KR101653967B1 - Apparatus and method for measuring battery residual quantity - Google Patents

Abstract

The present invention relates to a method of measuring the remaining amount of a battery, including the steps of: storing an initial value of a remaining amount of the battery; calculating an open circuit voltage of the battery using an OCV (Open Circuit Voltage) Calculating an input / output current of a battery using a battery model function including a voltage difference between an open circuit voltage and an output voltage as a factor and an internal resistance of the battery as a parameter, calculating a calculated input / Output current of the battery at a time different from the time for measuring the output voltage, and correcting the parameter for the internal resistance by using the difference between the measured input / output current and the calculated input / output current The method comprising the steps of:

Description

[0001] APPARATUS AND METHOD FOR MEASURING BATTERY RESIDUAL QUANTITY [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for measuring the remaining battery level.

Lithium-ion batteries are widely used in portable devices because of their high energy density, portability and non-toxicity. One of the important functions of portable electronic devices is to predict the remaining capacity of the battery. At this time, the battery remaining amount is expressed by Q [Ah] or SOC (State of Charge) [%].

If a conventional capacitor is used as a power source, the residual capacity prediction is easy because the general capacitor has a linear characteristic such as Q = CV. That is, if the capacitor C is known, the remaining capacity Q can be accurately predicted by measuring the voltage V. [

와 같이 비선형 함수 관계를 갖는다.On the other hand, in the case of a lithium ion battery, the battery remaining capacity (residual capacity) and the voltage have nonlinear characteristics. That is, the remaining battery voltage and voltage do not satisfy the linear Q = CV,

As shown in Fig.

Such a nonlinear function relationship between the remaining amount of the battery and the voltage is called an OCV (Open Circuit Voltage) curve.

1 is a diagram showing an example of an OCV curve of a lithium ion battery.

In Fig. 1, the unit of the X-axis is Ah. For example, 2-Ah means that current of 2A can be extracted for 1 hour. The reason for the open circuit in the name of the curve is that both ends of the lithium ion battery are opened and the voltage is measured.

Referring to the OCV curve shown in FIG. 1, when the remaining battery level is 1.9 Ah, the open circuit voltage of the battery becomes 4.0V. Conversely, when 4.0 V is measured as the open circuit voltage of the battery, the remaining amount of the battery is calculated to be 1.9 Ah as shown in the following equation (1).

When the measured open circuit voltage value is substituted into the OCV curve of the known nonlinear function relation, the remaining battery level is derived.

A method for obtaining the OCV curve shown in FIG. 1 is as follows.

First, the voltage of the fully charged battery is measured and the total amount of the battery is determined at this time. This is to determine the total capacity of the battery. The total capacity of the battery may have different values depending on the charging condition and the discharging condition. It should be noted that after charging, the voltage has to be measured in the open circuit state after waiting for sufficient time to stabilize the voltage. This is because the voltage changes when the current is used due to the chemical reaction of the battery.

When the voltage measurement in the battery buffering and the determination of the total amount of the battery are completed, a certain amount of current is discharged for a predetermined time, and then the voltage is measured in the open circuit state after waiting for the voltage to stabilize again. The time required for stabilization may vary depending on the type of the battery, but may be several hours.

Then, the discharge, stabilization, and voltage measurement processes are repeated to obtain a discrete OCV curve as shown in FIG.

Fig. 2 shows the discharge profile applied to obtain the OCV curve of Fig.

It takes a long time to stabilize the voltage after discharging. In the case of the 2.6Ah lithium ion battery, it takes 42 hours until the OCV curve as shown in FIG. 1 is derived.

On the other hand, even if the OCV curve as shown in FIG. 1 is obtained, it is still difficult to estimate the battery remaining amount using only the open circuit voltage.

As described above, the OCV curve is a value measured while the voltage is sufficiently stable. Therefore, in order to calculate the remaining battery capacity by substituting the open-circuit voltage for the OCV curve, a sufficiently stabilized open circuit voltage should be measured. However, in an actual application, since the discharge progresses from time to time and the amount of discharge also continuously changes, it is difficult to measure the open circuit voltage in a stabilized state.

In view of the foregoing, an object of the present invention is, in one aspect, to provide a technique for calculating the remaining battery level using a circuit model of a battery in addition to the OCV curve for accurate and rapid measurement of the remaining battery level.

