JP2011076778A - Battery monitoring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery monitoring device capable of detecting the glitch of a discharge circuit in failure diagnosis performed by comparing thresholds with cell voltages of battery cells. <P>SOLUTION: The battery monitoring device includes: diagnosis resistors 30, each of which are connected between the positive electrode side of the corresponding battery cell 10 and a monitoring circuit 50; and an equalization discharge circuit 40 feeding current flowing from the battery cells 10 through the diagnosis resistors 30 to the negative electrode sides of the battery cells 10 according to a command from a microcomputer 70. The microcomputer 70 detects the glitch of the equalization discharge circuit 40 when a comparison result of comparison between the cell voltages, which are given when the equalization discharge circuit 40 is turned on in the failure diagnosis, and the thresholds relatively varied across several levels is different from an estimation result of comparison between the cell voltages, which are estimated as voltages lowering drop voltages occurring at both ends of the diagnosis resistors 30 when a current flows through the diagnosis resistors 30, and the thresholds relatively varied across several levels. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a battery monitoring device.

  Conventionally, an assembled battery control device provided with a failure diagnosis function that detects that the threshold of overcharge detection or overdischarge detection of each battery of an assembled battery in which a plurality of batteries are connected in series has spontaneously changed is disclosed in, for example, Patent Document 1 Proposed in In this patent document 1, the structure which detects the voltage of an assembled battery and compares the said voltage and a threshold value is proposed.

  Specifically, a switch that switches the threshold value by one step from the original value of the threshold value is provided. Then, the battery pack controller switches the switch at the time of failure diagnosis to relatively change the threshold value by one level, and when the magnitude relationship between the threshold value and the battery voltage does not reverse even though the threshold value is forcibly changed, It is determined that the spontaneous change of is large. In this way, the failure of the assembled battery control device can be detected.

  Moreover, the assembled battery control device is provided with a discharge circuit for each battery to reduce voltage variation of each battery constituting the assembled battery. Each discharge circuit is connected in parallel to each battery, and serves as a current path through which a current flows from the positive electrode side to the negative electrode side of each battery.

JP 2003-92840 A

  However, in the above conventional technique, when the discharge circuit is faulty, the current is not properly supplied from the battery to the discharge circuit, so that the voltage variation of the battery is not improved. Moreover, although the failure diagnosis can detect the spontaneous change of the threshold value, the failure of the discharge circuit cannot be diagnosed.

  In view of the above points, an object of the present invention is to provide a battery monitoring device capable of detecting an abnormality in a discharge circuit when performing failure diagnosis by comparing a threshold value with a cell voltage of a battery cell.

In order to achieve the above object, according to the first aspect of the present invention, there is provided a battery monitoring device for monitoring the state of a plurality of battery cells connected in series,
Monitoring means for inputting the cell voltage at both ends of the battery cell for each of the plurality of battery cells, comparing the cell voltage with the threshold value, and outputting the comparison result, respectively;
A plurality of diagnostic resistors respectively connected between the positive electrode side of each of the plurality of battery cells and the monitoring means;
While determining the state of each of the plurality of battery cells based on the comparison result of the monitoring means, the threshold value of the monitoring means is relatively changed in a plurality of stages for each of the plurality of battery cells and compared with the cell voltage, and based on the comparison result Determination means for performing failure diagnosis for detecting abnormality of the monitoring means;
Battery cell discharge means for flowing a current flowing from the battery cell through the diagnostic resistor to the negative electrode side of the battery cell when turned on according to the instruction of the determination means,
The judging means is a diagnostic result when a comparison is made between the cell voltage when the battery cell discharging means is turned on at the time of failure diagnosis and the threshold value relatively changed in multiple stages, and when a current flows through the diagnostic resistor. Detecting an abnormality in the battery cell discharge means when the estimated cell voltage at which the drop voltage generated across the resistor drops and the estimation result comparing the cell voltage with the threshold value that is relatively changed in multiple stages are different It is characterized by.

  According to this, when the determination means turns on the battery cell discharge means at the time of failure diagnosis, and the current flows through the diagnostic resistance, the cell voltage in which the drop voltage that would have occurred at both ends of the diagnostic resistance drops is monitored. Therefore, when the battery cell discharge means is out of order, no current flows through the diagnostic resistor and the drop voltage does not drop from the cell voltage. For this reason, when the cell voltage is compared with the threshold value, the timing at which the magnitude relationship between the cell voltage and the threshold value is reversed shifts, so that the comparison result of the monitoring means is different from the estimation result of the determination means. Therefore, the abnormality of the battery cell discharging means can be detected.

The invention according to claim 2 comprises block voltage detection means for detecting block voltages at both ends of a plurality of battery cells connected in series and outputting them to the determination means,
The judging means estimates the cell voltage of the battery cell from the block voltage, and estimates the cell voltage in which the drop voltage generated at both ends of the diagnostic resistor drops when current flows through the diagnostic resistor using the cell voltage. It is characterized by.

According to this, since the cell voltage of each battery cell is in a certain range, it is not necessary to measure the cell voltage for each battery cell.
The cell voltage can be estimated with high accuracy from the block voltage.

  In the invention according to claim 3, the battery cell discharging means flows a current flowing from the battery cell through the diagnostic resistor when the cell voltage of the battery cell exceeds a certain range, to the negative electrode side of the battery cell, It is an equalizing discharge circuit that adjusts the cell voltage within a certain range.

  According to this, it is possible to share the circuit of the battery cell discharging means for flowing current to the diagnostic resistor and the equalizing discharge circuit.

As in the invention according to claim 4, the monitoring means has a plurality of resistors and a plurality of switches for dividing the cell voltage of the battery cell,
The determination means can be configured to relatively change the threshold value in a plurality of stages by switching the ON state or OFF state of the plurality of switches and dividing the voltage of the battery cell by the plurality of resistors.

