Cell balancing method and battery pack using the same

Abstract

The present invention relates to a cell balancing method and a battery pack to which the same is applied, and more particularly to a cell balancing method and a battery pack to which the same is applied, which can improve cell balancing efficiency by variably controlling a duty of a cell balancing switching pulse width modulation (PWM) according to a cell balancing current and a temperature and an operation mode of a battery management system (BMS).

Description

[Technical field]

[0001] The present invention relates to a cell balancing method and a battery pack to which the same is applied, and more particularly, to a cell balancing method that can increase cell balancing efficiency by controlling a cell balancing switching PWM (pulse width modulation) duty and a battery pack to which the same is applied. [Background technology]

[0002] Battery packs used in devices requiring rechargeable electrical storage, such as portable electronic devices, electric vehicles, energy storage devices, etc., contain multiple battery cells connected in series or parallel.

[0003] Each battery cell included in a battery pack has a capacity difference due to various reasons in the manufacturing process. As a result, a voltage difference occurs between the battery cells during the charge / discharge cycle of the battery pack, and the more the number of charge / discharge cycles increases, the more the voltage difference between the battery cells accumulates and increases. The more this phenomenon occurs repeatedly, the shorter the lifespan of the battery pack becomes. To solve this problem, cell balancing technology is applied to adjust the voltage difference between the battery cells that occurs during charge / discharge in the battery pack.

[0004] Cell balancing techniques are broadly divided into active cell balancing and passive cell balancing. Passive cell balancing is generally used because of its simple circuit configuration and low cost. Passive cell balancing is a method in which, when the voltage of a specific battery cell or module is higher than the reference voltage (the voltage of the smallest battery cell or module), it is forcibly discharged through a cell balancing resistor to lower it to the reference voltage level. More specifically, it uses a field effect transistor (FET) to discharge the connection circuit between the discharge resistor and the battery cell through PWM switching control. Here, in the case of PWM switching, the PWM duty is controlled to a predetermined value taking into account input values ​​such as temperature and cell voltage / current of the Battery Management System (BMS). In such a case, if the voltage difference between the battery cells or modules is large, the time required to complete cell balancing may be prolonged. For example, when it is necessary to stabilize the voltage difference between the battery cells or modules within a short period of time, it may be difficult to respond quickly, and balancing efficiency may be poor.

[0005] The following documents are cited as examples of conventional techniques: [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Republic of Korea Patent No. 1459539 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been devised to solve the above problems, and aims to provide a cell balancing method and a battery pack using the same, which can variably control a cell balancing switching PWM duty according to a cell balancing current, a temperature of a BMS, and an operation mode to improve cell balancing efficiency. [Means for solving the problem]

[0008] According to an embodiment of the present invention, a method for cell balancing among at least two or more battery banks included in a battery pack includes: a battery information acquisition step for acquiring battery information including a current, a voltage, and a temperature of a battery at a certain period; a cell balancing necessity determination step for determining whether cell balancing is necessary using the battery information acquired in the battery information acquisition step; a cell balancing start step for turning on a cell balancing switch with an initial duty ratio and executing an initial cell balancing mode if it is determined that cell balancing is necessary in the cell balancing necessity determination step; a cell balancing switch duty ratio change necessity determination step for determining whether the duty ratio of the cell balancing switch needs to be changed using the acquired battery information after the start of cell balancing; and a cell balancing switch duty ratio change necessity determination step. the cell balancing switch duty ratio increasing step of increasing the duty ratio of the cell balancing switch by a predetermined range when it is determined that the duty ratio of the cell balancing switch needs to be changed; a cell balancing continuation determination step of determining whether or not cell balancing is continuing using the acquired battery information; a diagnostic count increase determination step of increasing a diagnostic count when it is determined that cell balancing is continuing in the cell balancing continuation determination step and the number of cell balancing cycles exceeds a predetermined reference cell balancing cycle number; and a cell balancing mode change step of changing a cell balancing mode and returning to the cell balancing switch duty ratio change determination step when the number of diagnostic counts counted through the diagnostic count increase determination step is equal to or less than a predetermined reference diagnostic count.

[0009] In addition, the method further includes a cell balancing termination step of controlling a cell balancing switch to be off when it is determined in the cell balancing continuation determination step that the cell balancing is not continuing, and a diagnosis termination step of reporting the diagnosis result and terminating the procedure when the number of diagnosis counts counted through the diagnosis count increase determination step exceeds a predetermined reference diagnosis count.

[0010] Meanwhile, the cell balancing necessity determining step is characterized in that it determines that cell balancing is necessary when a bank voltage difference, which is the difference between the maximum voltage and the minimum voltage among the voltage values ​​of the battery bank included in the acquired battery information, exceeds a predetermined reference voltage difference value and the state of charge (SOC) is within a predetermined reference range.

[0011] Meanwhile, the step of determining whether or not the duty ratio of the cell balancing switch needs to be changed includes a step of determining that the duty ratio of the cell balancing switch needs to be changed if the temperature of the battery management system (BMS) included in the acquired battery information is lower than a predetermined reference temperature and the cell balancing current is lower than a reference current, and a step of determining that the duty ratio of the cell balancing switch does not need to be changed if either the temperature of the battery management system (BMS) or the cell balancing current does not satisfy the condition.

[0012] Meanwhile, the step of determining whether to continue cell balancing includes a step of determining that it is not necessary to continue cell balancing when a bank voltage difference value, which is a difference between a maximum voltage and a minimum voltage among voltage values ​​of the battery bank included in the acquired battery information, is equal to or less than a predetermined reference voltage difference, and a step of determining that it is necessary to continue cell balancing when the bank voltage difference value exceeds a predetermined reference voltage difference value.

[0013] Here, the cell balancing mode is any one of a charge mode, a standby mode, and a discharge mode, and the cell balancing mode changing step changes the cell balancing mode in the order of the charge mode, the standby mode, and the discharge mode.

