JPH09233713A - Protective circuit of secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inform used equipment such as a charger or a batter of its abnormality and prevent overcharge or overdischarge by changing the temperature detection output into the signal equivalent abnormal temperature, when this protective circuit detects the abnormality of the charge condition or discharge condition of a secondary battery. SOLUTION: Secondary batteries 1 and 2 are charged by fixed voltage charge method used for, for example, a lithium secondary battery, a lead battery, etc. The batteries 1 and 2 are connected in series, and n-channel FETs 3 and 4 constituting first and second switch elements are connected in series to the charge/discharge circuit. The parasitic diodes D1 and D2 of the FETs 3 and 4 get in forward direction at the time of charge and discharge. In a protective circuit, the + terminal, to the + terminal of the battery 1, and the - terminal, to the source of the FET 3, and a thermistor 1, between the outer terminal T and the - terminal, are connected. The thermistor 11 operates overcharge or overdischarge preventive circuits 5 or 6 through a transistor 12 and an abnormality detection circuit 10 so as to charge or discharge it properly when the temperature during charge or discharge deviates from the specified range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery protection circuit.

[0002]

2. Description of the Related Art Conventionally, in non-aqueous solvent type secondary batteries such as lithium secondary batteries and lead acid batteries, the terminal voltage (battery voltage) of the battery becomes too high during charging, or the battery voltage drops during discharging. If it passes, safety may be impaired or battery performance may be deteriorated. Particularly in the case of a lithium secondary battery, if the battery voltage becomes 4.5 V or higher during charging, gas is generated due to decomposition of the electrolytic solution, and as a result, the internal pressure of the battery rises, the safety valve operates, and leakage occurs. Sometimes. Further, when the battery voltage becomes 2 V or less during discharging, the copper of the current collector used for the negative electrode begins to dissolve in the electrolytic solution and the battery performance deteriorates. Therefore, it is necessary to monitor the battery voltage and control the 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 interrupted when the battery voltage rises to reach the charge inhibition voltage during charging, and the battery voltage decreases to the preset discharge inhibition voltage during discharging. A method of charging / discharging via a protection circuit having a function of interrupting a discharge current when the discharge reaches is generally adopted. Here, the charge inhibition voltage is a voltage slightly lower than the voltage at which decomposition of the electrolytic solution starts, for example, 4.3.
The discharge inhibition voltage is set to 5 V, and 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.

A conventional protection circuit having such a function is, for example, a voltage detection circuit for detecting a battery voltage and a first FET such as an FET for cutting off a charging current or a discharging current based on an output of the voltage detection circuit. When the battery voltage reaches the charge inhibition voltage, the first switch element is turned off to interrupt the charging current, and when the battery voltage reaches the discharge inhibition voltage, the second switch element is activated. The discharge current is cut off in the non-conducting state.

In general, when charging a secondary battery, the temperature range in which the battery can be charged is limited. Therefore, in the conventional charger, the temperature of the battery is detected by a temperature detecting element such as a thermistor, and the temperature is out of that range. If so, try not to charge.

[0006]

In the above-mentioned conventional secondary battery protection circuit, when the voltage detection circuit fails for some reason, the switching element is 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. In addition, if the switch element fails and becomes short-circuited, the charging current and discharge current cannot be cut off even if the voltage detection circuit outputs the charge prohibition signal or the discharge prohibition signal, which also causes a problem that the protection function does not work. It was

According to the present invention, the secondary battery can be surely protected from overcharging and overcharging even if the circuit system for preventing overcharging or overdischarging of the voltage detection circuit or the switch element fails. It is intended to provide a protection circuit for a secondary battery.

[0008]

In order to solve the above problems, the present invention changes the temperature detection output to a signal corresponding to an abnormal temperature when an abnormality in the charging state or discharging state of the secondary battery is detected. It has a function of notifying an abnormality to a device using a charger or a battery and preventing overcharge or overdischarge.

That is, the protection circuit for a secondary battery according to the present invention detects the switch element inserted in series in the charging / discharging circuit of the secondary battery and the terminal voltage of the secondary battery, and this terminal voltage is a predetermined value. Overcharge preventing means for preventing the overcharge of the secondary battery by setting the switch element to the non-conducting state when the charge inhibit voltage of the secondary battery is reached, and detecting the temperature of the secondary battery and outputting a signal corresponding to the temperature. The temperature detecting means for controlling the charging of the secondary battery when the temperature is out of the predetermined temperature range, the abnormality detecting means for detecting an abnormality in the charging state of the secondary battery, and the charging state by the abnormality detecting means. And an abnormality response means for forcibly changing the output of the temperature detection means to a signal corresponding to the outside of the predetermined temperature range in response to the abnormality detection.

