JPH11196533A - Charge/discharge controller for battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly control charging and discharging of a battery by disconnecting an external terminal and a battery from each other when at least one of battery cells is in an over-discharging state and at least one of the other battery cells is in an overcharged state. SOLUTION: A charge/discharge control circuit 21 separately detects the voltage value of each battery cell BC1 -BC3 in a battery 10 and stores '1' in its built-in register when at least one detected voltage value is higher than a prescribed overcharged voltage value or '0' in the other case. When it is discriminated that at least one of the battery cells is in an overcharged state and at least one of the other battery cells is in an over-discharging state, the circuit 21 inhibits charging operations by maintaining both a charge switch 30 and a discharge switch 40 in turned-off states until it is discriminated that no battery charger is connected to a battery pack or all of the battery cells BC1 -BC3 extricate themselves from over-discharging states. Therefore, the charging and discharging of the battery 10 can be controlled properly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charge / discharge control device mounted on a rechargeable battery pack.

[0002]

2. Description of the Related Art A portable device such as a camera-integrated VTR, a mobile phone, and a notebook personal computer is provided with a battery pack as a power source for the portable operation. In such a battery pack, in addition to a rechargeable battery that obtains a desired battery voltage by connecting a plurality of battery cells in series, a battery control circuit that controls charging and discharging of the battery is mounted. I have.

The battery control circuit applies a voltage from the charger to the battery when the battery voltage is lower than a predetermined voltage in a state where the charger is connected to the battery pack, and performs a charging operation. Start. Here, when the battery voltage reaches a predetermined overcharge voltage by the charging operation, the battery control circuit stops the charging operation.

However, depending on the state of use of the battery pack, a battery cell that is sufficiently charged up to the overcharge voltage and a battery cell in an overdischarged state coexist in one battery. Occurs. At this time, the battery voltage obtained by connecting the plurality of battery cells in series becomes lower than the desired voltage, and the battery control circuit starts the charging operation. However, since charging is also performed on the battery cells in the overcharged state as described above, there is a problem that appropriate charge / discharge control cannot be performed on a battery in which a voltage imbalance has occurred between the battery cells. there were.

[0005]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a battery charge / discharge control device capable of performing appropriate charge / discharge control even for a battery having a large voltage imbalance between a plurality of battery cells. The purpose is to provide.

[0006]

A battery charging / discharging control device according to the present invention derives a battery voltage generated by a battery to an external terminal and charges the external terminal when a load is connected to the external terminal. A battery charging / discharging control device that applies a charging voltage from the charger to the battery when the battery is connected, wherein the battery is formed by connecting a plurality of battery cells in series,
The charge / discharge control device, when at least one of the battery cells is in an overdischarged state and at least one of the battery cells is in an overcharged state, connects between the external terminal and the battery. Cut off.

[0007]

FIG. 1 is a diagram showing the internal configuration of a battery pack provided with a battery charge / discharge control device according to the present invention. In FIG. 1, a battery 10 is, for example,
It comprised a lithium ion battery, or three such rechargeable, such as nickel-hydrogen battery of the battery cells BC ₁ -BC ₃ connected in series. In the battery 10, a predetermined battery voltage V is set by connecting the battery cells BC _{1 to} BC ₃ in series.
_B has occurred.

The charge switch 30 composed of an n-channel MOS transistor or the like is turned off while the logic level of the charge signal CG supplied from the charge / discharge control circuit 21 described later is "0", while the charge switch 30 is turned off. During the period in which the logic level of the signal CG is "1", it is turned on. In this ON state, if a charger is connected to the positive battery terminal 50a and the negative battery terminal 50b, the charging voltage from the charger is applied to the battery 10 via the back gates of the charge switch 30 and the discharge switch 40. Is applied and charging is performed.

The discharge switch 40 composed of an n-channel MOS transistor or the like is turned off while the discharge signal DG of the logic level "0" is supplied from the charge / discharge control circuit 21, while the logic level is kept low. Discharge signal D of "1"
During the period in which G is supplied, the transistor is turned on. In this ON state, for example, a mobile phone as a load is connected to the positive battery terminal 50a and the negative battery terminal 50b.
When a portable device such as a notebook computer is connected, the battery voltage from the battery 10 is supplied to the load via the back gates of the discharge switch 40 and the charge switch 30.