[0014] a cell balancing necessity determination unit that determines whether or not cell balancing is required using the battery information acquired from the battery information measurement unit after a cell balancing operation is activated based on a determination result of the cell balancing necessity determination unit; a duty ratio change necessity determination unit that determines whether or not a duty ratio of a cell balancing switch needs to be changed using the battery information acquired from the battery information measurement unit after a cell balancing operation is activated based on a determination result of the cell balancing necessity determination unit; a counting unit that counts the number of cell balancing cycles and the number of diagnostic counts; a diagnostic count increase / increase determination unit that determines whether or not the number of diagnostic counts has increased depending on whether cell balancing needs to be continued and whether the number of cell balancing cycles exceeds a predetermined reference number of cell balancing cycles; and a cell balancing mode change / increase determination unit that determines whether or not the cell balancing mode needs to be changed depending on whether the number of diagnostic counts counted by the counting unit is equal to or smaller than a predetermined reference diagnostic count.

[0015] In addition, if the cell balancing necessity determination unit determines that cell balancing is necessary, a cell balancing operation is activated with an initial cell balancing switch duty ratio and an initial cell balancing mode. Next, the battery battery further includes a cell balancing control unit that changes and sets the duty ratio and cell balancing mode of the cell balancing switch depending on whether or not certain conditions associated with a change in the battery state are satisfied, and a cell balancing unit that includes cell balancing resistors connected to the positive electrodes of the battery banks and consuming the voltage of the battery banks, and cell balancing switches that turn on / off the connection paths between the cell balancing resistors and the battery banks.

[0016] Meanwhile, the cell balancing necessity determination unit includes a voltage difference calculation unit that calculates a bank voltage difference, which is the difference between a maximum voltage and a minimum voltage, among the voltage values ​​of the battery bank included in the battery information acquired from the battery information measurement unit; a voltage comparison unit that compares whether the bank voltage difference value calculated by the voltage difference calculation unit exceeds a predetermined reference voltage difference value and outputs a signal corresponding to the comparison result; a reference SOC comparison unit that compares whether the state of charge (SOC) included in the battery information acquired from the battery information measurement unit is within a predetermined reference SOC range and outputs a reference SOC sufficient signal if it is within the predetermined reference SOC range; and a necessity determination unit that determines that cell balancing is necessary if the calculated bank voltage difference value exceeds the predetermined reference voltage difference value and the SOC is within the predetermined reference SOC range.

[0017] More specifically, the voltage comparator outputs an over-voltage signal when the calculated bank voltage difference value exceeds a predetermined reference voltage difference value as a result of the comparison, and outputs an under-voltage signal when the calculated bank voltage difference value is equal to or less than the predetermined reference voltage difference value. The necessity determination unit determines that cell balancing is necessary when both the over-voltage signal and the SOC sufficient signal are output, and outputs a balancing start signal.

[0018] Meanwhile, the necessity determination unit determines that cell balancing is not continuing if a voltage below voltage signal is output from the voltage comparison unit after the output of the balancing start signal, and outputs a balancing end signal; and determines that cell balancing is continuing if a voltage above voltage signal is output from the voltage comparison unit after the output of the balancing start signal, and outputs a balancing continue signal.

[0019] Meanwhile, the duty ratio change necessity determination unit includes a temperature comparison unit that compares whether a temperature of a battery management system (BMS) included in the battery information acquired from the battery information measurement unit is less than a predetermined reference temperature after the balancing start signal is output from the necessity determination unit, and outputs a temperature sufficient signal if the temperature is less than the predetermined reference temperature; a current comparison unit that compares whether a cell balancing current included in the battery information acquired from the battery information measurement unit is less than a predetermined reference current after the balancing start signal is output from the necessity determination unit, and outputs a current sufficient signal if the current is less than the predetermined reference current; and a change determination unit that determines whether a duty ratio of a cell balancing switch of the cell balancing unit needs to be changed based on comparison results of the temperature comparison unit and the current comparison unit.

[0020] More specifically, the change judgment unit is characterized in that when both a temperature satisfaction signal and a current satisfaction signal are output from the temperature comparison unit and the current comparison unit, it judges that a change in the duty ratio of the cell balancing switch is necessary and outputs a duty ratio change signal, and when neither a temperature satisfaction signal nor a current satisfaction signal is output from the temperature comparison unit and the current comparison unit, it judges that a change in the duty ratio of the cell balancing switch is unnecessary.

[0021] Meanwhile, the counting unit includes a cycle number counting unit that counts the number of cell balancing cycles from a point in time when a balancing start signal is output from the necessity determining unit of the cell balancing necessity determining unit.

[0022] On the other hand, the diagnostic count increase / increase determination unit includes a number comparison unit which compares whether the number of cell balancing cycles counted in the cycle number counting unit of the counting unit exceeds a predetermined reference number of cell balancing cycles, and outputs a cycle number exceeded signal if the number of cell balancing cycles exceeds the predetermined reference number of cell balancing cycles; and an increase determination unit which determines to increase the number of diagnostic counts and outputs a diagnostic count increase signal if a balancing continuation signal is output from the necessity determination unit of the cell balancing necessity determination unit and a cycle number exceeded signal is output from the number comparison unit.

[0023] Meanwhile, the counting unit further includes a diagnostic count number counting unit which increases the number of the diagnostic count when a diagnostic count signal is output from the increment determining unit of the diagnostic count increment determining unit.

[0024] On the other hand, the cell balancing mode change determination unit is characterized in that, when the number of diagnostic counts counted in the diagnostic count count unit is equal to or less than a reference diagnostic count, it determines that a change in the cell balancing mode is necessary and outputs a mode change signal.

[0025] Meanwhile, the cell balancing control unit includes a switch control unit that sets a cell balancing switch of the cell balancing unit to an initial duty ratio and turns it on when a balancing start signal is output from the necessity judgment unit of the cell balancing necessity judgment unit, and a cell balancing mode setting unit that sets the cell balancing switch to an initial cell balancing mode when a balancing start signal is output from the necessity judgment unit of the cell balancing necessity judgment unit.

