Battery system and welding prevention method applied to the battery system

Abstract

A battery system, comprising: a battery including a plurality of battery cells; a first main relay connected between one pole of the battery and a first output terminal; a pre-charge relay connected in parallel with the first main relay; a second main relay connected between the other pole of the battery and a second output terminal; and a battery management system that controls charging and discharging of the battery and controls the first main relay, the pre-charge relay, and the second main relay, wherein the first main relay, the pre-charge relay, the second main relay, and the battery management system receive a power supply voltage from an external lead-acid battery, and the battery management system disconnects the first main relay, the pre-charge relay, and the second main relay when the power supply voltage is equal to or less than a predetermined reference voltage, closes the pre-charge relay and the second main relay for pre-charging when the power supply voltage is higher than the reference voltage, and closes the first main relay after the pre-charging is completed.

Description

Technical Field

[0001] The present disclosure relates to a method for preventing welding and a battery system applying the method for preventing welding. Background Art

[0002] When starting at low temperature, the voltage of a lead-acid battery drops significantly instantaneously more than normal. In this case, the voltage supplied to a battery management system (BMS) board is at a voltage level at which the BMS board can operate, but the voltage supplied to a relay may not reach the voltage level at which the relay can operate. Then, a phenomenon of relay disconnection may occur. Since the BMS board can operate, the BMS board attempts to close the relay. In this case, when the low-temperature start is completed and the voltage of the lead-acid battery returns to normal, the main relay closes without pre-charging, and the main relay may be welded. Summary of the Invention

[0003] Technical Problem

[0004] A method for preventing welding of a relay and a battery system applying the method are provided.

[0005] Technical Solution

[0006] The battery system according to the present invention includes: a battery including a plurality of battery cells; a first main relay connected between one electrode of the battery and a first output terminal; a pre-charge relay connected in parallel to the first main relay; a second main relay connected between the other electrode of the battery and a second output terminal; and a battery management system controlling charging and discharging of the battery and controlling the first main relay, the pre-charge relay, and the second main relay, wherein the first main relay, the pre-charge relay, the second main relay, and the battery management system receive a power supply voltage from an external lead-acid battery, when the power supply voltage is a predetermined reference voltage or lower, the battery management system disconnects the first main relay, the pre-charge relay, and the second main relay, when the power supply voltage is higher than the reference voltage, closes the pre-charge relay and the second main relay to perform pre-charging, and closes the first main relay after the pre-charging is completed.

[0007] When the power supply voltage is the reference voltage or less, the battery management system may disconnect the first main relay, the pre-charge relay, and the second main relay, and then supply a control voltage for closing the pre-charge relay and the second main relay, and when the power supply voltage is higher than the reference voltage, the pre-charge relay and the second main relay close.

[0008] The battery management system may disconnect the pre-charge relay after closing the first main relay after the pre-charging is completed.

[0009] The battery system may further include: a comparator that detects whether a power supply voltage is lower than a reference voltage; and an SR latch that includes a set terminal for inputting a comparison signal output from the comparator, a reset terminal for inputting a reset signal, and an output terminal for outputting a detection signal determined according to the comparison signal and the reset signal.

[0010] When the detection signal becomes a level corresponding to logic 1 through the comparison signal, the battery management system may detect that the power supply voltage is less than or equal to the reference voltage.

[0011] After pre-charging is completed, the battery management system may change the reset signal to a level corresponding to logic 1.

[0012] The battery management system may confirm that the detection signal becomes a level corresponding to logic 0 through the reset signal at a level corresponding to logic 1, and then change the reset signal to a level corresponding to logic 0.

