CN101626153A - Battery protection circuit and protection method thereof - Google Patents

Abstract

The invention provides a battery protection circuit and a protection method thereof, which are suitable for a rechargeable battery, wherein the rechargeable battery is provided with a positive voltage pin, a negative voltage pin and a temperature sensing pin. Wherein the impedance value output by the temperature sensing pin is changed along with the temperature of the rechargeable battery. The battery protection circuit comprises a temperature and voltage detection unit and a discharge unit. The temperature and voltage detection unit judges the temperature of the rechargeable battery according to the impedance value output by the temperature sensing pin. When the temperature of the rechargeable battery is higher than a preset temperature, the discharging unit discharges the rechargeable battery, and when the voltage value output by the positive voltage pin is lower than a preset voltage, the discharging unit stops discharging the rechargeable battery.

Description

Battery protection circuit and its protection method

technical field

The present invention relates to a battery protection circuit and its protection method, and in particular to a battery protection method for delaying battery expansion in a high temperature environment.

Background technique

With the advancement of light and portable electronic product technology, most of the high-performance components of the product are also advancing towards the ideal goal of "light, thin, short, and small". Therefore, a battery with light weight, small size and high charge capacity is particularly important. In addition, in addition to the small size and high storage capacity of the battery, the battery protection circuit that affects the battery life and user safety is also very important. Generally, the circuit for battery protection is generally the detection and protection of the charging and discharging status of the battery in use, such as overcharge monitoring, overdischarge monitoring, excess current (Excess current) and short-circuit current (Short) protection circuit.

The overcharge detection and protection circuit is mainly because the battery may be overcharged (Overcharge) due to user misuse during use, resulting in a rise in battery temperature, and gas generated due to the decomposition of the electrolyte, which increases its internal pressure , and the release of the chemical liquid inside the battery may cause fire and rupture. Therefore, it is necessary to use the protection circuit to detect whether the battery is overcharged, so as to prevent the characteristics of the battery from deteriorating, fire and rupture, and to ensure the safety of users. . The over-discharge detection and protection circuit is to detect whether the battery is abnormal when it is discharged, so as to ensure the service life of the battery. The over-current and short-circuit current protection circuit is used to provide that the battery pack will cut off the connection between the battery and the load when the working current is abnormal, and return to normal operation after the abnormal situation is resolved to achieve the protection function.

Although these battery protection circuits have the function of monitoring and protecting the batteries in operation, they cannot protect the batteries not in use. For example, when a mobile phone or a camera is placed in a high-temperature car, although the internal battery is not in use, due to the influence of high ambient temperature, the battery may be abnormal or swelling. As a result, the battery in the non-use state reduces the service life of the battery and causes danger to the user.

Contents of the invention

In view of this, the present invention provides a battery protection circuit, which can slow down the abnormal expansion and irreversible chemical variation of the battery in a high-temperature environment, so as to improve the service life of the battery.

To achieve the above and other objectives, the present invention proposes a battery protection circuit suitable for a rechargeable battery, and the rechargeable battery has a positive voltage pin, a negative voltage pin and a temperature sensing pin. Wherein the impedance value output by the temperature sensing pin changes with the temperature of the rechargeable battery. The battery protection circuit includes a temperature and voltage detection unit and a discharge unit. The temperature and voltage detection unit is coupled to the positive voltage pin and the temperature sensing pin of the rechargeable battery, and judges the temperature of the rechargeable battery according to the impedance value output by the temperature sensing pin. The discharge unit is coupled to the positive voltage pin and the temperature and voltage detection unit.

Wherein, when the temperature of the rechargeable battery is higher than a preset temperature, the discharging unit discharges the rechargeable battery. And if the voltage value output by the positive voltage pin is less than a first preset value, the discharge unit stops discharging the rechargeable battery.

In an embodiment of the present invention, the temperature and voltage detection unit includes a bias voltage unit and a voltage detection unit. The bias unit is coupled between a voltage stabilizing pin converted from the positive voltage of the rechargeable battery and the temperature sensing pin, and the bias unit outputs a first voltage according to the impedance value output by the temperature sensing pin of the rechargeable battery. The voltage detection unit is coupled to the voltage dividing pin in the bias voltage unit, and the voltage detecting unit outputs a discharge signal to the discharge unit according to the first voltage and the voltage value output by the voltage dividing pin. Wherein, when the first voltage is lower than a second preset value, the discharge unit discharges the rechargeable battery according to the discharge signal.

