JP2007014091A - Charge control circuit for secondary battery and battery pack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten charge time and restrain wasteful power consumption by eliminating trickle charge for checking whether voltage restoration is possible or not. <P>SOLUTION: This circuit is composed of: a voltage detection section 34 which detects voltages of respective voltage cells 28, 30, 32 of a secondary battery 16; a charge control switch 36 which turns on/off the charge circuit through which the charge current is supplied to the respective voltage cells 28, 30, 32; a voltage determination section 44 which determines whether the voltages of the respective voltage cells 28, 30, 32 satisfy their reference values or not; and a switch control section 48 which switches on the charge control switch 36 when it is determined that the voltages of the respective voltage cells 28, 30, 32 satisfy the reference values by the voltage determination section 44 and switches off the charge control switch 36 when it is determined that a voltage of at least one of the respective voltage cells 28, 30, 32 does not satisfy the reference value. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a charge control circuit that controls charging of a secondary battery and a battery pack including the charge control circuit.

  In recent years, battery packs have been widely used as power sources for driving various devices such as mobile phones, digital cameras, electric tools, and robots. This battery pack is a rechargeable battery composed of a plurality of battery cells such as lithium ion secondary batteries connected in series. Even if the voltage of each battery cell becomes too low, the battery is simply left for a long time. The secondary battery in a chargeable state can be charged. However, when the voltage of each battery cell falls below a certain voltage and the battery becomes incapable of charging, the battery case constituting the battery cell is melted to open a hole and lead to leakage, or used as a current collector for the negative electrode plate. In some cases, the copper foil is eluted in the form of copper ions in the non-aqueous electrolyte, and is deposited on the negative electrode plate in the form of needle crystals by charging, resulting in a minute short circuit with the positive electrode plate.

  Even if the secondary battery is in a state where it cannot be charged, even if it is charged, the charging energy is consumed in a very short-circuited state. If it is charged, it may lead to an unsafe state.

As described above, since the charging state varies depending on the state of the secondary battery, there is a possibility of voltage recovery by performing trickle charging at a charging current lower than the normal charging current first when performing charging. If it is in a chargeable state where there is a possibility of voltage recovery, it will be switched to rapid charging so that it can be charged in a short time, while it is in a state where charging is impossible without a possibility of voltage recovery Has proposed a charge control circuit that interrupts the charging circuit (for example, Patent Documents 1 and 2).
JP-A-8-140281 Japanese Patent Laid-Open No. 11-262197

  However, according to the charge control circuit, although the voltage of the secondary battery in the chargeable state is restored by charging, the time for performing trickle charging is required, so the charging time is shortened. If the battery is in a non-chargeable state with no potential for voltage recovery, it will not only consume unnecessary power by trickle charging, but it will also become unsafe if the battery is charged in a short-circuited state. There is a problem that it may occur and a case where a large load is applied to the charging device may occur.

  The present invention has been made in view of such circumstances, and enables charging of a secondary battery in a chargeable state and prohibits charging of a secondary battery in an unchargeable state. An object of the present invention is to provide a charging control circuit and a battery pack for a secondary battery that can shorten the charging time, suppress unnecessary power consumption, and avoid an unsafe state.

  In order to achieve the above object, the invention of claim 1 is a charge control circuit for controlling charging of a secondary battery, wherein the voltage detection unit detects the voltage of a battery cell constituting the secondary battery, and the battery A charging control switch for turning on and off a charging circuit to which a charging current is supplied to the cell; a voltage determining unit for determining whether or not a voltage of the battery cell satisfies a reference value; and Switch control that turns on the charge control switch when it is determined that the voltage meets a reference value, and turns off the charge control switch when it is determined that the voltage of the battery cell does not meet the reference value It is characterized by having a part.

  According to a second aspect of the present invention, in the first aspect, the secondary battery is configured by connecting a plurality of battery cells in series, and the voltage detection unit detects a voltage of each battery cell. The voltage determination unit determines whether or not the voltage of each battery cell satisfies a reference value, and the switch control unit determines that the voltage of each battery cell satisfies the reference value. The charging control switch is turned on when the battery is present, and the charging control switch unit is turned off when the voltage of at least one battery cell does not satisfy a reference value.

  According to a third aspect of the present invention, the voltage determining unit according to the first aspect determines whether or not the voltage of the battery cell satisfies a first reference value that is the reference value. Determining whether or not a second reference value larger than a reference value of 1 is satisfied, and the switch control unit determines that the voltage of the battery cell satisfies the first reference value by the voltage determination unit. The charging control switch is turned on when it is determined that the battery cell voltage is determined, and the charging control switch is turned off when it is determined that the voltage of the battery cell does not satisfy the first reference value. A current adjustment unit for adjusting a charging current supplied to the cell, and the voltage determination unit determines that the voltage of the battery cell satisfies the first reference value and does not satisfy the second reference value. If the power The control unit controls the charging current to a predetermined value, and when the voltage determining unit determines that the voltage of the battery cell satisfies a second reference value, the current adjusting unit is controlled to control the predetermined value. And a current control unit for making the charging current larger than that.