[0013] A method for preventing welding applied to a battery system according to the present invention, the battery system including a battery for providing a current path for the battery, a first main relay, a second main relay, a pre-charging relay, and an SR latch, the method for preventing welding including: determining whether a power supply voltage is less than or equal to a predetermined reference voltage by using a detection signal that is an output of the SR latch; according to the determination result, when the power supply voltage is less than or equal to the reference voltage, disconnecting the first main relay, the second main relay, and the pre-charging relay; after the disconnection, when the power supply voltage is higher than the reference voltage, closing the pre-charging relay and the second main relay to perform pre-charging; closing the first main relay after the pre-charging is completed; and disconnecting the pre-charging relay after the first main relay is closed, wherein the power supply voltage is a voltage supplied to the first main relay, the second main relay, and the pre-charging relay, and the pre-charging relay is connected in parallel with the first main relay.

[0014] The method for preventing welding of the battery system may further include the step of: after disconnecting the pre-charging relay, supplying a reset signal at a level corresponding to logic 1 to the reset terminal of the SR latch to reset the detection signal.

[0015] The method for preventing welding of the battery system may further include the steps of: determining whether the detection signal is reset; and changing the reset signal for resetting the detection signal to a level corresponding to logic 0.

[0016] The reference voltage may be set to a level for detecting that the power supply voltage is at a level capable of driving the battery management system, and is a level low enough to operate the first main relay, the second main relay, and the pre-charging relay.

[0017] Advantageous Effects

[0018] A method for preventing welding of a relay and a battery system applying the method are provided. Description of the Drawings

[0019] Figure 1 FIG. is a diagram showing a battery system according to an embodiment.

[0020] Figure 2 FIG. is a flowchart showing a welding prevention method according to an embodiment. Detailed Description of the Embodiments

[0021] Hereinafter, embodiments disclosed in the present specification will be described in detail with reference to the drawings. In the present specification, the same or similar components will be denoted by the same or similar reference numerals, and overlapping descriptions thereof will be omitted. The terms "module" and "unit" for components used in the following description are only for easy explanation. Therefore, these terms themselves do not have a meaning or function to distinguish them from each other. In addition, when determining that a detailed description of a well-known technology associated with the present invention may obscure the gist of the present invention when describing embodiments of the present specification, the detailed description thereof will be omitted. In addition, the drawings are provided only to allow easy understanding of the embodiments disclosed in the present specification, and should not be construed as limiting the spirit disclosed in the present specification, and it should be understood that the present invention includes all modifications, equivalents, and substitutions without departing from the scope and spirit of the present invention.

[0022] Terms including ordinal numbers such as first, second, etc. will only be used to describe various components and will not be construed as limiting these components. These terms are only used to distinguish one component from other components.

[0023] It should be understood that when a component is referred to as being "connected" or "coupled" to another component, the component can be directly connected or coupled to the other component, or can be connected or coupled to the other component with other components intervening therebetween. On the other hand, it should be understood that when a component is referred to as being "directly connected or coupled" to another component, the component can be connected or coupled to the other component without other components intervening therebetween.

[0024] It will be further understood that the terms "comprising" or "having" used in the present specification specify the presence of the described features, numbers, steps, operations, components, parts, or combinations thereof, but do not exclude the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0025] Figure 1 FIG. is a diagram showing a battery system according to an embodiment.

[0026] Figure 1The battery system 1 can be a power source installed on a vehicle and supplying power to an electrical load 3 (e.g., a motor) for driving the vehicle. Additionally, a charger is connected to the output terminals (P+, P-) instead of the electrical load 3, and the battery system 1 can be charged with the power supplied from the charger.

[0027] The battery system 1 can include a battery 10, a battery management system (BMS) 20, a first main relay 30, a second main relay 40, a pre-charge relay 50, a pre-charge resistor 60, a current sensor 70, a link capacitor 80, a fuse 90, and a welding prevention unit 100.

[0028] The lead-acid battery 2 supplies a power supply voltage VS to the board 4, the first main relay 30, the second main relay 40, and the pre-charge relay 50. The lead-acid battery 2 can supply the power supply voltage VS to the electrical load of the vehicle. On the board 4, the BMS 20 and the welding prevention unit 100, etc. can be positioned. Additional components can be further positioned on the Figure 1 board 4 shown.

