JP2024050293A - Semiconductor device, battery monitoring method, and battery monitoring system - Google Patents

Abstract

[Problem] A semiconductor device capable of calculating the remaining battery capacity in a time-efficient manner with a simple configuration [Solution] The semiconductor device comprises a counting unit that measures a count value relating to the inflow and outflow of current to the battery by the Coulomb counting method, an impedance measuring unit that measures the impedance of the battery, a correction unit that corrects the battery capacity used in calculations from the correlation between the impedance and the battery capacity based on the impedance, and a calculation unit that calculates the remaining battery capacity based on the count value and the corrected battery capacity. [Selected Figure] Figure 2

Description

This disclosure relates to a semiconductor device, a battery monitoring method, and a battery monitoring system.

There is a technology that uses an impedance function to estimate the state of a battery (see Patent Document 1). This technology involves a fitting process that adjusts the impedance function so that the error relative to the measured actual value data is reduced.

There is also a technology that improves the accuracy of estimating battery deterioration (see Patent Document 2). This technology detects when the battery has been charged or discharged a certain amount of charge based on the coulomb count value, and changes an indicator of deterioration each time this is detected.

JP 2014-102111 A JP 2017-116522 A

Conventional methods for estimating remaining battery capacity that take deterioration into account include a fitting method as in Patent Document 1, and a method using a lookup table (LUT) as in Patent Document 2. The LUT is a method in which the relationship between the battery capacity and the number of charging cycles is measured in advance and registered as a table showing the relationship, as shown in Figure 2 of Patent Document 2. Conventional methods for estimating remaining battery capacity are a method of estimating remaining battery capacity by counting how many times the battery has been charged and discharged while the actual system is operating, correcting the battery capacity based on the count, and using the corrected battery capacity to calculate the remaining battery capacity (SOC: State Of Charge).

However, the environment in which the actual system operates may differ from the environment in which the relationship between battery capacity and number of charging cycles was previously measured. In such cases, the progression of battery deterioration may differ, resulting in different remaining capacity estimation results.

The objective of this disclosure is to provide a semiconductor device, a battery monitoring method, and a battery monitoring system that can calculate the remaining battery charge in a time-efficient manner with a simple configuration.

The semiconductor device disclosed herein includes a counting unit that measures a count value related to the inflow and outflow of current to and from a battery using a coulomb counting method, an impedance measuring unit that measures the impedance of the battery, a correction unit that corrects the battery capacity used in the calculation from the correlation between the impedance and the battery capacity based on the impedance, and a calculation unit that calculates the remaining battery capacity based on the count value and the corrected battery capacity.

The semiconductor device, battery monitoring method, and battery monitoring system disclosed herein have the advantage of being able to calculate the remaining battery charge in a time-efficient manner with a simple configuration.

FIG. 1 is a block diagram showing an example of a configuration of an existing battery monitoring system. 1 is a block diagram showing an example of a configuration of a battery monitoring system according to a first embodiment; This is an example of the first LUT 37, and is table data in which a virtual number of charge/discharge cycles is associated with a battery capacity (mAh). This is an example of the second LUT 38, and is table data in which a virtual number of charge/discharge cycles is associated with an impedance (mΩ). 4 is a flowchart showing a processing flow of the battery monitoring system 1. FIG. 11 is a block diagram showing an example of a configuration of a battery monitoring system according to a second embodiment. 13 is an example of the second LUT 38 of the second embodiment, and is table data in which a virtual number of charge/discharge cycles is associated with an impedance (mΩ) corresponding to each temperature. 10 is a flowchart showing a processing flow of a battery monitoring system 1 of a second embodiment.