  According to a fourth aspect of the present invention, in the third aspect, the secondary battery is configured by connecting a plurality of battery cells in series, and the voltage detection unit detects a voltage of each battery cell. The voltage determination unit determines whether or not the voltage of each battery cell satisfies a first reference value, and determines whether or not the voltage of each battery cell satisfies a second reference value. The switch control unit turns on the charge control switch when the voltage of each battery cell satisfies the first reference value, and the voltage of at least one battery cell is the first voltage. The charge control switch is turned off when the reference value is not satisfied, and the current control unit is configured such that the voltage of each battery cell satisfies the first reference value and the second reference value is set. If it is determined that the current is not satisfied, the current is A charging current having a predetermined value is controlled by controlling the node, and when it is determined that the voltage of each battery cell satisfies the second reference value, the charging current larger than the predetermined value is controlled by controlling the current adjusting unit. It is characterized by that.

  According to a fifth aspect of the present invention, in the first or second aspect, the first reference value is set to a lower limit voltage value in a chargeable state in which voltage recovery is possible by charging. It is characterized by.

  A sixth aspect of the present invention is based on any one of the first to fifth aspects, wherein the switch control unit is operated by electric power supplied from a charging device for charging a secondary battery. It is said.

  The invention according to claim 7 is a battery pack configured to be connectable to the charging device, the secondary battery for supplying power to the load device, and the secondary battery according to any one of claims 1 to 6. The battery charging control circuit is integrally provided.

  According to the first aspect of the invention, the charge control switch is turned on when the voltage of the battery cell satisfies the reference value, and the charge control switch is turned off when the voltage of the battery cell does not meet the reference value. Therefore, by setting this reference value to a predetermined value for determining whether the secondary battery is in a chargeable state or a non-chargeable state, there is a possibility of voltage recovery as in the prior art. Trickle charging for confirming whether or not there is no longer necessary. For this reason, the time required for trickle charging as in the prior art becomes unnecessary, so that the charging time for the secondary battery can be shortened, and wasteful power consumption can be suppressed.

  According to the invention of claim 2, the charge control switch is turned on when the voltage of each battery cell satisfies the reference value, and the charge control switch is turned on when the voltage of at least one battery cell does not satisfy the reference value. Since the reference value is set to a predetermined value for determining whether the secondary battery is in a chargeable state or a non-chargeable state, the voltage recovery as in the conventional case is performed. No trickle charging is required to confirm whether or not there is a possibility. For this reason, the time required for trickle charging as in the prior art becomes unnecessary, so that the charging time for the secondary battery can be shortened, and wasteful power consumption can be suppressed.

  According to the invention of claim 3, the charge control switch is turned on when the voltage of the battery cell satisfies the first reference value, and the charge control is performed when the voltage of the battery cell does not satisfy the first reference value. Since the switch is turned off, the first reference value is set to a predetermined value for determining whether the secondary battery is in a chargeable state or a non-chargeable state. Thus, trickle charging for confirming whether or not there is a possibility of voltage recovery is not necessary. For this reason, the time required for trickle charging as in the prior art becomes unnecessary, so that the charging time for the secondary battery can be shortened, and wasteful power consumption can be suppressed.

  In addition, when the voltage of the battery cell satisfies the first reference value and does not satisfy the second reference value larger than the first reference value, the charging current is set to a predetermined value, and the voltage of the battery cell is When the second reference value is satisfied, the charging current is set to be larger than the predetermined value when the second reference value is not satisfied. Therefore, when the battery cell voltage is low, a large burden is imposed on the battery cell. As a result, the battery life can be prevented from being adversely affected.

  According to the invention of claim 4, when the voltage of each battery cell satisfies the first reference value, the charge control switch is turned on, and the voltage of at least one battery cell does not satisfy the first reference value. In this case, since the charge control switch is turned off, the first reference value is set to a predetermined value for determining whether the secondary battery is in a chargeable state or a non-chargeable state. This eliminates the need for trickle charging for confirming whether there is a possibility of voltage recovery as in the prior art. For this reason, the time required for trickle charging as in the prior art becomes unnecessary, so that the charging time for the secondary battery can be shortened, and wasteful power consumption can be suppressed.

  In addition, when the voltage of each battery cell satisfies the first reference value and the voltage of each battery cell does not satisfy the second reference value larger than the first reference value, the charging current of a predetermined value And when the voltage of each battery cell satisfies the second reference value, the charging current is larger than the predetermined value when the second reference value is not satisfied. As a result of not being able to place a heavy burden on the battery cell when the battery is low, the battery life can be prevented from being adversely affected.

  According to the invention of claim 5, since the first reference value is set to the lower limit voltage value of the chargeable state where the voltage can be restored by charging, the voltage of the battery cell satisfies the first reference value. Trickle charge to check whether there is a possibility of voltage recovery as in the prior art by charging when the first reference value is not met, and not charging when the first reference value is not met Is no longer necessary. For this reason, the time required for trickle charging as in the prior art becomes unnecessary, so that the charging time for the secondary battery can be shortened, and wasteful power consumption can be suppressed.

  In addition, when the voltage of the battery cell does not satisfy the first reference value, a metal such as a copper foil used for the current collector of the negative electrode plate of the battery cell is deposited in a needle-like crystal state by charging. Since the electrode plate may be short-circuited, safety can be ensured by preventing charging when the first reference value is not satisfied.

  According to the invention of claim 6, since the switch control unit is operated by the electric power supplied from the charging device for charging the secondary battery, the voltage of the battery cells constituting the secondary battery is low. Even if it becomes too much, the switch control unit can function reliably.