1 is an overall configuration diagram of a battery monitoring system including a battery monitoring device according to the present embodiment. It is the figure which showed the circuit structure of the monitoring circuit with respect to one battery cell. (A) is a timing chart of input / output of the first comparator and the second comparator when there is no threshold characteristic deviation as a monitoring circuit abnormality, and (b) is a threshold characteristic deviation as a monitoring circuit abnormality. is there. (A) is an input / output timing chart of the first comparator and the second comparator when the equalization discharge circuit is not broken down, and (b) is an input / output timing chart when the equalization discharge circuit is broken down.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an overall configuration diagram of a battery monitoring system including a battery monitoring apparatus according to the present embodiment. As shown in FIG. 1, the battery monitoring system includes a battery cell 10 and a battery monitoring device 20.

  The battery cell 10 is a voltage source capable of generating a constant voltage, and is a so-called single cell. The battery cell 10 is used, for example, as a power source for driving a load or a power source for an electronic device. For example, a rechargeable secondary battery is employed as the battery cell 10. In the present embodiment, a lithium ion secondary battery is used as the battery cell 10.

  In addition, a plurality of battery cells 10 are connected in series to form a block 11. The block 11 is a unit for dividing the plurality of battery cells 10 into a predetermined number. In the present embodiment, six battery cells 10 are connected in series to form a block 11. That is, the block 11 is obtained by modularizing a plurality of battery cells 10. In FIG. 1, only one block 11 is shown, but actually, a plurality of blocks 11 are set, and a plurality of blocks 11 are combined in series to form one assembled battery.

  The battery monitoring device 20 has an overcharge / discharge detection function for monitoring overcharge and overdischarge as the state of the battery cell 10, a failure diagnosis function for diagnosing a failure such as a deviation in threshold characteristics of the overcharge / discharge detection, It is an apparatus having. These overcharge and overdischarge states are abnormal in the battery cell 10.

  The overcharge / discharge detection function is a function of monitoring the voltage of the battery cell 10 by comparing the voltage of the battery cell 10 with a threshold value. When the battery cell 10 is a secondary battery, the battery monitoring device 20 monitors whether the voltage of the battery cell 10 is between a threshold value for detecting overcharge and a threshold value for detecting overdischarge.

  The failure diagnosis function is a function for detecting that the threshold for detecting overcharge / discharge has changed for some reason (for example, a circuit failure or the like). In other words, the failure diagnosis function uses the failure detection threshold for diagnosing whether there is an abnormality in the threshold for overcharge / discharge detection, and detects abnormalities (failures, disturbances, etc.) of each part that realizes the overcharge / discharge detection function. It is a function to detect.

  Such a battery monitoring device 20 includes a plurality of diagnostic resistors 30, an equalizing discharge circuit 40, a monitoring circuit 50, a block voltage detection unit 60, and a microcomputer 70 (hereinafter referred to as a microcomputer 70). ing.

  The plurality of diagnostic resistors 30 are resistors respectively connected between the positive electrode side of each battery cell 10 and the monitoring circuit 50. Each diagnostic resistor 30 has a known value of 1Ω to 100Ω, for example, and this resistance value is stored in the microcomputer 70.

  The equalizing discharge circuit 40 causes the current flowing from the battery cell 10 through the diagnostic resistor 30 to flow toward the negative electrode side of the battery cell when the cell voltage of the battery cell 10 exceeds a certain range, thereby causing the cell voltage to reach a certain range. It is a circuit that adjusts inside. The equalized discharge circuit 40 includes a discharge circuit for each battery cell 10 that serves as a current path through which current flows from the positive electrode side to the negative electrode side of the battery cell 10.

  The discharge circuit includes a resistor 41 and a switch 42. The resistor 41 is connected to a branch point between the diagnostic resistor 30 and the monitoring circuit 50, and a switch 42 is connected in series to the resistor 41. The switch 42 is connected to the negative electrode side of the battery cell 10. Therefore, when the switch 42 is turned on, a current flows from the positive electrode side of the battery cell 10 to the negative electrode side of the battery cell 10 via the diagnostic resistor 30, the resistor 41, and the switch 42. Thereby, the cell voltage of the battery cell 10 is lowered and adjusted so that the cell voltage is included in a certain range.

  The switch 42 is configured to spontaneously turn on to adjust the cell voltage within a certain range. The switch 42 is on / off controlled by a command from the microcomputer 70 at the time of failure diagnosis.

  Note that “in response to a command from the microcomputer 70” means either when the microcomputer 70 directly controls the switch 42 or when the microcomputer 70 issues a command to the monitoring circuit 50 and the monitoring circuit 50 controls the switch 42. It also includes the meaning.

  The monitoring circuit 50 is a circuit configured to input the cell voltages at both ends of the battery cell 10 for each battery cell 10, compare the cell voltage with a threshold value, and output the comparison result. This monitoring circuit 50 is provided for each block 11. Further, as the monitoring circuit 50, for example, an IC is used.

  FIG. 2 is a diagram showing a circuit configuration of the monitoring circuit 50 for one battery cell 10. The monitoring circuit 50 includes a first monitoring circuit 80 and a second monitoring circuit 90, and the first monitoring circuit 80 and the second monitoring circuit 90 constitute a dual circuit. That is, the first monitoring circuit 80 and the second monitoring circuit 90 have the same circuit configuration.

  The first monitoring circuit 80 compares the threshold value with the cell voltage of the battery cell 10 and outputs the comparison result, and includes a first switching unit 81, a first band gap unit 82, a first comparator 83, and A transistor 84 is provided.

