Cell balancing control method and battery system providing the same

Abstract

The present invention relates to a cell balancing control method and a battery system for providing the same. The battery system of the present invention includes a battery including a plurality of battery cells, a Battery Management System (BMS) that determines whether a predetermined sleep mode entry condition is satisfied and enters a sleep mode when the sleep mode entry condition is satisfied, and wakes up in the sleep mode state at predetermined wake-up periods to determine whether or not to perform cell balancing, and a power supply unit that includes a timer that counts a first wake-up time in synchronization with a time point when the BMS goes to sleep and supplies a driving voltage to the BMS when the counting result reaches the first wake-up time.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0178853 dated December 14, 2021, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a cell balancing control method for controlling the wake-up time of a Battery Management System (BMS) in sleep mode so that the BMS wakes up at predetermined intervals to perform auto-cell balancing, and a battery system that provides this method. [Background technology]

[0003] Due to imbalances that occur during the manufacturing process or operating conditions, the degree of deterioration of each battery cell may vary over time. Due to such differences in deterioration, some battery cells may be completely discharged even if the majority of battery cells still have sufficient charge. This causes the battery to be unable to supply any more power, reducing its usable capacity, which is considered a deterioration in battery performance.

[0004] To solve the above problems, a battery management system (BMS) performs cell balancing to correct imbalances in capacity (SOC, State of Charge) and / or cell voltage among multiple battery cells. Cell balancing maximizes battery capacity, enabling all of the battery's energy to be used and extending battery life.

[0005] Meanwhile, for the safety of systems equipped with batteries, such as automotive systems, cell balancing is performed in sleep mode when the automotive system is not operating. Specifically, when the automotive system is not operating, the BMS also enters sleep mode, or the BMS can wake up at predetermined intervals to perform cell balancing. To enable the BMS in sleep mode to wake up at predetermined intervals, conventional battery systems include separate wake-up components such as an RTC (Real Time Clock) IC.

[0006] However, adding wake-up components such as an RTC IC to a battery system can increase costs and complicate the circuit configuration. Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention provides a cell balancing control method that performs cell balancing by waking up a BMS (Battery Management System) in a sleep mode at predetermined intervals using a timer already included in a power supply unit that supplies a driving voltage to the BMS, and a battery system that provides this method. [Means for solving the problem]

[0008] According to one aspect of the present invention, a battery system includes a battery including a plurality of battery cells, a Battery Management System (BMS) that determines whether a predetermined sleep mode entry condition is met, enters a sleep mode when the sleep mode entry condition is met, and wakes up in the sleep mode at predetermined wake-up intervals to determine whether cell balancing is performed, and a power supply unit that includes a timer that counts a first wake-up time in synchronization with when the BMS goes to sleep, and supplies a driving voltage to the BMS when the counting result reaches the first wake-up time.

[0009] When the driving voltage is supplied, the BMS wakes up to determine whether cell balancing is to be performed on the plurality of battery cells, calculates a second wake-up time by subtracting the time taken to determine whether cell balancing is to be performed from the wake-up period, and sets the second wake-up time to a time counted by the timer.

[0010] The timer may suspend counting the first wake-up time in synchronization with a time when the BMS wakes up, and may count the second wake-up time in synchronization with a time when the BMS sleeps.

[0011] If the determination result indicates that cell balancing needs to be performed, the BMS may perform the cell balancing and set the second wake-up time, and may go to sleep when the cell balancing is completed.

[0012] If the determination result shows that cell balancing does not need to be performed, the BMS may set the second wake-up time and then go to sleep.

[0013] According to another aspect of the present invention, a cell balancing control method is a method in which a BMS (Battery Management System) wakes up at a predetermined wake-up period to control cell balancing, the method including the steps of: determining whether a predetermined sleep mode entry condition is met; setting a first wake-up time, which is a time for a timer of a power supply unit to count if the sleep mode entry condition is met as a result of the determination; setting the first wake-up time in the timer and then going to sleep; waking up by receiving a driving voltage from the power supply unit when the count result of the timer reaches the first wake-up time; and determining whether to perform cell balancing on a plurality of battery cells.

