Battery system

Abstract

To provide a battery system that does not have communication capabilities, in which the power supply recipient can detect a failure in the open-circuit function of an FET. [Solution] The battery system 1 according to this disclosure comprises secondary batteries 11A and 11B, a charge control FET 12 and a discharge control FET 14 connected in series with the secondary batteries 11A and 11B, and a control device 10 that controls the on and off of the charge control FET 12 and the discharge control FET 14. When the measured voltage of the secondary batteries 11A and 11B is below an over-discharge voltage threshold, the control device 10 instructs the discharge control FET 14 to turn off, and after instructing the discharge control FET 14 to turn off, when the measured voltage Vfd of the discharge control FET 14 is below a predetermined voltage threshold, it executes switching control processing for the charge control FET 12, repeatedly turning the charge control FET 12 on and off, thereby bringing the total voltage of the secondary batteries 11A and 11B supplied to the power supply target within a predetermined voltage range.

Description

Technical Field

[0001] The present disclosure relates to a battery system including a secondary battery.

Background Art

[0002] Conventionally, battery systems including secondary batteries have been used. Some battery systems do not communicate with the system of the power supply destination that supplies power. In such a battery system without such a communication function, if an abnormality occurs in the open-circuit function of the FET (Field Effect Transistor) included in the battery system, the secondary battery continues to discharge or charge, so the secondary battery may enter an over-discharged state or an over-charged state. However, when the battery system does not have a communication function, the system or device of the power supply destination cannot detect that the secondary battery is in an over-discharged state or an over-charged state.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Regarding this point, Patent Document 1 discloses a battery management system configured to detect a first voltage generated across a charging FET and a second voltage generated across a discharging FET while a first high-level voltage is applied to the gate of the charging FET and a second high-level voltage is applied to the gate of the discharging FET, and to determine the presence or absence of a failure in the current detection circuit based on at least one of the first voltage and the second voltage and a reference current detected by a current detection circuit. However, when this battery management system does not have a communication function, it cannot cause the system or device of the power supply destination to detect that the open-circuit function of the FET has failed.

[0005] This disclosure aims to solve such problems and to provide a battery system in which the power supply recipient can detect a failure in the open-circuit function of an FET in a battery system that does not have communication capabilities. [Means for solving the problem]

[0006] The battery system relating to this disclosure is At least one rechargeable battery, A charge control FET and a discharge control FET connected in series to a secondary battery, The system includes a control device that controls the charging and discharging of a secondary battery by controlling the on / off state of a charge control FET and a discharge control FET, The charge control FET includes a body diode that enables the flow of current discharged from the secondary battery. The discharge control FET includes a body diode that enables the flow of current to charge the secondary battery. The control device is A battery voltage acquisition unit that acquires the measured voltage of a secondary battery, The FET voltage acquisition unit acquires the measured voltage Vfd of the discharge control FET, It comprises an FET control unit that controls the on and off states of a charge control FET and a discharge control FET, The FET control unit instructs the discharge control FET to turn off if the measured voltage of the secondary battery is below the over-discharge voltage threshold. After instructing the FET control unit to turn off the discharge control FET, if the measured voltage Vfd of the discharge control FET is below a predetermined voltage threshold, the FET control unit executes a switching control process for the charge control FET, repeatedly turning it on and off, to bring the total voltage of the secondary battery supplied to the power supply target within a predetermined voltage range.

[0007] The FET voltage acquisition unit further acquires the measured voltage Vfc of the discharge control FET, The FET control unit instructs the charge control FET to turn off if the measured voltage of the secondary battery is above the overcharge voltage threshold. After instructing the charge control FET to turn off, the FET control unit executes a switching control process for the discharge control FET, repeatedly turning it on and off, if the measured voltage Vfc of the charge control FET is below another predetermined voltage threshold, thereby bringing the overall voltage within the predetermined voltage range.

[0008] The battery system relating to this disclosure is At least one rechargeable battery, A charge control FET and a discharge control FET connected in series to a secondary battery, The system includes a control device that controls the charging and discharging of a secondary battery by controlling the on / off state of a charge control FET and a discharge control FET, The charge control FET includes a body diode that enables the flow of current discharged from the secondary battery. The discharge control FET includes a body diode that enables the flow of current to charge the secondary battery. The control device is A battery voltage acquisition unit that acquires the measured voltage of a secondary battery, An FET voltage acquisition unit that acquires the measured voltage Vfc and the measured voltage Vfd of the discharge control FET, It comprises an FET control unit that controls the on and off states of a charge control FET and a discharge control FET, The FET control unit instructs the discharge control FET to turn off if the measured voltage of the secondary battery is below the over-discharge voltage threshold. After instructing the FET control unit to turn off the discharge control FET, if the measured voltage Vfd of the discharge control FET is below a predetermined voltage threshold, the FET control unit executes a switching control process for the charge control FET, repeatedly turning it on and off, to bring the total voltage of the secondary battery supplied to the power supply target within a predetermined voltage range. The FET control unit instructs the charge control FET to turn off if the measured voltage of the secondary battery is above the overcharge voltage threshold. After instructing the FET control unit to turn off the charge control FET, if the measured voltage Vfc of the charge control FET is below another predetermined voltage threshold, the FET control unit executes a switching control process for the discharge control FET, repeatedly turning it on and off, to bring the total voltage of the secondary battery within the predetermined voltage range.

