JP2000014020A - Safety device, battery pack and electronic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the safety of a battery by providing, separately from a first anomaly detecting means, a second anomaly detecting means which detects an anomaly in a battery voltage and informs externally connected electronic equipment of the anomaly information. SOLUTION: An anomaly signal control circuit 15 of a safety device 2 is a two-input storage circuit fed with the signal outputs from a second battery voltage detecting means 11 and a third battery voltage detecting means 1. When a signal output from the second battery voltage detecting means 11 is input, the anomaly signal control circuit produces a signal output to an anomaly signal notification terminal 19 for notifying the electronic equipment that the battery pack concerned is anomalous. Even after the signal output from the second battery voltage detecting means 11 has stopped, the anomaly signal control circuit continues to produce the signal output to notify that the battery pack concerned is anomalous. When the anomaly signal control circuit is fed with a signal output indicating that the battery voltage of a secondary battery 1 has fallen below a specified value from a third battery voltage detecting means 12, the anomaly signal control circuit stops producing the signal output to the anomaly signal notification terminal 19. As a result, the safety of the battery can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a safety device, a battery pack, and an electronic device for preventing a secondary battery from being overcharged.

[0002]

2. Description of the Related Art With the rapid spread of electronic portable devices in recent years, batteries serving as power sources have become increasingly important. In particular, secondary batteries that can be repeatedly used for charging and discharging are now widely used as power supplies for main electronic devices (for example, notebook computers, mobile phones, video movies, and the like).

When such a secondary battery is used as a power source, it is necessary to prevent the secondary battery from being overcharged and overdischarged. In general, a safety device is built in the secondary battery pack and the battery is used. Is protected. Specific protection actions include:
Overcharge, overdischarge, and overcurrent protection operations are included. Due to the rise of lithium-ion secondary batteries in recent years and the like, the number of safety devices that provide double protection especially for overcharge is increasing.

For example, Japanese Patent Application Laid-Open No. Hei 8-116627 proposes a safety device for a battery pack having both first control means and second control means for overcharging a secondary battery. FIG. 2 is a block diagram of the conventional battery pack. A safety device incorporated in the conventional battery pack will be briefly described below.

A switching circuit 24 for switching a charging current flowing through the secondary battery 4 and a battery voltage of the secondary battery 4 are detected.
A first control circuit 20 for controlling the battery 4, a non-recovery shutoff circuit 25 for interrupting the charging current, and a battery voltage of the secondary battery 4 are detected. In the safety device 5 of the battery pack 6 having the configuration including the second control circuit 21 for shutting off the voltage, the first control circuit 20 determines whether or not the battery voltage of the secondary battery 4 becomes equal to or exceeds the first specified voltage. After a predetermined period of time has elapsed, the switching circuit 24 has a function of outputting a signal for interrupting the charging current (first safety device). In addition, it outputs an operation prohibition signal to the second control circuit 21 for a predetermined time and a predetermined period after the lapse of the predetermined time.

The second control circuit 21 is a second safety device for overcharging, detects a second specified voltage higher than the first specified voltage, and detects an abnormal operation of the first control circuit 20. When it is determined that there is, a signal is output to the non-returning shutoff circuit 25 located on the charging path, and the charging path is cut off to stop charging and prevent overcharging. In this case, if the same terminal is used for the charge path and the discharge path,
That the charging path is interrupted means that the discharging path is also interrupted. In other words, the conventional example employs a method in which the charging / discharging path is cut off when the second safety device operates.

[0007] In addition, the charging current is higher than the first specified voltage and the charging current is kept for the predetermined time so that the second safety device as the final charging stop means does not operate earlier than the first safety device. To force the flow, it is necessary to set the second specified voltage higher than the voltage value obtained by adding the voltage drop due to the internal resistance of the battery. However, with such a set value, the second specified voltage becomes too high, and the battery is further overcharged.
Outputs an operation prohibition signal to the second control circuit 21 upon detection. The second control circuit 21 operates only when it is determined that the operation of the first control circuit 20 is abnormal.

[0008]

However, in the above-mentioned prior art, a non-recovery shutoff circuit (for example, a fuse or the like) is used for the shutoff circuit located in the charging / discharging path. When a certain second control circuit operates, not only charging but also discharging are permanently disabled.
This means that the secondary battery overcharged to the second specified value of the second control circuit in which the second safety device operates cannot be discharged and is left as it is, which is preferable for safety. is not.

