JPH11206025A - Battery management device and battery pack using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable safety procedure during the generation of irregular heating of a battery and a switch means for improving safe operation, without resulting in cost increase and surely disabling the use of battery pack depending on the over-current protecting function, even when a momentary current increases. SOLUTION: This apparatus comprises a battery voltage detecting means 1 for detecting the battery voltage, a current detecting means 2 for detecting the discharge current, a delay means 4 for inputting an output from the battery voltage detecting means 1 and the current detecting means 2 and outputting a signal after a predetermined delay time, a control circuit 3 for inputting outputs from the battery voltage detecting means 1, the current detecting means 2 and delay means 4 and switch means 5, 6 to be controlled by receiving an output from the control circuit. Moreover, a temperature fuse the blow delay characteristic which is longer than the over-current delay time of the control circuit 3 is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the technology of a battery management device.

[0002]

2. Description of the Related Art In recent years, the market for secondary batteries has been rapidly expanding. Among them, non-aqueous secondary batteries, for example, lithium ion secondary batteries, are used in portable electronic devices such as notebook computers and mobile phones. As widely used.

[0003] Lithium-ion secondary batteries which are used as a single battery or as a battery pack and used in a battery pack maintain safety and reliability because overcharge and overdischarge cause a decrease in safety and a deterioration in quality. For this reason, it is common to mount a function for preventing overcharge and overdischarge in a battery management device (commonly referred to by those skilled in the art as BMU or SU) to manage battery voltage and the like.

Generally, the functions of a battery management device include an overcharge protection function for protecting a battery from overcharge, an overdischarge protection function for protecting a battery from overdischarge, and an overcurrent protection function for protecting the battery from overcurrent such as a short circuit. It has an overcurrent protection function.

The battery pack is provided with a current fuse which has been used in many electronic devices for the purpose of preventing overcurrent, so that when an abnormally large current flows through the battery pack, it is instantaneous. By blowing the current fuse, the safety of the battery pack and the electronic device to which the battery pack is connected is maintained.

[0006]

However, in the above-mentioned conventional configuration, when an excessive current flows due to a short circuit between the output terminals of the pack for some reason, the current fuse is instantaneously blown and the battery pack becomes unusable. turn into. Originally, when an overcurrent flows, the current detection means of the control circuit detects it and turns off the switch means by the overcurrent protection function. Since the current fuse is very large, it has been considered that even if a delay-type current fuse is used, erroneous blowing in which the current fuse is blown first may occur. This will be described in detail in the embodiment section.

Further, if the switch means breaks down for some reason, even if the switch means generates abnormal heat due to charging and discharging,
Charging and discharging could not be prevented, and this was not a favorable state in consideration of safety.

Furthermore, it is natural that it is desirable to provide not only safety measures for abnormal heat generation of the switch means but also multiple layers of safety measures for abnormal heat generation of the secondary battery.

The present invention solves such a conventional problem, and does not increase the number of components, so that the cost is not increased, and even if an instantaneous current increases, the overcurrent protection function surely copes. To provide a battery management device and a battery pack using the same that can take safety measures at the time of abnormal heat generation of batteries and switch means without making the battery pack unusable by using the battery pack, and improve safety. It is assumed that.

[0010]

According to a first aspect of the present invention, there is provided a battery management device, comprising: a battery voltage detecting means for detecting a battery voltage; a current detecting means for detecting a discharge current; A delay unit that outputs a signal after a predetermined delay time has elapsed from an output from the battery voltage detection unit and the current detection unit as an input, the battery voltage detection unit, the current detection unit, and an output from the delay unit. And a switch means that is switch-controlled in response to an output from the control circuit, and uses a thermal fuse having a fusing delay characteristic equal to or longer than an overcurrent delay time of the control circuit.

According to this configuration, the overcurrent protection function always operates first when the current increases instantaneously, so that it is possible to prevent the fuse from being blown and the battery pack from becoming unusable.

According to a second aspect of the present invention, a temperature fuse is arranged on the same potential side as the switch means.

With this configuration, it is possible to prevent a short circuit of the battery due to short-circuiting of the switch means and the thermal fuse, which may occur at different polar potentials. Therefore, the safety of the battery management device and the battery pack using the same can be prevented. Can be improved.

According to a third aspect of the present invention, the thermal fuse is thermally coupled to the switch means, and when the switch means generates abnormal heat, the thermal fuse is blown.

