WO2019245215A1 - Current measuring device, current measuring method, and battery pack comprising current measuring device - Google Patents

Abstract

Provided are a current measuring device, a current measuring method, and a battery pack comprising the current measuring device. The current measuring device comprises: a switching circuit installed in a charge/discharge path for a battery; a current measuring unit including a shunt resistor element disposed in the charge/discharge path and outputting a current signal corresponding to a voltage across both ends of the shunt resistor element; a voltage measuring unit for measuring a voltage across both ends of the switching circuit; a temperature measuring unit for measuring a temperature of the switching circuit; and a control unit. The control unit determines a first current value representing a current flowing through the shunt resistor element on the basis of the current signal. The control unit determines a second current value representing a current flowing through the switching circuit on the basis of the measured voltage and the measured temperature. The control unit determines whether the shunt resistor element is in a normal state on the basis of the first current value and the second current value.

Description

Battery pack including current measuring device, current measuring method and the current measuring device

The present invention relates to an apparatus and method for measuring a current flowing through a charge and discharge path of a battery pack, and a battery pack including the device.

This application is a priority application for Korean Patent Application No. 10-2018-0072156, filed June 22, 2018 and Korean Patent Application No. 10-2019-0064721, filed May 31, 2019. All the contents disclosed in the specification and drawings of this application are incorporated in this application by reference.

Recently, as the demand for portable electronic products such as laptops, video cameras, mobile phones, etc. is rapidly increased, and development of electric vehicles, storage batteries for energy storage, robots, satellites, and the like is in earnest, high-performance batteries capable of repeatedly charging and discharging Research is actively being conducted.

Currently commercialized batteries include nickel cadmium batteries, nickel hydride batteries, nickel zinc batteries, and lithium batteries. Among them, lithium batteries have almost no memory effect compared to nickel-based batteries, and thus are free of charge and discharge, and have a very high self discharge rate. Its low and high energy density has attracted much attention.

In order to measure the current flowing through the battery, a shunt resistor can be installed in the charge / discharge path for the battery. The current measured using the shunt resistor element is essential for determining the overcurrent or estimating the state of charge (SOC) and the state of health (SOH) of the battery.

Current measurement using a shunt resistor element is based on dividing the voltage across the shunt resistor element by the reference resistance. The reference resistance is predetermined in consideration of the material, size and shape of the shunt resistor element. However, when the shunt resistor element is gradually degraded over time or damaged by vibration and shock, the actual resistance of the shunt resistor element has a large difference from the reference resistance.

In particular, in relation to ISO 26262, the international standard for automotive safety, the current measured by a current sensor with a shunt resistor is relied on to satisfy the highest class D of the four classes of Automotive Safety Integrity Level (ASIL). It is necessary to determine whether it is possible (ie, the current sensor is normal). Conventionally, current measurement results are compared with current measured by another current sensor (for example, Hall effect current sensor), thereby achieving reliability of the current measurement result. However, since two current sensors are essential, there are disadvantages in that they are expensive and have poor space utilization.

The present invention has been made to solve the above problems, an apparatus and method for diagnosing whether a shunt resistor element installed in a charge / discharge path for a battery is in a normal state without an additional current sensor, and the device. An object of the present invention is to provide a battery pack including a.

Other objects and advantages of the present invention can be understood by the following description, and will be more clearly understood by the embodiments of the present invention. It will also be readily apparent that the objects and advantages of the invention may be realized by the means and combinations thereof indicated in the claims.

The current measuring device according to an aspect of the present invention is for measuring a current flowing through a charge / discharge path for a battery. The current measuring device may include a switching circuit installed in the charge / discharge path; A current measuring unit including a shunt resistor element disposed in the charge / discharge path, and configured to output a current signal corresponding to a voltage across both ends of the shunt resistor element; A voltage measuring unit configured to measure a voltage across the switching circuit; A temperature measuring unit configured to measure a temperature of the switching circuit; And a control unit operatively coupled to the switching circuit, the current measuring unit, the voltage measuring unit, and the temperature measuring unit. The controller is configured to determine a first current value representing a current flowing through the shunt resistor element based on the current signal. The controller is configured to determine a second current value representing a current flowing through the switching circuit based on the measured voltage and the measured temperature. The control unit is configured to determine whether the shunt resistor element is in a steady state based on the first current value and the second current value.