  The first switching unit 81 generates a threshold voltage corresponding to the threshold from the cell voltage of the battery cell 10. For this reason, the 1st switching part 81 is between the 1st wiring 51 electrically connected to the positive voltage of the battery cell 10, and the 2nd wiring 52 electrically connected to the negative voltage of the battery cell 10. It is connected.

  Such a first switching unit 81 includes a plurality of resistors 85 and a plurality of switches 86 in order to generate a threshold voltage that is a threshold value. The plurality of resistors 85 are connected in series between the first wiring 51 and the second wiring 52 and are used to divide the cell voltage of the battery cell 10.

  The switch 86 is a path switching circuit configured by, for example, a resistance element or a transistor. Each switch 86 is connected to a connection point of each resistor 85, and each switch 86 is connected in parallel. A connection point where the switches 86 are connected in parallel is connected to a non-inverting input terminal (+ terminal) of the first comparator 83.

  In the present embodiment, 11 resistors 85 are connected in series, and 10 switches 86 are connected to the connection points of the resistors 85, respectively. The resistor 85 located closest to the second wiring 52 among the resistors 85 is a variable resistor for performing overcharge detection. On the other hand, the resistor 85 located closest to the first wiring 51 among the resistors 85 is a resistor for performing overdischarge detection.

  When any one of the switches 86 is turned on, the cell voltage of the battery cell 10 is divided by each resistor 85, and this divided voltage is used as a threshold voltage for the non-inverting input terminal of the first comparator 83. Is input. Therefore, when the switch 86 closest to the first wiring 51 among the switches 86 is turned on, there is one resistance 85 connected to the first wiring 51 and ten resistances 85 connected to the second wiring 52. The partial pressure is input to the first comparator 83 as an overdischarge detection threshold, that is, a threshold voltage. Each switch 86 is on / off controlled by the microcomputer 70.

  Thus, by switching each switch 86, the partial pressure of the battery cell 10 corresponding to any one of the overcharge detection threshold, the first threshold to the eighth threshold, and the overdischarge detection threshold is set as the threshold voltage. 1 is output from the first switching unit 81 to the first comparator 83.

  These overcharge detection threshold values, the first threshold value to the eighth threshold value, and the overdischarge detection threshold value are set within the voltage range of the battery cell 10. When a lithium ion battery is used as the battery cell 10, the overcharge detection threshold is set to 4.3V, for example, and the overdischarge detection threshold is set to 2.0V, for example. Therefore, the first threshold value to the eighth threshold value between the overcharge detection threshold value and the overdischarge detection threshold value are set in the working voltage range of the battery cell 10, and are set between 2.0 V and 4.3 V, for example. .

  In addition, each of the first to eighth threshold values is used by the microcomputer 70 to perform a failure diagnosis for detecting an abnormality of the monitoring circuit 50 such as a threshold characteristic deviation. Each of the first to eighth threshold values is set to be a constant value and relatively change in a plurality of stages. For example, if the constant value is 0.1 V, each threshold value is set so that the difference between the first threshold value and the second threshold value is 0.1 V, and the difference between the second threshold value and the third threshold value is 0.1 V. ing. In other words, the resistance value of each resistor 85 is determined so that each threshold value changes stepwise at a constant value. In the present embodiment, at the time of failure diagnosis, switching is performed in stages from the largest first threshold value to the smallest eighth threshold value.

  Thus, the first threshold value to the eighth threshold value are switched stepwise within the voltage range used in the battery cell 10. By setting each threshold in this way, it is not necessary to switch the threshold stepwise for the entire range from the minimum value of the voltage of the battery cell 10 to the maximum value (for example, 0 V to 5 V). Further, since the threshold value is divided more finely than when the threshold value is switched only in one stage, the failure detection accuracy of the first monitoring circuit 80 is improved.

  The first band gap unit 82 is a voltage source that generates a constant first reference voltage. The first band gap portion 82 is connected between the inverting input terminal (− terminal) of the first comparator 83 and the second wiring 52.

  The first comparator 83 receives the threshold voltage from the first switching unit 81 and the first reference voltage from the first band gap unit 82, and outputs the comparison result to the microcomputer 70 as the first output from the output terminal. This is a comparison circuit. As such a first comparator 83, a comparator can be used.

  As described above, the first reference voltage is input to the inverting input terminal of the first comparator 83, and the threshold voltage is input to the non-inverting input terminal. Therefore, when the threshold voltage is higher than the first reference voltage, the first output becomes a high level signal, and when the threshold voltage is lower than the first reference voltage, the first output becomes a low level signal.

  The transistor 84 is dark current blocking means for preventing dark current from flowing through the resistors 85 that connect the first wiring 51 and the second wiring 52 when the battery cell 10 is not used. Thereby, when the battery cell 10 is not used, the battery cell 10 can be prevented from being consumed by the dark current. The transistor 84 is controlled by the microcomputer 70.

  The second monitoring circuit 90 constitutes a dual circuit together with the first monitoring circuit 80. The circuit configuration of the second monitoring circuit 90 is the same as the circuit configuration of the first monitoring circuit 80. That is, the second monitoring circuit 90 compares the threshold value with the cell voltage of the battery cell 10 and outputs the comparison result. The second switching unit 91, the second band gap unit 92, and the second comparator 93 are output. , And a transistor 94.

  Similar to the first switching unit 81, the second switching unit 91 generates a threshold voltage corresponding to the threshold from the cell voltage of the battery cell 10, and is connected between the first wiring 51 and the second wiring 52. Has been. The second switching unit 91 has the same configuration as the first switching unit 81, and includes a plurality of resistors 95 and a plurality of switches 96.

