JP2016152720A - Cell balance circuit and failure diagnosis device thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cell balance circuit capable of measuring the battery voltage correctly even during discharge, and to provide a cell balance circuit failure diagnosis device that can be achieved with an inexpensive and simple circuitry, by eliminating the need for voltage measurement means dedicated to failure diagnosis.SOLUTION: A cell balance circuit 2 includes first resistor elements R1-R3 and switching elements Q1-Q3 connected in parallel with individual batteries 11-13 constituting a battery pack 1, second resistor elements R4-R7 connected between the electrodes of the batteries 11-13 and the voltage input terminals CV1-CV4 of a voltage measurement circuit 32, and first capacitors C4-C6 for failure diagnosis connected between the first resistor elements R1-R3 and switching elements Q1-Q3, and between the second resistor elements R4-R7 and voltage input terminals CV1-CV4.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a cell balance circuit that averages the remaining amounts of a plurality of batteries included in an assembled battery, and more particularly to a failure diagnosis device that diagnoses a failure of a cell balance circuit.

  In an electric vehicle such as an electric vehicle (EV) and a hybrid electric vehicle (HEV), an assembled battery in which a plurality of batteries are connected in series is used as a driving power source. The cell monitor unit is a device that monitors the voltage and temperature of the assembled battery.

  As for the assembled battery, the remaining amount of each battery varies due to variations during manufacturing and deterioration over time. If an assembled battery is used in a state where the remaining amount varies, overcharge or overdischarge may occur in each battery. In addition, when the battery is used while avoiding overcharge and overdischarge of individual batteries in a state where variations occur, there is a problem that the assembled battery cannot be used efficiently. For this reason, the cell monitor unit is equipped with a cell balance circuit that equalizes the remaining amount of batteries by discharging a plurality of batteries individually.

  If the cell balance circuit fails, there is a possibility that overdischarge may occur if the battery becomes incapable of discharging, and overdischarge may occur if it becomes continuous discharge. The cell monitor unit will self-diagnose the failure of the cell balance circuit. It is demanded.

  Conventionally, as a failure diagnosis method for a cell balance circuit, a method for detecting a discharge current of a battery and a method for detecting a voltage drop due to the discharge current flowing through a resistor have been developed. In the method of detecting the discharge current, a current detection means is required, so that the circuit configuration is expensive and complicated.

  Patent Document 1 discloses a failure diagnosis method for detecting a voltage drop of a discharge resistor. In the method of Patent Document 1, voltage measurement means dedicated to failure diagnosis is required in addition to the battery voltage measurement means, resulting in an expensive and complicated circuit configuration.

  Patent Document 2 discloses a failure diagnosis method for detecting a voltage drop due to a resistor inserted in a discharge circuit in addition to the discharge resistor. In the method of Patent Document 2, since a voltage drop can be detected by using a battery voltage measuring means, an inexpensive and simple circuit configuration is obtained. However, since the voltage drop occurs during discharging, there is a problem that the battery voltage cannot be correctly measured.

JP 2007-85847 A JP 2011-76778 A

  The failure diagnosis method of Patent Document 1 requires a voltage measurement unit dedicated to failure diagnosis in addition to the battery voltage measurement unit, and has a problem of an expensive and complicated circuit configuration. On the other hand, since the failure diagnosis method of Patent Document 2 can detect a voltage drop using a battery voltage measuring means, it is an inexpensive and simple circuit configuration. However, since the voltage drop occurs during discharging, the battery voltage cannot be measured correctly. There was a problem.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a cell balance circuit capable of correctly measuring a battery voltage even during discharge. It is another object of the present invention to provide a cell balance circuit failure diagnosis apparatus that can be realized with an inexpensive and simple circuit configuration without requiring a voltage measurement means dedicated to failure diagnosis.

  The cell balance circuit of the present invention includes a discharge first resistance element and a switching element connected in parallel to each battery constituting the assembled battery, and between the battery electrode and the voltage input terminal of the voltage measurement circuit. And a first capacitor for fault diagnosis connected between the first resistor element and the switching element, and between the second resistor element and the voltage input terminal. .

  A cell balance circuit failure diagnosis apparatus according to the present invention includes the cell balance circuit and a failure diagnosis circuit that diagnoses a failure of the cell balance circuit using a voltage value between voltage input terminals measured by the voltage measurement circuit. It is.

  The cell balance circuit of the present invention can correctly measure the battery voltage even during discharge by providing the first capacitor for failure diagnosis. Moreover, since the cell balance circuit failure diagnosis apparatus of the present invention diagnoses a failure of the cell balance circuit using the voltage value measured by the voltage measurement circuit that measures the battery voltage, voltage measurement means dedicated to failure diagnosis is unnecessary, It can be realized with an inexpensive and simple circuit configuration.

It is explanatory drawing which shows the structure of the principal part of the assembled battery, cell balance circuit, and IC which concern on Embodiment 1 of this invention. It is explanatory drawing which shows the electric current which flows into a cell balance circuit when switching a switching element from OFF to ON. It is explanatory drawing which shows the electric current which flows into a cell balance circuit, when a switching element is switched from ON to OFF. It is explanatory drawing which shows the voltage between voltage input terminals in a state with a normal cell balance circuit. It is explanatory drawing which shows the voltage between voltage input terminals in the state in which the cell balance circuit failed. It is explanatory drawing which shows the voltage between voltage input terminals in the state in which the cell balance circuit failed. It is explanatory drawing which shows operation | movement of the cell balance circuit failure diagnostic apparatus which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows the structure of the principal part of the assembled battery, cell balance circuit, and IC which concerns on Embodiment 2 of this invention. It is explanatory drawing which shows operation | movement of the cell balance circuit failure diagnostic apparatus which concerns on Embodiment 2 of this invention. It is explanatory drawing which shows the structure of the principal part of the assembled battery which concerns on Embodiment 3 of this invention, a cell balance circuit, and IC. It is explanatory drawing which shows the electric current which flows into a cell balance circuit when switching ON / OFF of a switching element. It is explanatory drawing which shows operation | movement of the cell balance circuit fault diagnostic apparatus which concerns on Embodiment 3 of this invention. It is explanatory drawing which shows the structure of the principal part of the assembled battery which concerns on Embodiment 4 of this invention, a cell balance circuit, and IC. It is explanatory drawing which shows the electric current which flows into a cell balance circuit when switching ON / OFF of a switching element. It is explanatory drawing which shows operation | movement of the cell balance circuit failure diagnostic apparatus which concerns on Embodiment 4 of this invention. It is explanatory drawing which shows the structure of the principal part of the assembled battery which concerns on Embodiment 5 of this invention, a cell balance circuit, and IC. It is explanatory drawing which shows the electric current which flows into a cell balance circuit when switching ON / OFF of a switching element. It is explanatory drawing which shows operation | movement of the cell balance circuit failure diagnostic apparatus which concerns on Embodiment 5 of this invention.

Embodiment 1 FIG.
FIG. 1 shows the configuration of the main parts of an assembled battery 1, a cell balance circuit 2, and an IC (Integrated Circuit) 3. With reference to FIG. 1, the cell balance circuit 2 and the cell balance circuit failure diagnosis apparatus 100 of Embodiment 1 will be described.

  The assembled battery 1 is composed of a plurality of batteries connected in series. FIG. 1 shows an example in which the assembled battery 1 is composed of three batteries 11 to 13.

  In parallel with the battery 11, a first resistance element R1 for discharging and a switching element Q1 are connected. The switching element Q <b> 1 is configured by a so-called “N-channel type” MOSFET (Metal-oxide-semiconductor Field-effect Transistor).

  Similarly, a first discharging resistance element R2 and a switching element Q2 are connected in parallel to the battery 12. In parallel with the battery 13, a first resistance element R3 for discharging and a switching element Q3 are connected.

  A second resistance element R4 is connected between the positive electrode of the battery 11 and the voltage input terminal CV1 of the IC3. A second resistance element R5 is connected between the negative electrode of the battery 11 and the positive electrode of the battery 12, and the voltage input terminal CV2 of the IC3.

  Similarly, the second resistance element R6 is connected between the negative electrode of the battery 12, the positive electrode of the battery 13, and the voltage input terminal CV3. A second resistance element R7 is connected between the negative electrode of the battery 13 and the voltage input terminal CV4.

  One electrode of the second capacitor C1 is connected to the voltage input terminal CV1, and the other electrode is electrically grounded. The second resistor element R4 and the second capacitor C1 constitute an RC filter for noise removal.

  Similarly, one electrode of the second capacitor C2 is connected to the voltage input terminal CV2, and the other electrode is electrically grounded. The second resistive element R5 and the second capacitor C2 constitute an RC filter for noise removal. One electrode of the second capacitor C3 is connected to the voltage input terminal CV3, and the other electrode is electrically grounded. The second resistance element R6 and the second capacitor C3 constitute an RC filter for noise removal.

  The second capacitor C1 may be connected between the voltage input terminals CV1 and CV2. Similarly, the second capacitor C2 may be connected between the voltage input terminals CV2 and CV3. The second capacitor C3 may be connected between the voltage input terminals CV3 and CV4.

  A first capacitor C4 for fault diagnosis is connected between the first resistance element R1 and the switching element Q1, and between the second resistance element R4 and the voltage input terminal CV1. Similarly, a first capacitor C5 for fault diagnosis is connected between the first resistance element R2 and the switching element Q2, and between the second resistance element R5 and the voltage input terminal CV2. A first capacitor C6 for fault diagnosis is connected between the first resistance element R3 and the switching element Q3, and between the second resistance element R6 and the voltage input terminal CV3. The cell balance circuit 2 is configured by the first resistance elements R1 to R3, the switching elements Q1 to Q3, the second resistance elements R4 to R7, the second capacitors C1 to C3, and the first capacitors C4 to C6.

  The IC 3 includes a control circuit 31, a voltage measurement circuit 32, and a failure diagnosis circuit 33. The control circuit 31 is electrically connected to the gate terminals of the switching elements Q1 to Q3, and is a circuit that controls on / off of the switching elements Q1 to Q3. In FIG. 1, the wiring connecting the control circuit 31 and the switching elements Q1 to Q3 is not shown. Hereinafter, control in which the control circuit 31 switches the switching elements Q1 to Q3 from off to on is referred to as “on control”, and control in which the control circuit 31 switches from on to off is referred to as “off control”. The control circuit 31 notifies the voltage measurement circuit 32 and the failure diagnosis circuit 33 of the timing for executing the on control and the off control before executing the on control and the off control of the switching elements Q1 to Q3.

  The voltage measurement circuit 32 synchronizes with the timing notified from the control circuit 31, and the voltage between the voltage input terminals CV1 and CV2, the voltage between the voltage input terminals CV2 and CV3, and the voltage between the voltage input terminals CV3 and CV4. It is a circuit that measures. The failure diagnosis circuit 33 is a circuit that diagnoses a failure of the cell balance circuit 2 using the voltage value measured by the voltage measurement circuit 32. The failure diagnosis circuit 33 outputs the diagnosis result to a BMU (Battery Management Unit) (not shown). Detailed operations of the voltage measurement circuit 32 and the failure diagnosis circuit 33 will be described later with reference to FIG. The cell balance circuit failure diagnosis apparatus 100 is configured by the cell balance circuit 2 and the IC 3.

  A microcomputer or system LSI (Large Scale Integration) (not shown) may be provided separately from the IC 3, and the microcomputer or system LSI may include the control circuit 31 and the failure diagnosis circuit 33. In this case, the cell balance circuit failure diagnosis apparatus 100 is configured by the cell balance circuit 2, the IC 3, and the microcomputer or the system LSI.

  Next, the discharge operation of the batteries 11 to 13 by the cell balance circuit 2 will be described. In the initial state, switching elements Q1 to Q3 are all off.

  When the switching element Q1 is switched from OFF to ON, a current flows through the first resistance element R1, and the battery 11 is discharged. Similarly, when the switching element Q2 is switched from OFF to ON, a current flows through the first resistance element R2, and the battery 12 is discharged. When the switching element Q3 is switched from OFF to ON, a current flows through the first resistance element R3, and the battery 13 is discharged.

  Here, in the conventional cell balance circuit that does not include the first capacitors C4 to C6, the voltage between the voltage input terminals CV1 and CV2 does not change regardless of whether the switching element Q1 is on or off. Similarly, the voltage between the voltage input terminals CV2 and CV3 does not change regardless of whether the switching element Q2 is on or off, and the voltage between the voltage input terminals CV3 and CV4 does not change regardless of whether the switching element Q3 is on or off. Therefore, even if the conventional cell balance circuit failure diagnosis apparatus measures the voltage between the voltage input terminals of IC3, it has not been able to detect the occurrence of an abnormality such as off-fixation or on-fixation of switching elements Q1 to Q3. .

  On the other hand, in the cell balance circuit 2 of the present invention, the voltage between the voltage input terminals changes when the switching elements Q1 to Q3 are switched on and off by providing the first capacitors C4 to C6 for failure diagnosis. It is like that. Hereinafter, the current flowing through the cell balance circuit 2 and the voltage between the voltage input terminals will be described with reference to FIGS.

  When the switching element Q2 is off, the drain-source voltage of the switching element Q2 is equal to the voltage of the battery 12, so that the first capacitor C5 is not charged. When the switching element Q2 is switched on in this state, in addition to the discharge current of the battery 12 passing through the first resistance element R2, a current flows through the path indicated by the solid line arrow in FIG. 2, and the first capacitor C5 is charged. . At this time, a current flows through the second resistance element R5 constituting the RC filter to cause a voltage drop, so that the voltage between the voltage input terminals CV2 and CV3 temporarily decreases as shown in FIG. The time for the voltage to drop is about several milliseconds to several microseconds.

  Next, when the switching element Q2 is switched from on to off, a current flows through a path indicated by a broken-line arrow in FIG. 3 due to discharge of the first capacitor C5. At this time, a current flows through the second resistance element R5 constituting the RC filter to cause a voltage drop, whereby the voltage between the voltage input terminals CV2 and CV3 temporarily rises as shown in FIG. The time for the voltage to rise is about several milliseconds to several microseconds.

  As described above, when the cell balance circuit 2 is operating normally, the voltage between the voltage input terminals CV2 and CV3 temporarily decreases when the control circuit 31 performs the on-control of the switching element Q2, and When the control circuit 31 executes the off control of the switching element Q2, the voltage between the voltage input terminals CV2 and CV3 temporarily rises. Similarly, when the control circuit 31 executes ON control and OFF control of the switching element Q1, the voltage between the voltage input terminals CV1 and CV2 temporarily changes, and when ON control and OFF control of the switching element Q3 are executed. The voltage between the voltage input terminals CV3 and CV4 temporarily changes.

  On the other hand, when the cell balance circuit 2 is out of order, when the control circuit 31 performs the on control or the off control of the switching elements Q1 to Q3, the voltage between the voltage input terminals does not change as follows.

  For example, when the switching element Q2 is fixed on or off, even if the control circuit 31 executes the on control and the off control, the switching element Q2 is not switched on and off. Therefore, charging / discharging of the first capacitor C5 is not performed, and the voltage between the voltage input terminals CV2 and CV3 is constant as shown in FIG.

  When the first resistance element R2 is disconnected, the first capacitor C5 is charged by turning on the switching element Q2. However, even if the switching element Q2 is turned off, the first capacitor C5 is not discharged. For this reason, as shown in FIG. 6, although the voltage between the voltage input terminals CV2 and CV3 temporarily decreases when the control circuit 31 executes the ON control of the switching element Q2, the voltage input terminal when the OFF control is executed. The voltage between CV2 and CV3 does not change.

  The cell balance circuit failure diagnosis apparatus 100 of the present invention diagnoses a failure of the cell balance circuit 2 using such a voltage change between the voltage input terminals. Hereinafter, a specific example of the detailed operation of the cell balance circuit failure diagnosis apparatus 100 will be described with reference to FIG.

  First, the control circuit 31 notifies the voltage measurement circuit 32 and the failure diagnosis circuit 33 of the timing for executing the ON control of the switching element Q2. Next, the control circuit 31 performs on control of the switching element Q2.

  Based on the timing notified from the control circuit 31, the voltage measurement circuit 32 measures the voltage between the voltage input terminals CV2 and CV3 immediately before the control circuit 31 performs the on-control and immediately after the on-control. The failure diagnosis circuit 33 is a first difference that is a difference between a voltage value measured immediately before the on-control by the voltage measurement circuit 32 and a voltage value measured immediately after the on-control based on the timing notified from the control circuit 31. The difference ΔV1 is calculated.

  Next, the control circuit 31 notifies the voltage measurement circuit 32 and the failure diagnosis circuit 33 of the timing for executing the OFF control of the switching element Q2. Next, the control circuit 31 executes the off control of the switching element Q2.

  Based on the timing notified from the control circuit 31, the voltage measurement circuit 32 measures the voltage between the voltage input terminals CV2 and CV3 immediately before the control circuit 31 executes the off control and immediately after the off control. The failure diagnosis circuit 33 is a second difference that is a difference between the voltage value measured immediately before the off control by the voltage measurement circuit 32 and the voltage value measured immediately after the off control based on the timing notified from the control circuit 31. The difference ΔV2 is calculated.

  Next, the failure diagnosis circuit 33 compares the values of the first difference ΔV1 and the second difference ΔV2 with a predetermined threshold value. This threshold value is a value set in advance according to the average voltage of the battery 12, the resistance value of the second resistance element R5, and the like. When the value of the first difference ΔV1 is larger than the threshold value and the value of the second difference ΔV2 is larger than the threshold value, the failure diagnosis circuit 33 diagnoses that the cell balance circuit 2 is normal.

  On the other hand, when the value of the first difference ΔV1 is less than or equal to the threshold value, or when the value of the second difference ΔV2 is less than or equal to the threshold value, the failure diagnosis circuit 33 diagnoses that the cell balance circuit 2 has failed. Specifically, for example, when the value of the first difference ΔV1 is equal to or smaller than the threshold value and the value of the second difference ΔV2 is equal to or smaller than the threshold value, the failure diagnosis circuit 33 causes the switching element Q2 to be locked on or off. Diagnose that When the value of the first difference ΔV1 is greater than the threshold value and the value of the second difference ΔV2 is equal to or less than the threshold value, the failure diagnosis circuit 33 diagnoses that the first resistance element R2 is disconnected.

  The failure diagnosis circuit 33 outputs the diagnosis result to a BMU or the like. The BMU outputs a warning image or a warning sound indicating a failure of the cell balance circuit 2 to an external device (not shown), so that a passenger of a mobile body using the assembled battery 1 as a drive power source can detect a failure of the cell balance circuit 2. I can grasp it.

  The failure diagnosis circuit 33 performs failure diagnosis of the cell balance circuit 2 when the voltage value immediately before the control circuit 31 performs the on control and the off control exceeds the voltage range that can be measured by the voltage measurement circuit 32. It is good to not. As described above, the failure diagnosis method using the first difference ΔV1 and the second difference ΔV2 shown in FIG. 7 has an advantage that the execution condition of the failure diagnosis can be set according to the situation such as the battery voltage.

  The failure diagnosis using the voltage values between the voltage input terminals CV1 and CV2 and between the voltage input terminals CV3 and CV4 is the same as the example shown in FIG.

  As described above, the cell balance circuit 2 according to the first embodiment includes the first discharging resistance elements R1 to R3 and the switching element Q1 connected in parallel to the individual batteries 11 to 13 constituting the assembled battery 1. To Q3, second resistance elements R4 to R7 connected between the electrodes of the batteries 11 to 13 and the voltage input terminals CV1 to CV4 of the voltage measurement circuit 32, the first resistance elements R1 to R3, and the switching elements Q1 to Q3. And a first capacitor C4 to C6 for failure diagnosis connected between Q3 and between the second resistance elements R4 to R7 and the voltage input terminals CV1 to CV4. By providing such a first capacitor for failure diagnosis, it is possible to provide the cell balance circuit 2 that can correctly measure the battery voltage even during discharge.

  In addition, the cell balance circuit 2 has one electrode connected to the voltage input terminals CV1 to CV4 and the other electrode is electrically grounded, or is connected between the voltage input terminals CV1 to CV4. C3 is provided. The second resistor elements R4 to R6 and the second capacitors C1 to C3 constitute an RC filter for noise removal. By removing noise of the measurement value of the voltage measurement circuit 32 by the RC filter, the accuracy of voltage measurement by the voltage measurement circuit 32 can be increased, and the accuracy of failure diagnosis by the cell balance circuit failure diagnosis apparatus 100 can be increased.

  In addition, the cell balance circuit failure diagnosis apparatus 100 according to the first embodiment uses the voltage value between the cell balance circuit 2 and the voltage input terminals CV1 to CV4 measured by the voltage measurement circuit 32 to check the failure of the cell balance circuit 2. And a failure diagnosis circuit 33 for diagnosis. Since the failure of the cell balance circuit 2 is diagnosed using the voltage value measured by the voltage measurement circuit 32 that measures the battery voltage, the cell balance circuit can be constructed with an inexpensive and simple circuit configuration without providing a voltage measurement means dedicated to failure diagnosis. The failure diagnosis apparatus 100 can be realized.

  In addition, the cell balance circuit failure diagnosis apparatus 100 includes a control circuit 31 that executes on control for switching the switching elements Q1 to Q3 from off to on and off control for switching the switching elements Q1 to Q3 from on to off. The failure diagnosis circuit 33 calculates a first difference ΔV1 that is a difference between voltage values before and after the on-control and a second difference ΔV2 that is a difference between voltage values before and after the off-control, and the first difference ΔV1 and the second difference The failure of the cell balance circuit 2 is diagnosed by comparing the value of the difference ΔV2 with a threshold value. When the voltage measuring circuit 32 has a function of measuring a voltage in synchronization with the on control and the off control of the control circuit 31, the configuration is such that the failure of the cell balance circuit 2 is diagnosed using the first difference ΔV1 and the second difference ΔV2. The failure processing execution conditions can be set according to the battery voltage and other conditions.

Embodiment 2. FIG.
With reference to FIG. 8, the cell balance circuit failure diagnosis apparatus 100 when the voltage measurement circuit 32 does not have a function of measuring a voltage in synchronization with the on control and the off control of the control circuit 31 will be described. In FIG. 8, the same components as those of the assembled battery 1, the cell balance circuit 2, and the IC 3 shown in FIG. The current flowing in the cell balance circuit 2 and the voltage between the voltage input terminals are the same as in the first embodiment, and will be described with reference to FIGS.

  The control circuit 31 notifies the failure diagnosis circuit 33 that the on / off control of the switching elements Q1 to Q3 has been executed. The voltage measurement circuit 32 measures the voltage between the voltage input terminals at regular time intervals. This time interval is a time interval that is at least short enough to detect a voltage change between the voltage input terminals when the switching elements Q1 to Q3 are switched on and off.

  The failure diagnosis circuit 33 has a first threshold value Vth1 lower than a voltage value between voltage input terminals (hereinafter referred to as “reference voltage value”) in a state in which the switching elements Q1 to Q3 are not switched on and off, and higher than the reference voltage value. The second threshold value Vth2 is stored. Note that the values of the first threshold value Vth1 and the second threshold value Vth2 may be fixed values, or may be values that change according to the usage period of the assembled battery 1 in consideration of the aging of the batteries 11 to 13 and the like.

  The failure diagnosis circuit 33 has a comparator that compares the voltage value measured by the voltage measurement circuit 32 with the first threshold value Vth1 and the second threshold value Vth2. When the failure diagnosis circuit 33 detects that the voltage value measured by the voltage measurement circuit 32 has become equal to or less than the first threshold value Vth1, the failure diagnosis circuit 33 latches the detection value. Further, when the failure diagnosis circuit 33 detects that the voltage value measured by the voltage measurement circuit 32 is equal to or higher than the second threshold value Vth2, the failure diagnosis circuit 33 latches the detection value.

  A specific example of the detailed operation of the cell balance circuit failure diagnosis apparatus 100 will be described with reference to FIG. In the initial state, the switching element Q2 is off, and the voltage measurement circuit 32 measures the voltage between the voltage input terminals CV2 and CV3 at regular time intervals.

  First, the control circuit 31 performs ON control of the switching element Q2. Next, the control circuit 31 notifies the failure diagnosis circuit 33 that the on-control of the switching element Q2 has been executed.

  At this time, when the cell balance circuit 2 is operating normally, the switching element Q2 is turned on, current flows through the path shown in FIG. 2, and the voltage between the voltage input terminals CV2 and CV3 temporarily decreases. The failure diagnosis circuit 33 detects that the voltage value measured by the voltage measurement circuit 32 has become equal to or lower than the first threshold value Vth1, and latches the detected value.

  Next, the control circuit 31 performs the off control of the switching element Q2. Next, the control circuit 31 notifies the failure diagnosis circuit 33 that the switching element Q2 has been turned off.

  At this time, when the cell balance circuit 2 is operating normally, the switching element Q2 is turned off, current flows through the path shown in FIG. 3, and the voltage between the voltage input terminals CV2 and CV3 temporarily rises. The failure diagnosis circuit 33 detects that the voltage value measured by the voltage measurement circuit 32 is equal to or higher than the second threshold value Vth2, and latches the detected value.

  The failure diagnosis circuit 33 diagnoses a failure in the cell balance circuit 2 according to the latched detection value after the control circuit 31 executes both the on control and the off control. That is, it is detected that the voltage value between the voltage input terminals CV2 and CV3 is equal to or lower than the first threshold value Vth1, and the voltage value between the voltage input terminals CV2 and CV3 is equal to or higher than the second threshold value Vth2. Is detected, the failure diagnosis circuit 33 diagnoses that the cell balance circuit 2 is normal.

  On the other hand, when it is not detected that the voltage value between the voltage input terminals CV2 and CV3 has become the first threshold value Vth1 or less, or the voltage value between the voltage input terminals CV2 and CV3 has become the second threshold value Vth2 or more. If this is not detected, the failure diagnosis circuit 33 diagnoses that the cell balance circuit 2 has failed. Specifically, for example, it is not detected that the voltage value between the voltage input terminals CV2 and CV3 is equal to or lower than the first threshold value Vth1, and the voltage value between the voltage input terminals CV2 and CV3 is the second threshold value. If it is not detected that the voltage Vth2 or higher is detected, the failure diagnosis circuit 33 diagnoses that the switching element Q2 is fixed on or off. Further, it is detected that the voltage value between the voltage input terminals CV2 and CV3 has become the first threshold value Vth1 or less, and the voltage value between the voltage input terminals CV2 and CV3 has become the second threshold value Vth2 or more. Is not detected, the failure diagnosis circuit 33 diagnoses that the first resistance element R2 is disconnected.

  In general, the voltage measurement IC 3 includes an analog comparator or a digital comparator for overcharge detection and overdischarge detection. The failure diagnosis method for comparing the voltage value between the voltage input terminals with the first threshold value Vth1 and the second threshold value Vth2 shown in FIG. 9 has the merit that an analog comparator or a digital comparator built in the IC3 can be used as the comparator of the failure diagnosis circuit 33. There is.

  The failure diagnosis using the voltage values between the voltage input terminals CV1 and CV2 and between the voltage input terminals CV3 and CV4 is the same as the example shown in FIG.

  As described above, in the cell balance circuit failure diagnosis apparatus 100 according to the second embodiment, the failure diagnosis circuit 33 compares the voltage value with the first threshold value Vth1 that is lower than the reference voltage value, and sets the voltage value from the reference voltage value. The failure of the cell balance circuit 2 is diagnosed by comparing with a higher second threshold value Vth2. A configuration in which the voltage measurement circuit 32 is a constant measurement type and does not have a function of measuring a voltage in synchronization with the on control and the off control of the control circuit 31 due to the configuration compared with the first threshold value Vth1 and the second threshold value Vth2. In addition, the failure of the cell balance circuit 2 can be diagnosed.

Embodiment 3 FIG.
The cell balance circuit 2 of the present invention is not limited to the circuit configuration shown in FIGS. A modification of the cell balance circuit 2 will be described with reference to FIG. In FIG. 10, the same components as those of the assembled battery 1, the cell balance circuit 2, and the IC 3 shown in FIGS.

  A switching element Q1 and a first resistance element R1 are connected in parallel to the battery 11. The switching element Q1 is configured by a so-called “P-channel type” MOSFET.

  Similarly, the switching element Q2 and the first resistance element R2 are connected in parallel to the battery 12. A switching element Q3 and a first resistance element R3 are connected in parallel to the battery 13.

  A first capacitor C4 is connected between the switching element Q1 and the first resistance element R1, and between the second resistance element R5 and the voltage input terminal CV2. Similarly, a first capacitor C5 is connected between the switching element Q2 and the first resistance element R2, and between the second resistance element R6 and the voltage input terminal CV3. A first capacitor C6 is connected between the switching element Q3 and the first resistance element R3, and between the second resistance element R7 and the voltage input terminal CV4.

With reference to FIG.11 and FIG.12, the electric current which flows into the cell balance circuit 2 comprised in this way and the voltage between voltage input terminals are demonstrated.
When the switching element Q2 is switched from OFF to ON, in addition to the discharge current of the battery 12 passing through the first resistance element R2, a current flows along the path indicated by the solid line arrow in FIG. 11, and the first capacitor C5 is charged. At this time, a current flows through the second resistance element R6 and a voltage drop occurs, so that the voltage between the voltage input terminals CV2 and CV3 temporarily decreases as shown in FIG.

  Next, when the switching element Q2 is switched from on to off, a current flows through a path indicated by a broken-line arrow in FIG. 11 due to discharge of the first capacitor C5. At this time, a current flows through the second resistance element R6 and a voltage drop occurs, whereby the voltage between the voltage input terminals CV2 and CV3 temporarily rises as shown in FIG.

  As shown in FIG. 12, the failure diagnosis circuit 33 calculates the first differences ΔV1 and ΔV2 similar to those of the first embodiment, and compares the values of the first difference ΔV1 and the second difference ΔV2 with a threshold value to thereby compare the cell balance circuit. 2 faults are detected.

  The control circuit 31, the voltage measurement circuit 32, and the failure diagnosis circuit 33 may have the same configuration as in the second embodiment. In this case, the failure diagnosis circuit 33 detects a failure in the cell balance circuit 2 by comparing the voltage value measured by the voltage measurement circuit 32 with the first threshold value Vth1 and the second threshold value Vth2 similar to those in the second embodiment.

Embodiment 4 FIG.
With reference to FIG. 13, another modification of the cell balance circuit 2 will be described. In FIG. 13, the same components as those of the assembled battery 1, the cell balance circuit 2, and the IC 3 shown in FIGS.

  A first resistance element R1 and a switching element Q1 are connected in parallel to the battery 11. The switching element Q1 is composed of an N channel type MOSFET.

  Similarly, the first resistance element R2 and the switching element Q2 are connected in parallel to the battery 12. A first resistance element R3 and a switching element Q3 are connected in parallel to the battery 13.

  A first capacitor C4 is connected between the first resistance element R1 and the switching element Q1, and between the second resistance element R5 and the voltage input terminal CV2. Similarly, a first capacitor C5 is connected between the first resistance element R2 and the switching element Q2, and between the second resistance element R6 and the voltage input terminal CV3. A first capacitor C6 is connected between the first resistance element R3 and the switching element Q3, and between the second resistance element R7 and the voltage input terminal CV4.

With reference to FIG.14 and FIG.15, the electric current which flows into the cell balance circuit 2 comprised in this way and the voltage between voltage input terminals are demonstrated.
When the switching element Q2 is switched from on to off, a current flows through a path indicated by a broken-line arrow in FIG. 14, and the first capacitor C5 is charged. At this time, a current flows through the second resistance element R6 to cause a voltage drop, whereby the voltage between the voltage input terminals CV2 and CV3 temporarily decreases as shown in FIG.

  Next, when the switching element Q2 is switched from OFF to ON, in addition to the discharge current of the battery 12 passing through the first resistance element R2, a current flows along the path indicated by the solid arrow in FIG. 14 due to the discharge of the first capacitor C5. At this time, a current flows through the second resistance element R6 to cause a voltage drop, whereby the voltage between the voltage input terminals CV2 and CV3 temporarily rises as shown in FIG.

  As shown in FIG. 15, the failure diagnosis circuit 33 calculates the first differences ΔV1 and ΔV2 similar to those of the first embodiment, and compares the values of the first difference ΔV1 and the second difference ΔV2 with a threshold value to thereby calculate the cell balance circuit. 2 faults are detected.

  The control circuit 31, the voltage measurement circuit 32, and the failure diagnosis circuit 33 may have the same configuration as in the second embodiment. In this case, the failure diagnosis circuit 33 detects a failure in the cell balance circuit 2 by comparing the voltage value measured by the voltage measurement circuit 32 with the first threshold value Vth1 and the second threshold value Vth2 similar to those in the second embodiment.

Embodiment 5 FIG.
With reference to FIG. 16, another modification of the cell balance circuit 2 will be described. In FIG. 16, the same components as those of the assembled battery 1, the cell balance circuit 2, and the IC 3 shown in FIGS.

  A switching element Q1 and a first resistance element R1 are connected in parallel to the battery 11. The switching element Q1 is composed of a P-channel type MOSFET.

  Similarly, the switching element Q2 and the first resistance element R2 are connected in parallel to the battery 12. A switching element Q3 and a first resistance element R3 are connected in parallel to the battery 13.

  A first capacitor C4 is connected between the switching element Q1 and the first resistance element R1, and between the second resistance element R4 and the voltage input terminal CV1. Similarly, a first capacitor C5 is connected between the switching element Q2 and the first resistance element R2, and between the second resistance element R5 and the voltage input terminal CV2. A first capacitor C6 is connected between the switching element Q3 and the first resistance element R3, and between the second resistance element R6 and the voltage input terminal CV3.

With reference to FIG.17 and FIG.18, the electric current which flows into the cell balance circuit 2 comprised in this way and the voltage between voltage input terminals are demonstrated.
When the switching element Q2 is switched from on to off, a current flows through a path indicated by a broken-line arrow in FIG. 17, and the first capacitor C5 is charged. At this time, a current flows through the second resistance element R5 and a voltage drop occurs, so that the voltage between the voltage input terminals CV2 and CV3 temporarily decreases as shown in FIG.

  Next, when the switching element Q2 is switched from OFF to ON, in addition to the discharge current of the battery 12 passing through the first resistance element R2, a current flows along the path indicated by the solid arrow in FIG. 17 due to the discharge of the first capacitor C5. At this time, a current flows through the second resistance element R5 and a voltage drop occurs, so that the voltage between the voltage input terminals CV2 and CV3 temporarily rises as shown in FIG.

  As shown in FIG. 18, the failure diagnosis circuit 33 calculates the first differences ΔV1 and ΔV2 similar to those of the first embodiment, and compares the values of the first difference ΔV1 and the second difference ΔV2 with a threshold value, thereby comparing the cell balance circuit. 2 faults are detected.

  The control circuit 31, the voltage measurement circuit 32, and the failure diagnosis circuit 33 may have the same configuration as in the second embodiment. In this case, the failure diagnosis circuit 33 detects a failure in the cell balance circuit 2 by comparing the voltage value measured by the voltage measurement circuit 32 with the first threshold value Vth1 and the second threshold value Vth2 similar to those in the second embodiment.

  In any of the cell balance circuits 2 according to the third to fifth embodiments, the second capacitor C1 may be connected between the voltage input terminals CV1 and CV2. Similarly, the second capacitor C2 may be connected between the voltage input terminals CV2 and CV3, and the second capacitor C3 may be connected between the voltage input terminals CV3 and CV4.

  Among the cell balance circuits 2 according to the first to fifth embodiments, the cell balance circuit 2 according to the first and second embodiments is an RC filter including the second resistance elements R4 to R6 and the second capacitors C1 to C3. The influence on the frequency characteristic can be minimized. Therefore, although any of the cell balance circuits 2 according to the first to fifth embodiments can correctly measure the battery voltage during discharging, it is particularly preferable to employ the cell balance circuit 2 according to the first and second embodiments.

  In the present invention, within the scope of the invention, any combination of the embodiments, or any modification of any component in each embodiment, or omission of any component in each embodiment is possible. .

  1 battery pack, 2 cell balance circuit, 3 IC, 11, 12, 13 battery, 31 control circuit, 32 voltage measurement circuit, 33 fault diagnosis circuit, 100 cell balance circuit fault diagnosis device, C1, C2, C3 second capacitor, C4, C5, C6 first capacitor, CV1, CV2, CV3, CV4 voltage input terminal, Q1, Q2, Q3 switching element, R1, R2, R3 first resistance element, R4, R5, R6, R7 second resistance element.

Claims (7)

A first resistance element and a switching element for discharging connected in parallel to the individual batteries constituting the assembled battery;
A second resistance element connected between the electrode of the battery and a voltage input terminal of the voltage measurement circuit;
A first capacitor for fault diagnosis connected between the first resistance element and the switching element, and between the second resistance element and the voltage input terminal;
A cell balance circuit comprising: One electrode is connected to the voltage input terminal and the other electrode is electrically grounded, or a second capacitor connected between the voltage input terminals,
The cell balance circuit according to claim 1, wherein an RC filter for noise removal is configured by the second resistance element and the second capacitor. The cell balance circuit according to claim 1 or 2,
Using a voltage value between the voltage input terminals measured by the voltage measurement circuit, a failure diagnosis circuit that diagnoses a failure of the cell balance circuit,
A cell balance circuit failure diagnosis apparatus comprising: A control circuit for performing on control for switching the switching element from off to on and off control for switching the switching element from on to off;
The failure diagnosis circuit calculates a first difference that is a difference between the voltage values before and after the on-control and a second difference that is a difference between the voltage values before and after the off-control, and the first difference and The cell balance circuit failure diagnosis device according to claim 3, wherein the failure of the cell balance circuit is diagnosed by comparing the value of the second difference with a threshold value. The fault diagnosis circuit is
If the value of the first difference is greater than the threshold value and the value of the second difference is greater than the threshold value, the cell balance circuit is diagnosed as normal,
5. The cell balance circuit is diagnosed as malfunctioning when the value of the first difference is less than or equal to the threshold value or when the value of the second difference is less than or equal to the threshold value. The cell balance circuit failure diagnosis apparatus described.   The failure diagnosis circuit compares the voltage value with a first threshold value that is lower than a reference voltage value, and compares the voltage value with a second threshold value that is higher than the reference voltage value, thereby detecting a failure in the cell balance circuit. The cell balance circuit failure diagnosis apparatus according to claim 3, wherein diagnosis is performed. A control circuit for performing on control for switching the switching element from off to on and off control for switching the switching element from on to off;
The fault diagnosis circuit is
After the control circuit executes the on control and the off control, it is detected that the voltage value has become the first threshold value or less, and the voltage value has become the second threshold value or more. Is detected, the cell balance circuit is diagnosed as normal,
After the control circuit has performed the on control and the off control, it has not been detected that the voltage value has become the first threshold value or less, or the voltage value has become the second threshold value or more. The cell balance circuit failure diagnosis apparatus according to claim 6, wherein if the detection is not detected, the cell balance circuit is diagnosed as having a failure.

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