  According to the invention of claim 7, the charge control switch is turned on when the voltage of the battery cell satisfies the reference value, and the charge control switch is turned off when the voltage of the battery cell does not meet the reference value. Therefore, by setting this reference value to a predetermined value for determining whether the secondary battery is in a chargeable state or a non-chargeable state, there is a possibility of voltage recovery as in the prior art. Trickle charging for confirming whether or not there is no longer necessary. As a result, the time required for trickle charging as in the prior art is not required, so that it is possible to shorten the charging time for the secondary battery and to effectively reduce wasteful power consumption. Realized.

  FIG. 1 is a diagram for explaining a circuit configuration of a battery pack using the charge control circuit according to the first embodiment of the present invention. In this figure, a battery pack 10 is for driving various load devices such as a mobile phone, a digital camera, a power tool, and a robot, and includes a pair of external terminals 12 and 14, a secondary battery 16, and a pair. The charging control circuit 18 is disposed between the external terminals 12 and 14 and the secondary battery 16.

  Here, the pair of external terminals 12 and 14 are connected to the pair of output terminals 22 and 24 of the charging device 20 that charges the secondary battery 16. The secondary battery 16 is a rechargeable battery made of a lithium ion secondary battery, and is configured by connecting a plurality (three in this embodiment) of battery cells 28, 30, and 32 in series. A secondary battery 16 made of this lithium ion secondary battery is an electrode in which a positive electrode plate and a negative electrode plate are wound in a flat shape in a battery case made of aluminum or aluminum alloy with a separator interposed therebetween. The plate group is accommodated and a non-aqueous electrolyte is injected.

  For example, the positive electrode plate is formed by applying a positive electrode paste to one or both surfaces of a foil or a lath-processed or etched positive electrode current collector having a thickness of 10 to 60 μm, drying it, rolling it, and rolling it. It is produced by forming a material layer. Moreover, the negative electrode plate is applied by drying a negative electrode paste on one or both sides of a negative electrode current collector having a thickness of 10 to 50 μm made of, for example, ordinary copper foil or lath processed or etched copper foil, and rolled. It was produced by forming a negative electrode active material layer.

  The charge control circuit 18 includes a voltage detection unit 34 that detects the voltage of each battery cell 28, 30, 32 that constitutes the secondary battery 16, and a charging circuit that supplies a charging current to each battery cell 28, 30, 32. The detection signal output from the charge control switch 36 disposed between the one external terminal 12 and the secondary battery 16 and the voltage detection unit 34 is input, and the level of the detection signal Corresponding to the charging control switch 36 for controlling on / off of the charging control switch 36.

  Here, the voltage detection unit 34 includes a first voltage detection unit 40 and a second voltage detection unit 42. The first voltage detection unit 40 is in a chargeable state (overdischarge state) in which the secondary battery 16 is capable of voltage recovery, or in a non-chargeable state (deep discharge state) in which there is no possibility of voltage recovery. The voltage dividing resistor circuit that divides the voltage of each battery cell 28, 30, 32, and the divided voltage of each battery cell 28, 30, 32 obtained by this voltage dividing resistor circuit is used as a reference. The comparator is configured to compare with a value and output the comparison result as a detection signal which is a high signal or a low signal. This comparator is driven by electric power supplied from the charging device 20.

  That is, according to the present invention, each of the battery cells 28, 30, the secondary battery 16 in a chargeable state with the possibility of voltage recovery and the secondary battery 16 in an unchargeable state without the possibility of voltage recovery, This is based on the experimental finding that there is a difference in the voltage value of 32, and whether the secondary battery 16 is in a chargeable state depending on whether or not this critical voltage value is satisfied, or cannot be charged. It is intended to detect whether the secondary battery 16 is in a state.

  Therefore, each of the battery cells 28, 30, and 32 that can discriminate between the secondary battery 16 in a chargeable state with the possibility of voltage recovery and the secondary battery 16 in an unchargeable state without the possibility of voltage recovery. A voltage value Vr as a critical value is experimentally obtained, and the voltage value Vr as the critical value is set as a reference value (critical reference value) Vr for comparing with the voltage value of each battery cell 28, 30, 32. It is what.

  The reference value Vr is set to 0.5 to 1.3 V (Vr = 0.5 to 1.3 V) in the present embodiment. However, considering the characteristic variation of the battery cell, the reference value Vr is 0.6 to 1.3 V ( Vr = 0.6 to 1.3 V) is preferable for securing higher safety. It has been experimentally confirmed that the reference value Vr is given a width in this way because the reference value needs to be different even for the same secondary battery depending on the application of the device in which the battery pack is used. For this reason, a predetermined value within the above range is selected and set according to the application of the device. The reference value input to the comparator is set to a value obtained from the reference value Vr corresponding to the voltage dividing ratio by the voltage dividing resistor circuit.

  The second voltage detector 42 is for detecting whether or not the secondary battery 16 is fully charged by the charging current supplied from the charging device 20. The first voltage detector 40 Similarly, the voltage dividing resistor circuit that divides the voltage of each battery cell 28, 30, 32, and the divided voltage of each battery cell 28, 30, 32 obtained by this voltage dividing resistor circuit are compared with a reference value, The comparator is configured to output a comparison result as a detection signal which is a high signal or a low signal. This comparator is driven by electric power supplied from the charging device 20.