[0009] Furthermore, the battery system includes a battery voltage determination unit that determines the overall voltage of the secondary battery. In the switching control process of the charge control FET, The FET control unit instructs the charge control FET to turn off. The battery voltage determination unit determines whether the total voltage after the charge control FET is instructed to turn off is below the first lower voltage threshold. If the overall voltage after the charge control FET is instructed to turn off is determined to be below the first lower limit voltage threshold, the FET control unit instructs the charge control FET to turn on. The battery voltage determination unit determines whether the total voltage after the charge control FET is instructed to turn on is equal to or greater than the first upper limit voltage threshold. If the FET control unit determines that the overall voltage after the charge control FET has been instructed to turn on is equal to or greater than the first upper voltage threshold, the FET control unit instructs the charge control FET to turn on.

[0010] Furthermore, the battery system includes a battery voltage determination unit that determines the overall voltage of the secondary battery. In the switching control process of a discharge-controlled FET, The FET control unit instructs the discharge control FET to turn off. The battery voltage determination unit determines whether the total voltage after the discharge control FET is instructed to turn off is equal to or greater than the second upper voltage threshold. If the total voltage after the discharge control FET has been instructed to turn off is determined to be equal to or greater than the second upper voltage threshold, the FET control unit instructs the discharge control FET to turn on. The battery voltage determination unit determines whether the total voltage after the discharge control FET is instructed to turn on is below the second lower voltage threshold. If the total voltage after the discharge control FET is instructed to turn on is determined to be below the second lower voltage threshold, the FET control unit instructs the discharge control FET to turn on.

[0011] FET can also be a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). [Effects of the Invention]

[0012] According to the present disclosure, it is possible to provide a battery system in which a power supply destination can detect that an open-circuit function of a FET has failed in a battery system that does not have a communication function.

Brief Description of the Drawings

[0013] [Figure 1] It is a diagram showing an example of a hardware configuration of a battery system according to the present disclosure. [Figure 2] It is a diagram showing an example of a configuration of a control device according to the present disclosure. [Figure 3] It is a flowchart showing an example of a process executed by a control device according to the present disclosure. [Figure 4] It is a diagram showing an example of an open / close control process of a charge control FET. [Figure 5] It is a diagram showing an example of an open / close control process of a discharge control FET. [Figure 6] It is a diagram showing a control instruction for a discharge control FET, a measured voltage Vfd, a control instruction for a charge control FET, a measured voltage Vfc, a control instruction for a charge control FET, and an overall voltage Vt when an open-circuit function of the discharge control FET fails during discharge. [Figure 7] It is a diagram showing a control instruction for a charge control FET, a measured voltage Vfc, a control instruction for a discharge control FET, a measured voltage Vfd, a control instruction for a discharge control FET, and an overall voltage Vt when an open-circuit function of the charge control FET fails during discharge. [Figure 8] It is a diagram showing a control instruction for a discharge control FET, a measured voltage Vfd, a control instruction for a charge control FET, a measured voltage Vfc, a control instruction for a charge control FET, and an overall voltage Vt when an open-circuit function of the discharge control FET fails during charging. [Figure 9] It is a diagram showing a control instruction for a charge control FET, a measured voltage Vfc, a control instruction for a discharge control FET, a measured voltage Vfd, a control instruction for a discharge control FET, and an overall voltage Vt when an open-circuit function of the charge control FET fails during charging. [Modes for carrying out the invention]

[0014] Figure 1 shows an example of the hardware configuration of battery system 1. Battery system 1 is a system that supplies power to a device or system to be powered. Battery system 1 comprises a control device 10, secondary batteries 11A and 11B, a charge control FET 12, a discharge control FET 14, voltage sensors 16 to 20, and a capacitor 22. Battery system 1 may have any number of secondary batteries.

[0015] The control device 10 controls the charging and discharging of the secondary batteries 11A and 11B by controlling the on / off states of the charge control FET 12 and the discharge control FET 14. Specific examples of the control device 10 include an ECU (Electronic Control Unit). The configuration of the control device 10 will be described later with reference to Figure 2.