In an embodiment of the present invention, the bias unit includes a first resistor and a second resistor. One end of the first resistor is coupled to a constant voltage pin converted from the positive voltage, and the second resistor is coupled between the other end of the first resistor and the temperature sensing pin, and the first resistor and the second A common node between the resistors outputs the first voltage.

In an embodiment of the present invention, the voltage detection unit includes a voltage sensor, a bipolar transistor, a first resistor, and a second resistor. The voltage sensor is coupled to the bias unit, and when the first voltage is lower than the second preset value, an output voltage of the voltage sensor is logic low. The bipolar transistor is coupled between the output of the voltage sensor and the discharge unit, and is used for generating a discharge signal. The first resistor is coupled between the base of the bipolar transistor and the positive voltage pin. A second resistor is coupled between a collector of a bipolar junction transistor (BJT for short) and the positive voltage pin.

In one embodiment of the present invention, the above-mentioned bipolar transistor is an NPN transistor, and the collector of the bipolar transistor is coupled to the discharge unit for generating the discharge signal, and the emitter of the bipolar transistor is coupled to the The output of the voltage sensor, wherein when the first voltage is less than the second preset value, the discharge signal is logic low. In addition, when the voltage output by the positive voltage pin is less than the first preset value, the discharge signal is logic high.

In an embodiment of the present invention, the discharge unit includes: a switch and a first resistor. One end of the switch is coupled to the positive voltage pin, and the resistor is coupled between the other end of the switch and the ground. Wherein, when the temperature of the rechargeable battery is higher than a preset temperature, the switch is turned on to discharge the rechargeable battery, and when the voltage value output by the positive voltage pin is lower than the first preset value, the switch is turned off to stop charging the rechargeable battery to discharge. In addition, the resistor used for discharging in the discharge unit can be realized by connecting two resistors in parallel to improve the discharge current and power tolerance.

In an embodiment of the present invention, the switch is a PMOS transistor (P channel metal oxide semiconductor transistor), the source of which is coupled to the positive voltage pin, the drain is coupled to the first resistor, and the gate is coupled to the discharge signal.

From another point of view, the present invention provides a battery protection method, which is suitable for rechargeable batteries, and the rechargeable battery has a positive voltage pin, a negative voltage pin and a temperature sensing pin. The above-mentioned battery protection method includes the following steps: detecting the temperature of the rechargeable battery and discharging the rechargeable battery when the temperature of the rechargeable battery is higher than a preset temperature, and when the output voltage value of the positive voltage pin of the rechargeable battery is lower than a preset value, stop discharging the rechargeable battery

In an embodiment of the present invention, in the step of detecting the temperature of the rechargeable battery, the temperature of the rechargeable battery is also determined according to the impedance value output by the temperature sensing pin.

In an embodiment of the present invention, the rechargeable battery has a built-in thermistor with a negative temperature coefficient, and the thermistor is coupled to the temperature sensing pin so that the output impedance of the temperature sensing pin changes with temperature.

In an embodiment of the present invention, the rechargeable battery has a built-in thermistor with a positive temperature coefficient, and the thermistor is coupled to the temperature sensing pin, so that the output impedance of the temperature sensing pin changes with temperature.

According to the above-mentioned embodiments and descriptions, the battery protection circuit and method thereof of the present invention can discharge a battery with a full voltage at high temperature, and at the same time avoid excessive discharge of the battery, so as to slow down the expansion, rupture and damage caused by the high temperature of the battery. Irreversible chemical damage, thereby prolonging the service life of the battery and improving the safety of the battery.

Description of drawings

In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and understandable, the specific embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

FIG. 1 is a functional block diagram of a battery protection circuit according to an embodiment of the invention.

FIG. 2 is a circuit block diagram of a battery protection circuit according to an embodiment of the invention.

FIG. 3 is a flowchart of a battery protection method according to an embodiment of the present invention.

FIG. 4 is a histogram of the expansion rate of the battery before charging according to an embodiment of the present invention.