According to this configuration, the switch circuit cannot be controlled because the control circuit does not operate for some reason.
When charging / discharging current flows to the battery management device, if the switch means is in an unsaturated state, that is, is not completely turned on and has a high on-resistance, abnormal heat is generated due to Joule heat, which has not been conventionally available. In this case, it is possible to solve the problem by blowing the thermal fuse thermally coupled to the switch means, so that the safety of the battery pack can be improved.

According to a fourth aspect of the present invention, there is provided a battery pack using the battery management device according to any one of the first to third aspects.

With this configuration, it is possible to provide a battery pack that has extremely high safety and reliability, has a long service life, and can be used repeatedly.

According to a fifth aspect of the present invention, there is provided a battery pack, an output-side positive terminal and an output-side negative terminal which are output terminals, a battery voltage detecting means for detecting a battery voltage, and a charging current. A current detection unit, a delay unit that outputs a signal after a predetermined delay time has elapsed from an output from the battery voltage detection unit and the output from the current detection unit, and the battery voltage detection unit, the current detection unit, and the delay unit. A control circuit having the output of the control circuit as an input, and switch means receiving and controlling the output from the control circuit, and a thermal fuse is arranged between the switch means and the output terminal.

With this configuration, it is possible to completely insulate the secondary battery from the output terminal when a situation such as the blowing of the thermal fuse occurs.

According to a sixth aspect of the present invention, the thermal fuse is thermally coupled to the battery, and when the battery is abnormally heated, the thermal fuse is blown.

[0021] With this configuration, it is possible to add a means for improving the safety of ensuring the safety of the battery pack by blowing the thermal fuse when the secondary battery is abnormally heated without increasing the number of parts.

According to a seventh aspect of the present invention, the thermal fuse is thermally coupled to the battery and the switch means.

With this configuration, it is possible to improve the safety of the battery pack in response to abnormal heat generation of both the battery and the switch means without increasing the cost.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a block diagram of a battery pack showing a configuration example in this embodiment. The battery pack shown in the figure uses a thermal fuse 8 of the present invention, and has a battery management device 21 including a configuration corresponding thereto and other functions such as an overcharge protection function, an overdischarge protection function, and an overcurrent protection function.
And a secondary battery 20 configured as a single or assembled battery
And an output-side positive terminal 3 and an output-side negative terminal 4 connected to the electronic device. In the present embodiment, as the secondary battery 20, a lithium ion secondary battery which is a non-aqueous solvent secondary battery and is charged by a constant voltage charging method will be described as an example. Regardless of the system, the present invention can be appropriately modified and applied even when other types of batteries such as a nickel-metal hydride storage battery and a lithium polymer secondary battery are used.

In this embodiment, an n-channel MOSFET having a parasitic diode used for trickle charging is used as the switch means, and is disposed on the negative electrode side. Specifically, the source terminal of the discharging FET 6 is connected to the negative side of the battery 20, and the drain terminal of the discharging FET 6 is connected to the drain terminal of the charging FET 5. The parasitic diode of the charging FET 5 is disposed in parallel between the drain terminal and the source terminal of the charging FET 5 so as to be in a forward direction at the time of discharging.
The parasitic diode of T6 is arranged in parallel between the drain terminal and the source terminal of the discharging FET 6 so as to be in the forward direction during charging. FE for charging at the time of overcharge detection described later
T5 is turned off to prevent charging, and when overdischarge is detected, the discharging FET 6 is turned off to prevent discharging. When overcurrent is detected, both the charging FET 5 and discharging FET 6 are turned off to prevent overcurrent.

This battery management device has a positive terminal 22 and a negative terminal 23 as external terminals. The positive electrode of the secondary battery 20 is connected to the positive battery voltage terminal 24, and the negative electrode of the secondary battery 20 is connected to the negative battery voltage terminal 25. Each is connected.

The output-side positive terminal 3 and the output-side negative terminal 4, which are external connection terminals, are connected to a charger (not shown) at the time of charging, and are connected to the output-side positive terminal 3 → the secondary battery 20 → the discharging FET.
The charging of the secondary battery 20 is performed by passing a charging current through the path of 6 → charging FET 5 → temperature fuse 8 → output side negative terminal 4.

The battery management device 21 includes a battery voltage detecting means 1 for detecting a voltage of the secondary battery 20, a current detecting means 2 for detecting a discharge current flowing through the secondary battery 20, a battery voltage detecting means 1 and a current detecting means. Delay means 4 for inputting the output of means 2 and outputting a signal to control circuit 3 after a predetermined delay time
And a control means 3 for controlling the switching means, a charging FET 5 and a discharging FET 6 which are switching means, and a temperature fuse 8 which is the last key of the safety control.