  The connection form of the plurality of resistors 95 and the plurality of switches 96 is the same as the connection form of the resistors 85 and the switches 86 described above. A connection point where the switches 96 are connected in parallel is connected to a non-inverting input terminal (+ terminal) of the second comparator 93. The configuration of the switch 96 is the same as that of the switch 86 of the first switching unit 81.

  In addition, the overcharge detection threshold, the first to eighth thresholds, and the overdischarge detection threshold in the second switching unit 91 are set to the same values as the thresholds of the first switching unit 81. Then, when each switch 96 is switched, the divided voltage corresponding to any one of the overcharge detection threshold value, the first threshold value to the eighth threshold value, and the overdischarge detection threshold value is set as the threshold voltage from the second switching unit 91. 2 is output to the comparator 93.

  Similar to the first band gap portion 82, the second band gap portion 92 is a voltage source that generates a constant second reference voltage. The second reference voltage generated by the second band gap unit 92 is a voltage having the same value as the first reference voltage generated by the first band gap unit 82. The second band gap portion 92 is connected between the inverting input terminal (− terminal) of the second comparator 93 and the second wiring 52.

  The second comparator 93 receives the threshold voltage from the second switching unit 91 and the second reference voltage from the second band gap unit 92, and outputs the comparison result as the second output from the output terminal. is there. As such a second comparator 93, a comparator is used similarly to the first comparator 83.

  The second reference voltage is input from the second band gap 92 to the inverting input terminal of the second comparator 93, and the threshold voltage is input from the second switching unit 91 to the non-inverting input terminal. When the threshold voltage is larger than the second reference voltage, the second output becomes a high level signal, and when the threshold voltage is smaller than the second reference voltage, the second output becomes a low level signal.

  Similar to the transistor 84 of the first monitoring circuit 80, the transistor 94 is dark current interrupting means for interrupting dark current flowing through each resistor 85 when the battery cell 10 is not used. The transistor 94 is controlled by the microcomputer 70.

  As described above, the first monitoring circuit 80 and the second monitoring circuit 90 have the same configuration. Note that the configurations of the first monitoring circuit 80 and the second monitoring circuit 90 shown in FIG. 2 are configurations for one battery cell 10. Therefore, actually, each monitoring circuit 80 and 90 shown in FIG. 2 is provided in each monitoring circuit 50 for each battery cell 10.

  The block voltage detector 60 shown in FIG. 1 detects the voltage across the block 11, that is, the block voltage in which six battery cells 10 are connected in series. For this reason, the block voltage detection part 60 is connected to the positive electrode side of the battery cell 10 located on the highest voltage side in the block 11 and the negative electrode side of the battery located on the lowest voltage side. The block voltage detected by the block voltage detector 60 is output to the microcomputer 70.

  The microcomputer 70 has a monitoring function for determining the state of each of the plurality of battery cells 10 based on the comparison result of the monitoring circuit 50, and a cell voltage by relatively changing the threshold value of the monitoring circuit 50 in a plurality of stages for each of the plurality of battery cells And a failure diagnosis function for detecting an abnormality in the monitoring circuit 50 and the equalizing discharge circuit 40 based on the comparison result. Such a microcomputer 70 includes a CPU, a ROM, an EEPROM, a RAM, and the like (not shown), and monitors the state of the battery cell 10 and diagnoses a failure of the monitoring circuit 50 according to a program stored in the ROM. Note that threshold information of the monitoring circuit 50 is also stored in the ROM.

  When monitoring the state of the battery cell 10 and diagnosing the failure of the monitoring circuit 50 and the equalizing discharge circuit 40, the microcomputer 70 turns on / off each switch 86 of the first switching unit 81 in the first monitoring circuit 80 and the second. The switch 96 of the second switching unit 91 in the monitoring circuit 90 is switched on / off. Thereby, the threshold voltage output from the first switching unit 81 and the second switching unit 91 is switched. That is, the microcomputer 70 switches the on / off states of the switches 86 and 96 and divides the voltage of the battery cell 10 by the resistors 85 and 95, respectively, thereby relatively changing the threshold value in a plurality of stages.

  When monitoring the battery cell 10, the microcomputer 70 outputs the threshold voltage corresponding to the overcharge detection threshold or the overdischarge detection threshold so that each of the first switching unit 81 and the second switching unit 91 outputs the threshold voltage. The switch 86 and the switch 96 are switched for the first switching unit 81 and the second switching unit 91, respectively. Then, overdischarge or overcharge of the battery cell 10 is monitored by the first output and the second output input from the first monitoring circuit 80 and the second monitoring circuit 90.

  On the other hand, at the time of failure diagnosis, the microcomputer 70 switches on / off of the switches 86 and 96 to thereby change the threshold from the first threshold to the eighth threshold for the first monitoring circuit 80 and the second monitoring circuit 90. Switch to multiple stages and compare with cell voltage. When the comparison result (first output) of the first monitoring circuit 80 is different from the comparison result (second output) of the second monitoring circuit 90, it is detected that an abnormality has occurred in the monitoring circuit 50. “An abnormality has occurred in the monitoring circuit 50” means that a failure has occurred in a component of the first monitoring circuit 80 or the second monitoring circuit 90.

  Further, the microcomputer 70 turns on the switch 42 of the equalizing discharge circuit 40 to discharge the battery cell 10 at the time of failure diagnosis, and relative to the cell voltage when the equalizing discharge circuit 40 is turned on in a plurality of stages. A comparison result obtained by comparing the changed threshold value is acquired from the monitoring circuit 50. Note that “turning on the equalizing discharge circuit 40” means turning on the switch 42 of the equalizing discharge circuit 40 as described above.