[0010] the charger connection detection circuit 22, based on the positive electrode side potential V _{+ B} terminal potential V _P and the battery 10 of the positive side battery terminal 50a, whether the charger to these connection terminals are connected When the connection is detected, a charger connection detection signal CN is generated and supplied to the charge / discharge control circuit 21. Further, the charger connection detection circuit 22, when the potential difference obtained by subtracting the positive electrode side potential V _{+ B} from the terminal potential V _P becomes larger than the predetermined potential difference, can be implemented a charging operation A charge enable signal Cv indicating that a suitable charge voltage is supplied is generated and supplied to the charge / discharge control circuit 21.

The charge pump circuit 23 starts and stops the charge pump operation according to the sleep signal SLP supplied from the charge / discharge control circuit 21. The activation of the charge pump operation causes the charge pump circuit 23
Starts the generation of a drive voltage to raise the signal level of each of the charge signal CG and the discharge signal DG to a voltage value at which each of the charge switch 30 and the discharge switch 40 can be switched. Here, the charge pump circuit 23 generates a drive voltage generation completion signal VG when the drive voltage reaches a desired voltage value, and supplies this to each of the charge / discharge control circuit 21 and the charger connection detection circuit 22.

The charge / discharge control circuit 21 performs charge / discharge control on the battery 10 according to a charge / discharge control routine as shown in FIG. In FIG. 2, first, the charge / discharge control circuit 21
_{1 to} BC ₃ are individually detected. If at least one of these voltage values is higher than a predetermined overcharge voltage value, the logic level is “1”. Otherwise, the logic level is “1”. "0" is stored in the built-in register OV (not shown) (step S1). Then, the charge and discharge control circuit 21, at least one of these battery cells BC ₁ -BC ₃ each voltage logic level "1" if lower than the prescribed overdischarge voltage value, otherwise Stores the logic level "0" in its built-in register UV (not shown) (step S).
2).

Next, the charge / discharge control circuit 21 determines whether or not the contents stored in the built-in register UV are at the logical level "1" (step S3). In such a step S3, the storage contents of the internal register UV is not a logic level "1", i.e., when none of the battery cells BC ₁ -BC ₃ is determined not to be over-discharged state, the charge-discharge control circuit 21 Then, it is determined whether or not the storage content of the internal register OV is at the logical level "1" (step S4).

[0014] In such a step S4, the storage contents of the internal register OV is not a logic level "1", i.e., when none of the battery cells BC ₁ -BC ₃ is determined not to be overcharged state, the charge and discharge control The circuit 21 supplies the discharge signal DG and the charge signal CG at the logical level "1" to the discharge switch 40 and the charge switch 30, respectively (step S5). That is, in step S3 and step S4, any of the battery cells BC ₁ -BC ₃ is in the overcharge state, when it is determined not to be over-discharged executing step S5, the discharge switch 40 and charging switch 30 are both turned on. On this occasion,
When a charger is connected to the positive battery terminal 50a and the negative battery terminal 50b, charging of the battery 10 from the charger is started. When a load is connected to the positive battery terminal 50a and the negative battery terminal 50b, the power supply voltage from the battery 10 is supplied to the load.

Meanwhile, in step S4, the storage contents of the internal register OV is a logic level "1", i.e., if at least one of the battery cells BC ₁ -BC ₃ has been determined to be in an overcharged state , Charge and discharge control circuit 2
1 is the discharge signal DG of the logic level “1” and the logic level “1”.
The charge signal CG of "0" is supplied to the discharge switch 40 and the charge switch 30, respectively (step S6). That is, in steps S3 and S4, the battery cell BC ₁ is supplied.
If none of .about.BC ₃ is in an overdischarged state, but it is determined that at least one of them is in an overcharged state, step S6 is executed and the charge switch 30 is turned off. . At this time, even if a charger is connected to the positive battery terminal 50a and the negative battery terminal 50b, the charging voltage from the charger is not supplied to the battery 10.

