JP6722036B2 - Rechargeable battery remaining amount detection circuit, electronic device using the same, automobile and charge state detection method - Google Patents

Description

The present invention relates to a battery management system.

Various battery-driven electronic devices such as mobile phone terminals, digital cameras, tablet terminals, portable music players, portable game devices, and notebook computers have a built-in rechargeable battery (secondary battery). Electronic circuits such as a CPU (Central Processing Unit) that performs system control and signal processing, a liquid crystal panel, a wireless communication module, and other analog and digital circuits operate by being supplied with power from a battery.

FIG. 1 is a block diagram of a battery-driven electronic device. The electronic device 500 includes a battery 502 and a charging circuit 504 that charges the battery 502. The charging circuit 504 receives the power supply voltage V _ADP from an external power supply adapter or USB (Universal Serial Bus) and charges the battery 502.

A load 508 is connected to the battery 502. The current _BAT flowing through the battery 502 is the difference between the charging current I _CHG from the charging circuit 504 and the load current (discharge current) I _LOAD flowing through the load 508.

In a battery-driven electronic device, detection of the remaining amount of the battery (state of charge: SOC) is an essential function, and the electronic device 500 is provided with a remaining amount detection circuit 506. The remaining amount detection circuit 506 is also referred to as a fuel gauge IC (Integrated Circuit). There are two main methods of detecting the remaining amount of the battery by the remaining amount detecting circuit 506: (1) voltage method and (2) Coulomb counting method (charge integration method). The remaining amount detection circuit 506 may be incorporated in the charging circuit 504.

In the voltage method, the open circuit voltage (OCV: Open Circuit Voltage) of the battery is measured in the open state (no-load state), and the remaining amount is estimated from the correspondence between OCV and SOC. OCV cannot be measured unless the battery is unloaded and in the relaxed state, and therefore cannot be accurately measured during charging and discharging.

In the Coulomb counting method, the charge current flowing into the battery and the discharge current flowing out from the battery (hereinafter, collectively referred to as charge/discharge current) are integrated, and the remaining charge is estimated by calculating the charge charge amount and the discharge charge amount to the battery. .. According to the Coulomb counting method, unlike the voltage method, the remaining amount can be estimated even during the period of use of the battery in which the open circuit voltage cannot be obtained.

The remaining amount detection circuit 506 of FIG. 1 estimates the remaining amount of the battery 502 by the Coulomb counting method. The remaining amount detection circuit 506 includes a Coulomb counter circuit 510 and an SOC calculation unit 512. Coulomb counter circuit 510 detects the current I _{BAT of} battery 502 and integrates it. The coulomb count value CC generated by the coulomb counter circuit 510 is expressed by the following equation.
CC=∫I _BAT dt
Strictly speaking, the battery current I _BAT is discretely sampled in time and calculated by the following formula. Δt indicates a sampling period.
CC=Σ(Δt×I _BAT )
This integration is performed with the current I _BAT flowing out of the battery 502 being positive and the current I _BAT flowing in the battery 502 being negative.

The SOC calculation unit 512 calculates the SOC of the battery 502 based on the Coulomb count value CC. The following formula is used for the calculation of SOC.
SOC [%]=(CC _FULL −CC)/CC _FULL ×100
CC _FULL indicates the amount of electric charge (coulomb count value) stored in the battery 502 in the fully charged state.

US Pat. No. 9,035,616 B2

As a result of examining the remaining amount detecting circuit 506 of FIG. 1, the present inventor has come to recognize the following problems. Here, the phenomenon at the time of discharging will be described without considering charging. FIG. 2 is a diagram showing a correspondence relationship between OCV and SOC (SOC-OCV characteristic) and a change in battery voltage V _BAT .

Here, taking a lithium ion cell as an example, when OCV=4.2V, it is in a fully charged state, that is, SOC=100%. _Further , when the minimum operating voltage at which the system including the load 508 can operate is V _{BAT_MIN} , SOC=0% when OCV=V _{BAT_MIN} . The intermediate SOC is also associated with the OCV on a one-to-one basis.

Now, when the load current I _LOAD flows continuously or discontinuously from the fully charged state, the OCV decreases in the direction shown by the arrow in the figure. The discharge current I _{BAT at} this time is integrated, the SOC is calculated based on the Coulomb count value CC, and approaches zero as time passes.

FIG. 2 shows the battery voltage V _BAT taken out from the battery 502 in addition to the OCV. Battery voltage V _BAT is dropping more than OCV. This drop amount (voltage drop) V _DROP includes a component based on the history of the past load current I _LOAD , in addition to a component proportional to the current load current I _LOAD (that is, an instantaneous value). Therefore, even after the load current I _LOAD becomes zero, it does not immediately become zero. The voltage drop V _DROP approaches zero after a long relaxation time (on the order of several hours) in the unloaded state.

As shown in FIG. 2, due to the voltage drop _{V DROP,} prior OCV decreases to _{V BAT_MIN,} the battery voltage _{V BAT} drops to _{V BAT_MIN,} the system shuts down. At this time, the SOC calculated based on the Coulomb counting method is a value X larger than 0. That is, the user of the electronic device 500 encounters a situation in which the system shuts down although the remaining X (%) is displayed.

The present invention has been made in view of the above problems, and one of the exemplary objects of an aspect thereof is to provide a method and a remaining amount detection circuit capable of improving the detection accuracy of the charge state of a battery.

An aspect of the present invention relates to a method for detecting SOC (State Of Charge) of a rechargeable battery. This method includes the following processes.
(1) The Coulomb count value CC is generated by integrating the charge/discharge current of the battery.
(2) SOC value SOC1,
SOC1=(CC _FULL -CC)/CC _FULL ×100 (1)
It is generated based on. However, CC _FULL is a Coulomb count capacity value corresponding to full charge.
Further, with this method, the following correction processing (3) is performed.
(3-1) A value OCV1 of OCV corresponding to the value SOC1 is generated based on the correspondence relationship (SOC-OCV characteristic) between SOC and OCV (Open Circuit Voltage) that is defined in advance for the battery.
(3-2) _{Detect the} battery voltage V _BAT1 .
(3-3) The difference V _DROP1 between the value OCV1 and the detected value V _BAT1 of the battery voltage V _BAT is generated.
(3-4) A voltage width ΔV corresponding to the difference V _DROP1 and a high value OCV2 are generated from the minimum operating voltage V _{BAT_MIN of the} system.
(3-5) Based on the SOC-OCV characteristic, the SOC value SOC2 corresponding to the value OCV2 is generated.
(3-6) At least one of the values SOC1, CC, CC _FULL, and SOC-OCV characteristics is corrected assuming that the value SOC2 corresponds to the remaining amount of zero (0%).