Also, the secondary battery protection circuit according to the present invention detects the terminal voltage of the secondary battery and the switch element inserted in series in the charging / discharging circuit of the secondary battery, and this terminal voltage is set to a predetermined value. When the discharge inhibit voltage is reached, the switch element is made non-conductive to prevent over-discharge of the secondary battery, and the temperature of the secondary battery is detected to output a signal corresponding to the temperature. The temperature detecting means for controlling the discharge of the secondary battery when the temperature is out of the predetermined temperature range, and the abnormality detecting means for detecting an abnormality in the discharge state of the secondary battery,
An abnormality response means for 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 of the discharge state by the abnormality detection means. .

Further, the protection circuit for a secondary battery according to the present invention detects the first and second switching elements inserted in series in the charging / discharging circuit of the secondary battery and the terminal voltage of the secondary battery. An overcharge prevention means for preventing the overcharge of the secondary battery by setting the first switch element to a non-conductive state when the terminal voltage reaches a predetermined charge inhibition voltage, and detecting the terminal voltage of the secondary battery. Then, when the terminal voltage reaches a predetermined discharge inhibition voltage, the second switch element is brought into a non-conducting state to prevent overdischarge of the secondary battery, and the temperature of the secondary battery is detected. Then, a signal corresponding to the temperature is output, and temperature detection means for controlling the charging of the secondary battery when the temperature is out of a predetermined temperature range, and an abnormality in the charging state and the discharging state of the secondary battery are detected. Abnormality detection means and the abnormality detection means An abnormality response means for forcibly changing the output of the temperature detection means to a signal corresponding to the outside of the predetermined temperature range in response to the abnormality detection of at least one of the charging state and the discharging state. And

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 discharging state of the secondary battery is detected, the output of the temperature detecting means is forced to fall outside the predetermined temperature range. By changing to a signal equivalent to, it is possible to inform the device using the charger or the secondary battery to that effect, thereby stopping the charging operation of the charger or discharging the device using the battery. It is possible to stop it. Therefore, even if the circuit system for preventing overcharge or overdischarge is broken, overcharge or overdischarge of the secondary battery is prevented, and 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 an exemplary embodiment of the present invention. Secondary batteries (hereinafter simply referred to as “batteries”) 1 and 2 to be protected by the protection circuit of the secondary battery are, for example, non-aqueous solvent secondary batteries such as lithium secondary batteries and constant voltage charging systems such as lead storage batteries. In this embodiment, a lithium secondary battery will be described as an example of a battery to be charged.

Batteries 1 and 2 are connected in series,
N-channel field effect transistors (hereinafter, referred to as FETs) 3 and 4 that form 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 FET 3. Further, the parasitic diode D1 of the first FET3 is connected in parallel between the drain terminal and the source terminal of the FET3 so as to be forward when discharging, and the parasitic diode D2 of the second FET4 is forward when charging. Thus, the drain terminal and the source terminal of the FET 4 are connected in parallel.

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

The positive terminal (+), the negative terminal (-) and the temperature detection terminal (T), which are external connection terminals, are connected to a charger (not shown) during charging, and the positive terminal (+) →
Battery 1 → Battery 2 → 2nd FET 4 → 1st FET 3 → By passing the charging current through the path of the minus 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 higher) or too low (for example, 0 ° C. or lower), that is, the battery temperature. If is out of the predetermined temperature range, it has a function of stopping charging.

The overcharge prevention circuit 5 monitors the terminal voltages of the batteries 1 and 2 and generates a charge prohibition output when the terminal voltage exceeds the first charge prohibition voltage during charging. Similarly, the over-discharge prevention circuit 6 monitors the terminal voltages of the batteries 1 and 2, and generates a discharge-prohibited output when the terminal voltage drops at the time of discharging and becomes equal to or lower than the discharge-prohibited 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. It is connected to each of the two 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 one of the batteries 1 and 2 exceeds the first charge inhibition 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 either of the batteries 1 and 2 becomes equal to or lower than the discharge inhibition voltage, the overdischarge prevention circuit 6 generates a discharge inhibition output, and its output terminal e is inverted from the high level to the low level.