When a battery pack is used as a power source of a notebook personal computer, for example, when an AC adapter is connected as a notebook personal computer system, power is supplied to electronic devices and the battery pack is charged. Even if the second safety device of the battery pack operates and the charging / discharging path is interrupted, the user does not notice the abnormal state of the battery pack because the notebook computer receives the power supply from the AC adapter. .

[0010] Further, when the user disconnects the AC adapter in the above-mentioned use environment, the power supply to the electronic equipment is normally supplied from the battery pack, but the battery pack is supplied through the charge / discharge path. Cannot be supplied because the power supply is shut off. Therefore, there is a problem that the notebook personal computer cannot operate suddenly, which may cause data loss or system damage.

Also, signals are transmitted and received between the first control circuit and the second control circuit so that the second safety device as the final charging stop means does not operate before the first safety device. However, if extraneous noise is injected into the signal line to the second control circuit, or if the operation prohibition signal continues to be output due to the failure of the first control circuit, a second safety device is required. There is a danger that it will operate when it is not, or will not operate when it must. That is, since the circuits are not completely independent, for example, the second control circuit malfunctions or does not operate due to the failure of the first control circuit, or is affected by the failure of the first safety device. As a result, double protection may not be provided as a whole, and security may not be maintained.

A safety device, a battery pack, and an electronic device according to the present invention solve the above-mentioned problems, and aim to further improve safety.

[0013]

In order to achieve the above object, the present invention provides a battery voltage detecting device, a switch control circuit and a charging path cutoff switch. A second abnormality detecting means for detecting an abnormality and informing the externally connected electronic equipment of the abnormality information, wherein the second abnormality detecting means includes a battery voltage detecting means, an abnormal signal control circuit and a hysteresis. An object of the present invention is to provide a safety device, a battery pack, and an electronic device using a detection unit.

In this way, when charging is performed by the electronic device (for example, charging by the AC adapter of a notebook computer) and the second safety device operates in the secondary battery pack, a battery pack abnormality signal is output to the electronic device. By doing so, the user can notice abnormality of the battery pack via the display means of the electronic device. Further, since the discharge is possible even when the second safety device operates, the battery can be restored to the normal state instead of being left in an overcharged state by discharging the battery. As a further effect, for example, even when the power supply is used as a power supply for a notebook computer and the user disconnects the AC adapter or when a momentary power failure occurs, power can be supplied from the battery pack. Using the abnormal signal, the electronic device can perform optimal processing in its operation, and can terminate the electronic device without destroying data.

Further, since the first abnormality detection means and the second abnormality detection means have independent inputs, even if one of the abnormality detection means has a failure, the other abnormality detection means is adversely affected. However, each role can be realized and security can be maintained as a whole.

If the abnormal signal from the abnormality detecting means is continuously output once it starts to be output, the abnormal battery signal is continuously output even after the abnormal battery pack is removed from the electronic device. Even if the battery pack is re-attached to the electronic device or the charger or attached to another electronic device, it can be recognized that the battery pack is abnormal.

Furthermore, the electronic device can receive the abnormality information from the safety device and stop charging the battery pack, thereby maintaining the safety of the battery pack.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a secondary battery pack according to the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of a secondary battery pack according to the present invention, which has a terminal group 16 such as a battery pack positive terminal 17, a battery pack negative terminal 18, and an abnormal signal notification terminal 19. A secondary battery pack 3 incorporating the device 2 and mounted on an electronic device such as a notebook computer or a video movie to supply power.

Further, at the time of charging, the terminal group 16 is attached to an electronic device such as a charger, so that a charging current is supplied and the secondary battery 1 is charged.

Next, the safety device 2 built in the secondary battery pack 3 according to one embodiment of the present invention will be described. Specifically, the safety device 2 includes first, second, and third battery voltage detecting means 10, 11, and 12 for monitoring battery voltage, a switch control circuit 13, a charging path cutoff switch 14, an abnormality signal And a control circuit 15. The first, second, and third battery voltage detecting means 10, 11, and 12 are configured by a voltage monitoring circuit, a comparing circuit, an output drive circuit, and the like, and the abnormal signal control circuit 15 includes a storage circuit and a level shift circuit. And an output drive circuit.

