JP2009254165A - Battery state detection circuit, battery pack, and charging system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery state detection circuit for detecting a failure in a voltage detection circuit and a current detection circuit without separately providing a group voltage detection circuit, a battery pack with it, and a charging system. <P>SOLUTION: The battery state detection circuit comprises: the voltage detection circuit 15 for detecting terminal voltage V1, V2, V3 of secondary batteries 141, 142, 143; a current detection resistor 16 for detecting a charge/discharge current Ic flowing in the secondary batteries 141, 142, 143; and a failure determination section 214 for determining that one of the voltage detection circuit 15, the current detection resistor 16 and an A/D converter 201 has the failure if a relationship between the terminal voltages V1, V2, V3 detected by the voltage detection circuit 15 and the charge/discharge current Ic detected by the current detection resistor 16 complies with a preset condition for indicating that the relationship is not normal. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a battery state detection circuit that detects a state of a secondary battery, a battery pack including the battery state detection circuit, and a charging system.

  For example, when a secondary battery such as a lithium ion secondary battery or a nickel metal hydride secondary battery is overcharged exceeding the full charge voltage, the characteristics may be deteriorated or the safety may be lowered. On the other hand, even if the battery discharges to a level below the specified discharge end voltage and overdischarges, the characteristics of the secondary battery may deteriorate due to the deposition of lithium or other electrode materials or metal materials, and the safety may decrease. There is a risk of doing so. Further, when the secondary battery is charged / discharged with an excessively large current, the characteristics may be deteriorated or the safety may be lowered.

  Therefore, devices using secondary batteries and battery packs are provided with a voltage detection circuit for detecting a terminal voltage of the secondary battery and a current detection circuit for detecting a charge / discharge current of the secondary battery. Charging is prohibited when the terminal voltage detected by such a voltage detection circuit exceeds the full charge voltage, or when the charge / discharge current detected by the current detection circuit exceeds a predetermined threshold value, discharge is performed. It is forbidden.

  In addition, if the terminal voltage drops or the terminal voltage drops due to excessive discharge that causes lithium or the like to precipitate, the terminal voltage drops. For example, the fuse is permanently disconnected, for example. There is also known a technique for making it unusable.

  Furthermore, when an assembled battery in which a plurality of secondary batteries are connected in series is used, if an imbalance such as deterioration between cells or variation in charging depth increases, the entire assembled battery is maintained at an appropriate terminal voltage. However, overcharge and overcharge may occur in some secondary batteries. Therefore, it is also known that the terminal voltage of each secondary battery is detected and the use of the secondary battery is prohibited when the imbalance increases beyond a predetermined limit. Moreover, the detection value of such a voltage detection circuit or a current detection circuit is also used for charge control of the secondary battery.

  For this reason, if the voltage detection circuit or the current detection circuit fails, it becomes difficult to protect the secondary battery from overcharge and overdischarge, which not only causes deterioration of the secondary battery but also may cause a reduction in safety. .

Therefore, for example, a cell voltage detection circuit that detects the terminal voltage of each secondary battery of the assembled battery and a group voltage detection circuit that measures the terminal voltage of the entire assembled battery are provided, and each secondary detected by the cell voltage detection circuit is provided. A technology that compares the total terminal voltage of the battery with the terminal voltage of the entire assembled battery detected by the assembled voltage detection circuit, and determines that an abnormality in the voltage detection circuit has occurred if both voltage values do not match. It is known (for example, see Patent Document 1).
JP-A-11-252809

  However, the technique described in Patent Document 1 has a disadvantage in that it requires a separate assembled voltage detection circuit in addition to the cell voltage detection circuit, resulting in an increase in cost. Further, if any one of the voltage detection circuit and the current detection circuit fails, the protection of the secondary battery becomes insufficient, which may cause deterioration of the secondary battery and a decrease in safety. With this technique, it was impossible to detect a failure in the current detection circuit.

  In addition to the cell voltage detection circuit described above, another set of cell voltage detection circuits may be connected to the connection terminals of each secondary battery, for example, for the purpose of duplicating the safety circuit. In this case, when the cell voltage detection circuit described in Patent Document 1 is disconnected from the secondary battery and an open failure occurs, the terminal voltage of the entire assembled battery is equally divided by the input impedance and terminal capacity of the cell voltage detection circuit for duplication. In some cases, the divided voltage is detected by a cell voltage detection circuit having an open failure. In such a case, the total terminal voltage of each secondary battery detected by the cell voltage detection circuit matches the terminal voltage of the entire assembled battery detected by the assembled voltage detection circuit. There was an inconvenience that an abnormality could not be detected.

  The present invention has been made in view of such circumstances, and includes a battery state detection circuit capable of detecting a failure of the voltage detection circuit and the current detection circuit without separately providing an assembled voltage detection circuit, and the same. Another object is to provide a battery pack and a charging system.

  A battery state detection circuit according to the present invention includes a voltage detection unit that detects a terminal voltage of a secondary battery, a current detection unit that detects a charge / discharge current flowing in the secondary battery, and a terminal detected by the voltage detection unit. If the relationship between the voltage and the charge / discharge current detected by the current detection unit satisfies a preset condition to indicate that it is not a normal relationship, at least one of the voltage detection unit and the current detection unit fails A failure determination unit that determines that the operation is being performed.