First and second voltage detection circuits 7 and 8
An abnormality detection circuit 10 composed of an OR circuit 9 and an OR circuit 9 is a circuit that detects an abnormality in the charging / discharging state of the batteries 1 and 2.
That is, in the first voltage detection circuit 7, the input terminal IN is connected to the positive electrode of the battery 1 via the terminal f, and the reference potential terminal GND is connected to the negative electrode of the battery 1 and the positive electrode of the battery 2 via the terminal g. The terminal voltage of the battery 1 is monitored by being connected to the connection point. The input terminal IN of the second voltage detection circuit 8 is connected to the connection point of 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 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
The output terminal OUT of is connected to the two input terminals of the OR circuit 9, respectively. When the terminal voltage of one of the batteries 1 and 2 exceeds the second charge inhibition voltage, the output of one of the voltage detection circuits 7 and 8 becomes high level, and the output of the OR circuit 9 becomes high level.

To the output terminal of the OR circuit 9, that is, the output terminal i of the abnormality detection circuit 10, the base of the NPN transistor 12 which constitutes the abnormality response switch circuit is connected. The collector of the transistor 12 is connected to the temperature detection terminal (T) which is an external connection terminal, and the emitter is connected to the minus terminal (-). This transistor 12 serves as an abnormality response means for forcibly changing the state of the temperature detection terminal (T) to a signal corresponding to the battery temperature being outside the predetermined temperature range in response to the abnormality detection output of the abnormality detection circuit 10. I am configuring.

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

If the battery temperature rises abnormally during charging to fall outside the predetermined temperature range, or if it is attempted to charge at a temperature lower than the predetermined temperature range, the resistance value of the thermistor 11 is too low. When it 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.

Since the charger charges the battery so that the charging voltage per battery is lower than the first charging inhibition voltage set in the overcharge prevention circuit 5, the battery 1 is normally charged.
Both the terminal voltages of 2 and 2 are lower than the first charge inhibition 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, when the charging voltage becomes high due to a failure of the charger or the like, and one or both of the batteries 1 and 2 exceed the first charge inhibition voltage, the output terminal d of the overcharge / discharge prevention circuit 5 becomes The level becomes low and the first FET 3 becomes non-conductive, so that 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 inhibition voltage, the output terminal e of the over-discharge prevention circuit 6 changes from the high level to the low level, Since the second FET 4 becomes non-conductive, the discharge is stopped and the battery is prevented from being over-discharged.

By the way, if the charger fails for some reason and the overcharge prevention circuit 5 also fails, the terminal voltage of either or both of the batteries 1 and 2 becomes equal to or higher than the first charge inhibition voltage. However, 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 is higher than the first charging inhibition voltage. When the prohibition is reached, the voltage detection circuits 7 and 8
One or both of the outputs become high level, and
The output of the R circuit 9 becomes high level.

Therefore, N which is a switch circuit for abnormal response
Since the PN-type transistor 12 becomes conductive and the impedance between the temperature detection terminal (T) and the negative terminal (-) becomes approximately 0Ω, the state of the temperature detection terminal (T) corresponds to the battery temperature outside the predetermined temperature range. Signal. As a result, the charger determines that the battery temperature deviates from the chargeable temperature and is abnormally high, and stops charging the batteries 1 and 2.

Also, the charger fails, and the first FE
Consider the case where T3 fails and the drain and source become conductive. 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 prevention circuit 5 becomes low level, the first FET 3 is in the conductive state. Therefore, the terminal voltage exceeds the first charge inhibition voltage, but when it reaches the second charge inhibition voltage higher than the first charge inhibition voltage, either or both of the voltage detection circuits 7 and 8 are reached. Output 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 abnormal response switch circuit, becomes conductive,
Since the impedance between the temperature detection terminal (T) and the negative terminal (-) is approximately 0Ω, the charger determines that the battery temperature deviates from 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, the output stages of the voltage detection circuits 7 and 8 are bipolar transistors Q1 and Q.
It has an open collector configuration of 2. It should be noted that the output stage transistor may be an FET instead of a bipolar transistor and may have an open drain configuration. The output terminals of the voltage detection circuits 7 and 8 are pulled up by resistors R1 and R2, respectively.