[0016] The charge control FET 12 is a switch element that controls the charging of secondary batteries 11A and 11B according to the control of the control device 10. The charge control FET 12 is connected in series with secondary batteries 11A and 11B. A specific example of the charge control FET 12 is a P-channel type MOSFET. When the charge control FET 12 is ON, it allows the flow of current to charge secondary batteries 11A and 11B. On the other hand, when the charge control FET 12 is OFF, it blocks the flow of current to charge secondary batteries 11A and 11B.

[0017] The charge control FET 12 includes a body diode 13. The body diode 13 allows current to flow from the secondary batteries 11A and 11B to discharge, while blocking the flow of current to charge the secondary batteries 11A and 11B.

[0018] The discharge control FET 14 is a switching element that controls the discharge of secondary batteries 11A and 11B according to the control of the control device 10. The discharge control FET 14 is connected in series with secondary batteries 11A and 11B. A specific example of the discharge control FET 14 is an N-channel MOSFET. When the discharge control FET 14 is ON, it allows the flow of current to discharge from secondary batteries 11A and 11B. On the other hand, when the discharge control FET 14 is OFF, it blocks the flow of current to discharge from secondary batteries 11A and 11B.

[0019] The discharge control FET 14 includes a body diode 15. The body diode 15 allows current to flow to charge the secondary batteries 11A and 11B, while blocking the flow of current to discharge from the secondary batteries 11A and 11B.

[0020] In this embodiment, the charge control FET 12 and the discharge control FET 14 are directly connected. In other words, the charge control FET 12 and the discharge control FET 14 are back-to-back connected. In other embodiments, the charge control FET 12 and the discharge control FET 14 do not need to be directly connected. Also, in this embodiment, the charge control FET 12 and the discharge control FET 14 are located on the negative electrode side of the secondary batteries 11A and 11B, but in other embodiments, the charge control FET 12 and the discharge control FET 14 may be located on the positive electrode side of the secondary batteries 11A and 11B.

[0021] Voltage sensors 16 and 17 measure the voltages of the secondary batteries 11A and 11B and provide signals indicating the measured voltages (hereinafter referred to as "measured voltage Vb") to the control device 10.

[0022] The voltage sensor 18 measures the total voltage of the secondary batteries 11A and 11B and provides the control device 10 with a signal indicating the measured total voltage Vt. The total voltage Vt is the voltage applied to the device and / or system to which power is supplied.

[0023] The voltage sensor 19 measures the voltage of the charge control FET 12 and provides the control device 10 with a signal indicating the measured voltage (hereinafter referred to as "measured voltage Vfc").

[0024] The voltage sensor 20 measures the voltage of the discharge control FET 14 and provides the control device 10 with a signal indicating the measured voltage (hereinafter referred to as "measured voltage Vfd"). Specific examples of voltage sensors 16-20 include digital voltage sensors.

[0025] Capacitor 22 is connected in parallel to the secondary batteries 11A and 11B. Capacitor 22 functions as a filter to suppress voltage fluctuations. An RC low-pass filter (LPF) is formed by capacitor 22, the wiring resistance in the battery system 1, and the contact resistance of the wiring fastening parts. This smooths the overall voltage Vt, as shown in the waveform of the overall voltage Vt in Figures 6-9. The voltage sensor 18 measures the overall voltage Vt that has been smoothed by this LPF. Details of Figures 6-9 will be described later.

[0026] Figure 2 shows an example of the configuration of the control device 10. The control device 10 comprises at least one arithmetic unit 100, an input / output interface (I / F) 110, and a storage device 120. Specific examples of the arithmetic unit 100 include processors such as a CPU (Central Processing Unit) and an MPU (Micro Processing Unit). The arithmetic unit 100 realizes the functions shown in Figure 2 by executing instructions contained in a program stored in the storage device 120. Alternatively, integrated circuits such as FPGAs (Field-Programmable Gate Arrays) and ASICs (Application Specific Integrated Circuits) may perform the processing executed by the control device 10. Integrated circuits such as processors, MPUs, FPGAs, and ASICs are equivalent to computers.

[0027] The input / output interface 110 is an interface that connects the control device 10 with the voltage sensors 16-20, the charge control FET 12, and the discharge control FET 14.

[0028] The storage device 120 is a storage device that stores programs executed by the arithmetic unit 100 and various information processed by the arithmetic unit 100.

[0029] The arithmetic unit 100 includes a battery voltage acquisition unit 101, an FET voltage acquisition unit 102, a total voltage acquisition unit 103, a battery voltage determination unit 104, an FET voltage determination unit 105, a total voltage determination unit 106, and an FET control unit 107. These functions can be implemented by a program.

