JP2003217534A - Battery pack - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery pack, of which each unit cell is charged in an optimum state with improved battery life and reliability despite different initial conditions or battery characteristics of a plurality of the unit cells. <P>SOLUTION: The battery pack is provided with a plurality of switching circuits 3, structured with power MOS FET, enabled to connect a plurality of chargeable polymer lithium ion cells with as many charging control circuits 2 in series during charging and enabled to connect each of the plurality of the polymer lithium ion cells with each of the charging control circuits 2 individually. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rechargeable electric power source used for electric products such as televisions and radios, electronic devices such as portable personal computers and mobile phones, or transportation equipment such as electric vehicles and electric wheelchairs. The present invention relates to a battery pack, and particularly to a battery pack suitable for a polymer lithium ion battery.

[0002]

2. Description of the Related Art Conventionally, a so-called battery pack has been used as a rechargeable power supply unit for electric products, electronic devices and the like. As an internal structure of a battery pack, it is widely used as a conventional technique to connect a plurality of rechargeable cells in series to obtain a required voltage and power. in this case,
The characteristics of multiple cells connected in series, for example, the capacity of the cells may differ, and when the cells with different characteristics are connected in series and charged, the voltage applied to both ends of each cell Since the values are different, some cells may not be fully charged or conversely may be overcharged and deteriorate. Further, the tendency that the characteristics of the unit cells are different becomes more remarkable as the unit cells deteriorate. Therefore, when charging and discharging are repeated, the deteriorated unit cell deteriorates more and more, and the battery life and reliability are significantly deteriorated.

As described above, there is a problem in charging a plurality of cells connected in series as they are.
Further, among rechargeable batteries, particularly a lithium ion battery is vulnerable to overcharge and overdischarge, and therefore a protection circuit for detecting the overcharge state and the overdischarge state and prohibiting charging and discharging is combined. Furthermore, in charging, constant current and constant voltage charging (so-called CCCV charging) are performed so that the characteristics of each unit cell, particularly the voltage, are matched.

[0004]

However, the prior art has the following problems. The characteristics of multiple cells connected in series, for example, the capacity of the cells may differ, and when the cells with different characteristics are connected in series and charged, the voltage applied to both ends of each cell Since the values are different, some cells may not be fully charged or conversely may be overcharged and deteriorate. Further, the tendency that the characteristics of the unit cells are different becomes more remarkable as the unit cells deteriorate. Therefore, when charging and discharging are repeated, the deteriorated unit cell deteriorates more and more, and the battery life and reliability are significantly deteriorated. As described above, there is a problem in charging a plurality of single cells connected in series as they are. An object of the present invention is to solve the above problems and provide a battery pack that is safe and easy to handle.

[0005]

Means for Solving the Problems A plurality of rechargeable cells (1), a charge control circuit (2) of the same number as the plurality of cells (1), and the plurality of cells (1) in series at the time of discharging. And a plurality of switch circuits (3) for individually connecting each of the plurality of unit cells (1) to each of the charge control circuits (2) during charging. (3) is composed of a power MOS FET, and preferably, a protection circuit (4) composed of an overcurrent prevention circuit, an overdischarge prevention circuit, and an overcharge prevention circuit is connected to the unit cell (1) to form a plurality of unit cells. (1) is a polymer lithium ion battery. More preferably, the power supply circuit (8)
And a cooling blower (7). The present invention is a battery pack having the above configuration.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

FIG. 1 is an overall block diagram showing a first example of a battery pack according to the present invention. The unit cell (1) is a rechargeable battery, and a plurality of cells are used to obtain a required voltage. In particular, in the present invention, a polymer lithium ion battery capable of obtaining a large power is most suitable. The charge control circuit (2) is used in the same number as the plurality of unit cells (1) and has an ability to supply appropriate voltage and current to the unit cells (1) during charging, for example, constant current / constant voltage charging (so-called CC / CV). It has a charging ability. The plurality of switch circuits (3) enable the plurality of unit cells (1) to be connected in series at the time of discharging,
Each of the plurality of cells (1) can be independently connected to each of the charge control circuits (2) during charging.