[0026] Meanwhile, the switch control unit of the cell balancing control unit is characterized in that when a duty ratio change signal is output from the change judgment unit of the duty ratio change necessity judgment unit, the switch control unit increases the duty ratio of the cell balancing switch by a predetermined range and turns it on, and when a balancing end signal is output from the necessity judgment unit of the cell balancing necessity judgment unit, the switch control unit turns off the cell balancing switch.

[0027] Meanwhile, the cell balancing mode setting unit of the cell balancing control unit changes and sets the cell balancing mode when a mode change signal is output from the cell balancing mode change / non-change determination unit.

[0028] Here, the cell balancing mode is any one of a charge mode, a standby mode, and a discharge mode, and the cell balancing mode is changed and set in the order of the charge mode, the standby mode, and the discharge mode. Effect of the Invention

[0029] According to an embodiment of the present invention, cell balancing is performed by variably controlling the PWM duty of the cell balancing switch according to the cell balancing current and the temperature and operation mode of the BMS. Therefore, even if the voltage difference between the battery cells or modules is large, the voltage difference can be stabilized in a short time, and the efficiency of cell balancing can be increased. [Brief description of the drawings]

[0030] [Figure 1] FIG. 2 is a flow chart illustrating a cell balancing method according to an embodiment of the present invention. [Diagram 2] 1 is a diagram illustrating an overall configuration of a battery pack according to an embodiment of the present invention; [Diagram 3] FIG. 2 is a diagram showing a detailed configuration of each component. [Figure 4] FIG. 2 is a diagram showing a detailed configuration of each component. [Diagram 5]FIG. 2 is a diagram showing a detailed configuration of each component. [Figure 6] FIG. 2 is a diagram showing a detailed configuration of each component. [Figure 7] FIG. 2 is a diagram showing a detailed configuration of each component. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] Hereinafter, the embodiments of the present invention will be described in detail with reference to the accompanying drawings so that a person having ordinary skill in the art to which the present invention pertains can easily carry out the present invention. However, the present invention can be embodied in various different forms and is not limited to the embodiments described herein. In the drawings, in order to clearly explain the present invention, parts that are not related to the description are omitted, and similar parts are denoted by similar reference numerals throughout the specification.

[0032] The present invention will now be described in detail with reference to the accompanying drawings.

[0033] 1. Cell Balancing Method According to the Present Invention

[0034] FIG. 1 is a flow chart showing a cell balancing method according to an embodiment of the present invention.

[0035] Referring to FIG. 1, the cell balancing method of the present invention may include the following steps.

[0036] 1.1. Battery information acquisition step (S100)

[0037] The battery information acquisition step (S100) is a step of acquiring battery information including the battery current, voltage, temperature, SOC, etc. at regular intervals.

[0038] Here, the battery voltage may be the voltage value of each battery bank 100 composed of a plurality of battery cells (not shown).

[0039] The battery temperature may be a temperature value of a BMS obtained by measuring the temperature of a resistor, a FET, or the like connected to a battery monitoring integrated circuit (BMIC).

[0040] 1.2. Cell Balancing Necessity Determination Step (S200)

[0041] The cell balancing necessity determining step (S200) is a step of determining whether cell balancing is necessary or not, using the battery information acquired in the battery information acquiring step (S100).

[0042] More specifically, when the bank voltage difference, which is the difference between the maximum and minimum voltage values ​​among the voltage values ​​of the battery bank included in the acquired battery information, exceeds the reference voltage difference and the SOC is within a predetermined reference range, it is determined that cell balancing is necessary.

[0043] 1.3. Cell balancing start step (S300)

[0044] The cell balancing start step (S300) is a step in which, if it is determined that cell balancing is necessary in the cell balancing necessity determination step (S200), a cell balancing switch (not shown) is set to an initial duty ratio, turned on (ON) to activate cell balancing, and an initial cell balancing mode is executed.

[0045] Here, the initial duty ratio may be set to, for example, 20%.

[0046] The cell balancing mode may be set to a charge mode, a standby mode, or a discharge mode.

[0047] At this time, when cell balancing is started, the cell balancing time can be counted from that point.

[0048] 1.4. Step for determining whether or not the duty ratio of the cell balancing switch needs to be changed (S400)

[0049] The step of determining whether or not to change the duty ratio of the cell balancing switch (S400) is a step of determining whether or not to change the duty ratio of the cell balancing switch using the temperature of the BMS and the cell balancing current included in the battery information acquired through the step of acquiring battery information (S100).

[0050] Specifically, by comparing whether the temperature of the BMS is lower than a reference temperature and whether the cell balancing current is lower than a reference cell balancing current, if both conditions are met, it can be determined that the duty ratio of the cell balancing switch needs to be changed.

[0051] On the other hand, if the temperature of the BMS is not lower than the reference temperature or the cell balancing current is not lower than the reference cell balancing current, that is, if either the temperature of the BMS or the cell balancing current does not satisfy the condition, it can be determined that the duty ratio of the cell balancing switch does not need to be changed. In this case, the initial duty ratio and the initial cell balancing mode set in the cell balancing start step (S300) are maintained (S410).

[0052] 1.5. Cell balancing switch duty ratio increase step (S500)

[0053] The cell balancing switch duty ratio increasing step (S500) is a step that is performed when it is determined in the cell balancing switch duty ratio change necessity determining step (S400) that the duty ratio of the cell balancing switch needs to be changed.

[0054] If it is determined that the duty ratio of the cell balancing switch needs to be changed, the duty ratio of the cell balancing switch is increased by an increment within a predetermined range.

[0055] For example, if the initial duty ratio of the cell balancing switch in the cell balancing start step (S300) is "A" and the increment within the predetermined range is "a", the duty ratio of the cell balancing switch is increased to "A+a".