[0030] The battery voltage acquisition unit 101 acquires the measured voltage Vb of the secondary batteries 11A and 11B from the voltage sensors 16 and 17.

[0031] The FET voltage acquisition unit 102 acquires the measured voltage Vfc of the charge control FET 12 from the voltage sensor 19. It also acquires the measured voltage Vfd of the discharge control FET 14 from the voltage sensor 20.

[0032] The overall voltage acquisition unit 103 acquires the overall voltage Vt from the voltage sensor 18.

[0033] The battery voltage determination unit 104 determines whether at least one of the measured voltages Vb of the secondary batteries 11A and 11B is below the over-discharge voltage threshold. The over-discharge voltage threshold is the voltage at which the secondary batteries 11A and 11B are in an over-discharge state.

[0034] Furthermore, the battery voltage determination unit 104 determines whether at least one of the measured voltages Vb of the secondary batteries 11A and 11B is above the overcharge voltage threshold. The overcharge voltage threshold is the voltage at which the secondary batteries 11A and 11B are in an overcharged state.

[0035] The FET voltage determination unit 105 determines whether the measured voltage Vfc of the charge control FET 12 is below a predetermined voltage threshold after the charge control FET 12 has been instructed to turn off. The predetermined voltage threshold is a value that is greater than or equal to the measured voltage Vfc expected when the charge control FET 12 is closed, and less than the measured voltage Vfc expected when the charge control FET 12 is open.

[0036] Furthermore, after the discharge control FET 14 is instructed to turn off, the FET voltage determination unit 105 determines whether the measured voltage Vfd of the discharge control FET 14 is below a predetermined voltage threshold. The predetermined voltage threshold is a value that is greater than or equal to the measured voltage Vfd expected when the discharge control FET 14 is closed, and less than the measured voltage Vfd expected when the discharge control FET 14 is open.

[0037] The overall voltage determination unit 106 determines the overall voltage Vt using a predetermined voltage threshold. Specifically, the overall voltage determination unit 106 determines whether the overall voltage Vt is equal to or greater than a first upper limit voltage threshold. The first upper limit voltage threshold is the value of the overall voltage Vt that is expected to occur when the open-circuit function of the charge control FET 12 fails.

[0038] Furthermore, the overall voltage determination unit 106 determines whether the overall voltage Vt is below a first lower voltage threshold. The first lower voltage threshold is the value of the overall voltage Vt that is expected when the open-circuit function of the charge control FET 12 fails. The first lower voltage threshold is smaller than the first upper voltage threshold.

[0039] Furthermore, the overall voltage determination unit 106 determines whether the overall voltage Vt is equal to or greater than the second upper limit voltage threshold. The second upper limit voltage threshold is the value of the overall voltage Vt that is expected to occur when the open-circuit function of the discharge control FET 14 fails.

[0040] Furthermore, the overall voltage determination unit 106 determines whether the overall voltage Vt is below the second lower voltage threshold. The second lower voltage threshold is the value of the overall voltage Vt that is expected when the open-circuit function of the discharge control FET 14 fails. The second lower voltage threshold is smaller than the second upper voltage threshold.

[0041] The FET control unit 107 controls the on / off state of the charge control FET 12 and the discharge control FET 14. Specifically, the FET control unit 107 turns on the charge control FET 12 and the discharge control FET 14 by applying a predetermined voltage to their gates. Conversely, the FET control unit 107 turns off the charge control FET 12 and the discharge control FET 14 by not applying a voltage to their gates.

[0042] Figure 3 is a flowchart showing an example of a process performed by the control device 10. In step S1, the battery voltage acquisition unit 101 acquires the measured voltage Vb of the secondary batteries 11A and 11B. In step S2, the battery voltage determination unit 104 determines whether at least one of the measured voltage Vb of the secondary batteries 11A and 11B is below the over-discharge voltage threshold.

[0043] If it is determined that at least one of the measured voltages Vb of the secondary batteries 11A and 11B is below the over-discharge voltage threshold (YES), in step S3, the FET control unit 107 instructs the discharge control FET 14 to turn off. In step S4, the FET voltage acquisition unit 102 acquires the measured voltage Vfd of the discharge control FET 14. In step S5, the FET voltage determination unit 105 determines whether the measured voltage Vfd of the discharge control FET 14 is below a predetermined voltage threshold.

[0044] If it is determined that the measured voltage Vfd of the discharge control FET 14 is below a predetermined voltage threshold (YES), the switching control process of the charge control FET is executed in step S6. On the other hand, if it is determined that the measured voltage Vfd of the discharge control FET 14 exceeds a predetermined voltage threshold (NO), the process shown in Figure 3 ends.