Fig. 5 is a histogram of the expansion rate of the battery after charging according to an embodiment of the present invention

Description of main component symbols:

100: battery protection circuit

102: Temperature and voltage detection unit

104: discharge unit

130: rechargeable battery

220: voltage detection unit

221: Voltage sensor

222: bipolar transistor

240: Bias unit

241: voltage stabilizing element

250: switch

V+, V-, NTC: pins

R1, R2, R3: precision adjustment resistors

R4: switch control resistor

R5, R6: discharge resistor

R7: Thermistor

FS: discharge signal

F: node

Vout: voltage detection response output

S301～S305: steps

Detailed ways

first embodiment

FIG. 1 is a functional block diagram of a battery protection circuit according to an embodiment of the invention. Referring to FIG. 1 , the battery protection circuit 100 can be applied to a rechargeable battery 130 . The rechargeable battery 130 has a positive voltage pin V+, a negative voltage pin V−, and a temperature sensing pin NTC. The battery protection circuit 100 includes a temperature and voltage detection unit 102 and a discharge unit 104 . The temperature and voltage detection unit 102 is coupled to the positive voltage pin V+ and the temperature sensing pin NTC. The discharge unit 104 is coupled to the positive voltage pin V+ and the temperature and sensing unit 102 . The impedance value output by the temperature sensing pin NTC of the rechargeable battery 130 will change with the temperature of the rechargeable battery 130 . Therefore, the temperature and voltage detection unit 102 determines the temperature of the rechargeable battery according to the impedance value output by the temperature sensing pin NTC. The discharge unit 104 discharges the rechargeable battery 130 according to the temperature detection result of the temperature and voltage detection unit 102 and the voltage of the rechargeable battery.

Due to the high temperature environment, the rechargeable battery 130 with normal voltage (about 3.7 volt) expands more slowly than the rechargeable battery 130 with full voltage (about 4.2 volt). Therefore, according to the battery characteristics of the above-mentioned rechargeable battery 130 , if the rechargeable battery with full voltage can be discharged at high temperature, it will help to reduce the expansion rate of the battery and avoid battery damage.

Therefore, when the temperature and voltage detection unit 102 detects that the temperature of the rechargeable battery 130 is greater than a preset value through the resistance value output by the temperature sensing pin NTC, the discharge unit 104 will discharge the rechargeable battery 130 to make the rechargeable battery 130 becomes a state of non-saturation voltage after being discharged, so as to slow down irreversible damages such as expansion, rupture and fire of the rechargeable battery 130 caused by high temperature.

Although discharging can slow down the expansion effect of the rechargeable battery 130 , over-discharging will also lead to permanent failure of the rechargeable battery 130 and shorten the service life of the rechargeable battery 130 . Therefore, in order to avoid over-discharging, when the voltage output by the positive voltage pin V+ is less than a first preset value, that is, when the power of the rechargeable battery is less than a preset value, the discharging unit 104 stops discharging the rechargeable battery 130 .

In summary, the discharge unit 104 will decide whether to discharge the rechargeable battery 130 according to the temperature detected by the temperature and voltage detection unit 102, and decide whether to stop the rechargeable battery 130 according to the power of the rechargeable battery 130 (the voltage value of the positive voltage pin V+). discharge. In this way, the rechargeable battery 130 at full voltage is prevented from being damaged due to expansion under high temperature, or the problem of lifespan loss or permanent failure due to over-discharging is avoided.

The temperature preset value used by the discharge unit 104 to determine whether to discharge and the voltage preset value (for example, 3.7 volts) to stop discharging can be set according to the circuit designer considering the use environment and characteristics of the rechargeable battery 130, and the so-called high temperature The environment can be, for example, parked in an airtight car under a sun-exposed outdoor environment, and its internal temperature is greater than 60 degrees Celsius, or even 100 degrees Celsius.

Next, the detailed circuit and operation mode of each circuit block in FIG. 1 will be further described. Please refer to FIG. 2 , which is a circuit block diagram of a battery protection circuit according to an embodiment of the present invention. The battery protection circuit 100 mainly includes a temperature and voltage detection unit 102 and a discharge unit 104 . Wherein, the temperature and voltage detection unit 102 further includes a voltage detection unit 220 and a bias voltage unit 240 . The voltage detection unit 220 is coupled to the bias voltage unit 240 and the positive voltage pin V+, and the bias voltage unit 240 is coupled between a constant voltage pin converted from the positive voltage V+ and the temperature sensing pin NTC.

