JP2010019805A - Detection current correction circuit and battery pack using it - Google Patents

Abstract

A detection current correction circuit capable of correcting a current measurement offset deviation and improving detection accuracy of a current flowing in a secondary battery, and a battery pack using the detection current correction circuit.
A control unit 105 that operates with an operating power supply current from a secondary battery B11, a first current path L1 that passes through a current sensor 104, a first switching element Q13 that opens and closes the first current path L1, The control unit 105 includes a second current path L2 that does not pass through the current sensor 104 and a second switching element Q14 that opens and closes the second current path L2. The control unit 105 turns off the first switching element Q13 and turns on the second switching element Q14. When detecting the offset current acquisition unit 110 that acquires the offset current value detected by the current sensor 104 and the current flowing through the secondary battery B11, the first switching element Q13 is turned on and the second switching element Q14 is turned on. I tried to turn it off.
[Selection] Figure 1

Description

  The present invention relates to a detection current correction circuit that detects a current flowing in a secondary battery, and a battery pack using the detection current correction circuit.

  In a rechargeable battery pack having a rechargeable secondary battery, it is necessary to prevent overcharge and overdischarge of the secondary battery in order to control the battery pack safely. For this purpose, it is necessary to accurately know the state of charge (SOC) of the battery pack. Therefore, a method for estimating the state of charge of the battery pack by measuring the charge / discharge current of the secondary battery and integrating the amount of charge / discharge current of the battery pack is generally known.

  However, the circuit for measuring the charge / discharge current has a problem that the output characteristic is deviated due to temperature characteristics and deterioration with time, and an error occurs in the detected charge / discharge current value. And when the error of a charging / discharging electric current value arises, the estimation precision of SOC will also fall.

Therefore, as a method of correcting the deviation of the output characteristics of the circuit that measures the charge / discharge current, the current value detected by the current detection circuit when the current is supplied to the load whose current consumption is known in advance, A method is known in which a correction value is calculated from the difference from the current consumption amount of the load acquired in step (b) and the offset of the current detection circuit is corrected (see, for example, Patent Document 1).
JP 2002-238181 A

  However, the technique disclosed in Patent Document 1 has a disadvantage in that the current sensor offset cannot be corrected correctly when the current consumption of the load changes due to temperature characteristics or deterioration over time.

  The present invention has been made in view of such circumstances, and in a circuit having a rechargeable secondary battery, the offset of current measurement due to temperature characteristics and circuit deterioration is corrected and flows to the secondary battery. An object of the present invention is to provide a detection current correction circuit capable of improving current detection accuracy, and a battery pack using the detection current correction circuit.

  A detection current correction circuit according to the present invention is connected in series with a secondary battery, detects a current flowing through the secondary battery, a charging circuit for charging the secondary battery, and the secondary battery A connection terminal for connecting a series circuit of the secondary battery and a current detection unit to at least one of the load circuits that receive the discharge current of the battery, and a current supplied from the secondary battery for operating power. A control unit that operates by using as a current, a first current path that guides a current supplied from the secondary battery via the current detection unit to the control unit as the operation power supply current, and the first current A first switching element that opens and closes a path; and a second current path that guides the current supplied from the secondary battery as the operation power supply current to the control unit without passing through the current detection unit. The second current A second switching element that opens and closes a path, and the control unit turns off the first switching element and obtains an offset current value detected by the current detection unit when the second switching element is turned on. When the current flowing through the secondary battery is detected by the current detection unit and the offset current acquisition unit, the current detection unit turns on the first switching element and turns off the second switching element. A current correction unit that corrects the detected current value detected based on the offset current value acquired by the offset current acquisition unit.

  According to this configuration, the offset current acquisition unit cuts off the first current path by turning off the first switching element and turning on the second switching element, and operates the control unit via the second current path. The current value detected by the current detection unit is acquired as the offset current value in a state where the power supply current is supplied. Then, since the operation power supply current is supplied to the control unit without going through the current detection unit, the operation power supply current of the control unit is determined from the current value detected by the current detection unit while maintaining the operation of the control unit. As a result, the accuracy of the offset current value acquired by the offset current acquisition unit is improved.