The first battery voltage detecting means 10 is connected in parallel with the positive terminal and the negative terminal of the secondary battery 1, detects the terminal voltage of the secondary battery 1, and based on the detection result, the switch control circuit 13 Then, the signal output and the signal output are stopped.

The second battery voltage detecting means 11 is connected in parallel with the positive terminal and the negative terminal of the secondary battery 1 like the first battery voltage detecting means 10, and detects the terminal voltage of the secondary battery 1. The signal output to the abnormal signal control circuit 15 and the stop of the signal output are performed based on the detection result. The third battery voltage detecting means 12 is connected in parallel with the positive terminal and the negative terminal of the secondary battery 1 like the first and second battery voltage detecting means 10 and 11, and the terminal of the secondary battery 1 The voltage is detected, and a signal output to the abnormal signal control circuit 15 and a stop of the signal output are performed based on the detection result.

The switch control circuit 13 is a signal transmission circuit which receives an output signal of the first battery voltage detecting means 10 and outputs a signal based on the input signal and stops the signal output. A signal for cutting off the charging path is output to the switch 14, and if charging is possible, a signal for turning on the charging path is output to the charging path cutoff switch 14.

The charge path cutoff switch 14 is a semiconductor switch formed of a field effect transistor (FET), and is normally in a conductive state. Switch control circuit 1
When the signal output from 3 is input, the charging path is cut off.

The abnormal signal control circuit 15 is a two-input storage circuit (latch circuit) which receives the respective signal outputs of the second battery voltage detecting means 11 and the third battery voltage detecting means 12 as inputs. When the signal output from the battery voltage detecting means 11 is input, a signal is output to the abnormal signal notification terminal 19 to notify the electronic device that the battery pack is abnormal. After that, even if the signal output from the second battery voltage detecting means 11 is stopped, the signal output is continued to the abnormal signal notification terminal 19 to continuously notify that the present battery pack is abnormal. When a signal output from the third battery voltage detecting means 12 is input to notify that the battery voltage of the secondary battery 1 has fallen below the specified value, a function of stopping the signal output to the abnormal signal notification terminal 19 is provided. Have. Here, the specified value at which the signal is output from the third battery voltage detecting means 12 may be set to a low value that is not actually obtained. For example, when a lithium ion secondary battery is used as the secondary battery 1, the specified value is set to 2.4.
It is set to 0V. Then, since the overdischarge is detected and shut down by the electronic device (including the charger) before reaching this value, it means that the value is hardly reduced to that value. This allows
Although the abnormality signal control circuit 15 requires two inputs but is configured by a flip-flop having a simple configuration, the secondary battery 1 once protected by the second protection can be disabled because of high danger. Becomes

In the above-described configuration, the operation of the embodiment of the present invention will be described below with reference to FIGS. For example, in charging a lithium ion secondary battery, a charge control voltage of 4.2
V (the voltage value described below is the voltage value per unit cell)
, The charging proceeds without any termination due to some trouble, and when the battery voltage becomes 4.25 V or more, the first battery voltage detecting means 10 detects overcharge and outputs a signal a ( Time a). The output signal a is input to the charging path cutoff switch 14 via the switch control circuit 13 to cut off the charging path and prohibit charging (first safety device).

However, further failures such as breakage of the first battery voltage detecting means 10, the switch control circuit 13, the charging path cutoff switch 14, etc.
Alternatively, when the control lines connecting them are broken, charging is continued without ending and the battery voltage further rises to an overcharged state.

When the battery voltage becomes 4.35 V or more, the second battery voltage detecting means 11, which is a second safety device, detects overcharge and outputs a signal b (time b). The output signal b is input to the abnormal signal control circuit 15.

The abnormal signal control circuit 15 receives the signal b from the second battery voltage detecting means 11 and receives an abnormal signal notification terminal 19.
An abnormal signal d is output to the
The electronic device such as a charger and a PC is notified that the battery pack is abnormal. The charger, the PC, and the like stop the charging current in response to the signal d.

In this way, charging of an abnormal battery pack whose charging is not completed can be stopped as a system with the electronic device, and overcharging of the battery can be prevented.