The bias unit 240 is composed of a voltage stabilizing element 241 and precision adjustment resistors R2 and R3 connected in series. Based on the principle of voltage division, the voltage of the node F will vary according to the impedance value output by the temperature sensing pin NTC. In this embodiment, a thermistor with a negative temperature coefficient is used as an example for illustration, so the thermistor (Thermistor) R7 in the rechargeable battery 130 will decrease its impedance as the temperature rises. Therefore, the voltage at node F will decrease with increasing temperature and increase with decreasing temperature.

The voltage detection unit 220 in the temperature and voltage detection unit 102 includes a voltage sensor 221 , a bipolar transistor 222 , a precision adjustment resistor R1 , and a switch control resistor R4 . In this embodiment, the bipolar transistor 222 is an NPN bipolar transistor, its collector is coupled to the discharge unit 104, its emitter is coupled to the output of the voltage sensor 221, and its base is coupled to the precision adjustment Resistor R1. The voltage sensor 221 is coupled between the node F of the bias unit 240 and the emitter of the bipolar transistor 222 . The precision adjustment resistor R1 is coupled between the positive voltage pin V+ of the rechargeable battery 130 and the base of the bipolar transistor 222 . The switch control resistor R4 is coupled between the collector of the bipolar transistor 222 and the positive voltage pin V+.

The voltage sensor 221 will adjust the potential of the voltage detection response output Vout according to the voltage of the node F. When the voltage of the node F is lower than the preset value (indicating that the temperature of the rechargeable battery is greater than the preset temperature), the voltage of the voltage sensor 221 will The detection response output Vout is a logic low potential. Since the precision adjustment resistor R1 is coupled between the base of the bipolar transistor 222 and the positive voltage pin V+, the switch control resistor R4 is coupled between the collector of the bipolar transistor 222 and the positive voltage pin V+, and The emitter of the bipolar transistor 222 is coupled to the voltage detection response output Vout of the voltage sensor 221 . Therefore, when the output voltage generated by the voltage detection response output Vout of the voltage sensor 221 is logic low, the potential difference between the positive voltage pin V+ and the voltage detection response output Vout will turn on the bipolar transistor 222 , thereby generating a lower potential at the collector terminal of the bipolar transistor 222 (due to the voltage difference caused by the current flowing through the switch control resistor R4).

The discharge signal FS output by the temperature and voltage detection unit 102 is formed by the collector voltage of the bipolar transistor 222 . When the discharge signal FS is reduced to a low potential due to the conduction of the bipolar transistor 222 (indicating that the temperature of the rechargeable battery is greater than the preset temperature), the switch 250 in the discharge unit 104 (replaced by a PMOS transistor in this embodiment) will follow When it is turned on, the rechargeable battery 130 is discharged through the discharge resistors R5 and R6.

In this embodiment, the switch 250 in the discharge unit is a PMOS transistor, and the discharge resistors R5 and R6 are coupled in parallel between the drain of the PMOS transistor 250 and the ground terminal GND. The discharge resistors R5 and R6 mainly provide a discharge path and power consumption for the rechargeable battery 130 , and the number of the discharge resistors R5 and R6 connected in parallel is not limited. In consideration of size, price and heat dissipation, this embodiment takes two 1/2W resistors as an example to realize the circuit of the discharge unit. The voltage sensor 221 in the temperature and voltage detection unit 102 can be, for example, a voltage sensor from Zhongkeguan Electronics Co., Ltd., whose model is R3112Q151A-TR-F.

In addition, because the rechargeable battery has a certain cut-off voltage limitation, and excessive discharge will cause its service life to be reduced, or even permanently invalidated. Therefore, the discharge cut-off voltage is designed in this embodiment. When the voltage of the rechargeable battery (the positive voltage pin V+) is lower than a preset value, the temperature and voltage detection unit 102 will cause the discharge unit 104 to stop discharging the rechargeable battery. In this embodiment, the resistance value of the precision adjustment resistor R1 (for example, 91K) is designed according to the internal resistance of the bipolar transistor 222 and the bias voltage required for conduction. When the voltage of the positive voltage pin V+ is too low, the discharge signal FS turns to a high potential to close the switch 250 , so that the discharge unit 104 stops discharging the rechargeable battery 130 .

During the discharge process, the voltage level of the rechargeable battery 130 tends to decrease downwards. This embodiment uses this to control the conduction state of the bipolar transistor 222, and the resistance value of the precision adjustment resistor R1 is used to set the The voltage level at which the bipolar transistor 222 is turned off. When the voltage level of the rechargeable battery 130 is lower than a preset value (for example, 3.7V), the bipolar transistor 222 is turned off, so that the discharge signal FS turns to a high potential (approaching the potential of the positive voltage pin V+). At this time, the switch 250 will be closed accordingly and stop discharging the rechargeable battery.