Hereinafter, each component will be described in detail. Battery voltage detecting means 1 inputs the battery voltage V _B, the overcharge detection voltage VCH1 a four specified value, the overcharge detection release voltage VCH2, overdischarge detection voltage VDCH1, overdischarge detection cancellation voltage VDCH2 voltage comparison Then, the detection result is output to the control circuit 3 and the delay unit 4. Note that the four voltage values have a magnitude relationship of VCH1>VCH2>VDCH2> VDCH1.

The current detecting means 2 determines that the excessive current on the discharge current side exceeds the specified current value I0 specified for the purpose of preventing the deterioration of the battery characteristics or preventing the power loss of the charge / discharge FET and the detection delay time t2. Outputs an overcurrent detection signal when exceeded. The overcurrent is released by outputting an overcurrent release signal that releases the overcurrent detection signal when the removal of the load that caused the discharge is detected.

The delay means 4 is used on the assumption that there is a malfunction due to noise when control is performed only by signals sent from the battery voltage detection means 1 and the current detection means 2 to the control circuit 3. In order to prevent malfunction, the battery voltage detecting means 1 and the current detecting means 2
When the input signal is input after the specified delay time has elapsed, the delay time elapse signal is output to the control circuit 3.

The control circuit 3 receives signals from the battery voltage detecting means 1, the current detecting means 2, and the delay means 4 and outputs signals corresponding to the respective states to the charging FET 5 and the discharging FET 6.

The thermal fuse 8 is a non-conventional component that can protect the secondary battery 20, the charging FET 5, and the discharging FET 6 from deterioration with a single component. This thermal fuse 8 has a fusing characteristic longer than the overcurrent delay time of the battery management device 21 even if an excessive current flows due to a short circuit between the output terminals of the battery pack. Since there is no fusing due to fusing and the fusing characteristics are less than the safe operation area of the charging FET 5 and the discharging FET 6, the fusing can be performed before the charging FET 5 and the discharging FET 6 deteriorate. it can.

In this configuration, when an excessive current flows through the charging path due to a short circuit between the output terminals of the battery pack, the battery has a fusing characteristic longer than the overcurrent delay time of the control circuit.
The thermal fuse 8 having a fusing characteristic less than the safe operation area of the charging FET 5 and the discharging FET 6 is not erroneously blown by an instantaneous overcurrent or the like, the overcurrent protection function of the battery management device 21 works first, and the switch means By turning off the battery, it is possible to take measures to keep the battery pack unusable while maintaining safety.

Here, in order to explain the advantage of using the thermal fuse 8 in the present invention in more detail, the mechanism of overcurrent will be described.

If the battery voltage detected by the battery voltage detecting means 1 is equal to or lower than the overcharge detection voltage VCH1 and equal to or higher than the overdischarge detection voltage VDDH2,
5. In a normal state in which a high level voltage is applied to the gate terminal of the discharging FET 6 and the gate is turned on, it is on the charging / discharging path and is driven by the voltage applied to the gate terminals of the charging FET 5 and the discharging FET 6 by the control circuit 3. Charging FET
5. A voltage drop caused by a discharge current flowing from a load (not shown) connected to the output terminal with respect to the on-resistance between the drain terminal and the source terminal of the discharging FET 6 is predetermined by the current detecting means 2. The detection is performed by determining whether or not the voltage exceeds the specified voltage value V0 corresponding to the specified current value I0, which is the specified value, and exceeds the detection delay time t2 specified by the delay means 4.

By outputting this overcurrent detection signal to the control circuit 3, the control circuit 3 makes a judgment together with the output signal from the delay means 4, and outputs a low-level voltage to the discharge FET 6 at the gate terminal of the discharge FET 6. Is applied, the discharge FET 6 is turned off, and the charging FE is turned off.
The FE for charging, which is a low level voltage, is connected to the gate terminal of T5.
A voltage having the same potential as the source terminal of T5 is applied, and the charging FET 5 is turned off, thereby stopping the discharging current.

The specified current value I0 at this time has a variation in the voltage actually detected by the current detecting means 2, and the voltage is determined by applying a current to the on-resistance of the charging FET 5 and the discharging FET 6. To detect, but use F
Although depending on the type of ET, the on-resistance of the FET generally has a variation of 1.6 times at the maximum with respect to the center value, so that it greatly varies from product to product and from detection to detection.

The specified detection delay time is determined by the delay circuit 4
A constant current flows to the capacitor within the circuit, and the voltage of the electric charge stored in the capacitor is determined by a comparison circuit based on a certain voltage value.When the voltage exceeds the reference value, a sufficient delay time elapses This is determined by making a determination as to whether it has occurred and outputting it to the control circuit 3. The delay time has a very large variation due to a variation due to a capacitor composed of a semiconductor and a variation in current of a constant current circuit composed of a semiconductor.