[0045] If, in step S2, it is determined that at least one of the measured voltages Vb of the secondary batteries 11A and 11B is not below the over-discharge voltage threshold (NO), in other words, if all measured voltages Vb exceed the over-discharge voltage threshold, the process branches to step S7.

[0046] In step S7, the battery voltage determination unit 104 determines whether at least one of the measured voltages Vb of the secondary batteries 11A and 11B is equal to or greater than the overcharge voltage threshold.

[0047] If it is determined that at least one of the measured voltages Vb of the secondary batteries 11A and 11B is equal to or greater than the overcharge voltage threshold (YES), in step S8, the FET control unit 107 instructs the charge control FET 12 to turn off. In step S9, the FET voltage acquisition unit 102 acquires the measured voltage Vfc of the charge control FET 12. In step S10, the FET voltage determination unit 105 determines whether the measured voltage Vfc of the charge control FET 12 is equal to or less than a predetermined voltage threshold.

[0048] If it is determined that the measured voltage Vfc of the charge control FET 12 is below a predetermined voltage threshold (YES), the switching control process of the discharge control FET is executed in step S11. On the other hand, if it is determined that the measured voltage Vfc of the charge control FET 12 exceeds a predetermined voltage threshold (NO), the process shown in Figure 3 ends.

[0049] Figure 4 shows an example of the switching control process for the charge control FET 12. In step S20, the FET control unit 107 turns off the charge control FET 12. In step S21, the total voltage acquisition unit 103 acquires the total voltage Vt of the battery system 1. In step S22, the total voltage determination unit 106 determines whether the total voltage Vt is below the first lower voltage threshold.

[0050] If it is determined that the total voltage Vt exceeds the first lower voltage threshold (NO), the process returns to step S20. On the other hand, if it is determined that the total voltage Vt is less than or equal to the first lower voltage threshold (YES), the process branches to step S23.

[0051] In step S23, the FET control unit 107 turns on the charge control FET 12. In step S24, the total voltage acquisition unit 103 acquires the total voltage Vt of the battery system 1. In step S25, the total voltage determination unit 106 determines whether the total voltage Vt is equal to or greater than the first upper limit voltage threshold.

[0052] If it is determined that the total voltage Vt is less than the first upper voltage threshold (NO), the process returns to step S24. On the other hand, if it is determined that the total voltage Vt is equal to or greater than the first upper voltage threshold (YES), the process branches to step S20.

[0053] Figure 5 shows an example of the switching control process for the discharge control FET 14. In step S30, the FET control unit 107 turns off the discharge control FET 14. In step S31, the total voltage acquisition unit 103 acquires the total voltage Vt of the battery system 1. In step S32, the total voltage determination unit 106 determines whether the total voltage Vt is equal to or greater than the second upper limit voltage threshold.

[0054] If it is determined that the total voltage Vt is less than the second upper voltage threshold (NO), the process returns to step S30. On the other hand, if it is determined that the total voltage Vt is equal to or greater than the second upper voltage threshold (YES), the process branches to step S33.

[0055] In step S33, the FET control unit 107 turns on the discharge control FET 14. In step S34, the total voltage acquisition unit 103 acquires the total voltage Vt of the battery system 1. In step S35, the total voltage determination unit 106 determines whether the total voltage Vt is below the second lower voltage threshold.

[0056] If it is determined that the total voltage Vt exceeds the second lower voltage threshold (NO), the process returns to step S34. On the other hand, if it is determined that the total voltage Vt is less than or equal to the second lower voltage threshold (YES), the process branches to step S30.

[0057] Figure 6 shows the control instructions for the discharge control FET 14, the measured voltage Vfd, the control instructions for the charge control FET 12, the measured voltage Vfc, the control instructions for the charge control FET 12, and the overall voltage Vt when the open-circuit function of the discharge control FET fails during discharge.

[0058] In the example shown in Figure 6, assume that the discharge control FET's open-circuit function is faulty, and at time t1, the FET control unit 107 instructs the discharge control FET 14 to turn off. When the discharge control FET's open-circuit function is normal, the measured voltage Vfd of the discharge control FET 14 increases as shown by the dotted line in Figure 6. However, when the discharge control FET's open-circuit function is faulty, i.e., when the discharge control FET remains closed, the measured voltage Vfd of the discharge control FET 14 does not change and remains below the predetermined voltage threshold. In this case, the switching control process of the charge control FET is executed.