According to this aspect, in consideration of the voltage drop V _DROP which changes from time to time, when the actual battery voltage V _BAT drops to the minimum operating voltage V _{BAT — MIN} , that is, when the system shuts down, the SOC becomes zero. The remaining amount detection process based on the Coulomb counting method can be corrected, and the SOC detection accuracy can be improved.

It may be ΔV=V _DROP1 . This is effective when the SOC dependency of the difference between the OCV and the battery voltage is small.

The SOC dependency of the difference V _DROP between the OCV and the battery voltage may be held in advance, may be held in a lookup table, or may be held as an arithmetic expression.
The correction process may further include the following process.
The provisional value of OCV OCV3= _{VBAT_MIN} + _VDROP1 is calculated.
The provisional value SOC3 of SOC corresponding to the provisional value OCV3 of OCV is generated.
The voltage drop ΔV at the provisional value SOC3 is calculated based on the difference V _{DROP1 at the} value SOC1 and the SOC dependency of the difference.
This can improve accuracy.

In addition to the SOC dependence of the voltage drop V _DROP , the temperature dependence may be maintained. This can further improve the accuracy.

In the correction process (3-6), the Coulomb count capacity value CC _FULL may be corrected to a new value CC _FULL ′ obtained by the equation (2).
CC _FULL '=CC _FULL x (100-SOC2)/100 (2)

In the correction process (3-6), the Coulomb count value CC may be corrected to a new value CC′ obtained by the equation (3).
CC'=CC-(CC _FULL -CC _FULL ') (3)

In the correction process (3-6), the Coulomb count value CC may be corrected to a new value CC′ obtained by the equation (4).
CC′=CC-CC _FULL ×SOC2/100 (4)

In the correction process (3-6), the new value SOC′ obtained by the equation (5) may be the corrected SOC.
SOC′=SOC1×100/(100−SOC2) (5)

In the correction process (3-6), the Coulomb count value CC may not be corrected.

In the correction process (3-6), the new value SOC′ obtained by the equation (6) may be the corrected SOC.
SOC′={CC _FULL −CC×100/(100−SOC2)}/CC _FULL ×100 (6)

In the correction process (3-6), the Coulomb count capacity value CC _FULL may not be modified and the Coulomb count value CC may be modified to a new value CC′ obtained by the equation (7).
CC′=CC×100/(100−SOC2) (7)

In the correction process (3-6), the Coulomb count value CC may be corrected to a new value CC′ obtained by the equation (8).
CC′=CC×(100−SOC2)/100 (8)

The SOC-OCV characteristics described above may associate a range of OCV below the lowest operating voltage of the system with a negative SOC.
This makes it possible to deal with the case where the effective remaining amount increases.

The correction process (3) may be enabled when the voltage of the battery is lower than a predetermined voltage value. Alternatively, the correction process (3) may be effective when the SOC is lower than a predetermined value.
By not performing the correction when the battery level is large, it is possible to suppress an increase in power consumption due to the correction.

The correction process (3) may be intermittently enabled in every predetermined cycle.
When the correction is always enabled, the power consumption increases. However, by performing the correction process intermittently at a predetermined cycle, it is possible to suppress the increase in the power consumption due to the correction.

The predetermined period may be longer than 1 second and shorter than 60 seconds. By performing the correction in this cycle, the effect of sufficiently improving the accuracy of SOC can be obtained within the range of reasonable increase in power consumption.

Another aspect of the present invention relates to a remaining amount detection circuit that detects SOC (State Of Charge) of a rechargeable battery. The remaining amount detection circuit is based on equation (1), a coulomb counter circuit that generates a coulomb count value CC by accumulating charge/discharge current of the battery, a voltage detection circuit that detects the voltage V _BAT of the battery, and an SOC based on equation (1). And a correction circuit that corrects at least one of the values SOC1, CC, CC _FULL and SOC-OCV characteristics.
SOC1=(CC _FULL -CC)/CC _FULL ×100 (1)
However, CC _FULL is equivalent to full charge Coulomb count capacity value correction circuit is based on the SOC-OCV characteristic which is a correspondence relationship between SOC and OCV (Open Circuit Voltage) which is defined in advance for the battery, and the OCV corresponding to the value SOC1. And a step of generating a difference V _DROP1 between the value OCV1 and the detected value V _{BAT1 of the} voltage detected by the voltage detection circuit, and a voltage width ΔV corresponding to the difference V _DROP1 from the lowest operating voltage of the system. , A step of generating a high value OCV2, a step of generating a SOC value SOC2 corresponding to the value OCV2 based on the SOC-OCV characteristic, and a value SOC2 corresponding to a remaining amount of zero (0%). Modifying at least one of SOC1, CC, CC _FULL and SOC-OCV characteristics.

Another aspect of the present invention is an electronic device. The electronic device includes a rechargeable battery and the above-described remaining amount detection circuit that detects the state of the battery.

Another aspect of the present invention is an automobile. The automobile includes a rechargeable battery and the above-described remaining amount detection circuit that detects the state of the battery.

It should be noted that any combination of the above constituent elements and constituent elements and expressions of the present invention that are mutually replaced among methods, devices, systems, etc. are also effective as an aspect of the present invention.

According to the present invention, it is possible to improve the detection accuracy of the charge state of the battery.