The advantages of using the thermal fuse 8 based on the characteristics of the overcurrent detection function as described above will be described in detail below with reference to the case of a conventional example using a current fuse.

FIG. 4 shows current fuse blowing, FET ASO
FIG. FIG. 2 shows characteristic diagrams of the thermal fuse blowing, the current fuse blowing, and the FET ASO.

The conventional battery management device 21 using a current fuse detects an overcurrent based on whether the specified current value I0 and the detection delay time t2 have been exceeded, and detects a charging FET 5 and a discharging FET.
6 is turned off to prevent overcurrent. Power MOS with overcurrent delay characteristics and DC rated current I1
A region corresponding to a hatched portion surrounded by I0 and I1 caused by the safe operation region characteristics of the charging FET 5 and the discharging FET 6 constituted by FETs deteriorates the charging FET 5 and the discharging FET 6 which are power MOSFETs. Has characteristics. Therefore, in the case of, for example, I2, which is a current value equal to or less than the specified current value I0 and equal to or more than I1, the charging FET after the lapse of t4.
5. The discharge FET 6 will be deteriorated.

To prevent this, the charging FET 5,
It is a DC fusing current I3 less than the DC rated current I1 of the discharging FET 6, and the current is blocked by using a current fuse having a fusing characteristic of fusing at a time t3 less than a time t4 that deteriorates the charging FET 5 and the discharging FET 6. , Charging FET
5. The discharge FET 6 is prevented from deteriorating and causing a safety problem.

In this case, the overcurrent protection function has a current value I0,
The detection is performed at the time t1 and the operation is performed with the minimum detection delay time t2 or longer. However, as described above, the detection has a very large variation, and when the detection is performed at the maximum, the detection delay time t5 It is configured to operate with.

The maximum current value due to a short circuit between the terminals of the battery pack is I4 as shown in FIG. According to the current fuse blowing characteristics, the current fuse blowing current becomes I5 larger than the maximum current value I4 at the minimum detection delay time t2, and the overcurrent protection function of the battery management device 21 operates sooner than the current fuse blows, which causes a problem. Absent. However, at the maximum detection delay time t5, the current fuse blowing current becomes I6 smaller than the maximum current value I4, so that the current fuse blows earlier than the overcurrent protection function of the battery management device 21 operates. May be lost. As a matter of course, the fusing operation makes the battery pack unusable.

Taking this into consideration, in the present invention, the charging F
ET5, DC fusing current I3 less than DC rated current I1 of discharging FET6, charging FET5, discharging FET6
The overcurrent is prevented by using a thermal fuse 8 having a fusing characteristic that is blown in a time equal to or less than the time when the charge
5. The deterioration of the discharging FET 6 is prevented.

Further, even when the maximum current value I4, which has been a problem in the conventional example using the current fuse, flows, the temperature fuse 8 used in the present embodiment is longer than the maximum detection delay time t5 of the battery management device 21. And the fusing characteristics of the charging FET 5 and the discharging FET 6 at the maximum current value I4 at the time t7 or less in the safe operation area (FIG. 2).
At the time t6), the overcurrent protection function of the battery management device 21 operates first to protect the instantaneous maximum current value due to the short circuit between the terminals of the battery pack, and the charging FET
5. The thermal fuse 8 can be prevented from being erroneously blown without the discharge FET 6 being deteriorated.

(Embodiment 2) This embodiment will be described with reference to FIG. The thermal fuse 8 is laterally attached to the FET 30 as shown in FIG. 3, and the FET 30 and the thermal fuse 8 are thermally coupled by a silicon bond 40 in order to efficiently conduct the heat of the FET 30 to the thermal fuse 8. The FET 30 shown in the present embodiment is different from the charging FET 5 and the discharging FET 6 in the first embodiment.

Since the FET 30 and the thermal fuse 8 are parts to be brought close to each other, there is a possibility that the FET 30 and the thermal fuse 8 may be short-circuited at different polarities and short-circuit the battery. . As shown in FIG. 1, n is provided on the negative electrode side of the secondary battery 20 as a switch means.
Since the channel type MOSFET is used, the temperature fuse 8 is also arranged at the battery negative electrode potential, and the charging FET 5 and the discharging FET 6 are used to completely insulate the secondary battery 20 and the output terminal after the temperature fuse 8 is blown. It is best to place it between output terminals.