The controller may be configured to determine an on-resistance of the switching circuit based on the measured temperature. The second current value is a value obtained by dividing the measured voltage by the on-resistance.

The current measuring device may further include a memory device in which a look-up table in which a corresponding relationship between temperature of the switching circuit and on-resistance is recorded is stored. The controller may be configured to determine the on-resistance recorded as associated with the measured temperature from the lookup table as the on-resistance of the switching circuit, using the measured temperature as an index.

The controller may be configured to determine a third current value representing a current flowing through the charge / discharge path based on the first current value and the second current value.

The controller may be configured to determine any one of the first current value, the second current value, and an average of the first current value and the second current value when a difference between the first current value and the second current value is within a normal range. It may be configured to determine one as the third current value.

The controller may be configured to determine the second current value as the third current value when a difference between the first current value and the second current value is out of a normal range.

The controller may be configured to output a fault message when a difference between the first current value and the second current value is out of a normal range.

The controller may be configured to determine the normal range based on the measured temperature. The control unit may be configured to enlarge the normal range as the measured temperature decreases.

A battery pack according to another aspect of the present invention includes the current measuring device.

A method according to another aspect of the invention is for measuring a current flowing through a charge / discharge path for a battery. The method includes measuring a voltage across both ends of a switching circuit installed in the charge / discharge path; Measuring a temperature of the switching circuit; Determining a first current value representing a current flowing through the shunt resistor element based on a voltage across the shunt resistor element provided in the charge / discharge path; Determining a second current value indicative of a current flowing through the switching circuit based on the measured voltage and the measured temperature; And determining whether the shunt resistor element is in a normal state based on the first current value and the second current value.

The second current value may be a value obtained by dividing the measured voltage by an on-resistance associated with the measured temperature.

In the determining whether the shunt resistor element is in a normal state, when the difference between the first current value and the second current value is within a normal range, it may be determined that the shunt resistor element is in a normal state.

According to at least one of the embodiments of the present invention, it is possible to diagnose whether the shunt resistor element installed in the charge / discharge path for the battery is in a normal state without an additional current sensor.

The effects of the present invention are not limited to the above-mentioned effects, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the claims.

1 is a view schematically showing a functional configuration of a current measuring device according to an embodiment of the present invention.

FIG. 2 is a diagram schematically illustrating a configuration of a battery pack including the current measuring device of FIG. 1.

3 exemplarily shows a first lookup table associated with the switching circuit of FIGS. 1 and 2.

4 exemplarily illustrates a logic circuit included in the controller of FIGS. 1 and 2.

5 is a flowchart schematically showing a current measuring method according to another embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms or words used in the present specification and claims should not be construed as being limited to the common or dictionary meanings, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention.

Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

Terms including ordinal numbers such as first and second are used for the purpose of distinguishing any one of the various components from the others, and are not used to limit the components by such terms.

Throughout the specification, when a part is said to "include" a certain component, it means that it may further include other components, without excluding the other components unless otherwise stated. In addition, the term <control unit> described in the specification means a unit for processing at least one function or operation, and may be implemented in hardware, software, or a combination of hardware and software.

In addition, throughout the specification, when a part is "connected" to another part, it is not only "directly connected" but also "indirectly connected" with another element in between. Include.

1 is a view schematically showing a functional configuration of a current measuring device according to an embodiment of the present invention, Figure 2 is a view schematically showing the configuration of a battery pack including the current measuring device of FIG.

1 and 2, the battery pack P includes a battery 10, a switching circuit 50, and a current measuring device 1 (hereinafter, referred to as an “device”).

The battery 10 includes at least one battery cell. When a plurality of battery cells are included in the battery 10, the plurality of battery cells may be electrically connected in series or in parallel with each other.