To sum up the above, in this embodiment, when the temperature of the rechargeable battery 130 is higher than the preset temperature, the discharge signal FS output by the temperature and voltage detection unit 102 will turn to a low potential (because the bipolar transistor 222 is turned on). , the discharge unit 104 discharges the rechargeable battery 130 . During the discharge process, when the voltage of the rechargeable battery 130 is lower than a preset value, the discharge signal FS will turn to a high potential (because the bipolar transistor 222 is turned off), at this time, the discharge unit 104 stops discharging the rechargeable battery 130 .

In addition, it is worth noting that the thermistor R7 of the rechargeable battery 130 is coupled to the temperature sensing pin NTC, and it can be negative temperature coefficient (Negative Temperature Coefficient, NTC) or positive temperature coefficient (Positive Temperature Coefficient, PTC) As for the thermistor, in this embodiment, a thermistor with a negative temperature coefficient is taken as an example. The circuit of the above-mentioned temperature and voltage detection unit 102 and the discharge unit 104 is only an embodiment of the present invention, and the present invention is not limited to the circuit of FIG. It should be easy to deduce the other implementation modes of the above circuit, which will not be repeated here.

second embodiment

Based on the above, the present invention can summarize a battery protection method. FIG. 3 is a flowchart of a battery protection method according to an embodiment of the present invention. Please refer to FIG. 3 , first, as described in step S301 , the temperature and voltage detection unit detects the temperature of the rechargeable battery according to the impedance value output by the temperature sensing pin of the rechargeable battery. Then, as described in step S302, it is judged whether the temperature of the rechargeable battery is greater than a preset temperature, and if the temperature is not greater than the preset temperature (that is, "No" indicated in step 302), then repeat step S301, and continue to detect the temperature of the rechargeable battery .

On the other hand, if step 302 is executed and the temperature of the rechargeable battery is greater than the preset temperature (that is, “Yes” indicated in step 302 ), then as shown in step 303 , the discharging unit discharges the rechargeable battery. Next, as described in step 304, it is determined whether the voltage value of the rechargeable battery (output from the positive voltage pin) is lower than a preset value or the temperature of the rechargeable battery is lower than a preset temperature. This step is to avoid damage to the rechargeable battery caused by over-discharging. Therefore, when the voltage value output by the positive voltage pin is not lower than the preset value (that is, "No" indicated in step 304), step S303 is repeated to continue discharging the rechargeable battery. If the voltage value output by the positive voltage pin is lower than the preset value or the temperature of the rechargeable battery is lower than the preset temperature (that is, "yes" marked in step 304), the discharge unit stops discharging the rechargeable battery, and then repeats the battery cycle. The protection method steps S301-S305, continuously detect and protect the rechargeable battery.

Those skilled in the art should be able to infer the rest of the details of this embodiment from the disclosure of the above-mentioned first embodiment, which will not be repeated here.

third embodiment

Table 1 shows the battery thickness measurements at 25°C and 85°C. Please refer to Table 1. Table 1 divides the state of the battery into three items, which are the thickness of the battery without the circuit of the present invention and the ambient temperature at room temperature (25°C), and the battery without the circuit of the present invention and placed at ambient temperature. It is the thickness of the battery for eight hours at 85°C and the thickness of the battery for applying the circuit of the present invention and placing the battery at an ambient temperature of 85°C for eight hours.

Table 1

And in three different states, measure the thickness of the battery before charging (3.8V) and after charging (4.2V). From the actual measurement of the three batteries in different states in Table 1, it can be found that when the temperature rises from room temperature (25°C) to a high temperature of 85°C, the battery with the circuit of the present invention is compared with the battery without the circuit of the present invention , the thickness expansion of the battery using the circuit of the present invention is indeed relatively small. In particular, for the battery in the charged state, the thickness expansion of the battery increases with the increase of temperature. Compared with the battery without the circuit of the present invention, the thickness expansion of the battery with the circuit of the present invention is significantly reduced. many. Next, the value of the expansion rate is used to clearly show the degree of slowing down of the thickness expansion of the battery by the circuit of the present invention.