  And when the current flowing through the secondary battery is detected by the current detection unit, the current correction unit cuts off the second current path by turning on the first switching element and turning off the second switching element, The operation power supply current of the control unit is supplied through the first current path. Then, since the operating power supply current is supplied to the control unit via the current detection unit, the detected current value detected by the current detection unit includes the operation power supply current of the control unit. This improves the accuracy of detection of the current flowing in the secondary battery. Furthermore, since the detected current value detected by the current detection unit in this way is corrected by the current correction unit based on the offset current value acquired by the offset current acquisition unit, the current due to temperature characteristics and circuit deterioration The offset deviation of the detection unit can be corrected, and the detection accuracy of the current flowing through the secondary battery can be improved.

  A first opening / closing unit that opens and closes a main current path from the secondary battery to the connection terminal; and the offset current acquisition unit further includes the first opening / closing unit when acquiring the offset current value. It is preferable to turn it off.

  According to this configuration, when the offset current acquisition unit acquires the offset current value, the first open / close unit is turned off to cut off the main current path, so that the secondary battery charged / discharged via the connection terminal Ensure that the current is zero. As a result, the certainty that the current flowing through the secondary battery becomes zero is improved, so that the detection accuracy of the offset current value is improved.

  In addition, a third current path for guiding the operating power supply current supplied from the secondary battery to the control unit and the third current path are set, and the voltage of the third current path is preset. And a one-shot switch unit that cuts off the third current path after conducting the third current path for a preset set time when the set voltage is exceeded, and the control unit receives supply of the operating power supply current. It is preferable to further include an activation processing unit that turns on at least one of the first and second switching elements within the set time when activated.

  If there is no third current path, the first and second current paths are interrupted because the first and second switching elements cannot be turned on when the control unit is not supplied with power and is stopped. There is a possibility that the control unit cannot be activated without the operation power supply current being supplied to the control unit.

  However, according to this configuration, even when the first and second current paths are interrupted and the control unit is stopped, for example, a secondary battery is attached to the detection current correction circuit, or the secondary battery is charged. When the output voltage of the secondary battery is applied to the one-shot switch unit, for example, by supplying the output voltage of the secondary battery to the third current path with a switch, the one-shot switch unit sets the third current path for the set time. Conduct. Then, the operation power supply current is supplied from the secondary battery via the third current path, and the control unit is activated. When the control unit is activated, at least one of the first and second switching elements is activated by the activation processing unit within a set time, that is, within a period in which the operation power supply current is supplied via the third current path. Turned on.

  Then, since the operating power supply current is supplied from the secondary battery to the control unit via at least one of the first and second current paths, the third current path is interrupted by the one-shot switch unit after the set time has elapsed. Even so, the control unit, that is, each unit included in the control unit is maintained in an operable state. Then, after the third current path is interrupted by the one-shot switch unit, the offset current value is acquired by the offset current acquisition unit, so that the offset current value is supplied to the control unit via the third current path. As a result, the accuracy of the offset current value is improved.

  And a protection circuit capable of interrupting the main current path when the current flowing in the main current path from the secondary battery to the connection terminal exceeds a preset current threshold, and returning to the conductive state. It is preferable that the third current path guides an operation power supply current supplied from the secondary battery to the control unit via the protection circuit.

  For example, when an overcurrent flows through the main current path and the protection circuit is activated, the first and second switching elements may be turned off by stopping the power supply to the control unit due to, for example, maintenance or the like. . In such a case, according to this configuration, for example, the overcurrent is resolved and the protection circuit is restored, the maintenance is completed and the maintenance operator performs the restoration operation of the protection circuit, or the protection circuit is used as a start switch. When the protection circuit is turned on by turning it on or the like, the control unit can be activated by the one-shot switch unit.

  In addition, it is preferable that a fourth current path for guiding an operation power supply current from the connection terminal to the control unit is further provided.

  According to this configuration, when the secondary battery cannot supply the operation power supply current for the control unit and the control unit cannot be activated, the secondary battery is deeply discharged and cannot be activated by the one-shot switch unit. By supplying the operation power supply current to the control unit via the connection terminal and the fourth current path, the control unit can be activated.