It is a block diagram of an electronic device. Is a graph showing changes in OCV and correspondence (SOC-OCV characteristics) of SOC and the battery voltage _{V BAT.} 1 is a block diagram of a battery management system including a remaining amount detection circuit according to an embodiment. It is a figure which shows an example of a SOC-OCV characteristic. 6 is a flowchart of remaining amount detection according to the embodiment. It is a figure which shows the correction|amendment process using the relationship between a voltage and SOC. It is a figure which shows the 1st correction method typically. It is a figure which shows an example of correction|amendment of a SOC-OCV characteristic. It is a figure which shows an example of correction|amendment of a SOC-OCV characteristic. It is a figure which shows an example of the SOC-OCV characteristic in a 1st modification. FIG. 11 is a diagram showing a correction process when the SOC-OCV characteristic of FIG. 10 is used. It is a look-up table showing the SOC dependence of the voltage drop V _DROP . It is a flowchart of the remaining amount detection which concerns on a 2nd modification. 14 is a flowchart showing a ΔV calculation routine of FIG. 13. It is a figure which shows the estimation result of SOC in the remaining amount detection which concerns on a 2nd modification. It is a figure which shows the expanded VDR lookup table. It is a figure which shows the estimation result of SOC in the remaining amount detection which concerns on a 4th modification. It is a figure which shows the motor vehicle provided with a battery management system. It is a figure which shows the electronic device provided with a battery management system.

Hereinafter, the present invention will be described based on preferred embodiments with reference to the drawings. The same or equivalent constituent elements, members, and processes shown in each drawing are denoted by the same reference numerals, and duplicated description will be omitted as appropriate. Further, the embodiments are merely examples and do not limit the invention, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

In the present specification, “the state in which the member A is connected to the member B” means that the member A and the member B are physically directly connected or that the member A and the member B are electrically connected to each other. It also includes the case of being indirectly connected via another member that does not substantially affect the connection state or does not impair the function and effect exerted by their connection.
Similarly, "the state in which the member C is provided between the member A and the member B" means that the members A and C or the members B and C are directly connected and their electrical It also includes a case where they are indirectly connected through other members that do not substantially affect the general connection state or do not impair the functions and effects achieved by their connection.

Further, in the present specification, the symbols attached to the voltage signal, the current signal, or the resistance represent the respective voltage value, current value, or resistance value as necessary.

FIG. 3 is a block diagram of the battery management system 100 including the remaining amount detection circuit according to the embodiment. The battery management system 100 includes a battery 102, a charging circuit 104, a load 108, and a remaining amount detection circuit 200. The battery 102 includes one or a plurality of cells. The type of cell is not particularly limited, and examples thereof include a lithium ion cell, a lithium air cell, a lithium metal-based cell, a nickel hydrogen cell, a nickel cadmium cell, and a nickel zinc cell. The number of cells depends on the application of the battery management system 100, but in the case of a portable electronic device, it is in the order of one cell to several cells, and in the application of in-vehicle batteries, industrial equipment, and industrial machines, it is on the order of several tens to several hundred cells. .. The configuration of the battery 102 is not particularly limited as the application of the present invention.

The battery voltage V _BAT from the battery 102 is supplied to the load 108. The type of the load 108 is not particularly limited. For example, if the battery management system 100 is mounted on an electronic device, the load 108 boosts or steps down the battery voltage V _BAT, and a power supply circuit for generating a supply voltage V _DD, various electronic operating by receiving power supply voltage V _DD Circuitry may be included. When the battery management system 100 is installed in an automobile or an industrial machine, the load 108 may include a motor and an inverter that converts the battery voltage V _BAT into alternating current and drives the motor.

The charging circuit 104 receives a power supply voltage V _EXT from an external power supply adapter, a USB (Universal Serial Bus), a charging station, etc., and charges the battery 102.

The remaining amount detection circuit 200 detects the state of charge (SOC) of the battery 102. Note that, in this specification, for ease of understanding, the SOC is described as a percentage (%) in which the minimum value is 0 and the maximum value is 100, but the present invention is not limited thereto. For example, when the SOC is represented by 10 bits, it should be noted that the SOC is represented by 1024 gradations of 0 to 1023 in the process of digital signal processing.

The remaining amount detection circuit 200 includes a Coulomb counter circuit 202, a voltage detection circuit 204, an SOC calculation unit 206, a correction circuit 208, and a lookup table 210. The coulomb counter circuit 202 generates a coulomb count value CC by integrating the charge/discharge current (I _BAT ) of the battery 102. The coulomb count value CC is represented by the following formula.
CC=∫I _BAT dt
The Coulomb counter circuit 202 samples the battery current I _BAT at a predetermined sampling period Δt. The coulomb count value CC is calculated by the following equation using the battery current I _BATi at each sampling time.
CC=Σ _i=1 (Δt×I _BATi ).
This integration is performed with the current I _BAT flowing out of the battery 102 being positive and the current I _BAT flowing in the battery 502 being negative.

The method of detecting the current I _BAT is not particularly limited. For example, the sense resistor R _S may be inserted in series with the battery 102 on the path of the current I _BAT to detect the voltage drop of the sense resistor R _S. The sense resistor R _S may be inserted on the positive electrode side or the negative electrode side of the battery 102. The Coulomb counter circuit 202 includes an A/D converter that samples the voltage drop V _CS (or a voltage obtained by amplifying the voltage drop V _CS ) of the sense resistor R _S , and an integrator that integrates the output data of the A/D converter. May be included.

The voltage detection circuit 204 monitors the voltage V _{BAT of the} battery 102 and generates data (voltage data) DV _BAT indicating the battery voltage V _BAT1 . The voltage detection circuit 204 may include an A/D converter that samples and digitizes the battery voltage V _BAT or a voltage obtained by multiplying the battery voltage V _BAT by a predetermined coefficient.

SOC calculation unit 206 receives coulomb count value CC from coulomb counter circuit 202. The SOC calculator 206 calculates the SOC value SOC1 based on the equation (1).
SOC1=(CC _FULL -CC)/CC _FULL ×100 (1)
However, CC _FULL is the coulomb count capacity value equivalent to full charge.

The correction circuit 208 is supplied with the value SOC1 and the voltage data DV _BAT . The correction circuit 208 corrects at least one of the values SOC1, CC, CC _FULL, and SOC-OCV characteristics based on these values.

