JPH0974689A - Power unit using battery pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the unbalance among cell banks without increasing the heat generating quantity of a circuit element by controlling each cell bank from the compared results of the output voltages of the cell banks and individually discharging all cell banks other than that outputting the lowest voltage until the voltages of the cell banks become nearly equal to the lowest voltage. SOLUTION: In a battery pack 10, three cell banks 1H, 1M, and 1L which are connected in parallel with each other are connected in series. The pack 10 is constituted by combining the cell banks 1H, 1M, and 1L, individual discharge circuits 3-1, 3-2, and 3-3 which are respectively provided in the banks 1H, 1M, and 1L, a comparator circuit 2 which compares the output voltages of the banks 1H, 1M, and 1L with each other, and a microcomputer 4. When the circuit 2 specifies the cell bank having the lowest voltage by comparing the output voltages of the banks 1H, 1M, and 1L with each other, the microcomputer 4 discharges the other cell banks than the cell bank having the lowest output voltage from the results of the comparison until the output voltages of the cell banks become nearly equal to the lowest voltage. Therefore, the unbalance among the cell banks 1H, 1M, and 1L can be eliminated perfectly with accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device using a battery pack, and more particularly to a power supply device having a function of safely and efficiently charging a battery pack formed by connecting secondary battery cells in series. .

[0002]

2. Description of the Related Art A battery pack in which a plurality of battery cells are connected in parallel to form a cell bank, and a plurality of the cell banks are connected in series is known. Since the voltage of the total number of cell banks can be taken out by serializing, the output of various capacities and voltages can be produced, and is attracting attention. A non-aqueous secondary battery used as a battery cell in such a battery pack, particularly a 3.6V-rated lithium-ion secondary battery is advantageous in constructing a compact battery pack because of its output voltage. It is suitable as a power supply device for various electronic devices such as personal computers and AV devices.

By the way, when charging such a battery pack, a charger is connected to the output terminal of the battery pack,
Often, multiple cell banks connected in series are charged simultaneously. For this reason, a lithium-ion secondary battery that requires constant current / constant voltage charging, which is charged at constant current at the beginning and then shifts to constant voltage charging when the battery voltage reaches a specified voltage, requires constant voltage charging. In this case, the voltage imbalance between the cell banks becomes a problem.

That is, if there is a variation in the output voltage of each cell bank, that is, a voltage imbalance between cell banks, in the case of a 3-series pack in which three cell banks are connected in series, one of the cell banks has a specified voltage. Even if it reaches 4.2V, constant current charging is continued until the output voltage of the entire battery pack reaches the specified voltage of 12.6V, so that at least one cell bank is overcharged. .

In order to solve the problem of overcharge due to the voltage imbalance between cell banks, a bypass circuit is provided for each cell bank, and the output voltage of each cell bank is compared at the time of charging. Has proposed a method in which a current is released to a bypass circuit in order to suppress charging (Japanese Patent Laid-Open No. 5-64377). But,
In this method, in order to bypass the charging current, the bypass circuit needs to turn on / off the charging current at the time of constant current charging at the maximum, which causes a problem of heat generation of circuit elements such as switches and resistors forming the bypass circuit. Become.

On the other hand, a method has also been proposed in which only the cell bank in which the protection circuit is cut off by overcharge is discharged to the charge release voltage (JP-A-5-49181). However, this method does not solve the problem of voltage imbalance between the cell banks because the output voltage of the cell bank where the overcharge interruption of the protection circuit does not work remains unchanged.

[0007]

As described above, when charging a battery pack configured by connecting a plurality of cell banks in series, in order to avoid the influence of the voltage imbalance between the cell banks, each of the cell banks is charged at the time of charging. In the method of comparing output voltages and for a cell bank whose output voltage is too high, the bypass circuit provided for each cell bank causes the current to escape, which causes a large amount of heat generation in the circuit elements such as switches and resistors forming the bypass circuit. In addition, there is a problem that the voltage imbalance between the cell banks cannot be eliminated by the method of discharging only the cell bank in which the protection circuit is overcharged and cut off to the charge release voltage.

It is an object of the present invention to provide a power supply device using a battery pack which can eliminate the voltage imbalance between cell banks with high accuracy without increasing the heat generation of circuit elements.