  According to this configuration, when at least one of the voltage detection unit and the current detection unit fails, the terminal voltage detected by the voltage detection unit and the charge / discharge current detected by the current detection unit no longer show a normal relationship. Thus, a preset condition is satisfied. Then, the failure determination unit determines that at least one of the voltage detection unit and the current detection unit has failed. Thereby, it is possible to detect a failure of the voltage detection unit and the current detection unit without separately providing a set voltage detection circuit as in the background art.

  As described above, when another cell voltage detection circuit is connected to the terminals of a plurality of secondary batteries constituting the assembled battery for the purpose of duplicating the safety circuit, the voltage detection unit is connected to the secondary battery. Even when it is disconnected from the battery, the terminal voltage of the entire assembled battery is evenly divided, and the divided voltage is detected by the voltage detecting unit that has the open failure, it is described in Patent Document 1. As in the above technique, the failure is not detected based on the total terminal voltage of each secondary battery detected by the cell voltage detection circuit and the terminal voltage of the entire assembled battery detected by the assembled voltage detection circuit. Therefore, it is possible to reduce the possibility that a failure cannot be detected as compared with the technique described in Patent Document 1.

  Further, the condition includes that the terminal voltage detected by the voltage detector rises when the charge / discharge current detected by the current detector is substantially zero. Is preferred.

  If the secondary battery is not charged or discharged, the terminal voltage does not increase even if the terminal voltage decreases due to self-discharge. Therefore, according to this configuration, although the current detection unit indicates that the secondary battery is not charged / discharged, the voltage detection unit indicates that the terminal voltage of the secondary battery has increased. In the case shown, since the detection result of the charge / discharge current by the current detection unit and the detection result of the terminal voltage by the voltage detection unit are inconsistent, at least one of the voltage detection unit and the current detection unit is out of order. Can be determined.

  The condition preferably includes that the terminal voltage detected by the voltage detector decreases when the charge / discharge current detected by the current detector indicates a charging direction. .

  According to this configuration, when the current detection unit indicates that the secondary battery is charged, the voltage detection unit indicates that the terminal voltage of the secondary battery is reduced. The failure determination unit determines that at least one of the voltage detection unit and the current detection unit has failed because the charge / discharge current detection result by the current detection unit and the terminal voltage detection result by the voltage detection unit are inconsistent. be able to.

  In addition, it is preferable that the condition includes that the terminal voltage detected by the voltage detector increases when the charge / discharge current detected by the current detector indicates a discharge direction. .

  According to this configuration, even when the current detection unit indicates that the secondary battery is discharged, the voltage detection unit indicates that the terminal voltage of the secondary battery is increased. The failure determination unit determines that at least one of the voltage detection unit and the current detection unit has failed because the charge / discharge current detection result by the current detection unit and the terminal voltage detection result by the voltage detection unit are inconsistent. be able to.

  Further, based on the charge / discharge current detected by the current detector, the secondary battery is obtained from an integrated value obtained by cumulatively adding the charge charge amount and subtracting the discharge charge amount in the secondary battery. And a storage unit for storing correspondence information indicating a correspondence relationship between the charge amount of the secondary battery and a terminal voltage, and the condition includes: The difference between the terminal voltage associated with the charge amount calculated by the remaining amount calculation unit in the correspondence relationship information stored in the storage unit and the terminal voltage detected by the voltage detection unit is set in advance. It is preferable that the determination threshold is exceeded.

  According to this configuration, the remaining amount calculation unit calculates the charge amount of the secondary battery based on the charge / discharge current detected by the current detection unit. When the difference between the terminal voltage associated with the calculated charge amount in the correspondence information stored in the storage unit and the terminal voltage detected by the voltage detection unit exceeds a preset determination threshold value This means that the terminal voltage detected by the voltage detection unit is outside the range of the terminal voltage predicted from the charge / discharge current detected by the current detection unit. The failure determination unit can determine that at least one of the voltage detection unit and the current detection unit has failed.

  Further, based on the charge / discharge current detected by the current detector, the secondary battery is obtained from an integrated value obtained by cumulatively adding the charge charge amount and subtracting the discharge charge amount in the secondary battery. And a storage unit for storing correspondence information indicating a correspondence relationship between the charge amount of the secondary battery and the terminal voltage, and the condition includes: The difference between the charge amount associated with the terminal voltage detected by the voltage detection unit in the stored correspondence information and the charge amount calculated by the remaining amount calculation unit exceeds a preset determination threshold. May be included.

  According to this configuration, the charge amount of the secondary battery is calculated based on the charge / discharge current detected by the current detection unit. Then, a determination threshold in which a difference between the charge amount associated with the terminal voltage detected by the voltage detection unit in the correspondence information stored in the storage unit and the charge amount calculated by the remaining amount calculation unit is set in advance. Means that the charge amount calculated based on the charge / discharge current is out of the range of the charge amount predicted from the terminal voltage detected by the voltage detection unit. As a cause obtained, the failure determination unit can determine that at least one of the voltage detection unit and the current detection unit has failed.