In another aspect, an object of the present invention is to provide a technique for correcting parameters of a battery circuit model in order to maintain the accuracy of the battery remaining amount measurement even when the battery characteristics change due to temperature or aging.

In another aspect, an object of the present invention is to provide a technique of measuring the voltage and current of a battery with one ADC (Analog Digital Converter) in order to minimize the circuit burden of the battery remaining amount measuring device.

In order to achieve the above object, in one aspect, the present invention provides a method of measuring the remaining amount of a battery, the method comprising: storing an initial value of a remaining amount of the battery; Calculating an open circuit voltage of the battery using an OCV (Open Circuit Voltage) function taking the battery remaining amount as a factor; Measuring an output voltage of the battery; Calculating an input / output current of the battery using a battery model function including a voltage difference between the open circuit voltage and the output voltage as a parameter and including an internal resistance of the battery as a parameter; Updating the battery remaining amount in time based on the calculated input / output current; Measuring an input / output current of the battery at a time different from a time for measuring the output voltage; And modifying the parameter for the internal resistance by using the difference between the measured input / output current and the calculated input / output current.

According to another aspect of the present invention, there is provided an apparatus for measuring the remaining amount of a battery, comprising: a memory for storing a battery model function including a battery remaining amount, an OCV (Open Circuit Voltage) function and an internal resistance of the battery; An ADC (Analog Digital Converter) for measuring an output voltage and an input / output current of the battery at different times; Calculating an open circuit voltage of the battery by inputting the remaining battery amount into the OCV function, inputting a voltage difference between the open circuit voltage and the output voltage to the battery model function to calculate an input / output current of the battery, A battery remaining amount estimating unit for updating the battery remaining amount in time based on the current; And

And a parameter compensator for correcting the parameter for the internal resistance by using the difference between the measured input / output current and the calculated input / output current.

As described above, according to the present invention, the remaining battery level can be measured accurately and quickly. Further, even when the battery characteristics are changed by temperature or aging, the residual battery amount can be accurately measured without necessity of temperature measurement or aging measurement. In addition, it is possible to minimize the circuit load of the battery remaining amount measuring device by measuring the voltage and current of the battery with one ADC.

1 is a diagram showing an example of an OCV curve of a lithium ion battery.
Fig. 2 shows the discharge profile applied to obtain the OCV curve of Fig.
3 is a block diagram of a remaining battery level measuring apparatus according to an embodiment of the present invention.
4 is a circuit diagram of a battery model that can be applied to an embodiment of the present invention.
5 is a flow diagram of an exemplary method for an apparatus according to an embodiment of the present invention to measure the remaining battery level.
6 is a graph showing Rs values measured at 10 degrees Celsius and 25 degrees Celsius, respectively.
7 is a graph showing Rs values measured in two different current patterns.
8 is a diagram for explaining a change in the Rs value according to the remaining battery level.
9 is a flow chart of a process for compensating for battery parameters.
10 is a diagram showing timing of measuring the battery output voltage and the input / output current of the ADC.
11 is an enlarged view of a portion A in Fig.
12 is a diagram showing an experimental result of an embodiment through charging / discharging of a random current.
13 is a graph showing the results of an experiment conducted at an ambient temperature of 10 degrees.

Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference symbols as possible even if they are shown in different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

In describing the components of the present invention, terms such as first, second, A, B, (a), and (b) may be used. These terms are intended to distinguish the constituent elements from other constituent elements, and the terms do not limit the nature, order or order of the constituent elements. When a component is described as being "connected", "coupled", or "connected" to another component, the component may be directly connected to or connected to the other component, It should be understood that an element may be "connected," "coupled," or "connected."

3 is a block diagram of a remaining battery level measuring apparatus according to an embodiment of the present invention.

Referring to FIG. 3, a remaining battery level measuring device 300 may include a memory 310, an ADC 320, a controller 330, and the like.

), 배터리모델함수, 배터리모델함수에 포함되는 배터리모델 파라미터, 배터리 출력전압 측정값, 배터리 입출력전류 측정값, 배터리 입출력전류 계산값 등을 저장할 수 있다.The memory 310 may store various variables, functions, and parameters necessary for performing calculations of the controller 330. [ For example, the memory 310 may store battery remaining amount, OCV function (

), A battery model function, a battery model parameter included in the battery model function, a battery output voltage measurement value, a battery input / output current measurement value, and a battery input / output current calculation value.