  That is, the second voltage detection unit 42 compares the voltage value Vc of each battery cell 28, 30, 32 with a reference value (full charge reference value) Vf for determining whether or not the battery cell 28, 30, 32 is fully charged. The result is output as a detection signal. The reference value input to the comparator is set to a value obtained from the reference value Vf corresponding to the voltage dividing ratio by the voltage dividing resistor circuit.

  The charging control switch 36 is configured by, for example, a field effect transistor, and is turned on by the charging control unit 38 to supply a charging current from the charging device 20 to the secondary battery 16 for charging. The charging control unit 38 turns off the charging current supply to the secondary battery 16 to inhibit charging.

  The charge control unit 38 includes a CPU (Central Processing Unit) that executes arithmetic processing, a ROM (Read-Only Memory) that stores control processing programs and data, and a RAM (Random Access Memory) that temporarily stores data. And is driven by electric power supplied from the charging device 20.

  The charge control unit 38 includes a function determination unit as a voltage determination unit 44, a full charge determination unit 46, and a switch control unit 48. The voltage determination unit 44 determines whether the detection signal output from the first voltage detection unit 40 is a high signal or a low signal. That is, it is determined whether or not the voltage value Vc of each battery cell 28, 30, 32 satisfies the reference value Vr.

  The full charge determination unit 46 determines whether the detection signal output from the second voltage detection unit 42 is a high signal or a low signal. That is, it is determined whether or not the voltage value Vc of each battery cell 28, 30, 32 has reached the reference value Vf.

  The switch control unit 48 controls on / off of the charge control switch 36, and when the voltage value Vc of each battery cell 28, 30, 32 satisfies the reference value Vr (Vc ≧ Vr), the charge control is performed by the control signal. When the switch 36 is turned on and the voltage value Vc of at least one of the battery cells 28, 30, 32 does not satisfy the reference value Vr (Vc <Vr), the charge control switch 36 is turned off by a control signal. To do.

  That is, when the charge control switch 36 is configured by a field effect transistor, a high signal is supplied to the gate when the voltage value Vc of each battery cell 28, 30, 32 satisfies the reference value Vr, thereby providing a field effect. When the voltage value Vc of at least one of the battery cells 28, 30, 32 does not satisfy the reference value Vr, a low signal is supplied to the gate to turn off the field effect transistor. To do.

  Further, the switch control unit 48 is fully charged when the charging device 20 charges the secondary battery 16, and the voltage value Vc of each battery cell 28, 30, 32 reaches the reference value Vf. The charging control switch 36 is turned off by a control signal at (Vc = Vf). That is, in the case where the charge control switch 36 is configured by a field effect transistor, when the voltage value Vc of each battery cell 28, 30, 32 reaches the reference value Vf, a low signal is supplied to the gate so that the field effect type is provided. The transistor is turned off and the supply of the charging current to the secondary battery 16 is stopped.

  FIG. 2 is a flowchart for explaining the control operation of the charging control circuit 18 when the battery pack 10 configured as described above is connected to the charging device 20. First, the voltage of each battery cell 28, 30, 32 is detected by the 1st voltage detection part 40, and this detection signal is supplied to the charge control part 38 (step S1). The detection signal in the voltage detection unit 34 is always supplied to the charge control unit 38 as monitoring information.

  Next, whether or not the detection signal for each battery cell 28, 30, 32 output from the first voltage detector 40 is a high signal, that is, the voltage value Vc of each battery cell 28, 30, 32 is a reference value. Whether or not Vr is satisfied is determined by the voltage determination unit 44 (step S3).

  When the determination in step S3 is affirmative (when the voltage value Vc of each battery cell 28, 30, 32 satisfies the reference value Vr), the charge control switch 36 is turned on by the control signal of the switch control unit 48. Then, a charging current is supplied from the charging device 20 to the secondary battery 16 to charge the secondary battery 16 (step S5). As described above, in the present invention, charging is executed when the voltage value Vc of each battery cell 28, 30, 32 satisfies the reference value Vr. The time required for trickle charging for confirming whether or not there is is not required, and the charging time for the secondary battery 16 can be effectively shortened. In step S5, quick charging can be performed.

  Next, the full charge determination unit 46 determines whether or not the detection signal from the second voltage detection unit 42 is a high signal, that is, whether or not the secondary battery 16 is fully charged after a predetermined time has elapsed. It is determined (step S7). If the determination in step S7 is affirmative, the charging circuit is shut off by turning off the charging control switch 36 by the control signal of the switch controller 48 (step S9). If the determination in step S7 is negative, the process proceeds to step S5 and the charging operation is continued.

  On the other hand, if the determination in step S3 is negative (if the voltage value Vc does not satisfy the reference value Vr even in at least one of the battery cells 28, 30, 32), the process proceeds to step S9. Transition. That is, the charge control switch 36 is turned off by the control signal of the switch control unit 48, thereby cutting off the charging circuit. Thus, since the charging is not started when the voltage value Vc of at least one of the battery cells 28, 30, 32 does not satisfy the reference value Vr, there is a possibility of voltage restoration as in the prior art. Trickle charging for confirming whether or not there is no need is made, and wasteful power consumption can be suppressed.