  The terminal voltage in the correspondence information is an open circuit voltage of the secondary battery, and the failure determination unit is detected by the current detection unit as a terminal voltage detected by the voltage detection unit in the condition. It is preferable to use the terminal voltage detected by the voltage detector when the charge / discharge current is substantially zero.

  The terminal voltage of the secondary battery includes an open circuit voltage when the flowing current is zero and a voltage drop caused by the current flowing through the internal resistance of the secondary battery. Therefore, even if the secondary batteries have the same charge amount, a difference occurs in the terminal voltage due to the flowing current. Therefore, if the condition is determined based on the terminal voltage detected by the voltage detector in various states of the current flowing through the secondary battery, the accuracy of the failure determination may be reduced. However, according to this configuration, when the charge / discharge current detected by the current detector is substantially zero, the terminal voltage detected by the voltage detector, that is, if the current detector is normal, it should be an open circuit voltage. Since the determination of the condition is performed based on the terminal voltage, it is possible to improve the accuracy of the failure determination.

  The terminal voltage in the correspondence information is an open circuit voltage of the secondary battery, and the failure determination unit is detected by the current detection unit as a terminal voltage detected by the voltage detection unit in the condition. You may make it use the voltage value which converted the terminal voltage detected by the said voltage detection part into the open circuit voltage based on charging / discharging electric current.

  Since the voltage drop due to the internal resistance of the secondary battery changes according to the current flowing through the secondary battery, the voltage drop can be calculated based on the charge / discharge current detected by the current detection unit. Then, the terminal voltage detected by the voltage detector is subtracted from the terminal voltage detected by the voltage detector during charging, and the voltage drop is added during discharging, thereby converting the terminal voltage detected by the voltage detector into the open circuit voltage. It can be converted. Then, by using the terminal voltage thus converted to the open circuit voltage as the terminal voltage detected by the voltage detection unit under the above conditions, the accuracy of failure determination can be achieved even when a current flows through the secondary battery. Can be improved.

  A battery pack according to the present invention includes the above-described battery state detection circuit and the secondary battery.

  According to this configuration, in the battery pack, it is possible to detect a failure in the voltage detection unit and the current detection unit without separately providing an assembled voltage detection circuit as in the background art.

  Further, the charging system according to the present invention includes the above-described battery state detection circuit, the secondary battery, a charging unit that charges the secondary battery, a terminal voltage detected by the voltage detection unit, and the current detection unit. And a control unit that controls the operation of the charging unit based on the charging / discharging current detected by.

  According to this configuration, in the charging system, it is possible to detect a failure in the voltage detection unit and the current detection unit without separately providing an assembled voltage detection circuit as in the background art.

  In the battery state detection circuit, the battery pack, and the charging system having such a configuration, when at least one of the voltage detection unit and the current detection unit fails, the terminal voltage detected by the voltage detection unit and the current detection unit are detected. The charge / discharge current does not show a normal relationship and satisfies a preset condition. Then, the failure determination unit determines that at least one of the voltage detection unit and the current detection unit has failed. Thereby, it is possible to detect a failure of the voltage detection unit and the current detection unit without separately providing a set voltage detection circuit as in the background art.

  Embodiments according to the present invention will be described below with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted. FIG. 1 is a block diagram illustrating an example of a configuration of a battery pack including a battery state detection circuit and a charging system according to an embodiment of the present invention. The charging system 1 shown in FIG. 1 is configured by combining a battery pack 2 and a charging device 3 (charging unit).

  The charging system 1 further includes a load device (not shown) to which power is supplied from the battery pack 2, electronic devices such as portable personal computers, digital cameras, and mobile phones, vehicles such as electric vehicles and hybrid cars, and the like. It may be configured as an electronic device system. In that case, although the battery pack 2 is charged from the charging device 3 in FIG. 1, the battery pack 2 may be attached to the load device and charged through the load device.

  The battery pack 2 includes connection terminals 11, 12, 13, an assembled battery 14, a current detection resistor 16, a battery state detection circuit 4, a communication unit 203, and switching elements Q1, Q2. The battery state detection circuit 4 includes an analog / digital (A / D) converter 201, a control unit 202, a voltage detection circuit 15, and a temperature sensor 17.

  Note that the charging system 1 is not necessarily limited to the battery pack 2 and the charging device 3 configured to be separable, and one battery state detection circuit 4 may be configured in the entire charging system 1. Further, the battery state detection circuit 4 may be shared by the battery pack 2 and the charging device 3.

  The charging device 3 includes connection terminals 31, 32, 33, a control IC 34, and a charging current supply unit 35. The control IC 34 includes a communication unit 36 and a control unit 37. The charging current supply unit 35 is a power supply circuit that supplies a current corresponding to a control signal from the control unit 37 to the battery pack 2 via the connection terminals 31 and 32. The control unit 37 is a control circuit configured using, for example, a microcomputer.

  The battery pack 2 and the charging device 3 are connected to each other by DC high-side connection terminals 11 and 31 that perform power supply, connection terminals 13 and 33 for communication signals, and connection terminals 12 and 32 for power supply and communication signals. Connected. The communication units 203 and 36 are communication interface circuits configured to be able to transmit / receive data to / from each other via the connection terminals 13 and 33.