[0009]

In order to solve the above problems, the present invention forms a cell bank by a single battery cell or a plurality of battery cells connected in parallel, and connects a plurality of these cell banks in series. In a power supply device using a configured battery pack, voltage comparison means for comparing the output voltage of each cell bank and controlled based on the comparison result of this voltage comparison means, all cell banks other than the cell bank of the minimum output voltage are controlled. It is characterized by comprising an individual discharge means for individually discharging until the output voltage becomes substantially the same as the minimum output voltage.

Further, the present invention provides a power supply device using a battery pack, which is constructed by forming a cell bank by a single battery cell or a plurality of battery cells connected in parallel, and connecting a plurality of these cell banks in series. , The voltage comparison means for comparing the output voltage of each cell bank, and the output voltage of the cell bank of the maximum output voltage is controlled to be substantially the same as the output voltage of the cell bank of the minimum output voltage, which is controlled based on the comparison result of the voltage comparison means. And an individual discharge means for individually discharging the

As described above, in the present invention, for example, after the constant voltage charging is completed for all the cell banks of the battery pack,
Immediately compare the voltage between each cell bank and operate the individual discharge means provided corresponding to all other cell banks or the cell bank with the maximum output voltage until they become almost equal to the output voltage of the cell bank with the minimum output voltage. Since individual discharge is performed and charging is completed, it becomes possible to eliminate the voltage imbalance between the cell banks with high accuracy, and thus the voltage between the cell banks can always be kept substantially equal.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a power supply device using a battery pack according to an embodiment of the present invention, showing a battery pack and a charger in which lithium ion secondary batteries are configured in three parallels and three series (3P3S). There is.

Referring to FIG. 1, a battery pack 10 has three parallel banks, each of which has three battery cells 1H, 1M, and 1L connected in series.
It is a battery pack of three series configuration, in which an inter-cell bank voltage comparison circuit 2 and individual discharge circuits 3-1, 3-2, 3-3 and a microcomputer 4 installed for each cell bank 1H, 1M, 1L are provided. It is composed by combining.

The inter-cell bank voltage comparison circuit 2 is a circuit for comparing the output voltages of the cell banks 1H, 1M, 1L to specify the cell bank having the minimum output voltage, and the individual discharge circuits 3-1, 3-2, 3. -3 is each cell bank 1H, 1
This is a circuit for individually discharging M and 1L. The microcomputer 4 controls the inter-cell bank voltage comparison circuit 2 and the individual discharge circuits 3-1, 3-2, 3-3 based on the comparison result of the inter-cell bank comparison circuit 2.

On the other hand, the charger 20 comprises a charging control circuit 5 and a charging DC power source 6, and cell banks 1H, 1M and 1L.
The battery pack is composed of a constant current / constant voltage charging system, for example.

Next, the operation of this embodiment will be described with reference to the flow chart shown in FIG. After the battery pack consisting of the cell banks 1H, 1M, 1L is charged with a constant current / constant voltage by the charger 20 to a specified voltage of 12.6V, first, based on a command from the microcomputer 4,
Each cell bank 1 by the inter-cell bank voltage comparison circuit 2
The output voltages VH, VM, and VL of H, 1M, and 1L are compared to specify the cell bank having the minimum output voltage (steps S11 to S13).

That is, in step S11, VH and VM,
The magnitude relationship between VH and VL is checked in step S12, and the magnitude relationship between VM and VL is checked in step S13. Here, if VH ≤ VM in step S11, the process proceeds to step S12, and if VH ≤ VL in S12, the minimum output voltage is VH.
Becomes If VH> VM in step S11,
In step S13, if VM> VL in S13,
The minimum output voltage is VL, and if VM≤VL in S13, the minimum output voltage is VM.

The comparison result of the inter-cell bank voltage comparison circuit 2 is sent to the microcomputer 4. The microcomputer 4 operates the individual discharge circuits connected to all cell banks other than the cell bank specified as the minimum output voltage by the cell bank voltage comparison circuit 2 to discharge that cell bank (steps S21 to S23).

That is, when the minimum output voltage is VH, that is, when the cell bank having the minimum output voltage is H bank 1H, the individual discharge circuits 3-2 and 3-3 connected to M bank 1M and L bank 1L are operated. Allow (Step S2
1). When the minimum output voltage is VL, that is, when the minimum output voltage cell bank is the L bank 1L, the individual discharge circuits 3-1 and 3 connected to the H bank 1H and the M bank 1M.
-2 is operated (step S22). When the minimum output voltage is VM, that is, when the minimum output voltage cell bank is M bank 1M, the individual discharge circuits 3-1 and 3-3 connected to the H bank 1H and the L bank 1L are operated (step S23). .