Here, although the switch circuit (3) can be realized by using a conventional technique such as a relay or a manual switch, the use of mechanical contacts has a problem in reliability and life. As shown in, power MOS FE
T is used as a switch element. Power MOS F
ET is a semiconductor that can easily control a large current flowing between the source and drain by controlling the gate voltage with a small amount of electric power, and has no mechanical contacts as compared with the relay or the manual switch and has high reliability. The life, the response time, and the like can be dramatically improved.

FIG. 2 specifically shows one of the plurality of switch circuits (3) shown in the block diagram of FIG. 1, and is a circuit unnecessary for the explanation of the switch operation thereafter. And the structure is omitted. The FET1 (11) and the FET2 (12) are provided to open and close the circuit between the charge control circuit (2) and the unit cell (1). Further, the FET3 (13) and the FET4 (14) are provided to open and close a circuit between a plurality of adjacent switch circuits (3). Further FET control circuit (17)
Is provided for controlling the gate voltage of each FET, and is configured to switch between a charging state and a discharging state depending on the presence or absence of power supplied from the power supply circuit (8). Here, the FET control circuit (17) can be easily realized by using a conventional technique using electronic parts such as a transistor, an IC, a photo coupler, a resistor and a capacitor.

The operation of the switch circuit (3) is explained as follows. First, in the power supply circuit (8) in FIG. 2, an external AC power supply, for example, AC 100V installed everywhere.
The power supply circuit (8) is activated by applying power,
Power is supplied to the FET control circuit (17). Then F
The ET control circuit (17) includes FET1 (11) and FE.
Each FE is set so that T2 (12) is turned on and FET3 (13) and FET4 (14) are turned off.
Control the gate voltage of T. In this state, a plurality of adjacent switch circuits (3) are disconnected, and the unit cell (1) is independently connected to the charge control circuit (2). The charge control circuit (2) is connected to the unit cell (1). ) Can start charging. Next, when the external AC power supply is disconnected and the power supply circuit (8) is stopped, the power supplied to the FET control circuit (17) is also stopped. Then, the FET control circuit (17) changes the FET1 (11) and the FET2 (12).
Turns off, and FET3 (13) and FET4
The gate voltage of each FET is controlled so that (14) is turned on. In this state, a plurality of adjacent switch circuits (3) are connected in series, and the unit cell (1) is disconnected from the charge control circuit (2), and discharging is possible. As described above, the switch circuit (3) of the present invention has a feature that the charging state and the discharging state are automatically switched by turning on / off the external AC power source, and provides a battery pack that is easy to operate and handle. be able to.

The power supply circuit (8) converts an AC voltage supplied from the outside into a DC voltage, and supplies necessary voltage and current to the charging circuit (2), the switch circuit (3) and the FET control circuit (17). It is provided to do. Specifically, it can be easily realized by using a conventional technique including a power transformer, but more preferably, a switching power supply that does not require a large power transformer can be used to reduce the size,
It has the effect of increasing efficiency and is most suitable for the present invention.

Usually, a protection circuit (4) composed of an overcurrent prevention circuit, an overdischarge prevention circuit and an overcharge prevention circuit is connected to the plurality of unit cells (1). These circuits detect the voltage value across the cell (1) and the passing current value,
This is provided in order to prevent the deterioration of the unit cell by shutting off the circuit when the set range value is not satisfied, and can be easily realized by the conventional technology.

By the way, the above-mentioned over-discharge prevention circuit functions to cut off the circuit when the voltage across the unit cell (1) falls below the reference voltage Vmin. However, as shown in FIG.
For example, when n single cells (1) having a battery voltage Vs are connected in series from E1 to En, the series connection switches S1 to S inside the plurality of switch circuits (3) are discharged.
n are connected with an indefinite time difference, but the switch circuit other than the side connected to the load, for example, the switch S1 between the first switch circuit and the second switch circuit is connected last. If the second cell E
At both ends of 2, the series addition potential of other unit cells- (n-1)
Since Vs is applied, which is below the overdischarge reference voltage Vmin, the circuit is cut off by opening the cutoff switch S22 in the protection circuit (4), and it becomes impossible to supply power to the load. .