  In the battery pack 2, the connection terminal 11 is connected to the positive electrode of the assembled battery 14 via the charging switching element Q2 and the discharging switching element Q1. As the switching elements Q1 and Q2, for example, p-channel FETs (Field Effect Transistors) are used. The switching element Q1 has a parasitic diode cathode in the direction of the assembled battery 14. The switching element Q2 has a parasitic diode cathode in the direction of the connection terminal 11.

  The connection terminal 12 is connected to the negative electrode of the assembled battery 14 via the current detection resistor 16, and the connection terminal 12 is connected from the connection terminal 11 via the switching elements Q 2 and Q 1, the assembled battery 14, and the current detection resistor 16. A current path leading to is configured. Of course, n-channel FETs may be used as the switching elements Q1 and Q2.

  The assembled battery 14 is an assembled battery in which a plurality of, for example, three secondary batteries 141, 142, and 143 (cells) are connected in series. The secondary batteries 141, 142, and 143 are secondary batteries such as a lithium ion secondary battery and a nickel hydride secondary battery. The assembled battery 14 may be, for example, a single battery, may be, for example, an assembled battery in which a plurality of secondary batteries are connected in parallel, or is an assembled battery connected in combination of series and parallel. May be.

  The current detection resistor 16 converts the charge / discharge current Ic of the assembled battery 14 into a voltage value and outputs the voltage value to the analog-digital converter 201 in the battery state detection circuit 4. The current value of the charging / discharging current Ic is obtained, for example, as a current value in which the charging direction is plus (+) and the discharging direction is minus (−).

  The temperature sensor 17 detects the temperature of the secondary batteries 141, 142, and 143, and outputs a voltage signal corresponding to the temperature to the analog / digital converter 201 in the battery state detection circuit 4. The terminal voltages V1, V2, and V3 of the secondary batteries 141, 142, and 143 are detected by the voltage detection circuit 15 and input to the analog / digital converter 201 in the battery state detection circuit 4, respectively.

  The voltage detection circuit 15 detects the terminal voltages V1, V2, and V3 of the secondary batteries 141, 142, and 143, respectively, and outputs them to the analog-digital converter 201. The analog-digital converter 201 converts each input value into a digital value and outputs the digital value to the control unit 202. In this case, the voltage detection circuit 15 and the analog / digital converter 201 correspond to an example of a voltage detection unit, and the current detection resistor 16 and the analog / digital converter 201 correspond to an example of a current detection unit.

  The control unit 202 includes, for example, a CPU (Central Processing Unit) that executes predetermined arithmetic processing, a ROM (Read Only Memory) that stores a predetermined control program, and a RAM (Random Access Memory) that temporarily stores data. And a timer circuit and peripheral circuits thereof. The control unit 202 functions as a protection control unit 211, a charge control unit 212 (control unit), a remaining amount calculation unit 213, and a failure determination unit 214 by executing a control program stored in the ROM.

  Further, for example, the above-described ROM has a correspondence indicating a correspondence relationship between a charge depth (SOC: State Of Charge) which is an example of a charge amount of the secondary batteries 141, 142 and 143 and the terminal voltages V 1, V 2 and V 3. The relationship information is stored as a data table, for example. Thereby, a part of the ROM is used as the correspondence information storage unit 215.

  The terminal voltage of the secondary battery increases as the charging depth increases. However, the terminal voltage and the charging depth are not in a simple proportional relationship. Also, the correspondence between the terminal voltage and the charging depth varies depending on the type of the secondary battery and the electrode material. Therefore, in the correspondence information storage unit 215, the correspondence between the charging depths of the secondary batteries 141, 142, and 143 and the terminal voltages V1, V2, and V3 is stored in advance as a data table. Note that the remaining charge amount charged in the secondary batteries 141, 142, and 143 may be used as the charge amount instead of the charging depth.

  The protection control unit 211 detects an abnormality outside the battery pack 2 such as a short circuit between the connection terminals 11 and 12 and an abnormal current from the charging device 3 from each input value from the analog-digital converter 201 or an abnormality in the assembled battery 14. Detect abnormalities such as excessive temperature rise. Specifically, for example, when the current value detected by the current detection resistor 16 exceeds a preset abnormal current determination threshold, an abnormality based on a short circuit between the connection terminals 11 and 12 or an abnormal current from the charging device 3. For example, when the temperature of the assembled battery 14 detected by the temperature sensor 17 exceeds a preset abnormal temperature determination threshold, it is determined that an abnormality has occurred in the assembled battery 14. If such an abnormality is detected, the protection control unit 211 turns off the switching elements Q1 and Q2, and performs a protection operation for protecting the assembled battery 14 from abnormalities such as overcurrent and overheating.

  In addition, the protection control unit 211 preliminarily detects any of the terminal voltages V1, V2, and V3 of the secondary batteries 141, 142, and 143 detected by the voltage detection circuit 15 in order to prevent the secondary battery from being overdischarged. When the voltage becomes lower than the set discharge inhibition voltage Voff, the switching element Q1 is turned off to prevent the secondary batteries 141, 142, 143 from being deteriorated due to overdischarge. The discharge inhibition voltage Voff is set to 2.50 V, for example.

