JP3294754B2 - Secondary battery protection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a protection circuit for a secondary battery.

[0002]

2. Description of the Related Art Conventionally, in a non-aqueous solvent secondary battery such as a lithium secondary battery or a lead storage battery, the terminal voltage (battery voltage) of the battery becomes excessively high during charging, or the battery voltage decreases during discharging. If too long, safety may be impaired or battery performance may be degraded. In particular, in the case of a lithium secondary battery, when the battery voltage becomes, for example, 4.5 V or more during charging, gas is generated by decomposition of the electrolytic solution, and as a result, the pressure inside the battery increases, the safety valve operates, and liquid leakage occurs. Sometimes. In addition, when the battery voltage becomes 2 V or less during discharging, the current collector copper used for the negative electrode starts to dissolve in the electrolytic solution, and the battery performance deteriorates. For this reason, it is necessary to monitor the battery voltage and control charging and discharging so that the battery voltage is within a predetermined range before use.

Therefore, when a lithium secondary battery is used, the charging current is cut off when the battery voltage rises and reaches a charging prohibition voltage during charging, and the battery voltage decreases when discharging and the battery voltage drops to a preset discharging prohibition voltage. In general, a method of charging / discharging via a protection circuit having a function of interrupting a discharge current when the current reaches a predetermined level has been adopted. Here, the charging prohibition voltage is a voltage slightly lower than the voltage at which the decomposition of the electrolytic solution starts, for example, 4.3.
The voltage is set to 5 V, and the discharge prohibition voltage is set to a voltage slightly higher than the voltage 2 V at which the negative electrode copper starts to melt, for example, 2.3 V.

Conventional protection circuits having such a function include, for example, a voltage detection circuit for detecting a battery voltage and a FET for interrupting a charging current or a discharging current based on an output of the voltage detection circuit. When the battery voltage reaches the charging inhibition voltage, the first switching element is turned off to interrupt the charging current when the battery voltage reaches the charging inhibition voltage, and when the battery voltage reaches the discharging inhibition voltage, the second switching element is turned off. The discharge current is cut off in a non-conductive state.

In general, when charging a secondary battery, the temperature range in which the secondary battery can be charged is limited. Therefore, in a conventional charger, the temperature of the battery is detected by a temperature detecting element such as a thermistor, and the temperature outside the temperature range is detected. In case of not charging.

[0006]

In the above-described conventional protection circuit for a secondary battery, if the voltage detection circuit fails for any reason, the switching element is not activated even if the battery voltage reaches the charge inhibition voltage or the discharge inhibition voltage. There is a problem that the protection function does not work because it cannot be turned off. Further, when the switch element fails and enters a short-circuit state, even if the voltage detection circuit outputs a charge prohibition signal or a discharge prohibition signal, the charging current or the discharge current cannot be cut off, and the protection function does not work. Was.

According to the present invention, a secondary battery can be reliably protected from overcharging and overcharging even when a circuit system for preventing overcharging or overdischarging of a voltage detecting circuit, a switch element, and the like breaks down. An object of the present invention is to provide a protection circuit for a secondary battery.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is to change a temperature detection output to a signal corresponding to an abnormal temperature when detecting an abnormality in a charge state or a discharge state of a secondary battery. Thus, a function of notifying the abnormality to a charger or a device using a battery and preventing overcharge or overdischarge is provided.

That is, a protection circuit for a secondary battery according to the present invention detects a switch element inserted in series in a charge / discharge circuit of the secondary battery and a terminal voltage of the secondary battery, and detects a terminal voltage of the secondary battery. Overcharging prevention means for preventing overcharging of the secondary battery by turning off the switch element when the charging inhibition voltage of the secondary battery is reached, and detecting a temperature of the secondary battery and outputting a signal corresponding to the temperature. When the temperature is outside a predetermined temperature range, a temperature detecting means for controlling charging of the secondary battery and a terminal voltage of the secondary battery are monitored, and the terminal voltage is controlled by the terminal voltage.
Reaching a second charging prohibition voltage higher than the first charging prohibition voltage
Abnormality detection means for detecting an abnormality in the state of charge, and an output of the temperature detection means forcibly changing to a signal corresponding to outside the predetermined temperature range in response to the abnormality detection in the state of charge by the abnormality detection means. Abnormality responding means for causing the abnormality to occur.