  Further, when the voltage of the battery cells 28, 30, 32 does not satisfy the reference value Vr, the metal such as the copper foil used for the current collector of the negative electrode plate of the battery cells 28, 30, 32 is contained in the non-aqueous electrolyte. May be eluted in the form of ions and deposited in the form of needle crystals by charging, causing the electrode plate to be short-circuited. Therefore, safety is ensured by not charging when the reference value Vr is not satisfied. can do. In addition, since the charging device 20 is not subjected to a large load unlike the case where the electrode plates of the battery cells 28, 30, and 32 are short-circuited, the charging device 20 can be downsized.

  Note that even if at least one of the battery cells 28, 30, 32 is at least one battery cell, the voltage control circuit 36 is turned off by turning off the charge control switch 36 when the voltage value Vc does not satisfy the reference value Vr. Even if it is one battery cell, if metal is deposited on the electrode plate in the form of needle crystals, there is a risk that the battery cell may be destroyed when a charging current flows. It is.

  FIG. 3 is a diagram for explaining a circuit configuration of a battery pack using the charge control circuit according to the second embodiment of the present invention. The battery pack 10 using the charge control circuit 18 according to the second embodiment is basically composed of the same components as the battery pack 10 using the charge control circuit 18 according to the first embodiment. Therefore, detailed description is omitted by assigning the same reference numerals to the constituent elements having the same function, and the difference from the battery pack 10 using the charging control circuit 18 according to the first embodiment is described below. The explanation will focus on the points.

  The battery pack 10 using the charge control circuit 18 according to the second embodiment includes the configuration of the first voltage detection unit 40 of the voltage detection unit 34, the configuration of the voltage determination unit 44 of the charge control unit 38, and the charging. The configuration of the switch control unit 48 of the control unit 38 is different from that of the battery pack 10 using the charge control circuit 18 according to the first embodiment, and includes a current adjustment unit 50 inserted in the charging circuit, The control unit 38 is different in that it has a function as a current control unit 52 that controls the operation of the current adjustment unit 50.

  That is, the first voltage detection unit 40 in the second embodiment sets the first reference value Vr1 and the second reference value Vr2 that is higher than the first reference value by a predetermined value as reference values. Whether the secondary battery 16 is in a chargeable state (overdischarge state) in which the voltage may be restored depending on whether or not the voltage value Vc of each battery cell 28, 30, 32 satisfies the first reference value Vr1. In addition, it is detected whether the battery is in a non-chargeable state (deep discharge state) with no possibility of voltage recovery, and when it is in a chargeable state with the possibility of voltage recovery, the voltage value Vc of each battery cell 28, 30, 32 Whether or not the battery satisfies the second reference value Vr2 is detected as to whether it is in a quick chargeable state in which quick charge is performed or in a charge allowable state in which it is preferable to perform slow charge.

  Therefore, the first voltage detector 40 in the second embodiment includes a voltage dividing resistor circuit that divides the voltage of each battery cell 28, 30, 32, and each battery cell 28 obtained by the voltage dividing resistor circuit. Each of the battery cells 28 obtained by the first comparator which compares the divided voltages 30 and 32 with the first reference value and outputs the comparison result as a detection signal which is a high signal or a low signal and the voltage dividing resistor circuit. , 30 and 32 are compared with a second reference value, and a comparison result is output as a detection signal which is a high signal or a low signal. These comparators are driven by electric power supplied from the charging device 20.

  That is, the invention of the second embodiment is similar to the case of the first embodiment in that the secondary battery 16 in the chargeable state with the possibility of voltage recovery and the non-chargeable state without the possibility of voltage recovery. A voltage value Vr1 as a critical value of each of the battery cells 28, 30, and 32 that can be distinguished from the secondary battery 16 is experimentally determined, and the voltage value Vr1 as the critical value is determined as the critical value. , 32 is set as a first reference value (first critical reference value) Vr1 for comparison with the voltage value of 32.

  Further, even if the secondary battery 16 is in a chargeable state, the secondary battery 16 in a quick chargeable state in which quick charge can be performed and the charge allowable state in which it is more preferable to perform slow charge. Since the secondary battery 16 exists, a voltage value Vr2 as a critical value of each battery cell 28, 30, 32 that can discriminate these states is experimentally obtained, and the voltage value Vr2 as the critical value is determined. This is set as a second reference value (second critical reference value) Vr2 for comparison with the voltage value of each battery cell 28, 30, 32.

  In the present embodiment, the first reference value Vr1 is set to 0.5 to 1.3 V (Vr1 = 0.5 to 1.3 V), and the second reference value Vr2 is set to 2.0 to 3.0 V (Vr2 = 2). 0.0 to 3.0 V). That is, as shown in FIG. 4, a range in which the voltage value Vc of the battery cells 28, 30, and 32 is less than 0.5 to 1.3 V (Vc <0.5 to 1.3 V) is set as a charge disapproval range, The voltage value Vc of the cells 28, 30, 32 satisfies 0.5 to 1.3V and does not satisfy 2.0 to 3.0V (0.5 to 1.3V ≦ Vc <2.0 to 3.0V) is a slow charging permission range, and a range in which the voltage value Vc of the battery cells 28, 30, 32 satisfies 2.0 to 3.0V (Vc ≧ 2.0 to 3.0V) is rapidly charged. It is within the permitted range.