Table 2 is a numerical table of the expansion rate calculated according to the thickness of the battery in Table 1. Please refer to Table 2. Table 2 presents the battery expansion rate divided into two states before charging and after charging to calculate the expansion rate when the temperature rises from 25°C to 85°C. In addition, Table 2 is further divided into the expansion rate of the battery thickness before and after the application of the circuit of the present invention, and the reduction value of the expansion rate (the difference in expansion rate after applying the electric rate of the present invention). The effectiveness of reducing and reducing the degree of expansion achieved by the circuit of the present invention can be clearly understood by the expansion rate reduction value.

Table 2

First of all, let’s first observe the decrease in the expansion rate of the battery before charging. From the decrease in the expansion rate of batteries 1, 2 and 3, it can be found that no matter whether the battery is in the state before recharging or after charging, using the circuit of the present invention can make The expansion rate of the battery decreases, this is because the ambient temperature of the battery is greater than the preset temperature, so the battery protection circuit of the present invention will be started to discharge the battery, and because the voltage value (3.8V) before charging is not less than the preset voltage, Therefore, the battery protection circuit will still discharge the battery before charging, so the effectiveness of the circuit of the present invention can be clearly understood according to the reduction of the expansion rate. Next, we observe the decrease in the expansion rate of the battery after charging. Compared with the decrease in the expansion rate of the battery before charging, the decrease in the expansion rate of the battery after charging is larger. This is because the battery without the circuit of the present invention after charging , the expansion problem caused by the influence of high temperature is quite serious, so that after the charged battery is applied with the circuit of the present invention, the expansion problem can be greatly reduced.

FIG. 4 is a bar graph of the expansion rate of the battery before charging according to an embodiment of the present invention, and FIG. 5 is a bar graph of the expansion rate of the battery after charging according to an embodiment of the present invention. FIG. 4 and FIG. 5 are bar graphs drawn using the expansion ratios in Table 2. Please refer to Figure 4, taking battery one as an example, the expansion rate of battery one before charging is 5.78% when the circuit is not used, but after using the circuit of the present invention, its expansion rate is 4.49, so battery one before charging After applying the circuit of the invention, the swelling reduction was 1.29%. Please refer to Figure 5, the battery after charging (4.2V) is affected by the high temperature of 85°C before the circuit of the present invention is applied, so that the expansion rate is as high as 11.28%, and after the circuit of the present invention is applied, the expansion rate decreases to 5.74%, so its expansion rate reduction value is 5.54%. Please refer to Figure 4 and Figure 5 together. From the expansion rates of batteries 1, 2, and 3, it can be found that the battery protection circuit of the present invention has an obvious slowing down effect on the battery expansion rate at high temperatures, and is especially effective for batteries after charging. Reduce and slow down the problem of its expansion.

Based on the above, the battery protection circuit and method provided by the present invention can discharge the battery according to the temperature of the battery, so that the battery can avoid swelling and abnormal damage when the battery is not in use, thereby improving the service life of the battery and improving the use of the battery. Or use the safety of the battery.

Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make some modifications and improvements without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection should be defined by the claims.

Claims (15)

1. battery protecting circuit; be applicable to a rechargeable battery; this rechargeable battery has a positive voltage pin, a negative voltage pin and a temperature sense pin, and wherein the resistance value exported of this temperature sense pin becomes with the temperature of this rechargeable battery, and this battery protecting circuit comprises:

One temperature and voltage detection unit are coupled to this positive voltage pin and this temperature sense pin, and judge the temperature of this rechargeable battery according to this resistance value that this temperature sense pin is exported; And

One discharge cell is coupled to this positive voltage pin and this temperature and voltage detection unit;

Wherein, when the temperature of this rechargeable battery during greater than a preset temperature, this discharge cell discharges to this rechargeable battery, and the magnitude of voltage of being exported when this positive voltage pin is during less than one first preset value, and this discharge cell stops this rechargeable battery is discharged.

2. battery protecting circuit as claimed in claim 1 is characterized in that, this temperature and voltage detection unit comprise:

One bias unit is coupled between this positive voltage pin and this temperature sense pin, exports one first voltage according to this resistance value that this temperature sense pin is exported; And

One voltage detection unit is coupled to this bias unit and this positive voltage pin, according to the magnitude of voltage that this first voltage and this positive voltage pin are exported, exports a discharge signal to this discharge cell;

Wherein, when this first voltage during less than one second preset value, this discharge cell discharges to this rechargeable battery according to this discharge signal.