The switching circuit 50 may include at least one charge switch and at least one discharge switch. Each charge switch may be electrically connected in series to each discharge switch. When the plurality of charging switches are included in the switching circuit 50, the plurality of charging switches may be electrically connected in parallel. When the plurality of discharge switches are included in the switching circuit 50, the plurality of discharge switches may be electrically connected in parallel.

Each charging switch can control the current flowing in the direction for charging the battery 10. For example, each charge switch is located between the positive terminal of the battery 10 and the positive terminal of the battery pack P, and is a current flowing from the positive terminal of the battery pack P to the positive terminal of the battery 10. The amount of charge current can be adjusted.

Each discharge switch can control the current flowing in the direction for discharging the battery 10. For example, each discharge switch is located between the positive terminal of the battery 10 and the positive terminal of the battery pack P, and is a current flowing from the positive terminal of the battery 10 to the positive terminal of the battery pack P. The magnitude of the discharge current can be adjusted.

For example, each charge switch and each discharge switch may be a field effect transistor (FET) including gate, drain, and source terminals. The FET can be turned on or off depending on the magnitude of the voltage applied between the gate terminal and the source terminal.

The device 1 is provided to measure the current flowing through the charge / discharge path for the battery 10. The apparatus 1 includes a voltage measuring unit 100, a temperature measuring unit 200, a current measuring unit 300, and a control unit 400. The apparatus 1 may further include a memory device 500.

The voltage measuring unit 100 may be electrically connected to both ends of the switching circuit 50. That is, the voltage measuring unit 100 may be electrically connected to the switching circuit 50 in parallel so as to measure the voltage across the switching circuit 50.

The voltage measuring unit 100 may measure the potential difference between one end and the other end of the switching circuit 50 as the voltage of the switching circuit 50. For example, one end of each charge switch is electrically connected to the positive terminal of the battery 10, one end of each discharge switch is electrically connected to the positive terminal of the battery pack P, and the other of each charge switch is different. When the stage and the other end of each discharge switch are electrically connected, the potential difference between one end of each charge switch and one end of each discharge switch may be measured by the voltage measuring unit 100 as a voltage of the switching circuit 50.

The voltage measuring unit 100 may be operatively coupled to the control unit 400 so as to exchange electrical signals with the control unit 400. The voltage measuring unit 100 measures the voltage of the switching circuit 50 every unit time in response to a voltage measurement command from the control unit 400, and controls the voltage signal indicating the measured voltage of the switching circuit 50. 400 can be output.

The temperature measuring unit 200 is located within a predetermined distance from the switching circuit 50 and is provided to measure the temperature of the switching circuit 50. The temperature measuring unit 200 may be operatively coupled to the control unit 400 so as to exchange electrical signals with the control unit 400. The temperature measuring unit 200 may measure the temperature of the switching circuit 50 every unit time, and may output a temperature signal indicating the measured temperature of the switching circuit 50 to the controller 400. A known temperature sensor such as a thermocouple may be utilized as the temperature measuring unit 200.

The current measuring unit 300 includes a shunt resistor element 30 and a signal processing circuit 32.

The shunt resistor element 30 may be located in the charge / discharge path between the negative terminal of the battery 10 and the negative terminal of the battery pack P. The voltage across the shunt resistor element 30 depends on the direction and intensity of the current flowing through the charge / discharge current.

The signal processing circuit 32 is operatively coupled to the control unit 400 so as to exchange electrical signals with the control unit 400. The signal processing circuit 32, in response to the current measurement command from the control unit 400, based on the voltage across the shunt resistor element 30, the current flowing through the shunt resistor element 30 every unit time. The current signal indicating the direction and magnitude of the measured current may be output to the controller 400.

The two input terminals of the signal processing circuit 32 may be electrically connected to one end and the other end of the shunt resistor element 30, respectively. The signal processing circuit 32 amplifies the voltage across both ends of the shunt resistor element 30 received through the two input terminals of the signal processing circuit 32, and then uses the digital signal representing the amplified voltage as the current signal. It may transmit to the control unit 400. The controller 400 may determine the first current value indicating the direction and intensity of the current flowing through the charge / discharge path based on the current signal from the signal processing circuit 32 for each unit time according to Ohm's law.