[0056] In this way, if the temperature and cell balancing current of the BMS do not meet certain conditions even after performing a cell balancing operation with an initial cell balancing switch duty ratio and cell balancing mode, the duty ratio of the cell balancing switch can be gradually increased to increase the cell balancing efficiency.

[0057] Meanwhile, the increment “a” of the duty ratio of the cell balancing switch can be set so that the operating range of cell balancing becomes larger in the order of charge mode-standby mode-discharge mode, thereby allowing the switch duty ratio to be increased more significantly according to the cell balancing mode.

[0058] 1.6. Step for determining whether cell balancing is continued (S600)

[0059] The cell balancing continuation determination step (S600) is a step of determining whether the currently operating cell balancing is to be continued or not, using the battery information acquired through the battery information acquisition step (S100).

[0060] More specifically, if the bank voltage difference, which is the difference between the maximum and minimum voltage values ​​among the voltage values ​​of the battery bank included in the acquired battery information, exceeds the reference voltage difference, it is determined that cell balancing during operation needs to be continued.

[0061] On the other hand, if the bank voltage difference is equal to or less than the reference voltage difference, it is determined that the ongoing cell balancing is not necessary, and a cell balancing termination step (S610) is performed to turn off the cell balancing switch.

[0062] 1.7. Step for determining whether diagnostic count has increased (S700)

[0063] The step of determining whether the diagnostic count has increased (S700) is a step of determining whether the diagnostic count has increased based on the result of the determination of whether cell balancing needs to be continued in the step of determining whether cell balancing needs to be continued (S600) and the result of comparing the number of cell balancing cycles with the number of reference cell balancing cycles.

[0064] Specifically, if it is determined that the cell balancing needs to be continued and the number of cell balancing cycles is equal to or less than a predetermined reference number of cell balancing cycles, it is determined that the diagnostic count does not need to be increased, and the process returns to the step of determining whether or not to change the duty ratio of the cell balancing switch (S400). On the other hand, if it is determined that the cell balancing is not needed to be continued even though the cell balancing has been continued for a predetermined number of cell balancing cycles or cell balancing time, that is, if the bank voltage difference does not exceed the reference voltage difference and falls within a predetermined reference range, the cell balancing mode can be changed in a manner different from the cell balancing mode change step (S800) described later before returning to the step of determining whether or not to change the duty ratio (S400). At this time, the cell balancing mode is changed in the order of discharge mode-standby mode-charge mode, thereby making it possible to reduce the increase in the duty ratio of the cell balancing switch. At this time, if the mode before the change was charge mode, the charge mode is maintained.

[0065] On the other hand, if it is determined that the cell balancing needs to be continued and the number of cell balancing cycles exceeds a predetermined reference number of cell balancing cycles, it is determined that the diagnosis count should be increased, and the diagnosis count is increased (S710). That is, if the bank voltage difference, which is the difference between the maximum and minimum voltage values ​​of the battery bank voltage values, exceeds the reference voltage difference even after cell balancing has been performed a predetermined number of times or time.

[0066] While one embodiment has been described in which the number of cell balancing cycles is used to determine whether the diagnostic count has increased, another embodiment may use the cell balancing operation time. In such a case, for example, the result of whether the cell balancing operation time is equal to or less than a predetermined reference cell balancing operation time or whether the cell balancing operation time exceeds a predetermined reference cell balancing operation time can be reflected in the determination of whether the diagnostic count has increased.

[0067] 1.8. Cell balancing mode change step (S800)

[0068] In the cell balancing mode change step (S800), the cell balancing mode in the cell balancing start step (S300) can be changed depending on whether the number of diagnostic counts counted through the diagnostic count increase / increase determination step (S700) is equal to or less than a predetermined reference diagnostic count.

[0069] Specifically, if the number of diagnostic counts is equal to or less than a predetermined reference diagnostic count, the cell balancing mode is changed, and the process returns to the step of determining whether or not the duty ratio of the cell balancing switch needs to be changed (S400).

[0070] Here, the cell balancing mode is any one of a charge mode, a standby mode, and a discharge mode, and the cell balancing mode can be changed in the order of the charge mode, the standby mode, and the discharge mode. For example, if the initial cell balancing mode is the charge mode, the cell balancing mode can be changed to the standby mode in the cell balancing mode changing step (S800). If the cell balancing mode before the change was the discharge mode, the discharge mode is maintained.

[0071] This is because, depending on the conditions under which cell balancing has been performed a set number of times or for a set amount of time in the previous diagnostic count increase determination step (S700) but the bank voltage difference does not decrease, the cell balancing mode is changed in the order of charge mode - wait mode - discharge mode, and cell balancing is continued, thereby making it possible to further increase the duty ratio of the cell balancing switch.

[0072] However, if the number of diagnostic counts exceeds a predetermined reference diagnostic count, no further cell balancing is performed, the diagnostic results are reported, and a diagnostic end step (S810) is performed to end the procedure.

[0073] 2. Battery pack according to the present invention

[0074] FIG. 2 is a diagram illustrating a schematic overall configuration of a battery pack according to an embodiment of the present invention.

[0075] Referring to FIG. 2, the battery pack of the present invention includes the following components:

[0076] 2.1. Battery Bank 100

[0077] As shown in FIG. 2, the battery pack of the present invention includes at least two or more battery banks 100 each including a plurality of battery cells (not shown).

[0078] 2.2. Battery Information Measurement Unit 200

[0079] The battery information measurement unit 200 is a component that measures battery information including the current, voltage, temperature, SOC, etc. of the battery at regular intervals.

[0080] Here, the voltage may be a voltage value for each battery bank. The voltage of the battery bank may be obtained, for example, by measuring the voltage of each battery cell and measuring / calculating based on the measured voltage value of the battery cell.

[0081] On the other hand, the temperature may be a temperature value of the BMS. The temperature of the BMS can be obtained by measuring the temperature of a resistor or a FET connected to a BMIC (Battery Monitoring).

