Battery pack control device and method

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to a battery pack control device and method, and is particularly suitable for controlling the charging / discharging of a battery pack mounted on an electronic device such as a camera-integrated video tape recorder or a portable compact disc player. Regarding devices and methods.

【0002】

[Conventional technology]

For example, a battery pack containing a secondary battery (battery) such as lithium ion or nickel-cadmium has a built-in protection circuit to prevent overcharging or overdischarging. This protection circuit cuts off the supply of charge / discharge current to the battery when overcharge or overdischarge is detected.

【0003】

By providing such a protection circuit, damage to the battery can be prevented. However, if the protection circuit does not operate normally, it will not be possible to prevent damage to the battery. Therefore, the applicant, for example, as Japanese Patent Application No. 6-249191, provided a double protection circuit so that when overcharge is detected, one of the recoverable protection circuits is operated, and the protection circuit is used. It was previously proposed to operate a protection circuit that cannot be restored when it is not operating normally. This makes it possible to more reliably protect the battery.

【0004】

[Problems to be Solved by the Invention]

However, in the previous proposal, since the battery pack is configured to incorporate a circuit for determining whether or not the protection circuit is operating normally inside the battery pack, the configuration of the battery pack becomes complicated and the cost is high. There was a problem of becoming expensive. Further, the battery pack becomes large, and there is a problem that it is disadvantageous for use in a portable electronic device.

【0005】

The present invention has been made in view of such a situation, and is intended to prevent damage to the battery while preventing the battery pack from becoming large and costly.

【0006】

[Means for solving problems]

When the battery pack control device according to claim 1 outputs a control signal for switching the protection circuit from the detection means for detecting the terminal voltage or charge / discharge current of the battery and the second connection means, and outputs the control signal. It is characterized in that it includes a determination means for determining the operation of the protection circuit from the detection result of the detection means.

【0007】

The battery pack control method according to claim 5 inputs a control signal for switching the protection circuit from the control terminal of the battery, detects the terminal voltage or charge / discharge current of the battery when the control signal is input, and uses the detection result. It is characterized in that the operation of the protection circuit is determined.

【0008】

[Action]

In the battery pack control device according to claim 1, the detection means detects the terminal voltage or charge / discharge current of the battery, and the determination means outputs a control signal for switching the protection circuit from the second connection means. The operation of the protection circuit is determined from the detection result of the detection means when the control signal is output.

【0009】

In the battery pack control method according to claim 5, a control signal for switching the protection circuit is input from the control terminal of the battery, and the detection result of the terminal voltage or charge / discharge current of the battery when the control signal is input is supported. Then, the operation of the protection circuit is determined.

【0010】

[Example]

FIG. 1 shows a configuration example of a battery pack to which the present invention is applied. This battery pack 1 contains a chargeable / dischargeable battery 11 such as lithium ion or nickel cadmium, and charge / discharge current is supplied from the charge / discharge terminals 31 and 32 to the battery 11 via FETs 12 and 14 and a fuse 16. It is made to be. The FET 12 as an over-discharge switch has a parasitic diode 13, and the FET 14 as an over-charge switch has a parasitic diode 15.

【0011】

The detection circuit 17 detects over-discharge from the terminal voltage of the battery 11 and controls the FET 12 as a protection circuit according to the detection result. Further, the detection circuit 18 detects the overcharge of the battery 11 from the terminal voltage of the battery 11 and controls the FET 14 as a protection circuit according to the detection result.

【0012】

This battery pack 1 has control terminals 33 and 34 in addition to the charge / discharge terminals 31 and 32. The control circuit 19 is connected to the control terminal 33 and controls the detection circuits 17 and 18 in response to a control signal from an external device (for example, the charger 2 in FIG. 2 described later) connected to the control terminal 33. It is made to do. Further, a control signal is input to the control terminal 34 from an external device, and this control signal is applied to the fuse 16 via a diode 20 for preventing backflow to melt and cut off the fuse 16.