The control unit 400 may be configured to include application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), and microprocessors. microprocessors) and electrical units for performing other functions. The controller 400 may include a memory device 500.

The control unit 400 determines the voltage value representing the voltage across the switching circuit 50 based on the voltage signal for each unit time from the voltage measuring unit 100. The control unit 400 determines the temperature value indicating the temperature of the switching circuit 50 based on the temperature signal for each unit time from the temperature measuring unit 200.

The controller 400 may determine, on a unit of time basis, a second current value indicating the direction and intensity of the current flowing through the switching circuit 50 based on the voltage value and the temperature value associated with the switching circuit 50.

Since both the first current value and the second current value represent directions and intensities of currents flowing through the charge / discharge path for the battery 10, the first current value and the second current value are the same as usual. Only within the acceptable range. On the other hand, when the shunt resistor element 30 is damaged or a short circuit failure occurs in the shunt resistor element 30, the difference between the first current value and the second current value may be significantly increased.

The controller 400 may estimate the on-resistance of the switching circuit 50 based on the temperature of the switching circuit 50 for each unit time. The on-resistance of the switching circuit 50 refers to the resistance of the switching circuit 50 while the switching circuit 50 is in the on-state and may be a parameter depending on the temperature. The controller 400 corresponds to the temperature of the switching circuit 50 measured at a specific time point with reference to the first lookup table in which the correspondence between the temperature of the switching circuit 50 and the on-resistance is recorded. The on-resistance recorded in the lookup table can be estimated as the on-resistance of the switching circuit 50 at this particular point in time. The first lookup table may be stored in advance in the memory device 500.

The controller 400 divides the voltage across the switching circuit 50 at the specific time point by the estimated on-resistance according to the Ohm's law, so that the current flowing through the switching circuit 50 at the specific time point. A second current value representing may be determined.

The controller 400 may determine a third current value representing a current flowing through the charge / discharge path based on the first current value and the second current value. For example, the controller 400 may determine the first current value as the current value flowing through the charge / discharge path based on the difference between the first current value and the second current value. As another example, the controller 400 may determine the average of the first current value and the second current value as the current value flowing through the charge / discharge path based on the first current value and the second current value. As another example, the controller 400 may determine the second current value as a current value flowing through the charge / discharge path based on the difference between the first current value and the second current value.

The controller 400 may diagnose whether the shunt resistor element 30 is in a normal state based on the difference between the first current value and the second current value. For example, the controller 400 may determine that the shunt resistor element 30 is in a normal state when the difference between the first current value and the second current value is within a normal range (eg, −10 to 10 mA). Can be.

The normal range may be predetermined. Alternatively, the normal range may be determined by the controller 400 based on the temperature of the switching circuit 50. In the switching circuit 50, as the temperature of the switching circuit 50 increases, the on-resistance of the switching circuit 50 decreases, and as the temperature of the switching circuit 50 decreases, the on-resistance of the switching circuit 50 decreases. It may have increasing properties. Therefore, the controller 400 may reduce the normal range as the temperature of the switching circuit 50 increases, and enlarge the normal range as the temperature of the switching circuit 50 decreases. The second lookup table in which the correspondence between the temperature of the switching circuit 50 and the normal range is recorded may be stored in the memory device 500 in advance. The controller 400 may use the temperature of the switching circuit 50 as an index to obtain a normal range associated with the temperature of the switching circuit 50 from the second lookup table.

When the difference between the first current value and the second current value exceeds the normal range, the controller 400 may determine that the shunt resistor element 30 is in a failure state. The failure state of the shunt resistor element 30 may mean a state in which the difference between the resistance and the reference resistance of the shunt resistor element 30 exceeds a predetermined level due to deterioration or damage of the shunt resistor element 30. . The data representing the normal range may be stored in advance in the memory device 500. The controller 400 may transmit a fault message to the external device 2 when it is determined that the shunt resistor element 30 is in a failure state. The external device 2 may be an ECU (Electronic Control Unit) of an electric system (eg, an electric vehicle) in which the battery pack P is mounted.