Hereinafter, the correction processing by the correction circuit 208 will be described.
Regarding the battery 102, the correspondence between SOC and OCV (Open Circuit Voltage) (SOC-OCV characteristic) is measured in advance. FIG. 4 is a diagram showing an example of SOC-OCV characteristics. The SOC-OCV characteristic is stored in the look-up table 210 of FIG. 3, for example. Intermediate values that are not stored in the look-up table 210 can be generated by calculation means such as linear interpolation. Alternatively, the correction circuit 208 may hold the SOC-OCV characteristic in the form of an arithmetic expression (for example, polynomial).

The correction circuit 208 generates a value OCV1 of OCV corresponding to the value SOC1 based on the SOC-OCV characteristic. _Then , the difference V _DROP1 between the value OCV1 and the battery voltage V _BAT1 detected by the voltage detection circuit 204 is generated.
V _DROP1 =OCV1-V _BAT1

Let the minimum operating voltage of the system including the load 508 be V _{BAT — MIN} . The correction circuit 208 generates a voltage width ΔV corresponding to the difference V _DROP1 and a value OCV2 higher than the lowest operating voltage V _{BAT_MIN} .
OCV2=V _{BAT_MIN} +ΔV
When ΔV=V _DROP1 ,
OCV2=V _{BAT_MIN} +V _DROP1
Becomes Alternatively, when ΔV=V _DROP1 ×α (α is a constant),
OCV2=V _{BAT_MIN} +V _DROP1 ×α
Becomes Or if ΔV=V _DROP1 +β (β is a constant),
OCV2=V _{BAT_MIN} +V _DROP1 +β
Becomes Alternatively,
OCV2=V _{BAT_MIN} +α×V _DROP1 +β
May be More generalized, a predetermined function f() may be defined and the voltage width ΔV may be calculated based on ΔV=f(V _DROP1 ).

The correction circuit 208 generates the SOC value SOC2 corresponding to the value OCV2 based on the SOC-OCV characteristic. Then, the correction circuit 208 corrects at least one of the values SOC1, CC, CC _FULL and SOC-OCV characteristics, assuming that the value SOC2 corresponds to the remaining amount of the battery 102 of zero (0%).

The Coulomb counter circuit 202 and the voltage detection circuit 204 can be implemented only by hardware, and they may be integrated in a single IC. The SOC calculation unit 206, the correction circuit 208, and the look-up table 210 may be implemented by a software-controllable processor such as a microcomputer. Alternatively, the entire remaining amount detection circuit 200 may be integrated on a single chip.

The SOC generated by the remaining amount detection circuit 200 is displayed on the display device as a numeral or as an icon indicating the remaining amount, or is used as an alert.

The above is the configuration of the remaining amount detection circuit 200 according to the embodiment. Next, the operation will be described. FIG. 5 is a flowchart of remaining amount detection according to the embodiment. For example, the process starts from the fully charged state. Note that the flowchart does not limit the order of each process (step), and the order of each process can be arbitrarily changed as long as the process does not fail. Further, this flowchart does not show that the frequency (frequency, cycle) at which each process is performed is the same.

The coulomb counter circuit 202 calculates the coulomb count value CC (S100). The SOC calculation unit 206 uses the Coulomb count value CC to calculate the value SOC1 based on the equation (1) (S102). For example, the coulomb counter circuit 202 updates the coulomb count value CC at a cycle of several tens to several hundreds of Hz, while the SOC computing unit 206 updates the SOC1 at a lower frequency, for example, a cycle of about 1 second to 60 seconds. You may calculate.

The voltage detection circuit 204 measures V _BAT (S104). When the increase in power consumption is not a problem, the voltage detection circuit 204 may measure the battery voltage V _BAT at a high frequency (for example, the same frequency as the Coulomb counter circuit 202).

Then, the correction process S110 is performed. The correction process S110 may be performed for each calculation of SOC1, or may be performed in a cycle shorter than that. FIG. 6 is a diagram showing a correction process S110 using the relationship between the voltage and the SOC. Each value is generated in the order of the numbers (i) to (v) attached to it.

The correction circuit 208 converts SOC1 to OCV1 based on the SOC-OCV characteristic (S112). Then, the voltage drop V _DROP1 is calculated (S114). Then, based on the voltage drop _{V DROP1} and minimum operating voltage _{V BAT_MIN,} it estimates the OCV value OCV2 of when the measured value _{V BAT1} a battery voltage _{V BAT} reaches the minimum operating voltage _{V BAT_MIN} (S116). Then, based on the SOC-OCV characteristic, the value OCV2 is inversely converted to the corresponding SOC value SOC2 (S118).

The value SOC2 represents the SOC at which the system can shut down. That is, when the SOC1 calculated by the SOC calculation unit 206 decreases to the value SOC2, the battery voltage V _BAT may decrease to the minimum operating voltage V _{BAT_MIN} and shut down may occur.

Therefore, in the correction process S120, at least one of the values SOC1, CC, CC _FULL, and SOC-OCV characteristics is corrected based on the value SOC2, assuming that the value SOC2 corresponds to the remaining amount of zero (0%).

The above is the remaining amount detection processing according to the embodiment. According to the remaining amount detecting circuit 200 (and the remaining amount detecting method) described here, when the actual battery voltage V _BAT drops to the minimum operating voltage V _{BAT_MIN} in consideration of the voltage drop V _DROP which changes from time to time, That is, the remaining amount detection process based on the Coulomb counting method can be corrected so that the SOC becomes zero when the system shuts down. This can improve the SOC detection accuracy.

The remaining amount detecting method according to the embodiment should not be confused with the SOC based on the voltage method. Although this embodiment is common to the voltage method in that the SOC-OCV characteristic is used, the process of measuring the OCV is not required, and therefore, it is not necessary to wait for the relaxation time to elapse.

The present invention extends to various devices, circuits, systems and methods understood as the block diagram of FIG. 3, the flowchart of FIG. 5 or derived from the above description, and is limited to particular configurations and methods. is not. Hereinafter, more specific configurations and methods will be described in order to help understanding of the essence of the invention and circuit operation and to clarify them, not to narrow the scope of the invention.

