the presence or absence of a disconnection in the low-voltage battery is detected when the DC / DC converter is controlled so that the low-voltage battery is discharged. However, if the low-voltage battery is allowed to remain in a charged state for a certain period of time, it will be overcharged. Furthermore, if the low-voltage battery is allowed to remain in a discharged state for a certain period of time, the charging rate of the low-voltage battery will decrease, and the remaining charge of the low-voltage battery will decrease. For example, in an emergency such as when the output power of the DC / DC converter cannot be supplied to the load, if the remaining charge of the low-voltage battery is low, it will be impossible to supply power from the low-voltage battery to the load.

[0006] An object of the present invention is to provide a power supply system capable of detecting an open circuit failure of a capacitor while preventing the capacitor from being overcharged or becoming depleted. [Means for solving the problem]

[0007] A power supply system according to one embodiment of the present invention includes a DC voltage converter, a first wiring connected to a load and electrically connected to the DC voltage converter, and receiving output power from the DC voltage converter, a second wiring electrically connected to the first wiring and the DC voltage converter, a storage battery connected to the second wiring, and supplying output power to the second wiring and receiving the output power of the DC voltage converter, a current detection unit that detects a current value of a current input to the storage battery and a current value of a current output from the storage battery, a control unit that executes open circuit failure detection control to vary the output power of the DC voltage converter so that, when the storage battery is normal, the current detection unit alternately detects the current value of the current input to the storage battery and the current value of the current output from the storage battery, and a determination unit that determines that an open circuit failure has occurred in the storage battery when a current value is not detected by the current detection unit when the open circuit failure detection control is being executed.

[0008] In such a power supply system, in a state where the battery is normal, open circuit failure detection control is executed to vary the output power of the DC voltage converter so that the current value of the current input to the battery and the current value of the current output from the battery are alternately detected by the current detection unit. When no current is detected by the current detection unit during execution of the open circuit failure detection control, it is determined that an open circuit failure has occurred in the battery. By varying the output power of the DC voltage converter so that the current value of the current input to the battery and the current value of the current output from the battery are alternately detected in this manner, charging and discharging of the battery are alternately executed in a state where the battery is normal. Therefore, the duration of the charged state of the battery is shortened compared to a case where the battery is only charged and the presence or absence of an open circuit failure of the battery is detected, so that the battery is prevented from being charged more than necessary. Furthermore, the duration of the discharged state of the battery is shortened compared to a case where the battery is only discharged and the presence or absence of an open circuit failure of the battery is detected, so that the charging rate of the battery is prevented from being reduced more than necessary. This prevents the capacitor from being overcharged or becoming depleted, while detecting an open circuit failure in the capacitor.

[0009] The control unit may execute open circuit failure detection control so that the average current value per unit time detected by the current detection unit approaches zero when the capacitor is normal. In this configuration, the capacitor is alternately charged and discharged so that the average current value per unit time detected by the current detection unit approaches zero. Thus, the execution of the open circuit failure detection control prevents the charge rate of the capacitor from fluctuating greatly.

[0010] The power supply system may further include a charging rate detection unit that detects the charging rate of the battery, and the control unit may control the DC voltage converter so that the output power of the DC voltage converter is continuously supplied to the battery until the charging rate of the battery reaches the specified value when the charging rate of the battery is lower than a specified value, and execute the open failure detection control after the charging rate of the battery reaches the specified value. In such a configuration, when the charging rate of the battery is lower than the specified value, the battery is charged until the charging rate of the battery reaches the specified value. Therefore, even if the charging rate of the battery decreases due to natural discharge of the battery, the charging rate of the battery is maintained at the specified value when the open failure detection control is executed. Effect of the Invention

[0011] According to the present invention, it is possible to detect an open circuit failure of a capacitor while preventing the capacitor from being overcharged or becoming depleted. [Brief description of the drawings]

[0012] [Figure 1] 1 is a block diagram showing a configuration of a power supply system according to an embodiment of the present invention; [Diagram 2] 2 is a flowchart showing details of a processing procedure executed by an ECU shown in FIG. 1. [Diagram 3] FIG. 11 is a timing diagram showing an example of an operation during normal operation when no open circuit failure occurs in the battery. [Figure 4] FIG. 11 is a timing diagram showing an example of an operation when an open circuit failure occurs in a battery. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0014] Fig. 1 is a block diagram showing the configuration of a power supply system according to one embodiment of the present invention. In Fig. 1, the power supply system 1 of this embodiment is mounted on a vehicle such as an automobile. The vehicle includes a plurality of loads 2. The loads 2 are operated by receiving power supplied from the power supply system 1. The loads 2 are, for example, lamps, a car navigation system, an air conditioner, windshield wipers, etc.