In recent years, the demand for batteries has been increasing in order to achieve carbon neutrality. There is also an increasing demand for the reuse of batteries. Particularly in Europe and other countries, battery regulations require that the deterioration of batteries used for vehicle and storage batteries be measured and recorded in the next few years. The method of this embodiment relates to battery monitoring using a battery remaining capacity estimation method that takes deterioration into account, which will become increasingly important in the future. The battery monitoring system of this embodiment is a system that monitors the supply of power from a battery (hereinafter referred to as "battery"), the remaining capacity, etc. The battery monitoring system is incorporated as part of a control system to which power is supplied to perform a specified function. Examples of the control system include a sensor system that measures and monitors the physical quantity of a specified object, such as an IoT device.

Here, an example of an existing battery monitoring system equipped with the LUT that is the premise of this embodiment is shown. As shown in FIG. 1, the existing battery monitoring system is configured with a semiconductor device, a battery, a load, and a sense resistor. The semiconductor device includes a charge/discharge count detection unit, a coulomb counter unit, an SOC calculation unit, a correction unit, and an LUT (Look Up Table).

The type of battery is not particularly limited, but a lithium-ion cell is used as an example. In the case of a lithium-ion cell, a fully charged state is when the OCV (Open Circuit Voltage) is 4.2V, that is, the SOC (State of Charge) is 100%. Here, OCV (open circuit voltage) refers to the voltage of the battery when no load is connected and no voltage or current is applied to the load. In addition, SOC (state of charge or charging rate) refers to the state of charge of the battery, where the fully discharged state according to the specifications is 0% and the fully charged state is 100%.

The load is a circuit that operates by receiving voltage and current from a battery. Battery monitoring system 1 is an example of a sensor system, and the load includes a sensor drive circuit of the sensor system, a transmitter that transmits monitoring information to the monitoring system, and the like. The sense resistor is a circuit that is inserted in series with the battery and detects voltage drops. In the battery monitoring system, the state of the battery is monitored when the load is connected.

As described in Patent Document 2, for example, the coulomb counter unit is a circuit that samples the battery current at a predetermined sampling period and measures a count value (ACC) related to the inflow and outflow of current. The SOC calculation unit is a circuit that calculates the SOC of the battery based on the count value. The correction unit is a circuit that uses the detected number of discharges to correct the battery capacity used in the calculations of the SOC calculation unit. The LUT is a table that records the correspondence (correlation) between the number of discharges obtained by measurement, etc. and the battery capacity.

The above is a description of the existing battery monitoring system. Below, the details of this embodiment will be explained with reference to the drawings.

(First embodiment)
As shown in FIG. 2, the battery monitoring system 1 according to the first embodiment includes a semiconductor device 10, a battery 20, a load 21, and a sense resistor 22. As shown in FIG. 2, the semiconductor device 10 according to the present embodiment includes a charge/discharge count detection unit 31, a coulomb counter unit 32, an impedance measurement signal generation unit 33, an impedance measurement unit 34, a correction unit 35, an SOC calculation unit 36, a first LUT 37, and a second LUT 38. Unlike the conventional technology, the battery monitoring system 1 includes the impedance measurement signal generation unit 33, the impedance measurement unit 34, and the second LUT 38. Note that the battery monitoring system 1 includes the charge/discharge count detection unit 31, but this is for convenience in accordance with the aspects of the existing technology. In this embodiment, since a virtual charge/discharge count is used, the actual charge/discharge count is used auxiliary for verification and is not used as a main configuration. The coulomb counter unit 32 is an example of a count unit of the present disclosure, and the SOC calculation unit 36 is an example of a calculation unit of the present disclosure.

The control unit 29 is a part that mainly executes the battery monitoring process, and is configured to include, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc. (not shown). The control unit 29 controls the charge/discharge count detection unit 31, the coulomb counter unit 32, the impedance measurement signal generation unit 33, the impedance measurement unit 34, the correction unit 35, and the SOC calculation unit 36. Note that each part of the correction unit 35 and the SOC calculation unit 36 may be configured as a calculation unit processed by the CPU, rather than being configured as a circuit.