Next, the correction process S120 in the flowchart of FIG. 5 will be described. There are various methods for the correction process as described below.

(First correction method)
FIG. 7 is a diagram schematically showing the first correction method. The coulomb count capacity value CC _FULL is modified to a new value CC _FULL ′ obtained by equation (2).
CC _FULL '=CC _FULL x (100-SOC2)/100 (2)
That is, CC _FULL is scaled so that SOC2 is zero (SOC=0%). When K=(100−SOC2)/100 is called a scaling factor, equation (2) can be rewritten as equation (2′).
CC _FULL '=CC _FULL ×K (2')

Further, the Coulomb count value CC is modified to a new value CC′ obtained by the equation (3).
CC'=CC-(CC _FULL -CC _FULL ')
=CC-CC _FULL ×SOC2/100 (3)
That _is, minute ΔCC with reduced by modifying the _{CC FULL (= CC FULL -CC FULL} '), CC also reduced.

The corrected coulomb count value CC' is written in the register for storing the coulomb count value CC inside the coulomb counter circuit 202 in FIG. Further, the coulomb count capacity value CC _FULL ′ is replaced with the coulomb count capacity value CC _FULL held by the SOC computing unit 206 of FIG.

The coulomb count value CC may be modified to a new value CC′ obtained by the equation (4).
CC′=CC-CC _FULL ×SOC2/100 (4)
The expression (3) is equivalent to the expression (4).

After correcting CC and CC _FULL , SOC1′ generated by the SOC calculation unit 206 after that is expressed by the following equation.
_{SOC1 '= (CC FULL' -CC} ') / CC FULL' × 100
_{= {(CC FULL -CC FULL ×} SOC2 / 100) - (CC-CC FULL × SOC2 / 100)} / {CC FULL × K} × 100
=(CC _FULL -CC)/CC _FULL ×100×1/K
Here, (CC _FULL −CC)/CC _FULL ×100 corresponds to SOC1 in Expression (1), and thus the corrected SOC′ is expressed by Expression (5).
SOC'=SOC1×1/K
=SOC1*100/(100-SOC2) (5)

In the first correction method, the coulomb count value CC and the coulomb count capacity value CC _FULL are corrected by one correction, and thereafter, the charge/discharge current I _BAT is integrated with the corrected coulomb count value CC′ as an initial value. Will be done. That is, the SOC detection by the Coulomb counting method is performed while the correction is reflected. That is, it is not always necessary to correct the correction circuit 208 for each calculation of SOC1 of the SOC calculation unit 206.

(Second correction method)
The second modification method is substantially the same as the first modification method, but without modifying the values _CC and CC _FULL , the value SOC′ calculated based on the equation (5) is corrected. The SOC is improved. The second correction method can be used when the correction processing is performed every time the SOC calculation unit 206 calculates SOC1.

(Third correction method)
In the third modification method, CC _FULL is modified based on the equation (2), but the Coulomb count value CC is not modified.

In this case, the new value SOC′ obtained by equation (6) is used as the corrected SOC.
_{SOC '= (CC FULL' -CC} ) / CC FULL '× 100
=(CC _FULL ×K-CC)/(CC _FULL ×K)×100
=(CC _FULL -CC×1/K)/CC _FULL ×100
={CC _FULL -CC×100/(100-SOC2)}/CC _FULL ×100 (6)

(Fourth correction method)
In the fourth correction method, the Coulomb count capacity value CC _FULL may not be modified and the Coulomb count value CC may be modified to a new value CC′ obtained by the equation (7).
CC′=CC×100/(100−SOC2) (7)

It can be said that the fourth correction method is equivalent because it gives the same SOC' as that of the third correction method.

(Fifth correction method)
In the fifth correction method, the Coulomb count capacity value CC _FULL is corrected based on the equation (2). Further, the Coulomb count value CC is corrected to a new value CC' obtained by the equation (8). That is, CC _FULL and CC are scaled by the same scaling factor K.
CC′=CC×(100−SOC2)/100
=CC×K (8)

In the fifth correction method, the SOC immediately after the correction is
_{SOC '= (CC FULL' -CC} ) / CC FULL '× 100
=(CC _{FULL xK} -CC _xK )/(CC _{FULL xK} ) _{x100
= (CC FULL -CC) / CC} FULL × 100
=SOC1
And the same value as it was just before the correction is maintained. However, since the coulomb count value CC and the coulomb count capacity value CC _FULL are corrected, the SOC1 calculated after the count is advanced after that is the one in which the correction is reflected. When the discontinuity of SOC is not preferable, the fifth correction method may be adopted.

(Sixth correction method)
In the first to fifth correction methods, at least one of the values CC, CC _FULL and SOC is corrected. On the other hand, in the sixth modification method, the SOC-OCV characteristic is modified. More specifically, in the sixth modification method, the SOC-OCV characteristic is modified so that the SOC2 becomes zero (0%) in the remaining amount. For example, the SOC (%) before correction and the SOC′ (%) after correction may satisfy the following Expression (9).
SOC′=100−(100−SOC)×1/K
=100−(100−SOC)×100/(100−SOC2) (9)
8 and 9 are diagrams showing an example of correction of the SOC-OCV characteristic.

The sixth correction method is not limited to this, and an arithmetic expression different from Expression (9) may be used. Alternatively, instead of modifying the SOC value, the OCV value corresponding to each SOC may be modified, or both may be corrected. The SOC-OCV characteristic correction may have variations corresponding to the above-described first to fifth correction methods.

The variations of the correction method have been described above. It will be understood by those skilled in the art that there are various correction methods other than the first to sixth correction methods and those are included in the scope of the present invention.

Further, which correction method should be adopted may be selected according to the application of the battery management system 100.
For example, in the first and second correction methods, when K<1, the SOC value is increased by the correction. On the contrary, in the third and fourth correction methods, when K<1, the SOC value becomes smaller due to the correction. In the fifth correction method, the SOC value is maintained before and after the correction.
K<1 represents an absolute decrease in the remaining amount. On the other hand, SOC indicates the relative remaining amount. From the viewpoint of the relative remaining amount, it can be said that the first and second correction methods are correct. However, many users do not perceive the SOC in% display as the relative remaining amount, but sometimes as the absolute remaining amount. In this case, it may be uncomfortable for the SOC (%) to increase even though the remaining amount has decreased (that is, the remaining usable time has decreased). In this case, the third to fifth correction methods may be used.