  Further, the protection control unit 211 has a maximum value of the terminal voltages V1, V2, and V3 of the secondary batteries 141, 142, and 143 detected by the voltage detection circuit 15 equal to or higher than a preset overcharge voltage Vovp. In such a case, the switching element Q2 is turned off, and charging of the assembled battery 14 is prohibited.

  In response to each input value from the analog-to-digital converter 201, the charging control unit 212 calculates a voltage value and a current value of a charging current that requires output from the charging device 3, and the communication unit 203 connects to the connection terminal. The assembled battery 14 is charged by, for example, CCCV (constant current constant voltage) charging by transmitting to the charging device 3 via 13 and 32.

  Specifically, the charging control unit 212 first performs constant current charging by supplying a charging / discharging current Ic having a preset current value Icc from the charging device 3. Then, the charging control unit 212 calculates the total value of the terminal voltages V1, V2, and V3 detected by the voltage detection circuit 15 as the terminal voltage Vt of the assembled battery 14. Further, when the terminal voltage Vt reaches a preset charging end voltage Vf, the terminal voltage Vt is switched to constant voltage charging for charging the assembled battery 14 by applying the charging end voltage Vf as a charging voltage. Then, when the charge / discharge current Ic flowing through the assembled battery 14 detected by the current detection resistor 16 becomes equal to or lower than the charge end current value Ia, the charging control unit 212 determines that the assembled battery 14 is fully charged. To finish charging.

  The current value Icc is set to about 0.7 It, for example. The charge termination current value Ia is set to about 0.02 It, for example. 1It (battery capacity (Ah) / 1 (h)) is the nominal capacity value NC of the secondary batteries 141, 142, 143 discharged at a constant current, and the remaining capacity of the secondary batteries 141, 142, 143 in one hour. Is the current value at which becomes zero.

  When the assembled battery 14 is configured by connecting a plurality of cells in parallel, for example, a current value obtained by multiplying 0.7 It by the number of parallel cells PN is used as the current value Icc. Specifically, the current value Icc is, for example, set to 3640 mA at 70% when the nominal capacity value NC = 2600 mAh and two are in parallel.

  When the secondary batteries 141, 142, 143 are lithium ion secondary batteries, for example, the end-of-charge voltage Vf is equal to the positive electrode potential when the negative electrode potential of the secondary batteries 141, 142, 143 is substantially 0V. When the potential difference from the negative electrode potential, that is, the terminal voltages V1, V2, and V3 of the secondary batteries 141, 142, and 143 are the reference voltage Ve, a voltage obtained by multiplying the reference voltage Ve by the number of series cells SN is used.

  Note that “substantially 0V” and “substantially zero” mean that a range such as a measurement error range and a design margin is allowed within the range of “0V” and “zero”.

  In the case of a lithium ion secondary battery, the reference voltage Ve is about 4.2 V when lithium cobaltate is used as the positive electrode active material, and about 4.3 V when lithium manganate is used as the positive electrode active material. For example, if the reference voltage Ve is about 4.2 V, for example, 4.2 V × 3 = 12.6 V is preset as the charge end voltage Vf.

  In addition, the protection control unit 211 and the charge control unit 212 stop the charging / discharging even when a failure is detected by the failure determination unit 214, thereby preventing an erroneous voltage by the voltage detection circuit 15 and the current detection resistor 16. Based on the detected current value, the assembled battery 14 is less likely to be overcharged or overdischarged.

  The remaining amount calculation unit 213 calculates the remaining charge amount charged in the assembled battery 14 as a charge amount by integrating the charge / discharge current Ic detected by the current detection resistor 16 every unit time. In this case, since the current in the direction in which the assembled battery 14 is charged is positive and the current in the direction in which the assembled battery 14 is discharged is negative, the remaining charge calculating unit 213 charges the assembled battery 14 with a charge. The amount is added, and the discharge charge amount discharged from the assembled battery 14 is subtracted to calculate the remaining charge amount Qr charged in the assembled battery 14.

  In addition, the remaining amount calculation unit 213 calculates the ratio of the remaining charge amount Qr to the full charge capacity FCC (actual capacity Full Charge Capacity) of the assembled battery 14 as a charge depth (SOC) corresponding to the charge amount. The charge depth (SOC) is given by the following equation (1). As the full charge capacity FCC, the nominal capacity value NC of the assembled battery 14 may be used, or a capacity value obtained by actual measurement may be used. Note that the remaining amount calculation unit 213 may use the remaining charge amount Qr as it is as the charge amount of the battery.

SOC = Qr / FCC × 100 (%) (1)
The failure determination unit 214 sets in advance to indicate that the relationship between the terminal voltages V1, V2, V3 detected by the voltage detection circuit 15 and the charge / discharge current Ic detected by the current detection resistor 16 is not a normal relationship. If the condition is satisfied, it is determined that any one of the voltage detection circuit 15, the current detection resistor 16, and the analog-digital converter 201 has failed.

  Specifically, the failure determination unit 214 detects, for example, the terminal voltages V1, V2, and V3 detected by the voltage detection circuit 15 every predetermined period tcyc, and the voltage detection circuit at the previous detection timing. The difference between the detected terminal voltages V1, V2 and V3 is calculated.