Then, while discharging the cell banks in steps S21 to S23, the cell bank voltage comparison circuit 2 always compares the cell bank voltage with the above-mentioned minimum output voltage, and when that is reached, the information is sent to the microcomputer 4, Upon receiving the information, the microcomputer 4 turns off the operated individual discharge circuit. This operation is steps S31 to S34, S41 to S44, and S51 to S54.

That is, in step S21, M bank 1M
And individual discharge circuits 3-2 connected to the L bank 1L
While operating 3-3, the cell bank inter-cell voltage comparison circuit 2 checks the magnitude relationship between VL and VH and VM and VH in steps S31 and S33, and VL≤V in step S31.
If it is H, the individual discharge circuit connected to the L bank 1L 3-
3 is turned off (step S32), and V is set in step S33.
If M ≦ VH, the individual discharge circuit 3-2 connected to the M bank 1M is turned off (step S34).

Further, the individual discharge circuits 3-1 and 3-connected to the H bank 1H and the M bank 1M in step S22.
While operating step 2, VM in steps S41 and S43
And VL and VH and VL are compared by the cell bank voltage comparison circuit 2, and if VM ≤VL in step S41, the individual discharge circuit 3-2 connected to M bank 1M is turned off (step S42), and step VH ≤ S43
If it is VL, the individual discharge circuit 3 connected to the H bank 1H
-1 is turned off (step S44).

Furthermore, the individual discharge circuits 3-1 and 3 connected to the H bank 1H and the L bank 1L in step S23.
-3 while operating, V in steps S51 and S53
The relationship between L and VM and VH and VM is checked by the cell bank voltage comparison circuit 2, and in step S51 VL ≤ VM
If so, the individual discharge circuit 3-3 connected to the L bank 1L
Is turned off (step S52), and VH is set in step S53.
If ≤VM, the individual discharge circuit 3-1 connected to the H bank 1H is turned off (step S54).

When all the individual discharge circuits are turned off in this way, the cell bank voltage imbalance correction ends (steps S61 to S63). By the control as described above, even if the cell bank 1H, 1M, 1L is unbalanced between the cell banks, all the cell banks 1H, 1M,
A 1 L output voltage can be reliably and safely kept approximately equal. In this case, unlike the method using the conventional bypass circuit, it is not necessary to pass the charging current through the bus.
Even if the charging current during constant current charging is large, the circuit element does not generate heat.

FIG. 3 is a configuration diagram of a power supply device using a battery pack according to another embodiment of the present invention, showing a battery pack having a configuration including a protection circuit for inhibiting overcharge / overdischarge.
FIG.

In this embodiment, the cell banks 1H, 1M,
1L has a configuration in which a protection circuit IC71 for prohibiting overcharge / overdischarge and a protection circuit 7 including two FET switches 72 and 73 connected in series to a series circuit of cell banks 1H, 1M and 1L are added. That is, the protection circuit 7 turns off the FET switch 73 by detecting the overcharge at the time of charging by the overcharge / overdischarge prohibition protection circuit IC71 to prevent the overcharge, and turns off the FET switch 72 by detecting the overdischarge at the time of discharging. It is configured to prevent discharge. The diodes connected in parallel to the FET switches 72 and 73 are parasitic diodes of the FETs, and their polarities are matched to the discharging direction and the charging direction, respectively.

In this embodiment, the cell voltage unbalance correction circuit is specifically shown. That is, the inter-cell bank voltage comparison circuit 2 includes the analog switch group 21 and the differential amplifier 22, and includes three cell banks 1H, 1M, 1
Of L, the analog switch group 21 is controlled by a command from the microcomputer 4 so that two cell bank voltages specified by the command from the microcomputer 4 can be sequentially selected and compared. .