[0014] The sleeping step may include counting the first wake-up time in synchronization with a time point at which the BMS goes to sleep.

[0015] After determining whether to perform cell balancing, the method may further include calculating a second wake-up time by subtracting the time taken to determine whether to perform cell balancing from the wake-up period, and setting the second wake-up time to a time counted by the timer.

[0016] The step of going to sleep may be performed after the step of setting the second wake-up time to the time counted by the timer, and the step of going to sleep may be performed by counting the second wake-up time in synchronization with the time when the BMS goes to sleep.

[0017] In the waking up step, counting of the first wake-up time may be stopped when the BMS wakes up.

[0018] After the step of determining whether to perform cell balancing, the method may further include the step of calculating a second wake-up time by subtracting the time taken to determine whether to perform cell balancing and the execution time of the cell balancing from the wake-up period, and setting the second wake-up time to the time counted by the timer. [Effects of the Invention]

[0019] The present invention utilizes a timer already included in the power supply unit to enable a BMS in sleep mode to wake up at predetermined intervals, which is expected to reduce costs and simplify the battery system.

[0020] In the present invention, the BMS calculates the next wake-up time and controls the timer to count according to the calculated wake-up time, thereby preventing the cell balancing period from being delayed by a timer that only has a counting function. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a diagram illustrating a battery system according to an embodiment. [Figure 2] 10 is an exemplary diagram illustrating a second wake-up time according to an embodiment. FIG. [Figure 3] 1 is a flowchart illustrating a cell balancing control method according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, the embodiments disclosed herein will be described in detail with reference to the accompanying drawings. Identical or similar elements will be designated by the same or similar reference numerals, and redundant descriptions thereof will be omitted. The suffixes "module" and / or "unit" used in the following description are used or mixed with other elements for the sake of ease of description, and do not have any distinct meanings or functions. Furthermore, when describing the embodiments disclosed herein, if a detailed description of related prior art is deemed to obscure the gist of the embodiments disclosed herein, such a detailed description will be omitted. Furthermore, the accompanying drawings are intended to facilitate understanding of the embodiments disclosed herein, and should not be construed as limiting the technical concept disclosed herein, but should be understood to include all modifications, equivalents, or alternatives within the concept and technical scope of the present invention.

[0023] Terms including ordinal numbers such as first, second, etc. may be used to describe various components, but the components are not limited by the terms. The terms are used only to distinguish one component from another.

[0024] When an element is referred to as being "coupled" or "connected" to another element, it should be understood that it may be directly coupled or connected to the other element, but that there may be additional elements in between. On the other hand, when an element is referred to as being "directly coupled" or "directly connected" to another element, it should be understood that there are no other elements in between.

[0025] In this application, the terms "comprise" or "have" and the like are intended to specify the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but are to be understood as not precluding the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0026] FIG. 1 is a diagram illustrating a battery system according to an embodiment, and FIG. 2 is an example diagram illustrating a second wake-up time according to an embodiment.

[0027] Referring to FIG. 1, a battery system 1 includes a battery 10, a relay 20, a current sensor 30, and a battery management system (hereinafter, referred to as BMS) 40.

[0028] A battery 10 includes a plurality of battery cells connected in series / parallel and can supply necessary power to an external device. In FIG. 1, the battery 10 includes a plurality of battery cells Cell1-Celln connected in series and is connected between two output terminals OUT1 and OUT2 of a battery system 1. A relay 20 is connected between the positive terminal of the battery system 1 and the output terminal OUT1, and a current sensor 30 is connected between the negative terminal of the battery system 1 and the output terminal OUT2. The configurations and the connections between the configurations shown in FIG. 1 are merely examples, and the present invention is not limited thereto.

[0029] The relay 20 controls the electrical connection between the battery system 1 and an external device. When the relay 20 is turned on, the battery system 1 and the external device are electrically connected to each other, allowing charging or discharging. When the relay 20 is turned off, the battery system 1 and the external device are electrically disconnected. The external device may be a load or a charger.