  Further, the current correction unit subtracts the offset current value from the current value detected by the current detection unit when turning on the first switching element and turning off the second switching element, It is preferable to correct the detection current value of the current detection unit.

  According to this configuration, the current correction unit can correct the detection current value of the current detection unit by subtracting the offset current value from the current value detected by the current detection unit. For example, the current detection unit may include offset correction means such as a variable resistance mechanism and a gain adjustment mechanism, and the current correction unit may adjust the current detection unit based on the offset current value. If the offset current value is subtracted and corrected from the current value detected by the unit, it is easy to simplify the configuration of the current detection unit.

  The first opening / closing section preferably includes a discharging FET and a charging FET.

  According to this configuration, it is possible to individually control the discharge and the charge of the secondary battery using an FET (Field Effect Transistor) having a low on-resistance.

  The battery pack according to the present invention includes the above-described detection current correction circuit and the secondary battery.

  According to this configuration, in the battery pack, the offset deviation of the current detection unit due to temperature characteristics and circuit deterioration can be corrected, and the detection accuracy of the current flowing through the secondary battery can be improved.

  The connection terminal further includes a connection detection unit that detects whether one of the charging circuit and the load circuit is connected to the connection terminal, and the offset current acquisition unit is configured to detect the connection terminal by the connection detection unit. An offset current value detected by the current detector by turning off the first switching element and turning on the second switching element when no connection between the charging circuit and the load circuit is detected. It is preferable to obtain

  According to this configuration, the offset current acquisition unit detects the current of the secondary battery that is charged / discharged via the connection terminal when the connection detection unit does not detect any connection of the charging circuit and the load circuit to the connection terminal. The offset current value is obtained when is surely zero. As a result, the certainty of obtaining the offset current value when the current flowing through the secondary battery is zero is improved, and the detection accuracy of the offset current value is improved.

  The detection current correction circuit and the battery pack having such a configuration acquire the offset current value of the current detection unit in a state where the operation power supply current of the control unit does not flow through the current detection unit, and detect based on the offset current value Since the current value is corrected, the offset deviation of the current detection unit due to temperature characteristics and circuit deterioration can be corrected, and the detection accuracy of the current flowing through the secondary battery can be improved.

  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 detection current correction circuit according to an embodiment of the present invention.

  The battery pack 100 shown in FIG. 1 includes connection terminals 101 and 102, a breaker 103 (protection circuit), a current sensor 104 (current detection unit), a control unit 105, a power supply unit 106, a one-shot switch circuit unit 107, a switching element Q11, Q12 (first opening / closing part), a first switching element Q13, a second switching element Q14, diodes D11, D12, D13, D14, and a secondary battery B11 are included.

  In this case, the circuit unit other than the secondary battery B11 in the battery pack 100 corresponds to an example of a detection current correction circuit. The detection current correction circuit is not limited to the example built in the battery pack. For example, the detection current correction circuit is used in various battery-driven devices such as portable personal computers, digital cameras, mobile phones, electric cars, hybrid cars, etc., and power supply systems that level the load of the power generation device with secondary batteries. May be.

  Further, the detection current correction circuit may be incorporated in a charging device such as a power generation device that charges the secondary battery. The charging device may be a solar power generation device, a wind power generation device, a power regeneration device in an electric vehicle, or the like.

  The connection terminal 101 is a positive terminal of the battery pack, and the connection terminal 102 is a negative terminal of the battery pack. The connection terminals 101 and 102 only need to electrically connect the battery pack 100 and a charging device (not shown), or the battery pack 100 and a load device (not shown). For example, the connection terminals 101 and 102 include electrodes, connectors, terminal blocks, and the like. Is done. Further, the connection terminals 101 and 102 may be a wiring pattern such as a land or a pad when the detection current correction circuit is built in a battery-driven device or a charging device.

  The connection terminal 101 is connected to the positive electrode of the secondary battery B11 via a switching element Q11 for charge control, a switching element Q12 for discharge, a breaker 103, and a current sensor 104. For example, FETs (Field Effect Transistors) are used as the switching elements Q11 and Q12. The switching element Q11 has a parasitic diode cathode in the direction of the connection terminal 101. In the switching element Q12, the cathode of the parasitic diode is directed to the breaker 103.