The purpose of this is to make the FET 30
When the battery is abnormally heated, the heat is blown to blow the thermal fuse 8, thereby preventing the entire battery management device 21 from being abnormally heated and malfunctioning, thereby further improving safety.

The cause of the abnormal heat generation of the FET 30 is that the control circuit 3 does not operate for some reason.
Can be controlled and Joule heat is generated when the FET 30 is in an unsaturated state, that is, when the FET 30 is not completely turned on and has a high on-resistance when a charge / discharge current flows to the control circuit 3. In this embodiment, the Joule heat is sensed by the adjacent thermal fuse 8 and blown when the temperature exceeds the blowout temperature of the thermal fuse, thereby forcibly charging and discharging the battery management device 21. To prevent the FET 30 from generating heat, so that the reliability of the battery management device 21, the battery pack, and the electronic device using the same can be improved, and the safety can be improved.

In this embodiment, a silicon bond 40 is applied between the FET 30 and the thermal fuse 8 to
The heat of 30 is reliably transmitted to the thermal fuse 8. In the present embodiment, the thermal fuse 8 is connected to the FET 3
0, but the thermal fuse 8 is connected to the secondary battery 2
The same result can be obtained by thermally bonding by applying a silicon bond 40 to the secondary battery 2.
0 and thermally coupled to the FET 30 can further improve safety without increasing the number of components. In the present invention, the FET 30 is arranged at the battery negative electrode potential by using an n-channel type. However, the same result can be obtained even when the FET 30 is arranged at the battery positive electrode potential by using a p-channel type. .

[0054]

As described above, the present invention does not merely replace the current fuse with the thermal fuse, but based on a completely different viewpoint of improving the safety and effectively using the battery pack. Using a thermal fuse with a fusing delay characteristic longer than the current delay time and thermally coupling the thermal fuse to the charging FET, discharging FET and secondary battery, the output terminals of the battery pack are momentarily excessive due to a short circuit, etc. There is a new effect that there is no erroneous melting of the thermal fuse even when a large current flows, and it enables a safety measure in case of abnormal heating of the charging FET and discharging FET, and abnormal heating of the secondary battery. It can also be used for safety measures at the time,
It is possible to provide a battery management device excellent in safety and a battery pack using the same without increasing costs due to an increase in the number of parts.

[Brief description of the drawings]

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

FIG. 2 is a thermal fuse blowing characteristic diagram of the embodiment.

FIG. 3 is a schematic diagram showing an example of thermal coupling between an FET and a thermal fuse according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a current fuse blowing characteristic of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery voltage detecting means 2 Current detecting means 3 Control circuit 4 Delaying means 5 Charging FET 6 Discharging FET 8 Thermal fuse 20 Secondary battery 21 Battery management device 22 Positive terminal 23 Negative terminal 24 Positive battery voltage terminal 25 Negative battery voltage terminal 30 FET 40 Silicon bond

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiromitsu Hayashi 1006 Odakadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (7)

[Claims] 1. A battery voltage detecting means for detecting a battery voltage, a current detecting means for detecting a discharge current, and receiving a signal after a predetermined delay time from an output from the battery voltage detecting means and the current detecting means as an input. Delay means for outputting, the battery voltage detecting means, the current detecting means, a control circuit to which an output from the delay means is input, and switch means for receiving and controlling the output from the control circuit, A battery management device using a temperature fuse having a fusing delay characteristic equal to or longer than an overcurrent delay time of the control circuit. 2. The battery management device according to claim 1, wherein a thermal fuse is arranged on the same potential side as the switch means. 3. The battery management device according to claim 1, wherein the thermal fuse is thermally coupled to the switch means, and when the switch means generates abnormal heat, the thermal fuse is blown. . 4. A battery pack using the battery management device according to claim 1. 5. A secondary battery, an output-side positive terminal and an output-side negative terminal, which are output terminals, a battery voltage detecting means for detecting a battery voltage, a current detecting means for detecting a discharge current, and the battery voltage detecting means. Means for outputting a signal after an elapse of a predetermined delay time with the output from the means and the current detection means as an input; a control circuit having the outputs from the battery voltage detection means, the current detection means and the delay means as inputs; 5. The battery pack according to claim 4, further comprising: switch means for receiving an output from said control circuit and being switch-controlled, wherein a thermal fuse is arranged between said switch means and said output terminal. 6. The battery pack according to claim 4, wherein the thermal fuse is thermally coupled to the battery, and when the battery is abnormally heated, the thermal fuse is blown. 7. The battery pack according to claim 4, wherein the thermal fuse is thermally coupled to the battery and the switch means.