The ADC 320 converts the analog electrical signal into a digital signal. The analog electrical signal may be, but is not limited to, a voltage signal.

The device 300 may measure the output voltage of the battery through the ADC 320 or may measure the input / output current of the battery.

The apparatus 300 may further include a selection circuit (not shown) for measuring two values (output voltage of the battery and input / output current of the battery) to one ADC 320. The selection circuit may be connected to the output terminal of the battery or connected to the current sensor of the battery, if necessary, to receive the output voltage of the battery or receive the sensing voltage of the current sensor.

At this time, the current sensor may be a sensing resistor connected in series with the battery, and the ADC 320 can measure the input / output current of the battery through the sensing voltage formed across the sensing resistance.

The controller 330 controls all functions of the apparatus 300 and may internally include a battery remaining amount estimating unit 332 and a parameter compensating unit 334. [

The remaining battery power estimation unit 332 is a block for calculating the remaining battery power using the OCV function and the battery model function.

There are many ways to model a battery. Physicochemical relationships can be modeled as equations, and the battery itself can be black-boxed and modeled numerically using methods such as neural networks, fuzzy or SVR (Support Vector Regression).

Below is an example of modeling a battery using a circuit modeling method that links the physicochemical properties of the battery to the circuit. However, the present invention is not limited thereto, and any method capable of deriving a battery model function can be applied to the present invention.

4 is a circuit diagram of a battery model that can be applied to an embodiment of the present invention.

Referring to FIG. 4, the battery model includes an OCV voltage source (Voc) modeling an open circuit voltage, a first ladder (R1 // C1) modeling diffusion of a battery as a ladder in which a resistor and a capacitor are connected in parallel, 2 ladder R2 / C2 and a third ladder R3 / C3, and a battery internal resistance Rs.

Although not shown in FIG. 4, the battery model may further include a resistance modeling a charge transfer, a capacitor modeling a double layer, and the like.

The internal resistance Rs includes both ends of the battery, which is an obstacle to the movement of the charge inside the battery. It is a value that includes both the resistance at the electrode and the resistance that interferes with the movement of the ions in the electrolyte. Usually, the largest part is the resistance component in the electrolyte, but the part that easily increases due to aging or damage of the battery is the resistance component in the electrode.

The internal resistance Rs corresponds to the circuit resistance R as the easiest part to describe in the circuit model.

The electrochemical reaction of the battery to space occurs only on the electrode surface. Therefore, the chemicals dissolved in the electrolyte are distributed at different concentrations depending on the distance from the electrode surface. For this reason, sufficient reactant exists in the battery, but terminal voltage drops rapidly due to a shortage of reactants in the electrode portion.

The phenomenon of the formation of a concentration gradient in the electrolyte due to a chemical reaction in the vicinity of the electrode or the movement of the material to solve this concentration gradient is called diffusion.

Diffusion can be modeled as a CPE (Constant Phase Element) in a circuit model. Developing a concentration gradient inside the electrolyte is a form of energy storage and interpreted as a capacitance. However, since this reacts only in the vicinity of the electrode in space and forms only the diffusion path of the material in the other regions, diffusion is a distributed system in which a resistor is connected in series and a capacitor is connected in series Can be modeled.

However, this CPE model for diffusion is too complex, so that the RC ladder of FIG. 3 (ladder in which resistors and capacitors are connected in parallel) can be used as an alternative model.

In the battery model shown in FIG. 4, diffusion is modeled by combining three RC ladders. The number of RC ladders used for spreading can be determined in consideration of the trade-off between accuracy and computation speed. As the number of RC ladders increases, the accuracy of the battery model increases, but the computation speed decreases inversely .

On the other hand, the relationship between the open circuit voltage Voc and the battery output voltage Vm can be confirmed.

4, if the input / output current (i) of the battery is 0A and the respective capacitors of the RC ladder are not charged, the RC circuit portions R1 // C1, R2 // C2, R3 // C3 and Rs Becomes 0 V, the open circuit voltage Voc becomes equal to the output voltage Vm.