  The connection terminal 102 is connected to the negative electrode of the secondary battery B11. The connection terminal 102 is connected from the connection terminal 101 to the connection terminal 102 via the switching elements Q11 and Q12, the breaker 103, the current sensor 104, and the secondary battery B11. A current path Lm is configured.

  The current sensor 104 is a current detection circuit that detects a current value Ib of a current flowing through the secondary battery B11. For example, the current sensor 104 represents the current in the direction of charging the secondary battery B11 as a positive current value Ib and the current in the direction of discharge of the secondary battery B11 as a negative current value Ib, and transmits the current to the control unit 105. It has become.

  The current sensor 104 includes, for example, a shunt resistor and a current transformer provided in the main current path Lm, and an analog value that converts the current value Ib converted into an analog voltage into a digital value and outputs the digital value to the control unit 105. It consists of a digital converter and the like. The analog / digital converter may be built in the control unit 105.

  Here, for example, the resistance value of the shunt resistor changes due to the influence of the temperature, or the detection current value fluctuates due to the influence of the temperature characteristics of the current transformer or the analog-digital converter, the accuracy variation thereof, or the like. The accuracy of the current value Ib detected at 1 may decrease.

  A connection point P1 between the breaker 103 and the current sensor 104 is connected to the power supply unit 106 via the first switching element Q13 and the diode D13. In this case, the current path from the connection point P1 to the power supply unit 106 via the first switching element Q13 and the diode D13 corresponds to the first current path L1.

  The breaker 103 is a circuit breaker including a handle that can be operated by a user, for example. The breaker 103 shuts off the main current path Lm when an overcurrent flows through the main current path Lm and exceeds a preset current threshold, and the user operates the handle to bring the main current path Lm into a conductive state. It comes to return. Moreover, the breaker 103 may be used as a start switch.

  The breaker 103 may be configured using a protective element such as a PTC (Positive Temperature Coefficient) or a bimetal switch. Then, when an overcurrent flows through the main current path Lm and exceeds a preset current threshold, the breaker 103 is turned off by self-heating to cut off the main current path Lm and protect the secondary battery B11 from the overcurrent. It may be a thing. Such a breaker 103 is turned on again when the current stops flowing and the temperature is lowered, so that the main current path Lm is returned to the conductive state.

  A connection point P2 between the secondary battery B11 and the current sensor 104 is connected to the power supply unit 106 via the second switching element Q14 and the diode D14. In this case, the current path from the connection point P2 to the power supply unit 106 via the second switching element Q14 and the diode D14 corresponds to the second current path L2. The first switching element Q13 and the second switching element Q14 are configured using, for example, FETs.

  Note that the switching elements Q11, Q12, the first switching element Q13, and the second switching element Q14 may be N-channel MOSFETs, P-channel MOSFETs, or other switching elements, Since the FET has a small on-resistance, the FET is suitable as the switching elements Q11 and Q12, the first switching element Q13, and the second switching element Q14.

  A connection point P3 between the breaker 103 and the switching element Q12 is connected to the power supply unit 106 via the one-shot switch circuit unit 107 and the diode D12. In this case, the current path from the connection point P3 to the power supply section 106 via the one-shot switch circuit section 107 and the diode D12 corresponds to the third current path L3.

  When the voltage of the third current path L3 exceeds a preset set voltage, the one-shot switch circuit unit 107 cuts off the third current path L3 after conducting the preset current for a preset time. The one-shot switch circuit unit 107 only needs to be conductive for a certain period of time. For example, the one-shot switch circuit unit 107 may be configured using a timer circuit or a switching element, or may have other circuit configurations.

  Further, the breaker 103 may not be provided. Then, a mechanical one-shot switch (push button switch) may be used as the one-shot switch circuit unit 107, and the third current path L3 may be conducted only while the user is pressing this switch. Further, the third current path L3 may be connected not to the connection point P3 but to the connection point P1 or the connection point P2.

  The connection terminal 101 is connected to the power supply unit 106 via the diode D11. In this case, the current path from the connection terminal 101 to the power supply unit 106 via the diode D11 corresponds to the fourth current path L4.