In order to prevent this, a delay circuit (6) is provided in the switch circuit (5) on the side connected to the load among the plurality of switch circuits (3) as shown in FIG. Series connection switch Sn inside switch circuit (5)
However, the series connection switch S inside the other switch circuit (3)
If the connection is made later than any one of 1 to Sn-1, Sn will have the same function as the load operation switch (10), and the plurality of unit cells (1) will operate without the protection circuit. It can be connected in series and can supply power to the load. Further, FIG. 5 specifically shows the inside of the switch circuit (5) on the side connected to the load in which the delay circuit (6) is provided, and the circuit and structure unnecessary for the explanation of the switch operation thereafter. Is omitted. FET5
(15) and the FET 6 (16) are provided to open and close the circuit between the switch circuit (5) on the side connected to the load and the load (9). The delay circuit (6) includes the F
ET5 (15) and FET6 (16) gate and FE
After the FET3 (13) and the FET4 inside the other switch circuit (3) provided between the T control circuits (17) have connected all the circuits between the plurality of adjacent switch circuits (3), FET5 (15) and FET6 (1
6) is a circuit that generates an appropriate time difference so that it is turned on. The delay circuit (6) can be easily realized by using a conventional technique using electronic parts such as a transistor, an IC, a resistor and a capacitor.

The load (9) is not limited to electric products such as televisions and radios, or electronic devices such as portable personal computers and mobile phones. In particular, polymer lithium ion batteries are used for the plurality of unit cells (1). In this case, it becomes possible to supply a large amount of electric power, and it can also be used as a power supply for supplying transportation equipment such as electric vehicles and electric wheelchairs.

FIG. 6 is an overall block diagram showing a second example of the battery pack according to the present invention. In this example, the power supply circuit (8) in the first example is provided inside the battery pack, and the other structures are substantially the same as those in the first example. Since this structure includes all circuits and mechanisms necessary for charging and discharging inside the battery pack, it is possible to perform charging and discharging with the battery pack alone. The battery pack according to the related art does not have a power supply circuit or a charge control circuit therein and requires a charger separately. Therefore, when the conventional battery pack is mounted on a transportation device such as an electric vehicle or an electric wheelchair, and the battery voltage becomes insufficient at the destination and operation becomes impossible, a dedicated charger is required. This is a problem because it limits the range of action of the transportation device. However, the second example of the battery pack according to the present invention solves such a problem and is installed in a general AC power supply, for example, everywhere even when the battery voltage becomes insufficient at the destination and operation becomes impossible. AC 100V
It is possible to charge the battery with a power source and restart the operation.

The present invention is a battery pack having the above-mentioned structure. When using the battery pack, first, in order to charge the plurality of unit cells (1) in FIG. 1, an external AC power supply,
For example, by applying an AC 100V power source installed everywhere to the power source circuit (8), the power source circuit (8) is operated, and power is supplied to the plurality of switch circuits (3) and the plurality of charging control circuits (2). To do. Then, the plurality of switch circuits (3) are switched so as to individually connect each of the unit cells (1) to each of the charge control circuits (2), and at the same time, each of the charge control circuits (2) is connected to each of the unit cells ( Start constant current / constant voltage charging in 1). By charging in this state, even if the initial state and battery performance of each unit cell (1) are different, each unit cell is charged in the optimum state, so that the unit cell will not be fully charged. On the contrary, there is no unit cell that is overcharged and deteriorates, and battery life and reliability can be improved.

By the way, the charge control circuit (2) normally outputs a full-charge display signal for indicating the completion of charging by a lamp, a light emitting diode or the like, but each charge control circuit (2) It is advisable to install a logic circuit (18) that processes the full-charge display signals output from all together so that the full-charge display signals are output only when all the cells (1) have been charged. .

Further, when it is determined that the temperature inside the battery pack rises due to the heat generation of the charging current control transistor and the current detection resistor during charging, which may impair safety, for example, It is advisable to provide a cooling blower (7) at an appropriate position inside the battery pack to prevent an excessive temperature rise inside the battery pack during charging. Of course, it is needless to say that an appropriate amount of ventilation holes are provided at appropriate places of the battery pack to assist ventilation.

