JPH10225005A - Circuit for equalizing potential difference of secondary cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize the power consumption of a secondary cell, at the time of equalizing the voltages of the cells. SOLUTION: In this circuit, positive pole side switching means 1, 2, 3 are provided between each positive pole of secondary cells VA, VB, VC connected in series and a capacitor C. Furthermore, negative pole side switching means 4, 5, 6 are provided between each negative pole of the secondary cells VA, VB, VC connected in series and a capacitor C. The circuit controls the positive pole side switching means 1, 2, 3 and the negative pole side switching means 4, 5, 6 in such a way that cyclic 'on' operation is repeated in pair of a positive pole side switching means and a negative pole side switching means connected to the positive and negative poles of a same secondary cell.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control circuit for a battery unit using a secondary battery (rechargeable battery) built in a portable device, a personal computer, or the like. The present invention relates to a secondary battery potential difference equalizing circuit for equalizing a potential difference between positive and negative electrodes of each of a plurality of secondary batteries constituting a battery unit (hereinafter, simply referred to as a potential difference).

Incidentally, the equalization of the potential difference of the secondary battery is performed for the following purpose. That is, due to the variation in the physical properties of the secondary battery, during charging of a plurality of secondary batteries connected in series, one of the secondary batteries is prevented from being overcharged, and This is to prevent one secondary battery from being overdischarged during use (during discharge).
This is because if a certain secondary battery is repeatedly charged and discharged with another potential difference from another secondary battery due to overcharge or overdischarge, the life of the secondary battery is shortened.

[0003]

2. Description of the Related Art FIG. 2 is a circuit diagram showing a conventional example of a potential difference equalizing circuit for equalizing a potential difference between secondary batteries in a control circuit of a battery unit using a plurality of secondary batteries connected in series. is there. In FIG. 2, VA, VB, V
C is a secondary battery, which is connected in series. R
1 is a resistor having one end connected to the positive electrode of the secondary battery VA, R
2 is a resistor having one end connected to the negative electrode of the secondary battery VA, ie, the positive electrode of the secondary battery VB; R3 is a resistor having one end connected to the negative electrode of the secondary battery VB, ie, the positive electrode of the secondary battery VC; R4 is a resistor having one end connected to the negative electrode of the secondary battery VC.

1b is a switch means having one end connected to the other end of the resistor R1, 2b is a switch means having one end connected to the other end of the resistor R2, 3b is a switch means having one end connected to the other end of the resistor R3, and 4b is a switch means. Switch means having one end connected to the other end of the resistor R4, and each of the switch means 1b, 2b, 3b,
The other end of 4b is connected in common, and realizes a conduction state and an open state, respectively.

[0005] The above-described resistors R1 to R4 and the switch means 1b, 2b, 3b, 4b equalize the potential difference between the three secondary batteries VA, VB, VC connected in series to minimize the potential difference. Circuit is configured. Hereinafter, the operation of the secondary battery potential difference equalizing circuit will be described. When the potential differences between the secondary batteries VA, VB, and VC are all equal, the switch means 1b, 2b, 3b, and 4b are all in the open state. However, each of the secondary batteries VA, VB,
When the potential difference of the secondary battery VA becomes smaller than the potential difference of the other secondary batteries VB and VC due to a difference in physical properties of the VC, for example, the switching means 2b and 3b are turned on and the secondary battery is turned on. By discharging VB through the resistors R2 and R3, the potential difference of the secondary battery VB is reduced until it becomes equal to the potential of the secondary battery VA. Next, the switching means 3b and 4b are turned on in the same manner as described above to make the secondary battery VC
Is discharged through the resistors R3 and R4 to reduce the potential difference of the secondary battery VC until it becomes equal to the potential of the secondary battery VA. By the above operation, the secondary batteries VA, V
The potential differences between B and VC are all equal.

Here, switches 1b, 2b, 3b, 4b
Will be described. That is, as a control procedure, first, a potential difference between the secondary batteries VA, VB, and VC is converted into a potential difference from the ground, and the voltage is transmitted to the microcomputer side. FIG. 2 or FIG. 1 described later is also used for a circuit that converts the signal to the ground potential and outputs the converted signal to the microcomputer. The microcomputer determines the voltage and sends a control signal indicating which switch to open. Using the control signal (once converted to a switch control voltage), the switches 1b, 2b,
On / off of 3b and 4b is controlled.