Now, when the terminal voltage of the battery 1, that is, the input of the voltage detection circuit 7 is lower than the second charge inhibition voltage, the output of the voltage detection circuit 7 becomes low level, and when it is high, the output 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, and the reference potential terminal of the voltage detection circuit 8 is connected to the input terminal h of the abnormality detection circuit 10. 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.

Here, when both the batteries 1 and 2 are lower than the second charge inhibition voltage, the output of the voltage detection circuit 7 becomes a low level, which is almost the same as the potential of the input terminal g.
Therefore, the input terminal of the voltage detection circuit 8 has a terminal g-h.
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 charge inhibition voltage, the output of the voltage detection circuit 8 becomes low level and the output terminal i becomes low level.

Next, when the terminal voltage of the battery 1 is higher than the second charge inhibition voltage, the output of the voltage detection circuit 7 becomes high level, and the 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, 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 becomes high level.

When the terminal voltage of the battery 1 is lower than the second charge inhibition voltage and the terminal voltage of the battery 2 is higher than the second charge inhibition 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 becomes high level.

The terminal voltages of the batteries 1 and 2 are both second
If it is higher than the charging prohibition voltage of, the output of the voltage detection circuit 7 becomes high level, and the output of the voltage detection circuit 8 also becomes high level, so that the output terminal i becomes high level.

Therefore, even when the abnormality detecting 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, but can be modified in various ways as follows.

(1) In the above embodiment, a non-aqueous solvent type battery such as a lithium secondary battery was described as an example of the secondary battery charged at a constant voltage, but 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, but other numbers of series including one series may be used, and a plurality of cell blocks connected in parallel may be connected in one series or a plurality of series. You may.

(3) In the above embodiment, the FET, which is a switch element, is connected to the negative electrode side of the battery, but it may be connected to the positive electrode side of the battery. Just insert it.

(4) In the above embodiment, the abnormality detection circuit 1
Although the case where 0 detects the battery voltage to detect the abnormality has been described, 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 0 generated an abnormal signal, both ends of the thermistor 11 were short-circuited. However, as shown in FIG. 3, a PNP transistor 12 for abnormal response is connected in series with the thermistor 11 so that the abnormality detection circuit 10 detects a transistor 12 may be cut off. In this case, the battery temperature is judged to be abnormally low on the charger side due to the interruption of the transistor 12.

(6) In the above embodiment, the abnormality detection circuit 1
Although 0 monitors only the terminal voltage at the time of charging the battery, it may monitor the terminal voltage at the time of discharging. In this case, the output of the temperature detection terminal may be monitored on the side of 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 charge inhibition voltage is higher than the first charge inhibition voltage, but the magnitude relationship between the two may be reversed or the same. (8) In the above-described embodiment, the second discharge voltage is higher than the second discharge prohibition voltage.
Although the discharge inhibition voltage of No. 2 is set to be low, the magnitude relationship between the two may be reversed or 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 in the charge / discharge circuit. (10) In the abnormality detection circuit of FIG. 2, the output stage of the voltage detection circuits 7 and 8 has an open collector configuration, but as described above, it may have an open drain configuration.
It may be configured.

(11) A filter circuit may be inserted in the abnormality detection circuit or the abnormality response switch circuit of the above embodiment. By inserting the filter circuit, 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 an abnormal state has continued for a certain period of time or more.

(12) In FIG. 2, 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, but the resistors R1 and R2 have the same resistance value and the resistor R2. May be connected to the input terminal g, that is, the positive electrode of the battery 2. By doing so, the currents flowing from the batteries 1 and 2 to the abnormality detection circuit 10 become equal, and the balance of the electric capacities of the batteries 1 and 2 is not disturbed even when left for a long time.

[0046]

As described above, according to the secondary battery protection circuit of the present invention, the overcharge prevention circuit or the overdischarge prevention circuit fails, or the switch element inserted in the charging / discharging path is short-circuited. Even if the error occurs, the abnormality detection circuit detects overcharge or overdischarge, and the output of the temperature detection terminal is forcibly set to an abnormal state as a signal corresponding to outside the specified temperature range. Since it is possible to stop the charging and discharging with the, it is possible to further enhance the reliability as a protection circuit.

[Brief description of drawings]

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

FIG. 2 is a diagram showing another configuration example of an abnormality detection circuit.

