JP3780977B2 - Failure diagnosis device and failure diagnosis method for cell voltage detection circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a diagnosis device and a failure diagnosis method that can specify a failure location of a cell voltage detection circuit that detects a cell voltage of an assembled battery.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a circuit failure diagnosis apparatus that detects a cell voltage of an assembled battery composed of a plurality of cells is known. In Japanese Patent Laid-Open No. 11-252809, the total voltage VA of the assembled battery is detected, and each cell voltage is detected and added to obtain an added voltage VT, and the two voltage values VA and VT are compared. If not, a technique for determining that an abnormality has occurred is disclosed.
[0003]
[Problems to be solved by the invention]
However, in the conventional failure diagnosis apparatus, when the voltage values VA and VT do not coincide with each other, it has not been possible to specify the location where the failure has occurred.
[0004]
An object of the present invention is to provide a failure diagnosis device and failure diagnosis method for a cell voltage detection circuit that performs failure diagnosis of the cell voltage detection circuit.
[0005]
[Means for Solving the Problems]
(1) A failure diagnosis apparatus for a cell voltage detection circuit according to the present invention includes a plurality of cell voltage detection circuits for detecting a cell voltage of a cell constituting an assembled battery, and any one of the plurality of cell voltage detection circuits. A reference voltage application circuit for applying a reference voltage to the detection circuit, an application voltage switching circuit for switching a cell voltage detection circuit for applying the reference voltage, a detection voltage detected by the cell voltage detection circuit to which the reference voltage is applied , The above object is achieved by providing a failure diagnosis circuit that performs failure diagnosis of the cell voltage detection circuit to which the reference voltage is applied based on the applied reference voltage .
(2) In the cell voltage detection circuit failure diagnosis method according to the present invention, a reference voltage is applied to any one of a plurality of cell voltage detection circuits for detecting a cell voltage of a cell constituting an assembled battery. The cell voltage detection circuit detects the applied reference voltage, and detects the cell voltage based on the detection voltage detected by the cell voltage detection circuit to which the reference voltage is applied and the reference voltage actually applied. The above object is achieved by performing circuit fault diagnosis.
[0006]
【The invention's effect】
According to the failure diagnosis apparatus for cell voltage detection circuit and the failure diagnosis method for cell voltage detection circuit according to the present invention, a detection voltage obtained by detecting a reference voltage applied to a cell voltage detection circuit provided for each cell, and a voltage that is actually applied. The failure diagnosis of the cell voltage detection circuit can be reliably detected by performing the failure diagnosis of the cell voltage detection circuit based on the reference voltage.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 and FIG. 2 are diagrams showing the configuration of an embodiment of a failure diagnosis apparatus for a cell voltage detection circuit according to the present invention. The assembled battery 1 is configured by connecting eight cells C1 to C8 in series. The capacity adjustment circuits E1 to E8 are connected in parallel to the cells for each of the cells C1 to C8, perform capacity adjustment by discharging the corresponding cells, and suppress capacity variation between the cells.
[0008]
The changeover switch unit 5 switches the switches SW <b> 1 to SW <b> 8 based on the control signal I sent from the CPU 10. When the control signal I is at the Lo level, SW1 to SW8 are set to the cell voltage circuit side, and when the control signal I is at the Hi level, SW1 to SW8 are set to the reference voltage circuit side. FIG. 1 shows a state in which all the switches SW1 to SW8 are set on the cell voltage circuit side. In this state, each cell voltage can be detected by the cell voltage detection circuit 3 described later.
[0009]
The cell voltage detection circuit 3 includes differential amplifiers D1 to D8. When the switches SW1 to SW8 are set on the cell voltage circuit side, the cell voltages Vc1 to Vc8 of the corresponding cells C1 to C8 are detected by the outputs of the differential amplifiers D1 to D8. On the other hand, when the switches SW1 to SW8 are set on the reference voltage circuit side, the reference voltage applied to the differential amplifiers D1 to D8 is detected. Each detected voltage value is transmitted to the CPU 10. The reference voltage is a voltage used at the time of failure diagnosis of the cell voltage detection circuit 3.