[0059] In the switching control process of the charge control FET, the FET control unit 107 instructs the charge control FET 12 to turn off. When the charge control FET 12 is turned off by this instruction, the measured voltage Vfc of the charge control FET 12 increases, and the total voltage Vt gradually decreases. When the total voltage Vt decreases to the first lower voltage threshold, the FET control unit 107 instructs the charge control FET 12 to turn on. When the charge control FET 12 is turned on by this instruction, the measured voltage Vfc of the charge control FET 12 decreases, and the total voltage Vt gradually increases. Then, when the total voltage Vt increases to the first upper voltage threshold, the FET control unit 107 instructs the charge control FET 12 to turn off. By repeatedly executing these processes, the total voltage Vt becomes a value within the range of the first upper voltage threshold and the first lower voltage threshold.

[0060] Figure 7 shows the control instructions for the charge control FET 12, the measured voltage Vfc, the control instructions for the discharge control FET 14, the measured voltage Vfd, the control instructions for the discharge control FET 14, and the overall voltage Vt when the open-circuit function of the charge control FET 12 fails during discharge.

[0061] In the example shown in Figure 7, assume that the open-circuit function of the charge control FET 12 is faulty, and at time t1, the FET control unit 107 instructs the charge control FET 12 to turn off. When the open-circuit function of the charge control FET 12 is normal, the measured voltage Vfc of the charge control FET 12 increases as shown by the dotted line in Figure 7. However, when the open-circuit function of the charge control FET 12 is faulty, that is, when the charge control FET remains closed, the measured voltage Vfc of the charge control FET 12 does not change and remains below the predetermined voltage threshold. In this case, the switching control process of the discharge control FET is executed.

[0062] In the switching control process of the discharge control FET, the FET control unit 107 instructs the discharge control FET 14 to turn off. When the discharge control FET 14 is turned off by this instruction, the measured voltage Vfd of the discharge control FET 14 increases, and the total voltage Vt gradually increases. When the total voltage Vt increases to the second upper voltage threshold, the FET control unit 107 instructs the discharge control FET 14 to turn on. When the discharge control FET 14 is turned on by this instruction, the measured voltage Vfd of the discharge control FET 14 increases, and the total voltage Vt gradually decreases. Then, when the total voltage Vt decreases to the second lower voltage threshold, the FET control unit 107 instructs the discharge control FET 14 to turn off. By repeatedly executing these processes, the total voltage Vt will be within the range of the second upper voltage threshold and the second lower voltage threshold.

[0063] Figure 8 shows the control instructions for the discharge control FET 14, the measured voltage Vfd, the control instructions for the charge control FET 12, the measured voltage Vfc, the control instructions for the charge control FET 12, and the overall voltage Vt when the open-circuit function of the discharge control FET fails during charging.

[0064] In the example shown in Figure 8, assume that the discharge control FET's open-circuit function is faulty, and at time t1, the FET control unit 107 instructs the discharge control FET 14 to turn off. When the discharge control FET's open-circuit function is faulty, the measured voltage Vfd of the discharge control FET 14 does not change and remains below the predetermined voltage threshold. In this case, the switching control process of the charge control FET is executed.

[0065] In the switching control process of the charge control FET, the FET control unit 107 instructs the charge control FET 12 to turn off. When the charge control FET 12 is turned off by this instruction, the measured voltage Vfc of the charge control FET 12 increases, and the total voltage Vt gradually decreases. When the total voltage Vt decreases to the first lower voltage threshold, the FET control unit 107 instructs the charge control FET 12 to turn on. When the charge control FET 12 is turned on by this instruction, the measured voltage Vfc of the charge control FET 12 decreases, and the total voltage Vt gradually increases. Then, when the total voltage Vt increases to the first upper voltage threshold, the FET control unit 107 instructs the charge control FET 12 to turn off. By repeatedly executing these processes, the total voltage Vt becomes a value within the range of the first upper voltage threshold and the first lower voltage threshold.

[0066] Figure 9 shows the control instructions for the charge control FET 12, the measured voltage Vfc, the control instructions for the discharge control FET 14, the measured voltage Vfd, the control instructions for the discharge control FET 14, and the overall voltage Vt when the open-circuit function of the charge control FET 12 fails during charging.

[0067] In the example shown in Figure 9, assume that the open-circuit function of the charge control FET 12 is faulty, and at time t1, the FET control unit 107 instructs the charge control FET 12 to turn off. When the open-circuit function of the charge control FET 12 is faulty, the measured voltage Vfc of the charge control FET 12 does not change and remains below the predetermined voltage threshold. In this case, the switching control process of the discharge control FET is executed.