【0013】

FIG. 2 shows a configuration example of the charger 2 that charges and discharges the battery pack 1. The charger 2 has terminals 51 and 52 (first connection means) that are connected to the charge / discharge terminals 31 and 32, respectively, when the battery pack 1 is attached. It also has terminals 53 and 54 (second connecting means) that are connected to the control terminals 33 and 34 of the battery pack 1.

【0014】

The transformer 61 has a primary coil 62 and a secondary coil 63,64, and the AC voltage induced in the secondary coil 63,64 is rectified by the diode 65 and smoothed by the capacitor 66. ing. Then, the smoothed DC voltage is supplied to the battery pack 1 via the terminals 51 and 52.

【0015】

The detection circuit 69 (detection means) detects the voltage between terminals 51 and 52, that is, the terminal voltage of the battery pack 1 (terminal voltage of the battery 11), and supplies the detection result to the control circuit 74 (determination means). ing. The resistor 70 is inserted as a discharge resistor when there is a leakage resistor in the switch (FET12, 14 in the case of the embodiment of FIG. 1) that switches the charge / discharge current of the battery pack 1.

【0016】

The resistor 72 is connected in series with the battery 11 to detect the charge / discharge current to the battery 11. The detection circuit 73 (detection means) detects the charge / discharge current of the battery pack 1 (battery 11) by detecting the voltage across the resistor 72, and outputs the detection result to the control circuit 74. ..

【0017】

Further, the voltage induced by the secondary coil 64 is rectified by the diode 67 and supplied from the terminal 54 to the control terminal 34 of the battery pack 1 via the switch 68. The control circuit 74 is designed to control switches 68 and 75.

【0018】

Next, the operation will be described. When the battery pack 1 is attached to, for example, an electronic device (not shown), the charge / discharge terminals 31 and 32 are connected to the corresponding terminals of the electronic device, and the battery 11 is connected to the electronic device via the charge / discharge terminals 31 and 32. Power is supplied. At this time, a discharge current flows through the paths of the battery 11, the charge / discharge terminal 31, the electronic device, the charge / discharge terminal 32, the fuse 16, the FET 14, and the FET 12.

【0019】

The detection circuit 17 detects the terminal voltage of the battery 11 and detects whether or not the terminal voltage is equal to or lower than a preset reference voltage (for example, 2.25V). The detection circuit 17 turns off the FET 12 when the terminal voltage of the battery 11 reaches the reference voltage or less. As a result, the discharge current is cut off and the battery 11 is prevented from being over-discharged.

【0020】

Further, when an excessive discharge current flows for some reason, the fuse 16 melts and the discharge current is cut off.

【0021】

On the other hand, when the battery pack 1 is attached to the charger 2, the charge / discharge terminals 31 and 32 of the battery pack 1 are connected to the terminals 51 and 52 of the charger 2, and the control terminals 33 and 34 of the battery pack 1 are charged. It is connected to terminals 53 and 54 of the device 2, respectively. Then, the control circuit 74 of the charger 2 starts the charging operation, but before that, as shown in the flowchart of FIG. 3, a process of inspecting whether or not the protection circuit is operating normally is executed. To do.

【0022】

First, in step S1, the control circuit 74 outputs a control signal from the terminal 53 to the battery pack 1 to turn on the FET 12 as the over-discharge switch and the FET 14 as the over-charge switch. When the control circuit 19 of the battery pack 1 receives the input of this control signal from the control terminal 33, it controls the detection circuit 17 and the detection circuit 18, and controls to turn on the FET 12 and the FET 14, respectively.

【0023】

Next, the process proceeds to step S2, the control circuit 74 of the charger 2 sets the discharge mode, and the switch 75 is turned off. As a result, a discharge current flows through the paths of the battery 11, the charge / discharge terminal 31, the terminal 51, the resistors 70, 72, the terminal 52, the charge / discharge terminal 32, the fuse 16, the FET 14, and the FET 12. At this time, the detection circuit 69 has a terminal voltage E of the battery 11._BAs, the voltage between terminals 51 and 52 is detected. Alternatively, the detection circuit 73 determines the discharge current I from the potential difference across the resistor 72._DIs detected. The control circuit 74 has a voltage E from the output of the detection circuit 69 or 73._BIs 0 or not, or the discharge current I_DIs 0 or not is determined in step S3.