On the other hand, if the input / output current (i) of the battery is not 0A or the charge of each capacitor of the RC ladder is charged, the voltage Vds of the RC circuit portions (R1 // C1, R2 // C2, R3 // C3 and Rs) Is not OV, the open circuit voltage (Voc) and the output voltage (Vm) have the relationship as shown in the following Equation (2).

On the other hand, the voltage Vds of the RC circuit parts R1 / C1, R2 // C2, R3 // C3 and Rs is the voltage of the circuit using R1, C1, R2, C2, R3, (i). Conversely, the relationship between the input / output current (i) and the voltage Vds of the RC circuit sections (R1 // C1, R2 // C2, R3 // C3 and Rs)

Battery input-output current (i) as shown in Equation 3, by substituting the voltage Vds of the RC circuit (R1 // C1, R2 // C2 , R3 // C3 , and Rs) a battery model function (f _i) it is possible to obtain .

The battery remaining amount estimating unit 332 can calculate the battery remaining amount using the relationship of Equations (2) and (3).

5 is a flow diagram of an exemplary method for an apparatus according to an embodiment of the present invention to measure the remaining battery level.

The remaining battery power estimation unit 332 may initialize the variables stored in the memory 310 (S502).

In step S502, the open circuit voltage Voc may be initialized to the battery output voltage Vm.

In step S502, initialization such as Equation (4) preferably proceeds when a certain condition is satisfied.

For example, when the battery input / output current i is maintained at 0A for a certain period of time, the battery output voltage Vm does not fluctuate for a certain period of time, or when the application (for example, Electric vehicle) is turned off for a predetermined time or is turned on, the initialization may be performed as in Equation (4).

In step S502, the battery remaining amount Q may be initialized.

The battery remaining amount Q can be initialized using the inverse function of the OCV as shown in Equation (5). In order to use Equation (5), the process of determining the open circuit voltage (Voc) must be preceded by Equation (4).

The battery remaining amount Q may be initialized to a constant value. For example, when the battery is sufficiently charged (full charge), the remaining battery charge Q can be initialized to the total capacity of the battery. When the total battery capacity is 2.6 Ah, the remaining battery power (Q) can be initialized to 2.6 Ah.

The battery remaining capacity estimating unit 332 may prepare the value of the previous time t [k-1] for calculation (S504).

The remaining battery power estimating unit 332 can calculate the remaining battery power at intervals of [Delta] t. Accordingly, the relationship between the current time t [k] and the previous time t [k-1] may be equal to Equation (6).

If the step S504 is performed immediately after the step S502, the values of the previous time t [k-1] for calculation may be the values initialized in the step S502. Otherwise, the battery remaining amount estimating unit 332 performs the processes for calculating the battery remaining amount and stores it in the memory 310 at the previous time t [k-1] Can be one value. The values of the previous time t [k-1] may be the values of step S520 in FIG.

5, the battery output voltage Vm is measured every period of? T, and when the battery output voltage Vm [k] of the current time t [k] is obtained, the battery remaining amount estimating unit 332 And calculates variables for estimating remaining battery power (S510).

Step S510 may be subdivided into several steps.

First, Vds can be calculated according to Equation (2) (S512). However, it is difficult to directly obtain the value of the current time t [k] although the value of the current time t [k] is determined by measuring the battery output voltage Vm in Equation (2) The value of the previous time (t [k-1]) can be used as shown in Equation (7).

Since the capacity of the battery is a relatively large value, the change in the open circuit voltage (Voc) during the time change of? T is very small. Therefore, even when the value of the previous time t [k-1] is used as the open circuit voltage Voc as shown in Equation (7), a large error does not occur in the calculation of Vds.

When Vds is calculated, the battery remaining amount estimating unit 332 can calculate the battery input / output current i using the battery model function described in Equation (3) (S514).

As described with reference to FIG. 4, the battery model may include capacitors C1, C2, and C3. However, since the capacitors C1, C2, and C3 constitute state variables, a battery model function including these capacitors C1, C2, and C3 can take the form of a state equation. According to this state equation, the voltages (Vdf1, Vdf2, Vdf3) of the capacitors (C1, C2, C3) can be calculated recursively. When the capacitor voltages Vdf1, Vdf2 and Vdf3 are determined, the voltage formed in Rs is calculated, so that the battery input / output current i can be calculated according to this voltage.