FIG. 3 is a diagram showing another connection example of the temperature detecting element and the abnormality 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

 ─────────────────────────────────────────────────── ─── Continuation of the front page (71) Applicant 000003539 Toshiba Battery Co., Ltd. 3-4-10 Minami-Shinagawa, Shinagawa-ku, Tokyo (72) Inventor Toshitsugu Mito 1623 Shimotsuruma, Yamato-shi, Kanagawa 14 Japan AIB・ M Corporation Yamato Works (72) Inventor Masahito Kizawa 1623 Shimotsuruma, Yamato City, Kanagawa Prefecture 14 Japan BM Co., Ltd. Yamato Works (72) Hiroshi Nakagawa 1623 Shimotsuruma, Yamato City, Kanagawa Prefecture 14 Japan ABM Co., Ltd. Yamato Plant (72) Inventor Kazuo Mukai 72 Horikawa-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Stock company, AT Battery (72) Inventor Nobuo Shiojima Minami Shinagawa-ku, Tokyo 3-4-10 Shinagawa Toshiba Battery Co., Ltd. (72) Inventor Masanori Isshiki 3-4-10 Minamishinagawa Shinagawa-ku, Tokyo Toshiba Battery In the formula company (72) inventor Ito, Noriyuki Shinagawa-ku, Tokyo Minamishinagawa 3-chome, No. 4, No. 10 Toshiba Battery Co., Ltd. in

Claims (5)

[Claims] 1. A switching element inserted in series with a charging / discharging circuit of a secondary battery, a terminal voltage of the secondary battery being detected, and the switching element being turned on when the terminal voltage reaches a predetermined charge inhibition voltage. Overcharge prevention means for preventing overcharge of the secondary battery in a non-conducting state, detecting a temperature of the secondary battery and outputting a signal corresponding to the temperature, and when the temperature is out of a predetermined temperature range, the secondary battery Temperature detecting means for controlling the charging of the battery, abnormality detecting means for detecting an abnormality in the charging state of the secondary battery, and in response to the abnormality detection of the charging state by the abnormality detecting means of the temperature detecting means A protection circuit for a secondary battery, comprising: abnormal response means for forcibly changing the output to a signal corresponding to a temperature outside the predetermined temperature range. 2. A switch element inserted in series with a charging / discharging circuit of a secondary battery; a terminal voltage of the secondary battery is detected; and when the terminal voltage reaches a predetermined discharge inhibition voltage, the switch element is turned on. Over-discharge prevention means for preventing over-discharge of the secondary battery in a non-conducting state, detecting a temperature of the secondary battery and outputting a signal corresponding to the temperature, the secondary battery when the temperature is out of a predetermined temperature range. Temperature detection means for controlling the discharge of the battery, an abnormality detection means for detecting an abnormality in the discharge state of the secondary battery, and the temperature detection means in response to the abnormality detection of the discharge state by the abnormality detection means A protection circuit for a secondary battery, comprising: abnormal response means for forcibly changing the output to a signal corresponding to a temperature outside the predetermined temperature range. 3. A first and second switch element inserted in series in a charge / discharge circuit of a secondary battery, and a terminal voltage of the secondary battery is detected, and the terminal voltage reaches a predetermined charge inhibition voltage. Then, the first switch element is made non-conductive to prevent overcharge of the secondary battery, and a terminal voltage of the secondary battery is detected, and this terminal voltage becomes a predetermined discharge inhibition voltage. When reaching, the second switch element is made non-conductive to prevent over-discharging of the secondary battery, and an over-discharge preventing unit that detects the temperature of the secondary battery and outputs a signal corresponding to the temperature, Temperature detection means for controlling charging of the secondary battery when the temperature is out of a predetermined temperature range, abnormality detection means for detecting abnormality in charging state and discharging state of the secondary battery, and the charging by the abnormality detection means Low state and discharge state And a secondary battery protection circuit forcibly changing the output of the temperature detecting means to a signal corresponding to the outside of the predetermined temperature range in response to the detection of one of the abnormalities. . 4. The secondary battery according to any one of claims 1 to 3, wherein the abnormality detecting means detects an abnormality from at least one of a terminal voltage and a temperature of the secondary battery. Protection circuit. 5. The temperature detecting means comprises a temperature detecting element whose resistance value changes with temperature, and the abnormality response means is connected in series or in parallel with the temperature detecting element and turned on by an output of the abnormality detecting means. The protection circuit for the secondary battery according to any one of claims 1 to 3, wherein the protection circuit includes an off-controlled switch circuit.