A protection circuit for a secondary battery according to the present invention detects a switch element inserted in series in a charge / discharge circuit of the secondary battery and a terminal voltage of the secondary battery, and detects a terminal voltage of the secondary battery. Overdischarge prevention means for turning off the switch element to prevent overdischarge of the secondary battery when the discharge inhibition voltage of the secondary battery is reached, and detecting a temperature of the secondary battery and outputting a signal corresponding to the temperature. A temperature detection unit for controlling discharge of the secondary battery when the temperature is outside a predetermined temperature range; and a terminal voltage of the secondary battery is monitored, and the terminal voltage is set to the first voltage.
Reaches the second discharge prohibition voltage lower than the discharge prohibition voltage of
Abnormality detection means for detecting abnormality in the discharge state; and forcibly changing the output of the temperature detection means to a signal corresponding to outside the predetermined temperature range in response to the abnormality detection in the discharge state by the abnormality detection means. Abnormality response means.

Further, a protection circuit for a secondary battery according to the present invention detects first and second switch elements inserted in series in a charging / discharging circuit of the secondary battery and a terminal voltage of the secondary battery. An overcharge preventing means for setting the first switch element to a non-conductive state to prevent overcharge of the secondary battery when the terminal voltage reaches a predetermined charging prohibition voltage; and detecting a terminal voltage of the secondary battery. When the terminal voltage reaches a predetermined discharge prohibition voltage, the second switch element is turned off to prevent overdischarge of the secondary battery, and a temperature of the secondary battery is detected. And outputting a signal corresponding to the temperature, and a temperature detecting means for controlling charging of the secondary battery when the temperature is out of a predetermined temperature range, and an end of the secondary battery.
The terminal voltage is monitored, and the terminal voltage is set to the first charge inhibition voltage.
When the second charging prohibition voltage that is higher than the
The terminal voltage is detected as normal and the first discharge inhibit
When the voltage reaches the second discharge inhibition voltage lower than the
An abnormality detecting means for detecting as normal, and a signal corresponding to forcibly changing the output of the temperature detecting means outside the predetermined temperature range in response to abnormality detection of at least one of the charge state and the discharge state by the abnormality detection means. And abnormal response means for changing the

As described above, in the abnormality detecting circuit for a secondary battery according to the present invention, when an abnormality in the charging state or the discharging state of the secondary battery is detected, the output of the temperature detecting means is forcibly out of the predetermined temperature range. By changing to a signal equivalent to the above, it is possible to notify the charger or the equipment using the secondary battery of the fact, thereby stopping the charging operation of the charger or stopping the discharging operation of the equipment using the battery. It can be stopped. Therefore, even when a circuit system for preventing overcharge or overdischarge fails, overcharge or overdischarge of the secondary battery is prevented, and a more reliable protection operation is achieved.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a protection circuit for a secondary battery according to one embodiment of the present invention. The secondary batteries (hereinafter simply referred to as batteries) 1 and 2 to be protected by the secondary battery protection circuit are of a constant voltage charging type such as a non-aqueous solvent secondary battery such as a lithium secondary battery or a lead storage battery. This embodiment is a battery to be charged. In this embodiment, a case of a lithium secondary battery will be described as an example.

The batteries 1 and 2 are connected in series,
N-channel field effect transistors (hereinafter, referred to as FETs) 3 and 4 constituting first and second switch elements are connected in series to the charge / discharge circuit.
Specifically, the source terminal of the second FET 4 is connected to the negative terminal of the battery 2 and the drain terminal of the FET 4 is the first terminal.
Is connected to the drain terminal of the FET3. The parasitic diode D1 of the first FET 3 is in parallel between the drain terminal and the source terminal of the FET 3 so as to be forward during discharge, and the parasitic diode D2 of the second FET 4 is forward during charging. As described above, the FET 4 is in parallel between the drain terminal and the source terminal.