[0007]

Conventionally, in a potential difference equalizing circuit for equalizing the potential difference of each secondary battery used in the battery unit, a relatively large potential difference is obtained every time the potential difference of each secondary battery is equalized. Since the discharge current flows, there is a problem that the power consumption of the secondary battery itself is increased and the life of the battery unit is shortened.

[0008] The life of the battery unit is used to mean the time during which the device can be driven.
The term "short life" means that the time during which the device can be driven is shortened because the energy stored in the secondary battery is wastedly released. However, even with respect to the original life, which is a guide for the replacement time of the secondary battery, if the energy consumption of the secondary battery is large as described above, the number of times of charging and discharging is increased, and the life of the secondary battery itself is shortened As a result, the timing of replacing the secondary battery of the battery unit is also accelerated.

The present invention solves the above-mentioned conventional problems, and provides a potential difference equalizing circuit capable of minimizing the power consumption of the secondary battery when equalizing the potential difference of the secondary battery. The purpose is to:

[0010]

In order to achieve this object, a potential difference equalizing circuit according to the present invention comprises a plurality of series-connected rechargeable batteries, each having a plurality of positive electrodes disposed between a positive electrode and a capacitor. While providing the positive electrode side switch means, providing a plurality of negative electrode side switch means between each negative electrode and the capacitor of the plurality of secondary batteries connected in series, a plurality of positive electrode side switch means A plurality of negative electrode-side switch means are cyclically turned on by a pair of the positive electrode-side switch means and the negative electrode-side switch means connected to the positive electrode and the negative electrode of the same secondary battery. Control.

As a result, a capacitor is selectively connected between both electrodes of each of the plurality of secondary batteries, and the connection state is sequentially changed in a cyclic manner. As a result, a plurality of secondary batteries and a capacitor in which a large potential difference among a plurality of secondary batteries charges a capacitor, and a small potential difference among a plurality of secondary batteries is charged by a capacitor. And a charge / discharge interaction occurs. As a result, among the plurality of secondary batteries, those having a large potential difference have a small potential difference due to discharging, and those having a small potential difference among the plurality of secondary batteries have a large potential difference due to discharging of a capacitor. The potential difference of the battery is equalized. Moreover,
Since the electric energy of one of the plurality of secondary batteries having a large potential difference is transferred to the one of the plurality of secondary batteries having a small potential difference via a capacitor, the potential difference of each of the secondary batteries is reduced with a minimum power consumption. It will be equalized.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A secondary battery potential difference equalizing circuit according to the present invention equalizes the potential difference between a plurality of secondary batteries connected in series. A plurality of positive electrode-side switch means having one end connected to the electrode and the other end commonly connected, and a plurality of switch means having one end connected to each negative electrode of the plurality of secondary batteries and the other end commonly connected Negative electrode side switch means, and a capacitor connected between the other end of the plurality of positive electrode side switch means and the other end of the plurality of negative electrode side switch means, wherein a plurality of positive electrode side switches Means and a plurality of negative electrode side switch means, and a pair of the positive electrode side switch means and the negative electrode side switch means connected to the positive electrode and the negative electrode of the same secondary battery are cyclically turned on. Is controlled to repeat.

According to this configuration, one of the plurality of rechargeable batteries having a large potential difference is discharged, whereby the capacitor is charged, and the charge stored in the capacitor is reduced to that of the plurality of rechargeable batteries having a small potential difference. In this case, the secondary battery is discharged, whereby the battery having a small potential difference among the plurality of secondary batteries is charged. Due to the charge / discharge interaction between the plurality of secondary batteries and the capacitor as described above, among the plurality of secondary batteries, the one having a large potential difference is reduced in potential by discharge, and the Among them, the one with a small potential difference has a large potential difference due to the discharge of the capacitor, and the potential differences between a plurality of secondary batteries are equalized. At this time, instead of discarding the electrical energy of the plurality of secondary batteries having a large potential difference, the electrical energy is temporarily stored in a capacitor and given to the small number of secondary batteries having a small potential difference. It is possible to minimize the power consumption of the secondary batteries when equalizing the potential difference between the secondary batteries.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a secondary battery potential difference equalizing circuit according to an embodiment of the present invention. In FIG. 1, VA, VB, and VC are secondary batteries, respectively, which are connected in series. Reference numerals 1, 2, and 3 denote a plurality of positive electrode side switch means for realizing a conductive state and an open state, respectively. One end is connected to each positive electrode of a plurality of secondary batteries VA, VB and VC, respectively. The ends are commonly connected. Reference numerals 4, 5, and 6 denote a plurality of negative electrode side switch means for realizing a conductive state and a released state, respectively. One end is connected to each of the negative electrodes of the plurality of secondary batteries VA, VB, VC, respectively. The ends are commonly connected. C is a capacitor connected between the other end of the plurality of positive electrode side switch means 1, 2, 3 and the other end of the plurality of negative electrode side switch means 4, 5, 6.