  When the increase amount of the terminal voltages V1, V2, V3 exceeds the voltage threshold Vth, the failure determination unit 214 determines that the terminal voltage detected by the voltage detection circuit 15 has increased within the period tcyc, When the decrease amount of the terminal voltages V1, V2, and V3 exceeds the voltage threshold Vth, the failure determination unit 214 determines that the terminal voltage detected by the voltage detection circuit 15 has decreased within the period tcyc, and the difference When the absolute value is equal to or less than the voltage threshold Vth, it is determined that the terminal voltage detected by the voltage detection circuit 15 has not changed within the period tcyc.

  Further, the failure determination unit 214 detects the charge / discharge current Ic detected by the current detection resistor 16 and the charge / discharge current Ic detected by the current detection resistor 16 at the previous detection timing (hereinafter referred to as PIc) for each period tcyc. Is compared with the current threshold Ith. If both Ic and PIc are larger than the current threshold Ith, the failure determination unit 214 determines that the charge / discharge current Ic detected by the current detection resistor 16 is in the charge direction (+) within the period tcyc. , Ic and PIc are negative values, and the absolute value thereof is larger than the current threshold value Ith, the failure determination unit 214 determines that the charge / discharge current Ic detected by the current detection resistor 16 is within the period tcyc. When it is determined that the discharge direction is (−) and the absolute values of Ic and PIc are less than or equal to the current threshold value Ith, the charge / discharge current Ic detected by the voltage detection circuit 15 is substantially zero within the period tcyc. It is determined that

  Note that the voltage threshold Vth and the current threshold Ith are, for example, a level obtained by adding some margin to the accuracy error of the voltage value and current value that can be detected by the voltage detection circuit 15, the current detection resistor 16, and the analog-digital converter 201. A voltage value and a current value are set. The period tcyc is set to a time such that a change in terminal voltage due to charging / discharging of the secondary battery can be observed, for example, a time of about 1 minute.

  Further, the determination of the direction of the charging / discharging current Ic during the period tcyc is not limited to an example in which only the current value detected for each period tcyc is performed, and the detected current value during the period tcyc is determined finely or constantly with the current threshold Ith. If the direction of charging / discharging is determined by comparison or the like, the determination accuracy of the charging / discharging direction is improved, and consequently the accuracy of failure detection is also improved.

  The failure determination unit 214 determines that a failure has occurred when any of the following conditions (1) to (4) is satisfied.

  Condition (1): When the charge / discharge current Ic detected by the current detection resistor 16 is maintained substantially zero during the period tcyc, it is detected by the voltage detection circuit 15 during the period tcyc. One of the terminal voltages V1, V2 and V3 increases.

  Condition (2): When the charge / discharge current Ic detected by the current detection resistor 16 indicates the charging direction (+) during the period tcyc, it is detected by the voltage detection circuit 15 during the period tcyc. One of the terminal voltages V1, V2, and V3 decreases.

  Condition (3): When the charge / discharge current Ic detected by the current detection resistor 16 indicates the discharge direction (−) during the period tcyc, it is detected by the voltage detection circuit 15 during the period tcyc. One of the terminal voltages V1, V2, V3 increases.

  Condition (4): the terminal voltage associated with the charge depth calculated by the remaining amount calculation unit 213 in the correspondence information stored in the correspondence information storage unit 215, and the terminal voltage V1 detected by the voltage detection circuit 15 , V2, or V3 exceeds a predetermined determination threshold value Vsth.

  Instead of the condition (4), the following condition (4) ′ may be used.

  Condition (4) ′: the charge depths associated with the terminal voltages V1, V2, and V3 detected by the voltage detection circuit 15 in the correspondence information stored in the correspondence information storage unit 215, and the remaining amount calculation unit 213 Any of the differences from the charging depth calculated by the above exceeds a preset determination threshold.

  As the determination threshold, for example, a value obtained by adding an error factor such as a calculation accuracy error of the charge amount by the remaining amount calculation unit 213 or an accuracy error of correspondence information and further adding a margin is used.

  In the charging device 3, a request from the control unit 202 is received by the communication unit 36 in the control IC 34, and the control unit 37 controls the charging current supply unit 35, and the voltage value according to the request from the control unit 202, The charging current is output from the charging current supply unit 35 at the current value. The charging current supply unit 35 is configured using a switching power supply circuit such as an AC-DC converter or a DC-DC converter, for example, and generates a charging voltage and a charging current instructed by the control unit 37 from, for example, a commercial AC power supply voltage. , And supplied to the battery pack 2 via the connection terminals 31, 11;

  Next, the operation of the charging system 1 configured as described above will be described. 2 and 3 are flowcharts showing an example of the operation of the charging system 1 shown in FIG. Here, the remaining amount calculation unit 213 performs a calculation process of the depth of charge (SOC) in parallel with steps S1 to S15 shown in FIGS. 2 and 3, and constantly updates the calculated value of the depth of charge (SOC). is doing. Further, the protection operation by the protection control unit 211 and the charge / discharge control by the charge control unit 212 are also performed in parallel with steps S1 to S15.