[0068] In the switching control process of the discharge control FET, the FET control unit 107 instructs the discharge control FET 14 to turn off. When the discharge control FET 14 is turned off by this instruction, the measured voltage Vfd of the discharge control FET 14 increases, and the total voltage Vt gradually increases. When the total voltage Vt increases to the second upper voltage threshold, the FET control unit 107 instructs the discharge control FET 14 to turn on. When the discharge control FET 14 is turned on by this instruction, the measured voltage Vfd of the discharge control FET 14 increases, and the total voltage Vt gradually decreases. Then, when the total voltage Vt decreases to the second lower voltage threshold, the FET control unit 107 instructs the discharge control FET 14 to turn off. By repeatedly executing these processes, the total voltage Vt will be within the range of the second upper voltage threshold and the second lower voltage threshold.

[0069] As described above, the FET control unit 107 of the control device 10 instructs the discharge control FET 14 to turn off if the measured voltage Vb of the secondary batteries 11A and 11B is below the over-discharge voltage threshold. After instructing the discharge control FET 14 to turn off, if the measured voltage Vfd of the discharge control FET 14 is below a predetermined voltage threshold, the FET control unit 107 executes a switching control process for the charge control FET, repeatedly turning the charge control FET 12 on and off, to bring the total voltage of the secondary batteries 11A and 11B supplied to the power supply target within the predetermined voltage range.

[0070] By adopting this configuration, after instructing the discharge control FET 14 to turn off, if the measured voltage Vfd of the discharge control FET 14 is below a predetermined voltage threshold, in other words, if there is a failure in the open-circuit function of the discharge control FET 14, the total voltage of the secondary batteries 11A and 11B will be brought within a predetermined voltage range. Therefore, the system and device to which the power is supplied can detect that there is a failure in the open-circuit function of the discharge control FET 14 based on this total voltage value.

[0071] Furthermore, the FET control unit 107 instructs the charge control FET 12 to turn off if the measured voltage Vb of the secondary batteries 11A and 11B is above the overcharge voltage threshold. After instructing the charge control FET 12 to turn off, if the measured voltage Vfc of the charge control FET 12 is below a predetermined voltage threshold, the FET control unit 107 executes switching control processing for the discharge control FET, repeatedly turning the discharge control FET 14 on and off, to bring the overall voltage within the predetermined voltage range.

[0072] By adopting this configuration, after instructing the charge control FET 12 to turn off, if the measured voltage Vfc of the charge control FET 12 is below a predetermined voltage threshold, in other words, if there is a failure in the open-circuit function of the charge control FET 12, the total voltage of the secondary batteries 11A and 11B will be brought within a predetermined voltage range. Therefore, the system and device to which the power is supplied can detect that there is a failure in the open-circuit function of the charge control FET 12 based on this total voltage value.

[0073] In the above example, the program describing the above-described process can be stored and provided to the computer using various types of non-transitory computer-readable medium. Non-transitory computer-readable mediums include various types of tangible storage mediums. Examples of non-transitory computer-readable mediums include magnetic storage media (e.g., flexible disks, magnetic tapes, hard disk drives), magneto-optical storage media (e.g., magneto-optical disks), CD-ROMs, CD-Rs, CD-R / Ws, and semiconductor memory (e.g., mask ROMs, PROMs (Programmable ROMs), EPROMs (Erasable PROMs), flash ROMs, RAMs). Alternatively, the program may be provided to the computer using various types of transient computer-readable mediums. Examples of transient computer-readable mediums include electrical signals, optical signals, and electromagnetic waves. Transitory computer-readable mediums can supply the program to the computer via wired communication channels such as electric wires and optical fibers, or via wireless communication channels.

[0074] This disclosure is not limited to the embodiments described above, and may be modified as appropriate without departing from the spirit of this disclosure. [Explanation of symbols]

[0075] 1: Battery System 10: Control device 100: Arithmetic device 101: Battery voltage acquisition unit 102: FET voltage acquisition section 103: Overall voltage acquisition unit 104: Battery voltage determination unit 105: FET voltage determination unit 106: Overall voltage determination unit 107: FET control unit 110: Input / Output Interface 120: Storage device 11A: Secondary battery 11B: Secondary battery 12: Charge control FET 13: Body Diode 14: Discharge-controlled FET 15: Body Diode 16-20: Voltage Sensor 22: Capacitor

Claims

1. At least one rechargeable battery, A charge control FET (Field Effect Transistor) and a discharge control FET are connected in series with the aforementioned secondary battery, The system includes a control device that controls the charging and discharging of the secondary battery by controlling the on and off states of the charge control FET and the discharge control FET, The charge control FET includes a body diode that enables the flow of current discharged from the secondary battery, The discharge control FET includes a body diode that enables the flow of current to charge the secondary battery, The control device is A battery voltage acquisition unit that acquires the measured voltage of the secondary battery, The FET voltage acquisition unit acquires the measured voltage Vfd of the discharge control FET, The system comprises an FET control unit that controls the on and off states of the charge control FET and the discharge control FET, The FET control unit instructs the discharge control FET to turn off when the measured voltage of the secondary battery is below the over-discharge voltage threshold. After instructing the FET control unit to turn off the discharge control FET, if the measured voltage Vfd of the discharge control FET is below a predetermined voltage threshold, the FET control unit executes a switching control process for the charge control FET, repeatedly turning the charge control FET on and off, to bring the total voltage of the secondary battery supplied to the power supply target within a predetermined voltage range. Battery system.