This protection circuit has a positive terminal (+), a negative terminal (-) and a temperature detecting terminal (T) as external connection terminals, and the positive electrode of the battery 1 is a positive terminal (+) as an external connection terminal. The source terminal of the first FET 3 is connected to a negative terminal (-) which is an external connection terminal. Further, one end of a thermistor 11 which is a temperature detecting element is connected to a temperature detecting terminal (T) which is an external connecting terminal, and the other end of the thermistor 11 is connected to a negative terminal (-) which is an external connecting terminal. .

The positive terminal (+), the negative terminal (-) and the temperature detecting terminal (T), which are external connection terminals, are connected to a charger (not shown) at the time of charging, and the positive terminal (+) →
By passing a charging current through a path of battery 1 → battery 2 → second FET 4 → first FET 3 → negative terminal (−),
The batteries 1 and 2 are charged. Here, the charger monitors the state of the temperature detection terminal (T) during charging, and when the battery temperature is too high (for example, 45 ° C. or more) or too low (for example, 0 ° C. or less), Has a function of stopping charging when the temperature is outside the predetermined temperature range.

The overcharge prevention circuit 5 monitors the terminal voltages of the batteries 1 and 2, and generates a charge inhibit output when the terminal voltage exceeds the first charge inhibit voltage during charging. The over-discharge prevention / prevention circuit 6 similarly monitors the terminal voltages of the batteries 1 and 2, and generates a discharge-inhibited output when the terminal voltage decreases during discharge and falls below the discharge-inhibited voltage.

That is, the input terminal a of the overcharge prevention circuit 5 and the overdischarge prevention circuit 6 is the positive electrode of the battery 1, the input terminal b is the negative electrode of the battery 1 and the positive electrode of the battery 2, and the input terminal c is the battery. 2 negative electrodes. The output terminal d of the overcharge prevention circuit 5 is connected to the gate terminal of the first FET 3, and the output terminal e of the overdischarge prevention circuit 6 is connected to the gate terminal of the second FET 4. Here, when the terminal voltage of any of the batteries 1 and 2 exceeds the first charge prohibition voltage, the overcharge prevention circuit 5
Generates a charge inhibition output, and its output terminal d is inverted from a high level to a low level. When the terminal voltage of any of the batteries 1 and 2 becomes equal to or lower than the discharge prohibition voltage, the overdischarge prevention circuit 6 generates a discharge prohibition output, and the output terminal e is inverted from the high level to the low level.

First and second voltage detection circuits 7 and 8
And an OR circuit 9 for detecting an abnormality in the charge / discharge state of the batteries 1 and 2.
That is, in the first voltage detection circuit 7, the input terminal IN is connected to the plus electrode of the battery 1 via the terminal f, and the reference potential terminal GND is connected to the minus electrode of the battery 1 and the plus electrode of the battery 2 via the terminal g. By being connected to the connection point, the terminal voltage of the battery 1 is monitored. In the second voltage detection circuit 8, the input terminal IN is connected to a connection point between the negative electrode of the battery 1 and the positive electrode of the battery 2 via the terminal g, and the reference potential terminal GND is connected to the connection point of the battery 2 via the terminal h. The terminal voltage of the battery 2 is monitored by being connected to the negative electrode.

First and second voltage detection circuits 7 and 8
Are connected to two input terminals of the OR circuit 9, respectively. When the terminal voltage of any of the batteries 1 and 2 exceeds the second charge inhibition voltage, the output of any of the voltage detection circuits 7 and 8 goes high, and the output of the OR circuit 9 goes high.

The output terminal of the OR circuit 9, that is, the output terminal i of the abnormality detection circuit 10, is connected to the base of an NPN transistor 12 constituting a failure response switch circuit. The collector of the transistor 12 is connected to a temperature detection terminal (T) which is an external connection terminal, and the emitter is connected to a minus terminal (-). The transistor 12 includes an abnormality response means for forcibly changing the state of the temperature detection terminal (T) to a signal corresponding to a battery temperature outside a predetermined temperature range in response to an abnormality detection output of the abnormality detection circuit 10. Make up.