[0016] Further, in step S3, the storage contents of the internal register UV is at logic level "1", i.e., if at least one of the battery cells BC ₁ -BC ₃ has been determined to be in the overdischarged state , Charge and discharge control circuit 2
Next, 1 judges whether or not the storage content of the internal register OV is at the logical level "1" (step S7).
If it is determined in step S7 that the storage content of the internal register OV is not at the logical level “1”, that is, if it is determined that none of the battery cells BC _{1 to} BC ₃ is in the overcharged state, the charge / discharge control circuit 21 Supplies the discharge signal DG of the logic level "0" and the charge signal CG of the logic level "0" to the discharge switch 40 and the charge switch 30, respectively (step S8). That is, in step S3 and S7, at least one of the battery cells BC ₁ -BC ₃
If it is determined that one of them is in the overdischarge state and none of them is in the overcharge state, step S8
Is executed to turn off both the charge switch 30 and the discharge switch 40. At this time, even if the charging voltage from the charger is applied to the positive battery terminal 50a and the negative battery terminal 50b, the battery 1
No charging to zero is performed.

After the execution of step S8, the charge / discharge control circuit 21 sends the sleep signal SLP of the logical level "1" to the charge pump circuit 23 in order to shift to the sleep mode in which the battery 10 performs a low power consumption operation. (Step S9). In response to the sleep signal SLP at the logical level “1”, the charge pump circuit 23 stops its charge pump operation and suppresses the power consumption of the battery 10. Next, the charge / discharge control circuit 21 determines whether or not the charge enable signal Cv has been supplied from the charger connection detection circuit 22 (step S10). That is, in step S10, the voltage at which the charging operation for the battery 10 can be started is changed to the positive battery terminal 50.
It is determined whether or not the voltage is applied between the terminal a and the negative battery terminal 50b. In step S10, the charge enable signal Cv is not supplied, that is,
When it is determined that the voltage that can start the charging operation is not applied between the positive battery terminal 50a and the negative battery terminal 50b, the charge / discharge control circuit 21 returns to the execution of the step S8 and returns to the step S8. The above operation is repeatedly executed. On the other hand, in the step S10,
When it is determined that the charge enable signal Cv is supplied,
The charge / discharge control circuit 21 supplies the sleep signal SLP of the logic level “0” to the charge pump circuit 23 in order to cancel the sleep mode as described above (step S11).
According to the sleep signal SLP of the logical level "1",
Charge pump circuit 23 activates the charge pump operation. Next, the charge / discharge control circuit 21 repeatedly determines whether or not the drive voltage generation completion signal VG is supplied from the charge pump circuit 23 until the drive voltage generation completion signal VG is supplied (step S12). . In step S12, the drive voltage generation completion signal VG
Is determined to have been supplied, the charge / discharge control circuit 21
The discharge signal DG and the charge signal CG at the logical level "1" are supplied to the discharge switch 40 and the charge switch 30, respectively (step S13). According to the execution of step S13, both the discharge switch 40 and the charge switch 30 are turned on. At this time, when a charger is connected to the positive battery terminal 50a and the negative battery terminal 50b, charging of the battery 10 from the charger is started. The power supply voltage is supplied to this load.

[0018] That is, by the execution of step S3 and step S7, when at least one of the battery cells BC ₁ -BC ₃ has been determined to be over-discharged, perform the steps S8 and S9, Once the discharge switch 40 and the charge switch 30 are both turned off, the charge pump operation is stopped and the mode is shifted to the sleep mode. The sleep mode is performed in step S10.
Accordingly, the charging voltage from the charger connected to the battery pack is maintained until it is applied to the positive battery terminal 50a and the negative battery terminal 50b. Here, when the charging voltage is applied, steps S11 to S13 are performed.
Then, the charge pump operation is restarted, and both the discharge switch 40 and the charge switch 30 are turned on to release the sleep mode. As a result, the charging operation for the battery 10 is started, and the battery cells in the overdischarged state are charged.

Meanwhile, in the step S7, the storage contents of the internal register OV is a logic level "1", i.e., if at least one of the battery cells BC ₁ -BC ₃ has been determined to be in an overcharged state , Charge and discharge control circuit 2
1 is the discharge signal DG of the logic level "0" and the logic level "
The charge signal CG of "0" is supplied to the discharge switch 40 and the charge switch 30, respectively (step S14).
In steps S3 and S7, the battery cell BC
₁ is in the at least one over-discharge state of the -BC _3, and those in the case where at least one of the battery cells has been determined to be in the overcharge state by performing the step S14, the charge switch 30 and The discharge switches 40 are both turned off. At this time, even if the charging voltage from the charger is applied to the positive battery terminal 50a and the negative battery terminal 50b, the battery 10 is not charged.