3. battery protecting circuit as claimed in claim 2 is characterized in that, this bias unit comprises:

One voltage stabilizing element, an end of this voltage stabilizing element is coupled to this positive voltage pin;

One first resistance, an end of this first resistance is coupled to this voltage stabilizing element pin; And

One second resistance is coupled between the other end and this temperature sense pin of this first resistance;

Wherein, the shared node between this first resistance and this second resistance is exported this first voltage.

4. battery protecting circuit as claimed in claim 2 is characterized in that, this voltage detection unit comprises:

One voltage-sensor is coupled to this bias unit, and when this first voltage during less than this second preset value, an output voltage of this voltage-sensor is a logic low potential;

One bipolar transistor is coupled between the output and this discharge cell of this voltage-sensor, in order to produce this discharge signal; And

One first resistance is coupled between the base stage and this positive voltage pin of this bipolar transistor; And

One second resistance is coupled between the collector electrode and this positive voltage pin of this bipolar transistor.

5. battery protecting circuit as claimed in claim 4; it is characterized in that; this bipolar transistor is a NPN transistor; and this collector electrode of this bipolar transistor is coupled to this discharge cell; in order to produce this discharge signal; one emitter of this bipolar transistor is coupled to the output of this voltage-sensor; wherein when this first voltage during less than this second preset value; this discharge signal is a logic low potential; the magnitude of voltage of being exported when this positive voltage pin is during less than this first preset value, and this discharge signal is a logic high potential.

6. battery protecting circuit as claimed in claim 1 is characterized in that, this discharge cell comprises:

One switch, an end of this switch is coupled to this positive voltage pin; And

One first resistance is coupled between the other end and an earth terminal of this switch;

Wherein, when the temperature of this rechargeable battery during greater than a preset temperature, this switch conduction to be discharging to this rechargeable battery, and the magnitude of voltage of being exported when this positive voltage pin is during less than one first preset value, and this switch cuts out stopping this rechargeable battery is discharged.

7. battery protecting circuit as claimed in claim 1 is characterized in that, this discharge cell comprises:

One second resistance is parallel to this first resistance.

8. battery protecting circuit as claimed in claim 6; it is characterized in that this switch is a PMOS transistor, the transistorized one source pole of this PMOS is coupled to this positive voltage pin; the transistorized drain electrode of this PMOS is coupled to this first resistance, and grid then is coupled to discharge signal.

9. battery protecting circuit as claimed in claim 1 is characterized in that, a thermistor of the built-in negative temperature coefficient of this rechargeable battery, this thermistor are coupled to this temperature sense pin, and the output impedance of this temperature sense pin is become with temperature.

10. battery protecting circuit as claimed in claim 1 is characterized in that, a thermistor of the built-in positive temperature coefficient of this rechargeable battery, this thermistor are coupled to this temperature sense pin, and the output impedance of this temperature sense pin is become with temperature.

11. battery protecting circuit as claimed in claim 1 is characterized in that, this negative voltage pin is coupled to an earth terminal.

12. a battery protecting method is applicable to a rechargeable battery, this rechargeable battery has a positive voltage pin, a negative voltage pin and a temperature sense pin, and this battery protecting method comprises:

Detect the temperature of this rechargeable battery;

When the temperature of this rechargeable battery during, this rechargeable battery is discharged greater than a preset temperature; And

The magnitude of voltage of being exported when this positive voltage pin of this rechargeable battery stops this rechargeable battery is discharged during less than a preset value.

13. battery protecting method as claimed in claim 12 is characterized in that, in the step of the temperature that detects this rechargeable battery, more the resistance value of being exported according to this temperature sense pin is judged the temperature of this rechargeable battery.

14. battery protecting method as claimed in claim 12; it is characterized in that; one thermistor of the built-in negative temperature coefficient of this rechargeable battery, this thermistor are coupled to this temperature sense pin, and the output impedance that makes this temperature sense pin becomes with the temperature of this rechargeable battery.

15. battery protecting method as claimed in claim 12; it is characterized in that; one thermistor of the built-in positive temperature coefficient of this rechargeable battery, this thermistor are coupled to this temperature sense pin, and the output impedance that makes this temperature sense pin becomes with the temperature of this rechargeable battery.

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