The present invention has been described above based on the embodiment. This embodiment is merely an example, and it will be understood by those skilled in the art that various modifications can be made to the combinations of the respective constituent elements and the respective processing processes, and that such modifications are also within the scope of the present invention. is there. Hereinafter, such modified examples will be described.

(First modification)
The SOC-OCV characteristic may associate a range of OCV below the lowest operating voltage of the system with a negative SOC. FIG. 10 is a diagram showing an example of SOC-OCV characteristics in the first modification. Although the case where the effective remaining amount (absolute value) of the battery decreases has been described above, when the voltage drop V _DROP becomes negative, the remaining amount increases conversely. By introducing a negative SOC value, it is possible to deal with a case where the effective remaining amount increases without adding any special processing. FIG. 11 is a diagram showing a correction process when the SOC-OCV characteristic of FIG. 10 is used.

(Second modified example)
In step S116 in the flowchart of FIG. 5, when OCV2 is generated,
OCV2=V _{BAT_MIN} +ΔV (10)
The following formula was used. As shown in FIG. 2, the difference V _DROP between OCV and V _BAT depends on the SOC. Therefore, if ΔV=V _DROP1 is used in process S116, the error increases when the difference between SOC1 and SOC2 is large.

Therefore, in this second modification, the SOC dependence of the voltage drop V _DROP is considered. Specifically, the SOC dependence of the voltage drop V _DROP is defined as a look-up table or an arithmetic expression. FIG. 12 is a look-up table showing the SOC dependence of the voltage drop V _DROP . This table represents the relative ratio of the voltage drop at a plurality of SOCs. For example, the voltage drop at each SOC is taken as a ratio (Voltage Drop Ratio) with reference to the voltage drop at a predetermined reference SOC (here, 100%). : VDR).
VDR(x)=V _DROP (x)/V _DROP (100)

Therefore, when the voltage drop at a certain SOC (= _{x 1)} was _{V DROP1,} the voltage drop _{V DROP2} in another SOC (= _{x 2)} it can be calculated from the following equation.
V _DROP2 =V _DROP1 ×VDR(x ₂ )/VDR(x ₁ ).

FIG. 13 is a flowchart of remaining amount detection according to the second modification. In this flowchart, a ΔV calculation routine S115 is added before the processing S116 of the flowchart of FIG. FIG. 14 is a flowchart showing the ΔV calculation routine S115.

_First , the provisional value OCV3 of OCV when the measured value V _BAT1 of the battery voltage V _BAT reaches the minimum operating voltage V BAT_MIN is calculated based on the voltage drop V _DROP1 and the minimum operating voltage V _{BAT_MIN} (S130).
OCV3=V _{BAT_MIN} +V _DROP1
Then, based on the SOC-OCV characteristic, the provisional value OCV3 is inversely converted to the corresponding SOC value SOC3 (S132).

Then, based on the look-up table of FIG. 12, the values VDR1 and VDR3 of VDR in SOC1 and SOC3 are acquired (S134). And
ΔV=V _DROP1 ×VDR3/VDR1
Based on this, ΔV is calculated (S136). Using the thus obtained ΔV, OCV2 is calculated in step S116 of FIG.

FIG. 15 is a diagram showing an SOC estimation result in remaining amount detection according to the second modification. The estimated SOC is shown when the battery is discharged at a constant load (0.35C). (I) is an ideal SOC, which becomes a straight line at a constant load. (Ii) shows the estimated SOC value based on the flowchart of FIG. 5, and (iii) shows the estimated SOC value based on the flowchart of the second modification. Further, FIG. 15 shows the error between each SOC estimated value and the ideal SOC. As can be seen from FIG. 15, according to the second modification, the error can be reduced and the estimation accuracy can be improved by considering the SOC dependence of the voltage drop V _DROP .

(Third modification)
In the second modified example, the SOC dependence of the voltage drop V _DROP is corrected using a look-up table, but this may be approximated by the following arithmetic expression.
VDR(SOC) = 10^α*ln(log ₁₀ (β*SOC))+θ
α, β, θ are deterioration and temperature coefficient

(Fourth modification)
The fourth modified example is one in which the accuracy of the second modified example is further improved. In the fourth modified example, the temperature dependence of VDR is further considered. FIG. 16 is a diagram showing an expanded VDR lookup table. As shown in FIG. 16, the VDR lookup table is provided for every several temperatures. When the routine of FIG. 14 is executed, the temperature is measured and the value of VDR is acquired based on the lookup table corresponding to the temperature. FIG. 17 is a diagram showing an SOC estimation result in remaining amount detection according to the fourth modification. According to the fourth modification, the error can be further reduced and the estimation accuracy can be improved by considering the temperature dependence of the voltage drop V _DROP .

In the fourth modification, the VDR table for each temperature may be approximated by an arithmetic expression.
(Fifth Modification)
If the correction process is always performed, the amount of calculation of the correction circuit 208 increases and power consumption increases. Therefore, the correction process may be enabled when the voltage V _{BAT of the} battery 102 is lower than the predetermined voltage value V _TH . As the voltage value V _TH , an appropriate value may be selected for each system. In many cases, the user is interested in the remaining charge (SOC) of the battery 102 when the SOC decreases, that is, when V _BAT decreases. According to the second modification, it is possible to request an increase in power consumption by enabling the correction process in a situation where the user is interested. The correction process may be valid when the SOC is lower than a predetermined value.

(Sixth Modification)
The correction process may be enabled intermittently at predetermined intervals. If the correction is always enabled, power consumption will increase. Therefore, by performing the correction process intermittently at a predetermined cycle, it is possible to suppress an increase in power consumption due to the correction.

The predetermined period may be longer than 1 second and shorter than 60 seconds. By performing the correction in this cycle, the effect of sufficiently improving the accuracy of SOC can be obtained within the range of reasonable increase in power consumption. In applications where the time scale over which the voltage drop V _DROP changes is longer than 60 seconds, the predetermined period can be longer.

