JPH11176483A - Pack battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct cell balances, while reducing losses in a pack battery when a low load current in the pack battery to be used in a notebook type personal computer or the like. SOLUTION: An ON/OFF type converter circuit, to which plural unit cells E1,... are serially connected, to which output voltages of the unit cells E1,... are inputted, and to which output is connected in a charging direction to the unit cells E1,... is provided. A current control circuit C1 to increase/decrease a primary side current Ip in accordance with the size of a load current Io is provided. Generation of unit cell getting into a charged condition is thus restricted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery pack used in a notebook computer or incorporated in an electric vehicle together with a solar system.

[0002]

2. Description of the Related Art FIG. 3 is a circuit diagram showing an example of a conventional battery pack.

Conventionally, this type of battery pack 1 has a configuration in which a plurality (for example, three) of unit cells E1, E2, and E3 are connected in series. In order to extend the life of the battery pack 1, At the time of charging and discharging, it is necessary to correct the balance of the cells E1, E2, E3, that is, the cell balance.

As a method for correcting the cell balance, FIG.
As shown in the figure, there is proposed a method using an ON / OFF type converter circuit in which output voltages of a plurality of unit cells E1, E2, E3 are input and outputs are connected in a direction for charging the unit cells E1, E2, E3. Have been. According to this method, since the output voltage of the converter circuit is determined by the turns ratio of the transformer, when the converter circuit is driven, the charging current flows intensively to the unit cell having the lowest voltage. There is a characteristic that the balance can be corrected.

[0005]

However, the load current Io
Is small, the unit cells E1, E2, and E3 that become charged when the battery pack 1 is being discharged also occur, and there is a disadvantage that the efficiency of the battery pack 1 decreases due to the loss of power flowing back.

In view of the above circumstances, it is an object of the present invention to provide a battery pack capable of correcting cell balance while reducing loss in the battery pack even with a small load current.

[0007]

That is, according to the present invention, a plurality of unit cells (E1, E2,..., En) are connected in series,
In the battery pack (1) provided with an ON / OFF type converter circuit in which the output voltages of these unit cells are input and the output is connected in the direction of charging each unit cell, the load current (I
A current control circuit (C1) for increasing or decreasing the primary current (Ip) according to the magnitude of o) is provided.

The present invention also relates to a plurality of unit cells (E1, E1).
, En) are connected in series, the output voltage of these cells is input, and the output is connected in the direction of charging each cell. , The primary current (Ip) is the load current (Ip
A current control circuit (C1) for controlling so that o) is substantially equal to a value obtained by dividing the number (n) of the unit cells is provided.

Further, the present invention relates to the above-described unit cells (E1, E1).
2,... En) are provided with current detectors (D1, D2,..., Dn-1) for detecting a current flowing into the connection section. When the value detected by the current detector becomes substantially zero, the current control is performed. An intermittent control circuit (C) that makes the circuit (C1) operate intermittently.
2) is added.

Note that the numbers in parentheses are for convenience showing the corresponding elements in the drawings, and therefore, the present invention is not limited to the description on the drawings. The same applies to the column of “Claims”.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing a first embodiment of a battery pack according to the present invention, and FIG. 2 is a circuit diagram showing a second embodiment of the battery pack according to the present invention.

As shown in FIG. 1, a battery pack 1 according to the present invention comprises a plurality (n) of unit cells E connected in series.
, En,..., En, and these unit cells E1,
, En include an ON / OFF type converter circuit. Further, a current control circuit C1 is incorporated in the battery pack 1.

Therefore, when the cell balance is achieved by the converter circuit, any unit cell Ek (k = 1, 2,...,
n) are the load current Io, the primary current Ip, and the current Ik (k) flowing into the positive electrode side connection of the unit cell Ek.
= 1, 2,..., N) as Io + Ip−Ik. Here, when the voltage of a certain unit cell Ek is lower than the voltage of another unit cell, the current Ik flowing into the positive electrode side connection part of the unit cell Ek becomes larger than the primary side current Ip, so if the load current Io is small, This unit cell Ek has a negative current,
That is, the battery is charged, and the loss in the battery pack increases.

Therefore, the current control circuit C1 outputs the load current Io
And increases or decreases the primary current Ip according to the magnitude of the load current Io. That is, the load current I
When o is small, the primary current Ip is also reduced. Then, since the current Ik is proportional to the primary current Ip, the current Ik also decreases with a decrease in the primary current Ip, so that it is possible to avoid a situation where the current of the unit cell Ek becomes negative. On the other hand, when the load current Io is large, the primary side current Ip is also made large. Then, the current Ik becomes the primary side current Ip
However, a situation in which the current of the unit cell Ek becomes negative does not occur.

