KR101578707B1 - A battery pack and method for controlling the same - Google Patents

Abstract

It is possible to prevent the battery cells from being automatically charged through the remaining parallel-connected battery cells when the specific battery cell is at a low voltage by blocking the current flow between the cells connected in parallel during the voltage measurement, A battery pack and its control method capable of accurately determining whether or not an abnormality is present and taking protective measures accordingly can be provided. The battery pack according to the present invention includes a plurality of battery cells connected in series and in parallel and a protection circuit thereof, each of which includes a current limiting element connected between parallel connected battery cells, and a switch connected in parallel with the current limiting element . The protection circuit measures battery cell voltages for at least two or more serially connected battery cells.

Description

[0001] The present invention relates to a battery pack and a control method thereof,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery pack and a control method thereof, and more particularly, to a battery pack and a control method thereof for preventing unbalance or undervoltage between cells of a battery pack.

2. Description of the Related Art Generally, rechargeable batteries capable of charging and discharging have been actively studied due to development of portable electronic devices such as cellular phones, notebook computers, camcorders, and personal digital assistants (PDAs). Particularly, such a secondary battery may be a nickel-cadmium battery, a lead acid battery, a nickel metal hydride battery (NiMH), a lithium ion battery, a lithium polymer battery ), Metal lithium batteries, and air zinc storage batteries. The secondary battery is combined with the circuit to form a battery pack, and charging and discharging are performed through the external terminal of the battery pack.

The conventional battery pack largely comprises a battery cell and a peripheral circuit including a charge / discharge circuit, which is fabricated as a printed circuit board, and then coupled to the battery cell. When the external power is connected through the external terminal of the battery pack, the battery cell is charged by the external terminal and the external power supplied through the charge / discharge circuit. When the load is connected through the external terminal, An operation to be supplied to the load occurs through the charge / discharge circuit and the external terminal. At this time, the charge / discharge circuit controls charge / discharge of the battery cell between the external terminal and the battery cell. Generally, a battery cell uses a plurality of battery cells connected in series and in parallel so as to match a consumption capacity of a load.

An embodiment of the present invention is to provide a battery pack capable of determining the presence or absence of a specific battery cell.

In another embodiment of the present invention, in a plurality of battery cells connected in series and in parallel, current flow between cells connected in parallel during voltage measurement is cut off, thereby preventing automatic charging through the remaining parallel-connected battery cells when the specific battery cell is at a low voltage The present invention also provides a battery pack and a method of controlling the battery pack, which can accurately detect the presence or absence of an abnormality of a specific battery cell by detecting voltages of battery cells connected in series and take protective measures accordingly.

According to an aspect of the present invention, there is provided a battery pack including a plurality of battery cells and a protection circuit therefor, wherein the plurality of battery cells are connected in series and in parallel, And a switch connected in parallel with the current limiting element. The protection circuit measures the battery cell voltage for at least two or more serially connected battery cells.

The current limiting element is at least two or more and is connected to at least two or more parallel-connected battery cells.

And the switch is turned on when charging or discharging the plurality of battery cells.

And the switch is turned off when voltage measurement is applied to the at least two or more series-connected battery cells.

Wherein the protection circuit compares the measured voltage with a reference voltage and controls a charging switch or a discharging switch for controlling charging or discharging of the plurality of battery cells when the difference between the measured voltage and the reference voltage is equal to or greater than a first threshold value And turning off the fuse or blowing the fuse disposed in the large current path of the plurality of battery cells.

The switch is an FET (Field Effect Transistor).

And the current limiting element is a PTC element.

And the current limiting element is a resistor.

According to another aspect of the present invention, there is provided a battery pack including a plurality of battery cells and a protection circuit therefor, wherein the plurality of battery cells include at least two or more battery cells connected in series and in parallel At least two current limiting elements connected between the positive terminals of at least two or more battery cells connected and connected in at least two or more in parallel; And a switch connected in parallel with the current limiting element connected to the large current end side of the plurality of battery cells among the at least two current limiting elements.

The protection circuit measures the battery cell voltage for each of at least two or more battery cells connected in series with each other.

The switch is turned on when charging or discharging the plurality of battery cells, and is turned off when measuring the battery cell voltage for each of at least two or more battery cells connected in series.