[0029] As Figure 1 shown, the battery 10 includes a plurality of battery cells 11 to 15 connected in series. In Figure 1 it, as an example, the battery 10 is illustrated as including five battery cells 11 to 15, but the present invention is not limited thereto.

[0030] The fuse 90 is connected between the positive electrode of the battery 10 and the output terminal (P+), and can disconnect when the temperature reaches a threshold due to excessive current.

[0031] The current sensor 70 can sense the current flowing through the battery 10 (hereinafter referred to as the battery current), and the current sensor 70 can send a signal indicating the sensed current to the BMS 20.

[0032] The BMS 20 is connected to the plurality of battery cells 11 to 15 to measure the cell voltages of the plurality of battery cells 11 to 15, receive information such as the battery current and temperature of the battery 10, control the charge and discharge currents of the battery 10 based on the cell voltages, battery current, temperature, etc. of the plurality of battery cells 11 to 15, and can control the cell balancing operation of the plurality of battery cells 11 to 15. The power supply voltage VS required for the operation of the BMS 20 can be supplied from the lead-acid battery 2.

[0033] The BMS 20 can control the operations of the first main relay 30, the second main relay 40, and the pre-charge relay 50 based on the detection signal QS input from the welding prevention unit 100. For example, when receiving the detection signal QS from the welding prevention unit 100 indicating that the power supply voltage VS has dropped below the predetermined reference voltage VR, after all the relays 30 to 50 are opened, the pre-charge relay 50 and the second main relay 40 are closed, allowing the pre-charge operation to proceed for a predetermined period. Subsequently, the BMS 20 closes the first main relay 30 and opens the pre-charge relay 50. After that, the BMS 20 can reset the welding prevention unit 100 to reset the detection signal QS.

[0034] The first main relay 30, the second main relay 40, and the pre-charge relay 50 form a current path such that the charging current or discharging current for the battery 10 can flow. The pre-charge relay 50 is connected in parallel to the first main relay 30.

[0035] The first main relay 30 includes a switch 31, an inductor 32, and a control switch 33. One terminal of the switch 31 is connected to the positive electrode of the battery 10, the other terminal of the switch 31 is connected to the output terminal (P+), and the switch 31 can be closed when current flows through the inductor 32 and can be opened if current does not flow through the inductor 32. One terminal of the inductor 32 is grounded, and the other terminal of the inductor 32 is connected to one terminal of the control switch 33. The power supply voltage VS is supplied to the other terminal of the control switch 33, and the control switch 33 is switched by the control voltage VG1 supplied from the BMS 20. For example, when the control voltage VG1 is at the conducting level, the control switch 33 conducts, and when the control voltage VG1 is at the cutoff level, the control switch 33 cuts off.

[0036] The second main relay 40 includes a switch 41, an inductor 42, and a control switch 43. One terminal of the switch 41 is connected to the negative electrode of the battery 10, the other terminal of the switch 41 is connected to the output terminal (P-), and the switch 41 can be closed when current flows to the inductor 42 and can be opened when current does not flow through the inductor 42. One terminal of the inductor 42 is grounded, and the other terminal of the inductor 42 is connected to one terminal of the control switch 43. The power supply voltage VS is supplied to the other terminal of the control switch 43, and the control switch 43 is switched by the control voltage VG2 supplied from the BMS 20. For example, when the control voltage VG2 is at the conducting level, the control switch 43 conducts, and when the control voltage VG2 is at the cutoff level, the control switch 43 cuts off.