  Further, the microcomputer 70 estimates the cell voltage in which the drop voltage generated at both ends of the diagnostic resistor 30 drops when the current flows through the diagnostic resistor 30 by turning on the equalizing discharge circuit 40, and the estimated cell An estimation result obtained by comparing the voltage and a threshold value relatively changed in a plurality of stages is acquired. And when this estimation result and the comparison result of the monitoring circuit 50 differ, abnormality of the equalization discharge circuit 40 is detected.

  The above is the overall configuration of the battery monitoring device 20 and the battery monitoring system according to the present embodiment. As described above, a plurality of blocks 11 are actually connected in series, and a plurality of monitoring circuits 50 are connected to each block 11. Each monitoring circuit 50 is electrically connected to a common microcomputer 70. In FIG. 1, one of the blocks 11 and one monitoring circuit 50 are shown.

  Next, the monitoring operation of the battery monitoring device 20, that is, the overcharge / discharge detection operation will be described. The monitoring operation and overcharge / discharge detection operation in the battery monitoring device 20 are, for example, when the battery monitoring device 20 is turned on or off, or when the battery monitoring device 20 receives an external command. To begin.

  The overcharge / discharge detection function of the battery monitoring device 20 includes an overcharge detection mode and an overdischarge detection mode. First, overcharge detection will be described. In the battery monitoring device 20, when the overcharge detection mode is started, the microcomputer 70 corresponds to the overcharge detection threshold value from the first switching unit 81 of the first monitoring circuit 80 and the second switching unit 91 of the second monitoring circuit 90. The switches 86 and 96 are switched so that the threshold voltage is output.

  The comparators 83 and 93 compare the threshold voltage corresponding to the overcharge detection threshold value with the first and second reference voltages, and the results are input from the comparators 83 and 93 to the microcomputer 70, respectively. The In the microcomputer 70, whether or not the voltage of the battery cell 10 is overcharged is detected based on whether the outputs of the comparators 83 and 93 are at a high level or a low level.

  On the other hand, in the battery monitoring device 20, when the overdischarge detection mode is started, the switches 86 and 96 are switched so that the microcomputer 70 outputs a threshold voltage corresponding to the overdischarge detection threshold from the switching units 81 and 91. It is done. Then, the comparators 83 and 93 compare the threshold voltage corresponding to the overdischarge detection threshold with the first and second reference voltages, and the results are input from the comparators 83 and 93 to the microcomputer 70, respectively. In the microcomputer 70, it is determined whether or not the voltage of the battery cell 10 is overdischarged based on whether the output of each of the comparators 83 and 93 is high level or low level.

  In the above description, overcharge / discharge detection is performed based on the output of each of the monitoring circuits 80, 90, but overdischarge detection is performed based only on the output of either one of the monitoring circuits 80, 90. It may be broken.

  Next, the operation of failure diagnosis of the battery monitoring device 20 will be described with reference to FIG. 3A shows the first comparator 83 and the second comparator when there is no threshold characteristic deviation as an abnormality of the monitoring circuit 50, and FIG. 93 is a timing chart of 93 input / output.

  In the upper and lower timing charts shown in FIGS. 3A and 3B, the vertical axis of the upper timing chart indicates the voltage (−) of the inverting input terminal of the first comparator 83 or the second comparator 93. (Terminal voltage) and non-inverting input terminal voltage (+ terminal voltage). Further, the vertical axis of the lower timing chart indicates the output voltage of the first output of the first comparator 83 or the second output of the second comparator 93, respectively. The horizontal axes of the upper and lower timing charts indicate the switching steps of the respective threshold values from the first threshold value to the eighth threshold value.

  In the battery monitoring device 20, when the failure diagnosis mode is started, the microcomputer 70 switches each switch 86 of the first switching unit 81 to divide the cell voltage of the battery cell 10. A threshold voltage corresponding to one threshold is output. Similarly, each switch 96 of the second switching unit 91 is switched to divide the cell voltage of the battery cell 10, and a threshold voltage corresponding to the first threshold is output from the second switching unit 91. In other words, it can be said that the first switching unit 81 and the second switching unit 91 relatively change the first reference voltage and the second reference voltage in a plurality of stages, respectively.

  The first comparator 83 compares the first reference voltage input from the first band gap unit 82 with the threshold voltage corresponding to the first threshold input from the first switching unit 81, and the comparison result is obtained. The first output is output to the microcomputer 70. Similarly, the second comparator 93 compares the second reference voltage input from the second band gap unit 92 with the threshold voltage corresponding to the first threshold input from the second switching unit 91, and the comparison result. Is output to the microcomputer 70 as the second output.

  In this case, when the threshold voltage is higher than the first and second reference voltages, the first output and the second output are high level signals, respectively, and when the threshold voltage is lower than the first and second reference voltages, the first output and Each of the second outputs is a low level signal.

  In the microcomputer 70, the first output input from the first monitoring circuit 80 is compared with the second output input from the second monitoring circuit 90. Thereafter, similarly to the above, the microcomputer 70 switches the threshold values of the monitoring circuits 80 and 90 from the second threshold value to the eighth threshold value. For each threshold, the first output of the first monitoring circuit 80 and the second output of the second monitoring circuit 90 are input to the microcomputer 70 and compared.

  When there is no failure such as threshold characteristic deviation in the first monitoring circuit 80 and the second monitoring circuit 90, the input / output of each switching unit 81, 91 is shown as shown in FIG.

  As described above, the configurations of the first switching unit 81 and the second switching unit 91 are exactly the same, and the first and second references generated by the first band gap unit 82 and the second band gap unit 92 are the same. The voltage is exactly the same voltage. Therefore, when there is no failure such as a threshold characteristic deviation in the first monitoring circuit 80 and the second monitoring circuit 90, the threshold voltage and the first reference voltage input to the first comparator 83 are shown in FIG. This waveform is the same as the threshold voltage and the second reference voltage input to the second comparator 93.