On the other hand, if the diffusion phenomenon in the battery is not large, the battery model may be modeled only as a resistor. In this case, the battery model function may have a form in which the input / output current (i) of the battery is obtained by dividing Vds by a resistance (for example, Rs).

When the battery input / output current i is calculated, the battery remaining amount estimating unit 332 updates the battery remaining amount Q in time based on the calculated input / output current i (S516).

As described above, the remaining amount of the battery may be expressed by a charge capacity or a state of charge (SOC). The remaining battery capacity calculated by Equation (9) is a value expressed by the charge capacity.

When the battery remaining amount Q is updated to the value of the current time t [k], the battery remaining amount estimating unit 332 calculates the open circuit voltage Voc using the battery remaining amount Q (S518). At this time, the OCV function can be used.

When all of the variables related to the calculation of the battery remaining amount Q are calculated, the calculated variables are stored in the memory 310 (S520), and if not the process end (NO in S522), they are used for the next battery remaining amount Q calculation. Then, the process step is repeated from step S504.

On the other hand, in the battery model, the parameters R1, C1, R2, C2, R3, C3, and Rs may vary depending on temperature, current pattern, battery remaining amount Q, number of times of battery use, .

6 is a graph showing Rs values measured at 10 degrees Celsius and 25 degrees Celsius, respectively.

6, the dotted line is the measured Rs value when the current pattern is given at 10 degrees Celsius, and the solid line is the measured Rs value when the current pattern is given at 25 degrees Celsius. Here, the Rs value may be measured through spectroscopy or an impedance analyzer, and may be obtained simply by calculating an Rs value for estimating the optimal SOC.

Referring to FIG. 6, it can be seen that the Rs value (dotted line) at 10 degrees Celsius is larger than the Rs value (solid line) at 25 degrees Celsius, and thus the Rs value can vary greatly depending on the temperature of the battery.

7 is a graph showing Rs values measured in two different current patterns.

Referring to FIG. 7, it can be seen that the Rs value also varies with the current pattern. It is generally known that the Rs value varies with current magnitude.

8 is a diagram for explaining a change in the Rs value according to the remaining battery level.

It is known that the Rs value also varies with the battery remaining amount Q, and FIG. 8 shows this fact.

8, reference numerals 810a, 820a, 830a, and 840a are values measured at the same points as 810b, 820b, 830b, and 840b, respectively.

In FIG. 8 (b), the voltage falling period is the period during which the current is discharged, and the voltage rising period is the period during which the input / output current is not present.

The period from the point where the slope of the battery voltage becomes equal to or less than the specific value in the period in which the voltage increases without the input / output current is referred to as a stabilization period. The t1, t2, t3 and t4 shown in FIG. (a), 810a, 820a, 830a, and 840a.

Referring to t1, t2, t3, and t4, it can be seen that as the battery remaining amount Q becomes smaller, the length of the stabilization period becomes longer. If the length of the stabilization period is long, it can be understood that the RC time constant of the battery becomes large, and the value of Rs becomes large. As described above, Rs also varies greatly depending on the battery remaining amount Q.

When these parameters are changed, an error may occur in the battery input / output current (i) calculated by Equation (8), and this error is accumulated by the temporal division of Equation (9) Can be increased more and more.

A parameter compensation process may be performed to reduce this parameter error.

The parameter compensating unit 334 can compensate the parameters without affecting the calculation process of the battery remaining amount estimating unit 332 by compensating the parameters of the battery model function according to a separate process.

The parameter compensating unit 334 can compensate the parameters of the battery model function through the difference between the input / output current i and the measured input / output current im calculated by Equation (8). If there is no error in the parameters of the battery model function, i [k] = im [k] should be established. However, if there is a difference between the calculated input / output current (i) and the measured input / output current (im), it can be determined that an error is caused in the parameters of the battery model function.

Equation (11) shows an example of modifying the battery internal resistance (Rs) parameter through the difference between the calculated input / output current (i) and the measured input / output current (im). Since it is the battery internal resistance (Rs) that reacts most sensitively to temperature and aging, a large effect of reducing the error can be seen even if only the formula (11) is used. However, the present invention is not limited to Equation (11), and the parameter compensating unit 334 may calculate the other parameters (for example, R1, R2, and?) Through the difference between the input / output current i and the measured input / R3, etc.) may be modified.