The coulomb counter unit 32 measures the count value related to the inflow and outflow of current to the battery using the coulomb counting method. For example, the integrated current value (Q(t)) may be measured as the count value.

The impedance measurement signal generator 33 generates an AC signal (sine wave) for impedance measurement. The AC signal may be a sine wave in the range of several tens of Hz to several MHz.

The impedance measurement unit 34 measures the impedance of the battery 20. The impedance measurement unit 34 is a circuit that measures the impedance from the voltage and current of the battery 20 when an AC signal is input.

In this embodiment, the LUT includes a first LUT 37 and a second LUT 38. The first LUT 37 is table data showing the correlation between the virtual number of charge/discharge cycles and the battery capacity. The virtual number of charge/discharge cycles is common to the battery capacity and the impedance. FIG. 3A is an example of the first LUT 37, and is table data in which the virtual number of charge/discharge cycles and the battery capacity (mAh) are associated. In the example, when the number of charge/discharge cycles is 1, the battery capacity is 1000 (mAh), and when the number of charge/discharge cycles is 500, the battery capacity is 900 (mAh), and the battery capacity decreases with each cycle. The second LUT 38 is table data showing the correlation between the virtual number of charge/discharge cycles and the impedance. FIG. 3B is an example of the second LUT 38, and is table data in which the virtual number of charge/discharge cycles and the impedance (mΩ) are associated. In this example, when the number of charge/discharge cycles is 1, the impedance is 10 (mΩ), and when the number of charge/discharge cycles is 500, the impedance is 100 (mΩ), and the battery capacity decreases with each cycle. Note that these values are merely examples for illustrative purposes, and in operation, values obtained from verification results or the like are used as table data. The first LUT 37 is an example of first correlation data of the present disclosure, and the second LUT 38 is an example of second correlation data of the present disclosure.

Based on the measured impedance, the correction unit 35 corrects the battery capacity used in the calculation by the SOC calculation unit 36 from the correlation between the impedance and the battery capacity. Specifically, the correction unit 35 selects a virtual number of charge/discharge cycles in the second LUT 38 that corresponds to the measured impedance, and performs correction so that the battery capacity in the first LUT 37 that corresponds to the selected number of charge/discharge cycles is used in the calculation.

The SOC calculation unit 36 calculates the SOC as the remaining capacity of the battery based on the measured count value and the corrected battery capacity. The SOC may be calculated using a method for estimating SOC using a general coulomb counting method, and may be calculated as SOC= _SOC0 +(Q(t)/FCC) using the charge rate before the start of discharge ( _SOC0 ), the integrated current value (Q(t)) which is the count value, and the full charge capacity (FCC) of the corrected battery capacity.

Next, the operation of the battery monitoring system 1 will be described. FIG. 4 is a flowchart showing the processing flow of the battery monitoring system 1. The processing routine is executed periodically, for example, at a battery monitoring cycle defined for the battery monitoring system 1.

In step S100, the coulomb counter unit 32 measures the count value related to the inflow and outflow of current to the battery using the coulomb counting method. Note that the charge/discharge count detection unit 31 may detect the number of charge/discharge cycles in conjunction with this step.

In step S102, the impedance measurement signal generator 33 generates an AC signal (sine wave) for impedance measurement.

In step S104, the impedance measurement unit 34 measures the impedance of the battery 20.

In step S106, the correction unit 35 selects a virtual charge/discharge count from the second LUT 38 that corresponds to the measured impedance.

In step S108, the correction unit 35 corrects the battery capacity in the first LUT 37 corresponding to the selected number of charge/discharge cycles to be used in the calculation.

In step S110, the SOC calculation unit 36 calculates the remaining battery charge (SOC) based on the measured count value and the corrected battery capacity.

As described above, the battery monitoring system 1 of this embodiment can calculate the remaining battery charge in a time-efficient manner with a simple configuration.