The plurality of positive electrode side switch means 1,
The on / off operations of the switches 2, 3, and the plurality of negative electrode side switch means 4, 5, 6 are controlled by a control circuit (not shown), but the positive and negative electrodes connected to the positive electrode and the negative electrode of the same secondary battery. The electrode-side switch means and the negative-electrode-side switch means are paired and controlled so as to cyclically repeat the ON operation. Specifically, the positive electrode side switch means 1
And the negative electrode side switch means 4 are on and all the rest are off, the positive electrode side switch means 2 and the negative electrode side switch means 5 are on and all the rest are off, and the positive electrode side switch means 3 and the negative The plurality of positive electrode-side switch means 1, 2, 3 and the plurality of negative electrode-side switch means 4, so that the state in which the electrode-side switch means 6 is ON and the rest are all OFF is sequentially and cyclically repeated. 5, 6 will be controlled.

The operation of the thus configured secondary battery potential difference equalizing circuit will be described. Here, the interlocking positive electrode switch means 1 and the negative electrode switch means 4, the interlocking positive electrode switch means 2 and the negative electrode switch means 5, and the interlocking positive electrode switch means 3 and the negative electrode switch means 6 and three switch means pairs S
1, S2, and S3. This switch means pair S1, S
2 and S3 respectively realize two types of a conductive state and an open state.

During operation of the secondary battery potential difference equalizing circuit,
Of the switch means pairs S1, S2, S3, one set is conductive and the other two sets are open, and the combination changes cyclically with time. In addition,
The order in which the switch means pairs S1, S2, and S3 are turned on is arbitrary, and the order in which they are turned on may be switched periodically.

For example, as an example, a switch means pair S1
Is a conductive state, the switch means pair S2 and S3 are in a released state, and then the switch means pair S2 is in a conductive state, the switch means pairs S1 and S3 are in a released state. The combination of S1 and S2 being in the released state is a ratio almost equal to time,
It is made to change sequentially.

A series of changes in the state of the switch means S1, S2, S3 over time can be achieved by charging the capacitor C with each of the rechargeable batteries VA, VB, VC, or transferring the charge of the capacitor C to the rechargeable batteries VA, VB, This has the effect of discharging to VC. That is, one of the secondary batteries VA, VB, and VC having a large potential difference is discharged, whereby the capacitor C is charged. The accumulated charge of the capacitor C is smaller than that of the secondary batteries VA, VB, and VC having a small potential difference. To discharge the secondary batteries VA, VB, and VC having a small potential difference.

Due to the charging / discharging interaction between the secondary batteries VA, VB, VC and the capacitor C as described above, the potential difference of the secondary batteries VA, VB, VC having a large potential difference is reduced by discharging. , Secondary batteries VA, VB, V
Among C, those having a small potential difference have a large potential difference due to the discharge of the capacitor C, and the potential differences between the secondary batteries VA, VB, and VC are equalized.

Explaining the above points concretely, when the potentials of the secondary batteries VA, VB, VC are all equal, the exchange of electric charge with respect to the capacitor C is hardly performed. Also, the potential difference between the secondary batteries VC is equal to the secondary batteries VB and VA.
If the potential difference is smaller than the potential difference between
Is in a conductive state and the switch means pair S1 and S2 are in a released state, the electric charge stored in the capacitor C by the secondary battery VB or VA is supplied to the secondary battery VC, and the potential of the secondary battery VC is Recovers to the potential difference of the secondary battery VB or the secondary battery VA. And the secondary battery V
The potential difference of the capacitor C lowered as a result of the discharge to C is determined by the following combination, for example, when the switch means pair S1 is conducting and the switch means pairs S2 and S3 are open.
The secondary battery VA is charged to a potential difference. Thereafter, in the case where the switch means pair S2 is in the conducting state and the switch means pairs S1 and S3 are in the open state, if the potential difference of the secondary battery VA is equal to the potential difference of the secondary battery VB, charging and discharging of the capacitor C is not performed. I can't. If the potential difference of the secondary battery VB is larger, the capacitor C is charged and the secondary battery VB is charged.
B is charged to the potential difference. Conversely, if the potential difference of the secondary battery VB is smaller, the capacitor C is discharged, the charge is supplied to the secondary battery VB, and the potential difference of the secondary battery VB increases. Therefore, the secondary batteries VA, V
The exchange of charges necessary for equalizing the potentials of B and VC is minimized.