[0030] The current sensor 30 is connected in series to the current path between the battery 10 and the external device. The current sensor 30 can measure the current flowing through the battery 10, i.e., the charging current and discharging current, and transmit the measurement result to the BMS 40.

[0031] The BMS 40 includes a cell balancing circuit 41 , a monitoring unit 43 , a power supply unit 45 , and a control unit 47 .

[0032] The cell balancing circuit 41 includes multiple switches SW1-SWn and multiple resistors R1-Rn. Each of the multiple switches SW1-SWn performs a switching operation in response to a corresponding one of multiple switching signals supplied from the monitoring unit 43. For each of the multiple battery cells Cell1-Celln, a corresponding switch SWi and resistor Ri are connected in series between the positive and negative electrodes of the corresponding cell Cell1. When the switch SWi is turned on, a discharge path is formed between the corresponding cell Cell1, the switch SWi, and the resistor Ri, and the corresponding cell Cell1 is discharged. Here, i is a natural number from 1 to n.

[0033] The monitoring unit 43 is electrically connected to the positive and negative electrodes of each of the plurality of battery cells Cell1-Celln and measures the cell voltage. The current (hereinafter referred to as battery current) value measured by the current sensor 30 can be transmitted to the monitoring unit 43. The monitoring unit 43 transmits information regarding the measured cell voltage and battery current to the control unit 47. Specifically, the monitoring unit 43 measures the cell voltage of each of the plurality of battery cells Cell1-Celln at predetermined intervals during a rest period in which no charging or discharging occurs, and transmits the measurement results to the control unit 47. For example, the monitoring unit 43 may include a Battery Monitoring Integrated Circuit (BMIC) or an Application Specific Integrated Circuit (ASIC).

[0034] The monitoring unit 43 may communicate with the control unit 47 using, but not limited to, a CAN communication (C) method, and may communicate with the control unit 47 using various communication methods. The monitoring unit 43 may discharge a cell targeted for cell balancing among the plurality of battery cells Cell1-Celln through the cell balancing circuit 41 in response to a cell balancing control signal transmitted from the control unit 47. For example, the monitoring unit 43 may generate a plurality of switching signals in response to the cell balancing control signal from the control unit 47. Each of the switching signals may control the switching operation of a corresponding switch SWi. When an on-level switching signal SC[i] is supplied to a corresponding switch SWi, the switch SWi is turned on, thereby discharging the corresponding cell Celli.

[0035] The power supply unit 45 may supply a driving voltage P (Power) to the control unit 47. According to one embodiment, the power supply unit 45 may include a timer that counts a wake-up time of the control unit 47. When the count result of the timer reaches the wake-up time, the power supply unit 45 may supply the driving voltage P to the control unit 47. For example, the power supply unit 45 may include a system basis chip (SBC) that safely manages the power supplied to the BMS 40.

[0036] The power supply unit 45 may communicate with the control unit 47 using, but not limited to, an SPI (Serial P) communication method, and may communicate with the control unit 47 using various communication methods. When the power supply unit 45 receives information about the first wake-up time A and the sleep time point of the control unit 47 from the control unit 47, the power supply unit 45 may set the first wake-up time in a timer. The power supply unit 45 may control the timer so that the first wake-up time is counted in synchronization with the time point at which the control unit 47 goes to sleep.

[0037] The timer performs counting while the monitoring unit 43, the control unit 47, and the power supply unit 45 are in sleep mode. Thereafter, the timer wakes up the power supply unit 45 when the counting result reaches the first wake-up time A. According to one embodiment, the timer may only have a counting function, without having a function for measuring real-time time.

[0038] The timer according to an embodiment may count from a count start point to a preset time, and may not include a function for checking the corresponding times of the count start point and the count end point. In addition, the timer may stop counting the wake-up time in synchronization with the time when the control unit 47 wakes up, and start counting the wake-up time in synchronization with the time when the control unit 47 goes to sleep.