  In consideration of variations in characteristics of battery cells, it is preferable to set a range of 0.6 to less than 1.3 V as a charge disapproval range in order to ensure higher safety. As described above, the first reference value Vr1 and the second reference value Vr2 have different widths because the first reference value Vr1 and the second reference value Vr2 are different even if the same secondary battery is used depending on the use of the device in which the battery pack is used. This is because it has been experimentally confirmed that the value Vr1 and the second reference value Vr2 need to be different from each other. For this reason, a predetermined value within the above range is selected according to the use of the device. Will be set. The reference value input to each comparator is set to a value obtained from the first reference value Vr1 and the second reference value Vr2 corresponding to the voltage dividing ratio by the voltage dividing resistor circuit.

  In addition, the voltage determination unit 44 in the second embodiment includes a first voltage determination unit 44a and a second voltage determination unit 44b. The first voltage determination unit 44a determines whether the detection signal output from the first comparator of the first voltage detection unit 40 is a high signal or a low signal. That is, it is determined whether or not the voltage value Vc of each battery cell 28, 30, 32 satisfies the first reference value Vr1. The second voltage determination unit 44b determines whether the detection signal output from the second comparator of the first voltage detection unit 40 is a high signal or a low signal. That is, it is determined whether or not the voltage value Vc of each battery cell 28, 30, 32 satisfies the second reference value Vr2.

  In addition, the switch control unit 48 in the second embodiment uses the control signal to switch the charge control switch when the voltage value Vc of each battery cell 28, 30, 32 satisfies the first reference value Vr1 (Vc ≧ Vr1). When the voltage value Vc does not satisfy the first reference value Vr1 (Vc <Vr1) even when at least one of the battery cells 28, 30, 32 is turned on, the charging control is performed by the control signal. The switch 36 is turned off.

  In addition, the current adjustment unit 50 in the second embodiment adjusts the charging current for the secondary battery 16, and includes, for example, a resistance element interposed in the charging circuit and a switch element that short-circuits the resistance element. It is composed of That is, when the resistance element is inserted in the charging circuit, the charging current is set to a predetermined value smaller than when the resistance element is not inserted, and when the resistance element is short-circuited by the switch element, the resistance element The charging current is set to be larger than a predetermined value when is inserted.

  In addition, the current control unit 52 in the second embodiment controls the operation of the current adjustment unit 50. That is, when the voltage value Vc of each battery cell 28, 30, 32 satisfies the first reference value Vr1 and does not satisfy the second reference value Vr2, the charging current is set to a small predetermined value. The secondary battery 16 is charged slowly and the voltage value Vc of each battery cell 28, 30, 32 does not satisfy the second reference value Vr2 when the voltage value Vc satisfies the second reference value Vr2. In this case, the secondary battery 16 is rapidly charged by setting a charging current larger than a predetermined value.

  FIG. 5 is a flowchart for explaining the control operation of the charge control circuit 18 when the battery pack 10 using the charge control circuit 18 in the second embodiment configured as described above is connected to the charging device 20. is there. First, the voltage of each battery cell 28, 30, 32 is detected by the first voltage detection unit 40 of the voltage detection unit 34, and this detection signal is supplied to the charge control unit 38 (step S21). The detection signal in the voltage detection unit 34 is always supplied to the charge control unit 38 as monitoring information.

  Next, whether or not the detection signal for each battery cell 28, 30, 32 output from the first comparator constituting the first voltage detector 40 is a high signal, that is, each battery cell 28, 30, 32. Whether the voltage value Vc satisfies the first reference value Vr1 is determined by the first voltage determination unit 44a (step S23).

  If the determination in step S23 is affirmative (when the voltage value Vc of each battery cell 28, 30, 32 satisfies the first reference value Vr1), the second voltage constituting the first voltage detector 40 is set. Whether or not the detection signal for each battery cell 28, 30, 32 output from the comparator of FIG. 1 is a high signal, that is, the voltage value Vc of each battery cell 28, 30, 32 satisfies the second reference value Vr2. Whether or not there is is determined by the second voltage determination unit 44b (step S25).

  If the determination in step S25 is negative (when the voltage value Vc of each battery cell 28, 30, 32 does not satisfy the second reference value Vr2), the charge control switch 36 is controlled by a control signal from the switch control unit 48. Is turned on, and the current adjustment unit 50 is activated by the control signal of the current control unit 52, so that the voltage value Vc of each battery cell 28, 30, 32 is smaller than when the second reference value Vr2 is satisfied. The charging current is supplied, and charging (slow charging) is performed on the secondary battery 16 (step S27).

  As described above, in the present invention, charging is performed when the voltage value Vc of each battery cell 28, 30, 32 satisfies the first reference value Vr1, so that the voltage recovery as in the prior art is performed. Therefore, the time required for trickle charging for confirming whether or not there is a possibility of this becomes unnecessary, and the charging time for the secondary battery 16 can be effectively shortened. In addition, since charging is performed with a small charging current, a large burden is not placed on the battery cell, so that the battery cell is not adversely affected.

  Next, whether or not the detection signal for each battery cell 28, 30, 32 output from the second comparator constituting the first voltage detection unit 40 is a high signal, that is, each battery cell 28, 30, 32. The second voltage determining unit 44b determines whether or not the voltage value Vc satisfies the second reference value Vr2 (step S29).