【0024】

Now, in step S1, since the control signal for turning on the FET 12 is output, the FET 12 should be turned on when the FET 12 is operating normally. If the FET 12 is on, even if the FET 14 is off, the discharge current will flow through the parasitic diode 15, so the voltage E_BIs not 0, but a predetermined value. Similarly, the discharge current I_DIs a predetermined value instead of 0. In this case, it is confirmed that FET12 is actually turned on.

【0025】

Then, next, in order to determine whether or not the FET 12 is in the short-circuited state, the control circuit 74 outputs a control signal for turning off the FET 12 in step S4. Similar to the above case, when the control circuit 19 of the battery pack 1 receives the input of this control signal from the control circuit 74 of the charger 2, it controls the detection circuit 17 and outputs a control signal for turning off the FET 12. ..

【0026】

Then, in step S5, the control circuit 74 receives the voltage E from the output of the detection circuit 69 or 73._BOr discharge current I_DDetermines whether is 0, that is, whether the FET 12 is actually turned off. Voltage E_BOr discharge current I_DIf is not 0 and becomes a predetermined value, it means that the discharge current is flowing even though the control signal for turning off the FET 12 is output in step S4 (FET 12 remains on). Therefore, the process proceeds to step S6, and it is determined that the FET 12 is abnormal (in a short state).

【0027】

On the other hand, when the FET 12 is turned off in response to the control signal output in step S4, the voltage E_BIs 0 and the discharge current I_DIs also 0. Therefore, in this case, the process proceeds to step S7, and it is determined that the FET 12 is normal.

【0028】

Since it has been determined that the FET 12 as the over-discharge switch is normal as described above, the next step is to determine whether or not the FET 14 as the over-charge switch is normal. Therefore, in step S8, the control circuit 74 sets the charging mode and turns on the switch 75. As a result, charging current flows through the paths of switch 75, terminal 51, charge / discharge terminal 31, battery 11, FET12, FET14, fuse 16, charge / discharge terminal 32, terminal 52, and resistor 72.

【0029】

At this time, since the FET 12 is turned off in step S4, the charging current flows through the parasitic diode 13 of the FET 12 as it is, but in order to allow the charging current to flow in the correct path, the FET 12 is turned on in step S9. The control circuit 74 outputs a control signal to be output. The control circuit 19 of the battery pack 1 that receives the supply of this control signal controls the FET 12 via the detection circuit 17 and turns on the FET 12.

【0030】

Next, in step S10, the control circuit 74 receives the charging current I flowing from the output of the detection circuit 73 to the resistor 72._CDetermines if is 0. That is, since the control signal for turning on the FET 14 is being output in step S1, if the FET 14 is operating normally, the FET 14 should be turned on and the charging current should flow. Therefore, the charging current I_CWhen is 0, the FET 14 is off regardless of the control signal. Therefore, in this case, the process proceeds to step S11, and it is determined that the FET 14 as the overcharge switch is abnormal (disconnected).

【0031】

On the other hand, the charging current I_CWhen is not 0 but a predetermined value, it means that FET 14 is actually turned on. Therefore, in this case, next, in order to determine whether or not the FET 14 can be turned off, a control signal for turning off the FET 14 is output from the control circuit 74 in step S12. When the control circuit 19 of the battery pack 1 receives the input of this control signal from the charger 2, it controls the detection circuit 18 and outputs a control signal for turning off the FET 14.

【0032】

When the FET 14 is actually turned off in response to this control signal, the charging current is cut off. Therefore, in step S13, the control circuit 74 receives the charging current I from the output of the detection circuit 73._CIs 0 or not, and if it is 0, the FET 14 operates correctly in response to the control signal in step S12. Therefore, the process proceeds to step S14, and the FET 14 as an overcharge switch is normal. Is determined to be.