  First, the terminal voltages V1, V2, and V3 are detected by the voltage detection circuit 15, and the charge / discharge current Ic is detected by the current detection resistor 16 (step S1). Next, the terminal voltage V1 is substituted into the variable PV1, the terminal voltage V2 is substituted into the variable PV2, the terminal voltage V3 is substituted into the variable PV3, and the charge / discharge current Ic is substituted into the variable PIc and stored ( Step S2).

  When the period tcyc elapses from step S1 (YES in step S3), terminal voltages V1, V2, and V3 are newly detected by the voltage detection circuit 15, and the charge / discharge current Ic is detected by the current detection resistor 16. (Step S4).

  Then, the failure determination unit 214 compares the charge / discharge current Ic and the variable PIc with the current threshold Ith (step S5), respectively, and when both are larger than the current threshold Ith (YES in step S5), that is, charge / discharge in the cycle tcyc. If the current Ic is in the charging direction, the process proceeds to step S11. If at least one of the charge / discharge current Ic and the variable PIc is equal to or less than the current threshold Ith (NO in step S5), the process proceeds to step S6.

  In step S11, the failure determination unit 214 subtracts the terminal voltages V1, V2, and V3 from the variables PV1, PV2, and PV3, and compares the subtraction results with the voltage threshold value Vth (step S11). If any of the subtraction results is larger than the voltage threshold value Vth, that is, if any of the terminal voltages V1, V2, and V3 decreases during the period tcyc (YES in step S11), the condition (2) Therefore, the terminal voltage has dropped even though the secondary battery is charged. Therefore, any one of the voltage detection circuit 15, the current detection resistor 16, and the analog-digital converter 201 is selected by the failure determination unit 214. It is determined that a failure has occurred in this (step S15).

  On the other hand, if any of the subtraction results is equal to or lower than the voltage threshold Vth (NO in step S11), that is, if none of the terminal voltages V1, V2, and V3 has decreased, the process proceeds to step S13.

  Returning to FIG. 2, in step S6, the charge determination unit 214 compares the charge / discharge current Ic and the variable PIc with −Ith obtained by inverting the sign of the current threshold Ith, respectively, and when both are smaller than the current threshold Ith (in step S6). YES), that is, when the charge / discharge current Ic is in the discharge direction in the period tcyc, the process proceeds to step S12. On the other hand, when at least one of the charging / discharging current Ic and the variable PIc is greater than or equal to −Ith (NO in step S6), that is, the charging or discharging current is not stably, or the charging / discharging current is substantially zero. If possible, the process proceeds to step S7.

  In step S12, failure determination unit 214 subtracts variables PV1, PV2, and PV3 from terminal voltages V1, V2, and V3, respectively, and compares the subtraction results with voltage threshold value Vth (step S12). If any of the subtraction results is larger than the voltage threshold Vth, that is, if any of the terminal voltages V1, V2, and V3 increases during the period tcyc (YES in step S12), the condition (3) Therefore, the terminal voltage has risen despite the secondary battery being discharged. Therefore, a failure has occurred in any of the voltage detection circuit 15, the current detection resistor 16, and the analog-digital converter 201. (Step S15).

  On the other hand, when all the subtraction results are equal to or lower than the voltage threshold Vth, that is, when none of the terminal voltages V1, V2, and V3 is increased (NO in step S12), the process proceeds to step S13.

  In Step S7, the failure determination unit 214 compares the absolute values of the charge / discharge current Ic and the variable PIc with the current threshold Ith (Step S7), respectively, and when both are equal to or less than the current threshold Ith (YES in Step S7), that is, When it is considered that the charging / discharging current Ic is maintained substantially zero in the period tcyc, the process proceeds to step S8, and at least one of the absolute values of the charging / discharging current Ic and the variable PIc exceeds the current threshold value Ith. If so (NO in step S7), the process proceeds to step S13.

  In step S8, failure determination unit 214 subtracts variables PV1, PV2, and PV3 from terminal voltages V1, V2, and V3, respectively, and compares the subtraction results with voltage threshold value Vth (step S8). If any of the subtraction results is larger than the voltage threshold Vth, that is, if any of the terminal voltages V1, V2, and V3 increases during the period tcyc (YES in step S8), the condition (1) Therefore, the terminal voltage has risen even though the secondary battery is not charged / discharged. Therefore, a failure occurs in any of the voltage detection circuit 15, the current detection resistor 16, and the analog-digital converter 201. It is determined that it has occurred (step S9).

  On the other hand, when all the subtraction results are equal to or lower than the voltage threshold Vth, that is, when none of the terminal voltages V1, V2, and V3 is increased (NO in step S8), the process proceeds to step S13.

  In step S13, the failure determination unit 214 acquires, as Vsoc, the voltage associated with the charge depth calculated by the remaining amount calculation unit 213 in the correspondence relationship information stored in the correspondence relationship information storage unit 215 ( Step S13).

  Next, when the failure determination unit 214 calculates the absolute value of the difference between the voltage Vsoc and the terminal voltages V1, V2, and V3, and any one of the absolute values of the difference exceeds the determination threshold value Vsth (step S14). YES), the terminal voltage predicted from the charging depth calculated based on the charging / discharging current Ic detected by the current detection resistor 16 and the terminal voltages V1, V2, V3 detected by the voltage detection circuit 15 are predicted accuracy. Therefore, it is determined that a failure has occurred in any of the voltage detection circuit 15, the current detection resistor 16, and the analog-digital converter 201 (step S15).