Next, the operation of the protection circuit according to the present embodiment will be described. When the terminal voltages of the batteries 1 and 2 are both between the discharge prohibition voltage and the charge prohibition voltage, the overcharge prevention circuit 5
The output terminals d and e of the over-discharge prevention circuit 6 both generate a high-level signal, so that the first and second FETs 3 and 4 are all in a conductive state, and both charging and discharging are performed normally. However, the charger normally charges only when the output of the temperature detection terminal (T) is a signal corresponding to the temperature within the predetermined temperature range.

If the battery temperature rises abnormally during charging and is out of the predetermined temperature range, or if charging is attempted at a temperature lower than the predetermined temperature range, the resistance value of the thermistor 11 is too low. If the temperature is too high or too high, the output of the temperature detection terminal (T) deviates from the signal corresponding to the predetermined temperature range, and the charger stops charging.

In addition, since the charger performs charging so that the charging voltage per battery is lower than the first charging prohibiting voltage set in the overcharge protection circuit 5, the battery 1 is normally charged.
Both the terminal voltages of the first and second terminals are lower than the first charge prohibition voltage, the output terminal d of the overcharge / discharge prevention circuit 5 becomes high level, and the first FET 3 maintains the conductive state. On the other hand, if the charging voltage becomes high due to a failure of the charger and one or both of the batteries 1 and 2 exceed the first charging inhibition voltage, the output terminal d of the overcharge / discharge prevention circuit 5 becomes Since the level becomes low and the first FET 3 is turned off, charging is stopped and overcharging of the battery is prevented.

On the other hand, when the terminal voltage of one or both of the batteries 1 and 2 drops during discharge and becomes lower than the discharge prohibition voltage, the output terminal e of the overdischarge prevention circuit 6 changes from a high level to a low level. Since the second FET 4 is in a non-conducting state, the discharge is stopped and overdischarge of the battery is prevented.

When the charger fails for some reason and the overcharge prevention circuit 5 fails, the terminal voltage of one or both of the batteries 1 and 2 becomes higher than the first charge inhibition voltage. Consider a situation in which the output terminal d of the overcharge prevention circuit 5 remains at a high level.
In such a case, since the charging is continued, the terminal voltage of one or both of the batteries 1 and 2 exceeds the first charging inhibition voltage, but the terminal voltage of the second charging is higher than the first charging inhibition voltage. When the voltage reaches the prohibition voltage , the output of one or both of the voltage detection circuits 7 and 8 goes high, and the output of the OR circuit 9 goes high.

Therefore, the abnormal response switch circuit N
Since the PN transistor 12 becomes conductive and the impedance between the temperature detection terminal (T) and the minus terminal (-) becomes substantially 0Ω, the state of the temperature detection terminal (T) corresponds to a state in which the battery temperature is out of the predetermined temperature range. Signal. Accordingly, the charger determines that the battery temperature is out of the chargeable temperature and is abnormally high, and stops charging the batteries 1 and 2.

Also, the charger fails and the first FE
Consider a case in which T3 fails and a conduction state is established between the drain and the source. In such a case, even if the terminal voltage of one or both of the batteries 1 and 2 becomes equal to or higher than the first charge inhibition voltage, and the output terminal d of the overcharge protection circuit 5 becomes low level, the first FET 3 becomes conductive. Therefore, the terminal voltage exceeds the first charging prohibition voltage, but when the terminal voltage further reaches the second charging prohibition voltage higher than the first charging prohibition voltage, one or both of the voltage detection circuits 7 and 8 are detected. Becomes high level, and the output of the OR circuit 9 becomes high level. Therefore, as in the case described above, the NPN transistor 12, which is the switch circuit for abnormality response, becomes conductive,
Since the impedance between the temperature detection terminal (T) and the minus terminal (-) is substantially 0Ω, the charger determines that the battery temperature is out of the chargeable temperature and is abnormally high, and stops charging.