[0037] The pre-charge relay 50 is connected in parallel with the pre-charge resistor 60 to the first main relay 30, and includes a switch 51, an inductor 52, and a control switch 53. One terminal of the switch 51 is connected to the positive electrode of the battery 10, the other terminal of the switch 51 is connected to one terminal of the pre-charge resistor 60, and the switch 51 can be closed when current flows through the inductor 52 and can be opened if current does not flow through the inductor 52. One terminal of the inductor 52 is grounded, and the other terminal of the inductor 52 is connected to one terminal of the control switch 53. The power supply voltage VS is supplied to the other terminal of the control switch 53, and the control switch 53 is switched by the control voltage VG3 supplied from the BMS 20. For example, when the control voltage VG3 is at the conducting level, the control switch 53 conducts, and when the control voltage VG3 is at the non-conducting level, the control switch 53 does not conduct.

[0038] The other terminal of the pre-charge resistor 60 is connected to the output terminal (P+). The link capacitor 80 is connected between the output terminal (P+) and the output terminal (P-), thereby filtering the noise components of the output voltage supplied from the battery 10 to the electrical load 3 or reducing the rapid change of the output voltage.

[0039] The welding prevention unit 100 includes a comparator 101 and an SR latch 102.

[0040] If the voltage of the input terminal (+) is higher than the voltage of the input terminal (-), the comparator 101 can output a high-level comparison signal CM indicating logic "1", and if the voltage of the input terminal (+) is lower than the voltage of the input terminal (-), it outputs a low-level comparison signal CM indicating logic "0". The power supply voltage VS can be input to the input terminal (-) of the comparator 101, and the reference voltage VR can be input to the input terminal (+) of the comparator 101. The power supply voltage VS is at a level that can drive the BMS 20, but the reference voltage VR can be set to a level at which it is detected to be low enough to operate the first main relay 30, the second main relay 40, and the pre-charge relay 50. For example, the power supply voltage of a vehicle equipped with the battery system 1 is 13V during normal startup, and during low-temperature startup, the power supply voltage VS input to the board 4 can drop to 5.5V within several tens of milliseconds (ms) and then rise to 13V. At this time, 5.5V is the voltage level that can operate the BMS 20, but it is not sufficient as the operating voltage of the first main relay 30, the second main relay 40, and the pre-charge relay 50. Therefore, the reference voltage VR can be set to 5.5V.

[0041] The SR latch 102 determines the detection signal QS of the output terminal Q based on the signal input to the set terminal S, and resets the detection signal QS of the output terminal Q based on the signal input to the reset terminal R. For example, when the input signal of the set terminal S is at a high level corresponding to logic "1", the detection signal QS becomes high level, and when the input signal of the reset terminal R is at a high level corresponding to logic "1", the detection signal QS becomes low level. When the inputs of the set terminal S and the reset terminal R are at a low level corresponding to logic "0", the detection signal QS is maintained. If the comparison signal CM of the output of the comparator 101 is at a high level, the SR latch 102 generates a high-level detection signal QS, and if the input of the reset terminal R is at a high level, the detection signal QS can be set to a low level.

[0042] Hereinafter, refer to Figure 2 Describe the welding prevention method according to the embodiment.

[0043] Figure 2 is a flowchart showing the welding prevention method according to the embodiment.

[0044] First, the BMS 20 determines whether the detection signal QS is at a high level indicating logic "1" (S1). When the detection signal QS is at a low level indicating logic "0" instead of "1", step (S1) is continuously repeated. The detection signal QS indicating logic 1 means that the power supply voltage VS is less than or equal to the reference voltage VR.

[0045] When the detection signal QS is "1" as a result of the determination in step (S1), the BMS 20 disconnects all the relays (S2). That is, regardless of the previous state, the first main relay 30, the second main relay 40, and the pre-charge relay 50 are all disconnected.