  The secondary battery B11 is an assembled battery in which a plurality of unit cells such as a lithium ion secondary battery, a nickel hydride secondary battery, and a lead storage battery are connected in series. Note that the secondary battery B11 is not limited to those in which unit cells are connected in series, and may be, for example, an assembled battery in which a plurality of unit cells are connected in parallel or a combination of series and parallel. Further, the secondary battery B11 may be a unit cell.

  The power supply unit 106 is a power supply circuit configured using, for example, a DC-DC converter, a switching regulator, or the like. The power supply unit 106 is connected to the connection terminals 101 and 102 via at least one of the first current path L1, the second current path L2, the third current path L3, and the fourth current path L4. An operation power supply voltage suitable for the operation of the control unit 105 is generated from the operation charging current supplied from the charging circuit (not shown), the secondary battery B11, or the like, and supplied to the control unit 105. In this case, the power supply unit 106 and the control unit 105 constitute an example of a control unit according to the claims.

  Note that the power supply unit 106 may not be provided as long as the control unit 105 can be directly operated by the output voltage of the secondary battery B11 or an external power supply voltage such as a charging device connected to the connection terminals 101 and 102.

  The switching elements Q11, Q12, the first switching element Q13, and the second switching element Q14 have gates connected to the control unit 105, and are turned on and off according to a control signal from the control unit 105. Yes.

  The control unit 105 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 these peripheral circuits and the like. Then, the control unit 105 executes a control program stored in the ROM, thereby performing an offset current acquisition unit 110, a current correction unit 111, a current integration unit 112, an SOC calculation unit 113, a charge / discharge control unit 114, and a startup process. It functions as the unit 115.

  The offset current acquisition unit 110 turns off the switching elements Q11 and Q12, turns on the second switching element Q14, turns off the first switching element Q13, and sets the current value detected by the current sensor 104 as the offset current value Iof. Acquired and stored in, for example, RAM.

  When the current sensor 104 detects the current value Ib flowing through the secondary battery by the current sensor 104, the current correction unit 111 turns on the first switching element Q13 and turns off the second switching element Q14. Furthermore, the current correction unit 111 obtains the current value Ib detected by the current sensor 104 constantly or periodically, and subtracts the offset current value Iof stored in the RAM from the current value Ib. The calculation of the correction current value Ix is repeated.

  The current integrating unit 112 calculates the integrated charge amount Q charged in the secondary battery B11 by continuously integrating the corrected current value Ix calculated by the current correcting unit 111, for example, every unit time. .

  The SOC calculation unit 113 calculates the SOC of the secondary battery B11 by, for example, calculating the ratio of the accumulated charge amount Q to the full charge capacity of the secondary battery B11, and stores it in the RAM.

  When the SOC calculated by the SOC calculation unit 113 reaches, for example, 100% or more, the charge / discharge control unit 114 turns off the switching element Q11 to prohibit charging of the secondary battery B11 and prevent overcharging. In addition, when the SOC calculated by the SOC calculation unit 113 becomes 0% or less, for example, the charge / discharge control unit 114 turns off the switching element Q12 to prohibit the discharge of the secondary battery B11 and prevent overdischarge. Thereby, the occurrence of overcharge and overdischarge of the secondary battery B11 is prevented, and the safety is improved.

  The activation processing unit 115 receives at least one of the first switching element Q13 and the second switching element Q14 within the set time when the control unit 105 is activated upon receiving the operation power supply voltage from the power supply unit 106. Turn on.

  Next, the operation of the battery pack 100 shown in FIG. 1 will be described. FIG. 2 is a flowchart for explaining a starting method 1 which is an example of a starting method when starting battery pack 100 shown in FIG. For example, when nothing is connected to the battery pack 100 or a load device that does not have a charging function of the battery pack 100 is connected, the control unit 105 operates with the power supplied from the secondary battery B11. Will do.

  Here, for example, when the control unit 105 is stopped, the first switching element Q13 and the second switching element Q14 are turned off, and the breaker 103 is cut off, the secondary battery B11 supplies the power supply unit. Since power is not supplied to 106, the power supply voltage for operation of the control unit 105 is not supplied, and thus the control unit 105 remains in a stopped state.