Wherein the protection circuit compares the measured battery cell voltage with a reference voltage and controls charging or discharging of the plurality of battery cells when the difference between the measured battery cell voltage and the reference voltage is equal to or greater than a first threshold value, Or the discharge switch is turned off, or fuses arranged in the large current path of the plurality of battery cells are blown.

According to another aspect of the present invention, there is provided a method of controlling a battery pack including a plurality of battery cells and a protection circuit therefor, the method comprising: Limiting current flow between the at least two battery cells connected in parallel; Measuring a battery cell voltage for each of at least two or more battery cells connected in series with each other; And comparing the measured battery cell voltage with a reference voltage to determine an abnormality of the plurality of battery cells.

The control method further includes turning off a charging switch or a discharging switch for controlling charging or discharging of the plurality of battery cells when the difference between the measured battery cell voltage and the reference voltage is equal to or greater than a first threshold value .

The control method may further include fusing a fuse disposed in a large current path of the plurality of battery cells when the difference between the measured battery cell voltage and the reference voltage is equal to or greater than a first threshold value.

The limiting step may further include canceling a limited current flow at the large current end side of the plurality of battery cells when charging or discharging the plurality of battery cells.

The battery pack according to an embodiment of the present invention can accurately determine whether there is an abnormality in a specific battery cell.

In addition, in a plurality of battery cells connected in series and in parallel, current flow between cells connected in parallel during voltage measurement is cut off, thereby preventing automatic charging through the remaining parallel-connected battery cells when the specific battery cell is at a low voltage, It is possible to accurately determine the presence or absence of an abnormality in a specific battery cell by detecting each of the voltages of the cells, and to take measures to protect the battery cell, thereby enhancing the stability of the battery pack.

1 is a circuit diagram of a battery pack 100 according to an embodiment of the present invention.
FIG. 2 is a view for explaining the connection relationship of the plurality of battery cells 100 shown in FIG. 1 and the voltage measurement of the battery cell.
3 is a view for explaining a battery pack according to another embodiment of the present invention.
4 is a view for explaining a battery pack according to another embodiment of the present invention.
5 is a flowchart illustrating a method of controlling a battery pack according to another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, only parts necessary for understanding the operation according to the embodiment of the present invention will be described, and descriptions of other parts may be omitted so as not to disturb the gist of the present invention.

In addition, terms and words used in the following description and claims should not be construed to be limited to ordinary or dictionary meanings, but are to be construed in a manner consistent with the technical idea of the present invention As well as the concept.

1 is a circuit diagram of a battery pack 100 according to an embodiment of the present invention.

Referring to FIG. 1, a battery pack 100 according to an embodiment of the present invention includes a rechargeable battery cell 130 and a protection circuit. The battery pack 100 is mounted on an external system such as a portable notebook computer, And discharge by the battery cell 130 are performed.

The battery pack 100 includes a battery cell 130, an external terminal (not shown) connected in parallel to the battery cell 130, and a high current path A fuse 160 connected in series with a high current path (HCP) between the discharging device 150 and the external terminal, a charging device 140 and a discharging device 150 connected in series to the battery cell 130 An analog front end (AFE) IC 120 connected in parallel with the charging device 140 and the discharging device 150, one end of the AFE IC 120 and the other end of the fuse 160 And a microcomputer 110 connected to the microcomputer 110. The microcomputer 110 may further include a self-protection control device (not shown) for fusing the fuse 160 under the control of the external system.

The microcomputer 110 turns off the charging device 140 and the discharging device 150 or fuses the fuse 160 as described above when the battery cell 130 is determined to be in an overcharged or overdischarged state, Thereby preventing the cell 130 from being overcharged or overdischarged. That is, when the microcomputer 110 determines that the battery cell 130 is in the overcharge or overdischarge state, the microcomputer 110 outputs a control signal corresponding to the overcurrent state and the overdischarge state to supply the fuse 160 through the control switch (not shown) .

The battery pack 100 constructed as described above is connected to an external system through an external terminal to perform charging or discharging. The large current path (HCP) between the external terminal and the battery cell 130 is used as a charge / discharge path, and a large current flows through the large current path (HCP). The battery pack 100 further includes an SMBUS (System Management Bus) between the microcomputer 110 and the external terminal of the protection circuit for communication with the external system.

Here, the external system connected through the external terminal may include a portable electronic device, for example, a portable notebook computer, and an adapter for separately supplying power. When the external system is connected to the adapter, the external system can be operated by the adapter, and the power of the adapter is supplied to the battery cell 130 through the high current path (HCP) through the external terminal, Can be charged. When the external system is disconnected from the adapter, the discharge from the battery cell 130 to the load of the external system can be performed through the external terminal. That is, when an external system to which an adapter is connected is connected to the external terminal, a charging operation is performed. At this time, the charging path leads from the adapter to the battery cell 130 via the external terminal, the discharging device 150, the charging device 140 . When the adapter is disconnected from the external system and the load of the external system is connected to the external terminal, a discharging operation is performed. The discharging path starts from the battery cell 130 to the charging device 140, the discharging device 150, To the load of the external system.

Here, the battery cell 130 is a secondary battery cell that can be charged and discharged. In the figure, B + and B- denote the large current terminals and both ends of the series connected battery cells. The battery cell 130 outputs cell-related information such as the temperature of the cell, the charging voltage of the cell, and the amount of current flowing in the cell to the AFE IC 120.

The charging device 140 and the discharging device 150 are connected in series on the high current path (HCP) between the external terminal and the battery cell 130 to perform charging or discharging of the battery pack. Each of the charging device 140 and the discharging device 150 is composed of a field effect transistor (FET).

The AFE IC 120 is connected in parallel between the battery cell 130 and the charging device 140 and the discharging device 150 and is connected in series between the battery cell 130 and the microcomputer 110. The AFE IC 120 detects the voltage of the battery cell 130 and transmits the detected voltage to the microcomputer 110 and controls the charging device 140 and the discharging device 150 under the control of the microcomputer 110. [ .

The microcomputer 110 is an integrated circuit that is connected in series between the AFE IC 120 and an external system and controls the charging device 140 and the discharging device 150 via the AFE IC 120, And overcharge, overdischarge, and overcurrent of the cell 130. That is, the voltage of the battery cell 130 received from the battery cell 130 via the AFE IC 120 is compared with the voltage level value set therein, and the control signal according to the comparison result is output to the AFE IC 120 The charging device 140 and the discharging device 150 are turned on or off to thereby prevent the battery cell 130 from being overcharged or overdischarged.

For example, when the voltage of the battery cell 130 received by the microcomputer 110 is the overcharge level voltage value set in the internal circuit, for example, 4.35 V or more, the microcomputer 110 determines that the battery cell 130 is overcharged, And outputs a control signal to the AFE IC 120 to turn off the field effect transistor FET1 of the charging device 140. [ Then, the charging of the external system 200 from the adapter 221 to the battery cell 130 is interrupted. On the contrary, if the voltage of the battery cell 130 received by the microcomputer 110 is the over-discharge level voltage value, for example, 2.30 V or less set in the microcomputer 110, the microcomputer 110 determines that the over- And outputs a control signal to the AFE IC 120 to turn off the field effect transistor FET2 of the discharging element 150. [ Then, the discharge from the battery cell 130 to the load of the external system is cut off. The AFE IC 120 controls the switching of the charging device 140 or the discharging device 150 under the control of the microcomputer 110. The microcomputer 110 may directly control the switching of the charging device 140 or the discharging device 150, The switching operation of the discharging element 150 may be controlled.

FIG. 2 is a view for explaining the connection relationship of the plurality of battery cells 100 shown in FIG. 1 and the voltage measurement of the battery cell.

1 and 2, a plurality of battery cells 231 to 236 are connected in series and in parallel, and the battery cells 231 and the battery cells 234, the battery cells 232 and the battery cells 235, And the AFE IC 120 measures the voltages of the battery cells 233 and the battery cells 236 or the battery cells 236 connected in parallel to each other and measures the measured battery cell voltages V1, V2, and V3 to the microcomputer 110 . Here, the measured voltage is the voltage of the battery cells connected in parallel. The microcomputer 110 compares the measured voltage with the reference voltage to determine overcharge or overdischarge. The protection measures of the battery pack 100, for example, turning off the charging device 140 or the discharging device 150, and blowing the fuse are taken according to the set reference level. However, when the voltage of the parallel-connected battery cell is measured, since the voltage of each of the parallel-connected battery cells V1, V2 and V3 is sensed and protected, even when a specific battery cell, for example, , The battery cell 232 is automatically charged from the battery cell 235 connected in parallel thereto. Therefore, there is a problem in that it is difficult to recognize that the battery cell 232 is in a low-voltage state and cope with it. In particular, although two parallel connections are described here, it is more difficult to determine which one of the four battery cells is defective or under-voltage in order to increase the battery capacity.

3 is a view for explaining a battery pack according to another embodiment of the present invention.

3, a plurality of battery cells 331 to 336 are connected in series and in parallel, and between the anodes of the parallel-connected battery cells 331 and 334, 332 and 335, 333 and 336, 337 to 339 are connected. That is, by preventing current flow between the cells connected in parallel through such a configuration, it is prevented that the specific battery cell is automatically charged through the remaining parallel-connected battery cells when the voltage is low.

1 and 3 together, a plurality of battery cells 331 to 336 are connected in series and in parallel, and the battery cells 331 and the battery cells 334, the battery cells 332 and the battery cells 335, And current limiting elements 337 to 339 are connected between the battery cell 333 and the battery cell 336, respectively. The AFE IC 120 measures the voltage V3a of the series connected battery cells 331, 332 and 333 and the voltage V3b of the battery cells 334, 335 and 336 connected in series and measures the battery cell voltages V3a and V3b, (110). Here, the measured voltage is the voltage of the battery cell connected in series. The microcomputer 110 compares the measured voltage with the reference voltage to determine overcharge or overdischarge. The protection measures of the battery pack 100, for example, the charging device 140 or the discharging device 150 are turned off or the fuse is blown in accordance with the set reference level. Therefore, when the specific battery cell 332 is unbalanced or under-voltage, the battery cell voltage V3a connected in series is measured and compared with the reference voltage to determine whether or not an abnormality exists. For example, if the voltage of the battery cells 331 to 336 is in the normal range of 3V, if the battery cell 332 is 2.8V and the battery cell 335 is 3.2V, the battery cell 332 Is in an overdischarge state, and the battery cell 335 can be determined to be in an overcharged state. In this case, if the voltage of the battery cells connected in parallel is measured as shown in FIG. 2, it is judged that the entire battery cell voltage is in the normal range of 9V. However, since the series-connected battery cell voltages V3a and V3b are measured in the manner shown in FIG. 3, it is determined that V3a is 8.8 V, V3b is 9.2 V, and the voltage falls outside the normal range of 9.0 V . That is, if the measured value of the series-connected battery is 8.8 V or 9.2 V, the reference voltage value is 9 V, and the threshold value for determining the difference is 0.2 V, the difference between the measured voltage value and the reference voltage value is ± 0.2 V It is judged that it is out of the normal range because it is equal to or higher than the threshold value, so that it is possible to take measures such as protection operation, charging / discharging prohibition, fuse blowing or the like.

The current limiting elements 337 to 339 shown in FIG. 3 may be a resistor, and in particular, may be a PTC (Positive Temperature Coefficient) element. A PTC device is a device with a constant coefficient of characteristic which rapidly increases its resistance value against temperature rise when a certain temperature is reached. It is one of N-type semiconductors in which BaTiO ₃ is the main component and dopant is added to make it conductive. In one embodiment of the present invention, a resistor or a PTC device is described as an example, but the present invention is not limited thereto, and an element that can restrict the current flow between parallel-connected battery cells is included in the scope of the present invention.

4 is a view for explaining a battery pack according to another embodiment of the present invention.

4, a plurality of battery cells 431 to 436 are connected in series and in parallel, and between the anodes of the parallel-connected battery cells 431 and 434, 432 and 435, 433 and 436, 437 to 439 are connected. Also shown is a switch 440 connected in parallel with the current limiting element 437. [ That is, by preventing current flow between the cells connected in parallel through such a configuration, it is possible to prevent the battery cells 430 from being automatically charged through the remaining parallel-connected battery cells when the specific battery cell is at a low voltage, and at the time of charging or discharging the battery cell 430 The switch 440 is turned on so that the current limiting element is short-circuited to release the flow of the cut-off current so as not to restrict the charging current to the battery cell 430 or the flow of the discharging current from the battery cell 430. To this end, the current limitation through the current limiting element 437 disposed on the side where the large current flows out, that is, the large current end side is released. That is, at the time of detecting the voltage of the battery cell 430, the switch maintains the turn-off state and turns on only at the time of charging or discharging to release the current limitation.

Such a switch 440 may be added to be connected in parallel with the remaining current limiting elements 438 and 439 according to the setting. Also, the switch 440 may use a FET and may be turned on or off by a control signal, which is transmitted from the AFE IC 120 or the microcomputer 110 shown in FIG. 1 .

5 is a flowchart illustrating a method of controlling a battery pack according to another embodiment of the present invention.

Referring to FIG. 5, in steps 500 and 502, for multiple battery cells connected in series and in parallel, current flow between two or more battery cells connected in parallel is limited. By disposing a current limiting element, for example, a PTC element, between two or more battery cells connected in parallel, current flow between the battery cells connected in parallel is limited due to the increased resistance component due to the temperature rise of the battery cell.

In step 504, it is determined whether the battery cell is charged or discharged. If the battery cell is in the charging or discharging state, the flow advances to step 514 to release the limited current flow on the large current side to determine the charging current to the battery cell or the discharging current Is not limited.

If it is determined in step 504 that the battery is not in the charging or discharging state, it is determined in step 506 whether it is the battery cell voltage measuring step. Battery cell voltage measurement can be performed periodically or non-periodically by monitoring on the protection circuit side. In step 508, the voltage of two or more series-connected battery cells is measured. In step 502, since the current flow between two or more parallel-connected battery cells is interrupted, the problem of automatic charging among the parallel-connected battery cells does not occur. Thus, it can be determined that the specific battery cell is in an unbalanced state or a low-voltage state through measurement of the series-connected battery cell voltage. If the measured battery cell voltage, that is, the difference between the measured battery cell voltage and the reference voltage is equal to or greater than the first threshold value in step 510, The stability of the battery pack can be ensured by turning off the charging or discharging switch or blowing the fuse arranged on the large current path. Here, the first threshold value is a value that can be arbitrarily determined, and can be determined differently according to the stability design specification of the battery pack. For example, when measuring the voltage of two or more series-connected and parallel-connected battery cells, even if one of the series battery cell voltages is measured at 8.8 V or 9.2 V, it is compared with a reference voltage value, For example, 0.2 V or more, it is determined that the voltage falls outside the normal range, and protection actions, charging / discharging inhibition, fuse blowing, and the like can be taken.

Meanwhile, the present invention can be embodied in computer readable code on a computer readable recording medium. A computer-readable recording medium includes all kinds of recording apparatuses in which data that can be read by a computer system is stored.

Examples of the computer-readable recording medium include ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage, and the like. In addition, the computer-readable recording medium may be distributed over network-connected computer systems so that computer readable codes can be stored and executed in a distributed manner. In addition, functional programs, codes, and code segments for implementing the present invention can be easily deduced by programmers skilled in the art to which the present invention belongs.

The present invention has been described above with reference to preferred embodiments. It will be understood by those skilled in the art that the present invention may be embodied in various other forms without departing from the spirit or essential characteristics thereof. Therefore, the above-described embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is indicated by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

100: Battery pack
110: microcomputer
120: AFE IC
130, 230, 330,
140: charging element
150: discharge element
337, 338, 339:
440: Switch

Claims (8)

A plurality of battery cells connected in series and in parallel;
Current limiting elements connected between battery cells connected in parallel among the plurality of battery cells;
At least one switch connected in parallel with at least one current limiting element of the current limiting elements to short-circuit the at least one current limiting element upon turn-on; And
And a protection circuit for measuring battery cell voltages for at least two or more serially connected battery cells among the plurality of battery cells. The method according to claim 1,
Wherein the at least one switch includes a plurality of switches connected in parallel with the current limiting elements. The method according to claim 1,
Wherein the at least one switch is turned on when charging or discharging the plurality of battery cells. The method according to claim 1,
Wherein the at least one switch is turned off when the protection circuit measures the battery cell voltages for the at least two or more serially connected battery cells. The method according to claim 1,
Wherein the protection circuit includes a charging switch and a discharging switch for controlling charging and discharging of the plurality of battery cells, respectively, and a fuse,
Wherein the charging switch, the discharging switch, and the fuse are disposed on a large current path of the plurality of battery cells,
Wherein the protection circuit compares the measured battery cell voltages with a reference voltage and turns off the charging switch or the discharging switch when the difference between the measured battery cell voltages and the reference voltage is equal to or greater than a first threshold value Or fuses the fuse. The method according to claim 1,
Wherein the at least one switch is a field effect transistor (FET). The method according to claim 1,
Wherein the current limiting element is a PTC (Positive Temperature Coefficient) element. The method according to claim 1,
And the battery cells connected in parallel are all the same type.

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