[0039] 1, the power supply unit 45 generates a driving voltage P using power supplied from the auxiliary battery 10 and supplies the generated driving voltage P to the control unit 47 to wake up the control unit 47. Thereafter, the control unit 47 transmits the driving voltage P to the monitoring unit 43 to wake up the monitoring unit 43. Although it has been described that the power supply unit 45, the control unit 47, and the monitoring unit 43 are woken up in sequence by a timer, this is not limiting. When the counting result reaches a first wake-up time, the power supply unit 45 wakes up, and thereafter the control unit 47 and the monitoring unit 43 can be woken up simultaneously by the driving voltage P supplied by the power supply unit 45.

[0040] 1, the power supply unit 45 is illustrated as being included in the BMS 40, but is not limited to this. For example, the power supply unit 45 may be configured as a separate device that is distinct from the BMS 40 and / or the battery system 1. Also, in FIG. 1, the auxiliary battery 10 may be a battery provided by a system (e.g., an automobile) in which the battery system 1 is installed, but is not limited to this. The auxiliary battery 10 may include various types of power sources that supply power to the power supply unit 45.

[0041] The control unit 47 determines whether a predetermined sleep mode entry condition is satisfied, and enters the sleep mode when the sleep mode entry condition is satisfied. The control unit 47 may wake up in the sleep mode at predetermined wake-up intervals and determine whether to perform cell balancing. For example, the control unit 47 may determine whether cell balancing is necessary based on the cell voltage and battery current received from the monitoring unit 43, and if cell balancing is necessary as a result of the determination, may transmit a cell balancing control signal to the monitoring unit 43. For example, the control unit 47 may include an MCU (Micro Controller Unit).

[0042] The conditions for entering the sleep mode may include, but are not limited to, when a vehicle equipped with the battery system 1 is parked for a long period of time, and may include various other conditions. In the sleep mode, the BMS 40 is turned off most of the time, wakes up at predetermined wake-up intervals, and then turns on for a predetermined time to perform cell balancing.

[0043] According to one embodiment, when the driving voltage P is supplied, the control unit 47 wakes up, determines whether to perform cell balancing on a plurality of battery cells, and calculates a second wake-up time B=t-α by subtracting the time α taken to determine whether to perform cell balancing from the wake-up period t. The control unit 47 may set the second wake-up time B to the time counted by a timer.

[0044] For example, suppose the wake-up period t is set to one hour. The control unit 47 must wake up every hour to determine whether or not to perform cell balancing. However, the timer suspends counting in synchronization with the time when the control unit 47 wakes up and resumes counting in synchronization with the time when the control unit 47 goes to sleep, so the time may be delayed (t+α) by the time α it takes for the control unit 47 to determine whether or not to perform cell balancing. That is, if the control unit 47 wakes up every Nth period (T N ) and then wakes up in the N+1th period (T N+1 ) may cause a problem that the time interval until the device wakes up becomes a time (1+α) that is further delayed than the 1 hour corresponding to the period (T).

[0045] 2, to solve the above problem, the control unit 47 can calculate a second wake-up time (B=t-α) by subtracting the time α taken to determine whether to perform cell balancing from the wake-up period t. The control unit 47 can set the second wake-up time B as the time counted by a timer. For reference, in FIG. 2, the first wake-up time A, which is counted in synchronization with the time T1 at which the control unit 47 goes to sleep after the sleep mode entry condition is satisfied, can correspond to the wake-up period t.

[0046] Furthermore, the control unit 47 can calculate the second wakeup time (B=t-α-β) by subtracting the time α required to determine whether or not to perform cell balancing and the cell balancing execution time β from the wakeup period t. For example, if the wakeup period t is 60 minutes, the time α required to determine whether or not to perform cell balancing is 3 minutes, and the time β required from the time cell balancing is executed to the time it is completed is 7 minutes, the control unit 47 can calculate the second wakeup time B as 50 minutes and set the timer to count down to 50 minutes.

[0047] Hereinafter, a cell balancing control method and a battery system that provides the method will be described in detail with reference to FIGS.

[0048] FIG. 3 is a flowchart illustrating a cell balancing control method according to an embodiment.