When the difference between the first current value and the second current value is within the normal range, the controller 400 selects one of the first current value, the second current value, and the average of the first current value and the second current value. It can be determined by the third current value. The difference between the first current value and the second current value is within the normal range because it means that the first current value is reliable.

When the difference between the first current value and the second current value is outside the normal range, the controller 400 may determine the second current value as the third current value.

The memory device 500 may be operatively coupled to the controller 400 to exchange electrical signals with the controller 400. The memory device 500 is not particularly limited as long as it is a storage medium capable of recording and erasing information. For example, the memory device 500 may be a RAM, a ROM, a register, a hard disk, an optical recording medium, or a magnetic recording medium. The memory device 500 may be electrically connected to the controller 400 through, for example, a data bus so as to be accessible by the controller 400. The memory device 500 may store and / or update and / or erase and / or transmit a program including various control logics performed by the controller 400, and / or data generated when the control logic is executed. .

3 exemplarily shows a first lookup table associated with the switching circuit of FIGS. 1 and 2.

Referring to FIG. 3, as described above, the controller 400 may refer to the first lookup table stored in the memory device 500 to determine the on-resistance of the switching circuit 50.

For example, when the temperature of the switching circuit 50 received from the temperature measuring unit 200 is a, the control unit 400 uses the temperature a as an index and associates it with the temperature a in the first lookup table. Can be determined as the on-resistance of the switching circuit 50. As another example, when the temperature of the switching circuit 50 is b, the controller 400 may determine y associated with the temperature b in the first lookup table as the on-resistance of the switching circuit 50.

The device 1 utilizes a characteristic in which the on-resistance of a semiconductor switch, such as a FET included in the switching circuit 50, varies depending on the temperature, so that the temperature of the switching circuit 50 and both ends of the switching circuit 50 are varied. A second current value representing the current flowing through the switching circuit 50 is determined based on the across voltage. The device 1 then compares the second current value with the first current value measured using the shunt resistor element 30, thereby improving the accuracy of the current measurement without adding a Hall effect sensor or the like. There is an advantage.

4 exemplarily illustrates a logic circuit included in the controller of FIGS. 1 and 2.

Referring to FIG. 4, the controller 400 may determine the second current value by using the logic circuit 450 included in the controller 400. Here, the logic circuit 450, when receiving the temperature (T _SW ) of the switching circuit 50 and the voltage (V _SW ) across the switching circuit 50 as an input value, the second current value (I _SW) ) May be a logic circuit configured to output as an output value.

The device 1 may be applied to a battery management system (BMS). In other words, the BMS may include the device 1. At least some of each component of the device 1 may be implemented by supplementing or adding the functionality of the components included in the conventional BMS. For example, the controller 400 and the memory device 500 of the apparatus may be implemented as components of a BMS.

5 is a flowchart schematically showing a current measuring method according to another embodiment of the present invention. The performing agent of each step included in the method of FIG. 5 may be referred to as each component of the apparatus 1.

Referring to FIG. 5, in step S100, the controller 400 collects a voltage signal from the voltage measuring unit 100, a temperature signal from the temperature measuring unit 200, and a current signal from the current measuring unit 300. do.

In step S110, the control unit 400 determines the voltage value indicating the voltage across the switching circuit 50 and the temperature value indicating the temperature of the switching circuit 50 based on the voltage signal and the temperature signal.

In step S120, the control unit 400 determines the first current value representing the current flowing through the shunt resistor element 30 based on the current signal. Since the shunt resistor element 30 is provided in the charge / discharge path, the first current value may also indicate the current flowing through the charge / discharge path.

In step S130, the controller 400 determines a second current value representing the current flowing through the switching circuit 50 based on the voltage value and the temperature value determined in step S110. Since the switching circuit 50 is installed in the charge / discharge path, the second current value may represent the current flowing through the charge / discharge path.