The magnitude of the absolute value of the correction coefficient K used for error correction may have a different value depending on the degree of correction. For example, the parameter compensating unit 334 can increase the magnitude of the absolute value of the correction coefficient K when the parameter compensation is to be performed sensitively, Can be reduced. However, when the magnitude of the absolute value of the correction coefficient K exceeds a predetermined value, the system may not be stable and may diverge or vibrate.

The sign of the correction coefficient K is determined by the sign of the input / output current. When both the measured input / output current (im) and the calculated input / output current (i) are positive, K has a positive value. When the calculated input / output current i is larger than the measured input / output current im, IERR has a positive value, which is multiplied by a positive correction coefficient K to increase the parameter for the internal resistance Rs Let i be small in the calculation. If the measured input / output current im and the calculated input / output current i are both negative values and the IERR is a positive value, then the absolute value of the measured input / output current im is larger than the absolute value of the calculated input / output current i . At this time, since the internal resistance Rs must be decreased to increase the absolute value of i, the correction coefficient K has a negative value.

If the sign of the measured input / output current im and the sign of the calculated input / output current i are different, the sign of the correction coefficient K varies depending on the application method of the algorithm. If the OCV curve is taken into consideration, the internal resistance Rs decreases Direction, or if the current is emphasized, the sign of the correction coefficient K should be determined in a direction in which the internal resistance Rs increases.

Meanwhile, the parameter compensating unit 334 can control the compensation coefficient K differently according to the magnitude of the current. The following is a control example for the compensation coefficient K when the current flows small.

The battery voltage (Vm) measured when the current flows small approaches OCV. Accordingly, the parameter compensating unit 334 can adjust the correction coefficient K so that Voc is converged to the measured voltage Vm when the current flows small. Such a method of adjusting the correction coefficient K is an embodiment in which the parameter compensating unit 334 adjusts the correction coefficient K with an emphasis on the OCV voltage.

Alternatively, the parameter compensating unit 334 may adjust the correction coefficient K so that the current value is more emphasized. For example, there is almost no change in the battery remaining amount Q when the current is almost not consumed. To this end, the parameter compensating unit 334 can adjust the correction coefficient K so that the battery input / output current i becomes small.

In contrast, the parameter compensating unit 334 can control the correction coefficient K differently by dividing the mode.

First, the parameter compensating unit 334 can operate in a mode that follows the OCV voltage (Voc). At this time, Voc is controlled so as to rapidly follow Vm. To this end, the parameter compensation unit 334 can adjust the correction coefficient K in such a direction that Rs is reduced such that the battery input / output current i is calculated to be large.

As another mode, the parameter compensating unit 334 can operate in a current-following mode. The parameter compensation unit 334 can enter this current tracking mode when the measured current value (see im in FIG. 6) is less than or equal to a certain value and several times below a certain value. In this current follow mode, the parameter compensating unit 334 can adjust the correction coefficient K in the direction of increasing Rs such that the battery input / output current i is calculated to be small.

9 is a flow chart of a process for compensating for battery parameters.

Referring to FIG. 9, the apparatus 300 measures the battery output voltage (Measured Voltage, Vm) and the battery input / output current (Measured Current, im) using the ADC 320.

Measured battery output voltage (Measured Voltage, Vm) is used for battery input / output current calculation (Current Estimation).

The difference between the estimated current (i) and the measured input / output current (measured current im) calculated through the battery input / output current calculation (Current Estimation) is used for the internal resistance parameter compensation (Rs calibration).

Apart from this parameter compensation process, the input / output current (Estimated Current, i) calculated through the battery input / output current calculation (Current Estimation) is used in the battery remaining amount calculation (SOC estimation) and finally the battery remaining amount (SOC) is derived.

In order to perform the above-described battery parameter compensation process, both the output voltage Vm of the battery and the input / output current im of the battery must be measured.

To this end, the device 300 may use two ADCs. However, when the device 300 is implemented in the form of an IC (Integrated Circuit), the two ADCs may be burdened with circuitry. Accordingly, in one embodiment of the present invention, a technique of measuring both the output voltage Vm of the battery and the input / output current im of the battery using one ADC 320 is proposed.