【0033】

On the other hand, the charging current I_CIf is not 0 but a predetermined value, the FET 14 remains on despite the control in step S12. In this case, proceed to step S15 and overcharge. The FET 14 as a switch is determined to be abnormal (in a short state).

【0034】

On the other hand, in step S3, the detection circuit 69 or 73 has a terminal voltage E._BIs 0 or the discharge current I_DWhen is detected to be 0, the FET 12 is off regardless of the control in step S1. Therefore, the process proceeds to step S16, and it is determined that the FET 12 is abnormal (disconnected state).

【0035】

Next, in order to determine whether or not the FET 14 is abnormal, the charging mode is set in step S17, and then the process proceeds to step S10 to execute the subsequent processing.

【0036】

As described above, when it is determined that the FET 12 or FET 14 is abnormal, the control circuit 74 displays a predetermined display on the display unit 71 and uses that the over-discharge switch or the over-charge switch is abnormal. Inform the person. Then, if the FET 14 as an overcharge switch is abnormal, the charging operation is not executed.

【0037】

Alternatively, at this time, the control circuit 74 turns on the switch 68. When the switch 68 is turned on, the voltage induced by the secondary coil 64 is rectified by the diode 67, and is routed through the switch 68, the terminal 54, the control terminal 34, the diode 20, the fuse 16, the charge / discharge terminal 32, and the terminal 52. A current flows and the fuse 16 is melted. This prevents the battery pack 1 from being inadvertently used and the battery 11 from being damaged.

【0038】

If the protection circuit is normal, the control circuit 74 of the charger 2 turns on the switch 75 to start the charging operation. As a result, a charging current flows and the battery 11 is charged.

【0039】

The detection circuit 18 monitors the terminal voltage of the battery 11 during the charging operation, determines whether or not the voltage has reached a preset reference value (for example, 4.3V), and when the reference value is reached, It is determined that the battery is overcharged, and the FET 14 is turned off. This prevents overcharging.

【0040】

When determining whether or not the protection circuit composed of FET 12 and FET 14 is operating normally, if the battery 11 is already in the over-discharged state or the over-charged state, the FET 12 or FET 14 operates normally. If so, it's already turned off. In this case, if the charger 2 controls the battery pack 1 to turn on the FET 12 or FET 14, the battery 11 may be damaged. Therefore, in such a case, the detection result of the detection circuit 17 or 18 inside the battery pack 1 is prioritized, and the control circuit 19 is set to the FET 12 or even if the control signal is input from the charger 2. It is possible to prevent the FET 14 from being turned on. In this case, the inspection of whether the FET 12 or the FET 14 operates normally is performed only when the terminal voltage of the battery 11 is not in the over-discharged state or the over-charged state.

【0041】

In addition, when only one of FET12 or FET14 is in the operating state (off), the inspection of the operating state is not performed and the one not in the operating state (turned on). Can only be inspected.

【0042】

Furthermore, for example, when the battery 11 is in an over-discharged state and the FET 12 is off, the control circuit 74 turns on the switch 75 and charges the battery 11 until the FET 12 does not turn off (on). After that, it is possible to inspect whether or not it operates normally. Similarly, when the battery 11 is in the overcharged state and the FET 14 is off, the control circuit 74 executes a discharge operation via, for example, the resistor 70, and the terminal voltage of the battery 11 is in the overcharged state. It is possible to discharge the battery until it becomes equal to or less than the reference value of, and then inspect whether or not it operates normally.

【0043】

4 and 5 show other configuration examples that melt the fuse 16 of the battery pack 1. In this embodiment, the fuse 16 is connected to the charge / discharge terminal 31, and a diode 81 is connected between the multi-end of the fuse 16 and the charge / discharge terminal 32. Then, in this embodiment, the battery pack 1 has three terminals.