As described above, according to the secondary battery potential difference equalizing circuit of this embodiment, the secondary batteries VA, VB, VC
Of the secondary batteries VA, VB, and VC are transferred to the one with a small potential difference through the capacitor C, and the electric energy of the one with a large potential difference among the secondary batteries VA, VB, and VC is transferred. Is not stored, but is temporarily stored in the capacitor C, and is given to the secondary battery VA, VB, VC having the smaller potential difference. Therefore, when equalizing the potential difference between the secondary batteries VA, VB, VC, , The power consumption of the secondary batteries VA, VB, and VC can be minimized.

In this embodiment, the configuration and operation of the secondary battery potential difference equalizing circuit for the three serially connected secondary batteries VA, VB, and VC have been described. There is no limitation, and it is possible to cope with all cases of two or more. Also, the positive electrode side switch means 1, 2, 3 and the negative electrode side switch means 4, 5,
6 is a mechanical or electronic relay device, P-type M
A single OS transistor, a transmission gate in which a P-type MOS transistor and an N-type MOS transistor are connected in parallel, or the like can be used.

The switching means is an N-type MOS.
It is also possible in principle to use a single transistor. However, when the switch 1 in FIG. 1 is turned on, N
It is necessary to make the gate voltage of the MOS transistor higher than the potential of the secondary battery VA, and the DC-
A DC converter and a charge pump are required, and the circuit becomes somewhat complicated.

[0025]

According to the rechargeable battery potential difference equalizing circuit of the present invention, the electric energy of the large potential difference among the plurality of rechargeable batteries is transferred to the rechargeable battery having the small potential difference through the capacitor. Instead of discarding the electrical energy of those with a large potential difference among a plurality of secondary batteries, the energy is temporarily stored in a capacitor and then given to a battery with a small potential difference among a plurality of secondary batteries. Therefore, it is possible to minimize the power consumption of the plurality of secondary batteries when equalizing the potential difference between the plurality of secondary batteries.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a secondary battery potential difference equalizing circuit according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration of a conventional secondary battery potential difference equalizing circuit.

[Explanation of symbols]

 VA, VB, VC Rechargeable batteries 1-3 Positive electrode side switch means 4-6 Negative electrode side switch means 1b, 2b, 3b, 4b Switch means R1-R4 Resistance C capacitor

Claims (3)

[Claims] 1. A secondary battery potential difference equalizing circuit for equalizing a potential difference between positive and negative electrodes of each of a plurality of secondary batteries connected in series, wherein each of the plurality of secondary batteries has a positive polarity. A plurality of positive electrode side switch means each having one end connected to the electrode and the other end commonly connected, and a plurality of positive electrode side switch means each having one end connected to each negative electrode of the plurality of secondary batteries and the other end commonly connected. A plurality of negative electrode side switch means, a capacitor connected between the other end of the plurality of positive electrode side switch means and the other end of the plurality of negative electrode side switch means, A positive electrode side switch means and the plurality of negative electrode side switch means are paired with a positive electrode side switch means and a negative electrode side switch means connected to a positive electrode and a negative electrode of the same secondary battery. I will repeat the ON operation cyclically Battery potential equalization circuit, characterized in that the controlled. 2. The secondary battery potential difference equalizing circuit according to claim 1, wherein each of the positive electrode side switch means and the negative electrode side switch means is constituted by a MOS transistor. 3. The secondary battery according to claim 1, wherein each of the positive electrode side switch means and the negative electrode side switch means is constituted by a transmission gate comprising a parallel circuit of a first conductivity type MOS transistor and a second conductivity type MOS transistor. Potential difference equalization circuit.