  The operation of starting the control unit 105 from this state will be described with reference to FIG. First, for example, when the user operates the handle of the breaker 103 to turn on the breaker 103 (step S1), the output voltage of the secondary battery B11 is applied to the one-shot switch circuit unit 107 via the current sensor 104 and the breaker 103. Is done.

  When the voltage applied to the one-shot switch circuit unit 107 exceeds a preset set voltage, the one-shot switch circuit unit 107 conducts for a preset set time, and the one-shot switch from the secondary battery B11. A current is supplied to the power supply unit 106 via the circuit unit 107 and the diode D12 (step S2).

  Then, the power supply unit 106 supplies the operation power supply voltage to the control unit 105 during the set time, and the control unit 105 is activated (step S3). In this case, if the third current path L3 including the one-shot switch circuit unit 107 is not provided, the first switching element Q13 and the second switching element Q14 cannot be turned on. Will not be able to start up the control unit 105.

  However, the battery pack 100 illustrated in FIG. 1 includes the third current path L3 including the one-shot switch circuit unit 107, so that the control unit 105 can be activated by the activation method 1.

  When the control unit 105 is activated, the first switching element Q13 is turned on by the activation processing unit 115 during the set time during which the one-shot switch circuit unit 107 is on (step S4). Then, since the output current of the secondary battery B11 is supplied to the power supply unit 106 via the current sensor 104, the first switching element Q13, and the diode D13, the one-shot switch circuit unit after the set time elapses thereafter. Even when the switch 107 is turned off, the output current of the secondary battery B11 is supplied to the power supply unit 106 via the first switching element Q13 and the diode D13. As a result, the control unit 105 is maintained in the operating state.

  In step S4, the activation processing unit 115 may turn on the second switching element Q14 instead of the first switching element Q13, and turn on the first switching element Q13 and the second switching element Q14. Also good.

  When the control unit 105 is activated, the charge / discharge control unit 114 determines that the SOC calculated by the SOC calculation unit 113 is less than 100%, for example, or the secondary battery B11 from the terminal voltage of the secondary battery B11. When it is determined that the battery pack 100 can still be charged, the switching element Q11 is turned on, and the secondary battery B11 can be charged by the unillustrated charging device connected to the connection terminals 101 and 102.

  Further, the charge / discharge control unit 114 can still discharge the secondary battery B11 and the battery pack 100 when the SOC calculated by the SOC calculation unit 113 exceeds 0%, for example, or from the terminal voltage of the secondary battery B11, etc. When it is determined that the switching element Q12 is turned on, the discharge current from the secondary battery B11 can be supplied to the load device (not shown) connected to the connection terminals 101 and 102.

  FIG. 3 is a flowchart for explaining a startup method 2 which is another example of the startup method of battery pack 100 shown in FIG. 1. When the secondary battery B11 has reached such a deep discharge that the operation power of the control unit 105 cannot be supplied, the secondary battery B11 turns on the one-shot switch circuit unit 107 in the startup method 1 shown in FIG. Even if the one-shot switch circuit unit 107 is turned on, the secondary battery B11 cannot supply the power necessary for operating the control unit 105 to the power source unit 106 even if the one-shot switch circuit unit 107 is turned on. Can not start.

  3, for example, the user operates the handle of the breaker 103 to turn on the breaker 103 (step S11), and connects an external power source such as a generator or a charging device to the connection terminals 101 and 102. (Step S12). Then, electric power is supplied from the external power supply to the power supply unit 106 via the diode D11 (step S13). Further, the power supply unit 106 supplies the power supply voltage for operation of the control unit 105, and the control unit 105 is activated (step S14).

  When the control unit 105 is activated, the charge / discharge control unit 114 confirms that there is no abnormality in the secondary battery B11 and the battery pack 100 from the terminal voltage, temperature, SOC, and the like of the secondary battery B11. The secondary battery B11 is determined to be chargeable / dischargeable, the switching elements Q11, Q12 are turned on, and power from an unillustrated external power source connected to the connection terminals 101, 102 is charged to the secondary battery B11 (step S15). ).

  FIG. 4 is a flowchart illustrating an example of the offset correction operation of the current sensor 104 by the offset current acquisition unit 110 and the current correction unit 111 illustrated in FIG. First, for example, in the state where the control unit 105 is activated by the activation method shown in FIG. 2 or FIG. 3, the offset current acquisition unit 110 turns off the switching elements Q11 and Q12 and turns on the second switching element Q14. Turn on (step S21).

  Thereby, switching elements Q11 and Q12 are turned off, and charging / discharging via connection terminals 101 and 102 of secondary battery B11 is prohibited. Then, the current flowing through the current sensor 104 is only the operating power supply current of the control unit 105 flowing from the secondary battery B11 to the power supply unit 106 via the current sensor 104, the first switching element Q13, and the diode D13.

  Next, the offset current acquisition unit 110 turns off the first switching element Q13 and interrupts the current supplied to the power supply unit 106 via the first current path L1 (step S22). At this time, since the second switching element Q14 is already turned on, the operation power supply current of the control unit 105 is supplied from the secondary battery B11 to the power supply unit 106 via the second current path L2. Even if the switching element Q13 is turned off, the operation of the control unit 105 is maintained.

  Since the current flowing through the second current path L2 to the power supply unit 106 does not pass through the current sensor 104, the current flowing through the current sensor 104 becomes zero. At this time, if there is no error in the detected current value of the current sensor 104, the detected current value of the current sensor 104 should also be zero. On the other hand, if the detected current value of the current sensor 104 is not zero, the detected current value indicates an error of the current sensor 104, that is, an offset current value.

  Therefore, the offset current acquisition unit 110 acquires the detected current value of the current sensor 104 at this time as the offset current value Iof (step S23). As a result, the offset current acquisition unit 110 can accurately detect an error in the detected current value due to the temperature characteristics of the current sensor 104 and the influence of aging degradation, so-called offset deviation, as the offset current value.

  Next, the current correction unit 111 turns on the first switching element Q13 so that power can be supplied again to the power supply unit 106 via the first current path L1 (step S24). Thereafter, the current correction unit 111 turns off the second switching element Q14 (step S25), and stops the power supply to the power supply unit 106 via the second current path L2.

  Through the processing in steps S24 and S25, the operation power supply current of the control unit 105 supplied to the power supply unit 106 is all detected by the current sensor 104. Therefore, since the current sensor 104 detects the charging / discharging current of the secondary battery B11 including the power supply current for operation of the control unit 105, the charging / discharging current value Ib of the secondary battery B11 by the current sensor 104 is detected. Detection accuracy is improved.

  Thereafter, the current correction unit 111 obtains the current value Ib detected by the current sensor 104 constantly or periodically, and subtracts the offset current value Iof from the current value Ib to calculate the correction current value Ix. Repeat (step S26). Then, the current integrating unit 112 calculates the integrated charge amount Q charged in the secondary battery B11 by continuously integrating the correction current value Ix obtained in this way, and the SOC calculating unit 113 Since the SOC of the secondary battery B11 is calculated from the accumulated charge amount Q, the SOC calculation accuracy is improved.

  Furthermore, when the calculation accuracy of the SOC is improved, the accuracy of the charge / discharge control of the secondary battery B11 based on the SOC by the charge / discharge control unit 114 is improved. As a result, the safety of the battery pack 100 is improved.

  Note that the battery pack 100 may further include, for example, a connection detection unit that detects whether or not a device including a charging circuit or a load circuit is connected to the connection terminals 101 and 102. Then, instead of turning off the switching elements Q11 and Q12 in step S21, the offset current acquisition unit 110 switches the second switching element when the connection detection unit does not detect the connection of the device to the connection terminals 101 and 102. After turning on, steps S22 to S25 may be executed.

  The connection detection unit may be a switch that is mechanically pressed when a device including a charging circuit or a load circuit is attached to the connection terminals 101 and 102, for example. It may be a communication circuit that detects that the device is connected by communicating with the device when it is attached to the device 102, and the device is connected to the connection terminals 101 and 102 by other methods. May be detected.

  Further, the offset current acquisition unit 110, for example, after detecting that the secondary battery B11 is fully charged, turns on the second switching element at the timing when the charging current is zeroed by the charging device, Steps S22 to S25 may be executed.

  A detection current correction circuit and a battery pack according to the present invention are a combination of a portable personal computer, a digital camera, an electronic device such as a mobile phone, a vehicle such as an electric vehicle or a hybrid car, a solar cell or a power generation device, and a secondary battery. It can be suitably used in battery-mounted devices and systems such as a power supply system.

It is a block diagram which shows an example of a structure of the battery pack provided with the detection current correction circuit which concerns on one Embodiment of this invention. It is a flowchart for demonstrating an example of the starting method at the time of starting the battery pack shown in FIG. 6 is a flowchart for explaining another example of a method for starting the battery pack shown in FIG. 1. It is a flowchart which shows an example of the offset correction operation | movement of the current sensor by the current correction part shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Battery pack 101,102 Connection terminal 103 Breaker 104 Current sensor 105 Control part 106 Power supply part 107 One shot switch circuit part 111 Current correction part 112 Current integration part 113 SOC calculation part 114 Charge / discharge control part B11 Secondary battery D11, D12, D13, D14 Diode Ib Current value Iof Offset current value Ix Correction current value L1 First current path L2 Second current path L3 Third current path L4 Fourth current path Lm Main current path Q11, Q12 Switching element Q13 First switching element Q14 Second switching element

Claims (9)

A current detection unit that is connected in series with the secondary battery and detects a current flowing through the secondary battery;
A connection terminal for connecting a series circuit of the secondary battery and a current detection unit to at least one of a charging circuit for charging the secondary battery and a load circuit receiving supply of a discharge current of the secondary battery When,
A control unit that operates by using the current supplied from the secondary battery as an operation power supply current;
A first current path for guiding current supplied from the secondary battery via the current detection unit to the control unit as the operation power supply current;
A first switching element that opens and closes the first current path;
A second current path that leads the current supplied from the secondary battery as the operation power supply current to the control unit without passing through the current detection unit;
A second switching element for opening and closing the second current path,
The controller is
An offset current acquisition unit that acquires an offset current value detected by the current detection unit when turning off the first switching element and turning on the second switching element;
When the current flowing through the secondary battery is detected by the current detection unit, the detected current value detected by the current detection unit is turned on while the first switching element is turned on and the second switching element is turned off. A detection current correction circuit comprising: a current correction unit configured to perform correction based on the offset current value acquired by the offset current acquisition unit. A first opening / closing part for opening / closing a main current path from the secondary battery to the connection terminal;
The offset current acquisition unit
The detection current correction circuit according to claim 1, wherein when the offset current value is acquired, the first opening / closing unit is further turned off. A third current path for guiding an operation power supply current supplied from the secondary battery to the control unit;
When the voltage of the third current path exceeds a preset setting voltage, the third current path is turned on after being set for a preset time when the voltage of the third current path exceeds the preset setting voltage. And a one-shot switch unit
The controller is
The power supply device further comprises a start processing unit that turns on at least one of the first and second switching elements within the set time when the power supply is started upon receiving the operation power supply current. 3. The detection current correction circuit according to 1 or 2. When the current flowing in the main current path from the secondary battery to the connection terminal exceeds a preset current threshold, the main current path is interrupted, and further includes a protection circuit capable of returning to the conductive state.
The third current path is
The detection current correction circuit according to claim 3, wherein an operation power supply current supplied from the secondary battery is guided to the control unit via the protection circuit. The detection current correction circuit according to claim 1, further comprising a fourth current path that guides an operation power supply current from the connection terminal to the control unit. The current correction unit is
By detecting the offset current value from the current value detected by the current detection unit when the first switching element is turned on and the second switching element is turned off, the detected current value of the current detection unit The detection current correction circuit according to claim 1, wherein the correction is performed. The first opening / closing part includes
The detection current correction circuit according to claim 2, further comprising: a discharge FET and a charge FET. The detection current correction circuit according to any one of claims 1 to 7,
A battery pack comprising the secondary battery. The connection terminal further includes a connection detection unit that detects whether one of the charging circuit and the load circuit is connected,
The offset current acquisition unit
By turning off the first switching element and turning on the second switching element when the connection detector does not detect any connection of the charging circuit and the load circuit to the connection terminal, The battery pack according to claim 8, wherein an offset current value detected by the detection unit is acquired.

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