[0049] In FIG. 3, first, the BMS 40 determines whether a predetermined sleep mode entry condition is met and sets a first wake-up time A, which is the time counted by a timer of the power supply unit 45 (S101, S102).

[0050] 2, the first wake-up time A may be a time counted in synchronization with time T1 when the sleep mode entry condition is satisfied and the BMS 40 goes to sleep. In this case, the sleep mode entry condition may include various situations in which the battery 10 enters a dormant state in which it is not charged or discharged for a predetermined period of time, and the BMS 40 also enters a sleep mode in which it is turned off for a predetermined period of time. For example, the sleep mode entry condition may include a situation in which the automobile equipped with the battery system 1 is parked for a long period of time.

[0051] Next, the BMS 40 controls the power supply unit 45 so that the first wake-up time A is set in the timer, and then enters the sleep mode (S103).

[0052] The power supply unit 45 may control the timer to count the first wake-up time A in synchronization with the time T1 when the BMS 40 goes to sleep. Thereafter, the power supply unit 45 may be turned off and remain in the sleep mode until the first wake-up time A is fully counted. That is, the power supply unit 45 may also remain in the sleep mode during the period when the BMS 40 is maintained in the sleep mode.

[0053] Next, when the count result of the timer reaches the first wake-up time A, the BMS 40 receives a drive voltage from the power supply unit 45 and wakes up (S104, S105, S106).

[0054] When the counting result of the timer reaches the first wake-up time A, the power supply unit 45 is woken up by the timer (S104, S105). Thereafter, the power supply unit 45 generates a driving voltage P using the power supplied from the auxiliary battery 10 and supplies the generated driving voltage P to the BMS 40 to wake up the BMS 40 (S106). For example, referring to FIG. 2, the power supply unit 45 can control the timer to stop counting the first wake-up time A in synchronization with time T2 when the BMS 40 wakes up.

[0055] Next, the BMS 40 determines whether or not to perform cell balancing on the plurality of battery cells (S107).

[0056] Referring to FIG. 1, after waking up, the monitoring unit 43 measures the cell voltages of each of the plurality of battery cells Cell1-Celln. The monitoring unit 43 then transmits information related to the measured cell voltage values and the battery current value received from the current sensor 30 to the control unit 47. The control unit 47 can detect battery cells that require cell balancing using various conventional methods based on at least one of the received cell voltage values and battery current values. If at least one battery cell that requires cell balancing is present among the plurality of battery cells, the control unit 47 determines that cell balancing is required (S107, Yes). If no battery cell that requires cell balancing is present, the control unit 47 determines that cell balancing is not required (S107, No).

[0057] Next, if the determination result indicates that cell balancing is necessary (Yes in S107), the BMS 40 performs cell balancing (S108).

[0058] 1, the control unit 47 may transmit a cell balancing control signal to the monitoring unit 43 so that cell balancing may be performed on battery cells that require cell balancing. Then, the monitoring unit 43 may discharge the cells that are the subject of cell balancing via the cell balancing circuit 41.

[0059] Next, the BMS 40 determines whether or not cell balancing is complete (S109), and when cell balancing is complete (S109, Yes), determines whether or not a sleep mode cancellation condition is met (S110).

[0060] The sleep mode release condition may include various situations in which the battery 10 enters a state in which it must be charged or discharged and the BMS 40 must also be turned on. For example, the sleep mode release condition may include a situation in which the automobile in which the battery system 1 is installed is switched from a parked state to a driving state.

[0061] Next, if the sleep mode is maintained because the sleep mode release conditions are not met (S110, No), BMS40 calculates a second wakeup time B by subtracting the time α taken to determine whether or not to perform cell balancing from the wakeup period t, and sets the second wakeup time B as the time counted by the timer (S111).

[0062] 2, for example, after a first wake-up time A, which is a time counted in synchronization with time T1 when the BMS 40 goes to sleep after the sleep mode entry condition is satisfied, a second wake-up time B can be set for each period. That is, if there is a time α taken to determine whether cell balancing should be performed, the BMS 40 can calculate the second wake-up time B and transmit information about the second wake-up time B to the power supply unit 45.