Next, another configuration example of the abnormality detection circuit 10 will be described with reference to FIG. In FIG. 2, output stages of voltage detection circuits 7 and 8 are bipolar transistors Q1, Q
2 and an open collector configuration. It should be noted that the output stage transistor may be replaced with a bipolar transistor by an FET, and may have an open drain configuration. The output terminal of the voltage detection known circuits 7 and 8 are pulled up by resistors R1 and R2.

Now, when the terminal voltage of the battery 1, that is, the input of the voltage detection circuit 7 is lower than the second charging prohibition voltage, the output of the voltage detection circuit 7 becomes low level, and when it is higher, it is open. The input terminal of the voltage detection circuit 7 is the abnormality detection circuit 1
0, the reference potential terminal of the voltage detection circuit 7 is connected to the input terminal g of the abnormality detection circuit 10, the reference potential terminal of the voltage detection circuit 8 is connected to the input terminal h of the abnormality detection circuit 10, and The output terminal of the detection circuit 7 is connected to the input terminal of the voltage detection circuit 8, and the output terminal of the voltage detection circuit 8 is connected to the output terminal i of the abnormality detection circuit 10, respectively.

Here, when both the batteries 1 and 2 are lower than the second charging prohibition voltage, the output of the voltage detection circuit 7 is at a low level, and is substantially equal to the potential of the input terminal g.
Therefore, the input terminals of the voltage detection circuit 8 are connected to the terminals gh
The voltage between them, that is, the terminal voltage of the battery 2 is applied,
Since the terminal voltage of the battery 2 is also lower than the second charging prohibition voltage, the output of the voltage detection circuit 8 is at a low level, and the output terminal i is at a low level.

Next, when the terminal voltage of the battery 1 is higher than the second charging prohibition voltage, the output of the voltage detection circuit 7 becomes high level, and a value of the terminal voltage of the battery 1 is generated. Therefore,
A voltage equal to or higher than the sum of the terminal voltages of the batteries 1 and 2, that is, a voltage equal to or higher than the second charge inhibition voltage is applied to the input terminal of the voltage detection circuit 8, and the output of the voltage detection circuit 8 is at a high level.

When the terminal voltage of the battery 1 is lower than the second charging prohibition voltage and the terminal voltage of the battery 2 is higher than the second charging prohibition voltage, the output of the voltage detection circuit 7 is at a low level, Since the terminal voltage of the battery 2 is applied to the input terminal of the detection circuit 8, the output terminal of the voltage detection circuit 8 is at a high level.

When the terminal voltages of the batteries 1 and 2 are both
When the voltage is higher than the charge prohibition voltage, the output of the voltage detection circuit 7 becomes high and the output of the voltage detection circuit 8 also becomes high, so that the output terminal i becomes high.

Therefore, even if the abnormality detection circuit 10 having the configuration shown in FIG. 2 is used, the same result as that of the previous embodiment can be obtained. The present invention is not limited to the above embodiment, and can be implemented with various modifications as follows.

(1) In the above embodiment, a non-aqueous solvent battery such as a lithium secondary battery has been described as an example of a secondary battery charged at a constant voltage. However, a lead storage battery may be used as the secondary battery. Other secondary batteries may be used.

(2) In the above embodiment, the case where two batteries are connected in series has been described. However, any other number of batteries including one battery may be used, and one or a plurality of cell blocks connected in parallel may be connected in series. You may.

(3) In the above embodiment, an example was described in which the FET as a switch element was connected to the negative electrode side of the battery. However, the FET may be connected to the positive electrode side of the battery, that is, in series with the charge / discharge circuit. Just insert it.

(4) In the above embodiment, the abnormality detection circuit 1
Although a case has been described where the abnormality detection is performed by detecting the battery voltage at 0, the battery temperature may be measured and an abnormality signal may be generated when the battery temperature becomes abnormally high.