To measure two values with a single ADC 320, the device 300 according to one embodiment measures the output voltage Vm of the battery and the input and output current im of the battery at different times.

10 is a diagram showing timing of measuring the battery output voltage and the input / output current of the ADC.

Referring to Fig. 10, the ADC 320 measures the battery output voltage Vm at intervals of [Delta] t. The ADC 320 measures the battery input / output current im at a time different from the battery output voltage Vm (see 'Current meas' in FIG. 10).

The ADC 320 measures the battery output voltage Vm every period of? T and measures the battery input / output current im (M is a natural number of 2 or more) every period of N? T (N is a natural number of 2 or more) .

Where N DELTA t is sufficiently large (greater than 6 seconds) and M has a sufficiently small value (minimum of 2) to reduce power consumption of the device 300. [ For example, N may be greater than M. In this case, the number of times of measurement with respect to the battery output voltage Vm in the same period becomes larger than the number of times of measurement with respect to the battery input / output current im.

Since the battery parameter changes in a slow cycle, setting the NΔt to a sufficiently large value does not lower the accuracy of the parameter compensation.

On the other hand, the calculated input / output current (i) and the measured input / output current (im) used for parameter compensation must be the same time value to increase the accuracy of calculation. However, when the output voltage Vm of the battery and the input / output current im of the battery are measured using one ADC 320, the measurement time may be different from each other.

The parameter compensating unit 334 can solve the above problem by measuring the input / output current im more than once and estimating the value between the measurement times using the measured input / output current im.

11 is an enlarged view of a portion A in Fig.

Referring to FIG. 11, the ADC 320 may continuously measure the battery input / output current im in about t [k] time when the battery output voltage is measured.

In turn, the ADC 320 measures the battery input / output current im at a first time t [k-0.5] to obtain a first current value im [k-0.5] (im [k + 0.5]) by measuring the battery input / output current im at the third time t [k + 0.5] by measuring the battery output voltage Vm at time t [k] .

The parameter compensating unit 334 compares the battery input and output current im (k) with the current time t [k] using the first current value im [k-0.5] and the second current value im [ ) Can be measured. In one example, when the average of the first time and the third time for measuring the battery input / output current im coincides with the second time, the parameter compensating unit 334 averages the first current value and the second current value It is possible to measure the battery input / output current im at the current time t [k].

As another example, the parameter compensating unit 334 may use the interpolation method to calculate the first and second current values of the first time, the second current value of the third time, and the calculated input / output current (i) The parameter for the internal resistance Rs may be modified using the difference Ierr of the internal resistance Rs.

12 is a diagram showing an experimental result of an embodiment through charging / discharging of a random current.

12, the green graph is a reference SOC to be compared. In this experiment, the result of the current integration method using a precision current meter is set as a reference SOC.

The red graph in the result of FIG. 12 is a result of applying the battery remaining amount measuring method described with reference to FIG.

12, the blue graph represents the difference between the green graph (reference SOC) and the red graph (the result SOC of one embodiment).

Referring to FIG. 12, it can be seen that the green graph and the red graph substantially coincide. Also, the blue graph, which is the difference between the two graphs, shows that the error of the battery residual amount measurement method according to one embodiment is within an error range of +/- 2%.

13 is a graph showing the results of an experiment conducted at an ambient temperature of 10 degrees.

In the left graph of FIG. 13, the blue graph is the reference SOC. In this experiment, the result of the current integration method using a precision current meter is set as a reference SOC.

The green graph in the left graph of FIG. 13 is a result of applying the parameter compensation method described with reference to FIG. 9 to the battery remaining amount measuring method described with reference to FIG.

Referring to FIG. 13, it can be seen that there is no significant difference between the reference SOC and the experimental result even at a low temperature condition (room temperature 10 degrees).

The right graph of FIG. 13 is a graph showing the battery internal resistance Rs compensated in the experiment.

Referring to the right graph of FIG. 13, the internal resistance Rs tends to increase, which is a typical characteristic of a battery when the temperature is low. As described above, since the internal resistance Rs is accurately compensated by the parameter compensation according to the embodiment, the residual error of the battery is small as shown in the left graph of FIG.