  If the determination in step S29 is affirmed, the current adjustment unit 50 is activated by the control signal of the current control unit 52, and the voltage value Vc of each battery cell 28, 30, 32 satisfies the second reference value Vr2. A charging current larger than the case where there is no charging is supplied, and charging (rapid charging) of the secondary battery 16 is performed (step S31).

  Next, the full charge determination unit 46 determines whether or not the detection signal from the second voltage detection unit 42 is a high signal, that is, whether or not the secondary battery 16 is fully charged after a predetermined time has elapsed. A determination is made (step S33). If the determination in step S33 is positive, the charging control switch 36 is turned off by the control signal from the switch control unit 48, thereby cutting off the charging circuit (step S35).

  On the other hand, if the determination in step S23 is negative (when the voltage value Vc does not satisfy the first reference value Vr1 even in at least one of the battery cells 28, 30, 32), Control goes to step S35. That is, the charge control switch 36 is turned off by the control signal of the switch control unit 48, thereby cutting off the charging circuit. As described above, since charging is not started when the voltage value Vc does not satisfy the first reference value Vr1 even in at least one of the battery cells 28, 30, 32, as in the conventional case. Trickle charging for confirming whether or not there is a possibility of a voltage recovery is unnecessary, and wasteful power consumption can be suppressed.

  Further, when the voltage of the battery cells 28, 30, 32 does not satisfy the first reference value Vr1, the metal such as the copper foil used for the current collector of the negative electrode plate of the battery cells 28, 30, 32 is non-aqueous. Since it elutes in the form of ions in the electrolytic solution and precipitates in the state of needle crystals by charging, the electrode plate may be short-circuited, so that charging is not performed when the first reference value Vr1 is not satisfied. By doing so, safety can be ensured. In addition, since the charging device 20 is not subjected to a large load unlike the case where the electrode plates of the battery cells 28, 30, and 32 are short-circuited, the charging device 20 can be downsized.

  Note that when the voltage value Vc of at least one of the battery cells 28, 30, 32 does not satisfy the first reference value Vr1, the charge control switch 36 is turned off to cut off the charging circuit. Even if it is one battery cell, if metal is deposited on the electrode plate in the form of needle crystals, there is a risk that the battery cell may be destroyed when a charging current flows. It is.

  When the determination in step S25 is affirmed (when the voltage value Vc of each battery cell 28, 30, 32 satisfies the second reference value Vr2), the process proceeds to step S31 and the subsequent steps are performed. Executed. Further, when the determination in step S29 is negative (when the voltage value Vc of each battery cell 28, 30, 32 does not satisfy the second reference value Vr2), the process proceeds to step S27 and a small charge current is obtained. Charging (slow charging) is continued. If the determination in step S33 is negative, the process proceeds to step S31 and charging with a large charging current (rapid charging) is continued.

  Since the battery pack 10 using the charge control circuit 18 and the charge control circuit 18 according to the present invention is configured as in the first embodiment or the second embodiment, the secondary battery 16 is charged. However, by eliminating the need for trickle charging for confirming whether or not there is a possibility of voltage recovery, it is possible to shorten the charging time and suppress wasteful power consumption. In addition, the battery pack 10 using the charging control circuit 18 and the charging control circuit 18 according to the present invention is not limited to the above-described embodiment, and various modifications as described below may be made as necessary. Can be adopted.

  (1) In the first and second embodiments, the secondary battery 16 is a lithium ion secondary battery, but is not limited thereto. For example, the secondary battery 16 may be a lithium polymer secondary battery, a nickel hydride secondary battery, a nickel cadmium secondary battery, or the like.

  (2) In the first and second embodiments, the secondary battery 16 is configured by connecting a plurality of battery cells 28, 30, and 32 in series, but is not limited thereto. For example, it may be composed of only one battery cell. Moreover, even if the case where the secondary battery 16 is comprised from one battery cell and the case where it is comprised when a some battery cell is connected in series, a some battery cell is connected in parallel, and one You may comprise the battery cell.

  (3) In the first and second embodiments, the voltage detector 34 (the first voltage detector 40 and the second voltage detector 42) detects the voltage of each battery cell 28, 30, 32. However, it is not limited to this. For example, you may make it detect the both-ends voltage of the secondary battery 16 comprised by connecting each battery cell 28,30,32 in series. In this case, the reference values Vr, Vr1, Vr2, and Vf may be set as corresponding to them.

  (4) In the first embodiment, when the voltage value Vc of each battery cell 28, 30, 32 satisfies the reference value Vr at the start of charging, the charging device 20 is turned on by turning on the charging control switch 36. The secondary battery 16 is supplied with a charging current to rapidly charge the secondary battery 16, but is not limited thereto. For example, even when the voltage value Vc of each battery cell 28, 30, 32 satisfies the reference value Vr at the start of charging, a slow charging is performed without flowing a large charging current until the battery is fully charged. Also good.

  (5) In the first and second embodiments, when the secondary battery 16 is fully charged by charging, the charging control switch 36 is turned off to cut off the charging circuit. This is not a limitation. For example, an appropriate display unit such as a liquid crystal display unit is provided in the charging device 20, and even when the secondary battery 16 is fully charged, a message indicating that the battery has been fully charged is displayed without interrupting the charging circuit. You may make it display on. In addition to interrupting the charging circuit, it is also possible to display a message indicating that the battery is fully charged on the display unit. It is also possible to perform constant voltage charging after full charging.