(5) In the above embodiment, the abnormality detection circuit 1
When an abnormal signal is generated, both ends of the thermistor 11 are short-circuited, but a PNP transistor 12 for abnormal response is connected in series with the thermistor 11 as shown in FIG. 12 may be blocked. In this case, the charger determines that the battery temperature is abnormally low due to the cutoff of the transistor 12.

(6) In the above embodiment, the abnormality detection circuit 1
Although 0 monitors only the terminal voltage during charging of the battery, the terminal voltage during discharging may also be monitored. In this case, the output of the temperature detection terminal may be monitored on the device using the battery, and the discharge may be stopped by the discharge control circuit in the device using the battery according to the signal.

(7) In the above embodiment, the second charging prohibition voltage is higher than the first charging prohibition voltage. However, the magnitude relationship between the two may be reversed or the same. (8) In the above embodiment, the second discharge inhibition voltage is equal to the second discharge inhibition voltage.
Although the discharge prohibition voltage is lowered, the magnitude relationship between them may be reversed or may be the same.

(9) In addition to the protection circuit described in the above embodiment, a protection element such as a PTC, a thermostat or a temperature fuse may be inserted into the charge / discharge circuit. (10) In the abnormality detection circuit of FIG. 2, the output stages of the voltage detection circuits 7 and 8 have an open collector configuration, but may have an open drain configuration as described above.
A configuration may be used.

(11) A filter circuit may be inserted in the abnormality detection circuit or the abnormality response switch circuit of the above embodiment. When a filter circuit is inserted, malfunction due to noise is reduced. The filter circuit may be a CR integration circuit including a capacitor and a resistor, or may be a pulse width detection circuit that detects that the abnormal state has continued for a predetermined time or more.

(12) In FIG. 2, although the resistors R1 and R2 are both pulled up to the same potential as the terminal f, that is, the positive electrode of the battery 1, the resistors R1 and R2 have the same resistance value, May be connected to the input terminal g, that is, the positive electrode of the battery 2. In this way, the currents flowing from the batteries 1 and 2 to the abnormality detection circuit 10 become equal, and the electric capacity balance of the batteries 1 and 2 does not break even after being left for a long time.

[0046]

As described above, according to the secondary battery protection circuit of the present invention, the overcharge prevention circuit and the overdischarge prevention circuit fail, or the switch element inserted in the charge / discharge path is short-circuited. In the case of, overcharge or overdischarge is detected by the abnormality detection circuit, and the output of the temperature detection terminal is forcibly set to an abnormal state as a signal corresponding to outside the predetermined temperature range, and based on the signal, the charger side or the device side , Charging and discharging can be stopped, so that the reliability of the protection circuit can be further improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a protection circuit for a secondary battery according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating another configuration example of the abnormality detection circuit;

FIG. 3 is a diagram showing another connection example of the temperature detection element and the abnormal response transistor;

[Explanation of symbols]

 1, 2, secondary battery 3, 4, first and second FET (switch element) 5, overcharge prevention circuit 6, overdischarge prevention circuit 7, 8, voltage detection circuit 10, abnormality detection circuit 11, thermistor ( Temperature detection element) 12: transistor for abnormal response

Continued on the front page (73) Patent holder 000003539 Toshiba Battery Co., Ltd. 3-4-1-10 Minamishinagawa, Shinagawa-ku, Tokyo (72) Inventor Toshishi Mito 1623-14 Shimotsuruma, Yamato-shi, Kanagawa Japan 14 IBM Japan, Ltd. (72) Inventor Masahito Kizawa 1623-14 Shimotsuruma, Yamato-shi, Kanagawa Prefecture Japan Yamato Office of IBM Corporation (72) Inventor Hiroshi Nakagawa 1623-14 Shimotsuruma, Yamato-shi, Kanagawa Japan 14 (72) Inventor Kazuo Mukai 72 Horikawa-cho, Saiwai-ku, Kawasaki City, Kanagawa Prefecture Inside A / T Battery Co., Ltd. (72) Inventor Nobuo Shioshima 3-4-10 Minamishinagawa, Shinagawa-ku, Tokyo No. Toshiba Battery Corporation (72) Inventor Masanori Isshiki 3-4-10 Minamishinagawa, Shinagawa-ku, Tokyo Toshiba Battery Corporation (72) Inventor Noriyuki Ito 3-4-1 Minamishinagawa, Shinagawa-ku, Tokyo No. Toshiba Battery Corporation (56) References JP-A-8-98414 (JP, A) JP-A-9-17455 (JP, A) JP-A-8-98422 (JP, A) JP-A-6-105458 (JP, A) Table 10-10-510975 (JP, A) ( 58) Field surveyed (Int.Cl. ⁷ , DB name) H02J ^7/ 00-7/12 H02J ⁷ /34-7/36