[0010]
FIG. 2 is a diagram showing a detailed configuration of the diagnostic circuit section of the cell voltage detection circuit 3. The diagnostic circuit unit includes a changeover switch unit 5, a reference voltage setting unit 6 for setting a reference voltage used when performing a failure diagnosis of the cell voltage detection circuit 3, and a reference voltage set by the reference voltage setting unit 6. An analog switch IC unit 7 for applying to the voltage detection circuit 3 and a CPU 10 are provided. The analog switch IC unit 7 includes a multiplexer MPX1 that defines a changeover switch unit 5 that applies a reference voltage, and a multiplexer MPX2 that defines a changeover switch unit 5 that applies a ground voltage. As described above, the changeover switch unit 5 switches the switches SW1 to SW8 based on the control signal I sent from the CPU. When the control signal I is at the Hi level, the switches SW1 to SW8 are switched to the reference voltage circuit. Set to the side.
[0011]
The reference voltage setting unit 6 having a D / A converter generates an analog signal of a reference voltage used for failure diagnosis based on a control signal sent from the CPU 10 and sends it to the X port of the multiplexer MPX1 of the analog switch IC unit 7. . Although an arbitrary value can be set as the reference voltage, a voltage value in the range of 2.0 (V) to 4.5 (V) is used as the reference voltage in the present embodiment. The analog switch IC unit 7 switches between cells to which the reference voltage is applied based on the control signals A, B, and C sent from the CPU 10. A method for switching between cells to which a reference voltage is applied will be described with reference to FIG.
[0012]
FIG. 3 is a table showing between which cells the reference voltage is applied according to the signal levels of the control signals I, A, B, and C of the CPU 10. When the control signal I is at the Lo level, the terminals X of the MPX1 and 2 and the terminals X0 to X7 are all turned off. When the control signal I is at the Hi level, the MPX1 and MPX2 are both connected between each terminal X and any one of the terminals X0 to X7 according to the levels of the control signals A, B, and C. Is turned on. For example, when all of the control signals A, B, and C are at the Lo level, the terminal X and the terminal X0 are turned on as shown in FIG. In this case, the reference voltage Vd set by the reference voltage setting unit 6 is applied to the plus side of the differential amplification unit D1 through the MPX1, and the ground voltage (0 V) is applied to the minus side through the MPX2. . Therefore, the differential amplifier D1 detects the applied reference voltage Vd as the input voltage Vin1, and outputs it to the CPU 10.
[0013]
Similarly, when the signal level of the control signal (A, B, C) is (H, L, L), the reference voltage Vd is applied to the differential amplifier D2 as the input voltage Vin2, and (L, H, L) In this case, the reference voltage Vd is applied as the input voltage Vin3 to the differential amplifier D3. The signal levels of the control signals (A, B, C) when the reference voltage Vd is applied to the differential amplifiers D4 to D8 are (H, H, L), (L, L, H), (H, L, H), (H, H, L), (H, H, H). Since the negative side of the differential amplifier D8 is grounded, no ground voltage is applied via MPX2.
[0014]
A failure diagnosis method for the cell voltage detection circuit 3 will be described. The CPU 10 sets the switches SW1 to SW8 to the reference voltage circuit side by setting the control signal I to the H level. When performing failure diagnosis of the differential amplifier D1, the signal level of the control signal (A, B, C) is set to (L, L, L). Thereby, since the reference voltage Vd is applied to the differential amplifier D1, the differential amplifier D1 detects the reference voltage Vd as the input voltage Vin1 and outputs it to the CPU 10. The CPU 10 compares the voltage Vin1 detected by the differential amplifier D1 with the actually applied reference voltage Vd. If the difference between the two voltages is not within a predetermined range, the differential amplifier D1 has a failure. Is determined. In this embodiment, the reference voltage Vd is 2.0 (V) and 4.3 (V), and the predetermined range is 0.15 (V).
[0015]
FIG. 4 is a flowchart of an embodiment showing a failure diagnosis control procedure by the failure diagnosis apparatus for a cell voltage detection circuit according to the present invention. The process starting from step S1 is performed by the CPU 10. In step S1, the control signal I is switched from the Lo level to the Hi level. As a result, the switches SW1 to SW8 are switched from the cell voltage circuit side to the reference voltage circuit side. In the next step S <b> 2, a digital signal for setting the diagnostic reference voltage Vd to 4.3 (V) is transmitted to the reference voltage setting unit 6. In this embodiment, since the voltage at the time of overcharging of each cell is 4.5 (V), failure diagnosis in the overcharge detection region is performed by setting the reference voltage Vd to 4.3 (V).