(Seventh modification)
The correction process may be enabled each time the SOC changes by a predetermined amount (n%, n is an arbitrary real number). According to this modification, it is possible to suppress an increase in power consumption due to the correction.

(8th modification)
In the embodiment, the dedicated voltage detection circuit 204 that monitors the voltage V _{BAT of the} battery 502 is provided, but the present invention is not limited thereto. In the battery management system 100, if a circuit for detecting the battery voltage V _BAT already exists, the battery voltage value V _BAT1 detected by the circuit may be used. Further, the battery voltage V _BAT may monitor the voltage of the positive electrode (+) of the battery 102, but not limited to this, the voltage of another node (line) may be monitored. For example, in a system in which a load switch is provided between the battery 102 and the load 108, the voltage of a node (line) closer to the load 108 than the load switch may be monitored. This is effective when the voltage drop of the load switch is large.

(Ninth Modification)
The correction of the SOC-OCV characteristic and the correction of the values CC, CC _FULL and SOC may be used together.

Finally, the usage of the battery management system 100 will be described. FIG. 18 is a diagram showing an automobile 300 including the battery management system 100. The vehicle 300 is an electric vehicle (EV), a plug-in hybrid vehicle (PHV), a hybrid vehicle (HV), or the like. The inverter 302 receives the voltage V _BAT from the battery management system 100, converts it into an alternating current, supplies it to the motor 304, and rotates the motor 304. In addition, during deceleration such as when the brake is depressed, the inverter 302 performs a regenerative operation and collects the current generated by the motor 304 in the battery 102 of the battery management system 100. PHVs and EVs additionally include a charging circuit that charges the battery 102 of the battery management system 100.

FIG. 19 is a diagram showing an electronic device 400 including the battery management system 100. The electronic device 400 includes a PMIC (power management IC) 402, a processor 404, and other electronic circuits (not shown) in addition to the battery management system 100. The PMIC 402 is an integrated plurality of power supply circuits that provide the processor 404 and other electronic circuits with appropriate power supply voltages.

In addition, the battery management system 100 can be used for an industrial device, an industrial machine, a home/factory power storage system, a power supply for an elevator system, and the like.

Although the present invention has been described based on the embodiments using specific terms, the embodiments merely show the principle and application of the present invention, and the embodiments define the scope of claims. Many modifications and changes in arrangement are possible without departing from the concept of the present invention.

Reference numeral 500... Electronic device, 502... Battery, 504... Charging circuit, 506... Remaining amount detection circuit, 508... Load, 510... Coulomb counter circuit, 512... SOC calculation section, 100... Battery management system, 102... Battery, 104... Charging Circuits, 108... Loads, 200... Remaining amount detection circuits, 202... Coulomb counter circuits, 204... Voltage detection circuits, 206... SOC calculation section, 208... Correction circuits, 210... Lookup tables, 300... Automobiles, 302... Inverters, 304... Motor, 400... Electronic device, 402... PMIC, 404... Processor.

Claims (36)