Claims (4)

(57) [Claims] 1. A switch element inserted in series in a charge / discharge circuit of a secondary battery, and a terminal voltage of the secondary battery is detected .
Overcharge prevention means for preventing the overcharge of the secondary battery by turning off the switch element when the charge inhibition voltage of the battery has been reached; detecting a temperature of the secondary battery and outputting a signal corresponding to the temperature; A temperature detection unit for controlling charging of the secondary battery when the temperature is outside a predetermined temperature range; anda terminal voltage of the secondary battery is monitored.
Reaching a second charging prohibition voltage higher than the first charging prohibition voltage
Then, abnormality detection means for detecting an abnormality of the state of charge, and in response to the abnormality detection of the state of charge by the abnormality detection means, forcibly changes the output of the temperature detection means to a signal corresponding to outside the predetermined temperature range. A protection circuit for a secondary battery, comprising: an abnormal response unit that changes the voltage. 2. A switch element inserted in series in a charge / discharge circuit of a secondary battery, and a terminal voltage of the secondary battery is detected .
Overdischarge prevention means for preventing overdischarge of the secondary battery by turning off the switch element when the discharge inhibition voltage of the secondary battery has been reached, detecting a temperature of the secondary battery and outputting a signal corresponding to the temperature. A temperature detecting means for controlling the discharge of the secondary battery when the temperature is outside a predetermined temperature range; anda terminal voltage of the secondary battery is monitored.
A second discharge prohibition voltage lower than the first discharge prohibition voltage is reached.
Abnormality detection means for detecting an abnormality in the discharge state, and in response to the abnormality detection in the discharge state by the abnormality detection means, forcibly changes the output of the temperature detection means to a signal corresponding to outside the predetermined temperature range. A protection circuit for a secondary battery, comprising: an abnormal response unit that changes the voltage. First and second switching element inserted in series in the charging and discharging circuit 3. A secondary battery, to detect the terminal voltage of the secondary battery, this terminal voltage first charging prohibition voltage reached the overcharge prevention means for preventing the overcharge of the secondary battery the first switching element as a non-conductive state when I, and detects the terminal voltage of the secondary battery, the terminal voltage is first
Overdischarge prevention means for preventing overdischarge of the secondary battery by turning off the second switch element when the discharge inhibition voltage of the secondary battery is reached, and detecting the temperature of the secondary battery and corresponding to the temperature. A signal detecting means for controlling charging of the secondary battery when the temperature is outside a predetermined temperature range, and monitoring a terminal voltage of the secondary battery, and the terminal voltage is
Reaching a second charging prohibition voltage higher than the first charging prohibition voltage
Is detected as an abnormal state of charge, and this terminal voltage is
A second discharge prohibition voltage lower than the first discharge prohibition voltage is reached.
Abnormality detection means for detecting an abnormality in the discharge state, and forcing the output of the temperature detection means in response to the abnormality detection of at least one of the charge state and the discharge state by the abnormality detection means in the predetermined temperature range. An abnormal response means for changing to a signal corresponding to the outside. 4. The temperature detecting means comprises a temperature detecting element whose resistance value changes according to the temperature. The abnormal response means is connected in series or parallel to the temperature detecting element, and is turned on by the output of the abnormal detecting means. The protection circuit for a secondary battery according to any one of claims 1 to 3, comprising a switch circuit that is turned off.