  On the other hand, if the absolute value of the difference between the voltage Vsoc and the terminal voltages V1, V2, and V3 is all equal to or less than the determination threshold Vsth (NO in step S14), the charge / discharge current Ic detected by the current detection resistor 16 is used. Since the terminal voltage predicted from the calculated charging depth and the terminal voltages V1, V2, and V3 detected by the voltage detection circuit 15 are within the prediction accuracy range, the step is performed again without detecting a failure. The process proceeds to S2, and thereafter, the processes in steps S2 to S15 are repeated every cycle tcyc.

  As described above, the processing of steps S1 to S15 can detect a failure in the voltage detection unit and the current detection unit without separately providing the assembled voltage detection circuit.

  The present invention relates to a charging system used as a battery-mounted device for an electronic device such as a portable personal computer, a digital camera, or a mobile phone, a vehicle such as an electric vehicle or a hybrid car, and a battery used as a power source for these battery-mounted devices. It can be suitably used as a pack and a battery state detection circuit used in such a battery pack or charging system.

It is a block diagram which shows an example of a structure of the battery pack provided with the battery state detection circuit which concerns on one Embodiment of this invention, and a charging system. It is a flowchart which shows an example of operation | movement of the charging system shown in FIG. It is a flowchart which shows an example of operation | movement of the charging system shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Charging system 2 Battery pack 3 Charging device 4 Battery state detection circuit 14 Battery assembly 15 Voltage detection circuit 16 Current detection resistor 17 Temperature sensor 141, 142, 143 Secondary battery 201 Analog-digital converter 202 Control unit 211 Protection control unit 212 Charging Control unit 213 Remaining amount calculation unit 214 Failure determination unit 215 Correspondence relation information storage unit Ic Charge / discharge current Ith Current threshold V1, V2, V3 Terminal voltage Vsth determination threshold tcyc Period

Claims (10)

A voltage detector for detecting the terminal voltage of the secondary battery;
A current detector for detecting a charge / discharge current flowing in the secondary battery;
If the relationship between the terminal voltage detected by the voltage detection unit and the charge / discharge current detected by the current detection unit satisfies a preset condition to indicate that it is not a normal relationship, the voltage detection unit and A battery state detection circuit comprising: a failure determination unit that determines that at least one of the current detection units has failed. The conditions include
The terminal voltage detected by the voltage detection unit is increased when the charge / discharge current detected by the current detection unit is substantially zero. The battery state detection circuit as described. The conditions include
3. The terminal voltage detected by the voltage detector is lowered when the charge / discharge current detected by the current detector indicates a charging direction. 3. The battery state detection circuit as described. The conditions include
The terminal voltage detected by the said voltage detection part is included when the charging / discharging current detected by the said current detection part shows the discharge direction, It is contained. The battery state detection circuit according to any one of the above. Based on the charge / discharge current detected by the current detector, the secondary battery is charged from an integrated value obtained by cumulatively adding the charge amount and subtracting the discharge charge amount in the secondary battery. A remaining amount calculation unit for calculating the charged amount,
A storage unit that stores correspondence information indicating the correspondence between the charge amount of the secondary battery and the terminal voltage;
The conditions include
The difference between the terminal voltage associated with the charge amount calculated by the remaining amount calculation unit in the correspondence relationship information stored in the storage unit and the terminal voltage detected by the voltage detection unit is set in advance. The battery state detection circuit according to claim 1, wherein exceeding the determination threshold is included. Based on the charging / discharging current detected by the current detection unit, the charging of the secondary battery is performed from an integrated value obtained by cumulatively adding the charging charge amount and subtracting the discharging charge amount in the secondary battery. A remaining amount calculation unit for calculating the amount;
A storage unit that stores correspondence information indicating the correspondence between the charge amount of the secondary battery and the terminal voltage;
The conditions include
A difference between the charge amount associated with the terminal voltage detected by the voltage detection unit in the correspondence information stored in the storage unit and the charge amount calculated by the remaining amount calculation unit is set in advance. The battery state detection circuit according to claim 1, wherein exceeding the determination threshold is included. The terminal voltage in the correspondence information is an open circuit voltage of the secondary battery,
The failure determination unit
The terminal voltage detected by the voltage detection unit when the charge / discharge current detected by the current detection unit is substantially zero is used as the terminal voltage detected by the voltage detection unit under the conditions. The battery state detection circuit according to claim 5 or 6. The terminal voltage in the correspondence information is an open circuit voltage of the secondary battery,
The failure determination unit
As the terminal voltage detected by the voltage detection unit under the condition, a voltage value obtained by converting the terminal voltage detected by the voltage detection unit into an open circuit voltage based on the charge / discharge current detected by the current detection unit is used. The battery state detection circuit according to claim 5 or 6. The battery state detection circuit according to any one of claims 1 to 8,
A battery pack comprising the secondary battery. The battery state detection circuit according to any one of claims 1 to 8,
The secondary battery;
A charging unit for charging the secondary battery;
A charging system comprising: a control unit that controls an operation of the charging unit based on a terminal voltage detected by the voltage detection unit and a charging / discharging current detected by the current detection unit.

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