That is, the battery voltage is monitored by the first battery voltage detecting means 10 and the second battery voltage detecting means 11 with respect to the overcharge of the secondary battery 1, so that the double Although protection is applied, the reliability of failures is increased by making the second protection independent of the first protection, and the second protection function is not processed by the battery pack itself. A series of charging / discharging systems that send information to the device to stop charging in the case of a charger, and to display information about abnormalities to the user while stopping charging while the PC is capable of discharging but stopping charging. Optimum safety control can be performed.

The voltage detecting means such as the first battery voltage detecting means 10 and the second battery voltage detecting means 11, which are generally used for overcharge protection, detect a signal output value (overcharge detection value). In many cases, there is a hysteresis between the detection value for stopping the signal output (the overcharge release detection value) and the hysteresis is about 30 mV. Charge detection is canceled. That is, by stopping the signal output, the first battery voltage detecting means 10 and the second battery voltage detecting means 11 return to the normal operation.

However, in the secondary battery pack according to one embodiment of the present invention, even if the battery voltage drops to the overcharge release detection value and the output signal b of the second battery voltage detection means 11 stops, the abnormal signal control is performed. Abnormal signal notification terminal 1 by latch function of circuit 15
By continuously outputting the signal d to 9, it is possible to continue to notify that the battery pack is abnormal (time c).

The abnormal signal control circuit 15 stops outputting the abnormal signal d when the output signal c of the third battery voltage detecting means 12 is inputted (time d). By setting the specified value to a voltage lower than the shutdown voltage of the electronic device, the abnormal signal control circuit 15 can also continue to output the abnormal signal d semipermanently.

FIG. 4 shows a signal after detection when an input of a prescribed voltage or more is applied to the first battery voltage detecting means 10 and the second battery voltage detecting means 11 having hysteresis in detection and release. The time relationship until output,
FIG. 4 is a diagram illustrating an abnormal signal output and a charging current output from a battery pack.

When a charging current is applied as an input to the first battery voltage detecting means 10 and the second battery voltage detecting means 11 as shown in FIG. 4, it is equal to or higher than the first specified voltage and equal to or higher than the second specified voltage. When a battery voltage is input such that
If the first safety device is normal, the first battery voltage detecting means 10 outputs a signal a after the first specified time has elapsed,
As described above, the charging current is cut off by the charging path cutoff switch 14.

If the first safety device shown in FIG. 4B is out of order, the second battery voltage detecting means 11 outputs a signal b after the lapse of the second specified time, and the battery When the pack notifies the abnormality signal d, the electronic device stops charging current.

Here, when the first safety device is normal as shown in FIG. 4A, the first specified time of the first battery voltage detecting means 10 is equal to the second battery voltage detecting means 11. Since it is shorter than the second specified time, the first battery voltage detecting means 10 always outputs a signal first. That is, by setting the second specified time longer than the first specified time, the first safety device can always be operated before the second safety device. This can prevent the second safety device from operating prior to the first safety device (malfunction), and only when the first safety device does not operate, can the second safety device be the final charging stop means. The heavy safety device can be activated.

In the above-described embodiment, the case where the battery pack 3 is mainly mounted on a notebook personal computer has been described as an example. However, the present invention can of course be mounted on other electronic devices. In the above embodiment, the case where a lithium ion secondary battery is used is mainly described.However, in the present invention, another secondary battery such as a nickel hydride storage battery or a lithium polymer secondary battery may be used. It goes without saying that the specified values of the first specified voltage, the second specified voltage, and the third specified voltage may be changed according to the characteristics of each battery. Furthermore, in the above embodiment, the case where the field effect transistor is used as the switch element has been described as an example.
Other electronic switches may be used in the present invention.

In the above embodiment, the case where one secondary battery 1 is used has been described as an example. However, the present invention can be applied to the case where a plurality of batteries are connected in series as shown in FIG. Can be. Further, in the above embodiment, the charge path cutoff switch 14 is disposed on the battery pack negative terminal 18 side, but may be disposed on the battery pack positive terminal 17 side as shown in FIG. 6 in the present invention.