As described above, according to the present invention, the remaining battery level can be measured accurately and quickly. Further, even when the battery characteristics are changed by temperature or aging, the residual battery amount can be accurately measured without necessity of temperature measurement or aging measurement. In addition, it is possible to minimize the circuit load of the battery remaining amount measuring device by measuring the voltage and current of the battery with one ADC.

Specifically, the apparatus and method according to an embodiment of the present invention can attain very high precision by intermittent current measurement rather than the Coulomb Counter.

In addition, the apparatus and method according to an embodiment of the present invention measure both current and voltage using a single ADC without using a separate current totalizer, and compare the current and voltage using a time sharing method Thereby compensating for battery parameters.

As described with reference to FIGS. 6 to 8, Rs varies greatly depending on the battery temperature, the current magnitude or the current pattern, and the battery remaining amount Q.

The apparatus and method according to an embodiment of the present invention can improve the short term accuracy in battery remaining amount estimation by correcting this changing Rs.

9, the parameter compensating unit 334 can operate in a mode in which the Voc follows the measured voltage Vm. Referring to this, the apparatus and method according to an embodiment of the present invention Can quickly follow the OCV voltage (Voc), and can also improve long term accuracy.

In this respect, the apparatus and method according to an embodiment of the present invention have both the advantages of the current integration method and the advantages of the voltage measurement algorithm.

It is to be understood that the terms "comprises", "comprising", or "having" as used in the foregoing description mean that the constituent element can be implanted unless specifically stated to the contrary, But should be construed as further including other elements. All terms, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, unless otherwise defined. Commonly used terms, such as predefined terms, should be interpreted to be consistent with the contextual meanings of the related art, and are not to be construed as ideal or overly formal, unless expressly defined to the contrary.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

Claims (9)

A method for measuring the remaining amount of a battery,
Storing an initial value of the battery remaining amount;
Calculating an open circuit voltage of the battery using an OCV (Open Circuit Voltage) function taking the battery remaining amount as a factor;
Output current of the battery is measured for a first time, a second time, and a third time sequentially by using one ADC (Analog Digital Converter) to acquire a first current value and a second time Measuring an output voltage of the battery and measuring a input / output current of the battery at a third time to obtain a second current value;
Calculating an input / output current of the battery using a battery model function including a voltage difference between the open circuit voltage and the output voltage as a parameter and including the internal resistance of the battery as a parameter;
Updating the battery remaining amount in time based on the calculated input / output current;
The interpolation method is used to calculate the internal resistance of the first and second transistors by using the difference between the first current value of the first time and the second current value of the third time into the value of the second time, And modifying a parameter for the battery. The method according to claim 1,
In modifying the parameters for the internal resistance,
Wherein the parameter for the internal resistance is modified according to the following equation.
Rs, new is the updated Rs, K is the correction factor, Iest is the calculated input / output current, Imea is the measured input / output current (Ie) 3. The method of claim 2,
Wherein the parameter for the internal resistance increases when the absolute value of the calculated input / output current is greater than the absolute value of the measured input / output current. The method according to claim 1,
In the step of measuring the output voltage and the input / output current of the battery,
Wherein the output voltage of the battery is measured in a cycle of T, and the input / output current of the battery is measured in a cycle of NT (N is a natural number of 2 or more). delete delete An apparatus for measuring the remaining amount of a battery,
A memory for storing a battery model function including a battery remaining amount, an OCV (Open Circuit Voltage) function and an internal resistance of the battery as parameters;
Output current of the battery at a first time to obtain a first current value for a first time, a second time and a third time, An ADC (Analog Digital Converter) for measuring an input / output current of the battery to obtain a second current value;
Calculating an open circuit voltage of the battery by inputting the remaining battery amount into the OCV function, inputting a voltage difference between the open circuit voltage and the output voltage to the battery model function to calculate an input / output current of the battery, A battery remaining amount estimating unit for updating the battery remaining amount in time based on the current; And
The interpolation method is used to calculate the internal resistance of the first and second transistors by using the difference between the first current value of the first time and the second current value of the third time into the value of the second time, And a parameter compensating unit for correcting the parameter for the battery. delete 8. The method of claim 7,
The ADC includes:
Wherein the number of times of measurement of the output voltage in the constant cycle is larger than the number of times of measurement of the input / output current.

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