Next, when the external AC power supply is disconnected and the power supply circuit (8) is stopped after the charging of each unit cell (1) is completed, a plurality of switch circuits (3) and a plurality of charge control circuits (2) are provided. The power that was being supplied to) is also stopped. Then, the plurality of switch circuits (3) disconnects each of the unit cells (1) from each of the charge control circuits (2), and at the same time, connects the unit cells (1) to each other.
Each of them and the load (9) are automatically switched so as to be connected in series to be in a dischargeable state. When the operation switch (10) is closed in this state, the series voltage of the plurality of cells (1) is applied to the load (9), and the load (9) can perform a predetermined operation.

Furthermore, when it is determined that the voltage of the plurality of unit cells (1) is reduced due to the power consumption of the load (9) and the operation of the load (9) is interrupted, the power supply circuit (8) is restarted. ) Is operated to supply electric power to the plurality of switch circuits (3) and the plurality of charging control circuits (2). By repeating the same operation and the control process of each circuit thereafter, it becomes possible to supply sufficient electric power to the load (9) again, and the load (9) can perform a predetermined operation.

[0022]

According to the present invention, even if the respective unit cells (1) have different initial states and different battery performances, each unit cell is charged in an optimum state, so that the unit cells can be fully charged. It is possible to suppress the generation of unreliable single cells or conversely, overcharged and deteriorated single cells, and it is possible to improve battery life and reliability. It is possible to provide a battery pack having such effects.

[Brief description of drawings]

FIG. 1 is an overall block diagram showing a first example of a battery pack according to the present invention.

FIG. 2 is a block diagram showing an example of a switch circuit according to the present invention.

FIG. 3 is a block diagram showing an example of discharging a battery pack according to the present invention.

FIG. 4 is a block diagram showing another example of discharging the battery pack according to the present invention.

FIG. 5 is a block diagram showing an example in which a delay circuit is provided in the switch circuit according to the present invention.

FIG. 6 is an overall block diagram showing a second example of the battery pack according to the present invention.

[Explanation of symbols]

1 unit cell 2 Charge control circuit 3 switch circuit 4 Protection circuit 5 Switch circuit on the side connected to the load 6 delay circuit 7 Blower for cooling 8 power supply circuit 9 load 10 Load operation switch 11 Power MOS FET1 12 Power MOS FET2 13 Power MOS FET3 14 Power MOS FET4 15 Power MOS FET5 16 Power MOS FET6 17 FET control circuit 18 logic circuits

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yuji Yamamichi             5-88, Fukushima, Yao-cho, Nisei-gun, Toyama Prefecture             Xel Hokuriku Seiki Co. (72) Inventor Akito Sawada             236 Ninagawa System Electric Industry Co., Ltd., Toyama City, Toyama Prefecture             Inside the company F-term (reference) 5H029 AJ02 AM16 BJ23 BJ27                 5H030 AA03 AA04 AA10 AS08 AS11                       AS14 BB01 DD08 FF43 FF44                 5H031 AA09 CC05 CC09 KK08                 5H040 AA28 AA36 AA40 AS04 AS07                       AS13 AS14 AS15 AY08 DD08

Claims (7)

[Claims] 1. A plurality of rechargeable cells (1), a charge control circuit (2) of the same number as the plurality of cells (1), and the plurality of cells (1) can be connected in series during discharging. A battery pack having a plurality of switch circuits (3) capable of independently connecting each of the plurality of unit cells (1) to each of the charge control circuits (2) during charging. 2. A plurality of switch circuits (3) are power MOS
The battery pack according to claim 1, wherein the battery pack is constituted by an FET. 3. A protection circuit (4) composed of an overcurrent protection circuit, an overdischarge protection circuit and an overcharge protection circuit is connected to a plurality of cells (1).
The battery pack according to claim 2. 4. The battery pack according to claim 1, wherein the plurality of cells (1) are polymer lithium ion batteries. 5. A delay circuit (6) is provided in a switch circuit (5) connected to a load among a plurality of switch circuits (3), and the switch circuit (5) connected to the load is 5. The discharge circuit is configured to be connected later than any of the other switch circuits (3) at the time of discharging, so that the plurality of unit cells (1) can be connected in series.
The battery pack described in. 6. A power supply circuit (8) for supplying power to a plurality of charge control circuits (2), a plurality of switch circuits (3) and a delay circuit (6). To the battery pack according to claim 5. 7. The battery pack according to claim 1, further comprising a cooling blower (7) for suppressing an increase in temperature inside the battery pack.