In the above embodiment, the second battery voltage detecting means 11, the third battery voltage detecting means 12, and the abnormal signal control circuit 15 are used as the second abnormal detecting means. The same effect can be obtained by using the hysteresis detecting means 7 in which these are integrated as shown in FIG.

Further, the electronic device according to the present invention has the above-mentioned P
The present invention is not limited to C or a charger, and the configuration shown in FIG. 5 is a technique that can be applied to an EV (electric vehicle) using a large number of batteries connected in series.

[0043]

As described above in detail, according to the present invention, the electronic device is notified of the operation of the second safety device by the notification of the abnormal signal of the battery pack. Can provide an excellent safety device and a battery pack that can recognize that the abnormality is occurring and can cope with the occurrence of the abnormality as a system integrated with the electronic device.

Further, even if the second safety device operates, only charging is stopped without interrupting the charging / discharging path, so that the secondary battery pack can be discharged. For this reason, it is possible to return the battery voltage to the normal voltage by discharging, instead of leaving the secondary battery overcharged, which has an advantageous effect that the secondary battery can be restored to a safe state. Play.

Further, by increasing the operation specified time of the second safety device, malfunction of the double safety device can be prevented. The safety device works to maintain safety.

[Brief description of the drawings]

FIG. 1 is a block diagram of a secondary battery pack according to the present invention.

FIG. 2 is a block diagram of a conventional secondary battery pack.

FIG. 3 is a timing chart illustrating the operation of the present embodiment.

FIG. 4 is another timing chart illustrating the operation of the present embodiment.

FIG. 5 is a block diagram of another secondary battery pack according to the present invention.

FIG. 6 is a block diagram of another secondary battery pack according to the present invention.

FIG. 7 is a block diagram of still another secondary battery pack according to the present invention;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Secondary battery 2 Safety device 3 Secondary battery pack 7 Hysteresis detector 10 First battery voltage detecting means 11 Second battery voltage detecting means 12 Third battery voltage detecting means 13 Switch control circuit 14 Charge path cutoff switch 15 Abnormal signal control circuit 16 Terminal group 17 Battery pack positive terminal 18 Battery pack negative terminal 19 Abnormal signal notification terminal

Claims (12)

[Claims] A first battery voltage detecting means for detecting a voltage of a battery, a switch control circuit for receiving an output from the first battery voltage detecting means, and a charging path for receiving an output from the switch control circuit. A safety device comprising: first abnormality detection means including a charge path cutoff switch for shutting off; and second abnormality detection means for detecting abnormality in battery voltage and notifying abnormality information to the outside. 2. The safety device according to claim 1, further comprising a second battery voltage detection unit and an abnormality signal control circuit as the second abnormality detection unit. 3. The safety device according to claim 2, further comprising third battery voltage detecting means. 4. The safety device according to claim 1, further comprising a hysteresis detecting means as the second abnormality detecting means. 5. The safety device according to claim 1, wherein the first abnormality detection unit and the second abnormality detection unit detect an abnormality in a state independent of each other. 6. The safety device according to claim 1, wherein after the abnormal signal is output from the second abnormality detecting means, the safety signal is continuously output throughout. 7. A first battery voltage detecting means for detecting a battery voltage, a switch control circuit for receiving an output from the first battery voltage detecting means, and a charging path for receiving an output from the switch control circuit. A first abnormality detecting means including a charging path disconnection switch for interrupting the power supply; and a second abnormality detecting means for detecting an abnormality in the battery voltage and notifying the abnormality information to the outside, wherein the second abnormality detecting means includes: A safety device wherein a specified time until output is set to be longer than a specified time until the first abnormality detection means outputs. 8. The safety device according to claim 1, a battery pack positive terminal and a battery pack negative terminal for connection to an external device, a built-in secondary battery, and the safety device. And an abnormal signal notification terminal for notifying the external device of the abnormal signal. 9. The battery pack according to claim 8, wherein the secondary battery is a lithium ion secondary battery. 10. An electronic device equipped with the battery pack according to claim 8. 11. The electronic apparatus according to claim 10, wherein charging of the battery pack is stopped in response to the abnormality information from the safety device according to claim 1. 12. The electronic apparatus according to claim 10, wherein the abnormality information from the safety device according to claim 1 is received, and an abnormality in the battery pack is displayed on a display unit.