At this time, it is preferable that the primary current Ip is substantially equal to a value obtained by dividing the load current Io by the number n of unit cells. The reason is as follows. In FIG. 1, I1 · E1 + I2 · E2 +... + In · En =
.. + En), but when the cell balance is maintained, E1, E2,..., En are almost constant, so that Ip = (I1 + I2 +... + In) / n. Then, since the output of the converter circuit is concentrated on the unit cell having a slightly lower voltage, for example, if the voltage of En is slightly lower than the others, I1 to In-1 are all zero, so the flowing current is Ip = In / N. Here, as described above, since In and Io should be substantially equal, it can be said that Ip = Io / n is preferable.

Further, as shown in FIG.
By incorporating 1, D2,..., Dn−1 and the intermittent control circuit C2, power loss can be reduced. That is, the current detectors D1, D2,..., Dn-1 detect the current flowing into the connection portion of each unit cell, and when all the detected values become substantially zero (± 0 A), the cell balance becomes steady. Therefore, the intermittent control circuit C2 causes the current control circuit C1 to operate intermittently. Then, wasteful recirculation of power is prevented, and power loss is reduced.

[0018]

As described above, according to the present invention, a plurality of unit cells E1, E2,..., En are connected in series, and the output voltages of these unit cells E1, E2,. , The primary-side current Ip is increased or decreased according to the magnitude of the load current Io in the battery pack 1 provided with the ON / OFF converter circuit whose output is connected in the direction of charging the unit cells E1, E2,. Since the current control circuit C1 is provided to reduce the loss in the battery pack 1 even when the load current is small, it is possible to suppress the generation of the unit cells Ek that become charged when the cell balance is achieved by the converter circuit. This makes it possible to correct the cell balance.

According to the present invention, a plurality of unit cells E
, En,... En are connected in series, and these unit cells E
, En, and the output voltage of En, and each cell E
1, E2,..., And O whose outputs are connected in the direction of charging En
Battery pack 1 with N / OFF converter circuit
, The current control circuit C1 for controlling the primary current Ip to be substantially equal to the value obtained by dividing the load current Io by the number n of the unit cells E1, E2,..., En is provided. When taking cell balance,
Since the generation of the unit cells Ek that are in a charged state can be further suppressed, it is possible to correct the cell balance while significantly reducing the loss in the battery pack 1 even if the load current is small.

Further, according to the present invention, each of the unit cells E
, Dn-1 for detecting a current flowing into a connection portion of 1, E2,..., En, and a detection value by the current detectors D1, D2,. In this case, the current control circuit C1 is provided with an intermittent control circuit C2 for intermittent operation, so that in addition to the above-described effects, the intermittent control circuit C2 can prevent wasteful recirculation of power. The power loss of the battery 1 can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of a battery pack according to the present invention.

FIG. 2 is a circuit diagram showing a second embodiment of the battery pack according to the present invention.

FIG. 3 is a circuit diagram showing an example of a conventional battery pack.

[Explanation of symbols]

 1. Pack battery C1 Current control circuit C2 Intermittent control circuit D1, D2,..., Dn-1 Current detector E1, E2,. Primary current n: Number of cells

Claims (3)

[Claims] A plurality of unit cells (E1, E2,..., E
n) are connected in series, the output voltages of these unit cells are input, and the output is connected in the direction of charging each unit cell.
In the battery pack (1) provided with the FF type converter circuit, the primary current (Ip) according to the magnitude of the load current (Io)
A battery pack provided with a current control circuit (C1) for increasing or decreasing the current. 2. A plurality of unit cells (E1, E2,..., E
n) are connected in series, the output voltages of these unit cells are input, and the output is connected in the direction of charging each unit cell.
In the battery pack (1) provided with the FF type converter circuit, current control for controlling the primary current (Ip) to be substantially equal to a value obtained by dividing the load current (Io) by the number (n) of the unit cells. A battery pack comprising a circuit (C1). 3. A current detector (D1, D2) for detecting a current flowing into a connection portion of each unit cell (E1, E2,..., En).
2,..., Dn-1), and an intermittent control circuit (C2) for intermittently operating the current control circuit (C1) when the value detected by the current detector becomes substantially zero. The battery pack according to claim 1 or 2, wherein