In step S140, it is determined whether the shunt resistor element 30 is in a normal state based on the first current value and the second current value. For example, when the difference between the first current value and the second current value is within the normal range, it may be determined that the shunt resistor element 30 is in a normal state. On the other hand, when the difference between the first current value and the second current value is outside the normal range, it may be determined that the shunt resistor element 30 is in a fault state. If the value of step S140 is "no", step S150 may proceed. If the value of step S140 is "Yes", the method may end.

In operation S150, the controller 400 may transmit a fault message to the external device 2. The fault message is for notifying the user or the external device 2 that the shunt resistor element 30 is in a fault condition.

The embodiments of the present invention described above are not implemented only through the apparatus and the method, but may be implemented through a program for realizing a function corresponding to the configuration of the embodiment of the present invention or a recording medium on which the program is recorded. Implementation may be easily implemented by those skilled in the art from the description of the above-described embodiments.

Although the present invention has been described above by means of limited embodiments and drawings, the present invention is not limited thereto and will be described below by the person skilled in the art and the technical spirit of the present invention. Of course, various modifications and variations are possible within the scope of the claims.

In addition, the present invention described above is capable of various substitutions, modifications, and changes within the scope without departing from the spirit of the present invention for those of ordinary skill in the art to which the present invention pertains to the above-described embodiments and attached Not limited by the drawings, all or part of the embodiments may be selectively combined to enable various modifications.

Claims (13)

In the current measuring device for measuring the current flowing through the charge and discharge path for the battery, A switching circuit installed in the charge / discharge path; A current measuring unit including a shunt resistor element disposed in the charge / discharge path, and configured to output a current signal corresponding to a voltage across both ends of the shunt resistor element; A voltage measuring unit configured to measure a voltage across the switching circuit; A temperature measuring unit configured to measure a temperature of the switching circuit; And A control unit operatively coupled to the switching circuit, the current measuring unit, the voltage measuring unit, and the temperature measuring unit, The control unit, And based on the current signal, determine a first current value representing a current flowing through the shunt resistor element, And based on the measured voltage and the measured temperature, determine a second current value representing a current flowing through the switching circuit, And determining whether the shunt resistor element is in a normal state based on the first current value and the second current value. The method of claim 1, The control unit, Based on the measured temperature, configured to determine an on-resistance of the switching circuit, And the second current value is a value obtained by dividing the measured voltage by the on-resistance. The method of claim 2, Further comprising a memory device storing a look-up table in which a corresponding relationship between temperature of the switching circuit and on-resistance is recorded, The control unit, And use the measured temperature as an index to determine an on-resistance recorded as associated with the measured temperature from the lookup table as the on-resistance of the switching circuit. The method of claim 1, The control unit, And a third current value indicating a current flowing through the charge / discharge path based on the first current value and the second current value. The method of claim 4, wherein The control unit, When the difference between the first current value and the second current value is within a normal range, any one of the first current value, the second current value, and an average of the first current value and the second current value may be determined. 3 is a current measuring device, characterized in that configured to determine the current value. The method of claim 4, wherein The control unit, And determine the second current value as the third current value when a difference between the first current value and the second current value is out of a normal range. The method of claim 4, wherein The control unit, And output a fault message when a difference between the first current value and the second current value is out of a normal range. The method of claim 6, The control unit, And determine the normal range based on the measured temperature. The method of claim 8, The control unit, And as the measured temperature decreases, expanding the normal range. A battery pack comprising the device according to claim 1. In the current measuring method for measuring the current flowing through the charge and discharge path for the battery, Measuring a voltage across both ends of a switching circuit installed in the charge / discharge path; Measuring a temperature of the switching circuit; Determining a first current value representing a current flowing through the shunt resistor element based on the voltage across the shunt resistor element provided in the charge / discharge path; Determining a second current value representing a current flowing through the switching circuit based on the measured voltage and the measured temperature; And And determining whether the shunt resistor element is in a normal state based on the first current value and the second current value. The method of claim 11, The second current value is, And the measured voltage divided by the on-resistance associated with the measured temperature. The method of claim 11, In the step of determining whether the shunt resistor element is in a steady state, And when the difference between the first current value and the second current value is within a normal range, the shunt resistor element is determined to be in a normal state.

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