[0046] Next, the BMS 20 outputs a control voltage VG2 and a control voltage VG3 for closing the pre-charge relay 50 and the second main relay 40 to the pre-charge relay 50 and the second main relay 40. If the power supply voltage VS is in a normal state higher than the reference voltage VR, the pre-charge relay 50 and the second main relay 40 are closed according to the control voltages VG2 and VG3 of the conduction level (S3). Then, pre-charging is performed by the current flowing through the battery 10, the pre-charge relay 50, the pre-charge resistor 60, and the second main relay 40. The link capacitor 80 is charged by the pre-charge current.

[0047] If the power supply voltage VS is less than the reference voltage VR, the pre-charge relay 50 and the second main relay 40 are not closed because, although the control voltages VG2 and VG3 are at the on level, the power supply voltage VS is also low. Thereafter, when the power supply voltage VS exceeds the reference voltage VR, the pre-charge relay 50 and the second main relay 40 are closed.

[0048] When the link voltage (which is the voltage across the two terminals of the link capacitor 80) reaches a predetermined ratio compared to the voltage across the two terminals of the pre-charged battery 10, it can be determined that the pre-charging is complete. The BMS 20 detects the link voltage to determine whether the pre-charging is complete (S4). The predetermined ratio can be set in the range of 95% to 97%. As a result of the determination in step S4, if the link voltage does not reach the predetermined ratio compared to the voltage across the two terminals of the battery 10, the pre-charging continues and step (S4) is continuously repeated.

[0049] As a result of step (S4), if the pre-charging is complete, the BMS 20 closes the first main relay 30 and opens the pre-charge relay 50 (S5). There may be a predetermined time delay between the closing timing of the first main relay 30 and the opening timing of the pre-charge relay 50.

[0050] Subsequently, the BMS 20 generates a reset signal RS with a high level corresponding to logic "1" (S6). Then, the high level is input to the reset terminal R of the SR latch 102, and the detection signal QS can become a low level corresponding to logic "0". That is, the detection signal QS is reset to the initial state.

[0051] The BMS 20 determines whether the detection signal QS is "0" (S7). If the detection signal QS is not 0 as a result of the determination in step (S7), the BMS 20 holds the reset signal RS at 1.

[0052] As a result of the determination in step S7, if the detection signal QS is 0, the BMS 20 generates a reset signal RS with a low level corresponding to logic "0" (S8).

[0053] Conventional techniques use capacitors to prevent the instantaneous voltage drop of lead-acid batteries. However, conventional techniques do not consider the case where the voltage drop of lead-acid batteries occurs within dozens of milliseconds. To prevent the voltage drop within dozens of milliseconds, multiple capacitors are required, which may increase the board size. In addition, the method of stopping the relay operation by detecting the voltage drop of lead-acid batteries using conventional software has problems in terms of operation speed. In other words, due to the time required to execute the software, the voltage drop may not be detected.

[0054] Embodiments of the present invention can detect a voltage drop of a lead-acid battery by using hardware. A battery system according to an embodiment of the present invention can detect the occurrence of a voltage drop of a lead-acid battery by using a comparator that compares the voltage of the lead-acid battery and an SR latch that operates according to the output of the comparator. Since the voltage drop is detected by hardware, an instantaneous voltage drop that may be missed according to the software operation speed can be detected, and welding of a relay can be prevented.

[0055] Although the present invention has been described in connection with what are presently considered to be practical embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. On the contrary, the present invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

[0056] Cross - reference to related applications

[0057] This application claims the priority and benefit of Korean Patent Application No. 10-2020-0074977, filed on June 19, 2020, with the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference.

Claims

1. A battery system, the battery system comprising: A battery, the battery including a plurality of battery cells; A first main relay, the first main relay being connected between one electrode of the battery and a first output terminal; A pre-charge relay, the pre-charge relay being connected in parallel to the first main relay; A second main relay, the second main relay being connected between the other electrode of the battery and a second output terminal; And A battery management system, the battery management system controlling charging and discharging of the battery, and controlling the first main relay, the pre-charge relay, and the second main relay, Wherein, the first main relay, the pre-charge relay, the second main relay, and the battery management system receive a power supply voltage from an external lead-acid battery, and The battery management system: disconnects the first main relay, the pre-charge relay, and the second main relay when the power supply voltage is a predetermined reference voltage or lower, closes the pre-charge relay and the second main relay to perform pre-charging when the power supply voltage is higher than the reference voltage, and closes the first main relay after the pre-charging is completed.