  When the microcomputer 70 switches the output of the first switching unit 81 and the second switching unit 91 step by step so that the threshold value increases in order from the first threshold, for example, the first threshold to the fifth threshold Until the threshold voltage corresponding to each of these threshold values is larger than the first and second reference voltages, the first output of the first comparator 83 and the second output of the second comparator 93 are at the same high level. Output voltage. That is, the comparison results of the first comparator 83 and the second comparator 93 are the same high level output voltage.

  Then, the magnitude relationship between the threshold voltage corresponding to the sixth threshold and the first and second reference voltages is inverted at the switching stage of the sixth threshold and the threshold voltage is smaller than the first and second reference voltages. Then, the first output of the first comparator 83 and the second output of the second comparator 93 have the same low level output voltage. That is, the switching timing from the fifth threshold value to the sixth threshold value becomes the inversion timing of each output of each comparator 83, 93, and each comparison result of each comparator 83, 93 becomes the same low level output voltage.

  As described above, when there is no failure such as a threshold characteristic deviation in the first monitoring circuit 80 and the second monitoring circuit 90, the input / output of the first comparator 83 and the second comparator 93 is shown in FIG. Will give exactly the same result. Therefore, the microcomputer 70 determines that the comparison results of the first monitoring circuit 80 and the second monitoring circuit 90 from the first threshold value to the eighth threshold value are the same, and the first monitoring circuit 80 and the second monitoring circuit are determined by this determination. It is detected that 90 is normal.

  On the other hand, when the first monitoring circuit 80 and the second monitoring circuit 90 have a failure such as a threshold characteristic shift, the inputs and outputs of the switching units 81 and 91 are not the same. A failure such as a threshold characteristic deviation occurs due to, for example, a characteristic change of the first band gap part 82 or the second band gap part 92, a change in resistance value of each of the resistors 85 and 95, and the like.

  Here, for example, a case where a threshold characteristic deviation occurs in the first monitoring circuit 80 and a threshold characteristic deviation does not occur in the second monitoring circuit 90 will be described as an example. Further, it is assumed that the threshold characteristic deviation in the first monitoring circuit 80 is a characteristic deviation in which the output of the first switching unit 81 is largely shifted by a certain value. That is, as shown in FIG. 3B, the voltage at the non-inverting input terminal of the first comparator 83 (+ terminal voltage) in the first monitoring circuit 80 is greater than the voltage at the non-inverting input terminal of the second comparator 93. Is also increased by a certain value.

  Then, when the microcomputer 70 sequentially switches the outputs of the first switching unit 81 and the second switching unit 91 from the first threshold, the second monitoring circuit 90 having no threshold characteristic deviation, for example, from the first threshold to the first threshold If the threshold voltage corresponding to each of these thresholds is larger than the second reference voltage up to five thresholds, the first output of the first comparator 83 and the second output of the second comparator 93 are the same as described above. The same high level output voltage. That is, from the first threshold value to the fifth threshold value, the comparison results of the first comparator 83 and the second comparator 93 are the same high level output voltage.

  However, when the microcomputer 70 switches the outputs of the first switching unit 81 and the second switching unit 91 to the sixth threshold value, the second monitoring circuit 90 having no threshold characteristic deviation has a magnitude difference between the threshold voltage and the second reference voltage. While the relationship is reversed, in the first monitoring circuit 80 having the threshold characteristic deviation, the magnitude relationship between the threshold voltage and the first reference voltage is not reversed. Therefore, the second output of the second comparator 93 is a low level output voltage, and the first output of the first comparator 83 is maintained at a high level output voltage. That is, the switching timing from the fifth threshold value to the sixth threshold value becomes the output inversion timing in the second monitoring circuit 90.

  Subsequently, when the microcomputer 70 switches the outputs of the switching units 81 and 91 to the seventh threshold value, the second output of the second comparator 93 is maintained at the low output voltage, and the first comparator 83 is maintained. The first output is maintained at a high level output voltage. That is, the comparison results of the first comparator 83 and the second comparator 93 are different between the sixth threshold value and the seventh threshold value.

  Thereafter, when the microcomputer 70 switches the outputs of the switching units 81 and 91 to the eighth threshold value, the magnitude relationship between the threshold voltage and the first reference voltage is reversed in the first monitoring circuit 80 having the threshold characteristic deviation. . Therefore, the first output of the first comparator 83 is maintained at a low level output voltage. The second output of the second comparator 93 is maintained at the low level output voltage from when the second comparator 93 is switched to the sixth threshold value. That is, the switching timing from the seventh threshold value to the eighth threshold value is the output inversion timing in the first monitoring circuit 80.

  In this way, when there is a failure such as a threshold characteristic deviation in the first monitoring circuit 80, the input and output of the first comparator 83 and the second comparator 93 are the sixth threshold and the second comparator 93 as shown in FIG. The comparison results of the comparators 83 and 93 differ at the seventh threshold value. Therefore, the microcomputer 70 determines that the comparison results of the first monitoring circuit 80 and the second monitoring circuit 90 from the first threshold value to the eighth threshold value are different, and this determination causes the first monitoring circuit 80 and the second monitoring circuit 90 to be different. Detect that something is wrong. That is, the microcomputer 70 detects a threshold characteristic deviation based on a difference in inversion timing between the first output and the second output. In this way, a fault such as a threshold characteristic deviation is detected.

  The microcomputer 70 performs the failure diagnosis as described above in order for each of the plurality of battery cells 10.