[0016]
When the diagnostic reference voltage Vd is set to 4.3 (V), the process proceeds to step S3. In step S3, the signal levels of the control signals A, B, and C are switched according to the cell in which the failure diagnosis is performed. When performing failure diagnosis of the differential amplifier D1 corresponding to the cell C1, all the control signals A, B, and C are set to Lo level. Thereby, the differential amplifier D1 detects the applied reference voltage Vd as the input voltage Vin1, and outputs it to the CPU 10. In the next step S4, it is determined whether or not the difference between the voltage Vin1 detected by the differential amplifier D1 and the reference voltage Vd set in step S2 is within a predetermined range (0.15 (V)). If it is determined that the difference between the voltages Vin1 and Vd is within the predetermined range, the process proceeds to step S5, and if it is determined that the voltage difference is not within the predetermined range, the process proceeds to step S11. In step S11, it is determined that a failure has occurred in the differential amplifying unit D1, and the processing according to this flowchart ends.
[0017]
In step S5, it is determined whether failure diagnosis has been performed for all the differential amplifiers D1 to D8. If it is determined that failure diagnosis has not been performed for all the differential amplification units D1 to D8, the process returns to step S3, and the above-described processing of steps S3 and S4 is performed on the differential amplification unit that has not been subjected to failure diagnosis. I do. If it is determined that failure diagnosis has been performed for all the differential amplifiers D1 to D8, the process proceeds to step S6.
[0018]
In step S6, since the voltage at the time of overdischarge of each cell is 1.8 (V), a digital signal for setting the diagnostic reference voltage Vd to 2.0 (V) is transmitted to the reference voltage setting unit 6. That is, in the processing after step S6, failure diagnosis is performed in the overdischarge detection region. In step S7 following step S6, the signal levels of the control signals A, B, and C are switched in accordance with the cells that perform failure diagnosis. The process performed in step S7 is the same as the process performed in step S3. When the signal levels of the control signals A, B, and C are switched according to the cells that perform failure diagnosis, the process proceeds to step S8. In step S8, the difference between the voltage Vin detected by the differential amplifier to which the reference voltage is applied by the signal level switching control in step S7 and the reference voltage Vd set in step S6 is within a predetermined range (0.15 (V). ). If it is determined that the difference between the voltages Vin and Vd is within the predetermined range, the process proceeds to step S9. If it is determined that the voltage difference is not within the predetermined range, the process proceeds to step S12. In step S12, it is determined that a failure has occurred in the differential amplifying unit D1, and the processing according to this flowchart ends.
[0019]
In step S9, it is determined whether or not a fault diagnosis has been performed for all the differential amplifiers D1 to D8 when the reference voltage Vd is 2.0 (V). If it is determined that failure diagnosis has not been performed for all the differential amplification units D1 to D8, the process returns to step S7, and the above-described processing of steps S7 and S8 is performed for the differential amplification unit that has not been subjected to failure diagnosis. I do. If it is determined that failure diagnosis has been performed for all the differential amplifiers D1 to D8, the process proceeds to step S10. In step S10, the control signal I is switched from the Hi level to the Lo level, and the processing according to this flowchart ends. As a result, the switches SW1 to SW8 are switched from the reference voltage circuit side to the cell voltage circuit side, and output from the MPXs 1 and 2 is prohibited.
[0020]
In addition, when it is determined in step S11 or step S12 that a failure has occurred in the differential amplifier, it is possible to notify that a failure has occurred by an indicator or speaker (not shown). In this case, since the failure diagnosis is performed for each of the differential amplification units D1 to D8, it is possible to identify the differential amplification unit in which the failure has occurred and notify that the failure has occurred.
[0021]
(1) According to the failure diagnosis apparatus for the cell voltage detection circuit in the present embodiment, the detection voltage Vin detected from the reference voltage applied to the differential amplifiers D1 to D8, and the reference voltage Vd actually applied Based on the above, failure diagnosis of the differential amplifiers D1 to D8 can be reliably detected by detecting the failure of the differential amplifiers D1 to D8. Since the differential amplifiers D1 to D8 to which the reference voltage is applied are sequentially switched by the analog switch IC unit 7, failure diagnosis of all the differential amplifiers D1 to D8 can be performed. Moreover, since the reference voltage used for the failure diagnosis can be set to an arbitrary value by the reference voltage setting unit 6 based on a command from the CPU 10, the entire voltage detection range of the differential amplifiers D1 to D8 can be set. Cross fault diagnosis can be performed.
[0022]
(2) Many assembled batteries configured by connecting a plurality of cells have a function of preventing overcharge and overdischarge of the assembled battery by detecting the cell voltage. Accordingly, the reference voltage used for failure diagnosis is set to the value of the overcharge voltage region and the value of the overdischarge voltage region of the cell, respectively, and diagnosed, whereby the overcharge detection region and the overcharge detection region of the differential amplifiers D1 to D8 are detected. Each failure diagnosis in the discharge voltage region is performed, and overcharge and overdischarge of the assembled battery can be surely prevented. By setting the reference voltage to a value in the overcharge voltage region of the cell and then setting it to a value in the overdischarge voltage region at the time of one failure diagnosis as in the failure diagnosis device of the cell voltage detection circuit in the present embodiment Failure diagnosis in the overcharge and overdischarge detection region can be performed at a time.
[0023]
(3) When performing fault diagnosis of the differential amplifiers D1 to D8, the reference voltage is applied to the differential amplifiers D1 to D8 by switching the switches SW1 to SW8 from the cell voltage circuit side to the reference voltage circuit side. I tried to do it. Thereby, at the time of failure diagnosis, the capacity adjustment circuits E1 to E8 and the differential amplifiers D1 to D8 are disconnected, so that the failure diagnosis can be performed regardless of whether or not the capacity adjustment of the cells C1 to C8 is performed. That is, even when performing fault diagnosis of the cell voltage detection circuit 3 (differential amplifiers D1 to D8) while performing capacity adjustment of the cells C1 to C8, it is not necessary to interrupt capacity adjustment.
[0024]
(4) Like the conventional failure diagnosis method, in the method of detecting the total voltage VA of the assembled battery and detecting and adding each cell voltage to obtain the added voltage VT, the two voltages are compared. It is impossible to specify whether a failure has occurred in the cell voltage detection circuit. In addition, the detection value of one cell voltage detection circuit shifts to the plus side, and the detection value of another cell voltage detection circuit shifts to the minus side, and when the addition voltage VT is obtained, the shift width between the two is canceled out. In some cases, it may be determined that there is no failure. On the other hand, in the cell voltage detection circuit failure diagnosis apparatus according to the present embodiment, failure diagnosis is performed for each differential amplification unit that detects a cell voltage, so that the differential amplification unit in which the failure has occurred is reliably identified. be able to. Further, it is not necessary to consider voltage sampling of the cell voltage and the total voltage of the assembled battery.
[0025]
(5) In an assembled battery in which a module is configured by connecting a predetermined number of cells, it is also possible to apply a reference voltage to a voltage detection circuit included in one module and perform a fault diagnosis of the voltage detection circuit. It is done. That is, this is a method of performing failure diagnosis by comparing a value obtained by dividing the applied reference voltage by the number of cells constituting the module with a voltage value detected by the voltage detection circuit. However, in this method, when performing failure diagnosis in the overcharge detection area of the cell, it is necessary to apply a voltage obtained by multiplying the cell voltage at full charge by the number of cells constituting the module as a reference voltage. It may lead to cost increase. According to the failure diagnosis device for a cell voltage detection circuit of the present embodiment, since the failure diagnosis is performed by applying the reference voltage for each cell unit, the above-described problem does not occur. In addition, failure diagnosis can be performed accurately and reliably compared to a method in which a value obtained by dividing the applied reference voltage by the number of cells constituting the module is used as the reference value.
[0026]
The present invention is not limited to the embodiment described above. For example, the reference voltage used at the time of failure diagnosis is not limited to 4.3 (V) or 2.0 (V) described above, and an arbitrary value can be set. In the description of the embodiment described above, the failure diagnosis of the overcharge detection region and the failure diagnosis of the overdischarge detection region are performed at the same time, but they can be performed separately. Furthermore, the present invention is not limited to the number of cells constituting the assembled battery or the method of sequentially switching the differential amplifiers D1 to D8 to which the reference voltage is applied, and the product using the assembled battery is not limited at all. Never happen. The cell voltage detection circuit failure diagnosis apparatus according to the present embodiment can be mounted on, for example, an electric vehicle using an assembled battery as a travel drive source.
[0027]
The correspondence between the constituent elements of the claims and the constituent elements of the embodiment is as follows. That is, the differential amplifiers D1 to D8 are cell voltage detection circuits, the reference voltage setting unit 6 and the analog switch IC unit 7 are reference voltage application circuits, the reference voltage setting unit 6 is a changing unit, and the analog switch IC unit 7 is The applied voltage switching circuit, the CPU 10 constitutes a failure diagnosis circuit, the capacitance adjustment circuits E1 to E8 constitute a capacitance adjustment circuit, and the switches SW1 to SW8 constitute disconnect means. In addition, as long as the characteristic function of this invention is not impaired, each component is not limited to the said structure.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an embodiment of a cell voltage detection circuit failure diagnosis apparatus according to the present invention. FIG. 2 is a diagram showing a detailed configuration of a reference voltage application circuit used when diagnosing a cell voltage detection circuit. FIG. 3 is a table showing which cell is applied with a reference voltage according to the signal level of CPU control signals I, A, B, and C. FIG. 4 is a fault diagnosis of a cell voltage detection circuit according to the present invention. Flowchart of an embodiment showing a failure diagnosis control procedure by the apparatus [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Battery assembly, 3 ... Cell voltage detection circuit, 5 ... Changeover switch part, 6 ... Reference voltage setting part, 7 ... Analog switch IC part, 10 ... CPU, C1-C8 ... Cell, D1-D8 ... Differential amplification part , E1 to E8 ... capacity adjustment circuit, SW1 to SW8 ... switch

Claims (8)

A plurality of cell voltage detection circuits provided for each of a plurality of cells constituting the assembled battery and detecting a cell voltage of a corresponding cell;
A reference voltage application circuit that applies a reference voltage to any one of the plurality of cell voltage detection circuits ;
An applied voltage switching circuit for switching the cell voltage detection circuit for applying the reference voltage;
A failure diagnosis circuit that performs failure diagnosis of the cell voltage detection circuit to which the reference voltage is applied based on the detection voltage detected by the cell voltage detection circuit to which the reference voltage is applied and the applied reference voltage A failure diagnosis apparatus for a cell voltage detection circuit. In the failure diagnosis device for a cell voltage detection circuit according to claim 1,
The failure diagnosis apparatus for a cell voltage detection circuit, wherein the reference voltage application circuit includes a changing unit that changes the reference voltage to be applied. In the failure diagnosis device for a cell voltage detection circuit according to claim 1 or 2,
The fault diagnosis device for a cell voltage detection circuit, wherein the reference voltage is a value in an overcharge voltage region of the cell. In the failure diagnosis device for a cell voltage detection circuit according to claim 1 or 2,
The fault diagnosis apparatus for a cell voltage detection circuit, wherein the reference voltage is a value in an overdischarge voltage region of the cell. In the failure diagnosis device for a cell voltage detection circuit according to claim 1 or 2,
The reference voltage application circuit applies a value of the overcharge voltage region of the cell and a value of the overdischarge voltage region of the cell as a reference voltage,
The fault diagnosis circuit according to claim 1, wherein the fault diagnosis circuit performs fault diagnosis of an overcharge detection region and an overdischarge detection region at a time using the applied reference voltage. In the failure diagnosis device for a cell voltage detection circuit according to any one of claims 1 to 5,
A capacity adjustment circuit which is provided for each of the plurality of cells and adjusts the capacity of the corresponding cell;
A separation means for separating the capacity adjustment circuit and the cell voltage detection circuit;
The disconnection means disconnects the capacity adjustment circuit and the cell voltage detection circuit when the reference voltage is applied to the cell voltage detection circuit by the reference voltage application circuit. Diagnostic device. In the failure diagnosis device for a cell voltage detection circuit according to any one of claims 1 to 6,
The fault diagnosis circuit detects the cell voltage when a difference between the applied reference voltage detected by the cell voltage detection circuit and the applied reference voltage is outside a predetermined range. A failure diagnosis apparatus for a cell voltage detection circuit, characterized in that it is determined that a failure has occurred in a circuit. A fault diagnosis method for a cell voltage detection circuit, which is provided for each of a plurality of cells constituting an assembled battery and performs a fault diagnosis of a plurality of cell voltage detection circuits for detecting a cell voltage of a corresponding cell,
Applying a reference voltage to any one of the plurality of cell voltage detection circuits ,
The applied reference voltage is detected by the cell voltage detection circuit,
Cell voltage detection characterized by performing a fault diagnosis of the cell voltage detection circuit based on a detection voltage detected by a cell voltage detection circuit to which the reference voltage is applied and a reference voltage actually applied Circuit fault diagnosis method.

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