The individual discharge circuits 3-1, 3-2 and 3-3 are
An analog switch 31 which is on / off controlled by a command from the microcomputer 4 and a discharging resistor 32 are connected in series, and the magnitude of the discharging current is determined in consideration of safety and individual discharging time. Is determined by the value of. In the case of a lithium-ion secondary battery, the specified output voltage per cell bank is around 4.2 V, so considering the discharge current to be about 10 to 100 mA for safety, the value of the discharge resistor 32 is 40 to It becomes 400Ω. Specifically, the value of the discharge resistor 32 may be comprehensively selected from both aspects of safety and setting of the discharge time.

In the above embodiment, the number of battery packs is three.
The case of the parallel / three series (3P3S) cell configuration has been described, but the number of parallel batteries may be other than 3P including a single cell, and the number of series may be other than 3S. Further, although the secondary battery is discharged via the resistor 32 in the embodiment of FIG. 3, it may be discharged via a constant current circuit.

Further, the timing for instructing the comparison between cell bank voltages from the microcomputer 4 to the cell bank voltage comparison circuit 2 is not limited to the constant current / constant voltage control charging end as in the embodiment, and the constant current is not limited. It may be performed during charging or when switching from constant current charging to constant voltage charging, or an open time for monitoring open circuit voltage may be provided and voltage comparison may be performed each time. It may be time. In short, it is only necessary to compare the voltages between the cell banks and always perform the individual discharge so that the other cell bank voltages are always matched with the minimum cell bank voltage.

In the above embodiment, the individual discharge circuit 3-based on the comparison result of the cell bank voltage comparison circuit 2.
The cell bank voltage imbalance is corrected by individually discharging all the cell banks other than the cell bank having the minimum output voltage by 1, 3-2 and 3-3 until the output voltage becomes substantially the same as the minimum output voltage. However, as a simple method of correcting the voltage imbalance between cell banks, only the cell bank having the maximum output voltage may be individually discharged to the output voltage of the cell bank having the minimum output voltage.

[0032]

As described above in detail, according to the present invention, an individual discharge circuit is provided for each cell bank connected in series, and the output voltage between each cell bank is compared to determine the cell bank having the minimum output voltage. By specifying and operating the individual discharge circuits corresponding to all other cell banks or the cell banks with the maximum output voltage until the output voltages of the cell banks with the minimum output voltage are almost equal, the discharge is completed for each cell bank and charging is completed. Therefore, the voltage imbalance between the cell banks can be completely eliminated with accuracy, and the voltage between the cell banks can be always kept substantially equal.

Therefore, it is possible to provide a power supply device using a battery pack that can be safely and stably used for a long period of time without overcharging a specific cell bank even if charging and discharging are repeated many times.

Further, according to the present invention, unlike the conventional method in which a bypass circuit is used to cope with the voltage imbalance between cell banks, it is not necessary to wastefully bypass the current at the time of charging, so that there is an advantage that the heat generation of the circuit element is small. is there.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a battery pack and a charger that are a power supply device according to an embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the embodiment;

FIG. 3 is a block diagram showing a configuration of a battery pack in a power supply device according to another embodiment of the present invention.

[Explanation of symbols]

 1H, 1M, 1L ... Cell bank 2 ... Cell bank voltage comparison circuit 3-1, 3-2, 3-3 ... Individual discharge circuit 4 ... Microcomputer 5 ... Charging control circuit 6 ... Charging DC power supply 7 ... Protection circuit 10 ... Battery pack 20 ... Charger 21 ... Analog switch group 22 ... Differential amplifier 31 ... Analog switch 32 ... Discharge resistor 71 ... Protection circuit IC 72, 73 ... FET switch

Claims (2)

[Claims] 1. A power supply device using a battery pack comprising a single battery cell or a plurality of battery cells connected in parallel to form a cell bank, and a plurality of the cell banks connected in series. And a voltage comparison means for comparing the output voltage of each of the cells, and is controlled based on the comparison result of the voltage comparison means, and individually discharges all cell banks other than the cell bank of the minimum output voltage until the output voltage becomes substantially the same as the minimum output voltage. A power supply device using a battery pack, comprising: an individual discharge means. 2. A power supply device using a battery pack comprising a single battery cell or a plurality of battery cells connected in parallel to form a cell bank, and a plurality of the cell banks connected in series. Of the voltage comparison means for comparing the output voltage of the cell bank and the individual discharge for controlling the cell bank of the maximum output voltage until the output voltage of the cell bank of the minimum output voltage becomes almost the same as the output voltage of the cell bank of the minimum output voltage. And a power supply device using a battery pack.