[0082] Alternatively, the current may be a cell balancing current value.

[0083] As a method for measuring battery information including the current, voltage, temperature, SOC, etc. of the battery, a known method can be used.

[0084] 2.3. Cell Balancing Necessity Determination Unit 300

[0085] The cell balancing necessity determination unit 300 is a component that determines whether or not cell balancing of the battery is required, using the battery information acquired from the battery information measurement unit 200. The cell balancing necessity determination unit 300 may include the following detailed components.

[0086] 2.3.1. Voltage difference calculation unit 310

[0087] The voltage difference calculation unit 310 is a component that calculates a bank voltage difference value, which is the difference between the maximum voltage value and the minimum voltage value among the voltage values ​​of the battery bank included in the battery information acquired from the battery information measurement unit 200.

[0088] 2.3.2. Voltage Comparison Unit 320

[0089] The voltage comparison unit 320 is a component that compares whether the bank voltage difference calculated by the voltage difference calculation unit 310 exceeds a predetermined reference voltage difference value, and outputs a signal corresponding to the comparison result.

[0090] More specifically, if the comparison result indicates that the calculated bank voltage difference value exceeds a predetermined reference voltage difference value, an exceeding voltage signal indicating this can be output.

[0091] On the other hand, if the result of the comparison indicates that the calculated bank voltage difference is equal to or less than a predetermined reference voltage difference, a below-voltage signal indicating this can be output.

[0092] 2.3.3.SOC Comparison Section 330

[0093] The SOC comparison unit 330 compares whether the SOC included in the battery information acquired from the battery information measurement unit 200 is within a predetermined reference SOC range, and if it is within the predetermined reference SOC range, it can output, for example, an SOC sufficient signal indicating this.

[0094] 2.3.4. Necessity judgment section 340

[0095] The necessity determining unit 340 is a component that determines whether or not cell balancing is necessary based on the comparison results of the voltage comparing unit 320 and the SOC comparing unit 330 .

[0096] More specifically, if the calculated bank voltage difference value exceeds a predetermined reference voltage difference value and the SOC is within a predetermined reference SOC range, it is determined that cell balancing is necessary.

[0097] That is, when the voltage comparator 320 outputs an over-voltage signal and the SOC comparator 330 outputs an SOC sufficient signal, it is determined that cell balancing is necessary, and for example, a balancing start signal indicating this is output.

[0098] On the other hand, if a voltage below voltage signal is output from the voltage comparison unit 320 after cell balancing has started (after the balancing start signal has been output), the necessity determination unit 340 may determine that it is not necessary to continue cell balancing and may output, for example, a balancing end signal indicating this.

[0099] In contrast, if an exceed-voltage signal is output from the voltage comparator 320 after cell balancing has started (after the balancing start signal has been output), it may be determined that cell balancing needs to be continued, and a balancing continue signal indicating this, for example, may be output.

[0100] 2.4. Duty ratio change necessity determination unit 400

[0101] The duty ratio change necessity determination unit 400 is a component that determines whether or not the duty ratio of a cell balancing switch (not shown) of the cell balancing unit 900 needs to be changed using the battery information acquired from the battery information measurement unit 200 after the cell balancing operation is activated based on the determination result of the cell balancing necessity determination unit 300.

[0102] The duty ratio change necessity determination unit 400 may include the following detailed components.

[0103] 2.4.1.Temperature comparison section 410

[0104] After activation of cell balancing (after output of a balancing start signal), the temperature comparison unit 410 compares whether the temperature of the BMS included in the battery information acquired from the battery information measurement unit 200 is below a predetermined reference temperature, and if it is below the predetermined reference temperature, it can output, for example, a temperature satisfaction signal indicating this.

[0105] 2.4.2. Current Comparator 420

[0106] After activation of cell balancing (after output of a balancing start signal), the current comparison unit 420 compares whether the cell balancing current included in the battery information acquired from the battery information measurement unit 200 is less than a predetermined reference current, and if it is less than the predetermined reference current, it can output, for example, a current sufficiency signal indicating this.

[0107] 2.4.3. Change Determination Unit 430

[0108] The change determination unit 430 is a component that determines whether or not the duty ratio of a cell balancing switch (not shown) needs to be changed based on the comparison results of the temperature comparison unit 410 and the current comparison unit 420 .

[0109] More specifically, when the temperature of the BMS is lower than a predetermined reference temperature and the cell balancing current is lower than a predetermined reference current, i.e., when both a temperature sufficient signal and a current sufficient signal are output from the temperature comparator 410 and the current comparator 420, it is determined that the duty ratio of the cell balancing switch needs to be changed. In this case, for example, a duty ratio change signal indicating this may be output.

[0110] On the other hand, if the temperature comparator 410 and the current comparator 420 do not output either the temperature satisfying signal or the current satisfying signal, it can be determined that there is no need to change the duty ratio of the cell balancing switch.

[0111] 2.5.Counter 500

[0112] The counter unit 500 is a component that counts the number of cell balancing cycles and the number of diagnostic counts.

[0113] 2.5.1. Cycle Counting Unit 510

[0114] The cycle number counter 510 is a component that counts the number of cell balancing cycles if cell balancing is activated based on the determination result of the cell balancing necessity determination unit 300. More specifically, if a balancing start signal is output from the necessity determination unit 340 of the cell balancing necessity determination unit 300, the cycle number counter 510 can be implemented in a form that counts the number of cell balancing cycles from that point on.

[0115] Meanwhile, as another embodiment of the cycle number counter 510, it can be realized as a balancing time counter that counts the operation time of cell balancing. In this case, for example, when a balancing start signal is output from the necessity determination unit 340 of the cell balancing necessity determination unit 300, it can be realized as a form that counts the operation time of cell balancing from that point.

[0116] 2.5.2. Diagnostic Count Number Counting Unit 520

[0117] The diagnostic count number counter 520 is a component that increases the number of diagnostic counts when it is determined that the number of diagnostic counts needs to be increased as a result of the determination made by a diagnostic count increment determination unit 600 described later.