【0044】

Correspondingly, in the charger 2 shown in FIG. 5, the voltage induced by the secondary coil 64 is rectified and smoothed by the diode 93 and the capacitor 92, and the negative DC voltage is terminald from the capacitor 92 via the switch 91. It is designed to be output from 51.

【0045】

Therefore, in this embodiment, when the control circuit 74 turns on the switch 91, the path of the capacitor 92, the resistor 72, the terminal 52, the charge / discharge terminal 32, the diode 81, the fuse 16, the charge / discharge terminal 31, the terminal 51, and the switch 91. A current flows through the fuse 16 and the fuse 16 is melted.

【0046】

6 and 7 show still other configuration examples. In this embodiment, the fuse 102 is melted by the heat generated by the heating element 101. The fuse 102 is connected between the charge / discharge terminal 32 and the FET 14, and the heating element 101 is connected between the charge / discharge terminal 32 and the control terminal 33 via a diode 103.

【0047】

Further, in the charger 2, as shown in FIG. 7, the voltage generated in the secondary coil 64 is rectified and smoothed by the diode 93 and the capacitor 92, and then output from the terminal 53 via the switch 91. It has been done.

【0048】

Therefore, in this embodiment, when the control circuit 74 turns on the switch 91, the path of the capacitor 92, the resistor 72, the terminal 52, the charge / discharge terminal 32, the heating element 101, the diode 103, the control terminal 33, the terminal 53, and the switch 91. Current flows and the heating element 101 generates heat. As a result, the fuse 102 is melted by the heat generated by the heating element 101.

【0049】

In the above embodiment, the check for whether or not the protection circuit of the battery pack 1 operates normally is executed in the charger 2, but it is executed in the electronic device to which the battery pack 1 is attached. It is also possible to do. In this case, the power supplied from the battery 11 is supplied to the detection circuit (detection means corresponding to the detection circuits 69 and 73) for detecting the terminal voltage or the discharge current from the outside of the battery pack 1 as a capacitor (not shown). ) To be charged and supplied.

【0050】

In this way, when determining whether or not the protection circuit operates normally in the mounted electronic device, the charging mode cannot be set, so whether or not the FET 12 as an over-discharge switch operates normally. However, it cannot be determined whether or not the FET 14 as an overcharge switch operates normally. However, since the battery pack 1 is currently attached to an electronic device and is not charged, even if it is not possible to determine whether or not the FET 14 operates normally, there is a particular problem in practical use. There is nothing to do.

【0051】

[Effect of the invention]

As described above, according to the battery pack control device according to claim 1 and the battery pack control method according to claim 5, when a control signal for switching the protection circuit is input from the control terminal of the battery and the control signal is input. Since the operation of the protection circuit is judged according to the detection result of the terminal voltage or charge / discharge current of the battery, it is not necessary to provide a judgment circuit inside the battery pack, the configuration of the battery pack is simplified, and it is low. It is possible to reduce the cost and size. As a result, it is particularly advantageous when used in a battery pack attached to a portable electronic device.

[Simple explanation of drawings]

[Figure 1]

It is a block diagram which shows the structural example of the battery pack of this invention.

[Figure 2]

It is a block diagram which shows the structural example of the charger which charges the battery pack of FIG.

[Fig. 3]

It is the flowchart explaining the operation of the Example of FIG. 1 and FIG.

[Fig. 4]

It is a block diagram which shows the other structural example of the battery pack of this invention.

[Fig. 5]

It is a block diagram which shows the structural example of the charger which charges the battery pack of FIG.

[Fig. 6]

It is a block diagram which shows still another structural example of the battery pack of this invention.

[Fig. 7]

It is a block diagram which shows the structural example of the charger which charges the battery pack of FIG.

[Explanation of symbols]

1 Battery pack 2 charger 11 Battery 12,14 FET 17,18 Detection circuit 19 Control circuit 31,32 Charge / discharge terminal 33,34 Control terminal 51 to 54 terminals 69 Detection circuit 73 Detection circuit 74 Control circuit