2. The FET voltage acquisition unit further acquires the measured voltage Vfc of the discharge control FET, The FET control unit instructs the charge control FET to turn off if the measured voltage of the secondary battery is equal to or greater than the overcharge voltage threshold. The battery system according to claim 1, wherein the FET control unit, after instructing the charge control FET to turn off, executes an on / off control process for the discharge control FET, which repeatedly turns the discharge control FET on and off, if the measured voltage Vfc of the charge control FET is below another predetermined voltage threshold, to bring the overall voltage within a predetermined voltage range.

3. At least one rechargeable battery, A charge control FET and a discharge control FET are connected in series with the aforementioned secondary battery, The system includes a control device that controls the charging and discharging of the secondary battery by controlling the on and off states of the charge control FET and the discharge control FET, The charge control FET includes a body diode that enables the flow of current discharged from the secondary battery, The discharge control FET includes a body diode that enables the flow of current to charge the secondary battery, The control device is A battery voltage acquisition unit that acquires the measured voltage of the secondary battery, An FET voltage acquisition unit that acquires the measured voltage Vfc and the measured voltage Vfd of the discharge control FET, The system comprises an FET control unit that controls the on and off states of the charge control FET and the discharge control FET, The FET control unit instructs the discharge control FET to turn off when the measured voltage of the secondary battery is below the over-discharge voltage threshold. After instructing the FET control unit to turn off the discharge control FET, if the measured voltage Vfd of the discharge control FET is below a predetermined voltage threshold, the FET control unit executes a switching control process for the charge control FET, repeatedly turning the charge control FET on and off, to bring the total voltage of the secondary battery supplied to the power supply target within a predetermined voltage range. The FET control unit instructs the charge control FET to turn off if the measured voltage of the secondary battery is equal to or greater than the overcharge voltage threshold. After instructing the FET control unit to turn off the charge control FET, if the measured voltage Vfc of the charge control FET is below another predetermined voltage threshold, the FET control unit executes a switching control process for the discharge control FET, repeatedly turning the discharge control FET on and off, to bring the total voltage of the secondary battery within a predetermined voltage range. Battery system.

4. The secondary battery is equipped with a battery voltage determination unit that determines the overall voltage of the secondary battery, In the switching control process of the aforementioned charge control FET, The FET control unit instructs the charge control FET to turn off, The battery voltage determination unit determines whether the overall voltage after the charge control FET is instructed to be turned off is below the first lower limit voltage threshold, If the overall voltage after the charge control FET is instructed to turn off is determined to be below the first lower limit voltage threshold, the FET control unit instructs the charge control FET to turn on. The battery voltage determination unit determines whether the overall voltage after the charging control FET is instructed to turn on is equal to or greater than the first upper limit voltage threshold. If the overall voltage after the charging control FET is instructed to turn on is determined to be equal to or greater than the first upper limit voltage threshold, the FET control unit instructs the charging control FET to turn on. The battery system according to any one of claims 1 to 3.

5. The secondary battery is equipped with a battery voltage determination unit that determines the overall voltage of the secondary battery, In the switching control process of the discharge control FET, The FET control unit instructs the discharge control FET to turn off, The battery voltage determination unit determines whether the overall voltage after the discharge control FET is instructed to turn off is equal to or greater than the second upper limit voltage threshold. If the total voltage after the discharge control FET has been instructed to turn off is determined to be equal to or greater than the second upper limit voltage threshold, the FET control unit instructs the discharge control FET to turn on. The battery voltage determination unit determines whether the overall voltage after the discharge control FET is instructed to be turned on is below the second lower limit voltage threshold, If the overall voltage after the discharge control FET is instructed to turn on is determined to be below the second lower voltage threshold, the FET control unit instructs the discharge control FET to turn on. The battery system according to any one of claims 1 to 3.

6. The battery system according to any one of claims 1 to 3, wherein the charge control FET and the discharge control FET are MOSFETs (Metal Oxide Semiconductor Field Effect Transistors).

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