[0118] More specifically, when the diagnostic count increment signal is output from the diagnostic count increment determination unit 600, the number of diagnostic counts can be incremented by +1.

[0119] 2.6. Diagnostic count increase determination unit 600

[0120] The diagnostic count increase determination unit 600 is a component that determines whether the diagnostic count has increased depending on whether cell balancing needs to be continued and whether the number of cell balancing cycles (or the operation time of cell balancing) exceeds a predetermined reference number of cell balancing cycles (or the operation time of cell balancing).

[0121] The diagnostic count increment determination unit 600 may include the following detailed components.

[0122] 2.6.1. Number of Times Comparison Unit 610

[0123] The number comparison unit 610 is a component that compares the number of cell balancing cycles counted in the cycle number count unit 510 of the count unit 500 with a predetermined reference number of cell balancing cycles, and outputs a signal corresponding to the comparison result.

[0124] More specifically, if the number of counted cell balancing cycles is less than or equal to the number of reference cell balancing cycles, for example, a cycle count less than or equal to signal may be output to indicate this.

[0125] On the other hand, if the counted number of cell balancing cycles exceeds the number of reference cell balancing cycles, for example, a cycle count exceeding signal indicating this can be output.

[0126] 2.6.2. Increase Determination Unit 620

[0127] The increase determination unit 620 is a component that determines whether the number of diagnostic counts is increased based on the comparison result of the number comparison unit 610 and the determination result of the cell balancing necessity determination unit 300 as to whether cell balancing is continued.

[0128] More specifically, if it is determined that cell balancing is continuing and the number of cell balancing cycles (or the operation time of cell balancing) is less than or equal to a predetermined reference number of cell balancing cycles (or the operation time of cell balancing), it is determined not to increase the number of diagnostic counts.

[0129] On the other hand, if it is determined that cell balancing is continuing and the number of cell balancing cycles (or the cell balancing operation time) exceeds a predetermined reference number of cell balancing cycles (or the cell balancing operation time), it is decided to increase the number of diagnostic counts.

[0130] In other words, when a balancing continuation signal is output from the necessity judgment unit 340 of the cell balancing necessity judgment unit 300 and a cycle count or less signal is output from the number comparison unit 610, it is determined that the diagnostic count should not be increased, and for example, a diagnostic count not increased signal indicating this can be output.

[0131] In contrast, when a balancing continuation signal is output from the necessity determination unit 340 of the cell balancing necessity determination unit 300 and a cycle count exceeded signal is output from the number comparison unit 610, it is determined that the diagnostic count should be increased, and for example, a diagnostic count increase signal indicating this can be output.

[0132] 2.7. Cell balancing mode change determination unit 700

[0133] The cell balancing mode change determination unit 700 is a component that determines whether or not the cell balancing mode has been changed depending on whether the number of diagnostic counts counted in the diagnostic count number counting unit 520 of the counting unit 500 is equal to or less than a predetermined reference diagnostic count.

[0134] More specifically, if the number of diagnostic counts counted by the diagnostic count number counting unit 520 is less than or equal to the reference diagnostic count, it can determine that a change in the cell balancing mode is necessary, and output, for example, a mode change signal indicating this.

[0135] On the other hand, if the number of diagnostic counts counted by the diagnostic count number counting unit 520 exceeds the reference diagnostic count, it can be determined that there is no need to change the cell balancing mode, and, for example, a mode no change signal indicating this can be output.

[0136] 2.8. Cell Balancing Control Unit 800

[0137] The cell balancing control unit 800 is a component that controls the cell balancing operation of the cell balancing unit 900 based on the result of the determination by the cell balancing necessity determination unit 300 .

[0138] More specifically, if the cell balancing necessity determination unit 300 determines that cell balancing is necessary, the cell balancing operation is activated with an initial cell balancing switch duty ratio and cell balancing mode, and then the duty ratio and cell balancing mode are changed and set depending on whether or not conditions associated with changes in the battery state are satisfied, to control the cell balancing operation.

[0139] 2.8.1. Switch Control Unit 810

[0140] When a balancing start signal is output from the necessity determining unit 340 of the cell balancing necessity determining unit 300, the switch control unit 810 turns on a cell balancing switch (not shown) of the cell balancing unit 900 with an initial duty ratio.

[0141] Here, the initial duty ratio of the cell balancing switch may be set to, for example, 20%.

[0142] Then, when a duty ratio change signal is output from the change determination unit 430 of the duty ratio change necessity determination unit 400, the duty ratio of the cell balancing switch (not shown) can be increased within a predetermined range and turned on.

[0143] Meanwhile, when a balancing end signal is output from the necessity determining unit 340 of the cell balancing necessity determining unit 300, the cell balancing switch (not shown) is controlled to be turned off to end the cell balancing operation.

[0144] 2.8.2. Cell balancing mode setting unit 820

[0145] The cell balancing mode setting unit 820 sets the cell balancing mode to an initial state when a balancing start signal is output from the necessity determination unit 340 of the cell balancing necessity determination unit 300. Then, when a mode change signal is output from the cell balancing mode change / non-change determination unit 700, the cell balancing mode setting unit 820 can change and set the cell balancing mode in a predetermined order.

[0146] Here, the cell balancing mode may be any one of a charge mode, a standby mode, and a discharge mode.

[0147] In addition, the order of changing the predetermined cell balancing mode can be set to the charge mode, the standby mode, and the discharge mode.

[0148] For example, if the initial cell balancing mode is the charging mode, when the mode change signal is output from the cell balancing mode change determination unit 700, the changed cell balancing mode becomes the waiting mode.

[0149] 2.9. Cell Balancing Unit 900

[0150] The cell balancing unit 900 is composed of a cell balancing resistor (not shown) connected to the positive electrode of each battery bank 100 to consume the voltage of the battery bank, and a cell balancing switch (not shown) that turns on / off the connection path between the cell balancing resistor (not shown) and the battery bank 100, and is a component that performs cell balancing operation under the control of the cell balancing control unit 800 to adjust the voltage difference between the battery banks 100.

[0151] Meanwhile, although the technical idea of ​​the present invention has been specifically described based on the above embodiment, it should be noted that the above embodiment is for the purpose of explanation and not for the purpose of limiting the present invention. It should be understood by those skilled in the art that various embodiments are possible within the scope of the technical idea of ​​the present invention.

[0152] The symbols and their names used in the drawings of the present invention are as follows: [Explanation of symbols]

[0153] 100: Battery bank 200: Battery information measurement unit 300: Cell balancing necessity determination unit 310: Voltage difference calculation unit 320: Voltage comparison section 330:SOC comparison section 340: Necessity Judgment Department 400: Duty ratio change necessity determination section 410: Temperature comparison section 420: Current comparison section 430: Change judgment unit 500:Counting section 510: Cycle counter 520: Diagnostic count count unit 600: Diagnostic count increase / decision unit 610: Number of times comparison unit 620: Increase judgment section 700: Cell balancing mode change determination unit 800: Cell balancing control unit 810: Switch control unit 820: Cell balancing mode setting unit 900: Cell balancing section

Claims

1. 1. A method for controlling cell balancing among at least two or more battery banks included in a battery pack, comprising: a battery information acquisition step of acquiring battery information including a current, a voltage, and a temperature of the battery at regular intervals; a cell balancing necessity determination step of determining whether cell balancing is necessary by using the battery information acquired in the battery information acquisition step; a cell balancing start step of turning on a cell balancing switch with an initial duty ratio and executing an initial cell balancing mode when it is determined that cell balancing is necessary in the cell balancing necessity determination step; a cell balancing switch duty ratio change determination step of determining whether or not a duty ratio of the cell balancing switch needs to be changed using the acquired battery information after the cell balancing is started; a cell balancing switch duty ratio increasing step of increasing the duty ratio of the cell balancing switch by a predetermined range when it is determined that the duty ratio of the cell balancing switch needs to be changed in the cell balancing switch duty ratio change determination step; determining whether cell balancing is to be continued by using the acquired battery information; a diagnostic count increase determination step of increasing a diagnostic count when it is determined that cell balancing is continuing in the cell balancing continuation determination step and the number of cell balancing cycles exceeds a predetermined reference cell balancing cycle number; a cell balancing mode changing step of changing a cell balancing mode and returning to the cell balancing switch duty ratio change determination step when the number of diagnostic counts counted through the diagnostic count increase determination step is equal to or less than a predetermined reference diagnostic count; The cell balancing method includes:

2. a cell balancing termination step of controlling a cell balancing switch to be off when it is determined that the cell balancing is not to be continued in the cell balancing continuation determination step; a diagnosis end step of reporting a diagnosis result and ending the procedure if the number of diagnosis counts counted through the diagnosis count increase determination step exceeds a predetermined reference diagnosis count; The cell balancing method of claim 1 , further comprising:

3. The cell balancing necessity determining step includes:

3. The cell balancing method according to claim 1, further comprising: determining that cell balancing is necessary when a bank voltage difference, which is a difference between a maximum voltage and a minimum voltage, among the voltage values ​​of the battery bank included in the acquired battery information exceeds a predetermined reference voltage difference value and a state of charge (SOC) is within a predetermined reference range.

4. The step of determining whether or not the cell balancing switch duty ratio needs to be changed includes: determining that a duty ratio of a cell balancing switch needs to be changed when a temperature of a battery management system (BMS) included in the acquired battery information is lower than a predetermined reference temperature and a cell balancing current is lower than a reference current; determining that it is not necessary to change the duty ratio of the cell balancing switch when either one of the temperature and the cell balancing current of the battery management system (BMS) does not satisfy a condition; The cell balancing method of claim 1 , comprising:

5. The cell balancing continuation determination step includes: determining that it is not necessary to continue cell balancing when a bank voltage difference, which is a difference between a maximum voltage and a minimum voltage, among voltage values ​​of the battery bank included in the acquired battery information is equal to or less than a predetermined reference voltage difference; determining that cell balancing is required to continue if the bank voltage difference value exceeds a predetermined reference voltage difference value; The cell balancing method of claim 1 , comprising:

6. The cell balancing mode is one of a charging mode, a standby mode, and a discharging mode, The cell balancing mode changing step includes: The cell balancing method of claim 1 , further comprising changing the cell balancing mode in the following order: a charge mode, a standby mode, and a discharge mode.

7. At least two or more battery banks including a plurality of battery cells; a battery information measurement unit that measures battery information including a current, a voltage, a temperature, and a state of charge (SOC) of the battery at regular intervals; a cell balancing necessity determination unit that determines whether cell balancing is necessary by using the battery information acquired from the battery information measurement unit; a duty ratio change necessity determination unit that determines whether or not a duty ratio of a cell balancing switch needs to be changed by using battery information acquired from the battery information measurement unit after a cell balancing operation is activated based on a determination result of the cell balancing necessity determination unit; a counting unit for counting the number of cell balancing cycles and the number of diagnostic counts; a diagnostic count increment determining unit that determines whether or not a diagnostic count should be increased depending on whether or not cell balancing needs to be continued and whether or not the number of cell balancing cycles exceeds a predetermined reference number of cell balancing cycles; a cell balancing mode change determination unit that determines whether or not a cell balancing mode is changed depending on whether the number of diagnostic counts counted by the count unit is equal to or less than a predetermined reference diagnostic count; A battery pack comprising:

8. a cell balancing control unit that activates a cell balancing operation with an initial cell balancing switch duty ratio and an initial cell balancing mode if the cell balancing necessity determination unit determines that cell balancing is necessary, and then changes and sets the cell balancing switch duty ratio and the cell balancing mode according to whether or not a predetermined condition is satisfied due to a change in a battery state; a cell balancing unit including a cell balancing resistor connected to a positive electrode of each battery bank and consuming the voltage of the battery bank, and a cell balancing switch that turns on / off a connection path between the cell balancing resistor and the battery bank; 8. The battery pack of claim 7, further comprising:

9. The cell balancing necessity determination unit is a voltage difference calculation unit that calculates a bank voltage difference, which is a difference between a maximum voltage and a minimum voltage, among voltage values ​​of the battery bank included in the battery information acquired from the battery information measurement unit; a voltage comparator that compares whether the bank voltage difference calculated by the voltage difference calculation unit exceeds a predetermined reference voltage difference value and outputs a signal corresponding to the comparison result; a reference state of charge (SOC) comparator for comparing whether a state of charge (SOC) included in the battery information acquired from the battery information measurement unit is within a range of a predetermined reference state of charge (SOC), and outputting a reference state of charge (SOC) sufficient signal if the state of charge (SOC) is within the range of the predetermined reference state of charge (SOC); a necessity determination unit that determines that cell balancing is necessary when the calculated bank voltage difference value exceeds a predetermined reference voltage difference value and the state of charge (SOC) is within a predetermined reference state of charge (SOC) range; 9. The battery pack of claim 8, comprising:

10. The voltage comparison unit is If the calculated bank voltage difference value exceeds a predetermined reference voltage difference value as a result of the comparison, an exceeding voltage signal is output; outputting an under-voltage signal when the calculated bank voltage difference value is equal to or less than a predetermined reference voltage difference value; The necessity determination unit is The battery pack of claim 9, further comprising: a balancing start signal outputted when it is determined that cell balancing is necessary if both the over-voltage signal and the state of charge (SOC) sufficient signal are outputted.

11. The necessity determination unit is If the voltage comparator outputs a voltage-low signal after the output of the balancing start signal, it is determined that cell balancing is not continuing, and a balancing end signal is output; and The battery pack according to claim 10, wherein if the voltage comparator outputs an over-voltage signal after the balancing start signal is output, it is determined that cell balancing is to be continued, and a balancing continue signal is output.

12. The duty ratio change necessity determination unit is a temperature comparator that compares whether a temperature of a battery management system (BMS) included in the battery information acquired from the battery information measurement unit is below a predetermined reference temperature after the balancing start signal is output from the necessity determination unit, and outputs a temperature satisfaction signal if the temperature is below the predetermined reference temperature; a current comparator that compares whether a cell balancing current included in the battery information acquired from the battery information measurement unit is less than a predetermined reference current after the balancing start signal is output from the necessity determination unit, and outputs a current satisfaction signal if the cell balancing current is less than the predetermined reference current; a change determination unit that determines whether or not a duty ratio of a cell balancing switch of a cell balancing unit needs to be changed based on comparison results of the temperature comparison unit and the current comparison unit; 12. The battery pack of claim 11, comprising:

13. The change determination unit is When both the temperature comparator and the current comparator output a temperature satisfaction signal and a current satisfaction signal, it is determined that a duty ratio of the cell balancing switch needs to be changed, and a duty ratio change signal is output; and 13. The battery pack according to claim 12, wherein when either one of the temperature satisfaction signal and the current satisfaction signal is not output from the temperature comparison unit and the current comparison unit, it is determined that there is no need to change the duty ratio of the cell balancing switch.

14. The counting unit is The battery pack according to any one of claims 11 to 13, further comprising a cycle number counting unit that, when a balancing start signal is output from the necessity determination unit of the cell balancing necessity determination unit, counts the number of cell balancing cycles from the time when the balancing start signal is output.

15. The diagnostic count increase determination unit a number comparison unit which compares whether the number of cell balancing cycles counted by the cycle number count unit of the count unit exceeds a predetermined number of reference cell balancing cycles, and outputs a cycle number exceeding signal if the number of cell balancing cycles exceeds the predetermined number of reference cell balancing cycles; an increase determination unit that determines to increase the number of diagnostic counts and outputs a diagnostic count increase signal when a balancing continuation signal is output from the necessity determination unit of the cell balancing necessity determination unit and a cycle count exceeding signal is output from the count comparison unit; 15. The battery pack of claim 14, comprising:

16. The counting unit is The battery pack according to claim 15, further comprising a diagnostic count number counter that increases the number of the diagnostic count when the diagnostic count signal is output from the increment determination unit of the diagnostic count increment determination unit.

17. The cell balancing mode change determination unit is 17. The battery pack according to claim 16, further comprising: a diagnostic count counter that determines that a cell balancing mode needs to be changed and outputs a mode change signal when the diagnostic count counted by the diagnostic count counter is equal to or less than a reference diagnostic count.

18. The cell balancing control unit is a switch control unit that sets a cell balancing switch of the cell balancing unit to an initial duty ratio and turns it on when a balancing start signal is output from the necessity determination unit of the cell balancing necessity determination unit; a cell balancing mode setting unit that sets an initial cell balancing mode when a balancing start signal is output from the cell balancing necessity determination unit of the cell balancing necessity determination unit; 20. The battery pack of claim 17, comprising:

19. The switch control unit of the cell balancing control unit, When a duty ratio change signal is output from the change determination unit of the duty ratio change necessity determination unit, the duty ratio of the cell balancing switch is increased by a predetermined range and turned on; and The battery pack of claim 18, wherein the cell balancing switch is turned off when a balancing end signal is output from the cell balancing necessity determining unit of the cell balancing necessity determining unit.

20. The cell balancing mode setting unit of the cell balancing control unit, The battery pack of claim 18, wherein the cell balancing mode is changed when the mode change signal is output from the cell balancing mode change determination unit.

21. The cell balancing mode is one of a charging mode, a standby mode, and a discharging mode, The battery pack of claim 20, wherein the cell balancing mode is changed and set in an order of a charge mode, a standby mode, and a discharge mode.

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