[0063] Next, if the sleep mode release condition is met and the sleep mode is released (S110, Yes), the BMS 40 maintains the turned-on state without entering the sleep mode (S112).

[0064] Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited to these examples, and various modifications and improvements made by those skilled in the art to which the present invention pertains also fall within the scope of the present invention.

Claims

1. a battery including a plurality of battery cells; a BMS (Battery Management System) that determines whether a predetermined sleep mode entry condition is satisfied, enters a sleep mode when the sleep mode entry condition is satisfied, wakes up in the sleep mode at predetermined wake-up intervals, and determines whether to perform cell balancing; a power supply unit that includes a timer that counts a first wake-up time in synchronization with a time point when the BMS goes to sleep, and that supplies a driving voltage to the BMS when the counting result reaches the first wake-up time. The BMS includes: When the driving voltage is supplied, the battery system wakes up and determines whether to perform cell balancing on the plurality of battery cells, calculates a second wake-up time so that the wake-up period is constant, and sets the second wake-up time to a time counted by the timer.

2. The BMS includes:

2. The battery system of claim 1, wherein, when the driving voltage is supplied, the battery system wakes up to determine whether cell balancing is to be performed on the plurality of battery cells, calculates a second wake-up time by subtracting a time taken to determine whether cell balancing is to be performed from the wake-up period, and sets the second wake-up time to a time counted by the timer.

3. The timer Stopping counting the first wake-up time in synchronization with the time when the BMS wakes up; The battery system according to claim 2 , wherein the second wake-up time is counted in synchronization with a time point when the BMS goes to sleep.

4. The BMS includes: If the result of the determination indicates that cell balancing needs to be performed, the cell balancing is performed and the second wake-up time is set; The battery system of claim 3 , wherein the battery system goes to sleep when the cell balancing is complete.

5. The BMS includes: The battery system according to claim 3 or 4, wherein if the determination result shows that cell balancing does not need to be performed, the battery system goes to sleep after setting the second wake-up time.

6. The BMS, 2. The battery system of claim 1, wherein, when the driving voltage is supplied, the battery system wakes up to determine whether cell balancing is to be performed on the plurality of battery cells, calculates a second wake-up time by subtracting a time taken to determine whether cell balancing is to be performed and a time taken to perform the cell balancing from the wake-up period, and sets the second wake-up time to a time counted by the timer.

7. A cell balancing control method in which a BMS wakes up at every predetermined wake-up period to control cell balancing, determining whether a predetermined sleep mode entry condition is met; If the sleep mode entry condition is met as a result of the determination, setting a first wake-up time, which is a time counted by a timer of a power supply unit; setting the first wake-up time in the timer and then going to sleep; receiving a driving voltage from the power supply unit and waking up when the count result of the timer reaches the first wake-up time; determining whether to perform cell balancing on the plurality of battery cells; a step of calculating a second wake-up time so that the wake-up period is constant, and setting the second wake-up time to a time counted by the timer, after the step of determining whether to perform the cell balancing.

8. The sleeping step includes: The cell balancing control method according to claim 7, wherein the first wake-up time is counted in synchronization with a time point when the BMS goes to sleep.

9. After determining whether to perform cell balancing, calculating a second wake-up time by subtracting the time taken to determine whether cell balancing should be performed from the wake-up period; The cell balancing control method of claim 7 , further comprising: setting the second wake-up time to a time counted by the timer.

10. After setting the second wake-up time to the time counted by the timer, Proceed to the sleep stage, The sleeping step includes: The cell balancing control method according to claim 9, wherein the second wake-up time is counted in synchronization with a time point when the BMS goes to sleep.

11. The waking up step includes: The cell balancing control method according to claim 7 , wherein when the BMS wakes up, counting of the first wake-up time is stopped.

12. After the step of determining whether to perform cell balancing, calculating a second wake-up time by subtracting from the wake-up period the time required to determine whether or not cell balancing should be performed and the time required to perform the cell balancing; The cell balancing control method of claim 7 , further comprising: setting the second wake-up time to a time counted by the timer.

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