  Next, an operation for detecting an abnormality in the equalizing discharge circuit 40 during failure diagnosis will be described with reference to FIG. FIG. 4A shows the input / output of the first comparator 83 and the second comparator 93 when the equalizing discharge circuit 40 has not failed, and FIG. 4B shows the input / output of the first comparator 83 and the second comparator 93 when the equalizing discharge circuit 40 has failed. It is a timing chart.

  In this case, first, the microcomputer 70 inputs a block voltage from the block voltage detection unit 60. The microcomputer 70 estimates the cell voltage of the battery cell 10 from the block voltage, and when the current flows through the diagnostic resistor 30 using this cell voltage, the drop voltage generated at both ends of the diagnostic resistor 30 drops. Estimate the voltage.

  This “estimated cell voltage” corresponds to a cell voltage in which the drop voltage that would have occurred at both ends of the diagnostic resistor 30 is lowered by turning on the equalizing discharge circuit 40 and causing a current to flow through the diagnostic resistor 30. To do.

  Then, the microcomputer 70 compares the estimated cell voltage with a threshold value relatively changed in a plurality of stages. Thereby, for example, if the equalizing discharge circuit 40 is operating normally, an estimation result is obtained that the outputs of the comparators 83 and 93 are inverted at the timing when the threshold value is switched from the fifth threshold value to the sixth threshold value. .

  Subsequently, the microcomputer 70 turns on the switch 42 related to the battery cell 10 that is the target of failure diagnosis, discharges the battery cell 10, and causes a discharge current to flow through the diagnosis resistor 30. As a result, the cell voltage of the battery cell 10 decreases by the drop voltage of the diagnostic resistor 30 if the equalizing discharge circuit 40 has not failed, and the diagnostic resistor 30 if the equalizing discharge circuit 40 has failed. The voltage corresponding to the drop voltage will not drop. Therefore, a difference occurs in the magnitude of the cell voltage depending on whether the equalizing discharge circuit 40 is abnormal.

  Then, the monitoring circuits 80 and 90 compare the cell voltage when the equalizing discharge circuit 40 is turned on with the threshold value relatively changed in a plurality of stages, and the comparison result is input to the microcomputer 70.

  Thereafter, the microcomputer 70 compares the estimation result estimated from the block voltage with the comparison results of the monitoring circuits 80 and 90. Then, as shown in FIG. 4A, when the comparison results of the monitoring circuits 80 and 90 are the results of inverting the outputs of the comparators 83 and 93 at the timing when the fifth threshold value is switched to the sixth threshold value, The comparison results of the monitoring circuits 80 and 90 coincide with the estimation results of the microcomputer 70. That is, no abnormality has occurred in the equalizing discharge circuit 40. Therefore, the microcomputer 70 determines that “the equalizing discharge circuit 40 is normal”.

  On the other hand, as shown in FIG. 4B, when the comparison result of the monitoring circuits 80 and 90 is a result that the outputs of the comparators 83 and 93 are inverted at the timing when the third threshold value is switched to the fourth threshold value, The comparison results of the monitoring circuits 80 and 90 are different from the estimation results of the microcomputer. That is, the equalization discharge circuit 40 has an abnormality that the discharge amount is large. Therefore, the microcomputer 70 determines that the equalizing discharge circuit 40 is abnormal.

  Only one of the comparison results of the monitoring circuits 80 and 90 may be employed, or both comparison results may be employed.

  Further, the abnormality of the equalizing discharge circuit 40 may be a failure of the resistor 41 or the switch 42 constituting the discharge circuit, a failure in which the wiring resistance of the current path in the discharge circuit increases, or the like. Due to these failures, if the equalizing discharge circuit 40 is turned on, the discharge current that should have flown from the battery cell 10 does not flow, so the drop voltage of the diagnostic resistor 30 does not drop from the cell voltage. For this reason, since the inversion timing of the output estimated from the block voltage by the microcomputer 70 and the inversion timing of the comparators 83 and 93 of the monitoring circuits 80 and 90 are shifted, the estimation result of the microcomputer 70 and the comparison result of the monitoring circuit 50 Is different. Therefore, an abnormality in the equalizing discharge circuit 40 can be detected.

  The microcomputer 70 sequentially performs the failure diagnosis of the equalizing discharge circuit 40 for each of the plurality of battery cells 10 during the failure diagnosis.

  As described above, in this embodiment, the cell voltage when the equalizing discharge circuit 40 is turned on during the failure diagnosis of the monitoring circuit 50 is compared with the threshold value, and the comparison result and the estimation result of the microcomputer 70 are compared. It is characterized by comparison.

  Thus, since the equalizing discharge circuit 40 is turned on at the time of failure diagnosis, if the equalizing discharge circuit 40 is not broken, a discharge current flows through the diagnosis resistor 30 and the cell voltage is reduced by the drop voltage. If the equalization discharge circuit 40 is faulty, the discharge current does not flow (or becomes difficult to flow) through the diagnostic resistor 30, and the cell voltage does not drop by the drop voltage. Thereby, it is possible to cause a difference in the cell voltage input to the monitoring circuit 50 in accordance with the abnormality of the equalizing discharge circuit 40. For this reason, when the cell voltage is compared with the threshold value, the timing at which the magnitude relationship between the cell voltage and the threshold value is inverted is shifted. Therefore, the abnormality of the equalization discharge circuit 40 is detected by detecting this timing shift. be able to.

  As an abnormality of the equalizing discharge circuit 40, a failure of the resistor 41 or the switch 42 or an increase in the wiring resistance of the discharge circuit can be detected. In addition, since no discharge current flows through the equalization discharge circuit 40, it can be determined that an increase in wiring resistance between the battery cell 10 and the equalization discharge circuit 40 and an abnormality has occurred in the diagnostic resistor 30. .