2. The battery system according to claim 1, wherein, The battery management system disconnects the first main relay, the pre-charge relay, and the second main relay when the power supply voltage is the reference voltage or less, and then supplies a control voltage for closing the pre-charge relay and the second main relay, and when the power supply voltage is higher than the reference voltage, the pre-charge relay and the second main relay are closed.

3. The battery system according to claim 1, wherein, The battery management system disconnects the pre-charge relay after closing the first main relay after the pre-charging is completed.

4. The battery system according to claim 1, the battery system further comprising: A comparator, the comparator being configured to detect whether the power supply voltage is equal to or lower than the reference voltage; And An SR latch, the SR latch including a set terminal for inputting a comparison signal output from the comparator, a reset terminal for inputting a reset signal, and an output terminal for outputting a detection signal determined according to the comparison signal and the reset signal.

5. The battery system according to claim 4, wherein, When the detection signal becomes a level corresponding to logic 1 through the comparison signal, the battery management system detects that the power supply voltage is less than or equal to the reference voltage.

6. The battery system according to claim 5, wherein, The battery management system changes the reset signal to a level corresponding to logic 1 after the pre-charging is completed.

7. The battery system according to claim 6, wherein, The battery management system confirms that the detection signal becomes a level corresponding to logic 0 through the reset signal of a level corresponding to logic 1, and then changes the reset signal to a level corresponding to logic 0.

8. The battery system according to claim 1, wherein, The reference voltage is set to a level for detecting that the power supply voltage is at a level capable of driving the battery management system, and is a level low enough to operate the first main relay, the second main relay, and the pre-charge relay.

9. A method for preventing welding in a battery system, the battery system including a battery, a first main relay, a second main relay, a pre-charge relay, and a battery management system, wherein, The first main relay, the pre-charge relay, the second main relay, and the battery management system receive a power supply voltage from an external lead-acid battery, and the welding prevention method includes the following steps: Determine whether the power supply voltage is less than or equal to a predetermined reference voltage; According to the determination result, when the power supply voltage is less than or equal to the reference voltage, disconnect the first main relay, the second main relay, and the pre-charge relay; After the disconnection, when the power supply voltage is higher than the reference voltage, close the pre-charge relay and the second main relay to perform pre-charging; Close the first main relay after the pre-charging is completed; and Disconnect the pre-charge relay after closing the first main relay, wherein the power supply voltage is the voltage supplied to the first main relay, the second main relay, and the pre-charge relay, and the pre-charge relay is connected in parallel with the first main relay.

10. The welding prevention method according to claim 9, Among them, The battery system includes a comparator and an SR latch. The comparator detects whether the power supply voltage is equal to or lower than the reference voltage. The SR latch includes a set terminal for inputting a comparison signal output from the comparator, a reset terminal for inputting a reset signal, and an output terminal for outputting a detection signal determined according to the comparison signal and the reset signal. The welding prevention method further includes the following steps: After disconnecting the pre-charge relay, supply a reset signal at a level corresponding to logic 1 to the reset terminal of the SR latch for inputting the reset signal to reset the detection signal.

11. The welding prevention method according to claim 10, the welding prevention method further includes the following steps: Determine whether the detection signal is reset; and Reset the detection signal and change the reset signal to a level corresponding to logic 0.

12. The welding prevention method according to claim 9, wherein, The reference voltage is set to a level for detecting that the power supply voltage is at a level capable of driving the battery management system, and is a level low enough to operate the first main relay, the second main relay, and the pre-charge relay.

Images