A method for detecting SOC (State Of Charge) of a rechargeable battery,
(1) a step of generating a Coulomb count value CC by accumulating charge/discharge currents of the battery,
(2) SOC value SOC1,
SOC1=(CC _FULL -CC)/CC _FULL ×100 (1)
However, CC _FULL has a step of generating based on the Coulomb count capacity value corresponding to full charge,
(3) Correction step,
Equipped with
(3) The correction step is
(3-1) generating a value OCV1 of OCV corresponding to the value SOC1 based on an SOC-OCV characteristic indicating a correspondence relationship between SOC and OCV (Open Circuit Voltage) which is defined in advance for the battery,
(3-2) detecting the voltage V _BAT of the battery,
(3-3) generating a difference V _DROP1 between the value OCV1 and the detected value V _BAT1 of the battery voltage V _BAT ,
(3-4) _Generating a voltage width ΔV and a high value OCV2 corresponding to the difference V _DROP1 from the minimum operating voltage V _{BAT_MIN of the} system,
(3-5) generating a value SOC2 of SOC corresponding to the value OCV2 based on the SOC-OCV characteristic,
(3-6) Correcting at least one of the values SOC1, CC, CC _FULL , and the SOC-OCV characteristic on the assumption that the value SOC2 corresponds to the remaining amount of zero.
A method comprising: The method of claim 1, wherein ΔV=V _DROP1 . A step of preliminarily retaining the SOC dependence of the difference V _DROP between the OCV and the battery voltage;
Calculating a provisional value of OCV OCV3= _{VBAT_MIN} + _VDROP1 ;
Generating a provisional value SOC3 of SOC corresponding to the provisional value OCV3 of OCV;
Calculating a voltage drop ΔV at a value SOC3 based on the SOC dependence of the difference V _DROP1 and the difference V _{DROP at} the value SOC1;
The method of claim 1, further comprising: (3-6) In the correcting step, the Coulomb count capacity value CC _FULL is CC _FULL '=CC _FULL ×(100-SOC2)/100 (2)
_4. A method as claimed in any one of claims 1 to 3, characterized in that it is modified to a new value CC _FULL ' obtained by (3-6) In the correcting step, the Coulomb count value CC is CC′=CC−(CC _FULL −CC _FULL ′) (3)
Method according to claim 4, characterized in that it is modified to a new value CC' obtained by (3-6) In the step of correcting, the Coulomb count value CC is
CC′=CC-CC _FULL ×SOC2/100 (4)
Method according to claim 4, characterized in that it is modified to a new value CC' obtained by (3-6) The correction step is
SOC′=SOC1×100/(100−SOC2) (5)
7. The method according to claim 1, wherein the new value SOC′ obtained by the above is used as the corrected SOC. (3-6) The method according to claim 4, wherein in the correcting step, the Coulomb count value CC is not corrected. (3-6) The correction step is
SOC′={CC _FULL −CC×100/(100−SOC2)}/CC _FULL ×100 (6)
The method according to any one of claims 1 to 3, wherein the value SOC' obtained by the above is used as the corrected SOC. (3-6) The correction step is
Without modifying the coulomb count capacity value CC _FULL ,
The coulomb count value CC is
CC′=CC×100/(100−SOC2) (7)
4. The method according to claim 1, wherein the method is modified to a new value CC′ obtained by (3-6) In the correcting step, the Coulomb count value CC is CC′=CC×(100−SOC2)/100 (8)
Method according to claim 4, characterized in that it is modified to a new value CC' obtained by (3-6) In the correcting step, the SOC-OCV characteristic is
SOC′=100−(100−SOC)×100/(100−SOC2) (9)
4. The method according to claim 1, wherein the correction is performed according to 13. The method according to claim 1, wherein the SOC-OCV characteristic associates a range of OCV lower than a minimum operating voltage of the system with a negative SOC. 14. Method according to any of claims 1 to 13, characterized in that the correction step is effective when the voltage of the battery is lower than a predetermined voltage value. 14. The method according to claim 1, wherein the correction step is effective when the SOC is lower than a predetermined value. 16. The method according to claim 1, wherein the correction step is intermittently activated every predetermined period. 17. The method of claim 16, wherein the predetermined period is longer than 1 second and shorter than 60 seconds. A remaining amount detection circuit for detecting SOC (State Of Charge) of a rechargeable battery,
A coulomb counter circuit for generating a coulomb count value CC by integrating charge/discharge current of the battery;
A voltage detection circuit for detecting the voltage V _BAT of the battery,
An SOC calculation unit that calculates the SOC value SOC1 based on the equation (1),
SOC1=(CC _FULL -CC)/CC _FULL ×100 (1)
However, CC _FULL is a coulomb count capacity value correction circuit equivalent to full charge,
Equipped with
The correction circuit is
Generating a value OCV1 of OCV corresponding to the value SOC1 based on an SOC-OCV characteristic indicating a correspondence relationship between SOC and OCV (Open Circuit Voltage) which is defined in advance for the battery;
Generating a difference V _DROP1 between the value OCV1 and the detected value V _{BAT1 of the} voltage detected by the voltage detection circuit;
A step of generating a voltage width ΔV corresponding to the difference V _DROP1 and a value OCV2 higher than the lowest operating voltage V _{BAT_MIN of the} system;
Generating a value SOC2 of SOC corresponding to the value OCV2 based on the SOC-OCV characteristic;
Correcting at least one of the values SOC1, CC, CC _FULL and the SOC-OCV characteristic, wherein the value SOC2 corresponds to a remaining amount of zero;
A remaining amount detection circuit for executing the following. _19. The remaining amount detection circuit according to claim 18, wherein ΔV=V _DROP1 . The correction circuit is
Holding the SOC dependence of the difference V _DROP between OCV and battery voltage;
Calculating a provisional value of OCV OCV3= _{VBAT_MIN} + _VDROP1 ;
Generating a SOC value SOC3 corresponding to the OCV provisional value OCV3;
Calculating a voltage drop ΔV at a value SOC3 based on the SOC dependence of the difference V _DROP1 and the difference V _{DROP at} the value SOC1;
19. The remaining amount detection circuit according to claim 18, further comprising: In the correcting step, the Coulomb count capacity value CC _FULL is CC _FULL '=CC _FULL ×(100−SOC2)/100 (2)
_21. The remaining amount detecting circuit according to claim 18, wherein the remaining amount detecting circuit is modified to a new value CC _FULL ′ obtained by In the correcting step, the coulomb count value CC is CC'=CC-(CC _FULL -CC _FULL ') (3).
22. The remaining amount detecting circuit according to claim 21, wherein the remaining amount detecting circuit is modified to a new value CC' obtained by In the step of correcting, the Coulomb count value CC is
CC′=CC-CC _FULL ×SOC2/100 (4)
22. The remaining amount detecting circuit according to claim 21, wherein the remaining amount detecting circuit is modified to a new value CC' obtained by In the step of correcting, the SOC1 is
SOC′=SOC1×100/(100−SOC2) (5)
24. The remaining amount detecting circuit according to claim 18, wherein the remaining amount detecting circuit is corrected to a new value SOC′ obtained by 21. The remaining amount detection circuit according to claim 18, wherein the step of correcting does not correct the Coulomb count value CC. The modifying step includes
SOC′={CC _FULL −CC×100/(100−SOC2)}/CC _FULL ×100 (6)
21. The remaining amount detection circuit according to claim 18, wherein the value SOC′ obtained by the above is set as the corrected SOC. The modifying step includes
Without modifying the coulomb count capacity value CC _FULL ,
The coulomb count value CC is
CC′=CC×100/(100−SOC2) (7)
21. The remaining amount detection circuit according to claim 18, which is modified to a new value CC′ obtained by In the step of correcting, the Coulomb count value CC is CC′=CC×(100−SOC2)/100 (8)
22. The remaining amount detecting circuit according to claim 21, wherein the remaining amount detecting circuit is modified to a new value CC' obtained by (3-6) In the correcting step, the SOC-OCV characteristic is
SOC′=100−(100−SOC)×100/(100−SOC2) (9)
21. The remaining amount detection circuit according to claim 18, wherein the remaining amount detection circuit is corrected in accordance with the following. 30. The remaining amount detection circuit according to claim 18, wherein the SOC-OCV characteristic associates a range of OCV lower than the minimum operating voltage of the system with a negative SOC. 31. The remaining amount detection circuit according to claim 18, wherein the correction circuit is effective when the voltage of the battery is lower than a predetermined voltage value. 31. The remaining amount detection circuit according to claim 18, wherein the correction circuit is effective when the SOC is lower than a predetermined value. 33. The remaining amount detection circuit according to claim 18, wherein the correction circuit is intermittently activated every predetermined period. The remaining amount detection circuit according to claim 33, wherein the predetermined period is longer than 1 second and shorter than 60 seconds. Rechargeable battery,
35. The remaining amount detection circuit according to claim 18, which detects the state of the battery,
An electronic device comprising: Rechargeable battery,
35. The remaining amount detection circuit according to claim 18, which detects the state of the battery,
An automobile comprising: