CN109669144B - Secondary battery state detector and method for detecting state of secondary battery - Google Patents
Secondary battery state detector and method for detecting state of secondary battery Download PDFInfo
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Abstract
A secondary battery state detector and a method of detecting a state of a secondary battery are provided, which are capable of detecting a voltage of the secondary battery using a differential amplification circuit that detects the state of the secondary battery. The first capacitor (C1) holds the voltages of the secondary batteries (Ce 1 to Ce 3) in the first state. The voltage of the secondary battery held by the first capacitor and the voltage of the secondary battery in the second state are input to a differential amplification circuit (16). The μCOM (19) detects a battery state based on a differential voltage between the voltage of the secondary battery in the first state and the voltage of the secondary battery in the second state, which are output from the differential amplification circuit (16). A change-over switch (SW 1) and a switching unit (12) switch the input of the differential amplification circuit (16) from the voltage of the secondary battery in the first and second states to the voltage of the secondary battery and a reference voltage (Vref). The μcom detects the voltage of the secondary battery based on a differential voltage between the voltage of the secondary battery output from the differential amplification circuit and a reference voltage (Vref).
Description
Technical Field
The present invention relates to a secondary battery state detector and a method of detecting a state of a secondary battery.
Background
As a power source of the motor, a secondary battery such as a lithium ion rechargeable battery or a nickel hydrogen rechargeable battery is mounted on various vehicles such as an Electric Vehicle (EV) or a Hybrid Electric Vehicle (HEV). In an EV or HEV, tens or hundreds of secondary batteries are connected in series, and the voltage across each secondary battery is detected. The voltage across the secondary battery is an important detection value for judging full charge or over discharge. Therefore, there are the following problems: if a failure occurs in the detection circuit, and even if one of the plurality of secondary batteries cannot be detected, all the charge and discharge operations must be stopped.
Further, as a method of calculating an internal resistance indicating an index of a degree of deterioration of a secondary battery, for example, a method described in patent document 1 is proposed. In the secondary battery state detector described in patent document 1, battery voltages in a discharge state and a discharge stop state are held in a capacitor, respectively, and a differential voltage between the held battery voltages is determined by a differential amplification circuit, and then an internal resistance (=secondary battery state) is determined from the differential voltage. However, in the conventional secondary battery state detector, when the detection circuit fails, the voltage across the secondary battery cannot be determined without the detection circuit.
List of documents
Patent literature
Patent document 1: JP 2014-219311A
Disclosure of Invention
Technical problem
The present invention has been made in view of the above background, and an object of the present invention is to provide a secondary battery state detector and a method of detecting a state of a secondary battery, which are capable of detecting a voltage across a secondary battery using a differential amplification circuit that detects a state of the secondary battery.
Problem solution
According to an aspect of the present invention, there is provided a battery state detector including:
a capacitor for maintaining a voltage across the secondary battery in the first state;
a differential amplifier circuit to which a voltage across the secondary battery held by the capacitor and a voltage across the secondary battery in the second state are input; and
a state detection section for detecting a battery state of the secondary battery based on a differential voltage output from the differential amplification circuit between a voltage across the secondary battery in the first state and a voltage across the secondary battery in the second state,
the battery state detector further includes:
a switching section for switching an input of the differential amplification circuit from a voltage across the secondary battery in the first state and the second state to a voltage across the secondary battery and a reference voltage; and
and a first voltage detection unit configured to detect a voltage across the secondary battery based on a differential voltage between the voltage across the secondary battery and the reference voltage, which is output from the differential amplification circuit.
Preferably, the reference voltage is a constant voltage output from a constant voltage source.
Preferably, the first voltage detecting section adjusts the constant voltage output from the constant voltage source such that the differential voltage is within a predetermined range, and detects the both-end voltage of the secondary battery based on the differential voltage after the adjustment of the constant voltage.
Preferably, a plurality of secondary batteries are provided,
the battery state detector further includes:
a second voltage detection section for detecting a voltage across each of the plurality of secondary batteries; and
a failure detection section for finding a secondary battery that cannot be detected due to a failure of the second voltage detection section,
wherein the reference voltage is a voltage across the secondary battery detected by the second voltage detecting section.
Preferably, when there are a plurality of secondary batteries, and the both-end voltage of each of the plurality of secondary batteries can be detected by the second voltage detecting section, the first voltage detecting section sets the both-end voltage of the secondary battery whose differential voltage is within a predetermined range as the reference voltage.
According to another aspect of the present invention, there is provided a method of detecting a state of a battery, comprising the steps of:
maintaining a voltage across the secondary battery in the first state using the capacitor;
inputting the both-end voltage of the secondary battery held by the capacitor and the both-end voltage of the secondary battery in the second state to a differential amplifying circuit; and
detecting a battery state based on a differential voltage between a voltage across the secondary battery in the first state and a voltage across the secondary battery in the second state, the differential voltage being output from the differential amplification circuit,
the method further comprises the steps of:
switching an input of the differential amplification circuit from a voltage across the secondary battery in the first state and the second state to a voltage across the secondary battery and a reference voltage; and
the both-end voltage of the secondary battery is detected based on a differential voltage between the both-end voltage of the secondary battery and the reference voltage, the differential voltage being output from the differential amplifying circuit.
ADVANTAGEOUS EFFECTS OF INVENTION
According to the above aspect, the voltage across the secondary battery can be detected by using the differential amplification circuit for detecting the state of the secondary battery.
Drawings
Fig. 1 is a circuit diagram showing a secondary battery state detector according to a first embodiment of the present invention;
fig. 2 is a flowchart showing a detection processing procedure of a voltage across the secondary battery using μcom as a component of the secondary battery state detector of fig. 1;
fig. 3 is a circuit diagram showing a secondary battery state detector according to a second embodiment of the present invention; and
fig. 4 is a flowchart showing a detection processing procedure of the voltage across the secondary battery using μcom as a component of the secondary battery state detector of fig. 3.
List of reference marks
1. Battery state detection circuit
16. Differential amplifying circuit
18CVS (second Voltage detection section, failure detection section)
19 μCOM (status detecting portion, first voltage detecting portion)
C1 First capacitor (capacitor)
Ce1-Ce3 secondary battery
Vm differential voltage
Detailed Description
(first embodiment)
A secondary battery state detector according to a first embodiment will be described below with reference to fig. 1. The secondary battery state detector 1 of this embodiment is mounted on an electric vehicle, for example, and detects the states of a plurality of secondary batteries Ce1 to Ce3, respectively, which constitute an assembled battery 2 shown in fig. 1 and included in the electric vehicle. The secondary batteries Ce1 to Ce3 are connected in series with each other.
As shown in fig. 1, a secondary battery state detector 1 of this embodiment includes: first and second capacitors C1, C2; a reference voltage source 8; a changeover switch SW1 and a switch unit 12; a charge/discharge unit 13; a voltage detection unit 14; an a/D converter 15; a differential amplifying circuit 16; an a/D converter 17; the CVS18 and a microcomputer (hereinafter referred to as μcom) 19.
The first and second capacitors C1, C2 are capacitors for maintaining voltages across the secondary batteries Ce1 to Ce3 in two states (e.g., a charged state and a discharged state). Further, the first capacitor C1 and the second capacitor C2 are capacitors for holding the voltage across the secondary batteries Ce1 to Ce3 and the reference voltage Vref, respectively. The first capacitor C1 and the second capacitor C2 are connected to a selected one of the plurality of secondary batteries Ce1 to Ce3 and the reference voltage source 8 through a switching unit 12 described later.
Further, one electrode of the first capacitor C1 is connected to a +input that is one of two inputs of a differential amplifier circuit 16 described later. One electrode of the second capacitor C2 is connected to an-input which is the other of the two inputs of the differential amplification circuit 16 described later.
The reference voltage source 8 is constituted by a constant voltage source, for example, and outputs a reference voltage Vref. Incidentally, in this embodiment, a well-known constant voltage source adjustable in reference voltage Vref (=constant voltage) is used as the reference voltage source 8.
The changeover switch SW1 is constituted by a switch for switching the c terminal between the a terminal and the b terminal. The a terminal is connected to one electrode of the first capacitor C1 and the +input of the differential amplification circuit 16. The b terminal is connected to one electrode of the second capacitor C2 and to the-input of the differential amplifying circuit 16. The c terminal is connected to an e+ terminal of a change-over switch sw+ described later. The changeover switch SW1 selects one of the first capacitor C1 and the second capacitor C2 and is connected to the e+ terminal of the changeover switch sw+.
The switching unit 12 is constituted by two changeover switches sw+, SW-. The changeover switch sw+ is configured by a switch for switching the e+ terminal between the a+, b+, c+, d+ terminals. The a+ to c+ terminals are connected to the positive electrodes of the secondary batteries Ce1 to Ce3, respectively. The d+ terminal is connected to the positive pole of the reference voltage source 8. The changeover switch sw+ selects the positive electrode of one of the plurality of secondary batteries Ce1 to Ce3 and the reference voltage source 8, and connects the positive electrode to one electrode of the capacitor C1, C2 selected by the changeover switch SW 1.
The changeover switch SW-is constituted by a switch for switching the e-terminal between the a-, b-, c-, d-terminals. The a-to c-terminals are connected to the negative electrodes of the secondary batteries Ce1 to Ce3, respectively. The d-terminal is connected to the negative pole of the reference voltage source 8. The change-over switch SW-selects the negative electrode of one of the plurality of secondary batteries Ce1 to Ce3 and the reference voltage source 8, and connects the negative electrode to the other electrode of the capacitor C1, C2.
The voltage detection unit 14 is a circuit for detecting the voltage across the assembled battery 2. The a/D converter 15 converts the voltage across the assembled battery 2 detected by the voltage detecting section 14 into a digital value and supplies the digital value to the μcom19.
The charge and discharge portion 13 is connected to both poles of the assembled battery 2, and is provided to apply a predetermined charge current Ic and discharge current Id during charge and discharge of the secondary batteries Ce1 to Ce3 constituting the assembled battery 2. The charge and discharge portion 13 is connected to a μcom19 described later, and charges the secondary batteries Ce1 to Ce3 by applying a charge current Ic and discharges the secondary batteries Ce1 to Ce3 by applying a discharge current Id in correspondence with a control signal from the μcom19.
The differential amplifier circuit 16 is a well-known differential amplifier circuit that outputs a differential voltage between a +input and an-input. The a/D converter 17 converts the differential voltage Vm output by the differential amplifying circuit 16 into a digital value, and supplies the digital value to the μcom19.
The CVS18 as the second voltage detection section is constituted by a detection circuit for detecting the voltages across the secondary batteries Ce1 to Ce3, and the CVS18 sequentially outputs the detection results to the μcom19.
The μcom19 is constituted by a well-known microcomputer having CPU, ROM, RAM or the like. The μcom19 serves as a state detection section, and detection processing of the internal resistances of the secondary batteries Ce1 to Ce3 is performed by on-off control of the changeover switch SW1 and the switch unit 12 and by controlling the charge-discharge section 13.
In the detection process of the internal resistance, in the first state, the μcom19 connects the e+ terminal of the change-over switch sw+ to the a+ terminal, the e-terminal of the change-over switch SW-to the a-terminal, and the c terminal of the change-over switch SW1 to the a terminal. Thus, the μcom19 causes the first capacitor C1 to hold the voltage across the secondary battery Ce1 in the first state. Then, in the second state, the μcom19 causes the c terminal of the changeover switch SW1 to be connected to the b terminal. Thus, the μcom19 causes the second capacitor C2 to hold the both-end voltage of the secondary battery Ce1 in the second state. Then, the voltages at both ends of the secondary battery Ce1 in the first state and the second state are input to the +input and the-input of the differential amplifier circuit 16, respectively.
Here, the first state and the second state represent states in which currents flowing through the secondary batteries Ce1 to Ce3 are different. In this embodiment, the first state is a state in which the charging current Ic flows, and the second state is a state in which the discharging current Id flows. The μcom19 controls the charge-discharge section 13 based on the detection voltage from the voltage detection section 14, and applies the charge current Ic and the discharge current Id to the secondary batteries Ce1 to Ce3.
Further, in the internal resistance detection process, the μcom19 acquires the differential voltage Vm, detects the internal resistance of the secondary battery Ce1, and detects the state of the secondary battery Ce 1. When described in detail, in this embodiment, the voltage Vc1 across the secondary battery Ce1 in the charged state is expressed in the following equation (1).
Vc1＝Ve1+r1*Ic(1)
Where Ve1 is the electromotive force of the secondary battery Ce1, and r1 is the internal resistance of the secondary battery Ce 1.
In contrast, the voltage Vd1 across the secondary battery Ce1 in the discharged state is expressed by the following formula (2).
Vd1＝Ve1–r1*Id (2)
Therefore, the differential voltage Vm output from the differential amplifying circuit 16 corresponds to Vc 1-vd1=r1 (ic+id). If the charging current Ic and the discharging current Id are known in advance, the internal resistance r1 can be determined from the differential voltage Vm. Similarly, the internal resistances r2, r3 of the secondary batteries Ce2, ce3 can be determined.
Further, the μcom19 controls on/off of the changeover switch SW1 and the switching unit 12, and performs detection processing of the voltages across the secondary batteries Ce1 to Ce3. This detection process of the both-end voltage of the secondary battery may be performed when a failure of the CVS18 is detected. Alternatively, the detection process may be performed in order to detect a failure of the CVS 18.
In the detection process of the voltage across the secondary battery, the μcom19 first controls the charge/discharge unit 13 to stop charging or discharging. Incidentally, there is no need to stop the charging current or the discharging current, i.e., there is no need to zero the charging current or the discharging current. The charge current or the discharge current does not have to be zero as long as the voltage drop generated in the internal resistances r1 to r3 is acceptable. Then, μCOM19 connects the e+ terminal of the change-over switch SW+ to the a+ terminal, the e-terminal of the change-over switch SW-to the a-terminal, and the c terminal of the change-over switch SW1 to the a-terminal. Thus, the μcom19 causes the first capacitor C1 to hold the voltage across the secondary battery Ce 1.
Then, μCOM19 connects the e+ terminal of the change-over switch SW+ to the d+ terminal, the e-terminal of the change-over switch SW-to the d-terminal, and the c terminal of the change-over switch SW1 to the b terminal. Thus, the μcom19 causes the second capacitor C2 to hold the reference voltage Vref. Then, the voltage across the secondary battery Ce1 and the reference voltage Vref are input to the +input and the-input of the differential amplifier circuit 16, respectively.
Further, the μcom19 acquires the differential voltage Vm at this time, and detects the both-end voltage of the secondary battery Ce 1. When described in detail, the differential voltage Vm at this time is expressed in the following formula (3).
Vm＝(Vc1–Vref)*Av (3)
Where Av is the gain of the differential amplifying circuit 16.
Therefore, since the gain Av and the reference voltage Vref are known, the μcom19 can determine the voltage Vc1 across the secondary battery Ce1 from the differential voltage Vm. Similarly, the voltages Vc2, vc3 of the secondary batteries Ce2, ce3 can be determined.
Next, details of the detection processing procedure of the both-end voltage of the secondary battery using the secondary battery state detector 1, which is substantially described, will be described with reference to the flowchart of fig. 2. First, the μcom19 connects both ends of the secondary battery Cen to the first capacitor C1 (step S1).
Then, the μcom19 waits for a predetermined time so that the both-end voltage of the first capacitor C1 becomes equal to the both-end voltage Vcn of the secondary battery Cen (n is initially set to 1), and then connects the reference voltage source 8 with the second capacitor C2 (step S2). Thus, the both-end voltage of the secondary battery Cen and the reference voltage Vref are input to the +input and the-input of the differential amplifier circuit 16, respectively.
Next, the μcom19 acquires the differential voltage Vm of the differential amplifying circuit 16, and determines whether Vm is greater than the first threshold Vthmax (step S3). When the differential voltage Vm > the first threshold Vthmax (yes in step S3), the μcom19 increases the reference voltage Vref by a predetermined amount (step S8) because there is a possibility that the voltage Vcn may be much larger than the reference voltage Vref and the output of the a/D converter 17 may saturate (step S1), and then returns to step S1.
In contrast, when the differential voltage Vm is equal to or smaller than the first threshold Vthmax (no in step S3), the μcom19 determines whether Vm is smaller than the second threshold Vthmin (step S4). When the differential voltage Vref < the second threshold Vthmin (yes in step S4), the μcom19 determines that the voltage Vcn is much smaller than the reference voltage Vref and the accuracy is poor, the μcom19 decreases the reference voltage Vref by a predetermined amount (step S9), and returns to step S1.
When the second threshold Vthmin is equal to or less than the differential voltage Vm is equal to or less than the first threshold Vthmax (no in step S3 and no in step S4), the μcom19 calculates the voltage Vcn from the differential voltage Vm (step S5). Then, μcom19 increments n (step S6), and determines whether n=3 (step S7). When n+.3 (no in step S7), the μcom19 determines that the voltages Vc1 to Vc3 across all the secondary batteries Ce1 to Ce3 constituting the assembled battery 2 are not detected, and returns to step S1.
In contrast, when n=3 (yes in step S7), the μcom19 determines that the voltages Vc1 to Vc3 across all the secondary batteries Ce1 to Ce3 constituting the assembled battery 2 are detected, and ends the process.
According to the first embodiment described above, by using the changeover switch SW1 and the switching unit 12 as the switching section, the input of the differential amplification circuit 16 can be switched from the two-terminal voltages of the secondary batteries Ce1 to Ce3 in the first state and the second state to the two-terminal voltages of the secondary batteries Ce1 to Ce3 and the reference voltage Vref. Then, the μcom19 detects the internal resistance (state) of the battery based on the differential voltage Vm between the voltages across the secondary batteries Ce1 to Ce3 in the first state and the second state output from the differential amplification circuit 16.
Further, the μcom19 detects the both-end voltages of the secondary batteries Ce1 to Ce3 based on the differential voltage Vm between the both-end voltages of the secondary batteries Ce1 to Ce3 and the reference voltage Vref. Thus, using the differential amplification circuit 16 for detecting the internal resistances of the secondary batteries Ce1 to Ce3, the both-end voltages of the secondary batteries Ce1 to Ce3 can be detected. Therefore, if the CVS18 malfunctions, since the both-end voltages of the secondary batteries Ce1 to Ce3 can be detected, it is not necessary to stop the charging and discharging of the secondary batteries Ce1 to Ce3, and the vehicle can continue running.
Further, by comparing the both-end voltages of the secondary batteries Ce1 to Ce3 detected by the CVS18 with the both-end voltages of the secondary batteries Ce1 to Ce3 detected using the differential amplification circuit 16, it is possible to perform fault diagnosis of the CVS18 and the battery state detector 1.
Further, according to the first embodiment described above, the reference voltage Vref is a constant voltage output from a constant voltage source. Thus, the accuracy of detecting the voltages across the secondary batteries Ce1 to Ce3 can be further improved.
Further, according to the first embodiment described above, as shown in steps S3, S4, and S9, the μcom19 adjusts the reference voltage Vref output from the reference voltage source 8 so that the differential voltage Vm is within a predetermined range (i.e., the first threshold Vthmax > Vm > the second threshold Vthmin). Then, the μcom19 detects the voltages across the secondary batteries Ce1 to Ce3 based on the regulated differential voltage Vm. Thus, the output of the a/D converter 17 is prevented from being saturated or excessively small, and the detection accuracy of the voltages across the secondary batteries Ce1 to Ce3 can be further improved.
Incidentally, according to the first embodiment described above, the assembled battery 2 is constituted by three secondary batteries Ce1 to Ce3. However, the present invention is not limited thereto. One or more than three secondary batteries may be provided.
Further, in the above-described first embodiment, two capacitors C1 and C2 are provided. However, the present invention is not limited thereto. A capacitor may be provided for maintaining the voltages across the secondary batteries Ce1 to Ce3 in the first state, and the voltages across the secondary batteries Ce1 to Ce3 in the second state may be directly input to the differential amplifying circuit 16.
Further, the switching section constituted by the changeover switch SW1 and the switching unit 12 as shown in the first embodiment is an example. The switching section may switch from the voltages across the secondary batteries Ce1 to Ce3 in the first state and the second state to the voltages across the secondary batteries Ce1 to Ce3 and the reference voltage Vref.
Further, in the above-described first embodiment, the μcom19 adjusts the reference voltage Vref output from the reference voltage source 8 so that the differential voltage Vm is within a predetermined range (i.e., the first threshold Vthmax > Vm > the second threshold Vthmin). However, the present invention is not limited thereto. Adjustment of the reference voltage Vref is not necessary.
Further, in the first embodiment described above, by controlling the charge and discharge portion 13 with the μcom19, the secondary batteries Ce1 to Ce3 are in the first state (state in which the charging current Ic flows) and the second state (state in which the discharging current Id flows). However, the present invention is not limited thereto. Variations in charge and discharge currents associated with load driving of the vehicle may be used. That is, the state before the change of the charge and discharge current may be the first state, and the state after the change of the charge and discharge current may be the second state.
(second embodiment)
Next, the secondary battery state detector 1 according to the second embodiment will be described with reference to fig. 3. In fig. 3, components similar to those of the secondary battery state detector 1 of fig. 1, which have been described in the first embodiment, will be denoted by the same reference numerals, and detailed description thereof will be omitted.
As shown in fig. 3, the secondary battery state detector 1 of the second embodiment includes: a first capacitor C1 and a second capacitor C2; a changeover switch SW1 and a switch unit 12; a charge/discharge unit 13; a voltage detection unit 14; an a/D converter 15; a differential amplifying circuit 16; an a/D converter 17; CVS18 and μCOM19. In the second embodiment, the reference voltage source 8 is not provided.
Since the first and second capacitors C1 and C2 and the change-over switch SW1 are similar to those of the first embodiment described above, detailed description thereof will be omitted here. The switching unit 12 is constituted by two changeover switches sw+, SW-. The changeover switch sw+ is configured by a switch for switching the e+ terminal between the a+, b+, and c+ terminals. The a+ terminals to c+ terminals are connected to the positive electrodes of the secondary batteries Ce1 to Ce3, respectively. The changeover switch sw+ selects the positive electrode of one of the plurality of secondary batteries Ce1 to Ce3, and connects the positive electrode to one electrode of the capacitor C1, C2 selected by the changeover switch SW 1.
The change-over switch SW-is constituted by a switch for switching the e-terminal between the a-, b-, c-terminals. The a-to c-terminals are connected to the negative electrodes of the secondary batteries Ce1 to Ce3, respectively. The change-over switch SW-selects the negative electrode of one of the plurality of secondary batteries Ce1 to Ce3 and connects the negative electrode to the other electrode of the capacitor C1, C2.
The CVS18 as the second voltage detection section is constituted by a detection circuit for detecting voltages across the secondary batteries Ce1 to Ce3, and the CVS18 sequentially outputs the detection results to the μcom19. There are the following cases: the CVS18 cannot detect the voltages across all the secondary batteries Ce1 to Ce3 due to, for example, an internal switching failure or the like. The CVS18 includes, for example, a well-known open circuit detection circuit, and is capable of determining some secondary batteries Ce1 to Ce3 that cannot be detected due to their own failure. The CVS18 then feeds the result to the μcom19.
Similar to the first embodiment, the μcom19 performs the detection process of the internal resistance and the detection process of the voltage across the secondary battery. Since the detection process of the internal resistance is similar to that of the first embodiment, a detailed description thereof will be omitted here.
In the detection process of the both-end voltages of the secondary batteries, the μcom19 inputs the both-end voltages of the secondary batteries Ce1 to Ce3 detected by the CVS18 as the reference voltage Vref to the differential amplification circuit 16 instead of the reference voltage Vref. Now, a case will be described in which the voltage across the secondary battery Ce1 cannot be detected using the CVS18, and the voltage across the secondary battery Ce2 can be detected. The μCOM19 connects the e+ terminal of the change-over switch SW+ to the a+ terminal, the e-terminal of the change-over switch SW-to the a-terminal, and the c-terminal of the change-over switch SW1 to the a-terminal. Thus, the μcom19 causes the first capacitor C1 to hold the voltage across the secondary battery Ce 1.
Then, μCOM19 connects the e+ terminal of the change-over switch SW+ to the b+ terminal, the e-terminal of the change-over switch SW-to the b-terminal, and the c-terminal of the change-over switch SW1 to the b-terminal. Thus, the μcom19 causes the second capacitor C2 to hold the voltage across the secondary battery Ce 2. Then, the voltages across the secondary batteries Ce1, ce2 are input to the + input and the-input of the differential amplifier circuit 16, respectively.
Further, the μcom19 acquires the differential voltage Vm at this time to detect the both-end voltage of the secondary battery Ce 1. When described in detail, the differential voltage Vm at this time is expressed in the following equation (4).
Vm＝(Vc1–Vc2)*Av(4)
Where Av is the gain of the differential amplifier circuit 16.
Therefore, since the gain Av and the voltage Vc2 are known, the μcom19 can determine the voltage Vc1 across the secondary battery Ce1 from the differential voltage Vm.
Next, details of the detection processing procedure of the both-end voltage of the secondary battery using the secondary battery state detector 1, which is substantially described, will be described with reference to the flowchart of fig. 4.
Incidentally, the secondary battery of the secondary batteries Ce1 to Ce3 that cannot detect the voltage across the battery is described as a secondary battery Cex, and the secondary battery of the secondary batteries Ce1 to Ce3 that can detect the voltage across the battery is referred to as a secondary battery Ceo.
First, the μcom19 connects one secondary battery Cex with the first capacitor C1, and causes the first capacitor C1 to hold the both-end voltage of the secondary battery Cex (step S11). Then, the μcom19 connects one secondary battery Ceo with the second capacitor C2, and causes the second capacitor C2 to hold the both-end voltage of the secondary battery Ceo (step S11). Thus, the voltages across the secondary batteries Cex, CEo are input to the +input and the-input of the differential amplifier circuit 16, respectively.
Next, the μcom19 acquires the differential voltage Vm of the differential amplifying circuit 16, and determines whether Vm is within a predetermined range, that is, whether the differential voltage Vm is equal to or greater than the second threshold Vthmin and equal to or less than the first threshold Vthmax (step S12). If the second threshold Vthmin is equal to or less than the differential voltage Vm is equal to or less than the first threshold Vthmax (yes in step S12), the μcom19 determines the voltage across the secondary battery Cex from the differential voltage Vm (step S13).
Next, if the μcom19 determines the voltages across all the secondary batteries Cex (yes in step S14), the process ends. If the μcom19 does not determine the both-end voltages of all the secondary batteries Cex (no in step S14), the undetermined secondary battery Cex is connected to the first capacitor C1, and the secondary battery Ceo is connected to the second capacitor C2 (step S15), and the process returns to step S12.
Further, if the second threshold Vthmin is not satisfied with the differential voltage Vm is not smaller than the first threshold Vthmax (no in step S12), the μcom19 determines whether all the secondary batteries Ceo are switched (step S16). If not (no in step S16), the μcom19 switches the secondary battery Ceo to be input to the differential amplifier circuit 16 (step S17), and the process returns to step S12. Thus, if there are a plurality of secondary batteries Ceo, when the voltage across the secondary battery Ceo is excessively large or excessively small with respect to the secondary battery Cex, the secondary battery Ceo to be input to the differential amplifier circuit 16 can be switched.
In addition, if the switching is performed (yes in step S16), the μcom19 determines whether the differential voltage Vm is greater than the first threshold Vthmax (step S18). If Vm > Vthmax (yes in step S18), the μcom19 determines that the voltage across the secondary batteries Cex is greater than the voltage across all the secondary batteries Ceo, and that some abnormality has occurred, and performs a predetermined abnormality process (step S19), and then ends the process.
In addition, if Vm is not more than Vthmax (no in step S18), the μcom19 determines that the both-end voltages of the secondary batteries Cex are smaller than the both-end voltages of all the secondary batteries Ceo, and determines whether step S21 described later has been performed (step S20). If not (no in step S20), the μcom19 exchanges the first capacitor C1 with the second capacitor C2 (step S21). That is, in step S12, the μcom19 connects the secondary battery Cex to the second capacitor C2, and connects the secondary battery Ceo to the first capacitor C1. Thus, the both-end voltage of the secondary battery Ceo is input to the +input of the differential amplifier circuit 16, and the both-end voltage of the secondary battery Cex is input to the-input of the differential amplifier circuit 16. Then μcom19 returns to step S12, and the secondary battery Ceo is switched to be input to the +input until the second threshold Vthmin is equal to or less than the differential voltage Vm is equal to or less than the first threshold Vthmax.
According to the above-described second embodiment, the both-end voltage of the secondary battery Ceo detected by the CVS18 is input as the reference voltage. Thus, the reference voltage source 8 showing the reference voltage need not be provided in addition to the secondary batteries Ce1 to Ce3, and cost reduction can be achieved.
Further, according to the above-described second embodiment, when there are a plurality of secondary batteries Ceo whose voltages are detected by the CVS18, the μcom19 can set the secondary battery Ceo whose differential voltage Vm is within a predetermined range as the reference voltage. Thus, the accuracy of detecting the voltages across the secondary batteries Ce1 to Ce3 can be further improved.
Incidentally, according to the above embodiment, when the differential voltage Vm is outside the predetermined range, the secondary battery Ceo is switched. However, the present invention is not limited thereto. A handover is not necessary.
Incidentally, the present invention is not limited to the above-described embodiments. That is, the present invention can be variously modified and implemented without departing from the scope of the present invention.
Claims (6)
1. A battery state detector comprising:
a first capacitor for maintaining a voltage across both ends of the secondary battery in a first state;
a second capacitor for maintaining a voltage across the secondary battery in a second state different from the first state, the second capacitor being for maintaining a current flowing through the secondary battery;
a differential amplifier circuit to which the voltage across the secondary battery held by the first capacitor and the voltage across the secondary battery held by the second capacitor are input; and
a state detection section for detecting a battery state of the secondary battery based on a differential voltage between a voltage across the secondary battery in the first state and a voltage across the secondary battery in the second state, the differential voltage being output from the differential amplification circuit,
the battery state detector further includes:
a switching unit and a change-over switch for switching an input of the differential amplification circuit from a voltage across the secondary battery in the first state and the second state to a voltage across the secondary battery and a reference voltage; and
a first voltage detection section for detecting a voltage across the secondary battery based on a differential voltage between the voltage across the secondary battery and the reference voltage, the differential voltage being output from the differential amplification circuit,
the switching unit selectively connects the changeover switch to the secondary battery and a reference voltage source that supplies the reference voltage, the changeover switch selectively connects to the first capacitor and the second capacitor,
in determining a differential voltage of both end voltages of the secondary battery in the first state and the second state, the switching unit connects the secondary battery to the switching switch in the first state while the switching switch is connected to the first capacitor, holds both end voltages of the secondary battery at the first capacitor, and then connects the switching switch to the second capacitor in the second state, holds both end voltages of the secondary battery at the second capacitor,
upon determining a differential voltage between the voltage across the secondary battery and the reference voltage,
the secondary battery is connected to the change-over switch through the switching unit while the change-over switch is connected to one of the first capacitor and the second capacitor, so that the voltage across the secondary battery is maintained at the one capacitor,
the switching unit connects the reference voltage source to the switching switch while the switching switch is connected to the other capacitor of the first capacitor and the second capacitor, so that the reference voltage is held at the other capacitor.
2. The battery state detector according to claim 1,
wherein the reference voltage is a constant voltage output from a constant voltage source.
3. The battery state detector according to claim 2,
wherein the first voltage detecting section adjusts the constant voltage output from the constant voltage source such that the differential voltage is within a predetermined range, and detects the both-end voltage of the secondary battery based on the differential voltage after the adjustment of the constant voltage.
4. The battery state detector according to claim 1,
wherein a plurality of secondary batteries are provided,
the battery state detector further includes:
a second voltage detection unit for detecting a voltage across each of the plurality of secondary batteries; and
a failure detection section for finding a secondary battery that cannot be detected due to a failure of the second voltage detection section,
wherein the reference voltage is a voltage across the secondary battery detected by the second voltage detecting section.
5. The battery status detector of claim 4,
wherein when there are a plurality of secondary batteries, and the both-end voltage of each of the plurality of secondary batteries is detectable by the second voltage detecting section, the first voltage detecting section sets the both-end voltage of the secondary battery whose differential voltage is within a predetermined range as the reference voltage.
6. A method for detecting a battery condition, comprising the steps of:
maintaining a voltage across the secondary battery in the first state with the first capacitor;
maintaining a voltage across the secondary battery in a second state different from the first state by a second capacitor;
inputting the both-end voltage of the secondary battery held by the first capacitor and the both-end voltage of the secondary battery held by the second capacitor to a differential amplifying circuit; and
detecting a battery state based on a differential voltage between a voltage across the secondary battery in the first state and a voltage across the secondary battery in the second state, the differential voltage being output from the differential amplification circuit,
the method further comprises the steps of:
switching an input of the differential amplification circuit from a voltage across the secondary battery in the first state and the second state to a voltage across the secondary battery and a reference voltage; and
detecting a voltage across the secondary battery based on a differential voltage between the voltage across the secondary battery and the reference voltage, the differential voltage being output from the differential amplification circuit,
in determining a differential voltage of both end voltages of the secondary battery in the first state and the second state, while the switching unit connects the secondary battery to the switching switch in the first state, the switching switch is connected to the first capacitor, holds both end voltages of the secondary battery at the first capacitor, and then the switching switch is connected to the second capacitor in the second state, holds both end voltages of the secondary battery at the second capacitor,
when determining the differential voltage between the voltage across the secondary battery and the reference voltage, the secondary battery is connected to the change-over switch through the switching unit while the change-over switch is connected to one of the first capacitor and the second capacitor so that the voltage across the secondary battery is held at the one capacitor, and the reference voltage source is connected to the change-over switch through the switching unit while the change-over switch is connected to the other of the first capacitor and the second capacitor so that the reference voltage is held at the other capacitor.
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| JP2017199071A JP6640169B2 (en) | 2017-10-13 | 2017-10-13 | Secondary battery state detection device and secondary battery state detection method |
| JP2017-199071 | 2017-10-13 |
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| CN109669144A CN109669144A (en) | 2019-04-23 |
| CN109669144B true CN109669144B (en) | 2023-05-16 |
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Also Published As
| Publication number | Publication date |
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| JP6640169B2 (en) | 2020-02-05 |
| CN109669144A (en) | 2019-04-23 |
| JP2019074348A (en) | 2019-05-16 |
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