[0015] The power supply system 1 includes an input wiring 3, a first wiring 4, a second wiring 5, a first battery 6, a second battery 7, a DC / DC converter 8, a voltage sensor 9, a current sensor 10, an ECU 11 (ECU: Electronic Control Unit), and an alarm 12.

[0016] The input wiring 3 electrically connects the second battery 7 and the DC / DC converter 8. The first wiring 4 connects the output terminal of the DC / DC converter 8 and each load 2. That is, the first wiring 4 is connected to each load 2 and is electrically connected to the DC / DC converter 8.

[0017] The second wiring 5 、D The output terminal of the DC / DC converter 8 is connected to the first battery 6. That is, the second wiring 5 is connected to the first battery 6 and is also electrically connected to the first wiring 4 and the DC / DC converter 8.

[0018] The first battery 6 and each load 2 are electrically connected via the first wiring 4, the output terminal of the DC / DC converter 8, and the second wiring 5. In other words, the first battery 6 and each load 2 are connected in parallel to the output terminal of the DC / DC converter 8, so that the power output from the first battery 6 can be supplied to each load 2 via the output terminal of the DC / DC converter 8.

[0019] The second battery 7 stores a voltage used to drive a vehicle's drive motor, for example. The second battery 7 in this embodiment has a higher voltage than the first battery 6.

[0020] The DC / DC converter 8 is a DC voltage converter that supplies output power to the first wiring 4 and the second wiring 5. The DC / DC converter 8 converts a DC voltage into a DC voltage having a different voltage value and outputs it. The DC / DC converter 8 of this embodiment steps down the voltage input from the second battery 7 and outputs it. The output power of the DC / DC converter 8 can be varied in response to a control signal from the ECU 11.

[0021] The first battery 6 is a power storage device that supplies output power to the second wiring 5 and is also supplied with output power from the DC / DC converter 8 via the second wiring 5. The first battery 6 stores a voltage required for the operation of the load 2. For example, a lead battery or a lithium ion battery is used as the first battery 6. The first battery 6 assists the supply of output power from the DC / DC converter 8 to the first wiring 4. Specifically, when the output power supplied from the DC / DC converter 8 to the first wiring 4 decreases, the first battery 6 supplies the first wiring 4 with power equivalent to the decrease via the second wiring 5.

[0022] The voltage sensor 9 is a sensor that detects the voltage of the first battery 6. The current sensor 10 is a sensor (current detection unit) that detects the current value of the current input to the first battery 6 and the current value of the current output from the first battery 6.

[0023] The ECU 11 is composed of a CPU, RAM, ROM, an input / output interface, etc. The ECU 11 controls the DC / DC converter 8 so that the first battery 6 performs charging and discharging based on the detection values ​​of the voltage sensor 9 and the current sensor 10, detects the presence or absence of an open circuit failure in the first battery 6, and controls the alarm 12 according to the detection result.

[0024] The alarm 12 is a device that issues a warning to the driver of the vehicle when an open circuit failure is detected in the first battery 6. The alarm 12 issues a warning by displaying a warning message, sounding a warning sound, etc. The alarm 12 may be, for example, a car navigation system.

[0025] The ECU 11 includes a charging rate estimating unit 13 , a charge / discharge control unit 14 , and an open circuit failure determining unit 15 .

[0026] The charging rate estimating unit 13 estimates the charging rate (SOC: State of charge) of the first battery 6 based on, for example, a detection value of the voltage sensor 9. The charging rate estimating unit 13 constitutes a charging rate detecting unit that detects the charging rate of the first battery 6 in cooperation with the voltage sensor 9.

[0027] The charge / discharge control unit 14 performs feedback control of the DC / DC converter 8 so that the first battery 6 charges and discharges based on the detection value of the current sensor 10. The charge / discharge control unit 14 constitutes a control unit that executes open circuit failure detection control to vary the output power of the DC / DC converter 8 so that the current value of the current input to the first battery 6 and the current value of the current output from the first battery 6 are alternately detected by the current sensor 10 when the first battery 6 is in a normal state.

[0028] In a state in which the first battery 6 is normal, when the first battery 6 is being charged, the current sensor 10 detects the current value of the current input to the first battery 6, and when the first battery 6 is being discharged, the current sensor 10 detects the current value of the current output from the first battery 6. The current value of the current input to the first battery 6 is detected by the current sensor 10 as a positive (+) current value. The current value of the current output from the first battery 6 is detected by the current sensor 10 as a negative (-) current value.

[0029] The open circuit failure detection control is a control for detecting an open circuit failure in the first battery 6. An open circuit failure in the first battery 6 occurs due to a wire break in the first battery 6, a terminal of the first battery 6 coming off, or the like. A wire break in the first battery 6 can occur due to mechanical damage in the first battery 6, the intrusion of a corrosive substance into the first battery 6, deterioration of the first battery 6 over time, or the like.

[0030] When the first battery 6 is in a normal state, the charge / discharge control unit 14 executes open circuit failure detection control so that the average current value per unit time detected by the current sensor 10 approaches zero.

[0031] Furthermore, when the charging rate of the first battery 6 estimated by the charging rate estimating unit 13 is lower than a specified value, the charging / discharging control unit 14 controls the DC / DC converter 8 so that the output power of the DC / DC converter 8 is continuously supplied to the first battery 6 until the charging rate of the first battery 6 reaches the specified value. Then, after the charging rate of the first battery 6 reaches the specified value, the charging / discharging control unit 14 executes open circuit failure detection control.

[0032] The open circuit failure judgment unit 15 constitutes a judgment unit that judges that an open circuit failure has occurred in the first battery 6 if at least a current value is not detected by the current sensor 10 when the charge / discharge control unit 14 is executing open circuit failure detection control, or when the output power of the DC / DC converter 8 is continuously supplied to the first battery 6 until the charging rate of the first battery 6 reaches a specified value.

[0033] For example, when a break occurs in the first battery 6, no current flows through the first battery 6, and the current value detected by the current sensor 10 becomes zero. For example, when the terminal of the first battery 6 is about to come off, a current flows, although the current value is lower than the current value of the current flowing through the first battery 6 when the first battery 6 is normal, and the current value is detected by the current sensor 10. If it is desired to detect a state in which an open circuit failure has not yet occurred but an open circuit failure will occur in the near future (hereinafter, referred to as a state in which an open circuit failure is about to occur), the open circuit failure determination unit 15 may determine that an open circuit failure has occurred in the first battery 6 not only when the current value detected by the current sensor 10 is zero, but also when the absolute value of the current value detected by the current sensor 10 is equal to or less than the failure threshold value for a predetermined time. The failure threshold value is at least a value lower than the absolute value of the current value detected when the first battery 6 is normal.

[0034] Fig. 2 is a flowchart showing the details of the processing procedure executed by the ECU 11. When the ignition switch 16 (see Fig. 1) is turned ON, the ECU 11 executes the flow shown in Fig. 2.

[0035] When the ECU 11 determines that the ignition switch 16 has been turned on, the ECU 11 acquires the detection value of the voltage sensor 9 (step S101). Then, the ECU 11 estimates the charging rate of the first battery 6 based on the detection value of the voltage sensor 9 (step S102).

[0036] Specifically, the ECU 11 estimates the open circuit voltage of the first battery 6 based on the detection value of the voltage sensor 9, and obtains the charging rate of the first battery 6 from the open circuit voltage of the first battery 6. Note that the first battery 6 has a characteristic that the charging rate increases as the open circuit voltage increases.

[0037] Next, the ECU 11 judges whether the charging rate of the first battery 6 is equal to or higher than a predetermined specified value (step S103). The specified value is an upper limit value of the charging rate of the first battery 6 (e.g., 85% to 95%), and is set to a value that allows the first battery 6 to supply power to the load 2 when the first battery 6 is not in an overcharged state and when the output power of the DC / DC converter 8 cannot be supplied to the load 2.

[0038] When the ECU 11 determines that the charging rate of the first battery 6 is lower than the specified value, the ECU 11 of The DC / DC converter 8 is controlled to output a charging voltage V1 (see FIG. 3(c) and FIG. 4(c)) for charging, and the detection value of the current sensor 10 is periodically acquired (step S104). As a result, power is supplied from the DC / DC converter 8 to the first battery 6.

[0039] Then, the ECU 11 determines whether the absolute value of the detection value (hereinafter referred to as the battery current value) of the current sensor 10 is equal to or less than the failure threshold value (described above) for a certain consecutive period of time (step S105).

[0040] When the ECU 11 does not satisfy the condition that the absolute value of the battery current value is equal to or less than the failure threshold value for a certain consecutive period of time, it determines that an open circuit failure has not occurred in the first battery 6 (step S106) and returns to the above step S101.

[0041] When the condition that the absolute value of the battery current value is equal to or less than the failure threshold value for a certain period of time is satisfied, the ECU 11 determines that an open failure has occurred in the first battery 6 (step S107). Then, the ECU 11 outputs a warning signal to the warning device 12 (step S108) and ends this process. Then, the warning device 12 issues a warning.

[0042] When the ECU 11 determines in step S103 that the charging rate of the first battery 6 is equal to or higher than a specified value, it executes open failure detection control to vary the output power of the DC / DC converter 8 so that, while the first battery 6 is in a normal state, the current sensor 10 alternately detects the current value of the current input to the first battery 6 and the current value of the current output from the first battery 6 for a predetermined time, and periodically acquires the detection value of the current sensor 10 (step S109).

[0043] The open circuit failure detection control is a control whose one cycle consists of a first period P1 in which the DC / DC converter 8 is controlled so that the current sensor 10 detects the current value of the current input to the first battery 6, and a second period P2 in which the DC / DC converter 8 is controlled so that the current sensor 10 detects the current value of the current output from the first battery 6 (see Figure 3(d)).

[0044] The ECU 11 of this embodiment controls the DC / DC converter 8 so that the first period P1 and the second period P2 occur alternately. As a result, as shown in Fig. 3(c) and Fig. 4(c), the first detection voltage V12 and the second detection voltage V22, which are lower voltage values ​​than the charging voltage V1, are alternately output from the DC / DC converter 8. That is, the output voltage V2 of the DC / DC converter 8 during open failure detection control has a rectangular waveform centered on (V12+V22) / 2.

[0045] More specifically, the ECU 11 of this embodiment controls the DC / DC converter 8 so that the integral value of the current value during the first period P1 matches the integral value of the current value during the second period P2 when the first battery 6 is normal. That is, it can be said that the ECU 11 of this embodiment executes open circuit failure detection control so that the average current value per unit time detected by the current sensor 10 approaches zero when the first battery 6 is normal.

[0046] In step S109, the ECU 11 obtains the detection value of the current sensor 10 at least once during the first period P1 and once during the second period P2.

[0047] Next, the ECU 11 determines whether the absolute value of the battery current value is equal to or less than the failure threshold value for a certain continuous period of time (step S110).

[0048] When the condition that the absolute value of the battery current value is equal to or less than the failure threshold value for a certain period of time is satisfied, the ECU 11 determines that an open failure has occurred in the first battery 6 (step S111). Then, the ECU 11 outputs a warning signal to the warning device 12 (step S112) and ends this process. Then, the warning device 12 issues a warning.

[0049] When the condition that the absolute value of the battery current value is equal to or less than the failure threshold value for a certain consecutive period of time is not satisfied, the ECU 11 determines that an open circuit failure has not occurred in the first battery 6 (step S113).

[0050] Next, the ECU 11 determines whether the ignition switch 16 (see FIG. 1) has been turned OFF based on an operation signal of the ignition switch 16 (step S114). If the ECU 11 determines that the ignition switch 16 has not been turned OFF, it executes the above step S109 again. If the ECU 11 determines that the ignition switch 16 has been turned OFF, it ends this process.

[0051] Here, the charging rate estimation unit 13 executes the above-mentioned steps S101 and S102. The charge / discharge control unit 14 executes the above-mentioned steps S103, S104, and S109. The open circuit failure determination unit 15 executes the above-mentioned steps S105, S106, S107, S110, S111, and S113.

[0052] In the above, before the ignition switch 16 is turned ON, the first battery 6 naturally discharges, and the charging rate of the first battery 6 is low, as shown in Figures 3(a) and (b). Therefore, when the ignition switch 16 is turned ON, a charging voltage V1 is output from the DC / DC converter 8, as shown in Figure 3(c). Then, when the output power from the DC / DC converter 8 is supplied to the first battery 6, the first battery 6 is charged, and the charging rate of the first battery 6 increases, as shown in Figure 3(b).

[0053] 3(b) and (c), at time t1, when the charging rate of the first battery 6 reaches a specified value A, the output of the charging voltage V1 from the DC / DC converter 8 is completed. Then, the ECU 11 executes the open circuit failure detection control.

[0054] Here, in a normal state in which no open circuit fault has occurred in the first battery 6 or the first battery 6 is not on the verge of an open circuit fault, as shown in FIG. 3(d), When open fault detection control is performed, The current sensor 10 alternately detects the current value of the current input to the first battery 6 (current value having an absolute value greater than the failure threshold) and the current value of the current output from the first battery 6 (current value having an absolute value greater than the failure threshold). In other words, the current value detected by the current sensor 10 alternately becomes positive and negative with zero as the center. In this embodiment, the absolute value of the current value of the positive current input to the first battery 6 is equal to the absolute value of the current value of the negative current output from the first battery 6.

[0055] On the other hand, if an open circuit failure occurs in the first battery 6 or the first battery 6 is on the verge of an open circuit failure during execution of the open circuit failure detection control, after time t2 when the open circuit failure occurs in the first battery 6, the current value is not detected by the current sensor 10 (see FIG. 4(d)), or the absolute value of the current value detected by the current sensor 10 becomes equal to or less than the failure threshold, so that it is determined that an open circuit failure has occurred in the first battery 6. Note that FIGS. 4(a) to (c) are similar to FIGS. 3(a) to (c).

[0056] When it is determined that an open circuit failure has occurred in the first battery 6, a warning is issued by the alarm device 12. Therefore, the driver of the vehicle is immediately informed of the occurrence of an open circuit failure in the first battery 6 by the warning from the alarm device 12. In this case, the automatic driving of the vehicle is terminated, and the vehicle is driven manually, for example, to a nearby dealer, repair shop, etc., where the first battery 6 is replaced.

[0057] Furthermore, even if an open circuit failure occurs in the first battery 6 while the ignition switch 16 is OFF or while the charging voltage V1 is being output from the DC / DC converter 8, the ECU 11 acquires the detection value of the current sensor 10 and determines whether or not an open circuit failure has occurred in the first battery 6 while the charging voltage V1 is being output from the DC / DC converter 8, and therefore it is possible to determine that an open circuit failure has occurred in the first battery 6.

[0058] As described above, in this embodiment, in a state where the first battery 6 is normal, the open circuit failure detection control is executed to vary the output power of the DC / DC converter 8 so that the current value of the current input to the first battery 6 and the current value of the current output from the first battery 6 are alternately detected by the current sensor 10. When the current value is not detected by the current sensor 10 during the execution of the open circuit failure detection control, it is determined that an open circuit failure has occurred in the first battery 6. By varying the output power of the DC / DC converter 8 so that the current value of the current input to the first battery 6 and the current value of the current output from the first battery 6 are alternately detected in this manner, the first battery 6 is alternately charged and discharged in a state where the first battery 6 is normal. Therefore, compared to a case where the first battery 6 is only charged and the presence or absence of an open circuit failure of the first battery 6 is detected, the duration of the charging state of the first battery 6 is shortened, and the first battery 6 is prevented from being charged more than necessary. Furthermore, compared to the case where the first battery 6 is only discharged and the presence or absence of an open circuit failure of the first battery 6 is detected, the duration of the discharged state of the first battery 6 is shortened, and therefore the charging rate of the first battery 6 is prevented from decreasing more than necessary. This prevents the first battery 6 from being overcharged or running out of charge, while detecting an open circuit failure of the first battery 6. As a result, there is no need to install a separate power source, etc., and costs can be reduced.

[0059] In addition, in this embodiment, when the first battery 6 is normal, the open circuit failure detection control is executed so that the average current value per unit time detected by the current sensor 10 approaches zero. Therefore, the first battery 6 is alternately charged and discharged so that the average current value per unit time detected by the current sensor 10 approaches zero. Therefore, the charging rate of the first battery 6 is prevented from fluctuating greatly due to the execution of the open circuit failure detection control.

[0060] In addition, in this embodiment, when the charging rate of the first battery 6 is lower than a specified value, the DC / DC converter 8 is controlled so that the output power of the DC / DC converter 8 is continuously supplied to the first battery 6 until the charging rate of the first battery 6 reaches the specified value, and after the charging rate of the first battery 6 reaches the specified value, the open failure detection control is executed. Therefore, when the charging rate of the first battery 6 is lower than the specified value, the first battery 6 is charged until the charging rate of the first battery 6 reaches the specified value. Therefore, even if the charging rate of the first battery 6 becomes low due to natural discharge of the first battery 6, the charging rate of the first battery 6 is maintained at the specified value when the open failure detection control is executed.

[0061] The present invention is not limited to the above embodiment. For example, the ECU 11 in the above embodiment controls the DC / DC converter 8 so that the integral value of the current value during the first period P1 and the integral value of the current value during the second period P2 match when the first battery 6 is normal, but the present invention is not particularly limited to such a form as long as the open circuit failure detection control is executed to vary the output power of the DC / DC converter 8 so that the current value of the current input to the first battery 6 and the current value of the current output from the first battery 6 are alternately detected by the current sensor 10.

[0062] For example, the DC / DC converter 8 may be controlled so that the integral value of the current value during the first period P1 is greater than the integral value of the current value during the second period P2. In this case, the charging rate of the first battery 6 can be gradually increased. Therefore, after the ignition switch 16 is turned ON, for example, depending on the situation, it may not be necessary to supply the charging voltage V1 to the first battery 6.

[0063] Also, the DC / DC converter 8 may be controlled so that the integral value of the current value during the first period P1 is smaller than the integral value of the current value during the second period P2. In this case, the charging rate of the first battery 6 can be gradually reduced. Therefore, for example, when the first battery 6 is close to being fully charged, overcharging of the first battery 6 can be prevented, and power can be supplied to the load 2 from the first battery 6 in an emergency such as when the output power of the DC / DC converter 8 cannot be supplied to the load 2.

[0064] In the above embodiment, the open failure detection control for varying the output power of the DC / DC converter 8 is continuously performed after the ignition switch 16 is turned ON until the ignition switch 16 is turned OFF, but the present invention is not limited to such an embodiment. For example, the open failure detection control may be performed intermittently after the ignition switch 16 is turned ON until the ignition switch 16 is turned OFF. In other words, the open failure detection control does not have to be performed continuously from the start of the open failure detection control until the ignition switch 16 is turned OFF.

[0065] In the above embodiment, the current value of the current input to the first battery 6 and the current value of the current output from the first battery 6 are detected by one current sensor 10, but the present invention is not limited to such an embodiment. Separate current sensors may be used, one for detecting only the current value input to the first battery 6 and the other for detecting only the current value output from the first battery 6. In this case, the two current sensors constitute a current detection unit.

[0066] In the above embodiment, the output voltage V2 of the DC / DC converter 8 during open circuit failure detection control has a rectangular waveform, but is not limited to such a form. The ECU 11 may vary the output power of the DC / DC converter 8 to have a sine wave, as long as the ECU 11 executes open circuit failure detection control that varies the output power of the DC / DC converter 8 so that the current sensor 10 alternately detects the current value of the current input to the first battery 6 and the current value of the current output from the first battery 6.

[0067] In addition, in the above embodiment, the open circuit voltage of the first battery 6 is estimated based on the voltage of the first battery 6 detected by the voltage sensor 9, and the charging rate of the first battery 6 is calculated from the open circuit voltage of the first battery 6, but the present invention is not limited to such an embodiment. For example, a current value of the current input to the first battery 6 and a current value of the current output from the first battery 6 may be detected by a current sensor, an integrated current value of the first battery 6 may be calculated, and the charging rate of the first battery 6 may be estimated from the integrated current value.

[0068] In the above embodiment, the DC / DC converter 8 is feedback-controlled so as to charge and discharge the first battery 6 based on the detection value of the current sensor 10, but the present invention is not limited to such an embodiment. For example, a voltage sensor that detects the output voltage of the DC / DC converter 8 may be used, and the DC / DC converter 8 may be feedback-controlled so as to charge and discharge the first battery 6 based on the detection value of the voltage sensor. Furthermore, the DC / DC converter 8 may be feedback-controlled so as to charge and discharge the first battery 6 based on the detection values ​​of the voltage sensor and the current sensor 10.

[0069] In the above embodiment, the ECU 11 includes the charging rate estimator 13, the charge / discharge controller 14, and the open circuit failure detector 15, but is not limited to this. The ECU 11 only needs to have the functions of at least the charge / discharge controller 14 and the open circuit failure detector 15.

[0070] Furthermore, in the above embodiment, the ECU 11 executes the above steps S101 to S106. However, if it is already known that the charging rate of the first battery 6 is equal to or higher than a specified value when the ignition switch 16 is turned ON, the open circuit failure detection control may be executed immediately after the ignition switch 16 is turned ON.

[0071] In the above embodiment, the first battery 6 and each load 2 are electrically connected via the first wiring 4, the output terminal of the DC / DC converter 8, and the second wiring 5, but the present invention is not limited to such a configuration. The first battery 6 and each load 2 are connected in parallel to the output terminal of the DC / DC converter 8, and may be connected in any manner as long as they are electrically connected so that the output power from the first battery 6 can be supplied to each load 2.

[0072] In the above embodiment, the first wiring 4 is connected to the output terminal of the DC / DC converter 8 and each load 2, but is not particularly limited to such a form. It is sufficient that the first wiring 4 is connected to at least the load 2 and electrically connected to the DC / DC converter 8. For example, the first wiring 4 may be electrically connected to the output terminal of the DC / DC converter 8 via a filter circuit.

[0073] In the above embodiment, the second wiring 5 is 、D The second wiring 5 is connected to the output terminal of the DC / DC converter 8 and the first battery 6, but is not limited to such a form. It is sufficient that the second wiring 5 is connected to the first battery 6 and is electrically connected to the first wiring 4 and the DC / DC converter 8. For example, the second wiring 5 may be electrically connected to the output terminal of the DC / DC converter 8 via a filter circuit.

[0074] In addition, in the above embodiment, the second battery 7 has a higher voltage than the first battery 6, but this is not particularly limited, and the first battery 6 may have a higher voltage than the second battery 7. In this case, the DC / DC converter 8 boosts the voltage input from the second battery 7 and outputs it.

[0075] Furthermore, the present invention is not particularly limited to batteries, but can also be applied to detection of an open circuit fault in a storage device such as a capacitor. [Explanation of symbols]

[0076] 1...power supply system, 2...load, 4...first wiring, 5...second wiring, 6...first battery (storage device), 8...DC / DC converter (direct current voltage converter), 9...voltage sensor (charging rate detection unit), 10...current sensor (current detection unit), 13...charging rate estimation unit (charging rate detection unit), 14...charge and discharge control unit (control unit), 15...open failure determination unit (determination unit).

Claims

1. A DC voltage converter; a first wiring connected to a load and electrically connected to the DC voltage converter to receive output power from the DC voltage converter; a second wiring electrically connected to the first wiring and the DC voltage converter; a storage battery connected to the second wiring, for supplying output power to the second wiring and for receiving the output power of the DC voltage converter; a current detection unit that detects a current value of a current input to the capacitor and a current value of a current output from the capacitor; a control unit that executes open circuit failure detection control to vary an output power of the DC voltage converter so that, when the battery is in a normal state, the current detection unit alternately detects a current value of a current input to the battery and a current value of a current output from the battery; a determination unit that determines that an open circuit failure has occurred in the storage battery when a current value is not detected by the current detection unit during execution of the open circuit failure detection control.

2. 2. The power supply system according to claim 1, wherein the control unit executes the open circuit failure detection control so that an average current value per unit time detected by the current detection unit approaches zero when the capacitor is normal.

3. A charging rate detection unit that detects the charging rate of the capacitor is further provided, 3. The power supply system according to claim 1 or 2, wherein the control unit, when a charging rate of the storage battery is lower than a specified value, controls the DC voltage converter so that the output power of the DC voltage converter is continuously supplied to the storage battery until the charging rate of the storage battery reaches the specified value, and executes the open circuit failure detection control after the charging rate of the storage battery reaches the specified value.

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