  (6) In the first and second embodiments, the battery pack 10 is integrally provided with only the charge control circuit 18, but the present invention is not limited to this. For example, in addition to the charge control circuit 18, a protection circuit that protects the secondary battery 16 from overcharge, deep discharge, and the like may be integrally provided.

  (7) In the first and second embodiments described above, the voltage detection unit 34 (the first voltage detection unit 40 and the second voltage detection unit 42) is assumed to be composed of a voltage dividing resistor circuit and a comparator. However, it is not limited to this. For example, the voltage detection unit 34 (the first voltage detection unit 40 and the second voltage detection unit 42) may be configured by only a voltage dividing resistor circuit, and the charge control unit 38 may have a function as a comparator. it can.

  The battery pack 10 using the charge control circuit 18 and the charge control circuit 18 according to the present invention does not perform trickle charge for confirming whether or not there is a possibility of voltage recovery when the secondary battery 16 is charged. Therefore, the charging time can be shortened, which is useful for configuring the charging control circuit 18 or the battery pack 10 using the charging control circuit 18.

It is a figure which shows the circuit structure of the battery pack using the charge control circuit which concerns on the 1st Embodiment of this invention. 3 is a flowchart for illustrating a control operation of a charge control circuit in the battery pack shown in FIG. 1. It is a figure which shows the circuit structure of the battery pack using the charge control circuit which concerns on the 2nd Embodiment of this invention. It is a figure which shows each charge range of the charge non-permission range in the battery pack shown in FIG. 3, a slow charge permission range, and a quick charge permission range. 4 is a flowchart for illustrating a control operation of a charge control circuit in the battery pack shown in FIG. 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Battery pack 16 Secondary battery 18 Charge control circuit 20 Charging apparatus 28, 30, 32 Battery cell 34 Voltage detection part 36 Charge control switch 38 Charge control part 40 1st voltage detection part 42 2nd voltage detection part 44 Voltage discrimination | determination Unit 46 full charge determination unit 48 switch control unit 50 current adjustment unit 52 current control unit

Claims (7)

  A charge control circuit for controlling charging of a secondary battery, wherein a voltage detector for detecting a voltage of a battery cell constituting the secondary battery and a charging circuit for supplying a charging current to the battery cell are turned on / off A charge control switch; a voltage determining unit that determines whether or not the voltage of the battery cell satisfies a reference value; and when the voltage determining unit determines that the voltage of the battery cell satisfies the reference value. A switch control unit that turns on the charge control switch and turns off the charge control switch when it is determined that the voltage of the battery cell does not satisfy a reference value. Charge control circuit.   The secondary battery is configured by connecting a plurality of battery cells in series, the voltage detection unit detects a voltage of each battery cell, and the voltage determination unit includes each battery cell. The switch control unit turns on the charge control switch when the voltage of each battery cell satisfies the reference value, and at least one battery is determined. 2. The charge control circuit for a secondary battery according to claim 1, wherein the charge control switch unit is turned off when the voltage of the cell does not satisfy a reference value.   The voltage determining unit determines whether or not the voltage of the battery cell satisfies a first reference value that is the reference value, and satisfies a second reference value that is greater than the first reference value. The switch control unit turns on the charge control switch when the voltage determination unit determines that the voltage of the battery cell satisfies a first reference value, A current adjusting unit for turning off the charge control switch when it is determined that the voltage of the battery cell does not satisfy a first reference value, and for adjusting a charging current supplied to the battery cell; When the voltage determination unit determines that the voltage of the battery cell satisfies the first reference value and does not satisfy the second reference value, the current adjustment unit is controlled to determine a predetermined value. Charge current and A current control unit configured to control the current adjusting unit to make a charging current larger than the predetermined value when the determination unit determines that the voltage of the battery cell satisfies a second reference value; The charge control circuit for a secondary battery according to claim 1.   The secondary battery is configured by connecting a plurality of battery cells in series, the voltage detection unit detects a voltage of each battery cell, and the voltage determination unit includes each battery cell. And whether or not the voltage of each battery cell satisfies the second reference value and whether or not the voltage of each battery cell satisfies the first reference value. The charge control switch is turned on when the voltage of the battery cell satisfies the first reference value, and the charge control switch is turned off when the voltage of at least one battery cell does not meet the first reference value. The current control unit controls the current adjustment unit when it is determined that the voltage of each battery cell satisfies the first reference value and does not satisfy the second reference value. To set the charging current to a predetermined value. 4. The control circuit according to claim 3, wherein the current adjustment unit is controlled to make the charging current larger than the predetermined value when it is determined that the voltage of the second battery satisfies the second reference value. 5. Secondary battery charge control circuit.   5. The charge control for a secondary battery according to claim 3, wherein the first reference value is set to a lower limit voltage value of a chargeable state in which voltage can be restored by charging. 6. circuit.   6. The secondary battery charging control circuit according to claim 1, wherein the switch control unit is operated by electric power supplied from a charging device for charging the secondary battery. .   A battery pack configured to be connectable to a charging device, comprising: a secondary battery for supplying power to a load device; and a charge control circuit for a secondary battery according to any one of claims 1 to 6. A battery pack characterized by being provided integrally.

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