  Further, the present embodiment is characterized in that the block voltage detection unit 60 detects the block voltage. Thereby, it is not necessary to measure the cell voltage for each battery cell 10 by the monitoring circuit 50. In addition, as described above, the equalizing discharge circuit 40 spontaneously operates so that the cell voltage of each battery cell 10 is within a certain range, so that the cell voltage of each battery cell 10 is within a certain range. . For this reason, the cell voltage can be estimated with high accuracy from the block voltage detected by the block voltage detection unit 60.

  Furthermore, the present embodiment is characterized in that the equalized discharge circuit 40 is used as a means for causing a discharge current to flow through the diagnostic resistor 30 during failure diagnosis. As a result, the circuit for passing a current to the diagnostic resistor 30 and the equalizing discharge circuit 40 can be shared. For this reason, it is not necessary to separately prepare a circuit for passing a current through the diagnostic resistor 30.

  As for the correspondence between the description of the present embodiment and the description of the claims, the equalization discharge circuit 40 corresponds to the “battery cell discharge means” in the claims, and the monitoring circuit 50 has the claims. Corresponds to “monitoring means”. The block voltage detection unit 60 corresponds to “block voltage detection means” in the claims, and the microcomputer 70 corresponds to “determination means” in the claims.

(Other embodiments)
In the above embodiment, the battery monitoring device 20 detects the overcharge / discharge of the secondary battery as the battery cell 10, but it is not necessary to monitor both overcharge / discharge, either overcharge or overdischarge. You can just monitor one.

  Furthermore, in the said embodiment, although the lithium ion secondary battery was demonstrated to the example as the battery cell 10, you may employ | adopt another secondary battery. Moreover, this secondary battery can be applied to a vehicle-mounted battery mounted on an electric vehicle such as a hybrid vehicle.

  In the above embodiment, each of the switching units 81 and 91 is configured to switch the threshold value for performing failure diagnosis such as a threshold characteristic deviation to eight levels from the first threshold value to the eighth threshold value. Is an example.

  In the above embodiment, the overdischarge detection threshold value is larger than the first threshold value, and the overcharge detection threshold value is smaller than the eighth threshold value. However, the values of these detection threshold values are examples. For example, the overdischarge detection threshold value may be a value between the second threshold value and the third threshold value, and the overcharge detection threshold value may be a value between the sixth threshold value and the seventh threshold value.

  The circuit configuration of the monitoring circuit 50 shown in the above embodiment shows an example, and other circuit configurations may be used. For example, in the above embodiment, the monitoring circuit 50 is provided with the two monitoring circuits 80 and 90 to configure the dual system circuit. However, the monitoring of the cell voltage of the battery cell 10 or the failure of the monitoring circuit is performed by one monitoring circuit. A diagnosis may be performed.

  The configuration of the discharge circuit in the equalized discharge circuit 40 shown in the above embodiment is an example, and other circuit configurations may be adopted.

  In the above embodiment, the equalizing discharge circuit 40 is used as a means for causing a current to flow from the battery cell 10 during failure diagnosis. However, a circuit for causing a current to flow may be provided separately.

10 battery cell 30 resistance for diagnosis 40 equalization discharge circuit (battery cell discharge means)
50 Monitoring circuit (monitoring means)
60 block voltage detector (block voltage detector)
70 Microcomputer (determination means)
85, 95 Resistance 86, 96 Switch

Claims (4)

A battery monitoring device for monitoring the state of a plurality of battery cells connected in series,
Monitoring means for inputting the cell voltage at both ends of the battery cell for each of the plurality of battery cells, comparing the cell voltage with a threshold value, and outputting the comparison result;
A plurality of diagnostic resistors respectively connected between the positive electrode side of each of the plurality of battery cells and the monitoring means;
While determining the state of each of the plurality of battery cells based on the comparison result of the monitoring means, the threshold value of the monitoring means is relatively changed in a plurality of stages for each of the plurality of battery cells and compared with the cell voltage. Determination means for performing failure diagnosis for detecting an abnormality of the monitoring means based on the comparison result;
Battery cell discharging means for flowing a current flowing from the battery cell via the diagnostic resistor to the negative electrode side of the battery cell when turned on according to the instruction of the determination means,
The determination means includes a comparison result obtained by comparing a cell voltage when the battery cell discharge means is turned on at the time of the failure diagnosis and a threshold value relatively changed in a plurality of stages, and a current flows through the diagnosis resistor. The battery cell discharging means when the estimation result obtained by estimating the cell voltage at which the drop voltage generated at both ends of the diagnostic resistor drops and comparing the cell voltage with a threshold value relatively changed in a plurality of stages is different. A battery monitoring device that detects an abnormality of the battery. Block voltage detection means for detecting a block voltage at both ends of the plurality of battery cells connected in series and outputting to the determination means;
The determination means estimates a cell voltage of the battery cell from the block voltage, and a cell in which a drop voltage generated at both ends of the diagnostic resistor drops when a current flows through the diagnostic resistor using the cell voltage The battery monitoring apparatus according to claim 1, wherein the voltage is estimated.   The battery cell discharging means flows the current flowing from the battery cell through the diagnostic resistor to the negative electrode side of the battery cell when the cell voltage of the battery cell exceeds a certain range, thereby causing the cell voltage to flow. The battery monitoring device according to claim 1, wherein the battery monitoring device is an equalizing discharge circuit that adjusts within a certain range. The monitoring means has a plurality of resistors and a plurality of switches for dividing the cell voltage of the battery cell,
The determination unit is configured to relatively change the threshold value in a plurality of stages by switching an ON state or an OFF state of the plurality of switches and dividing the voltage of the battery cell by the plurality of resistors. The battery monitoring device according to any one of 1 to 3.

Images