Next, the charge / discharge control circuit 21 determines whether or not the charger connection detection signal CN has been supplied from the charger connection detection circuit 22 (step S15). In step S15, if the charger connection detection signal CN is not supplied, that is, if it is determined that the charger is disconnected, the charge / discharge control circuit 21 proceeds to step S8 and proceeds to step S8 as described above.一連 S13 are executed.

On the other hand, when the charger connection detection signal CN is supplied from the charger connection detection circuit 22 in step S15, that is, when it is determined that the charger is connected, the charging / discharging control circuit 21 Is the above step S2
And the above-described operation is repeatedly executed.
That is, if it is determined in steps S3 and S7 that at least one of the battery cells is in the overcharged state and at least one is in the overdischarged state, the charger is connected to the battery pack in step S15. Is determined not to have been made, or step S
3 until it is determined that all the battery cells have escaped from the overdischarge state.
Both 0 are kept off.

As described above, once the battery cells BC ₁ to BC ₁
If it is determined that at least one of the BCs ₃ is in an overdischarged state and at least one of them is in an overcharged state, the charger is removed from the battery pack or all of the battery cells are removed. The charge switch 30 and the discharge switch 40 are both kept in the off state until the overdischarge state is released, and the charge operation is prohibited.

According to such an operation, when a battery cell in an overcharged state and a battery cell in an overdischarged state coexist in one battery, even if the charger is connected, the battery from the charger may be used. The charging operation is forcibly stopped. Therefore, the battery cell in the overcharged state is not recharged, and the life of the battery can be extended.

Here, the above steps S5, S6 and S1
When any of the steps 3 is completed, the charge / discharge control circuit 21 exits the charge / discharge control routine as shown in FIG. 2 and returns to the execution of the main flow. During the execution of the main flow, the charge / discharge control circuit 21 executes a charge / discharge control routine as shown in FIG. 2 at predetermined intervals, for example. In the present invention, the operation itself of the main flow is not important, and therefore, the description thereof is omitted.

In the above embodiment, the battery 10
The number of battery cells forming the series is three.
The number of stages is not limited as long as there are at least two.

[Brief description of the drawings]

FIG. 1 is a diagram showing an internal configuration of a battery pack including a battery charge / discharge control device according to the present invention.

FIG. 2 is a diagram showing a charge / discharge control routine by a charge / discharge control circuit 21;

[Description of Signs of Main Parts]

 DESCRIPTION OF SYMBOLS 10 Battery 21 Charge / discharge control circuit 22 Charger connection detection circuit 23 Charge pump circuit 30 Charge switch 40 Discharge switch

Claims (3)

[Claims] 1. A battery voltage generated by a battery is derived to an external terminal when a load is connected to an external terminal, and charging from the charger is performed when a charger is connected to the external terminal. A battery charge / discharge control device that applies a voltage to the battery, wherein the battery is formed by connecting a plurality of battery cells in series, and the charge / discharge control device includes at least one of the battery cells. A battery charge / discharge control device, wherein when one of the battery cells is in an overdischarged state and at least one of the battery cells is in an overcharged state, the external terminal is disconnected from the battery. 2. The charging / discharging control device applies the battery voltage to the external terminal when a load is connected to the external terminal, and applies the charging voltage when the charger is connected. A charge / discharge switch for applying a voltage to the battery; a charger connection detection circuit for detecting whether the charger is connected to or disconnected from the external terminal; and at least one of the battery cells is in an overdischarged state. And at least one of each of the battery cells
And a control circuit for turning off the charge / discharge switch to cut off the application of the charging voltage to the battery when the connection of the charger is detected when one is in an overcharged state. The battery charge / discharge control device according to claim 1. 3. The charge / discharge control device includes a charge pump circuit that generates a drive voltage for causing the charge / discharge switch to perform a switching operation, and the control circuit detects that the charger is disconnected from the external terminal. In this case, the operation of the charge pump circuit is stopped, and when the connection of the charger is detected again and the charging voltage is applied to the external terminal, the charge pump circuit is activated and the charge / discharge switch is further activated. 3. The battery charge / discharge control device according to claim 2, wherein the control unit turns on the battery to start applying the charge voltage to the battery.