Second Embodiment
5 is a diagram showing a configuration of the second embodiment. The second embodiment differs from the first embodiment in that the temperature of the battery 20 is measured and the LUT is referred to. As shown in FIG. 5, the semiconductor device 10 in the battery monitoring system 1 of the second embodiment includes a temperature measurement unit 41 that measures the temperature of the battery 20.

In this embodiment, the second LUT 38 has impedance data for each temperature. FIG. 6 shows an example of the second LUT 38 in the second embodiment, which is table data that associates a virtual number of charge/discharge cycles with the impedance (mΩ) corresponding to each temperature.

The correction unit 35 uses the measured temperature and impedance to select a virtual number of charge/discharge cycles from the second LUT 38 and corrects the battery capacity.

Figure 7 is a flowchart showing the processing flow of the battery monitoring system 1 of the second embodiment.

In step S200, the temperature measurement unit 41 measures the temperature of the battery 20.

In step S202, the correction unit 35 selects a virtual charge/discharge count from the second LUT 38 that corresponds to the measured temperature and impedance.

As described above, the battery monitoring system 1 of this embodiment can calculate the remaining battery charge in a time-efficient and accurate manner with a simple configuration.

In the above embodiment, the first LUT 37 uses the correlation between the charge/discharge cycle and the battery capacity, and the second LUT 38 uses the correlation between the charge/discharge cycle and the impedance to correct the battery capacity from the impedance, but this is not limited to this. For example, both LUTs may be integrated, and calculations may be performed using only the LUTs for impedance and battery capacity.

In addition, instead of using an LUT, the battery capacity may be corrected using a relationship between impedance and battery capacity.

In addition, in the above-described embodiment, a sine wave is used as the AC signal for impedance measurement, but a signal in which sine waves of multiple frequencies are superimposed, an impulse signal, etc. may also be used.

In addition, although the present specification has described an embodiment in which the program is pre-installed, the program can also be provided by storing it on a computer-readable recording medium.

REFERENCE SIGNS LIST 1 Battery monitoring system 20 Battery 21 Load 22 Sense resistor 29 Control unit 31 Charge/discharge count detection unit 32 Coulomb counter unit 33 Impedance measurement signal generation unit 34 Impedance measurement unit 35 Correction unit 36 SOC calculation unit 37 First LUT
38 Second LUT
41 Temperature measurement unit

Claims (5)

A counting unit that measures a count value related to the inflow and outflow of current of the battery by a coulomb counting method;
an impedance measuring unit that measures the impedance of the battery;
a correction unit that corrects a battery capacity used in a calculation based on a correlation between the impedance and a battery capacity, on the basis of the impedance;
a calculation unit that calculates a remaining capacity of the battery based on the count value and the corrected battery capacity;
A semiconductor device comprising: The correlation includes first correlation data indicating a correlation between a virtual number of charge/discharge cycles common to a battery capacity and an impedance and the battery capacity, and second correlation data indicating a correlation between the virtual number of charge/discharge cycles and the impedance,
The correction unit selects the number of times of charge and discharge of the second correlation data corresponding to the measured impedance,
2 . The semiconductor device according to claim 1 , further comprising: a correction unit configured to correct the battery capacity of the first correlation data corresponding to the selected number of times of charging and discharging so as to use the battery capacity in a calculation by the calculation unit. a temperature measuring unit that measures a temperature of the battery;
The second correlation data includes impedance data for each temperature,
The semiconductor device according to claim 2 , wherein the correction section selects the number of charge/discharge cycles using the impedance corresponding to a measured temperature, and performs the correction. Measure the count values related to the inflow and outflow of current of the battery using the coulomb counting method;
Measuring the impedance of the battery;
correcting a battery capacity used in a calculation based on a correlation between the impedance and a battery capacity, based on the impedance;
calculating a remaining battery capacity based on the count value and the corrected battery capacity;
A battery monitoring method that causes a computer to execute a process. A battery monitoring system including the battery and the semiconductor device according to claim 1.